Novel molecular mechanism of increased myocardial endothelin-1 expression in the failing heart involving the transcriptional factor hypoxia-inducible factor-1α induced for impaired myocardial energy metabolism

Background-Hypoxia-inducible factor (HIF)-1 alpha is an important transcriptional factor that activates the gene expression of glycolytic enzymes, which are activated as compensation for impaired beta -oxidation of fatty acid in the failing heart. We reported that cardiac endothelin (ET)-1 expression is markedly increased in heart failure. The mechanism, however, is unknown. Because we found an HIF-1 alpha binding site in the 5 ' -promoter region of the ET-1 gene, we hypothesized that HIF-1 alpha is involved in this mechanism. Methods and Results-In rat cardiomyocytes, luciferase assay and electrophoretic mobility shift assay showed that HIF-1 alpha transcriptionally activates ET-1 gene expression by direct interaction with the predicted DNA binding site in the 5 ' -promoter region. HIF-1 alpha mRNA and ET-1 mRNA in the failing heart increased during the aggravation of heart failure in vivo in animal models, ie, rats with myocardial infarction and hamsters with cardiomyopathy. In cultured cardiomyocytes treated with a mitochondrial inhibitor, HIF-1 alpha mRNA and ET-1 mRNA were markedly increased with activated glycolysis, and antisense oligonucleotide for HIF-1 alpha largely inhibited the increased gene expression of ET-1. Conclusions-The present study revealed a novel molecular mechanism of upregulation of myocardial ET-1 in heart failure, indicating that induction of HIF-1 alpha to stimulate glycolysis as an adaptation in heart failure against impaired energy metabolism alternatively causes an elevation of cardiac ET-1 gene expression as a maladaptation.