Chitinase 3-like 1 synergistically activates IL6-mediated STAT3 phosphorylation in intestinal epithelial cells in murine models of infectious colitis.

BACKGROUND: Chitinase 3-like 1 (CHI3L1) is an inducible molecule on intestinal epithelial cells during the development of inflammatory bowel disease. METHODS: To investigate the role of CHI3L1 in bacterial infectious colitis, we orally inoculated pathogenic Salmonella typhimurium and potentially pathogenic adherent-invasive Escherichia coli (AIEC) LF82 virulent strain into C57Bl/6 wild-type mice or CHI3L1 knockout (KO) mice. RESULTS: Both S. typhimurium and AIEC LF82 were found to efficiently induce severe intestinal inflammation in wild-type mice but not in CHI3L1 KO mice. These bacteria-infected CHI3L1 KO mice exhibit decreased cellular infiltration, bacterial translocation, and production of interleukin (IL)-6 and IL-22, as compared with those of wild-type mice. More importantly, CHI3L1 KO mice displayed aberrant STAT3 activation after bacterial infections. Co-stimulation of CHI3L1 and IL-6, but not IL-22, synergistically activates STAT3 signaling pathway in intestinal epithelial cells in an NF-κB/MAPK-dependent manner. CONCLUSIONS: CHI3L1 promotes the onset of selected gram-negative bacterial infectious colitis through IL-6/STAT3 pathway.

Novel methylxanthine derivative-mediated anti-inflammatory effects in inflammatory bowel disease.

Family 18 chitinases have a binding capacity with chitin, a polymer of N-acetylglucosamine. Recent studies strongly suggested that chitinase 3-like 1 (CHI3L1, also known as YKL-40) and acidic mammalian chitinase, the two major members of family 18 chitinases, play a pivotal role in the pathogenesis of inflammatory bowel disease (IBD), bronchial asthma and several other inflammatory disorders. Based on the data from high-throughput screening, it has been found that three methylxanthine derivatives, caffeine, theophylline, and pentoxifylline, have competitive inhibitory effects against a fungal family 18 chitinase by specifically interacting with conserved tryptophans in the active site of this protein. Methylxanthine derivatives are also known as adenosine receptor antagonists, phosphodiesterase inhibitors and histone deacetylase inducers. Anti-inflammatory effects of methylxanthine derivatives have been well-documented in the literature. For example, a beneficial link between coffee or caffeine consumption and type 2 diabetes as well as liver cirrhosis has been reported. Furthermore, theophylline has a long history of being used as a bronchodilator in asthma therapy, and pentoxifylline has an immuno-modulating effect for peripheral vascular disease. However, it is still largely unknown whether these methylxanthine derivative-mediated anti-inflammatory effects are associated with the inhibition of CHI3L1-induced cytoplasmic signaling cascades in epithelial cells. In this review article we will examine the above possibility and summarize the biological significance of methylxanthine derivatives in intestinal epithelial cells. We hope that this study will provide a rationale for the development of methylxanthine derivatives, in particular caffeine, -based anti-inflammatory therapeutics in the field of IBD and IBD-associated carcinogenesis.

Oral caffeine administration ameliorates acute colitis by suppressing chitinase 3-like 1 expression in intestinal epithelial cells.

BACKGROUND: The initial trigger of inflammatory bowel disease (IBD) can be partly attributed towards the interaction and invasion of intestinal epithelial cells (IECs) and submucosal compartments. Identifying safe and economical methods to block these interactions may help prevent the onset of early colitis. Chitinase 3-like 1 (CHI3L1) is an inducible host protein that facilitates bacterial attachment and invasion on/into IECs. Therefore, we test the hypothesis of inhibiting CHI3L1 using the pan-chitinase inhibitor caffeine to reduce the likelihood of early colitis onset. METHODS: IEC lines were treated with caffeine (2.5 or 5 mM) and analyzed for CHI3L1 expression and the impact on bacterial invasion. In vivo, mice were treated with 2.5 mM caffeine and induced with 3.5 % dextran sulfate sodium (DSS)-mediated colitis and subsequently analyzed colitis development. RESULTS: In vitro, caffeine treatment in IEC lines down-regulated CHI3L1 mRNA expression, which resulted in the reduction of bacterial invasion in a caffeine dose-dependent manner. In vivo, mice treated with caffeine displayed a delayed response towards DSS-induced colitis, characterized by lower body weight loss, clinical and histological scores. Bacterial translocation into other organs and pro-inflammatory cytokines production were also reduced in the caffeine-treated mice with DSS-induced colitis. Caffeine treatment also resulted in the loss of CHI3L1-associated AKT signaling pathway activation both in vitro and in vivo. CONCLUSION: Development of acute colitis is reduced upon caffeine treatment. The mechanism involves the down-regulation of CHI3L1 expression and its associated bacterial interaction effect. Therefore, caffeine is proposed as a safe and economical candidate for successful IBD management.

Chitin-binding domains of Escherichia coli ChiA mediate interactions with intestinal epithelial cells in mice with colitis.

BACKGROUND & AIMS: Inducible chitinase 3-like-1 is expressed by intestinal epithelial cells (IECs) and adheres to bacteria under conditions of inflammation. We performed a structure-function analysis of the chitin-binding domains encoded by the chiA gene, which mediates the pathogenic effects of adherent invasive Escherichia coli (AIEC). METHODS: We created AIEC (strain LF82) with deletion of chiA (LF82-ΔchiA) or that expressed chiA with specific mutations. We investigated the effects of infecting different IEC lines with these bacteria compared with nonpathogenic E coli; chitinase activities were measured using the colloidal chitin-azure method. Colitis was induced in C57/Bl6 mice by administration of dextran sodium sulfate, and mice were given 10(8) bacteria for 15 consecutive days by gavage. Stool/tissue samples were collected and analyzed. RESULTS: LF82-ΔchiA had significantly less adhesion to IEC lines than LF82. Complementation of LF82-ΔchiA with the LF82 chiA gene, but not chiA from nonpathogenic (K12) E coli, increased adhesion. We identified 5 specific polymorphisms in the chitin-binding domain of LF82 chiA (at amino acids 362, 370, 378, 388, and 548) that differ from chiA of K12 and were required for LF82 to interact directly with IECs. This interaction was mediated by an N-glycosylated asparagine in chitinase 3-like-1 (amino acid 68) on IECs. Mice infected with LF82, or LF82-ΔchiA complemented with LF82 chiA, developed more severe colitis after administration of dextran sodium sulfate than mice infected with LF82-ΔchiA or LF82 that expressed mutant forms of chiA. CONCLUSIONS: AIEC adheres to an N-glycosylated chitinase 3-like-1 on IECs via the chitin-binding domain of chiA. This mechanism promotes the pathogenic effects of AIEC in mice with colitis.

Role of chitotriosidase (chitinase 1) under normal and disease conditions.

Mammalian chitinases belong to the glycosyl hydrolase 18 family based on structural homology and the family includes a large number of bacterial and eukaryotic chitinases. Among the mammalian chitinases, chitotriosidase (CHIT1) and acidic mammalian chitinase (AMCase) are capable of hydrolyzing the ß-(1, 4)-linkage between the adjacent N-acetyl glucosamine residues of chitin. CHIT1 is one of the most abundantly secreted proteins, being mainly produced by activated macrophages and epithelial cells. CHIT1 plays a pivotal role in the context of infectious disease including malaria and fungi infections as a host defense towards chitin in pathogen's cell structure and as a diagnostic marker of disease. In contrast, CHI1 released by activated Kupffer cells in liver could induce hepatic fibrosis and cirrhosis. Increased serum levels of CHIT1 were observed in patients with many disorders, including Gaucher's disease, bronchial asthma, and atherosclerosis. Therefore, CHIT1 seems to have dual (regulatory and pathogenic) roles depending on the disease and producing cell types during the inflammatory conditions.