Sirtuin 3 (SIRT3) is well known as a conserved nicotinamide adenine dinucleotide⁺ (NAD⁺)-dependent deacetylase located in the mitochondria that may regulate oxidative stress, catabolism and ATP production. Accumulating evidence has recently revealed that SIRT3 plays its critical roles in cardiac fibrosis, myocardial fibrosis and even heart failure (HF), through its deacetylation modifications. Accordingly, discovery of SIRT3 activators and elucidating their underlying mechanisms of HF should be urgently needed. Herein, we identified a new small-molecule activator of SIRT3 (named 2-APQC) by the structure-based drug designing strategy. 2-APQC was shown to alleviate isoproterenol (ISO)-induced cardiac hypertrophy and myocardial fibrosis in vitro and in vivo rat models. Importantly, in SIRT3 knockout mice, 2-APQC could not relieve HF, suggesting that 2-APQC is dependent on SIRT3 for its protective role. Mechanically, 2-APQC was found to inhibit the mammalian target of rapamycin (mTOR)-p70 ribosomal protein S6 kinase (p70S6K), c-jun N-terminal kinase (JNK) and transforming growth factor-β (TGF-β)/ small mother against decapentaplegic 3 (Smad3) pathways to improve ISO-induced cardiac hypertrophy and myocardial fibrosis. Based upon RNA-seq analyses, we demonstrated that SIRT3-pyrroline-5-carboxylate reductase 1 (PYCR1) axis was closely assoiated with HF. By activating PYCR1, 2-APQC was shown to enhance mitochondrial proline metabolism, inhibited reactive oxygen species (ROS)-p38 mitogen activated protein kinase (p38MAPK) pathway and thereby protecting against ISO-induced mitochondrialoxidative damage. Moreover, activation of SIRT3 by 2-APQC could facilitate AMP-activated protein kinase (AMPK)-Parkin axis to inhibit ISO-induced necrosis. Together, our results demonstrate that 2-APQC is a targeted SIRT3 activator that alleviates myocardial hypertrophy and fibrosis by regulating mitochondrial homeostasis, which may provide a new clue on exploiting a promising drug candidate for the future HF therapeutics.

Sirtuin 3 (SIRT3) 是众所周知的一种保守的烟酰胺腺嘌呤二核苷酸⁺ (NAD ⁺ ) 依赖性脱乙酰酶，位于线粒体中，可调节氧化应激、分解代谢和 ATP 产生。最近越来越多的证据表明，SIRT3通过其去乙酰化修饰在心脏纤维化、心肌纤维化甚至心力衰竭（HF）中发挥着关键作用。因此，迫切需要发现 SIRT3 激活剂并阐明其心力衰竭的潜在机制。在此，我们通过基于结构的药物设计策略鉴定了一种新的SIRT3小分子激活剂（命名为2-APQC）。在体外和体内大鼠模型中，2-APQC 显示可减轻异丙肾上腺素 (ISO) 诱导的心脏肥大和心肌纤维化。重要的是，在 SIRT3 敲除小鼠中，2-APQC 无法缓解心力衰竭，这表明 2-APQC 的保护作用依赖于 SIRT3。从机械角度来看，2-APQC 可抑制哺乳动物雷帕霉素靶点 (mTOR)-p70 核糖体蛋白 S6 激酶 (p70S6K)、c-jun N 末端激酶 (JNK) 和转化生长因子 -β (TGF-β)/small母体对抗Decapentaplegic 3 (Smad3)途径，改善ISO引起的心脏肥大和心肌纤维化。基于RNA-seq分析，我们证明SIRT3-吡咯啉-5-羧酸还原酶1（PYCR1）轴与HF密切相关。通过激活 PYCR1，2-APQC 可增强线粒体脯氨酸代谢，抑制活性氧 (ROS)-p38 丝裂原激活蛋白激酶 (p38MAPK) 通路，从而防止 ISO 诱导的线粒体氧化损伤。此外，2-APQC 激活 SIRT3 可以促进 AMP 激活蛋白激酶 (AMPK)-Parkin 轴抑制 ISO 诱导的坏死。 总之，我们的结果表明，2-APQC 是一种靶向 SIRT3 激活剂，可通过调节线粒体稳态来减轻心肌肥厚和纤维化，这可能为开发未来心力衰竭治疗的有前途的候选药物提供新线索。