Myosin light chain kinase involved in change of intestinal mucosal barrier function in nonalcoholic steatohepatitis mice model

Abstract

To investigate the role of myosin light chain kinase (MLCK) in intestinal barrier function in a mouse model with nonalcoholic steatohepatitis (NASH). The C57BL/6 mice were randomly divided into five groups including control group, nonalcoholic fatty liver (NAFL) group, NAFL administrated with MLCK inhibitor ML-7 group, nonalcoholic steatohepatitis (NASH) group, NASH administrated with ML-7 group. Plasma ALT and AST were tested. The degree of liver steatosis was assessed by hematoxylin-eosin staining on liver tissue sections.Intestinal mucosal tight junction was observed by electron microscope. The expression of MLCK on intestinal mucosa was detected by immunohistochemistry staining. The level of lipopolysaccharide (LPS) in portal vein was determined by enzyme linked immune sorbent assay (ELISA). The protein and mRNA expression of inflammatory cytokines in liver tissue were tested using ELISA and real-time PCR. MLCK expression in intestinal mucosa was increased in NASH group compared with control group (P<0.01). The tight junctions of intestinal barrier were disrupted in NASH group and intercellular space was larger than control group [(26.60 ± 1.20) nm vs (14.90 ± 0.33) nm, P<0.05], which were improved after ML-7 administration [(14.9 0 ± 0.67) nm]. The LPS in portal vein was higher in NASH group than control group [(7.260 ± 3.184) U/L vs (2.962 ± 0.845) U/L, P<0.05], suggesting that the permeability of intestinal barrier was impaired, however the level of LPS was reduced by ML-7 [(3.772 ± 1.033) U/L, P<0.05]. ALT and AST in plasma, TNFα and IL-6 in liver tissue, the mRNA levels of TNFα and NF-κB in liver tissue were all elevated in NASH group compared with control group (all P<0.05), which were reduced by MLCK inhibitor ML-7. Epithelia MLCK probably plays a role in intestinal barrier impairment, which is critical to the pathogenesis of NASH.