Etoposide经由caspase依赖途径诱导RGC-5细胞凋亡

目的 研究etoposide诱导视网膜神经节细胞RGC-5细胞死亡的分子机制.方法 建立etoposide诱导的RGC-5细胞死亡模型,应用APOPercentageTM及原位TUNEL染色确定RGC-5细胞的死亡方式,并进而利用Western blot检测细胞内活化caspase-3及PARP-1的变化情况,并通过广谱caspase抑制剂间接证明是否有caspase依赖途径的激活.结果 相对高浓度的etoposide(1～10μmol/L)可以迅速降低RGC-5细胞的活性并诱导死亡;APOPercentageTM及原位TUNEL染色确定etoposide是以凋亡的方式诱导RGC-5细胞死亡;Western blot显示etoposide诱导后的RGC-5细胞中caspase-3被激活并伴有PARP-1的降解片段出现;广谱caspase抑制剂Z-VAD-fmk可以保护etoposide诱导的RGC-5细胞,提高细胞活性.结论 Etoposide经由caspase依赖途径诱导RGC-5细胞凋亡.     

转基因视网膜神经节细胞系RGC-5的研究进展

为研究青光眼性视网膜神经节细胞（RGCs）损害的细胞和分子机制，多种细胞培养模型已经建立，但是转基因的视网膜神经节细胞RGC-5细胞系在国内未见报道。RGC-5细胞系是应用鼠视网膜细胞通过转染技术建立的，除了其形态和电生理特性与RGCs有所不同外，细胞的生长条件以及细胞膜或者细胞内表达的物质与RGCs一致。应用RGC-5细胞系已经建立了多种凋亡模型，研究发现这些模型的细胞在凋亡时的基因变化以及对神经保护剂的反应都与RGCs一致。因此加强对RGC-5的研究和应用，对进一步阐明RGCs的损伤和保护机制将非常有意义。现就这个细胞系的建立及已做的相关研究做一综述。     

P2X7受体对缺氧诱发小鼠视网膜神经节细胞凋亡的影响

目的：：探讨嘌呤受体P2X7对缺氧诱发小鼠视网膜神经节细胞凋亡的影响。方法：以小鼠视网膜神经节细胞株RGC-5为研究对象,按照不同处理因素将细胞随机分为4组：正常对照组( G1)、缺氧组( G2)、缺氧+激动剂( BzATP )组( G3)、缺氧+拮抗剂(BBG)组(G4);采用四甲基偶氮唑蓝(MTT)法检测细胞的存活率;用Annxin V/PI染色流式细胞术检测细胞凋亡率;Western Blot检测细胞内cleave-caspase-3和cleave-PARP蛋白的表达。结果：与正常对照组相比, RGC-5细胞经缺氧处理后,细胞存活率明显降低;凋亡率显著升高;细胞内 cleave-caspase-3和cleave-PARP蛋白表达增加;P2X7受体激动剂BzATP能明显加重缺氧诱发的细胞凋亡,而BBG预处理可以显著拮抗缺氧所致的细胞凋亡。结论：缺氧能激活视网膜神经节细胞嘌呤受体P2X7,并参与视网膜神经节细胞的凋亡。     

Staurosporine诱导RGC-5细胞分化作用的研究

目的 观察Staurosporine是否可以诱导视网膜神经节细胞-5(RGC-5)的分化.方法 正常培养RGC-5细胞,应用500 nmol/L Staurosporine诱导RGC-5细胞分化,并在诱导后不同时间段连续观察细胞形态的变化.应用免疫荧光检测视网膜神经节细胞(RGCs)阳性标志因子Thy-1和Brn-3的表达,应用Western Blot、RT-PCR分别定量检测诱导分化后RGC-5细胞中的Thy-1和Brn-3蛋白表达及mRNA的转录情况.结果 应用500 nmol/L Staurosporine诱导后的RGC-5形态上表现出增生停止,胞体周围纤长轴突生长,轴突末端可见类似突触结构.500 nmol/L Staurosporine可以诱导RGC-5细胞中RGCs阳性标志因子Thy-1和Brn-3转录及表达上调.结论 500 nmol/L Staurosporine可以有效地诱导RGC-5细胞向成熟RGCs分化.     

PEDF对氧化应激损伤的RGC-5细胞的保护作用

目的:研究色素上皮衍生因子(PEDF)对分化的视网膜神经节细胞(RGC-5)氧化应激损伤的防护作用。方法:利用外源性活性氧(H₂O₂)造成分化的RGC-5细胞的氧化应激损伤,同时应用PEDF进行保护。用MTT检测其细胞活性,用Annexin V-FITC凋亡试剂盒测定凋亡。结果:H₂O₂以浓度依赖的方式降低RGC-5细胞活性,200μmoL/L H₂O₂在24h可以导致分化的RGC-5细胞活性降低40%;细胞凋亡百分数（36.60%±2.12%）较空白对照组（6.03%±1.45%）明显增加(P<0.01)。100ng/mL PEDF使H₂O₂损伤分化后RGC-5细胞的细胞活性提高了30%,凋亡率降低为（9.36±1.61）%。结论:PEDF能够有效地防护氧化应激对视网膜神经节细胞的损伤,是一种极具开发潜力的神经保护性药物。     

视网膜光损伤：Ⅰ.中,低强度循环光下光照强度及照射时间的作用

目的:研究中、低强度的循环光照射对鼠视网膜光损伤的影响及其与时间、强度的关系。方法:25只8～10周的雌性SD鼠随机分为5组。一组作对照,另外四组置于12小时亮、12小时暗的白色氙灯循环光下照射3～28天,照射强度分别为90～115Lux(100Lux)、400～650Lux(500Lux)、800～1150Lux(1000Lux)、1400～1650Lux(1500Lux)。照射不同时间后,对视网膜行光镜、电镜检查及组织测厚。结果:除100Lux组光强度外,500Lux、1000Lux、1500Lux组的光强度均能引起鼠视网膜光损伤。视网膜光感受器细胞最早受累。光强度越高、照射时间越长,光感受器细胞的丧失越多;损伤严重者,也伴有视网膜色素上皮的损伤。结论:中、低强度的循环光所造成的鼠视网膜光损伤,其损伤程度与光照强度和照射时间有关。是光损伤防护中值得注意的环节。眼科学报1998;14:215～219。     

青光眼视网膜神经节细胞损伤的研究进展

青光眼是严重损害视力的常见眼病,其病理基础是视网膜神经节细胞及其纤维的丧失。关于青光眼视网膜神经节细胞损伤的机制,迄今未明。以往曾有“机械学说”和“血流学说”等。近年来,随着分子生物学的发展,对青光眼视网膜神经节细胞损伤机制的研究进一步深入。综述了肝光眼视网膜神经节细胞超微结构、轴浆运输以及凋亡等几个方面的研究进展。     

青光眼视神经保护的免疫学途径

导致青光眼视功能损害的病理基础是视网膜神经节细胞进行性凋亡和丧失。目前对视网膜神经节细胞损伤和保护的治疗研究已取得一些进展,如:采用可溶性抗原诱导免疫耐受以避免对破坏性自身抗原应答的诱导;在避免自身免疫性疾病基础上,发挥T细胞神经保护性免疫反应的治疗作用;利用谷氨酸受体拮抗剂、钙离子通道阻滞剂、免疫抑制剂等非特异性治疗,减轻和预防视网膜神经节细胞的不可逆性损伤。本文就视网膜神经节细胞的凋亡、青光眼视神经损害的免疫学机制及视神经保护的免疫学途径进行综述,并从自身抗原、抗原多肽、免疫抑制剂等方面探讨视神经保护在免疫学的可能途径。     

Caspase 与视网膜细胞凋亡的研究进展

Caspase作为凋亡执行和效应过程中的关键酶,其级联活化反应是导致视网膜上光感受器细胞、神经节细胞等发生凋亡的共同途径,与多种常见眼病如青光眼、视网膜脱离、年龄相关性黄斑变性、缺血性视网膜损伤、视网膜母细胞瘤等的发生发展密切相关,有关Caspase抑制剂的实验研究近年来也备受关注,本文围绕Caspase在视网膜细胞凋亡中的作用及其相关机制进行综述。     

蓝光诱导的光感受器细胞凋亡与c-Fos蛋白的表达

目的:观察宽谱蓝光诱导Lewis大鼠视网膜光损伤后光感受器细胞的凋亡及c-Fos蛋白的表达。方法:8～10wk龄雌性Lewis大鼠24只,在循环光环境下饲养并随机分为6组。暗适应24h后,5组接受3012×115Lux的宽谱蓝光(400～500nm)照射1h,光照后予暗适应并于0,6,12,24及48h颈椎脱位法处死大鼠,摘除眼球;另1组为正常对照组,不予光照。采用透射电镜及TUNEL试剂盒检测视网膜细胞凋亡,免疫组化法检测视网膜内c-Fos蛋白的表达。结果:蓝光可特异性引起大鼠光感受器细胞凋亡和光感受器细胞内c-Fos蛋白的表达上调。光照后外核层细胞开始出现凋亡,24h达峰值,大量光感受器细胞出现核固缩并可见凋亡小体形成。c-Fos蛋白的表达在时间与空间分布上与TUNEL阳性细胞基本一致,在同一时间点,二者呈正相关(r =0.905,P <0.05)。结论:蓝光可诱导大鼠光感受器细胞凋亡,视网膜外核层中c-Fos蛋白的表达上调对视网膜蓝光损伤后光感受器细胞凋亡可能具有重要作用。     

Retinal ganglion cell survival in development: mechanisms of retinal growth hormone action

Several variants of growth hormone (GH) are found in the retina and vitreous of the chick embryo, where they appear to act as cell survival factors, having neuroprotective effects on retinal ganglion cells (RGCs). Here, we investigate the molecular mechanisms of the anti-apoptotic effect of GH in cultured RGCs. GH treatment increased Akt phosphorylation in these cells, which is an anti-apoptotic event. Whereas unphosphorylated Akt was detected in both nucleus and cytoplasm of RGCs by immunocytochemistry, the phosphorylated form of Akt (Akt-phos) was located primarily in the cytoplasm of both normal and apoptotic cells, although levels were markedly lower in the latter. It was found that GH treatment of RGCs reduced Akt levels, while concomitantly raising Akt-phos levels, consistent with a role for Akt signaling pathways in GH neuroprotective action. This was substantiated using Wortmannin, which, like GH antiserum, inhibited Akt phosphorylation and initiated apoptosis. The addition of Wortmannin to RGC cultures simultaneously with GH significantly reduced the anti-apoptotic effect of GH. The induction of apoptosis by GH antiserum was clearly accompanied by an increase in caspase-3 activation and PARP-1 cleavage, both of which were significantly reduced in the presence of the broad spectrum caspase inhibitor, Q-VD-OPh, which itself had a dramatic neuroprotective effect on cultured RGCs. Calpain activation appeared to be a major caspase-independent pathway to PARP-1 cleavage and apoptosis in these cells. Calpain inhibitor III (MDL 28170) was able to reduce PARP-1 cleavage and abrogate the apoptogenic effect of GH antiserum. The results support the view that caspase and calpain inhibitors are major neuroprotective agents for RGCs, and that pathways that activate both caspases and calpains are important for the anti-apoptotic actions of GH in these cells.     

Notch1和多聚二磷酸腺苷核糖聚合酶-1在糖尿病小鼠视网膜中的表达

背景 多聚二磷酸腺苷核糖聚合酶-1（PARP-1）在糖尿病视网膜病变（DR）发生过程中具有重要作用,而Notch1是生物体重要的信号转导通路,可能参与对视网膜新生血管性疾病的拮抗过程,Notch1是否参与了DR的发生还未得到证实. 目的 探讨Notch1、Dll4、PARP-1、Akt、核因子-κB（NF-κB）及caspase-3在糖尿病小鼠视网膜组织及高糖视网膜血管内皮细胞（RVECs）中的表达. 方法 建立糖尿病小鼠模型,应用免疫组织化学法和Western blot法检测Notch1、Dll4、PARP-1、Akt、NF-κB及caspase-3在糖尿病小鼠视网膜组织及RVECs的表达.结果 Notch1、Dll4、p-Akt在糖尿病小鼠视网膜组织中的表达量比正常对照组明显降低,而PARP-1、caspase-3在糖尿病小鼠视网膜组织中的表达量比正常对照组明显增加,差异均有统计学意义（均P＜0.05）,但NF-κB的表达量无明显变化,差异无统计学意义（t=0.748,P=0.530）.RVECs中Notch1、p-Akt的表达量随葡萄糖浓度的增高而增加,而剪切型PARP-1、caspase-3的表达量则随葡萄糖浓度的增高而降低,在葡萄糖浓度为30 mmol/L时上述变化最显著,与正常对照组比较差异均有统计学意义（均P＜0.05）,而NF-κB的表达量无明显变化. 结论 在糖尿病小鼠视网膜中,剪切型PARP和caspase-3蛋白的表达上调,但Notch1、p-Akt蛋白的表达量下调.剪切型PARP和caspase-3表达量随葡萄糖浓度的增高而增加,Notch1、p-Akt则相反.     

Acute energy reduction induces caspase-dependent apoptosis and activates p53 in retinal ganglion cells (RGC-5)

The energy reduction-induced death of retinal ganglion cells is associated with many ophthalmic diseases. The present study was designed to investigate the apoptosis pathway of retinal ganglion cells (RGC-5) following acute ATP reduction by using glucose deprivation (GD). RGC-5 cells were cultured in glucose-free or normal DMEM for 3 days. The changes in intracellular ATP and cell viability were monitored by ATP assay and MTT assay. APOPercentage™ and in situ TUNEL assays were used to determine the cell death pattern. The involvement of oxidative stress was assessed by measuring intracellular ROS generation, the HO-1 expression, the effect of antioxidants, and the ratio of GSSG to total GSH. The activation of p53 and apoptosis markers was evaluated by Western blotting. We found that glucose deprivation caused an acute decline of intracellular ATP level, concomitantly decreasing cell viability. The cell death exhibited typical features indicative of apoptosis, including cell shrinkage, phosphatidylserine externalization and DNA fragmentation. Oxidative stress was involved in the cell death process; an antioxidant significantly protected the cells against glucose deprivation. p53 and apoptosis markers, caspase-3 and PARP-1 were activated after RGC-5 cells were cultured in glucose-free media for 32 h. Z-VAD-fmk, a pan-caspase inhibitor, was sufficient to prevent apoptosis. These results suggest that acute energy reduction induced by glucose deprivation triggers caspase-dependent apoptosis and activates p53. Blocking the critical steps in this cell death pathway may have therapeutic effects, rescuing the retinal ganglion cells from damages associated with acute energy reduction.     

Association Analysis of Polymorphisms in Genes Related to Oxidative Stress in South Indian Type 2 Diabetic Patients with Retinopathy

Background: Diabetic Retinopathy (DR) is one of the most common microvascular complications of type 2 diabetes mellitus (T2DM) and is polygenic with a multitude of genes contributing to disease susceptibility. The present study aimed at exploring the association between DR and seven polymorphisms in oxidative stress-related genes, i.e. ACE, eNOS, p22phox subunit of NAD(P)H oxidase, PARP-1 and XRCC1 in South Indian T2DM subjects.

Materials and methods: The study included 149 T2DM subjects with DR (diagnosed through funduscopic examination) and 162 T2DM patients with no evidence of DR. The selected polymorphisms were genotyped by polymerase chain reaction (PCR) and Taqman allele discrimination assay.

Results: There was no significant difference in the genotype and allele distribution of ACE ins/del, eNOS-786T>C, 894G>T, 4a4b and p22phox 242C>T polymorphisms between T2DM groups with and without DR. Contrastingly, there appeared to be a significant association of PARP-1 Val762Ala and XRCC1 Arg399Gln polymorphisms with DR, wherein 762Ala allele seemed to confer significant protection against DR (p?=?0.01; OR?=?0.51 [0.3–0.86]), while the presence of 399Gln allele was associated with an enhanced risk for DR (p?=?0.02; OR?=?1.52 [1.07–2.15]). Multiple logistic regression analysis revealed a significant and independent association of Val762Ala and Arg399Gln polymorphisms and other putative risk factors with DR in T2DM individuals.

Conclusions: The polymorphisms in the DNA repair genes PARP-1 and XRCC1 tended to associate significantly with DR. While Val762Ala polymorphism was associated with reduced susceptibility to DR, the Arg399Gln polymorphism contributed an elevated to risk for DR in South-Indian T2DM individuals.     

Oxidative stress--induced single-strand breaks in chromosomal telomeres of human retinal pigment epithelial cells in vitro

PURPOSE: To demonstrate that chronic hyperoxia induces single-stranded breaks in chromosomal telomeres as a measure of oxidative DNA damage in cultured RPE cells. METHODS: RPE340 cells were cultured in 40% and 20% (control) O(2). DNA damage was assessed by mean terminal restriction fragment (TRF) length, and the S1 nuclease assay was used to determine the frequency of single-strand breaks in telomeric DNA. The degree of oxidative stress in cells was estimated by flow cytometric analysis of reactive oxygen intermediate (ROI)-induced 2',7'-dichlorodihydrofluorescein diacetate fluorescence and Northern blot analysis of heme oxygenase-1 (HO-1) mRNA induction. RESULTS: The mean TRF length of cells grown in 40% O(2) shortened at a faster rate than those grown in 20% O(2). The S1 nuclease assay showed that the accelerated mean TRF length shortening was due to an increased accumulation of single-stranded breaks in telomeric DNA. The degree of ROI production and HO-1 mRNA induction was greater in cells treated with 40% than 20% O(2), an effect that was also larger in old than young passaged cells. CONCLUSIONS: RPE340 cells in vitro grown in chronic hyperoxia exhibited evidence of DNA damage with accelerated telomeric shortening via an increased accumulation of single-strand breaks in telomeric DNA. These changes could provide insight into aging of RPE cells by oxidative DNA damage.     

Direct chemical measurement of DNA synthesis and net rates of differentiation of rat lens epithelial cells in vivo: applied to the selenium cataract

This report describes a direct chemical method for rapidly estimating DNA synthesis and net rates of epithelial cell differentiation in the ocular lens in vivo. DNA synthesis in the lens of control and selenium-treated rats (12- or 13 days of age) was estimated by chemically isolating and measuring trichloroacetic acid (TCA)-insoluble 3H from the lens following injection of [3H]thymidine. Labeled substrate for DNA synthesis peaked in the lens at 1 hr after injection, decreased markedly by the third hour and was essentially gone by hour 12. Synthesis of labeled DNA in the lens was largely complete by about 3 hr. The [3H]DNA content of the whole lens, measured as TCA-insoluble 3H, remained constant for at least 4 months. The distribution of labeled epithelial cells between the epithelial-cell layer and fiber-cell mass was followed for up to 1 month after injection by measuring the ratio of [3H]DNA in the capsule (epithelial-cell layer) to lens body. Between days 2-3 and day 14 after injection, the ratio of [3H]DNA in the epithelial-cell layer to lens fiber cells decreased linearly in a semilogarithmic plot of the ratio vs. time; i.e. the rate of change of the ratio followed first-order kinetics. Thus, the rate constant (k) for the rate of change in the ratio of [3H]DNA in the capsule layer to lens body can provide an estimate of the percentage of the labeled epithelial cells which leave the capsule per day through differentiation into fiber cells. An apparent rate constant of 0.27 day-1 was estimated from the mean of five experiments; i.e. 27% of labeled epithelial cells were differentiating into cortical fiber cells per day. Therefore, about 70% of the germinative epithelial cells would be replaced every 4 days in these rats. This value is in good agreement with results of studies using autoradiographic technics. The selenium cataract is reported to involve rapid damage to lens epithelial cells. Incorporation of [3H]thymidine into DNA was decreased by at least 60% in the lens of selenium-treated rats. Selenium did not decrease the availability of substrate in the lens for DNA synthesis. The cause of the decreased incorporation of [3H]thymidine into the selenium-exposed lenses remains to be determined.     

Retinal pigment epithelial cell DNA is damaged by exposure to benzo[a]pyrene,a constituent of cigarette smoke

This study examined the effect of exogenous benzo[ a ]pyrene (BaP), an important constituent of cigarette smoke, on cultured bovine retinal pigment epithelial (RPE) cells. Evidence is presented for its metabolic conversion into benzo[ a ]pyrene diol epoxide (BPDE) and the consequent formation of potentially cytotoxic nucleobase adducts in DNA. Cultured RPE cells were treated with BaP at concentrations in the range of 0-100 microM. The presence of BaP was found to cause inhibition of cell growth and replication. BaP induced the expression of a phase I drug metabolizing enzyme which was identified as cytochrome P450 1A1 (CYP 1A1) by RT-PCR and by Western blotting. Coincident with the increased expression of CYP 1A1, covalent adducts between the mutagenic metabolite BPDE and DNA could be detected within RPE cells by immunocytochemical staining. Additional support for their formation was afforded by nuclease P1 enhanced (32)P-postlabelling assays on cellular DNA. Single-cell gel electrophoresis (comet) assays showed that exposure of RPE cells to BaP rendered them markedly more susceptible to DNA damage induced by broad band UVB or blue light laser irradiation. In the case of UVB, this is consistent with the photosensitization of DNA cleavage by nucleobase adducts of BPDE. Collectively, these findings imply that BaP has a significant impact on RPE cell pathophysiology and suggest mechanisms whereby exposure to cigarette smoke might cause RPE dysfunction and cell death, thus possibly contributing to degenerative disorders of the retina.     

氮酮促进脂质体介导质粒DNA转染兔角膜内皮细胞及毒性的实验研究

目的探讨氮酮(AZONE)促进脂质体介导质粒DNA转染兔角膜内皮细胞的作用及其对细胞活性的影响。方法采用细胞培养方法,利用绿色荧光蛋白基因做报告基因,配制不同转染液,脂质体联合pEGFP-N1、氮酮联合脂质体及pEGFP-N1、氮酮联合pEGFP-N1、单纯pEGFP-N1、单纯脂质体、单纯氮酮,分别处理兔角膜内皮细胞,荧光显微镜观察细胞中绿色荧光蛋白的表达。用RT-PCR方法检测EGFPmRNA表达情况。采用MTT法研究不同转染液对细胞活性的影响。结果单纯氮酮、单纯脂质体及对照组处理的细胞不表达绿色荧光蛋白。氮酮联合脂质体及pEGFP2N1对兔角膜内皮细胞的转染效率为42.6%,脂质体联合pEGFP2N1组的转染效率为22.4%,氮酮联合PEGFP-N1组的转染效率为7.2%,单组质粒组的转染效率为1%。氮酮加脂质体加PEGFP-N1组转染效率高于其他转染组(P<0.01)。各组转染液对角膜内皮细胞活性无影响。结论氮酮可促进脂质体介导质粒DNA转染兔角膜内皮细胞,在有效的转染浓度下对细胞无明显毒性,有望成为促进角膜内皮细胞基因转染的新型试剂。