The Paneth Cell α-Defensin Deficiency of Ileal Crohn’s Disease Is Linked to Wnt/Tcf-4

Abstract

Ileal Crohn′s disease (CD), a chronic mucosal inflammation, is characterized by two pertinent features: a specific decrease of Paneth cell-produced antimicrobial α-defensins and the presence of mucosal-adherent bacteria. A mutation in NOD2, the muramyl dipeptide recognition receptor, is found in some patients, which leads to an even more pronounced α-defensin decrease. However, the underlying mechanism remains unclear for the majority of patients. In this study, we report a reduced expression in ileal CD of the Wnt-signaling pathway transcription factor Tcf-4, a known regulator of Paneth cell differentiation and α-defensin expression. Within specimens, the levels of Tcf-4 mRNA showed a high degree of correlation with both HD5 and HD6 mRNA. The levels of Tcf-4 mRNA were decreased in patients with ileal disease irrespective of degree of inflammation, but were not decreased in colonic CD or ulcerative colitis. As a functional indicator of Tcf-4 protein, quantitative binding analysis with nuclear extracts from small intestine biopsies to a Tcf-4 high-affinity binding site in the HD-5 and HD-6 promoters showed significantly reduced activity in ileal CD. Furthermore, a causal link was shown in a murine Tcf-4 knockout model, where the comparably reduced expression of Tcf-4 in heterozygous (+/−) mice was sufficient to cause a significant decrease of both Paneth cell α-defensin levels and bacterial killing activity. Finally, the association between Paneth cell α-defensins and Tcf-4 was found to be independent of the NOD2 genotype. This new link established between a human inflammatory bowel disease and the Wnt pathway/Tcf-4 provides a novel mechanism for pathogenesis in patients with ileal CD.

Intestinal Microbes in Inflammatory Bowel Diseases

“…However, a similar decrease in α -defensin production was not seen in patients with Crohn ' s disease of the colon, UC patients, or those with pouchitis. Th ese decreases in α -defensin production are probably the result of reduced expression of Wnt and Tcf-4, a transcription factor that controls the expression of several downstream target genes critical in the positioning, diff erentiation, and maturation of Paneth cells in intestinal crypts ( 34 ). Th e functional consequences of reduced α -defensin expression were subsequently confi rmed in a mouse transgenic model; in these mice, changes in HD5 expression had a profound eff ect on the intestinal microbiota, with a change from predominantly small bacilli and cocci in wild-type mice to a mixed population of bacilli and fusiform bacterial species in heterozygous mice, and fi nally to a population of predominantly fusiform bacteria in homozygous transgenic mice ( 35 ).…”

Peroxisome proliferator-activated receptor gamma activation is required for maintenance of innate antimicrobial immunity in the colon

“…Gel mobility shift assays were performed as described previously (24). In brief, human PPARγ and RXRα protein were synthesized using pSG5-h-PPARγ-1, pSG5-h-PPARγ-2, and pCDNA3.1-RXRα according to the protocol of the TNT T7 Quick-Coupled Transcription/ Translation System (Promega).…”

“…Extraction of cationic proteins from colonic and ileal tissue of Pparγ +/− (n = 6) and Pparγ +/+ (n = 5) mice was performed as described previously (24). C. albicans (clinical isolate 526; Institute of Laboratory Medicine, Klinik am Eichert), E. faecalis (clinical isolate 404), and E. coli (clinical isolate 304446) were grown aerobically at 37°C, whereas B. fragilis (ATCC 25285) was cultured anaerobically (Anaero Gen; Oxoid).…”

Increased Gut Permeability and Microbiota Change Associate with Mesenteric Fat Infl ammation and Metabolic Dysfunction in Diet-Induced Obese Mice

“…Supplementary, major proceedings in our understanding of the checks and balance systems within epithelial proliferative gut networks provide new views on different intestinal disorders. Our group could, for instance, elucidate an involvement of disturbed Wnt signalling, which is crucial for epithelial proliferation but also Paneth cell antimicrobial function, in chronic small intestinal inflammation (Koslowski et al, 2012;Wehkamp et al, 2007). Moreover, we also reported an influence of gut bacteria regarding the expression of transcription factors controlling epithelial secretory lineage decision making as well as Goblet cell differentiation (Becker et al, 2013).…”