Potential association between TLR4 and chitinase 3-like 1 (CHI3L1/YKL-40) signaling on colonic epithelial cells in inflammatory bowel disease and colitis-associated cancer

Inflammatory bowel disease (IBD) is a group of inflammatory disorders in the small and large intestines. Several studies have proved that persistent and disregulated host/microbial interactions are required for the development of IBD. It is well known that chronic IBD is strongly associated with an increased risk of developing colorectal cancer by 0.5-1% annually, 8-10 years after the initial diagnosis. To detect the tiny dysplasia or early stage of cancer in chronic IBD patients, a tremendous amount of effort is currently directed for improving colonoscopic technology and noninvasive serological marker development. However, there is only a limited amount of data available to understand the exact mechanism of how long term chronic colitis is connected to the development of colorectal tumors. Recently, our group has identified significantly increased expression of chitinase 3-like 1 (CHI3L1) molecule in non-dysplastic mucosa from patients with IBD and remote dysplasia/cancer, compared to patients with IBD without dysplasia or healthy controls. CHI3L1 seems to contribute to the proliferation, migration, and neoplastic progression of colonic epithelial cells (CECs) under inflammatory conditions. Furthermore, the TLR4-mediated intracellular signaling cascade is likely to interact with CHI3L1 signaling in CECs. In this review article, we have concisely summarized the cellular and molecular mechanisms underlining the development of IBD and colitis-associated cancer, with particular focus on the TLR4- and CHI3L1-signaling pathways in CECs.

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.

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.

Chitinase 3-like 1 enhances bacterial adhesion to colonic epithelial cells through the bacterial chitin-binding motif (112.9)

Chitinase 3-like-1 (CHI3L1) is an inducible molecule in colonic epithelial cells (CECs), and the chitin-binding motif (CBM) in CHI3L1 regulates host-microbial interactions. To examine the existence of CBMs in E. coli, we used ChtBD3 as a search in the SMART database. We found that 11 genomes of E. coli strains contain a gene encodes for ChiA, which has multiple CBMs. There are 5 different amino acids (Q362K, E370K, V378A, V388E & E548V) in CBMs, and the E.coli are grouped into pathogenic- and non-pathogenic strains by substitution. To examine the role of CBMs in E. coli, we generated a deletion mutant (ΔchiA) of the Adherent Invasive E. coli (AIEC) LF82, and performed in vitro assays. LF82 ΔchiA has 50% less adhesion to CECs as compared to LF82. This phenotype is fully recovered when the mutant carries out pHSG575 with LF82 ΔchiA, but not withLF82 chiA plus 5 mutations or E. coli K12 chiA. To test the in vivo influence, B6 mice were treated 2% DSS to enhance the CHI3L1 on CECs and were orally inoculated with LF82 (WT or ΔchiA) for 15 days. In contrast to LF82, mice infected with LF82 ΔchiA showed less body weight loss, a lower clinical score, less stool bacteria and less cellular infiltration in the colon. A significantly increased number of E. coli adhered/invaded the colon in LF82-infected mice, as compared to LF82 ΔchiA-infected or control mice. In conclusion, CBMs of AIEC play a critical role in their adhesion to CHI3L1-expressing CECs during 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 β-(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.

Risk of infection associated with umbilical vein catheterization. A prospective study in 75 newborn infants

To determine the risk of infection created by catheterization of the umbilical vein per se, 75 jaundiced, but otherwise healthy, newborn infants subjected to exchange transfusion were studied. Twenty-three were given antibiotics because of premature rupture of membranes. Fifty-three percent of the umbilici were contaminated before the insertion of the catheter, even after a very careful cleansing procedure. Sixty-two percent of the catheters were colonized upon removal. Bacteria were isolated from 44.9% of blood specimens drawn via the catheter at the onset of ET, but only in 14% of blood specimens drawn in the same way at the end of the procedure. Seven newborn infants (10%) were found to be bacteremic 4-6 after ET; four of these infants were not treated and were able to eliminate the bacteremia. Systemic antibiotic therapy did not reduce the overall prevalence of colonization of cord and catheter of positive blood cultures pre- and postexchanges transfusion or the rate of bacteremia.