Yong Qian Chen, Pan Ting-Ting, Hu Li-Fang, Bian Jin-Song
Cardiovascular Biology Research Group, Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
J Mol Cell Cardiol. 2008 Apr;44(4):701-10. doi: 10.1016/j.yjmcc.2008.01.007. Epub 2008 Feb 9.
Beta-adrenoceptor is over-stimulated during myocardial ischemia, in which hydrogen sulphide (H2S) concentration was found to be lowered. The present study attempted to investigate if H2S modulates beta-adrenoceptor function and the underlying mechanism. We examined the effect of NaHS (a H2S donor) on myocyte contraction and electrically-induced (EI) intracellular calcium (Ca2+) transients upon beta-adrenergic stimulation in rat ventricular myocytes with a video edge tracker method and a spectrofluorometric method using fura-2/AM as a calcium indicator, respectively. We found that isoproterenol (ISO, 10(-9)-10(-6) M), a beta-adrenoceptor agonist, concentration-dependently increased the twitch amplitude of ventricular myocytes, which was attenuated by NaHS (10(-5)-10(-3) M) in a dose-dependent manner. The amplitudes and maximal velocities (+/-dl/dt) of myocyte twitch and EI-Ca2+ transient amplitudes were enhanced by ISO, forskolin (an adenylyl cyclase activator), 8-bromoadenosine-3',5'-cyclic monophosphate (an activator of protein kinase A) and Bay K-8644 (a selective L-type Ca2+ channel agonist). Administration of NaHS (100 microM) only significantly attenuated the effects of ISO and forskolin. Moreover, NaHS reversed ISO-induced cAMP elevation and forskolin-stimulated adenylyl cyclase activity. In addition, stimulation of beta-adrenoceptor by ISO significantly decreased endogenous H2S production in rat ventricular myocytes. In conclusion, H2S may negatively modulate beta-adrenoceptor function via inhibiting adenylyl cyclase activity. Impairment of this negative modulation during ischemia may induce cardiac arrhythmias. Our study may provide a novel mechanism for ischemia-induced cardiac injury.
在心肌缺血期间，β-肾上腺素能受体受到过度刺激，同时发现硫化氢（H₂S）浓度降低。本研究试图探讨H₂S是否调节β-肾上腺素能受体功能及其潜在机制。我们分别使用视频边缘跟踪法和以fura-2/AM作为钙指示剂的荧光分光光度法，研究了NaHS（一种H₂S供体）对大鼠心室肌细胞β-肾上腺素能刺激后心肌细胞收缩和电诱导（EI）细胞内钙（[Ca²⁺]i）瞬变的影响。我们发现，β-肾上腺素能受体激动剂异丙肾上腺素（ISO，10⁻⁹ - 10⁻⁶ M）浓度依赖性地增加心室肌细胞的收缩幅度，而NaHS（10⁻⁵ - 10⁻³ M）以剂量依赖性方式减弱了这种作用。ISO、福斯可林（一种腺苷酸环化酶激活剂）、8-溴腺苷-3',5'-环磷酸（一种蛋白激酶A激活剂）和Bay K-8644（一种选择性L型钙通道激动剂）增强了心肌细胞收缩和EI-[Ca²⁺]i瞬变幅度以及最大速度（±dl/dt）。给予NaHS（100 μM）仅显著减弱了ISO和福斯可林的作用。此外，NaHS逆转了ISO诱导的cAMP升高和福斯可林刺激的腺苷酸环化酶活性。另外，ISO刺激β-肾上腺素能受体显著降低了大鼠心室肌细胞内源性H₂S的产生。总之，H₂S可能通过抑制腺苷酸环化酶活性对β-肾上腺素能受体功能产生负性调节作用。缺血期间这种负性调节受损可能诱发心律失常。我们的研究可能为缺血性心脏损伤提供一种新机制。
