Oxygen free radical scavengers and reperfusion injury in dog lung preserved in cold ischemia.

Oxygen-derived free radicals are now considered important contributors to tissue injury associated with ischemia and reperfusion. The purpose of this study was to determine the influence of oxygen free radical scavengers on reperfusion injury. The left lower lobes of 15 canine lungs were isolated, preserved, and then reperfused for 120 minutes. Three groups of lobes were studied: Group 1 (n = 5), without ischemia, group 2 (n = 5) four hours of cold ischemia in Euro-Collins solution, group 3 (n = 5) four hours cold ischemia+oxygen free radical scavenger glutathione (0.1 nmol/L) given at the moment of perfusion. Extravascular lung water (grams per gram of blood-free dry lobe weight) after reperfusion was 2.82 +/- 0.32, 5.06 +/- 0.45, 4.21 +/- 0.33 for groups 1 through 3 respectively (p less than 0.001 group 1 versus group 2, p less than 0.001 group 2 versus group 3). Lung tissue lipid peroxidation, measured as thiobarbituric acid reactive material was 125 +/- 11, 270 +/- 30, and 185 +/- 17 nmol/g dry lobe weight for groups 1, 2 and 3 respectively (p less than 0.05 group 2 versus 1 and group 3 versus group 2). The data suggest that oxygen free radical scavengers attenuate reperfusion injury.     

Oxygen free radical damage of isolated cardiomyocytes: comparative protective effect of radical scavengers and calcium antagonists

Summary Oxygen free radicals have been shown to play a major role in the development of perfusion abnormalities, contractile dysfunction, and irreversible injury in ischemic-reperfused myocardium. The aim of this study was to assess the direct protective effects of radical scavengers, calcium antagonists, and combination of these substances against free radical induced myocyte damage. Viability (% of rod-shaped cells) and adenine nucleotide content (AdN, high-pressure liquid chromatography) of isolated adult rat cardiomyocytes were measured after exposure to hypoxanthine (2 mM) and xanthine oxidase (25 mU/ml). After 90 min, viability of myocytes decreased to 4.2±3.4 % (mean±SEM) of pre-exposure control, and AdN decreased from 28.2±1.8 to 8.09±1.1 nmol/mg protein. Addition of catalase (1500 U/ml) resulted in the preservation of viability (77±6% of pre-exposure control, n=6, mean±SEM), and AdN 84±6%, p<0.001. These values are not significantly different from those measured in myocytes not exposed to free radicals (88±9% and 79±6%, respectively). Superoxide dismutase (2400 U/ml), dimethylthiourea (10 mM), and desferrioxamine (1 mM) did not preserve either viability or AdN. The calcium antagonist verapamil (10 M) also preserved myocyte viability significantly (23±9.7%, p<0.05 vs unprotected cells), but failed to prevent the loss of AdN (13.2±4%, not significant as compared to unprotected cells). Viability and AdN in myocytes treated with nifedipine (10 M) or diltiazem (10 M) were not higher than in unprotected cells. All combined treatment forms which included catalase resulted in the preservation of myocyte viability as well as AdN. These data show that only the hydrogen peroxide scavenger catalase protects isolated cardiomyocytes against free radicals generated in the purine catabolic pathway.     

Myocardial ischemia, reperfusion and free radical injury.

Reperfusion of coronary arteries to limit myocardial ischemic injury and extent of myocardial necrosis is possible by either the use of fibrinolytic therapy, coronary angioplasty or coronary artery bypass surgery. The concept that early reperfusion may salvage jeopardized myocardium is derived from basic experimental studies which purported to demonstrate that the ultimate extent of irreversible myocardial injury could be reduced by reperfusion of the ischemic myocardium within 3 hours from the onset of regional myocardial ischemia. It is firmly established that salvage of ischemic myocardium is dependent on early restoration of blood flow to the myocardium at risk. Despite dependency on reoxygenation for ultimate survival, myocardial tissue that is reperfused and reoxygenated may be subjected to additional injurious insult due to reactive metabolites of oxygen. The cytotoxic species of oxygen are referred to as "oxygen free radicals." Coincident with the influx of inflammatory cells into the reperfused region is an additional loss of otherwise viable myocardial cells. There is strong support for the concept that the polymorphonuclear leukocyte is a contributor to the phenomenon of "reperfusion" or "reoxygenation" injury in the blood perfused heart. This discussion focuses on the role of the neutrophil as a potential contributor to the extension of tissue injury and reviews those interventions, which although in the experimental stage, offer promise of becoming therapeutically important in the future and may help elucidate the mechanisms underlying the potentially deleterious role of the neutrophil in situations involving whole blood reperfusion of the ischemic myocardium.     

Free radical and granulocyte-mediated injury during myocardial ischemia and reperfusion

The success of thrombolytic/reperfusion therapy in limiting the extent of myocardial infarction may be limited by reperfusion injury. Damage from acute ischemia is not due solely to the interruption of blood flow; rather, ischemia initiates a cascade of reactions involving partially reduced oxygen, inflammatory mediators, mechanical capillary obstruction by granulocytes and other events that lead to irreversible injury. A surprising consequence is that reperfusion by delivering oxygen and granulocytes may counteract some of the benefits of restoring flow. Mechanisms of neutrophil and free radical injury include superoxide radical formation and lipid peroxidation, progressive leukocyte capillary plugging and capillary no-reflow, and edema. The interaction of various specific mechanisms of injury in the heart (i.e., xanthine oxidase, mitochondrial superoxide leak, neutrophil superoxide, degranulation and capillary plugging, and neutrophil-derived vasoconstrictors) deserves further study.     

Moderation of myocardial ischemia reperfusion injury by calcium channel and calmodulin receptor inhibition

Summary Intracellular Ca²⁺ accumulation is implicated in the pathogenesis of myocardial reperfusion injury. To study approaches designed to modify Ca²⁺ uptake during coronary revascularization after acute infarction, a pig heart surgical infarct model (left anterior descending artery occlusion for 60 min) was subjected to 60 min hypothermic potassium cardioplegic arrest, followed by 60 min of global reperfusion. Four groups of six hearts each were studied in a randomized manner, i.e., cardioplegia alone (control), cardioplegia + 10 µM diltiazem (Ca²⁺ slow channel blocker), cardioplegia + 10 µM trifluoperazine (TFP), (a Ca²⁺-calmodulin antagonist), and cardioplegia + diltiazem (10 µM) + TFP (10 µM). Left ventricular contractility (global and segmental), metabolism (coronary blood flow and O₂ consumption), and creatine kinase generation were measured during reperfusion. Both the Ca²⁺ channel blocker, diltiazem, and the calmodulin antagonist, TFP, improved myocardial global and regional function as well as myocardial metabolism. While diltiazem better restored global and regional contractility, trifluoperazine had a greater effect on coronary blood flow and myocardial oxygen consumption. Enzyme release and lipid peroxidation were equally moderated by both drugs. From this study it can be concluded that Ca²⁺ influx does play a role in ischemic and reperfusion injury. The mechanisms of its effect are complex, but can be successfully antagonized by Ca²⁺ blockers as well as by calmodulin antagonists, with improved myocardial preservation.Supported in part by grants NIH HL 22559 and HL 34360     

缺血期急性高血糖对大鼠心肌缺血/再灌注损伤的影响

目的 探讨缺血期急性高血糖对大鼠心肌缺血/再灌注(MI/R)后心肌损伤的影响,并分析血糖水平与心肌损伤之间的关系.方法 在制备急性大鼠MI/R(缺血30min,再灌注6h)模型的基础上,静脉输注高浓度的葡萄糖溶液,造成2个不同浓度的缺血期急性高血糖动物模型.将32只SD大鼠随机平均分配为4组:(1)假手术组(SHAM),(2)生理盐水对照组(CON),(3)高糖1组(HG1)和(4)高糖2组(HG2).术中监测血糖水平,再灌注结束后检测心肌酶谱水平和心肌梗死面积(IS).结果 (1)与CON组相比较,HG1组和HG2组缺血期血糖水平均显著升高,分别为(10.5±1.0)、(18.0±1.2)mmol/L vs(4.7±0.7)mmol/L(P<0.05).(2)HG1组和HG2组的血肌酸激酶和乳酸脱氢酶水平明显升高,且心肌酶谱与血糖水平存在正相关(r分别为0.80和0.73,P<0.01).(3)HG1组的IS较CON组有扩大趋势,但差异无统计学意义[(40.8±5.2)%vs(37.6±5.8)%,P>0.05),HG2组的IS明显扩大[(45.6±8.5)%v8(37.6±5.8)%,P<0.05],且IS与血糖水平存在正相关(r=0.57,P<0.01).结论 缺血期急性高血糖加重大鼠MI/R损伤,且血糖水平与心肌酶谱和IS之间存在正相关.     

Free radical effects on membrane protein in myocardial ischemia/reperfusion injury

Free radical generation may be the principal pathogenic factor responsible for the initiation of ischemia/reperfusion myocardial cell damage. Circumstantial evidence is in favour of the view that impaired function of the membraneous components of ischemic cells is associated with oxygen radical-induced alterations in proteins and lipids. Thus, lipid antioxidants and free radical scavengers as well as antagonists of protein modification may all be required for therapeutic intervention of this aspect of ischemia/reperfusion injury.     

Myocardial ischemia and reperfusion: direct evidence for free radical generation by electron spin resonance spectroscopy.

Electron spin resonance spectroscopy has recently been used by others to detect directly radical species in isolated perfused hearts. Sample processing prior to spectroscopy in this study involved pulverization of tissue, which can artifactually generate radical species. We assessed in isolated perfused hearts the influence of tissue pulverization on the identity of radical species detected by spectroscopy and then, using a processing technique less likely to induce artifacts, whether myocardial ischemia and reperfusion generate radical species. Rat and rabbit hearts (n = 8) were perfused aerobically for 10 min and freeze-clamped to -196 degrees C. Frozen tissue was processed at -196 degrees C for spectroscopic analysis by pulverization vs. chopping. Spectra of pulverized tissue consisted of three components: a semiquinone (g = 2.004), a lipid peroxy radical (g [ = 2.04 and g = 2.006), and a carbon-centered radical that is possibly a lipid radical (giso = 2.002 and AHzz approximately equal to 50 G). Chopped tissue consisted of a single component, a semiquinone (g = 2.004). Rat hearts (n = 8 per group) also underwent 10-min global no-flow normothermic ischemia followed by 5-60 sec of either aerobic or anaerobic reperfusion, with frozen tissue chopped prior to spectroscopy. Spectra of ischemic tissue consisted of an iron-sulfur center and a semiquinone. Aerobic reperfusion resulted in a spectrum similar to the control but with increased amplitude that peaked after 10-15 sec of reflow. Anaerobic reperfusion yielded a spectrum identical to that of ischemic tissue. We conclude that pulverization of frozen myocardial tissue arti-factually generates radical species. Using a nonpulverization technique for tissue processing, we found that myocardial ischemia and reperfusion produce radical species but that molecular oxygen is necessary for the burst of radical production during reflow.     

心肌缺血再灌注损伤研究进展

急性心肌梗死是主要的致死致残原因,再灌注治疗是其标准的治疗方案,然而再灌注治疗伴随着再灌注损伤,再灌注损伤的机理目前还未完全清楚,分子、细胞、组织上的改变均与参与再灌注损伤,本文就心肌缺血再灌注损伤的研究进展作一综述。     

比较依达拉奉和DIDS在大鼠急性缺血再灌注损伤心肌中的作用

目的:探讨氯离子通道阻断剂4,4′-二异硫氰基芪-2,2′-二磺酸(4,4′-diisothiocyanostilbene-2,2′-disulfonicacid,DIDS)与自由基清除剂依达拉奉(Edaravone,EDRV))在大鼠缺血/再灌注损伤(I/RI)心肌中的作用。方法:建立常规大鼠I/RI(30 min/4 h)模型,实验分为5组:假手术组、I/RI对照组、EDRV组、DIDS组和DIDS+EDRV组,每组8只大鼠(n=8)。再灌注前,给予EDRV(10 mg/kg),给药5 min;再灌注即刻,给予DIDS 4 ml[14 mg/(kg.h)]2 h。于缺血前、后和再灌注后,记录心脏的血流动力学指标:左室收缩压(LVSP)及左室等容收缩/舒张期压力上升或下降最大速率(±dp/dtmax)。再灌注结束时,检测大鼠心肌梗死(MI)面积、血清肌酸激酶(CK)和乳酸脱氢酶(LDH)的活性。结果:与I/RI组相比,DIDS组、EDRV组和DIDS+EDRV组MI面积显著减小(P0.05);LVSP和±dp/dtmax显著提高(P0.05),血清CK和LDH的活性显著降低(P0.05);DIDS组和EDRV组的上述指标无统计学差异;DIDS+EDRV组对心肌的保护作用强于DIDS或EDRV组(P0.05)。结论:DIDS与EDRV都具有对抗或减轻I/RI心肌的作用,但二者的差异不明显,联合使用具有相加作用。     

肝脏缺血再灌注损伤与钙超载

肝脏缺血再灌注损伤是临床上常见的病理过程,其发生机制与细胞内钙超载有关.钙超载的发生与胞质膜裂隙作用、Na /Ca2 交换、Ca2 -ATP酶活性下降、线粒体功能障碍以及氧自由基有关.钙超载防治措施包括:线粒体ATP敏感的K通道开放剂、麻醉荆、钙离子拮抗剂、线粒体通透性转换孔抑制剂和血红素氧合酶等.     

蛋白酶激活受体2与心肌缺血/再灌注损伤

氧化应激、炎症和细胞凋亡在心肌缺血/再灌注损伤(myocardial ischemia/reperfusion injury,MI/RI)中起重要作用，而蛋白酶激活受体（protease-activated receptor，PAR）-2与MI/RI之间存在密切关系。PAR-2广泛分布于心血管系统，可被多种蛋白酶激活，启动多种生物学效应。本文从上述几方面对PAR-2与MI/RI的关系进行阐述，为MI/RI的防治提供理论依据。     

促红细胞生成素与心肌缺血再灌注损伤

近年来促红细胞生成素(erythropoietin,EPO)的非造血生物作用逐渐引起关注。研究表明,EPO 可以减轻缺血缺氧时心肌细胞的损伤,减少心肌细胞的调亡,从而使其可能成为预防和治疗心肌缺血再灌注损伤的一条途径。     

Role of free radicals and neutrophils in canine myocardial reperfusion injury: myocardial salvage by a novel free radical scavenger, 2-octadecylascorbic acid

To define the role of oxygen free radicals and neutrophil involvement in evolving myocardial reperfusion injury, we evaluated the effect of 2-octadecylascorbic acid (CV-3611), a novel free radical scavenger, on neutrophil function and the extent of myocardial damage resulting from 90 min of ischaemia followed by 5 h of reperfusion in an experimental model of myocardial infarction. Dogs were randomly assigned to receive CV-3611 (5 mg.kg-1.[5 min]-1, intravenously) just before the onset of reperfusion. Infarct size, as a percent of area at risk, was reduced by 60% in CV-3611 treated group as compared with control, at 16.7(SEM 3.1)% v 41.5(4.5)%, p less than 0.01. Administration of CV-3611 markedly reduced function of neutrophils isolated from peripheral circulation during reperfusion ex vivo as estimated by free radical generation (ferricytochrome c reduction and luminol enhanced chemiluminescence), chemotactic activity, and aggregation induced by A23187. Under these conditions, the enhancement in neutrophil infiltration and free radical generation (luminol enhanced chemiluminescence) in myocardium within area at risk, especially in the border zone between viable and irreversible injured myocardium, was markedly reduced. Haemodynamic profiles were similar between control and CV-3611 treated group. These results suggest that activated neutrophils, especially their generation of oxygen free radicals, contribute to reperfusion induced myocardial injury.     

Nitrates and calcium antagonists for silent myocardial ischemia

Continuous Holter monitoring of patients with coronary heart disease can show transient ischemic episodes occurring spontaneously with or without angina throughout the day. A controlled double-blind trial was conducted comparing the effects of isosorbide-5-mononitrate (IS-5-MN) and nifedipine in patients with documented transient ischemic episodes. Seventy-five percent of the ischemic episodes were not accompanied by pain. Twenty patients with documented coronary heart disease were included; 15 finished the 4-week study (1 patient had headaches, 1 thyrotoxicosis, 1 hypertensive crisis and 2 unstable angina). On a dual-channel FM-recorded electrocardiogram, ischemic episodes were counted when ST deviation was greater than 1 mm for greater than 1 minute. Patients received IS-5-MN (20 mg 3 times a day or 50 mg in a sustained-release tablet) or nifedipine (20 mg in a sustained-release tablet 3 times a day) in random order over four 1-week periods. At the end of each week, Holter monitoring was repeated and showed reductions of episodes by 67% and 67% after weeks of IS-5-MN therapy and 56% and 58% after weeks of nifedipine therapy (all p less than 0.05). Painful and painless episodes were reduced to a similar extent. Individual responses showed great variability, and in all treatment periods not more than half of the patients were completely free of ischemic episodes. One of the 12 patients did not respond to either way of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxygen free radicals and myocardial reperfusion injury

Diseases involving tissue reperfusion following ischemia are gaining significance in emergency medicine. The significance of reperfusion injury and the probable role of oxygen-derived free radicals has been described in many tissues, particularly the heart. During myocardial reperfusion a burst of oxygen-derived free radicals overwhelms normal cellular defenses. These radicals may have several detrimental effects. They can oxidize lipids, leading to membrane dysfunction. They can also alter nucleic and other proteins. Cellular dysfunction and death may ensue. Prevention of oxygen-derived free radical injury appears possible and may be feasible for several disease processes, including myocardial reperfusion after infarction.     

白花前胡丙素对心肌缺血再灌注损伤的影响

目的观察白花前胡丙素（Pra—C）对抗大鼠心肌缺血再灌注损伤（MI／R）的机制及其保护作用。方法48只健康雄性SD大鼠随机分为6组：假手术组（A组）、缺血再灌注组（B组）、溶剂±缺血再灌组（C组）、Pra—C5mg／kg组（D组）、Pra—C15mg／kg组（E组）和Pra—C30mg／kg组（F组）。Pra—C各剂量组分别于实验前3d腹腔注射,每天2次,于实验前2h加强1次;A组给予等量的生理盐水腹腔注射;B组采用冠状动脉左前降支结扎40min,再灌120min建立;C组给予等量的50％PEG400,10ml／kg溶剂腹腔注射。分光光度计法检测心肌组织SOD活性和MDA含量。苏木素-伊红（HE）染色观察心肌组织病理改变,透射电镜观察心肌超微结构的变化,并比较各组之间的差异。结果六组SOD值（U／mgprot）分别为154．78±10．94、78．16±7．13、79．15±7．12、88．77±8．53、115．80±7．09和145．07±7．24;MDA值（nmol／mgprot）分别为2．70±0．26、6．77±0．23、6．48±0．64、5．07±0．38、3．41±0．32和2．72±0．32。B组和C组心肌组织SOD活性和MDA含量差异无统计学意义（P〉0．05）;与它们相比较,D、E、F组SOD活性显着增加（P〈0．05或P〈0．01）,MDA含量显著降低（P〈0．01）。D、E、F组心肌组织的病理改变有不同程度的减轻。结论Pra—C可以减轻MI／R对心肌组织的损伤作用。其机制可能与对抗氧自由基、对抗脂质过氧化有关。     

姜黄素对缺血再灌注损伤大鼠心肌线粒体呼吸链的影响

目的 探讨姜黄素对心肌缺血再灌注损伤大鼠心肌梗死面积及心肌线粒体呼吸链的影响。方法 采用健康雄性Wister大鼠（n=24）建立Langendorff离体心脏灌注模型,分为3组,正常对照组、缺血再灌注组和姜黄素预处理组。正常对照组持续灌注90 min;缺血再灌注组全心缺血30 min,再灌注60 min;姜黄素预处理组加入姜黄素（0.2 mmol/L）后,全心缺血30 min,再灌注60 min。再灌注结束时,TTC染色观察心肌梗死面积,应用紫外分光光度法测定缺血再灌注后心肌线粒体呼吸链复合体Ⅰ、Ⅳ的活性。结果[结果部分应列举主要数据,并修改英文摘要] ①缺血再灌注组心肌坏死面积约为26.9±2.5%。经姜黄素预处理后,心肌梗死面积为21.8±2.2%,较缺血再灌注组明显降低,差异有统计学意义;②缺血再灌注组心肌线粒体呼吸链复合体Ⅰ、Ⅳ活性分别为0.453±0.069、0.050±0.005,姜黄素预处理组心肌线粒体呼吸链复合体Ⅰ、Ⅳ活性分别为0.565±0.071、0.059±0.004,较缺血再灌注组均显著增加,差异有统计学意义（P<0.05）。结论 姜黄素预处理能够缩小心肌梗死面积,同时增加线粒体呼吸链复合体Ⅰ、Ⅳ的活性,从而对缺血再灌注损伤心肌起保护作用。