Disease relevance of RPE

• Preliminary data suggest that iron chelation can reduce RPE iron overload in mice and protect them from degeneration, suggesting that iron-binding drugs may one day prove useful in reducing RPE oxidative stress and decreasing the risk of AMD progression [1].
• Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane [2].
• We have found that, following retinal degeneration induced by devascularization, new retina is generated in the posterior eye from transdifferentiating pigment epithelial (RPE) cells and in the anterior eye from increased proliferation at the normal growth zone in the ora serrata [3].
• Current studies of RPE show that these cells protect the retina from ONOO- mediated damage in uveitis by releasing a novel protein called retinal pigment epithelial protective protein [4].
• PURPOSE: Drusen are risk factors for age-related macular degeneration and have been shown to negatively impact cells of the RPE and retina [5].

Psychiatry related information on RPE

• We conclude that an RPE motor neuron requires a signal, provided by its interaction with the target organ during a critical period, in order to stop extending axons, stabilize those axons that contact the target, and retract those that do not [6].
• PME was not related to ARTE after inclusion of RPE in the multiple regression model, suggesting that PME may be obtaining its relationship with ARTE through an increased perception of effort during physical activity [7].
• Paired t-tests revealed no differences between conditions for the measures of exercise intensity at pain threshold [aspirin vs placebo mean (+/- SD)]: power output: 150 (+/- 60.3 W) versus 153.5 (+/- 64.8 W); VO2: 21.3 (+/- 8.6 mL.kg-1.min-1) versus 22.1 (+/- 10.0 mL.kg-1.min-1); and RPE: 10.9 (+/- 3.1) versus 11.4 (+/- 2.9) [8].
• 4. The present study examined the effects of one night of total sleep deprivation on RPE potentials and motor abnormalities in Parkinson's patients [9].

High impact information on RPE

• A key step in the visual cycle is isomerization of an all-trans retinoid to 11-cis-retinol in the RPE (refs. 9-11) [10].
• To regenerate rhodopsin and maintain normal visual sensitivity, the all-trans isomer must be metabolized and reisomerized to produce the chromophore 11-cis-retinal in biochemical steps that constitute the visual cycle and involve the retinal pigment epithelium (RPE; refs. 3-8) [10].
• The retinal pigment epithelial cell (RPE cell) layer protects the photoreceptors of the retina against oxidative stress [11].
• Exposure of human adult RPE cells to UV light at predominantly 320-400 nm (UVA light) in the presence of all-trans-retinaldehyde results in photooxidative cytotoxicity [11].
• Significant protection of RPE cells was obtained by prior treatment with phase 2 gene inducers, such as the isothiocyanate sulforaphane or a bis-2-hydroxybenzylideneacetone Michael reaction acceptor [11].

Chemical compound and disease context of RPE

• The sensitivity of RPE metabolism to glucose fluctuations may relate to changes in the blood-retinal barrier that are known to occur in diabetes (e.g. macular edema) [12].
• Expression of alpha(5) integrin as a result of infection of RPE cells with an alpha(5) integrin-encoding adenovirus induced morphological transformation and an increase in mobility similar to that seen with vitreous [13].
• OBJECTIVE: To test whether acute metabolic (VO(2)), chronotropic (heart rate), and perceptual (rating of perceived exertion; RPE) responses to exercise by persons with paraplegia differ when the exercise is on a multistation isoinertial exercise system (MultiGym) or on a customized system of Thera-Band resistance bands (ElasticGym) [14].
• RESULTS: In disciform lesions, RPE transplants developed macular edema and fluorescein leakage concomitant with gradual reduction of visual acuity, implying host-graft rejection, over 1-6 months [15].
• It has been reported that retinoic acid (RA) may inhibit the growth of RPE and be used in the treatment of proliferative vitreoretinopathy (PVR) [16].

Biological context of RPE

• BACKGROUND: Topographic differences in RPE and choroid between macular and peripheral areas of the eye may predispose to morphologic and cell survival changes with aging [17].
• For example, herein it is shown that one regulator of systemic iron homeostasis, HFE, is expressed in the RPE [1].
• PURPOSE: We wish to identify transcriptional factors involved in regulation binding to the proximal promoter region of the RPE65 gene that confers RPE-specific expression [18].
• Deletion 2q31.3----2q33.3: gene dosage effect of ribulose 5-phosphate 3-epimerase [19].
• This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds [2].

Anatomical context of RPE

• 2. Both RPI and RPE were detected in all human tissues including red cells, lymphocytes and fibroblasts [20].
• Varied expression of functionally important genes of RPE and choroid in the macula and in the periphery of normal human eyes [17].
• Biochemical studies showed that the proband had half normal activities of both erythrocyte isocitrate dehydrogenase (IDH1) and ribulose 5-phosphate 3-epimerase (RPE) [21].
• AMD retinas have more iron within the photoreceptors, RPE, and drusen than do age-matched control retinas [1].
• RESULTS: Confluent monolayers of RPE cell cultures exhibited epithelial morphology and heavy pigmentation, and electron microscopy showed extensive apical membrane microvilli [22].

Associations of RPE with chemical compounds

• As compared with RPE cells in control group, the mRNA expression and the protein synthesis of VEGF in high glucose group were up-regulated [23].
• However, kinetic studies of ribulose-5-phosphate 3-epimerase and phosphoriboisomerase suggested that the ribulose 5-phosphate produced by this pathway is converted mostly to xylulose 5-phosphate instead of to ribose 5-phosphate so that this pathway produces little phosphoribosylpyrophosphate [24].
• As expected: most of these genes seem to be involved in basic metabolic and cellular functions (lipoic acid biosynthesis: ribulose-5-phosphate-3-epimerase: glycosyl transferase: beta-transducin: serine-threonine-kinase: ABC proteins: cation transporters) [25].
• The permeabilities of the RPE and bovine corneal endothelium monolayers to fluorescein (20 mug/mL) and 9-cis retinoic acid (3 x 10(-4) M) were also determined [26].
• Hepatocyte growth factor protects RPE cells from apoptosis induced by glutathione depletion [27].

Regulatory relationships of RPE

• CONCLUSIONS: The ELF3 transcription factor is highly expressed in the RPE and can regulate important ocular genes, such as TIMP3, in vitro [28].
• These findings suggest that RPE 28 SV4 cells possess regulated chloride channels including CFTR and members of the ClC chloride channel family [29].
• Macrophages and RPE express VEGF, thus perpetuating angiogenesis [30].
• Characterization of a novel C-kinesin (KIFC3) abundantly expressed in vertebrate retina and RPE [31].
• In summary, ET-1 production in RPE is regulated by at least two isoforms of ECE, (cytosolic and PM) as well as cathepsins [32].

Other interactions of RPE

• In conclusion, high concentration glucose mainly influence the protein synthesis of HIF-1alpha of RPE cell, and HIF-1alpha protein is able to be accumulated in high concentration glucose [23].
• The specific expression of ELF3 in the RPE may reflect an important role for this transcription factor in retinal function [28].
• Differential involvement of phosphoinositide 3-kinase/Akt in human RPE MCP-1 and IL-8 expression [33].
• Expression of MCT proteins in human RPE and ARPE-19 cells was evaluated by immunolocalization and Western blot analysis with isoform-specific anti-peptide antibodies [34].
• The data showed that VMD2 mutations caused defects of ocular patterning, supporting the hypothesized role for the RPE, and specifically VMD2, in the normal growth and development of the eye [35].

Analytical, diagnostic and therapeutic context of RPE

• METHODS: The mRNA levels of 29 genes with known functions or expression in the RPE/choroid were quantified in these sections by real time RT-PCR [17].
• Confocal microscopy of cultures probed with a hyaluronan-specific fluorotag established that the HA evident in these cultures is restricted to the apical border of the RPE cultures [36].
• It has been shown that photoreceptor degeneration can be limited in experimental animals by transplantation of fresh RPE to the subretinal space [37].
• Expression of Gal-1 in native, low- and high-density cultured RPE cells was determined by Western blot analysis [38].
• The effect of the coexpression on RGC differentiation was assayed in vivo in the developing chick retina and in vitro in RPE cell cultures derived from day 6 chick embryos [39].

References