Melatonin activates Nrf2/HO‐1 signalling pathway to antagonizes oxidative stress‐induced injury via melatonin receptor 1 (MT1) in cryopreserved mice ovarian tissue.

Our previous research has shown that melatonin (MLT) can reduce cryopreserved ovarian damage in mice. Yet, the molecular mechanism of MLT protection is still unclear. Some studies have shown that melatonin receptor 1 (MT1) is very important for animal reproductive system. To evaluate whether MLT exerts its protective effect on cryopreserved mice ovarian tissue via MT1, we added antagonist of MT1/MT2 (Luzindor) or antagonist of MT2 (4P‐PDOT) to the freezing solution, followed by cryopreservation and thawing of ovarian tissue. The levels of total superoxide dismutase (T‐SOD), catalase (CAT), nitric oxide (NO) and malondialdehyde (MDA) were detected. Besides, by using RT‐PCR and Western blotting, the expression of Bcl‐2, Bax and Nrf2/HO‐1 signalling pathway‐related proteins was detected. These findings demonstrated that compared with the melatonin group, the addition of Luzindor increased apoptosis, NO and MDA activities, decreased CAT and T‐SOD activities and inhibited Nrf2/HO‐1 signalling pathway. In conclusion, melatonin can play a protective role in cryopreserved ovarian tissue of mice through MT1 receptor. [ABSTRACT FROM AUTHOR]