Autophagy occurs at basal levels for cellular homeostasis under normal conditions and is increased in response to nutrient starvation or stress to ensure cell survival. However, excessive autophagy can be deleterious to cardiomyocytes. CCN1/Cyr61, a matricellular protein, is expressed in the stressed heart to induce cardiomyopathy. The role of autophagy in CCN1-associated cardiotoxicity was not clear. Here, we found that autophagy was induced in the myocardium of the isoproterenol (ISO; 100 mg/kg/day for 5 days; s.c.) treated mice, where CCN1 expression is colocalized. The knock-in mice carrying an integrin α6β1-binding-defective mutant allele Ccn1-dm were resistant to the ISO-induced cardiac injury and autophagy. Our in vitro studies demonstrated that CCN1 dose- and time-dependently induced GFP-LC3-labeled autophagosome formation in rat cardiomyoblast H9c2 cells. The formation of autolysosomes in response to CCN1 (5 μg/ml; 3 h) treatment was identified by the acridine orange staining. The autophagy induction was confirmed by the elevated protein levels of Beclin 1, Atg5, and LC3-II, and the decrease of p62. Inhibition of autophagy by 3-methyladenine or by silencing Atg5 gene enabled CCN1-induced apoptosis in H9c2 cells, suggesting a protective role of autophagy. CCN1 binds to integrin α6β1 to induce autophagy through reactive oxygen species, and the activation of ERK and JNK. Furthermore, mitophagy was observed after CCN1 treatment for the clearance of depolarized mitochondria. Together, these results demonstrated that autophagy is induced in response to CCN1/α6β1 signaling in cardiomyocytes to alleviate CCN1-associated cardiotoxicity.

中文翻译：

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CCN1触发心肌细胞的适应性自噬，以抑制其凋亡活动。

自噬在正常条件下发生于细胞稳态的基础水平，并随着营养缺乏或应激而增加，以确保细胞存活。然而，过多的自噬可能对心肌细胞有害。CCN1 / Cyr61是一种基质细胞蛋白，在压力强烈的心脏中表达，可诱发心肌病。自噬在CCN1相关的心脏毒性中的作用尚不清楚。在这里，我们发现在异丙肾上腺素（ISO； 100 mg / kg /天，共5天； sc）的心肌中诱导自噬，其中CCN1表达共定位。带有整合素α6β1结合缺陷型突变等位基因Ccn1-dm的敲入小鼠对ISO引起的心脏损伤和自噬有抵抗力。我们的体外研究表明，CCN1剂量和时间依赖性诱导了大鼠心肌母细胞H9c2细胞中GFP-LC3标记的自噬体的形成。通过a啶橙染色鉴定了响应CCN1（5μg/ ml; 3 h）处理的自溶酶体的形成。Beclin 1，Atg5和LC3-II的蛋白质水平升高以及p62的降低证实了自噬的诱导。3-甲基腺嘌呤或沉默Atg5抑制自噬该基因使CCN1诱导H9c2细胞凋亡，提示自噬具有保护作用。CCN1与整联蛋白α6β1结合，通过活性氧和ERK和JNK的活化诱导自噬。此外，CCN1处理后观察到线粒体对去极化线粒体的清除。在一起，这些结果表明，自噬是在心肌细胞中响应CCN1 /α6β1信号传导而诱导的，以减轻CCN1相关的心脏毒性。