衰老大鼠心肌线粒体PT孔开放对线粒体呼吸功能的影响

目的研究衰老大鼠心肌线粒体通透性转换(PT)孔开放对线粒体呼吸功能的影响及机制。方法左心室插管检测大鼠心功能;透射电镜检测大鼠心肌组织线粒体形态学改变;线粒体肿胀法检测心肌线粒体PT孔开放程度;氧电极法检测大鼠线粒体呼吸速率;荧光法检测线粒体膜电位。结果同3月龄组大鼠相比,15和18月龄组大鼠线粒体出现空泡肿胀、线粒体内膜脊出现断裂;大鼠左室收缩压(LVSP)和左室压上升/下降最大速率(±dp/dtmax)降低(P0.01);线粒体PT孔开放幅度明显增强(P0.01),左室舒张末压(LVEDP)升高(P0.01);线粒体膜电位下降(P0.01);线粒体呼吸速率明显降低(P0.01)。线粒体PT孔开放抑制了线粒体呼吸功能,降低了线粒体膜电位(P0.01),但是抑制线粒体呼吸功能对线粒体PT孔开放和线粒体膜电位无影响(P0.05)。结论衰老大鼠线粒体PT孔开放可能通过降低线粒体膜电位抑制线粒体呼吸功能。     

四周四氧嘧啶糖尿病大鼠主动脉超微结构和通透性变化

目的 了解糖尿病早期主动脉超微结构及通透性变化。方法 ４周四氧嘧啶糖尿病大鼠主动脉按透射电镜观察的要求进行固定、包埋、切片、染色及镧通透性检测的要求进行固定、染色、包埋和切片后,进行透射电镜观察。结果 糖尿病大鼠主动脉平滑肌细胞线粒体肿胀,有镧进入;内皮细胞紧密连接处有镧进入。结论 糖尿病早期主动脉平滑肌细胞膜及其线粒体膜通透性增加,线粒体肿胀,内皮通透性增加。     

蒿甲醚治疗实验大鼠肺孢子虫肺炎的电镜观察

用皮下注射醋酸可的松６周建立实验大鼠肺孢子虫肺炎动物模型，并用国产蒿甲醚进行试验治疗。治后大鼠肺组织超薄切片透射电镜观察，发现蒿甲醚可导致卡氏肺孢子虫产生以下３种超微结构改变：（１）胞浆内出现大量空泡；（２）线粒体肿胀；（３）核膜破裂。以上改变与戊烷脒对照组相似。     

亲环素A保护PC12细胞对抗β-淀粉样蛋白诱导的氧化应激损伤和凋亡

目的 探讨亲环素A(CyPA)对Aβ25 ～35诱导PC12细胞氧化应激损伤和凋亡的影响.方法 用不同浓度的CyPA预处理PC12细胞,再加入Aβ25 ～35继续培养,采用MTT法分析细胞存活率.用10 nmoL/LCyPA预处理PC12细胞,再加入Aβ25 ～35继续培养,碘化丙啶(PI)单染后流式细胞仪进行凋亡的定量检测;罗丹明123(Rd 123)染色流式细胞仪检测线粒体跨膜电位;二氯荧光黄双乙酸盐(DCFH-DA)染色,倒置荧光显微镜和流式细胞仪检测细胞内活性氧(ROS)含量.结果 CyPA可提高细胞的存活率,减少Aβ25 ～35引起的细胞凋亡,CyPA还可以改善由Aβ25 ～35引起的线粒体跨膜电位的下降,降低Aβ25 ～ 35诱导产生的大量ROS.结论CyPA可对抗Aβ25 ～ 35对PC12细胞的毒性作用,并通过增加线粒体跨膜电位和降低ROS产生从而减少细胞凋亡.     

蒿甲醚对小鼠体内弓形虫作用的超微结构研究

应用透射电镜观察蒿甲醚对弓形虫超微结构的影响。发现用药后弓形虫速殖子的主要病理改变为：虫体细胞膜、核膜断裂；线粒体肿胀，呈空泡变性或嵴凝集均质化；内质网扩张；棒状体及致密颗粒显著减少；甚至出现细胞核碎裂、溶解，胞质内基质破坏溶解呈大空泡，细胞成分可由细胞内脱出，整个虫体固缩或溶解死亡。     

肝性脑病大鼠脑超微结构的改变

目的：通过观察肝性脑病大鼠脑部分区域及氨对体外培养大鼠神经元超微结构的改变，讨论其病理发生机制。方法选用健康雄性SD大鼠12只，随机分为肝性脑病模型组和正常对照组两组，每组6只。用电子透射显微镜观察硫代乙酰胺诱导的肝性脑病大鼠和体外氨中毒大鼠皮质神经元的超微结构。结果肝性脑病大鼠神经元细胞数量减少；神经元线粒体肿胀，尼氏体数量明显减少；可见凋亡各期表现。神经胶质细胞细胞器减少，黑质的超微结构改变程度较基底核略重。体外培养氨中毒神经元变化：神经元细胞数量明显减少；细胞明显水肿，线粒体明显肿胀，尼氏体显著减少；可见不同时期的凋亡表现。结论肝性脑病大鼠脑超微结构改变明显，其主要机制可能与氨中毒引起的神经元凋亡有关。     

恒定及波动高糖下牛视网膜血管周细胞凋亡的线粒体机制

目的 研究恒定及波动高糖培养对牛视网膜血管周细胞凋亡的影响,并探讨其线粒体调控机制.方法 体外培养接近融合的视网膜血管周细胞在恒定及波动高糖中孵育6 d后,采用电镜观察周细胞超微结构改变;TUNEL法检测周细胞凋亡;激光共聚焦显微镜检测周细胞线粒体跨膜电位的改变;分光光度计检测周细胞胞质细胞色素c的变化;免疫组化和RT-PCR测定Bax、Bel-2基因的表达.结果 (1)恒定及波动高糖卜周细胞呈现出典型的细胞凋亡改,变,恒定高糖作用强于波动高糖组;(2)恒定及波动高糖培养使用细胞线粒体跨膜电位降低,周细胞线粒体跨膜电位与周细胞凋亡率负相关(r=-0.89,P<0.01);(3)恒定及波动高糖促使周细胞线粒体细胞色素c转移到胞质,胞质细胞色素c浓度增加,与细胞凋亡率正相关(P<0.01);(4)恒定及波动高糖能诱导凋亡基因Bax表达增加,抑制Bcl-2的表达,Bax/Bcl-2比值增加.Bax/Bcl-2比值与线粒体跨膜电位负相关,与胞质细胞色素c浓度正相关,与周细胞凋亡率正相关(均P<0.01).结论 恒定及波动高糖均可诱导培养的周细胞线粒体跨膜电位降低,细胞色素c释放,细胞发生凋亡,且恒定高糖作用强于波动高糖;线粒体凋亡途径在周细胞凋亡中起重要作用,凋亡基因Bax、Bcl-2可能参与其调控.     

阿司匹林对缺氧/缺糖大鼠皮质神经元细胞线粒体膜电位的影响

目的观察大鼠皮质神经元细胞在缺氧/缺糖(OGD)时线粒体膜电位(MMP)的变化及阿司匹林的保护作用。方法取体外培养7d的Wistar大鼠皮质神经元细胞,随机分为正常对照组、缺氧/缺糖模型组、缺氧/缺糖加阿司匹林组。缺氧/缺糖2h后在常氧下继续培养24h。流式细胞术检测不同时间段神经元细胞线粒体膜电位。结果缺氧/缺糖损伤2h,缺氧/缺糖组线粒体膜电位水平较正常对照组显著降低(P<0.01)。缺氧/缺糖加阿司匹林组皮质神经元细胞在缺氧2h及再复氧24h后细胞线粒体膜电位明显高于缺氧/缺糖模型组(P<0.01)。结论阿司匹林可抑制缺氧/缺糖损伤所致的线粒体膜电位的降低,从而具有稳定线粒体膜电位的作用,抑制神经细胞凋亡的发生。     

非糖尿病大鼠急性心肌梗死后急性高血糖对心肌细胞线粒体膜电位和细胞色素C的影响

目的 研究急性心肌梗死后急性高血糖对大鼠心肌细胞线粒体膜电位和细胞色素C的影响.方法 结扎40只雄性SD大鼠左冠状动脉前降支建立急性心肌梗死模型后随机分为4组:生理盐水组、高糖1组、高糖2组和胰岛素组,另取10只SD大鼠为假手术组,术中监测血糖水平,实验终点观察各组大鼠细胞凋亡指数、线粒体和胞浆内细胞色素C表达以及线粒体膜电位变化.结果 与假手术组比较,余各组细胞凋亡指数表达均增高,线粒体膜电位均降低;胞浆细胞色素C表达增加而线粒体内细胞色素C表达减少(P<0.05).与高糖2组比较, 其余各组细胞凋亡指数显著减低,线粒体膜电位显著增高,细胞色素C胞浆表达显著减少而线粒体表达显著增加(P<0.05).生理盐水组组、胰岛素组、高糖1组细胞凋亡指数、线粒体膜电位、胞质和线粒体中细胞色素C表达量差异无显著性(P>0.05).结论 急性心肌梗死后急性高血糖可能通过线粒体途径显著促进细胞凋亡,注射胰岛素降低血糖能有效地减少细胞凋亡.     

肝性脑病发病机制的研究进展

肝性脑病(hepatic encephalopathy,HE)是肝功能严重障碍和/或门体分流术后患者发生的以代谢紊乱为基础,神经、精神症状为主要表现的综合征.其症状包括意识混乱、定向力障碍、协调能力降低,甚至昏迷.其发病机制被认为是高氨血症使脑星形胶质细胞内谷氨酰胺浓度升高、钙离子内流启动氧化应激、破坏线粒体功能,干扰能量代谢并诱发炎症反应,破坏血脑屏障使内皮细胞、脑星形胶质细胞对水通透性增加,引发脑水肿.炎症反应又反过来升高脑内氨浓度,增加其中枢神经系统毒性,而锰是参与上述过程的重要组成成分,故目前公认为高氨血症和炎症反应的协同作用导致星形胶质细胞肿胀,进而引起脑水肿导致HE.本文就HE发病机制的研究进展作一综述.     

Progression of subcellular changes during chemical hypoxia to cultured rat hepatocytes: A laser scanning confocal microscopic study

The aim of this study was to evaluate changes in the subcellular organelles of cultured hepatocytes by laser scanning confocal microscopy during chemical hypoxia with cyanide and iodoacetate, inhibitors of mitochondrial respiration and glycolysis, respectively. Parameter-specific fluorophores used were calcein for cell topography and membrane permeability, rhodaminedextran for lysosomes, rhodamine 123 and tetramethylrhodamine methylester (TMRM) for mitochondrial membrane potential (ΓΨ) and propidium iodide for loss of cell viability. During the first 30 to 40 minutes of chemical hypoxia to cultured hepatocytes, numerous surface blebs formed and cell volume increased, but ΓΨ decreased relatively little. Subsequently, the nonspecific permeability of mitochondrial membranes increased, and mitochondria depolarized. These events were followed a few minutes later by disintegration of individual lysosomes. After a few more minutes, viability was lost as indicated by bleb rupture, gross plasma membrane permeability to calcein, and nuclear labeling with propidium iodide. Thus, the following sequence of intracellular events occurred during chemical hypoxia: adenosine triphosphate (ATP) depletion, bleb formation with cellular swelling, onset of a mitochondrial permeability transition, disintegration of lysosomes, plasma membrane failure from bleb rupture, and cell death. Any explanation of the pathophysiology of hypoxic injury must take into account this unique sequence of events.     

Cyclosporine A attenuates mitochondrial permeability transition and improves mitochondrial respiratory function in cardiomyocytes isolated from dogs with heart failure

We used isolated cardiomyocytes to investigate a possible role of mitochondrial permeability transition pore in mitochondrial abnormalities associated with heart failure. Cardiomyocytes were isolated from LV myocardium of normal control dogs and dogs with heart failure produced by intracoronary microembolizations. Mitochondrial permeability transition was measured in isolated cardiomyocytes with intact sarcolemma with and without 0.2 microM cyclosporin A using calcein AM and the fluorometer. State-3 mitochondrial respiration was also measured with the Clark electrode. Mitochondrial membrane potential was measured with JC-1 probe using the fluorometer. Propidium iodide was used to ensure sarcolemma integrity. 200 min after loading with calcein AM, mitochondria of failing cardiomyocytes showed only 50% of maximal level of calcein fluorescence while it remained unchanged in normal cells. The mitochondrial membrane potential in failing cardiomyocytes was significantly decreased by 38% compared to normal cardiomyocytes. Cyclosporine A significantly slowed the exit of calcein from mitochondria of failing cardiomyocytes and increased mitochondrial membrane potential by 29%. State-3 respiration was not affected with cyclosporine A in normal cardiomyocytes while it was significantly increased in failing cardiomyocytes by 20%. Exit of calcein (m.w. 1.0 kDa) from mitochondria of viable failing cardiomyocytes with intact sarcolemma suggests an existence of a reversible transitory permeability transition opening in high conductance mode. Attenuation of calcein exit, DeltaPsi(m) and improvement of state-3 respiration achieved with CsA (0.2 microM) show that permeability transition opening could be a cause of mitochondrial dysfunction described in the failing heart.     

Rebamipide suppresses diclofenac-induced intestinal permeability via mitochondrial protection in mice

AIM: To investigate the protective effect and mechanism of rebamipide on small intestinal permeability induced by diclofenac in mice.METHODS: Diclofenac (2.5 mg/kg) was administered once daily for 3 d orally. A control group received the vehicle by gavage. Rebamipide (100 mg/kg, 200 mg/kg, 400 mg/kg) was administered intragastrically once a day for 3 d 4 h after diclofenac administration. Intestinal permeability was evaluated by Evans blue and the FITC-dextran method. The ultrastructure of the mucosal barrier was evaluated by transmission electron microscopy (TEM). Mitochondrial function including mitochondrial swelling, mitochondrial membrane potential, mitochondrial nicotinamide adenine dinucleotide-reduced (NADH) levels, succinate dehydrogenase (SDH) and ATPase activities were measured. Small intestinal mucosa was collected for assessment of malondialdehyde (MDA) content and myeloperoxidase (MPO) activity.RESULTS: Compared with the control group, intestinal permeability was significantly increased in the diclofenac group, which was accompanied by broken tight junctions, and significant increases in MDA content and MPO activity. Rebamipide significantly reduced intestinal permeability, improved inter-cellular tight junctions, and was associated with decreases in intestinal MDA content and MPO activity. At the mitochondrial level, rebamipide increased SDH and ATPase activities, NADH level and decreased mitochondrial swelling.CONCLUSION: Increased intestinal permeability induced by diclofenac can be attenuated by rebamipide, which partially contributed to the protection of mitochondrial function.     

Mitochondrial membrane potential and apoptosis of blood mononuclear cells in untreated HIV-1 infected patients

Objectives

Infection with HIV leads to progressive CD4 T‐cell loss, resulting in AIDS. Apoptosis is the main mechanism for the loss of infected and bystander cells, but the complex interacting factors inducing and inhibiting apoptosis are not fully understood. Mitochondrial dysfunction is a pivotal step of the apoptotic cascade and can result in reduced mitochondrial membrane potential.

Methods

The mitochondrial membrane potential of peripheral blood mononuclear cells (PBMC) was measured by flow cytometry using the dye JC‐1 (Molecular Probes Inc). Apoptotic cells were identified using the Annexin V assay (Becton Dickinson GmbH).

Results

The mitochondrial membrane potential of PBMC was significantly decreased and apoptotic cell rate was increased in HIV‐infected therapy‐naïve patients compared with HIV‐negative controls. There was a highly significant correlation between the mitochondrial membrane potential and the rate of apoptosis. CD4 cell count was correlated negatively to the apoptotic rate and positively to the mitochondrial membrane potential.

Conclusions

The JC‐1 assay is a sensitive tool to detect changes of mitochondrial membrane potential associated with apoptosis in HIV‐infected therapy‐naïve patients. We could show in vivo that a reduction of mitochondrial membrane potential is correlated to apoptosis of PBMC, CD4 cell count and HIV viral load during HIV infection.     

The Influence of Hemorrhagic Shock on Rat Liver Regeneration after Partial Hepatectomy: Serum Aminotranspherases,Mitochondrial Function,and Hepatocellular Replication Studies

This study was designed to evaluate the influence of hemorrhagic shock on hepatic regeneration in rats submitted to partial hepatectomy. The experimental protocol included 26 male Wistar rats, randomly assigned to 4 groups: GI: simulated operation; GII: 30% hepatectomy without hemorrhagic shock; GIII: only hemorrhagic shock; GIV: 30% hepatectomy associated with hemorrhagic shock. The methodologies used were: determination of aminotranspherases plasma levels; analysis of mitochondrial respiration, membrane potential and osmotic swelling; and markers of hepatocellular replication. Aminotranspherases increased only in GIV. There were no differences in mitochondrial respiration. Mitochondrial membrane potential decreased only in the GIV. There were no differences in mitochondrial swelling among the groups; cellular replication markers increased significantly in the Groups II and IV but without difference between these two groups. Despite the conditions imposed on the organism by hemorrhagic shock, the hepatic regenerative capacity is preserved in animals submitted to partial hepatectomy.     

Clostridium difficile toxin A causes early damage to mitochondria in cultured cells

BACKGROUND & AIMS: The mechanism by which Clostridium difficile toxin A causes actin depolymerization and cell rounding involves toxin internalization and subsequent monoglucosylation of the Rho family of proteins. This study explored toxin internalization and effects on mitochondrial function before cell rounding. METHODS: Chinese hamster ovary (CHO) cells were exposed to toxin A, and mitochondrial localization was assayed by confocal microscopy. Mitochondrial function was measured by adenosine triphosphate (ATP) concentration, mitochondrial permeability, and leakage of cytochrome c. RESULTS: Confocal microscopy showed toxin A colocalization with the mitochondrial protein GRP 75 at 5 minutes after toxin exposure. Between 5 and 15 minutes, toxin A caused an 80% diminution in cellular ATP levels; cell rounding and Rho glucosylation commenced between 15 and 30 minutes. Toxin A also resulted in reduction of mitochondrial membrane potential and a 2-3-fold increase in reactive oxygen radicals. Preincubation of CHO cells with the antioxidants butylated hydroxyanisole or butylated hydroxytoluene blocked the toxin A-induced increase in oxygen radicals and diminished cell rounding. Western blot analysis of toxin A-exposed isolated mitochondria showed a direct effect of toxin A on leakage of cytochrome c. CONCLUSIONS: The results show that extensive mitochondrial damage occurs within 15 minutes in CHO cells exposed to toxin A. Diminished ATP concentrations and increased oxygen radicals are likely to contribute to cytotoxicity from this bacterial toxin.     

Opening of the mitochondrial permeability transition pore causes matrix expansion and outer membrane rupture in Fas-mediated hepatic apoptosis in mice

Although Fas stimulation has been reported to cause outer mitochondrial membrane rupture in Jurkat cells, the mechanism of this effect is debated, and it is not known if outer membrane rupture also occurs in hepatocyte mitochondria. We studied the in vivo effects of Fas stimulation on ultrastructural lesions and mitochondrial function in mice. Four hours after administration of an agonistic anti-Fas antibody (8 microg/animal), caspase activity increased 5.4-fold. Nuclear DNA showed internucleosomal fragmentation, whereas supercoiled mitochondrial DNA was replaced by circular and linear forms. Mitochondrial cytochrome c was partly released into the cytosol. Ultrastructurally, mitochondrial lesions were observed in both apoptotic hepatocytes (with nuclear chromatin condensation/fragmentation) and nonapoptotic hepatocytes (without nuclear changes). In nonapoptotic cells, outer mitochondrial membrane rupture allowed herniation of the inner membrane and matrix through the outer membrane gap. In apoptotic hepatocytes, the matrix became electron-lucent and no longer protruded through the outer membrane gap. Mitochondria clustered around the nucleus, whereas rough endoplasmic reticulum cisternae became peripheral. In liver mitochondria isolated after Fas stimulation, the membrane potential decreased, whereas basal respiration increased. Pretreatment with either z-VAD-fmk (an inhibitor of caspases) or cyclosporin A (a permeability transition inhibitor) totally or mostly prevented mitochondrial outer membrane rupture, membrane potential decrease, cytochrome c release, and apoptosis. In conclusion, in vivo Fas stimulation causes caspase activation, mitochondrial permeability transition (decreasing the membrane potential and increasing basal respiration), mitochondrial matrix expansion (as shown by matrix herniation), outer mitochondrial membrane rupture, and cytochrome c release.     

PM2.5通过线粒体介导的大鼠心肌细胞损伤作用机制的初步研究

目的 初步探讨PM2.5对大鼠心肌细胞的损害及线粒体介导的相关作用机制.方法 培养大鼠心肌细胞株H9C2细胞,给予PM2.5刺激,24 h后检查肌酸激酶（CK）和乳酸脱氢酶（LDH）,比色法检测线粒体的活性氧（ROS）和ATP酶的活性,流式细胞仪检测线粒体肿胀度及膜电位.结果 PM2.5组心肌细胞CK和LDH明显升高[（702±80）U/ml比（987±92）U/ml,（339±72）U/L比（485±84）U/L）],ATP酶活性下降明显[（34.2±5.2）U/mgprot比（54.1±6.9） U/mgprot],细胞内ROS明显增多[（67.2±8.2）U/well比（25.4±7.3） U/well],差异均有统计学意义（P＜0.05）.同时PM2.5组心肌细胞线粒体明显肿胀,线粒体膜电位明显下降（0.3476±0.1232比0.6476±0.1021）,差异均有统计学意义（P＜0.05）.结论 PM2.5可以导致心肌细胞损伤,其机制可能与PM2.5损害线粒体的结构与功能相关.     

Optical imaging of mitochondrial function uncovers actively propagating waves of mitochondrial membrane potential collapse across intact heart

Polarization of the mitochondrial membrane potential (ΔΨ_m) is critical for normal mitochondrial function and cellular energetics. Mitochondrial dysfunction, manifesting as disrupted ΔΨ_m polarization (i.e. depolarization or hyperpolarization), underlies several important and highly prevalent diseases, including a variety of cardiac and neurological disorders. As such, ΔΨ_m instability might form a unifying mechanism for a class of metabolic disorders affecting excitable tissues. Here, we measured the spatio-temporal kinetics of ΔΨ_m changes across the intact heart using high-resolution optical ΔΨ_m imaging and uncovered surprisingly complex spatial patterns and dynamically fluctuating changes in ΔΨ_m that developed into actively propagating waves of mitochondrial depolarization during global ischemia. Our data further indicated that the recovery of ΔΨ_m upon reperfusion is dictated by the duration of the preceding ischemic insult. Post-ischemic electrical and functional recovery was dependent on early ΔΨ_m recovery but independent of overall cellular injury measured using a standard assay of lactate dehydrogenase release. These findings reveal a novel mechanism by which instabilities in cellular energetic properties that are independent of irreversible cellular injury can scale to the level of the intact organ via an organized process of active conduction involving the multi-cellular network. This highlights the importance of investigating cellular metabolic properties in the context of the intact organ.     

人参皂甙Rg1对快速老化小鼠肝脏线粒体的保护作用

目的 探讨人参皂苷Rg1防治阿尔茨海默病的作用机制.方法 将8.5月龄快速老化小鼠(SAMP8)随机分为SAMP8对照组、SAMP8给Rg1 10 mg/kg组、SAMP8给Rg1 30 mg/kg组,每组10只.同月龄SAMR1 10只作为对照组.给药65 d后提取肝脏线粒体,测定线粒体呼吸功能、线粒体肿胀度和线粒体膜电位.线粒体于-20℃/20℃反复冻融3次破坏线粒体膜,测定线粒体内MDA含量、SOD活性和LDH含量.结果 与SAMR1相比,SAMP8肝脏线粒体呼吸功能显著降低,表现为线粒体3态呼吸显著降低,4态呼吸改变不明显,呼吸控制指数和磷氧比值显著降低;SAMP8小鼠线粒体膜肿胀度显著增高,线粒体膜电位显著降低.此外,SAMP8线粒体MDA含量显著增多、SOD活性显著升高、LDH显著增高.与SAMP8对照组相比,Rg1 10 和30 mg/kg均可显著改善这些线粒体结构和呼吸功能障碍,改善线粒体内生化功能的改变.结论 人参皂苷Rg1可改善快速老化小鼠线粒体结构和功能障碍.