| Summary: | 博士 === 國立臺灣大學 === 藥理學研究所 === 89 === Oxidative stress plays an important role in the pathogenesis of myocardial ischemia and infarction. Antioxidants might then be beneficial in the prevention of these diseases. In this study, we compared the antioxidant, free radical scavenging and cardioprotective activities of resveratrol and derivatives. And, we also examined the mechanisms of resveratrol protect myocardial ischemia-reperfusion (I/R) injury. Further, the beneficial effects and mechanisms of thaliporphine in ischemia or I/R was also evaluated.
Dietary antioxidants are thought to be beneficially in reducing the incidence of coronary heart disease. In this study, we compared the antioxidant, free radical scavenging, and cardioprotective activities of resveratrol (3,4’,5-trihydroxystilbene) and analogs. Astringinin (3,3’,4’,5-tetrahydroxystilbene) was shown to be a more potent inhibitor than other analogs of Cu2+-induced LDL oxidation, as measured by conjugated diene, thiobarbituric acid-reactive substance (TBARS) formations and by the electrophoretic mobility of the LDL. Both resveratrol and astringinin scavenged the stable free radical 1,1-diphenyl-2-picryl-hydrazyl (DPPH) with IC0.20 of 7.1 μM and 4.3 μM, respectively. Astringinin has a superoxide anion scavenging activity about 160-fold more potent than resveratrol. We also showed that astringinin is a more potent cardioprotective agent than resveratrol on I/R injury in Langendorff-perfused rat hearts. Our results showed that there is a correlation between the antioxidant and cardioprotective activities among these phenolic compounds. Since astringinin is more water-soluble than resveratrol, it is probably a better antioxidant and cardioprotective agent to be used in biological system.
Examine the cardioprotective effect of resveratrol, an antioxidant presents in the red wines, in the rat after ischemia and I/R. The left main coronary artery was occluded for 30 min or 5 min followed by a 30 min reperfusion in anesthetized rats. Animals were preinfused with and without resveratrol before occlusion and the severity of ischemia- and I/R-induced arrhythmias and mortality were compared. Resveratrol pretreatment had no effect on ischemia-induced arrhythmias nor on mortality. In contrast, dramatic protective effects were observed against I/R-induced arrhythmias and mortality. Resveratrol pretreatment both reduced the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF). During the same period, resveratrol pretreatment also increases nitric oxide (NO) and decreases lactate dehydrogenase (LDH) levels in the carotid blood. Resveratrol is a potent antiarrhythmic agent with cardioprotective property in I/R rats. The cardioprotective effects of resveratrol in the I/R rats may be correlated with its antioxidant activity and upregulation of NO production.
Astringinin, a resveratrol analogue with considerably higher antioxidative activity and free radical scavenging capacity, was introduced to examine its cardioprotective effects in ischemia or ischemia-reperfusion (I/R) rats. In the present study, the left main coronary artery was occluded by the following procedures: (1) 30 min occlusion, (2) 5 min occlusion followed by 30 min reperfusion, (3) 4 h occlusion. Animals were infused with and without astringinin before coronary artery occlusion. Mortality, and the severity of ischemia- and I/R-induced arrhythmias were compared. Pretreatment of astringinin dramatically reduced the incidence and duration of VT and VF during either ischemia or I/R period. Astringinin at 2.5×10-5 and 2.5×10-4 g/kg completely prevented the mortality of animals during ischemia or I/R. During the same period, astringinin pretreatment also increased NO and decreased LDH levels in the carotid blood. In animals subjected to 4 h coronary occlusion, the cardiac infarct size (expressed as % of occluded zone) was reduced from 44.4±4.1 to 19.1±2.4 % by astringinin (2.5×10-4 g/kg). We conclude that, astringinin is a potent antiarrhythmic agent with cardioprotective activity in ischemic and I/R rat heart. The beneficial effects of astringinin in the ischemic and I/R hearts may be correlated with its antioxidant activity and upregulation of NO production.
The role of NO in the mechanism of resveratrol protects myocardial I/R injury is not understood. Therefore, we planned to assess the correlation between the cardioprotection of resveratrol and NO in I/R injury. Animals were subjected to coronary artery occlusion 30 min followed by 2 h reperfusion, which may induce iNOS (inducible nitric oxide synthase) expression. In contrast, pretreatment of resveratrol caused a significant downregulation in iNOS and upregulation in eNOS (endothelial nitric oxide synthase) and nNOS (neuronal nitric oxide synthase) expression of myocardium in I/R. The severity of rhythm disturbances and mortality in anesthetized rats were monitored and compared in resveratrol vs. placebo-treated groups. Administration of resveratrol results in dramatic reduced cardiac infarct size and significantly decreased LDH and creatine kinase (CK) levels in the blood during the end period of I/R. These changes in LDH and CK levels by resveratrol were associated with a reduction in the ventricular arrhythmia, mortality rate and cardiac infarct zone in I/R. Inhibition of NO synthesis with 1×10-3 g/kg of Nw-nitro-L-arginine methyl ester (L-NAME) abolished the anti-infarct action and decreased the LDH and CK levels of resveratrol in I/R. However, the antiarrhythmic activity and mortality reduction efficacy of resveratrol during ischemia period was not antagonized by L-NAME. These results showed that resveratrol efficiently exerted the cardioprotections in I/R situations. The fact that resveratrol induced anti-infarct effect was abrogated by L-NAME indicates that NO is an important mediator for anti-infarct of resveratrol in I/R, whereas antiarrhythmic activities of resveratrol was not through NO-dependent mechanism, indicated that other mechanism may contribute to the protection of I/R injury.
Thaliporphine, a natural alkaloid with Ca2+ channel activating and Na+ or K+ channels blocking activities, increased NO level and exerted cardioprotective action in ischemic or I/R rats. Therefore, we planned to assess the role of NO in cardioprotective actions of thaliporphine. The severity of rhythm disturbances and mortality in anesthetized rats with either coronary artery occlusion for 30 min, or 5 min followed by 30 min reperfusion, were monitored and compared in thaliporphine vs. placebo-treated groups. Thaliporphine treatment significantly increased NO and decreased LDH levels in the blood during the end period of ischemia or I/R. These changes in NO and LDH levels by thaliporphine was associated with a reduction in the incidence and duration of VT and VF during ischemic or I/R period. The mortality of animals was also completely prevented by 3.5×10-6 g/kg of thaliporphine. In animals subjected to 4 h left coronary artery occlusion, 3.5×10-5 g/kg of thaliporphine dramatic reduced cardiac infarct zone from 46.0±6.0% to 7.1±1.9%. Inhibition of NO synthesis with 1×10-3 g/kg of L-NAME abolished beneficial effects of thaliporphine during 30 min or 4 h myocardial ischemia. However, the antiarrhythmic activity and mortality reduction efficacy of thaliporphine during reperfusion after 5 min of ischemia was only partially antagonized by L-NAME. These results showed that thaliporphine efficiently exerted the cardioprotections either in acute or prolonged coronary artery occlusion or occlusion-reperfusion situations. The fact that thaliporphine induced cardioprotective effects was abrogated by L-NAME indicates that NO is an important mediator for cardioprotection of thaliporphine in acute or prolonged ischemia, whereas antioxidant activities, which were proved by, further studies may contribute to the protection of I/R injury.
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