Retinal Pigment Epithelial ARPE-19 Cells Research Articles

Protective Effects of Purple Corn (Zea mays L.) Byproduct Extract on Blue Light-Induced Retinal Damage in A2E-Accumulated ARPE-19 Cells.

This study investigated the antioxidative characteristics of Zea mays L. purple corn cob and husk extract (PCHE) and its potential protective effects against blue light (BL)-induced damage in N-retinylidene-N-retinylethanolamine (A2E)-accumulated ARPE-19 retinal pigment epithelial cells. PCHE had a 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity and Trolox equivalent antioxidant capacity of 1.28±0.43 mM Trolox equivalents (TE)/g and 2,545.41±34.13 mM TE/g, respectively. Total content of anthocyanins, polyphenols, and flavonoids in the PCHE was 11.13±0.10 mg cyanidin-3-glucoside equivalents/100 g, 227.90±7.38 mg gallic acid equivalents/g, and 117.75±2.46 mg catechin equivalents/g, respectively. PCHE suppressed the accumulation of A2E and the photooxidation caused by BL in a dose-dependent manner. After initial treatment with 25 µM/mL A2E and BL, ARPE-19 cells showed increased cell viability following additional treatment with 15 µg/mL PCHE while the expression of the p62 sequestosome 1 decreased, whereas that of heme oxygenase-1 protein increased compared with that in cells without PCHE treatment. This suggests that PCHE may slow the autophagy induced by BL exposure in A2E-accumulated retinal cells and protect them against oxidative stress.

Glaucine inhibits hypoxia-induced angiogenesis and attenuates LPS-induced inflammation in human retinal pigment epithelial ARPE-19 cells

Glaucine is an aporphine alkaloid with anti-inflammatory, bronchodilator and anti-cancer activities. However, the effects of glaucine in the regulation of age-related macular degeneration (AMD) remain unclear. Herein, we aimed to investigate the anti-angiogenetic and anti-inflammatory effects of glaucine in ARPE-19 cells. ARPE-19 cells were treated with N-(methoxyoxoacetyl)-glycine, methyl ester (DMOG) and cobalt chloride (CoCl2) for induction of hypoxia, while lipopolysaccharide (LPS) treatment was used for elicitation of inflammatory response. Cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. The expression of hypoxia-inducible factor (HIF-1α) and vascular endothelial growth factor (VEGF) were measured by Western blot. The secretion of VEGF, interleukin (IL)-6 and monocyte chemoattractant protein-1 (MCP-1) was detected using enzyme-linked immunosorbent assay (ELISA). Human umbilical vein endothelial cells (HUVECs) were used for tube formation analysis. Expression of HIF-1α and secretion of VEGF were significantly increased under DMOG and CoCl2 induction, whereas glaucine significantly attenuated both HIF-1α expression and VEGF secretion by DMOG- and CoCl2-induced ARPE-19 cells. In addition, glaucine suppressed the tube formation by DMOG- and CoCl2-induced HUVEC cells. Moreover, glaucine also attenuated the production of IL-6 and MCP-1 by LPS-induced ARPE-19 cells. This study indicated that glaucine exhibited anti-angiogenic and anti-inflammatory effects, suggesting that glaucine might have benefits for the treatment of AMD.

Anthocyanins Inhibits Oxidative Injury in Human Retinal Pigment Epithelial ARPE-19 Cells via Activating Heme Oxygenase-1.

Anthocyanins belong to phenolic pigments and are known to have various pharmacological activities. This study aimed to investigate whether anthocyanins could inhibit hydrogen peroxide (H2O2)-induced oxidative damage in human retinal pigment epithelial ARPE-19 cells. Our results indicated that anthocyanins suppressed H2O2-induced genotoxicity, while inhibiting reactive oxygen species (ROS) production and preserving diminished glutathione. Anthocyanins also suppressed H2O2-induced apoptosis by reversing the Bcl-2/Bax ratio and inhibiting caspase-3 activation. Additionally, anthocyanins attenuated the release of cytochrome c into the cytosol, which was achieved by interfering with mitochondrial membrane disruption. Moreover, anthocyanins increased the expression of heme oxygenase-1 (HO-1) as well as its activity, which was correlated with the phosphorylation and nuclear translocation of nuclear factor-erythroid-2 related factor 2 (Nrf2). However, the cytoprotective and anti-apoptotic effects of anthocyanins were significantly attenuated by the HO-1 inhibitor, demonstrating that anthocyanins promoted Nrf2-induced HO-1 activity to prevent ARPE-19 cells from oxidative stress. Therefore, our findings suggest that anthocyanins, as Nrf2 activators, have potent ROS scavenging activity and may have the potential to protect ocular injury caused by oxidative stress.

Synthesis and Biological Evaluation of Novel Benzylidene Thiazolo Pyrimidin-3(5H)-One Derivatives

Starting compound 1 was synthesized according to reference. 1 Benzylidene thiazole pyrimidin-3(5H)-ones were synthesized reactions of 1 with bromoacetic acid and various aryl-aldehydes in the same vessel via one-step, unlike studies in the literature. Quantum chemical parameters and full geometry optimizations for all compounds were computed using DFT based on B3LYP. Cytotoxic action potential of synthesized compounds was evaluated using trypan blue dye exclusion and MTT assays in different cell lines including adenocarcinoma alveolar basal epithelial-like adherent A549 cells, the colon adenocarcinoma HT-29 cells, prostate adenocarcinoma DU-145 cells, and diploid ARPE-19 retinal pigment epithelial cells. Embryotoxicity and genotoxicity assessments were performed on pluripotent human embryonal carcinoma NT2 and human lymphocyte cells, respectively. Compound A1 exhibited good anticancer activity on A549 and DU-145 cell lines, and the compounds including A3, 4, 6, and 9 induced cytotoxicity on A549 cells. The compounds A1-10 also showed a good biosafety profile at relatively lower concentrations.

β-Asarone Alleviates High-Glucose-Induced Oxidative Damage via Inhibition of ROS Generation and Inactivation of the NF-κB/NLRP3 Inflammasome Pathway in Human Retinal Pigment Epithelial Cells.

Diabetic retinopathy (DR) is the leading cause of vision loss and a major complication of diabetes. Hyperglycemia-induced accumulation of reactive oxygen species (ROS) is an important risk factor for DR. β-asarone, a major component of volatile oil extracted from Acori graminei Rhizoma, exerts antioxidant effects; however, its efficacy in DR remains unknown. In this study, we investigated whether β-asarone inhibits high-glucose (HG)-induced oxidative damage in human retinal pigment epithelial (RPE) ARPE-19 cells. We found that β-asarone significantly alleviated cytotoxicity, apoptosis, and DNA damage in HG-treated ARPE-19 cells via scavenging of ROS generation. β-Asarone also significantly attenuated the excessive accumulation of lactate dehydrogenase and mitochondrial ROS by increasing the manganese superoxide dismutase and glutathione activities. HG conditions markedly increased the release of interleukin (IL)-1β and IL-18 and upregulated their protein expression and activation of the nuclear factor-kappa B (NF-κB) signaling pathway, whereas β-asarone reversed these effects. Moreover, expression levels of the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome multiprotein complex molecules, including thioredoxin-interacting protein, NLRP3, apoptosis-associated speck-like protein containing a caspase-recruitment domain, and cysteinyl aspartate-specific proteinase-1, were increased in ARPE-19 cells under HG conditions. However, their expression levels remained similar to those in the control group in the presence of β-asarone. Therefore, β-asarone protects RPE cells from HG-induced injury by blocking ROS generation and NF-κB/NLRP3 inflammasome activation, indicating its potential as a therapeutic agent for DR treatment.

Urban aerosol particulate matter promotes mitochondrial oxidative stress-induced cellular senescence in human retinal pigment epithelial ARPE-19 cells

Environmental exposure to urban particulate matter (UPM) is a serious health concern worldwide. Although several studies have linked UPM to ocular diseases, no study has reported effects of UPM exposure on senescence in retinal cells. Therefore, this study aimed to investigate the effects of UPM on senescence and regulatory signaling in human retinal pigment epithelial ARPE-19 cells. Our study demonstrated that UPM significantly promoted senescence, with increased senescence-associated β-galactosidase activity. Moreover, both mRNA and protein levels of senescence markers (p16 and p21) and the senescence-associated secretory phenotype, including IL-1β, matrix metalloproteinase-1, and −3 were upregulated. Notably, UPM increased mitochondrial reactive oxygen species-dependent nuclear factor-kappa B (NF-κB) activation during senescence. In contrast, use of NF-κB inhibitor Bay 11–7082 reduced the level of senescence markers. Taken together, our results provide the first in vitro preliminary evidence that UPM induces senescence by promoting mitochondrial oxidative stress-mediated NF-κB activation in ARPE-19 cells.

Reduction of high glucose-induced oxidative injury in human retinal pigment epithelial cells by sarsasapogenin through inhibition of ROS generation and inactivation of NF-κB/NLRP3 inflammasome pathway.

Hyperglycemia-induced accumulation of reactive oxygen species (ROS) is a major risk factor for diabetic retinopathy (DR). Sarsasapogenin is a natural steroidal saponin that is known to have excellent antidiabetic effects and improve diabetic complications, but its potential efficacy and mechanism for DR are unknown. The current study was designed to explore whether sarsasapogenin inhibits hyperglycemia-induced oxidative stress in human retinal pigment epithelial (RPE) ARPE-19 cells and to elucidate the molecular mechanisms. To mimic hyperglycemic conditions, ARPE-19 cells were cultured in medium containing high glucose (HG). The suppressive effects of sarsasapogenin on HG-induced cell viability reduction, apoptosis and ROS production were investigated. In addition, the relevance of the nuclear factor-kappa B (NF-κB)/NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome signaling pathway was explored to investigate the mechanism of antioxidant and anti-inflammatory activity of sarsasapogenin. Sarsasapogenin significantly alleviated cytotoxicity and apoptosis in HG-treated ARPE-19 cells through inhibition of intracellular ROS generation. Sarsasapogenin also effectively attenuated HG-induced excess accumulation of mitochondrial superoxide, reduction of glutathione content, and inactivation of manganese superoxide dismutase and glutathione peroxidase. The HG condition markedly increased the expression and maturation of interleukin (IL)-1β and IL-18 through the activation of the NF-kB signaling pathway, whereas sarsasapogenin reversed these effects. Moreover, although the expression of NLRP3 inflammasome multiprotein complex molecules was increased in ARPE-19 cells cultured under HG conditions, their levels remained similar to the control group in the presence of sarsasapogenin. Sarsasapogenin could protect RPE cells from HG-induced injury by inhibiting ROS generation and NF-κB/NLRP3 inflammasome pathway, suggesting its potential as a therapeutic agent to improve the symptoms of DR.

Isolation and Identification of Dihydrophenanthrene Derivatives from Dendrobium virgineum with Protective Effects against Hydrogen-Peroxide-Induced Oxidative Stress of Human Retinal Pigment Epithelium ARPE-19 Cells

Oxidative stress is a significant factor in the development of age-related macular degeneration (AMD), which results from cell damage, dysfunction, and death in the retinal pigmented epithelium (RPE). The use of natural compounds with antioxidant properties to protect RPE cells from oxidative stress has been explored in Dendrobium, a genus of orchid plants belonging to the family Orchidaceae. Two new compounds and seven known compounds from the MeOH extract of the whole plant of Dendrobium virgineum were successfully isolated and structurally characterized. Out of all the compounds isolated, 2-methoxy-9,10-dihydrophenanthrene-4,5-diol (3) showed the highest protective effect against hydrogen peroxide (H2O2)-induced oxidative stress in human retinal pigment epithelial (ARPE-19) cells. Therefore, it was selected to evaluate its protective effect and mechanism on oxidative-stress-induced ARPE-19 cells. Cells were pre-treated with compound 3 at 25, 50, and 100 µg/mL for 24 h and then induced with 400 µM H2O2 for 1 h. The results demonstrated that compound 3 significantly (p < 0.05) increased cell viability by 10-35%, decreased ROS production by 10-30%, and reduced phosphorylation of p38, ERK1/2, and SAPK/JNK by 20-70% in a dose-dependent manner without toxicity. Furthermore, compound 3 significantly (p < 0.05) modulated the expression of apoptosis pathway proteins (cytochrome c, Bax and Bcl-2) by 20-80%, and enhanced SOD, CAT, and GPX activities, and GSH levels in a dose-dependent manner. These results suggest that compound 3 protects ARPE-19 cells against oxidative stress through MAPKs and apoptosis pathways, including the antioxidant system. Thus, compound 3 could be considered as an antioxidant agent for preventing AMD development by protecting RPE cells from oxidative stress and maintaining the retina. These findings open up new possibilities for the use of natural compounds in the treatment of AMD and other oxidative-stress-related conditions.

Phloroglucinol Attenuates DNA Damage and Apoptosis Induced by Oxidative Stress in Human Retinal Pigment Epithelium ARPE-19 Cells by Blocking the Production of Mitochondrial ROS.

Phloroglucinol, a phenolic compound, is known to possess a potent antioxidant ability. However, its role in retinal cells susceptible to oxidative stress has not been well elucidated yet. Thus, the objective of this study was to evaluate whether phloroglucinol could protect against oxidative damage in cultured human retinal pigment epithelium ARPE-19 cells. For this purpose, ARPE-19 cells were stimula ted with hydrogen peroxide (H2O2) to mimic oxidative stress. Cell viability, cytotoxicity, apoptosis, reactive oxygen species (ROS) generation, mitochondrial function, DNA damage, and autophagy were then assessed. Our results revealed that phloroglucinol ameliorated cell viability, cytotoxicity, and DNA damage in H2O2-exposued ARPE-19 cells and blocked production of ROS. Phloroglucinol also counteracted H2O2-induced apoptosis by reducing Bax/Bcl-2 ratio, blocking activation of caspase-3, and inhibiting degradation of poly (ADP-ribose) polymerase. H2O2 caused mitochondrial impairment and increased expression levels of mitophagy markers such as PINK1and PARKIN known to be associated with mitochondrial ROS (mtROS) generation and cytosolic release of cytochrome c. However, these changes were significantly attenuated by phloroglucinol. Mito-TEMPO, a selective mitochondrial antioxidant, further enhanced the protective effect of phloroglucinol against dysfunctional mitochondria. Furthermore, H2O2 induced autophagy, but not when ARPE-19 cells were pretreated with phloroglucinol, meaning that autophagy by H2O2 contributed to the pro-survival mechanism and that phloroglucinol protected ARPE-19 cells from apoptosis by blocking autophagy. Taken together, these results suggest that phloroglucinol can inhibit oxidative stress-induced ARPE-19 cell damage and dysfunction by protecting DNA damage, autophagy, and subsequent apoptosis through mitigation of mtROS generation. Thus, phloroglucinol might have therapeutic potential to prevent oxidative stress-mediated damage in RPE cells.

Nrf2-mediated activation of HO-1 is required in the blocking effect of compound K, a ginseng saponin metabolite, against oxidative stress damage in ARPE-19 human retinal pigment epithelial cells

BackgroundThe beneficial effects of compound K (CK) on different chronic diseases have been shown to be at least related to antioxidant action. Nevertheless, since its antioxidant activity in human retinal pigment epithelial (RPE) cells is still unknown, here we investigated whether CK alleviates oxidative stress-stimulated damage in RPE ARPE-19 cells. MethodsThe cytoprotective consequence of CK in hydrogen peroxide (H2O2)-treated cells was evaluated by cell viability, DNA damage, and apoptosis assays. Fluorescence analysis and immunoblotting were performed to investigate the inhibitory action of CK on reactive oxygen species (ROS) production and mitochondrial dysfunction. ResultsH2O2-promoted cytotoxicity, oxidative stress, DNA damage, mitochondrial impairment, and apoptosis were significantly attenuated by CK in ARPE-19 cells. Furthermore, nuclear factor erythroid 2-related factor 2 (Nrf2) phosphorylation level and its shuttling to the nucleus were increased, which was correlated with upregulated activation of heme oxygenase-1 (HO-1). However, zinc protoporphyrin, a blocker of HO-1, significantly abrogated the preventive action of CK in H2O2-treated ARPE-19 cells. ConclusionThis study indicates that activation of Nrf2/HO-1 signaling by CK plays an important role in rescuing ARPE-19 cells from oxidative cellular damage.

Carvacrol protects the ARPE19 retinal pigment epithelial cells against high glucose-induced oxidative stress, apoptosis, and inflammation by suppressing the TRPM2 channel signaling pathways.

The concentration of plasma high glucose (HGu) in diabetes mellitus (DM) induces the retinal pigment epithelial cell (ARPE19) death via the increase of inflammation, cytosolic (cytROS), and mitochondrial (mitROS) free oxygen radical generations. Transient potential melastatin 2 (TRPM2) cation channel is stimulated by cytROS and mitROS. Hence, the cytROS and mitROS-mediated excessive Ca2+ influxes via the stimulation of TRPM2 channel cause to the induction of DM-mediated retina oxidative cytotoxicity. Because of the antioxidant role of carvacrol (CRV), it may modulate oxidative cytotoxicity via the attenuation of TRPM2 in the ARPE19. We aimed to investigate the modulator action of CRV treatment on the HGu-mediated TRPM2 stimulation, oxidative stress, and apoptosis in the ARPE19 cell model. The ARPE19 cells were divided into four groups as normal glucose (NGu), NGu + Carv, HGu, and HGu + CRV. The levels of cell death (propidium iodide/Hoechst rate) and apoptosis markers (caspases 3, 8, and 9), cytokine generations (IL-1β and TNF-α), ROS productions (cytROS, mitROS, and lipid peroxidation), TRPM2 currents, and intracellular free Ca2+ (Fluo/3) were increased in the HGu group after the stimulations of hydrogen peroxide and ADP-ribose, although their levels were diminished via upregulation of glutathione and glutathione peroxidase by the treatments of CRV and TRPM2 blockers. Current results confirmed that the HGu-induced overload Ca2+ influx and oxidative retinal toxicity in the ARPE19 cellswere induced by the stimulation of TRPM2, although they were modulated via the inhibition of TRPM2 by CRV. CRV may be noted as a potential therapeutic antioxidant to the TRPM2 activation-mediated retinal oxidative injury.

LncRNA FLG-AS1 Mitigates Diabetic Retinopathy by Regulating Retinal Epithelial Cell Inflammation, Oxidative Stress, and Apoptosis via miR-380-3p/SOCS6 Axis.

The objective of this study is to investigate lncRNA FLG-AS1-mediated miR-380-3p/SOCS6 axis in inflammation, oxidative stress, and apoptosis of retinal epithelial cells in diabetic retinopathy (DR). Fasting blood was collected from 60 DR patients and 60 healthy controls. The Pearson correlation was used to analyze the correlation between the expression levels of FLG-AS1 and miR-380-3p in DR patients. qRT-PCR and/or Western blotting were used to detect the expression of FLG-AS1, miR-380-3p, and SOCS6. After gain of function of FLG-AS1 or SOCS6 or loss of function of miR-380-3p, high glucose (HG)-treated human retinal pigment epithelial ARPE-19 cells were subjected to TUNEL assessment of apoptosis. ELISA was performed to detect the expression levels of IL-1β, IL-6, and TNF-α in cell culturesupernatant. DCFH-DA was used to detect the level of ROS in the cells. MDA and SOD assay kits were used to measure the activity of MDA and SOD in the cells. Dual-luciferase reporter assay was performed to verify the binding between miR-380-3p and FLG-AS1 or between miR-380-3p and SOCS6. Streptozotocin injections were used to induce diabetes in rats which were injected with FLG-AS1 overexpression lentiviral vectors in the eye. Twenty weeks later, retinal tissue was isolated and stained with hematoxylin-eosin or TUNEL. Compared to that in healthy controls, FLG-AS1 expression decreased 2.5-fold and miR-380-3p expression increased 2.6-fold in the serum of DR patients. The expression levels of FLG-AS1 and miR-380-3p were negatively correlated in DR patients (r = -0.3772, P = 0.003). Overexpression of FLG-AS1 reduced inflammation, oxidative stress, and apoptosis of HG-treated ARPE-19 cells and alleviated retinal injury in diabetic rats. FLG-AS1 promoted the expression of SOCS6 by targeting miR-380-3p. Inhibition of miR-380-3p or overexpression of SOCS6 reduced inflammation, oxidative stress, and apoptosis of HG-treated ARPE-19 cells. FLG-AS1 mitigates DR by regulating retinal epithelial cell inflammation, oxidative stress, and apoptosis via the miR-380-3p/SOCS6 axis.

Sulforaphane ameliorates amyloid-β-induced inflammatory injury by suppressing the PARP1/SIRT1 pathway in retinal pigment epithelial cells

ABSTRACT Age-associated macular degeneration (AMD) is a progressive eye disorder that leads to irreversible impairment of central vision, and effective therapies are lacking. Here, we explore how oligomeric amyloid-β1-42 can trigger inflammatory injury in retinal pigment epithelial cells and how sulforaphane can mitigate such injury. ARPE-19 retinal pigment epithelial cells expressing low, endogenous, or high levels of poly(ADP-ribose) polymerase (PARP1) were treated with oligomeric amyloid-β1-42 in the presence or absence of various signaling inhibitors or sulforaphane. Cell viability, apoptosis, inflammatory responses, and activity of the PARP1/Sirtuin (SIRT1) axis were assayed. Treating ARPE-19 cells with oligomeric amyloid-β1-42 promoted the production of IL-1β, IL-6, IL-8, and TNF-ɑ, which was partially reversed by inhibiting PARP1 and activating SIRT1. PARP1 was found to act upstream of SIRT1, and expression of the two proteins correlated negatively with each other. Sulforaphane also mitigated the injury due to oligomeric amyloid-β1-42 through a mechanism involving inactivation of the PARP1/SIRT1 pathway. Oligomeric amyloid-β1-42 can trigger AMD-like injury in retinal pigment epithelium by activating PARP1 and repressing SIRT1. Moreover, sulforaphane can induce cell viability and SIRT1 expression, but reduce cell apoptosis, the activity of caspase-3 or −9, and PARP1 expression in oAβ1-42-treated cells. However, PARP1 inactivation or SIRT1 activation weaken these effects. In summary, sulforaphane reduces the inflammatory injury induced by oAβ1-42 in ARPE-19 cell by inactivating the PARP1/SIRT1 pathway. Thus, the compound may be an effective therapy against AMD.

Chronobiological activity of cysteinyl leukotriene receptor 1 during basal and induced autophagy in the ARPE-19 retinal pigment epithelial cell line.

Autophagy is an important cellular mechanism for maintaining cellular homeostasis, and its impairment correlates highly with age and age-related diseases. Retinal pigment epithelial (RPE) cells of the eye represent a crucial model for studying autophagy, as RPE functions and integrity are highly dependent on an efficient autophagic process. Cysteinyl leukotriene receptor 1 (CysLTR1) acts in immunoregulation and cellular stress responses and is a potential regulator of basal and adaptive autophagy. As basal autophagy is a dynamic process, the aim of this study was to define the role of CysLTR1 in autophagy regulation in a chronobiologic context using the ARPE-19 human RPE cell line.Effects of CysLTR1 inhibition on basal autophagic activity were analyzed at inactive/low and high lysosomal degradation activity with the antagonists zafirlukast (ZTK) and montelukast (MTK) at a dosage of 100 nM for 3 hours. Abundances of the autophagy markers LC3-II and SQSTM1 and LC3B particles were analyzed in the absence and presence of lysosomal inhibitors using western blot analysis and immunofluorescence microscopy.CysLTR1 antagonization revealed a biphasic effect of CysLTR1 on autophagosome formation and lysosomal degradation that depended on the autophagic activity of cells at treatment initiation. ZTK and MTK affected lysosomal degradation, but only ZTK regulated autophagosome formation. In addition, dexamethasone treatment and serum shock induced autophagy, which was repressed by CysLTR1 antagonization. As a newly identified autophagy modulator, CysLTR1 appears to be a key player in the chronobiological regulation of basal autophagy and adaptive autophagy in RPE cells.

Effect of space flight on the behavior of human retinal pigment epithelial ARPE-19 cells and evaluation of coenzyme Q10 treatment.

Astronauts on board the International Space Station (ISS) are exposed to the damaging effects of microgravity and cosmic radiation. One of the most critical and sensitive districts of an organism is the eye, particularly the retina, and > 50% of astronauts develop a complex of alterations designated as spaceflight-associated neuro-ocular syndrome. However, the pathogenesis of this condition is not clearly understood. In the current study, we aimed to explore the cellular and molecular effects induced in the human retinal pigment ARPE-19 cell line by their transfer to and 3-day stay on board the ISS in the context of an experiment funded by the Agenzia Spaziale Italiana. Treatment of cells on board the ISS with the well-known bioenergetic, antioxidant, and antiapoptotic coenzyme Q10 was also evaluated. In the ground control experiment, the cells were exposed to the same conditions as on the ISS, with the exception of microgravity and radiation. The transfer of ARPE-19 retinal cells to the ISS and their living on board for 3days did not affect cell viability or apoptosis but induced cytoskeleton remodeling consisting of vimentin redistribution from the cellular boundaries to the perinuclear area, underlining the collapse of the network of intermediate vimentin filaments under unloading conditions. The morphological changes endured by ARPE-19 cells grown on board the ISS were associated with changes in the transcriptomic profile related to the cellular response to the space environment and were consistent with cell dysfunction adaptations. In addition, the results obtained from ARPE-19 cells treated with coenzyme Q10 indicated its potential to increase cell resistance to damage.

Neuroprotection of retinal cells by Caffeic Acid Phenylethyl Ester（CAPE) is mediated by mitochondrial uncoupling protein UCP2

Oxidative stress due to mitochondrial produced reactive oxygen species is a major cause of damage seen in many retinal degenerative diseases. Caffeic acid phenylethyl ester （CAPE） is protective agent in multiple tissues and is reported to have anti-oxidant properties. Systemically applied CAPE protected retinal ganglion cells from ischemic injury induced by increased intraocular pressure. CAPE provided complete protection for ARPE19 retinal pigment epithelial cells against tert-butyl hydrogen peroxide and reduced both basal and LPS-stimulated ROS production. The major effect of CAPE was mediated by the mitochondrial uncoupling protein UCP2 since both pharmacological inhibition of UCP2 and siRNA-induced knockdown removed the ability of CAPE to block ROS production. Based on common structural features, CAPE may be acting as a mimetic of the natural UCP2 homeostatic regulator 4-hydroxy-2-nonenal. CAPE may provide a valuable tool to treat oxidative stress-related damage in retinal and other degenerative diseases.

Astragalus Polysaccharide Regulates miR-182/Bcl-2 Axis to Relieve Metabolic Memory through Suppressing Mitochondrial Damage-Mediated Apoptosis in Retinal Pigment Epithelial Cells

Introduction: Metabolic memory is one of the causes of diabetic retinopathy, and astragalus polysaccharide (APS) has great advantages in the treatment of diabetes. However, the effect of APS on metabolic memory remains to be investigated. Methods: Retinal pigment epithelial cell line ARPE-19 and primary retinal pigment epithelial cells were used to verify the effect of APS on mitochondria damage and apoptosis induced by high glucose-induced metabolic memory. The relationship between miR-182 and Bcl-2 was confirmed by a luciferase activity assay. Western blotting and quantitative reverse-transcriptase polymerase chain reaction were conducted to investigate the changes in mitochondrial damage- and apoptosis-associated markers. The cell mitochondrial membrane potential was assessed by JC-1 fluorescence. Terminal deoxynucleotidyl transferase dUTP nick end labelling staining and flow cytometry assays were performed to determine the occurrence of apoptosis. Results: Treatment with high glucose followed by normal glucose significantly upregulated the expression of miR-182 and downregulated the expression of its target Bcl-2, and APS treatment reversed the above effects. Additionally, APS treatment restored mitochondrial function and inhibited apoptosis in cells in a state of metabolic memory. The effects of APS against mitochondrial damage and apoptosis were partially inhibited after miR-182 overexpression. Conclusion: APS alleviated mitochondrial damage and apoptosis induced by metabolic memory by regulating the miR-182/Bcl-2 axis, which might serve as a new strategy for the treatment of diabetic retinopathy.

MicroRNA-100 Mediates Hydrogen Peroxide-Induced Apoptosis of Human Retinal Pigment Epithelium ARPE-19 Cells.

This study investigated the regulatory role of microRNA 100 (miR-100) in hydrogen peroxide (H2O2)-induced apoptosis of human retinal pigment epithelial ARPE-19 cells. H2O2 induced oxidative cell death of cultured ARPE-19 cells was measured by cytotoxicity assay. qRT-PCR was used to quantify cytosolic and extracellular contents of miR-100. Kinase and miR-100 inhibition treatments were applied to determine the regulatory signaling pathways involved in cell death regulation. H2O2 dose-dependently reduced viability of ARPE-19 cells and simultaneously upregulated miR-100 levels in both cytosolic and extracellular compartments. Western blotting detection indicated that H2O2 elicited hyperphosphorylation of PI3K/Akt, ERK1/2, JNK, p38 MAPK, and p65 NF-κB. Further kinase inhibition experiments demonstrated that PI3K, p38 MAPK, and NF-κB activities were involved in oxidative-stress-induced miR-100 upregulation in ARPE-19 cells, while blockade of PI3K, JNK, and NF-κB signaling significantly attenuated the oxidative cell death. Intriguingly, MiR-100 antagomir treatment exerted a cytoprotective effect against the H2O2-induced oxidative cell death through attenuating the oxidation-induced AMPK hyperphosphorylation, restoring cellular mTOR and p62/SQSTM1 levels and upregulating heme oxygenase-1 expression. These findings support that miR-100 at least in part mediates H2O2-induced cell death of ARPE-19 cells and can be regarded as a preventive and therapeutic target for retinal degenerative disease.

Sodium iodate induces ferroptosis in human retinal pigment epithelium ARPE-19 cells

Sodium iodate (SI) is a widely used oxidant for generating retinal degeneration models by inducing the death of retinal pigment epithelium (RPE) cells. However, the mechanism of RPE cell death induced by SI remains unclear. In this study, we investigated the necrotic features of cultured human retinal pigment epithelium (ARPE-19) cells treated with SI and found that apoptosis or necroptosis was not the major death pathway. Instead, the death process was accompanied by significant elevation of intracellular labile iron level, ROS, and lipid peroxides which recapitulated the key features of ferroptosis. Ferroptosis inhibitors deferoxamine mesylate (DFO) and ferrostatin-1(Fer-1) partially prevented SI-induced cell death. Further studies revealed that SI treatment did not alter GPX4 (glutathione peroxidase 4) expression, but led to the depletion of reduced thiol groups, mainly intracellular GSH (reduced glutathione) and cysteine. The study on iron trafficking demonstrated that iron influx was not altered by SI treatment but iron efflux increased, indicating that the increase in labile iron was likely due to the release of sequestered iron. This hypothesis was verified by showing that SI directly promoted the release of labile iron from a cell-free lysate. We propose that SI depletes GSH, increases ROS, releases labile iron, and boosts lipid damage, which in turn results in ferroptosis in ARPE-19 cells.

MiR-132 mediates cell permeability and migration by targeting occludin in high-glucose -induced ARPE-19 cells.

This study investigated the effects and mechanisms of miR-132 related to the permeability and mobility of human retinal pigment epithelium ARPE-19 cells in high-glucose (HG) condition. ARPE-19 cells were cultured in normal and HG condition and identified by immunofluorescence staining. Cell viability was assessed by the MTT assay, cell permeability was assessed by the FITC-dextran assay and cell mobility was assessed by the wound healing assay. Different miRNA and mRNA expression levels were determined by quantitative real-time polymerase chain reaction (RT-qPCR). The expression of tight junction-related proteins was determined by Western blot assay and immunofluorescence. The interaction between occludin and miR-132 was confirmed by a dual-luciferase reporter assay. We revealed that HG-treated ARPE-19 cells exhibited significantly increased miR-132 expression, decreased expression of the tight-junction markers including occludin and E-cadherin, and increased cell mobility and permeability. Occludin is a direct target of miR-132, which could regulate cell viability, mobility and permeability under HG condition through the JAK/STAT3 signaling pathway. These are the first data to suggest that miR-132 may contribute to the progression of diabetic retinopathy (DR) and that targeting the effect of miR-132 on occudin and the JAK/STAT3 pathway could represent a novel effective DR-treatment strategy.