Males have a higher risk for developing Parkinson’s disease and parkinsonism after ischemic stroke than females. treatment with androgens after the oxidative insult increased cell death, and these effects were, in part, mediated by calcium influx into the mitochondria. Oddly enough, the unfavorable effects of androgens were not blocked by either androgen or estrogen receptor antagonists. Instead, a putative membrane-associated androgen receptor was implicated. Overall, our results indicate that androgens are neuroprotective when oxidative stress buy Etomoxir levels are minimal, but when oxidative stress levels are elevated, androgens exacerbate oxidative stress damage. Parkinson’s disease (PD) is usually a progressive neurodegenerative disorder, characterized by Lewy body formations and motor disturbances, such as bradykinesia, rigidity, resting tremor, and postural instability (1). The loss of dopamine neurons within the substantia nigra pars compacta is usually one of the main pathological features of PD (2C6) and has been clearly linked with the motor disturbances associated with PD (7, 8). Dopamine neurons are inherently vulnerable to oxidative stress due to the process of dopamine metabolism, which can generate reactive oxygenated species buy Etomoxir (ROS) and free radicals (9). Oxidative stress, in change, has been explained as a important factor in the pathogenesis of PD (10C12). Two clinically known risk factors for PD are aging and gender (9, 13C16). Oxidative stress increases with age (17), and PD incidence increases exponentially in individuals above the age of 65 years (18, 19). Furthermore, aged men have a greater prevalence of PD than aged women (9, 13C16). Oddly enough, men also have a higher incidence of parkinsonism after ischemic stroke than women (20, 21), buy Etomoxir a neurodegenerative condition in which oxidative stress is usually strongly implicated as an important factor in the progression of cell death (22, 23). Therefore, these studies indicate a potential role for androgens in oxidative stress-mediated neurodegeneration. The role of androgens, the major male buy Etomoxir sex hormone, in the higher incidence of PD is usually ambiguous. Although androgen levels decrease with age (24), androgen levels continue to remain higher in aged males than females (25). Some studies support a neuroprotective role for androgens, in which androgens can safeguard against oxidative stress damage (26, 27). A possible mechanism for androgen-induced neuroprotection is usually preconditioning because androgens alone can moderately increase oxidative stress and apoptosis (28). However, other studies indicate that androgens may not usually be neuroprotective. For example, in a preexisting oxidative stress environment, androgens can further exacerbate oxidative stress damage (29). These results suggest that the level of oxidative stress determines whether androgens play a positive or unfavorable role in neuronal function. We suggest that below a certain oxidative stress threshold, androgens can be neuroprotective, but once a certain oxidative stress threshold is usually reached, such as occurs with PD and ischemic stroke, androgens can become damage promoting. The oxidative stress-associated organelles, mitochondria, serve a variety of metabolic functions within the cell, including a crucial role in calcium buffering (30). From a calcium homeostasis point of view, mitochondria can modulate the amplitude and frequency of calcium transients (31, 32), producing in spontaneous and sustained depolarization of the mitochondria (33). Increased intracellular calcium accumulations have been implicated in the generation of increased oxidative stress (34) and the initiation of cell death in PD (35C38) and ischemic stroke (39, 40). These studies show a role for calcium in mediating neuronal vulnerability. Given the role of oxidative stress in regulating dopaminergic cell fate and the conflicting studies regarding androgens and oxidative stress-mediated neurodegenerative disorders, we examined in the present study whether oxidative stress functions as a molecular switch to define androgen actions on dopamine neurons. Materials and Methods Reagents Testosterone (T) propionate, dihydrotestosterone (DHT), flutamide, T-BSA, tert-butyl-hydrogen peroxide, ICI 182,780, and tetramethylrhodamine methyl ester (TMRM) were from Sigma. RICTOR Ruthenium 360 (Ru360) and calcein acetomethoxy (Was) were from Calbiochem. The esterified, membrane-permeant derivative 1-[2-(5-carboxyoxazol-2-yl)-6-aminobenzo furan-5-oxy]-2-(2-amino-5-methylphenoxy) ethane-N,N,N,N-tetraacetic acid, acetoxylmethyl ester Fura-2 Was, RPMI 1640 medium, fetal bovine serum buy Etomoxir (FBS), charcoal-stripped FBS, penicillin-streptomycin, and PBS were purchased from Invitrogen, Molecular Probes. T and DHT were dissolved in ethanol with a final concentration less than 0.0001% ethanol Cell culture.