Involvement of transcription factor p53 and leptin in control of porcine ovarian granulosa cell functions.

AbstractThe aim of our in vitro experiments was to examinethe role of transcription factor p53 and the metabolichormone leptin, in controlling basic functions (prolif-eration, apoptosis and secretory activity) of ovariancells, as well as involvement of p53 in mediating ormodulating actions of leptin, on ovarian cells. Por-cine ovarian granulosa cells, transfected and non-transfected with a gene construct encoding p53, werecultured with leptin (at concentrations of 0, 1, 10 or100 ng⁄ml). Accumulation of p53 and of apoptosis-related (bax) and proliferation-related (PCNA, cyclinB1) substances was evaluated by SDS–PAGE-wes-tern blotting. Secretion of progesterone (P4) wasmeasured by RIA. Transfection with the p53 geneconstruct promoted accumulation of this transcrip-tion factor within cells. It also stimulated expressionof bax (which can be thought of as a marker of apop-tosis), and reduced accumulation of proliferation-related substances PCNA and cyclin B1. Overex-pression of p53 resulted in reduced P4 secretion.Leptin, when added alone, increased accumulation ofp53, bax and PCNA, decreased accumulation ofcyclin B1 and had no effect on P4 secretion. Trans-fection of cells with p53 gene construct reversedeffects of leptin on cyclin B1 and induced stimula-tory effects of leptin on P4 release, but did not mod-ify leptin action on p53, bax and PCNA. Thesemultiple effects of the p53 gene construct on granu-losa cells, cultured with and without leptin, (i) dem-onstrate that leptin can be involved in control ofporcine ovarian cell proliferation, apoptosis andexpression of p53, but not on P4 release; and (ii) con-firm involvement of p53 in promoting apoptosis andsuppression of proliferation and P4 secretion in thesecells. (iii) The similarity of p53 and leptin’s actionson bax and cyclin B1, and inability of p53 to furtherpromote leptin action on this parameter suggest thatp53 can be a mediator of leptin’s action on ovariancell apoptosis. (iv) On the other hand, p53 can modu-late, but probably not mediate the effects of leptin onovarian cell proliferation and P4 release.Introduction