肝脏缺血/再灌注后线粒体损伤与促凋亡蛋白的释放

肝脏缺血／再灌注（I／R）损伤是临床上较为常见的组织器官损伤之一，细胞凋亡在肝脏I／R损伤中起到了重要作用。近年来的研究发现，I／R导致线粒体通透性改变，由此引起线粒体膜电位的降低和促凋亡蛋白的释放等一系列变化，在细胞凋亡中发挥关键作用。     

缝隙连接蛋白43与心肌缺血／再灌注损伤机制的研究进展

背景研究表明,心肌缺血／再灌注（ischemia／reperfusion,I／R）损伤的发病机制与氧自由基过量产生、钙超载、线粒体损伤及心肌细胞凋亡等密切相关,最新研究发现缝隙连接（gapjunction,GJ）也参与心肌I／R损伤。目的现主要针对GJ连接蛋白（connexin,Cx）43与心肌I／R损伤的关系作一综述。内容Cx43在心肌I／R损伤中参与心肌保护作用,其机制可能与钙超载、在线粒体中的分布及细胞凋亡等因素相关。趋向未来研究需要进一步探究Cx43与心肌细胞凋亡之间的关系,同时为临床实际工作提供依据。     

心肌缺血再灌注损伤的线粒体通透性转换机制

线粒体功能障碍存心肌缺血再灌注（ischema／reperfusion I／R）损伤中占有重要地位．近年研究发现线粒体的功能障碍和线粒体通透性转换孔道（mitochondfial permeability transition pore，mPTP）密切相关，     

异丙酚对肝缺血再灌注损伤犬肝细胞线粒体的作用

目的探讨异丙酚对肝缺血再灌注损伤犬肝细胞线粒体的作用及其机制。方法20只杂种犬随机分为4组（n=5）：假手术组（S组）、缺血再灌注组（I／R组）、小剂量异丙酚组（P1组）及大剂量异丙酚组（P2组）。以10ml／min速率静脉输注6％羟乙基淀粉150～200ml，同时从股动脉缓慢放血100～150ml，使平均动脉压（MAP）不低于85mmHg。S、I／R组静脉注射3％戊巴比妥钠30mg／kg、维库溴铵0．3mg／kg麻醉诱导，P1、P2组依次静脉注射异丙酚6mg／kg、维库溴铵0．3mg／kg麻醉诱导，气管插管后控制呼吸。S、I／R组间断静脉注射戊巴比妥钠维持麻醉，P1、P2组以血浆靶浓度6、12μg／ml靶控输注异丙酚维持麻醉30min后麻醉维持同S组。缺血期间回输自体血，维持MAP不低于80mmHg。I／R、P1组、P2组气管插管后30min制备肝缺血（缺血30min）再灌注模型。分别于缺血前即刻、缺血30min、再灌注60min抽取静脉血，测定血浆谷丙转氨酶（ALT）、谷草转氨酶（AST）及肝细胞线粒体Na^＋-K^＋-ATP酶活性，并在透射电镜下观察肝细胞线粒体的超微结构。结果肝缺血再灌注可导致血浆ALT、AST活性升高，肝细胞线粒体Na^＋-K^＋-ATP酶活性降低，肝线粒体损伤，异丙酚可减弱肝缺血再灌注导致的上述改变，以大剂量效果较好。结论异丙酚可减轻肝缺血再灌注损伤犬肝细胞线粒体损伤，呈剂量依赖性。     

丁羟茴香醚对衰老大鼠肾脏缺血再灌注损伤的保护作用

目的观察老年大鼠肾脏缺血再灌注（I／R）模型中。肾小管上皮细胞的损伤变化，探讨活性氧（ROS）清除剂对I／R损伤的保护作用。方法27月龄大鼠随机分为假手术组、I／R模型组、丁羟茴香醚（BHA）组和nicardipine组。夹闭双侧。肾动脉30min再灌注18h制成I／R模型。观察肾功能、肾脏病理改变、肾小管上皮细胞凋亡情况。检测肾组织半胱氨酸天冬氨酸蛋白酶（caspase）3、细胞色素C表达。测定肾组织脂质过氧化物丙二醛（MDA）含量和超氧化物歧化酶（SOD）活性。结果（1）肾脏I／R损伤时，老年大鼠肾功能明显减退，肾组织病理改变比较明显，大量肾小管上皮细胞凋亡，肾组织caspase-3、细胞色素C表达明显上调。肾组织中MDA增加、SOD活性下降（P均〈0．05）。（2）BHA或nicardipine均能明显改善肾功能。肾组织病理改变和凋亡相关指标（P〈0．05）；BHA或nicardipine均能减少组织中MDA含量，部分恢复肾组织中SOD含量。结论老年大鼠肾脏I／R损伤时肾小管上皮细胞凋亡增加，肾功能减退。ROS堆积后，线粒体损伤导致肾小管上皮细胞凋亡。清除ROS可以抑制‘肾小管上皮细胞凋亡，减轻I／R损伤。     

大鼠肝脏缺血再灌注损伤程度判定指标的选择

目的 探讨肝脏缺血再灌注（I／R）损伤程度及其判断指标的选择。方法 建立大鼠肝脏局部I／R模型，测定大鼠肝脏缺血60，90min再灌注0，1，2，4，6，12，24，48h时的血清丙氨酸转氨酶（ALT）水平，并行病理检查（相对细胞死亡率）。参照本院I／R损伤分级标准重新将动物分为4个不同的I／R损伤程度的实验组，分析ALT水平与病理改变的关系。结果 缺血60min组中轻度I／R损伤占75．0％，中度I／R损伤占14．6％，重度I／R损伤占10．4％；缺血90min组中轻度I／R损伤占41．7％，中度I／R损伤占25．0％，重度I／R损伤占16．7％，严重度I／R损伤占16．7％。损伤程度越重细胞死亡率越高，ALT水平也越高。结论 ALT水平可直接反映肝脏I／R损伤程度；损伤程度越重，转氨酶水平越高，细胞死亡率也越高。     

脊髓损伤后线粒体超微结构和呼吸功能的变化

[目的]探讨大鼠脊髓损伤后伤段脊髓线粒体超微结构的改变和线粒体呼吸功能的变化。[方法]48只SD大鼠，随机分为：对照组（假手术组）和脊髓损伤组（SCI组），每组又分为处理后6、12、24h三时相组，每组8只，采用Allen＇s打击法造成大鼠脊髓损伤模型，在各时相提取伤段脊髓线粒体，透射电镜观察线粒体超微结构的改变；Clark氧电极法测定线粒体呼吸功能，根据线粒体呼吸耗氧量换算出R3、R4、RCR、P／O比值。[结果]SCI组脊髓组织线粒体体积增大，嵴稍肿胀，嵴内腔扩大，部分线粒体出现膜结构不清、嵴紊乱，部分神经细胞内的高尔基器、内质网稍肿大。随着损伤后时间的延长，可见部分线粒体嵴断裂溶解、膜破裂和线粒体数量减少等。SCI组在伤后6、12h和24h R3、RCR和P／O显著低于对照组，R4显著高于对照组，有极显著统计学意义（P〈0．01）。[结论]大鼠脊髓损伤后线粒体的超微结构发生明显改变；伤段脊髓线粒体呼吸功能明显下降。     

胱硫醚β-合酶/硫化氢和血红素氧合酶-1/一氧化碳体系在大鼠脑缺血再灌注损伤中的作用

目的 研究胱硫醚β-合酶（CBS）／硫化氢（H2S）体系和血红素氧合酶-1（HO-1）／一氧化碳（CO）体系在大鼠脑缺血再灌注损伤中的作用。方法 30只Wistar大鼠随机分为5组（n=6）：对照组（C组）、脑缺血再灌注组（I／R组）、脑缺血再灌注＋锌原卟啉（HO-1抑制剂）组（I／R＋Z组）、脑缺血再灌注＋羟氨（CBS抑制剂）组（I／R＋H组）、脑缺血再灌注＋锌原卟啉＋羟氨组（I／R＋Z＋H组）。采用四血管阻断法建立全脑缺血再灌注损伤模型，I／R＋Z组、I／R＋H组和I／R＋Z＋H组夹闭两侧颈总动脉前30min分别腹腔注射锌原卟啉45／zmol／kg、羟氨5mmol／L、羟氨5mmol／L＋锌原卟啉45／maol／kg1ml，C、I／R组给予等量生理盐水。再灌注6h时处死大鼠，取海马，测定海马组织H2S、CO、还原型谷胱甘肽（GSH）、丙二醛（MDA）、超氧化物歧化酶（SOD）水平及CBSmRNA和HO-1mRNA的表达；电镜下观察海马线粒体变性情况。结果 与C组比较，I／R组海马组织CO、H2S、CBSmRNA和HO-1mRNA、MDA水平及线粒体变性率均升高，海马组织SOD、GSH水平降低（P〈0．01）；与I／R组比较，I／R＋Z组海马组织CO、HO-1mRNA水平降低，海马组织H2S、CBSmRNA、GSH、MDA水平升高，I／R＋H组海马组织CO、HO-1mRNA、MDA水平升高，H2S、CBSmRNA、GSH水平降低；I／R＋Z＋H组海马组织CO、RS、HO-1mRNA和CBSmRNA、SOD、GSH水平降低，线粒体变性率升高（P〈0．05）。结论 CBS／H1S体系和HO-1／CO体系可拮抗大鼠脑缺血再灌注损伤，其作用可相互代偿。     

甲基强的松龙对脊髓损伤后伤段脊髓线粒体功能的影响

目的：探讨脊髓损伤后伤段脊髓线粒体呼吸功能和线粒体内游离钙的变化和早期使用甲基强的松龙（MP）对其的影响。方法：54只SD大鼠，随机分组为假手术组（对照组）、脊髓损伤组（SCI组，采用Allen’s打击法造成大鼠脊髓损伤模型）和脊髓损伤后应用MP治疗组（MP组），每组又分为处理后6h、12h、24h三个时间相，每个时间相6只。在各时间相处死动物后提取伤段脊髓线粒体，测定线粒体呼吸Ⅲ态（R3）、呼吸Ⅳ态（R4）、呼吸控制率（RCR）、磷氧比（P／0）和线粒体内游离Ca^2＋浓度。结果：SCI组在伤后6h、12h和24hR3、RCR和P／0显著低于对照组，R4和线粒体内游离Ca^2＋浓度显著高于对照组。差异有显著性（P〈0．01）；伤后6h和12h MP组R3、RCR和P／0高于SCI组，R4和线粒体内游离Ca^2＋浓度低于SCI组，差异有显著性（P〈0．01）；MP组R3、R4和RCR在6h和12h时与对照组之间无显著性差异，24h时R3、RCR和P／0低于正常对照组，有显著性差异（P〈0．05）。结论：脊髓损伤后伤段脊髓线粒体呼吸功能和线粒体内游离Ca^2＋浓度明显受到影响，线粒体内膜通透性增加，线粒体氧化磷酸化的偶联程度明显受到抑制。早期使用甲基强的松龙可明显改善线粒体的呼吸功能，抑制Ca^2＋内流，保护伤段脊髓线粒体的稳定性。     

异氟醚预处理对沙士鼠脑缺血再灌注损伤的保护作用

目的探讨异氟醚预处理对沙士鼠脑缺血再灌注损伤的保护作用及可能的机制。方法75只雄性沙士鼠，随机分5组，每组15只。假手术组（SHAM组）；I／R组：夹闭双侧颈总动脉5min后开放造成缺血再灌注；异氟醚预处理组（ISO组）：缺血前60min吸入1．2％．1．5％异氟醚30min；5．羟葵酸盐组（5-HD组）：缺血前30min腹腔内注射线粒体ATP敏感性钾通道抑制剂5-HD 10mg／kg；5．HD＋ISO组：腹腔内注射5-HD10mg／kg，30min后同ISO组。再灌注24h，取鼠前脑，透射电镜下观察线粒体超微结构，用荧光分光光度计测定线粒体游离Ca^2＋浓度，用紫外分光光度计测定线粒体通透转运通道（MPTP）开放程度。结果I／R组、5-HD和5-HD＋ISO组线粒体肿胀，嵴断裂、溶解，内呈空泡状，ISO和SHAM组线粒体结构较完整，嵴及内膜间隙仍清晰可见。I／R、5．HD、5．HD＋ISO组线粒体游离Ca^2＋浓度及MFrP开放程度均高于SHAM组，ISO组线粒体游离Ca^2＋浓度及MPTP开放程度低于I/R组（P〈0．05）。结论异氟醚预处理对沙士鼠脑缺血再灌注损伤有保护作用，可能是通过激活线粒体ATP敏感性钾通道，减轻Ca^2＋超载，从而抑制MPTP开放而产生的。     

Hydrogen-rich saline attenuates neuronal ischemia–reperfusion injury by protecting mitochondrial function in rats

Background

Hydrogen, a popular antioxidant gas, can selectively reduce cytotoxic oxygen radicals and has been found to protect against ischemia–reperfusion (I/R) injury of multiple organs. Acute neuronal death during I/R has been attributed to loss of mitochondrial permeability transition coupled with mitochondrial dysfunction. This study was designed to investigate the potential therapeutic effect of hydrogen-rich saline on neuronal mitochondrial injury from global cerebral I/R in rats.

Materials and methods

We used a four-vessel occlusion model of global cerebral ischemia and reperfusion, with Sprague–Dawley rats. The rats were divided randomly into six groups (n = 90): sham (group S), I/R (group I/R), normal saline (group NS), atractyloside (group A), hydrogen-rich saline (group H), and hydrogen-rich saline + atractyloside (group HA). In groups H and HA, intraperitoneal hydrogen-rich saline (5 mL/kg) was injected immediately after reperfusion, whereas the equal volume of NS was injected in the other four groups. In groups A and HA, atractyloside (15 μL) was intracerebroventricularly injected 10 min before reperfusion, whereas groups NS and H received equal NS. The mitochondrial permeability transition pore opening and mitochondrial membrane potential were measured by spectrophotometry. Cytochrome c protein expression in the mitochondria and cytoplasm was detected by western blot. The hippocampus mitochondria ultrastructure was examined with transmission electron microscope. The histologic damage in hippocampus was assessed by hematoxylin and eosin staining.

Results

Hydrogen-rich saline treatment significantly improved the amount of surviving cells (P < 0.05). Furthermore, hydrogen-rich saline not only reduced tissue damage, the degree of mitochondrial swelling, and the loss of mitochondrial membrane potential but also preserved the mitochondrial cytochrome c content (P < 0.05).

Conclusions

Our study showed that hydrogen-rich saline was able to attenuate neuronal I/R injury, probably by protecting mitochondrial function in rats.     

Prevention of I/R injury in fatty livers by ischemic preconditioning is associated with increased mitochondrial tolerance: the key role of ATPsynthase and mitochondrial permeability transition

Ischemia/reperfusion (I/R) injury is a commonly encountered clinical problem and occurs probably as a consequence of irreversible mitochondrial injury. The increased susceptibility of fatty livers to ischemic injury is associated with depletion of adenosine triphosphate (ATP) content, which is preserved by preconditioning. Mitochondria being the main ATP production source for the cell, we aimed to evaluate whether ischemic preconditioning (IPC) of fatty livers prevents the impairment in mitochondrial function induced by I/R. Lean and steatotic animals were subjected to 90 min of hepatic warm ischemia and 12 h of reperfusion. IPC effect was tested in fatty livers. After reperfusion, serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured. Mitochondrial membrane potential, mitochondrial respiration and susceptibility to mitochondrial permeability transition (MPT) were evaluated, as well as ATPase activity and adenine nucleotides. IPC of fatty livers decreased serum AST and ALT levels. Fatty animals subjected to I/R exhibited decreased mitochondrial membrane potential and a delay in the repolarization after a phosphorylation cycle, associated with increased state 4 respiration. Increased tolerance to MPT induction, preservation of F₁F_o-ATPsynthase activity and mitochondrial bioenergetics were observed in ischemic preconditioned fatty livers. Thus, IPC is an endogenous protecting mechanism that preserves mitochondrial function and bioenergetics in fatty livers.     

丙泊酚在正颌外科控制性降压中的脑保护作用机理

目的:通过大鼠实验,研究丙泊酚在大鼠脑缺血再灌注损伤时对线粒体通透性转换孔活性的影响程度,及其抑制神经细胞凋亡坏死的作用机制。以探讨其在正颌外科控制性降压中的脑保护作用机理。方法:选取健康雄性大鼠30只,体重250～300g,采用"双侧颈总动脉阻断法"建立前脑缺血再灌注模型,左侧侧脑室于假手术组(C组)、缺血再灌注组(I/R)组注射生理盐水1ml/kg,丙泊酚干预组(P组)射注丙泊酚1mg/kg,24h后断头提取海马组织线粒体,加入CaCl2于37℃下形成钙超载后孵育5min。电镜观察其微观组织形态学改变,采用紫外分光光度计法来观察线粒体通透性转换孔开放程度。结果:电镜下C组线粒体结构完整,排列密集;I/R组可见线粒体明显肿胀、嵴断裂、膜破裂;P组可见线粒体部分肿胀,嵴部分断裂,但损伤程度轻于I/R组。与C组相比较,I/R组和P组线粒体吸光度值明显下降(P<0.05);与I/R相比,P吸光度值下降幅度减小(P<0.05)。丙泊酚组细胞肿胀坏死明显减轻,凋亡细胞及坏死细胞明显减少。结论:丙泊酚能够改善大鼠前脑缺血再灌注后线粒体形态,其机制可能与其抑制线粒体通透性转换孔(MPTP)开放有关,从而改善线粒体功能,抑制神经细胞凋亡坏死,减轻脑缺血再灌注损伤。这说明丙泊酚在正颌外科控制性降压中使用时对大脑有良好的保护作用,可以大幅度提高手术安全效果,具有重要的临床指导意义。     

Role of glycogen synthase kinase 3β in protective effect of propofol against hepatic ischemia–reperfusion injury

Background

It was previously reported that propofol, an intravenously administered hypnotic and anesthetic agent, protects organs from ischemia–reperfusion (I/R) injury. However, the underlying mechanisms are largely unknown. Glycogen synthase kinase 3β (GSK-3β) is known to play an important role in the oxidative stress–induced apoptosis. In this study, we investigated the role of GSK-3β and mitochondrial permeability transition pore (MPTP) in the protective effects of propofol against hepatic I/R injury.

Materials and methods

The left and median hepatic artery and the portal vein branches were blocked by no-damage artery clips to create the model of partial ischemia (70%), and liver lobes were subjected to warm ischemia for 30, 60, 90 min, respectively. Reperfusion of 120 min was then initiated by the removal of clamp. The MPTP opening was assessed by measuring mitochondrial large amplitude swelling and mitochondrial membrane potential.

Results

Pretreatment with propofol in conditions of hepatic I/R inhibits the apoptosis of hepatocytes as evidenced by decreased terminal deoxynucleotidyl transferase dUTP nick end labeling–positive cells. Importantly, propofol suppressed the mitochondrial GSK-3β by promoting or preserving its phosphorylation at Ser9, thus restraining the opening of MPTP and preventing the mitochondrial swell and mitochondrial membrane potential collapse.

Conclusions

Propofol protects liver from I/R injury by sustaining the mitochondrial function, which is possibly involved with the modulation of MPTP and GSK-3β.     

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.     

丙泊酚对大鼠前脑缺血/再灌注诱导线粒体损伤及解耦联蛋白2表达的影响

目的 探讨丙泊酚对大鼠前脑缺血/再灌注(ischemia reprfnsion,I/R)诱导线粒体损伤及解耦联蛋白2(uncoupling protein 2,UCP 2)表达的影响.方法 45只健康雄性Wistar大鼠,体重250 g～300 g,按随机数字表法分为3组(n=15).采用"二血管阻断法"制备大鼠前脑I/R损伤模型.假手术组(C组):暴露双侧颈总动脉后,侧脑室注射生理盐水1 mg/kg;缺血/再灌注(I/R组):脑缺血后侧脑室注射生理盐水1 mg/kg;丙泊酚干预组(P组):脑缺血后侧脑室注射丙泊酚1 mg/kg.各组分别于再灌注后24 h断头取海马组织,提取海马组织线粒体,加入CaCl2于37℃下孵育5 min.透射电镜下观察线粒体形态学改变(n=3);紫外分光光度计法检测线粒体通透性转换孔(mitochondrial permeability transition pore,MPTP)活性(n=6);Western blotting法检测解耦联蛋白2的表达(n=6).结果 电镜下C组线粒体结构完整,I/R组可见线粒体显著肿胀、嵴断裂、膜破裂,P组损伤程度轻于I/R组.C组、I/R组和P组线粒体吸光度值均下降;与C组相比,I/R组和P组线粒体吸光度值明显下降(p<0.05);与I/R组(0.028±0.007)相比,P组(0.017±0.007)吸光度值下降幅度减小(P<0.05).与C组(0.62±0.05)相比,I/R组(0.88±0.14)和P组(1.32± 0.10)UCP2蛋白表达上调(P<0.05);P组UCP2蛋白表达高于I/R组(P<0.05).结论 丙泊酚能够改善大鼠前脑t/R后线粒体形态,促进神经细胞线粒体UCP2表达上调,抑制线粒体经ca2+诱导后MPTP开放,从而改善线粒体功能,这可能是丙泊酚减轻脑I/R损伤的机制之一.     

The role of mitochondria in oxidative and nitrosative stress during ischemia/reperfusion in the rat kidney

Reoxygenation following ischemia causes tissue oxidative stress. We studied the role of oxidative stress caused by kidney ischemia/reperfusion (I/R) on the mitochondria of renal tissue slices. I/R caused the mitochondria to be swollen, fragmented, and have lower membrane potential. The mitochondria generated more reactive oxygen species (ROS) and nitric oxide (NO) in situ as measured by fluorescence of ROS- and NO-sensitive probes. Infusion of lithium ion, an inhibitor of glycogen kinase synthase-3, caused phosphorylation of its Ser-9 and restored the membrane potential and decreased ROS production of the mitochondrial fraction. Ischemic kidney and hypoxic rat preconditioning improved mitochondrial membrane potential and lowered ROS production caused by subsequent I/R similar to lithium ion infusion. Preconditioning normalized NO production in mitochondria as well. The drop in the mitochondrial membrane potential was prevented by NO synthase inhibition, demonstrating a strong contribution of NO to changes in mitochondrial energy metabolism during the I/R transition. Mitochondria in the I/R-stressed kidney contained less cytochrome c and more pro-apoptotic Bax, consistent with apoptotic degradation.     

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.     

Vitamin E Succinate Enhances Steatotic Liver Energy Status and Prevents Oxidative Damage Following Ischemia/Reperfusion

We have previously shown that treatment of steatotic livers with vitamin E succinate decreases liver injury and increases survival after ischemia/reperfusion (I/R). It is now understood that compromised energy status is associated with increased injury following liver ischemia in the setting of hepatic steatosis at least partially as a result of increased reactive oxygen species (ROS) and induction of mitochondrial uncoupling protein-2 (UCP2). Given the association between ROS, mitochondrial function, and UCP2, it was our goal to determine whether the protective effects of vitamin E succinate were associated with decreased ROS injury, down-regulation of UCP2, or improvement of ATP levels following I/R. To test this, leptin deficient (ob/ob) mice with steatotic livers that had received other 50 IU of vitamin E succinate supplement per day or control chow for 7 days were subjected to total hepatic ischemia (15 minutes) followed by reperfusion. We measured liver expressions of ATP, glutathione (GSH), and UCP2 as well as mitochondrial DNA damage. Vitamin E treatment decreased hepatic UCP2 expression and increased ATP and GSH levels prior to I/R. These levels were maintained at 1 hour after I/R. At 24 hours, while hepatic UCP2 expression, ATP, and GSH levels were similar to those of mice not receiving vitamin E, mitochondrial DNA damage was blocked. These results revealed that vitamin E succinate decreased hepatic UCP2 expression, reduced oxidative stress, and improved mitochondrial function in mice with steatotic livers before and after I/R, identifying mechanisms of protection in this setting.     

Selective mitochondrial KATP channel opening controls human myocardial preconditioning: too much of a good thing?

BACKGROUND: Paradoxically, patients with noninsulin-dependent diabetes mellitus experience a higher cardiovascular mortality rate than patients with insulin-dependent diabetes mellitus. We have shown that K(ATP) channel inhibition, with oral sulfonylureas, prevents myocardial preconditioning and may explain the paradox of cardiovascular death in patients with noninsulin-dependent diabetes mellitus. Cardiac preconditioning is an attractive protective strategy against any elective ischemia/reperfusion (I/R) injury. The relationship between the K(ATP) channels and human myocardial preconditioning has not previously been elucidated. METHODS: Human atrial trabeculae were harvested, placed in organ baths, and paced (1 Hz). Developed force was recorded during simulated 37 degrees C I/R (30/45 or 45/60 minutes). Before I/R, trabeculae were treated transiently with a selective mitochondrial K(ATP) channel opener for 5 minutes, followed by a 10-minute washout, or were exposed to the channel opener throughout ischemia. Recovery of function is expressed as percentage of baseline developed force. Conserved creatine kinase activity (units per gram of wet tissue) was measured at the end of reperfusion as an indicator of cellular protection. RESULTS: Transient mitochondrial K(ATP) channel opening provided protection from both I/R insults. Surprisingly, there was no protection afforded by continuous mitochondrial K(ATP) channel opening. CONCLUSIONS: Transient selective mitochondrial K(ATP) channel opening protects both viability and function of human myocardium against I/R injury, although prolonged opening of the mitochondrial K(ATP) channel does not. These results reinforce the concept of preconditioning as a transient event that must be completed before the onset of ischemia.