cAMP-induced apoptosis in granulosa cells is associated with up-regulation of P53 and bax and down-regulation of clusterin

Evidence indicates that cAMP induces apoptosis in granulosa cells of rat and human ovary. The mechanism by which cAMP induces apoptosis is not known. This study was carried out to evaluate changes in expression of cell death promoters, P53 and bax, and cell death repressor, bcl-2, in cAMP-treated granulosa cells. Treatment of granulosa cells with forskolin (FSK), or 8-bromo-cAMP induced apoptosis as evidenced by internucleosomal DNA fragmentation and chromatin condensation as revealed by gel electrophoresis and fluorescent DAPI staining, respectively. The apoptotic effect of cAMP was accompanied by an increase in the expression of P53 and bax proteins as evaluated by Western blot and immunocytochemistry. No change in bcl-2 protein level was observed in cAMP-treated granulosa cells as compared to control. These data suggest that cAMP may activate apoptosis in granulosa cells by shifting the ratio of the death promoter to death repressor genes via alteration of P53 and bax expression, cAMP was also shown to inhibit gene expression of clusterin, an apoptosis-associated protein, suggesting a role for this protein in cAMP-induced apoptosis in granulosa cells. The data of the present study provide a basis for future studies to elucidate the molecular mechanism of follicular atresia and regulation of apoptotic cell death in ovarian follicles.