The present study was designed to investigate the protective effects of 4-guanidino-n-butyl syringate (leonurine), a compound in Herba Leonuri (HL) on ischemic rat heart to determine the protective mechanisms associated with ischemic rat hearts. Rat heart ischemia was induced by ligation of the left coronary artery. Creatine kinase (CK) and lactate dehydrogenase (LDH) in plasma and superoxide dismutase (SOD) activity in heart homogenates were measured. We found leonurine significantly decreased levels of LDH and CK activities in plasma. This observation corresponded with decreased infarct size of ischemic rat heart induced by ligation of the left coronary artery. Moreover, the mRNA expression of the pro-apoptotic gene Bax was significantly down-regulated by 0.68-fold (p < 0.05) and the anti-apoptotic gene Bcl-2 was up-regulated by 1.41-fold (p < 0.05) in the leonurine treated groups as compared with acute myocardium ischemia (MI) controls measured by RT-PCR. Correspondingly, Bcl-2 and Bax protein levels detected by Western blotting coincided with gene expression levels. In addition, the mRNA expression level of the antioxidant enzyme Mn-SOD was significantly increased 1.23-fold (p < 0.05) and this finding corresponded with an observed increase in SOD activity and also with a committed decrease in lipid peroxidation. Taken together, our results demonstrated that leonurine attenuated myocardium injury during MI via antioxidative and anti-apoptotic effects and leonurine might become a useful adjuvant cardioprotective agent.
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