Introduction

Kaempferol (KAE) is a flavonoid found in various plants. Recent studies showed that high dietary intake of KAE was associated with a lower risk of myocardial infarction; however, the cardioprotective mechanism of KAE remains unknown.

Objectives

To determine the effect of KAE on cardiac injury in isoproterenol (ISO)-induced rats and cobalt chloride (CoCl₂)-treated cardiomyocytes, and the underlying mechanisms.

Methods

Male rats were pretreated with different doses of KAE for 14 days, and then injected with ISO to induce myocardial ischemia injury. We also established a model of myocardial cell injury using rat H9c2 cardiomyocytes stimulated with CoCl₂.

Results

We found that KAE pretreatment significantly alleviated myocardial injury and improved cardiac function in ISO-injected rats. In addition, KAE reduced oxidative stress in rats with myocardial ischemia by decreasing malondialdehyde concentration and increasing superoxide dismutase activity, and protection of the myocardial mitochondrial structure. KAE also attenuated CoCl₂-induced injury of H9c2 cardiomyocytes via suppression of oxidative stress. With regard to the mechanism, we found that KAE down-regulated HDAC3 expression and up-regulated Nrf2 expression in ISO-induced rats and CoCl₂-stimulated cardiomyocytes. Incubation of cardiomyocytes with HDAC3-selective inhibitor RGFP966 augmented the protective effect of KAE and reduced oxidative stress. By contrast, HDAC3 overexpression by adenovirus attenuated the effect of KAE on oxidative stress compared with KAE treatment group. HDAC3 also regulated Nrf2 expression in the cardiomyocytes with RGFP966 or an adenovirus overexpressing HDAC3; but Nrf2 inhibition reduced the effect of KAE on ROS generation in CoCl₂-induced cardiomyocytes. Immunoprecipitation assay showed that HDAC3 interacted with Nrf2 in cardiomyocytes. Further studies found that KAE increased the acetylation level of Nrf2, while HDAC3 overexpression decreased the acetylation of Nrf2 compared with KAE treatment group.

Conclusion

Our data show that KAE ameliorates cardiac injury by reducing oxidative stress via the HDAC3-mediated Nrf2 signaling pathway in cardiomyocytes.

中文翻译：

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山奈酚通过 HDAC3 介导的 Nrf2 信号通路减少氧化应激，从而减轻心肌缺血损伤

 介绍

山奈酚 （KAE） 是一种在各种植物中发现的类黄酮。最近的研究表明，高膳食摄入 KAE 与较低的心肌梗塞风险相关;然而，KAE 的心脏保护机制仍然未知。

 目标

确定 KAE 对异丙肾上腺素 （ISO） 诱导的大鼠和氯化钴 （CoCl₂） 处理的心肌细胞心脏损伤的影响及其潜在机制。

 方法

雄性大鼠用不同剂量的 KAE 预处理 14 d，然后注射 ISO 诱导心肌缺血损伤。我们还使用 CoCl₂ 刺激的大鼠 H9c2 心肌细胞建立了心肌细胞损伤模型。

 结果

我们发现 KAE 预处理显着减轻了 ISO 注射大鼠的心肌损伤并改善了心脏功能。此外，KAE 通过降低丙二醛浓度和增加超氧化物歧化酶活性，保护心肌线粒体结构来降低心肌缺血大鼠的氧化应激。KAE 还通过抑制氧化应激减轻了 CoCl₂ 诱导的 H9c2 心肌细胞损伤。关于机制，我们发现 KAE 在 ISO 诱导的大鼠和 CoCl₂ 刺激的心肌细胞中下调 HDAC3 表达，上调 Nrf2 表达。心肌细胞与 HDAC3 选择性抑制剂 RGFP966 一起孵育增强了 KAE 的保护作用并降低了氧化应激。相比之下，与 KAE 治疗组相比，腺病毒过表达 HDAC3 减弱了 KAE 对氧化应激的影响。HDAC3 还调节 RGFP966 或腺病毒过表达 HDAC3 的心肌细胞中 Nrf2 的表达;但 Nrf2 抑制降低了 KAE 对 CoCl₂ 诱导的心肌细胞中 ROS 生成的影响。免疫沉淀法显示 HDAC3 与心肌细胞中的 Nrf2 相互作用。进一步研究发现，与 KAE 处理组相比，KAE 增加了 Nrf2 的乙酰化水平，而 HDAC3 过表达降低了 Nrf2 的乙酰化。

 结论

我们的数据显示，KAE 通过心肌细胞中 HDAC3 介导的 Nrf2 信号通路减少氧化应激来改善心脏损伤。