Oxidative stress and androgen replacement as a model for neurodegeneration in the SN56 cell line

Background: 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.