Anti-inflammatory Activities of Lactococcus lactis subsp. cremoris FC in In Vitro and In Vivo Gut Inflammation Models

Many food factors such as probiotics are effective against human gastrointestinal disorders including inflammatory bowel disease. However, it remains unclear how probiotics act to protect against intestinal inflammation. Here, we describe a novel in vitro gut inflammation model for evaluating the anti-inflammatory activity of food factors, and in vitro and in vivo inflammation models for assessment of the gut anti-inflammatory activities of Lactococcus lactis subsp. cremoris FC (strain FC). A coculture system with intestinal epithelial Caco-2 cells and RAW264.7 macrophages can be used to assess the anti-inflammatory activity of food factors. Stimulation of RAW264.7 cells with lipopolysaccharide (LPS) increases tumor necrosis factor (TNF)-α production from RAW264.7 cells and interleukin (IL)-8 mRNA expression in Caco-2 cells and decreases the transepithelial electrical resistance of Caco-2 monolayers. The increases in TNF-α and IL-8 mRNA are suppressed by anti-TNF-α antibodies or budesonide. This indicates that this coculture model can imitate gut inflammation in vivo. Strain FC significantly downregulates IL-8 mRNA expression in Caco-2 cells and inhibits nuclear factor-κB nuclear translocation in RAW264.7 cells. A mouse model of dextran sulfate sodium (DSS)-induced colitis has been used to assess the anti-inflammatory activity of strain FC, which significantly ameliorates shortening of the colon and improves colon histology, especially in inflammatory cell infiltration, and proinflammatory cytokine and chemokine mRNA expression in inflamed tissue. These results indicate that oral administration of strain FC improves DSS-induced colitis through inhibition of inflammatory cell infiltration and that Caco-2/RAW264.7 cells stimulated with LPS can be used for screening anti-inflammatory factors and elucidating the mechanism of anti-inflammatory activity.