Neuroscience
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/21717
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Browsing Neuroscience by Author "Cunningham, Rebecca L."
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Item Novel Androgen Receptor Variant 45 in Brain Tissue(2016-03-23) Contreras, Jo; Duong, Phong; Cunningham, Rebecca L.; Downs, LincolnPurpose: A membrane associated androgen receptor has been implicated in the damaging effects of testosterone in neurodegenerative disorders, such as Parkinson’s disease. An androgen receptor variant (AR45) that has a C-terminus and a unique N-terminus has been found in peripheral tissues, such as the heart, skeletal muscle, uterus, and prostate, but has not been found in the brain. Recent findings have shown that a AR45 is present in the membrane fraction of a dopaminergic neuronal cell line (N27). Therefore, we wanted to determine if AR45 was present in cortical, hippocampal, and substantia nigral neurons that are lost during Alzheimer’s and Parkinson’s disease. Methods: In this study we used immunohistochemistry to determine the presence of AR45 presence in rat brain tissue. Tissue sections of 40 um were prepared using a cryostat. The sections were stained with primary antibodies specific for different androgen receptor sequences. The antibodies AR C-19 and AR N-20 were used to identify the C terminus and the N terminus, respectively. Results: Since AR-45 is lacking an N-terminus, we used N-20 antibody that binds to the N-terminus as a negative control. However, AR-45 does have a c-terminus, and thus we used the C-19 antibody as a marker for AR-45. C-19 immunofluorescence was present in the hippocampus, cortex, and substantia nigra. Interestingly, N-20 positive cells were not identified in the substantia nigra, indicating that only AR45 is present in these neurons. Conclusion: This is first study to show the presence of AR45-immunoreactive positive neurons in the brain. Now the receptor has been identified, more research is needed to determine the role of AR45 in neurodegenerative diseases.Item Oxidative stress and androgen replacement as a model for neurodegeneration in the SN56 cell line(2016-03-23) Smith, Charity; Cunningham, Rebecca L.; Schreihofer, Derek; Warren, MarshallBackground: Sleep apnea has been linked to oxidative stress (OxS) in the form of reactive oxygen species. The presence of oxidative stress has been shown to determine either the protective or toxic property of androgens in the N27 dopaminergic cell line, which has been used as a model of Parkinson’s disease. Androgen treatment prior to OxS protects N27 cells from injury, whereas androgen treatment after OxS increases the toxicity of OxS. We sought to determine whether similar oxidative stress dependent androgen effects also occurred in the SN56 cholinergic cell line, which has been used to model Alzheimer’s disease using intermittent hypoxia as an oxidative stress. Hypothesis: We hypothesize that testosterone given prior to oxidative stress is neuroprotective and testosterone given after oxidative stress is neurotoxic. Materials and Methods: The pre-treatment group was exposed to 100 nM of testosterone followed by 17-40 cycles of intermittent hypoxia in a chamber with fluctuating levels of oxygen. One cycle of IH involved reducing the chamber from 20% to 1.5% oxygen for 30 seconds followed by re-oxygenation for 4 minutes. The post-treatment group was first exposed to 17 cycles of IH and then treated testosterone. The control group used SN56 cells that were not exposed to androgen or IH. Cells were lysed at 6 & 24-hour intervals. Western blots were performed for two markers of apoptosis, Poly ADP ribose polymerase (PARP) and alpha spectrin, and were normalized for beta actin levels. Additional experiments used a cell viability assay to determine cell survival 24 hours after the same treatments and 30 or 40 cycles of IH. Results: Cleavage of PARP and alpha-spectrin was significantly increased in the post-treatment group that was lysed at 6 hours, but not in the pretreatment groups. Conversely, both pre and post treatment with testosterone appeared to reduce cell death induced by IH. Conclusions: The results of the cells lysed at 6 hours confirm the original hypothesis that androgens given prior to oxidative stress are neuroprotective while androgens given after oxidative stress are neurotoxic in SN56 cells. However, at longer time points, testosterone appeared to only be protective to SN56 cells. These data suggest that IH, such as occurs with sleep apnea, may interact with androgens in both detrimental and beneficial ways in cholinergic cells, as they do in dopaminergic cells.