p75 NTR受体在视网膜色素上皮细胞氧化损伤中的作用及机制

目的：研究p75 NTR受体在视网膜色素上皮细胞(retinal pigment epithelial cells,RPE)氧化损伤过程中的作用及机制。

方法：将转染p75 NTR受体的RPE细胞作为实验组,未转染的RPE细胞作为对照组。BrdU检测法检测细胞增殖活性; PI/Annexin V-FITC双染法检测细胞凋亡率; 激光显微镜观察细胞内ROS的表达情况; 流式细胞仪检测细胞内ROS、线粒体标志物、细胞色素C表达水平; Western blot法检测细胞中Fas蛋白、裂解Caspase-3、VEGF165蛋白的表达水平。

结果：随着p75 NTR受体转染时间的延长,实验组RPE细胞的增殖活性呈逐渐降低趋势,各转染时间点的RPE细胞增殖活性比较,差异有统计学意义(P<0.05); 实验组各转染时间点的RPE细胞增殖活性均明显低于对照组,差异均有统计学意义(P<0.05)。随着转染时间的延长,实验组RPE细胞凋亡率呈逐渐增加趋势,各转染时间点的RPE细胞凋亡率比较,差异有统计学意义(P<0.01); 实验组各转染时间点的RPE细胞凋亡率均明显高于对照组,差异均有统计学意义(P<0.01)。实验组ROS荧光信号明显强于对照组。流式细胞仪检测结果显示,实验组RPE细胞中ROS、细胞色素C水平均明显高于对照组,线粒体标志物水平明显低于对照组,差异均有统计学意义(P<0.01)。Western blot 法检测结果表明,实验组细胞内Fas蛋白、Caspase-3、VEGF₁₆₅蛋白的表达水平均明显高于对照组,差异均有统计学意义(P<0.01)。

结论：p75 NTR受体高表达可导致RPE细胞线粒体发生损伤,同时促进细胞凋亡,最终导致脉络膜新生血管的形成,表明p75 NTR受体可能是导致RPE细胞发生损伤的因素之一。     

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.     

SOD2 protects against oxidation-induced apoptosis in mouse retinal pigment epithelium: implications for age-related macular degeneration

PURPOSE: Oxidative stress from reactive oxygen species (ROS) has been implicated in many diseases, including age-related macular degeneration (AMD), in which the retinal pigment epithelium (RPE) is considered a primary target. Because manganese superoxide dismutase (SOD2), localized in mitochondria, is known to be a key enzyme that protects the cells against oxidative stress, this study was undertaken to examine oxidation-induced apoptosis in cultured RPE cells with various levels of SOD2. METHODS: Primary cultures of RPE cells were established from wild-type (WT), heterozygous Sod2-knockout mouse (HET) and hemizygous Sod2 mice with overexpression of the enzyme (HEMI). Purity of the RPE cell cultures was verified by immunostaining with antibody to RPE65 and quantified by flow cytometry. Oxidative stress was induced in RPE cells by exposing them to H(2)O(2) (0-500 muM) for 1 hour and reculturing them in normal medium for various times (0-24 hours). Apoptosis in the RPE was examined by TUNEL staining and quantified by cell-death-detection ELISA. Mitochondrial transmembrane potential (MTP) was measured by a cationic dye, and cytochrome c leakage from mitochondria was analyzed by Western blot analysis. RESULTS: More than 95% of the cells in each culture were RPE65 positive, and the relative SOD2 levels in HET, WT, and HEMI cells were 0.6, 1.0, and 3.4, respectively. H(2)O(2)-induced apoptotic cell death was both dose and time dependent, and apoptosis in these cells was related to the cellular SOD2 level. Disruption of MTP and release of cytochrome c were observed to occur before apoptotic cell death, and they correlated with cellular SOD2. CONCLUSIONS: The results demonstrate a critical role of SOD2 in protection against oxidative challenge. Cells from HET mice showed greater apoptotic cell death, whereas in those from HEMI mice, cell death induced by oxidative injury was suppressed.     

Rod outer segments mediate mitochondrial DNA damage and apoptosis in human retinal pigment epithelium

PURPOSE: To investigate the interrelationships between DNA damage, mitochondrial activity, and apoptosis in retinal pigment epithelial cells (RPE) after exposure to rod outer segments (ROS). METHODS: After incubation of cultured human RPE with ROS, mitochondrial redox function was evaluated from MTT reduction. Mitochondrial (mt) and nuclear (n) DNA damage were determined by quantitative polymerase chain reactions (QPCR). Apoptotic RPE cells were detected by binding of annexin V to phosphatidyl serine (PS) using fluorescence microscopy. The expression of the pro-apoptotic proteins, p53 and p21(waf-1), and DNA repair enzymes, apurinic/apyrimidinic endonuclease (APE(ref-1)) and DNA polymerase beta (beta-pol) were quantitatively determined by Western blotting analysis. RESULTS: Mitochondrial function decreased by 20 +/- 5% and annexin V immunofluorscent binding was enhanced after exposure of cells to physiological levels of ROS (3.8 x 10(6)cm(-2)) for 4 h. MtDNA was preferentially damaged after exposure to ROS with increased lesion frequencies of 1.49 +/- 0.37 and 2.2 +/- 0.14 per 10 kb base pairs (bp), respectively after 5 and 7 h contact, compared to untreated controls (zero class damage). APE(ref-1)expression increased more than 340% above controls after exposure to ROS for 7 and 24 h. The expression of beta-pol in cultures increased 110% above controls after 24 h contact with the ROS. The expression of p53 and p21 in cells increased 100 and 38% above controls after 24 h exposure to the ROS. CONCLUSIONS: Exposure of ROS to ROS induced mtDNA damage and dysfunction and activated nDNA repair pathways, which did not prevent apoptosis.     

Role of glycolysis in retinal vascular endothelium, glia, pigment epithelium, and photoreceptor cells and as therapeutic targets for related retinal diseases

Glycolysis produces large amounts of adenosine triphosphate (ATP) in a short time. The retinal vascular endothelium feeds itself primarily through aerobic glycolysis with less ATP. But when it generates new vessels, aerobic glycolysis provides rapid and abundant ATP support for angiogenesis, and thus inhibition of glycolysis in endothelial cells can be a target for the treatment of neovascularization. Aerobic glycolysis has a protective effect on Müller cells, and it can provide with a target for visual protection and maintenance of the blood-retinal barrier. Under physiological conditions, the mitochondria of RPE can use lactic acid produced by photoreceptor cells as an energy source to provide ATP for survival. In pathological conditions, because RPE cells avoid their oxidative damage by increasing glycolysis, a large number of glycolysis products accumulate, which in turn has a toxic effect on photoreceptor cells. This shows that stabilizing the function of RPE mitochondria may become a target for the treatment of diseases such as retinal degeneration. The decrease of aerobic glycolysis leads to the decline of photoreceptor cell function and impaired vision; therefore, aerobic glycolysis of stable photoreceptor cells provides a reliable target for delaying vision loss. It is of great significance to study the role of glycolysis in various retinal cells for the targeted treatment of ocular fundus diseases.     

Cadmium-induced apoptotic death of human retinal pigment epithelial cells is mediated by MAPK pathway

Cadmium (Cd), released from cigarette smoke and metal industrial activities, is known to accumulate in human body organs including retina and is particularly higher in retinal tissues of age-related macular degeneration (AMD) eyes compared to non-AMD eyes. We have determined the cytotoxic effects of Cd on human retinal pigment epithelial (RPE) cells. Upon Cd treatment, there was a dose- and time-dependent decline in ARPE-19 cell viability as well as early apoptotic changes such as altered mitochondrial membrane potential (MMP) and Cytochrome C release in cytosol. Depletion of GSH by buthionine-[S,R]-sulfoximine (BSO) resulted in increased Cd toxicity in ARPE-19 cells. Cadmium also caused reactive oxygen species (ROS) generation and activation of mitogen-activated protein kinases (MAPKs) pathway including c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (Erk1/2), and p38 in ARPE-19 cells. Antioxidants such as N-acetylcysteine (NAC) significantly reduced Cd-induced toxicity. These results indicate that elevated ROS-induced activation of the MAPK signaling pathway could be associated with Cd-induced RPE cell apoptosis, one of the major contributing factors in AMD. The toxic effects of Cd on ARPE-19 cells indicate that environmental heavy metals such as Cd could be important potential factors in RPE cells death associated retinal diseases particularly related to smoking.     

脂肪干细胞体外诱导获得RPE样细胞及其治疗AMD相关研究进展

年龄相关性黄斑变性（age-related macular degeneration,AMD）是一种随年龄增长而发病率逐渐升高的黄斑部疾病.主要由视网膜色素上皮（retinal pigment epithelium,RPE）和视网膜退行性变引起的不可逆性中心视力下降.人类脂肪干细胞（adipose-derived stem cells,ADSC）具有多向分化潜能.近年研究发现,ADSC联合视网膜细胞诱导因子可体外诱导ADSC向RPE细胞分化,并表达RPE细胞的标志.相关动物模型显示,由ADSC分化而来的RPE样细胞移植后可参与视网膜重建及修复.ADSC移植为AMD的治疗提供了新思路.     

Retinal pigment epithelium in the pathogenesis of age‐related macular degeneration and photobiomodulation as a potential therapy?

The retinal pigment epithelium (RPE) comprises a monolayer of cells located between the neuroretina and the choriocapillaries. The RPE serves several important functions in the eye: formation of the blood‐retinal barrier, protection of the retina from oxidative stress, nutrient delivery and waste disposal, ionic homeostasis, phagocytosis of photoreceptor outer segments, synthesis and release of growth factors, reisomerization of all‐trans‐retinal during the visual cycle, and establishment of ocular immune privilege. Age‐related macular degeneration (AMD) is the leading cause of blindness in developed countries. Dysfunction of the RPE has been associated with the pathogenesis of AMD in relation to increased oxidative stress, mitochondrial destabilization and complement dysregulation. Photobiomodulation or near infrared light therapy which refers to non‐invasive irradiation of tissue with light in the far‐red to near‐infrared light spectrum (630–1000 nm), is an intervention that specifically targets key mechanisms of RPE dysfunction that are implicated in AMD pathogenesis. The current evidence for the efficacy of photobiomodulation in AMD is poor but its safety profile and proposed mechanisms of action motivate further research as a novel therapy for AMD.     

A Model for the Formation of Ring Mitochondria in Retinal Pigment Epithelium

Purpose:To investigate the mechanism and sequence of formation of ring-shaped mitochondria in retinal pigment epithelial cells of a chick model of gyrate atrophy.Methods: Electron microscopic analysis of the ultrastructure of retinal pigment epithelial (RPE) mitochondria was carried out in chicks injected intravitreally with formoguanamine regularly (every 4 days) over the first 2 weeks or 4 weeks post-hatching. Formoguanamine is a triazine drug which induces hyperor-nithinemic symptoms in the chick eye similar to those seen in human gyrate atrophy.Results: A large population of irregularly shaped mitochondria was observed in the RPE of both peripheral and central retina. They showed extensive morphological changes. At 2 wk,the mitochondria appeared enlarged and abnormal in shape with vacuolisation, partial loss of their double membrane and reduced mitochon-drial cristae. By 4 wk, the mitochondria had assumed a rounder, almost circular profile,many with central holes,so-called ring mitochondria.Conclusi     

白藜芦醇对碘酸钠诱导后人视网膜色素上皮细胞凋亡的抑制作用

目的　研究白藜芦醇（resveratrol，RES）对碘酸钠诱导的人视网膜色素上皮（retinal pigment epithelial，RPE）细胞凋亡的抑制作用及机制，探索该药是否可用于干性年龄相关性黄斑变性（age-related macular degeneration,AMD)的治疗。方法　通过碘酸钠诱导的RPE细胞模拟干性AMD。RPE细胞传代培养分为空白对照组、碘酸钠损伤组、RES+碘酸钠损伤组，并观察各组细胞形态。MTT法检测RES对RPE细胞最佳保护作用的浓度以及最佳浓度下对不同浓度碘酸钠损伤的RPE细胞的保护作用。Western blot检测各组细胞的凋亡蛋白Bax和Bcl-2的表达情况。Hosste33342及流式细胞术检测各组细胞的凋亡总量变化以及凋亡种类之间的差别。结果　5 μmol·L^-1 RES对RPE细胞有较强的保护作用且此浓度下对不同损伤程度的RPE细胞都有较强的保护作用。RES+碘酸钠损伤组Bax蛋白的相对表达量（0.45±0.07）明显低于碘酸钠损伤组（0.90±0.09），差异有统计学意义（P<0.05），与空白对照组（0.34±0.06）差异无统计学意义（P>0.05）。RES+碘酸钠损伤组Bcl-2蛋白的相对表达量（0.56±0.14）与碘酸钠损伤组（0.24±0.04）差异有统计学意义（P<0.05），与空白对照组（0.73±0.08）差异无统计学意义（P>0.05）。Hosste33342检测结果显示，RES+碘酸钠损伤组凋亡细胞含量明显低于碘酸钠损伤组（P<0.05），且流式细胞术检测发现，RES+碘酸钠损伤组和碘酸钠损伤组比较，RES+碘酸钠损伤组早期凋亡的细胞含量相对较高，晚期凋亡细胞含量相对较少。结论　RES对碘酸钠诱导损伤的RPE细胞的凋亡具有良好的抑制作用，对干性AMD的治疗具有潜在价值。     

Cadmium accumulation in the human retina: effects of age, gender, and cellular toxicity

Tobacco smoking and aging are among the few factors linked to age-related macular degeneration (AMD), a major cause of blindness in the elderly. Recent studies indicate that cadmium (Cd), an environmental toxic trace metal, is approximately four-fold higher in the retinas of smokers compared to non-smokers. In this study, we determined the effects of age and gender on Cd accumulation in human retinal tissues, specifically the neural retina, retinal pigment epithelium (RPE), and choroid. Cadmium levels in cultured RPE cells or retinal tissues isolated from frozen donor eyes were measured using inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectrophotometry (GF-AAS). Cadmium uptake in cultured human RPE cells (ARPE-19) was also assessed using GF-AAS. Toxic effects of cadmium were determined from cell loss (measured as a decrease in cell density) and lactate dehydrogenase release (an indicator of membrane disruption). In "young" eyes (< 55 years) Cd was highest in the retinal pigment epithelium and lowest in the neural retina. Cd was higher in all tissues in aged eyes (>or=55 years) and was significantly higher in the neural retina and RPE in older females. Cultured RPE cells exposed to Cd showed altered cell morphology, decreased cell survival, elevated ROS levels and concentration-dependent disruption of membrane integrity. We conclude that cadmium is accumulated differently in the neural retinal and RPE of older men and women. The deleterious effects of Cd on RPE cells indicate that this environmental toxin is a potentially important factor in age-related retinal disease.     

Mitochondrial dysfunction in retinal diseases

The mitochondrion is a vital intracellular organelle for retinal cell function and survival. There is growing confirmation to support an association between mitochondrial dysfunction and a number of retinal degenerations. Investigations have also unveiled mitochondrial genomic instability as one of the contributing factors for age-related retinal pathophysiology. This review highlights the role of mitochondrial dysfunction originating from oxidative stress in the etiology of retinal diseases including diabetic retinopathy, glaucoma and age-related macular degeneration (AMD). Moreover, mitochondrial DNA (mtDNA) damage associated with AMD due to susceptibility of mtDNA to oxidative damage and failure of mtDNA repair pathways is also highlighted in this review. The susceptibility of neural retina and retinal pigment epithelium (RPE) mitochondria to oxidative damage with ageing appears to be a major factor in retinal degeneration. It thus appears that the mitochondrion is a weak link in the antioxidant defenses of retinal cells. In addition, failure of mtDNA repair pathways can also specifically contribute towards pathogenesis of AMD. This review will further summarize the prospective role of mitochondria targeting therapeutic agents for the treatment of retinal disease. Mitochondria based drug targeting to diminish oxidative stress or promote repair of mtDNA damage may offer potential alternatives for the treatment of various retinal degenerative diseases.     

Construction of a cDNA library from human retinal pigment epithelial cells challenged with rod outer segments

Background: To study genes expressed by retinal pigment epithelial (RPE) cells during phagocytosis and digestion of rod outer segments (ROS), a complementary (c)DNA library was produced using an in-vitro model. The cDNA library can be used to study molecular changes which contribute to the development of diseases due to a failure in outer segment phagocytosis and digestion by RPE cells. Here we demonstrate a way to study genes and their functions using a molecular biological approach and describing the first step involved in this process, the construction of a cDNA library.
Methods and results: Human RPE cells obtained from the eyes of a seven-year-old donor were cultured and challenged with bovine ROS. The culture was harvested and total RNA was extracted. Complementary DNA was transcribed from the messenger (m)RNA and was directionally cloned into the LambdaGEM-4 bacteriophage vector successfully. Some clones were picked and the DNA extracted, to determine the size of the inserts as a measure of the quality of the library.
Conclusions: Molecular biology and cell culture are important tools to be used in eye research, especially in areas where tissue is limiting and animal models are not available. We now have a ROS challenged RPE cDNA library which will be used to identify genes responsible for degrading phagocytosed debris within the retinal pigment epithelium.     

Low nitric oxide synthases (NOSs) in eyes with age-related macular degeneration (AMD)

Nitric oxide (NO) production by vascular endothelium is important in regulation of blood flow. Reduced production of NO can adversely affect blood flow and other vascular functions. We investigated the expression of three nitric oxide synthase (NOS) isoforms in retina and choroid of aged human eyes and eyes with AMD. Alkaline phosphatase immunohistochemistry was performed using antibodies against inducible (iNOS), neuronal (nNOS), and endothelial (eNOS) NOSs on cryopreserved sections from aged control donor eyes (n = 13) and eyes with AMD (n = 22). CD34 antibody was used as an endothelial cell (EC) marker. Three independent masked observers scored the intensity of the immunohistochemical reaction product. Mean scores from the aged control and AMD eyes were statistically compared. In aged control retinas, nNOS was in ganglion cells (RGCs) and neurons of both nuclear layers. In choroid, perivascular nerve fibers and retinal pigment epithelial (RPE) cells were nNOS⁺. eNOS and iNOS were confined to the retinal and choroidal vascular ECs. Some cells presumably melanocytes or dendritic cells in choroid were also eNOS⁺. In AMD eyes, nNOS was significantly lower in RGCs, neurons, retinal vessels and RPE (p ≤ 0.05) compared to the aged control eyes. iNOS and eNOS showed no significant differences between aged control and AMD eyes except that there was significantly less eNOS in choroidal arteries (p = 0.006) and choroidal cells (p = 0.03) of AMD eyes. Although NO was not measured directly, these findings suggest that there is less NO produced in AMD eyes. The decrease in retinal nNOS in AMD eyes is probably related to neuronal degeneration. The decrease in nNOS and eNOS in AMD choroid could be associated with vasoconstriction and hemodynamic changes.     

Thrombospondin-1 Expression in RPE and Choroidal Neovascular Membranes

Introduction Age-related macular degeneration (AMD) s the leading cause of blindness in the West or individuals more than 50 years of age[1-3].Severe visual loss in the late stages of AMD most commonly results from choroidal neovas- cularization (CNV), a process characterized by the growth of new vessels from the choriocapil- laris through Bruch′s membrane. These new vessels are prone to leakage and bleeding and may be associated with detachment of the retinal pigment epithelium (RPE). …     

缺氧诱导体外培养人视网膜色素上皮细胞凋亡

目的:了解缺氧条件下体外培养人视网膜色素上皮(retinal pigment epithelium,RPE)细胞的凋亡情况。方法:将培养的人RPE细胞置于含10mL/LO2、50mL/LCO2和940mL/LN2的培养箱内建立缺氧模型。于缺氧后1,3,6,12,24h,利用扫描电镜、透射电镜、脱氧核糖核苷酸末端转移酶介导的缺口末端标记法(terminal-deoxynucle-otidyl transferase mediated nick end labeling,TUNEL)技术和流式细胞仪测定RPE细胞凋亡水平。结果:常氧状态下RPE细胞生长良好,几乎没有凋亡(TUNEL法测凋亡指数为1.2)。缺氧条件下,RPE细胞发生了不同程度的凋亡,缺氧后3h凋亡水平达峰值(凋亡指数为34.43)。结论:缺氧可导致体外培养的人RPE细胞凋亡,提示RPE凋亡可能参与了某些缺血缺氧性眼病的发生。     

H2O2对体外培养视网膜色素上皮细胞中BMP-6及其相关受体的影响

目的　观察氧化应激对视网膜色素上皮（retinal pigment epithelium，RPE）细胞的损伤作用以及对骨形态发生蛋白（bone morphogenetic protein，BMP）-6及其相关受体的影响。方法　RPE细胞随机分为对照组:正常培养的RPE细胞；H₂O₂组:加入200 μmol·L^-1 H₂O₂处理的RPE细胞；实验组:加入200 μmol·L^-1 H₂O₂和0.1 ng·L^-1 BMP-6的RPE细胞。采用活性氧（reactive oxygen species,ROS）检测试剂盒运用流式细胞仪检测对照组与H₂O₂组RPE细胞内ROS的变化，运用PCR及Western blot法检查对照组与H₂O₂组BMP-6基因及蛋白水平的变化；TUNEL染色法观察三组细胞凋亡的变化，并运用PCR及Western blot法观察三组BMP受体及其共受体尤文素(Hemojuvelin，HJV）的变化。结果　H₂O₂组ROS水平（99.25±0.28）%较对照组（70.55±7.71）%明显升高，差异有统计学意义（P<0.05）；H₂O₂组相对于对照组BMP-6 mRNA水平及BMP-6蛋白水平均降低，差异均有统计学意义（均为P<0.05）；H₂O₂组的TUNEL染色阳性细胞数显著高于对照组（P<0.05），而实验组TUNEL染色阳性细胞数明显减少，与H₂O₂组相比，差异有统计学意义（P<0.05）；与对照组相比，H₂O₂组BMP三种相关受体的BMPR1A、BMPR1B及HJV的表达水平显著降低，而实验组三种受体表达水平较H₂O₂组显著升高，差异均有统计学意义（均为P<0.05)。结论　H₂O₂导致RPE细胞ROS增加，氧化应激可在基因及蛋白水平抑制BMP-6的表达；BMP-6可减轻氧化应激引起的细胞凋亡，且可能是通过激活其相关受体起作用的，这为探索年龄相关性黄斑变性的发病机制提供了一定的理论基础。     

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.     

高糖对牛视网膜微血管内皮细胞和周细胞线粒体活性氧的影响

目的探讨高糖条件下培养的牛视网膜微血管内皮细胞、周细胞线粒体活性氧产生量的变化及导致此种变化的原因和所致影响。方法采用选择性培养方法培养牛视网膜微血管内皮细胞、用细胞,通过共聚焦显微镜检测不同葡萄糖浓度下内皮细胞、周细胞线粒体活性氧产生量的变化,同时采用流式细胞仪检测线粒体膜电化、细胞死亡率的变化,RT—PCR检测培养细胞锰超氧化物歧化酶及解耦联蛋白（UCP）1、2、3表达情况和不同葡萄糖浓度下的变化。结果（1）随着培养基中葡萄糖浓度的增加,内皮细胞、周细胞线粒体活忆氧的产生呈增多趋势。（2）随着培养基中葡萄糖浓度的增加,内皮细胞线粒体膜电位逐渐升高,细胞死亡率逐渐增多,而周细胞则无此变化趋势。（3）培养的视网膜微血管内皮细胞、周细胞中,通过RT—PCR检测到UCPI、2mRNA,未检测到UCP3。UCP1、2及锰超氧化物歧化酶表达量随培养基中葡萄糖浓度的变化而变化。结论高糖可以诱导培养的视网膜微血管内皮细胞、周细胞线粒体活性氧产生增多;内皮细胞活性氧产生的增多与线粒体膜电位增高间存在反馈调节;高糖条件下UCP1、2及锰超氧化物歧化酶表达量代偿性增多调节活性氧的产生,但是当糖浓度达到一定程度时,代偿机制消失;内皮细胞、周细胞在高糖条件下表现出的不同特征,说明其在糖尿病性视网膜病变的发生中起着不同的作用。