Toll-like receptor 4 (TLR4) gene polymorphisms in celiac disease

Toll-like Receptors and Celiac Disease

Celiac disease (CD) is an immune-mediated disorder triggered by dietary gluten intake in some genetically predisposed individuals; however, the additional non-HLA-related genetic factors implicated in CD immunopathogenesis are not well-defined. The role of the innate immune system in autoimmunity has emerged in the last few years. Genetic polymorphisms of some pattern-recognition receptors, including toll-like receptors (TLRs), have been associated with several autoimmune disorders. In this review, we summarize and discuss the evidence from basic research and clinical studies as regards the potential role of TLRs in CD immunopathogenesis. The evidence supporting the role of TLRs in CD immunopathogenesis is limited, especially in terms of basic research. However, differences in the expression and activation of TLRs between active CD patients from one side, and controls and treated CD patients from the other side, have been described in some clinical studies. Therefore, TLRs may be part of those non-HLA-related genetic factors implicated in CD etiopathogenesis, considering their potential role in the interaction between the host immune system and some environmental factors (including viral infections and gut microbiota), which are included in the list of candidate agents potentially contributing to the determination of CD risk in genetically predisposed individuals exposed to dietary gluten intake. Further basic research and clinical studies focused on TLRs in the context of CD and other gluten-related disorders are needed.

Non-celiac wheat sensitivity: rationality and irrationality of a gluten-free diet in individuals affected with non-celiac disease: a review

Non-celiac gluten or wheat sensitivity (NCWS) is a “clinical entity induced by the ingestion of wheat leading to intestinal and/or extraintestinal symptoms that improve once the wheat-containing foodstuff is removed from the diet, and celiac disease and wheat allergy have been excluded”. This mostly accepted definition raises several points that remain controversial on this condition. In the present review, the authors summarize the most recent advances in the clinic and research on NCWS through an accurate analysis of different studies. We screened PubMed, Medline, Embase, and Scopus using the keywords “non-celiac gluten sensitivity”, “non-celiac wheat sensitivity”, and “diagnosis”. We would like to emphasize two main points, including (A) the controversial clinical and etiological aspects in different trials and experiences with particular attention to the Salerno criteria for the diagnosis of NCWS and (B) the histological aspects. The etiology of NCWS remains controversial, and the relationship with irritable bowel syndrome is obscure. Histologically, the duodenal mucosa may show a variable pattern from unremarkable to a slight increase in the number of T lymphocytes in the superficial epithelium of villi. The endorsement of this disease is based on a positive response to a gluten-free diet for a limited period, followed by the reappearance of symptoms after gluten challenge. The Salerno expert criteria may help to diagnose NCWS accurately. Social media and inaccurate interpretation of websites may jeopardize the diagnostic process if individuals self-label as gluten intolerant.

Association between AKT rs2494752 single nucleotide polymorphism and the risk of metastasis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of human tumors, which is characterized by high morbidity and mortality rates. AKT1 transcriptional activity is implicated in HCC initiation and development. In the present study, the effects of rs2494752 single nucleotide polymorphism (SNP) on AKT1 transcriptional activity in the progression of HCC cells were investigated. A case-control study was analyzed in 1,056 HCC patients and 1,080 healthy individuals using the PCR assay method. Results indicated AKT1 expression levels were up-regulated in HCC tissue compared to adjacent normal tissues. Furthermore, a higher frequency of AKT rs2494752 AG and AA genotypes were observed in HCC cases (P=0.0046). Gene polymorphism identified C and T alleles were frequency in HCC patients compared to healthy individuals. Individuals harboring AKT rs2494752 AG/AA genotype had a vital increased susceptibility to HCC in the dominant model (P=0.0028). In addition, AKT1 rs2494752 GG genotype showed an increasing of AKT1 promoter activity determined by the luciferase assay. Furthermore, it was demonstrated that AKT1 rs2494752 GG and C polymorphism was more aggressive than other AKT1 rs2494752 cancer cells. Moreover, AKT1 rs2494752 GG markedly increased rates of response to NCT chemotherapy. Additionally, results revealed that AKT1 rs2494752 GG and C increased the risk factors of HCC. In conclusion, these results indicate that AKT1 rs2494752 polymorphisms may be regarded as a candidate gene in assessing the susceptibility, metastasis and responses to chemotherapy in the progression of hepatocellular carcinoma.

Duodenal expression of Toll-like receptors and interleukins are increased in both children and adult celiac patients

BACKGROUND

Toll-like receptors (TLRs) have achieved an extraordinary amount of interest in inflammatory diseases due to their role in the inflammatory activation. By activating the production of several biological factors, TLRs induce type I interferons and other cytokines, which drive the inflammatory response and activate the adaptive immune system.

AIMS

The aim of this study was to investigate and compare the expression and clinical relevance of TLRs and interleukins in pediatric and adult celiac disease (CD), defined as intolerance to dietary proteins found in wheat, barley, and rye.

METHODS

The expression levels of TLR3, TLR4, and TLR7, interleukins, and different transcription factors were analyzed on duodenal biopsies from ten children and 31 adults with CD, and 21 duodenal controls biopsies without CD (ten children and 11 adults). The analyses were performed by immunohistochemistry and real-time PCR.

RESULTS

There were no significant differences in the studied parameters between adults and children. TLR4 expression level was increased twofold in CD specimens compared to controls. CD patients with high levels of TLR4 also showed high levels of interleukins (IL1, IL6, IL8, and IL17) as well as transcription factors (IRAK4, MyD88, and NF-κB).

CONCLUSIONS

TLR4 expression is associated with CD independently of age at diagnosis. Pediatric patients and adult patients have a similar inflammatory profile, making it possible to treat both with the same immunological therapy in the future.

Alteration of CXCR7 expression mediated by TLR4 promotes tumor cell proliferation and migration in human colorectal carcinoma

The link between inflammation and colorectal carcinoma has been acknowledged. However, the impact of bacterial lipopolysaccharide (LPS) binding to Toll-like receptor 4 (TLR4) on chemokine receptors in human colorectal carcinoma cells still remains to be elucidated. The present study shows that exposure to LPS elevated CXC chemokine receptor 7 (CXCR7) expression in colorectal carcinoma SW480 and Colo 205 cell lines expressing TLR4/myeloid differential protein (MD-2). CXCR7 is associated with SW480 cell proliferation and migration. However, exposure of SW480 and Colo 205 cells to LPS had no effect on CXCR4 expression. To further support the above results, the expression of TLR4, MD-2, and CXCR7 was analyzed in human colorectal carcinoma tissues. Higher rates of TLR4 (53%), MD-2 (70%), and CXCR7 (29%) expression were found in colorectal carcinoma tissues than in normal tissues. We demonstrated that the recombination of TLR4, MD-2 and CXCR7 strongly correlated with tumor size, lymph node metastasis and distant metastasis in colorectal carcinoma tissue samples (p = 0.037, p = 0.002, p = 0.042, resp.). Accordingly, simultaneous examination of the expression of TLR4, MD-2 and CXCR7 in cancer tissues of colorectal carcinoma may provide valuable prognostic diagnosis of carcinoma growth and metastasis. Interplay of TLR4, MD-2 and CXCR7 may be of interest in the context of novel immunomodulatory therapies for colorectal carcinoma.

Unraveling the ties between celiac disease and intestinal microbiota

Celiac disease is a multifactorial disorder that involves interactions between genetic and environmental factors. Gluten proteins are responsible for the symptoms of celiac disease, but other environmental factors that influence the intestinal ecosystem, including the milk-feeding type and gastrointestinal infections, may also play a role. Moreover, intestinal dysbiosis, characterized by increased Gram-negative bacteria and reduced bifidobacteria, has been detected in celiac disease patients. This review summarizes current knowledge of the associations between the intestinal microbiota and celiac disease and its possible modes of action in pathogenesis. Deeper understanding of these interactions can help redefine how this disorder is investigated.

Analysis of beta-defensin and Toll-like receptor gene copy number variation in celiac disease

Celiac disease (CD) is an immune-mediated disorder of the gut in which innate and adaptive responses are involved. Toll-like receptor (TLR) 2 and TLR4 participate in host defense through antigen recognition, and show altered expression in CD gut mucosa. beta-defensins are inducible antimicrobial peptides, and DEFB gene copy number polymorphisms have been associated with autoimmune and inflammatory disorders. We performed copy number analysis of TLR2, TLR4, and the beta-defensin cluster (DEFB4, DEFB103 and DEFB104) by gene-specific, real-time polymerase chain reaction (PCR) in 376 CD patients and 376 controls. TLR genes did not show copy number variation, and all samples presented with two copies. beta-defensin clusters varied between 2 and 9 copies per genome, and when grouped into bins, high copy numbers (>4) were underrepresented among patients (p = 0.023; odds ratio = 0.69, 95% CI = 0.50-0.96), suggesting that increased copy numbers could protect from CD, possibly by impeding bacterial infiltration more efficiently and preserving gut epithelial integrity.

Anti-microbial antibodies in celiac disease: Trick or treat?

AIM: To determine the prevalence of a new set of anti-glycan and anti-outer membrane protein (anti-OMP) antibodies in a Hungarian cohort of adult Celiac disease (CD) patients.

METHODS: 190 consecutive CD patients [M/F: 71/119, age:39.9 (SD:14.1) years], 100 healthy, and 48 gastrointestinal controls were tested for glycan anti-Saccharomyces cerevisiae (gASCA), anti-laminaribioside (ALCA), anti-chitobioside, anti-mannobioside, anti-OMP antibodies and major NOD2/CARD15 mutations. Thirty out of 82 CD patients enrolled at the time of diagnosis were re-evaluated for the same antibodies after longstanding gluten-free diet (GFD).

RESULTS: 65.9% of the CD patients were positive for at least one of the tested antibodies at the time of the diagnosis. Except anti-OMP and ALCA, anti-microbial antibodies were exclusively seen in untreated CD; however, the overall sensitivity was low. Any glycan positivity (LR+: 3.13; 95% CI: 2.08-4.73) was associated with an increased likelihood ratio for diagnosing CD. Significant correlation was found between the levels of anti-glycan and anti-endomysial or anti-transglutaminase antibodies. Anti-glycan positivity was lost after longstanding GFD. Anti-glycan antibody titers were associated with symptoms at presentation, but not the presence of NOD2/CARD15 mutations. Patients with severe malabsorption more frequently had multiple antibodies at diagnosis (P = 0.019).

CONCLUSION: The presence of anti-glycan antibodies in CD seems to be secondary to the impaired small bowel mucosa which can lead to increased antigen presentation. Furthermore, anti-glycan positivity may be considered an additional marker of CD and dietary adherence.

Recent advances in coeliac disease

PURPOSE OF REVIEW

Worldwide awareness of coeliac disease in all ages continues to grow. This article aims to summarize critically the recent research advances in coeliac disease.

RECENT FINDINGS

Large multicentre studies have provided further evidence of the role of environmental and nonhuman leucocyte antigen genetic factors in coeliac disease. Siblings of coeliac patients carry a high risk, but those found to have negative coeliac serology are very unlikely to develop the disease. Advances in the efficacy of serological antibody testing potentiate the possibility of future accurate screening programmes in the community. Adherence to a gluten-free diet remains paramount as the recognition of coeliac related complications increases.

SUMMARY

Despite the encouraging progress that has taken place in our genetic and immunological knowledge of coeliac disease, early introduction of a gluten-free diet remains the cornerstone of treatment. Alternatives, however, aimed at altering the toxicity of cereal proteins are now looking more promising.

A TLR2 polymorphism is associated with type 1 diabetes and allergic asthma

Type 1 diabetes (T1D) and allergic asthma are immune-mediated diseases. Pattern recognition receptors are proteins expressed by cells in the immune system to identify microbial pathogens and endogenous ligands. Toll-like receptors (TLRs) and CD14 are members of this family and could represent a molecular link between microbial infections and immune-mediated diseases. Diverging hypotheses regarding whether there exists a common or inverse genetic etiology behind these immune-mediated diseases have been presented. We aimed to test whether there exist common or inverse associations between polymorphisms in the pattern recognition receptors TLR2, TLR4 and CD14 and T1D and allergic asthma. Eighteen single nucleotide polymorphisms (SNPs) were genotyped in TLR2 (2), TLR4 (12) and CD14 (4) in 700 T1D children, 357 nuclear families with T1D children and 796 children from the 'Environment and Childhood Asthma' study. Allele and haplotype frequencies were analyzed in relation to diseases and in addition transmission disequilibrium test analyses were performed in the family material. Both T1D and allergic asthma were significantly associated with the TLR2 rs3804100 T allele and further associated with the haplotype including this SNP, possibly representing a susceptibility locus common for the two diseases. Neither TLR4 nor CD14 were associated with T1D or allergic asthma.

Curcumin attenuates inflammation through inhibition of TLR-4 receptor in experimental colitis

Curcumin, an active ingredient of Curcumin longa mediates its anti-inflammatory effects through inhibition of NFkB. Several pathways including toll-like receptors (TLR) induce NFkB leading to inflammation. In this study, we investigated the effects of curcumin on the expression of TLR-4 and MyD88, the upstream signaling pathway in experimental colitis induced in the Sprague-Dawley male rats by intra-rectal administration of trinitrobenzenesulfonic acid (TNBS). The animals which received TNBS were divided into two groups: Group 1, received aqueous suspension of curcumin (100 mg/Kg body weight) 2 h prior to inducing colitis, and the treatment was repeated every day for 5 days, and Group 2 and non-colitis (Group 3) animals received phosphate buffered saline (PBS) in a similar fashion. Non-colitis animals (Group 4) received curcumin and served as controls. Animals were sacrificed on day 5 post-TNBS by cervical dislocation, colon was taken out, and cleaned with PBS. Levels of TLR-4, MyD88, and NFkB proteins were measured using ECL Western blot analysis, and TLR-4 mRNA by a competitive RT-PCR method. Colitis was confirmed histologically by measuring myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels in the colonic tissues. TNBS-induced increase in the level of MPO activity and MDA concentrations was reversed by curcumin treatment, whereas the same dose of curcumin did not affect their levels in the non-colitis animals. Increases in the levels of TLR-4, MyD88, and NFkB proteins in inflamed tissue were also suppressed significantly by curcumin treatment. The level of TLR-4 mRNA remained unchanged in the colitis animals. These findings demonstrate that signaling pathway of curcumin-induced inhibition of inflammation involves TLR-4 and MyD88, and therefore may serve as an important therapeutic target in IBD.

Toll-like receptors, transduction-effector pathways, and disease diversity: evidence of an immunobiological paradigm explaining all human illness?

Membrane-bound Toll-like receptors (TLRs) are frontline guardians in the mammalian innate immune system. They primarily function to recognize pathogen-associated molecular patterns (PAMPs) of invading microorganisms and on activation mount rapid, nonspecific innate responses and trigger sequential delayed specific adaptive cellular responses, which are mediated by complex signal transduction pathways involving adaptor molecules, costimulatory ligands and receptors, kinases, transcription factors, and modulated gene expression. Increasing evidence of multiple functionality and diversity suggests TLRs play critical roles in noninfective medical conditions such as cardiovascular, gastrointestinal, neurologic, musculoskeletal, obstetric, renal, liver, and dermatologic diseases, allergy, autoimmunity, and tissue regeneration. The significance of TLR heterogeneity underscores the possibility for establishing a universal immunobiological model to explain all human disease. Novel immunomodulatory therapies targeting specific or multiple TLRs may in the future offer new tools to combat or eradicate pathogenesis potentially transforming the landscape of current medical treatments.