Abstract
Compromised gastrointestinal barrier function is strongly associated with the progressive and destructive pathologies of the two main forms of irritable bowel disease (IBD), ulcerative colitis (UC), and Crohn's disease (CD). Matriptase is a membrane-anchored serine protease encoded by suppression of tumorigenicity-14 (ST14) gene, which is critical for epithelial barrier development and homeostasis. Matriptase barrier-protective activity is linked with the glycosylphosphatidylinositol (GPI)-anchored serine protease prostasin, which is a co-factor for matriptase zymogen activation. Here we show that mRNA and protein expression of both matriptase and prostasin are rapidly down-regulated in the initiating inflammatory phases of dextran sulfate sodium (DSS)-induced experimental colitis in mice, and, significantly, the loss of these proteases precedes the appearance of clinical symptoms, suggesting their loss may contribute to disease susceptibility. We used heterozygous St14 hypomorphic mice expressing a promoter-linked β-gal reporter to show that inflammatory colitis suppresses the activity of the St14 gene promoter. Studies in colonic T84 cell monolayers revealed that barrier disruption by the colitis-associated Th2-type cytokines, IL-4 and IL-13, down-regulates matriptase as well as prostasin through phosphorylation of the transcriptional regulator STAT6 and that inhibition of STAT6 with suberoylanilide hydroxamic acid (SAHA) restores protease expression and reverses cytokine-induced barrier dysfunction. Both matriptase and prostasin are significantly down-regulated in colonic tissues from human subjects with active ulcerative colitis or Crohn's disease, implicating the loss of this barrier-protective protease pathway in the pathogenesis of irritable bowel disease.
Highlights
Compromised gastrointestinal barrier function is strongly associated with the progressive and destructive pathologies of the two main forms of irritable bowel disease (IBD), ulcerative colitis (UC), and Crohn’s disease (CD)
We show that the coordinate down-regulation of matriptase and prostasin by cytokines produced during inflammatory colitis likely contributes to the increased permeability associated with cytokine-mediated intestinal epithelial barrier dysfunction during colitis
The dramatic and early loss of matriptase and prostasin mRNA in murine colonic tissue during dextran sulfate sodium (DSS)-induced colitis suggests that even low levels of inflammation can cause the loss of this barrier-protective pathway, perpetuating disease progression
Summary
The early response to experimental colitis is similar between control and St14 hypomorphic mice. The mRNA expression was normalized to the mRNA of the epithelial cell marker EpCAM to account for the possible loss of signal because of epithelial cell death by DSS exposure (Fig. 3, A and B) Both matriptase and prostasin mRNA levels were significantly decreased as early as 1.5 days after DSS administration and remained low through 5 days of DSS treatment, compared with mice treated with water alone (Fig. 3, A and B). Ison of X-gal staining of colonic tissues from heterozygous St14 hypomorphic mice administered DSS for either 1.5 or 5 days, or water alone, shows a dramatic loss in the intensity of blue staining in the presence of DSS, even in areas where the intestinal epithelium remains intact (Fig. 3C, 40ϫ) These data show that mucosal inflammation induced by exposure to DSS down-regulates matriptase through suppression of the St14 gene promoter. We found that matriptase and prostasin mRNA levels are significantly reduced in colonic tissues from patients with both UC and CD (Fig. 7), consistent with the loss of this barrierprotective protease pathway in the dysregulation of barrier function during human IBD
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