Dougherty C, Barucha J, Schofield P R, Jacobson K A, Liang B T
Department of Medicine, Cardiovascular Division, and Department of Pharmacology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA.
FASEB J. 1998 Dec;12(15):1785-92. doi: 10.1096/fasebj.12.15.1785.
Adenosine is an important mediator of the endogenous defense against ischemia-induced injury in the heart. Adenosine can achieve cardioprotection by mediating the effect of ischemic preconditioning and by protecting against myocyte injury when it is present during the infarct-producing ischemia. A novel adenosine A3 receptor can mediate this protective function. One approach to achieve cardioprotection is to enhance myocardial sensitivity to the endogenous adenosine by increasing the number of adenosine receptors instead of administering an adenosine receptor agonist. The objective of the present study was to investigate whether genetic manipulation of the cardiac myocyte, achieved by gene transfer and overexpression of the human A3 receptor cDNA, renders the myocytes resistant to the deleterious effect of ischemia. Prolonged hypoxia with glucose deprivation, causing myocyte injury and adenosine release, was used to simulate ischemia in cultured chick embryo ventricular myocytes. During simulated ischemia, cultured myocytes with enhanced expression of the human A3 receptor and showed significantly higher ATP content, fewer cells killed, and less creatine kinase released into the medium than either control or mock-transfected myocytes. Also, increased expression of the A3 receptor caused an enhanced cardioprotective effect by the preconditioning ischemia. Overexpressing the adenosine A1 receptor also led to increased protection against ischemia-induced myocyte injury as well as an enhanced preconditioning effect. Thus, increasing the receptor level improves the myocyte sensitivity to the endogenous adenosine, which in turn causes all of the cardioprotective effects found for exogenously administered adenosine agonists. The study provides the first proof for the new concept that an increased expression of the human A3 receptor in the cardiac myocyte can be an important cardioprotective therapeutic approach.
腺苷是心脏内源性防御缺血性损伤的重要介质。腺苷可通过介导缺血预处理的作用以及在梗死性缺血期间存在时保护心肌细胞免受损伤来实现心脏保护。一种新型腺苷A3受体可介导这种保护功能。实现心脏保护的一种方法是通过增加腺苷受体的数量来增强心肌对内源性腺苷的敏感性，而不是给予腺苷受体激动剂。本研究的目的是调查通过基因转移和人A3受体cDNA的过表达对心肌细胞进行基因操作是否能使心肌细胞对缺血的有害影响产生抗性。用葡萄糖剥夺引起的长时间缺氧导致心肌细胞损伤和腺苷释放，以此模拟培养的鸡胚心室肌细胞中的缺血。在模拟缺血期间，与对照或mock转染的心肌细胞相比，人A3受体表达增强的培养心肌细胞显示出显著更高的ATP含量、更少的死亡细胞以及释放到培养基中的肌酸激酶更少。此外，A3受体表达的增加通过预处理缺血产生了增强的心脏保护作用。过表达腺苷A1受体也导致对缺血诱导的心肌细胞损伤的保护作用增强以及预处理作用增强。因此，增加受体水平可提高心肌细胞对内源性腺苷的敏感性，这反过来又会产生外源性给予腺苷激动剂所具有的所有心脏保护作用。该研究为心肌细胞中人A3受体表达增加可成为一种重要的心脏保护治疗方法这一新概念提供了首个证据。
