The role of melatonin as an antioxidant in the follicle

Abstract

Melatonin (N-acetyl-5-methoxytryptamine) is secreted during the dark hours at night by pineal gland, and it regulates a variety of important central and peripheral actions related to circadian rhythms and reproduction. It has been believed that melatonin regulates ovarian function by the regulation of gonadotropin release in the hypothalamus-pituitary gland axis via its specific receptors. In addition to the receptor mediated action, the discovery of melatonin as a direct free radical scavenger has greatly broadened the understanding of melatonin's mechanisms which benefit reproductive physiology. Higher concentrations of melatonin have been found in human preovulatory follicular fluid compared to serum, and there is growing evidence of the direct effects of melatonin on ovarian function especially oocyte maturation and embryo development. Many scientists have focused on the direct role of melatonin on oocyte maturation and embryo development as an anti-oxidant to reduce oxidative stress induced by reactive oxygen species, which are produced during ovulation process. The beneficial effects of melatonin administration on oocyte maturation and embryo development have been confirmed by in vitro and in vivo experiments in animals. This review also discusses the first application of melatonin to the clinical treatment of infertile women and confirms that melatonin administration reduces intrafollicular oxidative damage and increase fertilization rates. This review summarizes our recent works and new findings related to the reported beneficial effects of melatonin on reproductive physiology in its role as a reducer of oxidative stress, especially on oocyte maturation and embryo development.

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

“…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 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.…”

Melatonin receptor (MTNR1A and MTNR2B) expression during the breeding season in the yak (Bos grunniens)

“…Reactive oxygen species (ROS) and apoptosis are involved with a number of reproductive events, including folliculogenesis, follicular atresia, ovulation, oocyte maturation, and corpus luteum (CL) formation (Tamura et al, 2009). The ROS produced within the follicles, especially during the ovulation process, were scavenged by melatonin and reduced oxidative stress may be involved with oocyte maturation and embryo development (El-Raey et al, 2011;Tamura et al, 2012). We suggest that melatonin was involved with the growth and maturation of ovarian follicles and it also participated in the growth of oocytes.…”

Effects of Magnetized Medium on In Vitro Maturation of Porcine Cumulus Cell-Oocyte Complexes

“…Positive are those related to ROS involvement in energy production, phagocytosis, regulation of cell growth and intercellular signaling, and synthesis of biologically active compounds [7]. While physiological levels of oxygen are necessary for cells to live, the presence of excess ROS, such as superoxide radical (O 2 and hydrogen peroxide (H 2 O 2 ), can also have considerable impact on early embryonic viability, as these compounds have been implied to be involved in nuclear fragmentation and apoptosis, mitochondrial degeneration, developmental block during early cleavage stage and mitotic arrest [8][9][10].…”