京都大学 / 0048 / 新制・論文博士 / 博士(生命科学) / 乙第13352号 / 論生博第23号 / 新制||生||58(附属図書館) / 京都大学大学院生命科学研究科統合生命科学専攻 / (主査)教授 上村 匡, 教授 千坂 修, 教授 豊島 文子 / 学位規則第4条第2項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

Aging is characterized by an increase in inter-individual variability in cognitive capacity. Slight decrements in learning and memory emerge; however, age-related shifts in attentional function remain controversial. In pathological aging, however, attentional dysfunction is prominent and the circuitry critical to signal detection and thus attention as a whole, the corticopetal cholinergic system, exhibits substantial disruption and deterioration. One contributing factor to cholinergic dysfunction is the loss of neurotrophic support, specifically nerve growth factor’s high-affinity receptor tropomyosin-related kinase A (trkA). Previous cross-sectional studies demonstrated that reduced trkA receptor levels selectively impaired attentional capacity in aged rats. However, it remains unclear if reduced trkA receptors in the basal forebrain (BF) interact with aging to elicit these attentional deficits. Thus developmental suppression of trkA receptors on attentional capacity and BF cholinergic markers was examined, with the expectation that attentional deficits would emerge earlier in trkA-suppressed rats and cholinergic integrity would be altered. Despite persistent trkA suppression and reduced cholinergic cell size in 6-week-old rats, aged rats that were maintained on a cognitive task throughout life exhibited comparable attentional capacity and stable cholinergic markers compared to controls. Thus, activation of a compensatory mechanism may have stabilized the attentional network. Due to continuous performance on the attentional task, lifelong cognitive engagement may have served to bolster cholinergic integrity and stabilize attentional function. To examine the role of compensatory mechanisms in aging and their interactions with the attentional network, a consistently observed neural activation pattern in aging, termed the anterior-to-posterior shift in aging (PASA), was evaluated. PASA is characterized by enhanced frontal and reduced visual neural activity. Thus, the necessity of cholinergic afferents to the maintenance of PASA was investigated, as well as the role of PASA in stabilizing cognitive function in aging. If cholinergic afferents, specifically those innervating the prefrontal and posterior parietal cortices (PFC; PC), were crucial to PASA then partial cholinergic pruning of the PFC was expected to disrupt PASA and produce attentional deficits. Prefrontal infusion produced attentional deficits in aged rats regardless of infusion type, and elicited a corresponding age-related shift in neural activity, with decreases in visual and increases in parietal cortical activation in aged rats. Partial parietal cholinergic deafferentation impaired performance in both young and aged rats and altered prefrontal cortical recruitment, which was correlated with attentional performance in young rats. Increased recruitment of the attentional network was associated with worse performance in aged rats. Thus, prefrontal and parietal cholinergic afferents are not critical to PASA and increased activation may be representative of reduced neural efficiency rather than compensation. Moreover, aged rats rely heavily on the prefrontal cortex for attentional function, and aberrant prefrontal activity, via generalized damage or disruption of parietal cholinergic inputs, is associated with attentional impairments. Together these findings suggest that enhanced vulnerability of attentional capacity due to prefrontal disruption arises in aging; however, activation of compensatory mechanisms, such as lifelong cognitive activity, may bolster cholinergic integrity and stabilize cognitive function in aging. / Psychology

Orientador: Ricardo de Lima Zollner / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-11T22:15:47Z (GMT). No. of bitstreams: 1 Domingos_PriscilaPerez_D.pdf: 2379926 bytes, checksum: df7f068098f3454b58caf0a13e61f196 (MD5) Previous issue date: 2008 / Resumo: O camundongo não obeso diabético (NOD) é caracterizado por desenvolver naturalmente diabetes mellitus tipo 1 (DM-1) com similaridade ao diabetes mellitus tipo 1 em humanos. A manifestação espontânea do diabetes neste modelo animal é caracterizado por infiltração progressiva das ilhotas de Langerhans por células mononucleares linfócitos T (CD4+ e CD8+) e destruição das células ß pancreáticas produtoras de insulina. O fator de crescimento neural (NGF) e algumas citocinas estão associados a regeneração neural, além de atuarem sobre células do sistema imune. Em adição a estes efeitos, NGF age na liberação de insulina pelas células betas das ilhotas pancreáticas, tornando-se foco de interesse com relação as suas propriedades moduladoras no processo inflamatório na ilhota pancreática. O gangliosídeo GM1 liga-se ao receptor de alta afinidade (TrkA) do NGF-ß, mimetizando seus efeitos. No presente trabalho, avaliamos a ação modulatória de GM1 e NGF em cultura de ilhotas pancreáticas, provenientes de camundongos NOD. Foram avaliados por meio de RT-PCR a expressão gênica de NGF-ß, TrkA e insulina e, por ensaio imunoenzimático, a concentração de citocinas IL-1ß, IL-12, TNF-a, INF-y e insulina. Nossos resultados sugerem ação moduladora similar entre GM1 e NGF sobre as ilhotas de NOD não diabéticos e pré-diabéticos. NGF e GM1 aumentam a expressão gênica de NGF e TrkA e diminuem a expressão gênica de insulina em NOD não diabéticos e pré-diabéticos. Além disso, aumentam a liberação de insulina e diminui a de citocinas inflamatórias IL-1ß, IL-12, TNF-a, IFN-y que caracterizam a resposta Th1. / Abstract: The non-obese diabetic mice (NOD) lineage is characterized by developing type 1 diabetes mellitus (DM-1) naturally, bearing a similarity to DM-1 in human beings. The spontaneous manifestation of diabetes is characterized by gradual infiltration in pancreatic islets by mononuclear cells lymphocytes T (CD4+ and CD8+) and destruction of the ß-cells producers of insulin. One consequence of this effect, is the release of neurotrophins trying modulate the insulin release by the ß cells of pancreatic islets. Thus, the neurotrophins have been the focus of interest in the modulation of the inflammatory process in the pancreatic islets. The ganglioside GM1 binds to the high affinity receptor (TrkA) of the NGF-ß, enhancing its effect. In the present work, we evaluate the immune modulation properties of GM1 and NGF in culture of pancreatic islets from NOD mice. The gene expression of NGF-ß, TrkA and insulin for immune enzymatic assay, the concentration of cytokines IL 1ß, IL-12, TNF-a, IFN-y and insulin were evaluated by RT-PCR and ELISA. Our results suggest similar modulation action between GM1 and NGF on islets of NOD non-diabetic and pre-diabetic. GM1 and NGF action increases the gene expression of NGF and TrkA and the decrease of insulin in mice NOD non-diabetic and pre-diabetic. Moreover, GM1 and NGF increase the insulin release and decrease inflammatory cytokines that characterize the Th1 reply. / Doutorado / Ciencias Basicas / Doutor em Clínica Médica

O sarcoma de Ewing (SE) é um dos mais agressivos tipos de câncer pediátrico. Apesar dos significativos avanços no tratamento dessa doença, ainda há uma grande necessidade no aumento das taxas de cura, redução da toxicidade quimioterápica e redução da resistência ao tratamento. Tem sido proposto que SE provém de precursores neuronais, podendo ter sua fisiologia afetada, pois, por neurotrofinas (NTs). Examinamos a influência de receptores de NTs (Trks) em SE. Foram avaliadas a expressão proteica de NTs (NGF e BDNF) e seus receptores (TrkA e TrkB, respectivamente) em amostras de tumores de pacientes com SE, e a expressão de mRNA nas linhagens celulares RD-ES e SK-ES-1. O tratamento das linhagens com o pan-inibidor de Trks (K252a) modificou a morfologia celular e diminuiu a expressão de mRNA de NGF, TrkA, BDNF e TrkB. Ainda, a inibição de Trks diminuiu drasticamente a proliferação e capacidade clonogênica celular. Efeitos sinérgicos foram observados quando as células foram tratadas em conjunto com baixas doses de quimioterápicos, tanto em células selvagens de SE, quanto nas quais induzimos quimiorresistência. Esse estudo sugere, pela primeira vez, que a inibição de Trks reduz a proliferação e sobrevivência celular em SE, além de aumentar a sensibilidade ao tratamento quimioterápico. / Ewing's sarcoma (ES) is one of the most aggressive types of pediatric cancer. Despite significant advances in the treatment of this disease, there is still a great need in increasing cure rates, reducing chemotherapy toxicity and treatment resistance. It has been proposed that ES might derive from neuronal precursors and may be influenced, therefore, by neurotrophins (NTs). We have examined the influence of Trk neurotrophin receptors in ES. Protein expression of NTs (NGF and BDNF) and their receptors (TrkA, and TrkB, respectively) was detected in tumor samples from patients with ES, and mRNA expression was analyzed in the RD-ES, SK-ES-1 cell lines. Treating cells with a Trk Pan-inhibitor (K252a) altered cell morphology and decreased the mRNA expression of NGF, TrkA, BDNF, and TrkB. In addition, Trk inhibition dramatically decreased cell proliferation and clonogenic capacity. Synergistic effects were observed when cells were treated in combination with low doses of cytotoxic chemotherapeutics, both in normal ES cells and cells in which chemoresistance was induced. The results suggest for the first time that Trk inhibition can reduce the proliferation and survival of ES cells and sensitize them to cytotoxic chemotherapy.

At the plasma membrane, both NGF receptors have been shown to localized to lipid rafts, specific subdomains that are enriched in cholesterol, sphingolipids and the presence of caveolin proteins (Cav1 and/or Cav2). The focus of this work is on this membrane microenvironment mediated modulation of NGF signaling which via two receptors: p75NTR and TrkA. In the present work we found that overexpression of Cav-1 in mouse dorsal root ganglia neurons significantly impacted neurite extension. Similarly, overexpression of Cav-1 in PC12 cells strongly inhibits their ability to grow neurites in response to NGF. It inhibits NGF signaling without, impairing transient MAPK pathway activation. Rather, it does so by sequestering NGF receptors in lipid rafts, which correlates with the cell surface localization of downstream effectors, and phosphorylated-Rsk2, resulting in the prevention of the phosphorylation of CREB. By contrast, overexpression of Cav-2 potentiates NGF induced differentiation, which is accompanied by sustained activation of downstream effectors, and standard internalization of the receptors. This differential effect could be due to the different localization of Caveolins, that modifies the microenvironment, thereby affecting NGF signaling. Furthermore, PC12 cells expressing the non-phosphorylatable Cav-1 mutant (S80V), neither TrkA trafficking or CREB phosphorylation are inhibited and the response resembles that observed in Cav-2 expressing PC12 cells. These studies underline the interplay between caveolins and NGF signalling, offering insight into the potential impact of Caveolin-1 and mutations thereof in certain cancers where NGF signaling is involved.

O sarcoma de Ewing (SE) é um dos mais agressivos tipos de câncer pediátrico. Apesar dos significativos avanços no tratamento dessa doença, ainda há uma grande necessidade no aumento das taxas de cura, redução da toxicidade quimioterápica e redução da resistência ao tratamento. Tem sido proposto que SE provém de precursores neuronais, podendo ter sua fisiologia afetada, pois, por neurotrofinas (NTs). Examinamos a influência de receptores de NTs (Trks) em SE. Foram avaliadas a expressão proteica de NTs (NGF e BDNF) e seus receptores (TrkA e TrkB, respectivamente) em amostras de tumores de pacientes com SE, e a expressão de mRNA nas linhagens celulares RD-ES e SK-ES-1. O tratamento das linhagens com o pan-inibidor de Trks (K252a) modificou a morfologia celular e diminuiu a expressão de mRNA de NGF, TrkA, BDNF e TrkB. Ainda, a inibição de Trks diminuiu drasticamente a proliferação e capacidade clonogênica celular. Efeitos sinérgicos foram observados quando as células foram tratadas em conjunto com baixas doses de quimioterápicos, tanto em células selvagens de SE, quanto nas quais induzimos quimiorresistência. Esse estudo sugere, pela primeira vez, que a inibição de Trks reduz a proliferação e sobrevivência celular em SE, além de aumentar a sensibilidade ao tratamento quimioterápico. / Ewing's sarcoma (ES) is one of the most aggressive types of pediatric cancer. Despite significant advances in the treatment of this disease, there is still a great need in increasing cure rates, reducing chemotherapy toxicity and treatment resistance. It has been proposed that ES might derive from neuronal precursors and may be influenced, therefore, by neurotrophins (NTs). We have examined the influence of Trk neurotrophin receptors in ES. Protein expression of NTs (NGF and BDNF) and their receptors (TrkA, and TrkB, respectively) was detected in tumor samples from patients with ES, and mRNA expression was analyzed in the RD-ES, SK-ES-1 cell lines. Treating cells with a Trk Pan-inhibitor (K252a) altered cell morphology and decreased the mRNA expression of NGF, TrkA, BDNF, and TrkB. In addition, Trk inhibition dramatically decreased cell proliferation and clonogenic capacity. Synergistic effects were observed when cells were treated in combination with low doses of cytotoxic chemotherapeutics, both in normal ES cells and cells in which chemoresistance was induced. The results suggest for the first time that Trk inhibition can reduce the proliferation and survival of ES cells and sensitize them to cytotoxic chemotherapy.

O sarcoma de Ewing (SE) é um dos mais agressivos tipos de câncer pediátrico. Apesar dos significativos avanços no tratamento dessa doença, ainda há uma grande necessidade no aumento das taxas de cura, redução da toxicidade quimioterápica e redução da resistência ao tratamento. Tem sido proposto que SE provém de precursores neuronais, podendo ter sua fisiologia afetada, pois, por neurotrofinas (NTs). Examinamos a influência de receptores de NTs (Trks) em SE. Foram avaliadas a expressão proteica de NTs (NGF e BDNF) e seus receptores (TrkA e TrkB, respectivamente) em amostras de tumores de pacientes com SE, e a expressão de mRNA nas linhagens celulares RD-ES e SK-ES-1. O tratamento das linhagens com o pan-inibidor de Trks (K252a) modificou a morfologia celular e diminuiu a expressão de mRNA de NGF, TrkA, BDNF e TrkB. Ainda, a inibição de Trks diminuiu drasticamente a proliferação e capacidade clonogênica celular. Efeitos sinérgicos foram observados quando as células foram tratadas em conjunto com baixas doses de quimioterápicos, tanto em células selvagens de SE, quanto nas quais induzimos quimiorresistência. Esse estudo sugere, pela primeira vez, que a inibição de Trks reduz a proliferação e sobrevivência celular em SE, além de aumentar a sensibilidade ao tratamento quimioterápico. / Ewing's sarcoma (ES) is one of the most aggressive types of pediatric cancer. Despite significant advances in the treatment of this disease, there is still a great need in increasing cure rates, reducing chemotherapy toxicity and treatment resistance. It has been proposed that ES might derive from neuronal precursors and may be influenced, therefore, by neurotrophins (NTs). We have examined the influence of Trk neurotrophin receptors in ES. Protein expression of NTs (NGF and BDNF) and their receptors (TrkA, and TrkB, respectively) was detected in tumor samples from patients with ES, and mRNA expression was analyzed in the RD-ES, SK-ES-1 cell lines. Treating cells with a Trk Pan-inhibitor (K252a) altered cell morphology and decreased the mRNA expression of NGF, TrkA, BDNF, and TrkB. In addition, Trk inhibition dramatically decreased cell proliferation and clonogenic capacity. Synergistic effects were observed when cells were treated in combination with low doses of cytotoxic chemotherapeutics, both in normal ES cells and cells in which chemoresistance was induced. The results suggest for the first time that Trk inhibition can reduce the proliferation and survival of ES cells and sensitize them to cytotoxic chemotherapy.

To understand the functional interactions between the TrkA and p75 nerve growth factor (NGF) receptors, we employed several lines of investigation including biophysical, biochemical and cellular assays. A high-affinity nerve growth factor (NGF) receptor is thought to be a complex of two receptors, p75 and the receptor tyrosine kinase, TrkA. The existence of a gp75-TrkA complex was demonstrated by a copatching technique. p75 on the surface of intact cells is patched with an anti-p75 antibody and fluorescent secondary antibody, the cells are then fixed to prevent further antibody-induced redistributions, and the distribution of TrkA is probed with an anti-TrkA antibody and fluorescent secondary antibody. We utilize a baculovirus-insect cell expression system, which allows high level expression of wild-type and mutated NGF receptors. TrkA and p75 copatch in both the absence and presence of NGF. This association is specific, since p75 does not copatch with other tyrosine kinase receptors, including TrkB, platelet-derived growth factor receptor-β and Torso (Tor). To determine which domains of TrkA are required for copatching, we used a series of TrkA-Tor chimeric receptors and show that the extracellular domain of TrkA is sufficient for copatching with p75. A chimeric receptor with TrkA transmembrane and intracellular domains shows partial copatching with p75. Deletion of the intracellular domain of p75 decreases but does not eliminate copatching. A point mutation that inactivates the TrkA kinase has no effect on copatching, indicating that this enzymatic activity is not required for association with p75. Hence, although interactions between the p75 and TrkA extracellular domains are sufficient for complex formation, interactions involving other receptor domains also play a role. To study what signal transduction mechanisms were activated by the two receptors to bring about differentiation and survival, we stably transfected LAN5 neuroblastoma cells with an expression vector for ET-R, a chimeric receptor with the extracellular domain of the epidermal growth factor receptor (EGFR) and the TrkA transmembrane and intracellular domains. EGF activated the ET-R kinase and induced partial differentiation. NGF, which can bind to endogenous p75, did not induce differentiation, but enhanced the EGF-induced response, leading to differentiation of almost all of the cells. A mutated NGF, 3T-NGF, that binds to TrkA but not to p75 did not synergize with EGF. Enhancement of EGF-induced differentiation required at least nanomolar concentrations of NGF, consistent with the low-affinity p75 binding site. EGF may induce a limited number of neuronal cells because it also enhances apoptosis. Both NGF and a caspase inhibitor reduced apoptosis and, thereby, enhanced differentiation. NGF appears to enhance survival through the phosphatidylinositol-3 kinase (PI3K) pathway. Consistent with this hypothesis, Akt, a downstream effector of the PI3K pathway, was hyperphosphorylated in the presence of EGF+NGF. These results demonstrate that TrkA kinase initiates differentiation, and p75 enhances differentiation by rescuing differentiating cells from apoptosis via the PI3K pathway. Even though both EGF and NGF are required for differentiation of LAN5/ET-R cells, only NGF is required for survival of the differentiated cells. In the absence of NGF, the cells die by an apoptotic mechanism, involving caspase-3. An anti-p75 antibody blocked the survival effect of NGF. Brain-derived neurotrophic factor also enhanced cell survival, indicating that in differentiated cells, NGF acts through the p75 receptor to prevent apoptosis.

Στην παρούσα διατριβή μελετήθηκε το ντοπαμινεργικό και γλουταμινεργικό σύστημα των βασικών γαγγλίων, χρησιμοποιώντας δύο διαφορετικά μοντέλα ζώων. Ο πρώτος στόχος ήταν να εξεταστεί εάν η μεταφορά του γονιδίου TrkA σε νευρώνες της μέλαινας ουσίας (SN) ενήλικων επίμυων επιδρά στις νευροχημικές τους ιδιότητες, απουσία ή παρουσία εξωγενούς νευροαυξητικού παράγοντα (NGF) στο ραβδωτό σώμα. Η εκτοπική έκφραση του TrkA στην SN οδήγησε σε σημαντική μείωση του mRNA της υδροξυλάσης της τυροσίνης (TH), της TH ανοσοδραστικότητας και του mRNA του DAT στη δεξιά SN σε σύγκριση με την ετερόπλευρη, ενώ δεν βρέθηκε καμία διαφορά στο mRNA των υποδοχέων ντοπαμίνης D2 και της ειδικής δέσμευσης του [3Η]raclopride στην SN. Δεν παρατηρήθηκαν μεταβολές στις θέσεις δέσμευσης του [3Η]WIN35428 και της ανοσοδραστικότητας του DAT στο ομόπλευρο ραβδωτό σώμα, καθώς και στις θέσεις δέσμευσης των μετασυναπτικών υποδοχέων ντοπαμίνης D1 και D2, όπως καθορίζεται από τους ιχνηθέτες [3H]SCH23390 και [3Η] raclopride, αντίστοιχα. Επιπλέον, δεν βρέθηκαν σημαντικές μεταβολές στους υποδοχείς NMDA και AMPA. Τα αποτελέσματα αυτά δείχνουν ότι η εκτοπική έκφραση του TrkA στην SN ρυθμίζει αρνητικά την ΤΗ και οδηγεί σε ανεξάρτητες από τον NGF αποκρίσεις. O δεύτερος στόχος της διατριβής ήταν η μελέτη του ντοπαμινεργικού συστήματος σε ένα μοντέλο DYT1 δυστονίας μυός. Σε διαγονιδιακούς μυς με υπερκινητική και μη υπερκινητική συμπεριφορά παρατηρήθηκε μείωση των υποδοχέων ντοπαμίνης D2 στο ραβδωτό σώμα, όπως προσδιορίστηκε από τη δέσμευση του [3H]raclopride, και τoυ mRNA των D2 στην SNpc, σε σχέση με μη διαγονιδιακούς μυς. Δεν παρατηρήθηκε διαφορά στη δέσμευση του [3H]SCH23390 ή του [3H]WIN35428 στο ραβδωτό σώμα διαγονιδιακών μυών. Τα δεδομένα προτείνουν μία πιθανή εμπλοκή της ντοπαμινεργικής νευροδιαβίβασης στην παθοφυσιολογία της DY1 δυστονίας. / In the present thesis we examined the dopaminergic and glutamatergic neurotransmission systems of basal ganglia, using two different animal models. The first goal was to investigate whether TrkA gene transfer into substantia nigra (SN) neurons of adult rats influence some of their neurochemical properties, in the absence or presence of exogenous nerve growth factor (NGF) delivery in the striatum. Ectopic expression of TrkA in SN resulted in a significant decrease of tyrosine hydroxylase (TH) immunoreactivity, TH mRNA and DAT mRNA expression in the right SN compared to the contralateral side, while no difference was found in the mRNA expression of D2 DA receptors and [3H]raclopride binding in SN. No significant changes were seen in the density of DAT by measuring [3H]WIN35428 binding sites and DAT immunoreactivity in the ipsilateral striatum, as well as in the number of postsynaptic striatal D1 and D2 receptor binding sites, as determined by [3H]SCH23390 and [3H]raclopride, respectively. Furthermore, no significant changes were found in NMDA and AMPA receptors. These data suggest that ectopic TrkA expression in SN downregulates TH in nigral dopaminergic neurons and elicits NGF-independent responses. The second goal of the present thesis was to examine the dopaminergic system of basal ganglia in a mouse model of DYT1 dystonia. A decrease in striatal D2 binding sites, measured by [3H]raclopride binding, and D2 mRNA expression in substantia nigra pars compacta (SNpc) was revealed in affected and unaffected transgenic mice when compared with non-transgenic. No difference in D1 receptor binding and DAT binding, measured by [3H]SCH23390 and [3H]WIN35428 binding, respectively, was found in striatum of transgenic animals. These data suggest a possible involvement of dopamine neurotransmission in the pathophysiology of DYT1 dystonia.

Basal forebrain cholinergic neurons (BFCNs) are critical for learning and memory. Profound and early BFCN degeneration is a hallmark of aging and Alzheimer’s disease (AD). BFCNs depend for their survival on the retrograde axonal transport of neurotrophins, proteins critical for neuronal function. Neurotrophins like brain derived neurotrophic factor (BDNF) and pro-nerve growth factor (proNGF) are retrogradely transported to BFCNs from their synaptic targets. In AD, neurotrophin levels are increased within BFCN target areas and reduced in the basal forebrain, implicating dysfunctional neurotrophin transport in AD pathogenesis. However, neurotrophin transport within this highly susceptible neuronal population is currently poorly understood. We began by establishing protocols for the accurate quantification of axonal transport in BFCNs using microfluidic culture. We then determined the effect of age on neurotrophin transport. BFCNs were left in culture for up to 3 weeks to model aging in vitro. BFCNs initially displayed robust neurotrophin transport, which diminished with in vitro age. We observed that the levels of proNGF receptor tropomyosin-related kinase-A (TrkA) were reduced in aged neurons. Additionally, neurotrophin transport in BFCNs derived from 3xTg-AD mice, an AD model, was also impaired. Next, we sought to determine a mechanism for these transport deficits. First, we determined that proNGF transport was solely contingent upon the levels of TrkA. We then found that elevation of oxidative stress, an established AD contributor, significantly reduced both TrkA levels and proNGF retrograde transport. TrkA levels are partially regulated by protein tyrosine phosphatase-1B (PTP1B), an enzyme whose activity is reduced by oxidation. PTP1B antagonism significantly reduced TrkA levels and proNGF retrograde transport in BFCNs. Treatment of BFCNs with PTP1B-activating antioxidants rescued TrkA levels, proNGF transport, and proNGF-mediated axonal degeneration. Our results suggest that oxidative stress contributes to BFCN degeneration in aging and AD by impairing retrograde neurotrophin transport via oxidative PTP1B-mediated TrkA loss. / Thesis / Doctor of Philosophy (PhD) / During aging and Alzheimer’s disease (AD), the connections between neurons, a type of brain cell, break down, causing memory loss. This breakdown begins in a brain area called the basal forebrain. Basal forebrain neurons rely upon the transport of nutrients along their connections with other neurons, called axons, for proper function. This transport process becomes impaired in AD. Our goal was to understand why this happens. First, we determined that axonal transport was impaired with age and in basal forebrain neurons of mice genetically predisposed to develop AD. We recreated these impairments by increasing the levels of harmful molecules called reactive oxidative species (ROS). ROS levels increase with age and become abnormally high during AD. We found that increased ROS impair axonal transport and contribute to the breakdown of basal forebrain neurons. Our work suggests that reducing ROS will help prevent the breakdown of basal forebrain neurons in AD.