TLR4 single-nucleotide polymorphisms alter mucosal cytokine and chemokine patterns in Mexican patients with Helicobacter pylori-associated gastroduodenal diseases

Genetic association of Toll-like-receptor 4 and tumor necrosis factor-alpha polymorphisms with Plasmodium falciparum blood infection levels

Dysregulated innate immune responses due to inappropriate signaling by Toll-like receptors (TLRs) and aberrant production of pro-inflammatory cytokines are implicated in the immunopathology and disease outcome in Plasmodium falciparum malaria. This study investigates the relationship between polymorphic variability of candidate genes including TLR-2, -4, -9, tumor necrosis factor-alpha and lymphotoxin-alpha and blood infection level in Indian mild malaria patients. Genotyping was carried out by PCR-RFLP and sequencing. Association of parasite load with genotypes was examined using model based and model free approaches. Allele and haplotype based risk assessment for disease severity was performed by stratifying the patients into high and low parasitemic groups on the basis of a threshold value derived by employing a two-component mixture model and expectation-maximization algorithm. The mean parasitemia was significantly increased for variant homozygous genotype (C/C) at TNF-alpha promoter -1031 and major homozygous genotypes encoding Asp/Asp and Thr/Thr at codons 299 and 399, respectively, on TLR4 polypeptide. Individuals harboring combined genotype C/C-Asp/Asp-Thr/Thr on TNF-alpha and TLR4 presented the highest parasite load. The frequencies of variant allele C in TNF-1031 (OR=1.91 with 95% CI=1.24-2.94) and TNF-alpha promoter haplotypes C-C-G-G (OR=1.99 with 95% CI=1.21-3.27) and C-C-G-A (OR=2.96 with 95% CI=1.19-7.37) pertaining to loci TNF-1031/-857/-308/-238 were significantly elevated in the high parasitemic group. On the contrary, the frequencies of variant allele encoding Ile at 399 (OR=0.55 with 95% CI=0.32-0.94) and haplotype corresponding to Gly-Ile (299-399) (OR=0.51 with 95% CI=0.28-0.9) in TLR4 were higher in low parasitemic group. In silico analysis indicate differential binding of transcription factors to TNF-alpha promoter haplotypes and alteration in the surface charge distribution of the TLR4 variant proteins. Our results support a genetic role of TLR4 and TNF-alpha in controlling the blood infection level in mild malaria.

Increase in NF-kappaB binding affinity of the variant C allele of the toll-like receptor 9 -1237T/C polymorphism is associated with Helicobacter pylori-induced gastric disease

Colonization of the gastric mucosa by Helicobacter pylori can lead to serious clinical outcomes, including gastric cancer. Toll-like receptors (TLRs) play an important role in the host response to H. pylori through the recognition of pathogen-associated molecular patterns. TLR9, in particular, is partly responsible for initiating bacterial induced immunity by binding unmethylated CpG-DNA, which is abundant in bacteria. A well-documented single nucleotide polymorphism (SNP) within the TLR9 promoter (TLR9 -1237T/C), is associated with a variety of inflammatory disorders, including allergic asthma, inflammatory bowel disease, and atopy. Analysis of the TLR9 promoter gene sequence has shown that carriage of the variant "C" allele at position -1237 creates a potential NF-kappaB binding site that would theoretically increase the transcriptional activity of the gene. In this study, we report that the TLR9 -1237 C allele was significantly associated with the development of H. pylori-induced premalignant gastric changes. Functional analysis of the SNP, supporting the data generated from the genetic association study, showed that carriage of the C allele increased TLR9 transcriptional activity driven mainly by activation of NF-kappaB. Collectively, these findings confirm that the TLR9 -1237T/C polymorphism is a risk factor for the development of H. pylori-induced premalignant gastric changes and provide a plausible mechanistic explanation.

Helicobacter pylori and non-malignant diseases

It is well known that Helicobacter pylori infection is associated with many nonmalignant disorders such as gastritis, peptic ulcer, gastroesophageal reflux disease (GERD), gastric polyp, nonsteroidal anti-inflammatory drug (NSAID)/aspirin-induced gastric injury, and functional dyspepsia. In 2008, interesting articles on the association of H. pylori infection with these disorders were presented, some of which intended to reveal the mechanisms of inter-individual differences in response to H. pylori infection, and have demonstrated that genetic differences in host and bacterial factors as well as environmental factors account for these differences. A decline in the occurrence of peptic ulcer related to H. pylori was confirmed. An inverse relationship between H. pylori infection and GERD was also confirmed but the impact of gastric atrophy on the prevention of GERD remained debatable. For NSAID-induced gastric injury, eradication of H. pylori infection has been recommended. During this year, eradication of H. pylori infection was recommended for patients treated with antiplatelet therapy as well as aspirin and NSAID. It was also reported that for patients with functional dyspepsia, eradication of H. pylori offers a modest but significant benefit.

Association Between Toll-like Receptor 4 Gene Polymorphism and Biopsy-proven Giant Cell Arteritis

Objective.

Dendritic cells localized at the adventitia-media border of the normal medium-sized arteries play a pivotal role in the initiation of giant cell arteritis (GCA). These cells express a singular surface receptor profile, including a series of Toll-like receptors (TLR). Ligands of TLR-4 promote activation and differentiation of adventitial dendritic cells and are directly implicated in the pathogenesis of GCA. We aimed to assess the potential implication of the TLR4-(+896 A/G) gene polymorphism in the susceptibility to GCA.

Methods.

A total of 210 patients diagnosed with biopsy-proven GCA and 678 matched controls were included in our study. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the TLR4-(+896 A/G) (rs4986790) gene polymorphism by polymerase chain reaction, using a predesigned TaqMan allele discrimination assay.

Results.

The TLR4 +896 G allele was significantly increased in biopsy-proven GCA patients compared to controls [p = 0.01; odds ratio (OR) 1.65; 95% confidence interval (CI) 1.08–2.52]. The increase was due to a significantly increased frequency of heterozygosity for the TLR4 −896 A/G genotype in the group of patients with biopsy-proven GCA compared to controls (TLR4 −896 A/G heterozygous in patients with GCA 18.1% compared to 11.4% in controls: p = 0.01; OR 1.72; 95% CI 1.10–2.69). However, no significant differences were observed when patients with GCA were stratified according to the presence of specific clinical features of the disease.

Conclusion.

Our results show for the first time an association of TLR4-(+896 A/G) gene polymorphism with susceptibility to biopsy-proven GCA.