Innate Gender-based Proclivity in Response to Cytotoxicity and Programmed Cell Death Pathway*

Many central nervous system (CNS) diseases display sexual dimorphism. Exposure to circulating sex steroids is felt to be a chief contributor to this phenomenon; however, CNS diseases of childhood and the elderly also demonstrate gender predominance and/or a sexually dimorphic response to therapies. Here we show that XY and XX neurons cultured separately are differentially susceptible to various cytotoxic agents and treatments. XY neurons were more sensitive to nitrosative stress and excitotoxicity versus XX neurons. In contrast, XX neurons were more sensitive to etoposide- and staurosporine-induced apoptosis versus XY neurons. The responses to specific therapies were also sexually dimorphic. Moreover, gender proclivity in programmed cell death pathway was observed. After cytotoxic challenge, programmed cell death proceeded predominately via an apoptosis-inducing factor-dependent pathway in XY neurons versus a cytochrome c-dependent pathway in XX neurons. This gender-dependent susceptibility is related to the incapacity of XY neurons to maintain intracellular levels of reduced glutathione. In vivo studies further demonstrated an incapacity for male, but not female, 17-day-old rats to maintain reduced glutathione levels within cerebral cortex acutely after an 8-min asphyxial cardiac arrest. This gender difference in sensitivity to cytotoxic agents may be generalized to nonneuronal cells, as splenocytes from male and female 16–18-day-old rats show similar gender-dependent responses to nitrosative stress and staurosporine-induced apoptosis. These data support gender stratification in the evaluation of mechanisms and treatment of CNS disease, particularly those where glutathione may play a role in detoxification, such as Parkinson's disease, traumatic brain injury, and conditions producing cerebral ischemia, and may apply to non-CNS diseases as well.