Protective effects of carnosic acid against mitochondria-mediated injury in H9c2 cardiomyocytes induced by hypoxia/reoxygenation.

Myocardial ischemia and reperfusion occurs in myocardial infarction. Timely reperfusion will exacerbate the injury through the mitochondria-mediated apoptosis in cardiomyocytes due to the accumulation of excessive reactive oxygen species (ROS). In order to identify novel therapeutic approaches, the cardioprotective effects of carnosic acid and the underlying mechanisms were investigated in the present study in H9c2 cardiomyocytes injured by hypoxia/reoxygenation in vitro. The viability of H9c2 cardiomyocytes was detected by MTT assay and further confirmed by the detection of intracellular lactate dehydrogenase (LDH) release. The mitochondrial function in H9c2 cardiomyocytes was evaluated using fluorescence methods. The proteins related to apoptosis, including caspase-3, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax) were analyzed by western blot analysis, and the activity of caspase-3 was determined using a colorimetric method. As a result, carnosic acid was demonstrated to improve the viability of H9c2 cardiomyocytes and suppress the leakage of cytosolic lactate dehydrogenase under hypoxia/reoxygenation. In addition, the overproduction of intracellular ROS and intracellular calcium overload were ameliorated in the presence of carnosic acid. The dysfunction of mitochondria in H9c2 cardiomyocytes was also attenuated by carnosic acid through blocking the collapse of mitochondrial membrane potential (MMP) and mitochondrial permeability transition pore (mPTP) opening. Furthermore, the apoptosis of H9c2 cardiomyocytes resulted from hypoxia/reoxygenation was inhibited by carnosic acid through the upregulation of Bcl-2 and the downregulation of Bax and caspase-3 levels. These results provided evidence for further investigation that would assist in the development of novel therapeutic approaches for myocardial infarction.