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Myocardial infarction (MI) is one of the common diseases whose pathogenesis includes genetic factors. To reveal genetic backgrounds of this clinically heterogeneous disorder, we started our case-control association study by examining large-scale gene-based single nucleotide polymorphism (SNP) sets for ∼1,000 patients and controls. As a core genotyping method, a combination of multiplex PCR and Invader method was used, and after genotyping ∼65,000 SNPs, we found two SNPs located within lymphotoxin-α ( LTA) gene showing significant association with MI. LTA is one of the cytokines produced in the early stages of vascular inflammatory processes. These SNPs seem to be involved in inflammation by both qualitatively and quantitatively modifying the function of LTA protein, thereby conferring a risk of MI. The genetic association was further confirmed by other researchers using white European trios. To further understand the roles of LTA protein in the pathogenesis of MI, we searched for proteins that interact directly with LTA protein and identified galectin-2 protein as a binding partner of LTA protein. It is a member of galactose-binding lectin family whose function has not been well characterized. Genetic association study again revealed that an SNP in LGALS2 encoding galectin-2 was also associated with susceptibility to MI. This genetic substitution seemed to affect the transcriptional level of galectin-2, which led to altered secretion of LTA, thereby affecting the degree of inflammation. Thus, our findings indicate the importance of inflammation, especially the LTA cascade, in the pathogenesis of MI. Also, combined strategy of genetic and molecular-cellular biological approaches may be useful for clarification of the pathogenesis of common diseases in general. [ABSTRACT FROM AUTHOR]

By means of a large-scale, case-control association study using 92,788 gene-based single-nucleotide polymorphism (SNP) markers, we identified a candidate locus on chromosome 6p21 associated with susceptibility to myocardial infarction. Subsequent linkage-disequilibrium (LD) mapping and analyses of haplotype structure showed significant associations between myocardial infarction and a single 50 kb halpotype comprised of five SNPs in LTA (encoding lymphotoxin-α), NFKBIL1 (encoding nuclear factor of κ light polypeptide gene enhancer in B cells, inhibitor-like 1) and BAT1 (encoding HLA-B associated transcript 1). Homozygosity with respect to each of the two SNPs in LTA was significantly associated with increased risk for myocardial infarction (odds ratio = 1.78, χ2 = 21.6, P = 0.00000033; 1,133 affected individuals versus 1,006 controls). In vitro functional analyses indicated that one SNP in the coding region of LTA, which changed an amino-acid residue from threonine to asparagine (Thr26Asn), effected a twofold increase in induction of several cell-adhesion molecules, including VCAM1, in vascular smooth-muscle cells of human coronary artery. Moreover, the SNP, in intron 1 of LTA, enhanced the transcriptional level of LTA. These results indicate that variants in the LTA are risk factors for myocardial infraction and implicate LTA in the pathogenesis of the disorder. [ABSTRACT FROM AUTHOR]

Abstract: Aims: We previously reported the association of single nucleotide polymorphisms in the lymphotoxin alpha (LTα) gene with susceptibility to acute myocardial infarction (AMI) and increased mortality after discharge. In the present study, we investigated whether the adverse effect of LTα C804A polymorphism on mortality could be pharmacologically modified by statin treatment after AMI. Methods and results: We conducted a multicenter study that included 3486 post-AMI patients between 1998 and 2008. During a median follow-up period of 1775 days, 247 deaths were recorded. The mortality rate was significantly higher in LTα 804A allele carriers compared to non-804A allele carriers (7.9% vs. 5.7%, p = 0.011). The LTα 804A allele was significantly associated with increased mortality for post-AMI patients not receiving statins (hazard ratio [HR]: 1.48, 95% confidence interval [CI]: 1.03–2.12, p = 0.034), but not for those receiving statins (HR: 1.22, 95% CI: 0.70–2.10, p = 0.486). In-vitro experimental analyses demonstrated that the LTα 804A polymorphic protein, 26Asn-LTα3, induced monocyte-endothelial interaction and endoplasmic reticulum (ER) stress in cardiomyocytes more strongly than the LTα3 804C polymorphic protein 26Thr-LTα3. However, the effects of both LTα3 proteins were decreased and became comparable by the pretreatment of cells with pravastatin. Conclusion: LTα C804A polymorphism was associated with an increased risk of mortality for AMI patients, although this effect was masked in patients treated with statins. This finding is supported by the observed attenuation of 26Asn-LTα3-mediated monocyte-endothelial interaction and ER stress in cardiomyocytes treated with pravastatin. LTα C804A polymorphism may have potential as a novel therapeutic target for secondary prevention after AMI. [Copyright &y& Elsevier]