Background

Oxidative stress in cardiac myocytes is an important pathogenesis of cardiac lipotoxicity. Autophagy is a cellular self-digestion process that can selectively remove damaged organelles under oxidative stress, and thus presents a potential therapeutic target against cardiac lipotoxicity. Globular CTRP9 (gCTRP9) is a newly identified adiponectin paralog with established metabolic regulatory properties. The aim of this work is to investigate whether autophagy participates the protection effects of gCTRP9 in neonatal rat cardiac myocytes (NRCMs) under oxidative stress and the underlying mechanism.

Results

NRCMs were treated with PA of various concentrations for indicated time period. Our results showed that PA enhanced intracellular ROS accumulation, decreased mitochondrial membrane potential (Δψm) and increased activation of caspases 3. These changes suggested lipotoxicity due to excessive PA. In addition, PA was observed to impair autophagic flux in NRCMs and impaired autophagosome clearance induced by PA contributes to cardiomyocyte death. Besides, we found that gCTRP9 increased the ratio of LC3II/I and the expression of ATG5 which was vital to the formation of autophagosomes and decreased the level of P62, suggesting enhanced autophagic flux in the absence or presence of PA. The result was further confirmed by the methods of infection with LC3-mRFP-GFP lentivirus and blockage of autophagosome–lysosome fusion by BafA1. Moreover, gCTRP9 reestablished the loss of mitochondrial membrane potential, suppressed ROS generation, and reduced PA -induced myocyte death. However, the protective effect of gCTRP9 on the cardiac lipotoxicity was partly abolished by blockade of autophagy by autophagy-related 5 (ATG5) siRNA, indicating that the effect of gCTRP9 on cell survival is critically mediated through regulation of autophagy.

Conclusion

Autophagy induction by gCTRP9 could be utilized as a potential therapeutic strategy against oxidative stress-mediated damage in cardiomyocytes.

中文翻译：

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球状CTRP9通过增强自噬通量来保护心肌细胞免受棕榈酸诱导的氧化应激。

背景

心肌细胞中的氧化应激是心脏脂毒性的重要发病机理。自噬是一种细胞自我消化过程，可以在氧化应激下选择性去除受损的细胞器，因此提出了针对心脏脂毒性的潜在治疗靶标。球状CTRP9（gCTRP9）是新近鉴定的脂联素旁系同源物，具有确定的代谢调节特性。这项工作的目的是研究自噬是否参与gCTRP9在氧化应激下对新生大鼠心肌细胞（NRCM）的保护作用及其潜在机制。

结果

在指定的时间段内，用各种浓度的PA处理NRCM。我们的结果表明，PA增强了细胞内ROS的积累，降低了线粒体膜电位（Δψm）并增加了胱天蛋白酶3的激活。这些变化表明，过量的PA会引起脂毒性。此外，观察到PA会损害NRCM中的自噬通量，并且PA诱导的自噬体清除能力受损会导致心肌细胞死亡。此外，我们发现gCTRP9增加了LC3II / I的比例和ATG5的表达，这对自噬小体的形成至关重要，并且降低了P62的水平，表明在不存在或存在PA的情况下自噬通量增加。用LC3-mRFP-GFP慢病毒感染的方法以及BafA1阻断自噬体-溶酶体融合的方法进一步证实了这一结果。此外，gCTRP9重新建立了线粒体膜电位的丧失，抑制了ROS的产生，并减少了PA诱导的心肌细胞死亡。但是，gCTRP9对心脏脂质毒性的保护作用被自噬相关的5（ATG5）siRNA阻断了自噬作用，从而部分取消了该作用，这表明gCTRP9对细胞存活的影响是通过自噬调节来关键地介导的。

结论

gCTRP9的自噬诱导作用可被用作针对心肌细胞氧化应激介导的损伤的潜在治疗策略。