Enterococcus faecalis metalloprotease compromises epithelial barrier and contributes to intestinal inflammation

Background & Aims: Matrix metalloproteases (MMPs) mediate pathogenesis of chronic intestinal inflammation. We characterized the role of the gelatinase (GelE), a metalloprotease from Enterococcus faecalis, in the development of colitis in mice. Methods: Germ-free, interleukin-10deficient (IL-10 ^-/-) mice were monoassociated with the colitogenic E faecalis strain OG1RF and isogenic, GelE-mutant strains. Barrier function was determined by measuring E-cadherin expression, transepithelial electrical resistance (TER), and translocation of permeability markers in colonic epithelial cells and colon segments from IL-10^-/- and TNF^ΔARE/Wt mice. GelE specificity was shown with the MMP inhibitor marimastat. Results: Histologic analysis (score 04) of E faecalis monoassociated IL-10^-/- mice revealed a significant reduction in colonic tissue inflammation in the absence of bacteria-derived GelE. We identified cleavage sites for GelE in the sequence of recombinant mouse E-cadherin, indicating that it might be degraded by GelE. Experiments with Ussing chambers and purified GelE revealed the loss of barrier function and extracellular E-cadherin in mice susceptible to intestinal inflammation (IL-10^-/- and TNF^ΔARE/Wt mice) before inflammation developed. Colonic epithelial cells had reduced TER and increased translocation of permeability markers after stimulation with GelE from OG1RF or strains of E faecalis isolated from patients with Crohn's disease and ulcerative colitis. Conclusions: The metalloprotease GelE, produced by commensal strains of E faecalis, contributes to development of chronic intestinal inflammation in mice that are susceptible to intestinal inflammation (IL-10^-/- and TNF^ΔARE/Wt mice) by impairing epithelial barrier integrity.