AanatKnockdown and Melatonin Supplementation in Embryo Development: Involvement of Mitochondrial Function and DNA Methylation

Abstract

Aims: In addition to pineal gland, many cells, tissues, and organs also synthesize melatonin (N-acetyl-5methoxytryptamine). Embryos are a group of special cells and whether they can synthesize melatonin is still an open question. However, melatonin application promoted embryo development in many species in in vitro condition. The purpose of this study was to investigate whether embryos can synthesize melatonin; if it is so, what are the impacts of the endogenously produced melatonin on embryo development and the associated molecular mechanisms. These have never been reported previously. Results: Melatonin synthesis was observed at different stages of embryonic development. Aanat (aralkylamine N-acetyltransferase), a rate-limiting enzyme for melatonin production, was found to mostly localize in the mitochondria. Aanat knockdown significantly impeded embryonic development, and melatonin supplementation rescued it. The potential mechanisms might be that melatonin preserved mitochondrial intact and its function, thus providing sufficient adenosine 5¢-triphosphate for the embryo development. In addition, melatonin scavenged intracellular reactive oxygen species (ROS) and reduced the DNA mutation induced by oxidative stress. In the molecular level, Aanat knockdown reduced tet methylcytosine dioxygenase 2 (Tet2) expression and DNA demethylation in blastocyst and melatonin supplementation rescued these processes. Innovation: This is the first report to show that embryos synthesize melatonin, and its synthetic enzyme Aanat was located in the mitochondria of embryos. An effect of melatonin is to maintain Tet2 expression and normal methylation status, and thereby promote embryonic development. Conclusion: Embryos can produce melatonin that reduces ROS production, preserves mitochondrial function, and maintains Tet2 expression and the normal DNA methylation.

Mitochondria: the birth place, battle ground and the site of melatonin metabolism in cells

“…With the use of a protein degradation procedure, Suofu et al (39) deduced that the SNAT was located in the matrix of mitochondria; they claimed that melatonin was synthesized exclusively in the matrix of mitochondria. In contrast, Yang et al observed that the SNAT was present in the mitochondrial intermembrane space close to the outer membrane (42). This seems to support the observations of Kerenyi et al (43,44) that SNAT product was observed in the mitochondrial intermembrane space of pinealocytes.…”

Targeting Host Defense System and Rescuing Compromised Mitochondria to Increase Tolerance against Pathogens by Melatonin May Impact Outcome of Deadly Virus Infection Pertinent to COVID-19

“…Serum melatonin of pregnant women gradually increases in the course of gestation, especially during the third trimester of pregnancy, and reaches its peak at the time of delivery [ 232 , 233 ]. Since trophoblast [ 234 ] and placenta [ 235 , 236 ], as well as embryo [ 237 , 238 ] and stages of the fetus have the capacity to synthesize melatonin, the melatonin of pregnant women is probably derived from the mother, fetus, and placenta as a whole. Thus, pregnant women have a significantly elevated serum melatonin level, which is approximately twice as high as that of control subjects or even higher [ 181 ].…”

Melatonin, Its Beneficial Effects on Embryogenesis from Mitigating Oxidative Stress to Regulating Gene Expression

“…MT regulates the earliest stages of intrauterine growth in mice [ 15 ]. Interestingly, it was shown that AANAT is mostly located in mitochondria of embryonic cells.…”

“…Pineal MT regulates embryo and fetal development [ 14 ]. However, melatonin is produced in the mammalian embryo, within the mitochondria of the embryo [ 15 ]. Although requiring confirmation in future studies, including in human embryos, such data is challenging to the sole role of maternal, pineal MT in the regulation of fetal development.…”