Resveratrol, a natural ingredient of grape skin: antiarrhythmic efficacy and ionic mechanisms

Inhibitory effect of aloperine on transient outward potassium currents in rat cardiac myocytes

Objective

Aloperine (ALO) is an effective quinolizidine alkaloid. Previous research has demonstrated its antiarrhythmic effect by inhibiting voltage-gated sodium currents in rat ventricular myocytes. This study explored its effect on transient outward potassium currents (Ito) in rat atrial myocytes to identify potential targets in the context of ion channel currents.

Methods

The Ito characteristics in rat atrial myocytes were recorded using a whole-cell patch-clamp technique. Molecular docking was performed to validate ligand-protein binding interactions.

Results

ALO at concentrations of 3 and 10 μM significantly reduced Ito current densities. Gating kinetics analysis revealed ALO's ability to slow Ito activation, hasten inactivation, and prolong transition from inactive to resting state. Molecular docking revealed that ALO could stably bind to KCND2.

Conclusion

ALO may inhibit Ito by slowing the activation process, accelerating inactivation, and delaying the recovery time after inactivation, potentially preventing acetylcholine-induced AF.

A novel combination of metformin and resveratrol alleviates hepatic steatosis by activating autophagy through the cAMP/AMPK/SIRT1 signaling pathway

Nonalcoholic fatty liver disease (NAFLD) is a prevalent liver disorder that is associated with the accumulation of triglycerides (TG) in hepatocytes. Resveratrol (RSV), as a natural product, and metformin have been reported to have potential lipid-lowering effects for the treatment of NAFLD via autophagy, but the combined effects of both have not yet been studied. The current study aimed to investigate the role of autophagy in the lipid-lowering effects of RSV, alone and in combination with metformin, on the hepatic steatosis model of HepG2 cells and elucidate the mechanism of action. Triglyceride measurement and real-time PCR showed that RSV-metformin reduced lipid accumulation and the expression of lipogenic genes in palmitic acid (PA)-induced HepG2 cells. Additionally, the LDH release assay indicated that this combination protected HepG2 cells against PA-induced cell death through autophagy. The western blotting analysis revealed that RSV-metformin induced autophagy by reducing the expression of p62 and increasing LC3-I and LC3-II proteins. This combination also enhanced cAMP, phosphorylated AMP-activated protein kinase (p-AMPK), and Beclin-1 levels in HepG2 cells. Furthermore, SIRT1 inhibitor treatment inhibited autophagy induced by RSV-metformin, which indicated the autophagy induction is SIRT1-dependent. This study demonstrated for the first time that RSV-metformin reduced hepatic steatosis by triggering autophagy via the cAMP/AMPK/SIRT1 signaling pathway.

In silico mechanisms of arsenic trioxide-induced cardiotoxicity

It has been found that arsenic trioxide (ATO) is effective in treating acute promyelocytic leukemia (APL). However, long QT syndrome was reported in patients receiving therapy using ATO, which even led to sudden cardiac death. The underlying mechanisms of ATO-induced cardiotoxicity have been investigated in some biological experiments, showing that ATO affects human ether-à-go-go-related gene (hERG) channels, coding rapid delayed rectifier potassium current (I _Kr ), as well as L-type calcium (I _CaL ) channels. Nevertheless, the mechanism by which these channel reconstitutions induced the arrhythmia in ventricular tissue remains unsolved. In this study, a mathematical model was developed to simulate the effect of ATO on ventricular electrical excitation at cellular and tissue levels by considering ATO's effects on I _Kr and I _CaL . The ATO-dose-dependent pore block model was incorporated into the I _Kr model, and the enhanced degree of ATO to I _CaL was based on experimental data. Simulation results indicated that ATO extended the action potential duration of three types of ventricular myocytes (VMs), including endocardial cells (ENDO), midmyocardial cells (MCELL), and epicardial cells (EPI), and exacerbated the heterogeneity among them. ATO could also induce alternans in all three kinds of VMs. In a cable model of the intramural ventricular strand, the effects of ATO are reflected in a prolonged QT interval of simulated pseudo-ECG and a wide vulnerable window, thus increasing the possibility of spiral wave formation in ventricular tissue. In addition to showing that ATO prolonged QT, we revealed that the heterogeneity caused by ATO is also an essential hazard factor. Based on this, a pharmacological intervention of ATO toxicity by resveratrol was undertaken. This study provides a further understanding of ATO-induced cardiotoxicity, which may help to improve the treatment for APL patients.

Mechanism-based targeting of cardiac arrhythmias by phytochemicals and medicinal herbs: A comprehensive review of preclinical and clinical evidence

Cardiac arrhythmias, characterized by an irregular heartbeat, are associated with high mortality and morbidity. Because of the narrow therapeutic window of antiarrhythmic drugs (AADs), the management of arrhythmia is still challenging. Therefore, searching for new safe, and effective therapeutic options is unavoidable. In this study, the antiarrhythmic effects of medicinal plants and their active constituents were systematically reviewed to introduce some possible candidates for mechanism-based targeting of cardiac arrhythmias. PubMed, Embase, and Cochrane library were searched from inception to June 2021 to find the plant extracts, phytochemicals, and multi-component herbal preparations with antiarrhythmic activities. From 7337 identified results, 57 original studies consisting of 49 preclinical and eight clinical studies were finally included. Three plant extracts, eight multi-component herbal preparations, and 26 phytochemicals were found to have antiarrhythmic effects mostly mediated by affecting K+ channels, followed by modulating Ca2+ channels, upstream target pathways, Nav channels, gap junction channels, and autonomic receptors. The most investigated medicinal plants were Rhodiola crenulata and Vitis vinifera. Resveratrol, Oxymatrine, and Curcumin were the most studied phytochemicals found to have multiple mechanisms of antiarrhythmic action. This review emphasized the importance of research on the cardioprotective effect of medicinal plants and their bioactive compounds to guide the future development of new AADs. The most prevalent limitation of the studies was their unqualified methodology. Thus, future well-designed experimental and clinical studies are necessary to provide more reliable evidence.

Antioxidants in Arrhythmia Treatment—Still a Controversy? A Review of Selected Clinical and Laboratory Research

Antioxidants are substances that can prevent damage to cells caused by free radicals. Production of reactive oxygen species and the presence of oxidative stress play an important role in cardiac arrhythmias. Currently used antiarrhythmic drugs have many side effects. The research on animals and humans using antioxidants (such as vitamins C and E, resveratrol and synthetic substances) yields many interesting but inconclusive results. Natural antioxidants, such as vitamins C and E, can reduce the recurrence of atrial fibrillation (AF) after successful electrical cardioversion and protect against AF after cardiac surgery, but do not affect the incidence of atrial arrhythmias in critically ill patients with trauma. Vitamins C and E may also effectively treat ventricular tachycardia, ventricular fibrillation and long QT-related arrhythmias. Another natural antioxidant—resveratrol—may effectively treat AF and ventricular arrhythmias caused by ischaemia–reperfusion injury. It reduces the mortality associated with life-threatening ventricular arrhythmias and can be used to prevent myocardial remodelling. Statins also show antioxidant activity. Their action is related to the reduction of oxidative stress and anti-inflammatory effect. Therefore, statins can reduce the post-operative risk of AF and may be useful in lowering its recurrence rate after successful cardioversion. Promising results also apply to polyphenols, nitric oxide synthase inhibitors and MitoTEMPO. Although few clinical trials have been conducted, the use of antioxidants in treating arrhythmias is an interesting prospect.

A Comprehensive Analysis of the Efficacy of Resveratrol in Atherosclerotic Cardiovascular Disease, Myocardial Infarction and Heart Failure

Atherosclerosis, myocardial infarction (MI) and heart failure (HF) are the main causes of mortality and morbidity around the globe. New therapies are needed to better manage ischemic heart disease and HF as existing strategies are not curative. Resveratrol is a stilbene polyphenolic compound with favorable biological effects that counter chronic diseases. Current evidence suggests that resveratrol is cardioprotective in animal models of atherosclerosis, ischemic heart disease, and HF. Though clinical studies for resveratrol have been promising, evidence remains inadequate to introduce it to the clinical setting. In this narrative review, we have comprehensively discussed the relevant compelling evidence regarding the efficacy of resveratrol as a new therapeutic agent for the management of atherosclerosis, MI and HF.

Up-regulation of chemokine receptor type 4 expression in the ischemic reperfused heart by alcoholic extract of Cichorium intybus rescue the heart from ischemia injury in male rat

OBJECTIVES

Cichorium intybus is used in traditional medicine for various diseases including heart disease. This study aimed at evaluating the chemokine receptor type 4 up-regulation and cardioprotective effects of hydroalcoholic extract of C. intybus in a rat model of ischemic reperfusion.

METHODS

Animals in four groups of eight rats each received vehicle or one of three doses of C. intybus (50, 100 or 200 mg/kg/d) for 14 days. Then they were subjected to 30 min of ischemia followed by 7 days of reperfusion. At the end of the experiment, blood specimens were prepared for serum assays. The level of myocardium chemokine receptor type 4 was also measured using RT-PCR.

KEY FINDINGS

Cichorium intybus (CI-50) improved infarct size, episodes of the ventricular ectopic beat, ventricular tachycardia, and duration of ventricular tachycardia, QTc shortening. It also stabilized the ST segment changes and increased heart rate during ischemia. The blood pressure decreased in CI-50 group in comparison to the control and CI-200 group. C. intybus increased serum superoxide dismutase and reduced lactate dehydrogenase activity, Cardiac Troponin I and malondialdehyde levels. C. intybus led to an increase in the expression of chemokine receptor type 4.

CONCLUSIONS

These findings suggest that C. intybus administration before ischemia is able to induce cardioprotective effect against ischemic reperfusion injury, probably through chemokine receptor type 4 over-expression and antioxidant activity.

Cardioprotection stimulated by resveratrol and grape products prevents lethal cardiac arrhythmias in an animal model of ischemia and reperfusion

PURPOSE

To evaluate the preventive cardioprotective effects of resveratrol and grape products, such as grape juice and red wine, in animal model of cardiac ischemia and reperfusion.

METHODS

Male Wistar rats orally pretreated for 21-days with resveratrol and grape products were anesthetized and placed on mechanical ventilation to surgically induce cardiac ischemia and reperfusion by obstruction (ischemia) followed by liberation (reperfusion) of blood circulation in left descending coronary artery. These rats were submitted to the electrocardiogram (ECG) analysis to evaluate the effects of pretreatment with resveratrol and grape products on the incidence of ventricular arrhythmias (VA), atrioventricular block (AVB) and lethality (LET) resulting from cardiac ischemia and reperfusion.

RESULTS

It was observed that the incidence of AVB was significantly lower in rats pretreated with resveratrol (25%), grape juice (37.5%) or red wine (12.5%) than in rats treated with saline solution (80%) or ethanol (80%). Similarly, incidence of LET was also significantly lower in rats pretreated with resveratrol (25%), grape juice (25%) or red wine (0%) than in rats treated with saline solution (62.5%) or ethanol (75%).

CONCLUSIONS

These results indicate that the cardioprotective response stimulated by resveratrol and grape products prevents the lethal cardiac arrhythmias in animal model of ischemia and reperfusion, supporting the idea that this treatment can be beneficial for prevention of severe cardiac arrhythmias in patients with ischemic heart disease.

Hypotensive effect of Cichorium intybus extract in rats

Introduction: Oxidative stress is involved in many diseases, including hypertension, kidney failure, and heart disease. This study aimed to evaluate the effect of hydroalcoholic Cichorium intybus extract on blood pressure in rats. Antioxidant activity, phenolic and flavonoid contents of the plant extract were also evaluated. Methods: In this study, 32 male Wistar rats weighing 250-300 g were divided into four groups of eight each. Animals in the control group were administered with normal saline and in the C. intybus groups with extract at 25, 50, and 100 mg/kg for two weeks. Then, the homodynamic parameters were examined by the Power lab. The phenolic and flavonoid contents were also evaluated by a spectrophotometer and the rate of free radical scavenging activity was measured by the diphenyl-1-picyryl-hydrazyl (DPPH) free radical method. Results: The free radical scavenging activity of C. intybus extract was obtained 47.85% of DPPH, and flavonoid and phenolic contents were 8.21 and 27.19 mg/g of dry extract, respectively. Meanwhile, median (MAP), systolic (SAP) and diastolic arterial pressure (DAP) significantly decreased in the 50 mg/kg extract-treated group compared to the control and 200 mg/kg extract-treated groups. Conclusion: Ethanol extract of C. intybus plays a protective role against hypertension, which, in part, might be due to antioxidant compounds of the plant against free radicals.

Chronic resveratrol consumption prevents hypertension development altering electrophysiological currents and Ca2+ signaling in chromaffin cells from SHR rats

Resveratrol (RESV) is one of the most abundant polyphenol-stilbene compounds found in red wine with well-established cardioprotective and antihypertensive effects. Hyperactivity of the sympathoadrenal axis seems to be one of the major contributing factors in the pathogenesis of human essential hypertension. Alterations in outward voltage-dependent potassium currents (I_K) and inward voltage-dependent sodium (I_Na), calcium (I_Ca) and nicotinic (I_ACh) currents, CCs excitability, Ca²⁺ homeostasis, and catecholamine exocytosis were previously related to the hypertensive state. This raised the issue of whether in vivo long-term RESV treatment can directly act as a modulator of Ca²⁺ influx or a regulator of ion channel permeability in CCs. We monitored outward and inward currents, and cytosolic Ca²⁺ concentrations ([Ca²⁺]_c) using different pharmacological approaches in CCs from normotensive (WKY) and hypertensive (SHR) animals chronically exposed to trans-RESV (50 mg/L/v.o, 28 days). The long-term RESV treatment prevented the increase of the systolic blood pressure (SBP) in SHR, without reversion of cardiac hypertrophy. We also found an increase of the outward I_K, reduction in inward I_Na,I_Ca, and I_ACh, and the mitigation of [Ca²⁺]_c overload in CCs from SHR at the end of RESV treatment. Our data revealed that electrophysiological alterations of the CCs and in its Ca²⁺ homeostasis are potential new targets related to the antihypertensive effects of long-term RESV treatment.

Resveratrol-induced apoptosis is associated with regulating the miR-492/CD147 pathway in malignant melanoma cells

Resveratrol (RES) as a natural phytoalexin has anti-tumor effects on various cancers through its pro-apoptotic activities. Our aim was to determine that RES induces apoptosis in melanoma cells by regulating miR-492 resulting in decreased CD147 expression. We treated A375 and SK-MEL-28 melanoma cells via RES at different concentrations and time-points. The results have shown that the inhibition rate of A375 and SK-MEL-28 was significantly increased after RES treatment. Subsequently, we investigated cell apoptosis by flow cytometry, as well as detected apoptotic-associated proteins including PARP, Caspase-3, Bcl-2, and Bax by western blotting. Meanwhile, the expression of miR-492 and CD147 was analyzed. We found that RES remarkably induces apoptosis in melanoma cells, along with an upregulation of miR-492 and the inhibition of CD147 expression. Furthermore, the detection of luciferase reporter activity confirmed that miR-492 could target CD147 mRNA, and transfected with mimic miR-492 in cells reduced CD147 expression. We also performed the rescued experiment by using a miR-492 inhibitor in melanoma cells. The results showed that the ability of induced apoptosis by RES in melanoma cells was to be attenuated via inhibiting miR-492 expression resulting in CD147 augment. Finally, we determined that the effect of RES-induced apoptosis in melanoma cells is associated with, at least in part, its ability to regulate the miR-492/CD147 pathway.

Cardioprotective effects of resveratrol following myocardial ischemia and reperfusion

Resveratrol (RSV), a plant origin polyphenol, has shown beneficial cardiovascular effects. In this study, isolated hearts from male Wistar rats were studied using the Langendorff technique. Following 30 min stabilization, the hearts underwent 30 min global ischemia and 120 min reperfusion. The perfusion solution in the test group contained RSV (10 μM). Hemodynamics of the hearts, the markers of myocardial damage including creatine kinase-MB (CK-MB), lactate dehydrogenase (LDH), and troponin I were studied during the study. Furthermore, the infarct size and the markers of oxidative stress including catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GPX) were assayed in the homogenates of the hearts. The release of nitrite from the hearts and the occurrence of ventricular arrhythmias were also monitored throughout the experiment. Resveratrol caused a significant improvement in the restoration of the mechanical performance of the hearts following myocardial ischemia and reperfusion (MIR). Besides, the infarct size, CK-MB, LDH, and troponin I declined in the test group. Besides, the cardiac release of nitrite increased, and the redox status of the heart was improved as indicated by the levels of CAT, SOD, GPX, and MDA. Finally, the treatment caused significant decreases in the occurrences of single and salvo arrhythmias, ventricular tachycardia, and ventricular fibrillation. The current study suggests strong cardioprotective and antiarrhythmic effects for RSV following MIR.

A review on plants and herbal components with antiarrhythmic activities and their interaction with current cardiac drugs

This paper aimed to compile information on plants or their compounds which have experimentally shown antiarrhythmic effect and to scrutinize the efficacy and potency of them and their potential interaction with conventional cardiac drugs. Literature searches were accomplished by using numerous electronic databases, and the available knowledge on different parts of herbs and their ingredients with antiarrhythmic effects up to 2019 were identified and collected. The results indicate that 36 herbs or their derivatives can be effective in the treatment of arrhythmias, especially in animal and cellular models. They affect various ionic channels in different action potential phases. The alterations in ionic currents lead to changing in the amplitude and duration of the action potential, effective refractory period, maximum velocity, resting membrane potential, channel trafficking, or intracellular calcium concentration. The agents that prolong action potential duration and effective refractory period such as dauricine and sophocarpine seem to be more beneficial if more comprehensive studies confirm their efficacy and safety. It is noteworthy that the consumption of some herbal agents for cardiovascular (e.g. Hawthorn and Ginseng) or other (e.g. Ginseng and Licorice) therapeutic purposes may boost the pro-arrhythmogenic effect of current cardiovascular drugs such as cardiac glycosides. This study accentuates known plants or their derivatives with anti-arrhythmic effects, potential interaction with other cardiac drugs, and the possible mechanisms involved. It can assist clinicians and scientists in research and therapeutic approaches to the management of cardiac arrhythmias.

Linking cellular energy state to atrial fibrillation pathogenesis: Potential role of adenosine monophosphate-activated protein kinase

Adenosine monophosphate-activated protein kinase (AMPK) is the cellular stress-sensing molecule. Apart from maintaining cellular energy balance, AMPK controls expression and regulation of ion channels and ion transporters, including cytosolic Ca²⁺ handling proteins. Emerging evidence suggests that metabolic impairment plays a crucial role in the pathogenesis of atrial fibrillation. AMPK activation is thought to be protective by preventing metabolic stress, favorably modulating membrane electrophysiology including cytosolic Ca²⁺ dynamics; preventing cellular growth; and hypertrophic remodeling. This review considers current concepts and evidence from clinical and experimental studies regarding the role of AMPK in atrial fibrillation.

Cardioprotective Effect of Ethanolic Leaf Extract of Melissa Officinalis L Against Regional Ischemia-Induced Arrhythmia and Heart Injury after Five Days of Reperfusion in Rats

Melissa officinalis has antioxidant and anti-inflammatory activities and is used in various diseases. Aim of the study: We investigated the role of M. officinalis extract (MOE) against ischemia-induced arrhythmia and heart injury after five days of reperfusion in an in-vivo rat model of regional heart ischemia. The leaf extract of M. officinalis was standardized through HPLC analysis. Adult male Sprague-Dawley rats (n = 32) were subjected to 30 min of ischemia by occlusion of the left anterior descending coronary artery followed by 5 days of reperfusion. The rats (n = 8 in each group) were randomized to receive vehicle or M. officinalis as follows: group I served as saline control with ischemia, groups II, III and IV received different doses of MOE- (25, 50 and 100 mg/kg, respectively), by oral gavage daily for 14 days prior to ischemia. Administration of M. officinalis significantly improved ischemia/reperfusion (I/R)-induced myocardial dysfunction by reduction of infarct size, also, during the ischemic period, ventricular tachycardia, and ventricular ectopic beats episodes decreased as compared with that of the control group. Stabilized ST segment changes and QTc shortening increased the R and T wave amplitudes and the heart rate during ischemia. The extract also caused significant elevations in serum superoxide dismutase (SOD) activity as well as a significant decrease in serum cardiac troponin I (CTnI), lactate dehydrogenase (LDH), and malondialdehyde (MDA) levels, 5 days after reperfusion. MOE-100mg/kg was the effective dose. Cinamic acid (21.81 ± 1.26 mg/gr) was the main phenolic compound of plant sample. The ethanol extract of M. officinalis was observed to exhibit cardioprotective effects against I/R injury, probably due to antioxidant properties. The results indicate that MOE has antioxidant and cardio-protective effects against ischemia-induced arrhythmias and ischemia-reperfusion induced injury as was reflected by reduction of infarct size and cardiac injury biomarkers. These data support the potential uses of M. officinalis in the treatment of heart ischemia- reperfusion disorders and even developing new anti- arrhythmias drugs after further investigations.

Mechanism of As2O3-Induced Action Potential Prolongation and Using hiPS-CMs to Evaluate the Rescue Efficacy of Drugs With Different Rescue Mechanism

Arsenic trioxide (As2O3) has been verified as a breakthrough in the management of acute promyelocytic leukemia in recent decades. However, cardiotoxicity, especially long QT syndrome (LQTS) has become the most important issue during As2O3 treatment. The characterized mechanisms behind this adverse effect are inhibition of cardiac hERG channel trafficking and increase of cardiac calcium currents. In our study, we found a new pathway underlying As2O3-induced cardiotoxicity that As2O3 accelerates lysosomal degradation of hERG on plasma membrane after using brefeldin A (BFA) to block protein trafficking. Then we explored pharmacological rescue strategies on As2O3-induced LQTS, and found that 4 therapeutic agents exert rescue efficacy via 3 different pathways: fexofenadine and astemizole facilitate hERG trafficking via promotion of channel-chaperone formation after As2O3 incubation; ranolazine slows hERG degradation in the presence of As2O3; and resveratrol shows significant attenuation on calcium current increase triggered by As2O3. Moreover, we used human-induced pluripotent stem cell derived cardiomyocytes (hiPS-CMs) to evaluate the rescue effects of the above agents on As2O3-induced prolongation of action potential duration (APD) and demonstrated that fexofenadine and resveratrol significantly ameliorate the prolonged APD. These observations suggested that pharmacological chaperone like fexofenadine and resveratrol might have the potential to protect against the cardiotoxicity of As2O3.

The more effective treatment of atrial fibrillation applying the natural compounds; as NADPH oxidase and ion channel inhibitors

Atrial fibrillation (AF) is the most common cardiac arrhythmia that occurs because of several different risk factors, e.g., valvular heart disease, coronary artery disease, age ≥75 years, hypertension and diabetes mellitus. One key risk factor that results in AF, is oxidative stress. Evidence suggests that there is a correlation between oxidative processes and the genesis of AF. Oxidative stress occurs when the generation of reactive oxygen species (ROS) increase due to excessive activity of enzymes including NADPH oxidase (NOX) and xanthine oxidase; or its degradation decrease by dysfunctional antioxidant enzyme systems, such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx). Afterwards, elevated ROS may shift ion channel activity to increase AF susceptibility. The outbreak of AF continues to grow. Unfortunately, current treatment strategies may have limited efficacy or adverse effects. On the other hand, the inhibition of ROS formation and alteration of ion channel activity could be important therapeutic targets for prevention or treatments of AF. Additionally, many studies have been shown that several natural compounds have the ability to inhibit NADPH oxidases directly. This review focuses on natural compounds which specially inhibit NOX isoforms and have direct effects on ion channels, suggesting these compounds can be helpful in AF treatment.

Natural products modulating the hERG channel: heartaches and hope

This review covers natural products modulating the hERG potassium channel. Risk assessment strategies, structural features of blockers, and the duality target/antitarget are discussed.

Covering: 1996–December 2016

The human Ether-à-go-go Related Gene (hERG) channel is a voltage-gated potassium channel playing an essential role in the normal electrical activity in the heart. It is involved in the repolarization and termination of action potentials in excitable cardiac cells. Mutations in the hERG gene and hERG channel blockage by small molecules are associated with increased risk of fatal arrhythmias. Several drugs have been withdrawn from the market due to hERG channel-related cardiotoxicity. Moreover, as a result of its notorious ligand promiscuity, this ion channel has emerged as an important antitarget in early drug discovery and development. Surprisingly, the hERG channel blocking profile of natural compounds present in frequently consumed botanicals (i.e. dietary supplements, spices, and herbal medicinal products) is not routinely assessed. This comprehensive review will address these issues and provide a critical compilation of hERG channel data for isolated natural products and extracts over the past two decades (1996–2016). In addition, the review will provide (i) a solid basis for the molecular understanding of the physiological functions of the hERG channel, (ii) the translational potential of in vitro/in vivo results to cardiotoxicity in humans, (iii) approaches for the identification of hERG channel blockers from natural sources, (iv) future perspectives for cardiac safety guidelines and their applications within phytopharmaceuticals and dietary supplements, and (v) novel applications of hERG channel modulation (e.g. as a drug target).

Resveratrol enhances the inotropic effect but inhibits the proarrhythmic effect of sympathomimetic agents in rat myocardium

Background

Resveratrol is a cardioprotective agent with known antiarrhythmic effects that has recently been shown to inhibit phosphodiesterase (PDE) enzyme activity. Thus, it is possible that resveratrol increases the inotropic effect of sympathomimetic agents, as PDE inhibitors do but, unlike other PDE inhibitors, its effect may not be accompanied by proarrhythmia due to its antiarrhythmic action. This work is aimed to test this hypothesis.

Methods

This is an “in vitro” concentration-response relationship study. The effects of noradrenaline, tyramine and isoproterenol, alone or in combination with either resveratrol or with the typical PDE inhibitor 3-isobutylmethylxantine (IBMX), were studied in electrically driven strips of right ventricle or in the spontaneously beating free wall of the right ventricle of rat heart in order to investigate inotropic or proarrhythmic effects respectively. Also, the effects of resveratrol or IBMX on the sinoatrial node rate were examined in the isolated right atria of rat heart.

Results

Resveratrol (10 µM and 100 µM) produces a leftward shift in the concentration-response curves for the contractile effects of noradrenaline, tyramine or isoproterenol and reduces the –log EC₅₀ values of these three agents. IBMX produces similar effects. The spontaneous ventricular beating rate was increased by all three compounds, an effect that was further enhanced by the addition of IBMX. In contrast, resveratrol (100 µM) abolished the effects of these sympathomimetic agents on the ventricular rate. Resveratrol (1–100 µM) had no effect on the sinoatrial node rate, while IBMX produce a concentration dependent sinoatrial tachycardia.

Discussion

Taken together, the finding, indicate that resveratrol, like the PDE inhibitor IBMX enhances the contractile effects of sympathomimetic agents but, in contrast to IBMX, it does not enhance their proarrhythmic effect or produce sinoatrial tachycardia. This is most probably consequence of the antiarrhythmic effect of resveratrol which protect against the proarrhythmic effects resulting from PDE inhibition.

Resveratrol Reverses Functional Chagas Heart Disease in Mice

Chronic chagasic cardiomyopathy (CCC) develops years after acute infection by Trypanosoma cruzi and does not improve after trypanocidal therapy, despite reduction of parasite burden. During disease, the heart undergoes oxidative stress, a potential causative factor for arrhythmias and contractile dysfunction. Here we tested whether antioxidants/ cardioprotective drugs could improve cardiac function in established Chagas heart disease. We chose a model that resembles B1-B2 stage of human CCC, treated mice with resveratrol and performed electrocardiography and echocardiography studies. Resveratrol reduced the prolonged PR and QTc intervals, increased heart rates and reversed sinus arrhythmia, atrial and atrioventricular conduction disorders; restored a normal left ventricular ejection fraction, improved stroke volume and cardiac output. Resveratrol activated the AMPK-pathway and reduced both ROS production and heart parasite burden, without interfering with vascularization or myocarditis intensity. Resveratrol was even capable of improving heart function of infected mice when treatment was started late after infection, while trypanocidal drug benznidazole failed. We attempted to mimic resveratrol's actions using metformin (AMPK-activator) or tempol (SOD-mimetic). Metformin and tempol mimicked the beneficial effects of resveratrol on heart function and decreased lipid peroxidation, but did not alter parasite burden. These results indicate that AMPK activation and ROS neutralization are key strategies to induce tolerance to Chagas heart disease. Despite all tissue damage observed in established Chagas heart disease, we found that a physiological dysfunction can still be reversed by treatment with resveratrol, metformin and tempol, resulting in improved heart function and representing a starting point to develop innovative therapies in CCC.

Resveratrol protects the ovary against chromium-toxicity by enhancing endogenous antioxidant enzymes and inhibiting metabolic clearance of estradiol

Resveratrol (RVT), a polyphenolic component in grapes and red wine, has been known for its cytoprotective actions against several diseases. However, beneficial effects of RVT against early exposure to endocrine disrupting chemicals (EDCs) have not been understood. EDCs are linked to several ovarian diseases such as premature ovarian failure, polycystic ovary syndrome, early menopause and infertility in women. Hexavalent chromium (CrVI) is a heavy metal EDC, and widely used in >50 industries. Environmental contamination with CrVI in the US is rapidly increasing, predisposing the human to several illnesses including cancers and still birth. Our lab has been involved in determining the molecular mechanism of CrVI-induced female infertility and intervention strategies to mitigate CrVI effects. Lactating mother rats were exposed to CrVI (50ppm potassium dichromate) from postpartum days 1-21 through drinking water with or without RVT (10mg/kg body wt., through oral gavage daily). During this time, F1 females received respective treatments through mother's milk. On postnatal day (PND) 25, blood and the ovary, kidney and liver were collected from the F1 females for analyses. CrVI increased atresia of follicles by increasing cytochrome C and cleaved caspase-3; decreasing antiapoptotic proteins; decreasing estradiol (E2) biosynthesis and enhancing metabolic clearance of E2, increasing oxidative stress and decreasing endogenous antioxidants. RVT mitigated the effects of CrVI by upregulating cell survival proteins and AOXs; and restored E2 levels by inhibiting hydroxylation, glucuronidation and sulphation of E2. This is the first study to report the protective effects of RVT against any toxicant in the ovary.

Phytochemical Compounds and Protection from Cardiovascular Diseases: A State of the Art

Cardiovascular diseases represent a worldwide relevant socioeconomical problem. Cardiovascular disease prevention relies also on lifestyle changes, including dietary habits. The cardioprotective effects of several foods and dietary supplements in both animal models and in humans have been explored. It was found that beneficial effects are mainly dependent on antioxidant and anti-inflammatory properties, also involving modulation of mitochondrial function. Resveratrol is one of the most studied phytochemical compounds and it is provided with several benefits in cardiovascular diseases as well as in other pathological conditions (such as cancer). Other relevant compounds are Brassica oleracea, curcumin, and berberine, and they all exert beneficial effects in several diseases. In the attempt to provide a comprehensive reference tool for both researchers and clinicians, we summarized in the present paper the existing literature on both preclinical and clinical cardioprotective effects of each mentioned phytochemical. We structured the discussion of each compound by analyzing, first, its cellular molecular targets of action, subsequently focusing on results from applications in both ex vivo and in vivo models, finally discussing the relevance of the compound in the context of human diseases.

An overview of the efficacy of resveratrol in the management of ischemic heart disease

Ischemic heart disease is a leading cause of cardiac dysfunction and subsequent morbidity and mortality around the world. New therapies are required to complement or enhance the existing treatment regimen for the management of ischemic heart disease-related clinical complications. In this regard, compounds derived from natural sources have recently gained attention for their cardioprotective properties. In particular, the potential of food-derived compounds that exhibit medicinal properties (termed nutraceuticals) appears promising, an example being the plant polyphenol resveratrol. In the past two decades, many preclinical and a few pilot clinical studies have shown that resveratrol is beneficial in protecting against cardiovascular disease. In this short review, we will discuss current evidence on the efficacy of resveratrol in preventing or reversing deleterious effects on the heart in the setting of ischemic heart disease.

Monitoring trans-Resveratrol in Grape Berry Skins During Ripening and in Corresponding Wines by HPLC

Trans-resveratrol (3,5,4'-trihydroxy-trans-stilbene) is naturally present in the skin of grapes and therefore is expected to occur in grape products. Recently, there has been a renewal of interest in wine as medical treatment for various disorders. In this study, berry skins of five red grape varieties were analysed at weekly intervals for trans-resveratrol production, during 2012 and 2013 harvest. The obtained wines were also evaluated. Quantification of trans-resveratrol in grape skin extracts and wines was carried out by high-performance liquid chromatography. Favourable viticultural climate during harvest in 2012 resulted in a higher content of trans-resveratrol. The highest trans-resveratrol content was in Pinot Noir and Feteasca Neagra grape varieties, both in berry skins and wines, while the lowest amounts were identified in Cabernet Sauvignon variety. We can conclude that there was a significant correlation between the content of trans-resveratrol in grape skins and that in the respective wine.

The alkaloid matrine of the root of Sophora flavescens prevents arrhythmogenic effect of ouabain

Matrine, a alkaloid of the root of Sophora flavescens, has multiple protective effects on the cardiovascular system including cardiac arrhythmias. However, the molecular and ionic mechanisms of matrine have not been well investigated. Our study aimed at to shed a light on the issue to investigate the antiarrhythmic effects of matrine by using ouabain to construct an arrhythmic model of cardiomyocytes. In this experiment, matrine significantly and dose-dependently increased the doses of ouabain required to induce cardiac arrhythmias and decreased the duration of arrhythmias in guinea pigs. In cardiomyocytes of guinea pigs, ouabain 10 μM prolonged action potential duration by 80% (p<0.05) and increased L-type Ca(2+) currents and Ca(2+) transients induced by KCl (p<0.05). Matrine 100 μM shortened the prolongation of APD and prevented the increase of L-type Ca(2+) currents and Ca(2+) transients induced by ouabain. Taken together, these findings provide the first evidence that matrine possessed arrhythmogenic effect of ouabain by inhibiting of L-type Ca(2+) currents and Ca(2+) overload in guinea pigs.

Downregulation of miR-151-5p contributes to increased susceptibility to arrhythmogenesis during myocardial infarction with estrogen deprivation

Estrogen deficiency is associated with increased incidence of cardiovascular diseases. But merely estrogen supplementary treatment can induce many severe complications such as breast cancer. The present study was designed to elucidate molecular mechanisms underlying increased susceptibility of arrhythmogenesis during myocardial infarction with estrogen deprivation, which provides us a new target to cure cardiac disease accompanied with estrogen deprivation. We successfully established a rat model of myocardial ischemia (MI) accompanied with estrogen deprivation by coronary artery ligation and ovariectomy (OVX). Vulnerability and mortality of ventricular arrhythmias increased in estrogen deficiency rats compared to non estrogen deficiency rats when suffered MI, which was associated with down-regulation of microRNA-151-5p (miR-151-5p). Luciferase Reporter Assay demonstrated that miR-151-5p can bind to the 3′-UTR of FXYD1 (coding gene of phospholemman, PLM) and inhibit its expression. We found that the expression of PLM was increased in (OVX+MI) group compared with MI group. More changes such as down-regulation of Kir2.1/I_K1, calcium overload had emerged in (OVX+MI) group compared to MI group merely. Transfection of miR-151-5p into primary cultured myocytes decreased PLM levels and [Ca²⁺]_i, however, increased Kir2.1 levels. These effects were abolished by the antisense oligonucleotides against miR-151-5p. Co-immunoprecipitation and immunofluorescent experiments confirmed the co-localization between Kir2.1 and PLM in rat ventricular tissue. We conclude that the increased ventricular arrhythmias vulnerability in response to acute myocardial ischemia in rat is critically dependent upon down-regulation of miR-151-5p. These findings support the proposal that miR-151-5p could be a potential therapeutic target for the prevention of ischemic arrhythmias in the subjects with estrogen deficiency.

Resveratrol protects rabbit ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca2+ overload

AIM

To investigate whether resveratrol suppressed oxidative stress-induced arrhythmogenic activity and Ca(2+) overload in ventricular myocytes and to explore the underlying mechanisms.

METHODS

Hydrogen peroxide (H2O2, 200 μmol/L)) was used to induce oxidative stress in rabbit ventricular myocytes. Cell shortening and calcium transients were simultaneously recorded to detect arrhythmogenic activity and to measure intracellular Ca(2+) ([Ca(2+)]i). Ca(2+)/calmodulin-dependent protein kinases II (CaMKII) activity was measured using a CaMKII kit or Western blotting analysis. Voltage-activated Na(+) and Ca(2+) currents were examined using whole-cell recording in myocytes.

RESULTS

H2O2 markedly prolonged Ca(2+) transient duration (CaTD), and induced early afterdepolarization (EAD)-like and delayed afterdepolarization (DAD)-like arrhythmogenic activity in myocytes paced at 0.16 Hz or 0.5 Hz. Application of resveratrol (30 or 50 μmol/L) dose-dependently suppressed H2O2-induced EAD-like arrhythmogenic activity and attenuated CaTD prolongation. Co-treatment with resveratrol (50 μmol/L) effectively prevented both EAD-like and DAD-like arrhythmogenic activity induced by H2O2. In addition, resveratrol markedly blunted H2O2-induced diastolic [Ca(2+)]i accumulation and prevented the myocytes from developing hypercontracture. In whole-cell recording studies, H2O2 significantly enhanced the late Na(+) current (I(Na,L)) and L-type Ca(2+) current (I(Ca,L)) in myocytes, which were dramatically suppressed or prevented by resveratrol. Furthermore, H2O2-induced ROS production and CaMKII activation were significantly prevented by resveratrol.

CONCLUSION

Resveratrol protects ventricular myocytes against oxidative stress-induced arrhythmogenic activity and Ca(2+) overload through inhibition of I(Na,L)/I(Ca,L), reduction of ROS generation, and prevention of CaMKII activation.

Overexpression of M₃ muscarinic receptor is a novel strategy for preventing sudden cardiac death in transgenic mice

The present study was designed to investigate the cardiac benefits of M₃ muscarinic receptor (M₃-mAChR) overexpression and whether these effects are related to the regulation of the inward rectifying K⁺ channel by microRNA-1 (miR-1) in a conditional overexpression mouse model. A cardiac-specific M₃-mAChR transgenic mouse model was successfully established for the first time in this study using microinjection, and the overexpression was confirmed by both reverse transcriptase-polymerase chain reaction and Western blot techniques. We demonstrated that M₃-mAChR overexpression dramatically reduced the incidence of arrhythmias and decreased the mortality in a mouse model of myocardial ischemia-reperfusion (I/R). By using whole-cell patch techniques, M₃-mAChR overexpression significantly shortened the action potential duration and restored the membrane repolarization by increasing the inward rectifying K⁺ current. By using Western blot techniques, M₃-mAChR overexpression also rescued the expression of the inward rectifying K⁺ channel subunit Kir2.1 after myocardial I/R injury. This result was accompanied by suppression of upregulation miR-1. We conclude that M₃-mAChR overexpression reduced the incidence of arrhythmias and mortality after myocardial I/R by protecting the myocardium from ischemia in mice. This effect may be mediated by increasing the inward rectifying K⁺ current by downregulation of arrhythmogenic miR-1 expression, which might partially be a novel strategy for antiarrhythmias, leading to sudden cardiac death.

Emerging antiarrhythmic agents: a personal view from the Far East

INTRODUCTION

Arrhythmia treatments today take three different approaches. One uses electronic devices, such as electronic pacemakers or defibrillators, and this is regarded as life-saving in cases of bradyarrhythmias and ventricular fibrillation. Another is the ablation technique which eliminates abnormal pacemakers and/or conductive pathways by applying thermal or cryo-injury to pathological portions of the heart. The most classical one is the antiarrhythmic drugs, but are they effective and safe?

AREAS COVERED

Recent development of the understanding of arrhythmias, cardiac ionic channels and antiarrhythmic drugs covered by papers mostly published after 2000 are discussed.

EXPERT OPINION

The market size of the antiarrhythmic drugs is small, but various multichannel acting drugs may become candidates as antiarrhythmic drugs. As the cardiac ionic channels have become recognized as proteins, the molecular target for antiarrhythmic drugs has become apparent, but at the same time accurate data on clinical effectiveness and safety are required for drug approval; thus, few atrium selective drugs, such as IKur, IKACh and IKAde blocking drugs and amiodarone-like multichannel acting drugs are being developed.

Antiarrhythmic effects and ionic mechanisms of oxymatrine from Sophora flavescens

Accumulating evidence indicates that oxymatrine may exert protective effects on the cardiovascular system. This study was designed to evaluate the antiarrhythmic effects as well as the electrophysiological properties of oxymatrine. The antiarrhythmic activity of oxymatrine was observed in a rat model of arrhythmia induced by coronary ligation. Action potential duration (APD), L-type calcium current (I(Ca-L) ), transient outward potassium current (I(to) ) and inward rectifier potassium current (I(K1)) in rat ventricular myocytes were recorded by utilizing the whole cell patch-clamp technique. The results showed that administration of oxymatrine significantly delayed the onset of ventricular arrhythmia, decreased the duration of ventricular arrhythmia and reduced the arrhythmia score of arrhythmic rats. The beneficial effects of oxymatrine may be related to the shortening of APD through reduction of I(Ca-L) , enhancement of I(to) and inhibition of I(K1).

L-type calcium current (ICa,L) and inward rectifier potassium current (IK1) are involved in QT prolongation induced by arsenic trioxide in rat

The present study was designed to study the effects of As(2)O(3) on QT interval prolongation and to explore the potential ionic mechanisms in isolated rat ventricular cardiomyocytes. The rats of As(2)O(3) group were treated with 0.8 mg·kg(-1)·d(-1) As(2)O(3) intravenously for 7 days consecutively and the control group with saline. The ECG was recorded to calculate heart rate-corrected QT interval (QTc). Single cardiomyocytes were isolated by using collagenase II, and the action potential duration (APD) and ion currents were recorded by whole-cell patch clamp. [Ca(2+)](i) was examined by confocal laser scanning microscopy. Our data showed that both QTc and APD were prolonged significantly after As(2)O(3)treatment. Meanwhile, As(2)O(3) suppressed I(K1) and shifted the reversal potential to more positive direction. Moreover, the density of I(Ca,L) was augmented significantly, and the steady-state activation curve became more negative, whereas, the inactivation and reactivation of I(Ca,L) were not changed notably after As(2)O(3) administration. Furthermore, the maximal [Ca(2+)](i) was enhanced obviously by either KCl or caffeine stimulation in As(2)O(3)-treated cardiomyocytes. Our results show that the potential mechanism of As(2)O(3)-induced QT interval prolongation in rat might be relative to disturbing the fine balance of transmembrane currents (increasing I(Ca,L) and decreasing I(K1)) and causing APD prolongation.

Cellular and mitochondrial effects of alcohol consumption

Alcohol dependence is correlated with a wide spectrum of medical, psychological, behavioral, and social problems. Acute alcohol abuse causes damage to and functional impairment of several organs affecting protein, carbohydrate, and fat metabolism. Mitochondria participate with the conversion of acetaldehyde into acetate and the generation of increased amounts of NADH. Prenatal exposure to ethanol during fetal development induces a wide spectrum of adverse effects in offspring, such as neurologic abnormalities and pre- and post-natal growth retardation. Antioxidant effects have been described due to that alcoholic beverages contain different compounds, such as polyphenols as well as resveratrol. This review analyzes diverse topics on the alcohol consumption effects in several human organs and demonstrates the direct participation of mitochondria as potential target of compounds that can be used to prevent therapies for alcohol abusers.

Favorable effects of resveratrol on sympathetic neural remodeling in rats following myocardial infarction

Oxidative stress and inflammatory response induced by myocardial infarction play important roles in the development of sympathetic neural remodeling. The present study was designed to investigate whether resveratrol can improve sympathetic neural remodeling and hence cause less arrhythmias via its anti-oxidant and anti-inflammatory effects. Male Sprague Dawley rats were randomly assigned to either vehicle or resveratrol (1 mg/kg) treatment for 4 weeks post myocardial infarction. Another group of sham operated rats served as controls. Cardiac electrophysiology examination was performed to evaluate the severity of ventricular arrhythmias. Sympathetic neural remodeling characterized by heterogeneous nerve sprouting and sympathetic hyperinnervation was assessed by immunohistochemistry study. Western blotting and ELISA were used to evaluate inflammatory responses and oxidative stress was also quantified. Resveratrol treatment resulted in less episodes of inducible ventricular arrhythmias which was closely associated with attenuated sympathetic neural remodeling (P<0.001, respectively). Decreased nerve growth factor (NGF) expression was also observed in resveratrol treated rats in the peri-infarct area at 4 weeks after myocardial infarction (P<0.001). Interestingly, beneficial effects of resveratrol were also associated with less inflammatory responses and oxidative stress. Our data indicated that resveratrol can suppress sympathetic neural remodeling process after myocardial infarction via attenuated inflammatory responses and oxidative stress, which in turn leads to less inducibility of ventricular arrhythmias.

Resveratrol attenuates hyperglycemia-mediated oxidative stress, proinflammatory cytokines and protects hepatocytes ultrastructure in streptozotocin-nicotinamide-induced experimental diabetic rats

The present study was hypothesized to investigate the hepatoprotective nature of resveratrol in averting hyperglycemia-mediated oxidative stress by measuring extent of oxidant stress and levels of proinflammatory cytokines and antioxidant competence in the hepatic tissues of streptozotocin-nicotinamide-induced diabetic rats. After the experimental period of 30 days, the pathophysiological markers such as serum bilirubin and hepatic aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were studied in addition to hepatic TNF-alpha, IL-1 beta, IL-6, NF-kappaB p65 and nitric oxide (NO) levels in control and experimental groups of rats. The levels of vitamin C, vitamin E and reduced glutathione (GSH) and activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione-S-transferase (GST) and glutathione reductase (GR) were determined in the liver tissues. Extent of oxidative stress was also assessed by hepatic lipid peroxides, hydroperoxides and protein carbonyls. A portion of liver was processed for histological and ultrastructural studies. Oral administration of resveratrol (5mg/kg b.w.) to diabetic rats showed a significant decline in hepatic proinflammatory cytokines and notable attenuation in hepatic lipid peroxides, hydroperoxides and protein carbonyls. The diminished activities of hepatic enzymic antioxidants as well as the decreased levels of hepatic non-enzymic antioxidants of diabetic rats were reverted to near normalcy by resveratrol administration. Moreover, the histological and ultrastructural observations evidenced that resveratrol effectively rescues the hepatocytes from hyperglycemia-mediated oxidative damage without affecting its cellular function and structural integrity. The findings of the present investigation demonstrated the hepatocyte protective nature of resveratrol by attenuating markers of hyperglycemia-mediated oxidative stress and antioxidant competence in hepatic tissues of diabetic rats.

Repolarization of the cardiac action potential. Does an increase in repolarization capacity constitute a new anti-arrhythmic principle?

The cardiac action potential can be divided into five distinct phases designated phases 0-4. The exact shape of the action potential comes about primarily as an orchestrated function of ion channels. The present review will give an overview of ion channels involved in generating the cardiac action potential with special emphasis on potassium channels involved in phase 3 repolarization. In humans, these channels are primarily K(v)11.1 (hERG1), K(v)7.1 (KCNQ1) and K(ir)2.1 (KCNJ2) being the responsible alpha-subunits for conducting I(Kr), I(Ks) and I(K1). An account will be given about molecular components, biophysical properties, regulation, interaction with other proteins and involvement in diseases. Both loss and gain of function of these currents are associated with different arrhythmogenic diseases. The second part of this review will therefore elucidate arrhythmias and subsequently focus on newly developed chemical entities having the ability to increase the activity of I(Kr), I(Ks) and I(K1). An evaluation will be given addressing the possibility that this novel class of compounds have the ability to constitute a new anti-arrhythmic principle. Experimental evidence from in vitro, ex vivo and in vivo settings will be included. Furthermore, conceptual differences between the short QT syndrome and I(Kr) activation will be accounted for.

Grape skin improves antioxidant capacity in rats fed a high fat diet

This study was conducted to investigate the effect of dietary grape skin on lipid peroxidation and antioxidant defense system in rats fed high fat diet. The Sprague-Dawley rats were fed either control (5% fat) diet or high fat (25% fat) diet which was based on AIN-93 diet for 2 weeks, and then they were grouped as control group (C), control + 5% grape skin group (CS), high-fat group (HF), high fat + 5% grape skin group (HFS) with 10 rats each and fed corresponding diets for 4 weeks. The hepatic thiobarbituric acid reacting substances (TBARS) were increased in high fat group as compared with control group, but reduced by grape skin. The serum total antioxidant status, and activities of hepatic catalase and superoxide dismutase, xanthine oxidase and glucose-6-phosphatase were increased by supplementation of grape skin. Glutathione peroxidase activity was significantly higher in CS group than in C group. Grape skin feeding tended to increase the concentration of total glutathione, especially in control group. The ratio of reduced glutathione to oxidized glutathione was lower in high fat groups than in control groups. The ratio was increased by dietary supplementation of grape skin in control group. These results suggest that dietary supplementation of grape skin would be effective on protection of oxidative damage by lipid peroxidation through improvement of antioxidant defense system in rats fed high fat diet as well as rats with low fat diet.

Tanshinone IIA protects against sudden cardiac death induced by lethal arrhythmias via repression of microRNA-1

BACKGROUND AND PURPOSE

Tanshinone IIA is an active component of a traditional Chinese medicine based on Salvia miltiorrhiza, which reduces sudden cardiac death by suppressing ischaemic arrhythmias. However, the mechanisms underlying the anti-arrhythmic effects remain unclear.

EXPERIMENTAL APPROACH

A model of myocardial infarction (MI) in rats by ligating the left anterior descending coronary artery was used. Tanshinone IIA or quinidine was given daily, before (7 days) and after (3 months) MI; cardiac electrical activity was monitored by ECG recording. Whole-cell patch-clamp techniques were used to measure the inward rectifying K(+) current (I(K1)) in rat isolated ventricular myocytes. Kir2.1 and serum response factor (SRF) levels were analysed by Western blot and microRNA-1 (miR-1) level was determined by real-time RT-PCR.

KEY RESULTS

Tanshinone IIA decreased the incidence of arrhythmias induced by acute cardiac ischaemia and mortality in rats 3 months after MI. Tanshinone IIA restored the diminished I(K1) current density and Kir2.1 protein after MI in rat ventricular myocytes, while quinidine further inhibited I(K1)/Kir2.1. MiR-1 was up-regulated in MI, possibly due to the concomitant increase in SRF, a transcriptional activator of the miR-1 gene, accounting for decreased Kir2.1. Treatment with tanshinone IIA prevented increased SRF and hence increased miR-1 post-MI, whereas quinidine did not.

CONCLUSIONS AND IMPLICATIONS

Down-regulation of miR-1 and consequent recovery of Kir2.1 may account partially for the efficacy of tanshinone IIA in suppressing ischaemic arrhythmias and cardiac mortality. These finding support the proposal that miR-1 could be a potential therapeutic target for the prevention of ischaemic arrhythmias.

MicroRNA-1 downregulation by propranolol in a rat model of myocardial infarction: a new mechanism for ischaemic cardioprotection

AIMS

The present study was designed to investigate whether the beneficial effects of beta-blocker propranolol are related to regulation of microRNA miR-1.

METHODS AND RESULTS

We demonstrated that propranolol reduced the incidence of arrhythmias in a rat model of myocardial infarction by coronary artery occlusion. Overexpression of miR-1 was observed in ischaemic myocardium and strikingly, administration of propranolol reversed the up-regulation of miR-1 nearly back to the control level. In agreement with its miR-1-reducing effect, propranolol relieved myocardial injuries during ischaemia, restored the membrane depolarization and cardiac conduction slowing, by rescuing the expression of inward rectifying K(+) channel subunit Kir2.1 and gap junction channel connexin 43. Our results further revealed that the beta-adrenoceptor-cAMP-Protein Kinase A (PKA) signalling pathway contributed to the expression of miR-1, and serum response factor (SRF), which is known as one of the transcriptional enhancers of miR-1, was up-regulated in ischaemic myocardium. Moreover, propranolol inhibited the beta-adrenoceptor-cAMP-PKA signalling pathway and suppressed SRF expression.

CONCLUSION

We conclude that the beta-adrenergic pathway can stimulate expression of arrhythmogenic miR-1, contributing to ischaemic arrhythmogenesis, and beta-blockers produce their beneficial effects partially by down-regulating miR-1, which might be a novel strategy for ischaemic cardioprotection.

M3 muscarinic acetylcholine receptor is associated with beta-catenin in ventricular myocytes during myocardial infarction in the rat

1. The present study was designed to investigate whether the M(3) muscarinic acetylcholine receptors (mAChR) is associated with beta-catenin in the ventricular myocardium during ischaemic myocardial injury and to determine the possible mechanism/s involved. 2. Rat hearts were subjected to coronary artery ligation for 1 and 6 h or 1 month to establish a myocardial ischaemia (MI) model. In the acute MI model, 16 rats were randomized into four groups: (i) control; (ii) ischaemia (rats were subjected to 20 min coronary occlusion); (iii) choline (10 mg/kg, i.v., choline chloride, an M(3) receptor agonist, was administered 15 min before occlusion); and (iv) 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; 0.12 mg/kg 4-DAMP, an M(3) receptor antagonist, was administered 20 min before occlusion, followed 5 min later by 10 mg/kg, i.v., choline chloride). Immunochemistry, western blot analysis and immunoprecipitation were used to determine the expression and localization of beta-catenin and the M(3) mAChR. 3. Myocardial ischaemia caused a time-dependent increase in the expression of beta-catenin. Moreover, a physical association was found between beta-catenin and the M(3) mAChR in intercalated discs. This association was enhanced by prolonged ischaemia. Administration of choline before ischaemia not only increased beta-catenin expression, but also strengthened the association between beta-catenin and the M(3) mAChR. However, blockade of M(3) mAChR by 4-DAMP completely inhibited the effect of choline on the expression of beta-catenin. In addition, MI increased phosphorylation of the M(3) mAChR. 4. The results indicate that increased beta-catenin activity is associated with M(3) mAChR during MI. This association is likely to play a role in heart signal transduction during ischaemia between neighbouring ventricular myocardiocum.

Cardioprotective actions of grape polyphenols

The aim of this review is to discuss the accumulating evidence that suggests that grape extracts and purified grape polyphenols possess a diverse array of biological actions and may be beneficial in the prevention of some inflammatory-mediated diseases including cardiovascular disease. The active components from grape extracts, which include the grape seed, grape skin, and grape juice, that have been identified thus far include polyphenols such as resveratrol, phenolic acids, anthocyanins, and flavonoids. All possess potent antioxidant properties and have been shown to decrease low-density lipoprotein-cholesterol oxidation and platelet aggregation. These compounds also possess a range of additional cardioprotective and vasoprotective properties including antiatherosclerotic, antiarrhythmic, and vasorelaxation actions. Although not exclusive, antioxidant properties of grape polyphenols are likely to be central to their mechanism(s) of action, which also include cellular signaling mechanisms and interactions at the genomic level. This review discusses some of the evidence favoring the consumption of grape extracts rich in polyphenols in the prevention of cardiovascular disease. Consumption of grape and grape extracts and/or grape products such as red wine may be beneficial in preventing the development of chronic degenerative diseases such as cardiovascular disease.