Melatonin as a free radical scavenger in the ovarian follicle [Review]

Abstract

This review summarizes new findings related to beneficial effects of melatonin (N-acetyl-5-methoxytryptamine) on reproductive physiology. Recently many researchers have begun to study the local role of melatonin as an antioxidant. We focused on intra-follicular role of melatonin in the ovary. Melatonin, secreted by the pineal gland, is taken up into the follicular fluid from the blood. Reactive oxygen species (ROS) are produced within the follicles, during the ovulatory process. Melatonin reduces oxidative stress as an antioxidant, and contribute to oocyte maturation, embryo development and luteinization of granulosa cells. Our clinical study demonstrated that melatonin treatment for infertile women increases intra-follicular melatonin concentrations, reduces intra-follicular oxidative damage, and elevates fertilization and pregnancy rates. Melatonin treatment also improves progesterone production by corpus luteum in infertile women with luteal phase defect. Melatonin treatment could become a new cure for improving oocyte quality and luteal function in infertile women.

A pilot study to search possible mechanisms of ultralong gonadotropin-releasing hormone agonist therapy in IVF-ET patients with endometriosis

“…Melatonin is a powerful free radical scavenger and a broad-spectrum antioxidant [31,32]. We previously demonstrated that melatonin is present in human ovarian follicles and that its concentration increases during follicular growth [18][19][20]. We also reported that melatonin is taken up into the follicular fluid from the blood, and that it protects oocytes from ROS within the follicle during ovulation Figure 1 Tumor necrosis factor alpha (TNFα) concentrations in follicular fluids.…”

“…[ [18][19][20]33]. Reduced oxidative stress and increased antioxidant activities by melatonin in follicular fluids by ultralong GnRHa therapy may also have contributed to the improvement of implantation rate and pregnancy rate.…”

“…Oxidative stress reduces oocyte quality [18][19][20] and impairs endometrial receptivity [21]. Together, these findings strongly suggest that oxidative stress contributes to infertility in endometriosis patients.…”

Melatonin deprival modifies follicular and corpus luteal growth dynamics in a sheep model

“…The antioxidant properties of melatonin have been extensively studied , Tamura et al 2013. The scavenger activity of melatonin or of its metabolites may thus account for its beneficial effect on follicular and oocyte development (Tamura et al 2008).…”

Melatonin in human reproduction

“…Система окислителей и антиоксидантов присут-ствует и в яичнике, участвуя в процессах роста и со-зревания яйцеклеток [20]. Количество образующих-ся свободных радикалов тщательно контролируется для поддержания окислительно-восстановительного гомеостаза.…”