LXR/CD38 activation drives cholesterol-induced macrophage senescence and neurodegeneration via NAD+ depletion.

Although dysregulated cholesterol metabolism predisposes aging tissues to inflammation and a plethora of diseases, the underlying molecular mechanism remains poorly defined. Here, we show that metabolic and genotoxic stresses, convergently acting through liver X nuclear receptor, upregulate CD38 to promote lysosomal cholesterol efflux, leading to nicotinamide adenine dinucleotide (NAD+) depletion in macrophages. Cholesterol-mediated NAD+ depletion induces macrophage senescence, promoting key features of age-related macular degeneration (AMD), including subretinal lipid deposition and neurodegeneration. NAD+ augmentation reverses cellular senescence and macrophage dysfunction, preventing the development of AMD phenotype. Genetic and pharmacological senolysis protect against the development of AMD and neurodegeneration. Subretinal administration of healthy macrophages promotes the clearance of senescent macrophages, reversing the AMD disease burden. Thus, NAD+ deficit induced by excess intracellular cholesterol is the converging mechanism of macrophage senescence and a causal process underlying age-related neurodegeneration.

Roles of Sphingosine Kinase and Sphingosine-1-Phosphate Receptor 2 in Endotoxin-Induced Acute Retinal Inflammation.

PURPOSE: To investigate the roles of sphingosine kinases (SphKs) and sphingosine-1-phosphate receptors (S1PRs) in endotoxin-induced uveitis (EIU) mice. METHODS: EIU model was induced using an intraperitoneal injection of lipopolysaccharide (LPS). The expression of SphKs and S1PRs in the retina was assessed using quantitative polymerase chain reaction (qPCR) and immunofluorescence. The effects of S1PR antagonists on the expression of inflammatory cytokines in the retina were evaluated using qPCR and western blotting. Effects of leukocyte infiltration of the retinal vessels were evaluated to determine the effects of the S1PR2 antagonist and genetic deletion of S1PR2 on retinal inflammation. RESULTS: Retinal SphK1 expression was significantly upregulated in EIU. SphK1 was expressed in the GCL, IPL, and OPL and S1PR2 was expressed in the GCL, INL, and OPL. Positive cells in IPL and OPL of EIU retina were identified as endothelial cells. S1PR2 antagonist and genetic deletion of S1PR2 significantly suppressed the expression of IL-1α, IL-6, TNF-α, and ICAM-1, whereas S1PR1/3 antagonist did not. Use of S1PR2 antagonist and S1PR2 knockout in mice significantly ameliorated leukocyte adhesion induced by LPS. CONCLUSION: SphK1/S1P/S1PR2 signaling was upregulated in EIU and S1PR2 inhibition suppressed inflammatory response. Targeting this signaling pathway has potential for treating retinal inflammatory diseases.

Dysregulated CD200-CD200R signaling in early diabetes modulates microglia-mediated retinopathy.

Diabetic retinopathy (DR) is a neurovascular complication of diabetes. Recent investigations have suggested that early degeneration of the neuroretina may occur prior to the appearance of microvascular changes; however, the mechanisms underlying this neurodegeneration have been elusive. Microglia are the predominant resident immune cell in the retina and adopt dynamic roles in disease. Here, we show that ablation of retinal microglia ameliorates visual dysfunction and neurodegeneration in a type I diabetes mouse model. We also provide evidence of enhanced microglial contact and engulfment of amacrine cells, ultrastructural modifications, and transcriptome changes that drive inflammation and phagocytosis. We show that CD200-CD200R signaling between amacrine cells and microglia is dysregulated during early DR and that targeting CD200R can attenuate high glucose-induced inflammation and phagocytosis in cultured microglia. Last, we demonstrate that targeting CD200R in vivo can prevent visual dysfunction, microglia activation, and retinal inflammation in the diabetic mouse. These studies provide a molecular framework for the pivotal role that microglia play in early DR pathogenesis and identify a potential immunotherapeutic target for treating DR in patients.

Cytokine profiles in the aqueous humor following brolucizumab administration for exudative age-related macular degeneration.

PURPOSE: To identify the inflammatory cytokine profile in the aqueous humor (AH) of patients with intraocular inflammation (IOI) after intravitreal administration of brolucizumab (IVBr) for neovascular age-related macular degeneration. METHODS: Eight eyes from seven patients with IOI after initial IVBr (IVBrIOI +) were enrolled. Sixteen eyes from 16 patients without IOI after IVBr (IVBrIOI -) and aflibercept (IVA) were used as controls. AH samples were analyzed using a multiplex immunoassay. RESULTS: C-C motif chemokine ligand (CCL)2, C-X-C motif chemokine ligand (CXCL)1, CXCL10, CXCL13, interleukin (IL)-6, IL-8, IL-10, matrix metalloproteinase (MMP)-1, MMP-9, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), intercellular adhesion molecule (ICAM)-1, E-selectin, and P-selectin levels were significantly higher in IVBrIOI + than in IVBrIOI - and IVA. Vascular endothelial growth factor (VEGF) was significantly lower in IVBrIOI - compared to that in IVBrIOI + and IVA. In the IVBrIOI + group, there were significant correlations between CCL2, CXCL1, IL-6, IL-8, IL-10, G-CSF, GM-CSF, ICAM-1, and E-selectin, which also exhibited significant correlations in the IVBrIOI - group. CONCLUSION: The number of inflammatory cytokines increases during IOI, which is associated with type IV hypersensitivity and vascular inflammation. Some cytokines exhibit correlations even in non-inflamed eyes, indicating a subclinical response to IVBr.

Risk Factors and Treatment Strategy for Retinal Vascular Occlusive Diseases.

Retinal occlusive diseases are common diseases that can lead to visual impairment. Retinal artery occlusion and retinal vein occlusion are included in the clinical entity, but they have quite different pathophysiologies. Retinal artery occlusion is an emergent eye disorder. Retinal artery occlusion is mainly caused by thromboembolism, which frequently occurs in conjunction with life-threatening stroke and cardiovascular diseases. Therefore, prompt examinations and interventions for systemic vascular diseases are often necessary for these patients. Retinal vein occlusion is characterized by retinal hemorrhage and ischemia, which may impair visual function via several complications such as macular edema, macular ischemia, vitreous hemorrhage, and neovascular glaucoma. Even though anti-vascular endothelial growth factor therapy is the current established first-line of treatment for retinal vein occlusion, several clinical studies have been performed to identify better treatment protocols and new therapeutic options. In this review, we summarize the current findings and advances in knowledge regarding retinal occlusive diseases, particularly focusing on recent studies, in order to provide an update for a better understanding of its pathogenesis.

Oxidative Stress-Induced Cellular Senescence in Aging Retina and Age-Related Macular Degeneration.

Aging leads to a gradual decline of function in multiple organs. Cataract, glaucoma, diabetic retinopathy, and age-related macular degeneration (AMD) are age-related ocular diseases. Because their pathogenesis is unclear, it is challenging to combat age-related diseases. Cellular senescence is a cellular response characterized by cell cycle arrest. Cellular senescence is an important contributor to aging and age-related diseases through the alteration of cellular function and the secretion of senescence-associated secretory phenotypes. As a driver of stress-induced premature senescence, oxidative stress triggers cellular senescence and age-related diseases by inducing senescence markers via reactive oxygen species and mitochondrial dysfunction. In this review, we focused on the mechanism of oxidative stress-induced senescence in retinal cells and its role in the pathogenesis of AMD.

Relationship between the vessel density around the optic nerve head and visual field deterioration in eyes with retinitis pigmentosa.

PURPOSE: To analyze the vessel density around the optic nerve head (ONH) by optical coherence tomography angiography (OCTA) in patients with retinitis pigmentosa (RP), and to evaluate its correlation with visual functions. METHODS: Thirty-eight eyes with RP with visual field constriction within the central 10° were enrolled. The mean (± SD) age of the patients was 43.7 ± 15.1 years. In addition to visual acuity (VA) measurements and visual field tests (Humphrey Field Analyzer 10-2 test), we also measured the vessel density at the macula by OCTA (superficial and deep vessel density: sVD(m) and dVD(m)) and in multiple layers around the ONH (vessel density in the radial peripapillary capillary [RPC] layer and in the nerve head [NH] layer: VDrpc and VDnh). The vessel density was calculated by binarizing the OCTA images. The associations between the logMAR VA and mean deviation (MD) values and the variables of central retinal thickness (CRT), sVD(m), dVD(m), VDrpc, VDnh, and also the size of the foveal avascular zone were investigated. RESULTS: The mean logMAR VA was 0.16 ± 0.34 and the MD value was - 17.2 ± 10.3 dB; the MD value was significantly related to the logMAR VA (p = 0.0028). Multivariate analysis with AICc model selection suggested only dVD(m) was associated with logMAR VA. On the other hand, the optimal model for the MD value included the CRT, dVD(m), and VDnh. CONCLUSION: The vessel density in the deep layer around the ONH was significantly associated with the visual field deterioration in patients with RP.

Clinical features of cases with retinal pigment epithelium aperture.

PURPOSE: To report the clinical findings of the patients with retinal pigment epithelium (RPE) aperture secondary to age-related macular degeneration (AMD). METHODS: A retrospective data analysis was conducted of patients at the University of Tokyo Hospital eye clinic, from the year September 1st, 2012 to 2019. Review of the medical records of patients with RPE aperture accompanied by AMD was performed. We investigated age, best-corrected visual acuity (BCVA), images of spectral domain optical coherence tomography, short-wave fundus autofluorescence (FAF), fluorescein angiography (FA), indocyanine green angiography, and retinal sensitivity measured with microperimetry. The change in visual acuity or the area of the aperture during the follow-up period was analyzed. RESULTS: Five eyes of 5 patients (4 men, one woman) were included in the analysis. The mean age at presentation was 78.6 ± 9.1 years. The average length of follow-up was 23.6 ± 17.9 months. The RPE apertures appeared as round, either at the apex or at the base of PED, with no evidence of accompanying CNV but subretinal detachment (SRD) above the aperture. On FAF, the apertures appeared as sharply demarcated round areas of hypoautofluorescence. The FA revealed sharply demarcated round areas of window defects in the early and mid-phase with leakage in the late phase corresponding to SRD. The area of apertures enlarged during the follow-up period. Mean BCVA got worse from 0.20 logMAR at the initial presentation to 0.39 logMAR at the last visit. The retinal sensitivity was reduced but partly preserved above the area of aperture. CONCLUSIONS AND IMPORTANCE: RPE aperture was found in some patients with drusenoid PED secondary to AMD. It enlarged during follow-up. Visual acuity was declined. Retinal sensitivity was decreased but partly preserved.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY STUDY OF CHOROIDAL NEOVASCULARIZATION ASSOCIATED WITH EARLY-ONSET DRUSEN.

PURPOSE: To report three middle-aged cases with choroidal neovascularization (CNV) associated with early-onset drusen documented with optical coherence tomography angiography (OCTA). METHODS: Three patients with bilateral early-onset drusen were referred to our hospital. Fundus examination, fluorescein angiography, indocyanine green angiography, OCTA, and other multimodal imaging were performed. RESULTS: Case 1 involved a 47-year-old woman who presented with sudden unilateral anorthopia. She had no previous systemic pathologies. Funduscopic examination and fluorescein angiography revealed bilateral large colloid drusen accompanied by unilateral mild subretinal hemorrhage. Indocyanine green angiography revealed CNV, although it was unclear in fluorescein angiography. Optical coherence tomography angiography also showed interconnecting CNV beneath the retinal pigment epithelium. Case 2 involved a 40-year-old woman with membranoproliferative glomerulonephritis Type 3 who presented with unilateral anorthopia. On fluorescein angiography, cuticular drusen secondary to membranoproliferative glomerulonephritis were seen in both eyes. An interconnecting vascular network was revealed with OCTA and indocyanine green angiography indicating Type 1 CNV in the affected eye. Case 3 involved a 47-year-old man without any medical or family history. Predominant large colloid drusen associated with cuticular drusen were seen in both eyes. Unilateral mild serosanguinous changes were accompanied in the macula, where Type 1 CNV was detected with OCTA. CONCLUSION: All our cases with early-onset drusen showed Type 1 CNV that was detected by indocyanine green angiography or OCTA. Optical coherence tomography angiography has a potential to help noninvasively diagnose CNV in the cases of EOD.

Protective Effects and Molecular Signaling of n-3 Fatty Acids on Oxidative Stress and Inflammation in Retinal Diseases.

Oxidative stress and inflammation play crucial roles in the development and progression of retinal diseases. Retinal damage by various etiologies can result in retinopathy of prematurity (ROP), diabetic retinopathy (DR), and age-related macular degeneration (AMD). n-3 fatty acids are essential fatty acids and are necessary for homeostasis. They are important retinal membrane components and are involved in energy storage. n-3 fatty acids also have antioxidant and anti-inflammatory properties, and their suppressive effects against ROP, DR, and AMD have been previously evaluated. α-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and their metabolites have been shown to alleviate retinal oxidative stress and inflammation involving various biological signaling pathways. In this review, we summarize the current understanding of the n-3 fatty acids effects on the mechanisms of these retinal diseases and how they exert their therapeutic effects, focusing on ALA, EPA, DHA, and their metabolites. This knowledge may provide new remedial strategies for n-3 fatty acids in the prevention and treatment of retinal diseases associated with oxidative stress and inflammation.

Small Symptomatic Unilateral Choroidal Osteoma Diagnosed with Enhanced-Depth Imaging Optical Coherence Tomography and Thin-Slice Computed Tomography: 2 Clinical Cases.

BACKGROUND: Choroidal osteoma is a rare, benign, ossifying intraocular tumor of unknown etiology. While patients with choroidal osteoma usually show distinct large yellowish subretinal lesions, some could have small lesions, making the differential diagnosis difficult. We experienced 2 cases of small symptomatic unilateral osteoma approximately 1.0-mm disc diameter in size. METHODS: Retrospective medical charts of 2 patients with small symptomatic unilateral osteoma were reviewed. Fundus examination, spectral domain enhanced-depth optical coherence tomography (EDI-OCT), fluorescein angiography, indocyanine green angiography, B-scan ultrasonography (USG), and X-ray computed tomography (CT) were performed. RESULTS: Case 1: a case of a 41-year-old male. Fundus examination revealed a yellowish-white lesion of 1.0-mm disc diameter in size. EDI-OCT of the lesion shows sub-RPE elevation. B-scan USG was not definite for diagnosis. Thin-slice (2 mm) CT scan revealed a choroidal osteoma. Case 2: a case of a 70-year-old male. Fundus examination revealed a yellowish-white lesion of 0.9-mm disc diameter. EDI-OCT showed sub-RPE elevation without serous retinal detachment and horizontal lamellar-like structure within the lesion. B-scan USG suggested acoustic shadowing, but it was unclear. The thin-slice CT scan confirmed bony tissue at the lesion. CONCLUSIONS: We report 2 cases of small choroidal osteoma. Diagnosis of small yellowish subretinal lesions is sometimes difficult. Characteristic findings with EDI-OCT may sometimes suggest this disease, and thin-slice CT could help to diagnose choroidal osteoma.

Lipid Signaling in Ocular Neovascularization.

Vasculogenesis and angiogenesis play a crucial role in embryonic development. Pathological neovascularization in ocular tissues can lead to vision-threatening vascular diseases, including proliferative diabetic retinopathy, retinal vein occlusion, retinopathy of prematurity, choroidal neovascularization, and corneal neovascularization. Neovascularization involves various cellular processes and signaling pathways and is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor (HIF). Modulating these circuits may represent a promising strategy to treat ocular neovascular diseases. Lipid mediators derived from membrane lipids are abundantly present in most tissues and exert a wide range of biological functions by regulating various signaling pathways. In particular, glycerophospholipids, sphingolipids, and polyunsaturated fatty acids exert potent pro-angiogenic or anti-angiogenic effects, according to the findings of numerous preclinical and clinical studies. In this review, we summarize the current knowledge regarding the regulation of ocular neovascularization by lipid mediators and their metabolites. A better understanding of the effects of lipid signaling in neovascularization may provide novel therapeutic strategies to treat ocular neovascular diseases and other human disorders.

Association between pachychoroid and long-term treatment outcomes of photodynamic therapy with intravitreal ranibizumab for polypoidal choroidal vasculopathy.

We investigated long-term treatment responses in patients with treatment-naïve polypoidal choroidal vasculopathy (PCV) undergoing photodynamic therapy (PDT) with intravitreal ranibizumab (IVR). The medical charts of 14 patients with treatment-naïve PCV who underwent PDT with IVR were retrospectively reviewed. Patients were followed up and treated with additional IVR for ≥3 years. Best-corrected visual acuity (BCVA), central foveal thickness (CFT), greatest linear dimension (GLD) on angiography, polyp regression and central choroidal thickness (CCT) were assessed. Associations between these functional or anatomic outcomes with age, baseline CCT, baseline GLD or choroidal vascular hyperpermeability (CVH) were investigated using univariate and multivariate analysis. Mean logMAR BCVA improved significantly at 3 years (0.34 ± 0.24 to 0.12 ± 0.29, p = 0.003). Greater BCVA improvement and longer time to first recurrence was significantly associated with CVH. Fewer number of IVR retreatment within 3 years was associated with thicker baseline CCT. Mean CCT significantly decreased at 3 years (217 ± 33 µm to 197 ± 48 µm, p = 0.003). Greater decrease of CCT was significantly associated both with greater number of IVR retreatment within 3 years and absence of CVH. These results showed that pachychoroid characteristics at baseline was associated long-term functional and anatomic outcomes in patients with treatment-naïve PCV who had undergone combination PDT and IVR.

The role of sphingosine 1-phosphate receptors on retinal pigment epithelial cells barrier function and angiogenic effects.

Sphingosine-1-phosphate (S1P) is a lysophospholipid mediator, promoting angiogenesis and inflammation via interactions with its receptors (S1P1-5), but the receptors and signaling pathways responsible for the progression of choroidal neovascularization (CNV) remain unknown. We investigated the roles of S1P/S1P receptors in RPE cells. ARPE-19 cells were treated with S1P dissolved in carrier proteins of albumin or apolipoprotein M (ApoM). The mRNA expression levels of interleukin-8 (IL-8), C-C motif chemokine ligand 2 (CCL2), and vascular endothelial growth factor (VEGF) were evaluated using quantitative real-time polymerase chain reaction. The protein level of hypoxia-inducible factor (HIF)-1α was assessed via enzyme-linked immunosorbent assay. HIF transcriptional activity was evaluated with a dual-reporter luciferase assay. Cellular barrier integrity was evaluated using transepithelial electrical resistance and the FITC-dextran permeability assay. The suppressive effect of an S1P antagonist on CNV progression was investigated with a laser-induced CNV model in mice. The increase in expression of IL-8, CCL2, and VEGF due to albumin-bound S1P was significantly mitigated by an S1P2 antagonist. The expression of HIF-1α significantly decreased with inhibition of S1P2 and S1P3. In addition, albumin-bound S1P disrupted the barrier integrity of retinal pigment epithelial cells via S1P2, whereas integrity was strengthened by ApoM-bound S1P. CNV lesions were significantly reduced in the mouse model with intravitreal injection of S1P2 antagonist. This study demonstrated that S1P significantly promotes angiogenesis, inflammation, and barrier integrity, which was attenuated by inhibition of S1P2 or S1P3, suggesting that regulation of S1P2 and S1P3 is a novel therapeutic target for CNV.

Light Stress-Induced Increase of Sphingosine 1-Phosphate in Photoreceptors and Its Relevance to Retinal Degeneration.

Sphingosine 1-phosphate (S1P) is a potent lipid mediator that modulates inflammation and angiogenesis. In this study, we investigated the possible involvement of S1P in the pathology of light-induced retinal degeneration in vivo and in vitro. The intracellular S1P and sphingosine kinase (SphK) activity in a photoreceptor cell line (661W cells) was significantly increased by exposure to light. The enhancement of SphK1 expression was dependent on illumination, and all-trans-retinal significantly promoted SphK1 expression. S1P treatment reduced protein kinase B (Akt) phosphorylation and increased the protein expression of cleaved caspase-3, and induced photoreceptor cell apoptosis. In vivo, light exposure enhanced the expression of SphK1 in the outer segments of photoreceptors. Intravitreal injection of a SphK inhibitor significantly suppressed the thinning of the outer nuclear layer and ameliorated the attenuation of the amplitudes of a-waves and b-waves of electroretinograms during light-induced retinal degeneration. These findings imply that light exposure induces the synthesis of S1P in photoreceptors by upregulating SphK1, which is facilitated by all-trans-retinal, causing retinal degeneration. Inhibition of this enhancement may be a therapeutic target of outer retinal degeneration, including age-related macular degeneration.

Apolipoprotein M Inhibits Angiogenic and Inflammatory Response by Sphingosine 1-Phosphate on Retinal Pigment Epithelium Cells.

Sphingosine 1-phosphate (S1P) is a potent lipid mediator that modulates inflammatory responses and proangiogenic factors. It has been suggested that S1P upregulates choroidal neovascularization (CNV) and may be deeply involved in the pathogenesis of exudative age-related macular degeneration (AMD). Recent studies have suggested that apolipoprotein M (ApoM), a carrier protein for S1P, modulates the biological properties of S1P in the pathogenesis of atherosclerosis. However, the role of ApoM/S1P in AMD has not been explored. We investigated the effect of S1P on proangiogenic factors in human retinal pigment epithelium (RPE) cell lines in vitro. S1P promoted the expression of vascular endothelial growth factor in RPE cells. Hypoxia inducible factor-1α expression was also upregulated. These S1P-induced enhancements in growth factors and chemotactic cytokines in RPE cells were significantly inhibited by ApoM treatment. Additionally, in vivo experiments using a laser-induced CNV murine model demonstrated that intravitreal ApoM injection significantly reduced the progression of CNV formation. Although the detailed mechanisms remain to be elucidated, the present results provide a novel potential therapeutic target for AMD, and demonstrate a suppressive role for ApoM and S1P in the pathology of CNV progression.

Effect of vitreomacular adhesion on antivascular endothelial growth factor therapy for macular edema secondary to branch retinal vein occlusion.

PURPOSE: To investigate the association between vitreomacular adhesion (VMA) and the visual and anatomic outcomes of antivascular endothelial growth factor therapy for macular edema due to branch retinal vein occlusion (BRVO). METHODS: This study included 107 eyes of 107 patients with BRVO who underwent intravitreal injection of 1.25 mg bevacizumab. The presence of VMA was determined with spectral-domain optical coherence tomography (SD-OCT). All eyes underwent best-corrected visual acuity (BCVA) and central retinal thickness (CRT) measurements using SD-OCT immediately before the injection and at 3, 6, 9, and 12 months after the injection. The main outcome measures were changes in BCVA and CRT from baseline. RESULTS: The VMA(+) and VMA(-) groups consisted of 47 and 60 eyes, respectively, and patients' age differed significantly between the groups (P < 0.001). In both groups, BCVA and CRT improved after the injection. The VMA(+) group showed better improvement in BCVA than did the VMA(-) group (P = 0.0150), and the presence of VMA was associated with a greater decrease in CRT after adjusting for age (P = 0.0019). CONCLUSIONS: Presence of VMA may be associated with superior visual and anatomic outcome for intravitreal bevacizumab in the treatment of macular edema due to BRVO.