Inflammatory cytokines including the IL-1 family, TNF-α and IL-6 mediate the formation of thrombosis on the luminal surface of atherosclerotic plaques. Gene polymorphisms that regulate these cytokines' expression may explain part of the variation in susceptibility to stroke in patients with carotid atherosclerosis. The aim of this study was to evaluate the role of single-nucleotide polymorphisms (SNPs) and haplotypes in inflammatory genes as they relate to symptomatic carotid atherosclerosis.

The study included 95 subjects with symptomatic (transient ischaemic attacks or stroke) and 113 subjects with asymptomatic carotid atherosclerotic disease. A panel of evenly spaced SNPs including previously reported functionally significant polymorphisms were genotyped for IL-1β (10 SNPs), IL-1α (nine SNPs), IL-1RN (11 SNPs), IL-6 (seven SNPs) and TNF-α and TNF-β (seven SNPs).

Using single SNP analysis, IL-1RN rs315934 (P = 0·025), IL-1RN rs315946 (P = 0·042), IL-1RN rs315921 (P = 0·035), IL-6 rs1180243 (P = 0·018) and IL-1α rs2071373 (P = 0·025) were associated with decreased odds of symptomatic carotid disease. Additionally, two diplotypes of the IL-1 RN gene (P = 0·023 and 0·0064) and one diplotype in the IL-1α gene (P = 0·02) were associated with a protective affect from cerebral ischaemic events. Logistic analysis for interaction of the protective SNPs reveals an additive effect of all SNP pair combinations.

These results suggest that genetic polymorphisms in proinflammatory genes may contribute to interindi-vidual differences in the development of symptomatic carotid atherosclerotic disease.