Background: The direct effects of GnRH-I or GnRH-II on apoptosis in human granulosa cells are unknown and if present, can be influenced by FSH. Apoptosis involves activation of the intracellular proteolytic cascade of caspases. We therefore evaluated the roles of GnRH-I and II, and the effects of FSH, on apoptosis in human granulosa cells and on caspases.

Methods: Human immortalized granulosa cells treated with GnRH-I or GnRH-II or nothing were cultured with and without antide (a GnRH-I antagonist), a broad-spectrum caspase inhibitor or selective caspase-8, 3 or 7 inhibitor, or FSH in replicates for 72 hours. Apoptotic changes were evaluated by TUNEL assays, immunoblotting and expression levels of caspases and compared by ANOVA.

Results: GnRH-I and II induced TUNEL-positive apoptotic cells and increased cleavage activities of caspase-8, 3 and 7 by 48 hours and peaked at 72 hours, changes that were blocked by FSH co-treatment. Antide also effectively blocked these TUNEL-positive changes and expression levels of caspase-3 induced by GnRH-I or II. Activation of caspase-8, 3 and 7 was inhibited by the corresponding caspase inhibitor. Caspase-8 inhibitor also abolished cleavages of caspase-3 and 7 induced by GnRH-I and II.

Conclusion: GnRH-I and -II induce apoptosis in human granulosa cells through GnRH-I receptors, which mediate the proteolytic caspase cascade involving caspase-8 (the initiator) and caspase-3 and 7 (the effectors). FSH protects human granulosa cells from apoptosis induced by GnRH-I or II. This raises potentially important roles of GnRH-I and GnRH-II in regulating follicle development and atresia together with FSH.