Effects of Lycium barbarum polysaccharide on the photoinduced autophagy of retinal pigment epithelium cells

AIM: To investigate the relationship between autophagy and apoptosis in photoinduced injuries in retinal pigment epithelium (RPE) cells and how Lycium barbarum polysaccharide (LBP) contributes to the increased of RPE cells to photoinduced autophagy. METHODS: In vitro cultures of human RPE strains (ARPE-19) were prepared and randomly divided into the blank control, model, low-dose LBP, middle-dose LBP, high-dose LBP, and 3-methyladenine (3MA) groups. The viability of the RPE cells and apoptosis levels in each group were tested through cell counting kit-8 (CCK8) method with a flow cytometer (Annexin V/PI double staining technique). The expression levels of LC3II, LC3I, and P62 proteins were detected with the immunofluorescence method. The expression levels of beclin1, LC3, P62, PI3K, P-mTOR, mTOR, P-Akt, and Akt proteins were tested through Western blot. RESULTS: LBP considerably strengthens cell viability and inhibits the apoptosis of RPE cells after photoinduction. The PI3K/Akt/mTOR signal pathway is activated because of the upregulation of the phosphorylation levels of Akt and mTOR proteins, and thus autophagy is inhibited. CONCLUSION: LBP can inhibit the excessive autophagy in RPE cells by activating the PI3K/Akt/mTOR signaling pathways and thereby protect RPE cells from photoinduced injuries.

Common clinical features of unilateral retinal pigment epithelium dysgenesis and combined hamartoma of the retina and retinal pigment epithelium

Background Herein, we report two cases of unilateral retinal pigment epithelium dysgenesis (URPED) in Chinese patients and explore the relationship between URPED and combined hamartoma of the retina and retinal pigment epithelium (CHRRPE). Case presentation The lesion margins in the two cases showed pathognomonic clinical features of URPED, namely, a scalloped reticular margin in hyperplastic retinal pigment epithelium and mild fibrosis. The hypoautofluorescence observed by fundus autofluorescence was inverted compared with that observed by fundus fluorescence angiography. A large amount of fibroglial proliferation and disorganization of the retina involving the whole layer, which are also found in peripapillary CHRRPE, were found in the lesions. Conclusions URPED appears to share some clinical features with CHRRPE, and the relationship between URPED and CHRRPE needs further study.

Photodegradation of Lipofuscin in Suspension and in ARPE-19 Cells and the Similarity of Fluorescence of the Photodegradation Product with Oxidized Docosahexaenoate

Retinal lipofuscin accumulates with age in the retinal pigment epithelium (RPE), where its fluorescence properties are used to assess retinal health. It was observed that there is a decrease in lipofuscin fluorescence above the age of 75 years and in the early stages of age-related macular degeneration (AMD). The purpose of this study was to investigate the response of lipofuscin isolated from human RPE and lipofuscin-laden cells to visible light, and to determine whether an abundant component of lipofuscin, docosahexaenoate (DHA), can contribute to lipofuscin fluorescence upon oxidation. Exposure of lipofuscin to visible light leads to a decrease in its long-wavelength fluorescence at about 610 nm, with a concomitant increase in the short-wavelength fluorescence. The emission spectrum of photodegraded lipofuscin exhibits similarity with that of oxidized DHA. Exposure of lipofuscin-laden cells to light leads to a loss of lipofuscin granules from cells, while retaining cell viability. The spectral changes in fluorescence in lipofuscin-laden cells resemble those seen during photodegradation of isolated lipofuscin. Our results demonstrate that fluorescence emission spectra, together with quantitation of the intensity of long-wavelength fluorescence, can serve as a marker useful for lipofuscin quantification and for monitoring its oxidation, and hence useful for screening the retina for increased oxidative damage and early AMD-related changes.

KIAA0319 influences cilia length, cell migration and mechanical cell–substrate interaction

Following its association with dyslexia in multiple genetic studies, the KIAA0319 gene has been extensively investigated in different animal models but its function in neurodevelopment remains poorly understood. We developed the first human cellular knockout model for KIAA0319 in RPE1 retinal pigment epithelia cells via CRISPR-Cas9n to investigate its role in processes suggested but not confirmed in previous studies, including cilia formation and cell migration. We observed in the KIAA0319 knockout increased cilia length and accelerated cell migration. Using Elastic Resonator Interference Stress Microscopy (ERISM), we detected an increase in cellular force for the knockout cells that was restored by a rescue experiment. Combining ERISM and immunostaining we show that RPE1 cells exert highly dynamic, piconewton vertical pushing forces through actin-rich protrusions that are surrounded by vinculin-rich pulling sites. This protein arrangement and force pattern has previously been associated to podosomes in other cells. KIAA0319 depletion reduces the fraction of cells forming these actin-rich protrusions. Our results suggest an involvement of KIAA0319 in cilia biology and cell–substrate force regulation.

Inhibition of DUSP6 Activates Autophagy and Rescues the Retinal Pigment Epithelium in Sodium Iodate-Induced Retinal Degeneration Models In Vivo and In Vitro

Autophagy plays a protective role in the retinal pigment epithelium (RPE) by eliminating damaged organelles in response to reactive oxygen species (ROS). Dual-specificity protein phosphatase 6 (DUSP6), which belongs to the DUSP subfamily, works as a negative-feedback regulator of the extracellular signal-regulated kinase (ERK) pathway. However, the complex interplay between DUSP6 and autophagy induced by ROS in RPE is yet to be investigated. To investigate the relationship between DUSP6 and autophagy, we exposed the ARPE-19 cell line and C57BL/6N mice to sodium iodate (NaIO3) as an oxidative stress inducer. Our data showed that the inhibition of DUSP6 activity promotes autophagy flux through the ERK pathway via the upregulation of immunoblotting expression in ARPE-19 cells. Live imaging showed a significant increase in autophagic flux activities, which suggested the restoration autophagy after treatment with the DUSP6 inhibitor. Furthermore, the mouse RPE layer exhibited an irregular structure and abnormal deposits following NaIO3 injection. The retina layer was recovered after being treated with DUSP6 inhibitor; this suggests that DUSP6 inhibitor can rescue retinal damage by restoring the mouse retina’s autophagy flux. This study suggests that the upregulation of DUSP6 can cause autophagy flux malfunctions in the RPE. The DUSP6 inhibitor can restore autophagy induction, which may serve as a potential therapeutic approach for retinal degeneration disease.

Altered retinal structure and function in Spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 is an autosomal dominant neurodegenerative disorder caused by expansion of a polyglutamine (polyQ)-encoding CAG repeat in the ATXN3 gene. Because the ATXN3 protein regulates photoreceptor ciliogenesis and phagocytosis, we aimed to explore whether expanded polyQ ATXN3 impacts retinal function and integrity in SCA3 patients and transgenic mice. We evaluated the retinal structure and function in five patients with Spinocerebellar ataxia type 3 and in a transgenic mouse model of this disease (YACMJD84.2, Q84) using, respectively, optical coherence tomography (OCT) and electroretinogram (ERG). We further determined in the transgenic mice: a) the retinal expression pattern of ATXN3 and assessed the distribution of cones and rods by immunofluorescence (IF); and b) the retinal ultrastructure by transmission electron microscopy (TEM). Some patients with Spinocerebellar ataxia type 3 in our cohort revealed: i) reduced central macular thickness indirectly correlated with disease duration; ii) decreased thickness of the macula and the ganglion cell layer, and reduced macula volume inversely correlated with disease severity (SARA score); and iii) electrophysiological dysfunction of cones, rods, and inner retinal cells. Transgenic mice replicated the human OCT and ERG findings with aged homozygous Q84/Q84 mice showing a stronger phenotype accompanied by further thinning of the outer nuclear layer and photoreceptor layer and highly reduced cone and rod activities, thus supporting severe retinal dysfunction in these mice. In addition, Q84 mice showed progressive accumulation of ATXN3-positive aggregates throughout several retinal layers and depletion of cones alongside the disease course. TEM analysis of aged Q84/Q84 mouse retinas supported the IF ATXN3 aggregation findings by revealing the presence of high number of negative electron dense puncta in ganglion cells, inner plexiform and inner nuclear layers, and further showed thinning of the outer plexiform layer, thickening of the retinal pigment epithelium and elongation of apical microvilli. Our results indicate that retinal alterations detected by non-invasive eye examination using OCT and ERG could represent a biological marker of disease progression and severity in patients with Spinocerebellar ataxia type 3.

Proposing a Neurotropic Etiology for Acute Posterior Multifocal Placoid Pigment Epitheliopathy and Relentless Placoid Chorioretinitis

PurposeTo reassess the underlying pathophysiology of acute posterior multifocal placoid pigment epitheliopathy (APMPPE) and relentless placoid chorioretinitis (RPC) through comparison with the non-inoculated eye of the von Szily animal model of neurotropic viral retinal infection.MethodsNarrative review.ResultsLiterature reports of isolated neurotropic viral entities and rising serological viral titers in APMPPE after presentation support a potential direct infective etiology. In general, viral transport along axons results in mitochondrial stasis and disruption of axoplasmic flow. Clinical manifestations of axoplasmic flow disruption in APMPPE/RPC may signify the passage of virus along the neuronal pathway. From a case series of 11 patients, we demonstrate a timely, spatial, and proportional association of optic disc swelling with APMPPE lesion occurrence. Signs within the inner retina appear to precede outer retinal lesions; and acute areas of outer nuclear layer (ONL) hyperreflectivity appear to be the result of coalescence of multiple hyperreflective foci resembling axonal spheroids (which occur as a consequence of axoplasmic disruption) and follow the Henle fiber layer neurons. Underlying areas of retinal pigment epithelium (RPE) hyper-autofluorescence follow ONL hyperreflectivity and may signify localized infection. Areas of apparent choriocapillaris hypoperfusion mirror areas of RPE/Bruch’s membrane separation and appear secondary to tractional forces above. Increases in choroidal thickness with lesion occurrence and focal areas of choriocapillaris hypoperfusion are observed in both APMPPE/RPC and the von Szily model.ConclusionsThe neurotrophic infection model provides significant advantages over the existing primary choriocapillaris ischemia hypothesis to account for the range of imaging signs observed in APMPPE and RPC.

Caffeine Protects Against Retinal Inflammation

Caffeine, one of the most consumed central nervous system (CNS) stimulants, is an antagonist of A1 and A2A adenosine receptors. In this study, we investigated the potential protective effects of this methylxanthine in the retinal tissue. We tested caffeine by using in vitro and in vivo paradigms of retinal inflammation. Human retinal pigment epithelial cells (ARPE-19) were exposed to lipopolysaccharide (LPS) with or without caffeine. This latter was able to reduce the inflammatory response in ARPE-19 cells exposed to LPS, attenuating the release of IL-1β, IL-6, and TNF-α and the nuclear translocation of p-NFκB. Additionally, caffeine treatment restored the integrity of the ARPE-19 monolayer assessed by transepithelial electrical resistance (TEER) and the sodium fluorescein permeability test. Finally, the ischemia reperfusion (I/R) injury model was used in C57BL/6J mice to induce retinal inflammation and investigate the effects of caffeine treatment. Mouse eyes were treated topically with caffeine, and a pattern electroretinogram (PERG) was used to assess the retinal ganglion cell (RGC) function; furthermore, we evaluated the levels of IL-6 and BDNF in the retina. Retinal BDNF dropped significantly (p < 0.05) in the I/R group compared to the control group (normal mice); on the contrary, caffeine treatment maintained physiological levels of BDNF in the retina of I/R eyes. Caffeine was also able to reduce IL-6 mRNA levels in the retina of I/R eyes. In conclusion, these findings suggest that caffeine is a good candidate to counteract inflammation in retinal diseases.

Machine-learning and Automatically Segmented Retinal Biomarkers Generate Spatial Heatmaps Predictive for Standard and Low Luminance Visual Acuity in Geographic Atrophy

Objective: Predict visual function with machine-learning applied to automatically acquired quantitative imaging biomarkers in geographic atrophyDesign: Post-hoc analysis of data from a clinical trial and routine clinical care.Methods: Automated segmentation of OCT scans from 476 eyes (325 patients) with geographic atrophy. Machine learning modelling of resultant quantitative OCT (qOCT) biomarkers to predict cross-sectional visual acuity under both standard luminance (VA) and low luminance (LLVA) conditions.Main Outcome Measure: Correlation coefficient (R2) and mean absolute error (MAE) for cross-sectional VA and LLVA in Early Treatment Diabetic Retinopathy Study (ETDRS) letters.Results: Best-corrected VA under both standard luminance (R2 0.46 MAE 10.2 ETDRS letters) and low-luminance conditions (R2 0.25 MAE 12.1) could be predicted. The foveal region contributed the most (46.5%) toward model performance, with retinal pigment epithelium loss and outer retinal atrophy contributing the most (31.1%). For LLVA, however, features in the non-foveal regions were most important (74.5%), led by photoreceptor degeneration (38.9%).Conclusions: Our method of automatic qOCT segmentation demonstrates functional significance for vision in geographic atrophy, including LLVA. LLVA is itself predictive of geographic atrophy progression, implying that the predictive qOCT biomarkers provided by our model are also prognostic.

Ophthalmic artery angioplasty for age-related macular degeneration

BackgroundThere is considerable overlap of contributors to cardiovascular disease and the development of age-related macular degeneration (AMD). Compromised ocular microcirculation due to aging and vascular disease contribute to retinal dysfunction and vision loss. Decreased choroidal perfusion is evident in eyes with dry AMD and is thought to play a role in retinal pigment epithelial dysfunction, the rate of development of geographic atrophy, and the development of neovascularization. The aim of the study was to demonstrate that AMD is correlated with a compromised blood flow in the ocular pathway and show OA angioplasty as a potential treatment of late-stage AMD.MethodsBased on the potential for the ophthalmic artery (OA) to be an anatomical target for the treatment of AMD as outlined above, five patients were found to be eligible for compassionate use treatment, presenting clinically significant late-stage AMD with profound vision loss in one or both eyes, and are included in this retrospective study.ResultsOA narrowing, or significant calcium burden at the ophthalmic segment of the internal carotid artery compromising the origin of the OA was confirmed in all cases. Subsequent OA cannulation was achieved in all patients with some difficulty. Subjective patient reports indicated that all patients perceived a benefit following the procedure; however, improved postoperative visual acuity did not confirm that perceived benefit for one of the patients.ConclusionsFeasibility and safety of the OA angioplasty were demonstrated, and a benefit perceived in five patients with profound vision loss and a desire to achieve improved quality of life. A clinical trial with controlled schedule, imaging, and methodologies is needed to confirm these results.