A Promoter Polymorphism of the Endothelial Nitric Oxide Synthase Gene is Associated With Reduced mRNA and Protein Expression in Failing Human Myocardium

Abstract 

Background

Alterations of endothelial nitric oxide synthase (eNOS) enzyme activity via eNOS gene polymorphisms have been associated with significant cardiovascular morbidity and mortality. Both the thymidine to cytosine transition mutation (T⁻⁷⁸⁶→C) in the promoter region and the missense mutation in the exon 7 coding region of the eNOS gene (G⁸⁹⁴→T) have been associated with several cardiovascular disease states. We hypothesized that heart transplant recipients who carried at least 1 allele of either of the polymorphisms would have reduced myocardial tissue expression of eNOS measured in the explanted heart.

Methods and Results

Genomic DNA was isolated from myocardial tissue samples obtained from 43 explanted human hearts using standard methods. Regions of the eNOS gene were amplified from genomic DNA with a polymerase chain reaction using specific primers. Protein expression of eNOS was measured by Western blot analysis. There was a statistically significant decrease in mean eNOS expression in samples containing at least one allele for the T⁻⁷⁸⁶→C promoter polymorphism (P=.04) compared with patients homozygous for the T allele. There was no change in eNOS expression associated with the G⁸⁹⁴→T exonic polymorphisms.

Conclusions

Our data show in failing human myocardium that the T⁻⁷⁸⁶→C promoter polymorphism is associated with reduced eNOS expression, whereas the G⁸⁹⁴→T polymorphism of exon 7 is not associated with change in either eNOS mRNA or protein expression. Reduced eNOS expression associated with the promoter polymorphism may contribute to the vascular, contractile, and autonomic responses to ventricular failure.

Key Words: Nitric oxide, genetics, cardiomyopathy, pharmacogenetics