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Expression and function of TLR2, TLR4, and Nod2 in primary canine colonic epithelial cells.

ABSTRACT: The gut maintains a delicate balance between the downregulation of inflammatory reactions to commensal bacteria and the capacity to respond to pathogens with vigorous cellular and humoral immune responses. Intestinal epithelial cells, including colonic epithelial cells (CECs) possess many properties of cells of the innate immune system, in particular the ability to recognize and respond to microbial antigens. Recognition of microorganisms by CECs is based upon their recognition of signature molecules, called microbe-associated molecular patterns (MAMP), by pattern recognition receptors (PRR) including membrane toll-like receptors (TLR) and cytosolic Nod2, an intracellular counterpart of TLRs. The purpose of this study was to determine whether primary CECs from normal dogs express a functional TLR2, TLR4, and Nod2 and whether they are regulated by inflammatory mediators. We show that canine primary CECs express TLR2, TLR4, and Nod2 that can be modulated in response to their respective MAMPs, lipopolysaccharides (LPS) or peptidoglycans (PGN). Furthermore, we demonstrate that these receptors are functional as evidenced by the induction of cytokine gene expression in response to LPS or PGN.

SUBMITTER: Swerdlow MP

PROVIDER: S-EPMC1850225 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature

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Expression and function of TLR2, TLR4, and Nod2 in primary canine colonic epithelial cells.

Swerdlow Mathew P MP Kennedy Douglas R DR Kennedy Jeffrey S JS Washabau Robert J RJ Henthorn Paula S PS Moore Peter F PF Carding Simon R SR Felsburg Peter J PJ

Veterinary immunology and immunopathology 20061005 3-4

The gut maintains a delicate balance between the downregulation of inflammatory reactions to commensal bacteria and the capacity to respond to pathogens with vigorous cellular and humoral immune responses. Intestinal epithelial cells, including colonic epithelial cells (CECs) possess many properties of cells of the innate immune system, in particular the ability to recognize and respond to microbial antigens. Recognition of microorganisms by CECs is based upon their recognition of signature mole ...[more]

PMID: 17027090

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Project description:The colonic microbiota is a major modulator of the mucosal immune system; therefore, its manipulation through supplementation with probiotics may significantly affect the host's immune responses. Since different probiotics seem to exert various effects in vivo, we tested the relevance of the autoaggregation phenotype on the intestinal persistence of lactobacilli and their ability to modulate the host's innate immune responses. After 14 days of diet supplementation, the aggregating strain Lactobacillus crispatus M247 but not aggregation-deficient isogenic mutant MU5 was recovered from the feces and colonic mucosa of mice. This observation was confirmed by strain-specific PCR amplification and by Lactobacillus-specific denaturing gradient gel electrophoresis analysis. Indeed, L. crispatus M247 increased Toll-like receptor 2 (TLR2) mRNA levels, while it reduced TLR4 mRNA and protein levels in the colonic mucosa, whereas MU5 was ineffective. In colonic epithelial cells (CMT-93 cells) L. crispatus M247 but not MU5 induced time-dependent extracellular signal-regulated kinase-1 (ERK1) tyrosine phosphorylation and TLR modulation, which were abolished in the presence of PD98059 (an ERK1 inhibitor). To assess the functional relevance of probiotic-induced TLR modulation, we determined the consequences of L. crispatus preexposure on TLR4 (lipopolysaccharide [LPS]) and TLR2 [Pam3Cys-Ser-(Lys)4] ligand-mediated effects in intestinal epithelial cells. Preexposure to L. crispatus M247 blunted LPS-induced interleukin-6 (IL-6) release and inhibition of CMT-93 migration over a wound edge, whereas it enhanced TLR2-mediated IL-10 up-regulation. In summary, the aggregation phenotype is required for L. crispatus persistence in the colon and for modulation of TLR2/TLR4 expression through an ERK-dependent pathway. We speculate that the aggregation phenotype in L. crispatus M247 is required to temper epithelial cell responsiveness to bacterial endotoxins, which thus affects the evolution of intestinal inflammatory processes.

Project description:Hyperglycemia is thought to increase production of inflammatory cytokines and permeability of the large intestine. Resulting intestinal inflammation is then often characterized by excess secretion of tumor necrosis factor alpha (TNFα). Thus, hyperglycemia in hospitalized patients suffering from severe trauma or disease is frequently accompanied by TNFα secretion, and the combined impact of these insults on the intestinal epithelium is poorly understood. This study utilized a simple yet elegant model of the intestinal epithelium, comprised of primary human intestinal stem cells and their differentiated progeny, to investigate the impact of hyperglycemia and inflammatory factors on the colonic epithelium. When compared to epithelium cultured under conditions of physiologic glucose, cells under hyperglycemic conditions displayed decreased mucin-2 (MUC2), as well as diminished alkaline phosphatase (ALP) activity. Conditions of 60 mM glucose potentiated secretion of the cytokine IL-8 suggesting that cytokine secretion during hyperglycemia may be a source of tissue inflammation. TNFα measurably increased secretion of IL-8 and IL-1β, which was enhanced at 60 mM glucose. Surprisingly, intestinal permeability and paracellular transport were not altered by even extreme levels of hyperglycemia. The presence of TNFα increased MUC2 presence, decreased ALP activity, and negatively impacted monolayer barrier function. When TNFα hyperglycemia and ≤30 mM glucose and were combined, MUC2 and ALP activity remained similar to that of TNFα alone, although synergistic effects were seen at 60 mM glucose. An automated image analysis pipeline was developed to assay changes in properties of the zonula occludens-1 (ZO-1)-demarcated cell boundaries. While hyperglycemia alone had little impact on cell shape and size, cell morphologic properties were extraordinarily sensitive to soluble TNFα. These results suggest that TNFα acted as the dominant modulator of the epithelium relative to glucose, and that control of inflammation rather than glucose may be key to maintaining intestinal homeostasis.

Project description:AimTo evaluate the effect of promoter region polymorphisms of toll-like receptor (TLR)2-196 to -174del and TLR4-1607T/C (rs10759932) on mRNA and protein expression in tumor tissue and of TLR4+896A/G (rs4986790) on colorectal cancer (CRC) risk.MethodsThe TLR2-196 to -174del polymorphism was investigated using allele-specific polymerase chain reaction (PCR) and the TLR4-1607T/C and TLR4+896A/G by PCR-restriction fragment length polymorphism (RFLP). We genotyped 434 DNA samples from 194 CRC patients and 240 healthy individuals. The mRNA relative quantification (RQ) was performed in 40 tumor tissue samples by quantitative PCR TaqMan assay, using specific probes for TLR2 and TLR4 genes, and ACTB and GAPDH reference genes were used as endogenous controls. Protein expression was analyzed by immunohistochemistry with specific primary antibodies.ResultsNo association was found for TLR4-1607T/C and TLR4+896A/G by three statistical models (log-additive, dominant and recessive). However, based on dominant and log-additive models, the polymorphic variant TLR2-196 to -174del was associated with increased CRC risk [dominant: odds ratio (OR) = 1.72, 95%CI: 1.03-2.89; P = 0.038 and log-additive: OR =1.59, 95%CI: 1.02-2.48; P = 0.039]. TLR2 mRNA expression was increased in tumor tissue (RQ = 2.36) when compared to adjacent normal tissue (RQ = 1; P < 0.0001), whereas the TLR4 mRNA showed a basal expression (RQ = 0.74 vs RQ = 1, P = 0.452). Immunohistochemistry analysis of TLR2 and TLR4 protein expression was concordant with the findings of mRNA expression. In addition, the TLR2-196 to -174del variant carriers showed mRNA relative expression 2.19 times higher than wild-genotype carriers. The TLR2 protein expression was also higher for the TLR2-196 to -174del variant carriers [117 ± 10 arbitrary unit (a.u.) vs 95 ± 4 a.u., P = 0.03]. However, for the TLR4 -1607T/C polymorphism no significant difference was found for both mRNA (P = 0.56) and protein expression (P = 0.26).ConclusionOur findings suggest that TLR2-196 to -174del polymorphism increases TLR2 mRNA expression and is associated with higher CRC risk, indicating an important role in CRC genetic susceptibility.

Dataset Information

Expression and function of TLR2, TLR4, and Nod2 in primary canine colonic epithelial cells.

Publications

Expression and function of TLR2, TLR4, and Nod2 in primary canine colonic epithelial cells.

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