T cell subsets and sIL-2R/IL-2 levels in patients with glaucoma

Core genes and immune dysregulation in primary open-angle glaucoma: A molecular insight

BackgroundPrimary open-angle glaucoma (POAG) is a chronic, progressive and irreversible eye disease. Currently, there is no effective way to prevent optic nerve damage.ObjectiveThis study explored POAG gene markers to identify high-risk groups at an early stage and to find new effective therapeutic targets.MethodsThe mRNA and clinical information of POAG patients and normal samples were downloaded from the Gene Expression Omnibus (GEO) database. Through Weighted correlation network analysis (WGCNA) and generalized linear models (GLM), random forests (RF), support vector machines (SVM), and extreme gradient boosting (xGB) models, key risk genes were identified and an early diagnosis model was established. Functional enrichment analysis and CIBERSORT algorithm were used to further reveal the changes in the POAG immune environment and find emerging therapeutic targets.ResultsHERPUD1, IQCK, MRPL40, SRSF7 and TMEM243 were identified as risk genes, and the prediction model and nomogram constructed based on them had good early prediction efficiency. At the mechanistic level, the heterogeneity of T cell subsets seems to be a key factor affecting the progression of POAG and has potential therapeutic value.Conclusions: HERPUD1, IQCK, MRPL40, SRSF7, and TMEM243 are of great significance for the early prediction and disease progression of POAG and have the potential value of becoming therapeutic targets.

Exploring the causal influence of 731 immune cells on 4 different glaucoma subtypes using a two-sample mendelian randomization method

In the pathological progression of glaucoma, damage to the ocular nerves and associated tissue alterations can induce a systemic immune response, leading to the activation of various immune cells such as T cells, B cells, and macrophages. This complex process has the potential to intensify the clinical manifestations of glaucoma. Utilising Mendelian randomisation methods to identify the types and quantities of activated immune cells in different glaucoma-related lesions could provide robust evidence for the development of novel immunomodulators and immunosuppressants tailored to specific types of glaucoma, thereby facilitating personalised treatment strategies. We used five Mendelian randomisation (MR) methods-inverse variance weighted (IVW), MR-Egger, simple model, weighted median, and weighted mediation model - to assess causal relationships between immune cells and four glaucoma subtypes: neovascular glaucoma (NVG), primary open-angle glaucoma (POAG), primary closed-angle glaucoma (PACG), and normal-tension glaucoma (NTG). IVW aggregated causal estimates using Wald ratios and variance-weighted meta-analysis. MR-Egger considered horizontal pleiotropy under the InSIDE assumption. The weighted median model required ≥ 50% valid instrumental variables (IVs) for robust inference, while the weighted mediation model adjusted for SNP correlations. The simple model provided additional insight into causality. Glaucoma GWAS data were obtained from FinnGen ( https://finngen.gitbook.io/documentation/ ). Summary statistics for immune cell phenotypes (GWAS IDs: GCST90001391-GCST90002121) were obtained from the GWAS catalogue ( https://www.ebi.ac.uk/gwas/studies/GCST90002121 ). The study has identified a causal relationship between various immune cells and different types of glaucoma. It was found that 21 different types of immune cells had a causal relationship with NVG, 37 types of immune cells had a causal relationship with POAG, 40 different types of immune cells had a causal relationship with PACG, and 24 different types of immune cells had a causal relationship with NTG.

Risks of glaucoma among individuals with psoriasis: a population-based cohort study

BACKGROUND

Psoriasis is a chronic systemic disorder with ocular involvement.

OBJECTIVES

To evaluate the risk of glaucoma among patients with psoriasis.

METHODS

Participants in this cohort study were selected based on Chang Gung Research Database from 1 January 2003 to 31 December 2012. Follow-up ended on 31 December 2017. The participants in the control group were matched with the psoriasis group by sex, age and index date with a 4 : 1 ratio. The hazard ratios of glaucoma were estimated using Cox regression analysis. We also evaluated the relationship between the risk of glaucoma and systemic therapies as well as phototherapy and topical corticosteroid in patients with psoriasis.

RESULTS

In total, 6682 patients with psoriasis and 26 728 matched controls were enrolled. The study population was composed mainly of males accounting for 64.2% (21 445/33 410) of the study population. The psoriasis group had higher incidence rates than the control group for glaucoma (adjusted hazard ratio 1.405, 95% confidence interval, 1.051-1.879). Patients with psoriasis receiving psoralen-ultraviolet A (PUVA) therapy for > 200 sessions had an increased risk of glaucoma.

CONCLUSIONS

Patients with psoriasis had an increased risk of glaucoma. Long-term PUVA therapy raised the risk of glaucoma in people with psoriasis.

Role of T cell-induced autoimmune response in the pathogenesis of glaucoma

PURPOSE

This review aims to elucidate the role of T cell-induced autoimmune responses in the pathogenesis of glaucoma, focusing on the immunological changes contributing to retinal ganglion cell (RGC) damage.

METHODS

A comprehensive review of recent studies examining immunological mechanisms in glaucoma was conducted. This included analyses of T cell interactions, heat shock proteins (HSPs), and resultant autoimmune responses. Key findings from experimental models and clinical observations were synthesized to present a coherent understanding of immune dynamics in glaucoma.

RESULTS

Glaucoma is a neurodegenerative disease marked by optic nerve atrophy and irreversible vision loss due to RGC damage. The disease is etiologically heterogeneous, with multiple risk factors and pathogenic mechanisms. Recent research highlights the dual immunomodulatory role of T cells in immune protection and injury. T cells, pre-sensitized by bacterial HSPs, can cross-react with endogenous HSPs in RGCs under stress, leading to autoimmune damage. Elevated levels of HSP autoantibodies and abnormal T cell activity have been observed in glaucoma patients, indicating a significant autoimmune component in disease progression.

CONCLUSIONS

T cell-induced autoimmune responses are crucial in the pathogenesis of glaucoma, contributing to RGC degeneration beyond the effects of elevated intraocular pressure. Understanding these immunological mechanisms is vital for developing targeted neuroprotective therapies for glaucoma.

Mendelian randomization study shows no causal relationship between psychiatric disorders and glaucoma in European and East Asian populations

Background: Glaucoma is a leading cause of blindness strongly associated with psychiatric disorders, but the causal association between glaucoma and psychiatric disorders remains uncertain because of the susceptibility of observational studies to confounding and reverse causation. This study aims to explore the potential causal association between glaucoma and three highly related psychiatric disorders (Depression, Insomnia, and Schizophrenia) in the European and East Asian populations using a two-sample Mendelian randomization analysis. Methods: Instrumental variables (IVs) of depression, insomnia, and schizophrenia in the European population were obtained after strict filtering. Summary-level data for glaucoma and glaucoma subtypes (primary open-angle glaucoma and primary closed-angle glaucoma) were obtained as outcomes. The inverse variance weighting (IVW) method was used as the primary method. Additionally, the causal effect was evaluated in the East Asian population using the same methods to validate analysis results. The robustness of these results was confirmed using heterogeneity, pleiotropy, and Steiger directionality test. Results: The primary MR results indicated that genetically driven psychiatric disorders were not causally associated with glaucoma (Depression: odds ratio (OR): 1.15, 95% confidence interval (CI): 0.93-1.42, p = 0.20; Insomnia: OR: 1.14, 95% CI: 0.63-2.05, p = 0.66; Schizophrenia: OR: 1.00, 95% CI: 0.93-1.08, p = 0.95), either with the risk of glaucoma subtypes in the European population. Meanwhile, results in the East Asian population were consistent with the results among the European population (Depression: OR = 1.38, CI 0.75-2.53, p = 0.30; Insomnia: OR = 0.99, CI 0.83-1.18, p = 0.93; Schizophrenia: OR = 1.06, CI 0.94-1.20, p = 0.34) with similar causal estimates in direction. Consistency was obtained by corroborating with other supporting methods. Besides, the robustness of the results was proved and the directionality test confirmed our estimation of potential causal direction (p < 0.001). Conclusion: This study found a non-causal association between psychiatric disorders and the risk of glaucoma in the European and East Asian populations, which contradicts many existing observational reports, indicating that increased psychiatric disorders in glaucoma patients were more likely modifiable rather not inheritable.

Inflammation and Neurodegeneration in Glaucoma: Isolated Eye Disease or a Part of a Systemic Disorder? - Serum Proteomic Analysis

Introduction

Glaucoma is the most common optic neuropathy and the leading cause of irreversible blindness worldwide, which affects 3.54% of the population aged 40-80 years. Despite numerous published studies, some aspects of glaucoma pathogenesis, serum biomarkers, and their potential link with other diseases remain unclear. Recent articles have proposed that autoimmune, oxidative stress and inflammation may be involved in the pathogenesis of glaucoma.

Methods

We investigated the serum expression of 92 inflammatory and neurotrophic factors in glaucoma patients. The study group consisted of 26 glaucoma patients and 192 healthy subjects based on digital fundography.

Results

Patients with glaucoma had significantly lower serum expression of IL-2Rβ, TWEAK, CX3CL1, CD6, CD5, LAP TGF-beta1, LIF-R, TRAIL, NT-3, and CCL23 and significantly higher expression of IL-22Rα1.

Conclusion

Our results indicate that patients with glaucoma tend to have lower levels of neuroprotective proteins and higher levels of neuroinflammatory proteins, similar to those observed in psychiatric, neurodegenerative and autoimmune diseases, indicating a potential link between these conditions and glaucoma pathogenesis.

Th1 cells contribute to retinal ganglion cell loss in glaucoma in a VCAM-1-dependent manner

Glaucoma is a complex neurodegenerative disorder characterized by the progressive loss of retinal ganglion cells (RGC) and optic nerve axons, leading to irreversible visual impairment. Despite its clinical significance, the underlying mechanisms of glaucoma pathogenesis remain poorly understood. In this study, we aimed to unravel the multifaceted nature of glaucoma by investigating the interaction between T cells and retinas. By utilizing clinical samples, murine glaucoma models, and T cell transfer models, we made several key findings. Firstly, we observed that CD4+ T cells from glaucoma patients displayed enhanced activation and a bias towards T helper (Th) 1 responses, which correlated with visual impairment. Secondly, we identified the infiltration of Th1 cells into the retina, where they targeted RGC and integrated into the pro-inflammatory glial network, contributing to progressive RGC loss. Thirdly, we discovered that circulating Th1 cells upregulated vascular cell adhesion protein 1 (VCAM-1) on retinal microvessels, facilitating their entry into the neural retina. Lastly, we found that Th1 cells underwent functional reprogramming before reaching the retina, acquiring a phenotype associated with lymphocyte migration and neurodegenerative diseases. Our study provides novel insights into the role of peripheral CD4+ T cells in glaucoma pathogenesis, shedding light on the mechanisms underlying their infiltration into the retina and offering potential avenues for innovative therapeutic interventions in this sight-threatening disease.

Aqueous humor cytokine levels are associated with the severity of visual field defects in patients with primary open-angle glaucoma

BACKGROUND

To evaluate the aqueous humor (AH) levels of cytokines in primary open-angle glaucoma (POAG) patients and cataract patients.

METHODS

Thirty-eight POAG patients and 26 cataract patients were recruited. Peripheral blood (PB) was collected from each subject. The POAG group was divided into 2 subgroups according to the severity of visual field defects. The cutoff point of the mean deviation (MD) of the visual field was -12 dB. AH was obtained at the time of anterior chamber puncture during cataract or glaucoma surgery by using a 27-gauge needle attached to a microsyringe. AH and PB levels of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta2 (TGF-β2) and IL-4 were assayed by enzyme-linked immunosorbent assay. Postoperative intraocular pressures (IOPs) of POAG patients were recorded during the follow-up period.

RESULTS

TNF-α and TGF-β2 showed significantly higher AH levels in the POAG group than in the cataract group (P < 0.001 and P = 0.001, respectively). For the POAG group, preoperative IOPs were significantly positively correlated with AH levels of TNF-α (r² = 0.129, P = 0.027) and TGF-β2 (r² = 0.273, P = 0.001). AH levels of TGF-β2 were significantly different among cataract patients, POAG patients with MD> -12 dB and POAG patients with MD≤ -12 dB (P = 0.001). AH levels of TNF-α were significantly positively associated with IOP reduction after trabeculectomy (P = 0.025). AH and PB levels of cytokines were not related to the long-term success of trabeculectomy.

CONCLUSION

The levels of TNF-α and TGF-β2 showed different profiles in POAG patients and cataract patients. AH levels of TGF-β2 were correlated with the severity of glaucomatous neuropathy in POAG patients. The findings suggest possible roles for cytokines in the pathogenesis and development of POAG.

Glaucoma as a Neurodegenerative and Inflammatory Disease

Glaucoma is a neurodegenerative disease that leads to irreversible loss of vision through degeneration of the retinal ganglia cells (RGCs). Glaucoma is one of the most frequent causes of blindness in the world. Intraocular pressure is the main risk factor for the occurrence and development of this disease. Treatment is largely based on reducing internal optical pressure. However, some patients may deteriorate or become blind, despite normal or reduced internal optical pressure. The pathophysiological details are still unclear. Neuroinflammatory processes are also apparently an additional cause. In principle, innate or local responses of the adaptive immune system can be distinguished. The reaction of the innate immune system, particularly the local microglial cells, has long been studied. The macroglia with the astrocytes and Müller cells and their homeostatic effects have also long been known. On the other hand, it has long been thought that the retina with its RGZs was inert to adaptive immunological reactions - due to the function of the blood brain barrier. However, this system may be disturbed by antigen presentation, leading to a reaction of the adaptive immune system, with B cell and T cell responses. In this context, the key proteins are presumably heat shock proteins. We now know that neuroinflammation is important in glaucoma, as in other neurodegenerative diseases. It is important to increase our understanding of these phenomena. In this review article, we present our current knowledge of the role of the micro- and macroglia, the adaptive immune system, and the heat shock proteins.

Microbiome Dysbiosis: A Pathological Mechanism at the Intersection of Obesity and Glaucoma

The rate at which obesity is becoming an epidemic in many countries is alarming. Obese individuals have a high risk of developing elevated intraocular pressure and glaucoma. Additionally, glaucoma is a disease of epidemic proportions. It is characterized by neurodegeneration and neuroinflammation with optic neuropathy and the death of retinal ganglion cells (RGC). On the other hand, there is growing interest in microbiome dysbiosis, particularly in the gut, which has been widely acknowledged to play a prominent role in the etiology of metabolic illnesses such as obesity. Recently, studies have begun to highlight the fact that microbiome dysbiosis could play a critical role in the onset and progression of several neurodegenerative diseases, as well as in the development and progression of several ocular disorders. In obese individuals, gut microbiome dysbiosis can induce endotoxemia and systemic inflammation by causing intestinal barrier malfunction. As a result, bacteria and their metabolites could be delivered via the bloodstream or mesenteric lymphatic vessels to ocular regions at the level of the retina and optic nerve, causing tissue degeneration and neuroinflammation. Nowadays, there is preliminary evidence for the existence of brain and intraocular microbiomes. The altered microbiome of the gut could perturb the resident brain-ocular microbiome ecosystem which, in turn, could exacerbate the local inflammation. All these processes, finally, could lead to the death of RGC and neurodegeneration. The purpose of this literature review is to explore the recent evidence on the role of gut microbiome dysbiosis and related inflammation as common mechanisms underlying obesity and glaucoma.

Blood cell traits and risk of glaucoma: A two-sample mendelian randomization study

Importance: Glaucoma is the second leading cause of blindness in the world. The causal direction and magnitude of the association between blood cell traits and glaucoma is uncertain because of the susceptibility of observational studies to confounding and reverse causation. Objective: To explore whether there is a causal relationship of blood cell traits including white blood cell (WBC) count (WBCC) and its subtypes [basophil cell count (BASO), monocyte cell count (MONO), lymphocyte cell count (LYMPH), eosinophil cell count (EOS), neutrophil cell count (NEUT)], red blood cell (RBC) count (RBCC), red blood distribution width (RDW), platelet count (PLT), and plateletcrit (PCT) on glaucoma risk. Methods: A two-sample Mendelian randomization (MR) analysis was conducted. Genome-wide significant single nucleotide polymorphisms (SNPs) from published genome-wide association studies (GWAS) on human blood cell traits were utilized as exposure instruments and the dataset for outcome was from the GWAS summary data of glaucoma. In the univariable MR analysis, we examined the association between genetic evidence of blood cell traits and glaucoma. To further investigate the potential causal mechanisms underlying the observed association, we performed multivariable MR analysis with three models, taking into account the mediator effect of inflammation and oxidative stress. According to Bonferroni-corrected for the 10 exposures in 3 methods, the MR study yielded a statistically significant p-value of 0.0017. Results: Genetically BASO, PCT, LYMPH, and PLT were potentially positively associated with glaucoma in the European ancestry [BASO: Odds ratio (OR) = 1.00122, 95% confidence interval (CI), 1.00003-1.00242, p = 0.045; PCT: OR = 1.00078, 95% CI, 1.00012-1.00143, p = 0.019; LYMPH: OR = 1.00076, 95% CI, 1.00002-1.00151, p = 0.045; PLT: OR = 1.00065, 95% CI, 1.00006-1.00123, p = 0.030], There was insufficient evidence to support a causal association of MONO, NEUT, EOS, WBCC, RBCC and RDW (MONO: OR = 1.00050, p = 0.098; NEUT: OR = 1.00028, p = 0.524; EOS: OR = 1.00020, p = 0.562; WBCC: OR = 1.00008, p = 0.830; RBCC: OR = 0.99996, p = 0.920; RDW: OR = 0.99987, p = 0.734) with glaucoma. The multivariable MR with model 1, 2, and 3 demonstrated that BASO, PCT, LYMPH, and PLT were still potentially genetically associated with the risk of glaucoma. Conclusion: Our study reveals a genetic predisposition to higher LYMPH, BASO, PLT, and PCT are associated with a higher risk of glaucoma, whereas WBCC, MONO, EOS, NEUT, RBCC, and RDW are not associated with the occurrence of glaucoma. This finding also supports previous observational studies associating immune components with glaucoma, thus provide guidance on the predication and prevention for glaucoma.

Immune responses in mice after blast-mediated traumatic brain injury TBI autonomously contribute to retinal ganglion cell dysfunction and death

PURPOSE

The purpose of this study was to examine the role of the immune system and its influence on chronic retinal ganglion cell (RGC) dysfunction following blast-mediated traumatic brain injury (bTBI).

METHODS

C57BL/6J and B6.129S7-Rag1tm1Mom/J (Rag-/-) mice were exposed to one blast injury of 140 kPa. A separate cohort of C57BL/6J mice was exposed to sham-blast. Four weeks following bTBI mice were euthanized, and splenocytes were collected. Adoptive transfer (AT) of splenocytes into naïve C57BL/6J recipient mice was accomplished via tail vein injection. Three groups of mice were analyzed: those receiving AT of splenocytes from C57BL/6J mice exposed to blast (AT-TBI), those receiving AT of splenocytes from C57BL/6J mice exposed to sham (AT-Sham), and those receiving AT of splenocytes from Rag-/- mice exposed to blast (AT-Rag-/-). The visual function of recipient mice was analyzed with the pattern electroretinogram (PERG), and the optomotor response (OMR). The structure of the retina was evaluated using optical coherence tomography (OCT), and histologically using BRN3A-antibody staining.

RESULTS

Analysis of the PERG showed a decreased amplitude two months post-AT that persisted for the duration of the study in AT-TBI mice. We also observed a significant decrease in the retinal thickness of AT-TBI mice two months post-AT compared to sham, but not at four or six months post-AT. The OMR response was significantly decreased in AT-TBI mice 5- and 6-months post-AT. BRN3A staining showed a loss of RGCs in AT-TBI and AT-Rag-/- mice.

CONCLUSION

These results suggest that the immune system contributes to chronic RGC dysfunction following bTBI.

Endophthalmitis: Ursachen, Erreger, Therapie und Visusverlauf mit Fokus auf Glaukompatienten

Hintergrund Endophthalmitiden stellen einen der schwerwiegendsten Notfälle in der Ophthalmologie dar. Um deren Prävalenz zu minimieren, ist eine möglichst genaue Kenntnis auslösender Faktoren von Bedeutung. Eine chirurgische Therapie mit gezielter, Erreger-spezifischer Medikation und ein intaktes Immunsystem sind die Basis für den Visuserhalt. Ferner stellt sich die Frage, ob anhand zugrundeliegender Erkrankungen am Auge ein ungünstiger Verlauf prognostiziert werden kann, sodass ein Vergleich zwischen Glaukom- (G) und Nicht-Glaukompatienten (NG) im Hinblick auf ursächliche Faktoren, Erreger, Therapie und Visusverlauf gezogen wurde. Da bei Glaukompatienten eine potentielle Alteration des lokalen Immunsystems diskutiert wird, ist von Interesse, ob sich die klinischen Verläufe einer Endophthalmitis von Nicht-Glaukompatienten unterscheiden. Patienten und Methoden Es handelt sich um eine retrospektive Analyse von 75 Augen (13 G, 62 NG), die in einem 5-Jahres-Zeitraum aufgrund einer Endophthalmitis an der Augenklinik des Universitätsklinikums Erlangen-Nürnberg behandelt wurden. Auszuwertende Parameter waren u.a. das klinische Bild, operative und medikamentöse Behandlungen, das mikrobielle Spektrum und der Visusverlauf bei Glaukom- sowie Nicht-Glaukompatienten. Ergebnisse Bei Erstvorstellung dominierte bei allen Patienten eine akute Visusverschlechterung (44%) mit Vorderkammerreiz (62,7%), Hypopyon (52%) und reduziertem (40%) oder fehlendem (26,7%) Funduseinblick. Vorangehende intraokulär-chirurgische Eingriffe wurden bei insgesamt 53,3% beobachtet, insbesondere Kataraktoperationen. In beiden Gruppen konnten gram-positive Kokken als häufigster Erreger identifiziert werden (G: 23,1%; NG: 38,7%), wohingegen seltene Keime nur bei Glaukompatienten vorkamen. Bei 76% aller Patienten wurde eine pars-plana-Vitrektomie durchgeführt, eine Enukleation bei 20%, letzteres signifikant häufiger bei Glaukompatienten (p=0,01). Postoperativ konnte eine signifikante Visusverbesserung bei Nicht-Glaukompatienten erzielt werden (p<0,001); im Direktvergleich stellte sich ein schlechteres visuelles Outcome bei glaukomatös vorerkrankten Augen dar. Schlussfolgerung Stellt die Endophthalmitis eine sehr seltene Erkrankung dar, ist eine frühzeitige Diagnosestellung und Behandlung dennoch für die Prognose entscheidend. In der vorliegenden Kohorte zeigt sich ein schlechterer Endvisus bei Glaukompatienten als bei Nicht-Glaukompatienten. Background Endophthalmitis is one of the most serious emergencies in ophthalmology. In order to lower their prevalence, the most accurate knowledge of potential risk factors is important. Surgical therapy with targeted, pathogen-specific medication and an intact immune system are fundamental to preserve visual acuity. Furthermore, the question arises whether an unfavorable course can be predicted on the basis of underlying diseases of the eye, therefore a comparison between glaucoma patients (G) and non-glaucoma patients (NG) with regard to causative factors, pathogens, therapy and visual acuity course was drawn. Since a potential alteration of the local immune system in glaucoma disease has been described, it is of interest whether the clinical courses of endophthalmitis differ from non-glaucoma patients. Patients and methods A retrospective analysis of 75 eyes (13 G, 62 NG) who underwent treatment and surgery due to the diagnosis of endophthalmitis in the Department of Ophthalmology, University of Erlangen-Nuremberg has been evaluated over a period of 5 years. Clinical characteristics, surgical treatment, microbial spectrum and visual acuity in glaucoma and non-glaucoma eyes were investigated. Results A drastic vision impairment (44%) with inflammation of the anterior chamber (62.7%), hypopyon (52%) and reduced (40%) or complete missing sight (26.7%) of the fundus were predominantly present at first diagnosis in all patients. A previous eye surgery was observed in a total of 53%, especially cataract surgery. Gram-positive cocci were seen as the most common causing agent in both groups, (G: 23.1%; NG: 38.7%), whereas other rare pathogens were present only in glaucoma eyes. Pars-plana-vitrectomy was performed in 76% and enucleations in 20% of all patients, the latter significantly increased in glaucomateous eyes (p=0.01). A significant postoperative improvement of visual acuity was yielded in non-glaucoma patients (p<0.001); visual acuity outcome was worsen in glaucoma eyes. Conclusion Despite its rareness, early diagnosis and treatment of endophthalmitis is crucial for prognosis. In the present cohort, a worse visual acuity outcome was yielded in glaucoma patients in comparison to non-glaucoma patients.

Associations of statin use with the onset and progression of open-angle glaucoma: A systematic review and meta-analysis

Background

Statins, the first-line therapy for hyperlipidemia, have received considerable attention as candidates for glaucoma treatments given its neuroprotective effects. In this systematic review and meta-analysis, we intended to assess the association of statin use with the onset and progression of open-angle glaucoma (OAG).

Methods

Databases including PubMed, Embase and Web of Science Core Collection were searched for longitudinal studies reporting the association between statin use and OAG onset or progression on Feb 3, 2021. A meta-analysis was performed for the association between statin use and OAG onset. Relative risks (RRs) with 95% confidential intervals (CIs) were retrieved from included studies and pooled using random-effects models. Potential risks of bias were evaluated by the Newcastle-Ottawa Quality Assessment Scale for all eligible studies. This study had been registered on PROSPERO (CRD 42021232172).

Findings

515,788 participants (mean age 68.7 years, 62.3% female) from ten studies were included in the systematic review of the association between statin use and OAG onset, and 26,347 OAG patients (mean age 67.3 years, 52.2% female) from seven studies were included for the association between statin use and OAG progression. Potential risks of bias were detected in 12 studies, which were mainly attributed to selection and confounding bias. In addition, 515,600 participants from eight studies were included in the meta-analysis which collectively showed that statin use was associated with a reduced risk of OAG onset (Pooled RR: 0.95; 95%CI: 0.93-0.98; I2=0.199;). No significant heterogeneity or publication bias was found for studies included in the meta-analysis. There were inconsistent evidences for the association between statin use and OAG progression.

Interpretation

Statin use is associated with a slightly lower risk of OAG onset based on existing evidences from longitudinal observational studies, the association between statin use and OAG progression remains inconclusive. The included evidences were typically weak due to poor study design and under-powered studies. Current findings should be interpreted cautiously and still need to be validated in further research.

Funding

The National Key R&D Program of China (2018YFC0116500), Science and Technology Planning Project of Guangdong Province (2013B20400003), the China Postdoctoral Science Foundation (2019TQ0365), the National Natural Science Foundation of China (82000901 and 82101171).

Molecular regulation of neuroinflammation in glaucoma: Current knowledge and the ongoing search for new treatment targets

Neuroinflammation relying on the inflammatory responses of glial cells has emerged as an impactful component of the multifactorial etiology of neurodegeneration in glaucoma. It has become increasingly evident that despite early adaptive and reparative features of glial responses, prolonged reactivity of the resident glia, along with the peripheral immune cells, create widespread toxicity to retinal ganglion cell (RGC) axons, somas, and synapses. As much as the synchronized responses of astrocytes and microglia to glaucoma-related stress or neuron injury, their bi-directional interactions are critical to build and amplify neuroinflammation and to dictate the neurodegenerative outcome. Although distinct molecular programs regulate somatic and axonal degeneration in glaucoma, inhibition of neurodegenerative inflammation can provide a broadly beneficial treatment strategy to rescue RGC integrity and function. Since inflammatory toxicity and mitochondrial dysfunction are converging etiological paths that can boost each other and feed into a vicious cycle, anti-inflammatory treatments may also offer a multi-target potential. This review presents an overview of the current knowledge on neuroinflammation in glaucoma with particular emphasis on the cell-intrinsic and cell-extrinsic factors involved in the reciprocal regulation of glial responses, the interdependence between inflammatory and mitochondrial routes of neurodegeneration, and the research aspects inspiring for prospective immunomodulatory treatments. With the advent of powerful technologies, ongoing research on molecular and functional characteristics of glial responses is expected to accumulate more comprehensive and complementary information and to rapidly move the field forward to safe and effective modulation of the glial pro-inflammatory activities, while restoring or augmenting the glial immune-regulatory and neurosupport functions.

Anti-inflammatory Effects of GTE in Eye Diseases

Ocular inflammation is a common complication of various eye diseases with wide consequences from irritations to potentially sight-threatening complications. Green tea is a popular beverage throughout the world. One of the proven health benefits of consuming green tea extract (GTE) is anti-inflammation. Catechins are the biologically active constituents of GTE. In in vitro and in vivo studies, GTE and catechins present inhibition of inflammatory responses in the development of ocular inflammation including infectious, non-infectious or autoimmune, and oxidative-induced complications. Research on the ocular inflammation in animal models has made significant progress in the past decades and several key disease mechanisms have been identified. Here we review the experimental investigations on the effects of GTE and catechins on various ocular inflammation related diseases including glaucoma, age-related macular degeneration, uveitis and ocular surface inflammation. We also review the pharmacokinetics of GTE constituents and safety of green tea consumption. We discuss the insights and perspectives of these experimental results, which would be useful for future development of novel therapeutics in human.

Evaluating TNF-α and Interleukin-2 (IL-2) Levels in African American Primary Open-Angle Glaucoma Patients

Purpose: To establish if SNPs in TNF-α and IL-2 genes are associated with Primary Open-Angle Glaucoma (POAG) in African Americans (AA). We also determined whether plasma TNF-α and IL-2 levels could serve as biomarkers for POAG in African Americans using sandwich enzyme-linked immunosorbent assay. Methods: A single SNP association analysis was performed to investigate the association between potential gene variants in TNF-α and IL-2 genes and POAG in the AA population. Plasma samples from 190 African Americans (72 from normal subjects and 118 POAG cases) were obtained for TNF- α studies and 367 samples (135 from normal subjects and 232 from POAG cases) were obtained for IL-2 studies. TNF-α levels and IL-2 levels were measured by sandwich enzyme-linked immunosorbent assays (ELISA) and analyzed to see if they reached significance in cases with POAG and endophenotypes when compared to normal subjects. Results: The SNP, rs1800630, in TNF-α gene was found to be marginally associated with POAG. SNPs in IL-2 gene were not associated with POAG in the case-control analysis. No significant difference was found between TNF-α levels and IL-2 levels in normal and POAG case subjects in our study. IL-2 levels were inversely correlated with high IOP in POAG cases. Conclusions: Although we found a marginal SNP association of TNF-α, assessing the expression levels of TNF-α and IL-2 may serve as promising biomarkers for African American POAG. Further investigation is needed to determine if POAG can be subdivided into more specified cohorts of the disease, which may affect plasma cytokine levels differently.

Gut Microbes and Eye Disease

Microbial symbionts in the gut are increasingly recognized as having important effects on health and disease, but have only recently begun to be linked to diseases of the eye. We review current research on the intestinal microbiota's relationship to ocular disease, focusing on autoimmune uveitis, diabetic retinopathy, age-related macular degeneration, and primary-open angle glaucoma. We discuss findings and limitations of this exciting new area of ophthalmology research and explore possible future disease-modifying treatments.

Multifocal Visual Evoked Potentials (mfVEP) for the Detection of Visual Field Defects in Glaucoma: Systematic Review and Meta-Analysis

Some discrepancies have been observed in the diagnostic efficacy of multifocal visual evoked potential (mfVEP) when evaluating visual field defects in glaucoma patients. Therefore, we evaluated the diagnostic precision of the mfVEP in glaucoma to find its best diagnostic indicator. A systematic review and meta-analysis of quantitative studies published up to 1 April 2021 was performed. The methodological quality of the included articles was assessed. Publication bias analysis and heterogeneity tests were performed. The sensitivity, specificity and diagnostic odds ratio were calculated. The area under the curve (AUC) was calculated using the summary of receiver operating characteristics curve. Six studies with a total of 241 patients were included according to the inclusion and exclusion criteria. The AUC was 0.98. There was no evidence of publication bias or threshold effect. The pooled sensitivity and pooled specificity of the mfVEP amplitude for detection of visual field defects in all studies was 0.93 and 0.89, respectively. The positive and negative likelihood ratios of mfVEP amplitude were 6.56 and 0.08, respectively. The amplitude of mfVEP showed a good diagnostic precision in the prediction of visual field defects. Interocular mfVEP amplitude analysis can be a good diagnostic indicator for visual field study.

Candidate Glaucoma Biomarkers: From Proteins to Metabolites, and the Pitfalls to Clinical Applications

Glaucoma is an insidious group of eye diseases causing degeneration of the optic nerve, progressive loss of vision, and irreversible blindness. The number of people affected by glaucoma is estimated at 80 million in 2021, with 3.5% prevalence in people aged 40-80. The main biomarker and risk factor for the onset and progression of glaucoma is the elevation of intraocular pressure. However, when glaucoma is diagnosed, the level of retinal ganglion cell death usually amounts to 30-40%; hence, the urgent need for its early diagnosis. Molecular biomarkers of glaucoma, from proteins to metabolites, may be helpful as indicators of pathogenic processes observed during the disease's onset. The discovery of human glaucoma biomarkers is hampered by major limitations, including whether medications are influencing the expression of molecules in bodily fluids, or whether tests to validate glaucoma biomarker candidates should include human subjects with different types and stages of the disease, as well as patients with other ocular and neurodegenerative diseases. Moreover, the proper selection of the biofluid or tissue, as well as the analytical platform, should be mandatory. In this review, we have summarized current knowledge concerning proteomics- and metabolomics-based glaucoma biomarkers, with specificity to human eye tissue and fluid, as well the analytical approach and the main results obtained. The complex data published to date, which include at least 458 different molecules altered in human glaucoma, merit a new, integrative approach allowing for future diagnostic tests based on the absolute quantification of local and/or systemic biomarkers of glaucoma.

Neuroinflammatory Mechanisms of Mitochondrial Dysfunction and Neurodegeneration in Glaucoma

The exact mechanism of retinal ganglion cell loss in the pathogenesis of glaucoma is yet to be understood. Mitochondrial damage-associated molecular patterns (DAMPs) resulting from mitochondrial dysfunction have been linked to Leber's hereditary optic neuropathy and autosomal dominant optic atrophy, as well as to brain neurodegenerative diseases. Recent evidence shows that, in conditions where mitochondria are damaged, a sustained inflammatory response and downstream pathological inflammation may ensue. Mitochondrial damage has been linked to the accumulation of age-related mitochondrial DNA mutations and mitochondrial dysfunction, possibly through aberrant reactive oxygen species production and defective mitophagy. The present review focuses on how mitochondrial dysfunction may overwhelm the ability of neurons and glial cells to adequately maintain homeostasis and how mitochondria-derived DAMPs trigger the immune system and induce neurodegeneration.

Neuroimmunological Aspects in Glaucoma

Glaucoma pathogenesis hast still to be elucidated. Next to its main risk factor, an increased intraocular pressure, an e.g. altered biomechanics of the lamina cribrosa, oxidative stress-mediated changes and glutatmate toxicity are involved in this multifactorial pathophysiology. Recent experimental studies and clinical findings suggest an involvement of the immune system in glaucoma. This review will give an overview of the different immunologic aspects being involved in glaucoma pathogenesis.

Neuroinflammation in Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is the second leading cause of irreversible blindness worldwide. Increasing evidence suggests oxidative damage and immune response defects are key factors contributing to glaucoma onset. Indeed, both the failure of the trabecular meshwork tissue in the conventional outflow pathway and the neuroinflammation process, which drives the neurodegeneration, seem to be linked to the age-related over-production of free radicals (i.e., mitochondrial dysfunction) and to oxidative stress-linked immunostimulatory signaling. Several previous studies have described a wide range of oxidative stress-related makers which are found in glaucomatous patients, including low levels of antioxidant defences, dysfunction/activation of glial cells, the activation of the NF-κB pathway and the up-regulation of pro-inflammatory cytokines, and so on. However, the intraocular pressure is still currently the only risk factor modifiable by medication or glaucoma surgery. This present review aims to summarize the multiple cellular processes, which promote different risk factors in glaucoma including aging, oxidative stress, trabecular meshwork defects, glial activation response, neurodegenerative insults, and the altered regulation of immune response.

Glaucoma is an autoimmune disease

Glaucoma is characterized by retinal ganglion cell (RGC) neurodegeneration. Elevated intraocular pressure (IOP) is a major risk factor however, mechanisms independent of IOP play a role in RGC pathology. Both antibodies and CD4 T-cells as well as microbiota take part in the pathogenesis of both glaucoma and rheumatoid arteritis (RA).Heat shock proteins (HSPs) which originate in bacteria cross-react with RCG epitopes and were involved in rat model of retinal injury. Enhanced expression of HSPs in the retina was associated with glaucoma-like neuropathology and previous studies have also suggested a pathogenic role for HSPs in RA. In view of these data we suggest that glaucoma should be included in the spectrum of autoimmune diseases and that proven medications for RA should be adopted as an innovative IOP -independent therapeutic strategy for glaucoma.

Adaptive Immunity: New Aspects of Pathogenesis Underlying Neurodegeneration in Glaucoma and Optic Neuropathy

Glaucoma is a globally unmet medical challenge and the most prevalent neurodegenerative disease, which permanently damages the optic nerve and retinal ganglion cells (RGCs), leading to irreversible blindness. Present therapies target solely at lowering intraocular ocular pressure (IOP), a major risk factor of the disease; however, elevated IOP is neither necessary nor sufficient to cause glaucoma. Glaucomatous RGC and nerve fiber loss also occur in individuals with normal IOP. Recent studies have provided evidence indicating a link between elevated IOP and T cell-mediated autoimmune responses, particularly that are specific to heat shock proteins (HSPs), underlying the pathogenesis of neurodegeneration in glaucoma. Reactive glial responses and low-grade inflammation may initially represent an adaptive reaction of the retina to primary stress stimuli; whereas, sustained and excessive glial reactions lead to expanded immune responses, including adaptive immunity, that contribute to progressive neural damage in glaucoma. Emerging data suggest a similar mechanism in play in causing neurodegeneration of other forms of optic neuropathy, such as that resulted from acute ischemia and traumatic injuries. These studies may lead to the paradigm shift and offer a new basis for the development of novel mechanism-based diagnosis, therapy, and preventive interventions for glaucoma. As HSPs are induced under various conditions of neural stress and damage in the brain and spinal cord, these findings may have broader implications for our elucidating of the etiology of other neurodegenerative disorders in the central nervous system.

Discovery and Validation of Circulating Hsa-miR-210-3p as a Potential Biomarker for Primary Open-Angle Glaucoma

Purpose

Blood-based examination tools for glaucoma diagnosis in clinical practice, which can be useful for screening patients when traditional ophthalmic examinations cannot be utilized, are not available thus far. This study aimed to identify circulating microRNAs (miRNAs) associated with primary open-angle glaucoma (POAG) and explore their utility as diagnostic markers.

Methods

A total of 136 POAG patients and controls were enrolled. Next-generation RNA sequencing was used to explore the expression profile of circulating miRNAs in the sequencing set, and potential miRNAs from independent samples in both the screening and validation sets were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Receiver operating characteristic (ROC) analysis was used to evaluate the ability of certain miRNAs to distinguish POAG patients from control subjects.

Results

Using sequencing and qRT-PCR, hsa-miR-210-3p was found to be elevated in POAG patients in all sets. ROC analysis of the screening and validation sets revealed that hsa-miR-210-3p differentiated between POAG patients and matched controls with an area under the curve (AUC) of 0.846 (sensitivity: 84.6%; specificity: 80.8%) and 0.813 (sensitivity: 84.8%; specificity: 69.7%), respectively. In case of all nonsequencing participants, analysis revealed that hsa-miR-210-3p differentiated between severe POAG patients and controls with an AUC of 0.880 (sensitivity: 85.4%; specificity: 85.7%). In addition, the expression of hsa-miR-210-3p was associated with visual field defects of |mean deviation| (β = 0.237; P = 0.022) and average retinal nerve fiber layer thickness (β = -5.792; P = 0.014).

Conclusions

Circulating hsa-miR-210-3p may serve as a potential diagnostic marker for POAG (especially for severe POAG patients).

T-Lymphocyte Subset Distribution and Activity in Patients With Glaucoma

Purpose

Besides glia-driven neuroinflammation, growing evidence from analysis of human blood samples, isolated autoantibodies, and postmortem tissues also support systemic immune responses during neurodegeneration in glaucoma patients. To explore the T-cell–mediated component of systemic immunity, this study analyzed T lymphocytes in patients' blood.

Methods

Blood samples were collected from 32 patients with glaucoma and 21 nonglaucomatous controls, and mononuclear cells were isolated by Histopaque density gradient centrifugation. T-cell subset distribution was analyzed by multicolor flow cytometry after helper (Th) and cytotoxic fractions, and Th subpopulations, were stained with antibodies to CD4, CD8, or distinctive markers, such as IFN-γ (for Th1), IL-4 (for Th2), IL-17A (for Th17), and CD25/FoxP3 (for T regulatory cells [Tregs]). In addition, proliferative activity and cytokine secretion of T cells were analyzed after in vitro stimulation.

Results

Analysis of T-cell subset distribution detected a glaucoma-related shift. Despite similar frequencies of CD4+ or CD8+ T cells, or Th1, Th2, or Th17 subsets in glaucoma and control groups, glaucomatous samples exhibited a trend toward decreased frequency of CD4+ (or CD8+)/CD25+/FoxP3+ Tregs within the entire CD4+ (or CD8+) population (P < 0.001). Furthermore, CD4+ T cells in glaucomatous samples presented a greater stimulation response (∼3-fold) as characterized by increased proliferation and proinflammatory cytokine secretion (P < 0.05).

Conclusions

These findings suggest that the immunity activated in glaucoma may not be counterbalanced by an efficient immune suppression. More work is encouraged to determine whether shifted T-cell homeostasis may contribute to neurodegeneration in glaucoma, and/or whether T-cell subset imbalance may serve as a biomarker of autoimmune susceptibility.

Modulation of the Immune System for the Treatment of Glaucoma

Background:

At present intraocular pressure (IOP) lowering therapies are the only approach to treat glaucoma. Neuroprotective strategies to protect the retinal ganglion cells (RGC) from apoptosis are lacking to date. Substantial amount of research concerning the role of the immune system in glaucoma has been performed in the recent years. This review aims to analyse changes found in the peripheral immune system, as well as selected local changes of retina immune cells in the glaucomatous retina.

Methods:

By dividing the immune system into the innate and the adaptive immune system, a systematic literature research was performed to find recent approaches concerning the modulation of the immune system in the context of glaucoma. Also ClinicalTrials.gov was assessed to identify studies with a translational context.

Results:

We found that some aspects of the immune system, such as changes in antibody levels, changes in toll like receptor signalling, T cells and retinal microglial cells, experience more research activity than other areas such as changes in dendritic cells or macrophages. Briefly, results from clinical studies revealed altered immunoreactivities against retinal and optic nerve antigens in sera and aqueous humor of glaucoma patients and point toward an autoimmune involvement in glaucomatous neurodegeneration and RGC death. IgG accumulations along with plasma cells were found localised in human glaucomatous retinae in a pro-inflammatory environment possibly maintained by microglia. Animal studies show that antibodies (e.g. anti- heat shock protein 60 and anti-myelin basic protein) elevated in glaucoma patients provoke autoaggressive RGC loss and are associated with IgG depositions and increased microglial cells. Also, studies addressing changes in T lymphocytes, macrophages but also local immune responses in the retina have been performed and also hold promising results.

Conclusions:

This recapitulation of recent literature demonstrates that the immune system definitely plays a role in the pathogenesis of glaucoma. Multiple changes in the peripheral innate as well as adaptive immune system have been detected and give room for further research concerning valuable therapeutic targets. We conclude that there still is a great need to bring together the results derived from basic research analysing different aspects of the immune system in glaucoma to understand the immune context of the disease. Furthermore local immune changes in the retina of glaucoma patients still leave room for further therapeutic targets

Circulating biomarkers in glaucoma, age-related macular degeneration, and diabetic retinopathy

Biomarkers to predict the altering physiological conditions over the period leading toward the ocular disorders are of major importance in therapeutics. Isolation and validation of the biomarkers specific to ocular diseases are a challenging task. Glaucoma is a neurodegenerative disease of the eye where the correlation of biomarkers in circulating fluid may be made specific for the eye. However, conditions such as wet age-related macular degeneration (AMD) and proliferative diabetic retinopathy (DR), circulating biomarkers might be having some degree of overlap with other conditions like cancer where a common factor such as angiogenesis is involved. Diabetes, a systemic disorder affecting the target organs such as eye, kidney, heart, and nervous system can be predicted using common circulating biomarkers. However, these markers need to be validated along with various stages of disease progression to enable the possibility of targeted pharmacological interventions apart from good glycemic control alone. This review compiles the attempts made to correlate such circulating biomarkers in the ocular conditions such as glaucoma, AMD, and DR in the search for a surrogate marker for diagnostic and prognostic value. To make biomarkers for the common convenience, genetic markers are excluded from this review.

The Role of Microglia in Retinal Neurodegeneration: Alzheimer's Disease, Parkinson, and Glaucoma

Microglia, the immunocompetent cells of the central nervous system (CNS), act as neuropathology sensors and are neuroprotective under physiological conditions. Microglia react to injury and degeneration with immune-phenotypic and morphological changes, proliferation, migration, and inflammatory cytokine production. An uncontrolled microglial response secondary to sustained CNS damage can put neuronal survival at risk due to excessive inflammation. A neuroinflammatory response is considered among the etiological factors of the major aged-related neurodegenerative diseases of the CNS, and microglial cells are key players in these neurodegenerative lesions. The retina is an extension of the brain and therefore the inflammatory response in the brain can occur in the retina. The brain and retina are affected in several neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and glaucoma. AD is an age-related neurodegeneration of the CNS characterized by neuronal and synaptic loss in the cerebral cortex, resulting in cognitive deficit and dementia. The extracellular deposits of beta-amyloid (Aβ) and intraneuronal accumulations of hyperphosphorylated tau protein (pTau) are the hallmarks of this disease. These deposits are also found in the retina and optic nerve. PD is a neurodegenerative locomotor disorder with the progressive loss of dopaminergic neurons in the substantia nigra. This is accompanied by Lewy body inclusion composed of α-synuclein (α-syn) aggregates. PD also involves retinal dopaminergic cell degeneration. Glaucoma is a multifactorial neurodegenerative disease of the optic nerve, characterized by retinal ganglion cell loss. In this pathology, deposition of Aβ, synuclein, and pTau has also been detected in retina. These neurodegenerative diseases share a common pathogenic mechanism, the neuroinflammation, in which microglia play an important role. Microglial activation has been reported in AD, PD, and glaucoma in relation to protein aggregates and degenerated neurons. The activated microglia can release pro-inflammatory cytokines which can aggravate and propagate neuroinflammation, thereby degenerating neurons and impairing brain as well as retinal function. The aim of the present review is to describe the contribution in retina to microglial-mediated neuroinflammation in AD, PD, and glaucomatous neurodegeneration.

Analyzing cytokines as biomarkers to evaluate severity of glaucoma

AIM

To analyze cytokines as biomarkers for evaluation of severity of glaucoma.

METHODS

This was a prospective case-control study including 29 eyes with glaucoma. Besides, 28 eyes with senile cataract were used as control. Patients were classified into four groups: acute angle closure glaucoma (AACG), chronic angle closure glaucoma (CACG), primary open angle glaucoma (POAG) and senile cataract. Undiluted vitreous samples were collected, then vitreous concentrations of 9 types of cytokines were determined by cytometric bead assay system: γ-interferon (IFNg), interleukin (IL)-10, IL-2, IL-4, IL-5, interferon-γ-inducible protein (IP)-10, monocyte chemoattractant protein (MCP)-1, tumor necrosis factor (TNF)-α, and vascular endothelial growth factor (VEGF). We also recorded the intraocular pressure (IOP) of patients in each group and Pearson correlated analysis was performed to analysis the correlation between each type of cytokine with IOP.

RESULTS

Vitreous levels of IL-2, IL-5, MCP-1, TNF-α and IP-10 were significantly higher (P<0.05) in AACG group. Patients with AACG, CACG and POAG have higher IOP than senile cataract, but we didn't find any significant correlation between IOP with any type of the cytokines.

CONCLUSION

Inflammation and immune reaction have a strong link with the pathology of glaucoma especially AACG. Some cytokines may act as biomarkers to evaluate the severity of glaucoma. Anti-inflammatory treatments and controlling of IOP are necessary for the therapy of glaucoma.

Early immune responses are independent of RGC dysfunction in glaucoma with complement component C3 being protective

Various immune response pathways are altered during early, predegenerative stages of glaucoma; however, whether the early immune responses occur secondarily to or independently of neuronal dysfunction is unclear. To investigate this relationship, we used the Wlds allele, which protects from axon dysfunction. We demonstrate that DBA/2J.Wlds mice develop high intraocular pressure (IOP) but are protected from retinal ganglion cell (RGC) dysfunction and neuroglial changes that otherwise occur early in DBA/2J glaucoma. Despite this, immune pathways are still altered in DBA/2J.Wlds mice. This suggests that immune changes are not secondary to RGC dysfunction or altered neuroglial interactions, but may be directly induced by the increased strain imposed by high IOP. One early immune response following IOP elevation is up-regulation of complement C3 in astrocytes of DBA/2J and DBA/2J.Wlds mice. Unexpectedly, because the disruption of other complement components, such as C1Q, is protective in glaucoma, C3 deficiency significantly increased the number of DBA/2J eyes with nerve damage and RGC loss at an early time point after IOP elevation. Transcriptional profiling of C3-deficient cultured astrocytes implicated EGFR signaling as a hub in C3-dependent responses. Treatment with AG1478, an EGFR inhibitor, also significantly increased the number of DBA/2J eyes with glaucoma at the same early time point. These findings suggest that C3 protects from early glaucomatous damage, a process that may involve EGFR signaling and other immune responses in the optic nerve head. Therefore, therapies that target specific components of the complement cascade, rather than global inhibition, may be more applicable for treating human glaucoma.

Aqueous Humor Cytokines in Patients With Acute Nonarteritic Anterior Ischemic Optic Neuropathy

PURPOSE

To measure and compare the cytokine concentrations in the aqueous humor of patients with acute nonarteritic anterior ischemic optic neuropathy (NAION) and normal age-related cataract controls.

DESIGN

Prospective, comparative observational study.

METHODS

Aqueous humor samples were obtained in 10 patients with acute NAION (within 14 days of symptom onset) and 15 control patients with age-related cataract. The levels of 6 cytokines-vascular endothelial growth factor (VEGF), tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-2, IL-6, and IL-8-were determined using a multiplex bead immunoassay. The clinical characteristics of patients were also collected for correlation analysis.

RESULTS

The mean concentration of VEGF (94.1 ± 40.4 pg/mL) was significantly higher in the NAION group compared to the cataract controls (52.2 ± 20.8 pg/mL; P = .010) and the mean concentration of IL-2 (5.56 ± 1.27 pg/mL) was significantly lower in the NAION group than in the cataract controls (16.6 ± 14.0 pg/mL; P = .002). There were no differences in the concentration of TNF-α, IL-1β, IL-6, and IL-8. There was a strong negative correlation between the VEGF concentration and the peripapillary retinal nerve fiber layer (RNFL) thickness at presentation (r = -0.657, P = .055). There was no significant correlation between the RNFL thickness and any other cytokines, the mean deviation on 24-2 Humphrey visual fields, or the duration of vision loss.

CONCLUSIONS

Acute NAION is associated with higher VEGF and lower IL-2 concentrations without a change in other inflammatory cytokines. This has implications for future therapeutic interventions and diagnostic testing in patients with this acute optic neuropathy.

Neuroinflammation in glaucoma: A new opportunity

Mounting evidence suggests neuroinflammation is a key process in glaucoma, yet the precise roles are not known. Understanding these complex processes, which may also be a key in other common neurodegenerations such as Alzheimer's disease, will lead to targeted therapeutics for a disease that affects as many as 80 million people worldwide. Here, we define neuroinflammation as any immune-relevant response by a variety of cell types including astrocytes, microglia, and peripherally derived cells occurring in the optic nerve head and/or retina. In this review article, we first discuss clinical evidence for neuroinflammation in glaucoma and define neuroinflammation in glaucoma. We then review the inflammatory pathways that have been associated with glaucoma. Finally, we set out key research directions that we believe will greatly advance our understanding of the role of neuroinflammation in glaucoma. This review arose from a discussion of neuroinflammation in glaucoma at the 2015 meeting of The Lasker/IRRF Initiative for Innovation in Vision Science. This manuscript sets out to summarize one of these sessions; "Inflammation and Glaucomatous Neurodegeneration", as well as to review the current state of the literature surrounding neuroinflammation in glaucoma.

Elevated Regulatory T Cell Levels in Glaucoma Patients in Comparison to Healthy Controls

BACKGROUND

Many studies analyzing neurodegenerative diseases demonstrate altered frequencies of regulatory T cells (Tregs). Till date, there is hardly any information concerning Tregs in glaucoma. To gather first results concerning Treg levels in glaucoma patients, we aimed to investigate whether the number of CD4(+)CD25(+)T cells vary in the patients suffering from primary open-angle glaucoma (POAG) and healthy controls.

METHODS

Heparinized blood samples were collected from 16 healthy individuals and 16 POAG patients. The groups were age and gender matched. A density gradient centrifugation over Ficoll-Paque was performed to isolate the peripheral blood mononuclear cells. The resulting cells were stained with fluorescein isithiocyanate (FITC)-conjugated anti-CD4 and phycoerythrin (PE)-conjugated anti-CD25 in single and double staining procedures. Fluorescence-activated cell sorting (FACS) analyses were performed. A total of 200,000 lymphocytes were gated per measurement based on forward/side scatter. The measurements were performed in triplicate for each sample. Student's t-test was performed. The level of significance was set at p < 0.05. Results were expressed as mean value ± standard error of the mean.

RESULTS

We detected a mean percentage of 8.45% CD4(+)CD25(+) T cells of all CD4 (+) T-Lymphocytes in glaucoma patients (standard deviation ± 2.3%). In contrast, a significant smaller percentage of CD4(+)CD25(+) T cells of all CD4 (+) T-Lymphocytes was detected in healthy controls (5.79%; standard deviation ± 1.61%) (p < 0.01).

CONCLUSION

This study demonstrates increased numbers of CD4(+)CD25(+) T cells in the patients suffering from the neurodegenerative disease glaucoma. Tregs inherit suppressive functions that could be attenuated in glaucoma patients. These results underline the hypothesis of an immunologic involvement in glaucoma via the cellular immunity.

Glaucoma: Current and Developing Concepts for Inflammation, Pathogenesis and Treatment

Glaucoma is a prevalent neurodegenerative disorder of the eye. However, the mechanism leading to the disease is still unclear. Increased intraocular pressure (IOP) and subsequent retinal ganglion cell (RGC) death leading to the loss of visual field characterizes the pathology of primary open angle glaucoma, which is the most common form. Possible factors leading to glaucoma include glutamate-induced neurotoxicity, nitric oxide (NO) based damage, disruption of neurotrophic factor transport and immune-induced neurodestruction. Current treatment options primarily aim at decreasing IOP by utilizing pharmacological agents, laser therapy and surgery. Developing treatments target neuroprotection with vaccines, the inhibition of NO synthesis and apoptosis. Gaining a better understanding of the pathogenesis can aid in the development of new treatment options and, perhaps, even a cure for glaucoma.

Ribonuclease 5 coordinates signals for the regulation of intraocular pressure and inhibits neural apoptosis as a novel multi-functional anti-glaucomatous strategy

Glaucoma is a vision-threatening disorder characterized by progressive death of retinal ganglion cells (RGCs), although little is known about therapeutic milestones. Due to its complex and multifactorial pathogenesis, multipronged therapeutic approach is needed. Angiogenin (ANG), now called ribonuclease (RNase) 5, has been previously known as angiogenic factor and more recently its biologic activity is extended to promoting cell survival via its ribonucleolytic activity. Here, we revealed the defect of ANG in human glaucomatous trabecular meshwork (TM) cells and identified novel multiple functions of ANG as an anti-glaucomatous strategy. ANG was highly expressed in normal eyes and normal TM cells compared to glaucomatous TM cells. ANG induced intraocular pressure (IOP) lowering in rat models of both normal and elevated IOP, and as a possible mechanism, activated Akt-mediated signals for nitric oxide (NO) production, an important regulator of IOP in glaucomatous TM cell. Moreover, we demonstrated ANG-induced production of matrix metalloproteinase (MMP)-1 and -3 and rho-kinase inhibition for TM remodeling. For anti-glaucomatous defense optimization, ANG not only elicited immune-modulative pathways via indolamine 2,3-dioxygenase (IDO) activation in TM cells and suppression of Jurkat T cells, but also rescued neural stem cells (NSCs) from apoptosis induced by glaucomatous stress. These results demonstrate that novel multi-functional effects of ANG may have benefits against glaucoma in ocular tissues.

Adoptive transfer of immune cells from glaucomatous mice provokes retinal ganglion cell loss in recipients

INTRODUCTION

Several studies have indicated that autoimmune and neuroinflammatory processes contribute to the neurodegeneration of retinal ganglion cells in human glaucoma patients and in animal models. To test the involvement of cellular immune processes in the pathophysiology of retinal ganglion cell degeneration in vivo, we carried out adoptive transfer experiments from two independent genetic mouse models of glaucoma into normal recipient mice.

RESULTS

Our findings indicate that transfer results in a progressive loss of retinal ganglion cells and their axons despite normal intraocular pressure in recipient mice. Signs of pan-retinal inflammation were not detected. Similar findings were obtained following transfer of isolated T-lymphocytes, but not after transfer of splenocytes from immune deficient glaucomatous mice. Transferred lymphocytes were detected integrated in the spleen and in the retinal ganglion cell layer of recipient animals, albeit at very low frequencies. Furthermore, we observed cell-cell interaction between transferred T-cells and recipient microglia along with focal microglial activation in recipient eyes.

CONCLUSION

This study demonstrates that the pathophysiology of glaucomatous degeneration in the tested animal models includes T-cell mediated events that are capable of causing loss of healthy retinal ganglion cells.

Macro- and microglial responses in the fellow eyes contralateral to glaucomatous eyes

Most studies employing experimental models of unilateral glaucoma have used the normotensive contralateral eye as the normal control. However, some studies have recently reported the activation of the retinal macroglia and microglia in the uninjured eye, suggesting that the eye contralateral to experimental glaucoma should not be used as a control. This review analyzes the studies describing the contralateral findings and discusses some of the routes through which the signals can reach the contralateral eye to initiate the glial reactivation.

T-helper1/T-helper2 cytokine imbalance in the iris of patients with glaucoma

The mechanistic study of glaucoma pathogenesis has shifted to seeking to understand the effects of immune responses on retinal ganglion cell damage and protection. Cytokines mediate the biological effects of the immune system, and our previous study revealed an imbalance of T-helper (Th) 1-derived and Th2-derived cytokines in the serum of patients with glaucoma. In this study, we collected irises from normal individuals and patients with primary open-angle closure (POAG) or chronic angle-closure glaucoma (CACG). We used real-time polymerase chain reaction (PCR) to measure the expression of Th1 (interleukin (IL)-2, interferon-gamma (IFN-γ)), Th2 (IL-4, IL-6, IL-10), and Th3 (transforming growth factor-beta (TGF-β)) cytokines. We then performed immunohistochemical staining to characterize the localization of the upregulated cytokines in iris cryosections. We observed an upward trend in the expression of IL-2 and IFN-γ and a downward trend in IL-6 expression in the iris of POAG and CACG patients. Expression of TGF-β also increased. Immunohistochemistry revealed that IL-2 expression in POAG and CACG patients was localized in the anterior surface of the blood vessel wall in the stroma of the iris, in the cytoplasm of some cells, in the anterior epithelium, and in the posterior pigment epithelium. These findings indicate that immune status differed between the iris tissues of POAG and CACG patients and those of normal individuals. A T-helper cytokine imbalance may modulate the immune microenvironment in glaucomatous eyes and thus influence optic neuropathy.

Interferon-gamma (IFN-γ)-mediated retinal ganglion cell death in human tyrosinase T cell receptor transgenic mouse

We have recently demonstrated the characterization of human tyrosinase TCR bearing h3T-A2 transgenic mouse model, which exhibits spontaneous autoimmune vitiligo and retinal dysfunction. The purpose of current study was to determine the role of T cells and IFN-γ in retina dysfunction and retinal ganglion cell (RGC) death using this model. RGC function was measured by pattern electroretinograms (ERGs) in response to contrast reversal of patterned visual stimuli. RGCs were visualized by fluorogold retrograde-labeling. Expression of CD3, IFN-γ, GFAP, and caspases was measured by immunohistochemistry and Western blotting. All functional and structural changes were measured in 12-month-old h3T-A2 mice and compared with age-matched HLA-A2 wild-type mice. Both pattern-ERGs (42%, p = 0.03) and RGC numbers (37%, p = 0.0001) were reduced in h3T-A2 mice when compared with wild-type mice. The level of CD3 expression was increased in h3T-A2 mice (h3T-A2: 174 ± 27% vs. HLA-A2: 100%; p = 0.04). The levels of effector cytokine IFN-γ were also increased significantly in h3T-A2 mice (h3T-A2: 189 ± 11% vs. HLA-A2: 100%; p = 0.023). Both CD3 and IFN-γ immunostaining were increased in nerve fiber (NF) and RGC layers of h3T-A2 mice. In addition, we have seen a robust increase in GFAP staining in h3T-A2 mice (mainly localized to NF layer), which was substantially reduced in IFN-γ ((-/-)) knockout h3T-A2 mice. We also have seen an up-regulation of caspase-3 and -9 in h3T-A2 mice. Based on our data we conclude that h3T-A2 transgenic mice exhibit visual defects that are mostly associated with the inner retinal layers and RGC function. This novel h3T-A2 transgenic mouse model provides opportunity to understand RGC pathology and test neuroprotective strategies to rescue RGCs.

Biomarkers of primary open-angle glaucoma

Primary open-angle glaucoma (POAG) is a primary neuronal disease of the optic nerve without a definable cause, and is often associated with increased intraocular pressure. Worldwide, POAG is the second leading cause of blindness; there are 45 million people today with POAG and bilateral blindness is present in 4.5 million of these. In order to elucidate the possible etiologic factors in POAG, we have cataloged all known biomarkers in the aqueous humor, trabecular meshwork, optic nerve and blood into four categories, namely extracellular matrix (ECM), cell signaling molecules, aging/stress and immunity-related changes. We present a theoretical model to show possible signaling pathways of the ECM, cell signaling and innate immune response through activation of Toll-like receptor 4. Our article suggests that ECM and innate immune biomarkers are the lead candidates for developing the 'POAG biomarker signature'. We suggest that current research is critical to pinpoint the causes of the disease so that new treatment modalities can become available for better regulation of the intraocular pressure and neuroprotection of the optic nerve.

Western blot patterns of serum autoantibodies against optic nerve antigens in dogs with goniodysgenesis-related glaucoma

OBJECTIVE

To investigate whether differences existed between clinically normal dogs and dogs with goniodysgenesis-related glaucoma (GDRG) in serum autoantibodies against optic nerve antigens.

ANIMALS

16 dogs with GDRG, 17 healthy dogs with unremarkable pectinate ligament and iridocorneal angle morphology, and 13 euthanized dogs with no major ocular abnormalities or underlying diseases.

PROCEDURES

Western blotting was performed with optic nerve extracts from the euthanized dogs as an antigen source and serum from clinically normal dogs and dogs with GDRG as a primary antibody (autoantibody) source. Blots were evaluated for presence and density of bands.

RESULTS

Multiple bands were identified on western blots from all dogs with GDRG and all clinically normal dogs, with a high degree of variability among individual dogs. Dogs with GDRG were significantly more likely than healthy dogs to have bands present at 38, 40, and 68 kDa. Dogs with GDRG had significant increases in autoreactivity at 40 and 53 kDa and a significant decrease in autoreactivity at 48 kDa.

CONCLUSIONS AND CLINICAL RELEVANCE

Significant differences in serum autoantibodies against optic nerve antigens were found in dogs with versus without GDRG. Although it remains unclear whether these differences were part of the pathogenesis of disease or were sequelae to glaucomatous changes, these findings provide support for the hypothesis that immune-mediated mechanisms play a role in the development or progression of GDRG. However, the high degree of variability among individual dogs and the considerable overlap between groups suggest that the clinical usefulness of this technique for distinguishing dogs with GDRG from clinically normal dogs is likely limited.

CD4 positive T helper cells contribute to retinal ganglion cell death in mouse model of ischemia reperfusion injury

Neuron degeneration is a common pathological process associated with many disease conditions in the central nervous system including retina. Although immune responses have been proposed as one potential element in triggering neural damage, the mechanism of action of specific immune components underlying the pathogenesis is unclear. In this study we focus on adaptive immune activities to evaluate CD4 positive helper cells in the retinal ganglion cell (RGC) degeneration in response to transient retinal ischemic/reperfusion (I/R) injury. Transient retinal ischemia was induced in four mouse strains with different immune backgrounds, including wild type mice from C57BL/6 and BABL/c strains, severe combined immunodeficient (SCID) mice lacking T and B lymphocytes, SCID mice with transferred wild type CD4+ T cells, and the STAT6 deficient mice without T helper 2 (TH2) cells. In SCID mice RGCs showed a strong resistance to cell death in response to I/R injury (89% ± 3% of the survival cells in contralateral eye) compared with C57BL/6 (p = 0.018) and BALB/C (p = 0.038) wild types. By transferring the mature CD4+ T cells from matched wild type into SCID mice, the resistance of RGCs to injury was significantly compromised (p < 0.05). Furthermore a significant resistance of RGCs to cell death (p < 0.05) accompanied with an overexpression of STAT1 and STAT3 was confirmed in STAT6 deficient mice in response to I/R injury compared with the wild type controls, indicating that TH2 cells maturation might be involved in RGC damage. Adaptive immunity carried by CD4 T cells plays an essential role in RGC degeneration.

Immune regulation toward immunomodulation for neuroprotection in glaucoma

Although the immune system functions to preserve and restore tissue homeostasis, accumulating risk factors, prolonged glial activation, and sustained release of pro-inflammatory mediators in glaucoma may lead to a failure in the regulation of stress-induced immune response, and innate immune cells, autoreactive T cells, autoantibodies, and excess complement attack may exhibit potent stimuli that harm retinal ganglion cell somas, axons, and synapses. Identification of the cellular and molecular components of immune response pathways can provide immunomodulatory treatment strategies to attenuate neuroinflammation, protect neural tissue from collateral injury, and enhance endogenous recovery processes. This review highlights the current knowledge of molecular mechanisms regulating neuroinflammation in glaucoma.