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Title
The role of parkin in the recovery of central dopamine neurons from acute neurotoxicant exposure
Creator
Benskey, Matthew John
Date
2013
Collection
Electronic Theses & Dissertations
Description
Parkinson Disease (PD) pathology is associated with the selective degeneration of nigrostriatal dopamine (NSDA) neurons, while the tuberoinfundibular DA (TIDA) neurons of the hypothalamus remain intact. The same pattern of selective degeneration has been observed following exposure to 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyradine (MPTP), a mitochondrial complex I inhibitor which recapitulates many of the molecular pathologies associated with PD. The purpose of this dissertation is to...
Show moreParkinson Disease (PD) pathology is associated with the selective degeneration of nigrostriatal dopamine (NSDA) neurons, while the tuberoinfundibular DA (TIDA) neurons of the hypothalamus remain intact. The same pattern of selective degeneration has been observed following exposure to 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyradine (MPTP), a mitochondrial complex I inhibitor which recapitulates many of the molecular pathologies associated with PD. The purpose of this dissertation is to identify early molecular events that underlie TIDA neuron recovery from toxicant exposure and adapt these mechanisms in an attempt to rescue NSDA neurons from toxicity. NSDA neurons show loss of axon terminal DA concentrations following acute (20mg/kg; s.c.) and chronic (10 x 20mg/kg; s.c. over 35 days) MPTP administration and exhibit cell death following chronic MPTP administration. In contrast, TIDA neurons show no loss of axon terminal DA concentrations or cell death following acute or chronic MPTP exposure. The recovery of TIDA neurons is independent of extrinsic factors such as decreased toxicant exposure or hormonal activation. TIDA neuron recovery is associated with an increase in the PD-associated proteins, parkin and ubiquitin carboxy-terminal hydrolase L-1 (UCHL-1) within the arcuate nucleus (ARC) 24 h following MPTP. Additionally, parkin protein concentrations remain elevated in the ARC for up to 22 days following chronic MPTP administration. In contrast, the susceptibility of NSDA neurons is associated with decreased expression of both parkin and UCH-L1. The high correlation between the presence of the parkin protein and the recovery of DA neurons from MPTP toxicity is consistent with a role of parkin in DA neuron survival. In order to determine if parkin is necessary and sufficient in the recovery of TIDA neurons following MPTP, recombinant adeno-associated viral (rAAV) vectors containing parkin shRNA or a scrambled shRNA were created. Mice received stereotaxic ARC injections of rAAV containing either parkin shRNA or scrambled shRNA (250nl/side; 3.5x1013vg/ml), or remained naïve to surgery, and were administered a single injection of MPTP (20mg/kg; s.c.) 30 days following rAAV surgery. Twenty-four h post-MPTP, TIDA neurons were able to recover axon terminal DA concentrations following MPTP in control and scrambled shRNA treated animals. However, axon terminal DA was significantly reduced 24 hr following MPTP exposure following knockdown of parkin in TIDA neurons. To determine if parkin overexpression would protect NSDA neurons from MPTP toxicity, mice received unilateral stereotaxic injection of rAAV containing parkin into the substantia nigra (SN) (500nl; 3.4x1013vg/ml) and were administered a single injection of MPTP (20mg/kg; s.c.) 30 days following rAAV surgery. Twenty-four hours post-MPTP, parkin overexpression was unable to rescue MPTP-induced loss of DA in the striatum (ST), but did rescue MPTP-induced loss of tyrosine hydroxylase (TH) in the SN and ST. These findings are consistent with the following conclusions: 1) TIDA neuronal recovery from acute MPTP exposure is independent of extrinsic factors and is mediated by an intrinsic ability to increase expression of neuroprotective proteins, 2) The ability of TIDA neurons to up-regulate parkin is at least partially responsible for recovery of axon terminal DA following MPTP, 3) toxicant-induced loss of parkin contributes to MPTP toxicity within NSDA neurons.
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Title
TOWARD PRECISION MEDICINE : EFFECTS OF THE COMMON VAL66MET BDNF VARIANT IN THE AGING BRAIN AND IMPLICATIONS FOR THE FUTURE OF PARKINSON’S DISEASE THERAPEUTICS
Creator
Mercado-Idziak, Natosha Marie
Date
2021
Collection
Electronic Theses & Dissertations
Description
The rs6265 (Val66Met) single nucleotide polymorphism in the gene for brain-derived neurotrophic factor (BDNF) is a common genetic variant that has been shown to alter therapeutic responses in patients with Parkinson’s disease (PD). Possession of the variant Met allele results in decreased activity-dependent release of BDNF by disrupting BDNF transport and sorting into synaptic vesicles. In the experiments detailed in this thesis, I examine the effects of the Val66Met SNP, and its interaction...
Show moreThe rs6265 (Val66Met) single nucleotide polymorphism in the gene for brain-derived neurotrophic factor (BDNF) is a common genetic variant that has been shown to alter therapeutic responses in patients with Parkinson’s disease (PD). Possession of the variant Met allele results in decreased activity-dependent release of BDNF by disrupting BDNF transport and sorting into synaptic vesicles. In the experiments detailed in this thesis, I examine the effects of the Val66Met SNP, and its interaction with aging, on therapeutic efficacy and the development of aberrant side-effects following primary dopamine (DA) neuron transplantation, a restorative experimental therapeutic approach for PD that is currently experiencing a robust revitalization following a decade-long worldwide moratorium. In particular, I hypothesized that rs6265-mediated dysfunctional BDNF signaling is an unrecognized contributor to the limited clinical benefit observed in a subpopulation of individuals with PD despite robust survival of grafted DA neurons and extensive integration into the host brain. I also hypothesized that this genetic variant contributes to the development of graft-induced dyskinesias (GID). To test these hypotheses, we generated a novel CRISPR knock-in rat model of the rs6265 BDNF SNP to investigate for the first time the influence of a common genetic polymorphism on graft survival, functional efficacy, and side-effect burden in subjects grafted with embryonic ventral mesencephalic DA neurons. In two sister studies, I compared these primary endpoints between wild-type (Val/Val) rats and those homozygous for the variant Met allele (Met/Met), in both young adult (8 m.o. at grafting) and middle-aged (15 m.o. at grafting) cohorts. In each study, rats were rendered unilaterally parkinsonian with intranigral 6-hydroxydopamine and primed with levodopa (12 mg/kg M-Fr) to induce stable expression of levodopa-induced dyskinesias (LID), the primary behavioral endpoint for assessing graft function. After levodopa priming, rats received an intrastriatal graft of embryonic ventral mesencephalic neurons (200,000 cells in young adult rats, 400,000 cells in middle-aged rats; E14 wild-type donors) or a sham graft. LID were evaluated for 9-10 weeks post-engraftment, and GID were assessed 24-48 hr prior to sacrifice. In young adult graft recipients, this research demonstrates that: 1) Met/Met rats display enhanced graft efficacy and paradoxically enriched graft-derived neurite outgrowth compared to Val/Val rats, and 2) the Met allele is strongly linked to GID development and this behavioral phenotype is correlated with neurochemical signatures of glutamatergic neurotransmission by grafted DA neurons. In middle-aged graft recipients, this research indicates that: 1) behavioral enhancement associated with the Met allele is maintained with advancing age, and 2) advanced age is associated with the induction of GID in rats of both genotypes despite the presence of widespread intrastriatal grafts. In this rapidly evolving era of precision medicine, understanding mechanisms underlying the beneficial versus detrimental impact of the Val66Met polymorphism, and/or its interaction with aging, will aid in the development of safe and optimized therapeutic approaches for remodeling the parkinsonian striatum.
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Title
THE ROLE OF α-SYNUCLEIN IN CHOLINERGIC NEUROTRANSMISSION IN THE ENTERIC NERVOUS SYSTEM
Creator
Yelleswarapu, Narayana KrishnaChaithanya
Date
2021
Collection
Electronic Theses & Dissertations
Description
Parkinson’s disease (PD) is a slowly progressive neurodegenerative disorder that is manifested by significant motor impairments that decrease the quality of life and increase mortality in our elderly population. Non-motor symptoms in PD are common in patients and occur up to 2 decades prior to the onset of motor symptoms. Gastrointestinal (GI) complications, specifically constipation, is seen in over 50% of patients with PD and can be debilitating and result in malnutrition and weight loss....
Show moreParkinson’s disease (PD) is a slowly progressive neurodegenerative disorder that is manifested by significant motor impairments that decrease the quality of life and increase mortality in our elderly population. Non-motor symptoms in PD are common in patients and occur up to 2 decades prior to the onset of motor symptoms. Gastrointestinal (GI) complications, specifically constipation, is seen in over 50% of patients with PD and can be debilitating and result in malnutrition and weight loss. There is a need to elucidate the underlying mechanisms the lead to gut dysmotility in PD. Moreover, the pathologic event that causes cell death of dopaminergic neurons within the central nervous system (CNS) is observed with the enteric nervous system (ENS) decades prior to pathology in the CNS. This pathologic event is the toxic conversion and aggregation of a presynaptic terminal protein, α-synuclein (αSyn), into Lewy bodies. αSyn plays an important functional role in various cellular processes, including but not limited to, mitochondrial, lysosomal, synaptic vesicle regulation, and protease function. Therefore, we can predict the cascade of events that occur when this protein is no longer functional. Within the ENS, acetylcholine is the primary vesicular neurotransmitter involved in smooth muscle contractions. In this work I aimed to elucidate the role of pathologic αSyn on slow colonic transit disrupting cholinergic neurotransmission. In Chapter 2, we used two mouse models of hαSyn overexpression to target ENS pathology. In Chapter 3, we used a gene knockout of αSyn to further establish a functional role for the protein in cholinergic neurotransmission. We performed immunofluorescence, fecal pellet output, whole gut transit, colonic migrating motor complexes, studied longitudinal smooth muscle contractions, and junctional potentials to put together a thorough picture connecting phenotype to circuitry within the ENS. Our findings discussed in this dissertation shed light on 1) αSyn’s role in cholinergic neurotransmission, and 2) whether αSyn is necessary for normal colonic function and motility. Overall, cholinergic neurotransmission warrants a closer inspection in the ENS in PD. Strong evidence has continued to associate αSyn pathology to cholinergic neurons. Understanding this mechanism may allow for development of therapeutics that may alleviate GI symptoms in the PD population and help focus on discovering an early biomarker in diagnosing PD.
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Title
THE PERSISTENT AND MULTIDIMENSIONAL MICROGLIAL RESPONSE TO PATHOLOGICAL ALPHA-SYNUCLEIN AGGREGATION
Creator
Stoll, Anna C.
Date
2022
Collection
Electronic Theses & Dissertations
Description
Parkinson’s Disease, the second most common neurodegenerative disease, affects approximately 1 million people in the USA with 60,000 newly diagnosed people each year. Pathologically, PD is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies) and the progressive loss of the nigrostriatal dopamine (DA) neurons. While the exact cause of PD remains unknown, mounting evidence has suggested that neuroinflammation may play a significant role in PD...
Show moreParkinson’s Disease, the second most common neurodegenerative disease, affects approximately 1 million people in the USA with 60,000 newly diagnosed people each year. Pathologically, PD is characterized by the presence of proteinaceous alpha-synuclein (α-syn) inclusions (Lewy bodies) and the progressive loss of the nigrostriatal dopamine (DA) neurons. While the exact cause of PD remains unknown, mounting evidence has suggested that neuroinflammation may play a significant role in PD progression. The pathological features of PD can be recapitulated in vivo using the α-syn preformed fibril (PFF) model of synucleinopathy in rats. Specifically, in association with accumulation of phosphorylated α-syn (pSyn) inclusions in the SNpc, microglia increase soma size and MHC-II expression. This microglial response parallels pSyn inclusion formation, peaking at 2 months following intrastriatal PFF injection, months prior to the SNpc degeneration observed in the model. The overarching question of this dissertation is: does the microglial response to pathological α-syn accumulation contribute to degeneration? In Aim 1 of this dissertation an inhibitor of colony stimulating factor 1 receptor (CSF1R) was used to partially deplete microglia within the context of the α-syn PFF rat model in order to determine whether degeneration of the nigrostriatal system can be attenuated. Despite significant microglial depletion, increased soma size and expression of major-histocompatibility complex-II (MHC-II) on microglia within the α-syn inclusion bearing substantia nigra pars compacta (SNpc) was maintained. Further, partial microglia depletion did not impact degeneration of dopaminergic neurons in the SNpc. Paradoxically, long term partial microglial depletion increased the soma size of remaining microglia in both control and PFF rats was associated with widespread MHC-IIir expression in extranigral regions. These results suggest that partial microglial depletion is not a promising anti-inflammatory therapeutic strategy for PD and that this approach may induce a heightened proinflammatory state in remaining microglia. Aim 2 of this dissertation built on a previous study RNA-Seq dataset that identified multiple upregulated innate and adaptive immune transcripts in the inclusion bearing SNpc in the PFF model. Complementary approaches of fluorescent in situ hybridization (FISH) and droplet digital PCR (ddPCR) were used. FISH results identified an a-syn aggregate associated microglial (a-SAM) phenotype that is characterized by upregulation of CD74, CXCl10, RT1-A2, GRN, CSF1R, Tyrobp, C3, C1qa and Fcer1g. ddPCR results identified additional neuroinflammatory genes, Cd4, Stat1, Casp 1, Axl and IL18, that are significantly upregulated in inclusion bearing nigral tissue. Collectively these findings implicate that the deposition of pathological α-syn inclusions in the SNpc is associated with perturbations in immune functions related to complement, inflammasome and T cell activation, phagocytosis, and interferon gamma signaling. Collectively, the findings of these dissertation experiments demonstrate that the microglial response to pathological α-syn aggregation is persistent and multifaceted. This comprehensive understanding of the multidimensional response of microglia to pathological α-syn aggregates may help to uncover novel therapeutic targets that could facilitate future anti-inflammatory, disease-modifying strategies for PD.
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Title
Structural connectivity of an interoception network in schizophrenia
Creator
Yao, Beier
Date
2022
Collection
Electronic Theses & Dissertations
Description
Interoception refers to the processing, integration, and interpretation of bodily signals by the brain. Interoception is key to not only basic survival, but also many cognitive processes, especially motivational and affective functioning. There is emerging evidence suggesting altered interoception in schizophrenia, but its neural underpinning has not been examined. The current study aims to investigate the structural connectivity of a putative interoception network in schizophrenia, and its...
Show moreInteroception refers to the processing, integration, and interpretation of bodily signals by the brain. Interoception is key to not only basic survival, but also many cognitive processes, especially motivational and affective functioning. There is emerging evidence suggesting altered interoception in schizophrenia, but its neural underpinning has not been examined. The current study aims to investigate the structural connectivity of a putative interoception network in schizophrenia, and its relationship with affective functioning and clinical symptoms. Thirty-five participants with schizophrenia (SZ) and 36 healthy control participants (HC) underwent diffusion tensor imaging (DTI) and performed tasks measuring emotional functioning. Probabilistic tractography was used to identify white matter tracts connecting the key hubs forming the interoception network (i.e., rostral and caudal anterior cingulate cortex, ventral anterior insula, dorsal mid and posterior insula, and amygdala). Microstructural integrity of these tracts was compared across groups and correlated with measures of emotional functioning and symptom severity. I found that SZ exhibited altered structural connectivity in the putative interoception network, compared to HC. The structural connectivity of the network was correlated with emotion recognition in HC, supporting a link between the interoception network and emotional functioning. However, this correlation was much weaker in SZ, suggesting less reliance on this network. I did not find a correlation between the structural connectivity and clinical symptoms in SZ. These findings suggest that altered interoception may play a role in illness mechanisms of schizophrenia, especially in relation to emotional deficits.
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Title
Sexual dimorphisms and androgen influence in medial posterodorsal amygdala astrocytes
Creator
Johnson, Ryan T.
Date
2011
Collection
Electronic Theses & Dissertations
Description
The amygdala is a highly interconnected brain region involved in fear, anxiety, social and reproductive behaviors. In humans and laboratory species the amygdala exhibits sexual dimorphisms in neuroanatomy and function both in juveniles and adults. In rodents, the medial posterodorsal amygdala (MePD) is particularly sexually dimorphic and gonadal hormone sensitive, and while neurons have been examined in this region, few reports have examined the potential influence of gonadal hormones on...
Show moreThe amygdala is a highly interconnected brain region involved in fear, anxiety, social and reproductive behaviors. In humans and laboratory species the amygdala exhibits sexual dimorphisms in neuroanatomy and function both in juveniles and adults. In rodents, the medial posterodorsal amygdala (MePD) is particularly sexually dimorphic and gonadal hormone sensitive, and while neurons have been examined in this region, few reports have examined the potential influence of gonadal hormones on other cellular components of the MePD. Astrocytes are a subtype of glia involved in synapse formation and known to be plastic and dynamic cells sensitive to gonadal hormone influence in several brain regions. My dissertation reveals sexual dimorphisms in the number of astrocytes in the juvenile rat MePD and that this sexual dimorphism remains present in adult animals. I also found sex differences in the arbor complexity of astrocytes in adults that are not present prior to puberty. Astrocytes also respond to changes in circulating hormone levels in adulthood. Furthermore, while the sex difference in astrocyte numbers in juvenile animals is androgen receptor-independent, the sex differences found in adult astrocyte numbers and arbor complexity are both androgen receptor-dependent. Finally, I provide evidence that astrocytes in the MePD contain androgen receptors, suggesting that androgens may act directly on these cells. The influence of gonadal hormones on astrocytes in the MePD is likely an important part of pubertal development and has implications for our understanding of the cellular organization of the amygdala and its function.
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Title
ROLE OF VENTRAL TEGMENTAL AREA NEUROTENSIN RECEPTOR-1 NEURONS IN ENERGY BALANCE
Creator
Perez-Bonilla, Patricia
Date
2021
Collection
Electronic Theses & Dissertations
Description
Dopamine (DA) neurons in the ventral tegmental area (VTA) modulate physical activity and feeding behaviors that are disrupted in obesity. Although the heterogeneity of VTA DA neurons has hindered determination of which ones might be leveraged to support weight loss, we have characterized a subset of VTA DA neurons that express NtsR1 (VTA NtsR1 neurons) that are involved in the coordination of energy balance. We hypothesized that 1) increased activity VTA NtsR1 neurons might promote weight...
Show moreDopamine (DA) neurons in the ventral tegmental area (VTA) modulate physical activity and feeding behaviors that are disrupted in obesity. Although the heterogeneity of VTA DA neurons has hindered determination of which ones might be leveraged to support weight loss, we have characterized a subset of VTA DA neurons that express NtsR1 (VTA NtsR1 neurons) that are involved in the coordination of energy balance. We hypothesized that 1) increased activity VTA NtsR1 neurons might promote weight loss behaviors, and that 2) deleting NtsR1 specifically from VTA DA neurons would promote weight gain by increasing food intake and decreasing physical activity. We first used Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to activate VTA NtsR1 neurons in normal weight and diet-induced obese mice.Acute activation of VTA NtsR1 neurons (24hr) significantly decreased body weight in normal weight and obese mice by reducing food intake and increasing physical activity. Moreover, daily activation of VTA NtsR1 neurons in obese mice sustained weight loss over 7 days. Activating VTA NtsR1 neurons also suppressed how much mice worked to obtain sucrose rewards, even when there was high motivation to consume. However, VTA NtsR1 neural activation was not reinforcing, nor did it invoke anxiety, vasodepressor responses or hypothermia. We then used newly generated NtsR1 flox/flox mice to study NtsR1 deletion in both development and adulthood. Curiously, developmental deletion of VTA NtsR1 (by crossing DAT Cre mice with NtsR1 flox/flox mice) had no impact on feeding or body weight. Adult deletion of the receptor (by injecting adeno associated Cre into VTA of adult NtsR1 flox/flox mice), however, resulted in lower body weight and DA-dependent food intake. Altogether, these data suggest that modulating NtsR1 expression in the adult VTA may be useful to safely promote weight loss, and that NtsR1 is worth further exploration for managing obesity.
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Title
Pathology at the neuromuscular junction in mouse models of spinal bulbar muscular atrophy
Creator
Poort, Jessica Erin
Date
2014
Collection
Electronic Theses & Dissertations
Description
Spinal bulbar muscular atrophy (SBMA) is a progressive, late onset neuromuscular disease that results in muscle weakness and atrophy, as well as motoneuron death in men. While pathology at the neuromuscular junction (NMJ) is noted in numerous neurodegenerative diseases, disease-related changes at the NMJ in SBMA have not been explored. Characterizing such changes is not only important for determining whether the NMJ has any role in the functional changes underlying motor dysfunction, but also...
Show moreSpinal bulbar muscular atrophy (SBMA) is a progressive, late onset neuromuscular disease that results in muscle weakness and atrophy, as well as motoneuron death in men. While pathology at the neuromuscular junction (NMJ) is noted in numerous neurodegenerative diseases, disease-related changes at the NMJ in SBMA have not been explored. Characterizing such changes is not only important for determining whether the NMJ has any role in the functional changes underlying motor dysfunction, but also in determining how such potential pathology at the NMJ develops as disease progresses. If for example, pathology emerges first at the NMJ followed by motoneuron death, then the NMJ offers future promise as a therapeutic target for preventing or reversing symptoms of SBMA before motoneurons are lost. We evaluated three different mouse models of SBMA, one overexpressing a wildtype androgen receptor (AR) exclusively in muscle fibers (so called "myogenic" model), a second which expressed the endogenous AR gene with the first exon of the human mutant AR gene "knocked in" (the so called "knock-in" model), and a final model that broadly expresses a full length human AR transgene harboring the SBMA mutation (the so called "97Q" model). Using both confocal microscopy and electron microscopy, I found that all three mouse models show a pathological fragmentation of the NMJ suggestive of functionally weakened synapses. Other changes at the neuromuscular synapse suggesting decreases in synaptic strength that were found in some but not all models include a decline in the number of docked vesicles ready for release in nerve terminals, a widening of synaptic clefts, simplified postsynaptic folds, and an abnormal accumulation of synaptic vesicle and neurofilament proteins. Retrograde axonal transport of endosomes was also characterized in the 97Q model using live imaging confocal microscopy. Despite previously published data, I found no evidence for a disease-related defect in retrograde transport in the 97Q model. The strikingly abnormal morphology of NMJs in all three models raises the possibility that synaptic function is impaired. Such synaptic dysfunction may contribute to or underlie the impairments in motor function associated with SBMA.
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Title
PERTURBATION OF ASTROCYTIC KEAP1-NRF2-ARE PATHWAY AND GLUTAMATE TRANSPORTER EXPRESSION IN SPINAL ASTROCYTIC DEGENERATION
Creator
Wiwatratana, Duanghathai
Date
2021
Collection
Electronic Theses & Dissertations
Description
Several cellular mechanisms are known to be involved in methylmercury (MeHg) induced central nervous system (CNS) toxicity, including the dysregulation of intracellular Ca2+, redox, and glutamate homeostasis. However, the factors that make particular neurons susceptible to MeHg toxicity, and the latency period of neurological signs and symptoms, have not yet been clearly delineated. For example, the spinal dorsal root ganglia (DRG) is the primary target of MeHg. Mercury (Hg) granules are...
Show moreSeveral cellular mechanisms are known to be involved in methylmercury (MeHg) induced central nervous system (CNS) toxicity, including the dysregulation of intracellular Ca2+, redox, and glutamate homeostasis. However, the factors that make particular neurons susceptible to MeHg toxicity, and the latency period of neurological signs and symptoms, have not yet been clearly delineated. For example, the spinal dorsal root ganglia (DRG) is the primary target of MeHg. Mercury (Hg) granules are first detected in spinal cord motor neurons (SMNs) in the non-symptomatic phase, whereas Hg granules are detected in glia later, following with neurological symptoms (Møller-Madsen, 1991). This finding suggested that the latent period (non-symptomatic phase) is associated with Hg accumulation in neurons, while the symptomatic phase occurs following Hg accumulation in glia, and the susceptibility is not associated with Hg granule accumulation in cells (Møller-Madsen, 1991). Astrocytes generally provide glutathione (GSH) for neurons to detoxify toxic insult. In the spinal cord, MeHg might perturb the antioxidant pathway, Keap1-Nrf2-ARE pathway in the spinal cord astrocytes (SCAs) consequently contribute to DRG or SMN susceptibility to MeHg toxicity. In this study, the comparative responses of different SCAs maturity to a non-toxic MeHg concentration (0.1 μM) suggested that the fully mature SCAs (Day in vitro 30; DIV30), were more susceptible to MeHg than SCAs on DIV14. The perturbation of the Keap1-Nrf2-ARE pathway in SCAs (DIV 30) during exposure to sub-toxic MeHg concentration (0.50 μM) caused a biphasic increase in antioxidant genes such as Keap1, Nrf2, Gclc, Abcc1 mRNAs expression. The concomitant increase of glutamate transporter Slc7a11 encoded for the system Xc-, and Slc1a3 encoded for EAAT1, and Slc1a2 encoded for EAAT2 expression during MeHg exposure might suggest the cooperative expression or function of these glutamate transporters. This concomitant expression was further demonstrated in studies using Nrf2-knockout (Nrf2-KO) derived SCAs. The increase of basal Slc7a11 mRNA, was concurrent to the increase of basal Slc1a3 and Slc1a2 mRNA expressions in Nrf2-KO derived SCA. The function of time of MeHg exposure indicated that Nrf2-KO derived SCAs were more susceptible to MeHg than the wild-type (WT)-derived SCAs. The pronounced susceptibility of Nrf2-KO derived SCAs was mainly due to the loss of GSH) metabolism and transport genes Gclc, GPx1, GPx4, and Abcc1 mRNAs in this genotype. MeHg significantly reduced these mRNA expressions in both genotypes. However, not all Nrf2-ARE regulated genes were affected by MeHg in similar ways in these genotypes. For example, MeHg induced the increase of Slc7a11 mRNA expression in WT-derived SCAs, but it appears to cause the reduction of this mRNA expression in Nrf2 KO-derived SCAs. Administration of antioxidant N-acetyl-L-cystine (NAC) in pretreatment (NP), co-treatment (CO), and post-treatment of MeHg (MP) prevented the reduction of SCAs metabolic functions for over 160h. The mechanism of NAC action in preventing MeHg induced SCAs degeneration is primarily due to its thiol antioxidant property.In conclusion, this study suggests that age and genetic predisposition contribute to SCAs susceptibility to MeHg toxicity. The dysregulation of the antioxidant pathways and glutamate homeostasis in SCAs potentially contributes to SMNs or DRG susceptible to MeHg.
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Title
Neural mechanisms of female zebra finch mate choice : the role of the auditory perception sites, the social behavior network, and the reward system
Creator
Svec, Lace Ann
Date
2009
Collection
Electronic Theses & Dissertations
Title
Nanoengineered tissue scaffolds for regenerative medicine in neural cell systems
Creator
Tiryaki, Volkan Mujdat
Date
2013
Collection
Electronic Theses & Dissertations
Description
Central nervous system (CNS) injuries present one of the most challenging problems. Regeneration in the mammal CNS is often limited because the injured axons cannot regenerate beyond the lesion. Implantation of a scaffolding material is one of the possible approaches to this problem. Recent implantations by our collaborative research group using electrospun polyamide nanofibrillar scaffolds have shown promising results in vitro and in vivo. The physical properties of the tissue scaffolds have...
Show moreCentral nervous system (CNS) injuries present one of the most challenging problems. Regeneration in the mammal CNS is often limited because the injured axons cannot regenerate beyond the lesion. Implantation of a scaffolding material is one of the possible approaches to this problem. Recent implantations by our collaborative research group using electrospun polyamide nanofibrillar scaffolds have shown promising results in vitro and in vivo. The physical properties of the tissue scaffolds have been neglected for many years, and it has only recently been recognized that significant aspects include nanophysical properties such as nanopatterning, surface roughness, local elasticity, surface polarity, surface charge, and growth factor presentation as well as the better-known biochemical cues.The properties of: surface polarity, surface roughness, local elasticity and local work of adhesion were investigated in this thesis. The physical and nanophysical properties of the cell culture environments were evaluated using contact angle and atomic force microscopy (AFM) measurements. A new capability, scanning probe recognition microscopy (SPRM), was also used to characterize the surface roughness of nanofibrillar scaffolds. The corresponding morphological and protein expression responses of rat model cerebral cortical astrocytes to the polyamide nanofibrillar scaffolds versus comparative culture surfaces were investigated by AFM and immunocytochemistry. Astrocyte morphological responses were imaged using AFM and phalloidin staining for F-actin. Activation of the corresponding Rho GTPase regulators was investigated using immunolabeling with Cdc42, Rac1, and RhoA. The results supported the hypothesis that the extracellular environment can trigger preferential activation of members of the Rho GTPase family, with demonstrable morphological consequences for cerebral cortical astrocytes. Astrocytes have a special role in the formation of the glial scar in response to traumatic injury. The glial scar biomechanically and biochemically blocks axon regeneration, resulting in paralysis. Astrocytes involved in glial scar formation become reactive, with development of specific morphologies and inhibitory protein expressions. Dibutyryl cyclic adenosine monophosphate (dBcAMP) was used to induce astrocyte reactivity. The directive importance of nanophysical properties for the morphological and protein expression responses of dBcAMP-stimulated cerebral cortical astrocytes was investigated by immunocytochemistry, Western blotting, and AFM. Nanofibrillar scaffold properties were shown to reduce immunoreactivity responses, while PLL Aclar properties were shown to induce responses reminiscent of glial scar formation. Comparison of the responses for dBcAMP-treated reactive-like and untreated astrocytes indicated that the most influential directive nanophysical cues may differ in wound-healing versus untreated situations.Finally, a new cell shape index (CSI) analysis system was developed using volumetric AFM height images of cells cultured on different substrates. The new CSI revealed quantitative cell spreading information not included in the conventional CSI. The system includes a floating feature selection algorithm for cell segmentation that uses a total of 28 different textural features derived from two models: the gray level co-occurance matrix and local statistics texture features. The quantitative morphometry of untreated and dBcAMP-treated cerebral cortical astrocytes was investigated using the new and conventional CSI, and the results showed that quantitative astrocyte spreading and stellation behavior was induced by variations in nanophysical properties.
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Title
NOVEL IMPACTS OF HOST-ENVIRONMENT INTERACTIONS IN ENTERIC GLIA THROUGH SEQUENCING AND IN-SITU EXPRESSION
Creator
Ponnampalam, Christine Dharshika
Date
2021
Collection
Electronic Theses & Dissertations
Description
The enteric nervous system (ENS) is comprised of enteric neurons and glia that facilitate essential gastrointestinal (GI) function including motility, visceral sensation, absorption, and gut permeability. Enteric neurons and glia are responsive to environmental cues and stressors ranging from the local gut microenvironment to the host’s psychosocial state and understanding how the ENS integrates these cues to modulate local and systemic function is critical. Novel roles for enteric neurons in...
Show moreThe enteric nervous system (ENS) is comprised of enteric neurons and glia that facilitate essential gastrointestinal (GI) function including motility, visceral sensation, absorption, and gut permeability. Enteric neurons and glia are responsive to environmental cues and stressors ranging from the local gut microenvironment to the host’s psychosocial state and understanding how the ENS integrates these cues to modulate local and systemic function is critical. Novel roles for enteric neurons in host-environmental interactions have been discovered using specialized sequencing technologies but these tools have not yet readily investigated enteric glia. The goal of this dissertation was to develop and utilize genetic technologies to characterize enteric glial responses to environmental mediators. First we adapted existing genetic tools to study molecular changes in the ENS and specifically enteric glia. We developed effective means of characterizing enteric glial expression within complex in vivo models using the RiboTag model with RNA-sequencing and subsequently visualized changes in gene expression within enteric ganglia in situ. We then utilized these techniques to investigate sex-specific responses to early life stress in enteric glia. Enteric glia from male and female mice have contrasting expression profiles including differences in GPCR signaling that could contribute to sex-specific ENS signaling mechanisms and ultimately GI disease outcomes. This supports recent findings of sexual dimorphism in glial functional connectivity and may highlight a critical difference in the way enteric glia communicate with other cell types between males and females. Additionally enteric glia from male mice ‘feminize’ following iiiearly life stress through altered expression of GI and neurological disease genes including mechanisms of glial-immune communication like type I interferon signaling. Together these data highlight striking differences in the physiologic molecular patterns and nature of stress response in enteric glia between males and females that likely contribute to sexually dimorphic GI disease patterns and symptom presentation. Next we investigated ENS type I interferon responses through the stimulator of interferon genes (STING) pathway. STING responds to both microbial and host mediators to contribute to GI inflammation. However the role of STING signaling in the gut is complex and can either exacerbate or ameliorate inflammation likely dependent on complex microenvironmental factors. We provide the first known investigation of STING expression and signaling within the ENS. STING is expressed in both enteric neurons and glia but IFNB is only expressed in enteric neurons. ENS STING is activated by its canonical ligands toproduce type I interferons. However this is likely primarily mediated through canonical activation of enteric neuronal STING and the contribution of enteric glial STING to type I IFN response is minor. Additionally enteric glial STING does not alter gastrointestinal outcomes during acute colitis within the DSS colitis model. Taken together these findings suggest enteric glia do not utilize STING for canonical type I IFN signaling or contribute to disease pathology in acute DSS colitis. Enteric glial STING may instead utilize primordial and specialized signaling pathways that more selectively alter local function. Together our data provide novel genetic tools and data to further uncover molecular functions in enteric glia and their role in GI and systemic health. Using these we discovered entirely novel molecular interaction effects between sex and early life stress that shift the framework of these risk factors in GI disease. Furthermore we highlight a novel potential mediator of ENS-microbe communication with STING. Our findings further characterize the molecular patterns used by glia in response to complex environmental factors and highlight unique heterogeneity in glial intercellular communication.
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Title
NEUROTECHNOLOGY DESIGN FEATURES’ IMPACT ON THE FUNCTION AND IDENTITY OF REACTIVE ASTROCYTES
Creator
Riggins, Ti'Air
Date
2021
Collection
Electronic Theses & Dissertations
Description
Implantable neurotechnology offers substantial promise to improve the condition of many neurodegenerative diseases. Microelectrode arrays implanted in the brain have the capability to stimulate or record electrical activity from neighboring cells. However, shortly after implantation, a foreign body response occurs, which is what researchers believe decreases the electrical recording stability and longevity of signal detection of these devices. Established biomarkers such as astrogliosis, and...
Show moreImplantable neurotechnology offers substantial promise to improve the condition of many neurodegenerative diseases. Microelectrode arrays implanted in the brain have the capability to stimulate or record electrical activity from neighboring cells. However, shortly after implantation, a foreign body response occurs, which is what researchers believe decreases the electrical recording stability and longevity of signal detection of these devices. Established biomarkers such as astrogliosis, and stimuli such as the mechanical mismatch at the device-tissue interface, have been studied to understand the tissue response to the devices. However, the relationship of these factors with device performance is not well understood. Astrocytes play an important role in the brain’s immune system and recently, RNA analysis has confirmed transcriptional profiles of reactive astrocytes which are associated with specific injury states and neurodegenerative diseases. In this dissertation, I have investigated new biomarkers of astroglial reactivity at the electrode interface and characterized the surface topography and bending stiffness of devices. I induced two types of inflammatory astrocytic cell culture models, and I characterize each model’s reactivity in comparison to gene expression surrounding electrodes implanted in rat tissue. Atomic microscope microscopy (AFM) techniques were also used to measure surface roughness and bending stiffness as it may predict cellular adhesion and device performance. I aim to elucidate pathways in the neurological foreign body response which will give researchers new potential biomarkers to target to improve recording performance, motivating improved designs for implantable neurotechnology. The research presented in this dissertation investigates how design features influence the tissue interface and asks questions about possible ways to mitigate tissue response: (1) by exploring and summarizing the design space as a whole, suggesting ways to characterize designs and evaluating each designs’ successes and limitations (2) using a cutting edge imaging technique to image and measure material properties of three commonly used materials, (3) and creating a reactive tissue culture model, comparing its proteomic and genetic expression to the established rat model. Chapter 2 describes surface characterization techniques that could be used to better classify device features to predict performance and explores next generation probes from a design and performance standpoint. Chapter 3 uses atomic force microscopy to image and measure surface roughness on device surfaces while also measuring the bending stiffness to help determine possible micromotion in the brain. Here, we speculate what these findings mean for the performance and longevity of current probe design. Chapter 4 develops an astroglial culture model to mimic foreign body response in the brain and compare the genomic results to tissue culture near and far from the implanted device. Here, we report the transcriptomic results of the model in comparison to brain transcriptomic results, and what these biomarkers may implicate regarding tissue response and neurodegenerative signaling. This body of work uncovers knowledge recapitulating important factors of device features that affects tissue signaling at the tissue device interface, and biomarkers that play a role and cell signaling. Future directions aim at developing a more physiologically relevant tissue culture model that can predict clinical outcomes, and use high throughput screening techniques to help researchers address the challenge of long term suboptimal device performance.
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Title
Masking : the acute effects of light on the brain and behavior
Creator
Shuboni, Dorela Doris
Date
2013
Collection
Electronic Theses & Dissertations
Description
Masking of behavior by external stimuli works with the circadian system to ensure that animals are active during the correct time-of-day. Light for diurnal and nocturnal species produces different masking responses, enhancing activity for diurnal species and suppressing activity for nocturnal species. Few studies have examined the neural mechanisms of masking; none these experiments use animals active during the day. The first experiment of this dissertation uses the protein of the immediate...
Show moreMasking of behavior by external stimuli works with the circadian system to ensure that animals are active during the correct time-of-day. Light for diurnal and nocturnal species produces different masking responses, enhancing activity for diurnal species and suppressing activity for nocturnal species. Few studies have examined the neural mechanisms of masking; none these experiments use animals active during the day. The first experiment of this dissertation uses the protein of the immediate-early gene cFOS to compare activation of brain regions to light between nocturnal mice and diurnal grass rats during a time-point where they showed a distinct behavioral dichotomy in response. Grass rats showed a consistent increase in activation in areas that receive retinal innervation or were related to sleep/arousal, while mice showed either no difference or a decrease in activation with the exception of the SCN. This study demonstrates the differences in behavioral and neurological responses to masking pulse of light between a nocturnal and diurnal rodent species.We next examined the functional role of the ventral subparaventricular zone (vSPZ) on masking to light in the grass rat. The vSPZ uniquely responded to light in diurnal grass rats, receives direct retinal innervation from the eye and after ablation showed a possible alteration in masking. Schwartz et al. (2009)showed that grass rats with damage to the vSPZ had bouts of arrhythmia in LD conditions, indicating that the masking system may be altered. In Chapter 3, we tested the functional for of the region by bilateral lesioning the vSPZ and directly testing the effects of light on masking. Animals with complete ablations still increased activity in response to light in two different masking protocols. In Chapter 4, we examined another brain structure that could have played a role in masking, the pineal gland. Melatonin is a hormone produced by the pineal gland that plays a role in circadian rhythms and seasonality. The expression of melatonin is sensitive to light exposure, additionally, the presence of the hormone also feedbacks and influences the effects of light on the brain. Additionally, pinealectomy in rats alters the behavior profile of activity in LD conditions. Removal of the pineal gland in the grass rats did not influence the ability of animals to mask to light or the animal's circadian rhythm of activity.In summary, the work presented in this dissertation demonstrates the immediately impact of light on behavior and the possible brain regions that may play a functional role in the masking response. We established that two neural structures when ablated or removed do not impact the grass rat's ability to respond to light with an increase in activity. Here we broaden the scope of research into the neural mechanisms of masking to include a diurnal species, beginning the journey toward understanding the neural changes needed for a species to transition between temporal niches.
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Title
MIND-BODY STATE LITERACY : A PEDAGOGICAL APPROACH THAT USES MINDFULNESS AND BRAIN LITERACY TO SUPPORT LEARNING AND RELATIONAL NARRATIVE WORK
Creator
Schaefer, Erin Elizabeth
Date
2020
Collection
Electronic Theses & Dissertations
Description
Mind-Body State Literacy: A Pedagogical Approach that uses Mindfulness and Neuroscience to Support Learning and Relational Narrative Work describes the literacies necessary to develop the habits of minds presented in the Framework for Success in Postsecondary Writing: “curiosity, openness, engagement, creativity, persistence, responsibility, flexibility and metacognition” (WPA, NCTE, & NWP, 2011, par. 2). Such habits, because they deal with students’ openness in the learning process, are key...
Show moreMind-Body State Literacy: A Pedagogical Approach that uses Mindfulness and Neuroscience to Support Learning and Relational Narrative Work describes the literacies necessary to develop the habits of minds presented in the Framework for Success in Postsecondary Writing: “curiosity, openness, engagement, creativity, persistence, responsibility, flexibility and metacognition” (WPA, NCTE, & NWP, 2011, par. 2). Such habits, because they deal with students’ openness in the learning process, are key to students’ ability to receive a liberal education. I suggest that before instructors or students can develop these habits, they need to learn to develop an open mind-body state, defined as the ability to let one’s narrative incorporate other narratives/perspectives through listening. The Mind-Body State model is comprised of three facets: brainwaves, narratives, and emotions. The Mind-Body State Literacy (MBSL) approach suggests that students develop literacies related to these three facets, drawing primarily from mindfulness practices and philosophies the center the body and compassion. I anchor my presentation of the MBSL by suggesting why it might be especially relevant as students engage in personal narrative writing in the Rhetoric and Writing classroom.
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Title
MAPPING THE TAU PROTEIN INTERACTOME USING THE BIOID2 IN SITU LABELLING APPROACH
Creator
Atwa, Ahmed
Date
2022
Collection
Electronic Theses & Dissertations
Description
Pathological inclusions composed of tau protein are hallmarks of neurodegenerative diseases collectively known as tauopathies, of which the most common is Alzheimer’s Disease (AD). Tau is most well-known as a microtubule-associated protein involved in regulating microtubule dynamics, but accumulating evidence suggests tau is involved in many biological functions. Deciphering the tau protein interactome is critical for better understating the physiological and pathological roles of tau. This...
Show morePathological inclusions composed of tau protein are hallmarks of neurodegenerative diseases collectively known as tauopathies, of which the most common is Alzheimer’s Disease (AD). Tau is most well-known as a microtubule-associated protein involved in regulating microtubule dynamics, but accumulating evidence suggests tau is involved in many biological functions. Deciphering the tau protein interactome is critical for better understating the physiological and pathological roles of tau. This work aimed to identify tau interacting partners using the in situ protein labelling BioID2 method by creating fusion proteins between full-length human tau and either BioID2 on the N-terminus (BioID2-Tau) or C-terminus (Tau-BioID2). A total of 372 proteins were identified, of which 269 interacted with Tau-BioID2, 169 with BioID2-Tau, and 66 proteins overlapped between both tau proteins. Gene Ontology (GO) cellular component analysis mapped protein interactions in the mitochondria, cytoskeleton, dendrites, nucleus, synaptic vesicles, and the ribonucleoprotein complex. While GO molecular function pathways identified proteins involved in RNA binding, translation regulation, ubiquitin ligase activity, kinase binding, mitochondrial oxidoreductase, and peroxidase activity. KEGG pathway analysis identified proteins associated with neurodegenerative diseases, including AD, Parkinson’s disease, Huntington’s disease, and Amyotrophic lateral sclerosis. Thus, this approach can identify members of the tau interactome via in situ labeling, that may help shed light on tau’s functional roles and provide novel therapeutic strategies for neurodegenerative diseases.
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Title
Investigating Cognition in Howard Engel's Memory Book : Literary Interventions and Intercessions in Scientific Models of Memory
Creator
Cave, Kylene N.
Date
2022
Collection
Electronic Theses & Dissertations
Description
Crime fiction orbits around the concept of memory. At its core, crime narratives are concerned with reconstructing the past, bringing to light the events surrounding the criminal mystery. Memory also manifests in the genre’s detective figures, its modes of detection, and in the eyewitness testimonies used to solve the criminal mystery. In most crime narratives memory operates as a simplistic plot device used to temporarily complicate the mystery and, as such, it is rarely read beyond the...
Show moreCrime fiction orbits around the concept of memory. At its core, crime narratives are concerned with reconstructing the past, bringing to light the events surrounding the criminal mystery. Memory also manifests in the genre’s detective figures, its modes of detection, and in the eyewitness testimonies used to solve the criminal mystery. In most crime narratives memory operates as a simplistic plot device used to temporarily complicate the mystery and, as such, it is rarely read beyond the cursory scope of trauma. This dissertation, however, argues that crime narratives depicting extreme and rare cases of memory—like amnesia—help trace the boundaries around average functioning memory and reveal useful ways for conceptualizing how memory functions, and what disciplines have the impetus to do so. In this dissertation I argue that Howard Engel’s novel, Memory Book (2005), examines the complexities of memory by accomplishing three narratological tasks, distinguishing it from other crime fiction narratives and their more traditional handling of issues of memory and recall. The first task involves placing memory at the center of the narrative and elevating the mystery of the mind to the forefront of the plot. In placing memory at its center, the novel pushes back against traditional and widely popular scientific models of memory as merely the process of remembering and forgetting, advocating for a theory that is more complex and heterogenous. The second narratological task involves the novel’s ability to act as a literary intercessor on behalf of the sciences to translate and disseminate theories of memory to the layperson. Within this task, however, I assert that the novel not only passively intercedes, but actively intervenes in the study of memory by highlighting the inherent limitations of purely scientific or medical models of memory. In exposing these constraints, the novel also suggests a blended, transdisciplinary approach to conceptualizing human memory function and the mind. Lastly, the final task asserts that Memory Book is distinct because its narrative is infused with elements of lived experience, elements the scientific method is incapable of capturing in its probing of memory and cognition. Pointing specifically to Engel’s authorship and the circumstances surrounding the narrative’s composition following a stroke, I argue that the text intentionally blurs the boundaries between reality and fiction as a way of investigating the real-world implications of wrestling with memory loss and brain-injury based amnesia. Each of these narratological tasks is systematically analyzed by engaging with the Howard Engel’s memoir—The Man Who Forgot How to Read—deeply engaging with the novel’s paratextual elements, and through a detailed close reading of the novel.
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Title
Interview of Dr. Deborah Wagenaar, professor in the Michigan State University Department of Psychiatry
Creator
Wagenaar, Deborah
Date
2017-07-18
Collection
G. Robert Vincent Voice Library Collection
Description
Dr. Deborah Wagenaar DO, MS, professor in the Michigan State University Department of Psychiatry, talks about her career at MSU, specializing in geriatric psychiatry, and working with older adults and their multiple medical problems. Wagenaar says she was born and raised in Southeast Michigan and did her undergrad at Wayne State University. She describes the work environment in the College as "feeling like home." Wagenaar says she was initially reluctant to pursue psychiatry but it grew on...
Show moreDr. Deborah Wagenaar DO, MS, professor in the Michigan State University Department of Psychiatry, talks about her career at MSU, specializing in geriatric psychiatry, and working with older adults and their multiple medical problems. Wagenaar says she was born and raised in Southeast Michigan and did her undergrad at Wayne State University. She describes the work environment in the College as "feeling like home." Wagenaar says she was initially reluctant to pursue psychiatry but it grew on her over time. She says she has a goal of inspiring students to pursue geriatric psychiatry as a specialty and recommends exposing students to older patients early in their education. Wagenaar talks about the current state of psychiatric education and how the neurosciences are likely to change the field. She talks about some of the advances in the field for treating depression, dementia, and other maladies.
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Title
Heterogeneous Thalamic Reticular Nucleus Neurons and Their Functional Role in Thalamocortical Processing
Creator
Harding-Jackson, Laura
Date
2021
Collection
Electronic Theses & Dissertations
Description
The thalamic reticular nucleus (TRN) is an integral regulator of information flow between the thalamus and cortex. The TRN receives synaptic inputs from both cortical and thalamic regions and based upon this information it selectively inhibits thalamic activity. TRN neurons produce action potentials in two distinct modes: a fast, transient burst discharge from a hyperpolarized state, and a prolonged, tonic discharge from a relatively depolarized state. While previous studies have...
Show moreThe thalamic reticular nucleus (TRN) is an integral regulator of information flow between the thalamus and cortex. The TRN receives synaptic inputs from both cortical and thalamic regions and based upon this information it selectively inhibits thalamic activity. TRN neurons produce action potentials in two distinct modes: a fast, transient burst discharge from a hyperpolarized state, and a prolonged, tonic discharge from a relatively depolarized state. While previous studies have characterized burst discharge as a transient high frequency discharge (> 250 Hz), these electrophysiological studies reveal a highly variable range of burst frequencies (4- 342 Hz). In these studies, I aim to discover the mechanisms underlying these highly variable burst frequencies, as well as their functional role in thalamocortical processing.In chapter two, I found that bursts from TRN neurons with relatively higher frequency discharge (>100 Hz) contain more action potentials per burst. These neurons also have higher input resistances, broader action potentials, higher action potential thresholds, and larger somas. The amplitude of the T-type calcium channel-mediated low-threshold spike, which underlies the burst discharge, is positively correlated with both the burst discharge frequency and the number of action potentials per burst. I next investigated whether small conductance calcium-activated potassium channels (SK channels) could mediate the differences in burst firing rate and action potential number. Blocking SK channels increased the frequency and duration of the burst but did not increase the amplitude of the underlying T-type calcium current. Prior studies suggest that T-type calcium channels are distributed along the dendrites in TRN neurons with high frequency burst discharge. In chapter three, I examine the distribution of dendritic calcium activity within the lower frequency bursting neurons. While the calcium signal was lower in these neurons all along the dendrites, the calcium signal was evenly distributed across proximal, intermediate, and distal dendritic regions. Investigation of SK channel activity revealed significant location-specific effects. In lower frequency bursting neurons, SK channels had the greatest influence at proximal and distal locations. In higher frequency bursting neurons, SK channels had the greatest influence at proximal and intermediate dendritic locations. Heterogeneous TRN burst discharge frequencies may represent a diverse cell population with unique dendritic ion channel composition and distribution. These results may improve our understanding of the mechanisms of TRN neuron afferent synaptic integration as well as modulation of thalamocortical inhibition. In chapter four I investigate whether intrinsic properties of TRN neurons are altered in the Fmr1-KO mouse model of Fragile X Syndrome (FXS). Individuals with FXS experience a variety of comorbidities that could involve TRN function, such as altered sensory perceptions, sleep disorders, and epilepsy. Analysis of intrinsic cellular properties revealed no differences in TRN neuron properties. Further investigation of synaptic plasticity, which is an abnormal finding in several other brain regions in FXS, also revealed no pathology. These findings suggest that TRN dysfunction does not contribute to FXS pathology.
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Title
Enteric glial modulation of immune activation during inflammatory stress
Creator
Chow, Aaron Kin Yeung
Date
2020
Collection
Electronic Theses & Dissertations
Description
Gastrointestinal (GI) disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome, and other functional GI disorders are major health concerns and account for about $26.4 billion in yearly costs in the United States alone. Many of these GI disorders manifest symptoms such as GI dysmotility, intestinal secretion and absorption dysfunction, and abdominal pain. Inflammation plays a major role in the pathogenesis of these diseases, and current therapies for many GI disorders aim...
Show moreGastrointestinal (GI) disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome, and other functional GI disorders are major health concerns and account for about $26.4 billion in yearly costs in the United States alone. Many of these GI disorders manifest symptoms such as GI dysmotility, intestinal secretion and absorption dysfunction, and abdominal pain. Inflammation plays a major role in the pathogenesis of these diseases, and current therapies for many GI disorders aim to regulate the activation and progression of the inflammatory cascade. However, due to a gap in knowledge in how the immune system is regulated within the GI tract, there remains a lack of effective treatments for these common GI disorders. Interactions between the nervous system and immune system point to neurons having important roles in immune modulation, but the mechanisms of neuro-immune regulation in the gut is not completely understood.The enteric nervous system (ENS) consists of enteric neurons and enteric glia arranged in plexuses embedded in the gut wall. This neural network is responsible for the normal secretomotor functioning of the GI tract, and the disruption of the ENS network alters GI functioning and underlies pathological GI symptoms. As part of the ENS, enteric glia work in tandem with enteric neurons to coordinate GI functions. In addition to their contributions to maintain normal secretomotor functioning of the GI tract, enteric glia are activated by immunomodulatory signals, they can secrete and respond to cytokines, can exert immunosuppressive effects, and share characteristics with antigen presenting cells. Therefore, we hypothesize that enteric glia play an active role in immune regulation in the ENS.In this dissertation, we specifically examine the role enteric glial cells play as an antigen presenting cell to regulate immune activation. Our results show that enteric glia have the machinery necessary to act as an antigen presenting cell and can express major histocompatibility complex (MHC) type II molecules during inflammatory stress to interact with T-lymphocytes. Enteric glial MHC II expression has functional relevance, as it modulates the activation in Th17 and Treg subtypes, but not Th1 or Th2 T-lymphocyte subtypes. Although MHC II molecules are typically associated with the expression of phagocytosed extracellular antigens, our results show that enteric glia do not readily phagocytose extracellular antigens. Instead, MHC II expression in enteric glia is mediated by autophagy. The activation of autophagic pathways is necessary, but not sufficient in eliciting enteric glial MHC II expression. Finally, although enteric glia regulate T-lymphocyte activation, cytokine levels at the whole organism or regional tissue levels remain unchanged, suggesting that enteric glial cytokine effects primarily operate at the local microenvironment level.Our findings provide support for enteric glial cells having an active role as an immunomodulator. Specifically, we show that enteric glia modulate T-lymphocyte activation via autophagy-mediated MHC II expression and propose a novel mechanism of neuro-immune modulation in the gut.
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