洛伐他汀预处理的延迟性心肌保护作用及其机制

目的探究洛伐他汀在大鼠心脏急性缺血/再灌注中的延迟性心肌保护作用及其机制。方法SD大鼠24只随机分为3组（每组8只）:模型对照组（C）;Lovastatin组（L）,洛伐他汀直接灌胃两周15mg/（kg·d）;Lovastatin复合LNAME组（N）,洛伐他汀15mg/（kg·d）直接灌胃2周同时腹腔注射LNAME30mg/（kg·d）;2周后建立在体急性缺血/再灌注心脏模型,监测缺血/再灌注前后血流动力学各项指标,同时观察各组血脂水平及其血浆中MDA、SOD、LDH以及CK的变化情况。结果L组和N组较C组心率显著减慢（P<0.01）,缺血/再灌注心律失常消失和再灌注时-dp/dtmax下降显著改善（P<0.05）;各项血脂指标不变的情况下,洛伐他汀显著减少再灌注时血浆中MDA生成和LDH及CK的释放（P<0.01）,并且提高心肌组织SOD活性（P<0.05）。结论Lovastatin对在体大鼠心脏急性缺血/再灌注时具有非降脂外的延迟性心肌保护作用。NO合酶途径是其心脏保护作用的诸多途径之一。     

Aging reduces the cardioprotective effect of ischemic preconditioning in the rat heart

Multiple brief periods of ischemia in the mammalian heart elicits protection against morphologic and functional damage caused by longer-duration ischemia. Preconditioning-induced protection against post-ischemic contractile dysfunction has been reported to be depressed with aging of the adult heart. This study was undertaken to determine whether aging of the adult myocardium reduces the preconditioning-induced attenuation of necrosis observed with ischemia. Isolated, perfused hearts obtained from Fischer 344 rats of either 3 (young) or 22 (aged) months of age were paced and instrumented for determination of developed left ventricular pressure. Necrosis was determined with triphenyltetrazolium. In the absence of preconditioning, young and aged adult hearts made globally ischemic for 45 min developed necrosis involving 53+/-6% and 49+/-6% of the myocardium, respectively. Contractile function (+dP/dt(max)) at 90 min of reperfusion was depressed by 80% in young and 52% in aged hearts, compared to values obtained prior to preconditioning. Preconditioning with two 5 min ischemia/5 min reperfusion cycles significantly reduced necrosis development and enhanced reperfusion contractile function in young hearts. However, in aged adult hearts, the preconditioning did not significantly reduce the development of necrosis or enhance reperfusion contractile function. These data suggest that aging reduces the effectiveness of preconditioning in providing cardioprotection against ischemic-induced myocardial necrosis.     

心脏成纤维细胞缺氧预处理对心肌细胞的保护作用

目的 :探讨大鼠心脏成纤维细胞缺血预处理 (IPC)对成纤维细胞及心肌细胞的保护作用。方法 :实验分为 6组 [对照 (CON) 1组、CON 2组 ,预处理 (PC) 1组、PC 2组、SMT组、NS3 98组 )。用Westernblotting法测定心肌细胞的环氧化酶 2 (COX2 )、分泌型一氧化氮合酶 (iNOS)表达量。心肌细胞损伤程度以乳酸脱氢酶 (LDH)释放和台盼蓝排斥试验判断 ,成纤维细胞损伤程度以台盼蓝排斥试验判断。结果 :PC 1组的细胞存活率与CON1组差异无显著性意义 (P >0 .0 5 )。PC2组LDH释放较CON2组明显减少 ,细胞存活率明显增加 (P <0 .0 1)。SMT组和NS3 98组LDH释放、细胞存活率与CON2组相当 (P >0 .0 5 )。PC2组COX2 表达量明显增加 ,与CON2组比较差异有极显著性意义 (P <0 .0 1) ,SMT组与CON2组间COX2 量差异无显著性意义 (P >0 .0 5 )。PC2组和NS3 98组的iNOS表达量较CON2组明显增加 ,差异有极显著性意义 (P <0 .0 1)。结论 :IPC不能对心脏成纤维细胞产生保护作用。心脏成纤维细胞在缺氧后可能释放某些“保护性递质” ,触发心肌细胞产生类似IPC的保护效应 ,而且与iNOS ,COX2 的表达有关 ,在信号传导中iNOS是COX2 的上游     

远端缺血预处理心肌保护效应研究进展

远端缺血预处理(RIPC)是通过给予一个器官缺血预处理可以增加远处器官对缺血再灌注损伤的耐受性。基础研究和临床试验均证实RIPC是一项安全有效的干预措施,具有降低心肌缺血再灌注损伤的心肌保护效应。本文就近年来RIPC心肌保护效应和临床应用研究新进展做一综述。     

Mitiglinide, a novel oral hypoglycemic agent, preserves the cardioprotective effect of ischemic preconditioning in isolated perfused rat hearts

Diabetic patients often have manifestation of coronary heart disease. As a consequence, therapeutic strategies for diabetes should pay more attention to hypoglycemic agents which do not have adverse effects on myocardium. Mitiglinide is considered to have little or no impact on the cardioprotective effect of ischemic preconditioning (IP) because of its high selectivity for blocking sulfonylurea receptor1 (SUR1). However, glibenclamide, a nonselective SUR blocker, attenuates this beneficial effect. In the present study, we tested the hypothesis that mitiglinide preserves the protective action of IP evaluated by ischemia/reperfusion ventricular tachyarrhythmia (rVT) in isolated perfused rat hearts. After initial perfusion, the hearts were assigned to one of the following groups: 1) non-IP with control perfusion buffer (non-IP group); 2) IP with control perfusion buffer (IP-C group); 3) IP with perfusion buffer containing glibenclamide (IP-G group); and 4) IP with perfusion buffer containing mitiglinide (IP-M group). The protocol for the non-IP group consisted of 21 minutes of aerobic perfusion before 10 minutes of ischemia. In the other 3 groups (IP groups), there were 3 cycles of 2-minute ischemia followed by 5 minutes of reperfusion before 10 minutes of ischemia. The IP-C group had a significantly shorter rVT duration than the non-IP group (4.4 +/- 1.8 minutes versus 14.3 +/- 2.5 minutes; P < 0.05). rVT duration was the shortest in the IP-M group (3.9 +/- 1.0 minutes), but among the longest in the IP-G group (14.0 +/- 2.6 minutes). In conclusion, mitiglinide preserved the cardioprotective effect of IP, however, glibenclamide abolished this beneficial effect. Therefore, mitiglinide may offer a long-term benefit for myocardial ischemia in diabetic patients.     

洛伐他汀预适应在大鼠急性缺血再灌注中的心肌保护作用

目的:探讨洛伐他汀预适应对大鼠心脏急性缺血再灌注中的心肌保护作用及其机制。方法:将 24只SD大鼠随机分为3组(每组均8只):模型对照组(C组); 洛伐他汀组( L组),胃管直接灌注洛伐他汀 15 mg·kg-1·d-12周;洛伐他汀复合L 硝基精氨酸甲酯(L NAME)组(N组),洛伐他汀直接灌胃 2 周同时腹腔注射L NAME 30 mg·kg-1·d-1;2周后建立体内急性缺血再灌注心脏模型,监测缺血再灌注前后血流动力学各项指标,同时观察各组血脂水平及其血浆中丙二醛(MDA) 、心肌组织内超氧化物歧化酶(SOD)变化情况。结果: L组和N组较C组心率明显变慢(P<0.01),缺血再灌注心律失常消失和再灌注时-dp/dtmax下降明显改善(P<0.05);同时各项血脂指标不变,洛伐他汀能明显减少再灌注时血浆中MDA生成, 并且提高心肌组织SOD活性(P<0.05)。结论:洛伐他汀预适应对体内大鼠心脏急性缺血再灌注时具有非降脂外的心肌保护作用,其机制除与其增加一氧化氮(NO)合成相关外,可能还有其他物质或途径参与。     

Aging abolishes the cardioprotective effect of combination heat shock and hypoxic preconditioning in reperfused rat hearts

Hypoxic preconditioning (HP) does not improve post-ischemic function in the hearts of aging rats secondary to failure of protein kinase C (PKC) activation, but the effect of heat shock (HS) or preconditioning has not been studied. We studied whether HS increases tolerance to ischemia and whether its combination with HP would restore the cardioprotective effect in aging rat hearts. HS was performed in 12- and 50-week-old rats. Hearts were isolated and subjected to HP by 10 min hypoxic perfusion before 25 min ischemia followed by 30 min reperfusion 48 h after HS. Both HP and HS improved recovery of left ventricular function with translocation of PKC-δ from the cytosol to the nuclear fraction and induction of heat shock proteins, HSP27, HSP70, and αB-crystallin. The combination of HS and HP enhanced the translocation of PKC-δ in young rats, resulting in further improvement in functional recovery. In older rats, HP translocated PKC-δ from the membrane to the cytosol fraction, but did not improve functional recovery, although the combination of HS with HP induced HS proteins and translocated PKC-δ from the cytosol to the nuclear fraction. HS provided cardioprotection and had additive effects to HP with additional PKC-δ activation in young rats. However, in hearts from aging rats, HS alone was not cardioprotective, nor was its combination with HP, despite the induction of HS proteins and the activation of PKC-δ, resulting in its translocation to the nuclear fraction. Received: 14 March 2002, Returned for revision: 8 April 2002, Revision received: 24 May 2002, Accepted: 11 June 2002 Correspondence to: M. Tani, MD, PhD, FJCC, FACC, FAHA     

Loss of cardioprotection induced by ischemic preconditioning after an initial ischemic period in isolated rat hearts

BACKGROUND:

The beneficial effect of ischemic preconditioning (PC) has been extensively studied in normal hearts but its effects on diseased hearts remain largely unknown. The effect of PC in the already ischemic myocardium has not been previously studied, although ischemia in varying intervals, which is difficult to assess, is often encountered in clinical practice.

OBJECTIVE:

To investigate whether the cardioprotective effect of PC is preserved when it is applied after a period of ischemia of varying duration.

METHODS:

Male Wistar rats were used for this study. Isolated normal rat hearts were perfused in Langendorff mode. Before 20 min of zero flow global ischemia followed by 45 min of reperfusion, hearts were subjected to an initial 20-min period of ischemia followed by 10 min of reperfusion (group A1); an initial 20-min period of ischemia followed by 10 min of reperfusion and two-cycle PC (3 min of ischemia, 5 min of reperfusion followed by 5 min of ischemia and 5 min of reperfusion) (group A2); and two-cycle PC followed by the initial 20-min period of ischemia and 10 min of reperfusion (group A3).Groups B and C were subjected to an initial ischemia of 15 min and 10 min, respectively, and subgroups 1, 2 and 3 were treated as above. Left ventricular end-diastolic pressure was measured at 45 min of reperfusion (LVEDP45 in mmHg). Postischemic recovery of left ventricular developed pressure was expressed as a percentage of the initial value (LVDP%).

RESULTS:

LVDP% and LVEDP45 were similar between groups A1 and A2, while when ischemic preconditioning preceded the two periods of ischemia (group A3), it resulted in significantly higher LVDP% and significantly lower LVEDP45 compared with groups A1 and A2. Left ventricular functional recovery was not increased in group B2 compared with group B1. LVDP% and LVEDP45 were similar among groups C1, C2 and C3.

CONCLUSION:

Ischemic preconditioning does not improve functional recovery in isolated rat hearts that have been initially subjected to 20 min or 15 min of zero-flow global ischemia, while an initial 10-min ischemic period seems to precondition the heart.     

预处理对在体大鼠心肌细胞的保护作用

目的：探讨缺血预处理对心肌细胞的保护作用。方法：在体大鼠心肌细胞缺血／复灌模型中，观察缺血预处理对心肌细胞再次长时间缺氧／复氧或缺血／复灌损伤的保护作用（LDH释放，MDA，SOD的含量和心肌梗死范围及心律失常等）。结果；在体大鼠心肌缺血预处理组梗死范围和血清LDH较缺血复灌组减少（P＜0．01），预处理组MDA较缺血复灌组也显著降低（P＜0．01）。而且无论是再次的缺血还是复灌期室性心律失常的发生率预处理组明显低于非预处理组（P＜0．01）。结论：缺血预处理可以减少再次长时间的缺血／复灌对心肌的损伤。     

延迟相缺血预处理心肌保护时间窗的临床探讨

目的探讨心肌梗死患者延迟相缺血预处理的心肌保护时间窗。方法行直接冠状动脉介入治疗的急性心肌梗死患者150例,根据梗死前心绞痛发作时间分为三组：无心绞痛组（1组）55例,〈72 h心绞痛组（2组）55例,〉72 h心绞痛组（3组）40例。统计患者一般临床情况、院内预后指标、出院前的左室射血分数,肌酸激酶和肌酸激酶同工酶的曲线下面积反映患者的心肌梗死面积。结果除年龄外,其余各项临床指标在三组间均无统计学差异。2组和3组的心肌梗死面积明显低于1组（P〈0.01）,但2组的充血性心力衰竭/休克、复合终点发生率明显低于1组和3组（P〈0.01或0.05）。梗死前心绞痛的心肌保护作用与年龄、抗心绞痛药物以及侧支循环无关。结论临床缺血预处理的保护时间窗不同于动物实验,可能大于72 h。     

外源性溶血磷脂酰胆碱和缺血预处理对离体大鼠工作心脏的作用

目的 :观察外源性溶血磷脂酰胆碱 （L PC）对离体大鼠工作心脏的损伤作用及缺血预处理 （IP）对离体大鼠心脏的保护作用。方法 :制备离体大鼠工作心脏模型。随机分为 4组 :C组 :用 K- H液连续灌注 35 min; 组 :停灌注 40 m in,再灌注 30 m in;L 组 :用含 5 μmol/L L PC的 K- H液灌注 5 min,再用正常 K- H液灌注 30 min;P组 :停灌注 5 m in后再灌注 5 min,重复 3次 ,然后重复 L 组全过程。结果 :再灌后 ,L 组和 I组心功能均明显下降 ,室颤发生率提高 ,灌注液中乳酸脱氢酶 （L DH）和丙二醛 （MDA）含量明显升高 ,心肌组织中超氧化物歧化酶 （SOD）活力明显降低。与 L 组相比 ,P组心功能指标明显升高 ,L DH和 MDA含量明显降低 ,SOD活力较高 ,无室颤发生。结论 :L PC可导致与经典方法类似效果的类缺血再灌注损伤作用 ,IP对 L PC损伤有保护作用。     

脑缺血预处理和缺血耐受机制

脑缺血预处理系指机体对短暂缺血的适应性反应,能增强神经元对再次缺血的耐受性,其内源性保护机制涉及多个分子,如腺苷受体、热休克蛋白、阿片受体、低氧诱导因子、N-甲基-D-天冬氨酸受体、环氧合酶和抗氧化酶等.由于这种内源性保护具有临床应用价值,对脑保护机制研究和药物开发具有重要意义,因此受到牛命科学界广泛关注.     

Effects of ischemic preconditioning on the release of cardiac troponin T in isolated rat hearts

Summary The aim of this study was to examine the effect of ischemic preconditioning on the releases of cardiac troponin T (TnT) during reperfusion in isolated rat hearts. Experiments were done on 22 rat hearts, which were perfused according to the method of Langendorff and were divided into the control group (n=14) and the preconditioning group (n=8). Double 5 min of ischemia each followed by 5 min reflow were applied as ischemic preconditioning. After 20 min of global ischemia, the releases of TnT, creatine kinase (CK), and lactate dehydrogenase (LD) in coronary effluent and the left ventricular developed pressure (LVP) were measured during 60 min of reperfusion. Ischemic preconditioning significantly suppressed the amounts of TnT released during reperfusion, as with those of CK and LD, and also improved contractile dysfunction (nine hearts in which ventricular fibrillation was sustained were excluded from the evaluation for hemodynamics), though the release kinetics of TnT was different from that of CK and LD. There were good inverse relationships between the LVP and the total amounts of TnT released during reperfusion period ( TnT) or TnT levels at 60 min of reperfusion. Cardiac TnT can be used as a useful biochemical marker for hemodynamics and myocardial damage after reperfusion.     

Protection of cardiac mitochondria by diazoxide and protein kinase C: implications for ischemic preconditioning

Mitochondrial ATP-sensitive K (mitoK(ATP)) channels play a central role in protecting the heart from injury in ischemic preconditioning. In isolated mitochondria exposed to elevated extramitochondrial Ca, P(i), and anoxia to simulate ischemic conditions, the selective mitoK(ATP) channel agonist diazoxide (25-50 microM) potently reduced mitochondrial injury by preventing both the mitochondrial permeability transition (MPT) and cytochrome c loss from the intermembrane space. Both effects were blocked completely by the selective mitoK(ATP) antagonist 5-hydroxydecanoate. The protective effect against Ca-induced MPT was most evident under conditions in which the ability of electron transport to support membrane potential (Deltapsi(m)) was decreased and inner membrane leakiness was increased moderately. Under these conditions, mitoK(ATP) channel activity strongly regulated Deltapsi(m), and diazoxide prevented MPT by inhibiting the driving force for Ca uptake. Phorbol 12-myristate 13-acetate mimicked the protective effects of diazoxide, unless 5-hydroxydecanoate was present, indicating that protein kinase C activation also protects mitochondria by activating mitoK(ATP) channels. Because Deltapsi(m) recovery ultimately is required for heart functional recovery, these results may explain how mitoK(ATP) channel activation mimics ischemic preconditioning by protecting mitochondria as they pass through a critical vulnerability window during ischemia/reperfusion.     

糖尿病大鼠在心肌缺血及二氮嗪预处理中一氧化氮信号通路表达受抑的研究

目的:探讨糖尿病对心肌缺血预处理(IPC)及二氮嗪预处理(DPC)效果的影响及其机制。方法:取糖尿病及非糖尿病SD大鼠各40只,建立离体心脏Langendorff灌注模型,各分为5组(每组8只):①对照组(Con组):仅行全心灌流120min,不做其他处理;②缺血再灌注组(I/R组):心脏平衡灌流30min,缺血30min,再灌注60min;③IPC组:缺血30min前,心脏平衡灌流10min,2次缺血5min,再灌注5min后,余同I/R组;④DPC组:心脏依次平衡灌流10 min,重复2次灌注含二氮嗪(浓度为100μmol/L)的K-H液5min,间隔灌注K-H液5min,余同I/R组;⑤二甲基亚砜组(DMSO组):用DMSO取代二氮嗪,过程与DPC组处理相同。比较各组冠状动脉流出液中肌酸激酶(CK)、心肌组织中丙二醛(MDA)、超氧化物歧化酶(SOD)活性及环磷酸鸟苷(cGMP)、NO、一氧化氮合成酶(NOS)含量的变化。电镜对心肌线粒体行Flameng评分。结果:①灌流液CK含量:缺血前各组间差异无统计学意义(P0.05)。再灌注后CK含量比较(与I/R比较):非糖尿病大鼠的IPC组和DPC组明显降低(P0.01);而糖尿病大鼠的IPC组和DPC组无明显降低,(与I/R组比较)差异无统计学意义(P0.05)。②心肌MDA含量:非糖尿病大鼠的IPC组和DPC组含量明显比I/R组降低(P0.01),而糖尿病大鼠的各组差异无统计学意义(P0.05)。心肌SOD含量:非糖尿病大鼠的IPC组和DPC组明显高于I/R组(P0.01),而糖尿病大鼠的各组间差异无统计学意义(P0.05)。③心肌cGMP、NO、NOS含量的变化:非糖尿病大鼠的IPC组及DPC组与I/R组比较明显增加(P0.01);而糖尿病大鼠的组间比较差异无统计学意义(P0.05)。④心肌线粒体Flameng评分:糖尿病大鼠各组间比较,差异无统计学意义(P0.05)。结论:IPC及DPC对非糖尿病大鼠心肌有明显的保护作用,能正调NO、cGMP及NOS的表达。而糖尿病可抑制IPC及DPC的心肌保护作用,其机制可能与糖尿病大鼠心肌NO信号通路表达受抑制有关。     

细胞膜钠钙交换蛋白在大鼠心肌缺血预适应及腺苷诱导预适应中的作用及其信号转导

目的 探讨细胞膜钠钙交换蛋白（NCX）在心肌缺血预适应及药物诱导预适应中的作用及可能的信号转导途径.方法 培养乳鼠心肌细胞随机分为缺血/再灌注组、缺血预适应组、腺苷预处理组、钙调素依赖蛋白激酶Ⅱ（CaMKⅡ）抑制剂KN-93＋缺血预适应组、KN-93＋腺苷预处理组及对照组.各组乳酸脱氢酶（LDH）漏出量用生化法测定（n=5）,钠钙交换蛋白mRNA表达以半定量RT-PCR检测（n=5）,NCX活性以液闪仪测定Na^＋依赖的^45Ca^2＋摄取率表示（n=5）.结果 （1）缺血/再灌注组LDH漏出量显著增加（P＜0.05）,缺血预适应及腺苷预处理组LDH漏出量均显著降低 （P＜0.05）;KN-93预作用后,缺血预适应及腺苷预处理组LDH漏出量均显著增加（P＜0.05）. （2）缺血/再灌注组NCX ^45Ca^2＋摄取率比对照组高（P＜0.005）.缺血预适应及腺苷预处理组较缺血/再灌注时NCX ^45Ca^2＋摄取率显著低（P＜0.05）,且腺苷预处理组NCX ^45Ca^2＋摄取率较缺血预适应组更低（P＜0.05）. KN-93＋缺血预适应组与缺血/再灌注组NCX ^45Ca^2＋摄取率差异无统计学意义, KN-93＋腺苷预处理组较缺血/再灌注组NCX ^45Ca^2＋摄取率低（P＜0.05）.（3） 缺血/再灌注组NCX mRNA的表达比对照组显著高（P＜0.05）;缺血预适应及腺苷预处理组NCX mRNA的表达均显著低（P＜0.05）;KN-93处理后缺血预适应组及腺苷预处理组NCX mRNA的表达水平显著高（P＜0.05）,且腺苷预处理组NCX mRNA的表达较缺血预适应组更高（P＜0.05）.结论 缺血预适应及腺苷预处理对心肌的保护作用与细胞膜NCX有关,缺血预适应中NCX对心肌损伤保护作用经CaMKⅡ介导,而在腺苷预处理中NCX对心肌损伤保护作用仅部分经CaMKⅡ介导.