导言

线粒体是细胞内具有双层膜结构和独立基因组DNA的重要细胞器,在细胞生命活动中发挥着至关重要的作用。一方面它们是真核细胞的主要能量工厂,通过有氧代谢产生ATP,为细胞生命活动提供能量;另一方面,线粒体是细胞内活性氧产生中心,同时也是细胞内主要钙库之一,调节细胞内钙信号和细胞生长活动。更为重要的是,线粒体还是细胞凋亡和衰老的调控中心。在细胞凋亡过程中,线粒体释放促凋亡因子（如细胞色素C）,对细胞内凋亡信号进行整合和放大。不言而喻,线粒体在细胞生长、衰老和凋亡等生理、病理过程中扮演着重要的角色。     

线粒体在细胞凋亡中的介导作用

线粒体是细胞内产生能量的重要细胞器,被认为是细胞生存与死亡的调节中心。Bcl-2家族蛋白、内质网和溶酶体能引起线粒体膜通透性的改变,造成线粒体功能损伤,诱导细胞凋亡。本文主要综述线粒体在Bcl-2家族蛋白、内质网和溶酶体诱导细胞凋亡中作用的研究进展。     

黄芩甙对肝癌细胞BEL-7402形态学的影响

目的观察黄芩甙对肝癌细胞BEL-7402凋亡的影响,同时观察对肝癌细胞形态及超微结构、线粒体超微结构、线粒体膜电位和细胞内Ca^2＋的影响,探讨线粒体损伤在黄芩甙诱导肝癌细胞凋亡中的作用及可能的机制。方法应用细胞培养技术培养肝癌细胞BEL-7402,光镜、倒置显微镜、扫描电镜、透射电镜观察细胞形态及超微结构的变化尤其是线粒体的变化,应用流式细胞仪检测细胞凋亡百分率及线粒体膜电位、细胞内Ca^2＋的改变,免疫组化法检测细胞Bcl-2、Pax蛋白表达。结果黄芩甙诱导肝癌细胞BEL-7402凋亡呈剂量依赖关系,细胞形态、超微结构及线粒体超微结构出现明显改变,降低肝癌细胞线粒体膜电位,使细胞内Ca^2＋增加,细胞Pax表达增加,广泛分布于胞核和胞质中,Bcl-2表达减少。结论黄芩甙诱导肝癌细胞BEL-7402凋亡,线粒体损伤在黄芩甙诱导肝癌细胞凋亡中起重要作用,其机制可能为抑制肝癌细胞Bcl-2蛋白表达,促进Pax蛋白表达及细胞内Ca^2＋增加,激发线粒体膜通透性转运孔开放,线粒体跨膜电位降低,使肝癌细胞凋亡。     

PKCα 由线粒体向细胞核转运与胃癌细胞凋亡诱导密切相关

PKC在细胞生长、分化、凋亡和信号转导调节中具有重要作用.通过激光扫描共聚焦显微镜证实:在胃癌BGC-823细胞中,一部分PKCα 定位于线粒体,一部分定位在胞浆,细胞经TPA处理后,位于线粒体和胞浆的PKCα 向细胞核转运;Western blot检测则发现PKCα 蛋白表达水平在TPA处理前后没有发生变化.此外,应用凋亡诱导剂和特异性PKC抑制剂的实验结果进一步证实:胃癌细胞内PKCα由线粒体和胞浆向细胞核转运与细胞凋亡的诱导密切相关.提示PKCα在细胞内的定向转运可能是与细胞凋亡过程相关联的重要事件之一.     

线粒体在细胞凋亡中的变化与作用

要在各种凋亡信号的诱导下,线粒体会发生显著的结构与功能性的变化,包括各种促凋亡蛋白(如细胞色素c,凋亡诱导因子等）的释放,线粒体膜电位的丢失,电子传递链的变化,以及细胞内氧化还原状态的变化;核转录因子以线粒体为中介也参与了细胞凋亡的调控。线粒体在哺乳动物细胞凋亡中具有核心地位和作用,昆虫细胞凋亡的研究表明,线粒体与昆虫细胞凋亡也有密切的关系。线粒体在细胞凋亡中的作用可能具有普遍意义。     

线粒体分裂和融合相关蛋白质的研究进展

线粒体是多细胞生物的一个重要组成部分,它对细胞以及机体的健康具有十分重要的作用。线粒体可以产生能量,介导钙和活性氧信号转导,甚至调控细胞凋亡。近年来研究显示,线粒体在细胞中处于不断分裂与融合的状态,并且可以在细胞内重新分布,线粒体的这种特性统称为线粒体动力学。线粒体动力学对维持线粒体各种功能极其重要,成为了近年来的研究热点。本文重点综述了哺乳动物细胞内线粒体分裂和融合相关蛋白质的结构以及生物学功能。     

细胞凋亡中的Bcl-2家族蛋白及其BH3结构域的功能研究

凋亡相关蛋白中的Bcl-2家族是细胞凋亡的关键调节分子,由抗凋亡和促凋亡成员组成,这些成员之间通过相互协同作用调节了线粒体结构与功能的稳定性,从而在线粒体水平发挥着细胞凋亡的“开关”作用.抗凋亡成员大都分布于线粒体的外膜,与促凋亡成员的BH3结构域相互作用对细胞凋亡发挥抵抗作用.促凋亡成员则主要分布于细胞浆中,细胞接受死亡信号刺激后,促凋亡成员自身受到一系列的调节,如典型的Bax构象改变、BAD和Bik的磷酸化调节以及Bid和Bim的蛋白裂解效应等,使得促凋亡成员在凋亡信号的刺激下整合于线粒体外膜,最终导致线粒体通透转换孔的开放,进而释放包括细胞色素c、凋亡诱导因子、Smac等重要的凋亡因子,随后caspase被激活进而断裂重要的细胞内结构蛋白与功能分子,执行细胞凋亡.     

MFN1介导的线粒体融合在心肌细胞凋亡中的作用研究

目的:探讨线粒体融合关键蛋白MFN1介导的线粒体融合在调控心肌细胞凋亡中的作用。方法:通过si RNA降低体外培养H9C2心肌细胞中MFN1的表达后,采用Western blot检测线粒体细胞色素c(Cyto c)释放及其下游凋亡效应分子Caspase9与Caspase3活性,流式细胞术检测细胞内活性氧(ROS)的产生情况,流式细胞术检测细胞凋亡的情况。结果:干扰MFN1可显著促进H9C2心肌细胞内细胞色素c由线粒体释放至胞浆,促进Caspase9与Caspase3的激活,增加细胞内活性氧ROS产生并提高细胞凋亡率(均P0.05)。结论:MFN1介导的线粒体融合可保护心肌细胞凋亡,其机制可能与抑制ROS产生与细胞色素C释放有关。     

线粒体形态学改变与细胞凋亡

近年来,对于线粒体形态学以及其在凋亡过程中的改变和作用的研究打破了传统的观点。正常情况下,线粒体在细胞内相互连接成管网状结构,并发生着频繁的融合与分裂。融合和分裂由一系列蛋白质介导,二者之间的动态平衡维持着线粒体的形态和功能。在细胞凋亡的早期,线粒体融合和分裂失平衡,导致线粒体管网状结构碎裂和嵴的重构,这些改变对线粒体随后的变化以及凋亡的发生具有重要的意义。融合和分裂的蛋白质不仅调控线粒体形态和细胞凋亡过程,也和某些凋亡相关疾病有关。此外,促凋亡的Bcl-2蛋白可能通过改变线粒体的构形来调控凋亡过程。     

紫檀茋诱导白念珠菌凋亡的研究

目的探究紫檀茋(Pterostilbene,PTE)诱导白念珠菌凋亡的活性。方法通过分析白念珠菌凋亡细胞、坏死细胞和活细胞比例,检测Caspase酶活性、细胞内活性氧和线粒体膜电位,评价PTE诱导白念珠菌凋亡的活性。结果≥4μg/mL PTE处理后白念珠菌凋亡比例明显增加,Caspase酶活性显著升高,细胞内活性氧水平显著升高,线粒体膜电位显著降低。结论 PTE具有诱导白念珠菌凋亡的活性,该作用可能与活性氧积累和线粒体损伤相关。     

线粒体损伤相关模式分子与宿主免疫调节

线粒体是真核细胞至关重要的细胞器,参与机体细胞能量代谢和细胞凋亡等多种生物学过程。线粒体还参与机体的天然免疫反应的调节。线粒体不仅可以作为病毒免疫反应的载体,还可以通过产生ROS参与抗菌反应。线粒体受到损伤、刺激后,可释放mtDNA,TFAM,ROS,ATP,心磷脂和甲酰肽等内容物。这些分子可以作为损伤相关模式分子(damage associated molecular patterns, DAMPs)被模式识别受体识别,从而参与宿主的免疫调节。研究表明,线粒体已成为内源性DAMPs的重要来源,在先天性免疫应答以及疾病进展过程中发挥着重要的作用。本文就线粒体来源的损伤相关模式分子在机体免疫调节中的作用进行综述。     

Mitochondrial dynamics regulate the RIG‐I‐like receptor antiviral pathway

The intracellular retinoic acid‐inducible gene I‐like receptors (RLRs) sense viral ribonucleic acid and signal through the mitochondrial protein mitochondrial antiviral signalling (MAVS) to trigger the production of type I interferons and proinflammatory cytokines. In this study, we report that RLR activation promotes elongation of the mitochondrial network. Mimicking this elongation enhances signalling downstream from MAVS and favours the binding of MAVS to stimulator of interferon genes, an endoplasmic reticulum (ER) protein involved in the RLR pathway. By contrast, enforced mitochondrial fragmentation dampens signalling and reduces the association between both proteins. Our finding that MAVS is associated with a pool of mitofusin 1, a protein of the mitochondrial fusion machinery, suggests that MAVS is capable of regulating mitochondrial dynamics to facilitate the mitochondria–ER association required for signal transduction. Importantly, we observed that viral mitochondria‐localized inhibitor of apoptosis, a cytomegalovirus (CMV) antiapoptotic protein that promotes mitochondrial fragmentation, inhibits signalling downstream from MAVS, suggesting a possible new immune modulation strategy of the CMV.     

Fragmented mitochondria are sensitized to Bax insertion and activation during apoptosis

Recent studies have shown mitochondrial fragmentation during cell stress and have suggested a role for the morphological change in mitochondrial injury and ensuing apoptosis. However, the underlying mechanism remains elusive. Here we demonstrate that mitochondrial fragmentation facilitates Bax insertion and activation in mitochondria, resulting in the release of apoptogenic factors. In HeLa cells, overexpression of mitofusins attenuated mitochondrial fragmentation during cisplatin- and azide-induced cell injury, which was accompanied by less apoptosis and less cytochrome c release from mitochondria. Similar effects were shown by inhibiting the mitochondrial fission protein Drp1 with a dominant negative mutant (dn-Drp1). Mitofusins and dn-Drp1 did not seem to significantly affect Bax translocation/accumulation to mitochondria; however, they blocked Bax insertion and activation in mitochondrial membrane. Consistently, in rat kidney proximal tubular cells, small interfering RNA knockdown of Drp1 prevented mitochondrial fragmentation during azide-induced ATP depletion, which was accompanied by less Bax activation, insertion, and oligomerization in mitochondria. These cells released less cytochrome c and AIF from mitochondria and showed significantly lower apoptosis. Finally, mitofusin-null mouse embryonic fibroblasts (MEF) had fragmented mitochondria. These MEFs were more sensitive to cisplatin-induced Bax activation, release of cytochrome c, and apoptosis. Together, this study provides further support for a role of mitochondrial fragmentation in mitochondrial injury and apoptosis. Mechanistically, mitochondrial fragmentation may sensitize the cells to Bax insertion and activation in mitochondria, facilitating the release of apoptogenic factors and consequent apoptosis.     

Mitochondrial anti-viral immunity

In the cytosol, the sensing of RNA viruses by the RIG-I-like receptors (RLRs) triggers a complex signaling cascade where the mitochondrial antiviral signaling protein (MAVS) plays a crucial role in orchestrating the innate host response through the induction of antiviral and inflammatory responses. Hence, in addition to their known roles in the metabolic processes and the control of programmed cell death, mitochondria are now emerging as a fundamental hub for innate anti-viral immunity. This review summarizes the findings related to the MAVS adapter and mitochondria in the innate immune response to RNA viruses.     

COX5B Regulates MAVS-mediated Antiviral Signaling through Interaction with ATG5 and Repressing ROS Production

Innate antiviral immunity is the first line of the host defense system that rapidly detects invading viruses. Mitochondria function as platforms for innate antiviral signal transduction in mammals through the adaptor protein, MAVS. Excessive activation of MAVS-mediated antiviral signaling leads to dysfunction of mitochondria and cell apoptosis that likely causes the pathogenesis of autoimmunity. However, the mechanism of how MAVS is regulated at mitochondria remains unknown. Here we show that the Cytochrome c Oxidase (CcO) complex subunit COX5B physically interacts with MAVS and negatively regulates the MAVS-mediated antiviral pathway. Mechanistically, we find that while activation of MAVS leads to increased ROS production and COX5B expression, COX5B down-regulated MAVS signaling by repressing ROS production. Importantly, our study reveals that COX5B coordinates with the autophagy pathway to control MAVS aggregation, thereby balancing the antiviral signaling activity. Thus, our study provides novel insights into the link between mitochondrial electron transport system and the autophagy pathway in regulating innate antiviral immunity.     

Selective targeting of a redox-active ubiquinone to mitochondria within cells: antioxidant and antiapoptotic properties

With the recognition of the central role of mitochondria in apoptosis, there is a need to develop specific tools to manipulate mitochondrial function within cells. Here we report on the development of a novel antioxidant that selectively blocks mitochondrial oxidative damage, enabling the roles of mitochondrial oxidative stress in different types of cell death to be inferred. This antioxidant, named mitoQ, is a ubiquinone derivative targeted to mitochondria by covalent attachment to a lipophilic triphenylphosphonium cation through an aliphatic carbon chain. Due to the large mitochondrial membrane potential, the cation was accumulated within mitochondria inside cells, where the ubiquinone moiety inserted into the lipid bilayer and was reduced by the respiratory chain. The ubiquinol derivative thus formed was an effective antioxidant that prevented lipid peroxidation and protected mitochondria from oxidative damage. After detoxifying a reactive oxygen species, the ubiquinol moiety was regenerated by the respiratory chain enabling its antioxidant activity to be recycled. In cell culture studies, the mitochondrially localized antioxidant protected mammalian cells from hydrogen peroxide-induced apoptosis but not from apoptosis induced by staurosporine or tumor necrosis factor-alpha. This was compared with untargeted ubiquinone analogs, which were ineffective in preventing apoptosis. These results suggest that mitochondrial oxidative stress may be a critical step in apoptosis induced by hydrogen peroxide but not for apoptosis induced by staurosporine or tumor necrosis factor-alpha. We have shown that selectively manipulating mitochondrial antioxidant status with targeted and recyclable antioxidants is a feasible approach to investigate the role of mitochondrial oxidative damage in apoptotic cell death. This approach will have further applications in investigating mitochondrial dysfunction in a range of experimental models.     

Scission,spores, and apoptosis: a proposal for the evolutionary origin of mitochondria in cell death induction

Mitochondria fragment prior to caspase activation during many pathways of apoptosis. Inhibition of the machinery that normally regulates mitochondrial morphology in healthy cells inhibits the fission that occurs during apoptosis and actually delays the process of cell death. Interestingly, there are certain parallels between mitochondrial fission and bacterial sporulation. As bacterial sporulation can be considered a stress response we suggest that a primordial stress response of endosymbiont mitochondrial progenitors may have been adopted for the stress response of early eukaryotes. Thus, the mitochondrial fission process may represent an early stress response of primitive mitochondria that could have integrated the stress signals and acted as an initial sensor for the eukaryotic response system. The fact that mitochondria fragment during apoptosis using the machinery descended from or that superceded the bacterial stress response of sporulation is consistent with this hypothesis. This hypothesis would explain why what is generally considered the "power house" of the cell came to integrate the cell death response and regulate apoptosis.     

The role of mitochondria in pharmacotoxicology: a reevaluation of an old, newly emerging topic

In addition to their well-known critical role in energy metabolism, mitochondria are now recognized as the location where various catabolic and anabolic processes, calcium fluxes, various oxygen-nitrogen reactive species, and other signal transduction pathways interact to maintain cell homeostasis and to mediate cellular responses to different stimuli. It is important to consider how pharmacological agents affect mitochondrial biochemistry, not only because of toxicological concerns but also because of potential therapeutic applications. Several potential targets could be envisaged at the mitochondrial level that may underlie the toxic effects of some drugs. Recently, antiviral nucleoside analogs have displayed mitochondrial toxicity through the inhibition of DNA polymerase- (pol-). Other drugs that target different components of mitochondrial channels can disrupt ion homeostasis or interfere with the mitochondrial permeability transition pore. Many known inhibitors of the mitochondrial electron transfer chain act by interfering with one or more of the respiratory chain complexes. Nonsteroidal anti-inflammatory drugs (NSAIDs), for example, may behave as oxidative phosphorylation uncouplers. The mitochondrial toxicity of other drugs seems to depend on free radical production, although the mechanisms have not yet been clarified. Meanwhile, drugs targeting mitochondria have been used to treat mitochondrial dysfunctions. Importantly, drugs that target the mitochondria of cancer cells have been developed recently; such drugs can trigger apoptosis or necrosis of the cancer cells. Thus the aim of this review is to highlight the role of mitochondria in pharmacotoxicology, and to describe whenever possible the main molecular mechanisms underlying unwanted and/or therapeutic effects. mitochondrial diseases; nitric oxide; apoptosis; degenerative diseases; free radicals