Relaxin protects cardiomyocytes against hypoxia-induced damage in in-vitro conditions: Involvement of Nrf2/HO-1 signaling pathway.

Relaxin, a peptide hormone has emerged as a cardioprotective agent against the heart failure and has been found to protect cardiac muscle cells against hypoxia/reoxygenation injury under in vitro conditions. The present study was conducted to study its possible role in activating the Nrf2/HO-1 signaling pathway in cardiomyocytes, as a means to counter hypoxia associated oxidative damage and cell death. H9C2 cell line was induced with chemical hypoxia alone or together with relaxin. Hypoxia associated cellular damage and reactive oxygen species (ROS) production was accessed by Lactate dehydrogenase (LDH) release and DCFDA activity respectively. The anti-oxidative property of RLXH2 was measures by assessing the activities of different enzymes like Superoxide dismutase (SOD), Catalase (CAT) and Glutathione peroxidase (GSX). Expression levels of Nrf2 and HO-1 was studied by immunoblotting and quantitative real time PCR (qRT-PCR). Translocation of Nrf2 to nucleus was studied by immunoblotting. Our results found that hypoxia associated lactate dehydrogenase leakage and ROS production is countered by RLXH2 treatment. Similarly, RLXH2 was able to counter hypoxia induced oxidative damage as evident by increased activities of SOD, CAT and GSX. Furthermore, it was found that RLXH2 treatment induces translocation of Nrf2 from cytosol to nucleus and in turn enhances expression level of HO-1. Our results suggest that RLXH2 exerts cytoprotective action in cardiomyocytes against the hypoxia induced damage and activates Nrf2/HO-1 signaling pathway.