Phosphorylated-myosin light chain mediates the destruction of small intestinal epithelial tight junctions in mice with acute liver failure

Abstract

Tight junction dysregulation and epithelial damage contribute to intestinal barrier loss in patients with acute liver failure (ALF); however, the regulatory mechanisms of these processes remain poorly understood. The aim of the present study was to investigate the changes of intestinal tight junction and intestinal mucosa in mice with ALF and their mechanisms. In the present study, ALF was induced in mice through an intraperitoneal injection of D-galactosamine and lipopolysac- charide (D-GalN/LPS), and the morphological changes of the liver or small intestine were analyzed using hematoxylin and eosin staining, scanning electron microscopy (SEM) and trans- mission electron microscopy (TEM). The intestinal tissues and isolated serum were analyzed using western blotting, immuno- fluorescence staining and ELISA. D-GalN/LPS-induced mice exhibited signs of hepatocyte necrosis, alongside inflammatory cell infiltration into the liver tissue and partial microvilli detach- ment in the small intestinal mucosa. TEM demonstrated that the intestinal epithelial tight junctions were impaired, whereas SEM micrographs revealed the presence of abnormal micro- villi in D-GalN/LPS-induced mice. In addition, the expression levels of phosphorylated (p)-myosin light chain (MLC), MLC kinase (MLCK) and Rho-associated kinase (ROCK) were significantly increased in the D-GalN/LPS-induced mice compared with those in the control mice, whereas the subse- quent inhibition of MLCK or ROCK significantly reduced p-MLC expression levels. Conversely, the expression levels of occludin and zonula occludens-1 (ZO-1) were significantly decreased in the D-GalN/LPS-induced mice, and the inhibition of MLCK or ROCK significantly increased occludin and ZO-1 protein expression levels compared with those in the control group. Changes in the serum levels of tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were similar to the trend observedinp-MLCexpressionlevels.Inconclusion,thefindings of the present study suggested that in a D-GalN/LPS-induced ALF model, TNF-α and IL-6 signaling may increase MLCK and ROCK expression levels, further mediate phosphorylation of MLC, which may result in tight junction dysregulation and intestinal barrier dysfunction.