Antioxidant and cytoprotective effects of morin against hydrogen peroxide-induced oxidative stress are associated with the induction of Nrf-2‑mediated HO-1 expression in V79-4 Chinese hamster lung fibroblasts

Natural phytochemicals of plant origin, including flavonoids, have been found to be potent antioxidants providing beneficial effects against oxidative stress-related diseases. The present study was carried out to investigate the antioxidant properties of morin, a flavonoid originally isolated from the flowering plants of the Moraceae family. Superoxide dismutase (SOD)‑like activity and 2,2'‑azino‑bis‑(3‑ethylbenzothiazoline‑6‑sulfonic acid) (ABTS•+) radical scavenging activity were determined. We also investigated the cytoprotective effects of morin against hydrogen peroxide (H2O2)‑induced DNA damage and apoptosis in V79‑4 Chinese hamster lung fibroblasts. Our results demonstrated that morin had strong scavenging effects against ABTS•+ radicals with enhanced SOD activity, which varied in a dose-dependent manner. Morin was found to reduce H2O2‑induced intracellular reactive oxygen species generation and nuclear DNA damage, and it recovered cell viability damaged by H2O2 via inhibition of mitochondrial dysfunction‑mediated apoptosis. Notably, the treatment of V79‑4 cells with morin markedly enhanced the expression of heme oxygenase‑1 (HO‑1) but not quinone oxidoreductase-1, which was associated with the increased expression and phosphorylation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and the downregulation of Kelch‑like ECH‑associated protein 1 expression. Based on our findings, we conclude that morin effectively ameliorated oxidative stress‑induced DNA damage through intrinsic free radical scavenging activity and activation of the Nrf2/HO-1 pathway.