Pathological high intraocular pressure induces glial cell reactive proliferation contributing to neuroinflammation of the blood-retinal barrier via the NOX2/ET-1 axis-controlled ERK1/2 pathway.

BACKGROUND: NADPH oxidase (NOX), a primary source of endothelial reactive oxygen species (ROS), is considered a key event in disrupting the integrity of the blood-retinal barrier. Abnormalities in neurovascular-coupled immune signaling herald the loss of ganglion cells in glaucoma. Persistent microglia-driven inflammation and cellular innate immune system dysregulation often lead to deteriorating retinal degeneration. However, the crosstalk between NOX and the retinal immune environment remains unresolved. Here, we investigate the interaction between oxidative stress and neuroinflammation in glaucoma by genetic defects of NOX2 or its regulation via gp91ds-tat. METHODS: Ex vivo cultures of retinal explants from wildtype C57BL/6J and Nox2 -/- mice were subjected to normal and high hydrostatic pressure (Pressure 60 mmHg) for 24 h. In vivo, high intraocular pressure (H-IOP) was induced in C57BL/6J mice for two weeks. Both Pressure 60 mmHg retinas and H-IOP mice were treated with either gp91ds-tat (a NOX2-specific inhibitor). Proteomic analysis was performed on control, H-IOP, and treatment with gp91ds-tat retinas to identify differentially expressed proteins (DEPs). The study also evaluated various glaucoma phenotypes, including IOP, retinal ganglion cell (RGC) functionality, and optic nerve (ON) degeneration. The superoxide (O2-) levels assay, blood-retinal barrier degradation, gliosis, neuroinflammation, enzyme-linked immunosorbent assay (ELISA), western blotting, and quantitative PCR were performed in this study. RESULTS: We found that NOX2-specific deletion or activity inhibition effectively attenuated retinal oxidative stress, immune dysregulation, the internal blood-retinal barrier (iBRB) injury, neurovascular unit (NVU) dysfunction, RGC loss, and ON axonal degeneration following H-IOP. Mechanistically, we unveiled for the first time that NOX2-dependent ROS-driven pro-inflammatory signaling, where NOX2/ROS induces endothelium-derived endothelin-1 (ET-1) overexpression, which activates the ERK1/2 signaling pathway and mediates the shift of microglia activation to a pro-inflammatory M1 phenotype, thereby triggering a neuroinflammatory outburst. CONCLUSIONS: Collectively, we demonstrate for the first time that NOX2 deletion or gp91ds-tat inhibition attenuates iBRB injury and NVU dysfunction to rescue glaucomatous RGC loss and ON axon degeneration, which is associated with inhibition of the ET-1/ERK1/2-transduced shift of microglial cell activation toward a pro-inflammatory M1 phenotype, highlighting NOX2 as a potential target for novel neuroprotective therapies in glaucoma management.

Bioinformatics-Based Screening of Key LncRNAs for Modulating the Transcriptome Associated with Glaucoma in Human Trabecular Meshwork Cells.

OBJECTIVE: The morphology and functions of the human trabecular meshwork (HTM) are dysregulated in glaucoma, and the molecular mechanisms of this dysregulation remain unknown. According to an established in vitro model, whose function was to study the regulatory networks sustaining the response of HTM cells to the increased substrate stiffness, we systematically analyzed the expression pattern of long noncoding RNAs (lncRNAs), the important regulatory RNAs in cells. METHODS: Bioinformatics analysis was performed to identify the dysregulated lncRNAs in response to increased substrate stiffness using transcriptome sequencing data (RNA-seq). Then we interfered with the expression of several dysregulated lncRNAs in HTM cells to explore their molecular targets. The cross-linking immunoprecipitation and sequencing method (CLIP-seq) was used to identify enhancer of zeste homolog 2 (EZH2)-targeted RNAs in HTM cells. The chromatin IP and sequencing method (ChIP-seq) was used to identify the targets of EZH2 and histone H3 at lysine 27 (H3K27me3). RESULTS: The response of thousands of dysregulated lncRNAs to increased substrate stiffness was identified through RNA-seq. Functional prediction of these lncRNAs revealed that they potentially regulated key biological processes, including extracellular matrix (ECM) organization. By interfering with the expression of lncRNA SHNG8, ZFHX4-AS1, and RP11-552M11.4, the results demonstrated that those lncRNAs extensively regulated the expression levels of ECM-associated genes. Moreover, we found that EZH2 expression was significantly decreased at high substrate stiffness. Using CLIP-seq to identify EZH2-targeted RNAs in HTM cells, we found that SNHG8 was bound by EZH2. According to the CLIP-seq data of EZH2, we found that EZH2 binding sites were observed in the transcripts of SNHG8-regulated genes, but not in the ChIP-seq results of EZH2 and H3K27me3. CONCLUSION: Our results suggest that SNHG8 and EZH2 may cooperate to regulate the expression of a subset of genes by influencing their RNA abundance, explaining how they support HTM cell morphology and high density. This study contributes to the understanding of the alteration of HTM during the progression of glaucoma by identifying functional lncRNAs, especially SNHG8, and suggests novel therapeutic targets to treat glaucoma.

Intraocular pressure across the lifespan of Tg-MYOCY437H mice.

Transgenic C57BL/6 mice expressing human myocilinY437 (Tg-MYOCY437H) are a well-established model for primary open-angle glaucoma (POAG). While the reduced trabecular meshwork (TM) cellularity due to severe endoplasmic reticulum (ER) stress has been characterized as the etiology of this model, there is a limited understanding of how glaucomatous phenotypes evolve over the lifespan of Tg-MyocY437H mice. In this study, we compiled the model's intraocular pressure (IOP) data recorded in our laboratory from 2017 to 2023 and selected representative eyes to measure the outflow facility (Cr), a critical parameter indicating the condition of the conventional TM pathway. We found that Tg-MYOCY437H mice aged 4-12 months exhibited significantly higher IOPs than age-matched C57BL/6 mice. Notably, a decline in IOP was observed in Tg-MYOCY437H mice at 17-24 months of age, a phenomenon not attributable to the gene dosage of mutant myocilin. Measurements of the Cr of Tg-MYOCY437H mice indicated that the age-related IOP reduction was not a result of ongoing TM damage. Instead, Hematoxylin and Eosin staining, immunohistochemistry analysis, and transmission electron microscopic examination revealed that this reduction might be induced by degenerations of the non-pigmented epithelium in the ciliary body of aged Tg-MYOCY437H mice. Overall, our findings provide a comprehensive profile of mutant myocilin-induced ocular changes over the Tg-MYOCY437H mouse lifespan and suggest a specific temporal window of elevated IOP that may be ideal for experimental purposes.

Differential Effects of Benzalkonium Chloride on Human Trabecular Meshwork Cells Not Treated or Treated with Transforming Growth Factor-ß2 or Dexamethasone.

Purpose: The objective of the present study was to evaluate the effects of low concentrations of benzalkonium chloride (BAC) (10-7%, 10-6%, or 10-5%) on healthy and glaucomatous human trabecular meshwork (HTM) cells. For this purpose, we used in vitro models replicating a healthy HTM and HTM with primary open-angle glaucoma (POAG) or steroid-induced glaucoma (SG) using two-dimensional (2D) cultures of HTM cells not treated or treated with a 5 ng/mL solution of transforming growth factor-ß2 or 250 nM dexamethasone (DEX). Methods: Analyses were carried out for (1) the intercellular affinity function of 2D HTM monolayers, as determined by transepithelial electrical resistance (TEER) measurements; (2) cell viability; (3) cellular metabolism by using a Seahorse bioanalyzer; and (4) expression of extracellular matrix (ECM) molecules, an ECM modulator, and cell junction-related molecules. Results: In the absence and presence of BAC (10-7% or 10-5%), intercellular affinity function determined by TEER and cellular metabolic activities were significantly and dose dependently affected in both healthy and glaucomatous HTM cells despite the fact that there was no significant decrease in cell viabilities. However, the effects based on TEER values were significantly greater in the healthy HTM. The mRNA expression of several molecules that were tested was not substantially modulated by these concentrations of BAC. Conclusions: The findings reported herein suggest that low concentrations of BAC may have unfavorable adverse effects on cellular metabolic capacity by inducing increases in the intercellular affinity properties of the HTM, but those effects of BAC were different in healthy and glaucomatous HTM cells.

Lysyl oxidase like-1 deficiency in optic nerve head astrocytes elicits reactive astrocytosis and alters functional effects of astrocyte derived exosomes.

Glaucoma is a multifactorial progressive ocular pathology that manifests clinically with damage to the optic nerve (ON) and the retina, ultimately leading to blindness. The optic nerve head (ONH) shows the earliest signs of glaucoma pathology, and therefore, is an attractive target for drug discovery. The goal of this study was to elucidate the effects of reactive astrocytosis on the elastin metabolism pathway in primary rat optic nerve head astrocytes (ONHA), the primary glial cell type in the unmyelinated ONH. Following exposure to static equibiaxial mechanical strain, we observed prototypic molecular and biochemical signatures of reactive astrocytosis that were associated with a decrease in lysyl oxidase like 1 (Loxl1) expression and a concomitant decrease in elastin (Eln) gene expression. We subsequently investigated the role of Loxl1 in reactive astrocytosis by generating primary rat ONHA cultures with ∼50% decreased Loxl1 expression. Our results suggest that reduced Loxl1 expression is sufficient to elicit molecular signatures of elastinopathy in ONHA. Astrocyte derived exosomes (ADE) significantly increased the length of primary neurites of primary neurons in vitro. In contrast, ADE from Loxl1-deficient ONHA were deficient of trophic effects on neurite outgrowth in vitro, positing that Loxl1 dysfunction and the ensuing impaired elastin synthesis during reactive astrocytosis in the ONH may contribute to impaired neuron-glia signaling in glaucoma. Our data support a role of dysregulated Loxl1 function in eliciting reactive astrocytosis in glaucoma subtypes associated with increased IOP, even in the absence of genetic polymorphisms in LOXL1 typically associated with exfoliation glaucoma. This suggests the need for a paradigm shift toward considering lysyl oxidase activity and elastin metabolism and signaling as contributors to an altered secretome of the ONH that may lead to the progression of glaucomatous changes. Future research is needed to investigate cargo of exosomes in the context of reactive astrocytosis and identify the pathways leading to the observed transcriptome changes during reactive astrocytosis.

The Role of Complement Dysregulation in Glaucoma.

Glaucoma is a progressive neurodegenerative disease characterized by damage to the optic nerve that results in irreversible vision loss. While the exact pathology of glaucoma is not well understood, emerging evidence suggests that dysregulation of the complement system, a key component of innate immunity, plays a crucial role. In glaucoma, dysregulation of the complement cascade and impaired regulation of complement factors contribute to chronic inflammation and neurodegeneration. Complement components such as C1Q, C3, and the membrane attack complex have been implicated in glaucomatous neuroinflammation and retinal ganglion cell death. This review will provide a summary of human and experimental studies that document the dysregulation of the complement system observed in glaucoma patients and animal models of glaucoma driving chronic inflammation and neurodegeneration. Understanding how complement-mediated damage contributes to glaucoma will provide opportunities for new therapies.

Somatic Mutations within Myocilin due to Aging May Be a Potential Risk Factor for Glaucoma.

Glaucoma is a chronic optic neuropathy that leads to irreversible vision loss. Aging and family history are the two most important risk factors of glaucoma. One of the most studied genes involved in the onset of open-angle glaucoma is myocilin (MYOC). About 105 germline mutations within MYOC are known to be associated with glaucoma and result in endoplasmic reticulum (ER) stress, which leads to trabecular meshwork (TM) cell death and subsequent intraocular pressure (IOP) elevation. However, only about 4% of the population carry these mutations. An analysis of MYOC somatic cancer-associated mutations revealed a notable overlap with pathogenic glaucoma variants. Because TM cells have the potential to accumulate somatic mutations at a rapid rate due to ultraviolet (UV) light exposure, we propose that an accumulation of somatic mutations within MYOC is an important contributor to the onset of glaucoma.

SOX9 depletion attenuates retinal ganglion cell ferroptosis through blocking ERK/p38 signaling.

BACKGROUND: Retinal ischemia-refusion (I/R) is a leading cause of irreversible blindness worldwide. This study aims to explore the regulatory role of SOX9 in retinal I/R injury, and attempts to elucidate its potential regulatory mechanism. METHODS: Retinal I/R injury model was established in vivo, and the histological changes was examined by hematoxylin and eosin (H&E) staining and immunofluorescent assay was performed to examine SOX9 expression. Oxygenation-glucose deprivation/reoxygenation (OGD/R)-induced retinal ischemia/reperfusion (I/R) injury in 661 W cells was constructed as an in vitro cellular model of glaucoma. The production of cytokines, lactate dehydrogenase (LDH) and the antioxidant enzymes were assessed by their commercial kits. Cellular reactive oxygen species (ROS) and lipid ROS was detected using DCFH-DA and C11-BODIPY 581/591 staining, respectively. Lipid peroxidation and Fe2+ level were detected to assess the ferroptosis level. Protein expression was examined by western blot. LM22B-10, the agonist of ERK signaling, was used to pretreat 661 W cells for mechanism investigation. RESULTS: SOX9 was aberrantly upregulated following retinal I/R injury both in vivo and in vitro. SOX9 knockdown exerted a protective role against OGD/R-triggered oxidative stress, inflammatory response and ferroptosis in 661 W cells. Further, ERK/p38 signaling was activated in 661 W cells following OGD/R induction, which was repressed by SOX9 knockdown, and the ERK signaling agonist partially counteracted the protective role of SOX9 knockdown against oxidative stress, inflammatory response and ferroptosis in OGD/R-induced 661 W cells. CONCLUSION: Collectively, inhibiting SOX9 to block oxidative stress, inflammation and ferroptosis by inactivating ERK/p38 signaling might be effective to prevent retinal I/R injury, thereby alleviating glaucoma.

Influence of the calcium voltage-gated channel auxiliary subunit (CACNA2D1) absence on intraocular pressure in mice.

The etiology of elevated intraocular pressure (IOP), a major risk factor for glaucoma (optic nerve atrophy), is poorly understood despite continued efforts. Although the gene variant of CACNA2D1 (encoding α2δ1), a calcium voltage-gated channel auxiliary subunit, has been reported to be associated with primary open-angle glaucoma, and the pharmacological mitigation of α2δ1 activity by pregabalin lowers IOP, the cellular basis for α2δ1 role in the modulation of IOP remains unclear. Our recent findings reveled readily detectable levels of α2δ1 and its ligand thrombospondin in the cytoskeletome fraction of human trabecular meshwork (TM) cells. To understand the direct role of α2δ1 in the modulation of IOP, we evaluated α2δ1 null mice for changes in IOP and found a moderate (∼10%) but significant decrease in IOP compared to littermate wild type control mice. Additionally, to gain cellular insights into α2δ1 antagonist (pregabalin) induced IOP changes, we assessed pregabalin's effects on human TM cell actin cytoskeletal organization and cell adhesive interactions in comparison with a Rho kinase inhibitor (Y27632), a known ocular hypotensive agent. Unlike Y27632, pregabalin did not have overt effects on cell morphology, actin cytoskeletal organization, or cell adhesion in human TM cells. These results reveal a modest but significant decrease in IOP in α2δ1 deficient mice, and this response appears to be not associated with the contractile and cell adhesive characteristics of TM cells based on the findings of pregabalin effects on isolated TM cells. Therefore, the mechanism by which pregabalin lowers IOP remains elusive.

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.

Genistein stimulates the viability and prevents myofibroblastic transformation in human trabecular meshwork cells stimulated by TGF-ß.

Primary open-angle glaucoma (POAG) is the most common type of glaucoma leading to blindness. The search for ways to prevent/treat this entity is one of the main challenges of today's ophthalmology. One of such solution seems to be biologically active substances of natural origin, such as genistein (GEN), which can affect the function of isolated trabecular meshwork by the inhibition of protein tyrosine kinase. However, the role of GEN in viability as well as myofibroblastic transformation in human trabecular meshwork cells stimulated by TGF-ß is unknown. Using human trabecular meshwork cells (HTMCs) we investigated the effect of genistein on cell viability and myofibroblastic transformation stimulated by TGF-ß1 and TGF-ß2. Using Real-Time PCR, western blot and immunofluorescence we determined the effect on the expression changes of αSMA, TIMP1, collagen 1 and 3 at mRNA and protein level. We found that genistein increases the viability of HTMCs (1, 2, 3 µg/ml; P < 0.05 and 4, 5, 10, 15, 20 µg/ml; P < 0.01). Moreover, we found that addition of 10, 15 and 20 µg/ml is able to prevent myofibroblastic transformation of HTMCs by decreasing αSMA, TIMP1, collagen 1 and 3 mRNA and protein expression (P < 0.01). Based on the obtained results, we can conclude that genistein is a potential factor that can prevent the myofibroblastic transformation of HTMCs accompanying glaucoma. Describing GEN influence on myofibroblastic transformation processes in HTMC allows us to conclude that it can be considered a potential therapeutic agent or a substance supporting treatment in patients with glaucoma.

Cytokine Profiling in Aqueous Humor of Glaucoma Patients and in Retinas from an Ex Vivo Glaucoma Animal Model.

BACKGROUND: Although the current role of cytokines and neuroinflammation in glaucoma remains obscure, it represents an expanding field in research. The purpose of this study was to analyze cytokines in the aqueous humor (AH) of glaucoma patients and in retinas from an ex vivo glaucoma animal model, to aid in determining the role of neuroinflammation in glaucoma. METHODS: AH samples were collected from 20 patients during cataract surgeries (controls: n = 10, age = 70.3 ± 9.742; glaucoma: n = 10, age: 66.5 ± 8.073) in Shanghai East Hospital, an affiliate of Tongji University, between September 2018 and March 2019 and analyzed in duplicate by Luminex cytokine polystyrene color bead-based multiplex assay. Retinas from female Sprague-Dawley rats (n = 6) were harvested ex vivo and cultured with or without 60 mmHg of hydrostatic pressure for 24 hours. Retinal ganglion cells (RGCs) were quantified using Brn3a staining. Cytokines in the retina and culture medium were analyzed by rat cytokine array (Abcam). RESULTS: At baseline, patients with primary angle closure glaucoma (PACG) have significantly lower levels of IL-6 and IP-10 and a higher level of PDGF-BB in their AH, compared to the controls. Postoperatively, patients with PACG have significantly higher levels of IL-1ra, IL-13, and MIP-1α and a lower level of IL-6. Elevated hydrostatic pressure led to significant RGC loss in the retina, ex vivo, as well as the upregulation of ciliary neurotrophic factor (CNTF), IL-6, IL-10, IL-4, and TIMP-1 alongside the downregulation of PDGF-AA, MMP-8, TNF-α, and IFN-γ. Furthermore, eight cytokines were detected as being downregulated in the culture medium, including PDGF-AA, MMP-8, and IL-4. CONCLUSIONS: Proinflammatory cytokines showed changes in both AH and ex vivo. Further studies are needed on the role of these cytokines and their corresponding signaling pathways in both neurodegeneration and glaucoma.

Lipid mediators in glaucoma: Unraveling their diverse roles and untapped therapeutic potential.

Glaucoma is a complex neurodegenerative disease characterized by optic nerve damage and visual field loss, and remains a leading cause of irreversible blindness. Elevated intraocular pressure (IOP) is a critical risk factor that requires effective management. Emerging research underscores dual roles of bioactive lipid mediators in both IOP regulation, and the modulation of neurodegeneration and neuroinflammation in glaucoma. Bioactive lipids, encompassing eicosanoids, specialized pro-resolving mediators (SPMs), sphingolipids, and endocannabinoids, have emerged as crucial players in these processes, orchestrating inflammation and diverse effects on aqueous humor dynamics and tissue remodeling. Perturbations in these lipid mediators contribute to retinal ganglion cell loss, vascular dysfunction, oxidative stress, and neuroinflammation. Glaucoma management primarily targets IOP reduction via pharmacological agents and surgical interventions, with prostaglandin analogues at the forefront. Intriguingly, additional lipid mediators offer promise in attenuating inflammation and providing neuroprotection. Here we explore these pathways to shed light on their intricate roles, and to unveil novel therapeutic avenues for glaucoma management.

AIBP: A New Safeguard against Glaucomatous Neuroinflammation.

Glaucoma is a group of ocular diseases that cause irreversible blindness. It is characterized by multifactorial degeneration of the optic nerve axons and retinal ganglion cells (RGCs), resulting in the loss of vision. Major components of glaucoma pathogenesis include glia-driven neuroinflammation and impairment of mitochondrial dynamics and bioenergetics, leading to retinal neurodegeneration. In this review article, we summarize current evidence for the emerging role of apolipoprotein A-I binding protein (AIBP) as an important anti-inflammatory and neuroprotective factor in the retina. Due to its association with toll-like receptor 4 (TLR4), extracellular AIBP selectively removes excess cholesterol from the plasma membrane of inflammatory and activated cells. This results in the reduced expression of TLR4-associated, cholesterol-rich lipid rafts and the inhibition of downstream inflammatory signaling. Intracellular AIBP is localized to mitochondria and modulates mitophagy through the ubiquitination of mitofusins 1 and 2. Importantly, elevated intraocular pressure induces AIBP deficiency in mouse models and in human glaucomatous retina. AIBP deficiency leads to the activation of TLR4 in Müller glia, triggering mitochondrial dysfunction in both RGCs and Müller glia, and compromising visual function in a mouse model. Conversely, restoring AIBP expression in the retina reduces neuroinflammation, prevents RGCs death, and protects visual function. These results provide new insight into the mechanism of AIBP function in the retina and suggest a therapeutic potential for restoring retinal AIBP expression in the treatment of glaucoma.

Protective effect of the natural flavonoid naringenin in mouse models of retinal injury.

Glaucoma is an eye disease with a high rate of blindness and a complex pathogenesis. Ocular hypertension (OHT) is a critical risk factor, and retinal ischemia/reperfusion (I/R) is an important pathophysiological basis. This study was designed to investigate the retinal neuroprotective effect of oral naringenin in an acute retinal I/R model and a chronic OHT model and the possible mechanism involved. After the I/R and OHT models were established, mice were given vehicle or naringenin (100 mg/kg or 300 mg/kg). Hematoxylin-eosin (HE) staining and immunostaining of RBPMS and glial fibrillary acidic protein (GFAP) were used to evaluate retinal injury. GFAP, CD38, Sirtuin1 (SIRT1), and NOD-like receptor protein 3 (NLRP3) expression levels were measured by Western blotting. In the OHT model, intraocular pressure (IOP) was dynamically maintained at approximately 20-25 mmHg after injury. The retinal structure was damaged, and retinal ganglion cells (RGCs) were lost in both models. Naringenin ameliorated the abovementioned indications but also demonstrated that high concentrations of naringenin significantly inhibited retinal astrocyte activation and inhibited damage-induced increases in the expression of GFAP, NLRP3, and CD38 proteins, while SIRT1 protein expression was upregulated. This study showed for the first time that naringenin can reduce microbead-induced IOP elevation in the OHT model, providing new evidence for the application of naringenin in glaucoma. Naringenin may mediate the CD38/SIRT1 signaling pathway, inhibit astrocyte activation, and ultimately exert an anti-inflammatory effect to achieve retinal neuroprotection.

A new model of axon degeneration in the mouse optic nerve using repeat intraocular pressure challenge.

We characterize a new experimental model for inducing retinal ganglion cell (RGC) dysfunction and degeneration in mice. C57BL/6J mice were subjected to two acute periods of intraocular pressure (IOP) elevation (50 mmHg for 30 min) by cannulation of the anterior chamber. We used full-field electroretinography and visual evoked potentials (VEPs) to measure subsequent changes in retina and optic nerve function, and histochemical techniques to assess RGC survival and optic nerve structure. In 12 month old mice, a single IOP challenge caused loss and subsequent recovery of RGC function over the following 28 days with minimal cell death and no observed axonal damage. A second identical IOP challenge resulted in persistent RGC dysfunction and significant (36%) loss of RGC somas. This was accompanied by a 16.7% delay in the latency and a 27.6% decrease in the amplitude of the VEP. Severe axonal damage was seen histologically with enlargement of axons, myelin disruption, reduced axon density, and the presence of glial scarring. In contrast, younger 3 month old mice when exposed to a single or repeat IOP challenge showed quicker RGC functional recovery after a single challenge and full functional recovery after a repeat challenge with no detectable optic nerve dysfunction. These data demonstrate a highly reproducible and minimally invasive method for inducing RGC degeneration and axonal damage in mice. Resilience of the optic nerve to damage is highly dependent on animal age. The time-defined nature of functional versus structural loss seen in this model stands to facilitate investigation of neuroglial responses in the retina after IOP injury and the associated evaluation of neuroprotective treatment strategies. Further, the model may be used to investigate the impact of aging and the cellular switch between neurorecovery and neurodegeneration.

Segmental biomechanics of the normal and glaucomatous human aqueous outflow pathway.

The conventional aqueous outflow pathway, encompassing the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and inner wall endothelium of Schlemm's canal (SC), governs intraocular pressure (IOP) regulation. This study targets the biomechanics of low-flow (LF) and high-flow (HF) regions within the aqueous humor outflow pathway in normal and glaucomatous human donor eyes, using a combined experimental and computational approach. LF and HF TM/JCT/SC complex tissues from normal and glaucomatous eyes underwent uniaxial tensile testing. Dynamic motion of the TM/JCT/SC complex was recorded using customized green-light optical coherence tomography during SC pressurization in cannulated anterior segment wedges. A hyperviscoelastic model quantified TM/JCT/SC complex properties. A fluid-structure interaction model simulated tissue-aqueous humor interaction. FluoSpheres were introduced into the pathway via negative pressure in the SC, with their motion tracked using two-photon excitation microscopy. Tensile test results revealed that the elastic moduli of the LF and HF regions in glaucomatous eyes are 3.5- and 1.5-fold stiffer than the normal eyes, respectively. The FE results also showed significantly larger shear moduli in the TM, JCT, and SC of the glaucomatous eyes compared to the normal subjects. The LF regions in normal eyes demonstrated larger elastic moduli compared to the HF regions in glaucomatous eyes. The resultant strain in the outflow tissues and velocity of the aqueous humor in the FSI models were in good agreement with the digital volume correlation and 3D particle image velocimetry data, respectively. This study uncovers stiffer biomechanical responses in glaucomatous eyes, with LF regions stiffer than HF regions in both normal and glaucomatous eyes. STATEMENT OF SIGNIFICANCE: This study delves into the biomechanics of the conventional aqueous outflow pathway, a crucial regulator of intraocular pressure and ocular health. By analyzing mechanical differences in low-flow and high-flow regions of normal and glaucomatous eyes, this research unveils the stiffer response in glaucomatous eyes. The distinction between regions' properties offers insights into aqueous humor outflow regulation, while the integration of experimental and computational methods enhances credibility. These findings have potential implications for disease management and present a vital step toward innovative ophthalmic interventions. This study advances our understanding of glaucoma's biomechanical basis and its broader impact on ocular health.

Rho Kinase (ROCK) Inhibitors for the Treatment of Glaucoma.

Glaucoma is the most common cause of irreversible blindness worldwide. It is characterized by progressive optic nerve degeneration and loss of visual field. Pathological increased intraocular pressure is its main modifiable risk factor. Rho kinase inhibitors are developed as a new class of glaucoma medication that increases outflow facility from the conventional aqueous humor outflow pathway. Additionally, they also have neuroprotective and anti-scarring effects that can might increase the success rate of glaucoma filtration surgery. This review aims to summarize the current concept of Rho kinase inhibitors in the treatment of glaucoma from beach to bedside.

Vitamin B3 Supplementation for Optic Neuropathies: A Comprehensive Review.

Optic neuropathies, such as glaucoma, are some of the leading causes of irreversible blindness worldwide. There has been a lot of research for potential therapies that could attenuate and even reduce the impact of the pathological pathways that lead to the loss of retinal ganglion cells (RGCs). In recent years, vitamin B3 (nicotinamide) has gained some interest as a viable option for these neurodegenerative diseases due to its fundamental role in enhancing the mitochondria metabolism of the RGCs. This review focuses on elucidating the impact of vitamin B3 on retinal cells, especially when in a dysfunctional state like what happens in optic neuropathies, especially glaucoma. This review also summarizes the existing and future research on the clinical effects of vitamin B3 in these optic neuropathies, and determines appropriate recommendations regarding its dosing, efficacy, and eventual side effects.

Setanaxib mitigates oxidative damage following retinal ischemia-reperfusion via NOX1 and NOX4 inhibition in retinal ganglion cells.

Glaucoma, a prevalent cause of permanent visual impairment worldwide, is characterized by the progressive degeneration of retinal ganglion cells (RGCs). NADPH oxidase (NOX) 1 and NOX4 are pivotal nodes in various retinal diseases. Setanaxib, a potent and highly selective inhibitor of NOX1 and NOX4, can impede the progression of various diseases. This study investigated the efficacy of setanaxib in ameliorating retinal ischemia-reperfusion (I/R) injury and elucidated its underlying mechanisms. The model of retinal I/R induced by acute intraocular hypertension and the oxygen-glucose deprivation/reoxygenation (OGD/R) model of primary RGCs were established. By suppressing NOX1 and NOX4 expression in RGCs, setanaxib mitigated I/R-induced retinal neuronal loss, structural disruption, and dysfunction. Setanaxib reduced TUNEL-positive cells, upregulated Bcl-2, and inhibited Bax, Bad, and cleaved-caspase-3 overexpression after I/R injury in vitro and in vivo. Moreover, setanaxib also significantly reduced cellular senescence, as demonstrated by downregulating SA-ß-gal-positive and p16-INK4a expression. Furthermore, setanaxib significantly suppressed ROS production, Hif-1α and FOXO1 upregulation, and NRF2 downregulation in damaged RGCs. These findings highlight that the setanaxib effectively inhibited NOX1 and NOX4, thereby regulating ROS production and redox signal activation. This inhibition further prevents the activation of apoptosis and senescence related factors in RGCs, ultimately protecting them against retinal I/R injury. Consequently, setanaxib exhibits promising potential as a therapeutic intervention for glaucoma.