The Role of Up-Regulated Serine Proteases and Matrix Metalloproteinases in the Pathogenesis of a Murine Model of Colitis

Abstract

Proteinases are important at several phases of physiological and pathological inflammation, mediating cellular infiltration, cytokine activation, tissue damage, remodeling, and repair. However, little is known of their role in the pathogenesis of inflammatory bowel disease. The aim of this study was to assess the role of tissue proteases in a mouse model of colitis. Proteolytic activity was analyzed, using gel and in situ zymography, in colonic tissues from severe combined immunodeficient mice with colitis induced by transfer of CD4 ؉ T lymphocytes. Serine proteinase levels increased in colitic tissue, with major species of 23 kd, 30 kd, and 45 kd. Co-migration and inhibition studies indicated that the 23-kd proteinase was pancreatic trypsin and that the 30-kd species was neutrophil elastase. Matrix metalloproteinase (MMP)-9 expression, and MMP-2 and MMP-9 activation, was elevated in colitic tissues. Proteinase levels followed a decreasing concentration gradient from proximal to distal colon. Proteolysis was localized to infiltrating leukocytes in diseased severe combined immunodeficient mice. The inflammatory bowel diseases (IBD), Crohn's disease, and ulcerative colitis, probably share a common etiology, in terms of a dysregulation of mucosal T cell reactivity.

Trypsin-Sensitive Modulation of Intestinal Epithelial MD-2 as Mechanism of Lipopolysaccharide Tolerance

“…Protein analysis using ExPASy demonstrated that MD-2 contained multiple trypsin cleavage sites. High amounts of proteolytically active trypsin have recently been found predominantly at mucosal sites of acute inflammation in the small intestine (24,38,39). As confirmed by immunofluorescence microscopy, trypsin content was significantly increased in severely inflamed areas of ileal mucosa in active CD ileitis, whereas colitic samples of UC or CD patients exhibited negligible amounts of trypsin (Fig.…”

“…IEC of noninvolved areas close to ileal inflammation were positive for MD-2 in CD, suggesting that translational synthesis is not primarily disturbed and that reduction may rather reflect the secondary effect of some inflammatory mediator(s) present in active ileitis. Proteolytically active trypsin is known to be increased in acute mucosal inflammation of the small intestine and proximal colon (24,38,39). Decreased MD-2 correlated inversely with augmented trypsin activity in CD-associated ileal areas of severe inflammation, and increased MD-2 was associated with diminished trypsin expression in colonic areas of mucosal inflammation in CD or UC patients.…”

“…The serine protease trypsin has previously been implicated in tissue destruction in acute small intestinal inflammation (23,24). However, by acting as prodefensin convertase in Paneth cells, trypsin is also involved as host defense mechanism in the regulation of innate immunity in the small intestine (25).…”

Constitutive expression of MMP9 in intestinal epithelium worsens murine acute colitis and is associated with increased levels of proinflammatory cytokine Kc

“…Our laboratory has also shown that such MMP9 driven inflammation was largely mediated by MMP9 expressed by epithelial cells in response to the inflammatory challenge (12). Furthermore, MMP9 activity is correlated with active inflammation associated with fistula formation (43,48). In addition, MMP9 tissue and serum levels correlate with disease activity in UC (1,28,35).…”

Protease-Activated Receptors as Therapeutic Targets in Visceral Pain

“…Under physiological conditions, colonic trypsin activity is constantly counterbalanced by the presence of trypsin inhibitors [43]. On the contrary, in patients with inflammatory bowel disease (IBD), ulcerative colitis and Crohn's disease, there is a reduction of the expression of the trypsin inhibitor [44] [45] and thus, trypsin activity is increased in IBD patients [46]. Indeed, this phenomenon has also been observed in animal models of colitis [47].…”