Sirtuin3 (SIRT3), a class III histone deacetylase, is implicated in various cardiovascular diseases as a novel therapeutic target. SIRT3 has been proven to be cardioprotective in a model of Ang II-induced cardiac hypertrophy. However, a few small-molecule compounds targeting deacetylases could activate SIRT3. In this study, we generated a novel SIRT3 activator, 3-(2-bromo-4-hydroxyphenyl)-7-hydroxy-2H-chromen-2-one (SZC-6), through structural optimization of the first SIRT3 agonist C12. We demonstrated that SZC-6 directly bound to SIRT3 with K_d value of 15 μM, and increased SIRT3 deacetylation activity with EC₅₀ value of 23.2 ± 3.3 µM. In neonatal rat cardiomyocytes (NRCMs), pretreatment with SZC-6 (10, 20, 40 µM) dose-dependently attenuated isoproterenol (ISO)-induced hypertrophic responses. Administration of SZC-6 (20, 40 and 60 mg·kg⁻¹·d⁻¹_, s.c.) for 2 weeks starting from one week prior ISO treatment dose-dependently reversed ISO-induced impairment of diastolic and systolic cardiac function in wild-type mice, but not in SIRT3 knockdown mice. We showed that SZC-6 (10, 20, 40 µM) dose-dependently inhibited cardiac fibroblast proliferation and differentiation into myofibroblasts, which was abolished in SIRT3-knockdown mice. We further revealed that activation of SIRT3 by SZC-6 increased ATP production and rate of mitochondrial oxygen consumption, and reduced ROS, improving mitochondrial function in ISO-treated NRCMs. We also found that SZC-6 dose-dependently enhanced LKB1 phosphorylation, thereby promoting AMPK activation to inhibit Drp1-dependent mitochondrial fragmentation. Taken together, these results demonstrate that SZC-6 is a novel SIRT3 agonist with potential value in the treatment of cardiac hypertrophy partly through activation of the LKB1-AMPK pathway.

Sirtuin3 (SIRT3) 是一种 III 类组蛋白脱乙酰酶，作为一种新的治疗靶点与多种心血管疾病有关。SIRT3 已被证明在 Ang II 诱导的心脏肥大模型中具有心脏保护作用。然而，一些靶向脱乙酰酶的小分子化合物可以激活 SIRT3。在这项研究中，我们通过第一个 SIRT3 激动剂 C12 的结构优化，生成了一种新型 SIRT3 激活剂 3-(2-bromo-4-hydroxyphenyl)-7-hydroxy-2H-chromen-2-one (SZC-6)。我们证明 SZC-6 直接与 SIRT3 结合，K _d值为 15 μM，并通过 EC _{50增加 SIRT3 去乙酰化活性}值为 23.2 ± 3.3 µM。在新生大鼠心肌细胞 (NRCM) 中，用 SZC-6（10、20、40 µM）预处理剂量依赖性地减弱了异丙肾上腺素 (ISO) 诱导的肥大反应。SZC-6 给药（20、40 和 60 mg·kg ^-1 ·d ^-1 _，sc) 从 ISO 治疗前一周开始持续 2 周，在野生型小鼠中剂量依赖性地逆转了 ISO 诱导的舒张和收缩心脏功能损伤，但在 SIRT3 敲低小鼠中没有。我们发现 SZC-6（10、20、40 µM）剂量依赖性地抑制心脏成纤维细胞增殖和分化为肌成纤维细胞，这在 SIRT3 敲除小鼠中被废除。我们进一步揭示了 SZC-6 对 SIRT3 的激活增加了 ATP 的产生和线粒体耗氧率，并减少了 ROS，改善了 ISO 处理的 NRCM 中的线粒体功能。我们还发现 SZC-6 剂量依赖性地增强 LKB1 磷酸化，从而促进 AMPK 激活以抑制 Drp1 依赖性线粒体断裂。综合起来，