Polymorphism of tumor necrosis factor alpha (TNF-alpha) gene promoter, circulating TNF-alpha level, and cardiovascular risk factor for ischemic stroke

Abstract

Background: Tumor necrosis factor-α (TNF-α) is one of the most typical pro-inflammatory cytokines with both beneficial and destructive properties for the central nervous system. Increasing evidences have demonstrated the important role of TNF-α in the development of ischemic stroke, but studies examining the possible association with stroke or direct functional effects of polymorphisms in TNF-α have been contradictory.

Findings: In this study, a 2-kb length of the proximal promoter of the TNF-α was screened and four polymorphisms were investigated in the case-control study. Our data confirmed the association between -308G/A variant with stroke in 1,388 stroke patients and 1,027 controls and replicated in an independent population of 961 stroke patients and 821 controls (odds ratio (OR) = 1.34, 95% confidence interval (CI) =1.02 to 1.77 and OR = 1.56, 95% CI = 1.09 to 2.23, respectively). To reconcile the association between polymorphisms and stroke and to give a comprehensive picture of the genetic architecture of this important gene, we performed a meta-analysis of 15 published studies in an Asian population. Our results demonstrated an association between rs1800629 and ischemic stroke (OR = 1.43, 95% CI = 1.21 to 1.69). Another meta-analysis results of 14 studies demonstrated that ischemic stroke patients have higher serum TNF-α level than the control subjects (standardized mean difference (SMD) = 2.33, 95% CI = 1.85 to 2.81). In vitro evaluation of potential interaction between variants of the TNF-α gene (-308G/A, -857C/T, and -1031T/C) demonstrated that these three polymorphisms could interact together to determine the overall activity of the TNF-α gene.

Conclusions: These findings strongly implicate the involvement of TNF-α in the pathogenesis of stroke.

Figure 1

Meta-analysis of rs1800629 and ischemic stroke association in Asian populations. Gray squares indicate the OR, with the size of the square inversely proportional to its variance, and horizontal lines represent 95%CIs. The pooled results are indicated by the unshaded black diamond. All studies were conducted under a random-effects model.

Figure 2

Mean difference (95%CI) in cardiovascular traits by rs1800629 genotype. BMI, body mass index; BP, blood pressure; G1, Homozygous common-allele; G2, Heterozygous; G3, Homozygous rare-allele.

Figure 3

Genetic variants of TNF-α promoter in relation to serum TNF-α level. The data are presented as mean ± SEM. *P <0.05, ^※P <0.01.

Figure 4

Forest plot of the standardized mean difference (SMD) and 95% CIs of the serum TNF-α level between stroke patients and control subjects.

Figure 5

Mean differences in cardiovascular traits by quartiles (Q) of serum TNF-α level. Subjects from the bottom quartile (Q1) were used as the reference group. BMI, body mass index; BP, blood pressure.

Figure 6

Expression studies of TNF-α promoter constructs carrying -238A/G, -308G/A, -857C/T, -1031T/C, and -1376T/C and potential interact together between -308G/A, -857C/T, and -1031T/C polymorphisms. TNF-α promoter activity is expressed as fold increase of RLU relative to pGL3 basic. Mutant construct compared to the wild-type construct for each comparison. Values are mean ± SE of three independent experiments each corresponding to at least five replicates.