The NLRP3 Inflammasome and its Role in Age-Related Macular Degeneration

Association of Intermediate-Stage Age-Related Macular Degeneration with Plasma Inflammatory Biomarkers in Persons with AIDS

Purpose

To evaluate associations of plasma levels of inflammatory biomarkers with age-related macular degeneration (AMD) and cataract in persons with AIDS.

Design

Nested case-control study (analysis 1) and nested cohort study (analysis 2).

Participants

Analysis 1: persons with AIDS and incident intermediate-stage AMD (n = 26) and controls without AMD matched for age, race/ethnicity, and gender (n = 49) from The Longitudinal Study of Ocular Complications of AIDS. Analysis 2: 475 persons from LSOCA with baseline plasma biomarker levels followed prospectively for cataract.

Methods

In both analyses, cryopreserved plasma specimens obtained at baseline were assayed for monocyte chemoattractant protein (MCP)-1 (CC motif chemokine ligand [CCL] 2), macrophage inflammatory protein (MIP)-1β (CCL4), soluble tumor necrosis factor receptor (sTNFR) 2, interleukin (IL)-18, and fractalkine (CX3 motif chemokine ligand 1 [CX3CL1]).

Main Outcome Measures

Analysis 1: mean difference (cases - controls) in plasma biomarker levels. Analysis 2: incident cataract.

Results

After adjusting for plasma human immunodeficiency virus RNA level, CD4+ T-cell count, and smoking, elevated baseline plasma levels of sTNFR2 and IL-18 (mean differences [cases - controls] 0.11 log10[pg/mL]; 95% confidence interval [CI], 0.01-0.20; P = 0.024 and 0.13 log10[pg/mL]; 95% CI, 0.01-0.24; P = 0.037, respectively) each were associated with incident AMD. In a competing risk (with mortality) analysis, elevated baseline standardized log10 plasma levels of MCP-1, sTNFR2, IL-18, and fractalkine each were associated with a decreased cataract risk.

Conclusions

When combined with previous data suggesting that AMD is associated with elevated plasma levels of C-reactive protein, soluble CD14, and possibly IL-6, the association of elevated plasma levels of sTNFR2 and IL-18 with incident AMD, but not with incident cataract, suggests that innate immune system activation, and possibly NLRP3 inflammasome activation, may play a role in the pathogenesis of AMD in this population.

Financial Disclosures

The authors have no proprietary or commercial interest in any materials discussed in this article.

Up-regulation of scleral C5b-9 and its regulation of the NLRP3 inflammasome in a form-deprivation myopia mouse model

BACKGROUND

Myopia has become a major public health problem worldwide. Although the involvement of the complement system in myopia progression has been reported, the underlying mechanism has not been well established. In this study, we induced a form deprivation (FD) myopia mouse model to investigate the mechanisms.

METHODS

Both C6-knockout (KO) and wild-type (WT) mice were divided into FD and normal control (NC) groups. The FD myopia was induced in the right eyes of 24-day-old mice using a translucent balloon for 4 weeks. The left eye remained untreated and served as self-control. NC group received no treatment. Refractive error and axial length were measured at baseline, 2 weeks, and 4 weeks later under normal visual, 4 weeks after FD. Scleral transcriptome sequencing analysis was performed in in FD mice. The scleral levels of C5b-9, NLRP3, Caspase-1, IL-1β, MMP-2, and collagen I were evaluated using immunohistochemistry.

RESULTS

RNA-seq analysis showed 1058 differentially expressed genes. The GO analysis showed these genes were mainly related to the extracellular matrix, and immune response. The KEGG enrichment analysis showed that complement cascades were upregulated. Under normal visual conditions, both genotypes of mice exhibited comparable refractive error and axial length. However, after four weeks of FD, C6-KO mice showed a significantly less myopic shift (-2.28 ± 0.28 D versus -5.40 ± 1.33 D, P = 0.003), and axial shift (0.043 ± 0.032 mm versus 0.083 ± 0.026 mm, P = 0.042) in comparison to WT mice. Furthermore, the levels of C5b-9, NLRP3, caspase-1, IL-1β, and MMP-2 were found to be elevated in the deprived eyes of WT mice in comparison to their fellow eyes, whereas the extent of this increase was significantly lower in C6-KO mice.

CONCLUSIONS

Complement cascades are activated in FD myopia model. Upregulation of C5b-9 might participate in scleral remodeling during myopia progression via regulation of NLRP3 inflammasome activation.

The central role of the NLRP3 inflammasome pathway in the pathogenesis of age-related diseases in the eye and the brain

With increasing age, structural changes occur in the eye and brain. Neuronal death, inflammation, vascular disruption, and microglial activation are among many of the pathological changes that can occur during ageing. Furthermore, ageing individuals are at increased risk of developing neurodegenerative diseases in these organs, including Alzheimer's disease (AD), Parkinson's disease (PD), glaucoma and age-related macular degeneration (AMD). Although these diseases pose a significant global public health burden, current treatment options focus on slowing disease progression and symptomatic control rather than targeting underlying causes. Interestingly, recent investigations have proposed an analogous aetiology between age-related diseases in the eye and brain, where a process of chronic low-grade inflammation is implicated. Studies have suggested that patients with AD or PD are also associated with an increased risk of AMD, glaucoma, and cataracts. Moreover, pathognomonic amyloid-β and α-synuclein aggregates, which accumulate in AD and PD, respectively, can be found in ocular parenchyma. In terms of a common molecular pathway that underpins these diseases, the nucleotide-binding domain, leucine-rich-containing family, and pyrin domain-containing-3 (NLRP3) inflammasome is thought to play a vital role in the manifestation of all these diseases. This review summarises the current evidence regarding cellular and molecular changes in the brain and eye with age, similarities between ocular and cerebral age-related diseases, and the role of the NLRP3 inflammasome as a critical mediator of disease propagation in the eye and the brain during ageing.

The mechanisms of NLRP3 inflammasome/pyroptosis activation and their role in diabetic retinopathy

In the working-age population worldwide, diabetic retinopathy (DR), a prevalent complication of diabetes, is the main cause of vision impairment. Chronic low-grade inflammation plays an essential role in DR development. Recently, concerning the pathogenesis of DR, the Nod-Like Receptor Family Pyrin Domain Containing 3 (NLRP3) inflammasome in retinal cells has been determined as a causal factor. In the diabetic eye, the NLRP3 inflammasome is activated by several pathways (such as ROS and ATP). The activation of NPRP3 leads to the secretion of inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18), and leads to pyroptosis, a rapid inflammatory form of lytic programmed cell death (PCD). Cells that undergo pyroptosis swell and rapture, releasing more inflammatory factors and accelerating DR progression. This review focuses on the mechanisms that activate NLRP3 inflammasome and pyroptosis leading to DR. The present research highlighted some inhibitors of NLRP3/pyroptosis pathways and novel therapeutic measures concerning DR treatment.

Extracellular Vesicles as Biomarkers and Therapeutics for Inflammatory Eye Diseases

Extracellular vesicles (EVs) are a group of cell-derived membrane vesicles of varying sizes that can be secreted by most cells. Depending on the type of cell they are derived from, EVs may contain a variety of cargo including proteins, lipids, miRNA, and DNA. Functionally, EVs play important roles in physiological and pathological processes through intercellular communication. While there has already been significant literature on the involvement of EVs in neurological and cardiovascular disease as well as cancer, recent evidence suggests that EVs may also play a role in mediating inflammatory eye diseases. This paper summarizes current advancements in ocular EV research as well as new ways by which EVs may be utilized as novel biomarkers of or therapeutics for inflammatory eye diseases.

Construction of a ferroptosis-associated circRNA-miRNA-mRNA network in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of severe vision impairment in the aging population. However, the underlying molecular mechanism remains unclear. Ferroptosis is a novel non-apoptotic programmed cell death pathway, that contributes to AMD. In addition, non-coding RNA-led epigenetic profile was identified in the regulation of AMD progression. Considering that non-coding RNAs are vital regulators of ferroptosis-related genes in various pathological events, we explored and constructed a ferroptosis-associated circRNA-miRNA-mRNA network in AMD. Differential expression of fourteen ferroptosis-associated genes were identified based on our microarray analysis and the FerrDb tool at the threshold of P < 0.05 and log₂|fold change| ≥ 1, which were subsequently validated by the public datasets. We further screened eight miRNAs via public datasets and the miRNet database. Based on these eight miRNAs, 23 circRNAs were mined using the Starbase tool. Taking all these together, we obtained a ferroptosis-related network with 414 pairs of circRNA-miRNA-mRNA, which are potential targets in future AMD treatments.

Spotlight on pyroptosis: role in pathogenesis and therapeutic potential of ocular diseases

Pyroptosis is a programmed cell death characterized by swift plasma membrane disruption and subsequent release of cellular contents and pro-inflammatory mediators (cytokines), including IL‐1β and IL‐18. It differs from other types of programmed cell death such as apoptosis, autophagy, necroptosis, ferroptosis, and NETosis in terms of its morphology and mechanism. As a recently discovered form of cell death, pyroptosis has been demonstrated to be involved in the progression of multiple diseases. Recent studies have also suggested that pyroptosis is linked to various ocular diseases. In this review, we systematically summarized and discussed recent scientific discoveries of the involvement of pyroptosis in common ocular diseases, including diabetic retinopathy, age-related macular degeneration, AIDS-related human cytomegalovirus retinitis, glaucoma, dry eye disease, keratitis, uveitis, and cataract. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in ocular diseases, hoping to provide a summary of overall intervention strategies and relevant multi-dimensional evaluations for various ocular diseases, as well as offer valuable ideas for further research and development from the perspective of pyroptosis.

Xentry-Gap19 inhibits Connexin43 hemichannel opening especially during hypoxic injury

Hypoxic injury results in cell death, tissue damage and activation of inflammatory pathways. This is mediated by pathological Connexin43 (Cx43) hemichannel (HC) opening resulting in osmotic and ionic imbalances as well as cytokine production perpetuating the inflammatory environment. Gap19 is an intracellularly acting Cx43 mimetic peptide that blocks HC opening and thus promotes cell survival. However, native Gap19, which must enter the cell in order to function, exhibits low cell permeability. In this study, Gap19 was conjugated to the cell-penetrating peptide, Xentry, to investigate if cellular uptake could be improved while maintaining peptide function. Cellular uptake of Xentry-Gap19 (XG19) was much greater than that of native Gap19 even under normal cell culture conditions. Peptide function was maintained post uptake as shown by reduced ethidium homodimer influx and ATP release due to Cx43 HC block. While XG19 blocked pathologic HC opening though, normal gap junction communication required for cell repair and survival mechanisms was not affected as shown in a dye scrape-load assay. Under hypoxic conditions, increased expression of Syndecan-4, a plasma membrane proteoglycan targeted by Xentry, enabled even greater XG19 uptake leading to higher inhibition of ATP release and greater cell survival. This suggests that XG19, which is targeted specifically to hypoxic cells, can efficiently and safely block Cx43 HC and could therefore be a novel treatment for hypoxic and inflammatory diseases.

Cartilaginous endplate avulsion is associated with modic changes and endplate defects, and residual back and leg pain following lumbar discectomy

OBJECTIVE

While cartilaginous endplate (CEP) avulsion is a common finding in discectomy due to lumbar disc herniation, its roles in residual back and leg pain, associations with Modic changes (MCs) and endplate defects (EPD) remain unknown.

DESIGN

Patients with a single-level lumbar disc herniation who underwent endoscopic discectomy were studied. On MR images, the adjacent endplates of the herniated disc were assessed for MCs and EPD. The presence of CEP avulsion was examined under endoscopic and visualized inspection. Back and leg pain were evaluated by a numeric rating scale (NRS) and the Oswestry Disability Index. Associations of CEP avulsion with adjacent MCs, EPD, and residual back and leg pain were examined. In addition, histological features of avulsed CEP were determined using gross staining and immunohistochemical methods.

RESULTS

A total of 386 patients were included. CEP avulsion was found in 166 (43%) patients, and adjacent MCs and EPD were observed in 117 (30.3%) and 139 (36%) patients. The presence of CEP avulsion was associated with greater age, adjacent MCs (OR = 2.60, 95%CI [1.61-4.19]) and EPD (OR = 1.63, 95%CI [1.03-2.57]). Among the 187 patients with ≥2 years follow-up, CEP avulsion was associated with residual back pain (OR = 2.49, 95%CI [1.29-4.82]) and leg pain (OR = 2.25, 95%CI [1.04-4.84]). Histologically, the avulsed CEP was characterized by multiple defects, apparent inflammation, and nucleus invasion, as well as the upregulation of IL-1β, caspase-1, and NLRP3 inflammasome.

CONCLUSION

CEP avulsion was associated with MCs, EPD, and residual back and leg pain after discectomy, which may be attributed to NLRP3 inflammasome related inflammations.

Nutraceutical Strategies for Suppressing NLRP3 Inflammasome Activation: Pertinence to the Management of COVID-19 and Beyond

Inflammasomes are intracellular protein complexes that form in response to a variety of stress signals and that serve to catalyze the proteolytic conversion of pro-interleukin-1β and pro-interleukin-18 to active interleukin-1β and interleukin-18, central mediators of the inflammatory response; inflammasomes can also promote a type of cell death known as pyroptosis. The NLRP3 inflammasome has received the most study and plays an important pathogenic role in a vast range of pathologies associated with inflammation-including atherosclerosis, myocardial infarction, the complications of diabetes, neurological and autoimmune disorders, dry macular degeneration, gout, and the cytokine storm phase of COVID-19. A consideration of the molecular biology underlying inflammasome priming and activation enables the prediction that a range of nutraceuticals may have clinical potential for suppressing inflammasome activity-antioxidants including phycocyanobilin, phase 2 inducers, melatonin, and N-acetylcysteine, the AMPK activator berberine, glucosamine, zinc, and various nutraceuticals that support generation of hydrogen sulfide. Complex nutraceuticals or functional foods featuring a number of these agents may find utility in the prevention and control of a wide range of medical disorders.

Inflammasome Proteins as Inflammatory Biomarkers of Age-Related Macular Degeneration

Purpose

Age-related macular degeneration (AMD) can result in severe vision loss and blurriness in the older population. The early and intermediate stages of AMD typically start without noticeable symptoms and can only be detected with a comprehensive eye exam. Because of the quiet onset of the disease, it is necessary to identify potential biomarkers to aid in the diagnosis, staging, and association with disease onset. Inflammasome signaling proteins are prominent biomarkers in the central nervous system, and the inflammasome has been shown to play a role in the innate inflammatory response in aging and AMD.

Methods

Serum from healthy controls and AMD patients were analyzed for the protein levels of Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), interleukin (IL)-18 and C-reactive protein (CRP) to determine cutoff points, positive and negative predictive values, and receiver operator characteristic curves, as well as univariate and multivariate linear and logistic regression models.

Results

ASC, IL-18, and CRP were elevated in the serum of AMD patients when compared to healthy controls. The area under the curve (AUC) for ASC was 0.98 with a cutoff point of 365.6 pg/mL, whereas IL-18 had an AUC of 0.73 and a cutoff point of 242.4 pg/mL, and the AUC for CRP was 0.67 with a cutoff point of 8,684,152 pg/mL. Levels of IL-18 had a statistically significant linear correlation with that of ASC with an adjusted R² of 0.1906, indicating that 19% of IL-18 could be explained by ASC protein levels in serum. Moreover, a logistic regression model for the diagnosis of AMD consists of ASC and having a diagnosis of hypertension, indicating that these two factors (elevated levels of ASC and a diagnosis of hypertension [HTN]) are associated with the diagnosis of AMD.

Conclusions

ASC, IL-18, and CRP are elevated in patients with AMD, and the protein levels of IL-18 are partially the result of ASC protein expression. Moreover, elevated protein levels of ASC in serum and a diagnosis of HTN increase the odds of patients having a diagnosis of AMD.

Translational Relevance

Biomarkers of AMD may be used to monitor disease risk, response to treatment and disease progression.

Oxidative stress as a therapeutic target for the prevention and treatment of early age-related macular degeneration

Age-related macular degeneration, the leading cause of irreversible visual loss among older adults in developed countries, is a chronic, multifactorial, and progressive disease with the development of painless, central vision loss. Retinal pigment epithelial cell dysfunction is a core change in age-related macular degeneration that results from aging and the accumulated effects of genetic and environmental factors that, in part, is both caused by and leads to oxidative stress. In this review, we describe the role of oxidative stress, the cytoprotective oxidative stress pathways, and the impact of oxidative stress on critical cellular processes involved in age-related macular degeneration pathobiology. We also offer targeted therapy that may define how antioxidant therapy can either prevent or improve specific stages of age-related macular degeneration.

TRIM31 inhibits NLRP3 inflammasome and pyroptosis of retinal pigment epithelial cells through ubiquitination of NLRP3

NOD-like receptor protein 3 (NLRP3) is associated with age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells serve as the immune defense of macula, and their dysfunction causes clinically relevant changes in AMD. In the present study, oxidized low-density lipoprotein (ox-LDL) activated the NLRP3 inflammasome in human RPE cell line ARPE-19. Our data showed that the expression of NLRP3, interleukin-1β (IL-1β), and caspase-1 and the release of IL-1β in ARPE-19 cells were substantially increased by ox-LDL, whereas the addition of NLRP3 inhibitor INF39 dose-dependently reversed the effect of ox-LDL. Overexpression of tripartite motif-containing protein 31 (TRIM31) also suppressed the effect of ox-LDL in ARPE-19 cells. TRIM31 knockdown had similar effects with ox-LDL but INF39 could block the effect of TRIM31 knockdown. Moreover, TRIM31 could interact with NLRP3 in ARPE-19 cells. Overexpression of TRIM31 increased NLRP3 ubiquitination. In conclusion, the results propose that TRIM31 could enhance NLRP3 ubiquitination, therefore inhibiting NLRP3 inflammasome and pyroptosis in human RPE cells.

A C-terminal peptide from type I interferon protects the retina in a mouse model of autoimmune uveitis

Experimental autoimmune uveitis (EAU) in rodents recapitulates many features of the disease in humans and has served as a useful tool for the development of therapeutics. A peptide from C-terminus of interferon α1, conjugated to palmitoyl-lysine for cell penetration, denoted as IFNα-C, was tested for its anti-inflammatory properties in ARPE-19 cells, followed by testing in a mouse model of EAU. Treatment with IFNα-C and evaluation by RT-qPCR showed the induction of anti-inflammatory cytokines and chemokine. Inflammatory markers induced by treatment with TNFα were suppressed when IFNα-C was simultaneously present. TNF-α mediated induction of NF-κB and signaling by IL-17A were attenuated by IFNα-C. Differentiated ARPE-19 cells were treated with TNFα in the presence or absence IFNα-C and analyzed by immmunhistochemistry. IFNα-C protected against the disruption integrity of tight junction proteins. Similarly, loss of transepithelial resistance caused by TNFα was prevented by IFNα-C. B10.RIII mice were immunized with a peptide from interphotoreceptor binding protein (IRBP) and treated by gavage with IFNα-C. Development of uveitis was monitored by histology, fundoscopy, SD-OCT, and ERG. Treatment with IFNα-C prevented uveitis in mice immunized with the IRBP peptide. Splenocytes isolated from mice with ongoing EAU exhibited antigen-specific T cell proliferation that was inhibited in the presence of IFNα-C. IFNα-C peptide exhibits anti-inflammatory properties and protects mice against damage to retinal structure and function suggesting that it has therapeutic potential for the treatment of autoimmune uveitis.

Connexin43 hemichannel block protects against retinal pigment epithelial cell barrier breakdown

AIMS

The retinal pigment epithelium (RPE) is an important component of the outer blood-retinal barrier (BRB) that separates the choroid from the rest of the retina. Loss of RPE-mediated BRB integrity is a key feature of diabetic macular oedema (DME), a chronic pathology resulting from diabetic retinopathy (DR). Recent studies have shown that connexin43 hemichannel opening mediates key inflammatory pathways in DR, though its effect on the barrier properties of RPE cells remains unknown. Therefore, RPE breakdown was induced by exposing a monolayer of ARPE-19 cells to high glucose (HG) and 10 ng/mL each of the pro-inflammatory cytokines IL-1β and TNF-α. The role of connexin43 hemichannels was assessed using a connexin43 hemichannel blocker, Peptide5.

METHODS

Transepithelial resistance (TEER) and FITC-dextran dye leak across the ARPE-19 monolayer were used to measure RPE layer permeability. Immunohistochemistry was used to assess changes in connexin43, collagen IV and ZO-1 expression. ATP and lactate dehydrogenase (LDH) release were measured using commercially available kits.

RESULTS

Connexin43 hemichannel block with Peptide5 prevented TEER reduction and FITC-dextran dye leak induced by a combination of HG and inflammatory cytokines. Peptide5 also blocked LDH and ATP release induced by the addition of HG and inflammatory cytokines. ZO-1 and connexin43 disruption and internalisation as well as upregulated secretion of collagen IV following HG and inflammatory cytokine exposure were also prevented. The addition of exogenous ATP into the culture medium was able to reverse Peptide5 protection against LDH release and change in connexin43 localisation, indicating that the initiating pathway in RPE disruption is connexin43 hemichannel-mediated ATP release.

CONCLUSION

These findings support the idea that connexin43 hemichannels may mediate RPE disruption (and its role within the BRB) that occurs in DME through an ATP release/inflammasome pathway activation dependent manner. Connexin43 hemichannels are therefore a potential therapeutic target for the treatment of DME.

Cytokines in Inflammatory Disease

This review aims to briefly discuss a short list of a broad variety of inflammatory cytokines. Numerous studies have implicated that inflammatory cytokines exert important effects with regard to various inflammatory diseases, yet the reports on their specific roles are not always consistent. They can be used as biomarkers to indicate or monitor disease or its progress, and also may serve as clinically applicable parameters for therapies. Yet, their precise role is not always clearly defined. Thus, in this review, we focus on the existing literature dealing with the biology of cytokines interleukin (IL)-6, IL-1, IL-33, tumor necrosis factor-alpha (TNF-α), IL-10, and IL-8. We will briefly focus on the correlations and role of these inflammatory mediators in the genesis of inflammatory impacts (e.g., shock, trauma, immune dysregulation, osteoporosis, and/or critical illness).

The role of complement membrane attack complex in dry and wet AMD - From hypothesis to clinical trials

Data from human dry and wet age-related macular degeneration (AMD) eyes support the hypothesis that constant 'tickover' of the alternative complement pathway results in chronic deposition of the complement membrane attack complex (MAC) on the choriocapillaris and the retinal pigment epithelium (RPE). Sub-lytic levels of MAC lead to cell signaling associated with tissue remodeling and the production of cytokines and inflammatory molecules. Lytic levels of MAC lead to cell death. CD59 is a naturally occurring inhibitor of the assembly of MAC. CD59 may thus be therapeutically efficacious against the pathophysiology of dry and wet AMD. The first gene therapy clinical trial for geographic atrophy - the advanced form of dry AMD has recently completed recruitment. This trial is studying the safety and tolerability of expressing CD59 from an adeno-associated virus (AAV) vector injected once into the vitreous. A second clinical trial assessing the efficacy of CD59 in wet AMD patients is also under way. Herein, the evidence for the role of MAC in the pathophysiology of dry as well as wet AMD and the scientific rationale underlying the use of AAV- delivered CD59 for the treatment of dry and wet AMD is discussed.

Neuroinflammation in Retinitis Pigmentosa, Diabetic Retinopathy, and Age-Related Macular Degeneration: A Minireview

The eye is an immuno-privileged organ. However, certain diseases such as uveitis are intrinsically linked to inflammation. In several retinal degenerative diseases, there is a unique damage at the onset of the disease, but evidence suggests that chronic and low-grade inflammatory processes play an important role in their progression. Studies have identified similar signaling pathways and changes in resident immune cells within the retina among these diseases. Herein, we will discuss some of these studies and propose how understanding this inflammatory response could aid in the development of therapies.

Photo-Oxidative Blue-Light Stimulation in Retinal Pigment Epithelium Cells Promotes Exosome Secretion and Increases the Activity of the NLRP3 Inflammasome

PURPOSE

Age-related macular degeneration (AMD) is a major cause of blindness in the elderly, and the activation of the NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome is involved in AMD pathogenesis. We investigated whether photooxidative blue-light stimulation in retinal pigment epithelium (RPE) cells promotes exosome secretion and modulates the activity of the NLRP3 inflammasome in vitro.

METHODS

Exosomes were isolated from ARPE-19 cultures stimulated or not with blue-light photostimulation (488 nm). Isolated exosomes were characterized by transmission electron microscope and Western blot analyses. The contents of the NLRP3 inflammasome (IL-1β, IL-18, and caspase-1 as markers of the inflammasome) in exosomes were analyzed by Western blotting. After culture, IL-1β, IL-18, and caspase-1 in RPE cells were analyzed by both immunofluorescence and Western blotting. RT-PCR and Western blotting were conducted to assess the contents of NLRP3 in RPE cells.

RESULTS

Exosomes exhibited a typical characteristic morphology (cup-shaped) and size (diameter between 50 and 150 nm) in both groups. The exosome markers CD9, CD63, and CD81 were strongly present. After blue-light photostimulation, ARPE-19 cells were noted to release exosomes with higher levels of IL-1β, IL-18, and caspase-1 than those in the control group. The levels of IL-1β, IL-18, and caspase-1 in ARPE-19 cells were significantly enhanced when treated with stressed RPE exosomes. Additionally, the NLRP3 mRNA and protein levels were found to be markedly higher in the treated group than in the control group.

CONCLUSIONS

Under photooxidative blue-light stimulation, RPE-derived exosomes may aggravate a potentially harmful oxidative response through the upregulation of the NLRP3 inflammasome.

A Glimpse into Uveitis in the Aging Eye: Pathophysiology, Clinical Presentation and Treatment Considerations

Uveitis describes a group of inflammatory conditions of the eye that have various underlying causes and clinical presentations. Susceptibilities to uveitis in the elderly may be attributed to age-related risk factors such as immunosenescence, increased immunological inflammatory mediators, and autoimmunity. Overall, anterior uveitis is more common than posterior and panuveitis in the general population and also in the elderly. Some causes of uveitis in the elderly are herpes simplex virus, ocular ischemic syndrome, sarcoidosis, and central nervous system lymphoma, and these will be discussed in detail herein. Eye care professionals need to consider the wide differential for uveitis, obtain the appropriate history, conduct a detailed clinical examination, and tailor management to the clinical presentation and underlying cause of disease. The challenges of polypharmacy and nonadherence in the elderly impact patient outcomes and must be taken into consideration when considering treatment.