Cytoprotective and Cytotoxic Effects of Rice Bran Extracts in Rat H9c2(2-1) Cardiomyocytes

This study was aimed at preliminarily assessing the cytoprotective and antioxidative effects of rice bran extracts (RBEs) from a Sarawak local rice variety (local name: “BJLN”) and a commercial rice variety, “MR219,” on oxidative stress in rat H9c2(2-1) cardiomyocytes. The cardiomyocytes were incubated with different concentrations of RBE and hydrogen peroxide (H(2)O(2)), respectively, to identify their respective IC(50) values and safe dose ranges. Two nonlethal and close-to-IC(50) doses of RBE were selected to evaluate their respective effects on H(2)O(2) induced oxidative stress in cardiomyocytes. Both RBEs showed dose-dependent cytotoxicity effects on cardiomyocytes. H(2)O(2) induction of cardiomyocytes pretreated with RBE further revealed the dose-dependent cytoprotective and antioxidative effects of RBE via an increase in IC(50) values of H(2)O(2). Preliminary analyses of induction effects of RBE and H(2)O(2) on cellular antioxidant enzyme, catalase (CAT), also revealed their potential in regulating these activities and expression profile of related gene on oxidative stress in cardiomyocytes. Pretreated cardiomyocytes significantly upregulated the enzymatic activity and expression level of CAT under the exposure of H(2)O(2) induced oxidative stress. This preliminary study has demonstrated the potential antioxidant effects of RBE in alleviating H(2)O(2)-mediated oxidative injuries via upregulation in enzymatic activities and expression levels of CAT.