ACUTE RETINAL PIGMENT EPITHELIITIS: ASSOCIATION WITH ACUTE COXSACKIE A VIRUS INFECTION

PURPOSE

The purpose of this study was to describe the occurrence of acute retinal pigment epitheliitis in association with serologic evidence of acute Coxsackie A virus infection.

METHODS

This study is a case report.

RESULTS

A 37-year-old man noted an acute onset of paracentral scotomas in his right eye correlating with stippled retinal pigment epithelial pigment alterations with whitish halos surrounding the fovea. Spectral domain optical coherence tomography revealed scattered distinct retinal pigment epithelial elevations in the paracentral macular region arranged in an annular fashion, with associated alterations in the interdigitation and ellipsoid zone layers anterior to the retinal pigment epithelial, characteristic of acute retinal pigment E. Suspicion of acute Coxsackie A virus in the patient because of the presence of simultaneous viral exanthematous illness in the patient's 1-year-old son prompted serologic testing for Coxsackie virus. Titers showed strongly positive IgM ("early") antibody for several Coxsackievirus A serotypes, including A16 (most commonly associated with hand-foot-mouth disease). Spontaneous regression of the anatomical and clinical findings occurred over the next month, with complete resolution noted 16 months later.

CONCLUSION

This is the first documented case of acute retinal pigment epitheliitis associated with evidence of acute Coxsackie A virus infection. Corroboration with serology in future cases would add to evidence that acute retinal pigment epitheliitis is part of the apparently expanding spectrum of recognized "Coxsackie retinopathies."

Prolonged Exposure to High Glucose Induces Premature Senescence Through Oxidative Stress and Autophagy in Retinal Pigment Epithelial Cells

Chronic hyperglycemia involves persistent high-glucose exposure and correlates with retinal degeneration. It causes various diseases, including diabetic retinopathy (DR), a major cause of adult vision loss. Most in vitro studies have investigated the damaging short-term effects of high glucose exposure on retinal pigment epithelial (RPE) cells. DR is also a severe complication of diabetes. In this study, we established a model with prolonged high-glucose exposure (15 and 75 mM exogenous glucose for two months) to mimic RPE tissue pathophysiology in patients with hyperglycemia. Prolonged high-glucose exposure attenuated glucose uptake and clonogenicity in ARPE-19 cells. It also significantly increased reactive oxygen species levels and decreased antioxidant protein (superoxide dismutase 2) levels in RPE cells, possibly causing oxidative stress and DNA damage and impairing proliferation. Western blotting showed that autophagic stress, endoplasmic reticulum stress, and genotoxic stress were induced by prolonged high-glucose exposure in RPE cells. Despite a moderate apoptotic cell population detected using the Annexin V-staining assay, the increases in the senescence-associated proteins p53 and p21 and SA-β-gal-positive cells suggest that prolonged high-glucose exposure dominantly sensitized RPE cells to premature senescence. Comprehensive next-generation sequencing suggested that upregulation of oxidative stress and DNA damage-associated pathways contributed to stress-induced premature senescence of ARPE-19 cells. Our findings elucidate the pathophysiology of hyperglycemia-associated retinal diseases and should benefit the future development of preventive drugs. Prolonged high-glucose exposure downregulates glucose uptake and oxidative stress by increasing reactive oxygen species (ROS) production through regulation of superoxide dismutase 2 (SOD2) expression. Autophagic stress, ER stress, and DNA damage stress (genotoxic stress) are also induced by prolonged high-glucose exposure in RPE cells. Consequently, multiple stresses induce the upregulation of the senescence-associated proteins p53 and p21. Although both apoptosis and premature senescence contribute to high glucose exposure-induced anti-proliferation of RPE cells, the present work shows that premature senescence rather than apoptosis is the dominant cause of RPE degeneration, eventually leading to the pathogenesis of DR.

Endogenous Galectin-1 Modulates Cell Biological Properties of Immortalized Retinal Pigment Epithelial Cells In Vitro

In the eye, an increase in galectin-1 is associated with various chorioretinal diseases, in which retinal pigment epithelium (RPE) cells play a crucial role in disease development and progression. Since little is known about the function of endogenous galectin-1 in these cells, we developed a galectin-1-deficient immortalized RPE cell line (ARPE-19-LGALS1-/-) using a sgRNA/Cas9 all-in-one expression vector and investigated its cell biological properties. Galectin-1 deficiency was confirmed by Western blot analysis and immunocytochemistry. Cell viability and proliferation were significantly decreased in ARPE-19-LGALS1-/- cells when compared to wild-type controls. Further on, an increased attachment of galectin-1-deficient RPE cells was observed by cell adhesion assay when compared to control cells. The diminished viability and proliferation, as well as the enhanced adhesion of galectin-1-deficient ARPE-19 cells, could be blocked, at least in part, by the additional treatment with human recombinant galectin-1. In addition, a significantly reduced migration was detected in ARPE-19-LGALS1-/- cells. In comparison to control cells, galectin-1-deficient RPE cells had enhanced expression of sm-α-actin and N-cadherin, whereas expression of E-cadherin showed no significant alteration. Finally, a compensatory expression of galectin-8 mRNA was observed in ARPE-19-LGALS1-/- cells. In conclusion, in RPE cells, endogenous galectin-1 has crucial functions for various cell biological processes, including viability, proliferation, migration, adherence, and retaining the epithelial phenotype.

Internalization of Angiotensin-(1-12) in Adult Retinal Pigment Epithelial-19 Cells

Purpose: Angiotensin-(1-12) [Ang-(1-12)] serves as a primary substrate to generate angiotensin II (Ang II) by angiotensin-converting enzyme and/or chymase suggests it may be an unrecognized source of Ang II-mediated microvascular complication in hypertension-mediated retinopathy. We investigated Ang-(1-12) expression and internalization in adult retinal pigment epithelial-19 (ARPE-19) cultured cells. We performed the internalization of Ang-(1-12) in ARPE-19 cells in the presence of a highly specific monoclonal antibody (mAb) developed against the C-terminal end of the Ang-(1-12) sequence. Methods: All experiments were performed in confluent ARPE-19 cells (passage 28-35). We employed high-performance liquid chromatography to purify radiolabeled, 125I-Ang-(1-12) and immuno-neutralization with Ang-(1-12) mAb to demonstrate Ang-(1-12)'s internalization in ARPE-19 cells. Internalization was also demonstrated by immunofluorescence (IF) method. Results: These procedures revealed internalization of an intact 125I-Ang-(1-12) in ARPE-19 cells. A significant reduction (∼53%, P < 0.0001) in 125I-Ang-(1-12) internalization was detected in APRE-19 cells in the presence of the mAb. IF staining experiments further confirms internalization of Ang-(1-12) into the cells from the extracellular culture medium. No endogenous expression was detected in the ARPE-19 cells. An increased intensity of IF staining was detected in cells exposed to 1.0 μM Ang-(1-12) compared with 0.1 μM. Furthermore, we found hydrolysis of Ang-(1-12) into Ang II by ARPE-19 cells' plasma membranes. Conclusions: Intact Ang-(1-12) peptide is internalized from the extracellular spaces in ARPE-19 cells and metabolized into Ang II. The finding that a selective mAb blocks cellular internalization of Ang-(1-12) suggests alternate therapeutic approaches to prevent/reduce the RPE cells Ang II burden.

Effect of human umbilical cord mesenchymal stem cell exosomes on aerobic metabolism of human retinal pigment epithelial cells

PURPOSE

To investigate the effect of exosomes secreted by human umbilical cord mesenchymal stem cells (HUCMSC-Exo) on aerobic metabolism of cobalt chloride (CoCl2)-induced oxidative damage in the human retinal pigment epithelial cell line (ARPE-19), and to explore the protective mechanism of HUCMSC-Exo on oxidative damage in ARPE-19 cells.

METHODS

HUCMSC-Exo were extracted and identified; CCK-8 assay was used to established the oxidative damage mode of ARPE-19 cells induced by CoCl2; JC-1 flow cytometry was used to detect the effects of exosomes with different concentrations (0, 25, 50, or 100 μg/mL) on the mitochondrial membrane potential (MMP) of oxidatively damaged ARPE-19 cells. The effects of exosomes with different concentrations on the activity of oxidative metabolic enzymes (oxidative respiratory chain complexes I, III, IV, and V) and ATP synthesis in oxidatively damaged ARPE-19 cells were detected by spectrophotometry.

RESULTS

Under transmission electron microscope, HUCMSC-Exo were round or oval membrane vesicles with diameters of about 40-100 nm. Western blot results showed that HUCMSC-Exo expressed specific marker proteins CD63 and CD81. CCK-8 dates showed that the cell viability of ARPE-19 cells was significantly decreased with increasing CoCl2 concentration, and the concentration of 400 μmol/L CoCl2 was chosen to be the optimal concentration for oxidative damage. MMP was increased in exosomes intervention group (25, 50 or 100 μg/mL), and the dates were statistically different from 0 μg/mL exosome intervention group (P < 0.05). The activities of mitochondrial complexes I, IV, and V in exosomes intervention groups (100 μg/mL) were higher than those in 0 μg/mL exosome intervention group. In 50 μg/mL and 100 μg/mL exosome intervention group, ATP synthesis was significantly different from the 0 μg/mL exosome intervention group (P < 0.05).

CONCLUSION

HUCMSC-Exo had a certain protective effect on ARPE-19 cells induced by CoCl2 in vitro. The protective mechanism of HUCMSC-Exo on oxidative damage ARPE-19 cells might be through saving its aerobic metabolic function, restoring cell ATP synthesis, and improving the ability of cells to repair damage and deal with the hypoxic environment.

Characteristics of retinal pigment clumps in Type 2 macular telangiectasia (MacTel)

OBJECTIVE

To assess the relationship of retinal pigment clump (RPC) size and its location with visual acuity and retinal neovascularisation in eyes with type 2 macular telangiectasia (MacTel).

METHODS

In this cross-sectional study, eyes diagnosed with type 2 MacTel showing RPC were included. Area occupied by pigment was measured on the multicolour image using the area tool on the Spectralis, Heidelberg machine. Pigment location within retinal layers was noted with OCT. Analysis was performed to identify factors associated with poor vision and proliferative disease.

RESULTS

Sixty-two eyes of 42 patients diagnosed with type 2 MacTel and RPC were included. The mean age was 64.31 ± 10.19 years. There were 13 (31%) males and 29 (69%) females in the study. 74% of patients were diabetics and the mean logMAR visual acuity of the participants was 0.619 ± 0.359. Univariate and multivariate binary logistic regression analysis identified female gender (p = 0.026), increasing RPC size (p = 0.008) and its presence above the outer plexiform layer (p = 0.006) to be associated with poor vision and proliferative disease in type 2 MacTel.

CONCLUSION

Our data identified female gender, larger pigment size and its location above the OPL to be associated with poor vision and proliferative disease. This data may be useful for further improving the current system for staging disease severity in type 2 MacTel.

Mitophagy initiates retrograde mitochondrial-nuclear signaling to guide retinal pigment cell heterogeneity

Age-related macular degeneration (AMD), the leading cause of blindness among the elderly, is without treatment for early disease. Degenerative retinal pigment epithelial (RPE) cell heterogeneity is a well-recognized but understudied pathogenic factor. Due to the daily phagocytosis of photoreceptor outer segments, unique photo-oxidative stress, and high metabolism for maintaining vision, the RPE has robust macroautophagy/autophagy, and mitochondrial and antioxidant networks. However, the autophagy subtype, mitophagy, in the RPE and AMD is understudied. Here, we found decreased PINK1 (PTEN induced kinase 1) in perifoveal RPE of early AMD eyes. PINK1-deficient RPE have impaired mitophagy and mitochondrial function that triggers death-resistant epithelial-mesenchymal transition (EMT). This reprogramming is mediated by novel retrograde mitochondrial-nuclear signaling (RMNS) through superoxide, NFE2L2 (NFE2 like bZIP transcription factor 2), TXNRD1 (thioredoxin reductase 1), and phosphoinositide 3-kinase (PI3K)-AKT (AKT serine/threonine kinase) that induced canonical transcription factors ZEB1 (zinc finger E-box binding homeobox 1) and SNAI1 (Snail family transcriptional repressor 1) and an EMT transcriptome. NFE2L2 deficiency disrupted RMNS that paradoxically normalized morphology but decreased function and viability. Thus, RPE heterogeneity is defined by the interaction of two cytoprotective pathways that is triggered by mitophagy function. By neutralizing the consequences of impaired mitophagy, an antioxidant dendrimer tropic for the RPE and mitochondria, EMT (a recognized AMD alteration) was abrogated to offer potential therapy for early AMD, a stage without treatment.Abbreviations: ACTB: actin beta; AKT: AKT serine/threonine kinase; AMD: age-related macular degeneration; CCCP: cyanide m-chlorophenyl hydrazone; CDH1: cadherin 1; DAVID: Database for Annotation, Visualization and Integrated Discovery; DHE: dihydroethidium; D-NAC: N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; ECAR: extracellular acidification rate; EMT: epithelial-mesenchymal transition; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GSEA: Gene Set Enrichment Analysis; HSPD1: heat shock protein family D (Hsp60) member 1; IVT: intravitreal; KD: knockdown; LMNA, lamin A/C; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; MMP: mitochondrial membrane potential; NAC: N-acetyl-l-cysteine; NQO1: NAD(P)H quinone dehydrogenase 1; NFE2L2: NFE2 like bZIP transcription factor 2; O2-: superoxide anion; OCR: oxygen consumption rate; PI3K: phosphoinositide 3-kinase; PINK1: PTEN induced kinase 1; RMNS: retrograde mitochondrial-nuclear signaling; ROS: reactive oxygen species; RPE: retinal pigment epithelium; SNAI1: snail family transcriptional repressor 1; TJP1: tight junction protein 1; TPP-D-NAC: triphenyl phosphinium and N-acetyl-l-cysteine conjugated to a poly(amido amine) dendrimer; TIMM23: translocase of inner mitochondrial membrane 23; TOMM20: translocase of outer mitochondrial membrane 20; Trig: trigonelline; TXNRD1: thioredoxin reductase 1; VIM: vimentin; WT: wild-type; ZEB1: zinc finger E-box binding homeobox 1.

AMPK-induced mitochondrial biogenesis decelerates retinal pigment epithelial cell degeneration under nutrient starvation

The implications of nutrient starvation due to aging on the degeneration of the retinal pigment epithelium (RPE) is yet to be fully explored. We examined the involvement of AMPK activation in mitochondrial homeostasis and its relationship with the maintenance of a healthy mitochondrial population and epithelial characteristics of RPE cells under nutrient starvation. Nutrient starvation induced mitochondrial senescence, which led to the accumulation of reactive oxygen species (ROS) in RPE cells. As nutrient starvation persisted, RPE cells underwent pathological epithelial-mesenchymal transition (EMT) via the upregulation of TWIST1, a transcription regulator which is activated by ROS-induced NF-κB signaling. Enhanced activation of AMPK with metformin decelerated mitochondrial senescence and EMT progression through mitochondrial biogenesis, primed by activation of PGC1-α. Thus, by facilitating mitochondrial biogenesis, AMPK protects RPE cells from the loss of epithelial integrity due to the accumulation of ROS in senescent mitochondria under nutrient starvation. [BMB Reports 2023; 56(2): 84-89].

Significance of the p38MAPK-CRP2 axis in myofibroblastic phenotypic transition

We have recently demonstrated that a LIM domain protein, cysteine and glycine-rich protein 2 (CSRP2 [CRP2]), plays a vital role in the functional expression of myofibroblasts and cancer-associated fibroblasts. CRP2 binds directly to myocardin-related transcription factors (MRTF [MRTF-A or MRTF-B]) and serum response factor (SRF) to stabilize the MRTF/SRF/CArG-box complex, leading to the expression of smooth muscle cell (SMC) genes such as α-smooth muscle actin (α-SMA) and collagens. These are the marker genes for myofibroblasts. Here, we show that the adhesion of cultured human skin fibroblasts (HSFs) to collagen reduces the myofibroblastic features. HSF adhesion to collagen suppresses the expression of CRP2 and CSRP2-binding protein (CSRP2BP [CRP2BP]) and reduces the expression of SMC genes. Although CRP2BP is known as an epigenetic factor, we find that CRP2BP also acts as an adaptor protein to enhance the function of CRP2 mentioned above. This CRP2BP function does not depend on its histone acetyltransferase activity. We also addressed the molecular mechanism of the reduced myofibroblastic features of HSFs on collagen. HSF adhesion to collagen inhibits the p38MAPK-mediated pathway, and reducing the p38MAPK activity decreases the expression of CRP2 and SMC genes. Thus, the activation of p38MAPK is critical for the myofibroblastic features. We also show evidence that CRP2 plays a role in the myofibroblastic transition of retinal pigment epithelial cells (RPEs). Like HSFs, such phenotypic modulation of RPEs depends on the p38MAPK pathway.Key words: CRP2, p38MAPK, MRTF, myofibroblasts, retinal pigment epithelial cells.

Ginsenoside protopanaxadiol protects adult retinal pigment epithelial-19 cells from chloroquine by modulating autophagy and apoptosis

Chloroquine often causes serious eye and vision problems, which are mainly mediated by lysosomotropic alteration. In this study, we investigated whether the ginsenoside protopanaxadiol relieves chloroquine-induced retinopathy by restoring lysosomotropic abnormalities in human adult retinal pigment epithelial-19 cells. Cytotoxicity was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Morphological alterations in autophagosomes of adult retinal pigment epithelial-19 cells was detected using confocal microscopy. Apoptosis was examined using flow cytometry, whereas cellular reactive oxygen species levels were determined by measuring the fluorescence intensity of 5-(and-6)-carboxy-2'-7'-dichlorohydrofluorescein diacetate. Lysosomal function was assessed by measuring lysosomal pH and enzyme activity. Immunoprecipitation and western blotting analyses were performed. Adult retinal pigment epithelial-19 cells accumulated autophagosomes with fusion defects in lysosomes and reactive oxygen species formation following exposure to chloroquine. This effect trapped Beclin-1 and B-cell lymphoma 2 interfering with autophagy initiation and autophagosome development. Protopanaxadiol alleviated chloroquine-induced toxicity by modulating the interaction between Beclin-1 and Bcl-2, which was mediated by the AMP-activated protein kinase-mammalian target of rapamycin signal axis. Furthermore, autophagy and apoptosis were simultaneously controlled by protopanaxadiol via upregulation of autophagy flux and decreased reactive oxygen species formation and apoptotic protein expression. These findings suggest that protopanaxadiol is a promising treatment strategy for chloroquine-mediated retinopathy.

DANON DISEASE: A MODEL OF PHOTORECEPTOR DEGENERATION SECONDARY TO PRIMARY RETINAL PIGMENT EPITHELIUM DISEASE

PURPOSE

To describe in detail the retinal phenotype of LAMP2-associated Danon disease.

METHODS

Three LAMP2-positive patients from two unrelated families were studied with spectral-domain optical coherence tomography and with short-wavelength and near-infrared fundus autofluorescence (FAF) imaging. Visual function was measured with full-field electroretinography and chromatic perimetry. A patient with choroideremia was also studied for comparison.

RESULTS

A 45-year-old LAMP2-heterozygous woman, her 21-year-old hemizygous son, and an unrelated heterozygous 60-year-old woman had normal visual acuities. Central spectral-domain optical coherence tomographies were grossly normal in the younger two patients (mother and son). The oldest patient showed a tenuous interdigitation signal, interruptions of the inner segment ellipsoid zone band, and parafoveal outer nuclear layer thinning. Quantitatively, all patients had shorter than normal ellipsoid zone to retinal pigment epithelium distance in pericentral retina, normal at the foveola. A speckled hypoautofluorescence pattern on short-wavelength FAF contrasted with grossly abnormal near-infrared FAF in the heterozygous carriers. The oldest patient had reduced full-field electroretinography amplitudes (to ∼50% of normal) for rod- and cone-mediated responses and her perimetry showed severe rod dysfunction but substantial cone function. A disproportionate loss of the near-infrared FAF compared with the short-wavelength FAF, predominantly outer segment changes, and severe rod dysfunction with preserved cone function was similarly documented in a 9-year-old choroideremia hemizygous patient.

CONCLUSION

A disproportionate loss of the near-infrared FAF signal compared with the short-wavelength FAF signal, outer segment abnormalities, and severe rod dysfunction but relatively preserved cone vision suggests a stereotypical pattern of primary retinal pigment epithelial or parallel retinal pigment epithelial + photoreceptor disease in Danon disease.

PERIPHERAL OPTICAL COHERENCE TOMOGRAPHY FINDINGS IN A CHOROIDEREMIA CARRIER

PURPOSE

To describe the peripheral optical coherence tomography findings in a female choroideremia carrier.

METHODS

A 56-year-old woman was referred for visual disturbance complaining of some occasional photopsias and increasing difficulty with her vision at night in both eyes. Best-corrected visual acuity was 20/20 in the right eye and 20/150 in the left eye. Fundus examination revealed mildly tilted disks and peripapillary atrophy with subtle retinal pigment epithelial changes in the periphery.

RESULTS

Macular optical coherence tomography in the right eye appeared unremarkable, but the in the left eye, there was diffuse ellipsoid zone band disruption. Green-light fundus autofluorescence revealed mottled areas of decreased autofluorescence in the mid and far periphery creating an irregular mosaic pattern. Peripheral optical coherence tomography scans revealed more diffuse ellipsoid zone alterations than were apparent on the fundus autofluorescence imaging. Genetic testing revealed a heterozygous pathogenic variant in the CHM gene (c.715C>T, p.Arg239). An additional heterozygous mutation was noted in the CNGB1 gene (c.290+2T>C, splice donor).

CONCLUSION

Choroideremia carriers may manifest widespread photoreceptor alterations, which may be more extensive than apparent on fundus autofluorescence imaging.

MULTIMODAL IMAGING OF A CHOROIDAL NEVUS WITH CAVERNS IN THE SETTING OF PACHYCHOROID DISEASE

PURPOSE

To describe the multimodal imaging findings of extensive choroidal caverns within a choroidal nevus in an eye with pachychoroid spectrum disease.

METHODS

A 69-year-old woman was referred with a known history of branch retinal vein occlusion in the right eye and choroidal nevus in the left eye. Fundus examination of both eyes revealed subretinal yellow deposits, suggestive of pachydrusen. Retinal venous collaterals were noted in the temporal macular of the right eye. A lightly pigmented choroidal lesion with nearly confluent overlying drusen and retinal pigment epithelial alterations, consistent with chronic choroidal nevus, was noted in the macula of the left eye.

RESULTS

Optical coherence tomography B-scans revealed thickened choroid (pachychoroid) with subfoveal choroidal thickness of 504 µ m and 580 µ m with large hyporeflective spaces suggestive of pachyvessels in both eyes. In the region of the choroidal nevus, the choroidal vascular spaces appeared comparatively large and were classified as "caverns" measuring up to 480 µ m in diameter. Optical coherence tomography angiography and indocyanine green angiography demonstrated the absence of flow within the caverns. Indocyanine green angiography further illustrated choroidal vascular hyperpermeability with patchy hyperfluorescent areas in both eyes. Wide-field swept-source optical coherence tomography showed mild posterior scleral bowing, a feature occasionally documented with choroidal nevus, and highlighted greater hyporeflectivity and hypertransmission on optical coherence tomography within the caverns compared with the noncavernous choroidal vessels.

CONCLUSION

Choroidal caverns can occur within choroidal nevus in the setting of pachychoroid disease.

RETINAL PIGMENT EPITHELIAL LESIONS ASSOCIATED WITH A SPORADIC CASE OF FAMILIAL ADENOMATOUS POLYPOSIS

PURPOSE

To report a sporadic case of a familial adenomatous polyposis (FAP) discovered in a patient with bilateral retinal pigment epithelial lesions.

METHODS

Case report.

RESULTS

A 30-year-old Asian woman presented for evaluation of bilateral pigmented lesions at the level of the retinal pigment epithelium. She had no personal or family history of colonic polyps or colon cancer. Colonoscopy revealed innumerable adenomatous polyps and genetic testing revealed a mutation in the adenomatous polyposis coli gene consistent with FAP. She subsequently underwent prophylactic total colectomy.

CONCLUSION

The pigmented retinal pigment epithelium lesions of FAP have a characteristic appearance and it is vital for the retinal specialist to be familiar with them. De novo mutations in the APC gene are responsible for 20% to 30% of FAP cases. In the presence of the characteristic retinal pigment epithelium lesions, it is important to send the patient for work up of FAP even in the absence of family history of FAP.

Fundus-Vascular Responses to Color Deviation Caused by Non-Oxidative Blue Filtering

Aims

Short-wavelength blue light damaged retina by the oxidative stress in the retinal pigment epithelial (RPE) cells. Filtering blue light from screen could reduce blue hazard, whereas it inevitably altered color-gamut coverage and color-deviation level. Although abnormal fundus-vascular density (FVD) sometimes indicated fundus disease, few researchers noticed its responses to the variation of color-gamut coverage and color-deviation level.

Methods

In this study, we performed cellular experiments and analyzed the RPE cell viabilities (CVs) in spectrums with different blue (455-475 nm) ratios to describe the corresponding oxidative-stress levels. Further, we investigated the effects of color-gamut and deviation on FVD variations during the screen-watching task using human factor experiments with 30 participants (university students, including 17 males and 13 females, 21 to 30 years old).

Results

RPE CVs were similar in different spectrums, implying that non-oxidative blue filtering hardly contributed to CV improvement. Color-deviation level seems to induce more significant effects on the visual function compared to color-gamut coverage, and MTF and FVD presents similar variation trends during the visual task.

Conclusion

Oxidative-free blue filtering contributed little to decrease retinal oxidative stress yet caused color-deviation increase, which caused significant FVD reduction.

Tissue-specific modifier alleles determine Mertk loss-of-function traits

Knockout (KO) mouse models play critical roles in elucidating biological processes behind disease-associated or disease-resistant traits. As a presumed consequence of gene KO, mice display certain phenotypes. Based on insight into the molecular role of said gene in a biological process, it is inferred that the particular biological process causally underlies the trait. This approach has been crucial towards understanding the basis of pathological and/or advantageous traits associated with Mertk KO mice. Mertk KO mice suffer from severe, early-onset retinal degeneration. MERTK, expressed in retinal pigment epithelia, is a receptor tyrosine kinase with a critical role in phagocytosis of apoptotic cells or cellular debris. Therefore, early-onset, severe retinal degeneration was described to be a direct consequence of failed MERTK-mediated phagocytosis of photoreceptor outer segments by retinal pigment epithelia. Here, we report that the loss of Mertk alone is not sufficient for retinal degeneration. The widely used Mertk KO mouse carries multiple coincidental changes in its genome that affect the expression of a number of genes, including the Mertk paralog Tyro3. Retinal degeneration manifests only when the function of Tyro3 is concomitantly lost. Furthermore, Mertk KO mice display improved anti-tumor immunity. MERTK is expressed in macrophages. Therefore, enhanced anti-tumor immunity was inferred to result from the failure of macrophages to dispose of cancer cell corpses, resulting in a pro-inflammatory tumor microenvironment. The resistance against two syngeneic mouse tumor models observed in Mertk KO mice is not, however, phenocopied by the loss of Mertk alone. Neither Tyro3 nor macrophage phagocytosis by alternate genetic redundancy accounts for the absence of anti-tumor immunity. Collectively, our results indicate that context-dependent epistasis of independent modifier alleles determines Mertk KO traits.

Dabigatran and Wet AMD, Results From Retinal Pigment Epithelial Cell Monolayers, the Mouse Model of Choroidal Neovascularization, and Patients From the Medicare Data Base

Background

Age-related macular degeneration (AMD), the leading cause of irreversible blindness in elderly Caucasian populations, includes destruction of the blood-retina barrier (BRB) generated by the retinal pigment epithelium-Bruch’s membrane complex (RPE/BrM), and complement activation. Thrombin is likely to get access to those structures upon BRB integrity loss. Here we investigate the potential role of thrombin in AMD by analyzing effects of the thrombin inhibitor dabigatran.

Material and Methods

MarketScan data for patients aged ≥65 years on Medicare was used to identify association between AMD and dabigatran use. ARPE-19 cells grown as mature monolayers were analyzed for thrombin effects on barrier function (transepithelial resistance; TER) and downstream signaling (complement activation, expression of connective tissue growth factor (CTGF), and secretion of vascular endothelial growth factor (VEGF)). Laser-induced choroidal neovascularization (CNV) in mouse is used to test the identified downstream signaling.

Results

Risk of new wet AMD diagnosis was reduced in dabigatran users. In RPE monolayers, thrombin reduced TER, generated unique complement C3 and C5 cleavage products, led to C3d/MAC deposition on cell surfaces, and increased CTGF expression via PAR1-receptor activation and VEGF secretion. CNV lesion repair was accelerated by dabigatran, and molecular readouts suggest that downstream effects of thrombin include CTGF and VEGF, but not the complement system.

Conclusions

This study provides evidence of association between dabigatran use and reduced exudative AMD diagnosis. Based on the cell- and animal-based studies, we suggest that thrombin modulates wound healing and CTGF and VEGF expression, making dabigatran a potential novel treatment option in AMD.

Gene Delivery of a Caspase Activation and Recruitment Domain Improves Retinal Pigment Epithelial Function and Modulates Inflammation in a Mouse Model with Features of Dry Age-Related Macular Degeneration

Purpose: The NLRP3 inflammasome, a cytoplasmic signal transduction complex that regulates inflammation, has been implicated in the pathogenesis of age-related macular degeneration (AMD), the leading cause of visual impairment in industrialized countries. We tested the therapeutic effect of anti-inflammatory gene therapy, delivered preventively, in Liver-X-Receptor alpha knockout (LXRα^-/-) mice, which exhibit features of dry AMD. Methods:LXRα^-/- mice were treated with an adeno-associated virus (AAV) vector that delivers a secretable and cell-penetrating form of the caspase activation and recruitment domain (CARD). A sGFP-FCS-TatCARD-AAV or sGFP-FCS (control) vector was delivered intravitreally to 3-5 month-old, LXRα^-/- mice, who were then aged to 15-18 months (12-13 month treatment). Retinal function and morphology were assessed pre- and post-treatment. Results: TatCARD treated LXRα^-/- mice did not show improvement in rod and cone photoreceptor function, measured by dark adapted a- and b-wave amplitudes, and rod-saturated b-wave amplitudes. We found a sex-dependent, significant therapeutic effect in c-wave amplitudes in the TatCARD treated mice, which exhibited maintenance of amplitudes in comparison to the significant decline recorded in the control treated group, indicating a therapeutic effect mediated in part through retinal pigment epithelial (RPE) cells. Additionally, the retinas of the TatCARD treated mice exhibited a significant decline in the concentration of interleukin-1 beta (IL-1β) concomitant with modulation of several inflammatory cytokines in the retina and RPE-choroid tissues, as measured by ELISA and cytokine array, respectively. Conclusion: Collectively, these results support that anti-inflammatory gene constructs such as AAV-TatCARD may be considered for the treatment of inflammation in AMD and other ocular diseases of the posterior pole in which inflammation may play a role. Furthermore, our findings emphasize the need to carefully consider potential sex-different responses when assessing potential therapies in pre-clinical models.

Multinucleated Retinal Pigment Epithelial Cells Adapt to Vision and Exhibit Increased DNA Damage Response

Multinucleated retinal pigment epithelium (RPE) cells have been reported in humans and other mammals. Rodents have an extremely high percentage of multinucleated cells (more than 80%). Both mouse and human multinucleated RPE cells exhibit specific regional distributions that are potentially correlated with photoreceptor density. However, detailed investigations of multinucleated RPE in different species and their behavior after DNA damage are missing. Here, we compared the composition of multinucleated RPE cells in nocturnal and diurnal animals that possess distinct rod and cone proportions. We further investigated the reactive oxygen species (ROS) production and DNA damage response in mouse mononucleated and multinucleated RPE cells and determined the effect of p53 dosage on the DNA damage response in these cells. Our results revealed an unrealized association between multinucleated RPE cells and nocturnal vision. In addition, we found multinucleated RPE cells exhibited increased ROS production and DNA damage after X-ray irradiation. Furthermore, haploinsufficiency of p53 led to increased DNA damage frequency after irradiation, and mononucleated RPE cells were more sensitive to a change in p53 dosage. In conclusion, this study provides novel information on in vivo PRE topography and the DNA damage response, which may reflect specific requirements for vision adaption and macular function.

RETINAL PIGMENT EPITHELIAL IRREGULARITY AND ATROPHY AFTER INTERNAL MEMBRANE PEELING: A REPORT OF TWO CASES

PURPOSE

To report two cases of widespread retinal pigment epithelial clumping, irregularity, and atrophy after uncomplicated 25-gauge pars plana vitrectomy with brilliant blue-green-assisted internal limiting membrane peeling.

METHODS

Retrospective analysis of 2 eyes of 2 patients who underwent 25-gauge pars plana vitrectomy for macular diseases (macular hole with retinal detachment and vitreomacular traction) was performed. Surgical notes and video recordings were reviewed to determine the surgical procedures performed and the duration of the surgery. Multimodal imaging analysis, including fundus photography, fundus autofluorescence imaging, and optical coherence tomography were performed to determine the pathological changes in the postoperative period.

RESULTS

The mean age of the patients (all females) was 78 years. In all the patients, brilliant blue-green-assisted internal limiting membrane peeling was performed without any intraoperative complications. Four weeks after an uncomplicated surgery, the patients complained of progressive central visual disturbance and metamorphopsia. Retinal imaging demonstrated retinal pigment epithelial clumps and irregularity, which appeared as hyperautofluorescent on fundus autofluorescence, and widespread retinal pigment epithelial atrophy (hypoautofluorescent on fundus autofluorescence) in the posterior pole and peripapillary region, along with retinal and choroidal thinning.

CONCLUSION

In uncomplicated vitrectomy consisting of brilliant blue-green-assisted internal limiting membrane peeling, a remote risk of widespread retinal pigment epithelial damage exists even with the use of modern endoilluminators and relatively short surgical duration. Retinal phototoxicity seems to be the primary cause; however, dye-related cytotoxicity or a combination of both cannot be ruled out.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FINDINGS IN PIGMENTED PARAVENOUS CHORIORETINAL ATROPHY

PURPOSE

To analyze the retino-choroidal vascular characteristics of patients affected by pigmented paravenous chorio-retinal atrophy by means of optical coherence tomography (OCT) angiography.

METHODS

This study was designed as an observational, cross-sectional case series. Multimodal imaging included fundus autofluorescence, structural OCT, and OCT angiography. The quantitative OCT angiography analyses included the calculation of the vessel density and choriocapillaris porosity.

RESULTS

Overall, 12 patients (24 eyes) affected by pigmented paravenous chorio-retinal atrophy were recruited. Structural OCT of the areas involved by pigmented paravenous chorio-retinal atrophy as visualized on the fundus autofluorescence showed a complete ellipsoid zone and external limiting membrane absence, with thinning of ganglion cell complex, outer nuclear layer, and outer plexiform layer, but associated with the optical partial preservation of the retinal pigment epithelium. Optical coherence tomography angiography quantitative assessment of the retinal regions affected by PPRCA, as visualized by fundus autofluorescence, was characterized by normal vessel density at the level of superficial capillary plexus but significantly altered vessel density of deep capillary plexus and choriocapillaris, with higher choriocapillaris porosity. The presence of macular atrophy was significantly correlated with worse deep capillary plexus and choriocapillaris vessel density values. Furthermore, a statistically significant correlation between the fundus autofluorescence patterns and the retinal vascular status was found.

CONCLUSION

Optical coherence tomography angiography quantitative analyses in pigmented paravenous chorio-retinal atrophy demonstrate a specific impairment at the level of the deep capillary plexus, which could in turn bring about a thinning of ganglion cell complex and outer nuclear layer. The alterations at the level of the choriocapillaris and the choroid, in general, could then represent a secondary effect.

Acute retinal pigment epitheliitis (ARPE). A case report

A 35-year-old woman arrived in the emergency department due to loss of vision in the left eye. She had a subfoveal yellowish-looking lesion that, on optical coherence tomography (OCT), corresponded to a hyper-reflective lesion from the external nuclear layer to the retinal pigment epithelium. The lesion was reabsorbed at 6 weeks, leaving a discontinuity in the photoreceptor and retinal pigment epithelium lines. The patient was diagnosed with acute retinal pigmentary epitheliitis (ARPE). ARPE is a self-limiting disease with a good prognosis. Emphasis is placed on the importance of a correct diagnosis using funduscopy, OCT, and fluorescent angiography, in order to avoid unnecessary treatments.

Procyanidin protects human retinal pigment epithelial cells from high glucose by inhibiting autophagy

PURPOSE

The damage of hyperglycemia to the retinal pigment epithelial (RPE) cells is a critical event in diabetic retinopathy (DR). Procyanidin (PC), a kind of polyphenol compounds, has shown to be effective in preventing and treating diabetes as well as its complications, in which autophagy disorder is involved in the pathological mechanism. However, it remains unclear whether PC can play a protective role in DR by regulating the autophagy of RPE. Here, the effect of PC on RPE under high glucose conditions and the role of autophagy were investigated.

MATERIALS AND METHODS

The cell viability of ARPE-19, a human RPE cell line, was detected by cell counting kit-8 (CCK-8) and the apoptosis rate was measured by flow cytometry. The protein expressions of apoptosis markers, including Bax, Bcl-2, and Caspase-3, as well as autophagy markers including LC3, p62, p53, and mTOR were detected by Western blotting. Autophagic flux in ARPE-19 cells was detected by transfection with Ad-mCherry-GFP-LC3B.

RESULTS

Under high glucose conditions, the viability of ARPE-19 was decreased and the apoptosis rate increased, the protein expressions of Bax, Caspase-3, LC3-II/LC3-I, and p-p53 were all increased and the expressions of Bcl-2, p62, and p-mTOR decreased, and autophagic flux was increased compared with that of the controls. Treatment with PC weakened all these changes caused by high glucose. When rapamycin (RPM), an autophagy agonist was added, the cell viability of ARPE-19 by PC treatment was decreased while the apoptosis was increased.

CONCLUSIONS

Our findings indicate that through the p53/mTOR autophagy pathway, PC may protect RPE cells from high glucose-induced injury.

Discovery of sterically-hindered phenol compounds with potent cytoprotective activities against ox-LDL-induced retinal pigment epithelial cell death as a potential pharmacotherapy

Late-stage dry age-related macular degeneration (AMD) or geographic atrophy (GA) is an irreversible blinding condition characterized by degeneration of retinal pigment epithelium (RPE) and the associated photoreceptors. Clinical and genetic evidence supports a role for dysfunctional lipid processing and accumulation of harmful oxidized lipids in the pathogenesis of GA. Using an oxidized low-density lipoprotein (ox-LDL)-induced RPE death assay, we screened and identified sterically-hindered phenol compounds with potent protective activities for RPE. The phenol-containing PPARγ agonist, troglitazone, protected against ox-LDL-induced RPE cell death, whereas other more potent PPARγ agonists did not protect RPE cells. Knockdown of PPARγ did not affect the protective activity of troglitazone in RPE, confirming the protective function is not due to the thiazolidine (TZD) group of troglitazone. Prototypical hindered phenol trolox and its analogs potently protected against ox-LDL-induced RPE cell death whereas potent antioxidants without the phenol group failed to protect RPE. Hindered phenols preserved lysosomal integrity against ox-LDL-induced damage and FITC-labeled trolox was localized to the lysosomes in RPE cells. Analogs of trolox inhibited reactive oxygen species (ROS) formation induced by ox-LDL uptake in a dose-dependent fashion and were effective at sub-micromolar concentrations. Treatment with trolox analog 2,2,5,7,8-pentamethyl-6-chromanol (PMC) significantly induced the expression of the lysosomal protein NPC-1 and reduced intracellular cholesterol level upon ox-LDL uptake. Our data indicate that the lysosomal-localized hindered phenols are uniquely potent in protecting the RPE against the toxic effects of ox-LDL, and may represent a novel pharmacotherapy to preserve the vision in patients with GA.