Associations Between Polymorphisms In Toll-like Receptor4Signaling Pathway Genes And The Susceptibility To Sepsis

Backgrounds and aims:Sepsis is a main cause of death of critical ill patients. With complex pathogenesis and high mortality, sepsis has become a problem worldwide. More and more studies show that genetic factors influence the development and outcome of sepsis. Genetic variants, especially the single-nucleotide polymorphisms (SNPs), in the immune response pathway genes can affect the host immune responses to pathogens. TLR4, an innate immune receptor, and its single pathway play an important role in the development of sepsis. Previous studies have indicated that SNPs in TLR4and its single pathway genes are associated with the susceptibility to sepsis. TLR4Asp299Gly/Thr399Ile and CD14C-159T polymorphisms were mostly reported. However, the results are inconsistent and inconclusive. A variety of factors lead to these inconsistent results. The differences of SNPs existing in diferect populations and the interactions of SNPs in multiple genes have been considered to be the main reasons. Therefore, our purposes in this work were to find more sepsis-related SNPs in this pathway and simultaneously evaluate interactions between these SNPs within genes confined to a single pathway, while we further study the relations between these SNPs and the susceptibility to sepsis.Methods:Electronic searches of MEDLINE, EMBASE and Web of Science databases were performed. Original observational studies dealing with the association between polymorphisms Asp299Gly and/or Thr399Ile and sepsis risk were selected. The associations of these two common polymorphisms with sepsis susceptibility were estimated by performing a meta-analysis of previous data. Odds ratios (ORs) and95%confidence intervals (CIs) were calculated with random-effects model or fixed-effects model based on the heterogeneity analysis.The potential SNPs in TLR4、CD14、MD2and TIRAP/Mal genes were selected through bioinformatics analysis, including SNPs previously reported to be associated with immune and inflammatory diseases and tag SNPs. Genotypes of seven SNPs in four candidate genes were detected with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We conducted a case control study to investigate the associations of theses SNPs and the susceptibility to sepsis in Chinese Han population, and studied the SNP-SNP interactions using Multifactor Dimensionality Reduction (MDR). Finally, ex vivo LPS stimulation of human whole blood was performed to detect the associations of different genotypes of the related SNP and cytokine productions for functional evaluation of the related SNP.Results:Seventeen studies including2212cases and3880controls were included in the Meta-analysis for the association of Asp299Gly polymorphism with sepsis risk, and ten studies including711cases and1376controls were included in the Meta-analysis for the association of Thr399Ile polymorphism with sepsis risk. Most subjects were Caucasian populations. The odds ratio for the association of Asp299Gly polymorphism with sepsis risk was1.22(95%CI:0.90-1.65, P=0.21), and the association of Thr399Ile polymorphism was1.16(95%CI:0.70-1.91, P=0.57). Subgroup analysis and sensitivity analysis did not change the results. Seven SNPs in four genes were selected and genotyped,including TLR4rs10759932TLR4rs11536889、MD2rs10808798、CD14rs2569190and3tag SNPs in TIRAP/Mal gene (rs8177352、rs595209and rs8177375). Three hundred and thirty six patients with sepsis and three hundred and fifty nine control patients were enrolled.All subjects were divided into operation group and non-operation group. The TIRAP/Mal rs595209polymorphism AC/CC genotypes were significantly lower in sepsis patients than in control patients in two groups (P<0.05).After adjustment for age, gender, baseline conditions and surgery types, TIRAP/Mal rs595209polymorphism was significantly associated with the lower risk of sepsis in Chinese Han populations (OR=0.287,95%CI,0.089-0.922, P=0.036; OR=0.508,95%CI,0.282-0.918, P=0.025, respectively). Moreover, Multifactor Dimensionality Reduction analysis showed significant interactions between MD2rs10808798, TLR4rs10759932, TLR4rs11536889. CD14rs2569190and TIRAP/Malrs595209polymorphisms in the development of sepsis. The strongest interaction existed between MD2rs10808798and TLR4rs10759932polymorphisms. Under LPS-stimulation, the concentrations of TNF-a and IL-10in supernatants of the whole blood carrying TIRAP/Malrs595209AC/CC genotypes were significantly lower in those of AA genotype. Genetic variation (A> C) in TIRAP/Malrs595209locus significantly reduced whole blood leukocyte response to LPS.Conclusions:The two common TLR4SNPs (Asp299Gly and Thr399Ile) have no strong association with the risk of gram-negative bacteria sepsis and all-cause sepsis in Caucasian populations. TIRAP/Malrs595209polymorphism was significantly associated with the lower risk of developing sepsis in Chinese Han populations. Carriage of AC/CC genotype of TIRAP/Malrs595209polymorphism imparted a decreased sepsis risk. A combination of MD2rs10808798, TLR4rs10759932, TLR4rs11536889, CD14rs2569190and TIRAP/Malrs595209had a synergistic effect in the development of sepsis. TIRAP/Malrs595209polymorphism is a functional variation and might be used as a risk estimate for sepsis in patients.