Neuroprotective effect of a physiological ratio of testosterone and estradiol on corticosterone-induced apoptosis in PC12 cells via Traf6/TAK1 pathway.

Clinical and experimental studies suggested that testosterone or estradiol alone supplementation may have antidepressant-like effects. However, the synergistic effect of testosterone/estradiol on the treatment of depression and the underlying mechanism remain largely unknown. Here, we hypothesized that an appropriate dosage of testosterone combined with estradiol may became a new therapeutic strategy in depression. Our results indicated that an appropriate testosterone/estradiol ratio of 10:1 (10-8 mol/L testosterone and 10-9 mol/L estradiol) was found, which has a significant synergistic anti-apoptotic effect on PC12 cells injury stimulated by corticosterone. We then confirmed the synergistic effect of the defined testosterone/estradiol ratio in PC12 cells mainly depend on the inhibitory activation of Traf6/TAK1 signaling pathway. Furthermore, we found that the defined testosterone/estradiol ratio could suppress the expression and ubiquitination of Traf6 protein through AR/ERα-mediated pathways. Finally, endogenous interactions of Traf6 with AR/ERα in PC12 cells were found using co-immunoprecipitation assays, and further verified how the defined testosterone/estradiol ratio plays a synergistic role in injury of PC12 cells. The current study demonstrated that an appropriate testosterone/estradiol ratio has a synergistic effect on PC12 cells injury induced by corticosterone through suppressing the activation of Traf6/TAK1 signaling pathway, suggesting that testosterone/estradiol might synergistically protect against neuronal apoptosis to ameliorate depressive symptoms.