Enterococcus faecalis Strains Differentially Regulate Alix/AIP1 Protein Expression and ERK 1/2 Activation in Intestinal Epithelial Cells in the Context of Chronic Experimental Colitis

Monoassociation of germfree Interleukin 10 gene deficient (IL-10-/-) 129SvEv but not wild-type mice with Enterococcus faecalis induces severe chronic colitis. Bacterial strain-specific effects on the development of chronic intestinal inflammation are not understood. We investigated the molecular mechanisms of E faecalis OG1RF (human clinical isolate, colitogenic) and E. faecalis ms2 (endogenous isolate from an IL-10-/- mouse) in initiating chronic experimental colitis using IL-10-/- mice. Monoassociation of IL-10-/- mice for 14 weeks revealed significant differences in colonic inflammation (3.6 +/- 0.2 and 2.4 +/- 0.6 for OG1RF and ms2, respectively) (n = 5 mice in each group) (histological scoring (0-4)). Consistent with the tissue pathology, gene expression of the pro-inflammatory chemokine interferon-gamma inducible protein-10 (IP-10) was significantly higher in intestinal epithelial cells (IEC) derived from E. faecalis OG1RF monoassociated IL-10-/- mice. We further compared the differentially E faecalis induced colitis on the epithelial level by 2D-SDS PAGE coupled with MALD1-TOF MS. Proteome analysis identified 13 proteins which were differentially regulated during disease progression in the epithelium of E faecalis-monoassociated IL-10-/- mice. Regulation of Alix/AlP1 protein expression and ERK1/2 phosphorylation was validated in primary IEC and epithelial cell lines, suggesting a protective role for Alix/AlP1 in the process of disease progression. Alix/AlP1 protein expression was further characterized in epithelial cell lines using siRNA-mediated knock-down. Our study demonstrates E faecalis strain-specific induction of colitis in IL-10-/- mice after 14 weeks of monoassociation. Our study suggests that Alix/AlP1 protein expression and ERK1/2 activation are decreased in severe colitis.