Background: Inflammatory bowel disease (IBD) is a gastrointestinal disease characterized by diarrhea, rectal bleeding, abdominal pain, and weight loss. Recombinant probiotics producing specific proteins with IBD therapeutic potential are currently considered novel drug substitutes. In this study, aBifidobacterium bifidumBGN4-SK strain was designed to produce the antioxidant enzymes streptococcal superoxide dismutase (SOD) and lactobacillus catalase (CAT), and aB. bifidumBGN4-pBESIL10 strain was proposed to generate an anti-inflammatory cytokine, human interleukin (IL)-10. In vitro and in vivo efficacy of these genetically modifiedBifidobacteriumstrains were evaluated for colitis amelioration.Results: In a lipopolysaccharide (LPS)-stimulated HT-29 cell model, tumor necrosis factor (TNF)-α and IL-8 production was significantly suppressed in theB. bifidumBGN4-SK treatment, followed byB. bifidumBGN4-pBESIL10 treatment, when compared to the LPS-treated control. Synergistic effects on TNF-α suppression were also observed. In a dextran sodium sulphate (DSS)-induced colitis mouse model,B. bifidumBGN4-SK treatment significantly enhanced levels of antioxidant enzymes SOD, glutathione peroxidase (GSH-Px) and CAT, compared to the DSS-only group.B. bifidumBGN4-SK significantly ameliorated the symptoms of DSS-induced colitis, increased the expression of tight junction genes (claudin and ZO-1), and decreased pro-inflammatory cytokines IL-6, IL-1β and TNF-α.Conclusions: These findings suggest thatB. bifidumBGN4-SK ameliorated DSS-induced colitis by generating antioxidant enzymes, maintaining the epithelial barrier, and decreasing the production of pro-inflammatory cytokines. AlthoughB. bifidumBGN4-pBESIL10 exerted anti-inflammatory effects in vitro, the enhancement of IL-10 production and alleviation of colitis were very limited.

Bifidobacterium bifidum BGN4-SK (BGN4-SK), a recombinant strain which was constructed from B. bifidum 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 MnSO₄ and 30 μM hematin, with glucose as the carbon source. The viability and intracellular antioxidant enzyme activities of H₂O₂-stimulated HT-29 treated with BGN4-SK were significantly higher (p < 0.05) than those of cells treated with BGN4. The intracellular ROS levels of H₂O₂-stimulated HT-29 cells treated with BGN4-SK were significantly lower (p < 0.05) than those of cells treated with BGN4. BGN4-SK more significantly suppressed the production of interleukin (IL)-6 (p < 0.05), tumor necrosis factor-α (p < 0.01), and IL-8 (p < 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 H₂O₂-stimulated HT-29 cells and enhanced anti-inflammatory activities in LPS-stimulated HT-29 and RAW 264.7 cells.