Association between Toll-Like Receptor 4 T399I Gene Polymorphism and the Susceptibility to Crohn's Disease: A Meta-Analysis of Case-Control Studies

Associations of TLR4 and IL-8 genes polymorphisms with age-related macular degeneration (AMD): a systematic review and meta-analysis

BACKGROUND

The results of different studies have indicated the possible associations of TLR4 and IL-8 genes polymorphisms with Age-related Macular Degeneration (AMD). A meta-analysis study was designed to evaluate the possible associations of TLR4 (rs4986790/c.896A>G and rs4986791/ c.1196 C > T) and IL-8 (rs4073/c.251A>T and rs2227306/c.781 C > T) genes polymorphisms with AMD.

METHOD

A systematic literature search was carried out in PubMed, Embase, Web of Science, and Scopus databases to identify relevant publications. Pooled Odds Ratio (OR) with 95% Confidence Interval (CI) was used to evaluate the power of association.

RESULTS

A total of 12 case-control studies with 4804 AMD patients and 4422 healthy controls were included in this meta-analysis. The analysis of genotypic and allelic models demonstrated significant associations between IL-8 c.781 C > T (CC vs. TT+TC: OR = 0.62 [0.48-0.81], P < .01; CC vs. TC: OR = 0.65 [0.48-0.89], P < .01; TT vs. CC: OR = 1.64 [1.04-2.57], P = .03; and C vs. T: OR = 0.71 [0.65-0.79], P < .01) and risk of AMD, which all of them passed Bonferroni correction for multiple testing (P-value≤0.01), except for TT vs. CC model. In addition, we found associations under the genotypic model of TLR4 c.896A>G (AA vs. AG+GG: OR = 0.73 [0.55-0.97], P = .03; and AA vs. AG: OR = 0.71 [0.53-0.95], P = .02) although after Bonferroni correction (P'-value<0.02) none of these associations remained significant. However, the data from this meta-analysis declined the associations of TLR4 c.1196 C > T and IL-8 c.251A>T polymorphisms with AMD.

CONCLUSION

The current meta-analysis study suggested that IL-8 c.781 C > T polymorphism is associated with susceptibility to AMD.

TLR4 T399I Polymorphism and Endometriosis in a Cohort of Italian Women

Background: Endometriosis is a widespread multifactorial disease in which environmental, genetic, and epigenetic factors contribute to the phenotype. Single Nucleotide Polymorphisms (SNPs) in genes implicated in pivotal molecular mechanisms have been investigated as susceptible risk factors in distinct populations. Among these, Toll-like receptor 4 (TLR4) represents a good candidate due to its role in the immune/inflammatory response and endometriosis pathogenesis. Methods: The TRL4 gene T399I SNP (C/T transition, rs4986791) was investigated in 236 Italian endometriosis patients and 150 controls by using the PCR-RFLP method. One-tailed Fisher’s exact test was used to compare differences between categorical variables. T399I genotype distribution was evaluated for Hardy–Weinberg equilibrium in both groups using the Chi-squared test for given probabilities. Results: Fisher’s exact test comparing C and T allele frequencies showed a difference in the frequency of T alleles between patients and controls (OR = 1.96, 95% confidence interval 0.91–4.23; p-value = 0.0552). Genotype frequencies did not show any significant difference between patients and controls. The homozygous TT genotype was observed in 2% of endometriosis women and not in controls. Conclusions: Our results show that the TLR4 rs4986791 T variant may be considered a genetic risk factor for endometriosis in Italian women. More extensive studies in other populations are needed to confirm this result.

The association of toll-like receptor 4 gene polymorphisms with primary open angle glaucoma susceptibility: a meta-analysis

Primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) cause irreversible blindness while current medications cannot completely inhibit disease progression. An understanding of immunopathogenesis is thus a keystone to develop novel drug targets and genetic markers are still required for early diagnosis. Toll-like receptor 4 (TLR4) is an essential player in inflammation in various diseases. However, the TLR4 polymorphisms have not been completely elucidated in both types of glaucoma. The aim of the present study was to identify the association between TLR4 polymorphism and glaucoma (POAG and NTG) via the use of a comprehensive review and meta-analysis. The relevant studies were collected from PubMed, Excerpta Medica Database (EMBASE), and Web of Science to identify eight included articles, assessed for quality by a modified Newcastle-Ottawa Scale (NOS) for gene association study. A meta-analysis was applied to calculate the pooled odds-ratio and 95% confidence intervals (CIs) to evaluate the association between TLR4 polymorphism and glaucoma. The results revealed that TLR4 rs1927911 A/G, rs12377632 C/T, and rs2149356 G/T significantly decrease the risk of POAG and NTG in allele contrast models 0.71-, 0.71-, and 0.67-fold, respectively. Moreover, rs4986790 A/G and rs4986791 C/T showed a stringent association with POAG in allele contrast, heterozygous, recessive, and overdominant models. In conclusion, this meta-analysis represented a significant correlation between TLR4 polymorphisms and both types of glaucoma suggesting that TLR4 might be involved in the pathogenesis of glaucoma and may be applied as a genetic marker for disease screening.