Protective effects of a novel probiotic strain, Lactococcus lactis ML2018, in colitis: in vivo and in vitro evidence

Multiple articles have confirmed that an imbalance of the intestinal microbiota is closely related to aberrant immune responses of the intestines and to the pathogenesis of inflammatory bowel diseases (IBDs). Probiotic strains have been identified for the treatment and prevention of IBDs. The aim of this study was to screen a new probiotic strain with anti-inflammatory activity and investigate the potential mechanisms underlying its activity. We identified a new probiotic strain, L. lactis ML2018, that has anti-inflammatory properties and was isolated from traditional fermented food. In an in vitro experiment, L. lactis ML2018 prevented the release of nitric oxide (NO) and the production of inflammatory factors induced by lipopolysaccharides (LPS) in RAW264.7 cells. The in vivo anti-inflammatory effects of L. lactis ML2018 were evaluated using a dextran sulfate sodium (DSS)-induced animal model of colitis. Oral administration of L. lactis ML2018 significantly ameliorated colitis induced by DSS, which included preventing a decrease in body weight, shortening of the colon length and apoptosis of epithelial cells. L. lactis ML2018 could inhibit DSS-induced intestinal inflammation by preventing the overproduction of proinflammatory factors, suppressing the infiltration of macrophages, controlling the fibrosis, improving the integrity of the intestinal epithelial barrier and upregulating the concentrations of short-chain fatty acids (SCFAs). Moreover, L. lactis ML2018 could prevent inflammation by inhibiting the activation of the NF-κB and MAPK signaling pathways. These data suggest that L. lactis ML2018 could have therapeutic potential for treating IBDs.