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At least 253 records · Page 14Linked to original sources
PubMed2003

A2E-epoxides damage DNA in retinal pigment epithelial cells. Vitamin E and other antioxidants inhibit A2E-epoxide formation.

The autofluorescent pigments that accumulate in retinal pigment epithelial cells with aging and in some retinal disorders have been implicated in the etiology of macular degeneration. The major constituent is the fluorophore A2E, a pyridinium bisretinoid. Light-exposed A2E-laden retinal pigment epithelium exhibits a propensity for apoptosis with light in the blue region of the spectrum being most damaging. Efforts to understand the events precipitating the death of the cells have revealed that during irradiation (430 nm), A2E self-generates singlet oxygen with the singlet oxygen in turn reacting with A2E to generate epoxides at carbon-carbon double bonds. Here we demonstrate that A2E-epoxides, independent of singlet oxygen, exhibit reactivity toward DNA with oxidative base changes being at least one of these lesions. Mass spectrometry revealed that the antioxidants vitamins E and C, butylated hydroxytoluene, resveratrol, a trolox analogue (PNU-83836-E), and bilberry extract reduce A2E-epoxidation, whereas single cell gel electrophoresis and cell viability studies revealed a corresponding reduction in the incidence of DNA damage and cell death. Vitamin E, a lipophilic antioxidant, produced a more pronounced decrease in A2E-epoxidation than vitamin C, and treatment with both vitamins simultaneously did not confer additional benefit. Studies in which singlet oxygen was generated by endoperoxide in the presence of A2E revealed that vitamin E, butylated hydroxytoluene, resveratrol, the trolox analogue, and bilberry reduced A2E-epoxidation by quenching singlet oxygen. Conversely, vitamin C and ginkgolide B were not efficient quenchers of singlet oxygen under these conditions.

8-Hydroxy-2'-Deoxyguanosine↗
PubMedDate not supplied

Anthocyanins protect against A2E photooxidation and membrane permeabilization in retinal pigment epithelial cells.

The pyridinium bisretinoid A2E, an autofluorescent pigment that accumulates in retinal pigment epithelial cells with age and in some retinal disorders, can mediate a detergent-like perturbation of cell membranes and light-induced damage to the cell. The photodynamic events initiated by the sensitization of A2E include the generation of singlet oxygen and the oxidation of A2E at carbon-carbon double bonds. To assess the ability of plant-derived anthocyanins to modulate adverse effects of A2E accumulation on retinal pigment epithelium (RPE) cells, these flavylium salts were isolated from extracts of bilberry. Nine anthocyanin fractions reflecting monoglycosides of delphinidin, cyanidin, petunidin and malvidin were obtained and all were shown to suppress the photooxidation of A2E at least in part by quenching singlet oxygen. The anthocyanins tested exhibited antioxidant activity of variable efficiency. The structural characteristics relevant to this variability likely included the ability to form a stable quinonoidal anhydro base at neutral pH, a conjugated diene structure in the C (pyrane) ring, the presence of hydroxyl groups on the B (benzene) ring and the relative hydrophobicity conferred by the arrangement of substituents on the B ring. Cells that had taken up anthocyanins also exhibited a resistance to the membrane permeabilization that occurs as a result of the detergent-like action of A2E.

Anthocyanins↗
PubMed1989

Retinal pigment epithelial cells produce PDGF-like proteins and secrete them into their media.

Human retinal pigment epithelial cells at confluence were used to condition serum-free Dulbecco's modified Eagle's medium. Conditioned media were exhaustively dialyzed against 0.5 N acetic acid, lyophilized, and subjected to Western blot analysis, using as primary antibody an IgG fraction prepared from goat antiserum directed against human platelet-derived growth factor. Native platelet-derived growth factor was resolved as a band with Mr of 30 kDa under non-reducing conditions, while bands with Mr of 36-38 kDa and 18.5 kDa were resolved from retinal pigment epithelial cell-conditioned media. Acid extracts of retinal pigment epithelial cells also contained bands at 36-38 kDa and media conditioned for 48 hr exhibited much denser bands than media conditioned for 24 hr. No bands were detected when non-immune goat IgG fractions were substituted for primary antibody and when conditioned media were prepared from several human fibroblast lines in the same manner as those prepared from retinal pigment epithelial cells, no detectable bands or only a faint shadow at 36 kDa were seen. Retinal pigment epithelial cell-conditioned media prepared in the presence of [35S]methionine were loaded on an anti-platelet-derived growth factor IgG affinity column, eluted, and subjected to SDS-polyacrylamide gel electrophoresis. Bands with Mr slightly less than 36 kDa and 18 kDa were visualized by autoradiography, demonstrating that the platelet-derived growth factor-like proteins in retinal pigment epithelial cell-conditioned media are newly synthesized. Two fractions eluted from the column also markedly stimulated fibroblast chemotaxis and incorporation of [3H]thymidine, both of which were neutralized by soluble anti-platelet-derived growth factor IgG. These data suggest that retinal pigment epithelial cells in culture produce platelet-derived growth factor-like proteins and secrete them into their media where they are capable of stimulating fibroblast chemotaxis and proliferation.

Cell Line↗
PubMed1988

Retinal pigment epithelial cell plasma membrane: a monoclonal antibody study.

The plasma membranes of retinal pigment epithelial cells are highly specialized organelles with multiple functions including nutritional and metabolic support of the photoreceptor cells. Using purified bovine retinal epithelial cell plasma membranes as antigen, we produced two monoclonal antibodies, MAbD1-C6 and MAbD1-C8, that cross react with the plasma membranes from bovine, rat and human retinal pigment epithelial cells. In radioimmunoassay both MAbD1-C6 and MAbD1-C8 had similar affinities for bovine plasma membranes. Both monoclonal antibodies identified a protein of 72 Kd with an apparent subunit of 32-35 Kd. The protein was localized to the cell surface of human and bovine retinal pigment epithelium by immunocytohistochemistry. In the normal eye the antigen identified by the monoclonal antibodies was strongly associated with the retinal pigment epithelium and weakly associated with lens tissue. Using either monoclonal antibody, components of purified bovine or rat retinal pigment epithelial plasma membranes were precipitated from solution. Based on these results, we conclude that both monoclonal antibodies are closely related and that they may be useful for the isolation and study of retinal pigment epithelial cell structure.

Animals↗
PubMed1991

Synthesis of extracellular matrix by macrophage-modulated retinal pigment epithelium.

In proliferative vitreoretinopathy, macrophages and retinal pigment epithelial cells are associated with microfibrillar matrix proteins in the vitreous cavity, but the contribution of this extracellular matrix to the pathophysiology is not known. We used radiolabeling techniques on cultured human retinal pigment epithelial cells to correlate the secretion of extracellular matrix proteins with macrophage-induced modulation of cell proliferation and morphologic features. Retinal pigment epithelial cells incubated in a macrophage-conditioned medium assumed fibrocytelike morphologic characteristics, grew faster, and exhibited a decreased cellular release of fibrillar and nonfibrillar matrix components. However, due to a simultaneous greater increase in cell numbers in these modulated cultures, the total production of fibrillar and nonfibrillar matrix components by the culture population was increased.

Cell Division↗
PubMed2001

Transforming growth factor-beta1 induces alpha-smooth muscle actin expression and fibronectin synthesis in cultured human retinal pigment epithelial cells.

BACKGROUND: Proliferative vitreoretinopathy is a serious complication of retinal detachment, yet its pathogenesis is not fully understood. Retinal pigment epithelial cells and glial cells are found in the fibrous membranes in proliferative vitreoretinopathy. Many cytokines are involved in the pathology. Transforming growth factor (TGF)-beta, a cytokine found in serum, has been shown to be an important factor regulating the synthesis of fibrous extracellular matrix in proliferative vitreoretinopathy. METHODS: Cultured human retinal pigment epithelial cells were used in the experiments. The effects of TGF-beta1 on phenotype and function in retinal pigment epithelial cells were recorded as changes in the expression of alpha-smooth muscle actin and fibronectin synthesis using immunohistochemistry and enzyme-linked immunosorbent assay, respectively. RESULTS: TGF-beta1 induced the expression of alpha-smooth muscle actin (P < 0.0001, n = 3), and significantly increased the synthesis of fibronectin by cultured human retinal pigment epithelial cells (P < 0.01, n = 4). CONCLUSIONS: Elevated levels of TGF-beta1 in proliferative vitreoretinopathy may contribute to phenotype changes in retinal pigment epithelial cells leading to matrix deposition and contraction. Since the elevated levels of TGF-beta1 may emanate from a number of diverse sources in proliferative vitreoretinopathy, developing an antagonist to TGF-beta1 may offer an approach to the treatment of proliferative vitreoretinopathy.

Actins↗
PubMed1985

Repigmentation of human retinal pigment epithelial cells in vitro.

Cultured human retinal pigment epithelial (RPE) cells readily ingested both melanin and lipofuscin isolated from human RPE cells. Up to 7 days post-challenge ingested granules demonstrated no evidence of lysis or aggregation within secondary lysosomes. When cultures containing ingested melanin and lipofuscin were subcultured the cells gradually depigmented due to a redistribution of pigment granules amongst daughter cells. Quantitative analysis demonstrated that the accumulation of both types of granule was linear over a 24 hr challenge period. This study reports a technique of 'artificially' repigmenting cultured human RPE cells and thus offers the potential for in vitro investigations of the role of these inclusions in various dynamic aspects of cellular metabolism.

Adult↗
PubMed1981

Reactive changes in the human retinal pigment epithelium in vitro.

Explants from the retinal pigment epithelium and the underlying choroid and sclera were dissected from human eyes and transferred to culture wells. The mechanical trauma caused by the dissection and removal of the explants, and the changes in biological milieu caused by transfer of the tissue to an in vitro system causes injury, necrosis and detachment of cells from Bruch's membrane. In the retinal pigment epithelium, cells adjacent to damaged, spherical and detaching cells and smaller cell free zones from rosettes. At the periphery of big defects, the cells spread out to cover the denuded areas of Bruch's membrane. The present work has shown that cell injury in the human retinal pigment epithelium is followed by reactive cellular changes in vitro. The result of these reactive changes are increased variation in cellular form and magnitude and in pigment concentration per unit area.

Culture Techniques↗
PubMed1985

Synthetic activities of cultured retinal pigment epithelial cells from a patient with retinitis pigmentosa.

We established cultures of retinal pigment epithelial (RPE) cells from four normal individuals and a 56-year-old male patient with autosomal-dominant retinitis pigmentosa (RP) and examined the synthetic activities of these cells via radiolabeling experiments. The uptake of radioactive precursors per milligram of cell protein by RPE cells from the patient with RP was significantly higher than that found in the normal control cells. It appears that the net synthetic activities of glycosaminoglycans and proteins in our patient's cells were enhanced and that the cell metabolism was altered. This finding suggests that malfunctioning of the RPE cells may play a role in the deterioration of photoreceptor functions seen in at least some patients with autosomal-dominant RP.

Adult↗
PubMed1994

Platelet-derived growth factor is an autocrine growth stimulator in retinal pigmented epithelial cells.

The retinal pigmented epithelium (RPE) plays a major role in normal and exaggerated retinal wound repair; the latter can result in epiretinal membrane formation and loss of vision. The RPE forms a stable monolayer of highly differentiated cells that proliferates only during wound repair. The mechanism underlying the change to the proliferating phenotype is unknown. When grown on a plastic substratum, cultured RPE cells mimic the proliferating phenotype in situ; they escape density arrest and proliferate in serum-free medium. In this study, we have demonstrated that a platelet-derived growth factor (PDGF) autocrine loop is involved in RPE growth in serum-free medium, because: (1) RPE cells secrete PDGF into their media and express PDGF receptors; (2) the PDGF receptors on RPE cells are autophosphorylated in serum-free medium and suramin, an agent that displaces PDGF and other growth factors from their receptors, blocks the autophosphorylation; and (3) a neutralizing antibody to PDGF significantly decreases RPE growth in serum-free medium. When a linear scrape is made in an RPE monolayer, the cells migrate and proliferate to fill in the gap mimicking wound repair in situ. Cells along the edge of the scrape show increased expression of PDGF and PDGF-beta receptors, and increased staining for proliferating cell nuclear antigen. Immunohistochemistry and in situ hybridization demonstrate expression of PDGF in ganglion cells and cells of retinal blood vessels. PDGF is not detected in the outer retina or RPE in untreated eyes, but is detected in RPE participating in wound repair, either adjacent to laser burns or underlying retinal detachment. PDGF and PDGF receptors are also expressed in RPE in epiretinal membranes removed during vitreous surgery. These data suggest that PDGF is an autocrine stimulator of growth in RPE that plays a role in retinal wound repair and epiretinal membrane formation.

Animals↗
PubMed1986

Mechanisms involved in retinal pigment epithelial cell chemotaxis.

Retinal pigment epithelial (RPE) cell chemotaxis may play an important role in proliferative vitreoretinopathy (PVR). Fibronectin and platelet-derived growth factor are chemoattractants for RPE cells. In this study, we used these chemoattractants to examine mechanisms involved in RPE cell chemotaxis. Our results demonstrate that inhibition of RNA and protein synthesis, but not DNA synthesis, are associated with reduced chemotaxis. Microtubules and microfilaments are involved since cytochalasin B and colchicine are potent inhibitors of RPE cell migration. Dexamethasone, to which a beneficial effect has been attributed in an animal model of PVR, had no effect on RPE cell migration. Information concerning mechanisms involved in RPE cell migration may help to explore new avenues of treatment in PVR.

Biomechanical Phenomena↗
PubMed2004

Effects of indocyanine green on the retina and retinal pigment epithelium in a porcine model of retinal hole.

PURPOSE: This study was designed to emulate human macular hole surgery and to test the effects of indocyanine green (ICG) on the retina and retinal pigment epithelium (RPE). METHODS: Yorkshire Cross pigs (n = 23) underwent vitrectomy, separation of the posterior cortical vitreous, and creation of a single retinal hole. In three study groups (n = 6, each group), air-fluid exchange was performed, following which balanced salt solution (BSS), 1.0% ICG, or 0.5% ICG was applied over the retinal hole. In one additional group (n = 5), 0.5% ICG was injected into the fluid-filled eye. At 4 weeks, the eyes were examined clinically, and fundus photographs were obtained before enucleation and light microscopic examination. RESULTS: Clinical evaluations documented a statistically significant difference between study groups (P = 0.036). There was a higher rate of moderate or severe RPE atrophy among animals where 1% or 0.5% ICG was applied in air-filled eyes (83% and 67%, respectively) compared with BSS controls (17%) and fluid-filled eyes receiving 0.5% ICG (40%). Histologic evaluation demonstrated a statistically significant difference between groups (P = 0.044), with extensive outer retinal degeneration observed in air-filled eyes receiving 1% or 0.5% ICG (66% and 60%, respectively) compared with BSS controls or fluid-filled eyes receiving 0.5% ICG (none of the eyes in either group). None of the study groups had any changes in the inner retina except at the retinal hole site. CONCLUSIONS: Retina exposed to ICG concentrations used in human vitreoretinal surgery had greater RPE atrophy and outer retinal degeneration than control eyes undergoing the same surgery without ICG. Eyes filled with infusion fluid during ICG injection had less damage to the RPE and outer retina than did air-filled eyes receiving ICG.

Air↗
PubMedDate not supplied

Fundus autofluorescence imaging findings in retinal pigment epithelial tear.

PURPOSE: Retinal pigment epithelial (RPE) tear is a clinical and angiographic entity, which usually occurs in association with pigment epithelial detachments (PED), in the context of neovascular age-related macular degeneration (ARMD). The recording of fundus autofluorescence (FAF) has been introduced as a technique of retinal imaging, allowing the in vivo assessment of the integrity of RPE. The authors describe the FAF imaging findings in a patient with RPE tear. METHODS: Observational case report. RESULTS: A 70-year-old woman developed RPE tear after the application of photodynamic therapy for choroidal neovascularization associated with PED. The diagnosis of the RPE tear was confirmed by fluorescein angiography (FA) and indocyanine green angiography (ICGA). FAF imaging revealed absence of autofluorescence at the area which was denuded of RPE, while at the area where the RPE was rolled, a heterogeneous signal of FAF was recorded. The intensity of the signal in that area was, on average, not different from the normal background FAF signal expected in an unaffected RPE/photoreceptor complex. CONCLUSIONS: The authors report the FAF imaging findings in a patient with RPE tear. These findings can be interpreted from the ability of FAF imaging to access in vivo the integrity of RPE, and correlate well with the histopathology of this clinical entity. FAF imaging, as a fast and noninvasive technique, may be a useful modality, alternative to FA and ICGA, in the diagnosis and evaluation of such cases. Moreover, it may contribute to a more detailed phenotyping of the various clinical pictures associated with neovascular ARMD.

Aged↗
PubMed2003

[Retinal pigment epithelial atrophic tracks secondary to central serous pigment epitheliopathy].

PURPOSE AND METHODS: We report the cases of three patients with retinal pigment epithelial atrophic tracks secondary to central serous pigment epitheliopathy specially focusing on fluorescein angiographic findings. This entity is considered an atipical manifestation of central serous chorioretinopathy called chronic diffuse retinal pigment epitheliopathy. RESULTS AND CONCLUSIONS: We have studied 69 patients with the diagnose of central serous pigment epiteliopathy in our unit; 10.14% manifested diffuse retinal pigment epitheliopathy and 5.79% showed retinal pigment epithelial atrophic tracks. Both eyes were involved in 100% and all of them were males with a median age of 53.33 years. We can conclude that this entity usually affects adult males and it is frequently bilateral.

Fluorescein Angiography↗
PubMed1999

Role of hypoxia and extracellular matrix-integrin binding in the modulation of angiogenic growth factors secretion by retinal pigmented epithelial cells.

The retinal pigmented epithelium (RPE) is a monolayer of polarized cells located between retinal photoreceptors and blood vessels of the choroid. The basal surface of RPE cells rests on Bruch's membrane, a complex extracellular matrix structure which becomes abnormal in several disease processes, including age-related macular degeneration (AMD). Ruptures or abnormalities in Bruch's membrane are frequently accompanied by choroidal neovascularization. Disturbed interaction of RPE cells with their extracellular matrix (ECM) could play a role in this process. The present study was undertaken to examine the complex interactions between hypoxia, integrin, and ECM in the regulation of RPE functions. Antibody blocking experiments demonstrated that RPE cell adhesion to vitronectin is mediated primarily through alphavbeta5 and adhesion to fibronectin occurs through alpha5beta1. RPE adhesion to immobilized laminin demonstrated highest level of non-RGD-mediated adhesion as compared to that with collagen IV or the RGD matrices such as vitronectin (alphavalpha5) , fibronectin (alpha5beta1), or thrombospondin (alpha5beta1 + alphavbeta5). Addition of soluble vitronectin, or fibrinogen to RPE cell cultures resulted in a small to moderate increase in VEGF and FGF2 in the media, while each of these growth factors was dramatically increased after addition of thrombospondin 1 (TSP1). In contrast, soluble fibronectin resulted in differential upregulation of VEGF but not FGF2. Similarly, immobilized TSP1 resulted in differential greater upregulation in VEGF but not FGF2 release from RPE as compared to other ECMs under either normoxic or hypoxic conditions. Additionally, hypoxia resulted in a time-dependent increase in VEGF, but not FGF2 release in the media. RPE cells grown on TSP1-coated plates showed increased VEGF and FGF2 in their media compared to cells grown on plates coated with type IV collagen, laminin, vitronectin, or fibronectin. The TSP1-induced increase in secretion of growth factors was partially blocked by anti-alpha5beta1, anti-alphavbeta3, and anti-alphavbeta5 antibodies indicating that it may be mediated in part by TSP1 binding to those integrins. These data suggest that alterations in oxygen levels (hypoxia/ischemia) and ECM of RPE cells, a prominent feature of AMD, can cause increased secretion of angiogenic growth factors that might contribute to the development of choroidal neovascularization. These data also suggest the potential modulatory role of VEGF release from RPE by ECM and alphavbeta5 and alpha5beta1 integrins.

Antibodies, Monoclonal↗