Retinal Cell Damage Research Articles

Stem cells for retinal replacement therapy.

Retinal degenerative disease has limited therapeutic options and the possibility of stem cell-mediated regenerative treatments is being actively explored for these blinding retinal conditions. The relative accessibility of this central nervous system tissue and the ability to visually monitor changes after transplantation make the retina and adjacent retinal pigment epithelium prime targets for pioneering stem cell therapeutics. Prior work conducted for several decades indicated the promise of cell transplantation for retinal disease, and new strategies that combine these established surgical approaches with stem cell-derived donor cells is ongoing. A variety of tissue-specific and pluripotent-derived donor cells are being advanced to replace lost or damaged retinal cells and/or to slow the disease processes by providing neuroprotective factors, with the ultimate aim of long-term improvement in visual function. Clinical trials are in the early stages, and data on safety and efficacy are widely anticipated. Positive outcomes from these stem cell-based clinical studies would radically change the way that blinding disorders are approached in the clinic.

Visible light induce oxidative damage to human retinal pigment epithelial cells

Objective To observe the effect of visible light (white light, red light, blue light) on the expression of reactive oxygen species (ROS), 8-OHdG and hOGG1 in cultured human retinal pigment epithelial (RPE) cells. Methods Cultured human RPE-19 cells (4th-6th generations) were divided into white light, red light, blue light and control group. The illumination was 600 Lux. The cells of experimental groups were exposed to white light or red light for 6, 12, 24 and 48 hours, and exposed to blue light for 1, 3, 6 and 12 hours, while cells of the control group were cultured in foil packaged dishes to avoid light. The levels of ROS expression were detected by 2′, 7′-dichlorofluorescin-diacetate (DCFH-DA), the levels of 8-OHdG protein expression were observed by immunocytochemistry (ICC), and the levels of hOGG1 were measured by western blot. Results Compared to the control group, the ROS expression in RPE cells were increased in white and red light group after 12, 24 and 48 hours and in blue light group after 1, 3, 6 and 12 hours (Fwhite light=11. 611, Fred light =6.706, Fblue light =23. 259; P＜0.05 ). Additionally, the ROS expression had a tendency to increase gradually along with exposure time. Compared to the control group, the 8-OHdG expression in RPE cells were increased significantly in both white and red light group after 12, 24 and 48 hours and in blue light group after 1, 3, 6 and 12 hours (Fwhite light =16. 032,Fred light =6. 378, Fblue light =19. 484; P＜0.05). Additionally, the 8-OHdG expression in white and red light group were increased gradually with exposure time but decreased when exposure time was up to 48 hours, while that in blue light group was increased firstly though it started to decrease when exposure time was up to 6hours. Compared to the control group, the hOGG1 expression in RPE cells were increased in white and red light group after 12, 24 and 48 hours and in blue light group after 6 and 12 hours (Fwhite light =15. 121,Fred light=21. 041,Fblue light12. 479; P＜0.05). ConclusionsExposure to white, red or blue light could induce ROS production and DNA oxidative damage in RPE cells in a time-dependent way. Exposure to visible light could switch on self protection of RPE cells against DNA oxidative damage by up-regulating of the hOGG1 expression. Key words: Pigment epithelium of eye/ cytology; Reactive oxygen species; Deoxyguanine nucleotides; Cell culture techniques

LEDGF1-326 Decreases P23H and Wild Type Rhodopsin Aggregates and P23H Rhodopsin Mediated Cell Damage in Human Retinal Pigment Epithelial Cells

BackgroundP23H rhodopsin, a mutant rhodopsin, is known to aggregate and cause retinal degeneration. However, its effects on retinal pigment epithelial (RPE) cells are unknown. The purpose of this study was to determine the effect of P23H rhodopsin in RPE cells and further assess whether LEDGF1-326, a protein devoid of heat shock elements of LEDGF, a cell survival factor, reduces P23H rhodopsin aggregates and any associated cellular damage.MethodsARPE-19 cells were transiently transfected/cotransfected with pLEDGF1-326 and/or pWT-Rho (wild type)/pP23H-Rho. Rhodopsin mediated cellular damage and rescue by LEDGF1-326 was assessed using cell viability, cell proliferation, and confocal microscopy assays. Rhodopsin monomers, oligomers, and their reduction in the presence of LEDGF1-326 were quantified by western blot analysis. P23H rhodopsin mRNA levels in the presence and absence of LEDGF1-326 was determined by real time quantitative PCR.Principal FindingsP23H rhodopsin reduced RPE cell viability and cell proliferation in a dose dependent manner, and disrupted the nuclear material. LEDGF1-326 did not alter P23H rhodopsin mRNA levels, reduced its oligomers, and significantly increased RPE cell viability as well as proliferation, while reducing nuclear damage. WT rhodopsin formed oligomers, although to a smaller extent than P23H rhodopsin. Further, LEDGF1-326 decreased WT rhodopsin aggregates.ConclusionsP23H rhodopsin as well as WT rhodopsin form aggregates in RPE cells and LEDGF1-326 decreases these aggregates. Further, LEDGF1-326 reduces the RPE cell damage caused by P23H rhodopsin. LEDGF1-326 might be useful in treating cellular damage associated with protein aggregation diseases such as retinitis pigmentosa.

Promises of stem cell therapy for retinal degenerative diseases

With the development of stem cell technology, stem cell-based therapy for retinal degeneration has been proposed to restore the visual function. Many animal studies and some clinical trials have shown encouraging results of stem cell-based therapy in retinal degenerative diseases. While stem cell-based therapy is a promising strategy to replace damaged retinal cells and ultimately cure retinal degeneration, there are several important challenges which need to be overcome before stem cell technology can be applied widely in clinical settings. In this review, different types of donor cell origins used in retinal treatments, potential target cell types for therapy, methods of stem cell delivery to the eye, assessments of potential risks in stem cell therapy, as well as future developments of retinal stem cells therapy, will be discussed.

Photoreceptor layer thickness measurement in normal and glaucomatous eyes with spectral domain OCT

Background Glaucoma is primarily characterized by the damage of retinal ganglion cells in the inner layer.Whether the outer retinal layers are involved is controversial.Although the functional abnormality of the outer retinal layers have been determined,structural studies present difierent outcomes.Objective This study measured and compared photoreceptor layer thickness between normal and glaucomatous eyes using spectral domain optical coherence tomography(OCT). Methods A case-control study was designed.The macular area of 38 eyes from 38 normal volunteers and 48 primary open-angle glaucomatous eyes(POAG)were imaged by spectral domain OCT(SD OCT).The outer nuclear layer(ONL)and inner and outer segments(IS/OS)layer thicknesses in fovea and parafovea(1.5 mm from the fovea) were measured by a single masked observer using an image analysis software (SigmaScan Pro version 5.0).Retinal nerve fiber layer(RNFL)thicknesses of the 86 eyes were measured by Stratus OCT.The photoreceptor layer thicknesses between normal and glaucomatous eyes were compared.The correlation of photoreceptor with RNFL thicknesses was evaluated with linear and non-linear regression models. Results The outer nuclear layer(ONL)thickness in the fovea in normal and glaucomatous eyes were 96.7±10.7μm and 103.7±13.3 μm,respectively,with a significant difference(P=0.011).The inner and outer segments(IS/OS)layer thicknesses in the fovea in the two groups were 59.3±5.5 μm and 59.5±5.5μm,respectively,without significant difference(P=0.890).The outer nuclear layer(ONL)thicknesses in the parafovea in normal and glaucomatous eyes were 70.9±14.0μm and 68.7 ±10.7μm,respectively,(P=0.410).The inner and outer segments(IS/OS)layer thicknesses in the parafovea in the two groups were 45.2±6.4 μm and 43.6±5.5μm,respectively(P=0.228).The relationship between ONL and RNFL thickness was best described with a second order polynomial regression model assoeiation(Y=-0.019X2+2.73X+10.34,R2=0.211,P=0.005). Conclusion The foveal ONL thickness is increased in glaucomatous eyes.The alteration of foveal ON L thickness is associated with the severity of the disease. Key words: Glaucoma; Photoreceptor; Optical coherence tomography

Effects of Huoxue huayu decoction on expression of retinal glutamate transporter in acute ocular hypertension of rats

Background Hypertension,ischemia and hypoxia induce the increase of glutamate level in eye tissue and furthermore produce excitatory damage and apoptosis of retinal ganglion cells(RGCs).At present,the study on the protection of traditional Chinese medicine on glutamate-induced retinal excitatory damage is lack.objective Present study was to explore the protective effects of Huoxue huayu decoction,a Chinese herbal recipe,on RGCs in acute ocular hypertension model. Methods Fony-five healthy clean Wistar rats were divided into three groups randomly.The acute ocular hypertension models were established in 40 Wistar rats by injecting the normal saline solution into the anterior chamber to elevate the intraocular pressure for 60 minutes.Huoxue huayu decoction of 4 ml was administered intragastrically once per day in 20 model rats.Other matched 5 normal Wistar rats served as normal control group.The rats were sacrificed on 1,3,7 and 14 days after modeling and the retinas were isolated for the histopathologieal and uhrastructure examination.Expression of glutamate transporter in the retina of acute ocular hypertension and normal rat retina were detected using quantitative real-time polymerase chain reaction.The utilization of animals followed the Association for Research in vision and Ophthalmology. Results After acute ocular hypertension.the retina thickness attenuated and the numbers of RGCs decreased under the light microscope in 1,3,7 and 14 days after modeling in comparison with normal control rats.The degradation of the organelle and edema as well as changes of cell nuclei were seen in model rats under the transmission electron microscopy.The expression of glutamate transporter mRNA in model group and glutamate transporter group was rapidly elevated in the first day (P 0.05).Conclusion Huoxue huayu decoction can protect the retina against RGCs damage in the acute ocular hypertension by elevating the expression of glutamate transporters in retina. Key words: Huoxue huayu decoction; Glutamate transporter; intraocular pressure; Retinal ganglion cell

The Comparative Protective Effects of Ganoderma Spores Lipid and Fish Oil on N‐Methyl‐N‐Nitrosourea‐Induced Photoreceptor Cell Lesion in Rats

Purpose. To compare Ganoderma spores lipid (GSL) and fish oil (FO) in inhibiting retinal photoreceptor cell lesions induced by N-methyl-N-nitrosourea (MNU) in rats. Methods. 120 rats were untreated (normal control, NC group) or treated with a single intraperitoneal injection of 40 mg/kg MNU (MNU group) then treated with GSL (GSL group) or FO (FO group). Eyes were obtained at 1, 3, 5, 7, and 10 days. Results. Light microscopy assay demonstrated that GSL and FO alleviated rat retinal photoreceptor cell damage (GSL and FO versus MNU group P < .001) similarly (GSL versus FO group P = .980). Electron microscopy confirmed that GSL and FO reversed damage to photoreceptor segments and photoreceptor cell nuclei. GSL-treated rats showed significantly elevated a-wave and b-wave amplitudes over MNU group (P < .05) but less than NC group (P < .05) and not significantly different from FO group (P > .05). Conclusion. GSL, like FO, alleviates rat retinal photoreceptor cell damage induced by MNU.

Diarylheptanoid 7-(3,4 dihydroxyphenyl)-5-hydroxy-1-phenyl-(1E)-1-heptene from Curcuma comosa Roxb. protects retinal pigment epithelial cells against oxidative stress-induced cell death

Chronic exposure to oxidative stress causes damage to retinal pigment epithelial cells which may lead to the development of age-related macular degeneration, the major cause of vision loss in humans. Anti-oxidants provide a natural defense against retinal cell damage. The present study was designed to evaluate the potential anti-oxidant activity and protective effect of two diarylheptanoids isolated from a medicinal herb Curcuma comosa; 7-(3,4 dihydroxyphenyl)-5-hydroxy-1-phenyl-(1E)-1-heptene (compound A), and 1,7-diphenyl-4(E),6(E)-heptadien-3-ol (compound B) against oxidative stress (H 2O 2)-induced human retinal pigment epithelial (APRE-19) cell death. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay indicated that the anti-oxidant activity (IC 50) of compound A was similar to that of vitamin C. Pre-treatment of ARPE-19 cells with 20 μM compound A for 4 h afforded greater protection against the insult from 500 μM H 2O 2, compared to a similar protection period for compound B. Compound A lowered H 2O 2-induced lipid peroxidation, malondialdehyde formation and intracellular reactive oxygen species. Furthermore, compound A ameliorated the H 2O 2-induced decrease in anti-oxidant enzyme activities and subsequent apoptotic cell death in ARPE-19 cells in a dose and time-dependent manner. These results suggest that compound A protects ARPE-19 cells against oxidative stress, in part, by enhancing several anti-oxidant defense mechanisms. Therefore, compound A may have therapeutic potential for diseases associated with oxidative stress, particularly degenerative retinal diseases.

Crocetin prevents retinal degeneration induced by oxidative and endoplasmic reticulum stresses via inhibition of caspase activity

Crocetin is a carotenoid that is the aglicone of crocin, which are found in saffron stigmas ( Crocus sativus L.) and gardenia fruit ( Gardenia jasminoides Ellis). In this study, we investigated the effects of crocetin on retinal damage. To examine whether crocetin affects stress pathways, we investigated intracellular oxidation induced by reactive oxygen species, expression of endoplasmic reticulum (ER) stress-related proteins, disruption of the mitochondrial membrane potential (ΔΨ m), and caspases activation. In vitro, we employed cultured retinal ganglion cells (RGC-5, a mouse ganglion cell-line transformed using E1A virus). Cell damage was induced by tunicamycin or hydrogen peroxide (H 2O 2) exposure. Crocetin at a concentration of 3 μM showed the inhibitory effect of 50–60% against tunicamycin- and H 2O 2-induced cell death and inhibited increase in caspase-3 and -9 activity. Moreover, crocetin inhibited the enzymatic activity of caspase-9 in a cell-free system. In vivo, retinal damage in mice was induced by exposure to white light at 8000 lx for 3 h after dark adaptation. Photoreceptor damage was evaluated by measuring the outer nuclear layer thickness at 5 days after light exposure and recording the electroretinogram (ERG). Retinal cell damage was also detected with Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining at 48 h after light exposure. Crocetin at 100 mg/kg, p.o. significantly inhibited photoreceptor degeneration and retinal dysfunction and halved the expression of TUNEL-positive cells. These results indicate that crocetin has protective effects against retinal damage in vitro and in vivo, suggesting that the mechanism may inhibit increase in caspase-3 and -9 activities after retinal damage.

Systemic administration of a free radical scavenger, edaravone, protects against light-induced photoreceptor degeneration in the mouse retina

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger, is used for the clinical treatment of acute cerebral infarction. In this study, we investigated the protective effects of edaravone against light-induced retinal damage in the mouse. Retinal damage in the mouse was induced by exposure to white light at 8000 lx for 3 h after dark adaptation. Photoreceptor damage was evaluated by measuring the outer nuclear layer thickness at 5 days after the light exposure and recording the electroretinogram (ERG). Retinal cell damage was also detected by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and the expression of 8-hydroxy-2-deoxyguanosine (8-OHdG) and the phosphorylation of mitogen-activated protein kinases (MAPKs) such as extracellular signal regulated protein kinases (ERK), c-Jun N-terminal kinases (JNK), and p38 were analyzed in the retinal samples by immunohistochemistry and immunoblotting. According to evaluation of outer nuclear layer thickness, 3 mg/kg, i.p. of edaravone and 1 mg/kg. i.v. of edaravone significantly protected against light-induced photoreceptor degeneration at 5 days after exposure to light. In ERG measurement, 3 mg/kg, i.p. of edaravone inhibited retinal dysfunction at 5 days after exposure to light. In addition, 3 mg/kg, i.p. of edaravone decreased the numbers of TUNEL-positive cells, 8-OHdG, phosphorylated JNK, and phosphorylated p38, but not that of phosphorylated ERK, in the whole retina at 6 h after light exposure. These findings suggest that oxidative stress plays a pivotal role in light-induced retinal damage and that systemic administration of edaravone may slow the progression of photoreceptor degeneration.

Comparison of retinal thickness and fundus-related microperimetry with visual acuity in uveitic macular oedema

Macular oedema is a common complication and vision-limiting factor in uveitis. The aim of this study was to compare retinal thickness as measured by optical coherence tomography and photoreceptor function as measured by fundus-related microperimetry with respect to their correlation with visual acuity. Prospective observational monocentre study. Thirty-one patients (53 eyes) with endogenous uveitis and fluorescein angiographically confirmed macular oedema were evaluated. Foveal thickness was analysed using spectral-domain (Spectralis(TM) ; Heidelberg Engineering, Heidelberg, Germany) OCT and retinal sensitivity was assessed using fundus-related microperimetry (MP1; Nidek Technologies, Padova, Italy). All findings were correlated with best-corrected visual acuity (BCVA). Foveal thickness was correlated with BCVA [p = 0.005, r = 0.38, 95% confidence interval (CI) 0.12-0.59]. For microperimetry measurements, a negative correlation with logMAR visual acuity was found. Fixation abnormalities were not associated with poor visual acuity, increased foveal thickness or retinal sensitivity. In eyes with cystoid changes in the outer plexiform and inner nuclear layer, foveal thickness was increased (p < 0.0001). Epiretinal membrane formation was present in 70%. In these eyes, foveal thickness was significantly increased (p = 0.003) and visual acuity was worse (p = 0.08). Foveal thickness and fundus-related microperimetry were correlated with visual acuity. Cystoid changes in the outer plexiform and inner nuclear layer and the presence of epiretinal membrane were associated with poor visual acuity. Fixation abnormalities were not associated with poor visual acuity.

A Novel Calpain Inhibitor, ((1S)-1-((((1S)-1-Benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic Acid 5-Methoxy-3-oxapentyl Ester (SNJ-1945), Reduces Murine Retinal Cell Death In Vitro and In Vivo

We examined whether ((1S)-1-((((1S)-1-benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic acid 5-methoxy-3-oxapentyl ester (SNJ-1945), a new orally available calpain inhibitor, might reduce retinal cell death in vivo and/or in vitro. Retinal cell damage was induced in vivo in mice by intravitreal injection of N-methyl-d-aspartate (NMDA), and SNJ-1945 was intraperitoneally or orally administered twice. NMDA-induced calpain activity (measured as the cleaved products of alpha-spectrin) and its substrate, p35 (a neuron-specific activator for cyclin-dependent kinase 5), in the retina were examined by immunoblotting. In RGC-5 (a rat retinal ganglion cell line) cell culture, cell damage was induced by a 4-h oxygen-glucose deprivation (OGD) treatment followed by an 18-h reoxygenation period. In mouse retinas, SNJ-1945 (30 or 100 mg/kg i.p., 100 or 200 mg/kg p.o.) significantly inhibited the cell loss in the ganglion cell layer (GCL) and the thinning of the inner plexiform layer induced by NMDA. Furthermore, the number of positive cells for terminal deoxynucleotidyl transferase dUTP nick-end labeling was significantly reduced in the GCL and the inner nuclear layer of retinas treated with SNJ-1945 compared with vehicle-treated retinas 24 h after NMDA injection. Levels of cleaved alpha-spectrin products increased and p35 decreased 6 h after NMDA injection or later, and their effects were attenuated by SNJ-1945. In vitro, SNJ-1945 (10 and 100 muM) inhibited the OGD stress-induced reduction in cell viability. In conclusion, SNJ-1945 may afford valuable neuroprotection against retinal diseases, because it was effective against retinal damage both in vitro and in vivo. Our results also indicate that calpain activation and subsequent p35 degradation may be involved in the mechanisms underlying retinal cell death.

RETRACTED: PEDF prevents reactive oxygen species generation and retinal endothelial cell damage at high glucose levels

Oxidative stress is associated with the development of retinopathy in diabetes; dietary supplementations of multi-antioxidants have no beneficial effects clinically. An antioxidant which could specifically target pathogenesis of diabetic retinopathy is the need of the hour. Pigment epithelium-derived factor is a potent, endogenously produced, multifunctional factor (neurotrophic, anti-angiogenic, anti-inflammatory etc.,) in the eye which recently was also shown to possess anti-oxidative action. However, its anti-oxidative effect against high glucose-induced oxidative stress in retinal endothelial cells has not been investigated. Here, we examined its anti-oxidative effect on cell morphology, survival, reactive oxygen species generation, lipid peroxidation, antioxidant status and caspase-3 activation under high glucose conditions in bovine retinal endothelial cells (BRECs). Cells grown at 33 mM glucose in the presence of PEDF at concentrations 10-50 nM did not exhibit shrinkage. Pigment epithelium-derived factor inhibited the high glucose-induced rise in reactive oxygen species generation and lipid peroxidation. In these cells, reduced glutathione levels and mitochondrial and superoxide dismutase activities increased markedly while reactive oxygen species generation decreased significantly in presence of PEDF as compared with cells grown in the absence of PEDF under high glucose conditions (10-20 nM, *p < 0.01&**p < 0.001; 30-50 nM, ***p < 0.0001). Our results suggest that pigment epithelium-derived factor has an anti-oxidant effect in bovine retinal endothelial cells at a high glucose level. The action of pigment epithelium-derived factor not only varies with the cell type but also depends on its concentration and environmental conditions. Therefore, further studies are required to determine if pigment epithelium-derived factor might constitute a preventive and/or a curative treatment for retinal neovascularization.

Effects of maternal phenylketonuria on the development of the offspring's eye

AbstractPhenylketonuria (PKU) is an autosomal recessive disease caused by phenylalanine‐4‐hydroxylase (P‐4‐H) deficiency, which is a liver‐specific enzyme that catalyzes the hydroxylation of l‐phenylalanine (Phe) to l‐tyrosine (Tyr). The deficiency of this enzyme leads to the accumulation of Phe in the tissues and plasma of patients. Among the clinical symptoms of this disease are mental retardation and other neurological features. The mechanisms of retinal cell damage are still poorly understood. In order to evaluate the damage in offspring of PKU mothers, fifty pregnant rats were used and arranged into two main groups, i.e., a control group and a group consisting of rats with experimentally induced PKU. Induction of PKU was carried out by daily intragastrical administration of 30 mg DL–alpha methylphenylalanine/150 g b.w. plus 60 mg/kg b.w. Phe at 12 h intervals throughout pregnancy till parturition as well as throughout lactation period till 14 days post‐partum. Morphometric analysis of retina in 1, 7 and 14‐day‐old pups of PKU mothers revealed a marked reduction of retinal thickness. Histological observations revealed numerical reduction of pigment cells. Apoptic cell death of retinal pigment cells, and of nuclear layer and ganglionic cells were observed. The nerve layer showed apparent vacuolar degeneration. At transmission electron microscope (TEM) level, pigment epithelium showed distortion of apical microvilli, vacuolation of cytoplasm and reduction of cytoplasm organelles. The Brush's membrane showed apparent thickening. In 7‐day‐old pups of PKU mothers, photoreceptor inner segment showed apparent degeneration. In 14‐day‐old pups of PKU mothers, both the inner and outer photoreceptor segment were degenerated and the stacked membrane of the outer segment appeared vacuolated and degenerated.

COMBINATION ANGIOSTATIC THERAPIES

One of the most important obstacles to combining pharmaceutical agents to treat ocular diseases is the risk of physiochemical reactions. In intraocular administration, these reactions may produce incompatibility, instability, or both. They may change the nature of drug activity, and they may threaten normal cellular function, resulting in lens opacities, corneal toxicity, retinal cell damage, or other adverse outcomes. Although many medications have demonstrated efficacy or have shown promise when administered intravitreally, including antifungals, nonsteroidal antiinflammatory drugs, anti-tumor necrosis factor-alpha agents, mammalian target of rapamycin inhibitors, metalloproteinase inhibitors, antiviral agents, antineoplastic compounds, and antivascular endothelial growth factor therapies, these have been typically tested as single agents. The potential for these agents to be combined will be largely determined by their physiochemical compatibility.

Dietary Supplements Protect Retinal Pigment Epithelial Cells From Hyperglycemic Damage

ObjectiveTo determine the protective effects of wolfberry on hyperglycemic damage in retinal pigment epithelial cells.MethodsHuman retinal pigment epithelial ARPE‐19 cells were treated with 36 mM glucose for 60 hrs, with or without 1 mg/mL crude wolfberry extracts. PKCgamma activation was determined by enzyme activity assay. Gap junction activity was determined by scrape loading/dye transfer assay. Western blotting was used to determined activation of AMP‐activated protein kinase (AMPK), acetyl‐CoA carboxylase (ACC), and apoptosis‐inducing factor (AIF).ResultsHigh glucose‐activated PKCgamma phosphorylated Connexin 50 (Cx50) and Cx57 on serines, and subsequently inhibited gap junction activity. Wolfberry extracts abolished the effects of high glucose on PKCgamma activation. Application of wolfberry extracts abolished the inhibitory effect of high glucose on AMPK activation, completely restored ACC phosphorylation by AMPK, and inhibited AIF translocation out of mitochondria.ConclusionsHigh glucose‐induced AIF‐dependent apoptosis would be protected by application of wolfberry extracts through restoration of cellular gap junctional communication and rebalance of cellular energy homeostasis.

Zeaxanthin, a Retinal Carotenoid, Protects Retinal Cells against Oxidative Stress

Purpose: To investigate whether zeaxanthin, the predominant carotenoid pigment of the macular pigments in human retina, provides neuroprotection against retinal cell damage. Methods: We used in vitro cultured retinal ganglion cells (RGCs), specifically RGC-5, an E1A virus-transformed rat cell line. Cell damage was induced either by a 24-hr exposure to hydrogen peroxide (H2O2) or by serum deprivation. Cell viability was measured using the tetrazolium salt, WST-8. The scavenging capacity of zeaxanthin for H2O2, superoxide anion radical (O2·−), and hydroxyl radical (HO ·) was measured using a radical scavenging capacity assay with CM-H2DCFDA, a reactive oxygen species (ROS)-sensitive probe. Results: When added to RGC-5 cell cultures, 0.1, 10, and 1 μM zeaxanthin scavenged the free radicals induced by H2O2, O2·−, and HO ·, respectively. In addition, pretreatment with 1 μ M zeaxanthin permitted scavenging of staurosporine-induced intracellular radicals. Zeaxanthin also inhibited the neurotoxicity induced by H2O2 or serum deprivation and scavenged the intracellular radicals induced by H2O2 or serum deprivation. Conclusions: Our results suggest that zeaxanthin provides effective protection against oxidative stress-induced retinal cell damage.

Genotoxic Effects of Carotenoid Breakdown Products in Human Retinal Pigment Epithelial Cells

Purpose: To investigate the genotoxic effects of lutein (LBP) and β -carotene breakdown products (β -apo-8-carotenal, BA8C) and the preventive role of GSH in human retinal pigment epithelial cells (ARPE-19). Methods: LBP- and BA8C-induced DNA damage in human retinal pigment epithelial cells (ARPE-19) was determined by comet assay. The DNA damage was quantified by the image analysis system using Comet Score™ software. ARPE-19 cell viability was determined by CellTiter 96 AQueous one-solution cell proliferation assay kit. Intracellular GSH levels were measured by Ellman's reagent. Results: Incubation of serum-starved ARPE-19 cells with LBP and BA8C caused significant DNA damage in a dose- and time-dependent manner. The DNA damage and cell death incurred by LBP and BA8C were significantly prevented by N-acetylcysteine (NAC) but not by α -tocopherol + ascorbic acid (T + AA). Furthermore, BSO-induced GSH depletion in ARPE-19 cells caused a significant elevation in LBP- and BA8C-induced DNA damage, whereas increased GSH levels in ARPE-19 cells prevented it. Conclusions: Our results suggest that breakdown products of dietary carotenoids could be genotoxic in ARPE-19 cells. LBP-induced genotoxic effects could worsen oxidative stress. The intracellular GSH pool in ARPE-19 cells might play a critical role in carotenoid breakdown products-induced genotoxicity.

A Na+/Ca2+ exchanger isoform, NCX1, is involved in retinal cell death after N‐methyl‐D‐aspartate injection and ischemia–reperfusion

We investigated the expression of Na(+)/Ca(2+) exchanger (NCX) and the functional role of NCX in retinal damage by using NCX1-heterozygous deficient mice (NCX1(+/-)) and SEA0400 (2-[4-[(2,5-difluorophenyl)methoxy] phenoxy]-5-ethoxyaniline), a selective NCX inhibitor in vivo. We also examined the role of NCX in oxygen-glucose deprivation (OGD) stress with a retinal ganglion cell line (RGC-5) cell culture in vitro. The expression of NCX1 was confirmed and entirely localized in retina by immunoblotting and immunohistochemistry, respectively. NCX1(+/-) mice possessed significant protection against retinal damage induced by intravitreal injection of N-methyl-D-aspartate (NMDA). SEA0400 at 3 and 10 mg/kg significantly reduced NMDA- or high intraocular pressure-induced retinal cell damage in mice. Furthermore, SEA0400 reduced the number of TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling)-positive cells and the expression of phosphorylated mitogen-activated protein kinases (ERK1/2, JNK, p38) induced by NMDA injection. In RGC-5, SEA0400 at 0.3 and 1 microM significantly inhibited OGD-induced cell damage. OGD-induced cell damage was aggravated by ouabain (a Na(+),K(+)-ATPase inhibitor) at 100 microM, and this increased damage was significantly reduced by SEA0400 at 1 microM. In conclusion, these results suggest that NCX1 may play a role in retinal cell death induced by NMDA and ischemia-reperfusion.

Effect of an Inducer of BiP, a Molecular Chaperone, on Endoplasmic Reticulum (ER) Stress-Induced Retinal Cell Death

The effect of a preferential inducer of 78 kDa glucose-regulated protein (GRP78)/immunoglobulin heavy-chain binding protein (BiP; BiP inducer X, BIX) against tunicamycin-induced cell death in RGC-5 (a rat ganglion cell line), and also against tunicamycin- or N-methyl-D-aspartate (NMDA)-induced retinal damage in mice was evaluated. In vitro, BiP mRNA was measured after BIX treatment using semi-quantitative RT-PCR or real-time PCR. The effect of BIX on tunicamycin (at 2 microg/mL)-induced damage was evaluated by measuring the cell-death rate and CHOP protein expression. In vivo, BiP protein induction was examined by immunostaining. The retinal cell damage induced by tunicamycin (1 microg) or NMDA (40 nmol) was assessed by examining ganglion cell layer (GCL) cell loss, terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) staining, and CHOP protein expression. In vitro, BIX preferentially induced BiP mRNA expression both time- and concentration-dependently in RGC-5 cells. BIX (1 and 5 microM) significantly reduced tunicamycin-induced cell death, and BIX (5 microM) significantly reduced tunicamycin-induced CHOP protein expression. In vivo, intravitreal injection of BIX (5 nmol) significantly induced BiP protein expression in the mouse retina. Co-administration of BIX (5 nmol) significantly reduced both the retinal cell death and the CHOP protein expression in GCL induced by intravitreal injection of tunicamycin or NMDA. These findings suggest that this BiP inducer may have the potential to be a therapeutic agent for endoplasmic reticulum (ER) stress-induced retinal diseases.