MMP-9-induced increase in intestinal tight junction permeability is mediated by P38 kinase signaling pathway activation of Myosin Light Chain Kinase gene.

Matrix Metalloproteinase-9 (MMP-9) has been implicated to be an important pathogenic factor in inflammatory bowel disease (IBD). MMP-9 is markedly elevated in intestinal tissue of patients with IBD, and IBD patients have a defective intestinal tight junction (TJ) barrier manifested by an increase in intestinal permeability. The loss of intestinal barrier function is a contributing factor in the development of intestinal inflammation, the role of MMP-9 in intestinal barrier function remains unclear. The purpose of this study was to investigate the effect of MMP-9 on intestinal epithelial TJ barrier and to delineate the intracellular mechanisms involved using in-vitro and in-vivo model systems. MMP-9 caused a time- and dose-dependent increase in Caco-2 TJ permeability. MMP-9 also caused an increase in myosin light chain kinase (MLCK) gene activity, protein expression, and enzymatic activity. The inhibition of MLCK and siRNA-induced knock-down of MLCK inhibited the MMP-9-induced increase in Caco-2 TJ permeability. The MMP-9 caused a rapid activation of p38 kinase signaling pathway and inhibition of p38 kinase activity prevented the MMP-9 induced increase in MLCK gene activity and TJ permeability. MMP-9 also caused an increase in mouse intestinal permeability in-vivo and that was accompanied by an increase in MLCK expression. The MMP-9-induced increase in mouse intestinal permeability was inhibited in MLCK deficient mice. These data show that the MMP-9-induced increase in intestinal TJ permeability was mediated by p38 kinase signaling pathway activation of MLCK gene activity and therapeutic targeting of these pathways can prevent the MMP-9-induced increase in intestinal TJ permeability.