| Polydatin, 3, 4′, 5-trihydroxystibene-3-β-mono-D-glucoside, also named piceid, is a monocrystalline isolated from a traditional Chinese herbal medicine, polygonum Cuspidatum. So far, polydatin has been found in more than 70 varieties of plants, and it has a lot of biological activities. Some previous studies demonstrated that polydatin could inhibit the platelet aggregation, reduce the adhesion of neutrophil-endothenal cells, improve microcirculation, oppose shock, and have antioxidative activity. Besides, it was reported that polydatin protected cardiomyocytes against the injury induced by deprivation of oxygen and glucose, and reduced cerebral ischemic damage by inhibiting lipid peroxidation. Furthermore, it was proved that polydatin prevented intestine and remote organs from damage during intestinal ischemia-reperfusion. However, the effects of polydatin on myocardial ischemia/reperfusion injury have not been reported yet. The aim of the study is to investigated whether polydatin has a protective effect on heart, and to explore the underlying mechanism. Our study consists of four parts: (1) Protective effect of polydatin against ischemia/reperfusion injury in rat heart. (2) The role of KATP and mitochondrial permeability transition pore in the cardioprotection of polydatin. (3) Polydatin attenuates ischemia/reperfusion induced apoptosis in cardiac myocytes. (4) Antiarrhythmic effects of polydatin and the underlying electrophysiological mechanism.I Protective effect of polydatin against ischemia/reperfusion injury in rat heartObjective: The aim of this study was to investigate the effect of polydatin on myocardial ischemia/reperfusion injury in rats and the underlying mechanism. Methods: Male Sprague-Dawley (SD) rats were randomly divided into two groups: control group and polydatin group. In Langendorff isolated rat heart, cardiac function was recorded before and after 30 min global ischemia followed by 60 min reperfusion. The parameters of cardiac function including left ventricular developing pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal differentials of LVDP (±LVdp/dtmax) and coronary flow (CF) were measured. Myocardial ultrastructure was observed. Myocardial superoxide dismutase (SOD) activity, the contents of myocardial malondialdehyde (MDA) and nitric oxide (NO) as well as the activity of nitric oxide synthase (NOS) were measured in isolated rat heart.Results:(1) The recovery percent of LVDP, +LVdP/dtmax, and -LVdP/dtmax, were 43.3±8.7 %, 42.9±14.9 % and 42.4±21.3 %, respectively, in polydatin group, much higher than those in control group(22.5±11.2 %, 23.1±17.3 % and 24.1±8.5 %, respectively) (P<0.05~0.01).(2) The damage of ultrastructure in myocardium induced by I/R was markedly reduced in polydatin group.(3) The activity of SOD in polydatin group hearts was 965±77 U/g protein, higher than that in control hearts 788±137 U/g protein, but MDA content was lower in polydatin group than that in control group (P<0.05).(4) The level of NO was higher in polydatin group hearts than that in control hearts (P<0.05). Besides, the NOS activities, especially constitutive nitric oxide synthase (cNOS) activities in polydatin group were higher than that in control group (P<0.05).(5) L-NAME, a NO synthase inhibitor, could reverse the protective effects of polydatin against ischemia/reperfusion injury.Conclusion: The results suggest that polydatin has a protective effect against ischemia/reperfusion injury on rat heart. The cardioprotection of polydatin is mainly mediated by cNOS which leading to an increase in NO production. ⅡThe role of KATP and mitochondrial permeability transition pore in the cardioprotection of polydatinObjective: The aim of this study was to further investigate the protective effect of polydatin on heart against ischemia/reperfusion (I/R) injury and the role of ATP-dependent potassium channel (KATP) and mitochondrial permeability transition pore (MPTP) in the cardioprotection of polydatin. Methods: Male Sprague-Dawley (SD) rats were randomly divided into seven groups: control group, polydatin 25μmol/L group, polydatin 50μmol/L group, polydatin 75μmol/L group, glibenclamide group, 5-hydroxydecanoate (5-HD) group and atractyloside group. In Langendorff isolated rat heart, cardiac function was recorded before and after 30 min global ischemia followed by 60 min reperfusion. At the end of reperfusion, the infarct size of the heart was measured by triphenyltetrazolium chloride (TTC) staining.Results:(1) Compared with control hearts, polydatin (25, 50, 75μmol/L) displayed a better recovery of cardiac function during reperfusion after ischemia in a concentration-dependent manner. After 60 min of reperfusion, left ventricular developing pressure (LVDP), maximal differentials of LVDP (±LVdp/dtmax) and coronary flow (CF) were 41.7±9.2 mmHg, 1069.9±77.0 mmHg/s, -992.8±294.5 mmHg/s and 4.1±1.1 ml/min, respectively, in polydatin group, much higher than 20.8±12.0 mmHg, 598.3±219.5 mmHg/s, -506.9±180.5 mmHg/s and 2.4±0.4 ml/min, repectively, in control group, while left ventricular end-diastolic pressure (LVEDP) in polydatin group was 61.4±3.2 mmHg, lower than 76.2±6.0 mmHg in control group ( P<0.01).(2) Pretreatment with KATP antagonist glibenclamide (10μmol/L) completely abolished these protective effects of polydatin (50μmol/L). Besides, most of the effects of polydatin (50μmol/L) on cardiac function after 60 min of reperfusion were abolished by the selective mitochondria KATP antagonist 5-HD (100μmol/L).(3) Atractyloside (20μmol/L), an MPTP opener, administered at the beginning of 15 min of reperfusion completely abolished the protection of polydatin (50μmol/L).(4) Polydatin (50μmol/L) significantly reduced infarct size compared with control group (P<0.01), which was reversed by Glibenclamide, 5-HD and atractyloside.Conclusion: Polydatin has a protective effect on rat heart against ischemia/reperfusion injury, which is related with the opening of KATP channels, particularly those localized on the mitochondrial membrane, and the inhibiting of MPTP open.ⅢPolydatin attenuates ischemia/reperfusion induced apoptosis in cardiac myocytesObjective: The aim of this study was to investigate the effect of polydatin on apoptosis induced by ischemia/reperfusion (I/R) in rat myocardium and underlying mechanism.Methods: Male Sprague-Dawley (SD) rats were randomly divided into three groups: control group, I/R group and polydatin group. On the Langendorff apparatus, isolated rat heart was subjected to 30 min global ischemia followed by 60 min reperfusion. Cardiomyocytic apoptosis were measured.Results:(1) DNA ladder pattern in myocardium was revealed by agarose gel electrophoresis in I/R group, which was less apparent in polydatin group.(2) Compared with I/R group (TUNEL staining), the TUNEL-positive cells were significantly decreased in the polydatin group (18.1±4.0 % vs 35.1±5.4 %, P<0.01).(3) Apoptosis rate in I/R group and in polydatin group detected by flow cytometry were 15.43±4.55 % and 8.66±3.18 %, respectively.(4) Bax protein expressions in the myocardium of I/R group were higher than that in polydatin group (P<0.05), while Bcl-2 protein expressions and Bcl-2/Bax ratio were higher in polydatin group (P<0.05~0.01).Conclusion: Polydatin inhibits ischemia/reperfusion-induced apoptosis through increasing Bcl-2 protein expressions and decreasing Bax protein expressions in myocardium of rat.ⅣAntiarrhythmic effects of polydatin and the underlying electrophysiological mechanismObjective: The aim of the present study was to investigate the antiarrhythmic effects of polydatin and the underlying electrophysiological mechanism.Methods: In anesthetized Sprague-Dawley (SD) rat, ischemia/reperfusion arrhythmia produced by ligating and loosing coronary artery was recorded. The transmembrane action potentials were recorded using intracellular microelectrode technique.Results:(1) Arrhythmia score (AS) of ischemic and reperfusion arrhythmia in polydatin group were 1.0±1.5 and 2.0±1.8, respectively, and were lower than those in control group (3.5±1.0 and 4.5±1.6, P<0.05~0.01). Besides, myocardial infarct size after ischemic and reperfusion was significantly lower in polydatin group than those in control group (P<0.01).(2) In normal papillary muscles, polydatin (25μmol/L, 50μmol/L, and 100μmol/L) shortened APD50, and APD90 in a concentration-dependent manner. Polydatin (25μmol/L) had no significant effect on the parameters of AP. While polydatin (50μmol/L and 100μmol/L) significantly shortened APD50 (from 22.2±3.1 ms to 16.4±1.5 ms and 13.6±1.6 ms, respectively) and APD90 (from 114.9±11.2 ms to 88.1±15.7 ms and 70.7±9.9 ms, respectively) (P<0.05~0.01), but had no effect on RP, OS, APA and Vmax (P>0.05).(3) In partially depolarized papillary muscles, polydatin (50μmol/L) not only shortened APD50 and APD90 (P<0.05), but also decreased OS, APA and Vmax (P<0.05). APD90 was shortened from 72.8±14.4 ms to 49.7±8.2 ms. APA and OS were decreased from 53.2±8.5 mV to 42.9±4.6 mV and from 2.3±5.0 mV to -6.9±6.5 mV, respectively. Vmax was decreased from 46.9±6.6 V/s to 27.4±9.7 V/s. (4) After pretreatment with Glibenclamide, a KATP channel blocker, the electrophysiological effects of polydatin (50μmol/L) were partially inhibited. APD50 and APD90 were significantly different from those in the control group (P<0.05) and those in polydatin (50μmol/L) group (P<0.05).(5) Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), a nitric oxide (NO) synthase inhibitor, failed to abolish the effects of polydatin (50μmol/L) on AP.Conclusion: All these results indicate that polydatin has an antiarrhythmic effect and shorten the action potential duration in a concentration-dependent manner through opening of KATP, as well as inhibit action potential in partially depolarized papillary muscles, which might be one of electrophysiological mechanism for cardioprotection of polydatin.SUMMARY1 Polydatin has a protective effect against ischemia/reperfusion injury on rat heart. The cardioprotection of polydatin is mainly mediated by cNOS which leading to an increase in NO production.2 Opening of KATP channels, particularly those localized on the mitochondrial membrane, and inhibition of MPTP opening play important roles in the protective effects afforded by polydatin.3 Polydatin inhibits ischemia/reperfusion-induced apoptosis through increasing Bcl-2 protein expressions in myocardium of rat, which might be one of mechanisms for the cardioprotective effect of polydatin.4 Polydatin has an antiarrhythmic effect and prolong the action potential duration in a concentration-dependent manner through opening of KATP, as well as inhibit action potential in partial depolarized papillary muscle, which might be related with the decrease of calcium influx and the increase of potassium efflux through opening of KATP.
|
PDF Full Text Request