Light-induced Retinal Damage Research Articles

Upregulation of SYF2 Relates to Retinal Ganglion Cell Apoptosis and Retinal Glia Cell Proliferation After Light-Induced Retinal Damage.

SYF2 (SYF2 homologue, RNA splicing factor), also known as CCNDBP1-interactor or p29, belongs to the SYF2 family, which are involved in pre-mRNA splicing and cell cycle progression. Accumulating evidences demonstrate that SYF2 exerted multiple effects including pro-apoptosis, cell differentiation, and glial activation in the pathogenesis of various experimental central nervous system (CNS) diseases. However, SYF2 expression and functions in the retina are still with limited acquaintance. To investigate whether SYF2 was involved in retinal degeneration, we performed a light-induced retinal damage model in adult rats. The SYF2 protein expression was dramatically upregulated after retinal damage. Besides that, SYF2 localized in the retinal ganglion cell (RGC) layer (GCL), inner unclear layer (INL), and outer nuclear layer (ONL) after light exposure. In addition, the expression of cyclin D1, CDK4, and active caspase-3 was parallel with SYF2. We also found the co-localization of SYF2 with active caspase-3, PCNA, and CD11b. Collectively, SYF2 might participate in RGC apoptosis and retinal glia cell proliferation after light-induced retinal damage.

Effect of a sigma-1 receptor agonist, cutamesine dihydrochloride (SA4503), on photoreceptor cell death against light-induced damage

Cutamesine dihydrochloride is an agonist of sigma-1 receptor, which is a ligand-operated receptor chaperone at the mitochondrion-associated endoplasmic reticulum (ER) membrane. ER stress plays a pivotal role in light irradiation-induced retinal damage. In the present study, we examined whether cutamesine is effective against experimental degenerative retinal damages in vitro and in vivo. The effects of cutamesine against white light-induced retinal photoreceptor damage were evaluated in vitro by measuring cell death. The expression of sigma-1 receptor after the light exposure was examined by immunoblot analysis. The disruption of the mitochondrial membrane potential and caspase-3/7 activation after excessive light exposure were also examined. In addition, retinal damage in mice induced by irradiation to white light was evaluated using histological staining and electroretinography. Cutamesine reduced the cell death rate induced by light exposure, and the protective effect was prevented by N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(dimethylamino)ethylamine (BD-1047) dihydrobromide, a sigma-1 receptor antagonist. Sigma-1 receptor expression was decreased by light exposure, and cutamesine suppressed the decreased expression of sigma-1 receptor protein. Cutamesine also reduced the mitochondrial damage and reduced the elevated level of caspase 3/7 activity; this effect was attenuated by BD-1047. In in vivo studies, cutamesine suppressed the light-induced retinal dysfunction and thinning of the outer nuclear layer in the mouse retina. These findings indicate that cutamesine protects against retinal cell death in vitro and in vivo by the agonistic effect of sigma-1 receptor. Therefore, sigma-1 receptor may have a potential as a therapeutic target in retinal diseases mediated by photoreceptor degeneration.

Expression of RBMX in the light-induced damage of rat retina in vivo.

RNA-binding motif protein, X-linked (RBMX) is a 43 kDa nuclear protein in the RBM family and functions on alternative splicing of RNA. The gene encoding RBMX is located on chromosome Xq26. To investigate whether RBMX is involved in retinal neuron apoptosis, we performed a light-induced retinal damage model in adult rats. Western blotting analysis showed RBMX gradually increased, reached a peak at 12 h and then declined during the following days. The association of RBMX in retinal ganglion cells (RGCs) with light exposure was found by immunofluorescence staining. The injury-induced expression of RBMX was detected in active caspase-3 and TUNEL positive cells. We also examined the expression profiles of active caspase-3, bcl-2 and Bax, whose changes were correlated with the expression profiles of RBMX. To summarize, we uncovered the dynamic changes of RBMX in the light-induced retinal damage model for the first time. RBMX might play a significant role in the degenerative process of RGCs after light-induced damage in the retina.

17β-estradiol ameliorates light-induced retinal damage in Sprague-Dawley rats by reducing oxidative stress.

Oxidative stress is considered as a major cause of light-induced retinal neurodegeneration. The protective role of 17β-estradiol (βE2) in neurodegenerative disorders is well known, but its underlying mechanism remains unclear. Here, we utilized a light-induced retinal damage model to explore the mechanism by which βE2 exerts its neuroprotective effect. Adult male and female ovariectomized (OVX) rats were exposed to 8,000 lx white light for 12 h to induce retinal light damage. Electroretinogram (ERG) assays and hematoxylin and eosin (H&E) staining revealed that exposure to light for 12 h resulted in functional damage to the rat retina, histological changes, and retinal neuron loss. However, intravitreal injection (IVI) of βE2 significantly rescued this impaired retinal function in both female and male rats. Based on the level of malondialdehyde (MDA) production (a biomarker of oxidative stress), an increase in retinal oxidative stress followed light exposure, and βE2 administration reduced this light-induced oxidative stress. Quantitative reverse-transcriptase (qRT)-PCR indicated that the messenger RNA (mRNA) levels of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (Gpx) were downregulated in female OVX rats but were upregulated in male rats after light exposure, suggesting a gender difference in the regulation of these antioxidant enzyme genes in response to light. However, βE2 administration restored or enhanced the SOD and Gpx expression levels following light exposure. Although the catalase (CAT) expression level was insensitive to light stimulation, βE2 also increased the CAT gene expression level in both female OVX and male rats. Further examination indicated that the antioxidant proteins thioredoxin (Trx) and nuclear factor erythroid 2-related factor 2 (Nrf2) are also involved in βE2-mediated antioxidation and that the cytoprotective protein heme oxygenase-1 (HO-1) plays a key role in the endogenous defense mechanism against light exposure in a βE2-independent manner. Taken together, we provide evidence that βE2 protects against light-induced retinal damage via its antioxidative effect, and its underlying mechanism involves the regulation of the gene expression levels of antioxidant enzymes (SOD, CAT, and Gpx) and proteins (Trx and Nrf2). Our study provides conceptual evidence in support of estrogen replacement therapy for postmenopausal women to reduce the risk of age-related macular degeneration.

Protective effects of bilberry and lingonberry extracts against blue light-emitting diode light-induced retinal photoreceptor cell damage in vitro

BackgroundBlue light is a high-energy or short-wavelength visible light, which induces retinal diseases such as age-related macular degeneration and retinitis pigmentosa. Bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea) contain high amounts of polyphenols (anthocyanins, resveratrol, and proanthocyanidins) and thus confer health benefits. This study aimed to determine the protective effects and mechanism of action of bilberry extract (B-ext) and lingonberry extract (L-ext) and their active components against blue light-emitting diode (LED) light-induced retinal photoreceptor cell damage.MethodsCultured murine photoreceptor (661 W) cells were exposed to blue LED light following treatment with B-ext, L-ext, or their constituents (cyanidin, delphinidin, malvidin, trans-resveratrol, and procyanidin B2). 661 W cell viability was assessed using a tetrazolium salt (WST-8) assay and Hoechst 33342 nuclear staining, and intracellular reactive oxygen species (ROS) production was determined using CM-H2DCFDA after blue LED light exposure. Activation of p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor-kappa B (NF-κB), and LC3, an ubiquitin-like protein that is necessary for the formation of autophagosomes, were analyzed using Western blotting. Caspase-3/7 activation caused by blue LED light exposure in 661 W cells was determined using a caspase-3/7 assay kit.ResultsB-ext, L-ext, NAC, and their active components improved the viability of 661 W cells and inhibited the generation of intracellular ROS induced by blue LED light irradiation. Furthermore, B-ext and L-ext inhibited the activation of p38 MAPK and NF-κB induced by blue LED light exposure. Finally, B-ext, L-ext, and NAC inhibited caspase-3/7 activation and autophagy.ConclusionsThese findings suggest that B-ext and L-ext containing high amounts of polyphenols exert protective effects against blue LED light-induced retinal photoreceptor cell damage mainly through inhibition of ROS production and activation of pro-apoptotic proteins.

Angiotensin II type 1 receptor blockade suppresses light-induced neural damage in the mouse retina

Exposure to light contributes to the development and progression of retinal degenerative diseases. However, the mechanisms underlying light-induced tissue damage are not fully understood. Here, we examined the role of angiotensin II type 1 receptor (AT1R) signaling, which is part of the renin–angiotensin system, in light-induced retinal damage. Light-exposed Balb/c mice that were treated with the AT1R blockers (angiotensin II receptor blockers; ARBs) valsartan, losartan, and candesartan before and after the light exposure exhibited attenuated visual function impairment, compared to vehicle-treated mice. This effect was dose-dependent and observed across the ARB class of inhibitors. Further evaluation of valsartan showed that it suppressed a number of light-induced retinal effects, including thinning of the photoreceptor cell layer caused by apoptosis, shortening of the photoreceptor cell outer segment, and increased levels of reactive oxygen species (ROS). The role of ROS in retinal pathogenesis was investigated further using the antioxidant N-acetyl-l-cysteine (NAC). Treatment of light-exposed mice with NAC before the light exposure suppressed the visual function impairment and photoreceptor cell histological changes due to apoptosis. Moreover, treatment with valsartan or NAC suppressed the induction of c-fos (a component of the AP-1 transcription factor) and the upregulation of fasl (a proapoptotic molecule whose transcript is regulated downstream of AP-1). Our results suggest that AT1R signaling mediates light-induced apoptosis, by increasing the levels of ROS and proapoptotic molecules in the retina. Thus, AT1R blockade may represent a new therapeutic approach for preventing light-induced retinal neural tissue damage.

Very Low Risk of Light-Induced Retinal Damage During Boston Keratoprosthesis Surgery

The aim of this study was to assess the possibility of light damage to the retina by a surgical microscope during implantation of a Boston Keratoprosthesis (B-KPro) in rabbits. The retinal irradiance from a Zeiss OPMI Lumera S7 operating microscope was measured at the working distance (16.5 cm). Light transmittance through an isolated B-KPro was measured. A B-KPro was implanted into 1 eye of 12 rabbits with the optic covered during the procedure. The operated eyes were then continuously exposed to a fixed light intensity under the microscope for 1 hour. Fluorescein angiography was carried out on days 2 and 9 postsurgery, after which the animals were euthanized. Further, we compared the potential of these retinal exposures to well-accepted light safety guidelines applicable to humans. Light transmittance of B-KPro revealed a blockage of short wavelengths (<390 nm) and of long wavelengths (1660-1750 nm) of light. In addition, the surgical microscope filtered a part of the blue, ultraviolet, and infrared wavelengths. Neither fluorescein angiography nor a histological examination showed any morphological retinal changes in our rabbits. Moreover, the retinal exposures were well below the safety limits. Modern surgical microscopes have filters incorporated in them that block the most damaging wavelengths of light. The B-KPro is made of 100% poly(methyl methacrylate), which makes it in itself a blocker of short wavelengths of light. No damage could be demonstrated in the animal study, and the retinal exposures were well below the safety limits. Together, these results suggest that light exposures during B-KPro surgery present a low risk of photochemical damage to the retina.

Protective Effect of SUN N8075, a Free Radical Scavenger, against Excessive Light-Induced Retinal Damage in Mice

Although dry age-related macular degeneration (AMD) is one of the major causes of blindness, no effective therapies are developed. In this study, we investigated the effects of SUN N8075, a radical scavenger with neuroprotective properties, against light-induced retinal damage used as the model of dry AMD in mice. After dark adaption for 24 h, we exposed the mice at 8000 lx for 3 h. We evaluated the retinal damage by recording the electroretinagram (ERG) and measuring the thickness of outer nuclear layer (ONL) at 5 d after the light exposure. Retinal apoptotic cells were also detected by terminal deoxynucleotidyl transeferase mediated deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) staining, and the expression of 8-hydroxy-2-deoxyguanosine (8-OHdG) as an index for oxidative stress at 48 h after exposure to light. In ERG measurement, the intraperitoneal administration of SUN N8075 at 30 mg/kg improved the retinal dysfunction induced by the excess light exposure. In the histological evaluation, SUN N8075 inhibited the reduction of ONL thickness. In addition, SUN N8075 decreased in both numbers of TUNEL- and 8-OHdG-positive cells in ONL. These findings suggest that the systemic administration of SUN N8075 has protective effects on excess light-induced photoreceptor degeneration, via inhibition of oxidative stress.

Spatiotemporal Changes in NFATc4 Expression of Retinal Ganglion Cells After Light-Induced Damage

Nuclear factor of activated T cells, cytoplasmic 4 (NFATc4) is one of the four members of the NFAT family, which were described first as essential components of T cells activation and lately as important regulators for the initiation and coordination of the immune response, including B cells and natural killer cells. Accumulating evidence has demonstrated that NFATc4 exerted a pro-apoptotic effect in the pathogenesis of various experimental central nervous system diseases by upregulating Fas ligand (FasL) levels. However, the function of NFATc4 in the retina is still with limited acquaintance. To investigate whether NFATc4 is involved in retinal neuron apoptosis, we performed a light-induced retinal damage model in adult rats. A significant upregulation of NFATc4 was detected in the retina after light-induced damage by using Western blotting and reverse transcriptase PCR (RT-PCR). Besides this, NFATc4 was observed to be localized mainly in the retinal ganglion cells (RGCs). In addition, the expression patterns of active caspase-3, active caspase-8, and FasL were parallel with that of NFATc4. We also found the co-localization of NFATc4 with active caspase-3 and FasL in RGCs after light exposure. Collectively, we hypothesized that NFATc4 might participate in RGCs apoptosis by upregulating FasL levels.

Progranulin, a Major Secreted Protein of Mouse Adipose-Derived Stem Cells, Inhibits Light-Induced Retinal Degeneration

Adipose tissue stromal vascular fraction contains mesenchymal stem cells, which show protective effects when administered to damaged tissues, mainly through secreted trophic factors. We examined the protective effects of adipose-derived stem cells (ASCs) and ASC-conditioned medium (ASC-CM) against retinal damage and identified the neuroprotective factors in ASC-CM. ASCs and mature adipocytes were isolated from mouse subcutaneous tissue. ASCs were injected intravitreally in a mouse model of light-induced retinal damage, and ASC injection recovered retinal function as measured by electroretinogram and inhibited outer nuclear layer, thinning, without engraftment of ASCs. ASC-CM and mature adipocyte-conditioned medium were collected after 72 hours of culture. In vitro, H2O2- and light-induced cell death was reduced in a photoreceptor cell line with ASC-CM but not with mature adipocyte-conditioned medium. In vivo, light-induced photoreceptor damage was evaluated by measurement of outer nuclear layer thickness at 5 days after light exposure and by electroretinogram recording. ASC-CM significantly inhibited photoreceptor degeneration and retinal dysfunction after light exposure. Progranulin was identified as a major secreted protein of ASCs that showed protective effects against retinal damage in vitro and in vivo. Furthermore, progranulin phosphorylated extracellular signal-regulated kinase, cAMP response element binding protein, and hepatocyte growth factor receptor, and protein kinase C signaling pathways were involved in the protective effects of progranulin. These findings suggest that ASC-CM and progranulin have neuroprotective effects in the light-induced retinal-damage model. Progranulin may be a potential target for the treatment of the degenerative diseases of the retina.

Upregulation of CREM-1 Relates to Retinal Ganglion Cells Apoptosis After Light-Induced Damage In Vivo

Previous studies have shown activation of cyclic AMP response element-binding protein (CREB) family is involved in the retinal ganglion cells (RGCs) protection. However, the function of cyclic AMP response element modulator-1 (CREM-1), one member of the CREB family, is still with limited acquaintance. To investigate whether CREM-1 is involved in RGCs death, we performed a light-induced retinal damage model in adult rats. Upregulation of CREM-1 was observed in retina after light-induced damage by performing western blot. Immunofluorescent labeling indicated that upregulated CREM-1 was localized mainly in the RGCs. We also investigated co-localization of CREM-1 with active-caspase-3 and TUNEL (apoptotic markers) in the retina after light-induced damage. In addition, the expression patterns of B cell lymphoma/leukemia-2 and Bcl-2 associated X protein were parallel with that of CREM-1. Collectively, we hypothesized upregulation of CREM-1 in the retina was associated with RGCs death after light-induced damage.

The Protective Effects of Bilberry and Lingonberry Extracts against UV Light-Induced Retinal Photoreceptor Cell Damage in Vitro

Bilberry extract (B-ext) and lingonberry extract (L-ext) are currently used as health supplements. We investigated the protective mechanisms of the B-ext and L-ext against ultraviolet A (UVA)-induced retinal photoreceptor cell damage. Cultured murine photoreceptor (661W) cells were exposed to UVA following treatment with B-ext and L-ext and their main constituents (cyanidin, delphinidin, malvidin, trans-resveratrol, and procyanidin). B-ext, L-ext, and constituents improved cell viability and suppressed ROS generation. Phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and protein kinase B (Akt) were analyzed by Western blotting. B-ext and cyanidin inhibited phosphorylation of p38 MAPK, and B-ext also inhibited phosphorylation of JNK by UVA. L-ext, trans-resveratrol, and procyanidin alleviated the reduction of phosphorylated Akt levels by UVA. Finally, a cotreatment with B-ext and L-ext showed an additive effect on cell viability. Our findings suggest that both B-ext and L-ext endow protective effects against UVA-induced retinal damage.

The potential neuroprotective effect of human adipose stem cells conditioned medium against light-induced retinal damage

Human adipose-derived stem cells (hASCs) are present in adult adipose tissue and have been reported to secrete various factors that have neuroprotective effects. In the present study, we examined whether hASC-conditioned medium (hASC-CM) was effective against experimental degenerative retinal disease. Mature adipocytes (MAs) and hASCs were isolated from human subcutaneous adipose tissue. The isolated hASCs were identified based on their capacity for bone and neural differentiation. The effects of hASC-CM against tunicamycin-, H2O2-, and light-induced retinal photoreceptor damage were evaluated in vitro by measuring cell death. Moreover, we identified various factors present in hASC-CM using antibody arrays. Retinal damage induced in mice by exposure to white light was studied in vivo, and photoreceptor damage was evaluated according to the thickness of the outer nuclear layer and electroretinography results. In addition, the effect of hASC-CM on Akt phosphorylation at Ser473 was confirmed by western blotting. Finally, the effects of the secreted proteins identified in the hASC-CM on light-induced damage were evaluated in vivo. Isolated hASCs differentiated to osteocytes and neurons. hASC-CM protected against tunicamycin-, H2O2-, and light-induced cell death. In addition, hASC-CM inhibited photoreceptor degeneration and retinal dysfunction after exposure to light. Several proteins secreted by hASCs, such as the tissue inhibitor of metalloproteinase-1 (TIMP-1) and the secreted protein acidic and rich in cysteine (SPARC), protected against light-induced damage in vitro and in vivo. The results of the present study showed that hASC-CM has neuroprotective effects against light-induced retinal damage and suggest that hASCs have a therapeutic potential in retinal degenerative diseases via their secreted proteins, without requiring transplantation.

The association of blue light-induced human retinal pigment epithelium cell damage with intercellular free Ca2+ change in vitro

Background Investigating the association of blue light-induced damage of retinal pigmenepithelial (RPE) cellwith intracellulaCa2+ conteniimportanfounderstanding the mechanism of retinal disorders.Objective Thistudy wato establish blue light-induced damage model of human RPE celland explore the relationship between the damage of RPE cell and intracellulaCa2+ content.MethodHuman RPE cellwere cultured and passaged.Cell vitality waassayed by trypan blue staining.Fourth-generation cellwere used in these experiments.The cellwere exposed to blue lighwith an intensity of (2000±500)lx fo3,6,9 o12 hours,and the rate of apoptosiwaassayed by TUNEL to assesthe optimal irradiation time focellcultured.The cellwere then randomized into the withouirradiation group,irradiation only group,nifedipine group,ligh+ nifedipine group,(-) BayK8644 group and ligh+ (-) BayK8644 group.The laseconfocal microscope waused to determine the fluorescence intensity of intracellulafree Ca2+ aan excitation wavelength of 488 nm and an emission wavelength of 505 nm.The cell imagewere analyzed using computesoftware.The differenceof fluorescence intensity among the differengroupwere compared by one-way analysiof variance.ResultTrypan blue staining showed thathe viability of RPE cellwamore than 90％ afteculturing and passaging.No apoptoticell waseen aftelighexposure fo3 hours.However,differennumberof apoptoticellappeared aftelighexposure fo6,9 and 12 hours.The fluorescence intensity of intracellulafree Ca2+ in the nifedipine group wasignificantly lowethan thaof the withouirradiation group othe ligh+ nifedipine group(both aP=0.000).Lasescanning confocal microscopy showed thathe fluorescence intensitieof intracellulafree Ca2+ in the irradiation only group,(-) BayK8644 group,ligh+ (-)BayK8644 group were highethan thaof the withouirradiation group,with statistical significancebetween them(all P=0.000).No significandifferencewere found in the fluorescence intensity of intracellulafree Ca2+ between the ligh+ nifedipine group and withouirradiation group awell abetween the (-)BayK8644 group and the ligh+(-) BayK8644 group(P =0.339,P =0.410).ConclusionThe optical conditionfoblue light-induced RPE cell damage were exposure of blue-ligha(2000± 500) lx fo6 hourand culturing the cellfo24 hours.Blue lighexposure can induce damage of human RPE cellprobably by triggering the increase of intracellulafree Ca2+ concentration. Key words: Light/damage; Retinal pigmented epithelium; Calcium ion/intercellular, free, antagonist,agonist ; Apoptosis

Epigallocatechin-gallate (EGCG) regulates autophagy in human retinal pigment epithelial cells: A potential role for reducing UVB light-induced retinal damage

Autophagy is an intracellular catabolic process involved in protein and organelle degradation via the lysosomal pathway that has been linked in the pathogenesis of age-related macular degeneration (AMD). UVB irradiation-mediated degeneration of the macular retinal pigment epithelial (RPE) cells is an important hallmark of AMD, which is along with the change in RPE autophagy. Thus, pharmacological manipulation of RPE autophagy may offer an alternative therapeutic target in AMD. Here, we found that epigallocatechin-3-gallate (EGCG), a polyphenolic compound from green tea, plays a regulatory role in UVB irradiation-induced autophagy in RPE cells. UVB irradiation results in a marked increase in the amount of LC3-II protein in a dose-dependent manner. EGCG administration leads to a significant reduction in the formation of LC3-II and autophagosomes. mTOR signaling activation is required for EGCG-induced LC3-II formation, as evidenced by the fact that EGCG-induced LC3-II formation is significantly impaired by rapamycin administration. Moreover, EGCG significantly alleviates the toxic effects of UVB irradiation on RPE cells in an autophagy-dependent manner. Collectively, our study reveals a novel role of EGCG in RPE autophagy. EGCG may be exploited as a potential therapeutic reagent for the treatment of pathological conditions associated with abnormal autophagy.

Autophagy Protects the Retina from Light-induced Degeneration

Autophagy is a conserved feature of lysosome-mediated intracellular degradation. Dysregulated autophagy is implicated as a contributor in neurodegenerative diseases; however, the role of autophagy in retinal degeneration remains largely unknown. Here, we report that the photo-activated visual chromophore, all-trans-retinal, modulated autophagosome formation in ARPE19 retinal cells. Increased formation of autophagosomes in these cells was observed when incubated with 2.5 μM all-trans-retinal, a condition that did not cause cell death after 24 h in culture. However, autophagosome formation was decreased at concentrations, which caused cell death. Increased expression of activating transcription factor 4 (Atf4), which indicates the activation of oxidative stress, was recorded in response to light illumination in retinas of Abca4(-/-)Rdh8(-/-) mice, which showed delayed clearance of all-trans-retinal after light exposure. Expression of autophagosome marker LC3B-II and mitochondria-specific autophagy, mitophagy, regulator Park2, were significantly increased in the retinas of Abca4(-/-)Rdh8(-/-) mice after light exposure, suggesting involvement of autophagy and mitophagy in the pathogenesis of light-induced retinal degeneration. Deletion of essential genes required for autophagy, including Beclin1 systemically or Atg7 in only rod photoreceptors resulted in increased susceptibility to light-induced retinal damage. Increased photoreceptor cell death was observed when retinas lacking the rod photoreceptor-specific Atg7 gene were coincubated with 20 μM all-trans-retinal. Park2(-/-) mice also displayed light-induced retinal degeneration. Ultra-structural analyses showed mitochondrial and endoplasmic reticulum impairment in retinas of these model animals after light exposure. Taken together, these observations provide novel evidence implicating an important role of autophagy and mitophagy in protecting the retina from all-trans-retinal- and light-induced degeneration.

Protective effect of anthocyanidin extracts on light-induced retinal functional and structural damage in rat

Background Light leads to the damage of retinal function and structure by promoting the reproduction of radicals and lipid peroxides when retina is exposed to an intense light environment for a long time.It is necessary to study how to protect the retina against light-induced injury in ophthalmology.Objective The aim of this study was to evaluate the effect of anthocyanidin extracts in preventing retinal photic damage.Methods Eighteen clean male Sprague-Dawley (SD) rats were randomly assigned to normal saline group,anthocyanidin group and mixed (hydrogen-rich saline (HRS) + anthocyanidin,1:1 in volume) group and 6 rats for each.The electroretinogram (ERG) with international standardized 5 items was recorded from all the rats before experiment.Normal saline,anthocyanidin extracts or mixed solution of 5 ml/kg were intraperitoneally injected in the three groups,respectively,for consecutive 5 days.Then the diffused light with the luminance intensity of (5000±300)lx was used to irradiate the right eyes of the rats for consecutive 3 hours during 19:00 through 7:00 in a device made by our laboratory,and the left eyes were covered at the same time.The ERG was repeatedly recorded 5 days after light irradiation.The rats were sacrificed at the end of the experiment and retinal sections were prepared for the histopathological examination.The functional and structural changes of retinas were compared among the different groups.The use of the rats followed the Statement of ARVO.Results The differences of rat body weight were not statistically significant among the three groups (before experiment:F =0.472,P =0.841 ; after experiment:F =0.658,P=0.762).No any significant difference was found in scotopic 0.01 ERG b wave,scotopic 3.0 ERG a and b waves,scotopic 3.0 oscillatory potentials,photopic 3.0 ERG b wave and 3.0 flicker P1wave between the left eyes and the right eyes in the three groups before experiment (P＞0.05).The amplitudes of various waves of ERG were significantly declined in the right eyes compared with the left eyes (P＜0.05).The mean differential values of scotopic 0.01 ERG b wave,scotopic 3.0 ERG a and b waves,scotopic 3.0 oscillatory potentials were significantly different(F =4.594,P=0.029; F=3.834,P=0.037; F=12.823,P=0.000; F=3.976,P=0.032),but those in photopic 3.0 ERG b wave were not statistically significant (F =1.488,P =0.259).Compared with the normal saline group,the differential values of scotopic 0.01 ERG b wave,scotopic 3.0 ERG a and b waves,scotopic 3.0 oscillatory potentials were all reduced in the anthocyanidin group and mixed group (P ＜ 0.05).The cells of outer nuclear layer were decreased in the right eyes in the three groups compared with the left eyes,especially around the optic nerve head and the upside of the retina,with significant differences between them (P＜0.05),and those in the anthocyanidin group and mixed group were significantly less than normal saline group (P＜0.05).Conclusions Anthocyanidin has a protective effect on light-induced retinal damage of SD rats.The protective effect of anthocyanidin extracts is similar to the integrated effect of the mixed group. Key words: Anthocyanidin extracts ; Retinal photic damage ; Electroretinogram; Histopathotology

The Protective Effects of a Dietary Carotenoid, Astaxanthin, Against Light-Induced Retinal Damage

Dietary carotenoids exhibit various biological activities, including antioxidative activity. In particular, astaxanthin, a type of carotenoid, is well known as a powerful antioxidant. We investigated whether astaxanthin would protect against light-induced retinal damage. In an in vivo study, ddY male mice were exposed to white light at 8,000 lux for 3 h to induce retinal damage. Five days after light exposure, retinal damage was evaluated by measuring electroretinogram (ERG) amplitude and outer nuclear layer (ONL) thickness. Furthermore, expression of apoptotic cells, 8-hydroxy-deoxyguanosine (8-OHdG), was measured. In an in vitro study, retinal damage was induced by white light exposure at 2,500 lux for 24 h, and propidium iodide (PI)-positive cells was measured and intracellular reactive oxygen species (ROS) activity was examined. Astaxanthin at 100 mg/kg inhibited the retinal dysfunction in terms of ERG and ONL loss and reduced the expression of apoptotic and 8-OHdG-positive cells induced by light exposure. Furthermore, astaxanthin protected against increases of PI-positive cells and intracellular reactive oxygen species (ROS) activity in 661W cells. These findings suggest that astaxanthin has protective effects against light-induced retinal damage via the mechanism of its antioxidative effect.

補償光学を適用した眼底カメラrtx1&amp;trade;を用いて観察した網膜光傷害の一例

補償光学を適用した眼底カメラrtx1&amp;trade;を用いて観察した網膜光傷害の一例

NAD+ maintenance attenuates light induced photoreceptor degeneration

Light-induced retinal damage (LD) occurs after surgery or sun exposure. We previously showed that zinc (Zn2+) accumulated in photoreceptors and RPE cells after LD but prior to cell death, and pyruvate or nicotinamide attenuated the resultant death perhaps by restoring nicotinamide adenine dinucleotide (NAD+) levels. We first examined the levels of NAD+ and the efficacy of pyruvate or nicotinamide in oxidative toxicities using primary retinal cultures. We next manipulated NAD+ levels in vivo and tested the affect on LD to photoreceptors and RPE. NAD+ levels cycle with a 24-h rhythm in mammals, which is affected by the feeding schedule. Therefore, we tested the affect of increasing NAD+ levels on LD by giving nicotinamide, inverting the feeding schedule, or using transgenic mice which overexpress cytoplasmic nicotinamide mononucleotide adenyl-transferase-1 (cytNMNAT1), an NAD+ synthetic enzyme. Zn2+ accumulation was also assessed in culture and in retinal sections. Retinas of light damaged animals were examined by OCT and plastic sectioning, and retinal NAD+ levels were measured. Day fed, or nicotinamide treated rats showed less NAD+ loss, and LD compared to night fed rats or untreated rats without changing the Zn2+ staining pattern. CytNMNAT1 showed less Zn2+ staining, NAD+ loss, and cell death after LD. In conclusion, intense light, Zn2+ and oxidative toxicities caused an increase in Zn2+, NAD+ loss, and cell death which were attenuated by NAD+ restoration. Therefore, NAD+ levels play a protective role in LD-induced death of photoreceptors and RPE cells.