Elevated testosterone induces apoptosis in neuronal cells.
Testosterone plays a crucial role in neuronal function, but elevated concentrations can have deleterious effects. Here we show that supraphysiological levels of testosterone (micromolar range) initiate the apoptotic cascade. We used three criteria, annexin V labeling, caspase activity, and DNA fragmentation, to determine that apoptotic pathways were activated by testosterone. Micromolar, but not nanomolar, testosterone concentrations increased the response in all three assays of apoptosis. In addition, testosterone induced different concentration-dependent Ca2+ signaling patterns: at low concentrations of testosterone (100 nm), Ca2+ oscillations were produced, whereas high concentrations (1-10 microm) induced a sustained Ca2+ increase. Elevated testosterone concentrations increase cell death, and this effect was abolished in the presence of either inhibitors of caspases or the inositol 1,4,5-trisphosphate receptor (InsP3R)-mediated Ca2+ release. Knockdown of InsP3R type 1 with specific small interfering RNA also abolished the testosterone-induced cell death and the prolonged Ca2+ signals. In contrast, knockdown of InsP3R type 3 modified neither the apoptotic response nor the Ca2+ signals. These results support our hypothesis that elevated testosterone alters InsP3R type 1-mediated intracellular Ca2+ signaling and that the prolonged Ca2+ signals lead to apoptotic cell death. These effects of testosterone on neurons will have long term effects on brain function.
Estrada
Manuel
M
Department of Pharmacology and Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520, USA.iestrada@med.uchile.cl
Varshney
Anurag
A
Ehrlich
Barbara E
BE
D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction; D013739:Testosterone / Q000378:metabolism / Q000494:pharmacology*
D017304:Annexin A5; D013739:Testosterone; D002118:Calcium