MAP kinase pathways in UV-induced apoptosis of retinal pigment epithelium ARPE19 cells

Spatiotemporal roles of AMPK in PARP-1- and autophagy-dependent retinal pigment epithelial cell death caused by UVA

BACKGROUND

Although stimulating autophagy caused by UV has been widely demonstrated in skin cells to exert cell protection, it remains unknown the cellular events in UVA-treated retinal pigment epithelial (RPE) cells.

METHODS

Human ARPE-19 cells were used to measure cell viability, mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP), mitochondrial mass and lysosomal mass by flow cytometry. Mitochondrial oxygen consumption rate (OCR) was recorded using Seahorse XF flux analyzer. Confocal microscopic images were performed to indicate the mitochondrial dynamics, LC3 level, and AMPK translocation after UVA irradiation.

RESULTS

We confirmed mitochondrial ROS production and DNA damage are two major features caused by UVA. We found the cell death is prevented by autophagy inhibitor 3-methyladenine and gene silencing of ATG5, and UVA induces ROS-dependent LC3II expression, LC3 punctate and TFEB expression, suggesting the autophagic death in the UVA-stressed RPE cells. Although PARP-1 inhibitor olaparib increases DNA damage, ROS production, and cell death, it also blocks AMPK activation caused by UVA. Interestingly we found a dramatic nuclear export of AMPK upon UVA irradiation which is blocked by N-acetylcysteine and olaparib. In addition, UVA exposure gradually decreases lysosomal mass and inhibits cathepsin B activity at late phase due to lysosomal dysfunction. Nevertheless, cathepsin B inhibitor, CA-074Me, reverses the death extent, suggesting the contribution of cathepsin B in the death pathway. When examining the role of EGFR in cellular events caused by UVA, we found that UVA can rapidly transactivate EGFR, and treatment with EGFR TKIs (gefitinib and afatinib) enhances the cell death accompanied by the increased LC3II formation, ROS production, loss of MMP and mass of mitochondria and lysosomes. Although AMPK activation by ROS-PARP-1 mediates autophagic cell death, we surprisingly found that pretreatment of cells with AMPK activators (A769662 and metformin) reverses cell death. Concomitantly, both agents block UVA-induced mitochondrial ROS production, autophagic flux, and mitochondrial fission without changing the inhibition of cathepsin B.

CONCLUSION

UVA exposure rapidly induces ROS-PARP-1-AMPK-autophagic flux and late lysosomal dysfunction. Pre-inducing AMPK activation can prevent cellular events caused by UVA and provide a new protective strategy in photo-oxidative stress and photo-retinopathy.

Intravitreal Administration of Retinal Organoids-Derived Exosomes Alleviates Photoreceptor Degeneration in Royal College of Surgeons Rats by Targeting the Mitogen-Activated Protein Kinase Pathway

Increasing evidence suggests that exosomes are involved in retinal cell degeneration, including their insufficient release; hence, they have become important indicators of retinopathies. The exosomal microRNA (miRNA), in particular, play important roles in regulating ocular and retinal cell functions, including photoreceptor maturation, maintenance, and visual function. Here, we generated retinal organoids (ROs) from human induced pluripotent stem cells that differentiated in a conditioned medium for 60 days, after which exosomes were extracted from ROs (Exo-ROs). Subsequently, we intravitreally injected the Exo-RO solution into the eyes of the Royal College of Surgeons (RCS) rats. Intravitreal Exo-RO administration reduced photoreceptor apoptosis, prevented outer nuclear layer thinning, and preserved visual function in RCS rats. RNA sequencing and miRNA profiling showed that exosomal miRNAs are mainly involved in the mitogen-activated protein kinase (MAPK) signaling pathway. In addition, the expression of MAPK-related genes and proteins was significantly decreased in the Exo-RO-treated group. These results suggest that Exo-ROs may be a potentially novel strategy for delaying retinal degeneration by targeting the MAPK signaling pathway.

Intraocular Pressure-Lowering and Retina-Protective Effects of Exosome-Rich Conditioned Media from Human Amniotic Membrane Stem Cells in a Rat Model of Glaucoma

Glaucoma is one of the most devastating eye diseases, since the disease can develop into blindness and no effective therapeutics are available. Although the exact mechanisms and causes of glaucoma are unknown, increased intraocular pressure (IOP) has been demonstrated to be an important risk factor. Exosomes are lipid nanoparticles secreted from functional cells, including stem cells, and have been found to contain diverse functional molecules that control body function, inhibit inflammation, protect and regenerate cells, and restore damaged tissues. In the present study, exosome-rich conditioned media (ERCMs) were attained via hypoxic culture (2% O₂) of human amniotic membrane mesenchymal stem cells (AMMSCs) and amniotic membrane epithelial stem cells (AMESCs) containing 50 times more exosome particles than normoxic culture (20% O₂) medium (NCM). The exosome particles in ERCM were confirmed to be 77 nm in mean size and contain much greater amounts of growth factors (GFs) and neurotrophic factors (NFs) than those in NCM. The glaucoma-therapeutic effects of ERCMs were assessed in retinal cells and a hypertonic (1.8 M) saline-induced high-IOP animal model. CM-DiI-labeled AMMSC exosomes were found to readily penetrate the normal and H₂O₂-damaged retinal ganglion cells (RGCs), and AMMSC-ERCM not only facilitated retinal pigment epithelial cell (RPEC) proliferation but also protected against H₂O₂- and hypoxia-induced RPEC insults. The IOP of rats challenged with 1.8 M saline increased twice the normal IOP (12-17 mmHg) in a week. However, intravitreal injection of AMMSC-ERCM or AMESC-ERCM (3.9-4.5 × 10⁸ exosomes in 10 μL/eye) markedly recovered the IOP to normal level in 2 weeks, similar to the effect achieved with platelet-derived growth factor-AB (PDGF-AB, 1.5 μg), a reference material. In addition, AMMSC-ERCM, AMESC-ERCM, and PDGF-AB significantly reversed the shrinkage of retinal layers, preserved RGCs, and prevented neural injury in the glaucoma eyes. It was confirmed that stem cell ERCMs containing large numbers of functional molecules such as GFs and NFs improved glaucoma by protecting retinal cells against oxidative and hypoxic injuries in vitro and by recovering IOP and retinal degeneration in vivo. Therefore, it is suggested that stem cell ERCMs could be a promising candidate for the therapy of glaucoma.

MAPK Pathways in Ocular Pathophysiology: Potential Therapeutic Drugs and Challenges

Mitogen-activated protein kinase (MAPK) pathways represent ubiquitous cellular signal transduction pathways that regulate all aspects of life and are frequently altered in disease. Once activated through phosphorylation, these MAPKs in turn phosphorylate and activate transcription factors present either in the cytoplasm or in the nucleus, leading to the expression of target genes and, as a consequence, they elicit various biological responses. The aim of this work is to provide a comprehensive review focusing on the roles of MAPK signaling pathways in ocular pathophysiology and the potential to influence these for the treatment of eye diseases. We summarize the current knowledge of identified MAPK-targeting compounds in the context of ocular diseases such as macular degeneration, cataract, glaucoma and keratopathy, but also in rare ocular diseases where the cell differentiation, proliferation or migration are defective. Potential therapeutic interventions are also discussed. Additionally, we discuss challenges in overcoming the reported eye toxicity of some MAPK inhibitors.

UVA induces retinal photoreceptor cell death via receptor interacting protein 3 kinase mediated necroptosis

Ultraviolet light A (UVA) is the only UV light that reaches the retina and can cause indirect damage to DNA via absorption of photons by non-DNA chromophores. Previous studies demonstrate that UVA generates reactive oxygen species (ROS) and leads to programmed cell death. Programmed cell death (PCD) has been implicated in numerous ophthalmologic diseases. Here, we investigated receptor interacting protein 1 and 3 (RIPK1 and RIPK3) kinases, key signaling molecules of PCD, in UVA-induced photoreceptor injury using in vitro and ex vivo models. UVA irradiation activated RIPK3 but not RIPK1 and mediated necroptosis through MLKL that lie downstream of RIPK3 and induced apoptosis through increased oxidative stress. Moreover, RIPK3 but not RIPK1 inhibition suppresses UVA-induced cell death along with the downregulation of MLKL and attenuates the levels of oxidative stress and DNA fragmentation. In conclusion, these results identify RIPK3, not RIPK1, as a critical regulator of UVA-induced necroptosis cell death in photoreceptors and highlight RIPK3 potential as a neuroprotective target.

Dihydroquercetin composite nanofibrous membrane prevents UVA radiation-mediated inflammation, apoptosis and oxidative stress by modulating MAPKs/Nrf2 signaling in human epidermal keratinocytes

Exposure to ultraviolet (UV) radiation is a key cause of skin inflammation and photodamage in the environment. Dihydroquercetin composite nanofiber membrane (CPD) is a nano-scale membrane cloth prepared by electrospinning technology. The results in this study showed that CPD could enhance the activities of endogenous antioxidant enzymes such as SOD and GSH-Px induced by UVA radiation, and reduce the overexpression of ROS. MAPKs/Nrf2 signaling is associated with inflammation, apoptosis and oxidative stress. Compared with control HaCaT cells, we found that CPD pretreatment prevents MAPK (p-ERK, p-JNK, and p-P38)/Nrf2-induced inflammation, apoptosis, and oxidative stress signaling during UVA exposure pathway overexpression. Immunofluorescence experiments also showed that CPD could reduce the fluorescence intensity of Caspase-3 and TNF-α. These results suggest that CPD may be a successful healing agent that provides reinforcement against UVA-induced oxidative and irritating skin compensation.

Cyclopaldic Acid, the Main Phytotoxic Metabolite of Diplodia cupressi, Induces Programmed Cell Death and Autophagy in Arabidopsis thaliana

Cyclopaldic acid is one of the main phytotoxic metabolites produced by fungal pathogens of the genus Seiridium, causal agents, among others, of the canker disease of plants of the Cupressaceae family. Previous studies showed that the metabolite can partially reproduce the symptoms of the infection and that it is toxic to different plant species, thereby proving to be a non-specific phytotoxin. Despite the remarkable biological effects of the compound, which revealed also insecticidal, fungicidal and herbicidal properties, information about its mode of action is still lacking. In this study, we investigated the effects of cyclopaldic acid in Arabidopsis thaliana plants and protoplasts, in order to get information about subcellular targets and mechanism of action. Results of biochemical assays showed that cyclopaldic acid induced leaf chlorosis, ion leakage, membrane-lipid peroxidation, hydrogen peroxide production, inhibited root proton extrusion in vivo and plasma membrane H+-ATPase activity in vitro. qRT-PCR experiments demonstrated that the toxin elicited the transcription of key regulators of the immune response to necrotrophic fungi, of hormone biosynthesis, as well as of genes involved in senescence and programmed cell death. Confocal microscopy analysis of protoplasts allowed to address the question of subcellular targets of the toxin. Cyclopaldic acid targeted the plasma membrane H+-ATPase, inducing depolarization of the transmembrane potential, mitochondria, disrupting the mitochondrial network and eliciting overproduction of reactive oxygen species, and vacuole, determining tonoplast disgregation and induction of vacuole-mediated programmed cell death and autophagy.

The Effects of Different Degrees of Hypoxia on Retinal Pigment Epithelium

In age-related macular degeneration (AMD), hypoxia causes abnormal changes in tissue metabolism and retinal pigment epithelium (RPE). However, the changes in cell function and intracellular molecules in RPE cells induced by hypoxia are not fully understood. In our study, cell viability, apoptosis, oxidative stress and changes in intracellular molecules at different time points were evaluated in ARPE-19 cells using a hypoxia model. A short period of mild hypoxia stimulated cell proliferation and apoptosis was induced as the period of hypoxia increased and the oxygen concentration decreased. As hypoxia worsened, the mitochondrial reactive oxygen species (ROS) accumulation was often accompanied with increased oxidative stress, increased intracellular HIF-1α accumulation and VEGF secretion to induce neovascularization. Additionally, p-ERK1 and ERK2 level was increased and p-ERK2 was decreased during hypoxia. In conclusion, our results show that the changes in the RPE is a process that depends on the degree of hypoxia and exposure time.

Dendrobium nobile protects retinal cells from UV-induced oxidative stress damage via Nrf2/HO-1 and MAPK pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive UV irradiation and ROS exposure are the main contributors of ocular pathologies. Pseudobulb of Dendrobium nobile Lindl. is one of the sources of Shihu and has long been used in traditional Chinese medicine as a tonic to nourish stomach, replenish body fluid, antipyretic and anti-inflammation.

AIM OF STUDY

This study aimed to investigate whether D. nobile could protect ocular cells against oxidative stress damage.

MATERIALS AND METHODS

Retinal-related cell lines, ARPE-19 and RGC-5 cells, were pretreated with D. nobile extracts before H₂O₂- and UV-treatment. Cell viability and the oxidative stress were monitored by sulforhodamine B (SRB) and SOD1 and CAT assay kits, respectively. The oxidative stress related proteins were measured by Western blotting.

RESULTS

Under activity-guided fractionation, a sesquiterpene-enriched fraction (DN-2) and a major component (1) could ameliorate H₂O₂- and UV-induced cytotoxicity and SOD1 and CAT activity, but not dendrobine, the chemical marker of D. nobile. Western blotting showed both DN-2 and compound 1 protected ARPE-19 cells against UV-induced oxidative stress damage by regulating MAPK and Nrf2/HO-1 signaling.

CONCLUSION

Our results suggest D. nobile extract protects retinal pigment epithelia cells from UV- and oxidative stress-damage, which may have a beneficial effect on eye diseases.

The Amyloid Precursor Protein Plays Differential Roles in the UVA Resistance and Proliferation of Human Retinal Pigment Epithelial Cells

Background:

Age-related macular degeneration (AMD) can be characterised by degeneration of retinal pigment epithelial (RPE) cells and the accumulation, in retinal drusen deposits, of amyloid beta-peptides proteolytically derived, by secretases, from the amyloid precursor protein (APP). Ultraviolet (UV) light exposure is a risk factor for the development of AMD.

Objectives:

In the current study, we investigated whether APP and/or its proteolysis are linked to the UVA resistance or proliferation of ARPE-19 human RPE cells.

Methods:

Cell viability was determined, following UVA exposure, with prior small interfering RNA-mediated APP depletion or secretase inhibitor treatments. APP levels/proteolysis were analysed by immunoblotting. Cells were also grown in the presence/absence of secretase inhibitors to assess their effects on longer-term culture growth. Finally, the effects of APP proteolytic fragments on ARPE-19 cell proliferation were monitored following co-culture with human embryonic kidney cells stably over-expressing these fragments.

Results:

Endogenous APP was depleted following UVA irradiation and β-secretase, but not α- secretase, and the processing of the protein was reduced. Experimental APP depletion or γ-secretase (but not α- or β-secretase) inhibition ablated the detrimental effect of UVA on cell viability. In contrast, α-secretase, and possibly γ-secretase but not β-secretase activity, appeared to promote the longer-term proliferation of ARPE-19 cells in the absence of UVA irradiation.

Conclusions:

There are clear but differential links between APP expression/proteolysis and the proliferation and UVA resistance of ARPE-19 cells indicating that the protein should be investigated further in relation to the identification of possible drug targets for the treatment of AMD.

Novel Regulators of Retina Neovascularization: A Proteomics Approach

The purpose of this study was to identify proteins that regulate vascular remodeling in an ROP mouse model. Pups were subjected to fluctuating oxygen levels and retinas sampled during vessel regression (PN12) or neovascularization (PN17) for comparative SWATH-MS proteomics using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We developed a human retinal endothelial cell (HREC) ROP correlate to validate the expression of retina neovascular-specific markers. A total of 5191 proteins were identified in OIR retinas with 498 significantly regulated in elevated oxygen and 345 after a return to normoxia. A total of 122 proteins were uniquely regulated during vessel regression and 69 during neovascularization (FC ≥ 1.5; p ≤ 0.05), with several validated by western blot analyses. Expressions of 56/69 neovascular-specific proteins were confirmed in hypoxic HRECs with 23 regulated in the same direction as OIR neovascular retinas. These proteins control angiogenesis-related processes including matrix remodeling, cell migration, adhesion, and proliferation. RNAi and transfection overexpression studies confirmed that VASP and ECH1, showing the highest levels in hypoxic HRECs, promoted human umbilical vein (HUVEC) and HREC cell proliferation, while SNX1 and CD109, showing the lowest levels, inhibited their proliferation. These proteins are potential biomarkers and exploitable intervention tools for vascular-related disorders. The proteomics data set generated has been deposited to the ProteomeXchange/iProX Consortium with the Identifier:PXD029208.

Obacunone protects retinal pigment epithelium cells from ultra-violet radiation-induced oxidative injury

Ultra-violet (UV) radiation (UVR) causes significant oxidative injury to retinal pigment epithelium (RPE) cells. Obacunone is a highly oxygenated triterpenoid limonoid compound with various pharmacological properties. Its potential effect in RPE cells has not been studied thus far. Here in ARPE-19 cells and primary murine RPE cells, obacunone potently inhibited UVR-induced reactive oxygen species accumulation, mitochondrial depolarization, lipid peroxidation and single strand DNA accumulation. UVR-induced RPE cell death and apoptosis were largely alleviated by obacunone. Obacunone activated Nrf2 signaling cascade in RPE cells, causing Keap1-Nrf2 disassociation, Nrf2 protein stabilization and nuclear translocation. It promoted transcription and expression of antioxidant responsive element-dependent genes. Nrf2 silencing or CRISPR/Cas9-induced Nrf2 knockout almost reversed obacunone-induced RPE cytoprotection against UVR. Forced activation of Nrf2 cascade, by Keap1 knockout, similarly protected RPE cells from UVR. Importantly, obacunone failed to offer further RPE cytoprotection against UVR in Keap1-knockout cells. In vivo, intravitreal injection of obacunone largely inhibited light-induced retinal damage. Collectively, obacunone protects RPE cells from UVR-induced oxidative injury through activation of Nrf2 signaling cascade.

Photobiomodulation of the Visual System and Human Health

Humans express an expansive and detailed response to wavelength differences within the electromagnetic (EM) spectrum. This is most clearly manifest, and most studied, with respect to a relatively small range of electromagnetic radiation that includes the visible wavelengths with abutting ultraviolet and infrared, and mostly with respect to the visual system. Many aspects of our biology, however, respond to wavelength differences over a wide range of the EM spectrum. Further, humans are now exposed to a variety of modern lighting situations that has, effectively, increased our exposure to wavelengths that were once likely minimal (e.g., “blue” light from devices at night). This paper reviews some of those biological effects with a focus on visual function and to a lesser extent, other body systems.

Geographic distributions of age-related macular degeneration incidence: a systematic review and meta-analysis

PURPOSE

We performed a systematic review and meta-analysis to summarise the geographic distribution of age-related macular degeneration (AMD) incidence.

METHODS

Databases including PubMed, Embase and Web of Science were searched for publications of early and late AMD before September 2019. Studies were included if they applied a standardised photographic assessment and classification system. The proportion of participants with AMD in each eligible study was combined to obtain a pooled incidence from all studies using a random effects model. We also assessed sources of potential heterogeneity in the incidence of AMD using meta-regression analyses for both late and early AMD.

RESULTS

Twenty-four population-based studies (70 123 individuals aged 55 years or older) were included in the meta-analysis. The pooled global annual incidences of early and late AMD were 1.59% (95% CI 1.12% to 2.10%) and 0.19% (95% CI: 0.13% to 0.28%), respectively. Individuals of European descent had the highest annual incidence of both early (2.73%, 95% CI 1.63% to 4.57%) and late (0.36%, 95% CI 0.17% to 0.75%) AMD than other ethnic groups. Average age (p=0.001) at baseline, ethnicity (p=0.001), region (p=0.043) and gender (p=0.011) were predictors for incident late AMD, while only average age (p=0.01) at baseline and ethnicity (p=0.025) was associated with incidence of early AMD.

CONCLUSIONS

This meta-analysis offers an up-to-date overview of AMD globally, which may provide scientific guidance for the design and implementation of public health strategies such as screening programmes for AMD in both specific geographic locations and ethnic groups, as well as worldwide.

Association between daily sunlight exposure duration and diabetic retinopathy in Korean adults with diabetes: A nationwide population-based cross-sectional study

Purpose

To investigate the association between daily sunlight exposure duration and diabetic retinopathy in Korean adults with diabetes.

Methods

This study used data from the 2008–2011 Korea National Health and Nutrition Examination Survey. Overall, 1,089 patients with diabetes aged >40 years were included. The duration of daily sunlight exposure was assessed via health interviews. Comprehensive ophthalmic evaluations, including standard retinal fundus photography after pupil dilation, were conducted. Diabetic retinopathy was graded using the modified Airlie House Classification. Multivariate logistic regression analysis was performed to analyze the association between daily sunlight exposure duration and the diagnosis of diabetic retinopathy and non-proliferative diabetic retinopathy.

Results

The risk of diabetic retinopathy was 2.66 times higher in the group with ≥5 h of daily sunlight exposure than in the group with less exposure after adjusting for risk factors such as duration of diabetes, serum hemoglobin A1c level, hypertension, and dyslipidemia (P = 0.023). Furthermore, the risk of non-proliferative diabetic retinopathy was 3.13 times higher in the group with ≥5 h of daily sunlight exposure than in the group with less exposure (P = 0.009). In patients with diabetes for <10 years, the risks of diabetic retinopathy and non-proliferative diabetic retinopathy were 4.26 and 4.82 times higher in the group with ≥5 h of daily sunlight exposure than the group with less exposure, respectively (P < 0.05).

Conclusions

This study revealed that sunlight exposure for ≥5 h a day was significantly associated with an increased risk of diabetic retinopathy and non-proliferative diabetic retinopathy in Korean patients with diabetes. The risks were significantly higher in patients with diabetes for <10 years. Therefore, reducing daily sunlight exposure could be an early preventive strategy against diabetic retinopathy in people with diabetes.

APOE2 promotes the development and progression of subretinal neovascularization in age-related macular degeneration via MAPKs signaling pathway

Background

Neovascular age-related macular degeneration (nvAMD) is one of the main pathological features of wet AMD. Apolipoprotein E2 is involved in the formation of nvAMD but the molecular mechanism has not been reported.

Methods

The APOE alleles in AMD patients were detected by genotyping. Mouse models were divided into 4 groups according to transfection different gene segments and laser-induced treatment. APOE2, VEGF, PDGF-BB, b-FGF and inflammatory cytokines (including p-NF-κB, TNF-α, IL-1β and IL-6) were tested by ELISA in mice retinal lysate. The formation of nvAMD in the indicated treatment groups at 3rd, 7th and 14th day after laser-induced damage were detected by FFA. Besides, qRT-PCR was used to determine the mRNA levels of p38, JNK and ERK in ARPE-19 cells. Finally, the inflammatory cytokines and MAPK proteins (including P38, p-P38, JNK, p-JNK, ERK and p-ERK) were detected by western blot.

Results

The statistics of APOE alleles showed that APOE2 allele carriers were more likely to nvAMD. VEGF, PDGF-BB, b-FGF and related inflammatory cytokines were up-regulated significantly after treatment with APOE2, which were reduced after silencing the MAPK family genes, however. Further, the expression levels of neovascular growth factors and inflammatory cytokines were highly consistent between mouse models and ARPE-19 cells. Besides, the phosphorylation levels of p38, JNK and ERK were affected by APOE2.

Conclusion

nvAMD was affected directly by the overexpression of VEGF, PDGF-BB and b-FGF, which were regulated by APOE2 through activating MAPKs pathway.

Mitochondrial dysfunction in age-related macular degeneration: melatonin as a potential treatment

Introduction: Age-related Macular Degeneration (AMD), a retinal neurodegenerative disease is the most common cause of blindness among the elderly in developed countries. The impairment of mitochondrial biogenesis has been reported in human retinal pigment epithelium (RPE) cells affected by AMD. Oxidative/nitrosative stress plays an important role in AMD development. The mitochondrial respiratory system is considered a major site of reactive oxygen species (ROS) generation. During aging, insufficient free radical scavenger systems, impairment of DNA repair mechanisms and reduction of mitochondrial degradation and turnover contribute to the massive accumulation of ROS disrupting mitochondrial function. Impaired mitochondrial function leads to the decline in the autophagic capacity and induction of inflammation and apoptosis in human RPE cells affected by AMD.Areas covered: This article evaluates the ameliorative effect of melatonin on AMD and examines AMD pathogenesis with an emphasis on mitochondrial dysfunction. It also considers the potential effects of melatonin on mitochondrial function.Expert opinion: The effect of melatonin on mitochondrial function results in the reduction of oxidative stress, inflammation and apoptosis in the retina; these findings demonstrate that melatonin has the potential to prevent and treat AMD.

Synergistic Cytoprotective Effects of Rutin and Ascorbic Acid on the Proteomic Profile of 3D-Cultured Keratinocytes Exposed to UVA or UVB Radiation

The combination of ascorbic acid and rutin, often used in oral preparations, due to antioxidant and anti-inflammatory properties, can be used to protect skin cells against the effects of UV radiation from sunlight. Therefore, the aim of this study was to investigate the synergistic effect of rutin and ascorbic acid on the proteomic profile of UVA and UVB irradiated keratinocytes cultured in a three-dimensional (3D) system. Results showed that the combination of rutin and ascorbic acid protects skin cells against UV-induced changes. In particular, alterations were observed in the expression of proteins involved in the antioxidant response, DNA repairing, inflammation, apoptosis, and protein biosynthesis. The combination of rutin and ascorbic acid also showed a stronger cytoprotective effect than when using either compound alone. Significant differences were visible between rutin and ascorbic acid single treatments in the case of protein carboxymethylation/carboxyethylation. Ascorbic acid prevented UV or rutin-induced protein modifications. Therefore, the synergistic effect of rutin and ascorbic acid creates a potentially effective protective system against skin damages caused by UVA and UVB radiation.

Proteomic analysis of retinal pigment epithelium cells after exposure to UVA radiation

Background

Age-related macular degeneration (AMD) is the primary cause of blindness and severe vision loss in developed countries and is responsible for 8.7% of blindness globally. Ultraviolet radiation can induce DNA breakdown, produce reactive oxygen species, and has been implicated as a risk factor for AMD. This study investigated the effects of UVA radiation on Human retinal pigment epithelial cell (ARPE-19) growth and protein expression.

Methods

ARPE-19 cells were irradiated with a UVA lamp at different doses (5, 10, 20, 30 and 40 J/cm²) from 10 cm. Cell viability was determined by MTT assay. Visual inspection was first achieved with inverted light microscopy and then the DeadEnd™ Fluorometric TUNEL System was used to observe nuclear DNA fragmentation. Flow cytometry based-Annexin V-FITC/PI double-staining was used to further quantify cellular viability. Mitochondrial membrane potential was assessed with JC-1 staining. 2D electrophoresis maps of exposed cells were compared to nonexposed cells and gel images analyzed with PDQuest 2-D Analysis Software. Spots with greater than a 1.5-fold difference were selected for LC-MS/MS analysis and some confirmed by western blot. We further investigated whether caspase activation, apoptotic-related mitochondrial proteins, and regulators of ER stress sensors were involved in UVA-induced apoptosis.

Results

We detected 29 differentially expressed proteins (9 up-regulated and 20 down-regulated) in the exposed cells. Some of these proteins such as CALR, GRP78, NPM, Hsp27, PDI, ATP synthase subunit alpha, PRDX1, and GAPDH are associated with anti-proliferation, induction of apoptosis, and oxidative-stress protection. We also detected altered protein expression levels among caspases (caspase 3 and 9) and in the mitochondrial (cytosolic cytochrome C, AIF, Mcl-1, Bcl-2, Bcl-xl, Bax, Bad, and p-Bad) and ER stress-related (p-PERK, p-eIF2α, ATF4 and CHOP) apoptotic pathways.

Conclusions

UVA irradiation suppressed the proliferation of ARPE-19 cells in a dose-dependent manner, caused quantitative loses in transmembrane potential (ΔΨm), and induced both early and late apoptosis.

Protective effect of diphlorethohydroxycarmalol against oxidative stress-induced DNA damage and apoptosis in retinal pigment epithelial cells

Purpose: Reactive oxygen species (ROS) contribute to the onset and progression of disease pathogenesis in a variety of organs, including age-related macular degeneration (AMD). Diphlorethohydroxycarmalol (DPHC), a phlorotannin compound, is one of the major components of the brown alga Ishige okamurae Yendo, and has been shown to have strong antioxidant capacity. The purpose of this study was to evaluate the protective effects of DPHC against oxidative stress (hydrogen peroxide, H₂O₂)-induced DNA damage and apoptosis in cultured ARPE19 retinal pigment epithelial (RPE) cells. Materials and methods: Cell viability was assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay. Intracellular ROS generation was measured by flow cytometer using 2',7'-dichlorofluorescin diacetate. The magnitude of apoptosis was measured by flow cytometry using the annexin V/propidium iodide double staining. DNA damage was evaluated by DNA fragmentation assay, comet assay and 8-hydroxy-2'-deoxyguanosine (8-OHdG) analysis. To observe the mitochondrial membrane potential, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide staining was performed. In order to identify the underling mechanism of DPHC against H₂O₂-induced cellular alteration, we performed immune blotting. Results: The results of this study showed that the decreased survival rate brought about by H₂O₂ could be attributed to the induction of DNA damage and apoptosis accompanied by the increased production of ROS, which was remarkably reversed by DPHC. In addition, the loss of H₂O₂-induced mitochondrial membrane potential was significantly attenuated in the presence of DPHC. The inhibitory effect of DPHC on H₂O₂-induced apoptosis was associated with a reduced Bax/Bcl-2 ratio, the protection of the activation of caspase-9 and -3 and the inhibition of poly (ADP-ribose) polymerase cleavage, which was associated with the blockage of cytochrome c release to the cytoplasm. Conclusions: Our data proved that DPHC protects ARPE19 cells against H₂O₂-induced DNA damage and apoptosis by scavenging ROS and thus suppressing the mitochondrial-dependent apoptosis pathway. Therefore, this study suggests that DPHC has the therapeutic potential to prevent AMD by inhibiting oxidative stress-induced injury in RPE cells.

Anti-EMT properties of CoQ0 attributed to PI3K/AKT/NFKB/MMP-9 signaling pathway through ROS-mediated apoptosis

Background

Breast cancer is the most prevalent cancer among women. In triple-negative breast cancer (TNBC) cells, a novel quinone derivative, coenzyme Q₀ (CoQ₀), promotes apoptosis and cell-cycle arrest. This study explored the anti-epithelial–mesenchymal transition (EMT) and antimetastatic attributes of CoQ₀ in TNBC (MDA-MB-231).

Methods

Invasion, as well as MTT assays were conducted. Lipofectamine RNAiMAX was used to transfect cells with β-catenin siRNA. Through Western blotting and RT-PCR, the major signaling pathways’ protein expressions were examined, and the biopsied tumor tissues underwent immunohistochemical and hematoxylin and eosin staining as well as Western blotting.

Results

CoQ₀ (0.5–2 μM) hindered tumor migration, invasion, and progression. Additionally, it caused MMP-2/− 9, uPA, uPAR, and VEGF downregulation. Furthermore, in highly metastatic MDA-MB-231 cells, TIMP-1/2 expression was subsequently upregulated and MMP-9 expression was downregulated. In addition, CoQ₀ inhibited metastasis and EMT in TGF-β/TNF-α-stimulated non-tumorigenic MCF-10A cells. Bioluminescence imaging of MDA-MB-231 luciferase–injected live mice demonstrated that CoQ₀ significantly inhibited metastasis of the breast cancer to the lungs and inhibited the development of tumors in MDA-MB-231 xenografted nude mice. Silencing of β-catenin with siRNA stimulated CoQ₀-inhibited EMT. Western blotting as well as histological analysis established that CoQ0 reduced xenografted tumor development because apoptosis induction, cell-cycle inhibition, E-cadherin upregulation, β-catenin downregulation, and metastasis and EMT regulatory protein modulation were observed.

Conclusions

CoQ₀ inhibited the progression of metastasis as well as EMT (in vitro and in vivo). The described approach has potential in treating human breast cancer metastasis.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1196-x) contains supplementary material, which is available to authorized users.

P-TEFb Activation by RBM7 Shapes a Pro-survival Transcriptional Response to Genotoxic Stress

DNA damage response (DDR) involves dramatic transcriptional alterations, the mechanisms of which remain ill defined. Here, we show that following genotoxic stress, the RNA-binding motif protein 7 (RBM7) stimulates RNA polymerase II (Pol II) transcription and promotes cell viability by activating the positive transcription elongation factor b (P-TEFb) via its release from the inhibitory 7SK small nuclear ribonucleoprotein (7SK snRNP). This is mediated by activation of p38MAPK, which triggers enhanced binding of RBM7 with core subunits of 7SK snRNP. In turn, P-TEFb relocates to chromatin to induce transcription of short units, including key DDR genes and multiple classes of non-coding RNAs. Critically, interfering with the axis of RBM7 and P-TEFb provokes cellular hypersensitivity to DNA-damage-inducing agents due to activation of apoptosis. Our work uncovers the importance of stress-dependent stimulation of Pol II pause release, which enables a pro-survival transcriptional response that is crucial for cell fate upon genotoxic insult.

Rutin and ascorbic acid cooperation in antioxidant and antiapoptotic effect on human skin keratinocytes and fibroblasts exposed to UVA and UVB radiation

The combination of ascorbic acid and rutin is frequently used in oral preparations. However, despite numerous protective effects of each component individually, their combined effect on ultraviolet (UV)-irradiated skin cells has never been evaluated. The aim of this study was to evaluate the combined effect of ascorbic acid and rutin on human keratinocytes and fibroblasts exposed to UVA and UVB radiation. Skin keratinocytes and fibroblasts exposed to UVA and UVB radiation were treated with ascorbic acid or/and rutin. The total antioxidant properties of both components, as well as their effect on cellular pro- and antioxidant status, lipid and protein oxidation, transmembrane transport, and pro-inflammatory and pro/antiapoptotic protein expression were measured. The combination of ascorbic acid and rutin had higher antioxidant properties compared to the activity of the single compound alone, and showed a stronger effect against UV-induced reactive oxygen species generation. The ascorbic acid and rutin combination also showed increased antioxidant enzyme activity (catalase, superoxide dismutase, thioredoxin reductase), which was impaired following UV irradiation. Moreover, ascorbic acid additional stimulated UV-induced bilitranslocase activity responsible for rutin transport, and therefore favored rutin effect on Nrf2 pathway, simultaneously differentiating the reaction of keratinocytes and fibroblasts. In keratinocytes, Nrf2 is strongly activated, while in fibroblasts decreased Nrf2 activity was observed. Used mixture, also significantly silenced UV-induced expression of pro-inflammatory factor NFκB and pro-apoptotic proteins such as caspases 3, 8, and 9. These results showed that ascorbic acid and rutin are complementary in their antioxidant actions, transport and signaling functions. Their combined antioxidant, antiinflammatory and antiapoptotic actions suggest rutin and ascorbic acid are a potentially cytoprotective team against UV-induced skin damage.

Role of oxidative stress in Retinitis pigmentosa: new involved pathways by an RNA-Seq analysis

Retinitis pigmentosa (RP) is a very heterogeneous inherited ocular disorder group characterized by progressive retinal disruption. Retinal pigment epithelium (RPE) degeneration, due to oxidative stress which arrests the metabolic support to photoreceptors, represents one of the principal causes of RP. Here, the role of oxidative stress in RP onset and progression was analyzed by a comparative whole transcriptome analysis of human RPE cells, treated with 100 µg/ml of oxLDL and untreated, at different time points. Experiment was thrice repeated and performed on Ion Proton^TM sequencing system. Data analysis, including low quality reads trimming and gene expression quantification, was realized by CLC Genomics Workbench software. The whole analysis highlighted 14 clustered "macro-pathways" and many sub-pathways, classified by selection of 5271 genes showing the highest alteration of expression. Among them, 23 genes were already known to be RP causative ones (15 over-expressed and 8 down-expressed), and their enrichment and intersection analyses highlighted new 77 candidate related genes (49 over-expressed and 28 down-expressed). A final filtering analysis then highlighted 29 proposed candidate genes. This data suggests that many new genes, not yet associated with RP, could influence its etiopathogenesis.

A derivative of betulinic acid protects human Retinal Pigment Epithelial (RPE) cells from cobalt chloride-induced acute hypoxic stress

The Retinal Pigment Epithelium (RPE) is a monolayer of cells located above the choroid. It mediates human visual cycle and nourishes photoreceptors. Hypoxia-induced oxidative stress to RPE is a vital cause of retinal degeneration such as the Age-related Macular Degeneration. Most of these retinal diseases are irreversible with no efficient treatment, therefore protecting RPE cells from hypoxia stress is an important way to prevent or slow down the progression of retinal degeneration. Betulinic acid (BA) and betulin (BE) are pentacyclic triterpenoids with anti-oxidative property, but little is known about their effect on RPE cells. We investigated the protective effect of BA, BE and their derivatives against cobalt chloride-induced hypoxia stress in RPE cells. Human ARPE-19 cells were exposed to BA, BE and their eighteen derivatives (named as H3H20) that we customized through replacing moieties at C3 and C28 positions. We found that cobalt chloride reduced cell viability, increased Reactive Oxygen Species (ROS) production as well as induced apoptosis and necrosis in ARPE-19 cells. Interestingly, the pretreatment of 3-O-acetyl-glycyl- 28-O-glycyl-betulinic acid effectively protected cells from acute hypoxia stress induced by cobalt chloride. Our immunoblotting results suggested that this derivative attenuated the cobalt chloride-induced activation of Akt, Erk and JNK pathways. All findings were further validated in human primary RPE cells. In summary, this BA derivate has protective effect against the acute hypoxic stress in human RPE cells and may be developed into a candidate agent effective in the prevention of prevalent retinal diseases.

MiR-340/iASPP axis affects UVB-mediated retinal pigment epithelium (RPE) cell damage

Long-term exposure to ultraviolet B (UVB) light increases the risk of UVB damage due to increased UVB absorption by the retina and may further lead to age-related eye diseases. The retinal pigment epithelium (RPE) cell is a main target of UVB reaching the retina; its degeneration is an essential event in UVB-mediated age-related macular degeneration (AMD). Herein, we first evaluated the expression and effect of iASPP, an inhibitory regulator of apoptosis, in UVB-induced RPE cell damage. Through the mechanism of RNA interference at the post-transcriptional level, miRNA affects a variety of cellular processes, including UVB-mediated cell damage. We next screened for upstream candidate miRNAs that may regulate iASPP expression. Among 8 candidate miRNAs, UVB significantly increased miR-340 levels. We also confirmed the direct binding of miR-340 to the 3'UTR of iASPP, and assessed the combined effect of miR-340 and iASPP on UVB-induced RPE cell damage. Taken together, we demonstrated the possible mechanisms involved in UVB-induced retinal damage. In RPE cells, UVB irradiation inhibits iASPP expression through inducing miR-340 expression, thereby promoting RPE cell apoptosis and suppressing cell viability via affecting p53, p21 and caspase-3 protein expression. Targeting miR-340 to rescue iASPP expression in RPE cells may help treat UVB-mediated retinal damage.

UVB induces apoptosis via downregulation of CALML3-dependent JNK1/2 and ERK1/2 pathways in cataract

The aim of the current study was to understand the mechanisms of apoptosis occurring in cultured human lens epithelial cells (HLECs) following ultraviolet B (UVB) irradiation. The investigations intended to confirm the presence of apoptosis and to reveal the roles of oxidative stress, calcium (Ca2+), c‑Jun NH2‑terminal kinase (JNK)1/2, and extracellular signal‑regulated kinase (ERK)1/2 signaling pathway in these progresses. Cell apoptosis, ROS generation and intracellular Ca2+ concentration was measured by flow cytometry. The expression of CALML3, caspase-3, Bax, Bcl-2, p-JNK1/2, JNK1/2, p-ERK1/2 and ERK1/2 was measured by RT-qPCR and western blot analysis. Annexin V‑fluorescein isothiocyanate/propidium iodide staining demonstrated that UVB irradiation increased the apoptotic rate, reactive oxygen species (ROS) production and intracellular Ca2+ concentration of HLECs in dose‑ and time‑dependent manners. Overexpression of calmodulin like 3 (CALML3) reversed the effects of UVB irradiation on apoptosis, ROS production and Ca2+ concentration of HLECs, and decreased expressions of caspase‑3 and Bax, with increased expressions of Bcl‑2. Notably, silencing of CALML3 had similar effects to UVB irradiation and inhibited the activation JNK1/2 and ERK1/2 pathways. Nimodipine, a Ca2+‑channel antagonist, significantly attenuated the damages induced by CALML3 downregulation. In conclusion, UVB irradiation induced increase in apoptosis, ROS production and Ca2+ concentration of HLECs, in part, by downregulating the expression of CALML3 and involved oxidative stress, Ca2+, JNK1/2 and ERK1/2 signaling pathways, suggesting that investigating CALML3 may useful for developing cataract treatment.

Ultraviolet A radiation induces cortistatin overexpression and activation of somatostatin receptors in ARPE‑19 cells

Long-term exposure to ultraviolet (UV) radiation is associated with pathological alterations of the retinal pigment epithelium (RPE). It has been indicated that Cortistatin (CST) and somatostatin (SST) are able to inhibit the neurodegeneration of the RPE associated with diabetic retinopathy and retinal ischemia via activation of SST receptors (SSTRs). To the best of our knowledge, the present study indicated for the first time that treatment with UV‑A (30 and 60 min) causes an increase of CST expression, rather than SST, which was linked with the upregulation of STTR3,4,5 subtype receptor gene expression levels. The study revealed that: i) SST and CST mRNA expression were both detected under basal conditions in a human retinal pigment epithelial cell line (Arpe‑19); ii) SST expression remained constant from baseline to 1 h of UV‑A treatment; iii) CST mRNA expression levels were 80 times increased compared with time 0 and after 30 min of exposition to ultraviolet irradiation; iv) SSTR1, SSTR2 mRNA and low levels of SSTR4 were expressed in basal conditions, whereas SSTR3 and SSTR5 mRNA were not detected under the same conditions; and v) only SSTR3, SSTR4 and SSTR5 were overexpressed after UV‑A treatment, although in a different way. In conclusion, the findings provide reasonable evidence to support the pathophysiological role of the CST/SST/SSTRs system in the adaptive response of the RPE exposed to UV‑A radiation.

The Role of c-Jun N-Terminal Kinase (JNK) in Retinal Degeneration and Vision Loss

c-Jun N-terminal kinase (JNK), a member of stress-induced mitogen-activated protein (MAP) kinase family, has been shown to modulate a variety of biological processes associated with neurodegenerative pathology of the retina. In particular, various retinal cell culture and animal models related to glaucoma, age-related macular degeneration (AMD), and retinitis pigmentosa indicate that JNK signaling may contribute to disease pathogenesis. This mini-review discusses the impact of JNK signaling in retinal disease, with a focus on retinal ganglion cells (RGCs), photoreceptor cells, retinal pigment epithelial (RPE) cells, and animal studies, with particular attention to modulation of JNK signaling as a potential therapeutic target for the treatment of retinal disease.

Transcriptome analysis for UVB-induced phototoxicity in mouse retina

Throughout life, the human eye is continuously exposed to sunlight and artificial lighting. Ambient light exposure can lead to visual impairment and transient or permanent blindness. To mimic benign light stress conditions, Mus musculus eyes were exposed to low-energy UVB radiation, ensuring no severe morphological changes in the retinal structure post-exposure. We performed RNA-seq analysis to reveal the early transcriptional changes and key molecular pathways involved before the activation of the canonical cell death pathway. RNA-seq analysis identified 537 genes that were differentially modulated, out of which 126 were clearly up regulated (>2-fold, P < .01) and 51 were significantly down regulated (<2-fold, P < .01) in response to UVB irradiation in the mouse retina. Gene ontology analysis revealed that UVB exposure affected pathways for cellular stress and signaling (eg, Creb3, Ddrgk1, Grin1, Map7, Uqcc2, Uqcrb), regulation of chromatin and gene expression (eg, Chd5, Jarid2, Kat6a, Smarcc2, Sumo1, Zfp84), transcription factors (eg, Asxl2, Atf7, Per1, Phox2a, Rxra), RNA processing, and neuronal genes (eg, B4gal2, Drd1, Grm5, Rnf40, Rnps1, Usp39, Wbp4). The differentially expressed genes from the RNA-seq analysis were validated by quantitative PCR. Both analyses yielded similar gene expression patterns. The genes and pathways identified here improve the understanding of early transcriptional responses to UVB irradiation. They may also help in elucidating the genes responsible for the inherent susceptibility of humans to UVB-induced retinal diseases.

Loss of Extracellular Signal-Regulated Kinase 1/2 in the Retinal Pigment Epithelium Leads to RPE65 Decrease and Retinal Degeneration

Recent work suggested that the activity of extracellular signal-regulated kinase 1/2 (ERK1/2) is increased in the retinal pigment epithelium (RPE) of age-related macular degeneration (ARMD) patients and therefore could be an attractive therapeutic target. Notably, ERK1/2 pathway inhibitors are used in cancer therapy, with severe and noncharacterized ocular side effects. To decipher the role of ERK1/2 in RPE cells, we conditionally disrupted the Erk1 and Erk2 genes in mouse RPE. The loss of ERK1/2 activity resulted in a significant decrease in the level of RPE65 expression, a decrease in ocular retinoid levels concomitant with low visual function, and a rapid disorganization of RPE cells, ultimately leading to retinal degeneration. Our results identify the ERK1/2 pathway as a direct regulator of the visual cycle and a critical component of the viability of RPE and photoreceptor cells. Moreover, our results caution about the need for a very fine adjustment of kinase inhibition in cancer or ARMD treatment in order to avoid ocular side effects.

Visual function improvement using photocromic and selective blue-violet light filtering spectacle lenses in patients affected by retinal diseases

Background

To evaluate functional visual parameters using photocromic and selective blue-violet light filtering spectacle lenses in patients affected by central or peripheral scotoma due to retinal diseases.

Sixty patients were enrolled in this study: 30 patients affected by central scotoma, group 1, and 30 affected by peripheral scotoma, group 2.

Black on White Best Corrected Visual Acuity (BW-BCVA), White on Black Best Corrected Visual Acuity (WB-BCVA), Mars Contrast Sensitivity (CS) and a Glare Test (GT) were performed to all patients.

Test results with blue-violet filter, a short-pass yellow filter and with no filters were compared.

Results

All scores from test results increased significantly with blue-violet filters for all patients.

The mean BW-BCVA increased from 0.30 ± 0.20 to 0.36 ± 0.21 decimals in group 1 and from 0.44 ± 0.22 to 0.51 ± 0.23 decimals in group 2 (Mean ± SD, p < 0.0001 in both cases).

The mean WB-BCVA increased from 0.31 ± 0.19 to 0.38 ± 0.23 decimals in group 1 and from 0.46 ± 0.20 to 0.56 ± 0.22 decimals in group 2 (Mean ± SD, p < 0.0001 in both cases).

The letter count for the CS test increased from 26.7 ± 7.9 to 30.06 ± 7.8 in group 1 (Mean ± SD, p = 0.0005) and from 31.5 ± 7.6 to 33.72 ± 7.3 in group 2 (Mean ± SD, p = 0.031).

GT was significantly reduced: the letter count increased from 20.93 ± 5.42 to 22.82 ± 4.93 in group 1 (Mean ± SD, p < 0.0001) and from 24.15 ± 5.5 to 25.97 ± 4.7 in group 2 (Mean ± SD, p < 0.0001).

Higher scores were recorded with the Blue filter compared to Yellow filter in all tests (p < 0.05).

No significant differences in any test results could be detected between the Yellow filter and the No filter condition.

Conclusions

The use of a combination of photocromic lens with a selective blue-violet light filter showed functional benefit in all evaluated patients.

Exploring the cross talk between ER stress and inflammation in age-related macular degeneration

Increasing evidence demonstrates that inflammation and endoplasmic reticulum (ER) stress is implicated in the development and progression of age-related macular degeneration (AMD), a multifactorial neurodegenerative disease. However the cross talk between these cellular mechanisms has not been clearly and fully understood. The present study investigates a possible intersection between ER stress and inflammation in AMD. In this study, we recruited two collections of involved protein markers to retrieve their interaction information from IMEx-curated databases, which are the most well- known protein-protein interaction collections, allowing us to design an intersection network for AMD that is unprecedented. In order to find expression activated subnetworks, we utilized AMD expression profiles in our network. In addition, we studied topological characteristics of the most expressed active subnetworks to identify the hubs. With regard to topological quantifications and expressional activity, we reported a list of the most pivotal hubs which are potentially applicable as probable therapeutic targets. Furthermore, we introduced MAPK signaling pathway as a significantly involved pathway in the association between ER stress and inflammation, leading to promising new directions in discovering AMD formation mechanisms and possible treatments.

The inhibition of NOTCH2 reduces UVB-induced damage in retinal pigment epithelium cells

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the elderly. The pathogenesis of dry AMD remains indistinct and the mechanism of retinal pigment epithelium (RPE) cells death in dry AMD is controversial. The aim of the present study was to investigate the functions of Notch signaling in ultraviolet B (UVB)-induced damage of RPE cells. It was identified that, in RPE cells, UVB increased intracellular reactive oxygen species (ROS) and induced cell apoptosis. In addition, UVB activated Notch signaling in a dose dependent manner. Surprisingly, NOTCH2, but not NOTCH1, was demonstrated to be the major Notch receptor in RPE cells. Under normal conditions, the inhibition of NOTCH2 reduced cell growth and cell migration, but had no impact on intracellular ROS and cell apoptosis. However, in the presence of UVB, the inhibition of NOTCH2, but not NOTCH1, attenuated intracellular ROS and cell apoptosis. The function of Notch signaling involved in UVB damage of RPE cells may not only be significant to understanding the pathogenesis of AMD (especially dry AMD), but also useful for designing effective therapeutic agents for dry AMD.

Bis-Retinoid A2E Induces an Increase of Basic Fibroblast Growth Factor via Inhibition of Extracellular Signal-Regulated Kinases 1/2 Pathway in Retinal Pigment Epithelium Cells and Facilitates Phagocytosis

Age-related macular degeneration (ARMD) is the leading cause of vision loss in developed countries. Hallmarks of the disease are well known; indeed, this pathology is characterized by lipofuscin accumulation, is principally composed of lipid-containing residues of lysosomal digestion. The N-retinyl-N-retinylidene ethanolamine (A2E) retinoid which is thought to be a cytotoxic component for RPE is the best-characterized component of lipofuscin so far. Even if no direct correlation between A2E spatial distribution and lipofuscin fluorescence has been established in aged human RPE, modified forms or metabolites of A2E could be involved in ARMD pathology. Mitogen-activated protein kinase (MAPK) pathways have been involved in many pathologies, but not in ARMD. Therefore, we wanted to analyze the effects of A2E on MAPKs in polarized ARPE19 and isolated mouse RPE cells. We showed that long-term exposure of polarized ARPE19 cells to low A2E dose induces a strong decrease of the extracellular signal-regulated kinases' (ERK1/2) activity. In addition, we showed that A2E, via ERK1/2 decrease, induces a significant decrease of the retinal pigment epithelium-specific protein 65 kDa (RPE65) expression in ARPE19 cells and isolated mouse RPE. In the meantime, we showed that the decrease of ERK1/2 activity mediates an increase of basic fibroblast growth factor (bFGF) mRNA expression and secretion that induces an increase in phagocytosis via a paracrine effect. We suggest that the accumulation of deposits coming from outer segments (OS) could be explained by both an increase of bFGF-induced phagocytosis and by the decrease of clearance by A2E. The bFGF angiogenic protein may therefore be an attractive target to treat ARMD.

Auranofin Inhibits Retinal Pigment Epithelium Cell Survival through Reactive Oxygen Species-Dependent Epidermal Growth Factor Receptor/ Mitogen-Activated Protein Kinase Signaling Pathway

Abnormal survival of retinal pigment epithelium (RPE) cells contributes to the pathogenesis of proliferative vitreoretinopathy (PVR), a sight-threatening disease. In this study, we explored the effect of the anti-rheumatic agent auranofin (AF) on RPE cell survival and studied the underlying signaling mechanisms in vitro. Our results showed that AF inhibited ARPE-19 cell survival in a dose and time-dependent manner. Application of AF induced several effects: a significant decrease in total epidermal growth factor receptor (EGFR) and an increase in phosphorylated EGFR and mitogen-activated protein kinase (MAPK), including extracellular signal-regulated kinase (ERK), P38 mitogen-activated protein kinase (P38MAPK), c-Jun N-terminal kinase (JNK), c-Jun, mitogen activated protein kinase activated protein kinase 2(MAPKAPK2), and heat shock protein 27 (HSP27). AF also inhibited epidermal growth factor (EGF)-dependent cell proliferation and migration through affecting EGFR/MAPK signaling. The antioxidant N-acetylcysteine (NAC) blocked the AF-induced increase of reactive oxygen species (ROS) production, the reduction of total EGFR, and the phosphorylation of multiple nodes in EGFR/MAPK signaling pathway. P38MAPK inhibitor SB203580, but not inhibitors of EGFR (erlotinib), ERK (FR180204) and JNK (SP600125), suppressed AF-induced phosphorylation of EGFR/p38MAPK/MAPKAPK2/Hsp27. In conclusion, the ROS-dependent phosphorylation of EGFR/MAPK is an important signaling pathway for AF-induced inhibition of RPE cell survival, and AF may have the potential for treatment of abnormal survival of RPE cells in PVR.

Chemogenomic analysis of neuronal differentiation with pathway changes in PC12 cells

The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database creates networks from interrelations between molecular biology and underlying chemical elements. This allows for analysis of biologic networks, genomic information, and higher-order functional information at a system level. Through high throughput experiments and system biology analysis, we investigated the genes and pathways associated with NGF induced neuronal differentiation. We performed microarray experiments and used the KEGG database, system biology analysis, and annotation of pathway functions to study NGF-induced differentiation in PC12 cells. We identified 2020 NGF-induced genes with altered expressions over time. Cross-matching with the KEGG database revealed 830 genes; among which, 395 altered genes were found to have a 2-fold increase in gene expression over a two-hour period. We then identified 191 associated biologic pathways in the KEGG database; the top 15 pathways showed correlation with neural differentiation. These included the neurotrophin pathways, mitogen-activated protein kinase (MAPK) pathways, genes associated with axonal guidance and the Wnt pathways. The activation of these pathways synchronized with nerve growth factor (NGF)-induced differentiation in PC12 cells. In summary, we have established a model system that allows one to systematically characterize the functional pathway changes in a group of neuronal population after an external stimulus.

Martinique Crinkled Retinal Pigment Epitheliopathy: Clinical Stages and Pathophysiologic Insights

PURPOSE

To reappraise the autosomal dominant Martinique crinkled retinal pigment epitheliopathy (MCRPE) in light of the knowledge of its associated mutated gene mitogen-activated protein kinase-activated protein kinase 3 (MAPKAPK3), an actor in the p38 mitogen-activated protein kinase pathway.

DESIGN

Clinical and molecular study.

PARTICIPANTS

A total of 45 patients from 3 generations belonging to a family originating from Martinique with an autosomal dominant MCRPE were examined.

METHODS

Best-corrected visual acuity, fundus photographs, and spectral-domain optical coherence tomography (SD OCT) of all clinically affected patients and carriers for the causal mutation were reviewed at the initial visit and 4 years later for 10 of them. Histologic retinal lesions of Mapkapk3(-/-) mice were compared with those of the human disease.

MAIN OUTCOME MEASURES

The MCRPE natural history in view of MAPKAPK3 function and Mapkapk3(-/-) mouse retinal lesions.

RESULTS

Eighteen patients had the c.518T>C mutation. One heterozygous woman aged 20 years was asymptomatic with normal fundus and SD OCT (stage 0). All c.518T>C heterozygous patients older than 30 years of age had the characteristic dried-out soil fundus pattern (stages 1 and 2). Complications (stage 3) were observed in 7 cases, including polypoidal choroidal vasculopathy (PCV) and macular fibrosis or atrophy. One patient was homozygous and had a form with severe Bruch's membrane (BM) thickening and macular exudation with a dried-out soil pattern in the peripheral retina. The oldest heterozygous patient, who was legally blind, had peripheral nummular pigmentary changes (stage 4). After 4 years, visual acuity was unchanged in 6 of 10 patients. The dried-out soil elementary lesions radically enlarged in patients with a preferential macular extension and confluence. These findings are in line with the progressive thickening of BM noted with age in the mouse model. During follow-up, there was no occurrence of PCV.

CONCLUSIONS

MCRPE is an autosomal dominant, fully penetrant retinal dystrophy with a preclinical stage, an onset after the age of 30 years, and a preserved visual acuity until occurrence of macular complications. The natural history of MCRPE is in relation to the role of MAPKAPK3 in BM modeling, vascular endothelial growth factor activity, retinal pigment epithelial responses to aging, and oxidative stress.

Targeting MAPK Signaling in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a major cause of irreversible blindness affecting elderly people in the world. AMD is a complex multifactorial disease associated with demographic, genetics, and environmental risk factors. It is well established that oxidative stress, inflammation, and apoptosis play critical roles in the pathogenesis of AMD. The mitogen-activated protein kinase (MAPK) signaling pathways are activated by diverse extracellular stimuli, including growth factors, mitogens, hormones, cytokines, and different cellular stressors such as oxidative stress. They regulate cell proliferation, differentiation, survival, and apoptosis. This review addresses the novel findings from human and animal studies on the relationship of MAPK signaling with AMD. The use of specific MAPK inhibitors may represent a potential therapeutic target for the treatment of this debilitating eye disease.

A protective effect of anthocyanins and xanthophylls on UVB-induced damage in retinal pigment epithelial cells

Cyanidin-3-glucoside and zeaxanthin, alone or in combination, protect against UVB-induced retinal cells damage throw redox and MAPK activation regulation.

Fisetin and luteolin protect human retinal pigment epithelial cells from oxidative stress-induced cell death and regulate inflammation

Degeneration of retinal pigment epithelial (RPE) cells is a clinical hallmark of age-related macular degeneration (AMD), the leading cause of blindness among aged people in the Western world. Both inflammation and oxidative stress are known to play vital roles in the development of this disease. Here, we assess the ability of fisetin and luteolin, to protect ARPE-19 cells from oxidative stress-induced cell death and to decrease intracellular inflammation. We also compare the growth and reactivity of human ARPE-19 cells in serum-free and serum-containing conditions. The absence of serum in the culture medium did not prevent ARPE-19 cells from reaching full confluency but caused an increased sensitivity to oxidative stress-induced cell death. Both fisetin and luteolin protected ARPE-19 cells from oxidative stress-induced cell death. They also significantly decreased the release of pro-inflammatory cytokines into the culture medium. The decrease in inflammation was associated with reduced activation of MAPKs and CREB, but was not linked to NF- κB or SIRT1. The ability of fisetin and luteolin to protect and repair stressed RPE cells even after the oxidative insult make them attractive in the search for treatments for AMD.

Protective effects of resveratrol against UVA-induced damage in ARPE19 cells

Ultraviolet radiation, especially UVA, can penetrate the lens, reach the retina, and induce oxidative stress to retinal pigment epithelial (RPE) cells. Even though it is weakly absorbed by protein and DNA, it may trigger the production of reactive oxygen species (ROS) and generate oxidative injury; oxidative injury to the retinal pigment epithelium has been implicated to play a contributory role in age-related macular degeneration (AMD). Studies showed that resveratrol, an abundant and active component of red grapes, can protect several cell types from oxidative stress. In this study, adult RPE cells being treated with different concentrations of resveratrol were used to evaluate the protective effect of resveratrol on RPE cells against UVA-induced damage. Cell viability assay showed that resveratrol reduced the UVA-induced decrease in RPE cell viability. Through flow cytometry analysis, we found that the generation of intracellular H₂O₂ induced by UVA irradiation in RPE cells could be suppressed by resveratrol in a concentration-dependent manner. Results of Western blot analysis demonstrated that resveratrol lowered the activation of UVA-induced extracellular signal-regulated kinase, c-jun-NH₂ terminal kinase and p38 kinase in RPE cells. In addition, there was also a reduction in UVA-induced cyclooxygenase-2 (COX-2) expression in RPE cells pretreated with resveratrol. Our observations suggest that resveratrol is effective in preventing RPE cells from being damaged by UVA radiation, and is worth considering for further development as a chemoprotective agent for the prevention of early AMD.

Pharmacological protection of retinal pigmented epithelial cells by sulindac involves PPAR-α

The retinal pigmented epithelial (RPE) layer is one of the major ocular tissues affected by oxidative stress and is known to play an important role in the etiology of age-related macular degeneration (AMD), the major cause of blinding in the elderly. In the present study, sulindac, a nonsteroidal antiinflammatory drug (NSAID), was tested for protection against oxidative stress-induced damage in an established RPE cell line (ARPE-19). Besides its established antiinflammatory activity, sulindac has previously been shown to protect cardiac tissue against ischemia/reperfusion damage, although the exact mechanism was not elucidated. As shown here, sulindac can also protect RPE cells from chemical oxidative damage or UV light by initiating a protective mechanism similar to what is observed in ischemic preconditioning (IPC) response. The mechanism of protection appears to be triggered by reactive oxygen species (ROS) and involves known IPC signaling components such as PKG and PKC epsilon in addition to the mitochondrial ATP-sensitive K(+) channel. Sulindac induced iNOS and Hsp70, late-phase IPC markers in the RPE cells. A unique feature of the sulindac protective response is that it involves activation of the peroxisome proliferator-activated receptor alpha (PPAR-α). We have also used low-passage human fetal RPE and polarized primary fetal RPE cells to validate the basic observation that sulindac can protect retinal cells against oxidative stress. These findings indicate a mechanism for preventing oxidative stress in RPE cells and suggest that sulindac could be used therapeutically for slowing the progression of AMD.

Squamosamide derivative FLZ protects retinal pigment epithelium cells from oxidative stress through activation of epidermal growth factor receptor (EGFR)-AKT signaling

Reactive oxygen species (ROS)-mediated retinal pigment epithelium (RPE) cell apoptosis is attributed to age-related macular degeneration (AMD) pathogenesis. FLZ, a novel synthetic squamosamide derivative from a Chinese herb, Annona glabra, has displayed significant cyto-protective activity. In the current study, we explored the pro-survival effect of FLZ in oxidative stressed-RPE cells and studied the underlying signaling mechanisms. Our results showed that FLZ attenuated hydrogen peroxide (H2O2)-induced viability decrease and apoptosis in the RPE cell line (ARPE-19 cells) and in primary mouse RPE cells. Western blotting results showed that FLZ activated AKT signaling in RPE cells. The AKT-specific inhibitor, MK-2206, the phosphoinositide 3-kinase (PI3K)/AKT pan inhibitor, wortmannin, and AKT1-shRNA (short hairpin RNA) depletion almost abolished FLZ-mediated pro-survival/anti-apoptosis activity. We discovered that epidermal growth factor receptor (EGFR) trans-activation mediated FLZ-induced AKT activation and the pro-survival effect in RPE cells, and the anti-apoptosis effect of FLZ against H2O2 was inhibited by the EGFR inhibitor, PD153035, or by EGFR shRNA-knockdown. In conclusion, FLZ protects RPE cells from oxidative stress through activation of EGFR-AKT signaling, and our results suggest that FLZ might have therapeutic values for AMD.