Protective effect of lactic acid bacteria against H2O2-induced oxidative stress in Caco-2 cells

Abstract Text: Oxidative stress can be defined as an imbalance between production of free oxygen radicals and reactive oxygen metabolism or repair the organism damage. A number of studies indicate that lactic acid bacteria (LAB) possess antioxidant activity due to their ability to regulate the activity of antioxidant enzymes during the cell metabolizing. The objective of this study was to establish a model of oxidative stress in human colon carcinoma cell line, Caco-2 cells, and to compare the protective effect of Lactobacillus plantarum NDC75017, L. plantarum ATCC14917 and L. acidophilus NCFM against hydrogen peroxide (H₂O₂) -induced oxidative stress in Caco-2 cells. The Caco-2 cells were divided into 5 groups: control group; oxidative stress group; L. plantarum NDC75017-protected group; L. plantarum ATCC14917-protected group and L. acidophilus NCFM-protected group. Caco-2 cells were exposed to 500 μM H₂O₂ in FBS-free DMEM for 30 min to induce oxidative stress, and then the three protection groups were respectively treated with 1×10⁷ cfu/ml L. plantarum NDC75017, L. plantarum ATCC14917 and L. acidophilus NCFM suspended in FBS-free DMEM. After 4 h of incubation, the activity of intracellular antioxidant enzymes was measured. Superoxide dismutase (SOD) and catalase (CAT) activity were measured with the commercial kits based on colorimetric method, and the colorimetric reactions were determined at 450nm and 405nm respectively. The data showed that CAT activity increased by 81% in oxidative stress group compared with control group, however no significant difference was observed in CAT activity between oxidative stress group and protection groups. SOD activity decreased by 33% in oxidative stress group compared with control group. All the three strains of the protection groups provided protection (P<0.05) against H₂O₂-induced SOD activity reduction in different degrees, in which L. plantarum NDC75017-protected group showed the most significant increase in SOD activity by 44%. The results revealed that when the Caco-2 cell was suffering oxidative stress, the activity of intracellular antioxidant enzymes such as SOD and CAT would increase substantially. Some strains of LAB have positive effects on relieving oxidative stress and regulating intracellular antioxidant enzymes activity. Particularly L. plantarum NDC75017, which was isolated from traditional yogurt in Inner Mongolia of China, provided the greatest protection against H₂O₂-induced SOD activity reduction of the three strains, may have potential applications for use in the food industry. This work was supported by National Science and Technology Project (2011AA100902).

Keywords: oxidative stress, antioxidant enzyme, lactic acid bacteria