The red wine antioxidant resveratrol protects isolated rat hearts from ischemia reperfusion injury.

The consumption of red wine has been reported to impart a greater benefit in the prevention of coronary heart disease than the consumption of other alcoholic beverages. This beneficial effect is increasingly being attributed to certain antioxidants comprising the polyphenol fraction of red wine such as transresveratrol. In the present study, we investigated the potential cardioprotective effects of resveratrol in the face of ischemia reperfusion (I/R) injury. Isolated perfused working rat hearts after stabilization were perfused with Krebs-Henseleit Bicarbonate buffer (KHB) either in the presence or absence of transresveratrol (RVT) at a concentration of 10 microM for 15 min prior to subjecting them to 30 min of global ischemia followed by 2 h of reperfusion. Left ventricular functions were monitored at various timepoints throughout the reperfusion period to assess the extent of postischemic recovery in comparison with baseline values. Coronary perfusate samples were also collected to determine malonaldehyde (MDA) levels. The results demonstrated that RVT exhibited significant myocardial protection. This was evidenced by improved recovery of post-ischemic ventricular function including developed pressure and aortic flow as compared to the control group (KHB). Values for developed pressure in the RVT-treated group were significantly higher than those in the control group throughout the reperfusion period (71.09+/-4.88 mm Hg vs. 58.47+/-3.88 mm Hg, 68.87+/-5.07 mm Hg vs. 49.74+/-2.65 mm Hg and 51.67+/-3.95 mm Hg vs. 30.50+/-4.80 mm Hg at reperfusion timepoints R-15, R-60, and R-120, respectively). From R-30 onwards, aortic flow was markedly higher in the RVT treated group as compared with the control group, the differences being most significant at R-90 (32.45+/-2.19 ml/min vs. 19.83+/-1.62 ml/min) and R-120 (27.15+/-2.27 ml/min vs. 14.10+/-1.69 ml/min). In contrast to the KHB treated group, the RVT-treated group displayed significant reduction in MDA formation especially in the immediate early reperfusion period (63.71+/-8.19 pM/ml vs. 130.86+/-4.76 pM/ml, 63.84+/-15.62 pM/ml vs. 156.99+/-18.93 pM/ml, 71.29+/-2.80 pM/ml vs. 129.5+/-10.30 pM/ml and 56.25+/-5.79 pM/ml vs. 127.99+/-3.50 pM/ml at timepoints R-1, R-3, R-5, and R-7, respectively) indicating a reduction in I/R injury related oxidative stress. Infarct size was markedly reduced in the RVT group when compared with the control group (10.57+/-0.35% vs. 36.27+/-5.28%). In vitro studies revealed RVT to be a potent scavenger of peroxyl radicals suggestive of a probable mechanism involved in the protective ability of RVT. The results of this study indicate that resveratrol possesses cardioprotective effects which may be attributed to its peroxyl radical scavenging activity.     

Urotensin II protects ischemic reperfusion injury of hearts through ROS and antioxidant pathway

Urotensin II (UII) is a vasoactive peptide which is bound to a G protein-coupled receptor. UII and its receptor are upregulated in ischemic and chronic hypoxic myocardium, but the effect of UII on ischemic reperfusion (I/R) injury is still controversial. The aim of the present study was to investigate whether UII protects heart function against I/R injury. Global ischemia was performed using isolated perfused Langendorff hearts of Sprague-Dawley rats. Hearts were perfused with Krebs-Henseleit buffer for 20min pre-ischemic period followed by a 20min global ischemia and 50min reperfusion. Pretreatment with UII (10nM) for 10min increased recovery percentage of the post-ischemic left ventricular developed pressure and ±dp/dt, and decreased post-ischemic left ventricular end-diastolic pressure as compared with I/R group. UII decreased infarct size and an increased lactate dehydrogenase level during reperfusion. Cardioprotective effects of UII were attenuated by pretreatment with UII receptor antagonist. The hydrogen peroxide activity was increased in UII-treated heart before ischemia. The Mn-SOD, catalase, heme oxygenase-1 and Bcl-2 levels were increased, and the Bax and caspase-9 levels were decreased in UII-treated hearts. These results suggest that UII has cardioprotective effects against I/R injury partly through activating antioxidant enzymes and reactive oxygen species.     

胰岛素保护缺血/再灌注心脏:PI3-K/Akt和JNKs信号通路间的交互作用

我们前期研究表明胰岛素可激活细胞内信号转导机制如磷脂酰肌醇3．激酶．蛋白激酶B．内皮型一氧化氮合酶．一氧化氮（P13-K-Akt-eNOS-NO）信号通路,减轻心肌缺血／再灌注（ischemia／reperfusion,I／R）损伤,改善缺血后心肌功能恢复。然而c-Jun氨基末端激酶（c-JunNH2-terminal kinase,JNK）信号通路在胰岛素保护I／R心肌中的作用尚不清楚,本研究旨在探讨JNK信号通路在胰岛素保护I／R心肌中的作用及其与P13．K／Akt信号通路间的相互关系。离体Sprague-Dawley大鼠心脏缺血30min后施行2h或4h的再灌注,缺血前用LY294002（15mmol／L）和SP600125（10mmol／L）灌注15min,分别阻断P13．K／Akt和磷酸化JNK（phosphorylated．JNK,p-JNK）活化,观测心脏功能、心肌梗死、细胞凋亡和蛋白磷酸化水平。与对照组相比,胰岛素再灌注2h后,心率、左心室发展压和左心室收缩／舒张最大速率均明显增加,梗死面积减少约16．1％[（28．9±2．0）％vs（45．0±4．0）％,n=6,P〈O．01],细胞凋亡指数从（27．6±113）％减少到（16．0±0．7）％（n=6,P〈O．01）,Akt的活性增加1．7倍（n=6,P〈0．05）,同时JNK活性增加1．5倍铆=6,P〈O．05）。用LY294002处理后,胰岛素对I／R心肌的保护作用消失;而用SP600125处理可增强胰岛素的保护作用,且可部分逆转LY294002的抑制作用。进一步观察发现SP600125减弱了Akt的磷酸化m=6,P〈0．05）。上述结果表明,在I／R心肌中,胰岛素可同时激活P13．K／Akt及JNK信号通路,且通过后者进一步增加Akt活化,从而减轻I／R损伤,改善心肌功能。这种P13．K／Akt与JNK信号通路交互机制对胰岛素保护I／R心肌有重要意义。     

Blocking the MyD88-dependent pathway protects the myocardium from ischemia/reperfusion injury in rat hearts

We examined whether blocking the MyD88 mediated pathway could protect myocardium from ischemia/reperfusion (I/R) injury by transfecting Ad5-dnMyD88 into the myocardium of rats (n=8) 3 days before the hearts were subjected to ischemia (45min) and reperfusion (4h). Ad5-GFP served as control (n=8). One group of rats was (n=8) subjected to I/R without transfection. Transfection of Ad5-dnMyD88 significantly reduced infarct size by 53.6% compared with the I/R group (15.1+/-3.02 vs 32.5+/-2.59) while transfection of Ad5-GFP did not affect I/R induced myocardial injury (35.4+/-2.59 vs 32.5+/-2.59). Transfection of Ad5-dnMyD88 significantly inhibited I/R-enhanced NFkappaB activity by 50% and increased the levels of phospho-Akt by 35.6% and BCL-2 by 81%, respectively. Cardiac myocyte apoptosis after I/R was significantly reduced by 59% in the Ad5-dnMyD88 group. The results demonstrate that both inhibition of the NFkappaB activation pathway and activation of the Akt signaling pathway may be responsible for the protective effect of transfection of dominant negative MyD88.     

Transduction of anti-cell death protein FNK protects isolated rat hearts from myocardial infarction induced by ischemia/reperfusion

Artificial anti-cell death protein FNK, a Bcl-x(L) derivative with three amino acid-substitutions (Y22F, Q26N, and R165K) has enhanced anti-apoptotic and anti-necrotic activity and facilitates cell survival in many species and cell types. The objectives of this study were (i) to investigate whether the protein conjugated with a protein transduction domain (PTD-FNK) reduces myocardial infarct size and improves post-ischemic cardiac function in ischemic/reperfused rat hearts, and (ii) to understand the mechanism(s) by which PTD-FNK exerts a protective effect. Isolated rat hearts were subjected to 35-min global ischemia, followed by 120-min reperfusion using the Langendorff methods. PTD-FNK (a total of 30 microl) was injected intramuscularly into the anterior wall of the left ventricle either at 1 min after induction of global ischemia (group A) or at 30 min after induction of global ischemia (at 5 min before reperfusion) (group B). In group A, infarct size was significantly reduced from 47.8+/-6.8% in the control to 30.4+/-5.2, 28.7+/-3.8, and 30.4+/-6.8% with PTD-FNK at 5, 50, and 500 nmol/l, respectively (p<0.05). Temporal recovery of left ventricular developed pressure at 60 min and 120 min after reperfusion was significantly better in PTD-FNK (50 and 500 nmol/l)-treated groups than in the control (p<0.05). In contrast, PTD-FNK treatment had no effect on group B. Western blot analysis showed that PTD-FNK markedly inhibited procaspase-3 cleavage (activation of caspase-3) and reduced the number of nuclei stained by a terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphoshate nick-end labeling (TUNEL) assay. These findings suggest that PTD-FNK reduces the volume of myocardial infarction with corresponding functional recovery, at least in part, through the suppression of myocardial apoptosis following ischemia/reperfusion.     

Extracellular calcium protects isolated rat hepatocytes from injury

The incubation of isolated rat hepatocytes in calcium-free medium resulted in a pronounced increase in lipid peroxidation, mitochondrial and cytoplasmic glutathione depletion, glutathione disulfide formation and efflux of reduced glutathione as compared with hepatocytes incubated in calcium containing medium. These data suggest that extracellular calcium ions serve a protective role in isolated rat hepatocytes against cell injury.     

Cardioprotective effects of chloroquine pretreatment on ischemic and reperfusion injury via activation of ERK1/2 in isolated rat hearts

Molecular Biology Reports - Several therapeutic agents have been found to prevent myocardial ischemic and reperfusion (I/R) injury after cardiac surgery; however, no drug is routinely used to...     

Urocortin protects against ischemic and reperfusion injury via a MAPK-dependent pathway

Urocortin (UCN) is a peptide related to hypothalamic corticotrophin-releasing hormone and binds with high affinity to corticotrophin-releasing hormone receptor-2beta, which is expressed in the heart. In this study, we report that UCN prevented cell death when administered to primary cardiac myocyte cultures both prior to simulated hypoxia/ischemia and at the point of reoxygenation after simulated hypoxia/ischemia. UCN-mediated cell survival was measured by trypan blue exclusion, 3'-OH end labeling of DNA (TUNEL), annexin V, and fluorescence-activated cell sorting. To explore the mechanisms that could be responsible for this effect, we investigated the involvement of MAPK-dependent pathways. UCN caused rapid phosphorylation of ERK1/2-p42/44, and PD98059, which blocks the MEK1-ERK1/2-p42/44 cascade, also inhibited the survival-promoting effect of UCN. Most important, UCN reduced damage in isolated rat hearts ex vivo subjected to regional ischemia/reperfusion, with the protective effect being observed when UCN was given either prior to ischemia or at the time of reperfusion after ischemia. This suggests a novel function of UCN as a cardioprotective agent that could act when given after ischemia, at reperfusion.     

Sevoflurane postconditioning attenuates reperfusion-induced ventricular arrhythmias in isolated rat hearts exposed to ischemia/reperfusion injury

Sevoflurane postconditioning has been proven to protect the hearts against ischemia/reperfusion injury, manifested mainly by improved cardiac function, reduced myocardial specific biomarker release, and decreased infarct size. This study is to observe the effects of sevoflurane postconditioning on reperfusion-induced ventricular arrhythmias and reactive oxygen species generation in Langendorff perfused rat hearts. Compared with the unprotected hearts subjected to 25 min of global ischemia followed by 30 min of reperfusion, exposure of 3% sevoflurane during the first 15 min of reperfusion significantly improved cardiac function, reduced cardiac troponin I release, decreased infarct size and attenuated reperfusion-induced ventricular arrhythmia. Further analysis on arrhythmia during the 30 min of reperfusion showed that, sevoflurane postconditioning decreased both the duration and incidence of ventricular tachycardia and ventricular fibrillation. In the meantime, intracellular malondialdehyde and reactive oxygen species levels were also reduced. These above results demonstrate that sevoflurane postconditioning protects the hearts against ischemia/reperfusion injury and attenuates reperfusion-induced arrhythmia, which may be associated with the regulation of lipid peroxidation and reactive oxygen species generation.     

Protective effects of intermedin/adrenomedullin2 on ischemia/reperfusion injury in isolated rat hearts

Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene-related peptide (CT/CGRP) family identified from human and other vertebrate tissues. Preprointermedin can generate a 47-amino acid mature peptide (IMD(1-47)) and a shorter 40-amino acid one (IMD(8-47)) by proteolytic cleavage. The present study was designed to determine the protective effect of IMD on cardiac ischemia/reperfusion (I/R) injury and its possible mechanism. Isolated rat hearts were perfused on a Langendorff apparatus and subjected to 45-min global ischemia and 30-min reperfusion. Cardiac function was measured. The release of myocardial protein and lactate dehydrogenase (LDH) and the formation of malondialdehyde (MDA) were assayed. Myocardial cAMP content was determined by radioimmunoassay (RIA). Cardiac I/R induced a marked inhibition of cardiac function and myocardial injury. Reperfusion with IMD significantly attenuated the I/R injury. Compared with I/R alone, perfusion with 10(-8)mol/L IMD(1-47) and IMD(8-47) induced a 36% and 33% increase in Delta left ventricular pressure (DeltaLVP), 30% and 28% in maximal rate of increase of LV pressure (+LVdP/dt max), and 34% and 31% in maximal rate of decrease of LV pressure (-LVdP/dt max), respectively (all P<0.01) but an approximately 58% and 51% decrease in LV diastolic pressure, respectively (P<0.01). In addition, perfusion with IMD markedly attenuated the leakage of LDH, total protein and myoglobin from myocardia compared with I/R alone. The contents of ventricular myocardia cAMP after reperfusion with 10(-8)mol/L IMD(1-47) and IMD(8-47) were 130% and 91% higher, respectively, than that with I/R alone (all P<0.01). However, formations of myocardial MDA were 52% and 50% lower than that with I/R alone (all P<0.01), respectively. Interestingly, the above IMD effects were similar to those of adrenomedullin (10(-8)mol/L). These results suggest that IMD, like adrenomedullin, exerts cardio-protective effects against myocardial I/R injury.     

Erythropoietin pretreatment protects against acute chemotherapy toxicity in isolated rat hearts

The use of chemotherapeutic agents, such as anthracycline or trastuzumab, in oncology is limited by their cardiac toxicity. Recent experimental studies suggest that recombinant human erythropoietin (rhEPO) can be considered as a protective agent because its administration protects against cardiac ischemic injury, improving functional recovery, and reducing cell death. The aim of this study was to investigate whether pretreatment by rhEPO protects against acute cardiotoxicity induced by doxorubicin and trastuzumab, using the isolated rat heart model. Rats were treated with rhEPO (5000 IU/kg, intraperitoneally [i.p.]) or vehicle. One hour later, hearts were isolated and retrogradely perfused at constant flow. Following 20 mins of stabilization, hearts were perfused for 60 mins with modified-Krebs solution containing 6 mg/l doxorubicin or 10 mg/l trastuzumab. Hearts receiving doxorubicin were paced; those receiving trastuzumab were unpaced. Control hearts were perfused with modified-Krebs solution only. Doxorubicin exposure decreased left ventricular developed pressure (LVDP; approximately -40% of baseline) and increased end diastolic pressure (EDP; approximately +390% of baseline) and coronary perfusion pressure (CPP; approximately +70% of baseline). Incidence of ventricular tachycardia or fibrillation (VT/VF) was also significantly enhanced (86% vs. 0% in control group). Trastuzumab exposure increased CPP and EDP (approximately +70% of baseline for the both) without affecting LVDP. Prior rhEPO treatment significantly prevented doxorubicin-induced deleterious effects on LVDP, EDP, and VT/VF incidence. rhEPO administration also prevented trastuzumab-induced deleterious effects on CPP and EDP. This study shows that pretreatment by rhEPO protects myocardium against functional damage and electrophysiologic injury induced by acute doxorubicin or trastuzumab exposure. Further investigations are required to elucidate the precise mechanisms involved.     

异丙酚对离体大鼠心肌缺血、再灌注损伤后细胞凋亡及其机制研究

目的：观察异丙酚对离体大鼠心肌缺血/再灌注损伤的影响并从氧化应激和线粒体介导的凋亡方面探讨其作用机制。方法：应用Langendorff离体心脏灌注系统建立心肌缺血/再灌注损伤模型。40只SD大鼠随机分为正常对照组、缺血/再灌注模型（I/R）组、异丙酚15、30、60μmol.L-1组。除正常对照组外,各组分别平衡灌注20 min后,常温全心停灌25 min,再灌注30 min。Powerlab/8s仪记录各组平衡末、缺血前及再灌30 min时的各项心功能指标并测定冠脉流出液中乳酸脱氢酶（LDH）、肌酸激酶（CK）活性;检测心肌线粒体活力、膜肿胀度、锰超氧化物岐化酶（Mn-SOD）活性和丙二醛（MDA）含量;流式细胞仪检测心肌细胞凋亡;流式细胞术检测Bcl-2和Bax的表达,免疫组化法测定天冬氨酸特异的半胱氨酸蛋白酶（caspase）-3,9,8蛋白的表达。结果：与I/R组相比,异丙酚30、60μmol.L-1能明显改善缺血/再灌注后的心功能,减弱冠脉流出液中LDH、CK的活性（P〈0.05）;心肌线粒体活力有所恢复,膜肿胀度减轻,Mn-SOD活性升高,MDA生成明显减少（P〈0.05）,心肌细胞凋亡明显减少,Bcl-2表达上调,Bax表达下调,caspase-3,9阳性表达细胞数明显减少（P〈0.05）。结论：异丙酚明显减轻缺血/再灌注所致的心肌线粒体的过氧化损伤,抑制线粒体途径的凋亡,可能是其心肌保护作用机制之一。     

Effect of ischemic preconditioning on free radical centers of the isolated rat heart during ischemia and early reperfusion

The effect of ischemic preconditioning on the free-radical state of isolated rat myocardium fixed by rapid freezing at the 25th min of normothermic total ischemia and the 3rd min of reperfusion was studied by the EPR method. It was shown that EPR spectra registered at -40 degrees C consist of two free-radical signals: of the semireduced forms of ubiquinone and flavine coynzymes. It was found that during ischemia and at the beginning of reperfusion, the preconditioning results in a narrowing of the spectra (as compared with control) due to an increase in the narrow ubisemiquinone EPR signal portion, and a decrease in the total concentration of free-radical centers: by 16% in the case of ischemia, and 23% in the case of reperfusion. It was concluded that in both cases the changes were due to a decrease in the concentration of myocardial flavosemiquinones as a result of ischemic preconditioning. We registered the microvawe power saturation curves for these two stages, which corresponded to control and ischemic preconditioning. In the case of ischemia these dependences had similar shapes; however, in the case of reperfusion they differ from each other due to changes in the relative intensities of the EPR signals from ubisemiquinone and flavosemiquinones in the integral myocardial free-radical spectra.     

Cyclosporin A binding in mitochondrial cyclophilin inhibits the permeability transition pore and protects hearts from ischaemia/reperfusion injury

When loaded with high (pathological) levels of Ca²⁺, mitochondria become swollen and uncoupled as the result of a large non-specific increase in membrane permeability. This process, known as the mitochondrial permeability transition (MPT), is exacerbated by oxidative stress and adenine nucleotide depletion. These conditions match those that a heart experiences during reperfusion following a period of ischaemia. The MPT is caused by the opening of a non-specific pore that can be prevented by sub-micromolar concentrations of cyclosporin A (CsA). A variety of conditions that increase the sensitivity of pore opening to [Ca²⁺], such as thiol modification, oxidative stress, increased matrix volume and chaotropic agents, all enhance the binding of matrix cyclophilin (CyP) to the inner mitochondrial membrane in a CsA-sensitive manner. In contrast, ADP, membrane potential and low pH decrease the sensitivity of pore opening to [Ca²⁺] without affecting CyP binding. We present a model of pore opening involving CyP binding to a membrane target protein followed by Ca²⁺-dependent triggering of a conformational change to induce channel opening. Using the ischaemic/reperfused rat heart we have shown that the mitochondrial pore does not open during ischaemia, but does do so during reperfusion. Recovery of heart during reperfusion is improved in the presence of 0.2 µM CsA, suggesting that the MPT may be critical in the transition from reversible to irreversible reperfusion injury. (Mol Cell Biochem 174: 167–172, 1997)     

Effects of recombinant human extracellular-superoxide dismutase type C on myocardial reperfusion injury in isolated cold-arrested rat hearts.

The efficacy of recombinant human extracellular-superoxide dismutase type C (EC-SOD C) on myocardial reperfusion injury was explored in hypothermically arrested rat hearts, as was its site of action. Forty isolated working rat hearts were subjected to 30 min of global ischemia followed by 30 min of reperfusion. The hearts were arrested by the administration of 10 mL of cold perfusate at the onset of ischemia. At the same time, they were randomly assigned to one of five groups; A: cold perfusate only; B: cold perfusate + EC-SOD C 10.4 mg/L (30,000 U/L); C: cold perfusate+bovine CuZn-SOD 7.5 mg/L (30,000 U/L); D: cold perfusate + EC-SOD C 10.4 mg/L + heparin 50,000U/L; E: cold perfusate + heparin 50,000 U/L. Heparin was given to prevent binding of EC-SOD C to endothelial cell surfaces. Left ventricular function was studied before ischemia and at the end of reperfusion. Percent recovery of maximal left ventricular dP/dt after reperfusion was more pronounced in group B (109 +/- 24%; p less than .05) than in groups A (42 +/- 40%), C (47 +/- 36%), D (44 +/- 33%) and E (58 +/- 25%). Likewise, percent recovery of the double product (heart rate x systolic left ventricular pressure) was better in group B (104 +/- 18%; p less than .05) than in the other groups (A: 47 +/- 37%, C: 49 +/- 36%, D: 50 +/- 35%, E: 69 +/- 31%). Compared to the preischemic level, creatine kinase increased significantly in the coronary effluent after reperfusion in groups A, C, D, and E, but not in group B. The results suggest that EC-SOD C, which attaches to the endothelial cell surfaces, might be particularly effective as protection against myocardial reperfusion injury when given together with cardioplegic solution.     

Glycolysis and glucose oxidation during reperfusion of ischemic hearts from diabetic rats

Stimulationg of glucose oxidation by dichloroacetate (DCA) treatment is beneficial during recovery of ischemic hearts from non-diabetic rats. We therfore determined whether DCA treatment of diabetic rat hearts (in which glucose use is extremely low), increases recovery of function of hearts reperfused following ischemia. Isolated working hearts from 6 week streptozotocindiabetic rats were perfused with 11 mM [2-³H/U-¹⁴C]glucose, 1.2 mM palmitate, 20 μU/ml insulin, and subjected to 30 min of no flow ischemia followed by 60 min reperfusion. Heart function (expressed as the product of heart rate and peak systolic pressure), prior to ischemia, was depressed in diabetic hearts compared to controls (HR × PSP × 10^?3 was 18.2 ± 1 and 24.3 ± 1 beats/mm Hg/min in diabetic and control hearts respectively) but recover to pre-ischemic levels following ischemia, whereas recovery of control of control hearts was significantly decreased (17.8 ± 1 and 11.9 ± 3 beats/mm Hg/min in diabetic and control hearts respectively). This enhanced recovery of diabetic rat hearts occurred even though glucose oxidation during reperfusion was significantly reduced as compared to controls (39 ± 6 and 208 ± 42 nmol/min/g dry wt, in diabetic and control hearts respectively). Glycolytic rate (³G₂O production) during reperfusion were similar in diabetic and control hearts (1623 ± 359 and 2071 ± 288 nmol/min/g dry wt, respectively). If DCA (1 mM) was added at reperfusion, hearts from control animals exhibited a significant improvement in function (HR × PSP × 10^? recovered to 20 ± 4 beats/mm Hg/min) that was accompanied by a 4-fold increase in glucose oxidation (from 208 ± 42 to 753 ± 111 nmol/min/g dry wt). DCA was without effect on functional recovery of diabetic rat hearts during reperfusion but did significantly increase glucose oxidation from 39 ± 6 to 179 ± 44 nmol/min/g dry wt). These data suggests that, unlike control hearts, low glucose oxidation rates are not an important factor in reperfusion recovery of previouskly ischemic diabetic rat hearts.     

Magnesium: Effects on reperfusion arrhythmias and membrane potential in isolated rat hearts

Myocardial Na+,K+-ATPase was studied in patients with aortic valve disease, and myocardial Na+,K+- and Ca2+-ATPase were assessed in spontaneously hypertensive rats (SHR) and hereditary cardiomyopathic hamsters using methods ensuring high enzyme recovery. Na+,K+-ATPase was quantified by [3H]ouabain binding to intact myocardial biopsies from patients with aortic valve disease. Aortic stenosis, regurgitation and a combination hereof were compared with normal human heart and were associated with reductions of left ventricular [3H]ouabain binding site concentration (pmol/g wet weight) of 56, 46 and 60%, respectively (p < 0.01). Na+,K+ and Ca2+-ATPases were quantified by K+- and Ca2+-dependent p-nitrophenyl phosphatase (pNPPase) activity determinations in crude myocardial homogenates from SHR and hereditary cardiomyopathic hamsters. When SHR were compared to age-matched Wistar Kyoto (WKY) rats an increase in heart-body weight ratio of 75% (p < 0.001) was associated with reductions of K+- and Ca2+-dependent pNPPase activities (mol/min/g wet weight) of 42 (p < 0.01) and 27% (p < 0.05), respectively. When hereditary cardiomyopathic hamsters were compared to age-matched Syrian hamsters an increase in heart-body weight ratio of 69% (p < 0.001) was found to be associated with reductions in K+- and Ca2+-dependent pNPPase activities of 50 (p < 0.001) and 26% (p = 0.05), respectively. The reductions in Na+,K+- and Ca2+-ATPases were selective in relation to overall protein content and were not merely the outcome of increased myocardial mass relative to Na+,K+- and Ca2+-pumps. In conclusion, myocardial hypertrophy is in patients associated with reduced Na+,K+-ATPase concentration and in rodents with reduced Na+,K+- and Ca2+-ATPase concentrations. This may be of importance for development of heart f in hypertrophic heart disease.     

Cannabidiol, a nonpsychoactive Cannabis constituent, protects against myocardial ischemic reperfusion injury

Cannabidiol (CBD) is a major, nonpsychoactive Cannabis constituent with anti-inflammatory activity mediated by enhancing adenosine signaling. Inasmuch as adenosine receptors are promising pharmaceutical targets for ischemic heart diseases, we tested the effect of CBD on ischemic rat hearts. For the in vivo studies, the left anterior descending coronary artery was transiently ligated for 30 min, and the rats were treated for 7 days with CBD (5 mg/kg ip) or vehicle. Cardiac function was studied by echocardiography. Infarcts were examined morphometrically and histologically. For ex vivo evaluation, CBD was administered 24 and 1 h before the animals were killed, and hearts were harvested for physiological measurements. In vivo studies showed preservation of shortening fraction in CBD-treated animals: from 48 +/- 8 to 39 +/- 8% and from 44 +/- 5 to 32 +/- 9% in CBD-treated and control rats, respectively (n = 14, P < 0.05). Infarct size was reduced by 66% in CBD-treated animals, despite nearly identical areas at risk (9.6 +/- 3.9 and 28.2 +/- 7.0% in CBD and controls, respectively, P < 0.001) and granulation tissue proportion as assessed qualitatively. Infarcts in CBD-treated animals were associated with reduced myocardial inflammation and reduced IL-6 levels (254 +/- 22 and 2,812 +/- 500 pg/ml in CBD and control rats, respectively, P < 0.01). In isolated hearts, no significant difference in infarct size, left ventricular developed pressures during ischemia and reperfusion, or coronary flow could be detected between CBD-treated and control hearts. Our study shows that CBD induces a substantial in vivo cardioprotective effect from ischemia that is not observed ex vivo. Inasmuch as CBD has previously been administered to humans without causing side effects, it may represent a promising novel treatment for myocardial ischemia.