Cytoprotective effects of esculetin against oxidative stress are associated with the upregulation of Nrf2-mediated NQO1 expression via the activation of the ERK pathway

Esculetin, a coumarin derivative isolated from a variety of medicinal herbs, has been reported to possess multiple therapeutic and pharmacological actions. Although several studies have demonstrated the antioxidant activity of esculetin, its mechanisms of action have not been clearly established. The aim of this study was to evaluate the effects of esculetin against hydrogen peroxide (H2O2)-induced oxidative stress in C2C12 myoblasts and to investigate the mechanisms involved in this process. Our data indicated that esculetin preconditioning significantly attenuated H2O2-induced growth inhibition and DNA damage and the apoptosis of C2C12 cells by suppressing intracellular reactive oxygen species (ROS) accumulation. Treatment with esculetin effectively increased the phosphorylation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the expression of NAD(P)H:quinone oxidoreductase 1 (NQO1). Esculetin treatment also activated extracellular signal-regulated kinase (ERK), and pre-treatment with PD98059, an ERK-specific inhibitor, blocked esculetin-mediated phosphorylation of Nrf2 and the induction of NQO1 expression. In addition, the protective effects of esculetin against H2O2-induced ROS accumulation, apoptosis and growth inhibition were abrogated in the C2C12 cells pre-treated with PD98059. Thus, the present study demonstrates that esculetin protects C2C12 cells against oxidative stress-induced injury, possibly through the activation of the Nrf2/NQO1 pathway.