Vardenafil protects isolated rat hearts at reperfusion dependent on GC and PKG

BACKGROUND AND PURPOSE: The type-5 PDE inhibitor vardenafil reduces myocardial infarct size in situ, following ischemia/reperfusion, when applied at reperfusion in animal models. Little is known about the underlying protective signaling. Here, we test whether vardenafil is protective in rat isolated hearts and in a cell model of calcium stress. EXPERIMENTAL APPROACH: Infarct size in rat isolated hearts was measured after a 30 min regional ischemia and 120 min reperfusion. Vardenafil (1 nM-1 microM) was infused during reperfusion. HL-1 cardiomyocytes were loaded with tetramethylrhodamine ethyl ester (TMRE), a fluorescent marker of mitochondrial membrane potential (psi m). KEY RESULTS: Vardenafil at reperfusion reduced infarct size as percentage of the ischemic zone from 45.8+/-2.0% in control hearts to 26.2+/-2.7% (P<0.001) only at 10 nM, whereas higher or lower dosages failed to protect. This protective effect was blocked by co-administration of either the GC inhibitor, 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), or the PKG inhibitor, KT-5823. HL-1 cardiomyocytes, loaded with TMRE, were treated for 80 min with the calcium ionophore, calcimycin, to induce calcium stress. This reduced the mean cell fluorescence to 63.3 +/- 3.8% of baseline values and vardenafil protected against this fall (78.6 +/- 3.6%, P<0.01). The vardenafil-induced protection of HL-1 cells was blocked by ODQ, KT-5823 or the PKG-inhibiting peptides DT-2 and DT-3, confirming a role for GC and PKG. CONCLUSIONS AND IMPLICATIONS: These results further support the hypothesis that PDE-5 inhibitors are protective in ischemic hearts, in addition to their known clinical effects in the treatment of erectile dysfunction in men.     

热休克蛋白70对未成熟心肌间质保护作用的研究

目的探讨热休克蛋白70(HSP70)对未成熟心肌间质的影响。方法健康新生长耳大白兔随机分为2组。对照组:腹腔注射生理盐水0.4ml,注射后24h取离体心脏,常规建立Langendorff离体心脏灌注模型,灌注15min转为工作心15min后停灌45min,恢复灌注15min改为工作心30min;观察组:腹腔注射重酒石酸去甲肾上腺素,24h后取离体心脏,方法同对照组。测定心脏舒张功能指标、心肌细胞中HSP70含量、心肌羟脯氨酸(HP)和血清内皮素(ET)含量。结果HSP70含量观察组明显高于对照组;观察组HP含量高于对照组(P<0.05),ET含量低于对照组(P<0.05)。结论HSP70可明显减轻未成熟心肌间质缺血再灌注损伤。     

Antioxidant activity and protective effects of cocoa and kola nut mistletoe (Globimetula cupulata) against ischemia/reperfusion injury in Langendorff-perfused rat hearts

Protection against cardiomyocyte damage following ischemia/reperfusion (I/R) injury is highly desirable in patients with ischemic heart disease. Hydromethanol extracts of Globimetula cupulata (mistletoe) growing on cocoa (CGCE) and kola nut (KGCE) trees were assessed for antioxidant content and cardioprotective potential against I/R. Graded concentrations (1–50 μg/mL) of CGCE or KGCE were tested on Langendorff-perfused rat hearts to evaluate the effects on the flow rate, heart rate, and force of cardiac contraction, while another set of hearts were subjected to biochemical analyses. Both extracts showed good antioxidant content and activity, but KGCE (EC₅₀: 24.8±1.8 μg/mL) showed higher hydroxyl radical scavenging activity than CGCE (70.2±4.5 μg/mL). Both extracts at 3 μg/mL reversed (p < 0.001) membrane peroxidation and the significant decrease in nitrite level, coronary flow rate, and superoxide dismutase and catalase activity caused by the I/R cycle. It is concluded that G. cupulata protects against ischemia–reperfusion injury in rat hearts via augmenting endogenous antioxidants and significant restoration of altered hemodynamic parameters.     

AMPK抑制剂P5499拮抗无钙预处理心肌保护作用

目的:观察腺苷酸活化的蛋白激酶(AMPK)抑制剂P5499对短暂无钙预处理心肌保护作用的影响。方法:对健康SD雄性大鼠心脏行Langendorff离体灌流,实验全程记录心脏冠脉流量(CF)、左心室内压(LVP)、左室舒张末压(LVEDP)、室内压最大变化速率(±dp/dtmax)及心率(HR),并计算左室发展压(LVDP)和心率-压力乘积(RPP)评价心功能的变化。再灌注结束后,采用2、3、5-氯化三苯基四氮唑(TTC)染色法评价心肌梗死(MI)面积的变化。结果:缺血/再灌注(I/R)后,心功能显著降低,CF明显减少(P<0.01),MI面积的比率为(39.6±1.49)%。短暂无钙预处理(CPC)可使LVEDP明显降低(P<0.05),CF、LVDP、±dp/dtmax及RPP均明显改善(P<0.01),MI面积显著缩小(P<0.01)。缺血前单独给予P5499对心功能、CF及MI面积无明显影响,但其可显著逆转CPC的心肌保护作用(P<0.01)。结论:AMPK可能是Ca2+预处理产生心肌保护信号的下游分子。     

Erythropoietin and myocardial protection: what's new?

Erythropoietin (EPO), the principal hematopoietic cytokine produced by the kidney and the liver in fetuses, regulates mammalian erythropoiesis and exhibits diverse cellular effects in non-hematopoietic tissues. The introduction of recombinant human EPO (rhEPO) has marked a significant advance in the management of anemia associated with chronic renal failure. At the same time, experimental studies have unveiled its potential cardioprotective actions. As with other preconditioning agents, administration of exogenous rhEPO can confer myocardial protection against ischemia-reperfusion injury, in terms of reduction in cellular apoptosis and necrosis as well as improvement in myocardial functional recovery. The purpose of this study is to review current information regarding the various protocols used to investigate the effects of rhEPO administration as well as its cardioprotective properties. We also address the potential mechanisms underlying the protective effects of EPO. A better understanding of these mechanisms is essential for the development of clinical applications and the design of novel therapeutical strategies.     

Levosimendan cardioprotection reduces the metabolic response during temporary regional coronary occlusion in an open chest pig model

BACKGROUND: Inotropic and myocardial anti-ischemic effects have been demonstrated with levosimendan. The comparison of levosimendan started before an ischemia-reperfusion event as compared with levosimendan started during ischemia has not been studied. METHODS: In anesthetized pigs, a major branch of the circumflex artery was completely occluded for 30 min and then reperfused. The metabolism in the ischemic myocardium and in non-ischemic control myocardium was studied with microdialysis concomitantly with monitoring of global hemodynamics and coronary artery flow in the chosen artery. In the protection group (PRO, n= 6), a levosimendan infusion was started 30 min before coronary artery occlusion, and in the treatment group (TRE, n= 6), a levosimendan infusion was started 10 min after the coronary artery occlusion with a loading dose of 13.3 microg/kg followed by an infusion of 0.67 microg/kg/min. A two-way repeated measures ANOVA completed with Bonferroni's multiple comparison procedure was applied to the data. A P < 0.05 was considered significant. RESULTS: During the ischemic period, the cardiac output and contractility (dp/dt(max)) were higher in the PRO as compared with the TRE and the systemic vascular resistance was lower. The myocardial microdialysate glucose concentration in the ischemic area during ischemia was higher in the PRO as compared with the TRE, and the lactate/pyruvate ratio and the lactate concentration were lower. The differences in the metabolites persisted into the first 10 min of reperfusion. No differences were found for the non-ischemic areas. CONCLUSION: Levosimendan used throughout myocardial ischemia-reperfusion might have a cardioprotective affect on the response to myocardial ischemia as compared with levosimendan started during the ischemia.     

远隔器官缺血预处理心脏保护作用的研究进展

心肌缺血预处理现象的发现,为心肌缺血再灌注损伤的预防开拓了一个新的研究领域。近年来,随着预处理研究的不断深入,其方法学也有一些新的进展。研究发现,心外组织如肾脏、小肠及骨骼肌短暂缺血不仅能减轻局部组织的再灌注损伤,对远隔的心脏也有保护作用,并将这种现象称为远隔预处理。现就远隔器官缺血预处理对心脏的保护作用及其机制作一简要综述。     

Exogenous NAD+ supplementation protects H9c2 cardiac myoblasts against hypoxia/reoxygenation injury via Sirt1‐p53 pathway

Nicotinamide adenine dinucleotide (NAD⁺) not only transfers electrons in mitochondrial respiration, but also acts as an indispensable cosubstrate for Sirt1, the class III histone/nonhistone deacetylase. However, NAD⁺ is depleted in myocardial ischemia/reperfusion (IR) injury. The objective of this study was to investigate the role of exogenous NAD⁺ supplementation in hypoxia/reoxygenation (HR)‐stressed H9c2 cardiac myoblasts. Firstly, the effects of distinct treating time points and doses of NAD⁺ supplementation on the viability of HR‐stressed H9c2 cells were detected. Secondly, intracellular NAD⁺ levels in HR‐stressed H9c2 cells at various extracellular NAD⁺ concentrations were determined. Thirdly, the role of NAD⁺ supplementation in HR‐induced cell apoptosis and its relevance to Sirtuin 1‐p53 pathway were investigated. Exogenous NAD⁺ supplementation elevated intracellular NAD⁺ level and reduced HR‐induced cell death in both time‐ and concentration‐dependent manners. It appeared that NAD⁺ supplementation exerted the greatest protection when extracellular concentration ranged from 500 to 1000 μm and when NAD⁺ was added immediately after reoxygenation began. NAD⁺ replenishment restored Sirt1 activity, reduced the acetylation level of p53 (Lys373 & 382), and attenuated cell apoptosis in HR‐stressed H9c2 cells, whereas inhibition of Sirt1 activity alleviated the effects of NAD⁺ replenishment. These results indicated that exogenous NAD⁺ supplementation attenuated HR‐induced cell apoptosis, which was at least partly mediated by restoring Sirt1 activity and subsequently inhibiting p53 activity via deacetylating p53 at lysine 373 and 382.     

Therapeutic potential of H3-receptor agonists in myocardial infarction

Sympathetic over-activity accompanied by excessive noradrenaline (NA) release within the heart is a recognised cause of dysfunction in myocardial ischaemia. Myocardial infarction is often accompanied by arrhythmias with high morbidity and mortality. Indeed, NA enhances intracellular Ca²⁺by increasing its influx through voltage-dependent channels, mobilising it from intracellular stores and favouring its inward transport by Na⁺/Ca²⁺ exchange. Ca²⁺ overload eventually results in dysrhythmia and uncoordinated myocyte contraction. Moreover, NA increases metabolic demand. In concert with other contributing factors, this will aggravate the primary ischaemia and initiate a vicious cycle that can culminate in myocardial damage and heart failure. Therefore, reduction of NA release from cardiac sympathetic nerves is an important protective measure. Adrenergic nerves possess inhibitory receptors, such as ₂-adrenoceptors, adenosine A₁-receptors and histamine H₃-receptors (H₃R). In myocardial infarction, NA is released by both exocytotic (Ca²⁺-dependent) and carrier-mediated (Na⁺/H⁺ exchange-dependent) mechanisms, associated with short-term and protracted ischaemia, respectively. Unlike ₂-adrenoceptor agonists that reduce NA exocytosis, but enhance carrier-mediated NA release, H₃R agonists inhibit both exocytotic and carrier-mediated NA release. Moreover, unlike adenosine A₁-receptor agonists, H₃R agonists do not depress sinoatrial and atrioventricular nodes, nor cause bronchoconstriction. Therefore, stimulation of H₃R on cardiac sympathetic nerve endings is an important new way to protect the heart from the consequences of ischaemia and infarction. Although H₃R agonists alleviate reperfusion arrhythmias in isolated hearts by reducing NA release, this protective action needs to be demonstrated in classical in vivo models of occlusion/reperfusion. Regardless, H₃R agonists offer the promise of a novel strategy in the treatment of myocardial ischaemia and infarction.     

运动对心脏的保护作用及其机制的研究进展

运动训练有益心脏健康,可以改善心血管疾病患者的运动能力和生活质量,降低其致死率和致残率。尽管运动的益处显而易见,但是运动训练对于心脏疾病的保护机制尚不明确。本文重点综述了运动保护心脏的主要机制,以及运动对于心肌梗死、缺血再灌注损伤、病理性心肌肥厚、心脏衰老等心脏疾病的保护作用及最新研究进展,以期从"运动"这一独特视角,为心脏疾病的防治提供新思路和新策略。