Colitis-Associated Variant of TLR2 Causes Impaired Mucosal Repair Because of TFF3 Deficiency

Abstract

Background & aims Goblet cells (GC) facilitate mucosal protection and epithelial barrier repair, yet the innate immune mechanisms that selectively drive GC functions have not been defined. The aim of this study was to determine whether TLR2 and modulation of GC-derived TFF3 are functionally linked in the intestine. Methods GC modulation was assessed using qRT-PCR, western blotting and confocal microscopy. DSS colitis was induced in wild-type, TFF3−/− and TLR2−/− mice. Recombinant TLR2 ligand or TFF3 peptide were orally administered after DSS termination. Caco-2 overexpressing full-length TLR2 or mutant TLR2-R753Q were tested for TFF3 synthesis and functional-related effects in a wounding-assay. Results Data from in-vitro (Ls174T) and ex-vivo models of murine and human GC reveal that TLR2 activation selectively induces synthesis of TFF3. In-vivo studies using TFF3−/− or TLR2−/− mice demonstrate the ability for oral treatment with a TLR2 agonist to confer anti-apoptotic protection of the intestinal mucosa against inflammatory stress-induced damage through TFF3. Recombinant TFF3 rescues TLR2-deficient mice from increased morbidity and mortality during acute colonic injury. Severe ulcerative colitis has recently been found to be associated with the R753Q polymorphism of the TLR2 gene. The relevance of the observed functional effect of TLR2 in regulating GC is confirmed by the finding that the UC-associated TLR2-R753Q variant is functionally deficient in the ability to induce TFF3 synthesis, thus leading to impaired wound healing. Conclusions These data demonstrate a novel function of TLR2 in intestinal GC that links products of commensal bacteria to innate immune protection of the host via TFF3.

Culture of human intestinal epithelial cell using the dissociating enzyme thermolysin and endothelin-3

“…HIEC play a central role in absorptive and secretory functions, protecting the organisms from bacteria and toxins, providing an effective barrier against the complex antigenic load of intestinal contents (3,25). However, difficulties still exist in establishing an HIEC cell line in China.…”

“…Published May 14, 2010. Epithelial cells lining the intestinal mucosa play a key role in the homeostasis of the organisms (1,2). Depending on their location in the intestinal tract, they not only play a central role in absorptive and secretory functions, but also have the ability to protect the organism from various pathogens and toxins found even under the normal conditions in the intestine, providing an effective barrier to the complex antigenic load of intestinal contents (3). In addition, some of the most serious pathological conditions, such as inflammatory bowel disease (IBD), are known to be associated with alterations of the normal growth and functions of the intestinal epithelium (4).…”

Colonic mucosal DNA methylation, immune response, and microbiome patterns in Toll-like receptor 2-knockout mice

“…This result was particularly interesting since TLR2 has been associated with severe forms of UC implicating its role as a modifier in inflammatory bowel diseases. 39 Overall, we could conclude that the genetic deficiency of a molecule with distinctive roles in bacterial pattern recognition (Tlr2) induces a comprehensive response at the level of the colonic mucosa that involves the reconstitution of both the epithelial transcriptional network (including epigenetic modifications) and the associated microbiota. This reconstitution is likely sensitive to the genetic background of the host and may be responsive to nutritional exposures (such as folate supplementation) during specific stages of development.…”

Bifidobacterium bifidum reduces apoptosis in the intestinal epithelium in necrotizing enterocolitis

“…TLR-4 has been the most frequently studied in NEC models, and it is suggested that activation of TLR-4 signaling leads to increased intestinal injury (22,27,30). In colitis models, TLR-2 protects intestinal mucosa against injury via regulation of epithelial apoptosis (3,4,36), and, recently, a role for TLR-2 in NEC pathogenesis was also suggested (30,41). However, the role of TLR-2 in probiotics-mediated protection against NEC is not known.…”