The liver protective effect of ischemic preconditioning may be mediated by adenosine

Abstract We investigated the involvement of adenosine in ischemic preconditioning (IPC) by the unspecific antagonist, 8‐phenyltheophylline (8‐PT). Anesthetized Wistar rats were treated as follows: 1. nonischemic controls, 2. ischemic controls: 60 min of clamping of the common hepatic artery followed by 60 min reperfusion, 3. IPC: 10 min ischemia followed by 15 min reperfusion, prior to the identical ischemia‐reperfusion (IR) period as in group 2, 4. 8‐PT + IPC: 8‐PT 10 mg/kg i. v. was given 10 min prior to the identical procedure as in group 3. The peripheral liver blood flow was monitored by laser‐Doppler flowmetry. Blood alanine aminotransferase (ALT) was analyzed once every 60 min. IPC significantly reduced impairment of liver blood flow, as well as ALT increase during reperfusion. This effect was abolished by pretreatment with 8‐PT. Adenosine appears to be a crucial effector in IPC. Clinical studies need to be undertaken to explore a possible effect of IPC in liver transplantation.     

缺血预处理对体外循环缺血心肌的保护效果

观察缺血预处理对体外循环(CPB)心脏高钾、冷停跳心肌的保护作用。方法:10只健康犬随机分为对照组(C组)与预缺血组(PC组),每组5只。CPB期间心脏高钾停跳,全心缺血60分.恢复灌注30分。PC组在CPB开始后、心脏停跳前增加预缺血5分钟、再灌注10分钟,对比观察阻断升主动脉前、后心肌超微结构、腺苷酸含量(ATP、ADP、AMP、TAN、EC)、脂质过氧化物丙二醛(MDA)以及血流动力学的变化。结果:(1)PC组在缺血30分钟、60分钟及开放升主动脉20分钟时,正常线粒体和糖原含量均接近缺血前水平,并明显高于C组(P<0.01);(2)心脏阻断前、后PC组心肌组织ATP、EC含量无显著变化,与C组同时比较差异十分显著(P<0.05或0.01);(3)缺血60分钟以及开放20分钟C组心肌MDA含量显著升高,与PC组比较差异十分显著(P<0.05或0.01);(4)开放升主动脉后,PC组血流动力学各项参数迅速恢复,其中CO、SV、CI、LVSW与C组比较差异有显著性(P<0.05或0.01)。结论:心肌缺血预处理明显增强体外循环心脏缺血再灌注期超微结构的保护效果。降低ATP的消耗,减少脂质过氧化物的形成,加速血流动力学的恢复。     

Does adenosine administration during the early reperfusion period affect ischemic preconditioning?

We hypothesized that the adenosine administration during the early reperfusion period might affect ischemic preconditioning (IPC) and might reduce infarct size and enhance post-ischemic functional recovery. Twenty-four anesthetized rabbits underwent 30 min. normothermic global ischemia with 120 min. reperfusion in a buffer-perfused isolated, paced heart model and divided into four groups. Global ischemic hearts (GI, n = 6) were subjected to 30 min. global ischemia without intervention. Control hearts (n=6) were subjected to perfusion without ischemia. Ischemic preconditioned hearts (IPC, n=6) were subjected to one cycle of 5 min. global ischemia and 5 min. reperfusion prior to global ischemia. IPC + Ado hearts (n=6) received IPC and adenosine administration (100 m mol/L) during 3 min. early reperfusion period. Post-ischemic functional recovery was better in IPC + Ado hearts as compared to GI and IPC hearts, but the effect of post-ischemic functional recovery in IPC + Ado hearts became weaker during 120 min. reperfusion after prolong ischemic insult. Infarct size wre 1.0 ± 0.3% in Control hearts, 32.9 ± 5.1% in GI hearts, 13.8 ± 1.3% in IPC hearts and 8.1 ± 0.9% in IPC + Ado hearts. Infarct size in IPC hearts was significantly decreased (p<0.01) as compared to GI hearts. The reduction rate against myocardial necrosis in IPC + Ado hearts versus GI hearts was higher as compared to IPC hearts versus GI hearts (p<0.001, IPC+Ado hearts vs GI hearts; p<0.01, IPC hearts vs GI hearts; p = ns, IPC + Ado hearts vs Control hearts). These data suggest that adenosine administration during the early reperfusion period reinforce IPC effect and reduce myocardial reperfusion injury. Cardiomyoprotective effects of IPC and exogenous adenosine are exerted during early reperfusion after coronary occlusion in the isolated perfused rabbit hearts.     

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.     

缺血预处理对心内直视手术患者的心肌保护效应:meta分析

目的 采用meta分析评价缺血预处理对心内直视手术患者的心肌保护效应.方法 检索PubMed、EMBASE、Highwire、CENTREN及其下属各临床注册试验数据中心、中国生物医学文献数据库和中国期刊全文数据库,收集全身麻醉下缺血预处理对心内直视手术患者的心肌保护效果的随机对照研究.采用Cochrane系统评价法评价所纳入文献的质量,评价指标包括:术后心源性死亡率、心肌梗死发生率、室性心律失常发生率和正性肌力药物使用率.采用RevMan 5.0软件进行Meta分析.结果 纳入12项研究,8项研究为高等质量文献,4项研究为中等质量文献,共626例患者.缺血预处理可降低心内直视手术患者术后室性心律失常发生率和正性肌力药物使用率(P＜0.05),而对术后心源性死亡率及心肌梗死发生率无影响(P＞0.05).结论 缺血预处理可降低心内直视手术患者术后室性心律失常的发生,而对术后心源性死亡和心肌梗死发生没有影响.     

Impact of hypoglycemic agents on myocardial ischemic preconditioning

Murry et al in 1986 discovered the intrinsic mechanism of profound protection called ischemic preconditioning. The complex cellular signaling cascades underlying this phenomenon remain controversial and are only partially understood. However, evidence suggests that adenosine, released during the initial ischemic insult, activates a variety of G protein-coupled agonists, such as opioids, bradykinin, and catecholamines, resulting in the activation of protein kinases, especially protein kinase C(PKC). This leads to the translocation of PKC from the cytoplasm to the sarcolemma, where it stimulates the opening of the ATP-sensitive K+ channel, which confers resistance to ischemia. It is known that a range of different hypoglycemic agents that activate the same signaling cascades at various cellular levels can interfere with protection from ischemic preconditioning. This review examines the effects of several hypoglycemic agents on myocardial ischemic preconditioning in animal studies and clinical trials.     

蛋白激酶C和线粒体ATP敏感性钾通道在未成熟心肌预处理中的作用

目的探讨蛋白激酶C(PKC)和线粒体三磷酸腺苷敏感性钾通道(mitoKATP)在未成熟心肌预处理保护中的作用。方法采用Langendorff离体心脏灌注模型,30只新生日本长耳大白兔分为5组:缺血/再灌注组(I/R组),心脏缺血预处理组(E1组),蛋白激酶C(PKC)阻滞剂chelerythrine(CLT) 心脏缺血预处理(E2组),mitoKATP阻滞剂5-hydroxydecanoate(5-HD) 心脏缺血预处理(E3组),mitoKATP通道开放剂Diazoxide(Diaz)预处理组(E4组)。以血流动力学、生化指标、心肌超微结构等作为观察指标。结果E1和E4组心功能恢复、心肌含水量优于I/R、E2和E4组(P<0.05),三磷酸腺苷含量、超氧化物歧化酶活性、心肌线粒体Ca2 -ATPase活性、心肌线粒体合成三磷酸腺苷(ATP)的能力优于I/R、E2和E4组(P<0.01),丙二醛含量、血清肌酸激酶和乳酸脱氢酶漏出率、心肌细胞内Ca2 含量、心肌线粒体Ca2 含量低于I/R、E2和E4组(P< 0.01),心肌超微结构损伤较I/R、E2和E4组明显减轻。结论心肌缺血预处理对未成熟心肌具有明显的保护作用,其机制可能是通过PKC的激活和mitoKATP通道的开放起作用。     

Pretreatment with an adenosine A1 receptor agonist and lidocaine: a possible alternative to myocardial ischemic preconditioning

OBJECTIVE: The heart possesses an extraordinary ability to remember short episodes of sublethal ischemia and reperfusion (angina), which protects the myocardium and coronary vasculature from a subsequent lethal insult, a phenomenon known as ischemic preconditioning. A therapeutic goal for more than 2 decades has been to develop a pharmacologic mimetic comparable with ischemic preconditioning. Our aim was to investigate the preconditioning effect of a new combinatorial therapy targeting adenosine A1 receptors and voltage-dependent sodium fast channels in the in vivo rat model of regional ischemia. METHODS: Ischemia-reperfusion was achieved by placing a reversible tie around the left coronary artery in anesthetized and ventilated Sprague-Dawley rats (n = 37). Rats were randomly assigned to 1 of 5 groups: (1) saline control (n = 13); (2) ischemic preconditioning (n = 6); (3) lidocaine only (608 microg . kg -1 . min -1 , n = 5); (4) adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA; 5 microg/kg, n = 7); and (5) CCPA plus lidocaine (n = 6). Ischemic preconditioning was achieved by using 3 cycles of ischemia and reperfusion lasting 3 minutes each. Lidocaine was infused continuously 5 minutes before and throughout 30 minutes of ischemia and ceased at reperfusion. A bolus of CCPA was infused 5 minutes before ligation along with a constant infusion of lidocaine (as above). All animals were reperfused for 120 minutes for infarct size measurement. RESULTS: Fifty-four percent of saline control rats, 17% of ischemic preconditioning-treated rats, and 29% of CCPA-treated rats died during ischemia from ventricular fibrillation. Infarct size of saline control animals was 61% +/- 5%. Pretreating with CCPA and lidocaine infusion resulted in no deaths, no severe arrhythmias, and significant infarct size reduction compared with that seen in saline control animals (P < .05). Remarkably, infarct size reduction in CCPA plus lidocaine-treated rats (12% +/- 4%) was equivalent to that achieved with ischemic preconditioning (11% +/- 3%), whereas infarct size in rats undergoing CCPA-only and lidocaine-only treatments was 42% +/- 7% and 60% +/- 6%, respectively. Although CCPA plus lidocaine treatment reduced heart rate, mean arterial pressure, and systolic pressure during ischemia, no correlation was found between these variables and infarct size reduction. CONCLUSION: We conclude that activating adenosine A1 receptor subtype with CCPA and concomitantly modulating sodium fast channels with lidocaine was comparable with ischemic preconditioning and might offer a new therapeutic window to minimize myocardial damage during surgical ischemia and reperfusion.     

The role of remote ischemic preconditioning in organ protection after cardiac surgery: a meta-analysis

Background

Remote ischemic preconditioning (RIPC) appears to protect distant organs from ischemia–reperfusion injury. We undertook meta-analysis of clinical studies to evaluate the effects of RIPC on organ protection and clinical outcomes in patients undergoing cardiac surgery.

Methods

A review of evidence for cardiac, renal, and pulmonary protection after RIPC was performed. We also did meta-regressions on RIPC variables, such as duration of ischemia, cuff pressure, and timing of application of preconditioning. Secondary outcomes included length of hospital and intensive care unit stay, duration of mechanical ventilation, and mortality at 30 days.

Results

Randomized control trials (n = 25) were included in the study for quantitative analysis of cardiac (n = 16), renal (n = 6), and pulmonary (n = 3) protection. RIPC provided statistically significant cardiac protection (standardized mean difference [SMD], −0.77; 95% confidence interval [CI], −1.15, −0.39; Z = 3.98; P < 0.0001) and on subgroup analysis, the protective effect remained consistent for all types of cardiac surgical procedures. However, there was no evidence of renal protection (SMD, 0.74; 95% CI, 0.53, 1.02; Z = 1.81; P = 0.07) or pulmonary protection (SMD, −0.03; 95% CI, −0.56, 0.50; Z = 0.12; P = 0.91). There was no statistical difference in the short-term clinical outcomes between the RIPC and control groups.

Conclusions

RIPC provides cardiac protection, but there is no evidence of renal or pulmonary protection in patients undergoing cardiac surgery using cardiopulmonary bypass. Larger multicenter trials are required to define the role of RIPC in surgical practice.     

缺血预处理对缺血脊髓微循环影响的实验研究

目的 探讨缺血预处理（IPC）对缺血损伤脊髓的保护作用及其相关机制.方法 48只健康新西兰大白兔随机分为缺血预处理组（IPC组）和缺血组,应用腹主动脉夹闭法建立脊髓缺血模型.观察两组脊髓组织缺血前、缺血40min及再灌注后2、8、24、72 h内皮素-1（ET-1）、血栓素A2（TXA2）与前列环素（PGI2）含量,并观察脊髓组织病理形态学改变及双后肢神经功能评分.结果 IPC组各时间点ET-1含量、TXB2/6-keto-PGF1α比值均显著低于缺血组（P＜0.05）.两个时间点上IPC组后肢神经功能评分明显高于缺血组（P＜0.001、0.01）,病理学累积评分明显低于缺血组（P＜0.001）.结论 IPC对主动脉阻断所致脊髓缺血再灌注损伤有良好的保护作用,抗“无再灌流”作用可能是其保护作用的重要机制之一.     

Preventive insulin administration for myocardial protection in cardiac surgery

The object of this study was to determine whether high doses of insulin administered preventively in combination with glucose and potassium exert a protective effect upon the myocardium. This approach should result in a preoperative accumulation of the myocardial glycogen stores with an increased anaerobic provision of energy-rich substrates (ATP) during coronary ischemia. Two comparable groups of seven dogs each, undergoing experimental extracorporeal circulation (ECC) with 90-min aortic cross-clamping were examined. Cardiac output (CO), systolic left ventricular blood pressure (pventr), left ventricular enddiastolic pressure (LVEDP), mean central venous pressure (CVP), and heart rate (HR) were recorded at left atrial (LA) pressures of 5, 10, 15, and 20 mmHg in order to construct ventricular function curves. These data were registered prior to the onset of ECC (preischemic value), after termination of ECC and after two 10-min periods of reperfusion. The first group served as control and the second group received high iv doses of insulin (total 25 U/kg) within 60 min prior to the onset of the ECC. In the control group, pventr and CO after termination of the ECC and after the first reperfusion were significantly (P less than 0.05) less than the preischemic values; after the second reperfusion they reached the preischemic range. In contrast, pventr and CO in the insulin group already were within the preischemic range at the termination of the ECC. After the first and the second reperfusion, CO was even greater than the preischemic value. LVEDP changed inversely, while CVP and HR showed no significant differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

远程预处理对心肌缺血-再灌注损伤的保护作用

目的 观察远程预处理对急性心肌缺血-再灌注损伤的保护作用及对心肌信号转导和转录活化因子3 (STAT3)蛋白的影响.方法 健康雄性Wistar大鼠48只,体重240～280 g,随机均分为三组:对照组(N组)、缺血-再灌注组(IR组)、远程预处理组(rIPC2组).N组仅穿线不结扎血管;IR组结扎左冠状动脉前降支(LAD) 30 min,再灌注120min;rIPC组在LAD结扎前以止血带捆绑双下肢阻断血流5 min,放松5 min,反复4次.实验结束后用TTC染色法测定大鼠心肌梗死面积;取下腔静脉血3 ml离心后测定血中磷酸肌酸酶(CK)及乳酸脱氧酶(LDH)含量;Western Blot 法测定总STAT3(t-STAT3)和磷酸化STAT3(p-STAT3)蛋白表达水平.结果 rIPC组心肌梗死面积较IR组明显缩小(P＜0.05),N组无心肌梗死;IR组CK及LDH含量较N组显著升高(P＜0.01),rIPC组CK及LDH含量较IR组明显降低(P＜0.01);三组之间t-STAT3表达差异无统计学意义,IR组p-STAT3表达较N组显著降低(P＜0.05),rIPC组p-STAT3表达较IR组明显升高(P＜0.05).结论 远程预处理对心脏缺血-再灌注损伤具有早期保护作用,其机制可能与增加心肌p-STAT3蛋白表达有关.     

Protection of the human heart with ischemic preconditioning during cardiac surgery: role of cardiopulmonary bypass

OBJECTIVE: Studies on the effects of ischemic preconditioning in the human heart have yielded conflicting results and therefore remain controversial. This study investigated whether ischemic preconditioning was able to protect against myocardial tissue damage in patients undergoing coronary artery surgery with cardiopulmonary bypass and on the beating heart. METHODS: A total of 120 patients were studied and divided into 3 groups: group I: cardiopulmonary bypass with intermittent crossclamp fibrillation; group II: cardiopulmonary bypass with cardioplegic arrest using cold blood cardioplegia; group III: surgery on the beating heart. In each group (n = 40), patients were randomly subdivided (n = 20/subgroup) into control and preconditioning groups (1 cycle of 5 minutes of ischemia/5 minutes reperfusion before intervention). Ischemic preconditioning was induced by clamping the ascending aorta in groups I and II or by clamping the coronary artery in group III. Serial venous blood levels of troponin T were analyzed before surgery and at 1, 4, 8, 24, and 48 hours after termination of ischemia. In addition, in vitro studies using right atrial specimens obtained before the institution of cardiopulmonary bypass, and then again 10 minutes after initiation of bypass, were performed. The specimens were equilibrated for 30 minutes before being allocated to 1 of the following 2 groups (n = 6 per group): (1) ischemia alone (90 minutes of ischemia followed by 120 minutes of reoxygenation) or (2) preconditioning with 5 minutes of ischemia and 5 minutes of reoxygenation before the long ischemic insult. Creatine kinase leakage (U/g wet weight) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction (mmol/l per gram wet weight), an index of cell viability, were assessed at the end of the experiment. RESULTS: There were no perioperative myocardial infarctions or deaths in any of the groups studied. The total release of troponin T was similar in groups I and II (patients undergoing surgery with cardiopulmonary bypass) and in the release profile; they were unaffected by ischemic preconditioning. In contrast, the total troponin T release for the first 48 hours was significantly reduced by ischemic preconditioning in group III (patients undergoing surgery without cardiopulmonary bypass) from 3.1 +/- 0.1 to 2.1 +/- 0.2 ng. h. mL. Furthermore, the release profile that peaked at 8 hours in the control group shifted to the left at 1 hour. In the in vitro studies, the atrial muscles obtained before cardiopulmonary bypass were protected by ischemic preconditioning (creatine kinase = 2.6 +/- 0.2 and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction = 152 +/- 24 vs creatine kinase = 5.4 +/- 0.6 and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction = 87 +/- 16 in controls; P <.05); however, the muscles obtained 10 minutes after initiation of cardiopulmonary bypass were already protected (creatine kinase = 0.8 +/- 0.1 and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction = 316 +/- 38), and ischemic preconditioning did not result in further improvements. CONCLUSIONS: Ischemic preconditioning is protective in patients undergoing coronary artery surgery on the beating heart without the use of cardiopulmonary bypass, but it offers no additional benefit when associated with bypass regardless of the mode of cardioprotection used, because cardiopulmonary bypass per se induces preconditioning.     

Plasma adenosine changes during cardiac surgery.

Changes in plasma adenosine and inosine were measured during high-dose narcotic anesthesia and surgery for coronary artery bypass grafting (CABG), and mitral or aortic valve replacement (V). Arterial and mixed venous blood samples were obtained for measurement of adenosine and inosine at eight sampling intervals ranging from preanesthesia induction to discontinuation of cardiopulmonary bypass (CPB). Arterial but not mixed venous adenosine was markedly elevated in blood samples 10 minutes after intubation, but the fourfold elevation was significant only in the CABG patient group. Mixed venous inosine and adenosine were most consistently elevated in post-CPB samples. In a separate study of arterial adenosine changes during induction, a uniform drug administration protocol was used, and again adenosine was significantly increased immediately after intubation. It is possible that adenosine and perhaps inosine may contribute to cardiovascular responses following induction-intubation and also after discontinuing CPB.     

远端组织缺血预处理对心脑保护作用的研究进展

缺血/冉灌注(ischemia reperfusion,I/R)损伤可导致局部和/或远端组织器官的损伤;缺血预处理(ischemic preconditioning,IPC)是对I/R损伤的一种有效处理方式;远端预处理(remote preconditioning,RPC)是继IPC后一种新兴的,更简单又经济的,高效的保护组织器官免受缺血损伤的策略,其机制涉及神经和/或体液两大因素的调节作用,在临床上已有试用.     

远端组织缺血预处理对心脑保护作用的研究进展

缺血/冉灌注(ischemia reperfusion,I/R)损伤可导致局部和/或远端组织器官的损伤;缺血预处理(ischemic preconditioning,IPC)是对I/R损伤的一种有效处理方式;远端预处理(remote preconditioning,RPC)是继IPC后一种新兴的,更简单又经济的,高效的保护组织器官免受缺血损伤的策略,其机制涉及神经和/或体液两大因素的调节作用,在临床上已有试用.     

远端组织缺血预处理对心脑保护作用的研究进展

缺血/冉灌注(ischemia reperfusion,I/R)损伤可导致局部和/或远端组织器官的损伤;缺血预处理(ischemic preconditioning,IPC)是对I/R损伤的一种有效处理方式;远端预处理(remote preconditioning,RPC)是继IPC后一种新兴的,更简单又经济的,高效的保护组织器官免受缺血损伤的策略,其机制涉及神经和/或体液两大因素的调节作用,在临床上已有试用.