Cross-Talk between Fas/Fas ligand system and nitric oxide in the pathway subserving granulosa cell apoptosis: a possible regulatory mechanism for ovarian follicle atresia

Recent studies have shown the involvement of Fas/Fas ligand (FasL) system and nitric oxide (NO) in ovarian follicle atresia. Here we asked whether Fas/Fas ligand system interacts with NO using rat granulosa cell culture. Soluble recombinant Fas ligand (rFasL), at 100 ng/ml, significantly decreased cell viability, as measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, in the presence of 200 U/ml interferon-gamma, whereas the concurrent addition of a caspase inhibitor, Z-VAD-FMK, at 20 microm, significantly inhibited rFasL-induced cytotoxicity. Hoechst 33342 staining and flow cytometric analysis confirmed the induction of apoptosis in granulosa cells by 100 ng/ml rFasL in the presence of interferon-gamma, which was blocked by the concomitant addition of an NO donor, S-nitroso-N-acetylpenicillamine. Western blot analysis demonstrated that rFasL significantly up-regulated caspase-3, -8, and -9 activities in granulosa cells, which were attenuated by concurrent treatment with S-nitroso-N-acetylpenicillamine. Real-time quantitative RT-PCR revealed a significant decrease in inducible NO synthase mRNA levels in rFasL-induced apoptotic granulosa cells. In conclusio...Continue Reading