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- Title
- A role for DeltaFosB in the regulation of parkin in brain regions containing differentially susceptible dopaminergic neurons
- Creator
- Patterson, Joseph Robert
- Date
- 2016
- Collection
- Electronic Theses & Dissertations
- Description
-
The hallmark pathologies of Parkinson disease (PD) are the formation of Lewy bodies and the progressive loss of nigrostriatal dopamine (NSDA) neurons. In mice, the NSDA neurons are preferentially damaged through exposure to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Another population of DA neurons that are initially damaged by MPTP, but are able to recover are the tuberoinfundibular DA (TIDA) neurons. Parkin is a product of the PARK2 gene, which is linked to...
Show moreThe hallmark pathologies of Parkinson disease (PD) are the formation of Lewy bodies and the progressive loss of nigrostriatal dopamine (NSDA) neurons. In mice, the NSDA neurons are preferentially damaged through exposure to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Another population of DA neurons that are initially damaged by MPTP, but are able to recover are the tuberoinfundibular DA (TIDA) neurons. Parkin is a product of the PARK2 gene, which is linked to autosomal recessive or juvenile PD. Parkin has multiple functions in neurons and is predicted to protect against the neurotoxic effects of MPTP. Potential transcription factors of parkin were identified using TFSEARCH, PROMO, and Patch 1.0, and refined to 11 based the transcription factor being identified in all three programs, being known to be found in the brain, and known to respond to a type of stress that MPTP could cause. The candidate transcription factors were examined at 6 h after MPTP in regions containing the cell bodies of TIDA and NSDA neurons. From these candidates, only FosB and ΔFosB have expression patterns that mirror parkin.Further examination of the temporal expression and cellular localization of FosB and ΔFosB after acute neurotoxicant administration were examined. Regions containing the cell bodies of the TIDA (arcuate nucleus; ARC) and NSDA (substantia nigra; SN) neurons were dissected and processed for Western blot analysis. The results reveal that expression of FosB and ΔFosB correlates with parkin, increasing in the ARC and not in the SN. Furthermore, total FosB protein was localized to nuclei of NSDA and TIDA neurons, and expression of each FosB and ΔFosB examined in cytoplasmic and nuclear fractions derived from the ARC and SN. Though the number of DA neurons expressing total FosB does not change at 6 h post-MPTP, ΔFosB does increase in the nuclear fraction from the ARC.AAV-mediated expression vectors were used to increase ΔFosB in the NSDA and TIDA neurons, in both cases, parkin increased about 2-fold. The dominant negative protein ΔJunD, which lacks a DNA binding domain, predominantly dimerizes with the FosBs and inhibits their ability to act as transcription factors was injected into the ARC. The AAV-ΔJunD virus blocked the increase of parkin after MPTP in the TIDA neurons. Taken together, the results support the role of FosB and ΔFosB as transcription factors of parkin, since they are predicted to bind the Park2 promoter, their expression correlates with the differential expression of parkin, increases prior to parkin, are present in nuclei of TIDA neurons, ΔFosB is sufficient to drive parkin expression, and ΔJunD blocks the increase of parkin in the ARC in response to MPTP.
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- Title
- Parkin mediated mitochondrial quality control in central dopamine neurons
- Creator
- Hawong, Hae-young
- Date
- 2014
- Collection
- Electronic Theses & Dissertations
- Description
-
Parkinson disease (PD) is the second most common neurodegenerative disease. The hallmark pathology of PD is progressive degeneration of nigrostriatal dopamine (NSDA) neurons, but the hypothalamic tuberoinfundibular (TI) DA neurons remain intact. A similar pattern of susceptibility can be seen in these DA neuronal populations following single acute exposure to the mitochondrial Complex I inhibitor, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this dissertation, mitochondrial...
Show moreParkinson disease (PD) is the second most common neurodegenerative disease. The hallmark pathology of PD is progressive degeneration of nigrostriatal dopamine (NSDA) neurons, but the hypothalamic tuberoinfundibular (TI) DA neurons remain intact. A similar pattern of susceptibility can be seen in these DA neuronal populations following single acute exposure to the mitochondrial Complex I inhibitor, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this dissertation, mitochondrial structure and function in NSDA and TIDA axon terminals in WT mice were investigated. An increase in mitochondrial bioenergetics, mass, and mitophagosomes were observed in mitochondria derived from medial basal hypothalamus (MBH) containing TIDA neurons as compared to striatum (ST) containing NSDA neurons. The ultrastructure of the mitochondria from the two brain regions did not differ, but MBH had higher numbers of mitochondria per synaptosome than ST. Mitochondrial function differed depending on the brain regions in WT mice. However, mitochondria derived from ST and MBH responded to Complex I inhibition in a similar manner. This suggests that intrinsic differences in the sensitivity of mitochondrial electron transport chain (ETC) enzymes to neurotoxicant inhibition are not responsible for differential susceptibility of NSDA and TIDA neurons to MPTP.Parkin is a 52Kda cytosolic protein originally identified by linkage analysis in autosomal recessive early onset PD. Parkin is reported to mediate mitochondrial quality control through autophagy of mitochondria, and increased parkin expression is associated with resistance of TIDA neurons to acute MPTP exposure. Parkin may protect against DA neurodegeneration by maintaining mitochondrial homeostasis in central DA neurons. To test this hypothesis, mitochondrial structure and function in NSDA and TIDA neurons were investigated in parkin null mice. Reduced mitochondrial maximal and spare respirations, mitochondrial mass, number of mitochondria per synaptosome, and disrupted mitochondrial ultrastructure were all observed in the absence of parkin. These results suggest that impaired mitochondrial function is due to decreased numbers of high quality mitochondria in DA axon terminals in the ST of parkin deficient mice. This may be due to loss of parkin-mediated mitochondrial quality control in NSDA neurons. Parkin rescue via rAAV expression in the midbrain failed to alter impaired mitochondrial function in parkin null mice. However, parkin overexpression prevented inhibition of maximum and spare respiration by MPTP. These results suggest parkin overexpression maintained functional mitochondria likely through autophagy in response to acute neurotoxicant exposure. Therefore, loss of parkin mediated mitochondrial quality control may contribute to loss of NSDA neurons in a neurotoxicant model of DA neuronal degeneration in PD.
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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
- UCH-L1 as a susceptibility factor for nigrostriatal and mesolimbic dopamine neurons after neurotoxicant exposure and aging
- Creator
- Winner, Brittany Michele
- Date
- 2017
- Collection
- Electronic Theses & Dissertations
- Description
-
Parkinson disease (PD), the second most prevalent neurodegenerative disorder, is most commonly diagnosed in elderly individuals and is characterized by manifestation of motor deficits such as bradykinesia, postural instability, resting tremor, and shuffling gait. These motor symptoms of PD arise when dopamine (DA) neurons in the nigrostriatal DA (NSDA) pathway degenerate, causing loss of basal ganglia regulation of voluntary motor coordination. Other DA neuronal pathways in the central...
Show moreParkinson disease (PD), the second most prevalent neurodegenerative disorder, is most commonly diagnosed in elderly individuals and is characterized by manifestation of motor deficits such as bradykinesia, postural instability, resting tremor, and shuffling gait. These motor symptoms of PD arise when dopamine (DA) neurons in the nigrostriatal DA (NSDA) pathway degenerate, causing loss of basal ganglia regulation of voluntary motor coordination. Other DA neuronal pathways in the central nervous system are less affected by neuronal death, however: mesolimbic DA (MLDA) neurons are less vulnerable to loss in PD. Therefore, we seek to understand how MLDA neurons resist degeneration. Since Lewy bodies, which are proteinaceous deposits of misfolded and aggregated proteins, are the hallmark pathology of PD, we predict that major deficits in protein degradation are involved in development and progression of this disease. MPTP exposure in rodents recapitulates loss of DA and oxidative stress observed in patients with PD and can also be used to recapitulate the differential susceptibility of NSDA and MLDA neurons. A gene found mutated in a rare case of familial PD called ubiquitin carboxy-terminal hydrolase L1 (UCHL1) is involved in proteostasis functioning as a deubiquitinating enzyme to maintain pools of available monomeric ubiquitin. UCH-L1 protein is decreased in the SN of mice exposed to MPTP. The goal of this Dissertation research was to investigate the role of UCH-L1 in influencing susceptibility of NSDA and MLDA neurons to acute neurotoxic insult, and if aging plays a role in determining vulnerability of NSDA and MLDA neurons or expression and function of UCH-L1. The results reveal that UCH-L1 expression and function are maintained in non-susceptible MLDA neurons, which corresponds to the pattern of MLDA susceptibility to MPTP exposure. UCH-L1 expression is not affected by advanced age in NSDA or MLDA neurons, despite impairment of UPS function in cell body regions with advanced age. Additionally, aged mice are not more sensitive to MPTP exposure, but astrocytes in the axon terminal regions of MLDA neurons retain the protective ability to metabolize DA after MPTP administration, highlighting their protective role and potential contribution to differential susceptibility. These studies shed light on the potential contribution of the PD-linked neuronal deubiquitinating enzyme UCH-L1 to selective vulnerability in PD.
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- Title
- The function of sympathetic innervation in the spleen and the role of endogenous CB1/CB2 receptor signaling
- Creator
- Simkins, Tyrell Jonathan
- Date
- 2014
- Collection
- Electronic Theses & Dissertations
- Description
-
The spleen is a multifunction organ that sits at a unique intersection between the circulatory, immune, and neurologic systems. The work in this dissertation endeavored to shed light on the interaction of the sympathetic nervous system in the spleen with these other vital biologic systems. In addition, the role of signaling by the cannabinoid receptors 1 and 2 was explored as it relates the function of splenic sympathetic innervation. Specifically, it was found that splenic noradrenergic...
Show moreThe spleen is a multifunction organ that sits at a unique intersection between the circulatory, immune, and neurologic systems. The work in this dissertation endeavored to shed light on the interaction of the sympathetic nervous system in the spleen with these other vital biologic systems. In addition, the role of signaling by the cannabinoid receptors 1 and 2 was explored as it relates the function of splenic sympathetic innervation. Specifically, it was found that splenic noradrenergic neurons do not play a role in T cell independent humoral immunity, and that both norepinephrine and adenosine mediate spleen contraction. It was discovered that splenic sympathetic noradrenergic neurons are likely not regulated by CB1 and that cannabinoid-mediated immunosuppression of humoral immunity is likely due solely to CB2 on immune cells. It was also found that CB1/CB2 play a permissive role in maintaining the relationship between NE release from splenic sympathetic neurons and spleen contraction. These findings add to the knowledge base regarding both the spleen and extra-CNS cannabinoid effects and can be built upon for a more complete understanding of these systems.
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- Title
- Sex differences in the anatomical distribution, regulation, and anti-nociceptive function of the A11 diencephalospinal dopamine neuronal system
- Creator
- Pappas, Samuel Stahly
- Date
- 2011
- Collection
- Electronic Theses & Dissertations
- Description
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Dopamine (DA) neurons comprising the A11 diencephalospinal system represent the sole source of DA innervation to the spinal cord. These DA neurons project axons throughout the rostro-caudal extent of the spinal cord, terminating predominantly in the dorsal horn. Spinal cord administration of DA and DA agonists results in many diverse neuromodulatory effects on processes such as nociception, locomotion, movement, sexual functions, and regulation of the autonomic nervous system. Many spinal...
Show moreDopamine (DA) neurons comprising the A11 diencephalospinal system represent the sole source of DA innervation to the spinal cord. These DA neurons project axons throughout the rostro-caudal extent of the spinal cord, terminating predominantly in the dorsal horn. Spinal cord administration of DA and DA agonists results in many diverse neuromodulatory effects on processes such as nociception, locomotion, movement, sexual functions, and regulation of the autonomic nervous system. Many spinal cord DA-mediated functions contain a sex specific component, such as lower nociceptive thresholds and reduced response to analgesia in females. The purpose of the studies described in this dissertation is to examine the anatomy, regulation, and anti-nociceptive functions of A11 diencephalospinal DA neurons in male and female mice. Adult male mice have significantly higher DA concentrations in the lumbar spinal cord than females or males carrying the testicular feminization mutation (tfm) of the androgen receptor gene. Spinal cord DA concentrations are not changed following orchidectomy in adult male mice or testosterone administration to ovariectomized adult female mice. Administration of exogenous testosterone to postnatal day 2 female mice results in DA concentrations in the adult lumbar spinal cord comparable to those of males. Male mice display significantly more lumbar-projecting A11 DA neurons than females, as determined by retrograde tract tracing and immunohistochemistry directed toward tyrosine hydroxylase. There is no sex difference in the activity (DOPAC/DA ratio) of A11 DA neurons under basal conditions, but this activity is higher in the thoracic segment versus lumbar regions of the spinal cord. Blockade of D2 receptors with raclopride has no effect on A11 DA neuronal activity in the spinal cord, revealing a lack of D2 receptor regulatory mechanisms. Blockade of neuronal impulse flow with γ-butyrolactone increases DA concentrations in the spinal cord, indicating a relative high threshold for end-product inhibition of tyrosine hydroxylase in A11 DA neurons. Systemic administration of the μ-opioid agonist morphine led to a dose- and time-dependent increase in spinal cord DA neuronal activity in both male and female mice, which is blocked by the opioid antagonist naloxone. Conversely, the κ-opioid antagonist nor-binaltorphimine increases activity in the lumbar (but not thoracic) segment. Systemic administration of DA agonists increases the latency to escape in the nociceptive hot plate and tail immersion behavioral tests, while depletion of spinal cord DA with the catecholamine-specific neurotoxin 6-OHDA decreases these nociceptive latencies. The present findings reveal: (1) sex differences in the number of A11 DA neurons and lumbar spinal cord DA concentrations, organized by the presence of androgens early in life, (2) that spinal cord DA axon terminals lack pre- and post-synaptic DA receptor-mediated regulation of DA synthesis, but are activated by μ-opioids and inhibited by κ-opioids in a segment-specific manner, and (3) the A11 DA neuronal system is a tonic descending inhibitor of nociceptive processing in male and female mice.
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- Title
- The role of parkin in maintaining proteasome activity following acute neurotoxic insult
- Creator
- Lansdell, Theresa A.
- Date
- 2017
- Collection
- Electronic Theses & Dissertations
- Description
-
"The motor symptoms of Parkinson disease are primarily caused by the progressive degeneration of nigrostriatal dopamine neurons of the substantia nigra pars compacta. While these neurons are susceptible, tuberoinfundibular DA neurons are not affected. Exposure to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahyropyridine (MPTP) results in a similar pattern of DA neuronal susceptibility. The recovery of tuberoinfundibular DA neurons is dependent upon the increased expression of parkin...
Show more"The motor symptoms of Parkinson disease are primarily caused by the progressive degeneration of nigrostriatal dopamine neurons of the substantia nigra pars compacta. While these neurons are susceptible, tuberoinfundibular DA neurons are not affected. Exposure to the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahyropyridine (MPTP) results in a similar pattern of DA neuronal susceptibility. The recovery of tuberoinfundibular DA neurons is dependent upon the increased expression of parkin following MPTP exposure. Parkin is an E3 ligase that contains a ubiquitin like domain that can bind to the 26S proteasome and directly enhance its activity. The purpose of this dissertation was to test the hypothesis that increased parkin expression is both necessary and sufficient to maintain proteasome activity following oxidative insult by MPTP. MPTP caused similar oxidative damage to proteins in regions containing axons terminals of nigrostiatal (striatum; ST) and tuberoinfundibular (median eminence; ME) DA neurons, however proteasome activity followed the differential pattern of parkin expression and was decreased in the ST and maintained in the ME. The ST of parkin knockout mice had decreased proteasome activity, accumulation of ubiquitinated TH, and increased oxidatively modified proteins, while these were not affected in the ME. Proteasome activity in the ME of parkin deficient mice was decreased following MPTP but oxidatively modified proteins were not changed in either the ME or ST. To determine if parkin up-regulation could rescue proteasome activity following exposure to MPTP, rAAV expressing Flag-tagged human parkin was injected into the substantia nigra containing cell bodies of nigrostriatal DA neurons and proteasome activity was measured 24 h post MPTP. Parkin overexpression in the substantia nigra increased basal proteasome activity and prevented MPTP-induced loss of proteasome activity in the ST. rAAV-mediated parkin expression resulted in activation of 26S proteasome activity that was due to an increase in the amount of assembled 26S proteasome. Furthermore, increased parkin expression resulted in the rescue of proteasome mediated turnover of ubiquitinated TH. Although parkin over-expression was not sufficient to rescue NSDA axon terminal DA stores following MPTP exposure, DA turnover was decreased. The data presented here reveal that parkin is necessary and sufficient for the maintenance of 26S proteasome activity in dopaminergic axon terminal regions following acute MPTP exposure. Over-expression of parkin may be beneficial in protecting nigrostriatal DA neurons from cytosolic DA related oxidative damage. In addition, the discovery of small molecules that positively modulate the 26S proteasome may have potential therapeutic applications in the treatment of Parkinson disease."--Pages ii-iii.
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