Kaempferol alleviates myocardial ischemia injury by reducing oxidative stress via the HDAC3-mediated Nrf2 signaling pathway

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.