John Curtin School of Medical Research, Australian Capital Territory, Australia.
Mol Pharmacol. 2011 Sep;80(3):538-49. doi: 10.1124/mol.111.073478. Epub 2011 Jun 22.
Our aim was to examine the molecular basis for acute effects of the anthracycline daunorubicin on cardiac ryanodine receptor (RyR2) channels and cardiac calsequestrin (CSQ2). Cardiotoxic effects of anthracyclines preclude their chemotherapeutic use in patients with pre-existing heart conditions. To address this significant problem, the mechanisms of anthracycline toxicity must be defined but at present are poorly understood. RyR2 channel activity was assessed by measuring Ca²⁺ release from cardiac sarcoplasmic reticulum vesicles and by examining single RyR2 channels inserted into artificial lipid bilayers. We show that 0.5 to 10 μM daunorubicin increases the activity of RyR2 channels after 5 to 10 min and that activity then declines to very low levels when channels are exposed to daunorubicin concentrations of ≥ 2.5 μM for a further 10 to 20 min. Extensive dissection of these effects shows for the first time that the activation results from a redox-independent binding of daunorubicin to the RyR2 complex. Novel data include the demonstration of daunorubicin binding to RyR2. We provide compelling evidence that RyR2 channel inhibition is due to the oxidation of free SH groups. The oxidation reaction is prevented by the presence of 1 mM dithiothreitol. We also present novel data showing that CSQ2 modifies the response of RyR2 to daunorubicin, but that the response of RyR2 is not dependent on daunorubicin binding to CSQ2. We suggest that binding of daunorubicin to RyR2 and CSQ2, and oxidation of RyR2, are all likely to contribute to anthracycline-induced cardiotoxicity during chemotherapy.
我们的目的是研究蒽环类药物柔红霉素对心脏兰尼碱受体（RyR2）通道和心脏钙网蛋白（CSQ2）的急性作用的分子基础。蒽环类药物的心脏毒性排除了它们在有预先存在的心脏疾病的患者中的化疗用途。为了解决这个重大问题，必须定义蒽环类药物毒性的机制，但目前了解甚少。通过测量心脏肌浆网囊泡中的 Ca²⁺释放和检查插入人工脂质双层的单个 RyR2 通道来评估 RyR2 通道活性。我们表明，0.5 至 10 μM 的柔红霉素在 5 至 10 分钟后增加 RyR2 通道的活性，并且当通道在进一步的 10 至 20 分钟内暴露于≥2.5 μM 的柔红霉素浓度时，活性下降到非常低的水平。这些作用的广泛剖析首次表明，激活是由于柔红霉素与 RyR2 复合物的氧化还原独立结合所致。新数据包括证明柔红霉素与 RyR2 结合。我们提供了令人信服的证据，表明 RyR2 通道抑制是由于游离 SH 基团的氧化。存在 1 mM 二硫苏糖醇可防止氧化反应。我们还提供了新的数据，表明 CSQ2 修饰了 RyR2 对柔红霉素的反应，但 RyR2 的反应不依赖于柔红霉素与 CSQ2 的结合。我们认为，柔红霉素与 RyR2 和 CSQ2 的结合以及 RyR2 的氧化都可能导致化疗期间蒽环类药物引起的心脏毒性。
