Xanthine oxidase produces hydrogen peroxide which contributes to reperfusion injury of ischemic, isolated, perfused rat hearts.

Three lines of investigation indicated that hydrogen peroxide (H2O2) from xanthine oxidase (XO) contributes to cardiac dysfunction during reperfusion after ischemia. First, addition of dimethylthiourea (DMTU), a highly permeant O2 metabolite scavenger (but not urea) simultaneously with reperfusion improved recovery of ventricular function as assessed by ventricular developed pressure (DP), contractility (+dP/dt), and relaxation rate (-dP/dt) in isolated Krebs-Henseleit-perfused rat hearts subjected to global normothermic ischemia. Second, hearts from rats fed tungsten or treated with allopurinol had negligible XO activities (less than 0.5 mU/g wet myocardium compared with greater than 6.0 mU/g in control hearts) and increased ventricular function after ischemia and reperfusion. Third, myocardial H2O2-dependent inactivation of catalase occurred after reperfusion following ischemia, but not after ischemia without reperfusion or perfusion without ischemia. In contrast, myocardial catalase did not decrease during reperfusion of ischemic hearts treated with DMTU, tungsten, or allopurinol.     

Protection against myocardial dysfunction induced by global ischemia-reperfusion by antisense-oligodeoxynucleotides directed at beta(1)-adrenoceptor mRNA

Plasma catecholamine levels rise, and myocardial beta(1)-adrenoceptor (beta(1)-AR) sensitivity increases during ischemia. These factors enhance myocardial injury and cardiac dysfunction. beta(1)-AR blockers are clinically used to protect heart against ischemia and to improve cardiac dysfunction in patients with ischemic heart disease, but these agents often cause intolerable side effects. To examine the potential cardioprotective effect of therapy with antisense-oligodeoxynucleotides directed at beta(1)-AR mRNA (beta(1)-AS-ODNs) during myocardial ischemia-reperfusion, Sprague-Dawley rats were treated with beta(1)-AS-ODNs or inverted-oligodeoxynucleotides (IN-ODNs), each 200 microg/rat. Hearts were excised, perfused, and subjected to global ischemia (30 min) followed by reperfusion (30 min). Other rats were given selective beta(1)-AR blocker atenolol (2 mg/kg) or saline before excising the hearts. Ischemia-reperfusion resulted in cardiac dysfunction, indicated by an increase in coronary perfusion pressure and left ventricular end-diastolic pressure and a decrease in developed left ventricular pressure, as well as evidence of lipid peroxidation in saline-treated rats (all P <.05 versus control values). Administration of AS-ODNs or atenolol, but not IN-ODNs, protected hearts against functional deterioration and lipid peroxidation (P <.05 versus saline or IN-ODNs treatment). AS-ODNs therapy appeared to be equivalent to atenolol in these effects. Expression of beta(1)-AR protein as well as mRNA in the myocardium were markedly up-regulated after ischemia-reperfusion, and treatment with beta(1)-AS-ODNs, but not atenolol, decreased the rise in enhanced expression of beta(1)-AR. These observations imply that beta(1)-AS-ODNs can ameliorate cardiac dysfunction after ischemia-reperfusion by reducing the expression of beta(1)-AR in the ischemic-reperfused myocardium.     

Effects of different angiotensin-converting enzyme (ACE) inhibitors on ischemic isolated rat hearts: relationship between cardiac ACE inhibition and cardioprotection.

We determined the relationship between cardiac angiotensin-converting enzyme (ACE) inhibition and anti-ischemic efficacy of several structurally different ACE inhibitors or their prodrug esters perfused through the isolated rat heart. Seven ACE inhibitors inhibited cardiac ACE to varying degrees due to differences in uptake during perfusion through nonischemic rat hearts. Zofenopril-sulfhydryl and fosinoprilic acid were the most effective of the free inhibitors. Among the prodrugs, zofenopril and S-benzoylcaptopril, hydrolyzed rapidly by cardiac esterase, were more effective than their component ACE-inhibitors, whereas fosinopril, ramipril and enalapril were poorly active. For studies in ischemic rat hearts, vehicle or drug treatment was initiated 10 min before a 25-min period of global ischemia and during a 30-min reperfusion period. Of five unesterified ACE inhibitors studied for anti-ischemic activity, only captopril and zofenopril-sulfhydryl were found to improve postischemic contractile function and reduce cell death in the isolated rat hearts. Fosinoprilic acid, ramiprilat and enalaprilat were not cardioprotective at high perfusion concentrations, despite the fact that nearly complete inhibition of cardiac ACE was achieved with all of the compounds studied. The S-benzoyl prodrugs of zofenopril-sulfhydryl and captopril were at least as potent as their component ACE inhibitors in reducing ischemic-reperfusion damage in the same model. Neither zofenopril nor captopril, however, had any effect on coronary flow before or after ischemia. Thus, it appears that the cardioprotective effects of zofenopril and captopril are independent of cardiac ACE inhibition or, at least, that ACE inhibition alone is not sufficient. Both captopril and zofenopril are sulfhydryl-containing compounds whereas the inactive compounds are not; and, thus, this group appears to be important in mediating their cardioprotective actions.     

参附注射液对缺血再灌注心肌损伤的保护作用

目的：探讨参附注射液对缺血／再灌注（I／R）损伤心肌的保护作用及其机制。方法：32只雄性SD大鼠随机分为4组：正常对照组（n=8）、缺血／再灌注组（n=8）、参附注射液30mg／L组（n=8）和100mg／L组（n=8）。采用Langendorff离体心脏灌流模型，制备心肌缺血再灌注损伤模型，在心脏缺血前和再灌注后，给予参附注射液，观察离体大鼠心脏血流动力学指标和心肌组织中的高能磷酸化舍物ATP含量、MDA含量及SOD活性等的变化。结果：参附注射液100mg／L明显改善缺血／再灌注后心脏血流动力学指标。缺血／再灌注组大鼠心肌ATP含量和SOD活性明显降低，MDA含量明显升高。与缺血／再灌注组比较，参附注射液30mg／L组和100mg／L组心肌MDA值减少（P〈O．05），SOD值升高（P〈0．05）；参附注射液100mg／L组ATP含量增加（P〈0．05）。结论：参附注射液能通过提高心肌组织ATP含量和SOD活性，减少MDA含量，改善缺血／再灌注后心脏血流动力学紊乱，减轻大鼠心肌缺血再灌注损伤。     

Cardioprotective Effects of Red Blood Cells on Ischemia and Reperfusion Injury in Isolated Rat Heart: Release of Nitric Oxide as a Potential Mechanism

BACKGROUND: Circulating cells influence myocardial function during ischemia and reperfusion, (eg, neutrophils exacerbate, and platelets protect the myocardium from deterioration). This study was designed to determine the role of red blood cells on myocardial function following ischemia and reperfusion in isolated rat hearts. METHODS AND RESULTS: Exposure of buffer-perfused hearts to 40 minutes of total ischemia followed by 30 minutes of reperfusion resulted in myocardial dysfunction and injury, indicated by decrease in the force of cardiac contraction (FCC, -25 +/- 4%), increase in the coronary perfusion pressure (CPP, +20 +/- 3%) and decrease in myocardial superoxide dismutase (SOD, 2.5 +/- 0.2 vs 3.5 +/- 0.4 U/mg protein in sham ischemic hearts, P <.05). Perfusion of the hearts with washed rat red blood cells showed significant protective effects against ischemia and reperfusion, indicated by minimal change in FCC (-10 +/- 4%) and CPP (+3 +/- 3%) (both P <.01 vs buffer alone perfused hearts) and preservation of myocardial SOD activity (2.8 +/- 0.4 U/mg protein, P <.05 vs buffer alone perfused hearts). The cardioprotective effects of red blood cells were attenuated when the red blood cells were preincubated with the nitric oxide blood cells were attenuated when the red blood cells were preincubated with the nitric oxide blood cells were attenuated when the red blood cells were preincubated with the nitric oxide synthase inhibitors N(omicron)-nitro-l-arginine (l-NNA, 5 x 10(-4)M) or N(omicron)-nitro-l-arginine methyl ester (l-NAME, 5 x 10(-4)M) at 37 degrees C for 60 minutes before perfusion of the heart. Perfusion of hearts with the nitric oxide precursor l-arginine (2 x 10(-4)M) also exerted significant protective effects on FCC ( - 14 +/- 4%), CPP (+12 +/- 3%) and myocardial SOD activity (2.9 +/- 0.2 U/mg protein) following ischemia and reperfusion. In other studies, washed rat red blood cells expressed nitric oxide synthetase activity which was inhibited by both l-NNA and l-NAME. CONCLUSIONS: These results suggest that red blood cells exert cardioprotective effects against ischemia and reperfusion at least in part by the l-arginine-nitric oxide pathway in isolated rat hearts.     

心肌sMiMi-CK基因蛋白质对大鼠心肌缺血/再灌注损伤的影响

目的　本实验拟观察ｓＭｉＭｉ－ ＣＫ基因表达产物对大鼠心肌缺血／ 再灌注损伤的影响。方法　提取纯化ｓＭｉＭｉ－ ＣＫ基因蛋白质，建立大鼠离体心肌缺血／ 再灌注模型，以心肌超微结构的改变、能量代谢、自由基为指标观察其保护作用。结果　ｓＭｉＭｉ－ ＣＫ蛋白能明显保护缺血心肌超微结构，减轻线粒体内钙超载，明显提高ＡＴＰ、ＡＤＰ、ＡＭＰ水平，减少羟自由基的生成。结论　ｓＭｉＭｉ－ ＣＫ 蛋白对缺血／ 再灌注的大鼠心肌细胞具有明显的保护作用，从而为缺血性心脏病的基因治疗提供理论和实践基础。     

血红素加氧酶-1对心肌缺血再灌注损伤的保护作用

目的:探讨血红素加氧酶-1(HO-1)对心肌缺血再灌注损伤的保护作用及机制。方法:采用HO-1的诱导剂钴原卟啉(CoPP)和抑制剂锌原卟啉(ZnPP)分别进行干预处理后,建立大鼠的心肌缺血/再灌注损伤模型。观察大鼠再灌注后心肌形态变化,检测HO-1基因在大鼠心肌的表达情况,测定大鼠左心室心肌组织超氧化物歧化酶(SOD)活性及丙二醛(MDA)含量。结果:再灌注前使用CoPP进行预处理,可以诱导HO-1蛋白的表达上调;HO-1蛋白表达上调可以减少缺血再灌注后的心肌细胞坏死,提高心肌组织中SOD含量并降低MDA的含量。结论:CoPP诱导的HO-1过表达可以抑制心肌缺血再灌注损伤后的细胞坏死,从而减轻心肌的再灌注损伤,其主要机制与抗氧自由基有关。     

肢体缺血-再灌注后大鼠心肌中的氧化应激及HO-1 mRNA表达

目的 探讨肢体缺血-再灌注损伤后心肌的氧化损伤机制及HO-1的保护作用,为研究肢体缺血-再灌注损伤所致的心肌损伤的预防提供实验依据.方法 应用止血带构造SD大鼠双后肢IR模型,实验动物随机(随机数字法)分为正常对照组和缺血4 h再灌注2 h,4 h,6 h,8 h,16 h,24 h共7组,分别取心肌和血液标本检测MDA,SOD,MPO,心肌形态学及心肌组织中HO-1 mRNA的表达.方差分析方法进行统计学处理.结果 (1)血浆及心肌IR各组MDA均较对照组明显升高(P<0.05),且于IR 4 h达高峰.血浆及心肌IR各组SOD均较对照组明显降低(P<0.05),且血清SOD于IR4 h达最低值,心肌SOD于IR 8 h达最低值.血浆及心肌IR各组MPO均较对照组明显升高(P<0.05),且血清MPO于IR 4 h达高峰,心肌MPO于IR 6 h达高峰.(2)在肢体缺血4 h再灌注4-6 h组,心肌形态学损伤最重.(3)与对照组比较,IR2 h组HO-1 mRNA表达差异无统计学意义(P>0.05),其余各组HO-1 mRNA表达均显著上调(P<0.05)且于IR 16 h达高峰.结论 心肌局部组织的自由基和中性粒细胞聚集活化是LIR心肌损伤的机制且能上调HO-1 mRNA的表达,HO-I在心肌组织的高表达能减轻心肌组织的损伤.     

依达拉奉对大鼠缺血/再灌注心肌细胞凋亡的影响

目的：观察依达拉奉对心肌缺血／再灌注后心肌细胞凋亡的影响。方法：选择30只健康SD大鼠，采用结扎冠状动脉左前降支后再通的方法复制心肌缺血再灌注的动物模型，随机分为假手术组（n=10）、缺血／再灌注（I／R）组（n=10）和药物（依达拉秦）组（n=10）。检测各组3h后心肌组织的超氧化物歧化酶（SOD）和丙二醛（MDA）的含量。并用免疫组化法测定局部凋亡相关因子Bcl-2、Fas的表达，比较各组间差异。结果：与假手术组比较，I／R组中反映氧化损伤程度的MDA明显升高（P〈0．01），抗氧化酶SOD则明显减少（P〈0．01），Fas含量升高（P〈0、01），Bcl-2含量明显减少（P〈0、01）；药物组较I／R组MDA含量明显减少（P〈0．01），SOD活性显著增加（P〈0．01），Fas含量明显降低（P〈0，05），Bcl-2含量明显增加（P〈0．01）。结论：依达拉奉具有抗心肌缺血再灌注损伤作用，其机制可能是通过调节Bcl-2和Fas介导的细胞凋亡而实现     

Effect of naloxone on expression of Bcl-2 protein and tumor necrosis factor-alpha in rats with acute myocardial ischemia/reperfusion injury]

OBJECTIVE: To investigate the effect of naloxone on myocardial cell apoptosis and apoptosis-related gene Bcl-2 in rats with acute myocardial ischemia/reperfusion (AMIR) injury, and explore the mechanism of protective effect of naloxone on myocardium. METHODS: Thirty SD rats were randomly divided into three groups (n=10): ischemia/reperfusion group, naloxone preconditioning group (naloxone was injected intraperitoneally 10 minutes before ischemia and 2 hours after reperfusion), and normal control group. The left anterior descending branch (LAD) of rat coronary artery was tied and untied in ischemia/reperfusion group and naloxone preconditioning group to establish the AMIR model in rats. The animals were then sacrificed and hearts were harvested. The expression of Bcl-2 protein was observed by immunohistochemical technique. Radioimmunoassay (RIA) was used to determine tumor necrosis factor-alpha (TNF-alpha) in serum. RESULTS: In the normal control group, there was no Bcl-2 expression and TNF-alpha level was (0.39+/-0.06) mug/L. Higher expression of Bcl-2 and increased TNF-alpha levels were found in ischemia/reperfusion group. The expression of Bcl-2 protein increased significantly [(+++) vs. (+)], and TNF-alpha was significantly lower in naloxone preconditioning group than those in the normal control group [(0.55+/-0.12) microg/L vs. (0.86+/-0.11) microg/L, P<0.01]. CONCLUSION: Naloxone can protect myocardium from AMIR injury by inhibiting the apoptosis of cardiomyocytes induced by TNF-alpha and up-regulating protein expression of bcl-2 gene.     

脂肪乳预处理和后处理对大鼠心肌缺血/再灌注损伤的保护作用

目的 观察在心肌缺血/再灌注(I/R)损伤前(预处理)或损伤后(后处理)给予脂肪乳对心脏I/R损伤的改善作用,探讨脂肪乳在心脏保护方面的潜在价值.方法 实验采用大鼠Langendorff心脏离体灌流模型.将24只雄性SD大鼠随机分组:空白对照组(ISCH组)心脏离体平衡50 min,37 ℃缺血40 min,复灌120 min;脂肪乳预处理组(I-preC组)心脏离体平衡20 min,给予含30%的脂肪乳灌注液输注15 min,洗脱15 min,随后37 ℃缺血40 min,复灌120 min;脂肪乳后处理组(I-postC 组)心脏离体平衡50 min,37 ℃缺血40 min,复灌120 min,复灌开始即给予含30%的脂肪乳灌注液输注15 min.于平衡50 min和复灌120 min期间连续监测左室内压上升和下降最大速率(±dp/dt max)、左室舒张期末压(LVEDP)、左室舒张压(LVDP)、心率(HR).平衡20 min和复灌60 min时接取冠状动脉流出液,测定肌酸激酶(CK)和乳酸脱氢酶(LDH)的活性.复灌结束后计算心肌梗死面积.结果 心脏机械功能指标:与ISCH组比较,复灌期间I-postC组+dp/dt max、LVDP显著升高,-dp/dt max、LVEDP显著降低(P均＜0.05);而I-preC组各指标比较差异无统计学意义.冠状动脉生化指标:复灌60 min时I-preC组和I-postC组CK和LDH活性均较ISCH组显著降低(P均d＜0.05);I-preC组与I-postC组比较差异无统计学意义(尸均＞0.05).I-preC组和I-postC组心肌梗死面积较ISCH组显著降低[(21.6±1.8)%、(15.9±1.3)%比(46.5±3.9)%,P均<0.05)];I-preC组与I-postC组比较差异无统计学意义(P＞0v.05).结论 脂肪乳预处理和后处理均能减轻心肌I/R损伤后CK和LDH的释放,缩小心肌梗死面积.脂肪乳后处理能显著增强心肌I/R损伤后心脏的机械功能.     

链脲佐菌素诱导糖尿病大鼠NO变化对缺血再灌注损伤的影响

目的:探讨链脲佐菌素(STZ)诱导的不同周期糖尿病对心肌缺血/再灌注(I/R)损伤的影响及其与血浆一氧化氮(NO)变化的关系.方法:阻断和开放左冠状动脉前降支建立大鼠急性心肌I/R模型.分别用TTC染色测定大鼠心肌I/R后梗死面积;用硝酸还原酶法测定NO含量;用免疫印迹法定量分析代表细胞生存信号的磷酸化蛋白激酶B(P-Akt)的表达.结果:STZ处理后2周,糖尿病组(2WD+I/R)心肌梗死面积比相应周期对照组(2WC+I/R)明显缩小,STZ处理后16周(16WD+I/R),梗死面积比相应对照组(16WC+I/R)增加;血浆NO水平在2周糖尿病组中较对照组增高,但是在16周糖尿病组中较对照组显著减少;P-Akt在心肌的表达在2WD组比2WC组增加35%,在16WD组比16WD组明显减少.结论:STZ诱导的急、慢性期糖尿病对心肌I/R损伤呈现相反的作用.这可能是由于急、慢性期糖尿病相反的NO改变而引起的.     

PLCδ1 Protein Rescues Ischemia-reperfused Heart by the Regulation of Calcium Homeostasis

Myocardial Ca²⁺ overload induced by ischemia/reperfusion (I/R) is a major element of myocardial dysfunction in heart failure. Phospholipase C (PLC) plays important roles in the regulation of the phosphoinositol pathway and Ca²⁺ homeostasis in various types of cells. Here, we investigated the protective role of PLCδ1 against myocardial I/R injury through the regulation of Ca²⁺ homeostasis. To investigate its role, PLCδ1 was fused to Hph1, a cell-permeable protein transduction domain (PTD), and treated into rat neonatal cardiomyocytes and rat hearts under respective hypoxia-reoxygenation (H/R) and ischemia-reperfusion conditions. Treatment with Hph1-PLCδ1 significantly inhibited intracellular Ca²⁺ overload, reactive oxygen species generation, mitochondrial permeability transition pore opening, and mitochondrial membrane potential elevation in H/R neonatal cardiomyocytes, resulting in the inhibition of apoptosis. Intravenous injections of Hph1-PLCδ1 in rats with I/R-injured myocardium caused significant reductions in infarct size and apoptosis and also improved systolic and diastolic cardiac functioning. Furthermore, a small ions profile obtained using time-of-flight secondary ion mass spectrometry showed that treatment with Hph1-PLCδ1 leads to significant recovery of calcium-related ions toward normal levels in I/R-injured myocardium. These results suggest that Hph1-PLCδ1 may manifest as a promising cardioprotective drug due to its inhibition of the mitochondrial apoptotic pathway in cells suffering from I/R injury.     

Global ischemic duration and reperfusion function in the isolated perfused rat heart

Post-ischemic myocardial dysfunction has been observed in a variety of clinical situations including cardiac arrest. Potentially survivable cardiac arrest following short-term global myocardial ischemia may be of insufficient duration to cause irreversible myocyte injury, but still results in contractile and bioenergetic dysfunction. The purpose of this study was to characterize the ischemic transition from reversible to irreversible injury in the isolated perfused rat heart. Isolated, buffer perfused, male Sprague-Dawley rat hearts underwent normothermic ischemia of 15, 20, 25 or 30 min with or without 30 min of reperfusion and were freeze clamped in liquid nitrogen for bioenergetic analysis of LV tissue. Post-ischemic LV function and measurements of bioenergetic recovery were made between groups and with non-ischemic controls. Baseline LV function was similar in all groups. Post-ischemic contractile function was markedly depressed in the 25 and 30 min ischemia groups with persistent depression of high-energy phosphates, total adenine nucleotide pool, myocardial oxygen consumption, elevated CK release and evidence of significant mitochondrial edema in the 30 min group. In contrast with longer ischemic periods, the reduction in LV contractile function after 15 and 20 min of ischemia was mild, with more complete bioenergetic recovery, minimal CK release, and normal appearing mitochondrial. This data suggests a period of transition from reversible to irreversible injury occurring at approximately 20 min of normothermic global ischemia in the isolated perfused rat heart.     

AMP-activated protein kinase mediates ischemic glucose uptake and prevents postischemic cardiac dysfunction, apoptosis, and injury

AMP-activated protein kinase (AMPK) is an important regulator of diverse cellular pathways in the setting of energetic stress. Whether AMPK plays a critical role in the metabolic and functional responses to myocardial ischemia and reperfusion remains uncertain. We examined the cardiac consequences of long-term inhibition of AMPK activity in transgenic mice expressing a kinase dead (KD) form of the enzyme. The KD mice had normal fractional shortening and no heart failure, cardiac hypertrophy, or fibrosis, although the in vivo left ventricular (LV) dP/dt was lower than that in WT hearts. During low-flow ischemia and postischemic reperfusion in vitro, KD hearts failed to augment glucose uptake and glycolysis, although glucose transporter content and insulin-stimulated glucose uptake were normal. KD hearts also failed to increase fatty acid oxidation during reperfusion. Furthermore, KD hearts demonstrated significantly impaired recovery of LV contractile function during postischemic reperfusion that was associated with a lower ATP content and increased injury compared with WT hearts. Caspase-3 activity and TUNEL-staining were increased in KD hearts after ischemia and reperfusion. Thus, AMPK is responsible for activation of glucose uptake and glycolysis during low-flow ischemia and plays an important protective role in limiting damage and apoptotic activity associated with ischemia and reperfusion in the heart.     

L-NAME enhances microcirculatory congestion and cardiomyocyte apoptosis during myocardial ischemia-reperfusion in rats

Besides necrosis, apoptosis is the other major mode of cardiomyocyte loss in ischemic cardiovascular disease. In the present study, we examined the hypothesis that nitric oxide (NO) protects myocardial function by improving myocardial microcirculation and attenuating cardiomyocyte apoptosis in a rat model of myocardial ischemia/reperfusion (MI/R). The left main coronary artery of anesthetized male rats was ligated for 40 min, followed by 4 h reperfusion. Four groups of animals were studied: sham operated control + saline; sham operated control + N(W)-nitro-L-arginine methyl ester (L-NAME); MI/R + saline; MI/R + L-NAME (10 mg/kg, iv, 10 min prior to reperfusion). Results show that MI/R caused a decrease in mean arterial blood pressure (MABP), cardiac index (CI), and stroke volume index (SVI). Inhibition of NO synthesis by L-NAME attenuated plasma NO levels, but increased MABP and SVR in sham control rats and rats subjected to MI/R, and further depressed left ventricular function in rats subjected to MI/R as indicated by decreased CI and SVI. Furthermore, administration of L-NAME to rats subjected to MI/R enhanced cardiomyocyte apoptosis as indicated by a significant increase in DNA fragmentation compared to rats with MI/R alone. Histological study revealed that L-NAME caused arterial constriction and congestion of red blood cells in arteries and capillaries in the peri-ischemic areas of the hearts in rats subjected to MI/R and, interestingly, also in the sham control rats. Data suggest that the mechanism of increased reperfusion injury may be attributable to a "no-reflow" phenomenon induced by L-NAME, resulting in increased cardiomyocyte apoptosis secondary to ischemia and enhanced cytochrome-c release from mitochondria. In addition, cardiac injury may be increased due to the augmented oxygen consumption of cardiomyocytes caused by the increased SVR and afterload. These results suggest that endogenous NO may act to improve myocardial microvascular perfusion, reduce SVR, and limit cardiomyocyte apoptosis, thereby, attenuating myocardial dysfunction induced by MI/R.     

血红素氧合酶-1基因转染对大鼠心肌缺血/再灌注损伤诱导心肌细胞凋亡的影响

目的 探讨重组腺相关病毒(rAAV)介导大鼠血红素氧合酶-1(rHO-1)基因转染对心肌缺血/再灌注(I/R)损伤大鼠心肌细胞凋亡的影响.方法 95只体重225～250 g的雄性SD大鼠随机分为假手术组(SO组,n=8)、生理盐水组(NS组,,n=29)、rAAV-荧光蛋白组(rAAV-EGFP组,n=29)及rAAV-rHO-1组(n=29).NS组、rAAV-EGFP组和rAAV-rHO-1组分别于大鼠左心室前后壁共取4点分别注入生理盐水、rAAV-EGFP或rAAV-rHO-1病毒液共600 μl.在基因转染后3个月,各组处死3只大鼠,取注射部位心肌,荧光显微镜下观察荧光蛋白的表达并计算转染率;用免疫组化染色和逆转录-聚合酶链反应(RT-PCR)检测HO一1的蛋白和mRNA表达.采用结扎左冠状动脉前降支30 min、再灌注120 min建立心肌I/R模型;成模后处死大鼠测定其心肌梗死面及心肌细胞凋亡指数(AI),光镜下观察心肌组织病理学改变.结果 荧光显微镜下仅rAAV-EGFP组可见心肌有荧光蛋白表达,转染率为(53.5±2.0)%.与SO组比较,NS组、rAAV-EGFP组和rAAV-rHO-1组Al增加(P均<0.01),与NS组和rAAV-EGFP组比较,rAAV-rHO-1组HO-1的蛋白及mRNA表达增加,心肌梗死面积减小,A1减少(P均<0.01);NS组及rAAV-EGFP组心肌组织病理学损伤较SO组和rAAV-rHO-1组为重.NS组与rAAV-EGFP组间上述指标比较无统计学意义.结论 rAAV介导的rHO-1基因转染大鼠心肌细胞后,能够显著减少心肌细胞凋亡,从而减轻心肌I/R损伤.     

Possible involvement of PKC-δ in the abrogated cardioprotective potential of ischemic preconditioning in hyperhomocysteinemic rat hearts

The present study has been designed to investigate the possible role of protein kinase C-delta (PKC-δ) in hyperhomocysteinemia-induced attenuation of cardioprotective potential of ischemic preconditioning (IPC). Rats were administered l-methionine (1.7 g/kg/day, p.o.) for 4 weeks to produce hyperhomocysteinemia. Isolated Langendorff perfused normal and hyperhomocysteinemic rat hearts were subjected to global ischemia for 30 min followed by reperfusion for 120 min. Myocardial infarct size was assessed macroscopically using triphenyltetrazolium chloride (TTC) staining. Coronary effluent was analyzed for lactate dehydrogenase (LDH) and creatine kinase (CK) release to assess the degree of cardiac injury. Moreover, the oxidative stress in heart was assessed by measuring lipid peroxidation and superoxide anion generation. The ischemia-reperfusion (I/R) was noted to produce myocardial injury as assessed in terms of increase in myocardial infarct size, LDH and CK in coronary effluent and oxidative stress in normal and hyperhomocysteinemic rat hearts. In addition, the hyperhomocysteinemic rat hearts showed enhanced I/R-induced myocardial injury with high degree of oxidative stress as compared with normal rat hearts subjected to I/R. Four episodes of IPC (5 min each) afforded cardioprotection against I/R-induced myocardial injury in normal rat hearts as assessed in terms of reduction in myocardial infarct size, LDH, CK and oxidative stress. On the other hand, IPC mediated myocardial protection against I/R-injury was abolished in hyperhomocysteinemic rat hearts. Treatment with rottlerin (10 μM), a selective inhibitor of PKC-δ did not affect the cardioprotective effects of IPC in normal rat hearts; but its treatment significantly restored the cardioprotective potentials of IPC in hyperhomocysteinemic rat hearts. The high degree of oxidative stress produced in hyperhomocysteinemic rat hearts during reperfusion may activate PKC-δ, which may be implicated in the observed paradoxically abrogated cardioprotective potentials of IPC in hyperhomocysteinemic rat hearts.     

Protective Effect of Elastase Inhibition Against Myocardial Dysfunction and Injury Induced by Ischemia and Reperfusion in Isolated Rat Hearts

BACKGROUND: Elastase release has been incriminated in the genesis of reperfusion-induced myocardial dysfunction and injury, and elastase inhibitors have been reported to reduce myocardial dysfunction in dogs subjected to coronary artery occlusion and reperfusion. METHODS AND RESULTS: To examine if elastase inhibition will modify myocardial dysfunction and injured induced by ischemia and reperfusion in isolated hearts, hearts from male Sprague Dawley rats were subjected to 30 minutes of total ischemia followed by 30 minutes of reperfusion. Ischemia-reperfusion resulted in myocardial dysfunction (increase in coronary perfusion pressure and decrease in myocardial contraction), injury (measured as creatine kinase release), and lipid peroxidation (myocardial malondialdehyde). Perfusion of hearts with an elastase inhibitor, ICI200,880, protected against myocardial dysfunction, injury and lipid peroxidation following ischemia-reperfusion. As expected, perfusion with superoxide dismutase protected the hearts against hemodynamic deterioration following ischemia-reperfusion. In in vitro studies, there was no direct effect of ICI200,880 on superoxide anion generation. CONCLUSIONS: ICI200,880 seems to exert cardioprotective effects against ischemia-reperfusion-induced injury and myocardial dysfunction in isolated buffer-perfused hearts, most likely by an elastase-like protease inhibitory activity.