Epimorphin protects hepatocytes from oxidative stress by inhibiting mitochondrial injury

Background and Aims: Many investigations have demonstrated that cell injuries caused by generation of reactive oxygen species (ROS) is a common mechanism of various hepatic disorders. Recently, we have demonstrated that epimorphin, originally cloned as a mesenchymal protein, protects cultured intestinal epithelial cells from ROS. We therefore examine whether epimorphin protects primary cultured hepatocytes from ROS‐induced cell injury. Methods: We explored the cell viability and the intracellular ROS levels of purified murine hepatocytes after exposure to 0.5 mM H₂O₂ with or without pretreatment of epimorphin. Then, we observed mitochondrial permeability transition (MPT) and depolarization using confocal microscopy to make clear the mechanism that epimorphin inhibited cell injuries after exposure to H₂O₂. In addition, to clarify the signaling pathways related to cell survival, we carried out Western blotting analysis with phosphorylated stress‐activated protein kinase/c‐Jun N‐terminal kinase (SAPK/JNK) polyclonal antibody to evaluate the inhibition of JNK by epimorphin. Finally, we evaluated the cell viability in hepatocytes administered JNK inhibitor. Results: Epimorphin protected primary cultured hepatocytes from H₂O₂‐induced cell injuries independent of intracellular ROS levels. Epimorphin also inhibited onset of MPT, depolarization of the mitochondrial membrane potential, and eventually cell killing. The cell protective function of epimorphin after exposure to H₂O₂ was not dependent on Akt signaling but on JNK signaling. Conclusion: Epimorphin can protect hepatocytes from MPT‐dependent cell injury induced by ROS. Since hepatic disorders could be caused by MPT‐dependent cell injuries with excessive ROS, epimorphin might open a new therapeutic avenue for hepatic disorders.