Melatonin Alleviates Benzo(a)pyrene-induced Ovarian Dysfunction By Suppressing Apoptosis During Early Pregnancy

Objective:Benzo?a?pyrene?B?a?P?is a widespread environmental pollutant and has obvious reproductive toxicity.Our previous study has shown that B?a?P treatment decreases embryo implantation and impacts endometrium decidualization and decidual angiogenesis.These processes are closely related to ovarian function.However,the impact of B?a?P on ovarian function during early pregnancy is unclear.In this study,we first investigated the effect and mechanism of B?a?P on ovary function.Moreover,we explored the potent protective effect of melatonin on B?a?P-induced ovarian toxicity.Methods:Pregnant mice were received 0.2 mg/kg/d B?a?P from D1 to D7 of pregnancy.The serum and ovaries were collected respectively from D4 to D7 to detect the effect of B?a?P on ovarian function.Then intraperitoneal injection of melatonin was administered simultaneously with B?a?P to examine the protective effect of melatonin on B?a?P-induced ovarian toxicity in early pregnant mice.1.ELISA was used to detect the melatonin levels in ovarian tissues,and estrogen,progesterone levels in serum.2.qRT-PCR were applied to measure the mRNA expression of3?-HSD,17?-HSD and P450SCC in mouse ovarian tissues.3.ELISA and CM-H₂DCFDA were used to detect ovarian oxidative stress.4.TUNEL was used to observe cell apoptosis in ovary,and Western blot was used to detect the expression of apoptotic proteins Bax,Bcl2,Caspase3,and PI3K/AKT/GSK3?and ERK1/2/JNK pathways'key proteins.5.Western blot was used to determine the protein expression of melatonin receptor MT1 and MT2 in mouse ovarian tissues.Results:The results showed that B?a?P would decrease the level of estrogen and progesterone,and influence mRNA levels of its synthesized key enzyme,disrupt the normal ovarian function.In this process,B?a?P enhancedtheoxidativestressanddamagedthebalanceof PI3K/AKT/GSK3?and ERK1/2/JNK signal pathway,promoted the expression of Bax/Bcl2 and launched the Caspase family,finally leaded to cell apoptosis.Melatonin,which is a free radical scavenger,has strong antioxidant activity in vivo.Due to the effect of B?a?P on ovarian oxidative toxicity and melatonin receptors expression,melatonin is used as a therapeutic agent of B?a?P.Melatonin successfully alleviate the B?a?P-induced ovarian dysfunction via decaeasing oxidative stress and cell apoptosis.Conclusion:These results indicate that B?a?P can disrupt the ovarian function in early pregnancy,while exogenous melatonin can relieve B?a?P-induced ovarian toxicity.Thus,melatonin might be a potential therapeutic agent for B?a?P-induced reproductive toxicity during early pregnancy.