From Pat and Jim Calhoun Cardiology Center, University of Connecticut Medical Center, Farmington, CT (T.Y., J.S., R.Y., J.R., K.D.-K., J.G., B.T.L.); and Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, MD (K.A.J.).
Circ Heart Fail. 2014 May;7(3):510-8. doi: 10.1161/CIRCHEARTFAILURE.113.001023. Epub 2014 Mar 12.
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 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.
Mice established with conditional cardiac-specific P2X4R knockout were subjected to left anterior descending coronary artery ligation-induced postinfarct or transverse aorta constriction-induced pressure overload HF. Knockout cardiac myocytes did not show P2X4R by immunoblotting or by any response to the P2X4R-specific allosteric enhancer ivermectin. Knockout hearts showed normal basal cardiac function but depressed contractile performance in postinfarct and pressure overload models of HF by in vivo echocardiography and ex vivo isolated working heart parameters. P2X4R coimmunoprecipitated and colocalized with nitric oxide synthase 3 (eNOS) in wild-type cardiac myocytes. Mice with cardiac-specific P2X4R overexpression had increased S-nitrosylation, cyclic GMP, NO formation, and were protected from postinfarct and pressure overload HF. Inhibitor of eNOS, L-N(5)-(1-iminoethyl)ornithine hydrochloride, blocked the salutary effect of cardiac P2X4R overexpression in postinfarct and pressure overload HF as did eNOS knockout.
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.
心力衰竭（HF）尽管不断取得进展，但仍是导致死亡率和发病率的主要原因。P2X4 受体（P2X4R）已成为调节心脏功能的潜在重要分子，并成为 HF 治疗的潜在靶点。过表达转基因 P2X4R 可预防 HF，但这并不能解释内源性心肌 P2X4R 的作用。我们的目标是在心肌梗死或压力超负荷引起的 HF 期间，定义基础条件下内源性心肌细胞 P2X4R 的生理作用。
建立条件性心脏特异性 P2X4R 敲除小鼠，使其经历左前降支冠状动脉结扎诱导的心肌梗死后或横主动脉缩窄诱导的压力超负荷 HF。通过免疫印迹或 P2X4R 特异性变构增强剂伊维菌素的任何反应，敲除心肌细胞均未显示 P2X4R。在体内超声心动图和离体工作心脏参数的心肌梗死后和压力超负荷 HF 模型中，敲除心脏显示正常的基础心功能，但收缩功能受损。P2X4R 与一氧化氮合酶 3（eNOS）在野生型心肌细胞中共免疫沉淀和共定位。心脏特异性 P2X4R 过表达的小鼠具有增加的 S-亚硝基化、环鸟苷酸、NO 形成，并可预防心肌梗死后和压力超负荷 HF。eNOS 抑制剂 L-N（5）-（1-亚氨基乙基）鸟氨酸盐酸盐阻断了心脏 P2X4R 过表达在心肌梗死后和压力超负荷 HF 中的有益作用，eNOS 敲除也阻断了该作用。
本研究确立了内源性心肌细胞 P2X4R 在 HF 中的新保护作用，这是首次证明心肌细胞受体与 eNOS 之间存在物理相互作用，eNOS 是 HF 保护的介质。
