Effect Of Ginsenoside Rgl On Myocardial Ischemia Reperfusion Injury In Rats And Its Mechanism

Backgrounds:Ischemia and reperfusion (I/R) is responsible for the injury caused by interventional therapy. Protection of I/R induced myocardial injury remains a challenge for clinician. Energy metabolism disorder is the initial link, inflammatory reaction medium and apoptosis play an important role in the I/R injury. During myocardial ischemia hypoxia, ATP synthase delta subunits 5 d express lower ATP, lead to inadequate myocardial ATP generation. On the other hand, the heart pumps blood oxygen, and ATP increased degradation. ATP reduction is one of the main factors of myocardial contraction protein damage. I/R caused by abnormal energy metabolism and excess peroxide damaged cardiac muscle skeleton silk protein. Active oxygen free radicals (ROS) on the one hand, can be directly cellular structure damage and impaired; on the other hand, can activate the nuclear factor kappa B predominate (nuclear factor kappa B, predominate the NF-kappa B), through the NF-kappa B start the expression of inflammatory cytokines and adhesion factor, promote the reaction of white blood cells and vascular endothelial cells and swim out, increase blood vessels and myocardial injury, further induce the cell apoptosis. Rho kinase (Rho kinase, ROCK) signaling pathway and PI3K/Akt signaling pathway are important signaling pathways involved in cell apoptosis.PI3K and downstream molecules mediated by antiapoptotic effect has become a focus in the field of drug research. Ginseng saponin Rg1 (ginsenoside Rgl, Rg1) is one of the ginseng saponins isolated monomers, has a wide range of biological activities. A large number of studies have shown that ginseng saponins on the cardiovascular system, nervous system, immune system have influence, can inhibit apoptosis, dilate blood vessels, improve heart function, anti-aging, beauty, and so on. But there is no evidence of in vivo tests, from the perspective of energy metabolism, inhibit inflammation and apoptosis, and to explore the ginseng saponin Rgl on improvement of myocardial ischemia-reperfusion injury in rats and the mechanism.Objectives:The present study aims to detect the role of Rgl in I/R induced myocardial infarct area, cardiac microcirculation disturbance, cardiac function, energy metabolism disorder, cell apoptosis, inflammatory reaction and investigate the effects of Rg1 on NF-κB, ROCK and PI3K/Akt to explore the underlying mechanism.Methods:Male Spragu-Dawley (SD) rats were subjected to occlusion of left anterior descending coronary artery for 30 min, followed by reperfusion with or without administration of Rg1 (1mg/kg,5 mg/kg,10 mg/kg) for 90 min. The cardioprotective effects of Rg1 were evaluated by assessment of the myocardial infarct size by 2,3,5-triphenyltetrazolium chloride and Evans blue staining, the myocardial cell apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. The myocardial blood flow was observed by a Laser Doppler perfusion imager at baseline,30 min of ischemia,30,60,90 min of reperfusion. Cardiac function was monitored by a bio-function experiment system at baseline,30 min of ischemia,30,60,90 min of reperfusion. The morphology of myocardium was observed by light and electron microscopy. To gain insight into the rationale for the observed effects of Rg1, western blot was conducted for B-cell lymphoma-2 (Bcl-2), Bcl-2 associated x protein (Bax), cleaved caspase-3, Cardiac Troponin I(cTnI),Rho-kinase(ROCK), MYPT1, P-MYPT1, Phosphatidyl Inositol 3-kinase(PI3K),P-PI3K,Akt, P-Akt,ATP-5D,phosphorylated myosin light chain(P-MLC),nuclear factor KB(NF-κB)in cytoplasm and nucleus; real time polymerase chain reaction for ATP-5D mRNA; and enzyme-linked immunosorbent assay for content of malondialdehyde (MDA), adenosine triphosphate (ATP), adenosine diphosphate (ADP),adenosine monophosphate (AMP) in heart and cTnl in serum. The expression of MPO, ICAM-1 and CD 18 was detected by immunohistochemistry.Results:Administration of Rgl 30 min before ischemia till the end of reperfusion significantly:1. reduced I/R induced infarct size;2. improved myocardium and mitochondrial morphology after I/R challenge;3. ameliorated I/R induced reduction in cardiac function and myocardial blood flow;4. reversed I/R induced reduction in cTnI in heart and increase in cTnI in serum;5. diminished I/R induced myocardial apoptosis with upregulating anti-apoptotic molecule Bcl-2 and downregulating pro-apoptotic molecules Bax and cleaved Caspase-3;6. prevented hearts from I/R induced decrease in protein and mRNA expression of ATP-5D and the rise of MLC phosphorylation level;7. prevented hearts from I/R induced reduction in ratio of ATP/ADP and ATP/AMP, and MDA accumulation;8. increased the ratio of P-PI3K/PI3K and P-Akt/Akt to exert anti-apoptosis effect;9.inhibited I/R-induced insults in ROCK activation and Phosphorylation of MYPT-1;10.reversed I/R induced reduction in NF-kB P65 in cytoplasm and increase in NF-κB P65 in cell nucleus;11. inhibited the impairment of I/R on MPO、ICAM-1、CD18;Conclusions:In the present study, we confirmed the cardioprotective role of Rgl in an I/R-induced cardiac injury model of rat. The results showed that administration of Rgl ameliorated I/R-elicited insults by upregulating the expression of P-PI3K and P-Akt and improving NF-κB P65 nuclear translocation and inhibiting ROCK activation and Phosphorylation of MYPT-1; including increased in ATP production and decreased in MDA after I/R, resulting in reduced infarct size and apoptosis, and improved myocardium morphology, MBF and LV function. The present study provides evidence for identification of the signaling pathway thereby Rg1 exerts its beneficial effects, as well as for designing novel medicine to cope with I/R-induced cardiac injury.