Bovo Elisa, Mazurek Stefan R, de Tombe Pieter P, Zima Aleksey V
Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois.
Department of Cell and Molecular Physiology, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois.
Biophys J. 2015 Oct 20;109(8):1583-91. doi: 10.1016/j.bpj.2015.09.002.
While β-adrenergic receptor (β-AR) stimulation ensures adequate cardiac output during stress, it can also trigger life-threatening cardiac arrhythmias. We have previously shown that proarrhythmic Ca(2+) waves during β-AR stimulation temporally coincide with augmentation of reactive oxygen species (ROS) production. In this study, we tested the hypothesis that increased energy demand during β-AR stimulation plays an important role in mitochondrial ROS production and Ca(2+)-wave generation in rabbit ventricular myocytes. We found that β-AR stimulation with isoproterenol (0.1 μM) decreased the mitochondrial redox potential and the ratio of reduced to oxidated glutathione. As a result, β-AR stimulation increased mitochondrial ROS production. These metabolic changes induced by isoproterenol were associated with increased sarcoplasmic reticulum (SR) Ca(2+) leak and frequent diastolic Ca(2+) waves. Inhibition of cell contraction with the myosin ATPase inhibitor blebbistatin attenuated oxidative stress as well as spontaneous SR Ca(2+) release events during β-AR stimulation. Furthermore, we found that oxidative stress induced by β-AR stimulation caused the formation of disulfide bonds between two ryanodine receptor (RyR) subunits, referred to as intersubunit cross-linking. Preventing RyR cross-linking with N-ethylmaleimide decreased the propensity of Ca(2+) waves induced by β-AR stimulation. These data suggest that increased energy demand during sustained β-AR stimulation weakens mitochondrial antioxidant defense, causing ROS release into the cytosol. By inducing RyR intersubunit cross-linking, ROS can increase SR Ca(2+) leak to the critical level that can trigger proarrhythmic Ca(2+) waves.
虽然β-肾上腺素能受体（β-AR）刺激可确保应激期间有足够的心输出量，但它也可能引发危及生命的心律失常。我们之前已经表明，β-AR刺激期间的促心律失常钙（Ca2+）波在时间上与活性氧（ROS）生成的增加相吻合。在本研究中，我们测试了这样一个假设：β-AR刺激期间能量需求的增加在兔心室肌细胞线粒体ROS生成和Ca2+波产生中起重要作用。我们发现，用异丙肾上腺素（0.1μM）刺激β-AR会降低线粒体氧化还原电位以及还原型谷胱甘肽与氧化型谷胱甘肽的比率。结果，β-AR刺激增加了线粒体ROS的生成。异丙肾上腺素诱导的这些代谢变化与肌浆网（SR）Ca2+泄漏增加和频繁的舒张期Ca2+波有关。用肌球蛋白ATP酶抑制剂blebbistatin抑制细胞收缩可减轻β-AR刺激期间的氧化应激以及SR的自发性Ca2+释放事件。此外，我们发现β-AR刺激诱导的氧化应激导致两个兰尼碱受体（RyR）亚基之间形成二硫键，即亚基间交联。用N-乙基马来酰亚胺防止RyR交联可降低β-AR刺激诱导的Ca2+波的发生率。这些数据表明，持续的β-AR刺激期间能量需求的增加会削弱线粒体抗氧化防御，导致ROS释放到细胞质中。通过诱导RyR亚基间交联，ROS可将SR Ca2+泄漏增加到可触发促心律失常Ca2+波的临界水平。
