Analysis of Cd14 as a genetic modifier of experimental inflammatory bowel disease (IBD) in mice

Abstract

Background and Aim: By combining QTL and gene expression analyses, we have previously identified Cd14 as a potential candidate gene contributing to the differential IBD susceptibility of C3H/HeJBir (C3/J)–Il10−/− mice [carrying IBD‐resistance alleles at this QTL (Cdcs6)] and C57BL/6J (B6)–Il10−/− mice, corroborating studies that showed an association of a CD14‐promoter polymorphism with Crohn's disease and ulcerative colitis. The aim of the present study was to analyze the molecular mechanisms leading to differential intestinal expression of Cd14 and its contribution to IBD development. Methods: Intestinal CD14 expression was assessed by FACS, immunohistochemistry, and ELISA on supernatants of primary epithelial cell and tissue cultures. RAW264.7 cells were stimulated with LPS and PGN in the presence or absence of CD14. Cd14 alleles were sequenced and promoters cloned for luciferase assays in transfected RAW264.7 cells. The severity of typhlocolitis between Cd14−/− and wild‐type mice was compared in 2 distinct mouse models of IBD (acute DSS and Il10−/−). Results: In the gut, CD14 was detected mainly in its soluble form (sCD14), with higher expression in C3/J‐Il10−/− mice. Polymorphisms in C3/J mice caused higher activity of the Cd14 promoter (luciferase assays). Intestinal sCD14 concentrations influenced the LPS and PGN responses of RAW264.7 cells. In vivo, genetic deletion of Cd14 aggravated colitis in both mouse models of IBD. Conclusions: Our study shows that Cd14‐promoter polymorphisms affect CD14 expression and confirms the protective effect of CD14 against experimental IBD, potentially mediated by TLR2‐ and TLR4‐dependent effects on intestinal barrier function. These findings support the concept that human CD14‐promoter polymorphisms contribute to disease development. Inflamm Bowel Dis 2009

Cd14 SNPs regulate the innate immune response

“…Physiologic concentrations of human sCD14 had a dual effect on DCs. First, sCD14 functioned as a signal-amplifier, enabling DCs to respond to low concentrations of microbial products, which is consistent with similar findings by other investigators (Cauwels et al, 1999; Chase and Bosio, 2010; de Buhr et al, 2009). Second, sCD14 stimulated IL-6 production by human DCs.…”

Cardiolipins Act as a Selective Barrier to Toll-Like Receptor 4 Activation in the Intestine

“…Shed CL as well as the intestinal phospholipid barrier may represent another mechanism by which monophosphorylated family Bacteroidaceae-type LPS in the intestinal lumen due to significantly lower binding to LBP and transfer to CD14 (52) is neutralized before engagement of TLR4. In addition, both LBP and CD14 are made by intestinal epithelial cells (62,63), and evidence that they contribute to intestinal homeostasis has been reported (64,65). Furthermore, modulation of TLR4 activity by LPB may have some clinical utility in treating necrotizing enterocolitis (66).…”

Differences in Mucosal Gene Expression in the Colon of Two Inbred Mouse Strains after Colonization with Commensal Gut Bacteria

“…The latter strain shares a considerable proportion of its genetic background with the C57BL/10 mice that were used in our experiment because C57BL/6 and C57BL/10 are sub-strains of C57BL origin. For Cd14 , which is involved in the detection of lipopolysaccharides by TLR4, it was later demonstrated that a higher expression by gut epithelial cells is responsible for a lower colitis susceptibility in IL-10 -/- mice with a C3H than with a C57BL/6 background [36]. Whether or not differences in intestinal Cd14 expression are also involved in the selection of resident gut bacteria remains to be clarified.…”