A MAJOR ROLE FOR MATRIX METALLOPROTEINASES IN T-CELL INJURY IN THE GUT

Activated lamina propria T cells responding to luminal Ags are thought to be important in celiac disease and Crohn's disease, and T cells re sponding to foreign MHC products are also important in intestinal graf t-vs-host disease and intestinal transplant rejection, However, the me chanism(s) by which T cells mediate damage in the gut is not known. We have previously shown that activation of lamina propria T cells by PW M in explant cultures of second trimester human small intestine produc es severe tissue injury, with epithelial cell shedding and loss of vil li. In this study, we have investigated the role of matrix metalloprot einases in this system. Organ culture supernatants of explants stimula ted with PWM showed a 3-fold increase in the concentration of intersti tial collagenase and a 10-fold increase in stromelysin-1 compared with control explant culture supernatants. Tissue inhibitors of metallopro teinase-1 and -2 concentrations were unchanged. Increased metalloprote inase enzymatic activity was detected by gelatin and casein zymography . Western blotting revealed the active forms of interstitial collagena se and stromelysin-1 in PWM-stimulated culture supernatants, Up-regula tion of mRNA for interstitial collagenase, stromelysin-1, and gelatina se-B was also seen. Nanomolar amounts of recombinant stromelysin-1 add ed directly to explants produced rapid severe tissue injury. PWM-induc ed mucosal injury was inhibited by a synthetic peptidomimetic inhibito r of matrix metalloproteinases, Mesenchymal cells isolated from the mu cosa of human fetal small intestine produced increased amounts of inte rstitial collagenase, gelatinase A, and stromelysin-1 when stimulated with IL-1 beta or TNF-alpha. These results suggest that T cell activat ion in the lamina propria results in increased production of matrix me talloproteinases, which by degrading the lamina propria matrix represe nt a major pathway by which T cells cause injury in the gut.