缺血再灌注心律失常机制探讨

缺血再灌注心律失常是心内直视手术后常见的并发症和致死原因。其发生机制主要为缺血再灌注损伤所引起钙超载和氧自由基。除此之外，其他一些原因，例如：Na^ /H^ 交换活性加强、心肌细胞内游离脂肪酸增加、血小板激活因子释放加强、冠脉内皮的受损以及肾上腺素浓度升高等，对心律失常发生的影响作用越来越受到重视。目前，可通过临床常用心肌保护方法防治绝大多数再灌注心律失常。一些学者在研究缺血预处理的抗心律失常机制时，发现了通过腺苷受体、缓激肽B2受体以及类阿片受体触发这一保护机制,以及通过激活KATP^ 通道和PKC而产生的受体后机制都起到重要的作用。为防治缺血再灌注心律失常研究提供了新的思路。     

缺血再灌注心律失常机制探讨

缺血再灌注心律失常是心内直视手术后常见的并发症和致死原因。其发生机制主要为缺血再灌注损伤所引起钙超载和氧自由基。除此之外,其他一些原因,例如:Na+/H+交换活性加强、心肌细胞内游离脂肪酸增加、血小板激活因子释放加强、冠脉内皮的受损以及肾上腺素浓度升高等,对心律失常发生的影响作用越来越受到重视。目前,可通过临床常用心肌保护方法防治绝大多数再灌注心律失常。一些学者在研究缺血预处理的抗心律失常机制时,发现了通过腺苷受体、缓激肽B2受体以及类阿片受体触发这一保护机制,以及通过激活K+ATP通道和PKC而产生的受体后机制都起到重要的作用。为防治缺血再灌注心律失常研究提供了新的思路。     

缺血预处理对骨骼肌缺血再灌注损伤的保护机制及其与腺苷关系研究

目的 :探讨骨骼肌缺血预处理保护作用机制及其腺苷的关系。方法 :采用兔右后肢缺血模型 ,将 2 8只兔随机分为 4组 (n =7) ,对照组 :持续缺血 4h ,再灌注 1h ;预处理组 :缺血 5min ,再灌注 5min ,重复 3次后 ,持续缺血 4h再灌注1h。腺苷治疗组 :于缺血再灌注前经股动脉注入 0 5mg腺苷。腺苷受体拮抗剂 8-PT处理组 :在 3次循环IPC处理前 ,经股动脉注入 3 0mg 8-PT ,再缺血 4h ,再灌注 1h。通过高效液相色谱法测定处理前、缺血 4h ,再灌注 10min、3 0min及6 0min时血浆腺苷浓度变化。通过血浆CPK、MDA及骨骼肌99mTcMDP吸收量的测定判断骨骼肌损伤程度。结果 :预处理组、腺苷组及 8-PT组 ,在缺血 4h和再灌注 1h期间血浆腺苷浓度明显升高 (P <0 0 1) ,再灌注 10min时达到高峰 ,并随再灌注时间延长而逐渐降低。与对照组相比 ,预处理组和腺苷组血浆CPK、MDA及骨骼肌99mTcMDP吸收量显著降低 (P <0 0 1)。结论 :腺苷参与了缺血预处理对骨骼肌的保护作用 ,腺苷受体拮抗可阻断缺血预处理对骨骼肌的保护作用。腺苷释放和腺苷受体激活在骨骼肌缺血预处理中起重要作用。     

缺血预处理和后处理减轻缺血/再灌注损伤的分子机制

背景 组织长时间缺血后再灌注能导致缺血/再灌注(ischaemia/reperfusion,I/R)损伤.研究证实缺血预处理和缺血后处理可减轻I/R损伤大约75％. 目的 综述缺血预处理和缺血后处理减轻I/R损伤的分子机制. 内容 缺血预处理和缺血后处理的分子机制涉及腺苷、缓激肽、阿片和大麻素激活的细胞表面G耦联蛋白受体.这些物质依次兴奋生长受体,继而激活细胞保护性通路,其中包括通过有丝分裂原激活蛋白激酶(mitogen-activated protein kinase,MEK)/细胞外信号调节激酶1/2(extracellular signal-regular kinase 1/2,ERK1/2)途径减少细胞凋亡以及通过磷脂酰肌醇-3激酶途径减少线粒体通透性转换孔(mitochondrial permeability transition pore,mPTP)开放.mPTp开放能够导致细胞死亡.最近研究提示,细胞表面激活的肿瘤坏死因子-α受体通过激活Janus激酶以及信号转导子和转录激活因子3途径而发挥细胞保护作用. 趋向 缺血预处理和缺血后处理减轻I/R损伤的分子机制目前仍在研究中,有望在对此更深入理解的基础上获得可转化为有意义的临床治疗措施.     

缺血预处理对大鼠肝脏缺血再灌注损伤保护作用机制的研究

目的　探讨缺血预处理 (IPC)保护作用的发生机制。方法　建立大鼠部分肝脏热缺血再灌注模型。IPC采用肝脏缺血 10min ,再灌注 10min。结果　IPC后肝组织中腺苷和NO水平明显升高 ,与对照组相比差异显著 (P <0 0 1) ,但IPC前应用腺苷A2 受体拮抗剂后NO的升高被抑制 (P<0 0 1)。缺血再灌注 (I/R) 2h后血清中TNF α、AST、ALT、LDH及W/D水平和假手术组相比明显增加 ,而IL 10含量降低 (P <0 0 1) ;IPC、I/R前加入腺苷、IPC前应用腺苷A1受体拮抗剂显著地降低TNF α释放和AST、ALT、LDH及W /D水平 ,提高IL 10含量 ,与I/R组相比差异显著 (P <0 0 1) ;但IPC前应用腺苷A2 受体拮抗剂 (IPC +A2 antag)和NO合成酶抑制剂NAME并没有能像IPC组那样有效降低TNF α、AST、ALT、LDH及W /D的水平 ,提高IL 10的含量 (P <0 0 1) ;而IPC前给IPC+A2 antag组提供NO前体精氨酸又获得和IPC组同样的结果 (P >0 0 5 )。结论　IPC引起细胞外腺苷水平升高 ,腺苷A2 受体活化 ,介导了NO合成增加 ,最终通过抑制效应器TNF α的释放、增加IL 10的合成来实现对缺血组织的保护作用。     

缺血预处理对骨骼肌缺血再灌物保护机制及其与腺苷关系研究

目的：探讨骨骼肌缺血预处理保护作用机制及其腺苷的关系。方法：采用兔右后肢缺血模型，将２８史兔随机分为４组，对照组：持续缺血４ｈ，再灌注１ｈ；缺血５ｍｉｎ再灌注５ｍｉｎ重复３次后，持续缺血４ｈ再灌注１ｈ。腺苷治疗组：于血再灌注前经股动脉注入０．５ｍｇ腺苷。腺苷受体拮抗剂８－ＰＴ处理组；在３次循环ＩＰＣ处理前，经股动脉注射３．０ｍｇ８－ＰＴ，再缺血４ｈ，再灌注１ｈ。通过高铲液相色谱法测定处理胶、缺血４     

缺血预处理对肝脏缺血再灌注损伤保护作用的实验研究

在大鼠肝脏缺血再灌注模型基础上建立稳定的缺血预处理模型,观察其保护作用,结果发现预处理与缺血再灌注组相比比清肝酶（ＡＬＴ,ＡＳＴ）,透明质酸水平及肝组织局部ＭＤＡ含量均低,而组织ＡＴＰ含量及能荷值均高,形态学损伤改变轻;同时发现预处理组织腺苷含量明显高于缺血再灌注组。实验表明缺血预处理能有效减轻肝脏的缺血再灌注损伤,腺苷分子参与了这一保护机制。     

缺血预处理在肠缺血/再灌注损伤中的研究进展

缺血预处理是近年来提出的一种新的肠缺血/再灌注损伤的保护方法,即使在小肠长时间缺血/再灌注之前,进行一次或多次短暂的缺血,再灌注过程.研究表明缺血预处理对小肠缺血/再灌注损伤具有保护作用,但机制复杂,尚未明确.现就缺血预处理在肠缺血,再灌注损伤中的研究进展作一综述.     

缺血预处理对肾脏缺血再灌注损伤保护作用的研究进展

肾缺血再灌注损伤导致急性缺血性肾衰竭在临床上十分常见.研究显示缺血预处理对肾缺血再灌注损伤具有保护作用.近年来关于肾缺血预处理作用机制的报道较多,本文就缺血预处理对肾缺血再灌注损伤保护作用的研究现状作一综述.     

钙网蛋白在不同预处理心肌细胞缺血再灌注的保护作用

目的 观察3种不同预处理对在体缺血再灌注心肌的保护作用,探讨钙网蛋白(CRT)在预处理心肌细胞缺血再灌注损伤的作用.方法 将30只成年SD大鼠随机分成5组(n=6),分别为缺血再灌注组、缺血预处理组、腺苷预处理组、远程预处理组和假手术组.建立大鼠在体缺血冉灌注损伤模型,观察各组缺血再灌注前后心功能变化,并检测再灌注末血清肌钙蛋白T(cTnT)、丙二醛(MDA)、超氧化物歧化酶(SOD)的变化以及心肌组织CRT的表达.结果 缺血预处理组、远程预处理组与缺血再灌注组比较(±dp/dt max)有明显提高(P<0.05).缺血预处理组、腺苷预处理组、远程预处理组cTnT、MDA值均低于缺血再灌注组,SOD值高于缺血再灌注组(P<0.05);腺苷预处理组SOD值高于缺血预处理组和远程预处理组,cTnT值则低于后2组(P<0.05);缺血预处理组、腺苷预处理组、远程组与缺血再灌注组比较,CRT表达灰度值均显著降低(P<0.05).结论 腺苷预处理、远程预处理均可以模拟缺血预处理的心肌保护作用;预处理可能通过下调钙网蛋白高表达减轻在体大鼠心肌细胞缺血再灌注损伤.     

Biological Implications of Extracellular Adenosine in Hepatic Ischemia and Reperfusion Injury

The purine nucleoside adenosine is clinically employed in the treatment of supraventricular tachycardia. In addition, it has direct coronary vasodilatory effects, and may influence platelet aggregation. Experimental observations mechanistically link extracellular adenosine to cellular adaptation to hypoxia. Adenosine generation has been implicated in several pathophysiologic processes including angiogenesis, tumor defenses and neurodegeneration. In solid organ transplantation, prolonged tissue ischemia and subsequent reperfusion injury may lead to profound graft dysfunction. Importantly, conditions of limited oxygen availability are associated with increased production of extracellular adenosine and subsequent tissue protection. Within the rapidly expanding field of adenosine biology, several enzymatic steps in adenosine production have been characterized and multiple receptor subtypes have been identified. In this review, we briefly examine the biologic steps involved in adenosine generation and chronicle the current state of adenosine signaling in hepatic ischemia and reperfusion injury.     

Preconditioning and adenosine protect human proximal tubule cells in an in vitro model of ischemic injury

Renal ischemic reperfusion injury results in unacceptably high mortality and morbidity during the perioperative period. It has been recently demonstrated that ischemic preconditioning or adenosine receptor modulations attenuate renal ischemic reperfusion injury in vivo. An in vitro model of ischemic renal injury was used in cultured human proximal tubule (HK-2) cells to further elucidate the protective signaling cascades against renal ischemic reperfusion injury. ATP depletion preconditioning (1 h of antimycin A and 2-deoxyglucose treatment followed by 1 h of recovery), adenosine, an A(1) adenosine receptor selective agonist, or an A(2a) adenosine receptor selective agonist significantly attenuated subsequent severe ATP depletion injury of HK-2 cells. In contrast, an adenosine receptor antagonist failed to prevent protection induced by ATP depletion preconditioning. Cytoprotection by ATP depletion preconditioning or A(1) adenosine receptor activation was prevented by inhibitors of extracellular signal-regulated mitogen-activated kinases, protein kinase C, and tyrosine kinases. The A(1) and A(2a) adenosine receptor-mediated cytoprotection were also dependent on G(i/o) proteins and PKA activation, respectively. It is concluded that ATP depletion preconditioning and A(1) and A(2a) adenosine receptor activation protect HK-2 cells against severe ATP depletion injury via distinct signaling pathways.     

Post-ischemic intraportal adenosine administration protects against reperfusion injury of canine liver

Although adenosine has been postulated to inhibit ischemia-reperfusion injury in various tissues, its in vivo cytoprotective mechanism is not fully known. The aim of this study was to determine the effect of intraportally infused adenosine on reperfusion injury in the canine liver. Two h ischemia and reperfusion of the liver were induced in beagle dogs by clamping the portal triad. Either adenosine or saline was infused in the portal vein after reperfusion for 60 min. Levels of serum aspartate aminotransferase and alanine aminotransferase and the survival of animals were examined. Hepatic levels of protein carbonyls and glutathione were also measured, as markers of oxidative stress. One h after reperfusion, the liver was perfused with nitroblue tetrazolium and the formation of formazan was observed to evaluate superoxide formation. Twenty-four h after reperfusion, 100% of animals in the adenosine group and 33% of animals in the control group survived. Adenosine significantly decreased the reperfusion-induced increase in serum levels of aspartate aminotransferase and alanine aminotransferase. Adenosine also suppressed the formation of protein carbonyls and the decrease in glutathione levels. Histologically, neutrophil infiltration, superoxide formation, and apoptosis were decreased by adenosine. These results suggest that intraportally infused adenosine attenuates reperfusion injury of the liver, presumably by suppressing the activation of neutrophils and oxidative stress. Received for publication on Oct. 15, 1999; accepted on Nov. 11, 1999     

Extracellular nucleotide signaling in solid organ transplantation

The role of extracellular purine nucleotides, including adenosine triphosphate (ATP) and adenosine, as modulators of posttransplantation outcome and ischemia‐reperfusion injury is becoming increasingly evident. Upon pathological release of ATP, binding and activation of P2 purinergic surface receptors promote tissue injury and inflammation, while the expression and activation of P1 receptors for adenosine have been shown to attenuate inflammation and limit ischemia‐induced damage, which are central to the viability and long‐term success of allografts. Here we review the current state of the transplant field with respect to the role of extracellular nucleotide signaling, with a focus on the sources and functions of extracellular ATP. The connection between ischemia reperfusion, purinergic signaling, and graft preservation, as well as the role of ATP and adenosine as driving factors in the promotion and suppression of posttransplant inflammation and allograft rejection, are discussed. We also examine novel therapeutic approaches that take advantage of the ischemia‐reperfusion‐responsive and immunomodulatory roles for purinergic signaling with the goal of enhancing graft viability, attenuating posttransplant inflammation, and minimizing complications including rejection, graft failure, and associated comorbidities.     

Activation of protein kinase C delta reduces hepatocellular damage in ischemic preconditioned rat liver

Background

Liver ischemic preconditioning (IPC), pre-exposure of the liver to transient ischemia, has been applied as a useful surgical method to prevent liver ischemia and reperfusion (I/R) injury. Although activation of protein kinase C (PKC), especially novel PKCs, has been known as central signaling responsible for the liver protection of IPC, determination of the involved isozyme in strong protection afforded by IPC has not been elucidated.

Materials and methods

Rats were subjected to 90 min of partial liver ischemia followed by 3, 6, and 24 h of reperfusion. IPC was induced by 10 min of ischemia after 10 min of reperfusion before sustained ischemia. Rottlerin, a PKC-δ selective inhibitor; PKC-εV1-2 peptide, a selective PKC-ε inhibitor; and 3,7-dimethyl-1-[2-propargyl] xanthine, an adenosine A₂ receptor antagonist, were intravenously injected before IPC. N-acetyl-L-cysteine, a strong antioxidant, and Nω-nitro-L-arginine methyl ester, a nonselective nitric oxide synthase inhibitor, were injected intraperitoneally before IPC.

Results

IPC resulted in strong protection against liver I/R injury as evidenced by biochemical and histologic analyses. Inhibition of PKC-δ strongly attenuated the IPC-induced liver protection, whereas PKC-ε inhibition did not exert any effect on IPC-induced protection. Although inhibition of reactive oxygen species, adenosine, and nitric oxide attenuated the beneficial effects of IPC, inhibition of adenosine only attenuated PKC-δ and -ε translocation.

Conclusions

Our findings suggest that IPC protects against I/R-induced hepatic injury through activation of PKC-δ.     

线粒体通透件转换孔在缺血/再灌注损伤中的作用

背景 线粒体作为“能量工厂”提供细胞生长及代谢所需的三磷酸腺苷（adenosine triphosphate,ATP）,同时也是细胞存活与否的重要信号管理者.线粒体通透性转换孔（mitochondrial permeability transition pore,mPTP）是横跨线粒体内外膜之间的允许相对分子质量1.5 kD以下的分子自由通过的孔道.在脑缺血/再灌注（ischemia/reperfusion,I/R）损伤中,线粒体是研究的焦点,而mPTP作为线粒体的门户更是影响着线粒体膜电位（mitochondrial membrane potential,△ψm）、线粒体Ca2＋超载及促细胞死亡物质释放等一系列过程. 目的 对mPTP在I/R损伤中可能的作用机制及治疗方法进行综述. 内容 整理和阐述了mPTP的结构、mPTP与I/R损伤的机制和预防与治疗I/R损伤的可能方法. 趋向 随着mPTP在I/R损伤中的作用机制不断被揭示,其将成为治疗I/R损伤的重要靶点.     

Activation of A3 Adenosine Receptor Provides Lung Protection Against Ischemia-Reperfusion Injury Associated with Reduction in Apoptosis

Apoptosis has been described in various models of ischemia-reperfusion (IR) injury, including lung transplantation. A3 adenosine receptor (AR) has been linked to a variety of apoptotic processes. The effect of A3AR activation on lung injury and apoptosis, following IR, has not been reported to date. In a spontaneously breathing cat model, in which the left lower lobe of the lung was isolated and subjected to 2 h of ischemia and 3 h of reperfusion, we tested the effect of IB-MECA, a selective A3AR agonist, on lung apoptosis and injury. Significant increase in the extent of apoptosis was observed following lung reperfusion. IB-MECA, administered before IR, and before or with reperfusion, markedly (p < 0.01) attenuated indices of injury and apoptosis including the percentage of injured alveoli, wet/dry weight ratio, myeloperoxidase activity, in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling (TUNEL) positive cells, and caspase 3 activity and expression. The protective effects of IB-MECA were completely blocked by pretreatment with the selective A3AR antagonist MRS-1191. In summary, even when given after the onset of ischemia, the A3AR agonist IB-MECA conferred a powerful protection against reperfusion lung injury, which was associated with decreased apoptosis. This suggests a potentially important role for A3AR in lung IR injury.     

抑肽酶对成年豚鼠心肌再灌注损伤的保护作用

目的：探索抑肽酶的心肌保护作用。方法：建立离体心脏顺行灌注后左心做功模型，２０只成年豚鼠随机分为Ａ、Ｂ两组，分别以４℃Ｓｔ．ＴｈｏｍａｓＨｏｓｐｉｔａｌｃａｒｄｉｏｐｌｅｇｉｃｓｏｌｕｔｉｏｎＮｏ．２（ＳＴＳ）和ＳＴＳ＋抑肽酶（１５０ＫＩｕｍＬＳＴＳ）为心停搏液，测定缺血（９０分钟，２０℃）前、后和再灌注（６０分钟）时心脏动力学指标，心肌腺苷酸和丙二醛含量，并行心肌电镜观察。结果：Ｂ组再灌注后的心功能恢复，腺苷酸贮备和超微结构的改善明显高于或优于Ａ组，而丙二醛含量显著低于Ａ组（Ｐ＜０．０５）。结论：抑肽酶加入ＳＴＳ中可减少氧自由基产生，对成年豚鼠心肌缺血再灌注损伤有保护作用。     

Attenuation of renal ischemia–reperfusion injury by postconditioning involves adenosine receptor and protein kinase C activation

Significant organ injury occurs after transplantation and reflow (i.e., reperfusion injury). Postconditioning (PoC), consisting of alternating periods of reperfusion and re‐occlusion at onset of reperfusion, attenuates reperfusion injury in organs including heart and brain. We tested whether PoC attenuates renal ischemia–reperfusion (I/R) injury in the kidney by activating adenosine receptors (AR) and protein kinase C (PKC). The single kidney rat I/R model was used. Groups: (1) sham: time‐matched surgical protocol only. In all others, the left renal artery (RA) was occluded for 45 min and reperfused for 24 h. (2) Control: I/R with no intervention at R. All antagonists were administered 5 min before reperfusion. (3) PoC: I/R + four cycles of 45 s of R and 45 s of re‐occlusion before full R. (4) PoC + ARi: PoC plus the AR antagonist 8‐ρ‐(sulfophenyl) theophylline (8‐SPT). (5) PoC + PKCi: PoC plus the PKC antagonist chelerythrine (Che). In shams, plasma blood urea nitrogen (BUN mg/dl) at 24 h averaged 23.2 ± 5.3 and creatinine (Cr mg/dl) averaged 1.28 ± 0.2. PoC reduced BUN (87.2 ± 10 in Control vs. 38.8 ± 9, P = 0.001) and Cr (4.2 ± 0.6 in Control vs. 1.5 ± 0.2, P < 0.001). 8‐SPT and Che reversed renal protection indices after PoC. I/R increased apoptosis, which was reduced by PoC, which was reversed by 8‐SPT and Che. Postconditioning attenuates renal I/R injury by adenosine receptor activation and PKC signaling.     

活性氧的内源性心肌保护作用及其机制

既往认为在心肌缺血/再灌注过程中活性氧是一种有害的细胞损伤因子,但最近研究发现也是可产生细胞保护作用的信号分子.活性氧(reactive oxygen species,ROS)在缺血,再灌注及其内源性心肌保护作用中具有双重作用,内源性心肌保护过程中活性氧主要来自线粒体呼吸链,主要通过mKATP-ROS通路产生;活性氧通过改变细胞氧化还原状态和调节线粒体膜通透性转换孔道开放状态,传递线粒体和细胞之间的信息联系.因此.活性氧不单是缺血/再灌注氧化应激的损伤因子,也是产生内源性心肌保护作用的重要信号分子.