Comparative study of effect of Akkermansia muciniphila and its extracellular vesicles on toll-like receptors and tight junction

AIM: We assessed effect of Akkermansia muciniphila and its extracellular vesicles on toll-like receptors and tight junction expression in human epithelial colorectal adenocarcinoma cells (Caco-2). BACKGROUND: The intestinal microbiota plays an important role in the intestinal homeostasis through its metabolites and derivatives. Interacting with immune cells and intestinal epithelial pattern recognition receptors (PRRs), intestinal microbiota regulates the function of the digestive barrier and inflammation caused by the metabolic diseases. METHODS: A. muciniphila was cultured on a mucin-containing medium and its EVs was extracted by ultracentrifugation. This bacterium was treated in the MOI=10 and its EVs at the concentrations of 0.1, 0.5 and 5 µg on Caco-2 cells. After 24 hours, the expression of tight junction and toll-like receptor genes were investigated by quantitative real time PCR method. RESULTS: A. muciniphila increased the expression of tlr2 and tlr4. However, EVs at all of the concentrations showed a decrease in tlr4 expression. EVs at the concentrations of 0.1 and 0.5 µg/ml decreased the expression of tlr2. A. muciniphila significantly increased the expression of ocldn and cldn4. Both this bacterium and EVs increased the expression of zo2 in the cell line. Furthermore, this data show that A. muciniphila derived EVs have a dose-independent effect on Caco-2 cells. CONCLUSION: This preliminary research shows A. muciniphila and its EVs both may increase the integrity of the intestinal barrier. A. muciniphila derived EVs also reduces the inflammation so that EVs of this bacterium can be used as an appropriate target for the treatment of metabolic syndrome and inflammatory bowel diseases.