A Novel Protective Role of Endogenous Cardiac Myocyte P2X4 Receptors in Heart Failure
Background—Heart failure (HF), despite continuing progress, remains a leading cause of mortality and morbidity. P2X4 receptors (P2X4R) have emerged as potentially important molecules in regulating cardiac function and as potential targets for HF therapy. Transgenic (Tg) P2X4R overexpression can protect against HF, but this does not explain the role of native cardiac P2X4R. Our goal is to define the physiological role of endogenous cardiac myocyte P2X4R under basal conditions and during HF induced by myocardial infarction or pressure overload.
Methods and Results—Mice established with conditional cardiac-specific P2X4R knockout (KO) were subjected to left coronary ligation-induced post-infarct or transverse aorta constriction-induced pressure overload HF. KO cardiac myocytes did not show P2X4R by immunoblotting or by any response to the P2X4R-specific allosteric enhancer ivermectin. KO hearts showed normal basal cardiac function but depressed contractile performance in post-infarct and pressure overload models of HF by in vivo echocardiography and ex vivo isolated working heart parameters. P2X4R co-immunoprecipitated and co-localized with nitric oxide synthase 3 (eNOS) in wild type cardiac myocytes. Mice with cardiac-specific P2X4R overexpression had increased S-nitrosylation, cGMP, NO formation, and were protected from post-infarct and pressure overload HF. Inhibitor of eNOS L-NIO blocked the salutary effect of cardiac P2X4R overexpression in post-infarct and pressure overload HF as did eNOS knockout.
Conclusions—This study establishes a new protective role for endogenous cardiac myocyte P2X4R in HF and is the first to demonstrate a physical interaction between the myocyte receptor and eNOS, a mediator of HF protection.
- Received August 5, 2013.
- Accepted March 10, 2014.