Hypersensitivity of excitation-contraction coupling in dystrophic cardiomyocytes.
Hypersensitivity of excitation-contraction coupling in dystrophic cardiomyocytes.
复制标题
营养不良的心肌细胞兴奋-收缩耦合的超敏反应。
DOI：
10.1152/ajpheart.00602.2009
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Niggli,Ernst
中科院分区：
文献类型：
--
作者：
Ullrich,NinaD;Fanchaouy,Mohammed;Gusev,Konstantin;Shirokova,Natalia;Niggli,Ernst
杜氏肌营养不良症是一种严重的横纹肌遗传性疾病。它是由肌营养不良蛋白基因突变引起的，其特征是骨骼肌功能的进行性丧失。大多数患者还发展为营养不良性心肌病，导致扩张性肥大和心力衰竭，但导致心脏功能恶化的细胞机制仍然难以捉摸。在本研究中，我们测试了是否有缺陷的兴奋-收缩（E-C）耦合有助于受损的心脏性能。在对照组和肌养蛋白缺陷mdx小鼠的心肌细胞中测定“E-C偶联增益”。为此，L-型钙电流（ICaL）测定与全细胞膜片钳技术，而钙瞬变同时记录与共聚焦成像的fluo-3。初步研究结果表明，尽管肌浆网（SR）的Ca 2+负荷匹配，但mdx细胞的E-C偶联仍有细微的变化。然而，降低细胞外Ca 2+浓度（用于揭示潜在的E-C偶联问题的策略）令人惊讶地被mdx肌细胞耐受得更好，这表明了一种超敏的E-C偶联机制。通过缓慢升高胞内Ca ~（2+）浓度来抑制SR Ca ~（2+）释放，导致mdx细胞中Ca ~（2+）振荡的延迟时间大大缩短。这与SR Ca 2+释放通道[ryanodine受体（RyRs）]的Ca 2+敏感性增强一致。通过引入还原剂可以使超敏反应正常化，这表明营养不良中细胞ROS产生的升高是异常RyR敏感性和超敏E-C偶联的基础。我们的数据表明，在肌营养不良蛋白缺陷的心肌细胞，E-C耦合是改变由于潜在的致癌性变化的Ca 2+敏感性的氧化还原修饰的RyRs。
Duchenne muscular dystrophy represents a severe inherited disease of striated muscle. It is caused by a mutation of the dystrophin gene and characterized by a progressive loss of skeletal muscle function. Most patients also develop a dystrophic cardiomyopathy, resulting in dilated hypertrophy and heart failure, but the cellular mechanisms leading to the deterioration of cardiac function remain elusive. In the present study, we tested whether defective excitation-contraction (E-C) coupling contributes to impaired cardiac performance. “E-C coupling gain” was determined in cardiomyocytes from control and dystrophin-deficientmdxmice. To this end, L-type Ca2+currents (ICaL) were measured with the whole cell patch-clamp technique, whereas Ca2+transients were simultaneously recorded with confocal imaging of fluo-3. Initial findings indicated subtle changes of E-C coupling inmdxcells despite matched Ca2+loading of the sarcoplasmic reticulum (SR). However, lowering the extracellular Ca2+concentration, a maneuver used to unmask latent E-C coupling problems, was surprisingly much better tolerated bymdxmyocytes, suggesting a hypersensitive E-C coupling mechanism. Challenging the SR Ca2+release by slow elevations of the intracellular Ca2+concentration resulted in Ca2+oscillations after a much shorter delay inmdxcells. This is consistent with an enhanced Ca2+sensitivity of the SR Ca2+-release channels [ryanodine receptors (RyRs)]. The hypersensitivity could be normalized by the introduction of reducing agents, indicating that the elevated cellular ROS generation in dystrophy underlies the abnormal RyR sensitivity and hypersensitive E-C coupling. Our data suggest that in dystrophin-deficient cardiomyocytes, E-C coupling is altered due to potentially arrhythmogenic changes in the Ca2+sensitivity of redox-modified RyRs.