Letteratura scientifica selezionata sul tema "ABCA1/ABCG1"

ABCA1 and ABCG1 are two ABC-transporters well-recognized to promote the efflux of cholesterol to apoAI and HDL, respectively. As these two ABC-transporters are critical to cholesterol metabolism, several studies have assessed the impact of ABCA1 and ABCG1 expression on cellular cholesterol homeostasis through ABC-transporter ablation or overexpressing ABCA1/ABCG1. However, for the latter, there are currently no well-established in vitro models to effectively induce long-term ABC-transporter expression in a variety of cultured cells. Therefore, we performed proof-of-principle in vitro studies to determine whether a LoxP-Stop-LoxP (LSL) system would provide Cre-inducible ABC-transporter expression. In our studies, we transfected HEK293 cells and the HEK293-derived cell line 293-Cre cells with ABCA1-LSL and ABCG1-LSL-based plasmids. Our results showed that while the ABCA1/ABCG1 protein expression was absent in the transfected HEK293 cells, the ABCA1 and ABCG1 protein expression was detected in the 293-Cre cells transfected with ABCA1-LSL and ABCG1-LSL, respectively. When we measured cholesterol efflux in transfected 293-Cre cells, we observed an enhanced apoAI-mediated cholesterol efflux in 293-Cre cells overexpressing ABCA1, and an HDL2-mediated cholesterol efflux in 293-Cre cells constitutively expressing ABCG1. We also observed an appreciable increase in HDL3-mediated cholesterol efflux in ABCA1-overexpressing 293-Cre cells, which suggests that ABCA1 is capable of effluxing cholesterol to small HDL particles. Our proof-of-concept experiments demonstrate that the LSL-system can be used to effectively regulate ABC-transporter expression in vitro, which, in turn, allows ABCA1/ABCG1-overexpression to be extensively studied at the cellular level.

ABCA1 and ABCG1 genes encode the cholesterol transporter proteins that play a key role in cholesterol and phospholipids homeostasis. This study was aimed at evaluating and comparing ABCA1 and ABCG1 genes expression in metabolic syndrome patients and healthy individuals. This case-control study was performed on 36 patients with metabolic syndrome and the same number of healthy individuals in Hamadan (west of Iran) during 2013-2014. Total RNA was extracted from mononuclear cells and purified using RNeasy Mini Kit column. The expression of ABCA1 and ABCG1 genes was performed by qRT-PCR. Lipid profile and fasting blood glucose were measured using colorimetric procedures. ABCG1 expression in metabolic syndrome patients was significantly lower (about 75%) compared to that of control group, while for ABCA1 expression, there was no significant difference between the two studied groups. Comparison of other parameters such as HDL-C, FBS, BMI, waist circumference, and systolic and diastolic blood pressure between metabolic syndrome patients and healthy individuals showed significant differences (P<0.05). Decrease in ABCG1 expression in metabolic syndrome patients compared to healthy individuals suggests that hyperglycemia, related metabolites, and hyperlipidemia over the transporter capacity resulted in decreased expression of ABCG1. Absence of a significant change in ABCA1 gene expression between two groups can indicate a different regulation mechanism for ABCA1 expression.

Tissue specific expression of genes encoding cholesterol transporters ABCA1 and ABCG1 as well as genes encoding the most important transcriptional regulators of adipogenesis – LXRa, LXRb, PPARg and RORa has been investigated in intraabdominal adipose tissue (IAT) samples.A direct correlation between the content of ABCA1 and ABCG1 proteins with RORa protein level (r=0.480, p<0.05; r=0.435, p<0.05, respectively) suggests the role of the transcription factor RORa in the regulation of IAT ABCA1 and ABCG1 protein levels. ABCA1 and ABCG1 gene expression positively correlated with obesity indicators such as body mass index (BMI) (r=0.522, p=0.004; r=0.594, p=0.001, respectively) and waist circumference (r=0.403, p=0.033; r=0.474, p=0.013, respectively). The development of obesity is associated with decreased IAT levels of RORa and LXRb mRNA (p=0.016 and p=0.002, respectively). These data suggest that the nuclear factor RORa can play a significant role in the regulation of cholesterol metabolism and control IAT expression of ABCA1 and ABCG1, while the level of IAT LXRb gene expression may be an important factor associated with the development of obesity.

The zinc finger gene 202 (ZNF202) located within a hypoalphalipoproteinemia susceptibility locus on chromosome 11q23 is a transcriptional repressor of various genes involved in lipid metabolism. To provide further evidence for a functional linkage between ZNF202 and hypoalphalipoproteinemia, we investigated the effect of ZNF202 expression on ATP binding cassette transporter A1 (ABCA1) and ABCG1. ABCA1 is a key regulator of the plasma high density lipoprotein pool size, whereas ABCG1 is another mediator of cellular cholesterol and phospholipid efflux in human macrophage. We demonstrate here that the full-length ZNF202m1 isoform binds to GnT repeats within the promotors of ABCA1 (−229/−210) and ABCG1 (−572/−552). ZNF202m1 expression in HepG2 cells dose-dependently repressed the promotor activities of ABCA1 and ABCG1. This transcriptional effect required the presence of the SCAN domain in ZNF202 and the functional integrity of a TATA box at position −24 of ABCA1, whereas the presence of GnT binding motifs was nonessential. The state of ZNF202 SCAN domain oligomerization affected the ability of the adjacent ZNF202 Krüppel-associated box domain to recruit the transcriptional corepressor KAP1. Overexpression of ZNF202m1 in RAW264.7 macrophages prevented the induction of ABCA1 gene expression by 20(S)OH-cholesterol and 9-cis-retinoic acid, further substantiating the interference of ZNF202 in critical elements of transcriptional activation. Finally, HDL and apoAImediated lipid efflux was significantly reduced in RAW264.7 cells stably expressing ZNF202m1. In conclusion, we have identified ABCA1 and ABCG1 as target genes for ZNF202-mediated repression and thus, provide evidence for a functional linkage between ZNF202 and hypoalphalipoproteinemia.

Objective. Abnormal expression of ABCA1 and ABCG1 in the placenta can elicit lipid metabolism disorder and adverse pregnancy outcomes. However, whether it is associated with preterm delivery remains unclear. Our present study aimed to evaluate the relationship between abnormal expression of ABCA1 or ABCG1 and preterm delivery. Methods. Maternal blood and placental tissues from women with spontaneous deliveries (SPD), iatrogenic deliveries (IPD), and term deliveries (TD) were collected. The lipid content and expression of ABCA1 and ABCG1 were subsequently measured. Results. Compared with IPD and TD groups, the HDL, TD, LDL, and TC levels were lower in the maternal blood but higher (except TC) in the cord blood of the SPD group. The extracellular lipid content in the placentas of the SPD group was also notably lower relative to the IPD and TD groups. Moreover, the protein and mRNA expressions of ABCA1 in the placentas of the SPD group were significantly higher compared with the IPD and TD groups; however, there was no obvious difference among the three groups in the protein and mRNA expressions of ABCG1. Conclusions. Abnormal expression of ABCA1 may be associated with the dysregulation of placental lipid metabolism and the occurrence or development of SPD.

Cholesterol-laden macrophages are recognized as a major contributor to atherosclerosis. However, recent evidence indicates that vascular smooth muscle cells (VSMC) that accumulate cholesterol and transdifferentiate into a macrophage-like cell (MLC) phenotype also play a role in atherosclerosis. Therefore, removing cholesterol from MLC may be a potential atheroprotective strategy. The two transporters which remove cholesterol from cells are ABCA1 and ABCG1, as they efflux cholesterol to apoAI and HDL, respectively. In this study, the well-characterized immortalized VSMC line MOVAS cells were edited to generate ABCA1- and ABCG1-knockout (KO) MOVAS cell lines. We cholesterol-loaded ABCA1-KO MOVAS cells, ABCG1-KO MOVAS cells, and wild-type MOVAS cells to convert cells into a MLC phenotype. When we measured apoAI- and HDL-mediated cholesterol efflux in these cells, we observed a drastic decrease in apoAI-mediated cholesterol efflux within ABCA1-KO MOVAS MLC, but HDL-mediated cholesterol efflux was only partially reduced in ABCG1-KO MOVAS cells. Since SR-BI also participates in HDL-mediated cholesterol efflux, we assessed SR-BI protein expression in ABCG1-KO MOVAS MLC and observed SR-BI upregulation, which offered a possible mechanism explaining why HDL-mediated cholesterol efflux remains maintained in ABCG1-KO MOVAS MLC. When we used lentivirus for shRNA-mediated knockdown of SR-BI in ABCG1-KO MOVAS MLC, this decreased HDL-mediated cholesterol efflux when compared to ABCG1-KO MOVAS MLC with unmanipulated SR-BI expression. Taken together, these major findings suggest that SR-BI expression in MLC of a VSMC origin plays a compensatory role in HDL-mediated cholesterol efflux when ABCG1 expression becomes impaired and provides insight on SR-BI demonstrating anti-atherogenic properties within VSMC/MLC.

Members of the ATP-binding cassette (ABC) transporters play a pivotal role in cellular lipid efflux. To identify candidate cholesterol transporters implicated in lipid homeostasis and mammary gland (MG) physiology, we compared expression and localization of ABCA1, ABCG1, and ABCA7 and their regulatory genes in mammary tissues of different species during the pregnancy-lactation cycle. Murine and bovine mammary glands (MGs) were investigated during different functional stages. The abundance of mRNAs was determined by quantitative RT-PCR. Furthermore, transporter proteins were localized in murine, bovine, and human MGs by immunohistochemistry. In the murine MG, ABCA1 mRNA abundance was elevated during nonlactating compared with lactating stages, whereas ABCA7 and ABCA1 mRNA profiles were not altered. In the bovine MG, ABCA1, ABCG1, and ABCA7 mRNAs abundances were increased during nonlactating stages compared with lactation. Furthermore, associations between mRNA levels of transporters and their regulatory genes LXRα, PPARγ, and SREBPs were found. ABCA1, ABCG1, and ABCA7 proteins were localized in glandular MG epithelial cells (MEC) during lactation, whereas during nonlactating stages, depending on species, the proteins showed distinct localization patterns in MEC and adipocytes. Our results demonstrate that ABCA1, ABCG1, and ABCA7 are differentially expressed between lactation and nonlactating stages and in association with regulatory genes. Combined expression and localization data suggest that the selected cholesterol transporters are universal MG transporters involved in transport and storage of cholesterol and in lipid homeostasis of MEC. Because of the species-specific expression patterns of transporters in mammary tissue, mechanisms of cholesterol homeostasis seem to be differentially regulated between species.

oxLDL is involved in the pathogenesis of atherosclerotic lesions through cholesterol accumulation in macrophage foam cells. Andrographolide, the bioactive component of Andrographis paniculata, possesses several biological activities such as anti-inflammatory, anti-oxidant, and anticancer functions. Scavenger receptors (SRs), including class A SR (SR-A) and CD36, are responsible for the internalization of oxLDL. In contrast, receptors for reverse cholesterol transport, including ABCA1 and ABCG1, mediate the efflux of cholesterol from macrophage foam cells. Transcription factor liver X receptor [Formula: see text] (LXR[Formula: see text] plays a key role in lipid metabolism and inflammation as well as in the regulation of ABCA1 and ABCG1 expression. Because of the contribution of inflammation to macrophage foam cell formation and the potent anti-inflammatory activity of andrographolide, we hypothesized that andrographolide might inhibit oxLDL-induced macrophage foam cell formation. The results showed that andrographolide reduced oxLDL-induced lipid accumulation in macrophage foam cells. Andrographolide decreased the mRNA and protein expression of CD36 by inducing the degradation of CD36 mRNA; however, andrographolide had no effect on SR-A expression. In contrast, andrographolide increased the mRNA and protein expression of ABCA1 and ABCG1, which were dependent on LXR[Formula: see text]. Andrographolide enhanced LXR[Formula: see text] nuclear translocation and DNA binding activity. Treatment with the LXR[Formula: see text] antagonist GGPP and transfection with LXR[Formula: see text] siRNA reversed the ability of andrographolide to stimulate ABCA1 and ABCG1 protein expression. In conclusion, inhibition of CD36-mediated oxLDL uptake and induction of ABCA1- and ABCG1-dependent cholesterol efflux are two working mechanisms by which andrographolide inhibits macrophage foam cell formation, which suggests that andrographolide could be a potential candidate to prevent atherosclerosis.

Ожирение ассоциировано с повышенным риском развития метаболических нарушений и сердечно-сосудистых заболеваний. В нашем исследовании мы показали, что экспрессия генов транспортеров холестерина ABCA1 и ABCG1 в жировой ткани может играть роль в развитии ожирения, дислипидемии, метаболического синдрома и ишемической болезни сердца (ИБС). Obesity is linked to increased cardiometabolic risk. Our study shows that cholesterol transporters ABCA1 and ABCG1 gene expression plays a role in development of obesity, dyslipidemia, metabolic syndrome and ischemic heart disease.

The association of hypercholesterolemia and obesity with airway hyperresponsiveness has drawn increasing attention to the potential role of cholesterol and lipid homeostasis in lung physiology and in chronic pulmonary diseases such as asthma. We have recently shown that activation of the nuclear hormone receptor liver X receptor (LXR) stimulates cholesterol efflux in human airway smooth muscle (hASM) cells and induces expression of the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1, members of a family of proteins that mediate reverse cholesterol and phospholipid transport. We show here that ABCA1 is responsible for all LXR-mediated cholesterol and phospholipid efflux to both apolipoprotein AI and high-density lipoprotein acceptors. In contrast, ABCG1 does not appear to be required for this process. Moreover, we show that hASM cells respond to increased levels of cholesterol by inducing expression of ABCA1 and ABCG1 transporters, a process that is dependent on LXR expression. These findings establish a critical role for ABCA1 in reverse cholesterol and phospholipid transport in airway smooth muscle cells and suggest that dysregulation of cholesterol homeostasis in these cells may be important in the pathogenesis of diseases such as asthma.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第17986号
農博第2033号
新制||農||1019(附属図書館)
学位論文||H26||N4811(農学部図書室)
80830
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 植田 和光, 教授 植田 充美, 教授 三芳 秀人
学位規則第4条第1項該当

Orientadores: Eliana Cotta de Faria, Helena Coutinho Franco de Oliveira, Daniel Zanetti Scherrer
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-26T20:49:38Z (GMT). No. of bitstreams: 1 Zago_VanessaHelenadeSouza_D.pdf: 5059555 bytes, checksum: 854d9d1d1674a14d2ebcf5798acc31b3 (MD5) Previous issue date: 2015
Resumo: Dado o importante papel desempenhado pelos transportadores ATP binding cassete A1 (ABCA1), G1 (ABCG1), G5 (ABCG5), G8 (ABCG8) e pelo scavenger receptor class B type I (SR-BI) para a homeostase corpórea de colesterol e desenvolvimento da aterosclerose, este trabalho se propôs a: (i) investigar a relação dos polimorfismos rs2275543 (ABCA1), rs1893590 (ABCG1), rs6720173 (ABCG5), rs6544718 (ABCG8) e rs5888 (SCARB1) com gênero, idade e índice de massa corpórea (IMC) e suas interações sobre variáveis clínicas e bioquímicas (n=654); (ii) determinar a repercussão destes polimorfismos sobre os parâmetros estudados na população total e de forma gênero-específica (n=590) e (iii) avaliar se os miRNAs hsa-miR-33a e hsa-miR-128a são diferencialmente expressos em um subgrupo da população (n=51) e averiguar sua associação com as concentrações plasmáticas do colesterol da lipoproteína de alta densidade (HDL-C), aterosclerose subclínica e expressão de ABCA1, ABCG1 e SCARB1. Para tanto, foram selecionados voluntários normolipidêmicos e assintomáticos, de ambos os gêneros, com idade entre 20 e 75 anos. Dados clínicos e antropométricos foram obtidos, assim como sangue venoso periférico para as determinações bioquímicas e extração de DNA e RNA. O subgrupo de 51 voluntários foi classificado de acordo com HDL-C (mg/dL) em hipoalfalipoproteinêmicos (hipo, HDL-C?39), hiperalfalipoproteinêmicos (hiper, HDL-C?68) e controles (CTL, HDL-C?40<68) e determinadas a espessura íntimo-medial das artérias carótidas e proteínas relacionadas ao metabolismo de HDL. Determinamos que o rs1893590 interage com a idade e o IMC, modulando as concentrações de HDL-C, bem como o tamanho e volume da partícula, sugerindo que este pode modificar seu metabolismo e composição. Nas análises comparativas o rs2275543 apresentou efeitos diferentes, porém benéficos para ambos os gêneros; adicionalmente, o rs6720173 determinou um fenótipo lipoproteico proaterogênico no gênero masculino, enquanto as variantes rs5888 e rs6544718 repercutiram sobre marcadores de adiposidade no gênero feminino. A análise dos cinco polimorfismos nesta população fornece evidências de que estes atuam em diferentes vias do metabolismo lipoproteico, e tem na maioria dos casos características gênero-específicas. Adicionalmente, a avaliação da expressão de hsa-miR-33a, hsa-miR-128a, ABCA1, ABCG1 e SCARB1 revelou que os indivíduos hiper apresentam um aumento da expressão de ABCA1 e ABCG1 em relação ao grupo CTL, somado a uma redução de 72% na expressão do hsa-miR-33a; em conjunto, estes resultados indicam um potencial papel regulatório deste miRNA em indivíduos assintomáticos, possivelmente contribuindo para o aumento do efluxo e do transporte reverso de colesterol
Abstract: Given the important role played by ATP binding cassete transporters A1 (ABCA1), G1 (ABCG1), G5 (ABCG5), G8 (ABCG8) and by scavenger receptor class B type I (SR-BI) on body cholesterol homeostasis and atherosclerosis development, this study proposes to: (i) investigate the relationship of polymorphisms rs2275543 (ABCA1), rs1893590 (ABCG1), rs6720173 (ABCG5), rs6544718 (ABCG8) e rs5888 (SCARB1) with gender, age and body mass index (BMI) and its interactions with clinical and biochemical variables (n=654); (ii) determine the effects of these polymorphisms on the studied parameters in the total population and in a gender-specific manner (n=590) and (iii) evaluate if miRNAs hsa-miR-33a e hsa-miR-128a are differentially expressed in a subgroup of the population (n=51) and verify its association with plasma levels of high-density lipoprotein cholesterol (HDL-C), subclinical atherosclerosis plus ABCA1, ABCG1 and SCARB1 expression. Thus, normolipidemic and asymptomatic volunteers from both genders, with ages ranging from 20 to 75 years were selected. Clinical and anthropometric data were obtained, as well as peripheral venous blood for biochemical determinations plus DNA and RNA extraction. The subgroup of 51 individuals was classified according HDL-C (mg/dL) in hypoalphalipoproteinemics (hypo, HDL-C?39), hyperalphalipoproteinemics (hyper, HDL-C?68) and controls (CTL, HDL-C?40<68); then, were determinated the carotid intima-media thickness and proteins related to HDL metabolism. The polymorphism rs1893590 interacts with age and BMI, modulating HDL-C levels as well as the particle size and volume, suggesting its role on HDL metabolism and composition. Comparative analysis demonstrated that rs2275543 has different, but beneficial repercussions in both genders; furthermore, rs6720173 determines a pro-atherogenic lipoprotein profile in males, while the variants rs5888 and rs6544718 affect positively adiposity markers in females. The analyses of the five studied polymorphism in this population provide evidences of its role in several pathways of lipoproteins metabolism, in most cases in a gender-specific manner. Moreover, the ABCA1, ABCG1, SCARB1, hsa-miR-33a and hsa-miR-128a expression analysis revealed that hyper group presents a significant increase of ABCA1 and ABCG1 expression in relation to the control group; additionally, hsa-miR-33a decreased by 72%. Together, these results indicate a potential regulatory role of this miRNA in asymptomatic individuals, probably contributing to increased cholesterol efflux and reverse cholesterol transport
Doutorado
Ciencias Biomedicas
Doutora em Ciências Médicas

This thesis present a series of experimental approaches that aim to characterize the roles of three E3 ubiquitin ligase enzymes in the post-translational regulation of two ABC lipid transporters; ABCA1 and ABCG1. These E3 ligases, namely HECTD1 ( Homologous to E6Ap C-terminus Domain 1), HUWE1 (HECT, UBA, and WWE domain containing 1), and NEDD4-1 (Neural precursor cell-expressed developmentally down regulated gene 4), were identified during a previous work in our laboratory using peptide mass spectrometry analysis as associate proteins with ABCG1. The experiments presented in the following chapters investigate the effect of these ligases on the ABC transporters' protein expression and cholesterol activity. In addition, the possible mechanism underlying the mode of interaction between these ligases and the ABC transporters is also investigated in attempt to provide a more specific approach to future targeting strategies. Chapter1 provides an overview of atherosclerosis and the essential roles of ABCA1 and ABCG1 lipid transporters in maintaining cellular lipid homeostasis and mediating the macrophage reverse cholesterol transport (RCT) pathway. This chapter also presents a general overview regarding the developed anti-atherogenic therapeutic strategies, including those that attempted to upregulate these ABC transporters, although they were precluded due to drawbacks, indicating the need for a novel specific therapeutic strategy. In addition, it discusses the different regulatory pathways of ABCA1 and ABCG1, in particular the ubiquitin proteasomal pathway, and the role of E3 ligases that determine the specificity of the overall pathway. Chapter 2 describes the main experimental procedures that have been used throughout this thesis, including optimization of siRNA silencing as well as transient overexpression of the ligases in cultured cells, measurement of the ABC transporters' protein expression, immunoprecipitation approaches that detect the interaction between each ligase and ABC transporter, and cholesterol efflux assays that measure the activity of the transporter in exporting cholesterol from cultured cells to extracellular acceptors. Chapter 3 presents experiments investigating the role of the first E3 ligase, HECTD1, in the regulation of ABCA1 and ABCG1. These experiments propose that this newly discovered E3 ligase specifically regulates ABCA1 expression and activity, in a manner that is independent of any change in ABCG1. Silencing of HECTD1 substantially increased ABCA1 expression and cholesterol efflux from THP-1 macrophages to apoA-I, without affecting the ABCG1-mediated cholesterol export to HDL from these cells. The role of the other E3 ligases, HUWE1 and NEDD4-1, are addressed via experiments presented in chapter 4. These two E3 ligases seemed to have an additive effect on ABCG1 protein expression and activity, but not ABCA1. Simultaneous silencing of both ligases significantly increased ABCG1 protein levels and substantially more than the individual silencing. These effects on ABCG1 protein levels were translated to upregulation of the transporter activity. Silencing of both ligases significantly increased the ABCG1- mediated cholesterol export to HDL from cells overexpressing the transporter as well as from THP-1 macrophages. Reciprocally, overexpression of both ligases resulted in a significant decrease in ABCG1 protein levels, confirming their roles in the regulation of the transporter degradation. Chapter 5 illustrates a research strategy used to understand how NEDD4-1 can interact with ABCG1 and also to identify potential candidate adaptor proteins that may perhaps mediate this interaction. This strategy involved looking for specific proline-rich consensus sequences, which are essential for NEDD4-1 interaction with its substrate, in the original mass spectrometry peptide hits. Out of twenty three potential candidates that were investigated, four candidates fulfilled the requirements to act as an adaptor proteins. These findings highlight the probability that one of the identified candidate proteins might recruitNEDD4-1 to ABCG1 and thus facilitate ABCG1 ubiquitination. In conclusion, the work presented in this thesis explores the roles of three E3 ubiquitin ligases in the post-translational regulation of ABC lipid transporters. Identifying these ligases as specific molecular determinates for ABCA1 and ABCG1 ubiquitination and subsequent degradation would provide a new insight into the post-translational regulation of these lipid transporters, as well as into the discovery of a selective therapeutic approach to promote their upregulation.

Le cancer bronchique non à petites cellules (CBNPC), représentant jusqu'à 85% des cas de cancer de poumon, est la principale cause de décès par cancer dans le monde. La majorité des patients sont diagnostiqués à un stade avancé de cancer et malgré les progrès thérapeutiques, le taux moyen de survie à 5 ans est d’environ 20%. De ce fait, une meilleure compréhension de la biologie des cellules cancéreuses et l'exploration des vulnérabilités des CBNPC devraient ouvrir de nouvelles voies pour le développement de stratégies thérapeutiques. Dans ce contexte, je me suis intéressée aux altérations métaboliques des CBNPC. Ma première étude s’est portée sur le rôle de l’efflux cellulaire du cholestérol durant le développement des CBNPC. Les lipoprotéines de haute densité (HDLs), principalement constituées de l’apolipoprotéine A-I (ApoA-I) sont impliquées dans le processus d’efflux cellulaire du cholestérol dans lequel les HDLs épurent le cholestérol en excès des cellules des tissus périphériques. Ce processus implique un transport actif du cholestérol médié par les transporteurs membranaires ABC de types A1 et G1 (ABCA1 et ABCG1). Grâce à l’utilisation d’un modèle murin de cancer du poumon (CCSPCRE-ERTM/+;KrasG12D/+), nous avons pu mettre en évidence que l’invalidation spécifique des transporteurs ABCA1 et ABCG1 dans les cellules cancéreuses augmente la taille des lésions tumorales pulmonaires, ainsi que l’infiltration immunitaire vers un profil permissif. A l’inverse, l’augmentation des taux des HDLs plasmatiques grâce à la surexpression de l’ApoA-I permet d’une part de limiter l’accumulation du cholestérol pulmonaire, mais également de diminuer le développement d’adénocarcinome induit par la mutation KRASG12D. En effet, l’efflux cellulaire du cholestérol réduit l’activation des voies de signalisation de survie des cellules cancéreuses in vivo, diminuant ainsi l’expansion cellulaire. De plus, nous avons montré que l’élimination du cholestérol membranaire à l'aide de la méthyl-β-cyclodextrine induit la régression des adénocarcinomes pulmonaires établis. Les perturbations locales et systémiques des voies d'efflux du cholestérol ont été confirmé chez les patients atteints de CBNPC. Nos résultats positionnent la thérapie d’élimination du cholestérol comme une cible métabolique potentielle afin de réduire le développement des CBNPC. Ma seconde étude consista à élucider le rôle de la mitophagie durant le développement des CBNPC. L'élimination sélective des mitochondries endommagées par la machinerie de l’autophagie est cruciale afin de réguler l’activité des mitochondries, un processus appelé mitophagie. La voie de mitophagie la mieux caractérisée implique la kinase PINK1 (PTEN-induced kinase 1) et l’E3 ubiquitine ligase PARKIN. Nous avons alors exploré le rôle de la mitophagie médiée par PINK1 dans la lignée cellulaire de cancer du poumon LLC-1 et la lignée cellulaire dérivée d’adénocarcinome de souris KrasG12D/+;p53-/- (KP) in vitro et in vivo. Dans un premier temps, nous avons démontré in vitro la capacité des cellules LLC-1 et KP à éliminer les mitochondries endommagées par la mitophagie, nécessitant la formation des autophagosomes par la protéine ATG7 (autophagy related 7). Nous avons également pu mettre en évidence que les dommages mitochondriaux des cellules LLC-1 et KP stabilisent et activent PINK1, mais pas PARKIN, qui n’est pas exprimée dans ces cellules. Nous avons finalement observé que la perte de PINK1 dans les tumeurs implantées chez des souris immunocompétentes, tout comme de la perte d'ATG7, augmente la croissance des tumeurs LLC-1. D’un point de vue mécanistique, la production de cytokines inflammatoires est diminuée dans les tumeurs déficientes pour PINK1, ce qui entraîne une réduction de l'infiltration des neutrophiles. Ces résultats suggèrent que la mitophagie dépendante de PINK1 contribue au contrôle de la croissance des tumeurs pulmonaires, notamment en modulant la réponse immune anti-tumorale
Lung cancer is the leading cause of cancer death worldwide, with non-small cell lung cancer (NSCLC) accounting for up to 85% of all cases. Most of patients are diagnosed with late-stage lung cancer and despite recent advances in effective therapies such as targeted therapies and immunotherapies, the average 5-year survival rate is around 20%. Therefore, a better biological insights of cancer cells to exploit their vulnerabilities are essential to improve potential therapeutic targets and patient outcome. In this context, I got interested in metabolic alterations in NSCLC.First, I focused on the role of cholesterol efflux pathways during NSCLC development. High density lipoproteins (HDLs), mainly consisting of apolipoprotein A-I (ApoA-I), are involved in the process of cellular cholesterol efflux. HDLs remove cholesterol excess from peripheral tissue cells by active cholesterol transport, mediated by ABC transporters ABCA1 and ABCG1. Using a mouse model of lung-tumor bearing KRASG12D mutation (CCSPCRE-ERTM/+;KrasG12D/+), we identified that disruption of cholesterol efflux pathways by specific inactivation of Abca1 and Abcg1 in cancer cells promoted a pro-tolerogenic tumor microenvironment and tumor growth. Overexpression of the apolipoprotein A-I, to raise HDL levels, limited the cholesterol lung retention and protected these mice from tumor development and dire pathologic consequences. Cholesterol removal therapy with methyl-β-cyclodextrin inhalation also reduced tumor burden in progressing tumor by suppressing the proliferation and expansion of epithelial progenitor cells of tumor-origin. Local and systemic perturbations of cholesterol efflux pathways was confirmed in human lung adenocarcinoma. Our results position cholesterol removal therapy as a putative metabolic target in lung cancer progenitor cells.Next, I studied the role of mitophagy during NSCLC development. The selective elimination of damaged mitochondria by the machinery of autophagy is crucial to regulate mitochondrial activity, a process called mitophagy. The most-characterized mitophagy pathway relies on the PTEN-induced kinase 1 (PINK1) and the ubiquitin E3 ligase PARKIN. Hence, we explored the role of PINK1-mediated mitophagy in two murine lung cancer cell lines, LLC-1 and tumor-derived cell line from KrasG12D/+;p53-/- mouse (KP), in vitro and in vivo. First, we demonstrated in vitro the ability of two murine lung cancer cell lines, LLC-1 and KP cells, to remove damaged mitochondria by mitophagy following mitochondrial damages. This process requires the formation of autophagosomes by the ATG7 (autophagy related 7) protein. We also demonstrated that mitochondrial damages in LLC-1 and KP cells stabilize and activate PINK1, but not PARKIN, which is not expressed in those cells. Finally, using immunocompetent mice, we identified that disruption of PINK1-dependent mitophagy, similar to ATG7 loss as a complete autophagy/mitophagy inhibition, significantly increased LLC-1 tumor growth in vivo. PINK1-deficient tumors accumulated aberrant mitochondria and reduced inflammatory cytokines production, correlating with reduction of neutrophil infiltration. Those preliminary data suggest that PINK1-dependent PARKIN-independent mitophagy in lung cancer cells contributes to the control of lung tumor growth. We hypothesize that it may be based, at least in part, on the induction of an effective anti-cancer immune surveillance

Orientadora : Profª. Drª. Lupe Furtado-Alle
Coorientadora : Drª Luciane Viater Tureck
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Genética. Defesa: Curitiba, 31/03/2017
Inclui referências : f. 85-88
Resumo: A maioria dos casos de obesidade e de dislipidemias possui origem complexa, pois é resultante da interação entre fatores genéticos e ambientais. Diversos genes têm sido relacionados com a susceptibilidade a estas doenças, incluindo variantes alélicas dos genes FTO, ABCA1, ABCA7 e ABCG1. Desse modo, o objetivo deste trabalho foi verificar se há influência de polimorfismos de nucleotídeo único (SNPs) destes genes em variáveis relacionadas à obesidade e ao perfil lipídico em mulheres obesas e avaliar o efeito destes SNPs na mudança destas variáveis em resposta a uma dieta de restrição calórica. Para isso, foi coletado sangue de 211 mulheres obesas para análises bioquímicas (níveis de triglicerídeos - TG, colesterol total - CT, HDL-c, LDL-c e VLDL) e genotípicas, além de medidas antropométricas (índice de massa corporal - IMC, circunferência da cintura - CC, e circunferência abdominal - CA), antes e depois de uma dieta com redução de 600Kcal por dia. As amostras foram genotipadas por ensaio de discriminação alélica TaqMan® e posteriormente foram feitas análises estatísticas. Como resultado, as mulheres portadoras do alelo A do SNP rs9939609 (FTO) apresentaram uma menor redução de CA e maior redução dos níveis de HDL-c em resposta à dieta. As portadoras do alelo A do SNP rs1800977 (ABCA1) perderam menos IMC após a intervenção do que as não portadoras. As portadoras do genótipo TT do SNP rs2230806 (ABCA1) reduziram mais seus níveis de CT em resposta a dieta do que as portadoras do genótipo GG. Além disso, o alelo T foi mais frequente que o alelo C no grupo de mulheres com níveis de HDL-c maiores e níveis de LDL-c menores. As portadoras do genótipo GG do SNP rs2279796 (ABCA7) apresentaram níveis de CT e LDL-c maiores. Além disso, o alelo G foi mais frequente no grupo de mulheres com nível de CT e LDL-c maiores. Na resposta a intervenção dietética, as portadoras do genótipo GG aumentaram os níveis de TG e VLDL. As portadoras do alelo G do SNP rs692383 (ABCG1) apresentaram IMC maior, menor redução da CA em resposta a dieta e, em contrapartida, níveis de TG e VLDL menores e uma redução menor nos níveis de HDL-c. As portadoras do alelo A do SNP rs3827225 (ABCG1) tiveram uma maior redução de CA que as não portadoras, porém apresentaram um aumento maior nos níveis de LDL-c após a intervenção dietética. Esses resultados são indicativos de que possivelmente o alelo T do SNP rs2230806 (ABCA1) está associado com o efeito de proteção contra doenças cardiovasculares, pelos seus efeitos nos níveis de lipídeos séricos. Outrossim, o alelo G do SNP rs2279796 (ABCA7) pode estar conferindo um risco para doenças cardiovasculares, assim como o alelo A do SNP rs9939609 (FTO) sobre uma maior dificuldade em reduzir a CA e pela maior perda de HDL-c. Palavras-chave: Obesidade. Mulheres obesas. Intervenção dietética. Perfil lipídico. Gene FTO. Transportadores ABC. Estudo de associação.
Abstract: Obesity and dyslipidemias, in the majority of cases, have complex origin, as they result from the interaction between genetic and environmental factors. Many genes have been related to the susceptibility for these diseases, including FTO, ABCA1, ABCA7 and ABCG1 gene variants. Thus, the aim of this study was to verify if single nucleotide polymorphisms (SNPs) of these genes influence variables related to obesity and lipid profile in obese women and evaluate the effect of these SNPs in the variation of the variables in response to a calorie restriction diet. Thereunto, blood of 211 obese women was collected for biochemical (triglycerides - TG, total cholesterol - TC, HDL-c, LDL-c and VLDL levels) and genotypic analyses, besides anthropometric measures (body mass index - BMI, waist circumference - WC and abdominal circumference - AC), before and after a dietetic intervention with reduction of 600kcal per day. The samples were genotyped by allelic discrimination assay TaqMan® and analyzed statistically. As result, women carrying rs9939609 SNP (FTO) allele A had a lower AC reduction and a greater reduction of HDL-c levels in response to diet. A allele carriers of rs1800977 SNP (ABCA1) lost less BMI after intervention than non-carriers. TT genotype carriers of rs2230806 SNP (ABCA1) reduced more their TC levels than GG genotype carriers in response to diet. In addition, the T allele was more frequent than C allele in the group of women with higher HDL-c levels and lower LDL-c levels. GG genotype carriers of rs2279796 SNP (ABCA7) had higher TC and LDL-c levels. In addition, the G allele was more frequent in the group of women with higher TC and LDL-c levels. In response to dietary intervention, GG genotype carriers increased TG and VLDL levels. G allele carriers of rs692383 SNP (ABCG1) had higher BMI and lower AC reduction in response to diet but, on the other hand, lower TG and VLDL levels and a lower reduction in HDL-c levels. A allele carriers of SNP rs3827225 SNP (ABCG1) had a greater reduction in AC than non-carriers, but they had a higher increase in LDL-c levels after dietary intervention. These results are indicative that possibly T allele of rs2230806 SNP (ABCA1) is associated with the protective effect against cardiovascular diseases by their effects on serum lipid levels. In addition, the G allele of rs2279796 SNP (ABCA7) possibly is conferring a risk for cardiovascular diseases, as well as the A allele of rs9939609 SNP (FTO) on a greater difficulty in reducing AC and the greater loss of HDL-c. Keywords: Obesity. Obese women. Dietetic intervention. Lipid profile. FTO gene. ABC transporters. Association study.

Orientadora : Profª Drª Luciane Viater Tureck
Coorientadora : Profª Drª Lupe Furtado Alle
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Biológicas, Programa de Pós-Graduação em Genética. Defesa: Curitiba, 27/03/2017
Inclui referências
Resumo: A obesidade e as dislipidemias geralmente estão associadas, e na maior parte dos casos possuem origem complexa, sendo decorrentes da interação entre os fatores ambientais e fatores genéticos. Dentre os fatores genéticos já conhecidos encontram-se genes relacionados ao metabolismo, como o gene FTO (Fat Mass and Obesity Associated) e os genes dos transportadores ABC. Polimorfismos de nucleotídeo único (SNPs) no gene FTO foram associados com o ganho de peso, enquanto os transportadores ABC estão relacionados com o efluxo de colesterol, e, nesse trabalho, foram analisados SNPs dos genes ABCA1, ABCA7 e ABCG1. Visto isso, o objetivo desse estudo é avaliar se há influência de polimorfismos nesses genes sobre variáveis antropométricas (índice de massa corporal ajustado para idade e sexo (IMC escore-Z), circunferência abdominal (CA), circunferência da cintura (CC), gordura corporal (GC) e massa magra (MM)) e bioquímicas (glicose em jejum, glicose 120, insulina em jejum, insulina 120, HOMA-IR (do inglês homeostasis model assessment of insulin resistance), QUICKI (do inglês quantitative insulin sensitivity check index) e perfil lipídico) de 557 crianças e adolescentes (eutróficos, sobrepeso e obesos) estudantes de escolas de Curitiba (PR), além de verificar o efeito de tais polimorfismos nas mudanças desses marcadores em resposta a um programa de exercícios físicos. A genotipagem foi realizada por ensaio de discriminação alélica. As análises estatísticas realizadas foram contagem direta dos genótipos, cálculo de frequência alélica, comparação de médias (teste T e teste Mann Whitney), análise de regressão múltipla e predição de risco. Todos os SNPs analisados promoveram variação significativa em alguma das variáveis analisadas. Com relação ao gene FTO, o alelo A do SNP rs9939609 foi associado a um aumento da insulina e HOMA-IR, e diminuição de QUICKI. Em relação aos genes dos transportadores ABC, o alelo C do SNP rs1800977 (ABCA1) foi associado a aumento no IMC escore-Z, CA, GC, insulina 120 e redução em QUICKI; o alelo A do SNP rs2230806 (ABCA1) foi associado a aumento no IMC escore-Z, CA e redução em %MM; o alelo C do SNP rs2279796 (ABCA7) foi associado à maior IMC escore-Z; o SNP rs692383 (ABCG1) foi associado à maior IMC escore-Z, CA, HDL-C, glicose, insulina e HOMA-IR e o alelo G do SNP rs3827225 (ABCG1) foi associado à maior VLDL-C e glicose. Com relação ao efeito na resposta aos exercícios físicos, os genes FTO, ABCA7 e ABCG1 não apresentaram interação, enquanto o alelo C do SNP rs1800977 (ABCA1) foi associado à maior redução de IMC escore-Z e maior aumento de QUICKI em resposta ao exercício e o alelo A do SNP rs2230806 (ABCA1) foi associado à maior ganho de MM. Nesse trabalho nós verificamos os efeitos dos polimorfismos analisados em variáveis relacionadas ao metabolismo (adiposidade, metabolismo da glicose e de lipídeos), sendo que alguns desses polimorfismos também interagiram com os programas de exercícios físicos aplicados. Os resultados obtidos corroboram e abrem novas perspectivas de estudo quanto ao papel da interação entre fatores ambientais e genéticos na prevenção e tratamento de patologias complexas, como a obesidade e as dislipidemias, no sentido de tornar tais medidas cada vez mais individualizadas. Palavras chave: Obesidade, dislipidemias, exercício físico, FTO, ABCA1, ABCA7, ABCG1, rs9939609, rs1800977, rs2230806, rs2279796, rs692383, rs3827225.
Abstract: Obesity and dyslipidemias are usually associated, and in most cases have complex origin, resulting from interaction between environmental and genetic factors. Among these already know genetic factors there are genes related to metabolism, such as FTO (Fat Mass and Obesity Associated) and the ABC transporters genes. Single nucleotide polymorphisms (SNPs) in FTO gene are associated to weight gain, while ABC transporters are related to cholesterol efflux, and SNPs in ABCA1, ABCA7 and ABCG1 genes were analyzed in this work. The objective of this study is to evaluate the influence of polymorphisms in these genes on anthropometric (body mass index adjusted for age and sex (BMI Z-score), abdominal circumference (AC), waist circumference (WC), fat mass (FM) and lean body mass (LBM)) and biochemical variables (fasting glucose, glucose 120, fasting insulin, insulin 120, HOMA-IR (homeostasis model assessment of insulin resistance), QUICKI (quantitative insulin sensitivity check index) and lipid profile) of 557 children and adolescents (normal weight, overweight and obese) in Curitiba (PR), and verify these polymorphisms effects in the changes of these markers in response to a physical exercise program. Genotyping was carried out by allelic discrimination assay. The statistical analyzes made were direct counting of genotypes, allelic frequency calculation, comparison of means (T test and Mann-Whitney test), multiple regression analysis and risk prediction. All the analyzed SNPs promoted significant variation in some of the variables. Regarding FTO gene, the rs9939609 SNP A-allele was associated to higher insulin and HOMA-IR, and reduced QUICKI. In relation to the ABC transporter genes, SNP rs1800977 C-allele (ABCA1) was associated to higher BMI-Z score, AC, FM and insulin 120 increase and QUICKI reduction; SNP rs2230806 (ABCA1) A-allele was associated to higher BMI-Z score and AC and %LBM reduction; SNP rs2279796 (ABCA7) C-allele was associated to higher BMI Z-score; SNP rs692383 (ABCG1) was associated to higher BMI Z-score, AC, HDL-C, glucose, insulin and HOMA-IR, and SNP rs3827225 (ABCG1) G-allele was associated to higher VLDL-C and glucose. Regarding the effect on physical exercise response, FTO, ABCA7 and ABCG1 genes did not shown interaction, whereas rs1800977 (ABCAI) C-allele was associated to higher reduction of BMI Z-score and increase in QUICKI in response to physical exercise and rs2230806 SNP (ABCA1) A-allele was associated to higher gain of LBM. In this study, we verified the effects of the polymorphisms analyzed on variables related to metabolism (adiposity, glucose metabolism and lipid metabolism), and some of these polymorphisms also interacted with the applied physical exercise programs. The results obtained corroborate and open new perspectives on the role of the interaction between environmental and genetic factors in the prevention and treatment of complex pathologies, such as obesity and dyslipidemias, in order to make these measures more individualized. Key-words: Obesity, dyslipidemia, physical exercise, FTO, ABCA1, ABCA7, ABCG1, rs9939609, rs1800977, rs2230806, rs2279796, rs692383, rs3827225.