Academic literature on the topic 'Adult olfactory epithelium'

Olfactory neurons have a complex phenotype characterized by their expression of a specific odor receptor (OR) gene and their targeting of an equally specific locus in the olfactory bulb. In the adult fish, olfactory neurons expressing specific ORs are broadly distributed in the epithelium, intermingling with neurons expressing other OR phenotypes. This distributed adult pattern has led to the suggestion that olfactory neuron phenotype is determined by a stochastic process, independent of external positional cues. However, when the fish olfactory system is established during embryogenesis it is simple in its organization, with few olfactory neurons and an olfactory epithelium that has not yet folded into the adult morphology. It is possible that positional cues might act in the embryo to establish an initial population and pattern of olfactory neuron phenotypes and that subsequent morphogenesis and neuronal addition lead to the randomized distribution of neurons. To test this possibility, we examined the spatial patterns of olfactory neurons expressing specific OR genes in 48 h embryos, a time of relative simplicity in the developing olfactory epithelium. Three-dimensional plots of neuron distributions were made, and comparison of OR expression patterns were made between right and left epithelia, between individual animals and between different OR genes. The patterns of OR gene expression were not conserved in these comparison. Mathematical analysis of 21 epithelia for the degree of order in the distribution of olfactory neurons argued strongly that the neurons expressing given ORs are randomly distributed in the 48 h embryos. These results are consistent with those observed from adult tissue and support models suggesting that extrinsic positional cues do not have a major role in specifying olfactory neuron phenotypes.

Glucocorticoids (GCs) are commonly prescribed for treatment of olfactory dysfunction. However, the effects of GCs on olfactory epithelium are not well known. We investigated the effects of high-dose GCs on proliferating cells of olfactory epithelium. Five adult male rats (300 g) received a single daily subcutaneous dose of vehicle containing 0.3 mg dexamethasone (DEX) for 9 days (DEX+ group), and a control group received vehicle alone (DEX– group). We compared sections from the Two groups for numbers of Ki67-positive cells. The mean number of Ki67-positive cells per 500 olfactory epithelial cells was 9.6 for the DEX+ group and 58 for the DEX– group (significant difference). We conclude that high-dose GC suppressed proliferation of olfactory epithelium. We suggest that high-dose GC suppresses cytokines and growth factors, resulting in secondary suppression of proliferating ability.

Rat foetuses from intra-uterine days E13 through E22 (day before parturition) and adults were used for a qualitative electron-microscopic investigation of the development of ciliated/microvillous surfaces of the olfactory epithelium. In the E13 and most of the E14 embryos the epithelial surface is not yet characteristically olfactory. Apical cell profiles show primary cilia. These can arise at the epithelial surface or below. From E14 onwards the epithelial surface acquires olfactory characteristics. Dendritic endings of the olfactory receptor cells can be found amidst microvillous profiles of supporting cells. Either cell type may bear primary cilia. From E16 onwards the receptor cells sprout multiple olfactory cilia, but cells with primary cilia are found throughout pre-natal development. These primary cilia are, at least for a while, retained during the formation of the secondary cilia. Primary cilia always have distinct necklaces at their base. Otherwise, especially with respect to their tips, their morphology can vary. Originally they have expanded tips (up to E14); later on such wide tips are no longer encountered (E16 and E17). Primary cilia of receptor cells never have wide tips. Appreciable numbers of endings with tapering olfactory cilia are discerned around E18 and especially E19. Throughout pre-natal development posterior/superior parts of the septal olfactory epithelium are more precocious than anterior/inferior parts, in particular in the region of transition with the respiratory epithelium. This advance in development includes total densities of dendritic endings of olfactory receptor cells, densities of multiciliated endings alone and lengths of supporting cell microvilli. This difference is discussed with respect to the topography of the olfactory epithelial surface in adult animals. In addition to the systematic topographic variation, a number of more local, apparently not-systematically distributed, topographic variations present during development are described. Most of these also occur in adult animals and they include heterogeneity in length of supporting cell microvilli and the presence of patches of supporting cells with rounded apical protuberances, of patches displaying dendrites with polyaxonemes rather than individual cilia and of scattered atypical cells (neither typical olfactory receptor nor olfactory supporting cells). At their surfaces such atypical cells can resemble inner-ear hair cells. Relative to olfactory receptor and supporting cells there are only very few atypical cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Pituitary adenylate cyclase activating peptide (PACAP), a neuroregulatory peptide, is found in germinative regions of the CNS, including the olfactory bulb, throughout adulthood. We show that 1) PACAP immunoreactivity is also present in the neonatal mouse and adult mouse and rat olfactory epithelium, 2) PACAP expression pattern differs between neonatal and adult mice, and 3) PACAP is produced by olfactory ensheathing cells. PACAP may thus be a key factor in the uniquely supportive role of olfactory ensheathing cells in regeneration of neurons from olfactory epithelium and lesioned spinal cord. Using calcium imaging, we demonstrated physiological responses to PACAP in both neonatal and adult olfactory receptor neurons (ORNs). We propose that PACAP plays an important role in normal turnover of ORNs by providing neurotrophic support during development and regeneration and neuroprotective support of mature neurons.

AbstractDuring metamorphosis, the olfactory system of anuran tadpoles undergoes substantial restructuring. The main olfactory epithelium in the principal nasal cavity of Xenopus laevis tadpoles is associated with aquatic olfaction and transformed into the adult air-nose, while a new adult water-nose emerges in the middle cavity. Impacts of this metamorphic remodeling on odor processing, behavior, and network structure are still unexplored. Here, we used neuronal tracings, calcium imaging, and behavioral experiments to examine the functional connectivity between the epithelium and the main olfactory bulb during metamorphosis. In tadpoles, olfactory receptor neurons in the principal cavity project axons to glomeruli in the ventral main olfactory bulb. These projections are gradually replaced by receptor neuron axons from the newly forming middle cavity epithelium. Despite this reorganization in the ventral bulb, two spatially segregated odor processing streams remain undisrupted and behavioral responses to waterborne odorants are unchanged. Contemporaneously, new receptor neurons in the remodeling principal cavity innervate the emerging dorsal part of the bulb, which displays distinct wiring features. Glomeruli around its midline are innervated from the left and right nasal epithelia. Additionally, postsynaptic projection neurons in the dorsal bulb predominantly connect to multiple glomeruli, while half of projection neurons in the ventral bulb are uni-glomerular. Our results show that the “water system” remains functional despite metamorphic reconstruction. The network differences between the dorsal and ventral olfactory bulb imply a higher degree of odor integration in the dorsal main olfactory bulb. This is possibly connected with the processing of different odorants, airborne vs. waterborne.

The olfactory organ of the European sea bass (Dicentrarchus labrax) in adults and during development has been studied by light microscopy and by transmission and scanning electron microscopy. This organ includes two cavities, each extended by an accessory sac and opening to the outside through two nostrils. It contains a rosette consisting of about forty lamellae. The olfactory epithelium is characterized by the presence of two types of receptor cells, ciliated or with microvilli, and numerous ciliated nonsensory cells. Rod cells, essentially found in the altered epithelia of farmed bass, and rodlet cells are also observed. The olfactory organ forms very early in the developmental process. Two olfactory pits holding both types of sensory receptors appear 24 h before hatching. The ciliated nonsensory cells only appear at the end of the endotrophic period, shortly before the mouth opens. Although it is rather unspectacular during the larval stage, the development of the olfactory organ is characterized at the start of the juvenile stage by three important events: the formation of the nostrils, the hollowing of the accessory sacs, and the development of the rosette. This is created by raising the floor of the cavity and forming successive folds, which are the lamellae where the sensory epithelium is found.

In the olfactory epithelium of mice, cytokeratin was present in the basal cells but not in the olfactory cells. Our previous study using antikeratin antibodies showed that the basal cells were columnar or pyramidal in shape in the early postnatal period, but became flat in adult mice. In this study, structural changes of the basal cells after axotomy were investigated by immunohistochemistry, transmission electron microscopy (TEM), and scanning electron microscopy (SEM).The unilateral olfactory nerves of adult mice were sectioned at the level of the lamina cribrosa. The mice were sacrificed 4, 8-10, and 14 days postoperatively. The olfactory mucosae were removed, frozen with freon 22, and cut on a cryostat at 10 μm. The sections were stained by the PAP method using a PAP kit. The antikeratin antibody (PKK 2) against pig kidney epithelial cell line, which reacts with 40, 46, 48, and 54 kd subunits (Immunotech), was used. To label the dividing cells, bromodeoxyuridine (BrdU) was administered to mice each postoperative day 1 hour before sacrificing. The presence of BrdU was detected imrnunohistochemically using anti-BrdU antibody (Becton-Dickinson).

SUMMARY In Xenopus laevis, the formation of the adult olfactory epithelium involves embryonic, larval and metamorphic phases. The olfactory epithelium in the principal cavity (PC) develops during embryogenesis from the olfactory placode and is thought to respond to water-borne odorants throughout larval life. During metamorphosis, the PC undergoes major transformations and is exposed to air-borne odorants. Also during metamorphosis, the middle cavity (MC) develops de novo. The olfactory epithelium in the MC has the same characteristics as that in the larval PC and is thought to respond to water-borne odorants. Using in situ hybridization, we analyzed the expression pattern of the homeobox genes X-dll3 and Pax-6 within the developing olfactory system. Early in development, X-dll3 is expressed in both the neuronal and non-neuronal ectoderm of the sense plate and in all cell layers of the olfactory placode and larval PC. Expression becomes restricted to the neurons and basal cells of the PC by mid-metamorphosis. During metamorphosis, X-dll3 is also expressed throughout the developing MC epithelium and becomes restricted to neurons and basal cells at metamorphic climax. This expression pattern suggests that X-dll3 is first involved in the patterning and genesis of all cells forming the olfactory tissue and is then involved in neurogenesis or neuronal maturation in putative water- and air-sensing epithelia. In contrast, Pax-6 expression is restricted to the olfactory placode, larval PC and metamorphic MC, suggesting that Pax-6 is specifically involved in the formation of water-sensing epithelium. The expression patterns suggest that X-dll3 and Pax-6 are both involved in establishing the olfactory placode during embryonic development, but subtle differences in cellular and temporal expression patterns suggest that these genes have distinct functions.

Evidence from various sources suggests that schizophrenia may result from altered brain development. The adult olfactory epithelium provides an available 'window' on neuronal development because new neurons are formed there throughout life. This thesis set out to test the neurodevelopmental hypothesis of psychotic disease. Two cell-based models, skin fibroblast and olfactory mucosa culture, were employed to investigate this hypothesis. In order to first demonstrate the utility of olfactory mucosa culture as a model of neurodevelopment, and to allow the candidate to gain proficiency in the culture of this tissue, an investigation of the mitogenic and differentiating properties of insulin-like growth factor-I within this system was undertaken. Insulin-like growth factor-I has multiple effects within the developing nervous system but its role in neurogenesis in the adult nervous system is less clear. The adult olfactory mucosa is a site of continuing neurogenesis that expresses insulin-like growth factor-I, its receptor, and its binding proteins. The action of insulin-like growth factor-I was assayed in several serum-free culture systems combined with bromodeoxyuridine labelling of proliferating cells and immunochemistry for specific cell types. Once proficiency in olfactory mucosa culture was gained, this model was applied to biopsied olfactory mucosa from schizophrenia and bipolar disorder patients in order to test the developmental parameters of adhesion, cell proliferation, and cell death in a neural tissue. It was previously shown that olfactory cultures from individuals with schizophrenia had increased cell proliferation and attached less frequently than cultures from healthy controls suggesting disrupted neurogenesis. An aim of this study was to replicate those observations in individuals with schizophrenia and and extend them to individuals with bipolar disorder. After completion of the cell and tissue culture assays, microarray analysis of these cell-based models was used to reveal gene expression differences present between patients and healthy controls. Microarray analysis is a complicated technique and the limited amounts of RNA that can be extracted from a single nasal biopsy further compounds this issue. In order to obtain enough material for microarray hybridization RNA samples underwent antisense amplification. Therefore, with the aim of allowing the candidate to gain proficiency in both these techniques prior to microarray analysis of olfactory biopsies from patients with schizophrenia and bipolar disorder, a pilot microarray study of cultured skin fibroblasts from schizophrenia patients and healthy controls was performed. The present findings show that insulin-like growth factor-I and its receptor were expressed by globose basal cells (the neuronal precursor), by neurons and by olfactory ensheathing cells, the special glia of the olfactory nerve. Insulin-like growth factor-I reduced the numbers of proliferating neuronal precursors, induced their differentiation into neurons, and promoted morphological differentiation of neurons. In contrast, this growth factor was mitogenic for olfactory ensheathing cells. The evidence suggests that insulin-like growth factor-I is an autocrine/paracrine signal that induces neuronal precursors to differentiate into olfactory sensory neurons and induces olfactory ensheathing cells to proliferate and that olfactory mucosa culture is valuable in modelling neurodevelopmental processes. When the olfactory musoca culture model was applied to patients with psychosis, a two-fold increase in proliferation of neural cells was found in schizophrenia compared to controls and bipolars. In bipolar cultures there was a 3-fold increase in cell death compared to controls and schizophrenia. Microarray analysis of cultured skin fibroblasts revealed differential expression of over 1000 genes between patients and controls. Inspection of the significant data showed alterations to gene expression between groups in the cell cycle, oxidative phosphorylation, TCA cycle and oxidative stress pathways. Gene expression in each of these pathways was predominately decreased in schizophrenia. Quantitative PCR analysis of selected differentially expressed genes involved with cell cycle regulation validated the increased expression of vitamin D receptor, and decreased expression of proliferating cell nuclear antigen and DEAD (Asp-GIu-Ala-Asp) box polypeptide 5 in skin fibroblasts from patients with schizophrenia. Microarray analysis of biopsied olfactory mucosa showed 146 and 139 differentially expressed genes in schizophrenia and bipolar disorder respectively, compared to controls. Consistent with increased mitosis in schizophrenia biopsy cultures three genes that function to positively influence cell cycle had increased expression. In the bipolar disorder group a dysregulation of the phosphatidylinositolsignalling pathway was seen; five genes that either directly function within or interact with this pathway had decreased expression. There is speculation that the therapeutic effect of psychotropic drugs acting upon this pathway in bipolar disorder involves reduction of neuronal cell death. Increased mitosis of neural cells has now been observed in two separate groups of schizophrenic patients indicating a robust finding. The use of fibroblast and olfactory mucosal tissue can be used to study biological and genetic aspects of neurodevelopment in living humans both with and without psychotic disease. Biopsied olfactory mucosa provides benefits over the use of autopsied material for study of psychotic disease because post-mortem duration and agonal factors that lead to tissue, protein and nucleic acid degradation are not an issue. This study provides evidence for a neurodevelopmental aetiology of schizophrenia and bipolar disorder acting at the level of cell cycle control. Subtle changes in the timing of cell cycle regulation could account for the brain pathologies observed in these diseases. Olfactory mucosa culture is a valuable model of neurodevelopmental processes.

Evidence from various sources suggests that schizophrenia may result from altered brain development. The adult olfactory epithelium provides an available 'window' on neuronal development because new neurons are formed there throughout life. This thesis set out to test the neurodevelopmental hypothesis of psychotic disease. Two cell-based models, skin fibroblast and olfactory mucosa culture, were employed to investigate this hypothesis. In order to first demonstrate the utility of olfactory mucosa culture as a model of neurodevelopment, and to allow the candidate to gain proficiency in the culture of this tissue, an investigation of the mitogenic and differentiating properties of insulin-like growth factor-I within this system was undertaken. Insulin-like growth factor-I has multiple effects within the developing nervous system but its role in neurogenesis in the adult nervous system is less clear. The adult olfactory mucosa is a site of continuing neurogenesis that expresses insulin-like growth factor-I, its receptor, and its binding proteins. The action of insulin-like growth factor-I was assayed in several serum-free culture systems combined with bromodeoxyuridine labelling of proliferating cells and immunochemistry for specific cell types. Once proficiency in olfactory mucosa culture was gained, this model was applied to biopsied olfactory mucosa from schizophrenia and bipolar disorder patients in order to test the developmental parameters of adhesion, cell proliferation, and cell death in a neural tissue. It was previously shown that olfactory cultures from individuals with schizophrenia had increased cell proliferation and attached less frequently than cultures from healthy controls suggesting disrupted neurogenesis. An aim of this study was to replicate those observations in individuals with schizophrenia and and extend them to individuals with bipolar disorder. After completion of the cell and tissue culture assays, microarray analysis of these cell-based models was used to reveal gene expression differences present between patients and healthy controls. Microarray analysis is a complicated technique and the limited amounts of RNA that can be extracted from a single nasal biopsy further compounds this issue. In order to obtain enough material for microarray hybridization RNA samples underwent antisense amplification. Therefore, with the aim of allowing the candidate to gain proficiency in both these techniques prior to microarray analysis of olfactory biopsies from patients with schizophrenia and bipolar disorder, a pilot microarray study of cultured skin fibroblasts from schizophrenia patients and healthy controls was performed. The present findings show that insulin-like growth factor-I and its receptor were expressed by globose basal cells (the neuronal precursor), by neurons and by olfactory ensheathing cells, the special glia of the olfactory nerve. Insulin-like growth factor-I reduced the numbers of proliferating neuronal precursors, induced their differentiation into neurons, and promoted morphological differentiation of neurons. In contrast, this growth factor was mitogenic for olfactory ensheathing cells. The evidence suggests that insulin-like growth factor-I is an autocrine/paracrine signal that induces neuronal precursors to differentiate into olfactory sensory neurons and induces olfactory ensheathing cells to proliferate and that olfactory mucosa culture is valuable in modelling neurodevelopmental processes. When the olfactory musoca culture model was applied to patients with psychosis, a two-fold increase in proliferation of neural cells was found in schizophrenia compared to controls and bipolars. In bipolar cultures there was a 3-fold increase in cell death compared to controls and schizophrenia. Microarray analysis of cultured skin fibroblasts revealed differential expression of over 1000 genes between patients and controls. Inspection of the significant data showed alterations to gene expression between groups in the cell cycle, oxidative phosphorylation, TCA cycle and oxidative stress pathways. Gene expression in each of these pathways was predominately decreased in schizophrenia. Quantitative PCR analysis of selected differentially expressed genes involved with cell cycle regulation validated the increased expression of vitamin D receptor, and decreased expression of proliferating cell nuclear antigen and DEAD (Asp-GIu-Ala-Asp) box polypeptide 5 in skin fibroblasts from patients with schizophrenia. Microarray analysis of biopsied olfactory mucosa showed 146 and 139 differentially expressed genes in schizophrenia and bipolar disorder respectively, compared to controls. Consistent with increased mitosis in schizophrenia biopsy cultures three genes that function to positively influence cell cycle had increased expression. In the bipolar disorder group a dysregulation of the phosphatidylinositolsignalling pathway was seen; five genes that either directly function within or interact with this pathway had decreased expression. There is speculation that the therapeutic effect of psychotropic drugs acting upon this pathway in bipolar disorder involves reduction of neuronal cell death. Increased mitosis of neural cells has now been observed in two separate groups of schizophrenic patients indicating a robust finding. The use of fibroblast and olfactory mucosal tissue can be used to study biological and genetic aspects of neurodevelopment in living humans both with and without psychotic disease. Biopsied olfactory mucosa provides benefits over the use of autopsied material for study of psychotic disease because post-mortem duration and agonal factors that lead to tissue, protein and nucleic acid degradation are not an issue. This study provides evidence for a neurodevelopmental aetiology of schizophrenia and bipolar disorder acting at the level of cell cycle control. Subtle changes in the timing of cell cycle regulation could account for the brain pathologies observed in these diseases. Olfactory mucosa culture is a valuable model of neurodevelopmental processes.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Biomedical Sciences
Full Text

碩士
國立臺灣大學
解剖學暨生物細胞學研究所
100
Olfactory system is closely associatied with emotion and memory. Olfactory malfunction may lead to abnormal emotion, and this may play roles in mood-related disease, such as schizophrenia. Previous studies indicate that abnormal olfactory functions are common symptoms of schizophrenics, which include disturbed identification, discrimination, memory, and detection of odors. As shown by MRI scans, reduced bulb volumes were seen in schizophrenic patients. Neuregulin 1 (NRG1) is thought to be one of the susceptibility genes of schizophrenia. Neuregulin 1 (NRG1) and its receptors, ErbBs, may play important roles in the development of nervous system. Thus, the goal of this experiment was to examine the effects of the mutation of NRG1 gene on the olfaction and olfactory epithelium (OE) neurogenesis. Following behavioral observation 8 week-old wildtype (WT, NRG1+/+) and mutant (Mut, NRG1+/-) mice were intraperitoneally injected with bromodeoxyuridine (BrdU), 150 mg/kg, once daily for 3 consecutive days. On the 4th day (BrdU-D4), 10th day (BrdU-D10), 21st day (BrdU-D21) and 28th day (BrdU-D28) the mice were subjected to preparation for immunocytochemistry on their OE. Our results are as follows. 1. Behavior test results: NRG1 mutant mice showed decreased average body weight by about 9.2%. As revealed from the open field test, the distance and duration traveled by mutant mice were similar in the central and peripheral parts of the field respectively to that of WT. The olfactory habituation/dishabituation test revealed that, mutant mice were unable to discriminate different odors and litter odors. 2. Morphological results: (A) In the dorsal region of OE (i) The numbers of BrdU-positive cells were increased by 94.6% and 65.8% in the BrdU-D4 and BrdU-D10 mutant mice, compared to WT, whereas BrdU-D21 and BrdU-D28 mutant mice were similar to WT. (ii) Mutant mice contained 45.6% less number of the doublecortin (DCX) , a marker for neuroblasts, positive cells than that of WT. (iii) The levels of the olfactory marker protein (OMP) for mature olfactory receptor neurons (ORNs) were decreased by 28.9% and 18.6% in its expression area and OD in the Mutant mice. (iv) OE of mutant mice had 37.6% lower number of calretinin (CR) positive cells. (v) Mutant mice had 75.8% more number of cleaved caspase 3 positive cells. (B) In the septal region of OE (i) The numbers of BrdU-positive cells were increased by 62.1%, 54.5% and 54.6% in the BrdU-D4, BrdU-D10 and BrdU-D28 mutant mice, compared to WT, whereas BrdU-D21 mutant mice were similar to WT. (ii) Mutant mice contained 31.5% less number of the doublecortin (DCX) positive cells than that of WT. (iii) Mutant mice had 38.5% more number of cleaved caspase 3 positive cells, whereas OMP and CR expression were similar to WT. (C) Electron microscopy revealed that compared to that of WT, the number of nuclear membrane pores seemed incereased in the mutant basal cell and a single cilium arose from its basal part in the mutant ORN, instead of the multiple cilia arising from one single basal part in WT ORNs. Our results also confirmed the presence of NRG1 and ErbB 2 receptor in OE. These point out that the abnormal NRG1 protein may bind to the ErbB 2, leading to altered intracellular signaling of those specific cells. In the mutant mice, the decreased number and abnormal ultrastructure of olfactory receptor neurons may be related to their abnormal behavior and increased neurogenesis and apoptosis. NRG1 gene activity apparently is critically involved in the proliferation, differentiation and survival of neural cells, and thus may play important roles in the pathogenesis of schizophrenia.

Alzheimer’s and Parkinson’s diseases (AD, PD) have a pediatric and young adult onset in Metropolitan Mexico City (MMC). The SARS-CoV-2 neurotropic RNA virus is triggering neurological complications and deep concern regarding acceleration of neuroinflammatory and neurodegenerative processes already in progress. This review, based on our MMC experience, will discuss two major issues: 1) why residents chronically exposed to air pollution are likely to be more susceptible to SARS-CoV-2 systemic and brain effects and 2) why young people with AD and PD already in progress will accelerate neurodegenerative processes. Secondary mental consequences of social distancing and isolation, fear, financial insecurity, violence, poor health support, and lack of understanding of the complex crisis are expected in MMC residents infected or free of SARS-CoV-2. MMC residents with pre-SARS-CoV-2 accumulation of misfolded proteins diagnostic of AD and PD and metal-rich, magnetic nanoparticles damaging key neural organelles are an ideal host for neurotropic SARS-CoV-2 RNA virus invading the body through the same portals damaged by nanoparticles: nasal olfactory epithelium, the gastrointestinal tract, and the alveolar-capillary portal. We urgently need MMC multicenter retrospective-prospective neurological and psychiatric population follow-up and intervention strategies in place in case of acceleration of neurodegenerative processes, increased risk of suicide, and mental disease worsening. Identification of vulnerable populations and continuous effort to lower air pollution ought to be critical steps.

Millions of children and young adults are exposed to fine particulate matter (PM2.5) and ozone, associated with Alzheimer’s disease (AD) risk. Mexico City (MC) children exhibit systemic and brain inflammation, low cerebrospinal fluid (CSF) Aβ1-42, breakdown of nasal, olfactory, alveolar-capillary, duodenal, and blood-brain barriers, volumetric and metabolic brain changes, attention and short-term memory deficits, and hallmarks of AD and Parkinson’s disease. Airborne iron-rich strongly magnetic combustion-derived nanoparticles (CDNPs) are present in young urbanites’ brains. Using transmission electron microscopy, we documented CDNPs in neurons, glia, choroid plexus, and neurovascular units of young MC residents versus matched clean air controls. CDNPs are associated with pathology in mitochondria, endoplasmic reticulum (ER), mitochondria-ER contacts (MERCs), axons,and dendrites. There is a significant difference in size and numbers between spherical CDNPs (>85%) and the angular, euhedral endogenous NPs (<15%). Spherical CDNPs (dogs 21.2 ± 7.1 nm in diameter versus humans 29.1 ± 11.2 nm, p = 0.002) are present in neurons, glia, choroid plexus, endothelium, nasal and olfactory epithelium, and in CSF at significantly higher in numbers in MC residents (p < 0.0001). Degenerated MERCs, abnormal mitochondria, and dilated ER are widespread, and CDNPs in close contact with neurofilaments, glial fibers, and chromatin are a potential source for altered microtubule dynamics, mitochondrial dysfunction, accumulation and aggregation of unfolded proteins, abnormal endosomal systems, altered insulin signaling, calcium homeostasis, apoptotic signaling, autophagy, and epigenetic changes. Highly oxidative, ubiquitous CDNPs constitute a novel path into AD pathogenesis. Exposed children and young adults need early neuroprotection and multidisciplinary prevention efforts to modify the course of AD at early stages.