Cone-rod homeobox transcriptionally activates TCF7 to promote the proliferation of retinal pigment epithelial and retinoblastoma cells in vitro

AIM:To investigate the proliferation regulatory effect of cone-rod homeobox(CRX)in retinal pigment epithelium(RPE)and retinoblastoma(RB)cells to explore the potential application and side effect(oncogenic potential)of CRXbased gene therapy in RPE-based retinopathies.METHODS:Adult human retinal pigment epithelial(ARPE)-19 and human retinal pigment epithelial(RPE)-1 cells and Y79 RB cell were used in the study.Genetic manipulation was performed by lentivirus-based technology.The cell proliferation was determined by a CellTiter-Glo Reagent.The mRNA and protein levels were determined by quantitative real-time polymerase chain reaction(qPCR)and Western blot assay.The transcriptional activity of the promoter was determined by luciferase reporter gene assay.The bindings between CRX and transcription factor 7(TCF7)promoter as well as TCF7 and the promoters of TCF7 target genes were examined by chromatin immunoprecipitation(ChIP)assay.The transcription of the TCF7 was determined by a modified nuclear run-on assay.RESULTS:CRX overexpression and knockdown significantly increased(n=3,P<0.05 in all the cells)and decreased(n=3,P<0.01 in all the cells)the proliferation of RPE and RB cells.CRX overexpression and knockdown significantly increased and deceased the mRNA levels of Wnt signaling target genes[including MYC proto-oncogene(MYC),JUN,FOS like 1(FOSL1),CCND1,cyclin D2(CCND2),cyclin D3(CCND3),cellular communication network factor 4(CCN4),peroxisome proliferator activated receptor delta(PPARD),and matrix metallopeptidase 7(MMP7)]and the luciferase activity driven by the Wnt signaling transcription factor(TCF7).TCF7 overexpression and knockdown significantly increased and decreased the proliferation of RPE and RB cells and depletion of TCF7 significantly abolished the stimulatory effect of CRX on the proliferation of RPE and RB cells.CRX overexpression and knockdown significantly increased and decreased the mRNA level of TCF7 and the promoter of TCF7 was significantly immunoprecipitated by CRX antibody.CONCLUSION:CRX transcriptionally activates TCF7 to promote the proliferation of RPE and RB cells in vitro.CRX is a potential target for RPE-based regenerative medicine.The potential risk of this strategy,tumorigenic potential,should be considered.

Regulation role of miR-204 on SIRT1/VEGF in metabolic memory induced by high glucose in human retinal pigment epithelial cells

AIM:To examine the regulatory role of microRNA-204(miR-204)on silent information regulator 1(SIRT1)and vascular endothelial growth factor(VEGF)under highglucose-induced metabolic memory in human retinal pigment epithelial(hRPE)cells.METHODS:Cells were cultured with either normal(5 mmol/L)or high D-glucose(25 mmol/L)concentrations for 8d to establish control and high-glucose groups,respectively.To induce metabolic memory,cells were cultured with 25 mmol/L D-glucose for 4d followed by culture with 5 mmol/L D-glucose for 4d.In addition,exposed in 25 mmol/L D-glucose for 4d and then transfected with 100 nmol/L miR-204 control,miR-204 inhibitor or miR-204 mimic in 5 mmol/L D-glucose for 4d.Quantitative reverse transcription-polymerase chain reaction(RT-qPCR)was used to detect miR-204 mRNA levels.SIRT1 and VEGF protein levels were assessed by immunohistochemical and Western blot.Flow cytometry was used to investigate apoptosis rate.RESULTS:It was found that high glucose promoted miR-204 and VEGF expression,and inhibited SIRT1 activity,even after the return to normal glucose culture conditions.Upregulation of miR-204 promoted apoptosis inhibiting SIRT1 and increasing VEGF expression.However,downregulation of miR-204 produced the opposite effects.CONCLUSION:The study identifies that miR-204 is the upstream target of SIRT1and VEGF,and that miR-204 can protect hRPE cells from the damage caused by metabolic memory through increasing SIRT1 and inhibiting VEGF expression.

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.

LIN28A attenuates high glucose-induced retinal pigmented epithelium injury through activating SIRT1-dependent autophagy

AIM:To evaluate the effects of LIN28A(human)on high glucose-induced retinal pigmented epithelium(RPE)cell injury and its possible mechanism.METHODS:Diabetic retinopathy model was generated following 48h of exposure to 30 mmol/L high glucose(HG)in ARPE-19 cells.Quantitative real-time polymerase chain reaction(qRT-PCR)and Western blot tested the expression of the corresponding genes and proteins.Cell viability as well as apoptosis was determined through cell counting kit-8(CCK-8)and flow cytometry assays.Immunofluorescence assay was adopted to evaluate autophagy activity.Caspase 3 activity,oxidative stress markers,and cytokines were appraised adopting their commercial kits,respectively.Finally,ARPE-19 cells were preincubated with EX527,a Sirtuin 1(SIRT1)inhibitor,prior to HG stimulation to validate the regulatory mechanism.RESULTS:LIN28A was downregulated in HG-challenged ARPE-19 cells.LIN28A overexpression greatly inhibited HGinduced ARPE-19 cell viability loss,apoptosis,oxidative damage as well as inflammatory response.Meanwhile,the repressed autophagy and SIRT1 in ARPE-19 cells challenged with HG were elevated after LIN28A overexpression.In addition,treatment of EX527 greatly inhibited the activated autophagy following LIN28A overexpression and partly abolished the protective role of LIN28A against HG-elicited apoptosis,oxidative damage as well as inflammation in ARPE-19 cells.CONCLUSION:LIN28A exerts a protective role against HG-elicited RPE oxidative damage,inflammation,as well as apoptosis via regulating SIRT1/autophagy.

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.

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.

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.

Spontaneous or secondary to intravitreal injections of anti-angiogenic agents retinal pigment epithelial tears in age-related macular degeneration

·AIM:Toevaluatethevisualfunctionevolutionofretinal pigment epithelial(RPE) tears in patients with age-related macular degeneration(AMD) according to type of occurrence [spontaneous or secondary to anti-vascular endothelial growth factor(anti-VEGF) injection] and the topographic location of the tear after a two-year followup period.·METHODS: A total of 15 eyes of 14 patients with RPE tears in exudative AMD were analyzed retrospectively at the University Eye Clinic of Trieste. Inclusion criteria were: patient age of 50 or older with AMD and RPE tears both spontaneous occurring or post anti-VEGF treatment. Screening included: careful medical history,complete ophthalmological examination, fluorescein angiography(FA), indocyanine green angiography(ICG),autofluorescence and infrared imaging and optical coherence tomography(OCT). Patients were evaluated every month for visual acuity(VA), fundus examination and OCT. Other data reported were: presence of PED,number of injections before the tear, location of the lesion.·RESULTS:Meanfollow-up was24wk(SD±4wk). Atotal of 15 eyes were studied for RPE tear. In 6 cases(40%),the RPE tears occurred within two years of anti-VEGF injections the others occurred spontaneously. In 13cases(86.6%), the RPE tear was associated with pigment epithelial detachment(PED). In 7 cases(46.6%), the RPE tear occurred in the central area of the retina and involved the fovea. Two lesions were found in the parafoveal region, six in the extra-macular area. In all cases visual acuity decreased at the end of the follow-up period(P <0.01) independently of the type or the topographical location of the lesion.·CONCLUSION: RPE tear occurs in exudative AMD as a spontaneous complication or in relation to anti-VEGF injections. Visual acuity decreased significantly and gradually in the follow-up period in all cases. No correlation was found between visual loss and the type of onset or the topographic location of the tears.

Toxicity of endogenous peroxynitrite and effects of puerarin on transplanted retinal pigment epithelial sheets in the subretinal space in mice

AIM: To evaluate the toxicity of endogeneous peroxynitrite on transplanted retinal pigment epithelial (RPE) sheets and the effect of puerarin on their survival in the C57BL/6 mice after RPE sheets have been transplanted into SD rats' subretinal space. METHODS: C57BL/6 mice eyes were used to culture RPE cells. Ninety-six SD rats were involved in the experiment. They were divided into control( block control), streptozotocin (STZ, negative control), untransplanted RPE (positive control) and transplanted RPE groups respectively. Diabetes was induced in SD rats by intra-peritoneal STZ injection in the latter three groups. Saline was injected into the subretinal space of 24 SD rats in the untransplanted RPE group and primary RPE sheets were injected into the subretinal space of 24 SD rats in the transplanted RPE group. Puerarin (45 mg/kg) was administrated into both untransplanted RPE and transplanted RPE groups of diabetic rats through intra-peritoneal injection route after RPE sheets transplantation. At 20,40,60 days after surgery, Western blotting analysis, DNA ladder and RT-PCR were used for determining the differences in expression of nitrotyrosine (NT, the foot print of peroxynitrite), apoptosis and iNOS mRNA in the control, STZ, untransplanted RPE and transplanted RPE groups respectively. HE staining was used for determining the RPE survival in the subretinal space of the transplanted RPE group. RESULTS: Apoptosis and expression of NT and iNOS mRNA were observed in STZ, untransplanted RPE and transplanted RPE groups, but were delayed in untransplanted RPE and transplanted RPE groups in a time-dependent manner compared with control and STZ groups (P < 0.01). There were no differences between the two groups (P > 0.01). NT, DNA ladder, iNOS mRNA were down-regulated, which were associated with the decrease of expression of peroxynitrite. Numerous pigmented cells emerged and increased in number in the subretinal space during the 60-day observation period after transplantation. On day 20, heavily pigmented cells were visible at the transplant site; On day 40, monolayer and multilayered transplant was visible in the subretinal space; On day 60, heavily pigmented monolayer and multilayered transplants with round apical profile were present along Bruch's membrane. CONCLUSION: Puerarin increased the 60-day survival of C57BL/6 mice RPE xenografts in the SD rats' subretinal space, which may be related to its direct inhibition of apoptosis of RPE cells and antagnism of damage of peroxynitrite to RPE 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.

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.

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.

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.

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.

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.

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.

Bevacizumab modulates retinal pigment epithelial-tomesenchymal transition via regulating Notch signaling

AIM: To investigate the effect of bevacizumab treatment on Notch signaling and the induction of epithelial-of-mesenchymal transition(EMT) in human retinal pigment epithelial cells(ARPE-19) in vitro.METHODS: In vitro cultivated ARPE-19 cells were treated with 0.25 mg/m L bevacizumab for 12, 24, and 48 h.Cell morphology changes were observed under an inverted microscope. The expression of zonula occludens-1(ZO-1), vimentin and Notch-1 intracellular domain(NICD) was examined by immunofluorescence.The m RNA levels of ZO-1, α-SMA, Notch-1, Notch-2,Notch-4, Dll4, Jagged-1, RBP-Jk and Hes-1 expression were evaluated with quantitative real-time polymerase chain reaction(q RT-PCR). The protein levels of α-SMA,NICD, Hes-1 and Dll-4 expression were examined with Western blot.RESULTS: Bevacizumab stimulation increased the expression of α-SMA and vimentin in ARPE-19 cells which changed into spindle-shaped fibroblast-like cells.Meanwhile, the m RNA expression of Hes-1 increased and the protein expression of Hes-1 and NICD also increased, which Notch signaling was activated. The m RNA expression of Notch-1, Jagged-1 and RBP-Jk increased at 48 h, and while Dll4 m RNA and protein expression did not change after bevacizumab treatment.CONCLUSION: Jagged-1/Notch-1 signaling may play a critical role in bevacizumab-induced EMT in ARPE-19 cells, which provides a novel insight into the pathogenesis of intravitreal bevacizumab-associated complication.

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.