Belevych Andriy, Kubalova Zuzana, Terentyev Dmitry, Hamlin Robert L, Carnes Cynthia A, Györke Sandor
Davis Heart and Lung Research Institute, Department of Physiology and Cell Biology, Ohio State University Medical Center, Columbus, Ohio 43210, USA.
Biophys J. 2007 Dec 1;93(11):4083-92. doi: 10.1529/biophysj.107.114546. Epub 2007 Sep 7.
In this study, we investigated the role of elevated sarcoplasmic reticulum (SR) Ca(2+) leak through ryanodine receptors (RyR2s) in heart failure (HF)-related abnormalities of intracellular Ca(2+) handling, using a canine model of chronic HF. The cytosolic Ca(2+) transients were reduced in amplitude and slowed in duration in HF myocytes compared with control, changes paralleled by a dramatic reduction in the total SR Ca(2+) content. Direct measurements of Ca(2+) in both intact and permeabilized cardiac myocytes demonstrated that SR luminal [Ca(2+)] is markedly lowered in HF, suggesting that alterations in Ca(2+) transport rather than fractional SR volume reduction accounts for the diminished Ca(2+) release capacity of SR in HF. SR Ca(2+) ATPase (SERCA2)-mediated SR Ca(2+) uptake rate was not significantly altered, and Na(+)/Ca(2+) exchange activity was accelerated in HF myocytes. At the same time, SR Ca(2+) leak, measured directly as a loss of Ca(2+) after inhibition of SERCA2 by thapsigargin, was markedly enhanced in HF myocytes. Moreover, the reduced Ca(2+) in HF myocytes could be nearly completely restored by the RyR2 channel blocker ruthenium red. The effects of HF on cytosolic and SR luminal Ca(2+) signals could be reasonably well mimicked by the RyR2 channel agonist caffeine. Taken together, these results suggest that RyR2-mediated SR Ca(2+) leak is a major factor in the abnormal intracellular Ca(2+) handling that critically contributes to the reduced SR Ca(2+) content of failing cardiomyocytes.
在本研究中，我们使用慢性心力衰竭犬模型，研究了通过兰尼碱受体（RyR2）的肌浆网（SR）Ca²⁺泄漏增加在心力衰竭（HF）相关的细胞内Ca²⁺处理异常中的作用。与对照组相比，HF心肌细胞的胞质Ca²⁺瞬变幅度降低，持续时间延长，同时SR总Ca²⁺含量显著降低。对完整和透化心肌细胞中[Ca²⁺]SR的直接测量表明，HF时SR腔[Ca²⁺]明显降低，这表明Ca²⁺转运改变而非SR体积分数降低是HF时SR Ca²⁺释放能力降低的原因。HF心肌细胞中SR Ca²⁺ATP酶（SERCA2）介导的SR Ca²⁺摄取率没有显著改变，而Na⁺/Ca²⁺交换活性加快。同时，在用毒胡萝卜素抑制SERCA2后，直接测量的HF心肌细胞中SR Ca²⁺泄漏（以[Ca²⁺]SR的损失来衡量）明显增强。此外，HF心肌细胞中降低的[Ca²⁺]SR几乎可以被RyR2通道阻滞剂钌红完全恢复。RyR2通道激动剂咖啡因可以很好地模拟HF对胞质和SR腔Ca²⁺信号的影响。综上所述，这些结果表明，RyR2介导的SR Ca²⁺泄漏是细胞内Ca²⁺处理异常的主要因素，对衰竭心肌细胞SR Ca²⁺含量降低起关键作用。
