视网膜脱离后光感受器细胞死亡机制及潜在治疗策略

视网膜脱离(RD)是临床上常见的致盲眼病之一,患者术后视功能恢复不理想.近年来研究表明,光感受器细胞死亡是导致RD后视功能损伤的主要原因,其发生机制复杂,涉及半胱氨酸蛋白酶依赖性的经典凋亡途径、内质网应激等非半胱氨酸蛋白酶依赖性凋亡途径以及坏死性凋亡、自噬等多种信号通路及其相互作用.阐明RD光感受器细胞的死亡机制,并在此基础上采取联合抑制多条死亡通路、干预上游靶点和加强内源性保护等策略有助于保护光感受器细胞,最终改善RD患者的视功能.本文综述了近年来RD光感受器细胞死亡机制的研究进展,探讨了可能存在的干预靶点以及未来潜在的治疗策略.     

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。     

青光眼动物模型中自噬与视网膜神经节细胞的关系

青光眼的主要病理特征是视网膜神经节细胞(RGCs)渐进性丢失,而其损伤机制尚未明确.自噬是溶酶体降解物质的过程,该过程消除了受损的细胞成分,包括细胞器和长寿蛋白,这对维持细胞内环境的稳定有着重要作用.最近的研究表明,自噬参与了青光眼发病的病理生理过程.本文总结了视神经损害模型、视网膜缺血-再灌注模型、高眼压模型等不同青光眼动物模型中自噬与RGCs的关系,发现在不同青光眼动物模型中,自噬既可促进RGCs存活,又可促进其死亡,而在相同动物模型中,自噬对RGCs的调节也发挥着双刃剑的作用.同时阐述了自噬与具有神经元保护作用的Sirt1之间的相互作用.     

自噬与青光眼关系的研究进展

自噬是溶酶体降解或再循环利用细胞器、蛋白质等胞内物质成分的过程,在细胞内环境稳态中发挥重要作用.近年来的研究表明,自噬与众多眼病包括青光眼的发生和发展有着密切联系.自噬可能是导致小梁网细胞功能异常的重要因素之一,其对视网膜神经节细胞发挥保护作用还是促进其死亡,仍存在争议.目前与青光眼有关的自噬基因的研究主要是OPTN基因,其编码的蛋白质optineurin与正常眼压性青光眼的发生发展相关.通过调控自噬而保护视网膜神经节细胞免于损伤可能是青光眼视神经保护的一种新方法.     

自噬在视网膜和眼部疾病中的研究进展

自噬维持细胞内成分降解和再循环的稳态,是一种关键的细胞质量控制机制。在应激反应中,自噬促进细胞成分的降解,以提供细胞代谢所需的营养物质和能量。视网膜是眼睛中转导和处理视觉信息的光敏组织,对物质和能量需求极高,基础水平的自噬对维持视网膜细胞的稳态和视觉系统的正常功能至关重要。本文总结了自噬途径参与青光眼、年龄相关性黄斑变性、糖尿病视网膜病变、视网膜营养不良和视网膜脱离等眼科疾病的最新研究,为未来通过调控自噬治疗眼部疾病提供理论依据。     

外源性促红细胞生成素对大鼠视网膜脱离光感受器细胞的保护作用

目的 观察外源性促红细胞生成素(EPO)对大鼠视网膜脱离(RD)状态下光感受器细胞的保护作用.方法 采用计算机产生随机数字的方法将162只正常雄性SD大鼠分为正常对照组(NC组)、RD组、RD+磷酸盐缓冲液(PBS)组、RD+EPO 100、200、400 ng组.RD后3 d,采用蛋白免疫印迹(Western blot)检测半胱氨酸蛋白酶3(caspase-3)活性和B细胞淋巴瘤/白血病-XL(bcl-XL)的表达,免疫荧光检测caspase-3活性,脱氧核糖核苷酸末端转移酶介导的缺口末端标记法(TUNEL)检测光感受器细胞凋亡情况.RD后14、28 d,2个月,视网膜组织病理学观察并测量外核层(ONL)厚度.结果 Western bolt检测发现,各组间活化caspase-3条带灰度值差异有统计学意义(F=35.96,P<0.01),bcl-XL条带灰度值差异也有统计学意义(F=30.75,P<0.01).免疫荧光和TUNEL检测发现,caspase-3免疫阳性光感受器细胞数目与TUNEL阳性细胞核趋势表现一致.RD后14 d、2个月,各组间ONL差异有统计学意义(F=21.52,96.25;P<0.01).结论 RD后补充外源性EPO可通过抑制caspase-3活性并增加bcl-XL的表达拮抗凋亡,从而发挥对光感受器细胞的保护作用.     

光感受器与双极细胞间突触在视网膜脱离后的重塑

视网膜脱离（RD）是严重的致盲性眼病。近年来研究发现,RD后光感受器与双极细胞间突触结构会遭到破坏,这一组织学上的变化对RD患者术后视功能的恢复有着重要影响。现就光感受器与双极细胞间突触在RD后的重塑进行综述,探讨RD术后视功能恢复不良的可能机制。     

依达拉奉对视网膜脱离模型大鼠早期感光细胞自噬的调控作用

目的:研究氧自由基清除剂依达拉奉对视网膜脱离(RD)模型大鼠早期视网膜自噬的调控及感光细胞的保护作用。方法:取51只成年雄性Sprague-Dawley大鼠进行RD造模,另取24只大鼠作为PBS注射组。造模组采用右眼视网膜下注射0.5%透明质酸钠的方法制作RD动物模型。将造模成功大鼠按照随机数字表法随机分为RD模型组和...     

兔眼视网膜脱离后玻璃体内谷氨酸变化及毒性

目的　研究视网膜脱离 (RD)后玻璃体内谷氨酸 (G1u)含量改变及对视网膜的神经毒性。方法　兔眼玻璃体内注射透明质酸酶 ( 10U/mL)造成一眼RD ,另眼作对照。RD后不同时间抽取玻璃体液用高压液相色谱法检测Glu含量 ,并作视网膜电镜观察。结果　RD后 8h～ 7d ,Glu含量增加 ,与对照眼比较差异有显著性 (P <0 0 5 ) ,以后逐渐下降 ,至 14d与对照眼差异无显著性 (P >0 0 5 )。电镜观察显示 ,RD后 8h～ld ,视网膜水肿严重 ,4～ 7d视网膜各层细胞均出现变性坏死 ,外核层最严重 ,14～ 2 8d则以光感受器丢失及胶质细胞增生为主。结论　RD后玻璃体内Glu明显增多 ,并对视网膜尤其是光感受器产生损伤作用。     

神经营养素家族因子对视网膜神经细胞保护作用的研究进展

现有大量研究表明神经营养素家族因子对视网膜神经细胞具有重要的保护作用。在所有家族成员中,神经生长因子能够有效保护视网膜光感受器细胞;阻断视网膜神经节细胞中神经生长因子与受体p75的结合,可以抑制神经节细胞的凋亡。脑源性神经营养因子可以防止光感受器细胞变性,增强光感受器细胞损伤后的修复。在刺激神经节细胞轴突生长和突触形成方面,脑源性神经营养因子、神经营养素-3及神经营养素-4/5均具有显著效应。通过对神经营养素家族因子的研究,了解其作用机制,以期能够应用于视网膜神经细胞变性及损伤性疾病的治疗中。     

有裂孔的视网膜变性的临床特征和氩激光治疗

目的 探讨有裂孔的视网膜变性的临床特征和氩激光治疗效果。 方法 回顾性分析本院210例224只眼相应视网膜变性的氩激光治疗资料，并与同期尚无裂孔的视网膜变性氩激光治疗对照。 结果 有裂孔的视网膜变性患者，小于60岁者89.7%，男性53.3%，女性46.7%，格子样变性65.6%，变性范围≤1个象限者87.5%，卵圆形裂孔60.7%，伴有局限性视网膜浅脱离者23.7%。与尚无裂孔的视网膜变性患者相比，≥35岁、囊样变性、视网膜纵向小皱襞、有自觉症状的患眼构成比明显偏高，而氩激光视网膜脱离预防性治疗对已出现局限性孔源性视网膜脱离的视网膜变性患者疗效明显偏低(P<0.01)。 结论 有裂孔的视网膜变性常见于青壮年，多数患者为1个象限内的格子样变性；裂孔多数为卵圆形，多不伴有视网膜脱离；裂孔没有明显的性别差异，多数没有自觉症状。不伴有视网膜脱离的视网膜单纯性裂孔的视网膜变性，氩激光视网膜脱离预防性治疗可获得满意疗效。 (中华眼底病杂志, 2006, 22: 39-41)     

内源性促红细胞生成素对大鼠脱离视网膜光感受器细胞的保护作用

背景促红细胞生成素（EPO）对多种视网膜疾病模型中视网膜神经元具有一定的保护作用,但EPO对视网膜脱离（RD）后光感受器细胞是否具有保护作用尚不清楚。目的探讨内源性EPO对RD状态下光感受器细胞的保护作用及可能机制。方法利用视网膜下腔注射质量分数1．4％透明质酸钠建立大鼠RD模型,按每组情况各组玻璃体腔内分别单次注射PBS或不同剂量的外源性可溶性EPO受体（EPOsR）,采用计算机产生随机数字法将72只SD大鼠随机平均分为正常对照组、RD组、RD＋PBS组、RD＋EPOsR2、20、200ng组。分别于造模后3d和14d用过量麻醉法处死大鼠并获得大鼠视网膜标本,采用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记（TUNEL）法检测光感受器细胞的凋亡情况,并分别采用Westernblot和免疫荧光法检测视网膜中caspase-3的活性,RD造模后14d进行组织病理学检查并测量外核层（ONL）厚度。结果RD造模后3d,RD组ONL出现凋亡细胞核,玻璃体腔注射EPOsR组光感受器细胞凋亡进一步增加,随着玻璃体腔注射EPOsR的剂量增加,ONL凋亡细胞核有增加趋势。Westernblot和免疫荧光检测结果均显示,各组视网膜caspase-3表达的条带灰度值分别为（0．15±0．04）、（0．49±0．03）、（0．50±0．07）、（0．63±O．03）、（0．69±0．04）、（0．83±0．04）,各组的总体差异有统计学意义（F=76．016,P=0．000）,RD＋EPOsR200ng组的caspase-3活性均强于其他各组,差异均有统计学意义（P〈0．01）。RD造模后14d,正常对照组、RD组、RD＋PBS组、RD＋EPOsR2、20、200ng组的ONL厚度分别为（47．39±3．39）、（33．96±3．54）、（31．83±5．21）、（31．40±2．63）、（24．99±2．06）、（19．30e3．71）μm,总体差异有统计学意义（F=44．733;P=0．000）;EPOsR处理组ONL厚度明显薄于单纯RD组和RD＋PBS组,差异均有统计学意义（P〈0．05）。结论RD状态下,EPOsR通过剂量依赖的方式诱导视网膜细胞的凋亡和caspase-3活性增强,而缺氧状态下视网膜神经上皮的内源性EPO表达增强可通讨抑制casDase-3活性和抗凋亡作用发挥对光感受器细胞的保护作用。     

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。     

实验性视网膜脱离时外源性bFGF对视网膜细胞凋亡的干预作用

目的 研究实验性视网膜脱离(RD)后家兔视网膜细胞凋亡情况,探讨RD后视功能损伤机制,观察碱性成纤维细胞生长因子(bFGF)对细胞凋亡的干预作用.方法 从42只青紫兰兔中随机选取40只兔,将每只兔的左、右眼分为实验对照组和治疗组.视网膜下注射玻璃酸钠(爱维)建立RD动物模型后,取右眼在玻璃体腔内注射10IU/20μl bFGF溶液,作为治疗组;左眼注射平衡盐溶液(BSS)20μl作为实验对照组.剩余2只家兔设为正常对照组,不作任何处理,在实验观察结束时取眼球.三组均采用HE染色、原位末端标记法(TUNEL)和透射电子显微镜观察视网膜细胞凋亡情况,并进行细胞计数和统计学检验.结果 RD早期就有细胞凋亡的发生.视网膜各层细胞均可见凋亡细胞,内核层、节细胞层分布最多.凋亡细胞数随脱离时间延长而变化(P<0.01).bFGF组的凋亡细胞数比BSS组少(P<0.01).电镜下可见除正常对照组基本无凋亡细胞外,其余两组均观察到凋亡细胞,.bFGF组中典型凋亡细胞明显少于实验对照组.结论 实验性RD时视网膜组织细胞中存在异常凋亡,可能是RD后视功能损伤机制之一.玻璃体腔内给予bFGF可以抑制视网膜细胞凋亡,为临床治疗视网膜脱离提供参考.     

RPE transplantation and its role in retinal disease

Retinal pigment epithelial (RPE) transplantation aims to restore the subretinal anatomy and re-establish the critical interaction between the RPE and the photoreceptor, which is fundamental to sight. The field has developed over the past 20 years with advances coming from a large body of animal work and more recently a considerable number of human trials. Enormous progress has been made with the potential for at least partial restoration of visual function in both animal and human clinical work. Diseases that have been treated with RPE transplantation demonstrating partial reversal of vision loss include primary RPE dystrophies such as the merTK dystrophy in the Royal College of Surgeons (RCS) rat and in humans, photoreceptor dystrophies as well as complex retinal diseases such as atrophic and neovascular age-related macular degeneration (AMD). Unfortunately, in the human trials the visual recovery has been limited at best and full visual recovery has not been demonstrated. Autologous full-thickness transplants have been used most commonly and effectively in human disease but the search for a cell source to replace autologous RPE such as embryonic stem cells, marrow-derived stem cells, umbilical cord-derived cells as well as immortalised cell lines continues. The combination of cell transplantation with other modalities of treatment such as gene transfer remains an exciting future prospect. RPE transplantation has already been shown to be capable of restoring the subretinal anatomy and improving photoreceptor function in a variety of retinal diseases. In the near future, refinements of current techniques are likely to allow RPE transplantation to enter the mainstream of retinal therapy at a time when the treatment of previously blinding retinal diseases is finally becoming a reality.     

Photoreceptor cell death and rescue in retinal detachment and degenerations

Photoreceptor cell death is the ultimate cause of vision loss in various retinal disorders, including retinal detachment (RD). Photoreceptor cell death has been thought to occur mainly through apoptosis, which is the most characterized form of programmed cell death. The caspase family of cysteine proteases plays a central role for inducing apoptosis, and in experimental models of RD, dying photoreceptor cells exhibit caspase activation; however, there is a paradox that caspase inhibition alone does not provide a sufficient protection against photoreceptor cell loss, suggesting that other mechanisms of cell death are involved. Recent accumulating evidence demonstrates that non-apoptotic forms of cell death, such as autophagy and necrosis, are also regulated by specific molecular machinery, such as those mediated by autophagy-related proteins and receptor-interacting protein kinases, respectively. Here we summarize the current knowledge of cell death signaling and its roles in photoreceptor cell death after RD and other retinal degenerative diseases. A body of studies indicate that not only apoptotic but also autophagic and necrotic signaling are involved in photoreceptor cell death, and that combined targeting of these pathways may be an effective neuroprotective strategy for retinal diseases associated with photoreceptor cell loss.     

Defects in retinal pigment epithelial cell proteolysis and the pathology associated with age-related macular degeneration

Maintenance of protein homeostasis, also referred to as “Proteostasis”, integrates multiple pathways that regulate protein synthesis, folding, translocation, and degradation. Failure in proteostasis may be one of the underlying mechanisms responsible for the cascade of events leading to age-related macular degeneration (AMD). This review covers the major degradative pathways (ubiquitin-proteasome and lysosomal involvement in phagocytosis and autophagy) in the retinal pigment epithelium (RPE) and summarizes evidence of their involvement in AMD. Degradation of damaged and misfolded proteins via the proteasome occurs in coordination with heat shock proteins. Evidence of increased content of proteasome and heat shock proteins in retinas from human donors with AMD is consistent with increased oxidative stress and extensive protein damage with AMD. Phagocytosis and autophagy share key molecules in phagosome maturation as well as degradation of their cargo following fusion with lysosomes. Phagocytosis and degradation of photoreceptor outer segments ensures functional integrity of the neural retina. Autophagy rids the cell of toxic protein aggregates and defective mitochondria. Evidence suggesting a decline in autophagic flux includes the accumulation of autophagic substrates and damaged mitochondria in RPE from AMD donors. An age-related decrease in lysosomal enzymatic activity inhibits autophagic clearance of outer segments, mitochondria, and protein aggregates, thereby accelerating the accumulation of lipofuscin. This cumulative damage over a person’s lifetime tips the balance in RPE from a state of para-inflammation, which strives to restore cell homeostasis, to the chronic inflammation associated with AMD.     

Mitochondrial DNA damage and its potential role in retinal degeneration

Mitochondria are central to retinal cell function and survival. There is increasing evidence to support an association between mitochondrial dysfunction and a number of retinal pathologies including age-related macular degeneration (AMD), diabetic retinopathy and glaucoma. The past decade has highlighted mitochondrial genomic instability as an important factor in mitochondrial impairment culminating in age-related changes and age-related pathology. This represents a combination of the susceptibility of mitochondrial DNA (mtDNA) to oxidative damage and a limited base excision repair pathway. This random cumulative mtDNA damage leads to cellular heteroplasmy and, if the damage affects a sufficient proportion of mitochondria within a given cell, results in loss of cell function and greater susceptibility to stress. mtDNA damage is increased in the neural retina and RPE with ageing and appears to be greatest in AMD. It thus appears that the mitochondrial genome is a weak link in the antioxidant defenses of retinal cells and that deficits in mitochondrial DNA (mtDNA) repair pathways are important contributors to the pathogenesis of retinal degeneration. Specifically targeting mitochondria with pharmacological agents able to protect against oxidative stress or promote repair of mtDNA damage may offer potential alternatives for the treatment of retinal degenerations such as AMD.