自由基与心肌缺血再灌注损伤

1960年Jennings第一次提出心肌缺血再灌注损伤的概念，证实再灌注会引起心肌超微结构不可逆坏死，并逐渐引起医学界的高度重视。国内外大量实验证明缺血再灌注可加重心、脑、肾、肝、肺、肠等器官损伤，成为影响缺血治疗效果的一个重要因素。自由基、钙超载、心肌纤维能量代谢障碍、血管内皮细胞、中性粒细胞、细胞粘附分子和细胞凋亡等均可能参与缺血再灌注损伤的发病过程．现就自由基与心肌缺血再灌注损伤关系作一综述。     

补体及其抑制剂与心肌缺血/再灌注损伤

心肌缺血／再灌注可诱发导致心肌损伤的炎症状态。由于在临床上抗氧自由基和中性粒细胞激活治疗效果的不尽如人意，人们又把目光转向其他在临床上对心肌缺血／再灌注损伤可能更重要的致病因素，如补体、氧化剂和凋亡等。目前，补体系统已被证实在心肌缺血／再灌注损伤中起重要作用，并成为实验缺血／再灌注损伤的一个主要治疗靶点。在过去的十余年中，已经有几个补体抑制剂从实验室进入临床试验，并取得了一定成果。近几年，随着对补体与心肌缺血／再灌注损伤研究的不断深入，又有了一些新的发现。本文主要就补体及其抑制剂在心肌缺血／再灌注损伤中的研究及目前的新发现做一综述。     

心肌缺血再灌注损伤的研究进展

心肌缺血再灌注损伤的防治主要有缺血预处理、缺血后处理、抗炎治疗、改善心脏代谢等方面,本文对此作一综述。     

黄芪注射液抗心肌缺血再灌注损伤的临床研究

目的：探讨黄芪注射液防治体外循环心内直视手术中心肌缺血－再灌注损伤（ＭＩＲＩ）的作用机制。方法：将１２例风湿性心肌病瓣膜置换术和先天性心脑病室内隔缺损修补术患者随机分为对照组和治疗组,每组６例。治疗组通过锁骨下静脉注黄芪注射液４０ｇ;对照组不加中药。检测２组在不同时间的心肌酶、氧自由基含量,一氧化氮（ＮＯ）和一氧化氮合酶（ＮＯＳ）活性。结果：主动脉阻断致心肌缺血及心脏恢复灌注后心肌酶均呈上升趋势,     

细胞凋亡在心肌缺血再灌注损伤中的研究进展

急性心肌梗死发病率和死亡率居高不下。随着现代医疗技术不断进步,溶栓、经皮冠状动脉介入（PCI）等治疗使得急性心肌梗死病死率明显下降,但随之出现的再灌注损伤则会再次加重心肌损伤。再灌注损伤发生的机制复杂多样,其主要包括氧化应激、炎症、细胞凋亡,其中细胞凋亡起着关键作用,通过抑制细胞凋亡可有效减轻心肌缺血再灌注损伤（MIRI）。本文重点介绍细胞凋亡在MIRI中的作用机制,旨在为提高MIRI临床治疗效果及改善预后提供新的策略。     

心肌缺血-再灌注损伤的瘦素机制研究新进展

心肌缺血-再灌注损伤是心血管疾病领域研究的重点与热点问题之一.大量研究资料显示瘦素参与心肌缺血-再灌注损伤的损伤与修复机制,但其具体机制尚不明确.新近研究工作发现:瘦素参与心肌缺血-再灌注损伤疾病的损伤作用,而瘦素预处理却产生显著性的心肌保护作用.本文就心肌缺血-再灌注中瘦素的作用予以综述,对瘦素机制进行深入探讨,期望为心肌缺血-再灌注损伤的防治提供新的思路和方法.     

血塞通预处理对心肌缺血再灌注损伤的早期保护作用

目的观察血塞通预处理对大鼠心肌缺血再灌注(I/R)损伤的早期保护作用,并研究其可能机制.方法采用开胸冠状动脉结扎建立缺血再灌注模型,25只雄性SD大鼠随机分为假手术组,缺血再灌注组(I/R组),缺血预处理组(IPC组),血塞通预处理组(PNS预处理组).再灌注后2 h测定各组血清肌酸磷酸激酶-MB(CK-MB)含量以及心肌细胞凋亡情况和心肌细胞Bcl-2和Bax蛋白的表达,并观察心肌超微结构变化.结果IPC组及PNS预处理组血清CK-MB均明显低于I/R组(P＜0.05).IPC组及PNS预处理组TUNEL阳性细胞数,Bax阳性细胞数均明显低于I/R组(P＜0.05).和I/R组相比,IPC组及PNS预处理组心肌超微结构损伤减轻.结论PNS预处理后心肌细胞凋亡减少,心肌细胞损伤减轻,对I/R损伤产生有和缺血预处理类似的早期保护作用.     

舒心注射液治疗心肌缺血再灌注损伤的临床与实验研究

目的 :探讨舒心注射液对心肌缺血再灌注损伤的保护作用。方法 :对初次发病且发病后 36小时内的10 1例急性心肌梗死患者采用舒心注射液治疗 1周 ,观察治疗前后血清中红细胞超氧化物歧化酶 (SOD)、血浆乳酸脱氢酶 (L DH)活性及丙二醛 (MDA)含量的变化。将 2 0只心肌缺血再灌注模型兔随机分为缺血再灌注对照组和舒心注射液治疗组 ,每组各 10只。治疗组于缺血 10分钟时从耳缘静脉注入舒心注射液 2 m l/kg,对照组注入生理盐水 2 m l/kg,实验过程中记录左心室收缩内压 (L VSP) ,左室内压最大变化速率 (± dp/dt)及心电图 导联 ST段 ,测定血浆肌酸磷酸激酶 (CPK)活性和 MDA含量。结果 :急性心肌梗死患者用舒心注射液治疗后 ,SOD活性明显升高 (P<0 .0 1) ,L DH活性及 MDA含量明显降低 (P<0 .0 1)。动物缺血 40分钟及再灌注 40分钟时 ,治疗组 L VSP、± dp/dt值高于对照组 ,ΣST段、血浆 CPK活性和 MDA含量均明显低于对照组 (P均<0 .0 1)。结论 :舒心注射液对心肌缺血再灌注损伤有明显治疗作用 ,其机制可能与减轻氧自由基损伤有关。     

中药对心肌缺血再灌注损伤保护作用研究概况

<正>缺血性心、脑血管疾病是严重危害人类健康的常见病,预计到2020年冠心病将成为世界范围内的头号死亡原因。缩短组织缺血时间、尽早恢复血流是防治缺血损伤最有效的措施[1]。然而,在成功恢复心脏血流的同时,心肌损伤往往也会进一步加重,出现心率失常、梗死面积扩大等现象,这就是心肌缺血再灌注损伤(MIRI)。     

心肌缺血再灌注损伤与热休克蛋白

目的:热休克蛋白是细胞在应激条件下产生的一类高度保守的蛋白质,它可以从抵抗损伤和加速修复两个方面对细胞进行保护。研究表明热休克蛋白对心肌缺血再灌注损伤有内源性的抵抗作用。本文对热休克蛋白及其内源性抵抗心肌缺血再灌注损伤的作用机制进行综述。资料来源:①从图书馆手工查阅相关领域的学术期刊,重点是核心期刊,查阅有关心肌损伤与热休克蛋白之间关系的文献,关键词为“心肌损伤、热休克蛋白、缺血再灌注”。②在cnki数据库及PubMed检索2000/2006心肌缺血再灌注损伤保护方面的文献资料,关键词是“心肌损伤、热休克蛋白”。资料选择:手工和应用计算机分别检索到13篇和29篇与热休克蛋白与心肌缺血再灌注损伤有关的文献。纳入标准:选择实验性文献,即一次性文献。对于内容相近的文献选择在核心期刊发表或年限较近的文章。排除标准:重复性研究。资料提炼:共得到35篇文献,其中2004/2006的文献有14篇,2000/2003的文献7篇。资料综合:热休克蛋白是细胞在应激情况下启动热休克基因从而产生的一种结构高度保守的蛋白质,几乎存在于从原核生物到真核生物的所有生物体。它具有非特异性、高度保守性、热休克蛋白70表达突出性、时间性、弱的ATP酶的活性和交叉耐受性等特性。热休克蛋白对细胞具有保护作用,主要表现在抵抗损伤和加速修复这两方面。20世纪80年代末,人们开始注意到热休克蛋白具有心肌保护作用,1988年,Currie等将SD大鼠进行热休克预处理,待其恢复24h后,进行离体心肌缺血再灌注,结果发现热休克组大鼠心肌缺血再灌注损伤后力学指标的恢复明显改善,心肌超微结构的损伤也有不同程度的减轻。热休克蛋白抵抗心肌缺血再灌注损伤的机制包括:稳定细胞内变性的蛋白质;减轻细胞内的离子紊乱;保护血管内皮细胞的功能;干扰应激所启动的细胞调亡程序等4个方面。结论:热休克蛋白对心肌缺血再灌注损伤具有内源性的抵抗作用。     

Role of Na+-H+ Exchange on Reperfusion Related Myocardial Injury and Arrhythmias in an Open-Chest Swine Model

The inhibition of Na⁺-H⁺ exchange (NHE) with amiloride analogues in vitro has been shown to prevent reperfusion arrhythmias and additional cell necrosis. Inhibition of intracellular Ca²⁺ overload via NHE inhibition has been suggested as a mechanism of these protective effects. The aim of this study was to examine whether treatment with amiloride analogues reduces the incidence of reperfusion arrhythmias and limits infarct size in vivo. Open-chest swine were exposed to a 30-minute left anterior descending artery (LAD) occlusion and 180 minutes of reperfusion during atrial pacing at 150 ppm. Intravenous 5-(N,N-dimethyI)-amiloride (AML, 5 μg/kg per min) was administered in the treatment group (n = 7) and intravenous saline in the control group (n = 7), starting 10 minutes before coronary occlusion. The infusion was continued during ischemia and reperfusion. The area at risk was defined by monastral blue dye and infarct size by triphenyltetrazolium chloride staining. Limb leads ECG and monophasic action potentials (MAPs) from the epicardium in the ischemic area were recorded. There was no significant difference in the size of the area at risk and hemodynamic parameters between the groups. However, the infarcted area was 0.4%± 1.0% of the area at risk in the treatment group, whereas it was 62%± 29% in the control group (P < 0.05). Pathological examination (Hematoxylin-eosin and mallory s phosphotungstic acid-hematoxylin staining) revealed that all of the infarcted area consisted of contraction band necrosis. MAP duration in both groups was significantly shortened during ischemia. After reperfusion, MAP duration in the treatment group recovered earlier than that of control group. However, there was no significant difference in the incidence of ventricular tachyarrhythmia between the groups. Inhibition of NHE with AML prevented reperfusion related cell necrosis in the in vivo swine model, but did not reduce the incidence of ventricular tachyarrhythmia.     

反向模式钠钙离子交换体抑制剂降低造影剂诱导的肾小管上皮细胞凋亡

目的 探讨反向模式钠钙离子交换体抑制剂KB-R7943是否对造影剂肾损伤具有保护作用.方法 培养大鼠肾小管上皮细胞分别与不同浓度KB-R7943(10-5,10-6 mol/L)作用12 h后,加入造影剂作用1 h.采用LDH检测细胞损伤,倒置显微镜观察细胞形态变化,流式细胞仪检测细胞凋亡,共聚焦显微镜测定细胞内钙和反应氧产物水平,RT-PCR检测钠钙离子交换体mRNA表达.相同渗透压甘露醇作对照.数据以均数±标准差(x±s)表示,统计采用方差分析和q检验,简单直线相关分析两者相关性,以P<0.05为差异具有统计学意义.结果 造影剂作用1 h诱导了明显细胞损伤和细胞凋亡,细胞内钙和反应氧产物增加,KB-R7943降低了细胞内钙和反应氧产物水平,同时降低了细胞损伤和细胞凋亡并呈剂量效应;钠钙离子交换体mRNA表达无变化.结论 KB-R794对造影剂诱导的肾小管上皮细胞损伤具有保护作用.     

Activation of Na+/H+ exchanger is associated with hyperinsulinemia in borderline hypertensive rats

Activation of Na+/H+ exchanger (NHE) is known to be related to elevated blood pressure in hyperinsulinemia. To test whether there is the change in NHE activity in insulin resistance, we measured NHE activity of platelets in fructose-induced hyperinsulinemia in Wistar-Kyoto rats (WKY), in borderline hypertensive rats (BHR), and in spontaneously hypertensive rats (SHR). All rats were fed a 60% fructose diet for 4 weeks to induce hyperinsulinemia and hypertriglyceridemia. Intracellular pH (pHi) was measured with a pH-sensitive fluorescent dye 2'7'-bis (2-carboxyethyl)-5-carboxyfluorescein acetoxymethyl ester. NHE activity was evaluated by the recovery of pHi following addition of sodium propionate (Vmax). Measurement of intracellular calcium ([Ca2+]i) was performed using fura2/acetoxymethylester. Systolic blood pressure in fructose diet BHR elevated significantly greater than that in control diet BHR with the increase of both [Ca2+]i and Vmax. In WKY, there was no significant increase in systolic blood pressure and [Ca2+]i except Vmax in a fructose diet. Vmax in control diet SHR was greater than in control diet WKY and BHR, and we found no additional increase in Vmax with a fructose diet in SHR. In BHR, a high salt diet increased systolic blood pressure and Vmax to a similar degree as a fructose diet or a high salt combined with a fructose diet. Plasma insulin concentration correlated positively with Vmax in WKY and BHR, but not SHR. A fructose diet induces hyperinsulinemia and elevates blood pressure in BHR. Hyperinsulinemia appears to activate NHE in a different manner in SHR, and might be associated with an elevation in blood pressure in BHR.     

Erythrocyte Na+–H+ exchanger kinetics and Na+–Li+ countertransport activity in essential hypertensive patients

The authors measured Na⁺–H⁺ exchanger kinetics together with Na⁺–Li⁺ countertransport V _max in the erythrocytes of 21 subjects with essential hypertension and 16 normotensive control subjects. Na⁺–H⁺ exchanger V _max appeared to be increased in patients with essential hypertension, while the Na⁺–H⁺ exchanger affinity for intracellular proton sites ( K _50%) proved to be unchanged and the index of cooperativity among intracellular proton binding sites as measured by Hill's coefficient (Hill's n ) decreased as compared with normotensive control subjects. Na⁺–Li⁺ countertransport V _max appeared to be higher in patients with essential hypertension than in control subjects. The authors were unable to find any correlations between Na⁺–H⁺ exchanger kinetic parameters and metabolic variables such as parameters of insulin resistance and plasma lipids. On the basis of the data obtained, erythrocyte Na⁺–H⁺ exchanger activity was found to be abnormal in two kinetic variables in essential hypertensive patients and showed no simple linear correlations with the main variables of glucose metabolism, plasma lipids, renin or aldosterone.     

Effect of Na+ reduction and monensin on ion content and contractile response in normoxic and ischaemic reperfused rat hearts

Summary— The possibility was explored whether the functional properties of Na+/Ca²⁺ exchange are altered after ischaemia, thereby contributing to the elevated intracellular (i) Ca²⁺ levels in ischaemic reperfused hearts. The intracellular Na+, K+ and Ca²⁺ contents in rat Langendorff heart preparations were determined by atomic absorption spectrometry under normoxic conditions, after ischaemia (30 min) and after ischaemia (30 min) plus reperfusion (30 min). In addition, the influence of modulating the Na+ gradient (Na+_o/Na+_i) across the sarcolemma was studied with respect to cardiac contractility and intracellular ion content. This was done by either decreasing extracellular (o) Na+ or by increasing Na+_i with monensin, both in normoxic and reperfused hearts. Both Na+_o reduction and monensin led to an increase in contractility and coronary flow, an effect which was nearly abolished in reperfused hearts. Under normoxic conditions the intracellular ion contents amounted to Na+ = 12.4 ± 0.4, K+ = 99.0 ± 3.1 and Ca²⁺ = 0.64 ± 0.02 mmol/kg cell (means ± SEM, n = 7). In normoxic hearts, lowering Na+_o reduced and monensin increased Na+_i, thereby both leading to a decrease in Na+ gradient; no effect on total Ca²⁺_i content was observed. Na+_i increased twofold after ischaemia as compared to the normoxic situation, an effect which was aggravated (4 fold increase) in reperfused hearts. The opposite effects were observed for K+_i with a 25% decrease after ischaemia and a 40% decrease in reperfused hearts. Only after ischaemia plus reperfusion was Ca²⁺_i increased (6 fold). In reperfused hearts, lowering Na+_o again reduced and monensin increased Na+_i, whereas a further rise in Ca²⁺_i was now observed depending on the Na+ gradient across the sarcolemma: the larger the drop in Na+ gradient, the more pronounced the increase in Ca²⁺_i in the reperfused heart. We conclude that the Ca²⁺_i increase in reperfused hearts can be modulated by changing the Na+ gradient across the sarcolemma. This suggests that inhibited or reversed Na+/Ca²⁺ exchange is predominantly responsible for the rise in Ca²⁺_i in ischaemic hearts that are subjected to reperfusion.     

Fas和FasL在Na+/H+交换器-1抑制诱导缺氧大鼠肺动脉平滑肌细胞凋亡中的作用

目的探讨Fas、FasL在Na^＋／H^＋交换器-1（NHE-1）抑制所诱导的缺氧大鼠肺动脉平滑叽细胞（PASMCs）凋亡中的作用。方法将转染NHE-1特异性核酶基因的大鼠PASMCs置于缺氧条件下（O2的体积分数低下1％）培养。缺氧培养2、6、12、24和48h后用原位末端标记法（TUNEL）检测细胞凋亡情况；半定量逆转录-聚合酶链反应（sqRT—PCR）疗法检测细胞内fas和fasL mRNA表达变化；免疫细胞化学法检测细胞内Fas和FasL蛋白表达变化。结果转染NHE-1特异性核酶基因的大鼠PASMCs在缺氧培养时，其细胞凋亡率随缺氧时间的延长而逐渐升高，但细胞内fas、fasL mRNA及Fas、FasL蛋白表达与对照组细胞比较差异均无显著性。结论Fas／FasL死亡通路可能不参与NHE-1抑制而诱导缺氧大鼠PASMCs凋亡的调控。     

Overexpression of the Na+/Ca2+ exchanger influences ouabain‐mediated spontaneous Ca2+ activity but not positive inotropy

Administration of digitalis in heart failure (HF) increases quality of life but does not carry a prognostic benefit. Digitalis is an indirect inhibitor of the Na⁺/Ca²⁺ exchanger (NCX), which is overexpressed in HF. We therefore used the cardiac glycoside ouabain in Ca²⁺ imaging experiments and patch‐clamp experiments in isolated ventricular myocytes from nonfailing transgenic NCX overexpressor mice (OE). In field‐stimulated myocytes, ouabain (1–100 μm ) increased the amplitude of the Ca²⁺ transient in OE and wild‐type (WT) similarly. Ouabain‐mediated spontaneous Ca²⁺‐activity was significantly more pronounced in OE compared to WT myocytes at higher concentrations (100 μm). Also, at very high concentrations (1000 μm ) of ouabain, the number of cells with hypercontraction leading to cell death was higher in OE. Ouabain (10 μm ) shortened the action potential duration in both genotypes. Our findings suggest that the proarrhythmic but not the inotropic effects of cardiac glycosides are enhanced by increased NCX expression. This may offer an explanation for the observed lack of prognostic benefit but increased quality of life in HF, which is accompanied by NCX upregulation.     

Acute saline infusion induces extracellular acidification and activation of the Na+/H+ exchanger in man

The effect of acute expansion of the extracellular fluid volume (ECV) with isotonic (0.9%) saline on the activity of the lymphocyte Na⁺/H⁺ antiport (NHE) was studied in a total of 18 healthy volunteers. Saline was infused at a constant rate so that 4 mmol kg^?1 b.w. was administered over 2 h. NHE activity was measured by quantifying cytosolic pH (pH_i) recovery following acidification of the cells with propionic acid and by pH clamping at various pH_i values between 7.2 and 5.8 using nigericin. Both methods demonstrate NHE activation associated with intravenous saline infusion, the kinetic difference being a marked decrease in the Hill coefficient n from 3.28 ± 0.21 (SEM) to 2.22 ± 0.11 in the absence of changes in baseline pH_i (7.14 ± 0.02 vs. 7.08 ± 0.02; P = 0.15), V_max (42.8 ± 2.7 vs. 48.1 ± 2.8 mmol L^?1 min^?1; P = 0.08) and pK (6.32 ± 0.04 vs. 6.35 ± 0.02). NHE activation was associated with significant decreases in serum chloride (P = 0.016), calcium (P = 0.008), total cholesterol (P = 0.008), low-density lipoproteins (P = 0.016) and high-density lipoproteins (P = 0.008). Moreover, saline infusion induced extracellular acidification with a decrease in pH from 7.39 ± 0.01 to 7.37 ± 0.01 (P = 0.016), HCO₃^? from 23.3 ± 0.43 mmol L^?1 to 21.3 ± 0.25 mmol L^?1 (P = 0.008) and base excess from ?1.03 ± 0.38 mmol L^?1 to ?3.00 ± 0.31 mmol L^?1 (P = 0.008). Our results show for the first time that acute ECV expansion with isotonic saline is followed by an activation of the lymphocyte NHE. The underlying mechanism(s) remain to be investigated. However, the demonstration in our study of marked changes in acid–base balance induced by acute saline points to a possible inter-relationship of antiporter activation and extracellular acidification.