Inhibitory effects of edaravone on the production of tumor necrosis factor-α in the isolated heart undergoing ischemia and reperfusion

We evaluated the effects of edaravone, a hydroxyl radical scavenging agent, on the production of tumor necrosis factor-α (TNF-α) in myocardium, and the release of TNF-α and P-selectin from myocardium after ischemia–reperfusion injury in isolated Langendorff-perfused rat hearts. Cardiodynamic function at stable points during perfusion and 5, 15, 30, and 60 min after the initiation of reperfusion was evaluated by left ventricular developed pressure, rate of increase in left ventricular pressure and rate of decrease in ventricular pressure, coronary flow, and heart rate. At 60 min after the initiation of reperfusion, myocardial infarct size was estimated microscopically using triphenyltetrazolium chloride staining, and expression of TNF-α in myocardium was detected by Western blot and immunohistochemistry. At the same time points as the measurement of cardiodynamic function, TNF-α and the soluble form of P-selectin in coronary effluent were measured by enzyme immunoassay. At all time points during reperfusion, edaravone markedly improved cardiodynamic function and reduced myocardial infarct size in comparison to the control. In myocardium in the control, TNF-α was detected in the endothelial cells and other cells bearing some resemblance to interstitial cells and monocyte cells. Edaravone suppressed this cytokine expression in the corresponding sites. P-selectin as well as TNF-α was found in the coronary effluent of the control, and edaravone significantly decreased soluble P-selectin levels in comparison to the control (P < 0.01). Edaravone might have protective effects on cardiac function through reduction of infarct size via decrease of production of TNF-α in myocardium induced by ischemia–reperfusion injury and through reduction of the release of adhesion molecules such as P-selectin from vascular endothelial cells.     

Locally targeted cytoprotection with dextran sulfate attenuates experimental porcine myocardial ischaemia/reperfusion injury.

AIMS: Intravascular inflammatory events during ischaemia/reperfusion injury following coronary angioplasty alter and denudate the endothelium of its natural anticoagulant heparan sulfate proteoglycan (HSPG) layer, contributing to myocardial tissue damage. We propose that locally targeted cytoprotection of ischaemic myocardium with the glycosaminoglycan analogue dextran sulfate (DXS, MW 5000) may protect damaged tissue from reperfusion injury by functional restoration of HSPG. METHODS AND RESULTS: In a closed chest porcine model of acute myocardial ischaemia/reperfusion injury (60 min ischaemia, 120 min reperfusion), DXS was administered intracoronarily into the area at risk 5 min prior to reperfusion. Despite similar areas at risk in both groups (39+/-8% and 42+/-9% of left ventricular mass), DXS significantly decreased myocardial infarct size from 61+/-12% of the area at risk for vehicle controls to 39+/-14%. Cardioprotection correlated with reduced cardiac enzyme release creatine kinase (CK-MB, troponin-I). DXS abrogated myocardial complement deposition and substantially decreased vascular expression of pro-coagulant tissue factor in ischaemic myocardium. DXS binding, detected using fluorescein-labelled agent, localized to ischaemically damaged blood vessels/myocardium and correlated with reduced vascular staining of HSPG. CONCLUSION: The significant cardioprotection obtained through targeted cytoprotection of ischaemic tissue prior to reperfusion in this model of acute myocardial infarction suggests a possible role for the local modulation of vascular inflammation by glycosaminoglycan analogues as a novel therapy to reduce reperfusion injury.     

Left ventricular dilation in toll-like receptor 2 deficient mice after myocardial ischemia/reperfusion through defective scar formation

Restoration of myocardial blood flow after ischemia triggers an inflammatory response involving toll-like receptors (TLRs). TLR2^−/−-mice show short-term advantages upon reperfusion injury as compared with WT controls. Accordingly, it has been shown that transient TLR2-blockade prior to reperfusion is associated with improved left-ventricular performance after myocardial scar formation. We present here adverse myocardial remodeling due to a chronic lack of TLR2 expression. Myocardial ischemia/reperfusion (MI/R) was surgically induced in C3HeN-mice by ligation of the left anterior descending coronary artery for 20 min, followed by 24 h or 28 days of reperfusion. TLR2^−/−-mice and TLR2-Ab treated (T2.5) WT-mice displayed a reduction of infarct size, plasma troponin T concentrations, and leukocyte infiltration as compared with untreated controls after 24 h of reperfusion. After 28 days, however, magnetic resonance imaging revealed a marked left ventricular dilation in TLR2^−/−-animals, which was associated with pronounced matrix remodeling characterized by reduced collagen and decorin density in the infarct scar. Our data show adverse effects on myocardial remodeling in TLR2^−/−-mice. Although interception with TLR2 signaling is a promising concept for the prevention of reperfusion injury after myocardial ischemia, these data give cause for serious concern with respect to the time-point and duration of the potential treatment.     

The neutrophil as a mediator of myocardial ischemia-reperfusion injury: time to move on

Granulocytes, especially neutrophils, are recruited in myocardium during the evolution of acute myocardial infarction. Because the neutrophil reaction is most intense during reperfusion and because these cells are a rich source of toxic oxidant species and proteolytic enzymes, it has become a widely held view that neutrophils are an important mechanism of myocardial injury extension during reperfusion. However, on close examination the evidence underlying this contention is equivocal. The basic experimental situation can be summarised thus. (1) All forms of reperfusion injury (i.e., cytotoxic or lethal cell injury, myocardial stunning, endothelial dysfunction, and reperfusion-induced arrhythmias) can be observed in neutrophil-free conditions. (2) “Anti-neutrophil” interventions (e.g., anti-inflammatory drugs, adenosine, anti-neutrophil antisera, leukocyte filters and inhibitors of the various pathways of neutrophil adhesion) do not consistently prevent reperfusion injury and they certainly do not consistently limit infarct size. (3) The time course of neutrophil accumulation in post-ischaemic myocardium may be different to the time course of injury. (4) Despite more than two decades of research, no double-blind, randomised controlled clinical trial assessing an anti-neutrophil therapy in myocardial infarction has yet reported a positive benefit that is attributable to inhibition of neutrophil recruitment. The evidence weighs against a pivotal role of neutrophils as a causal factor in most forms of ischemia-reperfusion injury. An exception may be microvascular injury and capillary plugging leading to the “no-reflow” phenomenon but even here the evidence suggests that the extent of neutrophil accumulation and microvascular injury is determined by, rather than a cause of, myocyte necrosis.     

Role of osteopontin in heart failure associated with aging

Cardiovascular disease is one of the leading causes of death in the elderly. Much of the morbidity and mortality in the elderly is attributable to acute ischemic events leading to myocardial infarction (MI) and death of cardiac myocytes. Evidence has been provided that aging associated with adverse remodeling post MI as demonstrated by less effective myocardial repair, greater infarct expansion, and septal hypertrophy. Expression of osteopontin (OPN) increases in the heart post MI. Transgenic mice studies suggest that increased expression of OPN plays a protective role in post-MI LV remodeling by modulating collagen deposition and fibrosis. OPN, a multifunctional protein, has the potential to influence the molecular and cellular changes associated with infarct healing. The post-MI infarct healing process involves temporarily overlapping phases that include the following—(1) inflammation with migration and adhesion of neutrophils and macrophages, phagocytosis and inflammatory gene expression; (2) tissue repair with fibroblast adhesion and proliferation, myofibroblast differentiation, extracellular matrix deposition and scar formation; and (3) structural and functional remodeling of infarcted and non-infarcted myocardium through cardiac myocyte apoptosis, hypertrophy and myocardial angiogenesis. This review is focused on the expression of OPN in the heart post MI and its role in various phases of infarct healing.     

Exogenous hydrogen sulfide (H2S) protects against regional myocardial ischemia–reperfusion injury

Hydrogen sulfide (H₂S) is a gaseous mediator, produced by the metabolic pathways that regulate tissue concentrations of sulfur–containing amino acids. Recent studies indicate that endogenous or exogenous H₂S exerts physiological effects in the cardiovascular system of vertebrates, possibly through modulation of K_ATP channel opening. The present study was undertaken to examine the hypothesis that H₂S is cytoprotective against myocardial ischemia–reperfusion injury and that this protective action is mediated by K_ATP opening. Rat isolated hearts were Langendorff–perfused and underwent 30 min left main coronary artery occlusion and 120 min reperfusion. The resulting injury was assessed as infarct size, determined by tetrazolium staining. Treatment of hearts with the H₂S–donor, NaHS, commencing 10 min prior to the onset of coronary occlusion and maintained until 10 min reperfusion, resulted in a concentration–dependent limitation of infarct size (control, 41.0 ± 2.6% of risk zone; NaHS 0.1 μM, 33.9 ± 2.1%, [0.05 > P < 0.1]; NaHS 1 μM, 20.2 ± 2.1% [P < 0.01]). Pretreatment with the K_ATP channel blockers glibenclamide 10 μM or sodium 5–hydroxydecanoate (5HD) 100 μM led to abrogation of the infarct–limiting effect of NaHS 1 μM (glibenclamide + NaHS 42.5 ± 3.6%; 5HD + NaHS 44.7 ± 2.2%). No statistically significant effects of NaHS treatment on coronary flow, heart rate or left ventricular developed pressure were observed in this experimental preparation. These data provide the first evidence that exogenous H₂S protects against irreversible ischemia–reperfusion injury in myocardium and support the involvement of K_ATP opening in the mechanism of action. Further work is required to elucidate the potential role of endogenous H₂S as a cytoprotective mediator against myocardial ischemia–reperfusion injury, the mechanisms regulating its generation, and the nature of its interaction with protein targets such as the K_ATP channel.     

Granulocyte Colony-Stimulating Factor Mediates Cardioprotection Against Ischemia/Reperfusion Injury via Phosphatidylinositol-3-Kinase/Akt Pathway in Canine Hearts

Purpose Recent studies suggest that G-CSF prevents cardiac remodeling following myocardial infarction (MI) likely through regeneration of the myocardium and coronary vessels. However, it remains unclear whether G-CSF administered at the onset of reperfusion prevents ischemia/reperfusion injury in the acute phase. We investigated acute effects of G-CSF on myocardial infarct size and the incidence of lethal arrhythmia and evaluated the involvement of the phosphatidylinositol-3 kinase (PI3K) in the in vivo canine models. Methods In open-chest dogs, left anterior descending coronary artery (LAD) was occluded for 90 minutes followed by 6 hours of reperfusion. We intravenously administered G-CSF (0.33 μ/kg/min) for 30 minutes from the onset of reperfusion. Wortmannin, a PI3K inhibitor, was selectively administered into the LAD after the onset of reperfusion. Results G-CSF significantly (p<0.05) reduced myocardial infarct size (38.7±4.3% to 15.7±5.3%) and the incidence of ventricular fibrillation during reperfusion periods (50% to 0%) compared with the control. G-CSF enhanced Akt phospholylation in ischemic canine myocardium. Wortmannin blunted both the infarct size-limiting and anti-arrhythmic effects of G-CSF. G-CSF did not change myeloperoxidase activity, a marker of neutrophil accumulation, in the infarcted myocardium. Conclusion An intravenous administration of G-CSF at the onset of reperfusion attenuates ischemia/reperfusion injury through PI3K/Akt pathway in the in vivo model. G-CSF administration can be a promising candidate for the adjunctive therapy for patients with acute myocardial infarction. Takahama and Hirata contributed equally to this work.     

远隔预处理和后处理对兔急性心肌缺血再灌注损伤的作用

目的探讨远隔预处理和后处理是否具有减轻兔心肌缺血再灌注损伤的作用及其机制。方法新西兰大白兔40只，随机平均分为4组：对照组、心肌缺血预处理组、肢体缺血预处理组和肢体缺血后处理组，分组进行干预。测定血浆磷酸肌酸激酶（CK）和丙二醛（MDA）活性及心肌梗死面积并检测组织髓过氧化物酶（MPO）活性。结果心肌缺血预处理组、肢体缺血预处理组和肢体缺血后处理组心肌梗死面积、再灌注末MDA活性、缺血组织MPO活性均明显低于对照组（均P〈0．01）。结论远隔预处理和后处理均有显著的心脏保护作用，其作用可能与减轻活性氧的损伤及抗氧化作用加强有关。     

Protection of the myocardium during myocardial infarction: pharmacologic protection during thrombolytic therapy

The most effective way to protect injured myocardium during the early phases of evolving myocardial infarction is with reperfusion. However, reperfusion may induce further myocardial injury. Alterations in the major determinants of myocardial oxygen demand, including increases in heart rate, contractile state and myocardial wall tension may also increase infarct size. An understanding of the basic mechanisms involved in the evolution of myocardial injury during myocardial infarction is important to the development of protective strategies that may reduce infarct size or attenuate reperfusion-induced myocardial injury, or both. Selective calcium antagonists, beta blockers, and phospholipase antagonists or inhibitors may reduce infarct size in association with early reperfusion. Reperfusion injury may be attenuated by free radical scavengers and calcium antagonists. Reinfarction, after the initial event, may ultimately be reduced in frequency by pharmacologic strategies that interfere with platelet adhesion, aggregation, and mediator release from activated platelets and white cells that promote further platelet aggregation or induce coronary artery vasoconstriction. Included among protective strategies are thromboxane receptor antagonists and synthesis inhibitors, serotonin receptor antagonists, possibly leukotriene synthesis inhibitors or receptor antagonists, and aspirin. Future clinical trials should test the combined efficacy of reperfusion and selected pharmacologic strategies that alter calcium accumulation in the injured myocardium, diminish the injurious effects of beta- and alpha-adrenergic mechanisms and oxygen-derived free radicals on injured myocytes, and prevent reocclusion mediated by platelets and platelet mediators.     

Inhibition of Rho-kinase protects the heart against ischemia/reperfusion injury

OBJECTIVE: To investigate the role of Rho A and Rho-kinase in acute myocardial ischemia/reperfusion injury and the protective effect of Rho-kinase inhibitor, Y-27632 [(R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide]. METHODS AND RESULTS: Male CD1 mice were subjected to 30 min of coronary occlusion and 24 h reperfusion. Ischemia/reperfusion upregulated expression of Rho A in ischemic myocardium, and subsequently activated Rho-kinase. Y-27632 significantly inhibited the activation of Rho-kinase following ischemia/reperfusion. Treatment with Y-27632 at 10 and 30 mg/kg oral administration, reduced infarct size by 30.2% and 41.1%, respectively (P<0.01 vs. vehicle). Y-27632 also enhanced post-ischemia cardiac function. Left ventricular systolic pressure, +dP/dt and -dP/dt were significantly improved by 23.5%, 52.3%, and 59.4%, respectively (P<0.01 vs. vehicle). Moreover, Y-27632 reduced ischemia/reperfusion-induced myocardial apoptosis. The apoptotic myocytes in ischemic myocardium after 4 h reperfusion were reduced from 13.1% in vehicle group to 6.4% in Y-27632-treated group (P<0.01). Meanwhile, ischemia/reperfusion-induced downregulation of Bcl-2 in myocardium was remarkably attenuated in the treated animals. Ischemia/reperfusion resulted in remarkable elevation in serum levels of proinflammatory cytokines, interleukin-6 (IL-6), keratinocyte chemoattractant (KC) and granulocyte colony-stimulating factor (G-CSF), which was significantly suppressed by Y-27632. In addition, Y-27632 decreased ischemia/reperfusion-induced accumulation of neutrophils in the heart by 45% (P<0.01). CONCLUSIONS: These results suggest that Rho-kinase plays a pivotal role in myocardial ischemia/reperfusion injury. The cardiac protection provided by treatment with a selective Rho-kinase inhibitor is likely via anti-apoptotic effect and attenuation of ischemia/reperfusion-induced inflammatory responses. The finding of this study suggest a novel therapeutic approach to the treatment of acute myocardial ischemia/reperfusion injury.     

腺苷介导大鼠心脏缺血后适应的保护效应

目的观察大鼠心肌缺血再灌注时NFκ-B mRNA表达和炎性细胞因子的变化及腺苷后适应对其影响,初步探讨腺苷后适应对缺血再灌注损伤心肌的保护机制。方法健康雄性SD大鼠48只随机分为4组:假手术组、缺血再灌注组、缺血后处理组及腺苷后适应组,每组12只,建立大鼠心肌缺血再灌注模型。光镜下观察心肌组织形态学改变;TTC染色计算各组大鼠心肌梗死面积;RT-PCR检测心肌NF-κB mRNA表达水平,ELISA测定组织中TNF-α及白细胞介素6(IL-6)含量。结果假手术组心肌组织无改变,缺血再灌注组心肌损伤较重,腺苷后适应组及缺血后处理组心肌组织病理学改变明显减轻。与缺血再灌注组比较,腺苷后适应组NF-κB mRNA的表达水平、心肌梗死面积及TNF-α与IL-6的含量明显降低(P<0.01);与缺血后处理组比较,腺苷后适应组NFκ-B mRNA表达及TNF-α、IL-6的分泌均下降(P<0.05)。NFκ-B mRNA的表达与心肌中TNF-α、IL-6浓度呈正相关(P<0.01)。结论腺苷后适应可抑制再灌注后心肌NF-κB的表达活化,从而通过促使炎性细胞因子TNFα-、IL-6分泌减少来减轻缺血再灌注损伤。     

Ischemia/reperfusion injury is increased and cardioprotection by a postconditioning protocol is lost as cardiac hypertrophy develops in nandrolone treated rats

We hypothesized that nandrolone (ND)-abuse induces cardiac hypertrophy, increases myocardial susceptibility to ischemia/reperfusion (I/R) injury, and reduces responsiveness to postconditioning (PostC) cardioprotection. Wistar-rats were ND treated for 2 weeks (short_ND) or 10 weeks (long_ND). Vehicle-treated rats served as controls. Hearts were retrogradely perfused and left ventricular pressure (LVP) was measured before and after 30-min global ischemia. In subgroups of hearts, to induce cardioprotection a PostC protocol (five cycles of 10-s reperfusion and 10-s ischemia) was performed. β-adrenoreceptors, kinases (Akt and GSK-3β) and phosphatases (PP2A sub A and PP2A sub B) were examined by Western blot before and after ischemia. After 120-min reperfusion, infarct size was measured. Short_ND slightly increased cardiac/body weight ratio, but did not affect cardiac baseline nor post-ischemic contractile function or infarct size when compared to vehicle hearts. However, PostC limited cardiac dysfunction much more in short_ND hearts than the other groups. Although cardiac/body weight ratio markedly increased after long_ND, baseline LVP was not affected. Yet, post-ischemic contracture and infarct size were exacerbated and PostC was unable to reduce infarct size and ventricular dysfunction. While short_ND increased phosphatases, non-phosphorylated and phosphorylated Akt, long_ND reduced phosphatase-expression and Akt phosphorylation. Both short_ND and long_ND had no effect on the GSK-3β-phosphorylation but increased the expression of β₂-adrenoreceptors. In reperfusion, PostC increased Akt phosphorylation regardless of protective effects, but reduced phosphatase-expression in protected hearts only. In conclusion, short_ND improves post-ischemic myocardial performance in postconditioned hearts. However, long_ND increases myocardial susceptibility to I/R injury and abolishes cardioprotection by PostC. This increased susceptibility might be related to steroid-induced hypertrophy and/or to altered enzyme expression/phosphorylation.     

The Paradoxical Role of Inflammation in Cardiac Repair and Regeneration

Inflammation has emerged as a critical biological process contributing to nearly all aspects of cardiovascular diseases including heart failure. Heart failure represents the final consequence of a diverse set of initial insults to the myocardium, among which myocardial infarction (MI) is the most common cause. After MI, the lack of perfusion often leads to the death of cardiomyocytes. The necrotic cells trigger a cascade of inflammatory pathways that work to clear the dead cells and matrix debris, as well as to repair and heal damaged tissues. For the heart, an organ with limited regeneration capacity, the consequence of MI (termed post-MI remodeling) comprises a series of structural and functional changes, including scar formation at the infarct zone, reactive hypertrophy of the remaining cardiomyocytes at the noninfarct area, ventricular chamber dilatation, and molecular changes marked by fetal gene up-regulation, all of which have been linked to the activation of the inflammatory pathways. Inadequate or excessive inflammatory response may lead to improper cellular repair, tissue damage, and dysfunction. Herein, we summarize the current understanding of the role of inflammation in cardiac injury and repair and put forth the hypothesis that temporally regulated activation and suppression of inflammation may be critical for achieving effective cardiac repair and regeneration.     

Oxygen-derived free radicals and myocardial reperfusion injury: An overview

Reperfusion of acutely ischemic myocardium is associated with various distinctive pathophysiologic derangements, which are collectively referred to as reperfusion injury. Among these, three have been atributed to oxygen radicals: a) arrhythmias, b) transient mechanical dysfunction (“stunning”), and c) cell death. a) Reperfusion-induced arrhythmias. Although the precise mechanism for reperfusion arrhythmias remains to be determined, considerable evidence suggests that oxygen radicals play an important pathogenetic role in these rhythm disturbances. b) Transient mechanical dysfunction (“myocardial stunning”). Studies suggest that this abnormality is caused by events occurring in the initial seconds of reperfusion, and therefore represents a manifestation of sublethal, reversible reperfusion injury. Although our understanding of the mechanism of myocardial stunning is still fragmentary, there is overwhelming evidence for a pathogenetic role of oxygen radicals. c) Cell death. The evidence that reperfusion causes extension of the infarct produced by the antecedent ischemia is highly controversial. Although several studies have reported reduction of infarct size with antioxidants applied at the time of reperfusion, numerous other investigations have failed to reproduce these results. At present, there is no obvious explanation for this discrepancy. What is clear is that short-term administration of antioxidants at the time of reperfusion will not produce sustained limitation of infarct size. However, the possibility that long-term administration of antioxidants will produce sustained limitation of infarct size merits further consideration. In conclusion, there is strong evidence that the generation of oxygen radicals upon reperfusion plays an important pathogenetic role in two manifestations of reperfusion injury, namely, arrhythmias and stunning. Intense controversy persists regarding whether oxygen radicals contribute to extending cell death upon reperfusion and whether reperfusion in itself causes cell death. On the basis of the evidence available at this time, oxygen radicals appear to be important in the genesis of relatively mild, sublethal forms of myocellular damage, but their role in the genesis of lethal myocellular injury remains to be established.     

A Single Intravenous sTNFR-Fc Administration at the Time of Reperfusion Limits Infarct Size—Implications in Reperfusion Strategies in Man

Background  Reperfusion of the ischemic myocardium is associated with increased inflammatory processes that can exert deleterious effects and therefore contribute to cardiac dysfunction. The aim of the present study was to verify whether the administration of sTNFR-Fc, a scavenger of the pro-inflammatory cytokine TNF-α, at the time of reperfusion would protect against myocardial infarction and reduce the severity of early mechanical dysfunction. Methods  Male Wistar rats were subjected to 60 min coronary occlusion followed by reperfusion. A bolus of sTNFR-Fc (10 μg/kg, i.v.) (MI + sTNFR-Fc group) or a placebo (MI group) was injected prior to reperfusion. Cardiac geometry was assessed by echocardiography 1, 3 and 7 days after reperfusion. Eight days after reperfusion, left ventricular (LV) function was evaluated under basal conditions and during an experimental challenge of volume overload. Finally, infarct size was measured after euthanasia. Results  sTNFR-Fc administration markedly reduced infarct size (P < 0.01) and decreased LV dilation as assessed by the echocardiographic measurement of the LV end diastolic area, 7 days post-MI (P < 0.01). Moreover, LV end-diastolic pressure was significantly preserved by sTNFR-Fc 1 week after myocardial infarction, under basal conditions (P < 0.05) as well as during cardiac overload (P < 0.05). Conclusion  A single administration of sTNFR-Fc at the time of reperfusion after myocardial infarction is able to limit infarct size and to reduce early LV diastolic dysfunction in rats. These findings suggest that intravenous neutralization of TNF-α during surgical cardiac reperfusion might improve the outcome of myocardial infarction in humans.     

Long-term inhibition of myocardial infarction by postconditioning during reperfusion

Cardioprotection with postconditioning has been well demonstrated after a short period of reperfusion. This study tested the hypothesis that postconditioning reduces infarct size, vascular dysfunction, and neutrophil accumulation after a long-term reperfusion. Canines undergoing 60 min left anterior descending artery (LAD) occlusion were divided into two control groups of either 3 h or 24 h of full reperfusion and two postconditioning groups with three 30 s cycles of reperfusion and re-occlusion applied at the onset of either 3 h or 24 h of reperfusion. Size of the area at risk (AAR) and collateral blood flow during ischemia were similar among groups. In controls, infarct size as percentage of the AAR (30 ± 3 vs. 39 ± 2* %) by TTC staining, superoxide anion generation from the post-ischemic coronary arteries by lucigenin-enhanced chemiluminescence [(89 ± 5 vs. 236 ± 27* relative light units (RLU/mg)], and neutrophil (PMN) accumulation by immunohistochemical staining in the AAR (52 ± 11 vs. 84 ± 14* cells/mm² myocardium) significantly increased between 3 and 24 h of reperfusion. Postconditioning reduced infarct size (15 ± 4† and 27 ± 3.6† %), superoxide anion generation (24 ± 4† and 43 ± 11† RLU/mg), and PMN accumulation (19 ± 6† and 45 ± 8† cells/mm² myocardium) in the 3 and 24 h reperfusion groups relative to time-matched controls. These data suggest that myocardial injury increases with duration of reperfusion; reduction in infarct size and attenuation in inflammatory responses with postconditioning persist after a prolonged reperfusion. * p < 0.05 24 vs. 3 h control; † p < 0.05 postconditioning vs. time-matched control.     

缺血后适应减轻家兔急性心肌缺血/再灌注损伤的作用研究

目的: 探讨缺血后适应减轻家兔急性缺血/再灌注损伤的作用。方法: 将56只大耳白兔随机分为对照组(n=28)及缺血后适应组(n=28)。采用夹闭左室支40 min,再灌注3 h方法建立兔急性心肌梗死-再灌注模型。对照组不施加干预,缺血后适应组于再灌注开始初再次缺血30 s、再灌注30 s,连续重复3次循环后,恢复冠脉血流,观察两组兔于再灌注前至再灌注后2 h期间心电的变化;并测定缺血前、灌注0 h、1 h及3 h血清丙二醛（MDA）、超氧化物岐化酶（SOD）及谷胱甘肽过氧化物酶（GSH-PX）水平的变化。实验结束后,两组中各随机处死半数兔用伊文氏蓝及氯化三苯基四氮唑红（TTC）染色法,测定心肌梗死的面积;另半数兔于4 周后进行经胸心脏超声心动图检查。结果: 缺血后适应组再灌注2 h末心肌再灌注的有效率（心肌获得有效再灌注的百分比率）高于对照组(P<0.05);而心肌梗死的面积低于对照组(P<0.05)。缺血后适应组再灌注1 h血清MDA的水平低于对照组;SOD、GSH-PX的活性高于对照组(P<0.05)。心肌梗死4周后,心脏超声检查缺血后适应组左室后壁室壁的厚度及收缩期室壁增厚率△T均明显高于对照组(P<0.05);左室射血分数(LVEF)、左室缩短分数(LVFS)较对照组明显改善(P<0.05)。结论: 缺血后适应可通过抑制再灌注早期氧自由基的活化,减轻心肌急性缺血/再灌注损伤,改善心肌的有效灌注,降低心肌梗死的面积及减轻心梗近期（恢复期）心脏结构与功能的损害。     

Dl-3-n-butylphthalide attenuates myocardial ischemia reperfusion injury by suppressing oxidative stress and regulating cardiac mitophagy via the PINK1/Parkin pathway in rats

BackgroundAcute myocardial infarction (AMI) is one of the leading causes of mortality worldwide. Undesirable myocardial damage may occur during reperfusion of the ischemic myocardium, and this is known as “ischemic reperfusion injury” (IRI). Currently, there are few effective drugs to alleviate IRI. Dl-3-n-butylphthalide (NBP) is recommended for the treatment of acute ischemic stroke in China. This study investigated the effects of NBP on IRI and its underlying mechanisms.MethodsThe left anterior descending (LAD) coronary arteries of rats were occluded for 30 minutes and reperfused for 6 hours to establish the ischemia/reperfusion (I/R) model. NBP was administered intraperitoneally 2 hours before modeling and immediately after reperfusion. At 6 hours after reperfusion, 2,3,5-triphenyltetrazolium chloride (TTC) staining, enzyme-linked immunosorbent assay (ELISA), oxidative stress index, myocardial injury index, hematoxylin and eosin (HE) staining, transmission electron microscopy (TEM), real-time polymerase chain reaction (PCR), immunofluorescence staining, and Western blot analyses were performed to investigate the protective effects of NBP against IRI.ResultsIn the rat I/R model, NBP remarkably reduced the myocardial infarct size, alleviated myocardial injury and oxidative stress, improved the pathological alteration of cardiomyocytes and mitochondria, and upregulated mitophagy. In addition, the study demonstrated that the protective effects of NBP against IRI involved mitophagy mediated by the PTEN-induced putative kinase protein-1 (PINK1)/Parkin signaling pathway.ConclusionsNBP was able to protect the myocardium from IRI in rats through inhibiting oxidative stress and activating mitophagy, mediated by the PINK1/Parkin pathway.     

Effect of sulfur dioxide preconditioning on rat myocardial ischemia/reperfusion injury by inducing endoplasmic reticulum stress

Sulfur dioxide has recently been found to be produced endogenously in the cardiovascular system and have important positive biological effects. However, it is unknown whether sulfur dioxide preconditioning has a protective effect on rat myocardial ischemia/reperfusion (I/R) injury and whether this process involves endoplasmic reticulum stress (ERS). In this study, we showed that preconditioning with sulfur dioxide 10 min before ischemia (with a low concentration of sulfur dioxide of 1–10 μmol/kg) could reduce myocardial infarct size and plasma activities of lactate dehydrogenase and creatine kinase in rats with I/R in vivo. Sulfur dioxide preconditioning also reduced myocardium apoptosis induced by I/R. In addition, sulfur dioxide preconditioning increased cardiac function in vitro. Sulfur dioxide preconditioning induced expression of myocardial glucose-regulated protein 78 (GRP78) and phosphorylated eukaryotic initiation of the factor 2α-subunit (p-eIF2α) prior to myocardial I/R but suppressed expression of myocardial GRP78, C/EBP homologous protein, and p-eIF2α during myocardial I/R, in association with improved myocardial injury in vivo and in vitro. Pretreatment with dithiothreitol, an ERS stimulator mimicked the above cardioprotective effect. However, pretreatment with the ERS inhibitor 4-phenylbutyrate reversed the cardioprotection provided by sulfur dioxide preconditioning. These data indicated that sulfur dioxide preconditioning reduced I/R-induced myocardial injury in vivo and in vitro, and that augmenting ERS by sulfur dioxide preconditioning prior to I/R contributed to protection against myocardial I/R injury.     

Mechanisms and Consequences of Inflammatory Signaling in the Myocardium

To further understand chronic heart disease, such as heart failure and cardiomyopathy, we must fully define signaling pathways within the myocardium. Recent studies suggest that some forms of heart disease are associated with a chronic low-grade inflammation that promotes adverse ventricular remodeling and correlates with disease progression. Several inflammatory mediators, including TNF-??, IL-1??, and IL-6, are involved in cardiac injury subsequent to myocardial ischemia and reperfusion, sepsis, viral myocarditis, and transplant rejection. Once activated, components of the inflammatory response can have both beneficial and deleterious effects on the heart. In this review, we discuss the complex inflammatory signaling pathways in the myocardium and potential therapeutic implications.