Kim Tae Yun, Terentyeva Radmila, Roder Karim H F, Li Weiyan, Liu Man, Greener Ian, Hamilton Shanna, Polina Iuliia, Murphy Kevin R, Clements Richard T, Dudley Samuel C, Koren Gideon, Choi Bum-Rak, Terentyev Dmitry
Department of Medicine, Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, The Warren Alpert Medical School of Brown University, 1 Hoppin Street, Providence, RI, 02903-4141, USA.
Division of Cancer and Genetics, School of Medicine, Wales Heart Research Institute, Cardiff University, Heath Park, Cardiff, CF14 4XN, UK.
Cardiovasc Res. 2017 Mar 1;113(3):343-353. doi: 10.1093/cvr/cvx005.
Plasmamembrane small conductance Ca2+-activated K+ (SK) channels were implicated in ventricular arrhythmias in infarcted and failing hearts. Recently, SK channels were detected in the inner mitochondria membrane (IMM) (mSK), and their activation protected from acute ischaemia-reperfusion injury by reducing intracellular levels of reactive oxygen species (ROS). We hypothesized that mSK play an important role in regulating mitochondrial function in chronic cardiac diseases. We investigated the role of mSK channels in Ca2+-dependent ventricular arrhythmia using rat model of cardiac hypertrophy induced by banding of the ascending aorta thoracic aortic banding (TAB).
Dual Ca2+ and membrane potential optical mapping of whole hearts derived from TAB rats revealed that membrane-permeable SK enhancer NS309 (2 μM) improved aberrant Ca2+ homeostasis and abolished VT/VF induced by β-adrenergic stimulation. Using whole cell patch-clamp and confocal Ca2+ imaging of cardiomyocytes derived from TAB hearts (TCMs) we found that membrane-permeable SK enhancers NS309 and CyPPA (10 μM) attenuated frequency of spontaneous Ca2+ waves and delayed afterdepolarizations. Furthermore, mSK inhibition enhanced (UCL-1684, 1 μM); while activation reduced mitochondrial ROS production in TCMs measured with MitoSOX. Protein oxidation assays demonstrated that increased oxidation of ryanodine receptors (RyRs) in TCMs was reversed by SK enhancers. Experiments in permeabilized TCMs showed that SK enhancers restored SR Ca2+ content, suggestive of substantial improvement in RyR function.
These data suggest that enhancement of mSK channels in hypertrophic rat hearts protects from Ca2+-dependent arrhythmia and suggest that the protection is mediated via decreased mitochondrial ROS and subsequent decreased oxidation of reactive cysteines in RyR, which ultimately leads to stabilization of RyR-mediated Ca2+ release.
质膜小电导钙激活钾（SK）通道与梗死和衰竭心脏的室性心律失常有关。最近，在内线粒体膜（IMM）中检测到SK通道（mSK），其激活通过降低细胞内活性氧（ROS）水平来保护心脏免受急性缺血再灌注损伤。我们假设mSK在慢性心脏疾病中线粒体功能调节中起重要作用。我们使用升主动脉缩窄（TAB）诱导的大鼠心脏肥大模型研究了mSK通道在钙依赖性室性心律失常中的作用。
对来自TAB大鼠的全心进行双钙和膜电位光学映射显示，膜通透性SK增强剂NS309（2μM）改善了异常的钙稳态，并消除了β-肾上腺素能刺激诱导的室性心动过速/心室颤动。使用来自TAB心脏（TCM）的心肌细胞进行全细胞膜片钳和共聚焦钙成像，我们发现膜通透性SK增强剂NS309和CyPPA（10μM）降低了自发钙波的频率并延迟了后去极化。此外，mSK抑制增强（UCL-1684，1μM）；而激活则降低了用MitoSOX测量的TCM中的线粒体ROS产生。蛋白质氧化分析表明，SK增强剂可逆转TCM中兰尼碱受体（RyRs）氧化增加的现象。在透化的TCM中进行的实验表明，SK增强剂恢复了肌浆网钙含量，提示RyR功能有显著改善。
这些数据表明，肥厚大鼠心脏中mSK通道的增强可保护心脏免受钙依赖性心律失常的影响，并表明这种保护作用是通过降低线粒体ROS以及随后降低RyR中反应性半胱氨酸的氧化来介导的，这最终导致RyR介导的钙释放稳定。
