The present study aims to investigate the roles of steroidogenic acute regulatory protein (StAR) in Yangjing Capsule (YC) induced anti-apoptotic effects on Leydig cells and the related mechanism. Leydig tumor cells (MLTC-1) were cultured and treated with YC, and immunofluorescence assay was performed to examine the expression of StAR; furthermore, luciferase reporter assay was conducted to evaluate the impact of YC on StAR promoter; next, MLTC-1 cells were treated with StAR small interfering RNA (siRNA), and flow cytometry was carried out to examine the effect of StAR siRNA on the apoptosis of the cells; furthermore, quantitative (q)RT-PCR and Western blot methods was used to determine the expression of StAR and apoptosis related molecules Bcl-2, Bax and Caspase-3 on both mRNA and protein levels in different groups; finally the secretion of testosterone in different groups was examined by radioimmunoassay. We observed that the YC can increase the expression of StAR in a dose-dependent manner, and YC can activate the promoter of StAR; moreover, transfection of StAR siRNA can block YC induced anti-apoptotic effects and increased production of testosterone. In conclusion, our results suggested that YC might suppress the apoptosis of MLTC-1 cells and enhance the production of testosterone through regulating the expression of StAR.
Keywords: Leydig cell; Yangjing Capsule (YC); apoptosis; steroidogenic acute regulatory protein (StAR); testosterone.