Melatonin in Sperm Biology: Breaking Paradigms

Abstract

ContentsMelatonin is a ubiquitous molecule, present in a wide range of organisms, and involved in multiple functions. Melatonin relays the information about the photoperiod to the tissues that express melatonin-binding sites in both central and peripheral nervous systems. This hormone has a complex mechanism of action. It can cross the cell plasma membrane and exert its actions in all cells of the body. Certain melatonin actions are mediated by receptors that belong to the superfamily of G-protein-coupled receptors (GPCRs), the MT 1 and MT 2 membrane. Melatonin can also bind to calmodulin as well as to nuclear receptors of the retinoic acid receptor family, RORa1, RORa2 and RZRb. The purpose of this review is to report on recent developments in the physiological role of melatonin and its receptors. Specific issues concerning the biological function of melatonin in mammalian seasonal reproduction and spermatozoa are considered. The significance of the continuous presence of melatonin in seminal plasma with a fairly constant concentration is also discussed.

Melatonin affects the motility and adhesiveness of in vitro capacitated boar spermatozoa via a mechanism that does not depend on intracellular ROS levels

“…either at 0 h or at 4 h), five different treatments were assayed: a positive control (C+), which consisted of spermatozoa incubated in CM containing bicarbonate and bovine serum albumin (BSA); three treatments with different concentrations of melatonin (0.5, 1, 5 lM) in CM; and a negative control (CÀ), which consisted of spermatozoa incubated in non-capacitating medium without bicarbonate or BSA (NCM). As aforementioned, the tested concentrations of melatonin were within the physiological range of the genital tract, as described in previous works (Luboshitzky et al, 2002;Casao et al, 2009Casao et al, , 2010Ashrafi et al, 2013;Cebri an-P erez et al, 2014;P erez-Patiño et al, 2016).…”

“…The first one aimed at testing how melatonin affected the achievement of IVC (i.e. As aforementioned, the tested concentrations of melatonin were within the physiological range of the genital tract, as described in previous works (Luboshitzky et al, 2002;Casao et al, 2009Casao et al, , 2010Ashrafi et al, 2013;Cebri an-P erez et al, 2014;P erez-Patiño et al, 2016). The second part sought to determine the impact of melatonin upon triggering IVAE in fully in vitro capacitated boar spermatozoa (i.e.…”

Effect of chelating and antioxidant agents on morphology and DNA methylation in freeze‐drying rabbit (Oryctolagus cuniculus) spermatozoa

“…Melatonin (MLT) is a key regulator of the circadian wake–sleep cycle and reproduction in animals characterized by photoperiod (Chemineau et al, ); it has also a relevant role in sperm biology (Cebrián‐Pérez et al, ). In fact, MLT contrasts a variety of ROS species due to its well established antioxidant activity (Jang et al, ).…”

Presence of melatonin‐catabolizing non‐specific enzymes myeloperoxidase and indoleamine 2,3‐dioxygenase in the ram reproductive tract

“…On the other hand, melatonin is a key hormone in ovine reproduction. The melatonin main function is the regulation of seasonal sheep reproduction through the hypothalamus‐pituitary‐gonadal axis (Malpaux et al, ), although recent studies also suggest a direct action on sheep gametes and embryos, increasing their survival and quality (Abecia, Forcada, Casao, & Palacin, ; Cebrian‐Perez et al, ). Furthermore, we have detected the presence of melatonin‐synthesizing enzymes (Gonzalez‐Arto et al, ) and the melatonin receptors MT1 and MT2 in the testis and other organs of the ram reproductive tract (González‐Arto et al, ), as well as MT1 and MT2 receptors in ram spermatozoa (Casao et al, ).…”