The protective effect of Escherichia coli Nissle 1917 on the intestinal barrier is mediated by inhibition of RhoA/ROCK2/MLC signaling via TLR-4

This study investigated the protective effect of Escherichia coli Nissle 1917 (EcN) on intestinal barrier and the mechanism in the context of acute severe inflammation. In this study, mice received lipopolysaccharide (LPS) intraperitoneal injection with or without EcN administration to construct a mouse model of endotoxemia. Clinical scores, intestinal permeability, inflammatory cytokines and histopathological analysis of four main organs from different groups were assessed. The expression of tight junction proteins and activation of RhoA/ROCK2/MLC signaling were examined using western blotting. The localization of tight junction proteins was examined by immunofluorescence. Caco-2 monolayers with or without TLR-4 knockdown were incubated with EcN or TNF-α/IFN-γ and the monolayer barrier function was assessed by transepithelial electrical resistance (TER) and FITC-dextran 4000 Da (FD-4) flux. The expression of tight junction proteins and activation of RhoA/ROCK2/MLC signaling were examined by western blotting. The localization of tight junction proteins was examined by immunofluorescence. We found that EcN downregulated the RhoA/ROCK2/MLC signaling pathway to preserve barrier function and alleviated systemic inflammation in mouse model. And EcN also protected barrier function of Caco-2 monolayers by inhibiting the activation of RhoA/ROCK2/MLC signaling via TLR-4. The results indicated that EcN protected the intestinal barrier function in endotoxemia through inhibiting the activation of RhoA/ROCK2/MLC signaling via TLR-4.