Abstract
Advanced glycation end products accumulate in the ovarian granulosa-cell layer of women with polycystic ovarian syndrome. Taken that the MAPK/ERK-pathway is a key regulator of oocyte maturation and function, consisting the main pathway used by the gonadotrophic hormones (luteinizing hormone, follicle stimulating hormone) to control ovulation, the present study aims to assess advanced glycation end products' interference into luteinizing hormone-and follicle stimulating hormone-signaling via the MAPK/ERK-pathway in the human granulosa KGN cell line. KGN cells were treated with luteinizing hormone or follicle stimulating hormone in the absence or presence of human glycated albumin. The specific activation of the main components of the MAPK/ERK1/2-pathway (namely c-Raf, MEK and ERK1/2) was assessed. Treatment of KGN cells with an MEK1/2-inhibitor or a blocking anti-RAGE-antibody was also performed to shed further light on the mechanism of the involvement of advanced glycation end products in luteinizing hormone and/or follicle stimulating hormone-related signaling pathways. Luteinizing hormone treatment increased p-ERK1/2 levels in human granulosa cells, while the combined treatment of luteinizing hormone and human glycated albumin provoked a decrease of p-ERK1/2 levels. A similar reducing effect was also observed for the upstream molecule phospho-cRaf upon combined treatment, while treatment with an MEK-inhibitor confirmed that the phenomenon is MAPK/ERK-pathway-dependent. Similarly, follicle stimulating hormone treatment increased p-ERK1/2 and p-MEK1/2 levels, while the combined treatment of follicle stimulating hormone and human glycated albumin downregulated their levels. Advanced glycation end products reduce the luteinizing hormone- and follicle stimulating hormone-induced ERK1/2 activation that is critical for granulosa cell mitogenesis and proliferation. Inappropriate activation of ERK1/2 in granulosa cells may block the granulosa cell differentiation pathway and/or impair follicular responses to hormones, potentially leading to ovulation failure that characterizes polycystic ovarian syndrome.