CaMKII activation participates in doxorubicin cardiotoxicity and is attenuated by moderate GRP78 overexpression

The clinical use of the chemotherapeutic doxorubicin (Dox) is limited by cardiotoxic side-effects. One of the early Dox effects is induction of a sarcoplasmic reticulum (SR) Ca2+ leak. The chaperone Glucose regulated protein 78 (GRP78) is important for Ca2+ homeostasis in the endoplasmic reticulum (ER)—the organelle corresponding to the SR in non-cardiomyocytes—and has been shown to convey resistance to Dox in certain tumors. Our aim was to investigate the effect of cardiac GRP78 gene transfer on Ca2+ dependent signaling, cell death, cardiac function and survival in clinically relevant in vitro and in vivo models for Dox cardiotoxicity.By using neonatal cardiomyocytes we could demonstrate that Dox induced Ca2+ dependent Ca2+ /calmodulin-dependent protein kinase II (CaMKII) activation is one of the factors involved in Dox cardiotoxicity by promoting apoptosis. Furthermore, we found that adeno-associated virus (AAV) mediated GRP78 overexpression partly protects neonatal cardiomyocytes from Dox induced cell death by modulating Ca2+ dependent pathways like the activation of CaMKII, phospholamban (PLN) and p53 accumulation. Most importantly, cardiac GRP78 gene therapy in mice treated with Dox revealed improved diastolic function (dP/dtmin) and survival after Dox treatment. In conclusion, our results demonstrate for the first time that Ca2+ dependent CaMKII activation fosters Dox cardiomyopathy and provide additional insight into possible mechanisms by which GRP78 overexpression protects cardiomyocytes from Doxorubicin toxicity.

化疗药物多柔比星（Dox）的临床应用受到其心脏毒性副作用的限制。多柔比星早期效应之一是诱导细胞质网（SR）钙离子泄漏。分子伴侣葡萄糖调节蛋白78（GRP78）对于内质网（ER）中钙离子的稳态至关重要——该细胞器对应于非心肌细胞中的SR——并且已有研究表明，GRP78在特定肿瘤中可以传递对多柔比星的抗性。我们的目标是研究心脏GRP78基因转移对钙离子依赖性信号传导、细胞死亡、心脏功能和生存的影响，通过在多柔比星心脏毒性相关的体外和体内模型中实施，并使用新生心肌细胞，我们证明了多柔比星诱导的钙离子依赖性钙/钙调蛋白依赖性蛋白激酶II（CaMKII）激活是多柔比星心脏毒性因素之一，通过促进细胞凋亡。此外，我们发现通过腺相关病毒（AAV）介导的GRP78过表达可以部分保护新生心肌细胞免受多柔比星诱导的细胞死亡，通过调节钙离子依赖性途径，如CaMKII、磷脂酸肌醇（PLN）和p53的积累。最重要的是，对接受多柔比星治疗的啮齿动物进行心脏GRP78基因治疗，发现其舒张功能（dP/dtmin）在多柔比星治疗后得到改善，且生存率提高。总之，我们的研究首次证明了钙离子依赖性CaMKII激活促进多柔比星引起的心肌病，并进一步揭示了GRP78过表达保护心肌细胞免受多柔比星毒性的可能机制。