线粒体动力学与视网膜神经节细胞

线粒体动力学是指细胞中的线粒体不断地分裂、融合、移动、运输和线粒体自噬等,这些动态的过程在调节线粒体的形态与功能中发挥关键作用,并对细胞的存活、代谢、功能等有重要影响.视网膜神经节细胞(RGCs)作为视网膜中一类特殊且重要的神经元,对线粒体的动力学改变特别敏感.有关常染色体显性遗传性视神经萎缩疾病的研究发现,控制线粒体融合的相关基因与RGCs功能密切相关.实验性青光眼模型提示,眼压升高引起RGCs的线粒体分裂增多,改变调节线粒体融合基因的表达,最终诱导RGCs的凋亡;线粒体在RGCs中的正常运输和分布对于RGCs轴突的功能至关重要.以上遗传性和实验性视神经病变的研究表明,线粒体动力学在调节RGCs的生存中发挥着核心作用,通过调控线粒体动力学来保护RGCs可能是一个非常有前景的治疗策略.本文将对线粒体动力学的主要内容和RGCs中的线粒体动力学进行阐述.     

线粒体功能缺陷在遗传性视神经病变发病机制中的作用

线粒体是普遍存在于真核细胞胞质中的一种动态细胞器．其通过氧化磷酸化提供了细胞代谢活动必须的ATP,而且调控细胞凋亡并产生大量的活性氧（reactive oxygen species,ROS）,线粒体DNA突变可导致ATP产量减少而影响细胞的生物能量．然而．绝大部分维持线粒体结构和功能的蛋白质由核基因编码,因此,核基因的突变也可导致细胞能量代谢缺陷。线粒体功能缺陷可引起多种临床疾病,以视觉器官、神经系统及肌肉系统受累为主。视神经对能量缺乏的敏感性较高,因此在线粒体功能异常时最先受累。     

线粒体自噬参与糖尿病视网膜病变的研究进展

线粒体功能对于需氧真核细胞的生存至关重要，因为线粒体通过产生三磷酸腺苷(ATP)提供能量、调节细胞代谢、提供氧化还原平衡、参与免疫信号传导并启动细胞凋亡。线粒体自噬是一种细胞内针对功能障碍线粒体的选择性降解机制，参与线粒体的质量控制及细胞稳态的维持。近年来，越来越多的研究发现异常的线粒体自噬参与多种眼部疾病的发生发展，如糖尿病视网膜病变(DR)、年龄相关性黄斑变性和青光眼等。因此，本文总结已知的线粒体自噬定义，整理各种使用细胞培养、动物和人体组织模型进行研究的结果，并就线粒体自噬的分子生物学过程及其在DR中的作用展开综述，以期为DR的治疗手段提供新思路。     

PINK1/Parkin介导的线粒体自噬在眼科疾病中作用的研究进展

线粒体自噬作为一种选择性自噬过程,通过清除受损和多余线粒体来维持细胞正常生理功能。线粒体自噬与多种眼科疾病的发生发展有密切联系,而PINK1/Parkin信号通路作为线粒体自噬的主要通路之一,在白内障、青光眼、年龄相关性黄斑变性等多种眼科疾病中发挥了重要作用,靶向该通路的治疗手段也为多种眼科疾病的治疗提供了新思路。本文将对PINK1/Parkin介导的线粒体自噬通路在眼科疾病中的相关作用及机制进行综述,以期深入了解线粒体自噬在眼科相关疾病中的影响与价值。     

线粒体自噬在眼科相关疾病中的研究进展

线粒体自噬是一种选择性自噬,是指细胞通过自噬的机制选择性地清除线粒体的过程。线粒体自噬在清除功能失调的线粒体、降低线粒体数量及维持细胞稳态中起着重要的作用。它的分子机制涉及PINK1/Parkin、BNIP3、NIX和FUNDC1等多种蛋白。线粒体发生功能障碍或损坏都可能造成严重的后果,甚至导致细胞死亡。研究发现线粒体自噬紊乱与多种眼科疾病的发生有关,如白内障、青光眼、年龄相关性黄斑变性(age-related macular degenration, AMD)、糖尿病视网膜病变(diabetic retinopathy, DR)等。本文就线粒体自噬的发生机制和它在眼科相关疾病中的研究进行综述。     

线粒体在视神经病变中的作用

线粒体是真核细胞中一种重要的细胞器,具有内外双层膜,其通过氧化呼吸作用提供细胞生命活动所需的能量,同时与人体内的氧化应激、细胞凋亡等有关,具有自身的遗传物质和遗传体系.线粒体在耗能较高的组织器官中广泛分布,视网膜和视神经含有丰富的线粒体,为视觉信号传导和细胞内物质运输提供必需的能量.越来越多的研究表明,线粒体功能不全参与视神经病变,从而影响视网膜神经节细胞的存活.本文就线粒体在视神经和视网膜神经节细胞中的分布、功能以及功能障碍介导视神经病变的研究进展作一综述.     

线粒体功能紊乱在糖尿病视网膜病变中作用的研究进展

糖尿病视网膜病变 (DR) 作为最常见的视网膜血管病变,是40岁以上人群主要致盲性眼病之一。抗血管内皮生长因子 (VEGF) 疗法在 DR 患者中有显著的临床效果,但需要长期不间断治疗,且大多数患者未能实现具有临床意义的视力改善。因此,寻找新的治疗靶点和方法迫在眉睫。线粒体是真核细胞中负责产生化学能量并协调细胞信号的细胞器,对维持细胞结构和功能起着关键作用。越来越多的研究表明,线粒体参与了 DR 病理生理过程。本文就线粒体功能紊乱在 DR 发病过程中的作用展开综述,为 DR 的发病机制和治疗方案提供新的思路。     

线粒体功能障碍与角膜疾病研究进展

角膜是眼光学系统的重要组成部分，角膜疾病则是引起眼部刺激、不适及视力下降的重要原因。越来越多的研究表明，某些角膜疾病与线粒体功能障碍有关。正常角膜自身具有一套氧化与抗氧化应激系统。先天或后天长时间暴露于外界紫外线和高氧环境等原因，角膜内的氧化与抗氧化应激水平失衡，线粒体DNA突变并逐渐积累，最终角膜细胞能量产生障碍引起临床疾病。本文就线粒体功能障碍与某些遗传角膜疾病以及后天性角膜疾病的关系进行总结，旨在阐明氧化应激和粒体功能障碍在角膜疾病中作用，指导相关疾病靶向治疗药物的开发和应用。     

线粒体在原发性青光眼视神经损害中的作用机制

青光眼是全球常见且不可逆的严重致盲眼病,其视功能损害的病理基础是视网膜神经节细胞的进行性死亡和神经纤维的丢失.神经节细胞死亡主要是通过细胞凋亡的方式进行的,其在本质上与大多数神经系统疾病的病理生理特征包括氧化应激与能量障碍是一致的.而线粒体在细胞凋亡中起着主开关的作用.     

线粒体功能异常与青光眼的关系

线粒体既是细胞内能量转换器,又是决定细胞存活的重要因素。线粒体损伤、功能失调与多种神经元退行性变疾病发生发展均密切相关。青光眼为视神经病变的一种,近年来研究发现线粒体功能异常在其视神经损害过程,如氧化应激、谷氨酸兴奋性毒性、钙超载、机械压力、神经营养因子的剥夺、胶质细胞的激活等的病理机制中起着尤为重要的作用。本文对线粒体功能异常与青光眼关系的最新研究进展作以综述。（国际眼科纵览,2012,36：302-306）     

Elevated hydrostatic pressure triggers mitochondrial fission and decreases cellular ATP in differentiated RGC-5 cells

PURPOSE: Mitochondrial fission is a cellular response to stress that has an important role in neuronal cell death in neurodegenerative diseases. The purpose of this study was to determine whether elevated hydrostatic pressure induces mitochondrial fission and dysfunction in cultured retinal ganglion cells. METHODS: RGC-5 cells were differentiated with succinyl concanavalin A (50 microg/mL) and transferred to a pressurized incubator in which 30 mm Hg of pressure was applied for 1, 2, or 3 days. As a control, differentiated cells from an identical passage were incubated simultaneously in a conventional incubator at each of the time points. Live RGC-5 cells were then labeled with a red fluorescent mitochondrial dye and mitochondrial morphology was assessed by fluorescence microscopy and electron microscopy. After elevated hydrostatic pressure, the cellular adenosine triphosphate (ATP) levels were also measured by a luciferase-based assay. RESULTS: Mitochondrial fission, characterized by the conversion of tubular fused mitochondria into isolated small organelles, was triggered in >74.3% +/- 1.9% of mitochondria at 3 days after elevated hydrostatic pressure. Only 4.7% +/- 1.4% of nonpressurized control cells displayed mitochondrial fission after 3 days. Electron microscopy showed that elevated hydrostatic pressure for 3 days induced abnormal cristae depletion and decreased the length of the mitochondria. On elevation of hydrostatic pressure, the fission-linked protein, Drp-1 was translocated from the cytosol to the mitochondria. Elevated hydrostatic pressure also resulted in a significant, time-dependent reduction of cellular ATP. CONCLUSIONS: Elevated hydrostatic pressure triggered mitochondrial fission, abnormal cristae depletion, Drp-1 translocation, and cellular ATP reduction in differentiated RGC-5 cells. Increased understanding of the molecular mechanisms that regulate the cellular response to elevated pressure including mitochondrial fission may provide new therapeutic targets for protecting RGCs from elevated hydrostatic pressure.     

Newly-found functions of metformin for the prevention and treatment of age-related macular degeneration

AIM: To explore the temporal mitochondrial characteristics of retinal pigment epithelium (RPE) cells obtained from human embryonic stem cells (hESC)-derived retinal organoids (hEROs-RPE), to verify the optimal period for using hEROs-RPE as donor cells from the aspect of mitochondria and to optimize RPE cell-based therapeutic strategies for age-related macular degeneration (AMD). METHODS: RPE cells were obtained from hEROs and from spontaneous differentiation (SD-RPE). The mitochondrial characteristics were analyzed every 20d from day 60 to 160. Mitochondrial quantity was measured by MitoTracker Green staining. Transmission electron microscopy was adopted to assess the morphological features of the mitochondria, including their distribution, length, and cristae. Mitochondrial membrane potentials (MMPs) were determined by JC-1 staining and flow cytometry. ROS levels were evaluated by flow cytometry, and ATP levels were measured by a luminometer. Differences between two groups were analyzed by the independent-samples t-test, and comparisons among multiple groups were made using one-way ANOVA or Kruskal-Wallis H test when equal variance is not assumed. RESULTS: hEROs-RPE and SD-RPE cells from day 60 to 160 were successfully differentiated from hESCs and expressed RPE-specific markers (Pax6, mitf, Bestrophin-1, RPE65, Cralbp). RPE features, including a cobblestone-like morphology with tight junctions (ZO-1), pigments and microvilli, were also observed in both hERO-RPE and SD-RPE cells. The mitochondrial quantities peaked in both hEROs-RPE and SD-RPE cells at day 80. However, the cristae of hEROs mitochondria were less mature and abundant than those of SD mitochondria at day 80, with hEROs mitochondria becoming mature at day 100. Both hEROs-RPE and SD-RPE cells showed low ROS levels from day 100 to 140 and maintained a normal MMP during this period. However, hEROs mitochondria maintained a longer time to produce high levels of ATP (from day 120 to 140) than SD-RPE cells (only day 120). CONCLUSION: Mitochondria of hEROs-RPE cells develop slower and maintain a longer time to supply high-levels of energy than SD-RPE cells. From a mitochondrial aspect, hEROs-RPE cells from day 100 to 140 are an optimal cell source for treating AMD.     

Mitochondrial Targeting of the Ammonia-Sensitive Uncoupler SLC4A11 by the Chaperone-Mediated Carrier Pathway in Corneal Endothelium

PurposeSLC4A11, an electrogenic H⁺ transporter, is found in the plasma membrane and mitochondria of corneal endothelium. However, the underlying mechanism of SLC4A11 targeting to mitochondria is unknown.MethodsThe presence of mitochondrial targeting sequences was examined using in silico mitochondrial proteomic analyses. Thiol crosslinked peptide binding to SLC4A11 was screened by untargeted liquid chromatography/tandem mass spectrometry (LC-MS/MS) analysis. Direct protein interactions between SLC4A11 and chaperones were examined using coimmunoprecipitation analysis and proximity ligation assay. Knockdown or pharmacologic inhibition of chaperones in human corneal endothelial cells (HCECs) or mouse corneal endothelial cells (MCECs), ex vivo kidney, or HA-SLC4A11–transfected fibroblasts was performed to investigate the functional consequences of interfering with mitochondrial SLC4A11 trafficking.ResultsSLC4A11 does not contain canonical N-terminal mitochondrial targeting sequences. LC-MS/MS analysis showed that HSC70 and/or HSP90 are bound to HA-SLC4A11–transfected PS120 fibroblast whole-cell lysates or isolated mitochondria, suggesting trafficking through the chaperone-mediated carrier pathway. SLC4A11 and either HSP90 or HSC70 complexes are directly bound to the mitochondrial surface receptor, TOM70. Interference with this trafficking leads to dysfunctional mitochondrial glutamine catabolism and increased reactive oxygen species production. In addition, glutamine (Gln) use upregulated SLC4A11, HSP70, and HSP90 expression in whole-cell lysates or purified mitochondria of HCECs and HA-SLC4A11–transfected fibroblasts.ConclusionsHSP90 and HSC70 are critical in mediating mitochondrial SLC4A11 translocation in corneal endothelial cells and kidney. Gln promotes SLC4A11 import to the mitochondria, and the continuous oxidative stress derived from Gln catabolism induced HSP70 and HSP90, protecting cells against oxidative stress.     

Mitochondrial dysfunction in glaucomatous degeneration

Glaucoma is a kind of optic neuropathy mainly manifested in the permanent death of retinal ganglion cells (RGCs), atrophy of the optic nerve, and loss of visual ability. The main risk factors for glaucoma consist of the pathological elevation of intraocular pressure (IOP) and aging. Although the mechanism of glaucoma remains an open question, a theory related to mitochondrial dysfunction has been emerging in the last decade. Reactive oxygen species (ROS) from the mitochondrial respiratory chain are abnormally produced as a result of mitochondrial dysfunction. Oxidative stress takes place when the cellular antioxidant system fails to remove excessive ROS promptly. Meanwhile, more and more studies show that there are other common features of mitochondrial dysfunction in glaucoma, including damage of mitochondrial DNA (mtDNA), defective mitochondrial quality control, ATP reduction, and other cellular changes, which are worth summarizing and further exploring. The purpose of this review is to explore mitochondrial dysfunction in the mechanism of glaucomatous optic neuropathy. Based on the mechanism, the existing therapeutic options are summarized, including medications, gene therapy, and red-light therapy, which are promising to provide feasible neuroprotective ideas for the treatment of glaucoma.     

线粒体相关内质网膜在年龄相关性黄斑变性发病机制中的作用研究进展

内质网和线粒体是真核细胞广泛存在的负责蛋白修饰加工以及能量物质转化交互的一组密切接触的细胞器,尤其在代谢活跃的视网膜组织细胞中。它们之间的结构功能以及相互协作制约关系,在疾病发生发展中起重要调控作用。目前研究证明,线粒体功能障碍、内质网应激、自噬等均参与年龄相关性黄斑变性(age-related macular degeneration,AMD)的发生发展过程,其中线粒体相关内质网膜的作用是近年来研究的热点。本文对近年来与视网膜神经退行性疾病以及AMD相关的内质网和线粒体之间,通过物理连接平台进行对话的作用机制方面的相关研究进展进行综述,以期为治疗AMD的药物研发提供新思路,发现治疗新靶点。     

Mitochondrial dysfunction in glaucoma and emerging bioenergetic therapies

The similarities between glaucoma and mitochondrial optic neuropathies have driven a growing interest in exploring mitochondrial function in glaucoma. The specific loss of retinal ganglion cells is a common feature of mitochondrial diseases – not only the classic mitochondrial optic neuropathies of Leber’s Hereditary Optic Neuropathy and Autosomal Dominant Optic Atrophy – but also occurring together with more severe central nervous system involvement in many other syndromic mitochondrial diseases. The retinal ganglion cell, due to peculiar structural and energetic constraints, appears acutely susceptible to mitochondrial dysfunction. Mitochondrial function is also well known to decline with aging in post-mitotic tissues including neurons. Because age is a risk factor for glaucoma this adds another impetus to investigating mitochondria in this common and heterogeneous neurodegenerative disease. Mitochondrial function may be impaired by either nuclear gene or mitochondrial DNA genetic risk factors, by mechanical stress or chronic hypoperfusion consequent to the commonly raised intraocular pressure in glaucomatous eyes, or by toxic xenobiotic or even light-induced oxidative stress. If primary or secondary mitochondrial dysfunction is further established as contributing to glaucoma pathogenesis, emerging therapies aimed at optimizing mitochondrial function represent potentially exciting new clinical treatments that may slow retinal ganglion cell and vision loss in glaucoma.