ABSTRACT
Naringin (NRG) is a flavonoid with recognized cardioprotective effects. Then, it was investigated the cardioprotective mechanisms of NRG against ischemia-reperfusion (I/R) injury. The rats were pretreated for 7 days (v.o.) with NRG (25 mg/kg) or n-acetylcysteine (NAC, 100 mg/kg) and their isolated hearts were subjected to global ischemia (30 min) and reperfusion (60 min). Furthermore, isolated hearts were perfused with 5 µM NRG in the presence of 10 µM glibenclamide (GLI) and subjected to I/R protocol. In healthy ventricular cardiomyocyte, it was evaluated the acute effect of 5 µM NRG on the GLI sensitive current. The results showed that NRG pretreatment restored the cardiac function and electrocardiogram (ECG) alterations induced by I/R injury, decreasing arrhythmia scores and the occurrence of severe arrhythmias. Lactate dehydrogenase and infarct area were decreased while superoxide dismutase (SOD), catalase and citrate synthase activities increased. Expression of SOD CuZn and SOD Mn not was altered. NRG treatment decreased reactive oxygen species (ROS) generation and lipid peroxidation without alter sulfhydryl groups and protein carbonylation. Also, NRG (5 µM) increased the glibenclamide sensitive current in isolated cardiomyocytes. In isolated heart, the cardioprotection of NRG was significantly reduced by GLI. Furthermore, NRG promoted downregulation of Bax expression and Bax/Bcl-2. Histopathological analysis showed that NRG decreased cell edema, cardiomyocytes and nucleus diameter. Thus, NRG has a cardioprotective effect against cardiac I/R injury which is mediated by its antioxidant and antiapoptotic actions and KATP channels activation.
ABSTRACT
BACKGROUND: Myocardial infarction (MI) is associated with high mortality rates, despite the fact that there are therapies available. Importantly, excessive oxidative stress may contribute to ischemia/reperfusion injury leading to death related to MI. In this scenario, naturally occurring antioxidant compounds are an important source of possible therapeutic intervention. Thus, this study sought to elucidate the mechanisms of cardioprotection of s-limonene in an isoproterenol-induced MI animal model. METHODS: Wistar rats were treated with 1 mg/kg s-limonene (SL) or 100 mg/kg N-acetylcysteine (NAC, positive control) once, 30 min after isoproterenol-induced MI (applied in two doses with a 24 h interval). The protective effects of SL in the heart were examined via the serum level of creatine kinase myocardial band (CK-MB), electrocardiographic profile, infarct size and histological parameters. Using isolated cardiomyocytes, we also assessed calcium transient amplitude, cytosolic and mitochondrial oxidative stress and the expression of proteins related to oxidative stress. RESULTS: SL at a concentration of 1 mg/kg attenuated isoproterenol-induced MI injury, by preventing ST-segment elevation and QTc prolongation in the ECG. SL reduced the infarct size and collagen content in cardiac tissue. At the cellular level, SL prevented increased Ca2+, associated with attenuation of cytosolic and mitochondrial oxidative stress. These changes resulted in a reduction of the oxidized form of Ca2+ Calmodulin-Dependent Kinase II (CaMKII) and restored superoxide dismutase and glutathione peroxidase activity. CONCLUSION: Our data show that s-limonene promotes cardioprotection against MI injury, probably through inhibition of increased Ca2+ and attenuation of oxidative stress via CaMKII.
