Effects of melatonin on development of early mouse embryos treated with Lipopolysaccharide

다국어 초록 (Multilingual Abstract)

Lipopolysaccharide (LPS) is an endotoxin factor present in the cell wall of Gram-negative bacteria and induces various immune responses to severe infections. Recent studies have been reported that LPS induces cellular stress in various cell lines, oocytes, and blastocyst. Antioxidants are used as one of the ways to overcome the LPS-mediated cytotoxic effect, but the effect of co-administration with LPS and melatonin (N-acetyl-5-methoxytryptamine) on early embryonic development has not yet been confirmed. Melatonin is a regulation hormone of circadian rhythm and a powerful antioxidant. It has been known that melatonin has an effective function in scavenging oxygen free radicals. Therefore, we cultured mouse embryos until the blastocyst stage (day 5) in the in vitro culture medium containing two reagents, we evaluated the development rate and the level of reactive oxygen species (ROS) in the embryos. First, we cultured embryos in medium at concentrations of 0 (control), 12.5, 25, 50, and 100 μg/mL LPS. As a result, morula development rate was inhibited in the high concentration of 100 μg/mL LPS group (41.4 ± 5.89% vs control 65.6 ± 2.04%; p<0.05), and blastocyst development rate was decreased from the concentration of 12.5 μg/mL LPS group (35.0 ± 7.33%) compared to the control group (61.3 ± 1.83%; p<0.01). In the subsequent experiment, 12.5ug/mL LPS was selected as optimal concentration and used. Next, to confirm the effect on melatonin of embryonic development, embryos were cultured in medium of melatonin 10-8, 10-7, and 10-6 M concentrations. There was no statistical difference in embryo development rate in all melatonin-treated groups, and no toxic effects were observed. Co-administration with LPS and melatonin (10-7 or 10-6 M) significantly increased the blastocyst development rate (MT 10-7 M 52.8 ± 4.96%, MT 10-6 M 59.8 ± 9.20%; P<0.01) inhibited by LPS (LPS 34.6 ± 4.22% vs control 70.4 ±3.96%; p<0.01). ROS levels were measured during the two-cell and the blastocyst development stage. In both stages, ROS level of embryos exposed to LPS had elevated than control group, and the ROS level of embryos in co-administration group was significantly decreased. In conclusion, this experiment demonstrated the protective effect of melatonin on the inhibition of embryonic development induced by LPS. These results suggest that melatonin may possibly be a potential infertile therapeutic agent for women exposed to bacterial infections.