心肌梗塞非梗塞区心肌重构中炎症反应的研究进展

心肌梗塞(MI)后伴随着一系列的炎症反应(inflammato- ry response,IR),这是心肌损伤修复和瘢痕形成的前提。以往的研究集中于 IR 在 MI 愈合阶段的作用,却忽略了 IR 对心室重构的潜在损害。有资料表明 MI 后几小时内就可诱发 IR, 过度和持久的 IR 在急性期有对损伤的修复作用,但在后期还可导致梗塞区和非梗塞区的心肌纤维化,从而使心功能受损, 进而导致心衰的发生。本文就 MI 后炎症因子的激活,炎症细胞的浸润及 IR 导致非梗塞区心肌重构的机制等进行阐述。     

温阳通脉方预处理对心肌缺血再灌注大鼠MDA及SOD的影响

目的 观察温阳通脉方预处理对大鼠心肌缺血再灌注损伤（IR）模型丙二醛（MDA）、超氧化物歧化酶（SOD）含量的影响，探讨温阳通脉方对大鼠再灌注心肌的保护机制。方法 采用结扎大鼠冠状动脉左前降支，缺血30min，再灌注120min的方法建立心肌缺血再灌注损伤模型；缺血5min，再灌注5min，反复3次后缺血30min，再灌注120min建立心肌缺血预适应（IP）模型。检测大鼠灌胃14d后温阳通脉方组、心肌缺血预适应组（IP组）、再灌注损伤纽（IR组）、假性处理组血清MDA、SOD含量。结果 温阳通脉方组、IP组MDA含量低于IR组，SOD高于IR组，差异有统计学意义（P〈0．05）。结论 温阳通脉方预处理后，能降低大鼠心肌缺血再灌注损伤模型MDA含量，升高SOD含量，减轻大鼠急性心肌缺血所致心肌损伤，其机制可能是通过模拟心肌缺血预适应参与心肌保护作用。     

前列地尔后处理对离体大鼠缺血再灌注损伤心肌的影响

目的:采用Langendorff离体心脏灌注模型,探讨前列地尔后处理对离体大鼠缺血再灌注损伤心肌的影响及其机制。方法:24只SD大鼠随机分为:缺血再灌注损伤组(IR组)、前列地尔预处理组(ALP-PreC组)、前列地尔后处理组(ALP-PostC组),每组8只。检测平衡液灌注末及再灌注后不同时间点心功能、冠脉流出液及再灌注末心肌组织中生化指标和心肌梗死面积百分比。结果:平衡末,冠脉流出液中乳酸脱氢酶(LDH)、肌酸激酶(CK)、肿瘤坏死因子(TNF)-α含量,各组间无显著性差异(P均>0.05),再灌注后各组LDH、CK、TNF-α均有显著增加,再灌注后ALP-PreC组和ALP-PostC组各时间点的CK、LDH、TNF-α释放量均明显低于IR组(P<0.05)。ALP-PreC组和ALP-PostC组超氧化物歧化酶(SOD)活性显著高于IR组(P<0.01),丙二醛(MDA)含量低于IR组(P<0.05)。ALP-PreC组和ALP-PostC组心肌梗死面积百分比明显低于IR组(34.48%、32.84%比39.29%,P<0.05),ALP-PreC组和ALP-PostC组之间差别无显著性(P>0.05)。结论:前列地尔后处理可以对缺血再灌注心肌发挥保护作用,其机制可能与抑制早期炎症反应,抑制再灌注后氧自由基的过量生成,增强心肌抗氧化能力,从而发挥保护作用。     

吸入麻醉药后处理心肌保护作用的研究进展

吸入麻醉药可模拟缺血后处理发挥心肌保护效应,因为能够在心肌缺血后早期再灌注时实施而有着广泛的临床应用前景。吸入麻醉药后处理产生的心肌保护作用与抑制钙超载、增强一氧化氮的保护作用、激活再灌注损伤补救激酶途径、开放三磷酸腺苷敏感性钾通道和抑制线粒体通透性转换孔开放等机制有关,现就吸入麻醉药后处理对心肌缺血-再灌注损伤的保护作用及其机制做一综述。     

心肌缺血预适应保护机制的研究进展

心肌遭受一次或几次反复的短暂缺血再灌注后,表达出一种对随后而来的长时间缺血损伤抵抗能力的增强,称为缺血预适应(IPC).主要表现能缩小心肌梗死的面积,改善心肌收缩力,保护冠状动脉内皮和心肌细胞的超微结构,降低心律失常的发生率,更快地使心肌从再灌注中恢复心肌顿抑等.早期保护产生在预缺血后3 h内,延迟保护产生在预缺血后24～72 h之间.心肌IPC的保护机制目前尚未完全阐明,研究资料主要可分为特异性和非特异性受体依赖型的保护机制.本文就目前IPC的保护机制研究现状综述如下.     

巨噬细胞在心肌缺血再灌注损伤中的作用

正心肌梗死是当今世界范围内心血管事件死亡的主要原因,及时有效的恢复冠状动脉血流是治疗心肌梗死等缺血性心脏病的有效方法,但恢复血运过程中,会引起心肌的组织结构、能量代谢、电生理及心功能的损伤,这种现象称为心肌缺血再灌注(IR)损伤~([1])。心肌IR通常会导致4种类型心肌功能障碍:心肌顿抑、无复流现象、再灌注心律失常和致死性再灌注损伤。其发病机制有线粒体功能障碍、钙超载、白细胞浸润以及炎症和能量耗竭等。IR过程会导致心脏炎症级联反应,过度炎性反应对存活的心肌细胞造成进一步的损伤,抑制这种炎性反应可以减轻心肌损伤~([2])。有效的治疗方法不仅要减少炎性反应的损害,还要促进修复途径的激活,为满足这种需求,研究者把目光转向巨噬细胞。巨噬细胞是心脏炎症的中枢介质,不仅参与炎症启动和消退,还参与组织修复,靶向巨噬细胞可能成为IR损伤新的治疗手段~([3])。本综述就组织巨噬细胞的来源、分型和功能,以及巨噬细胞对心肌IR损伤的影响最新研究进展等方面进行阐述。     

缺血预处理减轻肥厚心肌缺血再灌注损伤及其信号途径

目的探讨缺血预处理(IPC)对肥厚心肌体外缺血再灌注(IR)损伤的影响及其信号机制。方法48只心肌肥厚大鼠随机分为4组:IR对照组I、PC组I、PC加磷脂酰肌醇-3激酶(PI3K)抑制剂Wortmannin处理组、Wortmannin处理对照组,观察IPC对心肌肥厚大鼠体外IR心脏左心室收缩压、冠状动脉流量、肌酸磷酸激酶(CPK)和乳酸脱氢酶(LDH)释放、心肌梗死范围以及心肌蛋白激酶B(Akt)、糖原合成酶激酶-3β(GSK-3β)磷酸化的影响。结果与IR对照组比较,IPC组心脏左心室收缩压、冠状动脉流量显著提高,CPK、LDH释放减少,心肌梗死范围减小,心肌Akt、GSK-3β磷酸化水平增高,Wortmannin能够抑制IPC所致的Akt、GSK-3β磷酸化,但只能部分消除IPC的心脏保护效应。结论IPC能够减轻心肌肥厚大鼠体外心脏IR损伤,PI3K、Akt、GSK-3β信号途径参与介导IPC对体外IR肥厚心肌的保护作用。     

胰岛素抵抗大鼠心脏间质和心肌细胞变化的实验研究

目的探讨胰岛素抵抗(IR)对心肌组织的损伤作用。方法6月龄Wistar大鼠,分为正常对照组和IR组,正常血糖胰岛素钳夹技术(EICT)测定各组大鼠IR,葡萄糖输注速率(GIR)表示IR情况;测量大鼠心脏重量(HW)和体重(BW)并计算心脏重量与体重之比(HW/BW);原位末端酶标记法(TUNEL)检测各组大鼠心肌细胞凋亡情况;观察心脏微细结构和心肌细胞超微结构;免疫组化检测心脏间质Ⅰ、Ⅲ型胶原水平。结果IR组大鼠GIR明显低于正常对照组(P<0.01),HW及HW/BW高于正常对照组,心肌细胞凋亡增多(P<0.01),GIR与心肌细胞凋亡指数呈负相关(r=-0.7452,P<0.05),心脏间质Ⅰ、Ⅲ型胶原水平增加(Ⅰ型胶原P<0.05,Ⅲ型胶原P<0.01);光镜和电镜可见IR组大鼠心肌组织发生损伤性改变。结论胰岛素抵抗可损伤心肌组织,导致心脏肥大、心肌细胞凋亡、心脏间质纤维化。     

TLR-4信号通路在小鼠心肌缺血再灌注损伤中的作用

目的探讨toll样受体-4(TLR-4)信号转导通路在心肌缺血再灌注(IR)损伤中的作用。方法雄性TLR-4突变小鼠及野生型小鼠为实验对象,分为C3H/Hej及C57BL/6组,各组随机分为假手术组及IR组,比较观察两种小鼠IR后心肌梗死面积,检测心肌丙二醛(MDA)、超氧化物歧化酶(SOD)、髓过氧化物酶(MPO)活性以及血清中肿瘤坏死因子-α(TNF-α)、白介素-1(IL-1)、白介素-6(IL-6)、单核细胞趋化蛋白-1(MCP-1)的浓度,采用Western印迹法检测缺血心肌中TLR-4蛋白表达水平。结果 TLR-4突变小鼠与野生型小鼠相比较,能显著降低再灌注心肌损伤及梗死面积,提高心肌中SOD活性,降低心肌中MDA、MPO水平,血清中TNF-α、IL-1、IL-6、MCP-1的表达也明显降低,Western印迹所显示的TLR-4的蛋白表达水平在心肌缺血后上升(P<0.05)。结论 TLR-4信号通路在心肌IR损伤中发挥重要作用,TLR-4突变后能减弱其后信号转导从而减轻心肌IR损伤及炎症反应。     

NLRP3在大鼠急性心肌缺血再灌注免疫损伤中的作用

目的:研究NOD样受体蛋白3(NLRP3)、白细胞介素-6(IL-6)在大鼠心肌缺血再灌注(IR)损伤模型中的表达变化。方法:选择雄性SD大鼠60只,设置IR组30只和假手术组30只。IR组在呼吸机辅助呼吸的前提下,开胸挤出心脏,结扎前降支主干1h,再灌注1h,建立大鼠IR模型。假手术组穿线但不结扎前降支主干,余操作同IR组。造模成功后将心脏组织进行免疫组织化学检测NLRP3的含量,ELISA检测心肌IL-6表达情况。结果:IR组NLRP3较假手术组明显升高,差异有统计学意义(t=55.138,P0.05);IR组IL-6样本浓度较假手术组明显升高,差异有统计学意义(t=68.106,P0.05);对于2个变量进行线性相关分析,差异有统计学意义(R=0.989,P0.05),两者存在正相关性。结论:大鼠心肌IR损伤后NLRP3炎性体表达增加,激活先天免疫系统,促进IL-6的表达增多。     

Pathophysiology of superoxide radical as potential mediator of reperfusion injury in pig heart

Summary The role of oxygen0derived free radicals in myocardial reperfusion injury was studied using the isolated in situ pig heart model. The free radical scavengers, superoxide dismutase (SOD) and catalase, protected the ischemic pig heart subjected to one hour of normothermic regional ischemia followed by one hour of global hypothermic arrest and one hour normothermic reperfusion. A significant increase in thiobarbituric acid reactive material and oxidized glutathione appeared in the perfusate demonstrating free radical-mediated lipid peroxidation during reperfusion, and this was prevented by the addition of SOD plus catalase. The values of three important antioxidative enzymes, SOD, catalase, and glutathione peroxidase, showed reduced activities after 2 hours of ischemia. These values did not change significantly after 60 minutes of reperfusion following the 2 hours ischemic insult. The concentrations of high-energy phosphate compounds including creatine phosphate (CP), adenosine triphosphate (ATP), and total adenine nucleotide were reduced significantly during ischemia and reperfusion in hearts which were not protected by SOD and catalase. The plasma creatine phosphokinase levels were lowered appreciably as a result of SOD and catalase treatment. It may be concluded from these experiments that oxygen-derived free radicals are present during reperfusion and SOD and catalase play a significant role in the protection of ischemic myocardium from reperfusion injury.     

心脏直视手术再灌注时血浆和心肌组织氧自由基及超微结构改变的观察

为进一步探讨心脏直视手术患者血浆、心肌组织氧自由基变化及临床意义，对１５例心脏直视手术患者血浆、心肌组织丙二醛（ＭＤＡ）含量及超氧化物歧化酶（ＳＯＤ）活性进行测定，并对心肌组织进行超微结构观察。结果表明，血浆ＭＤＡ含量在体外循环过程中逐渐升高，心脏复跳后较缺血期更明显，而血液ＳＯＤ活性呈下降趋势；心肌组织缺血再灌注后ＭＤＡ含量较心脏停跳前、停跳后明显增加，而ＳＯＤ活性降低。心脏复跳后，心肌组织超微结构损害较停跳后更明显．这一结果提示，心肌组织氧自由基的产生主要是在再灌注期，是心肌缺血再灌注损伤的重要原因。     

Direct detection of oxygen free radicals produced by myocardial reperfusion using electron spin resonance spectroscopy

There is a growing evidence for the role of oxygen free radicals (OFR) in mediating myocardial tissue injury during myocardial ischemia and particularly during reperfusion. But almost all of the evidence was indirect, using electron spin resonance (ESR) spectroscopy, we have directly measured OFR generated in ischemic and reperfused isolated rabbit hearts. 17 hearts were rapidly frozen in liquid nitrogen after their arrest by cardioplegic solution and sampled after 150 min of sustained hypothermic global ischemia or after reperfusion. The ESR spectra obtained from experiment have directly demonstrated that OFR is produced in significant amounts in the isolated rabbit hearts during early stage of reperfusion but only small amount during ischemia. The mitochondrial electron transport chain appeared to be the main source of OFR. We found that superoxide dismutase scavenged OFR generated during reperfusion efficiently, but catalase did not. We believe that superoxide anion, not hydroxyl radical, is the main OFR which is responsible for myocardial reperfusion injury. We also found that Salvia, a traditional Chinese medicine, a very efficient OFR scavenger, had the similar effect as superoxide dismutase.     

Oxygen free radicals and cardiac reperfusion abnormalities.

Oxygen free radicals are highly reactive compounds causing peroxidation of lipids and proteins and are thought to play an important role in the pathogenesis of reperfusion abnormalities including myocardial stunning, irreversible injury, and reperfusion arrhythmias. Free radical accumulation has been measured in ischemic and reperfused myocardium directly using techniques such as electron paramagnetic resonance spectroscopy and tissue chemiluminescence and indirectly using biochemical assays of lipid peroxidation products. Potential sources of free radicals during ischemia and reperfusion have been identified in myocytes, vascular endothelium, and leukocytes. In several different experimental models exogenous free radical-generating systems have been shown to produce alterations in cardiac function that resemble the various reperfusion abnormalities described above. Injury to processes involved in regulation of the intracellular Ca2+ concentration may be a common mechanism underlying both free radical-induced and reperfusion abnormalities. Direct effects of free radicals on each of the known Ca(2+)-regulating mechanisms of the cell as well as the contractile proteins and various ionic membrane currents have been described. Free radicals also inhibit critical enzymes in anaerobic and aerobic metabolic pathways, which may limit the metabolic reserve of reperfused myocardium and contribute to intracellular Ca2+ overload. Inhibiting free radical accumulation during myocardial ischemia/reperfusion with free radical scavengers and inhibitors has been demonstrated to reduce the severity of myocardial stunning, irreversible injury, and reperfusion arrhythmias in many, but not all, studies. This evidence strongly implicates free radical accumulation during myocardial ischemia/reperfusion as an important pathophysiological mechanism of reperfusion abnormalities, although many issues remain unresolved.     

Deleterious effects of oxygen radicals in ischemia/reperfusion. Resolved and unresolved issues

Oxygen free radicals are known to be generated during periods of ischemia followed by reperfusion. There is still some controversy, however, concerning the use of electron paramagnetic resonance spectroscopy to accurately detect and identify the free radical species that are formed. There is no doubt that oxygen radicals are deleterious to the myocardium; free radicals cause left ventricular dysfunction and structural damage to myocytes and endothelial cells in both in vitro and in vivo preparations. Potential sources of these cytotoxic oxygen species include the xanthine oxidase pathway, activated neutrophils, mitochondria, and arachidonate metabolism, yet the crucial source of free radicals in the setting of ischemia and reperfusion is unresolved. There is little doubt that oxygen radicals play a role in the phenomenon of stunned myocardium induced by brief periods of ischemia followed by reperfusion; numerous studies have consistently observed that pretreatment with free radical scavengers and antioxidants enhances contractile function of stunned, postischemic tissue. Whether oxygen free radical scavengers administered only during reperfusion enhance recovery of stunned myocardium in models of brief ischemia remains to be determined. In models of prolonged ischemia (2 hours) followed by reperfusion, we have not observed a beneficial effect of scavengers on stunned myocardium. The issue of whether oxygen free radical scavengers are capable of reducing so-called irreversible or lethal reperfusion injury remains, in our opinion, unresolved. Although some studies have observed that agents such as superoxide dismutase and catalase reduce infarct size in ischemia and reperfusion models, many others have reported negative results. Additional studies will be needed to resolve this ongoing controversy. Oxygen free radicals may also contribute to reperfusion-induced arrhythmias in rodent heart preparations; however, less data are available in other animal models. The concept of reperfusion injury should not be considered a deterrent to reperfusion for the treatment of acute myocardial infarcts in the clinical setting. Thrombolytic therapy reduces myocardial infarct size, enhances recovery of left ventricular function, and improves survival. Whether incremental beneficial effects on these parameters will be obtained when oxygen radical-scavenging agents are used as adjuvant therapy to thrombolysis in patients remains to be determined.     

The oxygen free radical system: potential mediator of myocardial injury

The sequential univalent reduction of oxygen gives rise to very reactive intermediate products including superoxide anion radical, hydrogen peroxide and free hydroxyl radicals. Normally, the tissue concentration of these intermediate products of oxygen is severely limited; however, if oxygen free radicals are produced in excess of the capacity of the tissues to eliminate them, they may cause serious damage. The biochemistry and possible sources of free radical generation in animal models of ischemic/reperfusion injury are reviewed. The ability of scavengers of oxygen free radicals to improve mechanical, mitochondrial and sarcoplasmic reticulum function in animal models of ischemic/reperfusion injury suggests that oxygen free radicals are partly responsible for myocardial injury in these models. Future research should be directed at establishing the relevance of oxygen radical-mediated myocardial injury in the experimental setting to analogous clinical situations.     

Molecular oxygen: friend and foe. The role of the oxygen free radical system in the calcium paradox, the oxygen paradox and ischemia/reperfusion injury

We strongly support the original intriguing hypothesis of Hearse et al. that the oxygen paradox and the calcium paradox are facets of the same problem. We would propose that the major similarity is a final common pathway leading to intracellular calcium overload and the sequelae of the resultant increase in intracellular calcium. In addition, we would propose that the oxygen paradox and ischemic/reperfusion injury are also facets of the same problem with the major similarity being the reintroduction of molecular oxygen to a previously hypoxic myocardium. Finally, we would suggest that the common pathway leading to intracellular calcium overload in the oxygen paradox and ischemic/reperfusion injury and to a lesser extent the calcium paradox involves the generation of oxygen free radicals. The source of oxygen free radical generation in the calcium paradox is perhaps less obvious than in the oxygen paradox. It is proposed that during calcium-free perfusion, calcium is leached from the plasmalemma of the myocyte. There is a resulting increase in membrane fluidity. Within the plasmalemma are a number of calcium sensitive phospholipases. Upon reperfusion with a calcium replete medium, calcium could pool around these membrane bound phospholipases initiating a chain reaction of lipid peroxidation which actually is perpetuated by free radical generation (Equations 5A-5C). Lipid peroxidation opens channels within the plasmalemma rendering a 'leaky' sarcolemma. It is through these channels that calcium could flow down its concentration gradient into the cell. The increased calcium accumulation at the mitochondria would lead to an uncoupling of oxidative phosphorylation. With depleted energy stores, the mitochondria and sarcoplasmic reticulum no longer serve as calcium sinks. This would contribute to the calcium overload seen upon reperfusion. The role of oxygen free radical production would appear to occur during the hypoxic phase of the oxygen paradox and the ischemic phase of ischemic/reperfusion injury and during the reoxygenation/reperfusion phases. With the onset of hypoxia and/or myocardial ischemia there is an increase in reducing equivalents, disturbance and dissociation of intramitochondrial electron transport and release of ubisemiquinone, flavoproteins and superoxide radicals. The increase in reducing equivalents includes NADPH and, in ischemia, catecholamines, hypoxanthine and an increase on xanthine oxidase activity. All of these substrates are capable of participating in free radical production. This increase in free radical production in ischemic tissue is enhanced by acidosis which in the ischemic and hypoxic myocardium approaches pH 6.0-6.4.(ABSTRACT TRUNCATED AT 400 WORDS)     

Reperfusion Injury: Basic Concepts and Protection Strategies

Prolonged ischemia such as that following myocardial infarction or occurring during long-term coronary bypass procedures causes serious damage to the myocardium. Early reperfusion is an absolute prerequisite for the survival of ischemic tissue. However, reperfusion has been referred to as the double edged sword because reperfusing ischemic myocardium carries with it a component of injury known as reperfusion injury. Reperfusion injury includes a number of events, such as reperfusion arrhythmias, myocardial infarction, stunning, vascular damage, and endothelial dysfunction. The underlying mechanism of reperfusion injury is not entirely known, but the existing evidence suggests that oxygen free radicals generated during the first few minutes of reflow lead to damage of cellular membranes, intracellular calcium overload, and uncoupling of excitation-contraction coupling. Although controversial, free radical scavengers, in general, are highly effective in the attenuation of reperfusion injury in animal models. Newer endogenous protection strategies, which include ischemic and heat shock preconditioning, are known to reduce reperfusion injury following ischemia.     

Evaluation of free radical and lipid peroxide formation during global ischemia and reperfusion in isolated perfused rat heart

Summary Free radical species have been implicated as important agents involved in myocardial ischemic and reperfusion injuries. In our study, formation of free radicals was measured directly with electron paramagnetic resonance spectroscopy before ischemia, during 10 minutes of global ischemia, and 20 seconds after reperfusion in the rat heart. We also investigated the formation of thiobarbituric acid-reactive material as index of lipoperoxidation induced by free radicals and measured arrhythmias. Production of free radicals takes place during ischemia since the signal intensity with a g value of 2.004 attributed to free radical species was increased by 50% after 10 minutes of global ischemia. In hearts reperfused with oxygenated perfusate for 20 seconds, the signal doubled. These experiments supply evidence that free radicals are generated in isolated rat heart during a short period of global ischemia and reperfusion. However, this increase was not associated with a concomitant increase of lipid peroxides in the myocardium nor with the development of reperfusion arrhythmias.     

Ischemic preconditioning protects against cold ischemic injury through an oxidative stress dependent mechanism.

BACKGROUND/AIMS: Ischemic injury in cold preserved livers is characterized by sinusoidal endothelial cell (SEC) detachment and matrix metalloproteinase activity. Upon reperfusion reversible ischemic injury becomes permanent with SEC rapidly undergoing apoptosis. Ischemic preconditioning prevents reperfusion injury after normothermic ischemia. We hypothesized that ischemic preconditioning, through an oxygen free radical burst, protects against injury during cold preservation and reperfusion. METHODS: Ischemic preconditioning was achieved in rats by clamping blood supply to the left and median lobes for 10 min followed by 15 min of reperfusion prior to preservation in cold University of Wisconsin solution for 30 h. In a second set of experiments, rats were pretreated with N-acetyl-cysteine (NAC). SEC apoptosis upon reperfusion was assessed in an isolated perfused rat liver (IPRL) model. RESULTS: SEC detachment and activities of matrix metalloproteinase were significantly reduced in preconditioned livers. A decrease of SEC apoptosis after 1h of reperfusion in the IPRL was noted in preconditioned livers compared to controls. Pretreatment with NAC reversed the beneficial effects of ischemic preconditioning on SEC detachment and apoptosis. CONCLUSIONS: Ischemic preconditioning is an effective strategy to prevent injury during cold preservation and after reperfusion. The protective effect is possibly mediated by oxygen free radicals.