Leucine protects bovine intestinal epithelial cells from hydrogen peroxide-induced apoptosis by alleviating oxidative damage

BACKGROUND The present study aimed to investigate whether leucine (Leu) alleviates oxidative injury in bovine intestinal epithelial cells (BIECs) induced by hydrogen peroxide (H2O2), as well as the underlying molecular mechanisms. RESULTS BIECs were treated with H2O2 (1 mmol L-1) and/or Leu (0, 0.9, 1.8 or 3.6 mmol L-1) for 2 h. Leu increased cell viability (P < 0.05) and decreased the release of lactate dehydrogenase (P < 0.05) in BIECs challenged by H2O2. Then, the cells were treated with H2O2 (1 mmol L-1) and/or Leu (1.8 mmol L-1) for 2 h. Compared with the H2O2 group, cells treated with Leu and Leu + H2O2 exhibited increased (P < 0.05) mRNA and protein expression of superoxide dismutase 2 (SOD2), catalase (CAT), glutathione peroxidase 1 (GPx1), heme oxygenase 1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2). BIECs treatment with Leu significantly reduced (P < 0.05) apoptosis induced by H2O2. BIECs were transfected with Nrf2 small interfering RNA (siRNA) for 48 h and/or treated with H2O2 (1 mmol L-1) and/or Leu (1.8 mmol L-1) for another 2 h. Transfection with Nrf2 siRNA abrogated the protective effect of Leu against H2O2-induced apoptosis and the mRNA and protein expression of SOD2 (P < 0.05). CONCLUSION These results indicate that Leu promotes the relative expression of antioxidant enzymes (SOD2, CAT and GPx1) and phase II detoxification enzymes (HO-1) by upregulating nuclear Nrf2 and activating the Nrf2 signaling pathway, thus enhancing the antioxidant capacity of cells. (c) 2022 Society of Chemical Industry.