Wagner D R, Combes A, McTiernan C, Sanders V J, Lemster B, Feldman A M
Division of Cardiology, University of Pittsburgh Medical Center, PA 15213, USA.
Circ Res. 1998;82(1):47-56. doi: 10.1161/01.res.82.1.47.
Tumor necrosis factor-alpha (TNF-alpha) is elevated in the failing heart. Very little is known about regulation of TNF-alpha in cardiomyocytes. TNF-alpha expression by macrophages is diminished by adenosine. Therefore, we hypothesized that a similar mechanism might occur in the heart. Neonatal rat myocytes were stimulated with lipopolysaccharide (LPS), and TNF-alpha was measured by ELISA. In the absence of LPS, myocytes did not release TNF-alpha in the medium. After exposure to LPS, TNF-alpha increased to 70.1+/-3.5 pg/mL at 6 hours. Immunofluorescent staining confirmed that TNF-alpha was expressed in myocytes. Adenosine decreased TNF-alpha in a dose-dependent manner (1 to 100 micromol/L, 37% to 65% decrease, P<.01). Adenosine also decreased TNF-alpha in cell homogenates by 78% (P<.0001). The effect of adenosine could be replicated by the A2 agonist PD-125944 (DPMA), by cAMP agonists 8-bromo-cAMP, forskolin, and Ro 20-1724, but not by A1 and A3 agonists. Conversely, the effect of adenosine could be suppressed by the adenylate cyclase inhibitor MDL-12,330. Adenosine also inhibited TNF-alpha in adult rat ventricular myocytes (-60%, P<.005) and rat papillary muscles (-55%, P<.05). In neonatal myocytes, adenosine normalized LPS-induced calcium changes and improved LPS-induced negative inotropic (P<.01) and negative lusitropic (P<.01) effects. Our results demonstrate that adenosine can significantly diminish TNF-alpha levels in the heart. The effect appears to be mediated by the A2 receptor and transduced through a G protein-adenylyl cyclase pathway. These results may explain some cardioprotective effects of adenosine and provide a novel pharmacological intervention in congestive heart failure.
肿瘤坏死因子-α（TNF-α）在衰竭心脏中水平升高。目前对心肌细胞中TNF-α的调节知之甚少。巨噬细胞表达的TNF-α会被腺苷减少。因此，我们推测心脏中可能发生类似机制。用脂多糖（LPS）刺激新生大鼠心肌细胞，并用酶联免疫吸附测定法（ELISA）检测TNF-α。在无LPS情况下，心肌细胞不会在培养基中释放TNF-α。暴露于LPS后，6小时时TNF-α增加至70.1±3.5 pg/mL。免疫荧光染色证实心肌细胞中表达了TNF-α。腺苷以剂量依赖方式降低TNF-α（1至100 μmol/L，降低37%至65%，P<0.01）。腺苷还使细胞匀浆中的TNF-α降低78%（P<0.0001）。腺苷的作用可被A2激动剂PD-125944（DPMA）、cAMP激动剂8-溴-cAMP、福斯可林和Ro 20-1724复制，但不能被A1和A3激动剂复制。相反，腺苷酸环化酶抑制剂MDL-12,330可抑制腺苷的作用。腺苷还抑制成年大鼠心室肌细胞中的TNF-α（-60%，P<0.005）和大鼠乳头肌中的TNF-α（-55%，P<0.05）。在新生心肌细胞中，腺苷使LPS诱导的钙变化恢复正常，并改善LPS诱导的负性肌力作用（P<0.01）和负性变时作用（P<0.01）。我们的结果表明，腺苷可显著降低心脏中的TNF-α水平。该作用似乎由A2受体介导，并通过G蛋白-腺苷酸环化酶途径传导。这些结果可能解释了腺苷的一些心脏保护作用，并为充血性心力衰竭提供了一种新的药物干预方法。
