Cardioprotective effects of cyclosporine A in an in vivo model of myocardial ischemia and reperfusion

BACKGROUND: Recent evidence indicates that reperfusion of the heart after a period of ischemia leads to the opening of the mitochondrial permeability transition pore (MPTP). The aim of this study was to investigate cardioprotective effects of cyclosporine A (CsA), an inhibitor of the MPTP, in an in vivo model of myocardial ischemia and reperfusion. METHODS: Male Sprague-Dawley rats were subjected to occlusion of the left anterior descending coronary artery for 30 min followed by 180 min of reperfusion. CsA (10 mg/kg) or vehicle was given 10 min prior to ischemia via the femoral vein. Sham myocardial ischemia-reperfusion rats (sham-operation group) were used as controls. Infarct size was measured using the staining agent TTC (2,3,5-triphenyl tetrazolium chloride) and myocardial apoptosis by caspase-3 activity was determined by fluorescent assay. The myocardium mitochondria ultrastructure was observed through a transmission electron microscope. RESULTS: CsA significantly reduced infarct size (48.8 +/- 5.8% of left ventricle in vehicle + I/R group and 30.3 +/- 2.7% of left ventricle in CsA + I/R, respectively) and decreased caspase-3 activity in the myocardium [(0.62 +/- 0.17)/microg of protein and (0.42 +/- 0.15)/microg of protein, respectively] and relieved the injury of mitochondria. CONCLUSION: CsA reduced the cardiac damage associated with ischemia-reperfusion injury of the heart. The cardioprotective effects of CsA might be associated with the protection of mitochondria and the inhibition of caspase-3 activity. It also suggests that the MPTP might play an important role in cardiomyocytes death after ischemia-reperfusion injury.     

Age-associated differences in response to sevoflurane postconditioning in rats

Background Experimental evidence suggests that anesthetic preconditioning and postconditioning could effectively attenuate myocardial ischemia/reperfusion (I/R) injury. In this study, we aimed at investigating whether there are age-associated differences in response to sevoflurane postconditioning during myocardial I/R injury in young and old rats, and explore the underlying molecular mechanisms. Methods Young and old rats were subjected to 30 min myocardial ischemia, followed by 2 h of reperfusion, with or without sevoflurane postconditioning. Results Both 1 and 2 minimal aveolar concentration (MAC) sevoflurane postconditioning reduced infarct size (IS) (34?±?3% and 32?±?2% vs. 58?±?5%, p?<?0.05) and apoptotic index (8?±?1% and 7?±?1% vs. 15?±?2%, p?<?0.05) in young rats, compared to young control group. In contrast, they could not reduce IS (45?±?3% and 43?±?3% vs. 47?±?3%, p?>?0.05) and apoptotic index (28?±?3% and 25?±?2%, vs. 26?±?2%, p?>?0.05) in old rats, compared to old control group. Mechanistically, we found that the phosphorylation of both Akt and ERK1/2 but not STAT3 was substantially enhanced after sevoflurane postconditioning in young rats, compared to young control group, but not in old rats, relative to old control group. Conclusion There are age-related differences after exposure to sevoflurane postconditioning that protects young, but not old rat hearts against I/R injury, which may be at least associated with the inability to activate Akt and ERK1/2.     

线粒体通透性转换孔在七氟醚延迟预处理减轻大鼠心肌缺血再灌注损伤中的作用

目的 探讨线粒体通透性转换孔(mPTP)在七氟醚延迟预处理减轻大鼠心肌缺血再灌注损伤中的作用.方法 雄性SD大鼠80只,体重250～300 g,随机分为5组(n=16):假手术组(S组)、缺血再灌注组(IR组)、七氟醚延迟预处理组(SP组)、mPTP开放剂苍术苷+七氟醚延迟预处理组(A+SP组)和苍术苷组(A组).IR组、SP组、A+SP组和A组采用结扎左冠状动脉前降支30 min后进行再灌注的方法制备心肌缺血再灌注模型.SP组和A+SP组吸入2.5%七氟醚l h,其余组吸入纯氧1 h,停止吸入后24 h进行心肌缺血.A+SP组和A组在缺血前15 min经尾静脉注射苍术苷5 mg/kg.再灌注120 min时采集颈动脉血样,测定血清肌钙蛋白I(cTnI)浓度.然后处死大鼠,测定心肌梗死体积,检测心肌组织Bcl-2及Bax表达水平,电镜下观察心肌超微结构.结果 与S组比较,其他各组血清cTnI浓度升高,心肌梗死体积扩大,Bcl-2表达下调,Bax表达上调(P＜0.05).与IR组比较,SP组血清cTnI浓度降低,心肌梗死体积缩小,Bcl-2表达上调,Bax表达下调(P＜0.05),心肌病理学损伤减轻.苍术苷可取消七氟醚延迟预处理减轻大鼠心肌缺血再灌注损伤的效应(P＜0.05).结论 抑制mPTP开放后可导致Bcl-2表达上调,Bax表达下调,参与了七氟醚延迟预处理减轻大鼠心肌缺血再灌注损伤.     

Inhibition of mitochondrial permeability transition enhances isoflurane-induced cardioprotection during early reperfusion: the role of mitochondrial KATP channels

Inhibition of the mitochondrial permeability transition pore (mPTP) mediates the protective effects of brief, repetitive ischemic episodes during early reperfusion after prolonged coronary artery occlusion. Brief exposure to isoflurane immediately before and during early reperfusion also produces cardioprotection, but whether mPTP is involved in this beneficial effect is unknown. We tested the hypothesis that mPTP mediates isoflurane-induced postconditioning and also examined the role of mitochondrial KATP (mKATP) channels in this process. Rabbits (n = 102) subjected to a 30-min coronary occlusion followed by 3 h reperfusion received 0.9% saline (control), isoflurane (0.5 or 1.0 MAC) administered for 3 min before and 2 min after reperfusion, or the mPTP inhibitor cyclosporin A (CsA, 5 or 10 mg/kg) in the presence or absence of the mPTP opener atractyloside (5 mg/kg) or the selective mK(ATP) channel antagonist 5-hydroxydecanoate (5-HD; 10 mg/kg). Other rabbits received 0.5 MAC isoflurane plus 5 mg/kg CsA in the presence and absence of atractyloside or 5-HD. Isoflurane (1.0 but not 0.5 MAC) and CsA (10 but not 5 mg/kg) reduced (P < 0.05) infarct size (21% +/- 4%, 44% +/- 6%, 24% +/- 3%, and 43% +/- 6%, respectively, mean +/- sd of left ventricular area at risk; triphenyltetrazolium staining) as compared with control (42% +/- 7%). Isoflurane (0.5 MAC) plus CsA (5 mg/kg) was also protective (27% +/- 4%). Neither atractyloside nor 5-HD alone affected infarct size, but these drugs abolished protection by 1.0 MAC isoflurane, 10 mg/kg CsA, and 0.5 MAC isoflurane plus 5 mg/kg CsA. The results indicate that mPTP inhibition enhances, whereas opening abolishes, isoflurane-induced postconditioning. This isoflurane-induced inhibition of mitochondrial permeability transition is dependent on activation of mitochondrial KATP channels in vivo.     

The influence of B-cell lymphoma 2 protein, an antiapoptotic regulator of mitochondrial permeability transition, on isoflurane-induced and ischemic postconditioning in rabbits

Brief exposure to isoflurane or repetitive, transient ischemia during early reperfusion after prolonged coronary artery occlusion protects against myocardial infarction by inhibiting the mitochondrial permeability transition pore (mPTP). Inhibition of mPTP during delayed ischemic preconditioning occurred concomitant with enhanced expression of the antiapoptotic protein B cell lymphoma-2 (Bcl-2). We tested the hypothesis that Bcl-2 mediates myocardial protection by isoflurane or brief ischemic episodes during reperfusion in rabbits (n = 91) subjected to a 30-min left anterior descending coronary artery occlusion followed by 3 h reperfusion. Rabbits received 0.9% saline, isoflurane (0.5 or 1.0 minimum alveolar concentration, MAC) administered for 3 min before and 2 min after reperfusion, 3 cycles of postconditioning ischemia (10 or 20 s each) during early reperfusion, 0.5 MAC isoflurane plus 3 cycles of postconditioning ischemia (10 s), or the direct mPTP inhibitor cyclosporin A (CsA, 10 mg/kg) in the presence or absence of the selective Bcl-2 inhibitor HA14-1 (2 mg/kg, i.p.). Isoflurane (1.0, but not 0.5, MAC) and postconditioning ischemia (20 s but not 10 s) significantly (P < 0.05) reduced infarct size (mean +/- sd, 21% +/- 4%, 43% +/- 7%, 19% +/- 7%, and 39% +/- 11%, respectively, of left ventricular area at risk) as compared with control (44% +/- 4%). Isoflurane (0.5 MAC) plus 10 s postconditioning ischemia and CsA alone also exerted protection. HA14-1 alone did not affect infarct size nor block protection produced by CsA but abolished reductions in infarct size caused by 1.0 MAC isoflurane, 20 s postconditioning ischemia, and 0.5 MAC isoflurane plus 10 s postconditioning ischemia. The results suggest that Bcl-2 mediates isoflurane-induced and ischemic postconditioning by indirectly modulating mPTP activity in vivo.     

Hyperglycaemia blocks sevoflurane-induced postconditioning in the rat heart in vivo: cardioprotection can be restored by blocking the mitochondrial permeability transition pore

Background: Recent studies showed that hyperglycaemia (HG) blocks anaesthetic-inducedpreconditioning. The influence of HG on anaesthetic-inducedpostconditioning (post) has not yet been determined. We investigatedwhether sevoflurane (Sevo)-induced postconditioning is blockedby HG and whether the blockade could be reversed by inhibitingthe mitochondrial permeability transition pore (mPTP) with cyclosporineA (CsA). Methods: Chloralose-anaesthetized rats (n=7–11 per group) weresubjected to 25 min coronary artery occlusion followed by 120min reperfusion. Postconditioning was achieved by administrationof 1 or 2 MAC sevoflurane for the first 5 min of early reperfusion.HG was induced by infusion of glucose 50% (G 50) for 35 min,starting 5 min before ischaemia up to 5 min of reperfusion.CsA (5 or 10 mg kg^–1) was administered i.v. 5 min beforethe onset of reperfusion. At the end of the experiments, heartswere excised for infarct size measurements. Results: Infarct size (% of area at risk) was reduced from 51.4 (5.0)%[mean (SD)] in controls to 32.7 (12.8)% after sevoflurane postconditioning(Sevo-post) (P<0.05). This infarct size reduction was completelyabolished by HG [51.1 (13.2)%, P<0.05 vs Sevo-post], butwas restored by administration of sevoflurane with CsA [35.2(5.2)%, P<0.05 vs HG+Sevo-post]. Increased concentrationsof sevoflurane or CsA alone could not restore cardioprotectionin a state of HG [Sevo-post2, 54.1 (12.6)%, P>0.05 vs HG+Sevo-post;CsA10, 58.8 (11.3)%, P>0.05 vs HG+CsA]. Conclusions: Sevoflurane-induced postconditioning is blocked by HG. Inhibitionof the mPTP with CsA is able to reverse this loss of cardioprotection.     

Postconditioning Prevents Reperfusion Injury by Activating [delta]-Opioid Receptors

Background: While postconditioning has been proposed to protect the heart by targeting the mitochondrial permeability transition pore (mPTP), the detailed mechanism underlying this action is unknown. The authors hypothesized that postconditioning stimulates opioid receptors, which in turn protect the heart from reperfusion injury by targeting the mPTP.

Methods: Rat hearts (both in vivo and in vitro) were subjected to 30 min of ischemia and 2 h of reperfusion. Postconditioning was elicited by six cycles of 10-s reperfusion and 10-s ischemia. To measure nitric oxide concentration, cardiomyocytes loaded with 4-amino-5-methylamino-2',7'-difluorofluorescein were imaged using confocal microscopy. Mitochondrial membrane potential was determined by loading cardiomyocytes with tetramethylrhodamine ethyl ester.

Results: In open chest rats, postconditioning reduced infarct size, an effect that was reversed by both naloxone and naltrindole. The antiinfarct effect of postconditioning was also blocked by the mPTP opener atractyloside. In isolated hearts, postconditioning reduced infarct size. Morphine mimicked postconditioning to reduce infarct size, which was abolished by both naltrindole and atractyloside. N-nitro-l-arginine methyl ester and guanylyl cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one blocked the action of morphine. Further experiments showed that morphine produces nitric oxide in cardiomyocytes by activating [delta]-opioid receptors. Moreover, morphine could prevent hydrogen peroxide-induced collapse of mitochondrial membrane potential in cardiomyocytes, which was reversed by naltrindole, N-nitro-l-arginine methyl ester, and the protein kinase G inhibitor KT5823.     

海马神经细胞线粒体通透性转换孔在富氢液减轻大鼠全脑缺血再灌注损伤中的作用

目的 评价海马神经细胞线粒体通透性转换孔(mPTP)在富氢液减轻大鼠全脑缺血再灌注损伤中的作用.方法 雄性SD大鼠72只,体重250 ～ 300 g,采用随机数字表法,将其随机分为6组(n=12):假手术组(S组)、缺血再灌注组(IR组)、生理盐水组(NS组)、富氢液组(H组)、苍术苷组(A组)和富氢液+苍术苷组(HA组).采用四血管阻塞法建立大鼠全脑缺血再灌注模型,缺血15 min后恢复灌注.H组和HA组于再灌注即刻腹腔注射富氢液5 ml/kg,其余组腹腔注射等容量生理盐水;A组和HA组于再灌注前10 min行侧脑室注射苍术苷15 μl,NS组和H组侧脑室注射等容量生理盐水.再灌注24h时行神经行为学损伤评分后各组随机处死8只大鼠,迅速断头,分离海马神经细胞线粒体,采用分光光度计法测定mPTP的开放程度,Rhodamine123法测定线粒体膜电位.再灌注72 h时各组处死4只大鼠,取海马组织,光镜下观察CA1区病理学结果,计数该区神经细胞存活数.结果 与S组比较,其余组再灌注24h时行为学损伤加重,mPTP活性升高,线粒体膜电位降低(P＜0.05);与IR组比较,H组和HA组再灌注24h时行为学损伤减轻,mPTP活性降低,线粒体膜电位升高(P＜0.05);与H组比较,HA组行为学损伤加重,mPTP活性升高,线粒体膜电位降低(P＜0.05).再灌注72 h时HA组较IR组神经细胞存活数增加(P＜0.05),H组海马CA1区神经元损伤较IR组、NS组、A组和HA组减轻.结论 富氢液可减轻大鼠全脑缺血再灌注损伤,其机制与抑制海马神经细胞mPTP开放,减少线粒体膜电位降低,从而维持线粒体功能有关.     

Sevoflurane improves myocardial ischaemic tolerance in a closed‐chest porcine model

Aims: Volatile anaesthetics prevent experimental myocardial ischaemia–reperfusion injury (I/R) in several species, but this finding is partially inconsistent with clinical evidence. Some experimental models may not accurately represent the complex signal transduction pathways triggered by volatile anaesthetics. We therefore investigated sevoflurane I/R prevention in vivo in a porcine model with greater likeness to human physiology than models previously used and compared it with neutral anaesthetic. Methods and results: Myocardial infarct size [IS/AAR] was compared in three groups of pigs (N=35) randomised to Control anaesthesia (pentobarbital infusion, n=12), sevoflurane inhalation alone (end‐tidal concentration 3.2%) (Sevo, n=9), or both Combined (n=14), throughout ischaemia and reperfusion. Anterior/septal myocardial infarcts resulted from distal LAD coronary artery occlusion by balloon catheter for 45 min followed by 120 min of reperfusion. [IS/AAR] was measured in tetrazolium‐stained heart slices after standardised image processing with computer‐assisted planimetry. Measurements included full invasive monitoring. Control animals developed infarction in 55.0±3.9% (SEM) of the area at risk, Sevo in 17.5±4.4% (P=0.0002), and Combined with pentobarbital in 24.3±3.8% (P=0.0001) of the AAR, sevoflurane reducing infarct size significantly (68% and 60%, respectively). Conclusions: Sevoflurane markedly decreased myocardial infarct size after prolonged coronary occlusion in a porcine model. In addition to novel sevoflurane cardioprotection in the closed‐chest model, which is more comparable to normal human hearts than models previously used, sevoflurane cardioprotection is substantiated in the juvenile intact organism. The perspectives underline recommending volatile anaesthetics in risk patients and in cardiac surgery.     

Tissue factor and thrombin mediate myocardial ischemia-reperfusion injury

Reperfusion of the ischemic heart is necessary to prevent irreversible injury of the myocardium, which leads to permanent organ dysfunction. However, reperfusion in itself leads to myocardial ischemia/reperfusion (I/R) injury, which is characterized by an acute inflammatory response mediated by activated inflammatory cells, chemokines, cytokines, and adhesion molecules. The molecular mechanisms of myocardial I/R injury are not completely known. Tissue factor (TF) and thrombin, two potent procoagulant and proinflammatory mediators, are recognized to play significant roles in myocardial I/R injury. To investigate the role of TF and thrombin in myocardial I/R injury, we used rabbit and murine in situ coronary artery ligation models. Increased TF mRNA, antigen, and activity were found in ischemic cardiomyocytes. Administration of an inhibitory antirabbit TF monoclonal antibody before or during the onset of ischemia resulted in a significant reduction in infarct size. Functional inhibition of thrombin with hirudin also reduced the infarct size. However, defibrinogenating rabbits with ancrod had no effect on infarct size, suggesting a requirement of thrombin generation but not fibrin deposition in myocardial I/R injury.     

大鼠血红素加氧酶-1基因转染对大鼠离体心肌缺血再灌注心肌细胞凋亡的影响

目的 观察重组腺相关病毒介导大鼠血红素加氧酶-1基因转染对大鼠离体心肌缺血再灌注心肌细胞凋亡的影响.方法 雄性SD大鼠30只随机分成3组,对照组(C组,n=6),缺血再灌注组(I/R组,n=12),腺相关病毒介导血红索加氧酶-1基因组(A-r组,n=12).基因转染3个月后,建立大鼠离体心脏Langendorff灌流模型,C组持续灌注100 min,其他各组均平衡15 rain,停灌40min与再灌注45 min,记录冠脉流量(CF),测定冠脉流出液肌酸激酶(CK)活性,测定再灌注后45 min时的心肌心肌组织超氧化物岐化酶(SOD)活性活性及丙二醛(MDA)含量,同时取每组大鼠心肌检测梗死面积、心肌细胞凋亡率以及心肌组织bax、bcl-2蛋白表达量.结果 离体心肌Langendorff灌注后,与I/R组比较,A-r组在复灌后冠脉流出液CK活性降低(P＜0.01),复灌后45min后心肌MDA含量降低(P＜0.01),SOD活性增高(P＜0.01),梗死面积较小(P＜0.01),心肌组织bax表达量、心肌细胞凋亡率均显著下降,心肌组织bel-2表达量明显增加(P＜0.01).结论 重组腺相关病毒血红素加氧酶1基因转染心肌后,可抑制离体缺血再灌注心肌细胞凋亡和增强心肌抗氧化能力,对大鼠离体心肌缺血再灌注损伤有显著保护作用.     

七氟醚延迟预处理对大鼠缺血再灌注心肌ARC表达的影响

目的 评价七氟醚延迟预处理对大鼠缺血再灌注心肌带有Caspase富集功能域的凋亡抑制蛋白(ARC)表达的影响.方法 成年雄性SD大鼠64只,体重270～350 g,采用随机数字表法,将其随机分为4组(n=16):假手术组(S组)、心肌缺血再灌注组(I/R组)、七氟醚+假手术组(S-S组)和七氟醚延迟预处理+心肌缺血再灌注组(S-VR组).S-S组和S-I/R组分别吸入33%氧气和2.5%七氟醚2 h,停止吸入后24 h行假手术或心肌缺血再灌注;I/R组和S-I/R组采用结扎左冠状动脉前降支30 min,再灌注2 h的方法制备心肌缺血再灌注模型.于再灌注2 h时处死8只大鼠,取左心室组织,测定心肌梗死范围及细胞凋亡情况,计算凋亡指数,于缺血前即刻及再灌注2 h时各处死4只大鼠,取左心室组织,测定ARC及Caspase-8的表达水平.结果 与S组比较,I/R组和S-I/R组心肌梗死范围及细胞凋亡指数升高,缺血前即刻S-S组和S-I/R组ARC表达上调,再灌注2 h时I/R组Caspese-8、表达上调(P＜0.05);与I/R组比较,S-I/R组心肌梗死范围和细胞凋亡指数降低,再灌注2 h时S-S组和S-I/R组ARC表达上调,Caspase-8表达下调(P＜0.05).结论 七氟醚延迟预处理可上调心肌ARC表达,减少细胞凋亡的发生,从而减轻大鼠心肌缺血再灌注损伤.

Abstract：

Objective To investigate the effects of sevoflurane delayed preconditioning on caspase recruitment domain (ARC) expression during myocardial ischemia-reperfusion (I/R) in rats. Methods Sixty-four adult male SD rats weighing 270-350 g were randomly divided into 4 groups ( n = 16 each): sham operation (group S); myocardial I/R group; sevoflurane + sham operation group (group S-S) and sevoflurane delayed preconditioning + myocardial I/R group (group S-I/R) . Myocardial I/R was induced by occlusion of anterior descending branch of left coronary artery for 30 min followed by 2 h of reperfusion in groups I/R and S-I/R. Group S-S inhaled 33% oxygen for 2 h, and sham operation was performed 24 h later. Group S-I/R inhaled 2.5% sevoflurane for 2 h, and then myocardial I/R was induced 24 h later. Eight animals were sacrificed at the end of 2 h reperfusion in each group and the hearts removed for determination of myocardial infarct size (IS) as a percentage of area at risk (AAR) by triphenyl tetrazolium chloride staining (IS/AAR) . Myocardial apoptosis was detected using TUNEL and apoptosis index was calculated. Another 4 animals were sacrificed immediately before ischemia and at the end of 2 h reperfusion to determine the expression of ARC and Caspase-8 in myocardium by Western blot. Results Compared with group S, the infarct size and apoptosis index were significantly increased in groups I/R and S-I/R, and ARC expression was up-regulated immediately before ischemia in groups S-S and S-I/R, and Caspase-8 expression was up-regulated at 2 h of reperfusion in group I/R ( P ＜ 0.05) . Compared with group I/R, the infarct size and apoptosis index were significantly decreased in group S-I/R, and ARC expression was up-regulated, while Caspase-8 expression was down-regulated at 2 h of reperfusion in groups S-S and S-I/R ( P ＜ 0.05) . Conclusion Sevoflurane delayed preconditioning can attenuate myocardial I/R injury through up-regulating the ARC expression and decreasing the myocardial apoptosis.     

缺血预处理和缺血后处理对大鼠心肌缺血再灌注时炎性反应影响的比较

目的 比较缺血预处理和缺血后处理对大鼠心肌缺血再灌注时炎性反应的影响.方法 雄性SD大鼠40只,体重290～320 g,随机分为4组(n=10),缺血再灌注组(I/R组)、缺血预处理组(IPC组)和缺血后处理组(IPOC组)采用结扎左冠状动脉前降支30 min进行再灌注的方法制备心肌缺血再灌注模型,假手术组(S组)仅在左冠状动脉前降支下穿线.监测再灌注期间HR和MAP,并计算HR和MAP的乘积(心肌氧耗指数,RPP).分别于再灌注30和180 min时采集静脉血样,测定血清TNF-α、IL-6、高迁移率组蛋白1(HMGB1)和心肌肌钙蛋白I(cTnI)的浓度.采集完血样,取心肌组织,测定心肌梗死体积.结果 与S组比较,I/R组MAP和RPP降低,血清cTnI和炎性细胞因子浓度升高,心肌梗死体积增大(P＜0.05);与I/R组比较,IPC组MAP升高,IPOC组MAP和RPP均升高,两组血清cTnI和炎性细胞因子浓度降低,心肌梗死体积缩小(P＜0.05);与IPC组比较,IPOC组血清炎性细胞因子浓度升高,心肌梗死体积增大(P＜0.05).结论缺血预处理减轻大鼠心肌缺血再灌注时炎性反应的作用强于缺血后处理,从而使心肌保护效应较好.     

Post‐conditioning with cyclosporine A fails to reduce the infarct size in an in vivo porcine model

Background: Cyclosporine A has generated intense interest in the field of cardioprotection due to its ability to protect the mitochondria at reperfusion by blocking the opening of the mitochondrial permeability transition pore. The aim of our study was to examine the cardioprotective effect of Sandimmun^®, a clinically available formulation of cyclosporine A, in an in vivo large mammal model. Methods: Forty‐eight pigs were randomly allocated to one of three groups: (i) Control group (Con, n=19), (ii) Cyclosporine group, (Cyclo, n=19) Sandimmun^® 10 mg/kg i.v. bolus 5 min before reperfusion and (iii) Pre‐conditioning group (Precon, n=10) two cycles of 10 min ischemia interspersed with 30‐min reperfusion. The study was further sub‐divided into a metabolic protocol, evaluating myocardial metabolism by measuring changes in the interstitial lactate concentration, and a coronary flow protocol. All animals were subjected to 40 min of left anterior descending coronary artery occlusion, followed by 180 min of reperfusion before histochemical staining and assessment of infarct size by planimetry. Results: Infarct sizes were measured as: Con 51.4 ± 16.5%, Cyclo 47.3 ± 15.7% and Precon 2.4 ± 3.6%, with no significant difference between the Con and Cyclo groups but a highly significant difference between the Precon and Cyclo and Con groups (P<0.0001 for both comparisons). In the Cyclo group, the interstitial lactate concentration was significantly increased compared with the Con group at 6‐min reperfusion, although significantly lower at 14 min presumably due to accelerated washout. Conclusion: In this large animal model, a 10 mg/kg bolus administration of Sandimmun^® 5 min before reperfusion did not reduce the infarct size.     

JAK2/STAT3信号通路在川芎嗪减轻大鼠心肌缺血再灌注损伤中的作用

目的 评价Janus激酶2/信号转导与转录激活子3(JAK2/STAT3)信号通路在川芎嗪减轻大鼠心肌缺血再灌注损伤中的作用.方法 健康成年雄性Wistar大鼠64只,体重250～300 g,采用随机数字表法,将大鼠随机分为4组(n＝ 16):假手术组(S组)、缺血再灌注组(I/R组)、川芎嗪组(T组)和JAK2特异性抑制剂AG490组(AG组).采用结扎左冠状动脉前降支30 min,再灌注120 min的方法制备心肌缺血再灌注损伤模型.S组开胸暴露心脏,左冠状动脉前降支仅穿线;T组于阻断左冠状动脉前降支前20 min静脉注射川芎嗪20 mg/kg; AG组于阻断左冠状动脉前降支前20min静脉注射川芎嗪20 mg/kg,再灌注前5min静脉注射AG490 3 μg/g.再灌注l20 nin时,取下腔静脉血样,测定血清肌酸激酶(CK)及乳酸脱氢酶(LDH)的活性;观察心肌超微结构,计算心肌梗死体积百分比.结果 与S组比较,I/R组、T组和AG组血清CK和LDH的活性升高(P<0.01);与I/R组比较,T组血清CK、LDH活性和心肌梗死体积百分比降低,AG组血清CK、LDH活性降低(P<0.01);与T组比较,AG组血清CK、LDH活性和心肌梗死体积百分比升高(P<0.05).T组心肌病理学损伤较I/R组和AG组减轻.结论 JAK2/STAT3信号通路参与了川芎嗪减轻大鼠心肌缺血再灌注损伤的作用.     

Nitric oxide synthase inhibition in rats: melatonin reduces blood pressure and ischemia/reperfusion-induced infarct size

Reduction in the synthesis or bioavailability of nitric oxide plays a significant role in the development of myocardial infarction and hypertension. Numerous studies suggest that melatonin reduces blood pressure (BP) and ischemia/reperfusion (I/R) injury in rats. The effects of melatonin on the BP and I/R-induced cardiac infarct size in L-NAME-induced hypertensive rats remains unknown. This study was designed to investigate the effects of melatonin on BP and the I/R-induced infarct size in chronic nitric oxide synthase inhibited rats by L-NAME. Rats received L-NAME for 15 days to produce hypertension and melatonin the last 5 days before I/R studies. To produce cardiac damage, the left coronary artery was occluded for 30 min, followed by 120 min reperfusion. L-NAME led to a significant increase in BP. Melatonin administration (10 mg/kg) to L-NAME treated rats significantly reduced BP and infarct size. Also, melatonin attenuated the mortality resulting from I/R, but this was not statistically significant. Melatonin administration would seem important to reduce BP and infarct size resulting from I/R in L-NAME-induced hypertensive rats.     

Isoflurane postconditioning prevents opening of the mitochondrial permeability transition pore through inhibition of glycogen synthase kinase 3beta

BACKGROUND: Postischemic administration of volatile anesthetics activates reperfusion injury salvage kinases and decreases myocardial damage. However, the mechanisms underlying anesthetic postconditioning are unclear. METHODS: Isolated perfused rat hearts were exposed to 40 min of ischemia followed by 1 h of reperfusion. Anesthetic postconditioning was induced by 15 min of 2.1 vol% isoflurane (1.5 minimum alveolar concentration) administered at the onset of reperfusion. In some experiments, atractyloside (10 microm), a mitochondrial permeability transition pore (mPTP) opener, and LY294002 (15 microm), a phosphatidylinositol 3-kinase inhibitor, were coadministered with isoflurane. Western blot analysis was used to determine phosphorylation of protein kinase B/Akt and its downstream target glycogen synthase kinase 3beta after 15 min of reperfusion. Myocardial tissue content of nicotinamide adenine dinucleotide served as a marker for mPTP opening. Accumulation of MitoTracker Red 580 (Molecular Probes, Invitrogen, Basel, Switzerland) was used to visualize mitochondrial function. RESULTS: Anesthetic postconditioning significantly improved functional recovery and decreased infarct size (36 +/- 1% in unprotected hearts vs. 3 +/- 2% in anesthetic postconditioning; P < 0.05). Isoflurane-mediated protection was abolished by atractyloside and LY294002. LY294002 inhibited isoflurane-induced phosphorylation of protein kinase B/Akt and glycogen synthase kinase 3beta and opened mPTP as determined by nicotinamide adenine dinucleotide measurements. Atractyloside, a direct opener of the mPTP, did not inhibit phosphorylation of protein kinase B/Akt and glycogen synthase kinase 3beta by isoflurane but reversed isoflurane-mediated cytoprotection. Microscopy showed accumulation of the mitochondrial tracker in isoflurane-protected functional mitochondria but no staining in mitochondria of unprotected hearts. CONCLUSIONS: Anesthetic postconditioning by isoflurane effectively protects against reperfusion damage by preventing opening of the mPTP through inhibition of glycogen synthase kinase 3beta.     

Nitric oxide synthase inhibition in rats: Melatonin reduces blood pressure and ischemia/reperfusion-induced infarct size

Reduction in the synthesis or bioavailability of nitric oxide plays a significant role in the development of myocardial infarction and hypertension. Numerous studies suggest that melatonin reduces blood pressure (BP) and ischemia/reperfusion (I/R) injury in rats. The effects of melatonin on the BP and I/R-induced cardiac infarct size in L-NAME-induced hypertensive rats remains unknown. This study was designed to investigate the effects of melatonin on BP and the I/R-induced infarct size in chronic nitric oxide synthase inhibited rats by L-NAME. Rats received L-NAME for 15 days to produce hypertension and melatonin the last 5 days before I/R studies. To produce cardiac damage, the left coronary artery was occluded for 30 min, followed by 120 min reperfusion. L-NAME led to a significant increase in BP. Melatonin administration (10 mg/kg) to L-NAME treated rats significantly reduced BP and infarct size. Also, melatonin attenuated the mortality resulting from I/R, but this was not statistically significant. Melatonin administration would seem important to reduce BP and infarct size resulting from I/R in L-NAME-induced hypertensive rats.     

迷走神经电刺激后处理对大鼠心肌缺血再灌注损伤的影响

目的 评价迷走神经电刺激后处理对大鼠心肌缺血再灌注损伤的影响.方法 雄性SD大鼠60只,体重250～350 g,采用随机数字表法,将其随机分为3组(n＝20):假手术组(S组)、缺血再灌注组(I/R组)和迷走神经电刺激后处理组(POES组).I/R组和POES组采用结扎左冠状动脉前降支30 min和再灌注120 min的方法制备心肌缺血再灌注损伤模型,S组仅穿线.POES组在心肌缺血15 min时对右侧迷走神经干实施电刺激30 min,电刺激参数:波宽2ms,频率10 Hz,电流强度随大鼠HR进行调整,以保持HR较刺激前降低10％.于缺血前(基础状态)、缺血1、10 min和再灌注30、60、120 min时记录HR和MAP,计算HR和MAP的乘积(RPP).各组随机取10只大鼠,于再灌注120 min时,采集颈动脉血样,采用ELISA法检测血清cTnI、CK-MB、TNF-α、高迁移率族蛋白1(HMGB1)、细胞间粘附分子1(ICAM-1)、IL-1、IL-6和IL-10的浓度;颈动脉采血后,采用伊文蓝和TTC双重染色法测定心肌梗死体积.再灌注120 min时,各组随机处死10只大鼠,取缺血区和非缺血区心肌组织,采用ELISA法检测TNF-α、HMGB1、ICAM-1、IL-1、IL-6和IL-10的含量.结果 与S组比较,I/R组缺血10 min和再灌注30 min时HR增快,缺血1min时MAP和RPP降低,心肌梗死体积、血清cTnI、CK-MB、TNF-α、HMGB1、ICAM-1、IL-1和IL-6的浓度、缺血区和非缺血区心肌组织TNF-α、HMGB1、ICAM-1、IL-1、IL-6和IL-10的含量升高;POES组缺血10 min时HR增快,血清TNF-α浓度降低,心肌梗死体积、血清cTnI、CK-MB、ICAM-1和IL-10的浓度、缺血区心肌组织ICAM-1、IL-1、IL-6和IL- 10的含量、非缺血区心肌组织HMGB1、ICAM-1、IL-1、IL-6和IL-10的含量升高(P<0.05);与I/R组比较,POES组HR、MAP和RPP差异无统计学意义(P＞0.05),心肌梗死体积、血清cTnI、CK-MB、TNF-α、HMGB1、ICAM-1、IL-1和IL-6的浓度、缺血区和非缺血区心肌组织TNF-α、HMGB1、ICAM-1、IL-1和IL-6的含量降低,IL- 10含量升高(P<0.05).结论 迷走神经电刺激后处理可减轻大鼠心肌缺血再灌注损伤,其机制与抑制局部和全身炎性反应有关.     

七氟烷预处理对大鼠心肌缺血再灌注损伤时细胞凋亡的影响

目的 探讨七氟烷预处理对大鼠心肌缺血再灌注损伤时细胞凋亡的影响.方法 成年雄性SD大鼠64只,体重270～350 g,随机分为4组(n=16):假手术组(S组)仅穿线不结扎,心肌缺血再灌注组(I/R组)阻断左冠状动脉前降支缺血30 min,恢复灌注2 h制备心肌缺血再灌注损伤模型,七氟烷组(Sevo组)吸入2.5%七氟烷30 min,七氟烷预处理+心肌缺血再灌注组(SR组)吸入2.5%七氟烷30 min,15 min后制备模型.于再灌注2 h时随机取4只大鼠处死取左心室,采用氯化三苯四唑染色法测定心肌梗死范围,随机取4只大鼠处死取左心室,采用TUNEL法检测凋亡心肌细胞,计算凋亡指数,于缺血前即刻和再灌注2 h时分别随机取4只大鼠处死取左心室,采用Western blot法测定Bcl-2及caspase-3的蛋白表达水平.结果 与S组相比,再灌注2 h时I/R组和SR组心肌梗死范围增大,心肌细胞凋亡指数升高,caspase-3蛋白表达上调,Sevo组Bcl-2蛋白表达上调,I/R组Bcl-2蛋白表达下调,Sevo组和SR组缺血前即刻Bcl-2蛋白表达上凋(P＜0.05);与I/R组相比,再灌注2 h时SR组心肌梗死范围缩小、心肌细胞凋亡指数降低,Sevo组和SR组Bcl-2蛋白表达上调,SR组caspase-3蛋白表达下调(P＜0.05);与缺血前即刻相比,I/R组和SR组再灌注2 h时Bcl-2蛋白表达下调,caspase-3蛋白表达上调(P＜0.05).结论 七氟烷预处理可通过抑制细胞凋亡减轻大鼠心肌缺血再灌注损伤.