Genetic contribution of the leukotriene pathway to coronary artery disease

Abstract

We evaluated the genetic contribution of the leukotriene (LT) pathway to risk of coronary artery disease (CAD) in 4,512 Caucasian and African American subjects ascertained through elective cardiac evaluation. Of the three previously associated variants, the shorter "3" and "4" alleles of a promoter repeat polymorphism in ALOX5 increased risk of CAD in African Americans (OR = 1.4, 95% CI 1.0-1.9; p = 0.04), whereas a haplotype of LTA4H (HapK) was associated with CAD in Caucasians (OR = 1.2, 95% CI 1.01-1.4; p = 0.03). In Caucasians, first-stage analysis of 254 haplotype-tagging SNPs in 15 LT pathway genes with follow-up of 19 variants in stage 2 revealed an LTA4H SNP (rs2540477) that increased risk of CAD (OR = 1.2, 95% CI 1.1-1.5; p = 0.003) and a PLA2G4A SNP (rs12746200) that decreased risk of CAD (OR = 0.7, 95% CI 0.6-0.9; p = 0.0007). The PLA2G4A rs12746200 variant also decreased risk of experiencing a major adverse cardiac event (MACE = myocardial infarction, stroke, or death) over 3 years of follow-up (HR = 0.7, 95% CI 0.5-0.9; p = 0.01), consistent with its cardioprotective effect. Functional experiments demonstrated that stimulated monocytes from carriers of LTA4H variants HapK or rs2540477 had 50% (p = 0.002) and 33% (p = 0.03) higher LTB(4) production, respectively, compared to non-carriers. These ex vivo results are consistent with LTB(4) being the direct product of the reaction catalyzed by LTA4H and its role in promoting monocyte chemotaxis to sites of inflammation, including the artery wall of atherosclerotic lesions. Taken together, this study provides additional evidence that functional genetic variation of the LT pathway can mediate atherogenic processes and the risk of CAD in humans.

Fig. 1

Relationship between LT pathway variants and incident risk of MACE. a Kaplan–Meier survival analyses demonstrating that carriers (AG/GG) of PLA2G4A variant rs12746200 have significantly lower a rate of MACE over three years of follow-up (p = 0.03). b There is no difference in the rate of MACE between carriers and non-carriers of the LTA4H variant rs2540477. MACE were defined as the occurrence of MI, stroke, or all-cause mortality over 3 years of follow-up from the time of enrollment

Fig. 2

Effect of LTA4H variants on gene expression and ex vivo LTB₄ production. a LTA4H mRNA levels in monocytes are not significantly different between carriers and non-carriers of the HapK or rs2540477 variants. Real-time PCR was carried out in triplicate and expression levels were normalized to GUSB as an endogenous control. b Monocytes isolated from carriers of HapK or rs2540477 produce significantly higher levels of LTB₄ than non-carriers. Monocytes were isolated from healthy subjects and stimulated with the calcium ionophore A23187 for 60 min. LTB₄ was measured in the supernatant by negative mode electrospray ionization tandem mass spectrometry. Data are shown as mean ± SE and the number of samples analyzed for each genotype is given in parentheses