Impact of Adenosine Receptor Signaling and Metabolism on Pathophysiology in Patients with Chronic Heart Failure

Adenosine is well known to be a cardioprotective substance in ischemic heart disease. However, the modulation of adenosine receptors and the production and degradation of endogenous adenosine in chronic heart failure (CHF) are not fully understood. We analyzed the gene expression patterns of adenosine-related genes in human failing and nonfailing myocardium using DNA microarray analysis and quantitative real time-polymerase chain reaction (RT-PCR). DNA microarray analysis revealed that the gene expression of adenosine A2a, A2b, and A3 receptors (A2aR, A2bR, and A3R) as well as that of adenosine deaminase (ADA) decreased in failing myocardium. The down-regulation of these genes was verified by quantitative RT-PCR. We also measured the activities of these adenosine metabolism-related enzymes in failing myocardium and cardiac adenosine levels in patients with CHF. In CHF patients, we observed the decreased enzyme activity of ADA and the elevation of cardiac adenosine levels in CHF patients. To enhance the signaling of adenosine receptors, we increased plasma adenosine levels using dipyridamole, which decreased the severity of CHF. The gene expression of A2aR, A2bR, A3R, and ADA was decreased in the failing hearts, and this decrease may impair adenosine-related signal transduction. The activities of adenosine-related enzymes were altered, thus increasing the myocardial adenosine levels; this increase may compensate for the impairment of adenosine-related signal transduction in patients with CHF. The impairment of adenosine-related signal transmission contributes to the pathophysiology of CHF.