Hepatocyte growth factor promotes retinal pigment epithelium cell activity through MET/AKT signaling pathway

AIM:To explore the effects of hepatocyte growth factor(HGF)on retinal pigment epithelium(RPE)cell behaviors.METHODS:The human adult retinal pigment epithelial cell line-19(ARPE-19)were treated by HGF or mesenchymalepithelial transition factor(MET)inhibitor SU11274 in vitro.Cell viability was detected by a Cell Counting Kit-8 assay.Cell proliferation and motility was detected by a bromodeoxyuridine incorporation assay and a wound healing assay,respectively.The expression levels of MET,phosphorylated MET,protein kinase B(AKT),and phosphorylated AKT proteins were determined by Western blot assay.The MET and phosphorylated MET proteins were also determined by immunofluorescence assay.RESULTS:HGF increased ARPE-19 cells’viability,proliferation and migration,and induced an increase of phosphorylated MET and phosphorylated AKT proteins.SU11274 significantly reduced cell viability,proliferation,and migration and decreased the expression of MET and AKT proteins.SU11274 suppressed HGF-induced increase of viability,proliferation,and migration in ARPE-19 cells.Additionally,SU11274 also blocked HGF-induced phosphorylation of MET and AKT proteins.CONCLUSION:HGF enhances cellular viability,proliferation,and migration in RPE cells through the MET/AKT signaling pathway,whereas this enhancement is suppressed by the MET inhibitor SU11274.HGF-induced MET/AKT signaling might be a vital contributor of RPE cells survival.

Bone morphogenetic protein-6 suppresses TGF-β_(2)-induced epithelial-mesenchymal transition in retinal pigment epithelium

AIM:To evaluate the effect of bone morphogenetic protein-6(BMP-6)on transforming growth factor(TGF)-β_(2)-induced epithelial-mesenchymal transition(EMT)in retinal pigment epithelium(RPE).METHODS:Adult retinal pigment epithelial cell line(ARPE-19)were randomly divided into control,TGF-β_(2)(5μg/L),and BMP-6 small interfering RNA(siRNA)group.The cell morphology was observed by microscopy,and the cell migration ability were detected by Transwell chamber.The EMT-related indexes and BMP-6 protein levels were detected by Western blotting.Furthermore,a BMP-6 overexpression plasmid was constructed and RPE cells were divided into the control group,TGF-β_(2)+empty plasmid group,BMP-6 overexpression group,and TGF-β_(2)+BMP-6 overexpression group.The EMT-related indexes and extracellular regulated protein kinases(ERK)protein levels were detected.RESULTS:Compared with the control group,the migration of RPE cells in the TGF-β_(2) group was significantly enhanced.TGF-β_(2) increased the protein expression levels ofα-smooth muscle actin(α-SMA),fibronectin and vimentin but significantly decreased the protein levels of E-cadherin and BMP-6(P<0.05)in RPE.Similarly,the migration of RPE cells in the BMP-6 siRNA group was also significantly enhanced.BMP-6 siRNA increased the protein expression levels ofα-SMA,fibronectin and vimentin but significantly decreased the protein expression levels of E-cadherin(P<0.05).Overexpression of BMP-6 inhibited the migration of RPE cells induced by TGF-β_(2) and prevented TGF-β_(2) from affecting EMT-related biomarkers(P<0.05).CONCLUSION:BMP-6 prevents the EMT in RPE cells induced by TGF-β_(2),which may provide a theoretical basis for the prevention and treatment of proliferative vitreoretinopathy.

Effect of miR-27b-3p and Nrf2 in human retinal pigment epithelial cell induced by high-glucose

AIM:To determine whether the microRNA-27b-3p(miR-27b-3p)/NF-E2-related factor 2(Nrf2)pathway plays a role in human retinal pigment epithelial(hRPE)cell response to high glucose,how miR-27b-3p and Nrf2 expression are regulated,and whether this pathway could be specifically targeted.METHODS:hRPE cells were cultured in normal glucose or high glucose for 1,3,or 6d before measuring cellular proliferation rates using cell counting kit-8 and reactive oxygen species(ROS)levels using a dihydroethidium kit.miR-27b-3p,Nrf2,NAD(P)H quinone oxidoreductase 1(NQO1)and heme oxygenase-1(HO-1)mRNA and protein levels were analyzed using reverse transcription quantitative polymerase chain reaction(RT-qPCR)and immunocytofluorescence(ICF),respectively.Western blot analyses were performed to determine nuclear and total Nrf2 protein levels.Nrf2,NQO1,and HO-1 expression levels by RT-qPCR,ICF,or Western blot were further tested after miR-27b-3p overexpression or inhibitor lentiviral transfection.Finally,the expression level of those target genes was analyzed after treating hRPE cells with pyridoxamine.RESULTS:Persistent exposure to high glucose gradually suppressed hRPE Nrf2,NQO1,and HO-1 mRNA and protein levels and increased miR-27b-3p mRNA levels.High glucose also promoted ROS release and inhibited cellular proliferation.Nrf2,NQO1,and HO-1 mRNA levels decreased after miR-27b-3p overexpression and,conversely,both mRNA and protein levels increased after expressing a miR-27b-3p inhibitor.After treating hRPE cells exposed to high glucose with pyridoxamine,ROS levels tended to decreased,proliferation rate increased,Nrf2,NQO1,and HO-1 mRNA and protein levels were upregulated,and miR-27b-3p mRNA levels were suppressed.CONCLUSION:Nrf2 is a downstream target of miR-27b-3p.Furthermore,the miR-27b-3p inhibitor pyridoxamine can alleviate high glucose injury by regulating the miR-27b-3p/Nrf2 axis.

Protective Effect and Autophagy Mechanism of Lycium barbarum Polysaccharides on Retinal Pigment Epithelial Cells Under High-Glucose Conditions

Objective:To study the effects of Lycium barbarum polysaccharide(LBP)on the proliferation,apoptosis,and autophagy of retinal pigment epithelial(RPE)cells cultured under high-glucose conditions.Methods:The ARPE-19 cell line was randomly divided into a control group(normally cultured in Dulbecco's Modified Eagle Medium/Nutrient Mixture F-12[DMEM/F-12]medium),a high-glucose group(HG;50 mmol/L glucose added to DMEM/F-12 medium),and a HG+LBP group(incubated in DMEM/F-12 medium containing 1 mg/mL LBP for 24 h,and then treated with 50 mmol/L glucose for 24 h).Following Ad-mCherry-GFP-LC3B infection,cell proliferation,apoptosis,mammalian target of rapamy-cin(mTOR)expression,and autophagic flux were determined by Cell Counting Kit-8(CCK-8),AnnexinV-APC/7-AAD Apoptosis Detection Kit,Western blot,and laser confocal microscopy,respectively.Results:The proliferation rate of ARPE-19 cells in the HG group was significantly lower than that in the control group(P<0.05),while the proliferation rate of ARPE-19 cells in the HG+LBP group was significantly higher than that in the HG group(P<0.05).The apoptosis rate of ARPE-19 cells in the HG group was significantly higher than that in the control group(P<0.05),while the apoptosis rate of ARPE-19 cells in the HG+LBP group was significantly lower than that in the HG group(P<0.05).The relative expression of phosphorylated mTOR(p-mTOR)of ARPE-19 cells in the HG group was significantly lower than that in the control group(P<0.05),with enhanced autophagic flux;when compared with the HG group,the HG+LBP group had significantly higher expression of p-mTOR(P<0.05),with diminished autophagic flux.Conclusion:LBP has a protective effect on RPE cells with high glucose-induced injury,and its mechanism may be related to LBP inhibition of high glucose-induced abnormal autophagy.

Oxidative stress affects retinal pigment epithelial cell survival through epidermal growth factor receptor/AKT signaling pathway

AIM：To investigate the cross-talk between oxidative stress and the epidermal growth factor receptor（EGFR）/AKT signaling pathway in retinal pigment epithelial（ RPE） cells.METHODS：Human RPE cell lines（ARPE-19 cell） were treated with different doses of epidermal growth factor（EGF） and hydrogen peroxide（H2O2）.Cell viability was determined by a methyl thiazolyl tetrazolium assay.Cell proliferation was examined by a bromodeoxyuridine（Brd U） incorporation assay.EGFR/AKT signaling was detected by Western blot.EGFR localization was also detected by immunofluorescence.In addition,EGFR/AKT signaling was intervened upon by EGFR inhibitor（erlotinib）,PI3 K inhibitor（A66） and AKT inhibitor（MK-2206）,respectively.H2O2-induced oxidative stress was blocked by antioxidant N-acetylcysteine（NAC）.RESULTS：EGF treatment increased ARPE-19 cell viabili ty and proliferation through inducing phosphorylation of EGFR and AKT.H2O2 inhibited ARPE-19 cell viability and proliferation and also suppressed EGF-stimulated increase of RPE cell viability and proliferation by affecting the EGFR/AKT signaling pathway.EGFR inhibitor erlotinib blocked EGF-induced phosphorylation of EGFR and AKT,while A66 and MK-2206 only blocked EGF-induced phosphorylation of AKT.EGF-induced phosphorylation andendocytosis of EGFR were also affected by H2O2 treatment.In addition,antioxidant NAC attenuated H2O2-induced inhibition of ARPE-19 cell viability through all eviating reduction of EGFR,and phosphorylated and total AKT proteins.CONCLUSION：Oxidative stress affects RPE cell viability and proliferation through interfering with the EGFR/AKT signaling pathway.The EGFR/AKT signaling pathway may be an important target in oxidative stress-induced RPE cell dysfunction.

PI3K/AKT/mTOR signaling pathway inhibitors in proliferation of retinal pigment epithelial cells

AIM: To determine whether the PI3K/AKT/mTOR pathway is activated in proliferative vitreoretinopathy (PVR) in homo-sapiens. METHODS: The retina of controls and patients with PVR were collected and their levels of PI3K, phospho-AKT, phospho-mTOR, phospho-p70S6k and phospho-4EBP-1 were determined by Western blot. The cultured human retinal pigment epithelial cell line D407 was treated with a specific mTOR inhibitor, rapamycin (RAPA) or a PI3K inhibitor, LY294002, of various concentrations and durations. Cell morphology was observed by phase contrast microscopy and the proliferation and apoptosis of treated cells were determined by MTT assay and flow cytometry. RESULTS: Levels of PI3K, phospho-AKT, phospho-mTOR, phospho-P70S6K and phospho-4EBP1 was increased in the retina in PVR (P <0.05). In D407 cells, both RAPA and LY294002 significantly inhibited cell proliferation and cell cycle progression, and promoted apoptosis (P <0.05); morphologically, the cells became smaller. Both RAPA and LY294002 reduced levels of phospho-AKT, phospho-mTOR, phospho-p70S6k and phospho-4EBP1 expression (P <0.05). RAPA, but not LY294002, had no significant effect on PI3K expression. CONCLUSION: PI3K/AKT/mTOR signaling pathway is highly activated in the retinal pigment epithelial cells of PVR. The inhibitors of PI3K/AKT/mTOR signaling pathway, RAPA and LY294002, could inhibited the PI3K/AKT/mTOR signaling pathway by reducing the levels of phosphorylation of mTOR pathway components.

Up-regulation of HIF-1α and VEGF Expression by Elevated Glucose Concentration and Hypoxia in Cultured Human Retinal Pigment Epithelial Cells

Summary： In order to explore the effect of high glucose concentration and high glucose concentration with hypoxia on the production of hypoxia-inducible factor-1α （HIF-1α） and vascular endothelial growth factor （VEGF）, human RPE cells were cultured in 5,56 mmol/L glucose （control group）, 5.56 mmol/L glucose with 150 !a mol/L COCl2 （hypoxic group）, 25 mmol/L glucose （high glucose group） and 25 mmol/L glucose with 150 μmol/L COCl2 （combination group）. RT-PCR was used to detect the expression of HIF-1α and VEGF mRNAs. Western blot analysis was used to measure the levels of HIF-1α and VEGF proteins. Although the small amount of HIF-1α protein was able to be detected in high glucose group but not in control group, there was no significant difference between the expression of HIF-1α mRNA of RPE cells in high glucose group and that of RPE cells in control group. As compared with RPE cells in control group, the mRNA expression and the protein synthesis of VEGF in high glucose group were up-regulated. As compared with RPE cells in hypoxic group, the expression of HIF-1α mRNA of RPE cells in combination group was not different, but the protein synthesis of HIF-1α, the mRNA expression and the protein synthesis of VEGF were more obviously up-regulated. In conclusion, high concentration glucose mainly influence the protein synthesis of HIF-1α of RPE cell, and HIF-1α protein is able to be accumulated in high concentration glucose. Under hypoxia, the HIF-1α protein induced by high concentration glucose is more stable, and the expression of VEGF is obviously increased. It is suggested that high concentration glucose may play a role in retinal neovascularization, especially at ischemia stage of diabetic retinopathy.

Inhibition of Obtusifolin on retinal pigment epithelial cell growth under hypoxia

AIM: To explore the effect of Obtusifolin on retinal pigment epithelial cell growth under hypoxia.METHODS: In vitro chemical hypoxia model of ARPE-19 cells was established using cobalt chloride(CoCl2). Cell viability was tested by cell counting kit-8(CCK-8) assay. Western blot and real-time quantitative polymerase chain reaction were applied to detect proteins and mRNAs respectively. Flow cytometry was used to examine the cell cycle. Secretion of vascular endothelial growth factor(VEGF) was tested by using enzyme linked immunosorbent assay(ELISA).RESULTS: Under the chemical hypoxia model established by CoCl2, hypoxia inducible factor-1α(HIF-1α) mRNA and protein levels was up-regulated. Cell viability was increased and the proportion of S phase was higher. Obtusifolin could reduce cell viability under hypoxic conditions and arrest cells in G1 phase. Obtusifolin reduced the expression of Cyclin D1 and proliferating cell nuclear antigen(PCNA) in the hypoxic environment and increased the expression of p53 and p21. The levels of VEGF, VEGFR2 and eNOS proteins and mRNA were significantly increased under hypoxia while Obtusifolin inhibited the increasing.CONCLUSION: Obtusifolin can inhibit cell growth under hypoxic conditions and down-regulate HIF-1/VEGF/eNOS secretions in ARPE-19 cells.

4-HNE Induces Apoptosis of Human Retinal Pigment Epithelial Cells by Modifying HSP70

The role of heat shock protein 70 (HSP70) in apoptosis of human retinal pigment epithelial cells (ARPE-19) induced by 4-hydroxy-2-nonenal (4-HNE) was explored. Different concentrations of 4-HNE were used to stimulate ARPE-19 cells, and apoptosis was measured by flow cytometry. The expression of apoptotic-related proteins, HSP70, X-linked inhibitorof- apoptosis (XIAP), Bcl-2, and Bax were quantified by Western blotting. HSP70 and XIAP overexpression plasmids, or their corresponding siRNAs were transfected into ARPE-19 cells using Lipofectamine. 2000. Co-immunoprecipitation and Western blotting were used to detect the effect of 4-HNE on the expression of HSP70 and the binding level between 4-HNE and HSP70. The results showed that 4-HNE induced late apoptosis in ARPE-19 cells, accompanied by elevated levels of 4-HNE-modified IISP70, but it did not affect HSP70 protein expression. 4-HNE-modified HSP70 down-regulated the expression of the apoptosis inhibitory protein XIAP. Overexpression of HSP70 or XIAP inhibited 4-HNE-induced apoptosis of ARPE-19 cells. It was suggested that 4-HNE could promote XIAP degradation by modification of HSP70 to induce late apoptosis of human retinal pigment epithelial cells.

Cholecystokinin octapeptide antagonizes apoptosis in human retinal pigment epithelial cells

Although cholecystokinin octapeptide-8 is important for neurological function, its neuroprotective properties remain unclear. We speculated that cholecystokinin octapeptide-8 can protect human retinal pigment epithelial cells against oxidative injury. In this study, retinal pigment epithelial cells were treated with peroxynitrite to induce oxidative stress. Peroxynitrite triggered apoptosis in these cells, and increased the expression of Fas-associated death domain, Bax, caspase-8 and Bcl-2. These changes were suppressed by treatment with cholecystokinin octapeptide-8. These results suggest that cholecystokinin octapeptide-8 can protect human retinal pigment epithelial cells against apoptosis induced by peroxynitrite.

Peroxynitrite-induced expression of inducible nitric oxide synthase and activated apoptosis via nuclear factor-kappa B pathway in retinal pigment epithelial cells and antagonism of cholecystokinin octapeptide-8 in vitro

AIM: To explore that if peroxynitrite induced the expression of inducible nitric oxide synthase (iNOS)via nuclear factor-kappa B (NF-kappa B)pathway in retinal pigment epithelial (RPE) cells and the antagonism of cholecystokinin octapeptide-8 (Melatonin, CCK-8) in vitro. METHODS: RPE cells were obtained from eyes of C57BL/6 mouse and divided into control, peroxynitrite and CCK-8 groups. Control group was treated with saline, peroxynitrite group was treated with peroxynitrite, and CCK-8 group was treated with CCK-8 after added with peroxynitrite. All changes were observered at 6, 12 and 24 hours after treatment. Gene array analysis, Reverse Transcription Polymerase Chain Reaction (RT-PCR) were used to determine the expression of inducible nitric oxide synthase ( iNOS)mRNA in RPE cells. Western blotting was used to test the apoptosis of RPE cells. Immunofluorescent staining was used to determine the NF-kappa B pathway signal transduction. RESULTS: Compared to the control group, the expression of iNOS mRNA was up-regulated in peroxynitrite group and down-regulated in CCK-8 group with gene array analysis. Apoptosis was increased in peroxynitrite group and decreased in CCK-8 group with western blotting. The NF-kappa B pathway signal transduction was more and more stronger in the peroxynitrite group. But in CCK-8 group, little stronger could be observed at 12 hours, then weak at 24 hours with immunofluorescent staining (P<0.001). CONCLUSION: This study suggested that apoptosis of RPE cells was partly induced by peroxynitrite, which may be the new way of oxidative damage to the RPE cells. The NF-kappa B signal transduction may affect and reinforce apoptosis mediated by peroxynitrite. CCK-8 decreased apoptosis of RPE cells induced by peroxynitrite and is a potential agent for therapy of retinopathy. The mechanism of CCK-8 dealing with RPE cells may be related to its direct inhibition of the formation of iNOS to produce peroxynitrite and antagnism of damage of peroxynitrite to the RPE cells.

Expression of IGFBP-6 in a proliferative vitreoretinopathy rat model and its effects on retinal pigment epithelial cell proliferation and migration

AIM: To investigate the expression of insulin-like growth factor binding protein-6(IGFBP-6) in a proliferative vitreoretinopathy(PVR) model and its effects on proliferation and migration in retinal pigment epithelial(RPE) cells. ·METHODS: A PVR Wistar rat model was established by the intravitreal injection of RPE-J cells combined with platelet-rich plasma(PRP). The expression levels of IGFBP-6 were tested by ELISA. ARPE-19 cell proliferation was evaluated by the MTS method,and cell migration was evaluated by wound healing assays. ·RESULTS: The success rate of the PVR model was 89.3%(25/28). IGFBP-6 was expressed at higher levels in the vitreous,serum and retina of rats experiencing advanced PVR(grade 3) than in the control group(vitreous: 152.80 ±15.08ng/mL vs 105.44 ±24.81ng/mL,P 】 0.05; serum: 93.48 ±9.27ng/mL vs 80.59 ±5.20ng/mL,P 【 0.05; retina: 3.02±0.38ng/mg vs 2.05±0.53ng/mg,P 【0.05). In vitro,IGFBP-6(500ng/mL) inhibited the IGF-II(50ng/mL) induced ARPE-19 cell proliferation(OD value at 24h: from 1.38±0.05 to 1.30±0.02; 48h: from 1.44±0.06 to 1.35± 0.05). However,it did not affect basal or VEGF-,TGF-β-and PDGF-induced cell proliferation. IGFBP-6(500ng/ml) reduced the IGF-II(50ng/mL)-induced would healing rate [24h: from(43.91 ±3.85)% to(29.76 ±2.49)%; 48h: from(66.09±1.67)% to(59.88±3.43)%]. ·CONCLUSION: Concentrations of IGFBP-6 increased in the vitreous,serum,and retinas only in advanced PVR in vivo. IGFBP-6 also inhibited IGF-II-induced cell proliferation in a not dose or time dependent manner and migration. IGFBP-6 participates in the development of PVR and might play a protective role in PVR.

Gac fruit extracts ameliorate proliferation and modulate angiogenic markers of human retinal pigment epithelial cells under high glucose conditions

Objective: To investigate the impact of the extracts of Gac fruit parts(peel, pulp, seed, and aril) on the cell viability and angiogenesis markers of human retinal pigment epithelial(ARPE-19) cells under high glucose conditions. Methods: The effect of the extracts of Gac fruit peel, pulp, seed and aril on the ARPE-19 cells was determined using MTT viability assay, Trypan blue dye and morphological changes were observed using light microscopy. Enzyme-linked immunosorbent-based assay was performed to evaluate the effect of Gac fruit parts on the reactive oxygen species(ROS), vascular endothelial growth factor(VEGF) and pigmented epithelium-derived factor(PEDF) secretions. Results: High glucose(HG) at 30 mmol/L increased ARPE-19 cell viability and ROS and VEGF secretions. While, the exposure of ARPE-19 cells in high glucose condition to Gac fruit extracts led to inhibition of cell viability, induced morphological changes, decreased ROS and VEGF secretions, and increased PEDF level. Gac pulp, seed, and aril at 1 000 μg/mL showed significant inhibition activities [(7.5 ± 5.1)%,(2.7 ± 0.5)%,(3.2 ± 1.1)%, respectively] against HG-induced ARPE-19 cell viability. The findings also demonstrated that Gac aril at 250 μg/mL significantly decreased ROS and VEGF levels [(40.6 ± 3.3) pg/mL,(107.4 ± 48.3) pg/mL, respectively] compared to ROS [(71.7 ± 2.9) pg/mL ] and VEGF [(606.9 ± 81.1) pg/mL] in HG untreated cells. Moreover, 250 μg/mL of Gac peel dramatically increased PEDF level [(18.2 ± 0.3) ng/mL] compared to that in HG untreated cells [(0.48 ± 0.39) ng/mL]. Conclusions: This study indicates that the extracts of Gac peel, pulp, seed and aril reduced cell viability, minimized ROS generations and showed angiogenic activities. Therefore, our findings open new insights into the potentiality of Gac fruit against HG-related diabetic retinopathy disease.

Puerarin antagonizes peroxyntrite-induced injury in retinal pigment epithelial cells

A rat model of diabetes mellitus was established by intraperitoneal injection of streptozotocin. Three days later, the rats were intraperitoneally administered 140 mg puerarin/kg daily, for a total of 60 successive days. DNA ladder results showed increased apoptosis over time in retinal pigment epithelial cells from rats with streptozotocin-induced diabetes mellitus. Western blot analysis, Reverse transcription-PCR, immunohistochemistry, and flow cytometry results showed increased expression of 3-nitrotyrosine, a peroxyntrite marker, as well as inducible nitric synthase and Fas/FasL, in retinal pigment epithelial cells. Puerarin reversed these changes, and results demonstrated that puerarin inhibited Fas/FasL expression and alleviated peroxyntrite injury to retinal pigment epithelial cells. These results suggested that puerarin inhibited production of inducible nitric oxide synthase and directly antagonized peroxyntrite injury in retinal pigment epithelial cells.

Control of peroxyntrite -induced production of inducible nitric oxide synthase isoforms and antagonism of cholecystokinin octapeptide-8 in retinal pigment epithelial cells in vivo

AIM: To explore if peroxyntrite (ONOO(-)) induced iNOS vi;7 Fas/ Fas/L pathway in diabetic rats and the effection of cholecystokinin octapeptide-8 (CCK-8) as therapeutic agent for decrease diabetic retinopathy. METHODS: Thirty-six rats were taken as control group, seventy two were given (streptozotocin) STZ (45mg/kg) and then divided into ONOO(-) group and CCK-8 group (peritoneal injection CCK-8). STZ-induced diabetic rats were treated with CCK-8 for 60 days. Western blotting analysis, DNA ladder, RT-PCR, immunohistochemistry and flow cytometry were used for determining the expression of nitrotyrosine (NT, the foot print of ONOO(-)); apoptosis and inducible nitric oxide synthase (iNOS) mRNA as well as Fas/Fasl signal transduction in RPE cells. RESULTS: Both RPE cells in ONOO(-) and CCK-8 group developed apoptosis and expressed NT, iNOS mRNA and Fas/Fasl. But latter delayed the all changes in a time-dependent manner compared with control and ONOO(-) group (P<0.001). iNOS and Fas/Fasl were up-regulated and associated with an increase of expression of ONOO(-) in vivo. CONCLUSION: The study suggested that apoptosis of RPE was partly induced by ONOO(-) may be the new way of oxidative damage to the RPE cells. CCK-8 decreased RPE cells apoptosis partly induced by ONOO(-) and is a potential drug for therapy of diabetic retinopathy. The mechanism of CCK-8 dealing with RPE cells may be related to its direct inhibition of the formation of iNOS to produce ONOO(-) and antagnism of damage of ONOO(-) to RPE cells.

Cross-talk between microRNA-let7c and transforming growth factor-β2 during epithelial-to-mesenchymal transition of retinal pigment epithelial cells

AIM: To explore the roles of microRNA-let7 c(miR-let7 c) and transforming growth factor-β2(TGF-β2) and cellular signaling during epithelial-to-mesenchymal transition(EMT) of retinal pigment epithelial cells. METHODS: Retinal pigment epithelial(ARPE-19) cells were cultured with no serum for 12 h, and then with recombinant human TGF-β2 for different lengths of time. ARPE-19 cells were transfected with 1×106 TU/mL miR-let7 c mimcs(miR-let7 cM), miR-let7 c mimcs negative control(miR-let7cMNC) and miR-let7 c inhibitor(miR-let7 cI) using the transfection reagent. The expression of keratin-18, vimentin, N-cadherin, IKB alpha, p65 were detected by Western blot, quantitative polymerase chain reaction and immunofluorescence. RESULTS: The expression of miR-let7c was dramatically reduced and the nuclear factor-kappa B(NF-κB) signaling pathway was activated after induction by TGF-β2(P<0.05). In turn, overexpressed miR-let7 c significantly inhibited TGF-β2-induced EMT(P<0.05). However, miR-let7 c was unable to inhibit TGF-β2-induced EMT when the NF-κB signaling pathway was inhibited by BAY11-7082(P<0.01). CONCLUSION: The miR-let7 c regulates TGF-β2-induced EMT through the NF-κB signaling pathway in ARPE-19 cells.

A Trojan horse biomimetic delivery system using mesenchymal stem cells for HIF-1α siRNA-loaded nanoparticles on retinal pigment epithelial cells under hypoxia environment

AIM: To demonstrate the feasibility of mesenchymal stem cell(MSC)-mediated nano drug delivery, which was characterized by the “Trojan horse”-like transport of hypoxiainducible factor-1α small interfering RNA(HIF-1α si RNA) between MSCs and retinal pigment epithelial cells(RPE) under hypoxia environment.METHODS: Plasmid and lentivirus targeting the human HIF-1α gene were designed and constructed. HIF-1α si RNA was encapsulated into poly(lactic-co-glycolic acid) nanoparticles(PLGA-NPs) through the water-in-oil-in-water(w/o/w) multiple emulsion technique. The effect of PLGANPs uptake on the expression of HIF-1α m RNA was tested in RPE cells by real-time quantitative polymerase chain reaction(q PCR) and additional transfected conditions were used as control, including lentivirus group, nude plasmid group and blank PLGA group. MSCs were transfected with the NPs and the transfection efficacy was evaluated by flow cytometry. Transwell co-culture system of transfected MSCs and RPE cells was constructed under hypoxia environment. The effects of MSC-loaded HIF-1α si RNA PLGA-NPs on proliferation, apoptosis, and migration of RPE cells were then evaluated. The effect of transfected MSCs on HIF-1α expression of RPE cells was analyzed by using q PCR at the time points 24h, 3d, and 7d.RESULTS: The average diameter of PLGA-NPs loaded with HIF si RNA was 314.1 nm and the zeta potential was-0.36 m V. The transfection efficiency of PLGA-NPs was 67.3%±5.2% into MSCs by using flow cytometry. Compared with the lentivirus group, the PLGA-NPs loaded with HIF-1α si RNA can effectively reduce the expression of HIF-1α m RNA up to 7d in RPE(0.63±0.05 at 7d, P<0.001). In the Transwell co-culture system of transfected MSCs and RPE, the abilities of proliferation(2.34±0.17, 2.40±0.28, 2.47±0.24 at 48h, F=0.23, P=0.80), apoptosis(14.83%±2.43%, 12.94%±2.19%, 12.39%±3.21%;F=0.70, P=0.53) and migration(124.5±7.78, 119.5±5.32, 130±9.89, F=1.33, P=0.33) of the RPE cells had no differences between MSCloaded HIF-1α si RNA PLGA-NPs and other groups. The inhibition of PLGA on the HIF-1α m RNA expression in RPE cells could continue until the 7th day, the level of HIF-1α m RNA was lower than that of other groups(F=171.98, P<0.001). CONCLUSION: The delivery of PLGA-NPs loaded with HIF-1α si RNA carried by MSCs is found to be beneficial temporally for HIF-1α m RNA inhibition in RPE cells under hypoxia environment. The MSC-based bio-mimetic delivery of HIF-1α si RNA nanoparticles is a potential method for therapy against choroidal neovascularization.

Effects of curcumin nanoparticles on proliferation and VEGF expression of human retinal pigment epithelial cells

AIM:To investigate the effects of curcumin(Cur)nanoparticles loaded with chitosan derivatives grafted by deoxycholic acid(Chit-DC)on human retinal pigment epithelial(h RPE)cell proliferation and vascular endothelial growth factor(VEGF)m RNA expression.METHODS:Cur nanoparticles were synthesized with Chit-DC as the carrier and Cur as the supported drug.Cell counting kit-8(CCK-8)method was used to detect the effects of different concentrations of Cur/Chit-DC,Chit-DC,and Cur on the proliferation of h RPE cells for different times.The changes of Cur/Chit-DC and Cur on h RPE cell cycle were determined by flow cytometry.Semi-quantitative reverse transcription-polymerase chain reaction(RT-PCR)was used to detect the m RNA expression levels of VEGF in h RPE cells treated with Cur,Chit-DC and Cur/Chit-DC at 10μg/m L for 24 h.RESULTS:Different concentrations of Chit-DC nanoparticle treated h RPE cells had no significant difference in terms of optical density(OD)values compared with the control group at 24 h and 48 h.Moreover,there was no change in the cell morphology under a light microscope.After 24 h treatment with Cur/Chit-DC and Cur,the percentage of G0-G1 phase cells increased and the percentage of S phase cells decreased in all concentration groups.Cur/Chit-DC and Cur in all concentration groups inhibited the proliferation of h RPE cells in a time and dose dependent manner,and reduced the expression level of VEGF m RNA.CONCLUSION:The Cur/Chit-DC nanoparticles can release Cur continuously and have sustained release function.Both Cur/Chit-DC nanoparticles and Cur could inhibit h RPE cells cultured in vitro,and could reduce the expression level of VEGF m RNA in h RPE cells.

Blocking VEGF signaling augments interleukin-8 secretion via MEK/ERK/1/2 axis in human retinal pigment epithelial cells

AIM:To identify proangiogenic factors engaged in neovascular age-related macular degeneration(AMD)except vascular endothelial growth factor(VEGF)from human retinal pigment epithelial(h RPE)cells and investigate the underlying mechanisms.METHODS:VEGF receptor 2(VEGFR2)in ARPE-19 cells was depleted by si RNA transfection or overexpressed through adenovirus infection.The m RNA and the protein levels of interleukin-8(IL-8)in ARPE-19 cells were measured by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay respectively.The protein levels of AKT,p-AKT,MEK,p-MEK,ERK1/2,p-ERK1/2,JNK,p-JNK,p38 and p-p38 were detected by Western blotting.A selective chemical inhibitor,LY3214996,was employed to inhibit phosphorylation of ERK1/2.Cell viability was determined by MTT assay.RESULTS:Knockdown of VEGFR2 in ARPE-19 cells robustly augmented IL-8 production at both the m RNA and the protein levels.Silencing VEGFR2 substantially enhanced phosphorylation of MEK and ERK1/2 while exerted no effects on phosphorylation of AKT,JNK and p38.Inhibiting ERK1/2 phosphorylation by LY3214996 reversed changes in VEGFR2 knockdown-induced IL-8 upregulation at the m RNA and the protein levels with no effects on cell viability.VEGFR2 overexpression significantly reduced IL-8 generation at the m RNA and the protein levels.CONCLUSION:Blockade of VEGF signaling augments IL-8 secretion via MEK/ERK1/2 axis and overactivation of VEGF pathway decreases IL-8 production in h RPE cells.Upregulated IL-8 expression after VEGF signaling inhibition in h RPE cells may be responsible for being incompletely responsive to anti-VEGF remedy in neovascular AMD,and IL-8 may serve as an alternative therapeutic target for neovascular AMD.

Influence of IL-1β and TNF-α on Fas Expression of Human Retinal Pigment Epithelial Cells in Vitro

Purpose:To observe Fas expression change of cultured human retinal pigment epithelial (RPE) cells by IL-1β and TNF-α.Methods:With flow cytometry, immunohischemistry, and color imaging system, Fas expressions by exposure to IL-1β and/or TNF-α were measured.Results:The gray degree values of Fas expression were 67.5±6.1 in IL-1β+TNF-α-treated group, 80.1±9.2 in IL-1β-treated group, and 70.4±6.4 in TNF-α-treated group, respectively. There were significant differences (P < 0.005) compared with control group (107.0±10.2). Flow cytometry showed that 15.0% cultured human RPE cells expressed Fas. Fas-positive in IL-1β, TNF-α, and IL-1β+TNF-α-treated groups expressed was 28.1%, 34.5%, and 65.2%, respectively. Conclusion:IL-1β, TNF-α, and combining both of them can up-regulate Fas protein expression, which may contribute to more Fas (+) cells in proliferative vitreoretinopathy (PVR). Minimizing this process by means of inducing apoptosis of Fas (+) proliferative cells of Fas/FasL pathway is a future preventive and therapeutic possibility for PVR. Eye Science 2004;20:39-41.