| Summary: | <i>Bifidobacterium bifidum</i> BGN4-SK (BGN4-SK), a recombinant strain which was constructed from <i>B. bifidum</i> BGN4 (BGN4) to produce superoxide dismutase (SOD) and catalase, was analyzed to determine its antioxidant and anti-inflammatory properties in vitro. Culture conditions were determined to maximize the SOD and catalase activities of BGN4-SK. The viability, intracellular radical oxygen species (ROS) levels, intracellular antioxidant enzyme activities, and pro-inflammatory cytokine levels were determined to evaluate the antioxidant and anti-inflammatory activities of BGN4-SK in human intestinal epithelial cells (HT-29) and murine macrophage cells (RAW 264.7). Antioxidant enzymes (SOD and catalase) were produced at the highest levels when BGN4-SK was cultured for 24 h in a medium containing 500 μM MnSO<sub>4</sub> and 30 μM hematin, with glucose as the carbon source. The viability and intracellular antioxidant enzyme activities of H<sub>2</sub>O<sub>2</sub>-stimulated HT-29 treated with BGN4-SK were significantly higher (<i>p</i> < 0.05) than those of cells treated with BGN4. The intracellular ROS levels of H<sub>2</sub>O<sub>2</sub>-stimulated HT-29 cells treated with BGN4-SK were significantly lower (<i>p</i> < 0.05) than those of cells treated with BGN4. BGN4-SK more significantly suppressed the production of interleukin (IL)-6 (<i>p</i> < 0.05), tumor necrosis factor-α (<i>p</i> < 0.01), and IL-8 (<i>p</i> < 0.05) in lipopolysaccharide (LPS)-stimulated HT-29 and LPS-stimulated RAW 264.7 cells compared to BGN4. These results suggest that BGN4-SK may have enhanced antioxidant activities against oxidative stress in H<sub>2</sub>O<sub>2</sub>-stimulated HT-29 cells and enhanced anti-inflammatory activities in LPS-stimulated HT-29 and RAW 264.7 cells.
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