Artículos de revistas: "ApoE-/- mouse"

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Zuniga, Nathan R., Noah E. Earls, Ariel E. A. Denos, Jared M. Elison, Benjamin S. Jones, Ethan G. Smith, Noah G. Moran, et al. "Quantitative and Kinetic Proteomics Reveal ApoE Isoform-dependent Proteostasis Adaptations in Mouse Brain." PLOS Computational Biology 20, no. 12 (December 12, 2024): e1012407. https://doi.org/10.1371/journal.pcbi.1012407.

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Apolipoprotein E (ApoE) polymorphisms modify the risk of Alzheimer’s disease with ApoE4 strongly increasing and ApoE2 modestly decreasing risk relative to the control ApoE3. To investigate how ApoE isoforms alter risk, we measured changes in proteome homeostasis in transgenic mice expressing a human ApoE gene (isoform 2, 3, or 4). The regulation of each protein’s homeostasis is observed by measuring turnover rate and abundance for that protein. We identified 4849 proteins and tested for ApoE isoform-dependent changes in the homeostatic regulation of ~2700 ontologies. In the brain, we found that ApoE4 and ApoE2 both lead to modified regulation of mitochondrial membrane proteins relative to the wild-type control ApoE3. In ApoE4 mice, lack of cohesion between mitochondrial membrane and matrix proteins suggests that dysregulation of proteasome and autophagy is reducing protein quality. In ApoE2, proteins of the mitochondrial matrix and the membrane, including oxidative phosphorylation complexes, had a similar increase in degradation which suggests coordinated replacement of the entire organelle. In the liver we did not observe these changes suggesting that the ApoE-effect on proteostasis is amplified in the brain relative to other tissues. Our findings underscore the utility of combining protein abundance and turnover rates to decipher proteome regulatory mechanisms and their potential role in biology.

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Tai, Leon M., Katherine L. Youmans, Lisa Jungbauer, Chunjiang Yu та Mary Jo LaDu. "Introducing HumanAPOEinto AβTransgenic Mouse Models". International Journal of Alzheimer's Disease 2011 (2011): 1–9. http://dx.doi.org/10.4061/2011/810981.

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Apolipoprotein E (apoE) and apoE/amyloid-β(Aβ) transgenic (Tg) mouse models are critical to understanding apoE-isoform effects on Alzheimer's disease risk. Compared to wild type,apoE−/−mice exhibit neuronal deficits, similar to apoE4-Tg compared to apoE3-Tg mice, providing a model for Aβ-independent apoE effects on neurodegeneration. To determine the effects of apoE on Aβ-induced neuropathology,apoE−/−mice were crossed with Aβ-Tg mice, resulting in a significant delay in plaque deposition. Surprisingly, crossing human-apoE-Tg mice withapoE−/−/Aβ-Tg mice further delayed plaque deposition, which eventually developed in apoE4/Aβ-Tg mice prior to apoE3/Aβ-Tg. One approach to address hAPOE-induced temporal delay in Aβpathology is an additional insult, like head injury. Another is crossing human-apoE-Tg mice with Aβ-Tg mice that have rapid-onset Aβpathology. For example, because 5xFAD mice develop plaques by 2 months, the prediction is that human-apoE/5xFAD-Tg mice develop plaques around 6 months and 12 months before other human-apoE/Aβ-Tg mice. Thus, tractable models for human-apoE/Aβ-Tg mice continue to evolve.

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Vecchio, Filomena Lo, Paola Bisceglia, Bruno Pietro Imbimbo, Madia Lozupone, Raffaela Rita Latino, Emanuela Resta, Maurizio Leone, et al. "Are apolipoprotein E fragments a promising new therapeutic target for Alzheimer’s disease?" Therapeutic Advances in Chronic Disease 13 (January 2022): 204062232210816. http://dx.doi.org/10.1177/20406223221081605.

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Human apolipoprotein E (ApoE) is a 299-amino acid secreted glycoprotein that binds cholesterol and phospholipids. ApoE exists as three common isoforms (ApoE2, ApoE3, and ApoE4) and heterozygous carriers of the ε4 allele of the gene encoding ApoE ( APOE) have a fourfold greater risk of developing Alzheimer’s disease (AD). The enzymes thrombin, cathepsin D, α-chymotrypsin-like serine protease, and high-temperature requirement serine protease A1 are responsible for ApoE proteolytic processing resulting in bioactive C-terminal-truncated fragments that vary depending on ApoE isoforms, brain region, aging, and neural injury. The objectives of the present narrative review were to describe ApoE processing, discussing current hypotheses about the potential role of various ApoE fragments in AD pathophysiology, and reviewing the current development status of different anti-ApoE drugs. The exact mechanism by which APOE gene variants increase/decrease AD risk and the role of ApoE fragments in the deposition are not fully understood, but APOE is known to directly affect tau-mediated neurodegeneration. ApoE fragments co-localize with neurofibrillary tangles and amyloid β (Aβ) plaques, and may cause neurodegeneration. Among anti-ApoE approaches, a fascinating strategy may be to therapeutically overexpress ApoE2 in APOE ε4/ε4 carriers through vector administration or liposomal delivery systems. Another approach involves reducing ApoE4 expression by intracerebroventricular antisense oligonucleotides that significantly decreased Aβ pathology in transgenic mice. Differences in the proteolytic processing of distinct ApoE isoforms and the use of ApoE fragments as mimetic peptides in AD treatment are also under investigation. Treatment with peptides that mimic the structural and biological properties of native ApoE may reduce Aβ deposition, tau hyperphosphorylation, and glial activation in mouse models of Aβ pathology. Alternative strategies involve the use of ApoE4 structure correctors, passive immunization to target a certain form of ApoE, conversion of the ApoE4 aminoacid sequence into that of ApoE3 or ApoE2, and inhibition of the ApoE-Aβ interaction.

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James, Niaya, Oyinkansola Shonde, Nahdia Jones, Verona E. Mulgrave, G. William Rebeck, and Joanne Allard. "Impact of APOE Genotype on Diet-induced Mitochondrial Adaptations in Mouse Skeletal Muscle." Innovation in Aging 5, Supplement_1 (December 1, 2021): 971. http://dx.doi.org/10.1093/geroni/igab046.3496.

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Abstract Apolipoprotein E (APOE), a component of lipoproteins that facilitates cholesterol transportation, has three variants in the human genome: APOE2, E3, and E4. Prior research found that carriers of APOE4 are more susceptible to developing Alzheimer's disease (AD) and other brain disorders than those who possess other APOE alleles, and that these carriers are also predisposed to mitochondrial impairment– an early characteristic of neuronal dysfunction. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1ɑ) is a major biomarker for mitochondrial biogenesis and function and cytochrome c oxidase subunit IV (COX4) is the terminal enzyme of the mitochondrial respiratory chain. Decreased measures of these proteins indicate reduced mitochondrial function. Aside from genetic inheritance, lifestyle factors such as diet and exercise significantly impact one’s risk for mitochondrial dysfunction and AD. In these studies, we examined the impact of APOE variance on physiological adaptations induced by either exercise or a high-fat diet, with a focus on biomarkers of mitochondrial function. Western blots were used to measure COX4 and PGC-1ɑ levels in skeletal muscle tissue from female APOE3 and APOE4 knock-in transgenic mice. Based on performance on a motorized rotating rod and voluntary wheel-running, we deduced that female APOE4 mice exhibit reduced motor coordination and activity relative to APOE3 mice. APOE4 mice also had reduced COX4 levels that were increased by the high-fat diet. In contrast, COX4 levels in APOE3 mice were reduced in the high-fat diet group. Our data show that diet and APOE genotype interact to produce adaptations in mitochondrial proteins in skeletal muscle.

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Watson, Yassin, Brenae Nelson, Jamie Hernandez Kluesner, Caroline Tanzy, Shreya Ramesh, Zoey Patel, Kaci Hernandez Kluesner, Anita Singh, Vibha Murthy, and Cassie S. Mitchell. "Aggregate Trends of Apolipoprotein E on Cognition in Transgenic Alzheimer’s Disease Mice." Journal of Alzheimer's Disease 83, no. 1 (August 31, 2021): 435–50. http://dx.doi.org/10.3233/jad-210492.

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Background: Apolipoprotein E (APOE) genotypes typically increase risk of amyloid-β deposition and onset of clinical Alzheimer’s disease (AD). However, cognitive assessments in APOE transgenic AD mice have resulted in discord. Objective: Analysis of 31 peer-reviewed AD APOE mouse publications (n = 3,045 mice) uncovered aggregate trends between age, APOE genotype, gender, modulatory treatments, and cognition. Methods: T-tests with Bonferroni correction (significance = p < 0.002) compared age-normalized Morris water maze (MWM) escape latencies in wild type (WT), APOE2 knock-in (KI2), APOE3 knock-in (KI3), APOE4 knock-in (KI4), and APOE knock-out (KO) mice. Positive treatments (t+) to favorably modulate APOE to improve cognition, negative treatments (t–) to perturb etiology and diminish cognition, and untreated (t0) mice were compared. Machine learning with random forest modeling predicted MWM escape latency performance based on 12 features: mouse genotype (WT, KI2, KI3, KI4, KO), modulatory treatment (t+, t–, t0), mouse age, and mouse gender (male = g_m; female = g_f, mixed gender = g_mi). Results: KI3 mice performed significantly better in MWM, but KI4 and KO performed significantly worse than WT. KI2 performed similarly to WT. KI4 performed significantly worse compared to every other genotype. Positive treatments significantly improved cognition in WT, KI4, and KO compared to untreated. Interestingly, negative treatments in KI4 also significantly improved mean MWM escape latency. Random forest modeling resulted in the following feature importance for predicting superior MWM performance: [KI3, age, g_m, KI4, t0, t+, KO, WT, g_mi, t–, g_f, KI2] = [0.270, 0.094, 0.092, 0.088, 0.077, 0.074, 0.069, 0.061, 0.058, 0.054, 0.038, 0.023]. Conclusion: APOE3, age, and male gender was most important for predicting superior mouse cognitive performance.

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Sheng, Huaxin, Daniel T. Laskowitz, Ellen Bennett, Donald E. Schmechel, Robert D. Bart, Ann M. Saunders, Robert D. Pearlstein, Allen D. Roses, and David S. Warner. "Apolipoprotein E Isoform-Specific Differences in Outcome from Focal Ischemia in Transgenic Mice." Journal of Cerebral Blood Flow & Metabolism 18, no. 4 (April 1998): 361–66. http://dx.doi.org/10.1097/00004647-199804000-00003.

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Apolipoprotein E (apoE), a 34-kD glycosylated lipid-binding protein, is expressed as three common isoforms in humans (E2, E3, or E4). Clinical evidence suggests that the apoE genotype (APOE) may be a risk factor for poor outcome after acute central nervous system injury. This was examined further in transgenic mice constructed with the human APOE3 or APOE4 gene under the control of human promoter and tissue expression elements. Presence of human apoE3 and apoE4 proteins in brains of human APOE homozygous transgenic mice was confirmed by Western blotting. APOE3 (n = 12) and APOE4 (n = 10) mice underwent 60 minutes of middle cerebral artery occlusion. After 24-hour recovery, infarct size was measured. Infarct volumes (mean ± standard deviation) were smaller in the APOE3 group (cortex: APOE3 = 18 ± 4 mm3; APOE4 = 30 ± 11 mm3, P = 0.04; subcortex: APOE3 = 12 ± 4 mm3; APOE4 = 18 ± 4 mm3, P = 0.003). Hemiparesis was less severe in APOE3 mice ( P = 0.02). These data indicate that human isoform-specific effects of apoE are relevant to acute pathomechanisms of focal ischemic brain damage when examined in the mouse. APOE transgenic mice may provide an appropriate model to examine the mechanistic basis for the differential effects of human apoE isoforms in acute central nervous system injury.

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Allphin, Alex J., Ali Mahzarnia, Darin P. Clark, Yi Qi, Zay Y. Han, Prajwal Bhandari, Ketan B. Ghaghada, Alexandra Badea, and Cristian T. Badea. "Advanced photon counting CT imaging pipeline for cardiac phenotyping of apolipoprotein E mouse models." PLOS ONE 18, no. 10 (October 5, 2023): e0291733. http://dx.doi.org/10.1371/journal.pone.0291733.

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Background Cardiovascular disease (CVD) is associated with the apolipoprotein E (APOE) gene and lipid metabolism. This study aimed to develop an imaging-based pipeline to comprehensively assess cardiac structure and function in mouse models expressing different APOE genotypes using photon-counting computed tomography (PCCT). Methods 123 mice grouped based on APOE genotype (APOE2, APOE3, APOE4, APOE knockout (KO)), gender, human NOS2 factor, and diet (control or high fat) were used in this study. The pipeline included PCCT imaging on a custom-built system with contrast-enhanced in vivo imaging and intrinsic cardiac gating, spectral and temporal iterative reconstruction, spectral decomposition, and deep learning cardiac segmentation. Statistical analysis evaluated genotype, diet, sex, and body weight effects on cardiac measurements. Results Our results showed that PCCT offered high quality imaging with reduced noise. Material decomposition enabled separation of calcified plaques from iodine enhanced blood in APOE KO mice. Deep learning-based segmentation showed good performance with Dice scores of 0.91 for CT-based segmentation and 0.89 for iodine map-based segmentation. Genotype-specific differences were observed in left ventricular volumes, heart rate, stroke volume, ejection fraction, and cardiac index. Statistically significant differences were found between control and high fat diets for APOE2 and APOE4 genotypes in heart rate and stroke volume. Sex and weight were also significant predictors of cardiac measurements. The inclusion of the human NOS2 gene modulated these effects. Conclusions This study demonstrates the potential of PCCT in assessing cardiac structure and function in mouse models of CVD which can help in understanding the interplay between genetic factors, diet, and cardiovascular health.

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Zhao, Na, Olivia N. Attrebi, Yingxue Ren, Wenhui Qiao, Berkiye Sonustun, Yuka A. Martens, Axel D. Meneses та ін. "APOE4 exacerbates α-synuclein pathology and related toxicity independent of amyloid". Science Translational Medicine 12, № 529 (5 лютого 2020): eaay1809. http://dx.doi.org/10.1126/scitranslmed.aay1809.

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The apolipoprotein E (APOE) ε4 allele is the strongest genetic risk factor for late-onset Alzheimer’s disease mainly by driving amyloid-β pathology. Recently, APOE4 has also been found to be a genetic risk factor for Lewy body dementia (LBD), which includes dementia with Lewy bodies and Parkinson’s disease dementia. How APOE4 drives risk of LBD and whether it has a direct effect on α-synuclein pathology are not clear. Here, we generated a mouse model of synucleinopathy using an adeno-associated virus gene delivery of α-synuclein in human APOE-targeted replacement mice expressing APOE2, APOE3, or APOE4. We found that APOE4, but not APOE2 or APOE3, increased α-synuclein pathology, impaired behavioral performances, worsened neuronal and synaptic loss, and increased astrogliosis at 9 months of age. Transcriptomic profiling in APOE4-expressing α-synuclein mice highlighted altered lipid and energy metabolism and synapse-related pathways. We also observed an effect of APOE4 on α-synuclein pathology in human postmortem brains with LBD and minimal amyloid pathology. Our data demonstrate a pathogenic role of APOE4 in exacerbating α-synuclein pathology independent of amyloid, providing mechanistic insights into how APOE4 increases the risk of LBD.

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Zhang, Xin, Long Wu, Russell H. Swerdlow, and Liqin Zhao. "Opposing Effects of ApoE2 and ApoE4 on Glycolytic Metabolism in Neuronal Aging Supports a Warburg Neuroprotective Cascade against Alzheimer’s Disease." Cells 12, no. 3 (January 25, 2023): 410. http://dx.doi.org/10.3390/cells12030410.

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Apolipoprotein E4 (ApoE4) is the most recognized genetic risk factor for late-onset Alzheimer’s disease (LOAD), whereas ApoE2 reduces the risk for LOAD. The underlying mechanisms are unclear but may include effects on brain energy metabolism. Here, we used neuro-2a (N2a) cells that stably express human ApoE isoforms (N2a-hApoE), differentiated N2a-hApoE neuronal cells, and humanized ApoE knock-in mouse models to investigate relationships among ApoE isoforms, glycolytic metabolism, and neuronal health and aging. ApoE2-expressing cells retained robust hexokinase (HK) expression and glycolytic activity, whereas these endpoints progressively declined with aging in ApoE4-expressing cells. These divergent ApoE2 and ApoE4 effects on glycolysis directly correlated with markers of cellular wellness. Moreover, ApoE4-expressing cells upregulated phosphofructokinase and pyruvate kinase with the apparent intent of compensating for the HK-dependent glycolysis reduction. The introduction of ApoE2 increased HK levels and glycolysis flux in ApoE4 cells. PI3K/Akt signaling was distinctively regulated by ApoE isoforms but was only partially responsible for the ApoE-mediated effects on HK. Collectively, our findings indicate that human ApoE isoforms differentially modulate neuronal glycolysis through HK regulation, with ApoE2 upregulating and ApoE4 downregulating, which markedly impacts neuronal health during aging. These findings lend compelling support to the emerging inverse-Warburg theory of AD and highlight a therapeutic opportunity for bolstering brain glycolytic resilience to prevent and treat AD.

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Tang, Yanan. "APOE-ε4 genes may accelerate the activation of the latent form of HSV-1 which would lead to a faster progression of AD". BIO Web of Conferences 72 (2023): 01006. http://dx.doi.org/10.1051/bioconf/20237201006.

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This study investigates the impact of APOE alleles and latent Herpes Simplex Type 1 virus (HSV-1) activation on Alzheimer’s disease (AD) progression using the 5xFAD mouse model. APOE ε4 is recognized as a substantial genetic risk factor for sporadic AD, while HSV-1 has been linked to AD pathogenesis through inflammation and plaque formation. The experimental approach involves the introduction of human neurons carrying latent HSV-1 into 5xFAD mice harboring various APOE alleles (APOE2, APOE3, APOE4), along with stress induction and pharmacological interventions. The study aims to elucidate the combined impact of these variables on AD progression and the formation of Aβ plaques. Our anticipated results suggest that APOE ε4 may accelerate AD development, especially in conjunction with HSV-1 activation, while APOE ε2 may exert a mitigating influence. These findings have the potential to advance our understanding of the intricate mechanisms underpinning AD and provide insights into potential therapeutic approaches. Further exploration of these interactions could offer critical insights into the pursuit of effective AD treatments.

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Sung, Jin Hee, Yang Ou та Steven W. Barger. "Amyloid β-Peptide Effects on Glucose Regulation Are Dependent on Apolipoprotein E Genotype". eneuro 10, № 4 (квітень 2023): ENEURO.0376–22.2023. http://dx.doi.org/10.1523/eneuro.0376-22.2023.

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AbstractThe apolipoprotein E gene (APOE) confers the greatest genetic risk factor for Alzheimer’s disease (AD), wherein the ε4 allele confers an elevated risk compared with the ε3 allele. Biological mechanisms that differ across these alleles have been explored in mouse models wherein the murineApoegene has undergone targeted replacement with sequences encoding human ApoE3 or ApoE4 (ApoE-TR mice). Such models have indicated that the two variants of ApoE produce differential effects on energy metabolism, including metabolic syndrome. However, glucose regulation has not been compared in ApoE-TR mice with and without amyloid β-peptide (Aβ) accumulation. We crossed ApoE3-TR and ApoE4-TR mice with a transgenic line that accumulates human Aβ1-42. In male ApoE3-TR mice, introduction of Aβ caused aberrations in glucose tolerance and in membrane translocation of astrocytic glucose transporter 1 (GLUT1). Phosphorylation of Tau at AD-relevant sites was correlated with glucose intolerance. These effects appeared independent of insulin dysregulation and were not observed in females. In ApoE4-TR mice, the addition of Aβ had no significant effects because of a trend toward perturbation of the baseline values.

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Allphin, Alex J., Rohan Nadkarni, Zay Y. Han, Darin P. Clark, Ketan B. Ghaghada, Alexandra Badea, and Cristian T. Badea. "Assessing the cardioprotective effects of exercise in APOE mouse models using deep learning and photon-counting micro-CT." PLOS ONE 20, no. 4 (April 10, 2025): e0320892. https://doi.org/10.1371/journal.pone.0320892.

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Background The allelic variations of the apolipoprotein E (APOE) gene play a critical role in regulating lipid metabolism and significantly impact cardiovascular disease risk (CVD). This study aimed to evaluate the impact of exercise on cardiac structure and function in mouse models expressing different APOE genotypes using photon-counting computed tomography (PCCT) and deep learning-based segmentation. Methods A total of 140 mice were grouped based on APOE genotype (APOE2, APOE3, APOE4), sex, and exercise regimen. All mice were maintained on a controlled diet to isolate the effects of exercise. Low dose cardiac photon counting micro-CT imaging with intrinsic gating was performed using a custom-built micro-PCCT system and data was reconstructed with an iterative algorithm incorporating both temporal and spectral dimensions. A liposomal-iodine nanoparticle contrast agent was intravenously administered to uniformly opacify cardiovascular structures. Cardiac structures were segmented using a 3D U-Net deep learning model that was trained and validated on manually labeled data. Statistical analyses, including ANOVA, post-hoc analysis, and stratified group comparisons, were used to assess the effects of genotype, sex, and exercise on key cardiac metrics, including ejection fraction and cardiac index. Results The PCCT imaging pipeline provided high-resolution images with enhanced contrast between blood compartment and myocardium allowing for precise segmentation of cardiac features. Deep learning-based segmentation achieved high accuracy with an average Dice coefficient of 0.85. Exercise significantly improved cardiac performance, with ejection fraction increasing by up to 18% and cardiac index by 46% in exercised males, who generally benefited more from exercise. Females, particularly those with the APOE4 genotype, also showed improvements, with a 31% higher ejection fraction in exercised versus non-exercised mice. Stratified analyses confirmed that both sexes benefited from exercise, with males showing larger effect sizes. APOE3 and APOE4 genotypes derived the greatest benefit, while APOE2 mice showed no significant improvement. Conclusions This study demonstrates the utility of PCCT combined with deep learning segmentation in assessing the cardioprotective effects of exercise in APOE mouse models. These findings highlight the importance of genotype-specific approaches in understanding and potentially mitigating the impact of CVD through lifestyle interventions such as exercise.

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Grenon, Martine B., Maria-Tzousi Papavergi, Praveen Bathini, Martin Sadowski, and Cynthia A. Lemere. "Temporal Characterization of the Amyloidogenic APPswe/PS1dE9;hAPOE4 Mouse Model of Alzheimer’s Disease." International Journal of Molecular Sciences 25, no. 11 (May 25, 2024): 5754. http://dx.doi.org/10.3390/ijms25115754.

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Alzheimer’s disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aβ) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aβ immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aβ deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aβ, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy.

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Dafnis, Ioannis, Christina Raftopoulou, Christina Mountaki, Evgenia Megalou, Vassilis I. Zannis та Angeliki Chroni. "ApoE isoforms and carboxyl-terminal-truncated apoE4 forms affect neuronal BACE1 levels and Aβ production independently of their cholesterol efflux capacity". Biochemical Journal 475, № 10 (31 травня 2018): 1839–59. http://dx.doi.org/10.1042/bcj20180068.

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The β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) initiates the production of amyloid-β peptide (Aβ), which is central to the pathogenesis of Alzheimer's disease (AD). Changes in brain cholesterol homeostasis have been suggested to affect Aβ metabolism. Cholesterol homeostasis is maintained in the brain by apolipoprotein E (apoE). The apoE4 isoform constitutes the major risk factor for AD. Here, we investigated the effect of apoE forms on Aβ generation and on BACE1 levels. We also examined the potential involvement in these processes of cholesterol transporters ABCG1 and ABCG4 or the lipoprotein receptor SR-BI, which are implicated in cholesterol efflux to apoE. It was found that reconstituted lipoprotein-associated apoE isoforms promoted the increase of Aβ production and oligomerization and of BACE1 levels in human neuroblastoma SK-N-SH cells, with an apoE4 ≥ apoE3 > apoE2 potency rank order. Progressive carboxyl-terminal apoE4 deletions between residues 230–299 decreased the protein's ability to increase BACE1, while further truncations up to residue 166 prevented apoE4 from increasing BACE1 and Aβ levels in SK-N-SH and primary mouse neuronal cells. ABCG1, but not ABCG4 or SR-BI, moderately increased Aβ production and BACE1 levels in SK-N-SH cells. All apoE forms affected Aβ production/oligomerization and BACE1 levels in a pattern that did not follow that of their capacity to promote ABCG1, ABCG4 or SR-BI-mediated cholesterol efflux. Overall, our data indicate that apoE-containing lipoprotein particles can have a direct effect on BACE1 levels and Aβ secretion and possibly contribute to AD pathogenetic processes, independently of their capacity to promote cholesterol efflux.

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Huang, Yadong. "Roles of apolipoprotein E4 (ApoE4) in the pathogenesis of Alzheimer's disease: lessons from ApoE mouse models." Biochemical Society Transactions 39, no. 4 (July 20, 2011): 924–32. http://dx.doi.org/10.1042/bst0390924.

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ApoE4 (apolipoprotein E4) is the major known genetic risk factor for AD (Alzheimer's disease). In most clinical studies, apoE4 carriers account for 65–80% of all AD cases, highlighting the importance of apoE4 in AD pathogenesis. Emerging data suggest that apoE4, with its multiple cellular origins and multiple structural and biophysical properties, contributes to AD in multiple ways either independently or in combination with other factors, such as Aβ (amyloid β-peptide) and tau. Many apoE mouse models have been established to study the mechanisms underlying the pathogenic actions of apoE4. These include transgenic mice expressing different apoE isoforms in neurons or astrocytes, those expressing neurotoxic apoE4 fragments in neurons and human apoE isoform knock-in mice. Since apoE is expressed in different types of cells, including astrocytes and neurons, and in brains under diverse physiological and/or pathophysiological conditions, these apoE mouse models provide unique tools to study the cellular source-dependent roles of apoE isoforms in neurobiology and in the pathogenesis of AD. They also provide useful tools for discovery and development of drugs targeting apoE4's detrimental effects.

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Staurenghi, Erica, Valerio Leoni, Marco Lo Iacono, Barbara Sottero, Gabriella Testa, Serena Giannelli, Gabriella Leonarduzzi, and Paola Gamba. "ApoE3 vs. ApoE4 Astrocytes: A Detailed Analysis Provides New Insights into Differences in Cholesterol Homeostasis." Antioxidants 11, no. 11 (November 1, 2022): 2168. http://dx.doi.org/10.3390/antiox11112168.

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The strongest genetic risk factor for sporadic Alzheimer’s disease (AD) is the presence of the ε4 allele of the apolipoprotein E (ApoE) gene, the major apolipoprotein involved in brain cholesterol homeostasis. Being astrocytes the main producers of cholesterol and ApoE in the brain, we investigated the impact of the ApoE genotype on astrocyte cholesterol homeostasis. Two mouse astrocytic cell lines expressing the human ApoE3 or ApoE4 isoform were employed. Gas chromatography–mass spectrometry (GC-MS) analysis pointed out that the levels of total cholesterol, cholesterol precursors, and various oxysterols are altered in ApoE4 astrocytes. Moreover, the gene expression analysis of more than 40 lipid-related genes by qRT-PCR showed that certain genes are up-regulated (e.g., CYP27A1) and others down-regulated (e.g., PPARγ, LXRα) in ApoE4, compared to ApoE3 astrocytes. Beyond confirming the significant reduction in the levels of PPARγ, a key transcription factor involved in the maintenance of lipid homeostasis, Western blotting showed that both intracellular and secreted ApoE levels are altered in ApoE4 astrocytes, as well as the levels of receptors and transporters involved in lipid uptake/efflux (ABCA1, LDLR, LRP1, and ApoER2). Data showed that the ApoE genotype clearly affects astrocytic cholesterol homeostasis; however, further investigation is needed to clarify the mechanisms underlying these differences and the consequences on neighboring cells. Indeed, drug development aimed at restoring cholesterol homeostasis could be a potential strategy to counteract AD.

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Mhatre-Winters, Isha, Aseel Eid, Yoonhee Han, Kim Tieu, and Jason R. Richardson. "Sex and APOE Genotype Alter the Basal and Induced Inflammatory States of Primary Astrocytes from Humanized Targeted Replacement Mice." ASN Neuro 15 (January 2023): 175909142211445. http://dx.doi.org/10.1177/17590914221144549.

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Apolipoprotein E4 (APOE4) genotype and sex are significant risk factors for Alzheimer's disease (AD), with females demonstrating increased risk modulated by APOE genotype. APOE is predominantly expressed in astrocytes, however, there is a lack of comprehensive assessments of sex differences in astrocytes stratified by APOE genotype. Here, we examined the response of mixed-sex and sex-specific neonatal APOE3 and APOE4 primary mouse astrocytes (PMA) to a cytokine mix of IL1b, TNFa, and IFNg. Pro-inflammatory and anti-inflammatory cytokine profiles were assessed by qRT-PCR and Meso Scale Discovery multiplex assay. Mixed-sex APOE4 PMA were found to have higher basal messenger RNA expression of several pro-inflammatory cytokines including Il6, Tnfa, Il1b, Mcp1, Mip1a, and Nos2 compared to APOE3 PMA, which was accompanied by increased levels of these secreted cytokines. In sex-specific cultures, basal expression of Il1b, Il6, and Nos2 was 1.5 to 2.5 fold higher in APOE4 female PMA compared to APOE4 males, with both being higher than APOE3 PMA. Similar results were found for secreted levels of these cytokines. Together, these findings indicate that APOE4 genotype and female sex, contribute to a greater inflammatory response in primary astrocytes and these data may provide a framework for investigating the mechanisms contributing to genotype and sex differences in AD-related neuroinflammation.

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Demby, Tamar, G. William Rebeck, Christopher Albanese, Olga C. Rodriguez, Yichien Lee, and Jeanne Mandelblatt. "3367 A Mouse Model of APOE Genotype in Chemotherapy Related Cognitive Impairment." Journal of Clinical and Translational Science 3, s1 (March 2019): 1. http://dx.doi.org/10.1017/cts.2019.6.

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OBJECTIVES/SPECIFIC AIMS: Chemotherapy-related cognitive impairment (CRCI) affects 15-35% of breast cancer survivors and constitutes a significant challenge for survivor quality of life. Among older breast cancer survivors who received chemotherapy treatment, carriers of at least one ɛ4 allele of the APOE gene, which encodes apolipoprotein E, are at higher risk for developing CRCI than non-carriers. APOE4 is well characterized as the strongest genetic risk factor for Alzheimer’s disease, but how it contributes to CRCI is not yet understood, and no animal models of APOE genotype and CRCI have yet been established. To better understand how APOE4 acts as a risk factor for CRCI, we used APOE targeted replacement (TR) mice to develop a model of its effects on cognition following treatment with doxorubicin, a chemotherapy drug commonly used in breast cancer treatment. METHODS/STUDY POPULATION: Twelve-to-thirteen month old APOE3 and APOE4 targeted replacement mice expressing human APOE3 or human APOE4 under control of the endogenous murine promoter were treated with 10 mg/kg doxorubicin or equivolume saline given via two IP injections spaced one week apart. One week post-treatment, mice were tested using Open Field and Elevated Zero apparatuses to assess baseline locomotive activity and anxiety and exploratory behaviors. Five weeks post-treatment, mice were assessed using the Barnes Maze over four days of training trials and one 72 hour memory probe. RESULTS/ANTICIPATED RESULTS: We found no differences in Open Field and Elevated Zero behavior, indicating limited influence of doxorubicin treatment on locomotive and anxiety behaviors in both genotypes. During Barnes Maze training, APOE4 mice treated with doxorubicin showed increased latency compared to untreated APOE4 mice as well as treated and untreated APOE3 mice, indicating deficiencies in spatial learning. In APOE3 mice, no differences in performance were seen between doxorubicin-treated and untreated mice (n = 15-16/group, p <.0001). DISCUSSION/SIGNIFICANCE OF IMPACT: These results indicate that APOE4 targeted replacement mice have specific cognitive vulnerabilities to doxorubicin treatment that can be reliably detected using the Barnes Maze assessment. Future directions include experiments to determine how other chemotherapy drugs or drug combinations impact cognition of APOE4 mice. Ultimately this model may be used to assess preventive measures or therapies for CRCI in the vulnerable APOE4 carrier population with the ability to validate cognitive impacts of these interventions.

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Zhu, Li, Minghao Zhong, Gregory A. Elder, Mary Sano, David M. Holtzman, Sam Gandy, Christopher Cardozo, Vahram Haroutunian, Nikolaos K. Robakis, and Dongming Cai. "Phospholipid dysregulation contributes to ApoE4-associated cognitive deficits in Alzheimer’s disease pathogenesis." Proceedings of the National Academy of Sciences 112, no. 38 (September 8, 2015): 11965–70. http://dx.doi.org/10.1073/pnas.1510011112.

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The apolipoprotein E4 (ApoE4) allele is the strongest genetic risk factor for developing sporadic Alzheimer’s disease (AD). However, the mechanisms underlying the pathogenic nature of ApoE4 are not well understood. In this study, we have found that ApoE proteins are critical determinants of brain phospholipid homeostasis and that the ApoE4 isoform is dysfunctional in this process. We have found that the levels of phosphoinositol biphosphate (PIP2) are reduced in postmortem human brain tissues of ApoE4 carriers, in the brains of ApoE4 knock-in (KI) mice, and in primary neurons expressing ApoE4 alleles compared with those levels in ApoE3 counterparts. These changes are secondary to increased expression of a PIP2-degrading enzyme, the phosphoinositol phosphatase synaptojanin 1 (synj1), in ApoE4 carriers. Genetic reduction of synj1 in ApoE4 KI mouse models restores PIP2 levels and, more important, rescues AD-related cognitive deficits in these mice. Further studies indicate that ApoE4 behaves similar to ApoE null conditions, which fails to degrade synj1 mRNA efficiently, unlike ApoE3 does. These data suggest a loss of function of ApoE4 genotype. Together, our data uncover a previously unidentified mechanism that links ApoE4-induced phospholipid changes to the pathogenic nature of ApoE4 in AD.

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Mori, Takashi, Terrence Town, Mariko Kobayashi, Jun Tan, Shinobu C. Fujita, and Takao Asano. "Augmented Delayed Infarct Expansion and Reactive Astrocytosis after Permanent Focal Ischemia in Apolipoprotein E4 Knock-In Mice." Journal of Cerebral Blood Flow & Metabolism 24, no. 6 (June 2004): 646–56. http://dx.doi.org/10.1097/01.wcb.0000120787.53851.a4.

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Using homozygous human apolipoprotein E2 (apoE2) (2/2)-, apoE3 (3/3)-, or apoE4 (4/4)-knock-in (KI) mice, we aimed to examine whether an apoE isoform-specific exacerbation of delayed infarct expansion occurs after permanent middle cerebral artery occlusion (pMCAO). Compared with 2/2- or 3/3-KI mice, 4/4-KI mice exhibited significantly larger infarct volumes and worse neurologic deficits after pMCAO, with no significant differences between the latter two groups. Infarct volume in 4/4-KI mice was significantly increased from 1 to 5 days after pMCAO, whereas that in 2/2- or 3/3-KI mice was not significantly altered. DNA fragmentation in the peri-infarct area as detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphatenick end-labeling was increased to a similar degree in all of the KI mice by 5 days after pMCAO, with no significant differences among the mouse groups. At every time-point examined, human apoE was most markedly expressed in the peri-infarct area, with similar immunoreactivity among the three lines of KI mice. The glial fibrillary acidic protein immunoreactive burden in the peri-infarct area was progressively increased through 7 days in 4/4-KI mice, but not in 2/2- or 3/3-KI mice. Taken together, these data show that the apoE4 isoform acts to aggravate delayed infarct expansion and peri-infarct reactive astrocytosis during the subacute phase of pMCAO in genetically engineered apoE-KI mice.

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McLean, John W., Avnish Bhattrai, Francesca Vitali, Adam C. Raikes, Jean-Paul L. Wiegand, and Roberta Diaz Brinton. "Contributions of sex and genotype to exploratory behavior differences in an aged humanized APOE mouse model of late-onset Alzheimer's disease." Learning & Memory 29, no. 9 (September 2022): 321–31. http://dx.doi.org/10.1101/lm.053588.122.

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Age, genetics, and chromosomal sex have been identified as critical risk factors for late-onset Alzheimer's disease (LOAD). The predominant genetic risk factor for LOAD is the apolipoprotein E ε4 allele (APOE4), and the prevalence of LOAD is higher in females. However, the translational validity of APOE4 mouse models for AD-related cognitive impairment remains to be fully determined. The present study investigated the role of both sex and genotype on learning and memory in aged, humanized APOE knock-in mice. Aged (23.27 mo ± 1.21 mo; 39 male/37 female) APOE3/3, APOE3/4, and APOE4/4 mice performed a novel object recognition (NOR) assay. Task-related metrics were analyzed using two-way sex by genotype ANOVAs. Sex differences were more prominent relative to APOE genotype. Prior to NOR, female mice exhibited thigmotaxic center zone avoidance during the open field task relative to males, regardless of genotype. Within object familiarization and NOR tasks, females had greater object interaction and locomotion. Interestingly, only APOE4/4 females on average recognized the novel object. These results suggest that APOE4, although strongly related to LOAD pathogenesis, does not drive cognitive decline in the absence of other risk factors even in very aged mice. Chromosomal sex is a key driver of behavioral phenotypes and thus is a critical variable for translatability of interventions designed to preserve learning and memory in animal models of LOAD. Last, there was a very high degree of variability in behavioral performance across APOE genotypes. A cluster analysis of the behavioral data revealed a low-activity and a high-activity cluster. APOE4 carriers were overrepresented in the low-activity cluster, while male:female distributions did not differ. Collectively, the behavioral data indicate that chromosomal sex has the greatest impact on behavioral phenotype, and APOE4 carrier status may confer greater risk for cognitive decline in some animals.

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Chang, Ya-Hsuan, Jared Hoffman, Lucille Yanckello, Scott McCulloch, Penghui Lin, Andrew Lane, George Chlipala, Stefan Green, and Ai-Ling Lin. "Apolipoprotein E Genotype-Dependent Nutrigenetic Effects to Prebiotic Inulin for Reducing Risk for Alzheimer's Disease in a Mouse Model." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 1197. http://dx.doi.org/10.1093/cdn/nzaa057_013.

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Abstract Objectives Apolipoprotein E ε4 (APOE4) allele is the strongest genetic risk factor for Alzheimer's disease (AD). Cognitively normal APOE4 carriers show an early decline in brain metabolic functions and gut microbiome dysbiosis before the onset of AD compared to APOE3 carriers. Our laboratory previously found that inulin, a prebiotic, is effective to restore metabolic functions and gut microbiome balance, and thus reduce risk for AD in an ApoE4 mouse model. However, whether the responses to the inulin are APOE allele-dependent remains unknown. Therefore, our objective was to identify whether inulin would differently contribute to metabolic and gut microbiome changes due to APOE genotypes. Methods We fed 3-month-old asymptomatic ApoE3 (E3FAD) and ApoE4 (E4FAD) mice prebiotic inulin or cellulose as a control for 4 months (N = 60; Male: Female = 1:1). After 4 months, we used magnetic resonance spectroscopy to measure in vivo brain scyllo-inositol level, a compound that has been demonstrated to inhibit amyloid β aggregation. We collected the fecal samples for gut microbiome sequencing, and cecal and blood samples for metabolomic profiling. Results Inulin induced scyllo-inositol in hippocampus of the brain with a higher level in E4FAD mice. Inulin increased blood metabolites in tryptophan and tyrosine metabolic pathways that enhance nervous system in E3FAD mice. It increased blood metabolites in pentose phosphate pathway and citric acid cycle that support nucleotides and nucleic acids biosynthesis and energy production in E4FAD mice. These alterations in hippocampus and blood showed inulin's impacts on systemic metabolism depending on mouse ApoE genotypes. Inulin enhanced short chain fatty acids in cecum with a greater increase in E3FAD mice. E3FAD mice showed more distinct gut microbiome patterns between inulin and control groups compared to E4FAD mice. Conclusions Inulin-induced systemic metabolism and gut microbiome changes are APOE genotype-dependent. Future studies can design human interventions that may facilitate the guide of personalized nutrition in AD prevention. Funding Sources This research was supported by grants from NIH, NIH/CTSA, and American Federation for Aging Research to A-LL and NIH/NIDDK to JDH and LMY. The 7T ClinScan small animal MRI scanner was funded by the S10 NIH Shared Instrumentation Program Grant.

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Braunersreuther, Vincent, Fabienne Burger, Sébastien Lenglet, Graziano Pelli, Federico Carbone, Rodrigo Fraga-Silva, Nikolaos Stergiopulos, et al. "Anti-apoA-1 auto-antibodies increase mouse atherosclerotic plaque vulnerability, myocardial necrosis and mortality triggering TLR2 and TLR4." Thrombosis and Haemostasis 114, no. 08 (2015): 410–22. http://dx.doi.org/10.1160/th14-12-1039.

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SummaryAuto-antibodies to apolipoprotein A-1 (anti-apoA-1 IgG) were shown to promote inflammation and atherogenesis, possibly through innate immune receptors signalling. Here, we aimed at investigating the role of Toll-like receptors (TLR) 2 and 4 on anti-apoA-1 IgG-induced athero-sclerotic plaque vulnerability, myocardial necrosis and mortality in mice. Adult male apolipoprotein E knockout (ApoE)-/- (n=72), TLR2-/-ApoE-/- (n=36) and TLR4-/-Apo-/- (n=28) mice were intravenously injected with 50 µg/mouse of endotoxin-free polyclonal anti-apoA-1 IgG or control isotype IgG (CTL IgG) every two weeks for 16 weeks. Atherosclerotic plaque size and vulnerability were assessed by histology. Myocardial ischaemia and necrosis, respectively, were determined by electrocardiographic (ECG) changes assessed by telemetry and serum troponin I (cTnI) measurements. Impact on survival was assessed by Kaplan-Meier analyses. In ApoE-/- mice, anti-apoA-1 IgG passive immunisation enhanced histological features of athero-sclerotic plaque vulnerability (increase in neutrophil and MMP-9 and reduction in collagen content), induced a substantial cTnI elevation (p=0.001), and increased mortality rate by 23 % (LogRank, p=0.04) when compared to CTL IgG. On a subgroup of ApoE-/- mice equipped with telemetry (n=4), a significant ST-segment depression was noted in anti-apoA-1 IgG-treated mice when compared to CTL IgG recipients (p< 0.001), and an acute ST-segment elevation myocardial infarction preceding mouse death was observed in one case. The deleterious effects of anti-apoA-1 IgG on atherosclerotic plaque vulnerability, myocardial necrosis and death were partially reversed in TLR2-/-ApoE-/- and TLR4-/-ApoE-/- backgrounds. In conclusion, anti-apoA-1 auto-antibodies seem to be active mediators of atherosclerotic plaque vulnerability, myocardial necrosis, and mortality in mice through TLR2- and TLR4-mediated pathways.

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Yang, Hong, Ningya Zhang, Emmanuel Okoro, and Zhongmao Guo. "Transport of Apolipoprotein B-Containing Lipoproteins through Endothelial Cells Is Associated with Apolipoprotein E-Carrying HDL-Like Particle Formation." International Journal of Molecular Sciences 19, no. 11 (November 14, 2018): 3593. http://dx.doi.org/10.3390/ijms19113593.

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Passage of apolipoprotein B-containing lipoproteins (apoB-LPs), i.e., triglyceride-rich lipoproteins (TRLs), intermediate-density lipoproteins (IDLs), and low-density lipoproteins (LDLs), through the endothelial monolayer occurs in normal and atherosclerotic arteries. Among these lipoproteins, TRLs and IDLs are apoE-rich apoB-LPs (E/B-LPs). Recycling of TRL-associated apoE has been shown to form apoE-carrying high-density lipoprotein (HDL)-like (HDLE) particles in many types of cells. The current report studied the formation of HDLE particles by transcytosis of apoB-LPs through mouse aortic endothelial cells (MAECs). Our data indicated that passage of radiolabeled apoB-LPs, rich or poor in apoE, through the MAEC monolayer is inhibited by filipin and unlabeled competitor lipoproteins, suggesting that MAECs transport apoB-LPs via a caveolae-mediated pathway. The cholesterol and apoE in the cell-untreated E/B-LPs, TRLs, IDLs, and LDLs distributed primarily in the low-density (LD) fractions (d ≤ 1.063). A substantial portion of the cholesterol and apoE that passed through the MAEC monolayer was allotted into the high-density (HD) (d > 1.063) fractions. In contrast, apoB was detectable only in the LD fractions before or after apoB-LPs were incubated with the MAEC monolayer, suggesting that apoB-LPs pass through the MAEC monolayer in the forms of apoB-containing LD particles and apoE-containing HD particles.

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Rijpma, A., D. Jansen, I. A. C. Arnoldussen, X. T. Fang, M. Wiesmann, M. P. C. Mutsaers, P. J. Dederen, C. I. F. Janssen, and A. J. Kiliaan. "Sex Differences in Presynaptic Density and Neurogenesis in Middle-Aged ApoE4 and ApoE Knockout Mice." Journal of Neurodegenerative Diseases 2013 (January 27, 2013): 1–9. http://dx.doi.org/10.1155/2013/531326.

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Atherosclerosis and apolipoprotein E ε4 (APOE4) genotype are risk factors for Alzheimer’s disease (AD) and cardiovascular disease (CVD). Sex differences exist in prevalence and manifestation of both diseases. We investigated sex differences respective to aging, focusing on cognitive parameters in apoE4 and apoE knockout (ko) mouse models of AD and CVD. Presynaptic density and neurogenesis were investigated immunohistochemically in male and female apoE4, apoE ko, and wild-type mice. Middle-aged female apoE4 mice showed decreased presynaptic density in the inner molecular layer of the dentate gyrus of the hippocampus. Middle-aged female apoE ko mice showed a trend towards increased neurogenesis in the hippocampus compared with wild-type mice. No differences in these parameters could be observed in middle-aged male mice. Specific harmful interactions between apoE4 and estrogen could be responsible for decreased presynaptic density in female apoE4 mice. The trend of increased neurogenesis found in female apoE ko mice supports previous studies suggesting that temporarily increased amount of synaptic contacts and/or neurogenesis is a compensatory mechanism for synaptic failure. To our knowledge, no other studies investigating presynaptic density in aging female apoE4 or apoE ko mice are available. Sex-specific differences between APOE genotypes could account for some sex differences in AD and CVD.

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Guardia-Escote, Laia, Jordi Blanco, Pia Basaure, Judit Biosca-Brull, Rikst Nynke Verkaik-Schakel, Maria Cabré, Fiona Peris-Sampedro, et al. "Sex and Exposure to Postnatal Chlorpyrifos Influence the Epigenetics of Feeding-Related Genes in a Transgenic APOE Mouse Model: Long-Term Implications on Body Weight after a High-Fat Diet." International Journal of Environmental Research and Public Health 18, no. 1 (December 29, 2020): 184. http://dx.doi.org/10.3390/ijerph18010184.

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Developmental exposure to toxicants and diet can interact with an individual’s genetics and produce long-lasting metabolic adaptations. The different isoforms of the apolipoprotein E (APOE) are an important source of variability in metabolic disorders and influence the response to the pesticide chlorpyrifos (CPF). We aimed to study the epigenetic regulation on feeding control genes and the influence of postnatal CPF exposure, APOE genotype, and sex, and how these modifications impact on the metabolic response to a high-fat diet (HFD). Both male and female apoE3- and apoE4-TR mice were exposed to CPF on postnatal days 10–15. The DNA methylation pattern of proopiomelanocortin, neuropeptide Y, leptin receptor, and insulin-like growth factor 2 was studied in the hypothalamus. At adulthood, the mice were given a HFD for eight weeks. The results highlight the importance of sex in the epigenetic regulation and the implication of CPF treatment and APOE genotype. The body weight progression exhibited sex-dimorphic differences, apoE4-TR males being the most susceptible to the effects induced by CPF and HFD. Overall, these results underscore the pivotal role of sex, APOE genotype, and developmental exposure to CPF on subsequent metabolic disturbances later in life and show that sex is a key variable in epigenetic regulation.

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Hewes, Amanda, Kate Foley, Jennifer Thompson, Lindsey Lagerstrom, Taylor Mcmillan, Gareth Howell, and Fayeza Ahmed. "6 Exercise Induced Growth Factor Increases Directly and Indirectly Reduce Systemic Vascular Risk Parameters: Translational Project Amongst Midlife Human and Animal Models of Preclinical Alzheimer’s disease and Vascular Dementia." Journal of the International Neuropsychological Society 29, s1 (November 2023): 218–19. http://dx.doi.org/10.1017/s1355617723003259.

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Objective:Using a humanized APOE3/4 (Alzheimer’s disease genetic risk allele) mouse model we investigated the potential modulating effects of exercise on systemic risk factors and the ability of this mouse model to translate to active or sedentary, midlife, human participants. We present preliminary results of an ongoing, translational pilot study.Participants and Methods:26 Midlife individuals, ages 40-65, were recruited from the community and dichotomized into active or sedentary groups following health screening and cognitive assessment. Blood samples were drawn from human participants for lipid assessment and other general health measures as well as peripheral growth factors concentrations (VEGF, BDNF and FGF21). Traditional, transgenic mouse models have helped the scientific community to understand biological mechanisms of Alzheimer’s disease (AD), but they do not develop significant neuronal loss, a hallmark of AD pathology. The MODEL-AD consortium has created a new “humanized” APOE4 model that has the human APOE4 allelic sequence in place of the mouse APOE gene; the model has shown known human phenotypes including deficits in cholesterol trafficking, amyloid clearance and BBB integrity. Of upmost importance, this model does not develop a full AD phenotype indicating that additional genetics and/or environmental factors are required as would be seen in human populations. We used males and females of this model to complete identical sedentary and active measures of each APOE genotype.Results:Lipid and general health marker assessment between mouse and human were similar and reproduced published literature. In both humans and mice we saw increased total cholesterol and HDL in active females and decreased total cholesterol and HDL in active males. We also saw similar relationships between APOE genotype, sex, and activity with regards to triglycerides. Although total cholesterol, HDL and LDL measures are the primary lipids needed to confirm or deny translation, other lipid measurements were not equivalent between the two models. Growth factor assessment in both species are also similar and reproduce published literature with regards to VEGF and BDNF as we see trending elevated levels in the active group. Less published on is the finding seen between active females and these elevated growth factors levels; our results indicates that although elevated as a result of exercise, this increase may be more prominent in females.Conclusions:Based on the results found here we conclude that The Jackson Laboratory’s humanized APOE3/4 mouse model is a translatable model of vascular dysfunction, dementia and Alzheimer’s disease. We also conclude that exercise modulates these aspects by growth factor activation and increases resulting in downstream effects that reduce peripheral vascular risk factors and therefore reduce the risk of Alzheimer’s disease as a result of neuroinflammation. Complete, APOE genotype results from human participants are still ongoing. Descriptive analysis is limited by human samples size.

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wang, chao, Aimin Li, Rebecca Spellman, Xin Bao, Nathan Scott, Melissa Manis, Mary Beth Finn, et al. "Effects of human LDLR overexpression on apoE-related tau pathology and brain dysfunction." Journal of Immunology 204, no. 1_Supplement (May 1, 2020): 64.6. http://dx.doi.org/10.4049/jimmunol.204.supp.64.6.

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Abstract ApoE4 is the strongest genetic risk factor for late-onset Alzheimer Disease. It has been reported that apoE isoforms directly affect tauopathy and tau-mediated neurodegeneration in P301S tau transgenic mice expressing different human apoE isoforms, with apoE4 resulting in markedly increased tau-mediated neurodegeneration and the absence of apoE being marked protective against neurodegeneration. In the brain, low-density lipoprotein receptor (LDLR) is one of the main apoE receptors that regulates apoE levels, but LDLR has very few identified ligands compared to other apoE receptors. LDLR overexpression in the brain can dramatically lower apoE and Aβ levels, as well as decrease Aβ accumulation and deposition. Therefore, we propose to evaluate whether AAV-mediated overexpression of human LDLR (hLDLR) is an efficient way to reduce apoE levels, tau pathology, and neurodegeneration. To study the effect of LDLR overexpression on apoE4-related tau pathology and neurodegeneration, P301S Tau/ApoE4 (TE4) male mice received bilateral intracerebroventricular injection with AAV expressing hLDLR or GFP-control, starting before the onset of tau pathology development. Brains were isolated after 9 month, divided into hemispheres, and analyzed by histological and biochemical techniques. Widespread expression of hLDLR throughout the brain was observed and apoE levels were significantly decreased. Furthermore, mouse nest-building impairment was rescued after hLDLR overexpression. Strikingly, there is a significant decrease in brain atrophy, phosphorylated tau deposition in TE4 mice overexpressing hLDLR. In summary, these data suggest that LDLR may be a promising target to lower apoE levels and decrease neurodegeneration.

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Liu, Min, David G. Kuhel, Ling Shen, David Y. Hui, and Stephen C. Woods. "Apolipoprotein E does not cross the blood-cerebrospinal fluid barrier, as revealed by an improved technique for sampling CSF from mice." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 303, no. 9 (November 1, 2012): R903—R908. http://dx.doi.org/10.1152/ajpregu.00219.2012.

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Apolipoprotein E (apoE) is a 34-kDa glycoprotein that is important in lipoprotein metabolism both peripherally and centrally. Because it is primarily produced in the liver, apoE observed in the brain or cerebrospinal fluid (CSF) could have originated in the periphery; i.e., circulating apoE may cross the blood-brain barrier (BBB) and/or enter CSF and be taken up by brain cells. To determine whether this occurs, a second-generation adenovirus encoding human apoE3 was administered intravenously (iv) to C57BL/6J mice, and the detection of human apoE3 in the CSF was used as a surrogate measure of central availability of this protein utilizing an improved method for sampling CSF from mice. This improved technique collects mouse CSF samples with a 92% success rate and consistently yields relatively large volumes of CSF with a very low rate of blood contamination, as determined by molecular assessment of apolipoprotein B, a plasma-derived protein that is absent in the central nervous system. Through this improved method, we demonstrated that in mice receiving the administered apoE3 adenovirus, human apoE3 was expressed at high levels in the liver, leading to high levels of human apoE3 in mouse plasma. In contrast, human apoE3 levels in the CSF, as assessed by a sensitive ELISA, were essentially undetectable in human apoE3 adenovirus-treated mice, and comparable to levels in LacZ adenovirus-treated control mice. These data indicate that apoE in the CSF cannot be derived from the plasma pool and, therefore, must be synthesized locally in the brain.

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Provost, Pierre R., Eric Boucher, and Yves Tremblay. "Apolipoprotein A-I, A-II, C-II, and H expression in the developing lung and sex difference in surfactant lipids." Journal of Endocrinology 200, no. 3 (December 23, 2008): 321–30. http://dx.doi.org/10.1677/joe-08-0238.

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A sex difference in surfactant lipids is associated with a higher incidence of respiratory distress syndrome for males in cases of preterm birth. In animal models, the sex difference in surfactant lipids was shown to be androgen receptor-dependent. This report examines expression of apolipoprotein (apo)A-I, apoA-II, apoC-II, apoE, apoH, and lipoprotein lipase (LPL) by quantitative real-time PCR in pools of male and female fetal lung tissues from various mouse litters from gestation day (GD) 15.5 to 18.5, and in various adult tissues. Although the expression profiles of ApoA-I, ApoA-II, ApoC-II, and ApoH are complex, these genes are co-regulated and they all present a sex difference (P=0.0896, 0.0896, 0.0195, and 0.0607 respectively) with higher expression for females for several litters. Pulmonary expression of apoA-I, apoA-II, and apoH were specific to the developing lung. ApoE and LPL mRNAs showed a significant increase from GD 17.5 to 18.5. An increase in apoA-I-, apoA-II-, apoC-II-, and apoH-mRNA accumulation was observed from GD 16.5 to 17.5 in correlation with the emergence of mature type II pneumonocytes. These four apolipoprotein genes are co-regulated with type 2 and 5 17β-hydroxysteroid dehydrogenases, which are respectively involved in inactivation and synthesis of androgens. Finally, apoC-II was detected by immunohistochemistry in epithelial cells of the distal epithelium. Positive signals looking like secretory granules were located near the basal membrane. Our results are compatible with a role for apolipoproteins in lipid metabolism and transport in the developing lung in association with the sex difference in surfactant lipid synthesis.

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Liu, Ke, Bangzhu Chen, Fanwen Zeng, Gang Wang, Xin Wu, Yueshu Liu, Guiling Li, Jiarong Yan, and Shouquan Zhang. "ApoE/NOS3 Knockout Mice as a Novel Cardiovascular Disease Model of Hypertension and Atherosclerosis." Genes 13, no. 11 (November 1, 2022): 1998. http://dx.doi.org/10.3390/genes13111998.

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Hypertension is an independent risk factor for atherosclerosis. However, few models of hypertensive atherosclerosis have been established in medical research. In this study, we crossed the ApoE knockout (ApoE-KO; ApoE−/−) atherosclerotic mouse model with the NOS3 knockout (NOS3-KO; NOS3−/−) hypertensive mouse model to establish an ApoE/NOS3 double knockout (ApoE/NOS3-KO; ApoE/NOS3−/−) hypertensive atherosclerosis mouse model. We found that ApoE/NOS3−/− mice reproduced normally, had a blood pressure of 133.00 ± 3.85 mmHg, and developed hypertensive fundus retinopathy and hypertensive nephropathy. In addition, serum total cholesterol (TC) and low-density lipoprotein (LDL) levels in the blood were abnormally elevated, steatosis was observed in the liver cells, and atherosclerotic lesions were observed in the aortic vessels in ApoE/NOS3−/− adult mice. In conclusion, ApoE/NOS3−/− adult mice are a satisfactory model of hypertension and atherosclerosis and can be utilized for studies on cardiovascular diseases.

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Marottoli, Felecia M., Yuriko Katsumata, Kevin P. Koster, Riya Thomas, David W. Fardo та Leon M. Tai. "Peripheral Inflammation, Apolipoprotein E4, and Amyloid-β Interact to Induce Cognitive and Cerebrovascular Dysfunction". ASN Neuro 9, № 4 (14 липня 2017): 175909141771920. http://dx.doi.org/10.1177/1759091417719201.

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Cerebrovascular dysfunction is rapidly reemerging as a major process of Alzheimer’s disease (AD). It is, therefore, crucial to delineate the roles of AD risk factors in cerebrovascular dysfunction. While apolipoprotein E4 ( APOE4), Amyloid-β (Aβ), and peripheral inflammation independently induce cerebrovascular damage, their collective effects remain to be elucidated. The goal of this study was to determine the interactive effect of APOE4, Aβ, and chronic repeated peripheral inflammation on cerebrovascular and cognitive dysfunction in vivo. EFAD mice are a well-characterized mouse model that express human APOE3 (E3FAD) or APOE4 (E4FAD) and overproduce human Aβ42 via expression of 5 Familial Alzheimer’s disease (5xFAD) mutations. Here, we utilized EFAD carriers [5xFAD+/−/ APOE+/+ (EFAD+)] and noncarriers [5xFAD−/−/ APOE+/+ (EFAD−)] to compare the effects of peripheral inflammation in the presence or absence of human Aβ overproduction. Low-level, chronic repeated peripheral inflammation was induced in EFAD mice via systemic administration of lipopolysaccharide (LPS; 0.5 mg/kg/wk i.p.) from 4 to 6 months of age. In E4FAD+ mice, peripheral inflammation caused cognitive deficits and lowered post-synaptic protein levels. Importantly, cerebrovascular deficits were observed in LPS-challenged E4FAD+ mice, including cerebrovascular leakiness, lower vessel coverage, and cerebral amyloid angiopathy-like Aβ deposition. Thus, APOE4, Aβ, and peripheral inflammation interact to induce cerebrovascular damage and cognitive deficits.

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Martinsen, Anneloes, Rasha N. M. Saleh, Raphael Chouinard-Watkins, Richard Bazinet, Glenn Harden, James Dick, Noemi Tejera, Matthew G. Pontifex, David Vauzour, and Anne-Marie Minihane. "The Influence of APOE Genotype, DHA, and Flavanol Intervention on Brain DHA and Lipidomics Profile in Aged Transgenic Mice." Nutrients 15, no. 9 (April 23, 2023): 2032. http://dx.doi.org/10.3390/nu15092032.

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The apolipoprotein E4 (APOE4) genotype is predictive of Alzheimer’s disease (AD). The brain is highly enriched with the omega-3 polyunsaturated fatty acid (n3-PUFA), docosahexaenoic acid (DHA). DHA’s metabolism is defective in APOE4 carriers. Flavanol intake can play a role in modulating DHA levels. However, the impact of flavanol co-supplementation with fish oil on brain DHA uptake, status and partitioning, and according to APOE genotype is currently unknown. Here, using a humanised APOE3 and APOE4 targeted replacement transgenic mouse model, the interactive influence of cocoa flavanols (FLAV) and APOE genotype on the blood and subcortical brain PUFA status following the supplementation of a high fat (HF) enriched with DHA from fish oil (FO) was investigated. DHA levels increased in the blood (p < 0.001) and brain (p = 0.001) following supplementation. Compared to APOE3, a higher red blood cell (RBC) DHA (p < 0.001) was evident in APOE4 mice following FO and FLAV supplementation. Although FO did not increase the percentage of brain DHA in APOE4, a 17.1% (p < 0.05) and 20.0% (p < 0.001) higher DHA level in the phosphatidylcholine (PC) fraction in the HF FO and HF FO FLAV groups, and a 14.5% (p < 0.05) higher DHA level in the phosphatidylethanolamine (PE) fraction in the HF FO FLAV group was evident in these animals relative to the HF controls. The addition of FLAV (+/− FO) did not significantly increase the percentage of brain DHA in the group as a whole. However, a higher brain: RBC DHA ratio was evident in APOE3 only (p < 0.05) for HF FLAV versus HF. In conclusion, our data shows only modest effects of FLAV on the brain DHA status, which is limited to APOE3.

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Williams, Tristan, Tim Bathe, Quan Vo, Patricia Sacilotto, Karen McFarland, Alejandra Jolie Ruiz, Gabriela P. Hery, et al. "Humanized APOE genotypes influence lifespan independently of tau aggregation in the P301S mouse model of tauopathy." Acta Neuropathologica Communications 11, no. 1 (June 19, 2023). http://dx.doi.org/10.1186/s40478-023-01581-2.

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AbstractApolipoprotein (APOE) E4 isoform is a major risk factor of Alzheimer’s disease and contributes to metabolic and neuropathological abnormalities during brain aging. To provide insights into whether APOE4 genotype is related to tau-associated neurodegeneration, we have generated human P301S mutant tau transgenic mice (PS19) that carry humanized APOE alleles (APOE2, APOE3 or APOE4). In aging mice that succumbed to paralysis, PS19 mice homozygous for APOE3 had the longest lifespan when compared to APOE4 and APOE2 homozygous mice (APOE3 > APOE4 ~ APOE2). Heterozygous mice with one human APOE and one mouse Apoe allele did not show any variations in lifespan. At end-stage, PS19 mice homozygous for APOE3 and APOE4 showed equivalent levels of phosphorylated tau burden, inflammation levels and ventricular volumes. Compared to these cohorts, PS19 mice homozygous for APOE2 showed lower induction of phosphorylation on selective epitopes, though the effect sizes were small and variable. In spite of this, the APOE2 cohort showed shorter lifespan relative to APOE3 homozygous mice. None of the cohorts accumulated appreciable levels of phosphorylated tau compartmentalized in the insoluble cell fraction. RNAseq analysis showed that the induction of immune gene expression was comparable across all the APOE genotypes in PS19 mice. Notably, the APOE4 homozygous mice showed additional induction of transcripts corresponding to the Alzheimer’s disease-related plaque-induced gene signature. In human Alzheimer’s disease brain tissues, we found no direct correlation between higher burden of phosphorylated tau and APOE4 genotype. As expected, there was a strong correlation between phosphorylated tau burden with amyloid deposition in APOE4-positive Alzheimer’s disease cases. Overall, our results indicate that APOE3 genotype may confer some resilience to tauopathy, while APOE4 and APOE2 may act through multiple pathways to increase the pathogenicity in the context of tauopathy.

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Medegan Fagla, Bani, Jason York, Amy Christensen, Cielo Dela Rosa, Deebika Balu, Christian J. Pike, Leon M. Tai, and Irina A. Buhimschi. "Apolipoprotein E polymorphisms and female fertility in a transgenic mouse model of Alzheimer’s disease." Scientific Reports 14, no. 1 (July 10, 2024). http://dx.doi.org/10.1038/s41598-024-66489-w.

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AbstractApolipoprotein E (APOE) is a major cholesterol carrier responsible for lipid transport and injury repair in the brain. The human APOE gene (h-APOE) has 3 naturally occurring alleles: ε3, the common allele; ε4, which increases Alzheimer’s disease (AD) risk up to 15-fold; and ε2, the rare allele which protects against AD. Although APOE4 has negative effects on neurocognition in old age, its persistence in the population suggests a survival advantage. We investigated the relationship between APOE genotypes and fertility in EFAD mice, a transgenic mouse model expressing h-APOE. We show that APOE4 transgenic mice had the highest level of reproductive performance, followed by APOE3 and APOE2. Intriguingly, APOE3 pregnancies had more fetal resorptions and reduced fetal weights relative to APOE4 pregnancies. In conclusion, APOE genotypes impact fertility and pregnancy outcomes in female mice, in concordance with findings in human populations. These mouse models may help elucidate how h-APOE4 promotes reproductive fitness at the cost of AD in later life.

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Adaku, Nneoma, Benjamin N. Ostendorf, Wenbin Mei, and Sohail F. Tavazoie. "Apolipoprotein E2 Stimulates Protein Synthesis and Promotes Melanoma Progression." Cancer Research, June 19, 2023. http://dx.doi.org/10.1158/0008-5472.can-23-1252.

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Abstract The secreted lipid transporter apolipoprotein E (APOE) plays important roles in atherosclerosis and Alzheimer’s disease and has been implicated as a suppressor of melanoma progression. The APOE germline genotype predicts human melanoma outcomes, with APOE4 and APOE2 allele carriers exhibiting prolonged and reduced survival, respectively, relative to APOE3 homozygotes. While the APOE4 variant was recently shown to suppress melanoma progression by enhancing anti-tumor immunity, further work is needed to fully characterize the melanoma cell-intrinsic effects of APOE variants on cancer progression. Using a genetically engineered mouse model, we showed that human germline APOE genetic variants differentially modulate melanoma growth and metastasis in an APOE2&gt;APOE3&gt;APOE4 manner. The LRP1 receptor mediated the cell-intrinsic effects of APOE variants on melanoma progression. Protein synthesis was a tumor cell-intrinsic process differentially modulated by APOE variants, with APOE2 promoting translation via LRP1. These findings reveal a gain-of-function role for the APOE2 variant in melanoma progression, which may aid in predicting melanoma patient outcomes and understanding the protective effect of APOE2 in Alzheimer’s disease.

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Williams, Tristan, Alejandra Jolie Ruiz, Angelica Maria Ruiz, Quan Vo, Wangchen Tsering, Guilian Xu, Karen McFarland, et al. "Impact of APOE genotype on prion-type propagation of tauopathy." Acta Neuropathologica Communications 10, no. 1 (April 19, 2022). http://dx.doi.org/10.1186/s40478-022-01359-y.

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AbstractApolipoprotein (APOE) is a major risk factor of Alzheimer’s disease (AD), with the E2, E3 and E4 isoforms differentially regulating the burden of AD-associated neuropathologies, such as amyloid β and tau. In AD, pathological tau is thought to spread along neuroanatomic connections following a prion-like mechanism. To provide insights into whether APOE isoforms differentially regulate the prion properties of tau and determine trans-synaptic transmission of tauopathy, we have generated human P301S mutant tau transgenic mice (PS19) that carry human APOE (APOE2, APOE3 or APOE4) or mouse Apoe allele. Mice received intrahippocamal injections of preformed aggregates of K18-tau at young ages, which were analyzed 5 months post-inoculation. Compared to the parental PS19 mice with mouse Apoe alleles, PS19 mice expressing human APOE alleles generally responded to K18-tau seeding with more intense AT8 immunoreactive phosphorylated tau athology. APOE3 homozygous mice accumulated higher levels of AT8-reactive ptau and microgliosis relative to APOE2 or APOE4 homozygotes (E3 > E4~2). PS19 mice that were heterozygous for APOE3 showed similar results, albeit to a lesser degree. In the timeframe of our investigation, we did not observe significant induction of argentophilic or MC1-reactive neurofibrillary tau tangle in PS19 mice homozygous for human APOE. To our knowledge, this is the first comprehensive study in rodent models that provides neuropathological insights into the dose-dependent effect of APOE isoforms on phosphorylated tau pathology induced by recombinant tau prions.

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Litvinchuk, Alexandra. "The relationship between ApoE4 and lipid dysregulation in glia of the PS19 mouse model of tauopathy." Alzheimer's & Dementia 19, S13 (December 2023). http://dx.doi.org/10.1002/alz.071023.

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AbstractBackgroundApolipoprotein E4 (apoE), the major lipoprotein in the brain, plays an essential role in brain`s lipid homeostasis; furthermore, the presence of the apoE4 allele is the strongest genetic risk factor for developing late‐onset AD compared to most common apoE3 and protective apoE2 alleles. Recent studies in iPSC microglia and astrocytes demonstrate that apoE modulates cholesterol dysfunction and inflammatory responses in an isoform‐specific fashion. However, it is not known if lipid accumulation in glia mediates toxic effects in vivo in the context of tauopathy and neurodegeneration.MethodIn this work we used the combination unbiased lipidomics coupled with immunostainings to dissect the role of apoE and apoE isoforms in glial lipid metabolism of tauopathy P301S tau transgenic mice with a targeted replacement of murine apoE with human ApoE4, ApoE3, or ApoE KO. We further treated the P301S/ApoE4 mice with the LXR agonist GW3965 to test if promoting cholesterol efflux in P301S mice would reduce tau pathology and neurodegeneration in this model.ResultsBy performing unbiased lipidomic analysis of forebrain samples, we demonstrate that P301S/ApoE KI mice accumulate significant amounts of specific cholesteryl esters, oxidized sterols and endolysosomal BMP lipids in an ApoE‐isoform and Tau‐dependent manner. We further show that microglia from aged 9.5 months old P301S/ApoE4 mice accumulate significant amounts of neutral BODIPY‐positive lipid inclusions within lysosomes. Next, we demonstrate that the oral administration of the LXR agonist GW3965 for 3 months significantly reduces p‐tau‐positive AT8 immunostaining in cortex and hippocampus, protects from associated brain neurodegeneration, and improves nesting behavior in 9.5 months old P301S/ApoE4 mice. Using bulk RNA sequencing and immunostaining, we show that LXR agonist diet induces changes in cholesterol biosynthesis and metabolism that result in a significant reduction of neuroinflammatory responses in aged P301S/ApoE4 mice. Lastly, using unbiased lipidomics of forebrain tissues we demonstrate that P301S/ApoE4 mice on LXR diet exhibit significantly lower levels of cholesterol esters when compared to tau transgenic animals on control diet.ConclusionsTogether, we demonstrate that ApoE4 promotes lipid accumulation in glia in the setting of tauopathy and that reducing the accumulation of these lipids by LXR activation is neuroprotective.

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Siano, Dahlia, Lesley R. Golden, Steven M. MacLean, Gabriela Hernandez, and Lance A. Johnson. "Validation of Various Pan‐ApoE and Isoform‐Specific ApoE Antibodies." Alzheimer's & Dementia 20, S1 (December 2024). https://doi.org/10.1002/alz.091634.

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AbstractBackgroundApolipoprotein E (ApoE) exists in three protein isoforms: E2, E3, and E4, which differ by only one or two amino acids. These slight differences profoundly effect protein structure and function, allowing each isoform to differentially impact Alzheimer’s Disease (AD) risk. Relative to the most common E3 isoform, E4 dramatically increases risk, while E2 confers a substantial decrease in risk. The close similarity between protein isoforms makes it difficult to develop isoform‐specific antibodies that are reliable and selective. Here, we aim to validate and optimize a number of common, commercially available ApoE antibodies to determine isoform specificity.MethodControl samples included plasma and brain collected from APOE knockout (KO), homozygous E2, E3 and E4 humanized APOE (hAPOE) mice, and human plasma from all 6 possible APOE genotypes. Western blotting was used on plasma and brain homogenates to determine isoform specificity of E2, E3, or E4 antibodies. Commercial antibodies tested included pan‐ApoE antibodies from Cell Signaling Technologies (CST) and Abcam, ApoE4 antibodies from Novus and CST, ApoE2 antibodies from CST, and ApoE3 antibodies from Abcam and Novus. Additionally, pan‐ApoE antibodies were kindly gifted to us by collaborators (Drs. Lammich and Haass, LMU) and tested. Antibodies were also tested for use in immunohistochemistry (IHC) using hAPOE and APOE KO mouse brain sections (30 uM).ResultDespite the ApoE3 antibodies being marketed as isoform‐specific, they did not show efficacy in either application. Commercial pan‐ApoE antibodies were outperformed by the LMU antibodies, but still showed efficacy. When used for western blotting, the CST ApoE4 and ApoE2 antibodies showed clear isoform specificity in hAPOE mouse and human samples. While none of the isoform‐specific antibodies passed controls for IHC purposes, multiple pan‐ApoE antibodies were variably effective for staining of brain tissue.ConclusionThese data identify several isoform‐specific ApoE antibodies that are reliable and selective across multiple sample types and applications; albeit some display higher affinity for one application over another. Overall, we hope these results will provide AD researchers with important resources that are crucial for visualizing and quantifying ApoE isoform distribution in heterozygote individuals and across a number of AD models, systems, and studies.

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Rueter, Johanna, Gerald Rimbach, Christian Treitz, Anke Schloesser, Kai Lüersen, Andreas Tholey, and Patricia Huebbe. "The mitochondrial BCKD complex interacts with hepatic apolipoprotein E in cultured cells in vitro and mouse livers in vivo." Cellular and Molecular Life Sciences 80, no. 3 (February 7, 2023). http://dx.doi.org/10.1007/s00018-023-04706-x.

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Abstract Background and aims Apolipoprotein E (APOE) is known for its role in lipid metabolism and its association with age-related disease pathology. The aim of the present work was to identify previously unknown functions of APOE based on the detection of novel APOE protein–protein interaction candidates. Approach and results APOE targeted replacement mice and transfected cultured hepatocytes expressing the human isoforms APOE3 and APOE4 were used. For 7 months, APOE3 and APOE4 mice were fed a high-fat and high-sugar diet to induce obesity, while a subgroup was subjected to 30% dietary restriction. Proteomic analysis of coimmunoprecipitation products from APOE mouse liver extracts revealed 28 APOE-interacting candidate proteins, including branched-chain alpha-keto acid dehydrogenase (BCKD) complex subunit alpha (BCKDHA) and voltage-dependent anion-selective channel 1 (VDAC1). The binding of APOE and BCKDHA was verified in situ by proximity ligation assay in cultured cells. The activity of the BCKD enzyme complex was significantly higher in obese APOE4 mice than in APOE3 mice, while the plasma levels of branched-chain amino acids and mTOR signalling proteins were not different. However, the protein–protein interaction with VDAC1 was strongly induced in APOE3 and APOE4 mice upon dietary restriction, suggesting a prominent role of APOE in mitochondrial function. Conclusions The protein–protein interactions of APOE with BCKDHA and VDAC1 appear to be of physiological relevance and are modulated upon dietary restriction. Because these are mitochondrial proteins, it may be suggested that APOE is involved in mitochondria-related processes and adaptation to hepatic energy demands.

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WANG, NA, Sydney V. Doss, Yuzhou Chang, William Tauer, Yingxue Ren, Fangfang Qi, Guojun Bu, Chia‐Chen Liu та Long‐Jun Wu. "Specific expression of APOE in astrocytes reduces Aβ accumulation and plaque‐related pathology in a mouse model of amyloidosis". Alzheimer's & Dementia 20, S1 (грудень 2024). https://doi.org/10.1002/alz.090129.

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AbstractBackgroundAccumulation of the amyloid‐β (Aβ) peptide into amyloid plaque is one of the key pathological markers of Alzheimer’s disease (AD). Apolipoprotein E (APOE) is known to modify AD risk and has been reported to influence Aβ accumulation in the brain in an isoform‐dependent manner. ApoE can be produced by various cell types in the brain, with astrocytes being the main producer. Increasing studies show that altering apoE levels can influence Aβ plaque pathology. However, it is not fully understood how apoE produced by specific cell types, such as astrocytes, contributes to amyloid pathology.MethodWe utilized mouse models expressing APOE isoforms in astrocytes and crossed them with 5xFAD mouse models of amyloidosis. We analyzed the changes to amyloid plaques and assessed the impact on cellular responses to amyloid plaques in condition of astrocytic APOE expression.ResultSpecific expression of APOE3 in astrocytes resulted in compact amyloid plaques and a large increase in plaque deposition, while the total plaque burden was reduced. Astrocytic APOE2 expression led to similar changes to amyloid plaques, but the fold change is lower comparing to that in astrocytic APOE3 models. Intriguingly, the total microglial response increased dramatically in condition of astrocytic APOE3 expression but not in condition of astrocytic APOE2 expression. Further, the ratio of plaque associated Lgals3/Iba1 is higher in condition of astrocytic APOE3 expression, indicating increased microglial activation. Additionally, astrocyte GFAP levels only increased in astrocytic APOE3 models, but not in astrocytic APOE2 models. Finally, APOE isoform effect on dystrophic neurites amount was also observed.ConclusionTogether, our study reveals an important role of astrocytic APOE on the deposition and accumulation of Aβ plaques as well as on Aβ‐associated downstream effects.

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Wang, Shaowei, Boyang Li, Victoria Solomon, Alfred Fonteh, Stanley I. Rapoport, David A. Bennett, Zoe Arvanitakis, Helena C. Chui, Patrick M. Sullivan, and Hussein N. Yassine. "Calcium-dependent cytosolic phospholipase A2 activation is implicated in neuroinflammation and oxidative stress associated with ApoE4." Molecular Neurodegeneration 17, no. 1 (June 15, 2022). http://dx.doi.org/10.1186/s13024-022-00549-5.

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Abstract Background Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and the risk of developing late-onset Alzheimer’s disease (AD), but the mechanisms for this association are not clear. The activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within the plaques of AD brains. The relation between APOE4 genotype and cPLA2 activity is not known. Methods Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation, and activity in relation to measures of inflammation and oxidative stress. Results Greater cPLA2 phosphorylation, cPLA2 activity and leukotriene B4 (LTB4) levels were identified in ApoE4 compared to ApoE3 in primary astrocytes, brains of ApoE-targeted replacement (ApoE-TR) mice, and in human brain homogenates from the inferior frontal cortex of persons with AD dementia carrying APOE3/4 compared to APOE3/3. Higher phosphorylated p38 MAPK but not ERK1/2 was found in ApoE4 primary astrocytes and mouse brains than that in ApoE3. Greater cPLA2 translocation to cytosol was observed in human postmortem frontal cortical synaptosomes with recombinant ApoE4 than ApoE3 ex vivo. In ApoE4 astrocytes, the greater levels of LTB4, reactive oxygen species (ROS), and inducible nitric oxide synthase (iNOS) were reduced after cPLA2 inhibition. Conclusions Our findings implicate greater activation of cPLA2 signaling system with APOE4, which could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

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Avila‐Munoz, Maria Evangelina, Deebika Balu, Jason York, Shivesh Ghura, Nicole Collins, and Mary Jo Ladu. "The effect of sex on APOE‐modulated AD pathology in EFAD mice." FASEB Journal 31, S1 (April 2017). http://dx.doi.org/10.1096/fasebj.31.1_supplement.814.3.

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APOE4 allele of apolipoprotein E (apoE) is the greatest genetic risk factor for Alzheimer's disease (AD) and is associated with accelerated accumulation of both amyloid plaques and and soluble oligomeric forms of the amyloid‐β peptide (oAβ), likely a proximal neurotoxin. Importantly, female APOE4 carriers have a greater lifetime risk for developing AD, an increased rate of cognitive decline and accelerated accumulation of Aβ compared to male APOE4 carriers. In vivo progress has been limited by the lack of a tractable familial AD‐transgenic (FAD‐Tg) mouse model expressing human (h)‐ rather than mouse (m)‐APOE. To study the interactions among sex, h‐APOE and AD pathology, we developed the EFAD‐Tg mice by introducing the h‐APOE genotypes into the 5×FAD‐Tg mice. We previously demonstrated that in the EFAD mice, confirmed in human control and AD samples of CSF and brain, that apoE lipidation is lower and soluble Aβ levels are higher with APOE4 vs. APOE3. Thus, we have developed the mechanistic hypothesis that AD pathology and APOE4 cause a reduction in apoE lipidation, resulting in inefficient clearance of soluble A β synaptic loss, memory/cognitive deficits, and dementia. Novel preliminary data demonstrate that the differences in female vs. male E4FAD mice mimic these established APOE4 vs. APOE3 differences in Aβ aggregation/accumulation, and apoE levels/lipidation. In addition, amyloid deposition, neuroinflammation and tau pathology is significantly greater in the EFAD females compared to males. These data suggest that sex profoundly influences APOE genotype‐specific effects on AD pathology, with apoE lipidation and oAβ levels possibly at the intersection between these two AD risk factors. Together, these data will help to address the critical need for treatment options for women at high risk for AD from the APOE4 allele.Support or Funding InformationCurrent LaDu lab funding includes NIH (NIA) P01AG044682, R21AG030128, R21AG048498, R21AG051233, CCTS (UL1RR029879)

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Peng, Katherine Y., Braison Liemisa, Jonathan Pasato, Pasquale D'Acunzo, Monika Pawlik, Adriana Heguy, Sai C. Penikalapati, et al. "Apolipoprotein E2 Expression Alters Endosomal Pathways in a Mouse Model With Increased Brain Exosome Levels During Aging." Traffic 25, no. 5 (May 2024). http://dx.doi.org/10.1111/tra.12937.

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ABSTRACTThe polymorphic APOE gene is the greatest genetic determinant of sporadic Alzheimer's disease risk: the APOE4 allele increases risk, while the APOE2 allele is neuroprotective compared with the risk‐neutral APOE3 allele. The neuronal endosomal system is inherently vulnerable during aging, and APOE4 exacerbates this vulnerability by driving an enlargement of early endosomes and reducing exosome release in the brain of humans and mice. We hypothesized that the protective effects of APOE2 are, in part, mediated through the endosomal pathway. Messenger RNA analyses showed that APOE2 leads to an enrichment of endosomal pathways in the brain when compared with both APOE3 and APOE4. Moreover, we show age‐dependent alterations in the recruitment of key endosomal regulatory proteins to vesicle compartments when comparing APOE2 to APOE3. In contrast to the early endosome enlargement previously shown in Alzheimer's disease and APOE4 models, we detected similar morphology and abundance of early endosomes and retromer‐associated vesicles within cortical neurons of aged APOE2 targeted‐replacement mice compared with APOE3. Additionally, we observed increased brain extracellular levels of endosome‐derived exosomes in APOE2 compared with APOE3 mice during aging, consistent with enhanced endosomal cargo clearance by exosomes to the extracellular space. Our findings thus demonstrate that APOE2 enhances an endosomal clearance pathway, which has been shown to be impaired by APOE4 and which may be protective due to APOE2 expression during brain aging.

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Davies, Caitlin, Jane Tulloch, Ellie Yip, Lydia Currie, Marti Colom-Cadena, Susanne Wegmann, Bradley T. Hyman, et al. "Apolipoprotein E isoform does not influence trans-synaptic spread of tau pathology in a mouse model." Brain and Neuroscience Advances 7 (January 2023). http://dx.doi.org/10.1177/23982128231191046.

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A key hallmark of Alzheimer’s disease (AD) is the accumulation of hyperphosphorylated tau in neurofibrillary tangles. This occurs alongside neuroinflammation and neurodegeneration. Pathological tau propagates through the AD brain in a defined manner, which correlates with neuron and synapse loss and cognitive decline. One proposed mechanism of tau spread is through synaptically connected brain structures. Apolipoprotein E4 ( APOE4) genotype is the strongest genetic risk factor for late-onset AD and is associated with increased tau burden. Whether the apolipoprotein E ( APOE) genotype influences neurodegeneration via tau spread is currently unknown. Here, we demonstrate that virally expressed human tau (with the P301L mutation) injected into mouse entorhinal cortex at 5–6 months or 15–16 months of age spreads trans-synaptically to the hippocampus by 14 weeks post-injection. Injections of tau in mice expressing human APOE2, APOE3 or APOE4, as well as APOE knock-outs, showed that tau can spread trans-synaptically in all genotypes and that APOE genotype and age do not affect the spread of tau. These data suggest that APOE genotype is not directly linked to synaptic spread of tau in our model, but other mechanisms involving non-cell autonomous manners of tau spread are still possible.

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Fotakis, Panagiotis, Dimitris Kardassis, and Vassilis Zannis. "Abstract 584: ApoE3[K146N/R147W] Acts as a Dominant Negative ApoE Form that Prevents Remnant Clearance and Inhibits the Biogenesis of HDL." Arteriosclerosis, Thrombosis, and Vascular Biology 34, suppl_1 (May 2014). http://dx.doi.org/10.1161/atvb.34.suppl_1.584.

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Introduction: The K146N/R147W substitutions in human apolipoproteinE3 (apoE3) have been associated with a dominant form of type III hyperlipoproteinemia which is expressed at an early age. Methods: The effects of the K146N,R147W substitutions on the lipid and lipoprotein profiles and the HDL phenotypes were studied by adenovirus mediated gene transfer of the full length and a truncated apoE3[K146N/R147W]-202 mutant using different mouse models. Results: A low dose of adenovirus expressing the apoE3[K146N/R147W] mutant in apoE deficient or in apoA-I x apoE double deficient mice exacerbated the hypercholesterolemia and increased greatly plasma apoE and triglycerides levels. In apoE deficient mice, the apoE3[K146N/R147W] mutant displaced apoA-I from the VLDL/LDL/HDL region and resulted in the accumulation of discoidal apoE containing HDL particles in plasma. Similar doses of WT apoE3 cleared the cholesterol of apoE deficient mice without induction of hypertriglyceridemia and promoted formation of spherical HDL particles. A unique feature of the truncated apoE3[K146N/R147W]-202 mutant is that it prevented the induction of hypertriglyceridemia but did not correct the hypercholesterolemia. Other apoE-202 truncated mutants tested did not induce hypertriglyceridemia but corrected hypercholesterolemia. Infection of apoE deficient mice with adenoviruses expressing the apoE3[K146N/R147W] and lipoprotein lipase corrected the hypertriglyceridemia but did not prevent the formation of discoidal HDL particles. Infection of apoE deficient mice with adenoviruses expressing the apoE3[K146N/R147W] and lecithin:cholesterol (LCAT) acyltransferase corrected hypertriglyceridemia, normalized the plasma cholesteryl ester to total cholesterol ratio and generated spherical HDL particles. The combined data indicate that the K146N/R147W substitutions in the full length and the truncated apoE3[K146N/R147W] mutant prevent receptor mediated remnant clearance. Conclusion: The lipid/lipoprotein and HDL abnormalities observed in the different mouse models suggest that the apoE3[K146N/R147W] mutant acts a dominant negative ligand that exacerbates the dyslipidemia and also affects the activity of LCAT and thus inhibits the maturation of HDL.

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Golden, Lesley R., Steven M. MacLean, Cathryn T. Smith, Sangderk Lee, Nicholas L'Italien, Callie M. Whitus, Danielle S. Goulding, et al. "Mid‐life APOE4 to APOE2 ‘Switching’ Alters the Cerebral Transcriptome and Lipidome in a Transgenic Mouse Model." Alzheimer's & Dementia 19, S12 (December 2023). http://dx.doi.org/10.1002/alz.074217.

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AbstractBackgroundCompared to the ‘neutral’ E3, the E4 allele of Apolipoprotein E (APOE) confers up to a 15‐fold increase in Alzheimer’s Disease (AD) risk. Conversely, the neuroprotective E2 allele decreases AD risk by a similar degree. APOE’s strong risk profile and multitude of effects make it a promising therapeutic target. Here, we aimed to assess the therapeutic potential of allelic ‘switching’ by investigating the physiological changes associated with an inducible, in vivo APOE4 to APOE2 transition in a novel transgenic mouse model.MethodThe APOE “switch mouse” (APOE4s2) uses the Cre‐loxP system to allow for inducible APOE allele switching from APOE4 to APOE2. These mice express a floxed human APOE4 coding region followed by the human APOE2 coding region. To study the effects of full body APOE switching, APOE4s2 mice were crossed to ubiquitous ROSA26‐CreERT1 mice. Gene expression and proteomic analyses were used to validate that the model worked as expected. Untargeted lipidomics and single‐cell RNAseq were used to measure physiological changes following the APOE4 to APOE2 allele switch.ResultmRNA and protein analyses confirm that APOE4s2 mice synthesize full‐length human APOE4/ApoE4 pre‐switch and that the inducible switch results in successful and efficient recombination and expression of human APOE2/ApoE2. Single‐cell RNAseq shows that global, genetic replacement of APOE4 with APOE2 results in distinct alterations to glial cell transcriptomes affecting pathways involved with lipid and mitochondrial metabolism, inflammation, blood‐brain barrier integrity, and amyloid beta. Excitingly, differentially expressed genes associated with an E4 to E2 ‘switch’ included several AD GWAS, and both aging‐ and AD‐associated pathways. Additionally, nontargeted lipidomics reveals changes to several lipid classes in the brain, in particular glycerophospholipids.ConclusionTogether, these data suggest that a successful transition from APOE4 to APOE2 has broad impact on the cerebral transcriptome as well as peripheral and cerebral metabolism. Ongoing studies aim to determine whether cell‐specific replacement of APOE4 with APOE2 will rescue E4‐associated metabolic dysfunction, disease‐associated gene signatures, and AD pathology.

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Balu, Deebika, Ana Valencia‐Olvera, Nicole Collins, Ryan Salzman, Jason York, and Mary Jo Ladu. "The effect of aging on APOE‐modulated AD pathology in EFAD mice." FASEB Journal 31, S1 (April 2017). http://dx.doi.org/10.1096/fasebj.31.1_supplement.814.5.

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The APOE ɛ4 allele of apolipoprotein E (apoE) is the greatest genetic risk factor for Alzheimer's disease (AD) compared to APOE3, with APOE2 providing a protective effect. APOE4 is associated with accelerated amyloid‐β (Aβ) accumulation, both as amyloid plaque and soluble oligomeric forms of Aβ (oAβ), the latter considered a proximal neurotoxin. Using EFAD mice, a novel, tractable human‐APOE/familial AD‐transgenic (FAD‐Tg) preclinical mouse model, we have developed the mechanistic hypothesis that APOE4 causes a reduction in apoE lipidation, resulting in inefficient clearance of soluble Aβ, synaptic loss, and memory deficits. By 6‐months (M), E4FAD mice have greater cognitive impairment, AD pathology and soluble Aβ levels, with lower apoE lipidation levels compared to E3FAD. However, the effect of aging on EFAD mice has not been analyzed beyond 6M. In this study, at 8M, 10M, 14M and 18M, we measured amyloid deposition, neuroinflammation and tau pathology, as well apoE lipidation, and soluble levels of Aβ42, oAβ and apoE/Aβ complex. AD pathology continues with age (E4FAD > E3FAD) spreading from the subiculum and deep layers of the frontal cortex to the entire length of the cortex and particularly the thalamus. Comparison of Aβ deposition identified with an Aβ mAb vs. Thio‐S staining revealed both regional and age‐dependent changes in plaque morphology. Importantly, while the levels of soluble Aβ42 plateaued at 10M in E4FAD and 14M in E3FAD mice, oAβ levels continued to increase, from 6–18M with E4FAD > E3FAD. The predictive validity of preclinical FAD‐Tg mouse models that lack h‐APOE, the major genetic risk factor for AD, remains unclear. As the greatest risk factor for AD is age, aged EFAD mice address both these critical risk factors.Support or Funding InformationNIH (NIA) P01AG044682, R21AG030128, R21AG048498, R21AG051233, CCTS (UL1RR029879)

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Konings, Sabine C., Laura Torres-Garcia, Isak Martinsson, and Gunnar K. Gouras. "Astrocytic and Neuronal Apolipoprotein E Isoforms Differentially Affect Neuronal Excitability." Frontiers in Neuroscience 15 (September 21, 2021). http://dx.doi.org/10.3389/fnins.2021.734001.

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Synaptic changes and neuronal network dysfunction are among the earliest changes in Alzheimer’s disease (AD). Apolipoprotein E4 (ApoE4), the major genetic risk factor in AD, has been shown to be present at synapses and to induce hyperexcitability in mouse knock-in brain regions vulnerable to AD. ApoE in the brain is mainly generated by astrocytes, however, neurons can also produce ApoE under stress conditions such as aging. The potential synaptic function(s) of ApoE and whether the cellular source of ApoE might affect neuronal excitability remain poorly understood. Therefore, the aim of this study was to elucidate the synaptic localization and effects on neuronal activity of the two main human ApoE isoforms from different cellular sources in control and AD-like in vitro cultured neuron models. In this study ApoE is seen to localize at or near to synaptic terminals. Additionally, we detected a cellular source-specific effect of ApoE isoforms on neuronal activity measured by live cell Ca2+ imaging. Neuronal activity increases after acute but not long-term administration of ApoE4 astrocyte medium. In contrast, ApoE expressed by neurons appears to induce the highest neuronal firing rate in the presence of ApoE3, rather than ApoE4. Moreover, increased neuronal activity in APP/PS1 AD transgenic compared to wild-type neurons is seen in the absence of astrocytic ApoE and the presence of astrocytic ApoE4, but not ApoE3. In summary, ApoE can target synapses and differentially induce changes in neuronal activity depending on whether ApoE is produced by astrocytes or neurons. Astrocytic ApoE induces the strongest neuronal firing with ApoE4, while the most active and efficient neuronal activity induced by neuronal ApoE is caused by ApoE3. ApoE isoforms also differentially affect neuronal activity in AD transgenic compared to wild-type neurons.

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Chen, Junru, Haibing Chen, Qinjun Wei, Yajie Lu, Tianming Wang, Xiuhong Pang, Guangqian Xing, Zhibin Chen, Xin Cao, and Jun Yao. "APOE4 impairs macrophage lipophagy and promotes demyelination of spiral ganglion neurons in mouse cochleae." Cell Death Discovery 11, no. 1 (April 21, 2025). https://doi.org/10.1038/s41420-025-02454-4.

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Abstract The ApoE-ε4 gene is a well-established genetic risk factor for neurodegenerative diseases, such as Alzheimer’s disease and multiple sclerosis, which are characterized by axonal demyelination in the central nervous system. Recent studies have implicated ApoE-ε4 in age-related hearing loss (ARHL), suggesting a potential role of APOE4 isoform in peripheral nervous system degeneration. However, the role of APOE4 in ARHL are still unclear. In this study, we explored the potential role of APOE4 in axonal demyelination of spiral ganglion neurons (SGNs). ApoE-ε4/ε4 (APOE4) and ApoE-ε3/ε3 (APOE3) mice were used to characterize SGNs. The effect of APOE4 on phagocytosis and autophagy as well as intracellular cholesterol level was evaluated in resident cochlear macrophages (RCMs) and mouse bone marrow-derived macrophages (BMDMs). The results showed that significant axonal demyelination was observed in SGNs of 10-month-old APOE4 mice, accompanied by the presence of myelin debris engulfed by RCMs. Meanwhile, inhibited phagocytosis of myelin debris and impaired lipophagy were detected in APOE4 RCMs and APOE4 BMDMs with an aberrant accumulation of lipid droplets (LDs), which could be reversed by trehalose treatment. This study provided a deep insight into the pathogenesis of APOE4-induced axonal demyelination of SGNs associated with the impaired lipophagy in RCMs, which helped to elucidate the underlying mechanism of ApoE-ε4 in ARHL.

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