Neuroprotective agents in the management of glaucoma

The potential impact of a vegetarian diet on glaucoma

Treatment of primary open-angle glaucoma has centered on the lowering of intraocular pressure that damages the optic nerve; however, this strategy is not uniformly successful, especially in normal tension glaucoma, and there is interest in antioxidant, anti-inflammatory, and other neuroprotective strategies. Vegetarian diets are known to be rich in antioxidant and anti-inflammatory components and have a number of established health benefits. Thus, it would be reasonable to assume that vegetarian diets would be beneficial in glaucoma, but this approach has not been well studied. We examine the possible role of vegetarian diets and their components in the incidence and progression of glaucoma.

Dysregulation of neuroprotective lipoxin pathway in astrocytes in response to cytokines and ocular hypertension​

Glaucoma leads to vision loss due to retinal ganglion cell death. Astrocyte reactivity contributes to neurodegeneration. Our recent study found that lipoxin B4 (LXB4), produced by retinal astrocytes, has direct neuroprotective actions on retinal ganglion cells. In this study, we aimed to investigate how the autacoid LXB4 influences astrocyte reactivity in the retina under inflammatory cytokine-induced activation and during ocular hypertension. The protective activity of LXB4 was investigated in vivo using the mouse silicone-oil model of chronic ocular hypertension. By employing a range of analytical techniques, including bulk RNA-seq, RNAscope in-situ hybridization, qPCR, and lipidomic analyses, we discovered the formation of lipoxins and expression of the lipoxin pathway in rodents (including the retina and optic nerve), primates (optic nerve), and human brain astrocytes, indicating the presence of this neuroprotective pathway across various species. Findings in the mouse retina identified significant dysregulation of the lipoxin pathway in response to chronic ocular hypertension, leading to an increase in 5-lipoxygenase (5-LOX) activity and a decrease in 15-LOX activity. This dysregulation was coincident with a marked upregulation of astrocyte reactivity. Reactive human brain astrocytes also showed a significant increase in 5-LOX. Treatment with LXB4 amplified the lipoxin biosynthetic pathway by restoring and amplifying the generation of another member of the lipoxin family, LXA4, and mitigated astrocyte reactivity in mouse retinas and human brain astrocytes. In conclusion, the lipoxin pathway is functionally expressed in rodents, primates, and human astrocytes, and is a resident neuroprotective pathway that is downregulated in reactive astrocytes. Novel cellular targets for LXB4's neuroprotective action are inhibition of astrocyte reactivity and restoration of lipoxin generation. Amplifying the lipoxin pathway is a potential target to disrupt or prevent astrocyte reactivity in neurodegenerative diseases, including retinal ganglion cell death in glaucoma.

Navigating the Unknown: A Comprehensive Review of Spaceflight-Associated Neuro-Ocular Syndrome

Spaceflight-associated neuro-ocular syndrome (SANS) is a complex and multifaceted condition that affects astronauts during and after their missions in space. This comprehensive review delves into the various aspects of SANS, providing a thorough understanding of its definition, historical context, clinical presentation, epidemiology, diagnostic techniques, preventive measures, and management strategies. Various ocular and neurological symptoms, including visual impairment, optic disc edema, choroidal folds, retinal changes, and increased intracranial pressure, characterize SANS. While microgravity is a primary driver of SANS, other factors like radiation exposure, genetic predisposition, and environmental conditions within spacecraft contribute to its development. The duration of space missions is a significant factor, with longer missions associated with a higher incidence of SANS. This review explores the diagnostic criteria and variability in SANS presentation, shedding light on early detection and management challenges. The epidemiology section provides insights into the occurrence frequency, affected astronauts' demographics, and differences between long-term and short-term missions. Diagnostic tools, including ophthalmological assessments and imaging techniques, are crucial in monitoring astronaut health during missions. Preventive measures are vital in mitigating the impact of SANS. Current strategies, ongoing research in prevention methods, lifestyle and behavioral factors, and the potential role of artificial gravity are discussed in detail. Additionally, the review delves into interventions, potential pharmacological treatments, rehabilitation, and long-term management considerations for astronauts with SANS. The conclusion underscores the importance of continued research in SANS, addressing ongoing challenges, and highlighting unanswered questions. With the expansion of human space exploration, understanding and managing SANS is imperative to ensure the health and well-being of astronauts during long-duration missions. This review is a valuable resource for researchers, healthcare professionals, and space agencies striving to enhance our knowledge and address the complexities of SANS.

Signalling pathways and cell death mechanisms in glaucoma: Insights into the molecular pathophysiology

Glaucoma is a complex multifactorial eye disease manifesting in retinal ganglion cell (RGC) death and optic nerve degeneration, ultimately causing irreversible vision loss. Research in recent years has significantly enhanced our understanding of RGC degenerative mechanisms in glaucoma. It is evident that high intraocular pressure (IOP) is not the only contributing factor to glaucoma pathogenesis. The equilibrium of pro-survival and pro-death signalling pathways in the retina strongly influences the function and survival of RGCs and optic nerve axons in glaucoma. Molecular evidence from human retinal tissue analysis and a range of experimental models of glaucoma have significantly contributed to unravelling these mechanisms. Accumulating evidence reveals a wide range of molecular signalling pathways that can operate -either alone or via intricate networks - to induce neurodegeneration. The roles of several molecules, including neurotrophins, interplay of intracellular kinases and phosphates, caveolae and adapter proteins, serine proteases and their inhibitors, nuclear receptors, amyloid beta and tau, and how their dysfunction affects retinal neurons are discussed in this review. We further underscore how anatomical alterations in various animal models exhibiting RGC degeneration and susceptibility to glaucoma-related neuronal damage have helped to characterise molecular mechanisms in glaucoma. In addition, we also present different regulated cell death pathways that play a critical role in RGC degeneration in glaucoma.

Dysregulation of Neuroprotective Lipoxin Pathway in Astrocytes in Response to Cytokines and Ocular Hypertension

Glaucoma leads to vision loss due to retinal ganglion cell death. Astrocyte reactivity contributes to neurodegeneration. Our recent study found that lipoxin B4 (LXB4), produced by retinal astrocytes, has direct neuroprotective actions on retinal ganglion cells. In this study, we aimed to investigate how the autacoid LXB4 influences astrocyte activity in the retina under inflammatory cytokine-induced activation and during ocular hypertension. The protective activity of LXB4 was investigated in vivo using the mouse silicone-oil model of chronic ocular hypertension (n=40). By employing a range of analytical techniques, including bulk RNA-seq, RNAscope in-situ hybridization, qPCR, and lipidomic analyses, we discovered the formation of lipoxins and expression of the lipoxin pathway in rodents (including the retina and optic nerve), primates (optic nerve), and human brain astrocytes, indicating the presence of this neuroprotective pathway across various species. Findings in the mouse retina identified significant dysregulation of the lipoxin pathway in response to chronic ocular hypertension, leading to an increase in 5-lipoxygenase (5-LOX) activity and a decrease in 15-LOX activity. This dysregulation was coincident with a marked upregulation of astrocyte reactivity. Reactive human brain astrocytes also showed a significant increase in 5-LOX. Treatment with LXB4 amplified the lipoxin biosynthetic pathway by restoring and amplifying the generation of another member of the lipoxin family, LXA4, and mitigated astrocyte reactivity in mouse retinas and human brain astrocytes. In conclusion, the lipoxin pathway is functionally expressed in rodents, primates, and human astrocytes, and is a resident neuroprotective pathway that is downregulated in reactive astrocytes. Novel cellular targets for LXB4's neuroprotective action are inhibition of astrocyte reactivity and restoration of lipoxin generation. Amplifying the lipoxin pathway is a potential target to disrupt or prevent astrocyte reactivity in neurodegenerative diseases, including retinal ganglion cell death in glaucoma.

Therapeutic Potential of Cannabinoids in Glaucoma

Glaucoma is a leading cause of irreversible blindness worldwide. To date, intraocular pressure (IOP) is the only modifiable risk factor in glaucoma treatment, but even in treated patients, the disease can progress. Cannabinoids, which have been known to lower IOP since the 1970s, have been shown to have beneficial effects in glaucoma patients beyond their IOP-lowering properties. In addition to the classical cannabinoid receptors CB1 and CB2, knowledge of non-classical cannabinoid receptors and the endocannabinoid system has increased in recent years. In particular, the CB2 receptor has been shown to mediate anti-inflammatory, anti-apoptotic, and neuroprotective properties, which may represent a promising therapeutic target for neuroprotection in glaucoma patients. Due to their vasodilatory effects, cannabinoids improve blood flow to the optic nerve head, which may suggest a vasoprotective potential and counteract the altered blood flow observed in glaucoma patients. The aim of this review was to assess the available evidence on the effects and therapeutic potential of cannabinoids in glaucoma patients. The pharmacological mechanisms underlying the effects of cannabinoids on IOP, neuroprotection, and ocular hemodynamics have been discussed.

Proteomics-Based Identification of Retinal Protein Networks Impacted by Elevated Intraocular Pressure in the Hypertonic Saline Injection Model of Experimental Glaucoma

Elevated intraocular pressure is considered a major cause of glaucomatous retinal neurodegeneration. To facilitate a better understanding of the underlying molecular processes and mechanisms, we report a study focusing on alterations of the retina proteome by induced ocular hypertension in a rat model of the disease. Glaucomatous processes were modeled through sclerosing the aqueous outflow routes of the eyes by hypertonic saline injections into an episcleral vein. Mass spectrometry-based quantitative retina proteomics using a label-free shotgun methodology identified over 200 proteins significantly affected by ocular hypertension. Various facets of glaucomatous pathophysiology were revealed through the organization of the findings into protein interaction networks and by pathway analyses. Concentrating on retinal neurodegeneration as a characteristic process of the disease, elevated intraocular pressure-induced alterations in the expression of selected proteins were verified by targeted proteomics based on nanoflow liquid chromatography coupled with nano-electrospray ionization tandem mass spectrometry using the parallel reaction monitoring method of data acquisition. Acquired raw data are shared through deposition to the ProteomeXchange Consortium (PXD042729), making a retina proteomics dataset on the selected animal model of glaucoma available for the first time.

Fluoxetine Protects Retinal Ischemic Damage in Mice

BACKGROUND

To evaluate the neuroprotective effect of the topical ocular administration of fluoxetine (FLX) in a mouse model of acute retinal damage.

METHODS

Ocular ischemia/reperfusion (I/R) injury in C57BL/6J mice was used to elicit retinal damage. Mice were divided into three groups: control group, I/R group, and I/R group treated with topical FLX. A pattern electroretinogram (PERG) was used as a sensitive measure of retinal ganglion cell (RGC) function. Finally, we analyzed the retinal mRNA expression of inflammatory markers (IL-6, TNF-α, Iba-1, IL-1β, and S100β) through Digital Droplet PCR.

RESULTS

PERG amplitude values were significantly (p < 0.05) higher in the I/R-FLX group compared to the I/R group, whereas PERG latency values were significantly (p < 0.05) reduced in I/R-FLX-treated mice compared to the I/R group. Retinal inflammatory markers increased significantly (p < 0.05) after I/R injury. FLX treatment was able to significantly (p < 0.05) attenuate the expression of inflammatory markers after I/R damage.

CONCLUSIONS

Topical treatment with FLX was effective in counteracting the damage of RGCs and preserving retinal function. Moreover, FLX treatment attenuates the production of pro-inflammatory molecules elicited by retinal I/R damage. Further studies need to be performed to support the use of FLX as neuroprotective agent in retinal degenerative diseases.

Morphometric Analysis of Retinal Ganglion Cell Axons in Normal and Glaucomatous Brown Norway Rats Optic Nerves

Purpose

A reference atlas of optic nerve (ON) retinal ganglion cell (RGC) axons could facilitate studies of neuro-ophthalmic diseases by detecting subtle RGC axonal changes. Here we construct an RGC axonal atlas for normotensive eyes in Brown Norway rats, widely used in glaucoma research, and also develop/evaluate several novel metrics of axonal damage in hypertensive eyes.

Methods

Light micrographs of entire ON cross-sections from hypertensive and normotensive eyes were processed through a deep learning-based algorithm, AxoNet2.0, to determine axonal morphological properties and were semiquantitatively scored using the Morrison grading scale (MGS) to provide a damage score independent of AxoNet2.0 outcomes. To construct atlases, ONs were conformally mapped onto an ON "template," and axonal morphometric data was computed for each region. We also developed damage metrics based on myelin morphometry.

Results

In normotensive eyes, average axon density was ∼0.3 axons/µm2 (i.e., ∼80,000 axons in an ON). We measured axoplasm diameter, eccentricity, cross-sectional area, and myelin g-ratio and thickness. Most morphological parameters exhibited a wide range of coefficients of variation (CoV); however, myelin thickness CoV was only ∼2% in normotensive eyes. In hypertensive eyes, increased myelin thickness correlated strongly with MGS (P < 0.0001).

Conclusions

We present the first comprehensive normative RGC axon morphometric atlas for Brown Norway rat eyes. We suggest objective, repeatable damage metrics based on RGC axon myelin thickness for hypertensive eyes.

Translational Relevance

These tools can evaluate regional changes in RGCs and overall levels of damage in glaucoma studies using Brown Norway rats.

Local neuroplasticity in adult glaucomatous visual cortex

The degree to which the adult human visual cortex retains the ability to functionally adapt to damage at the level of the eye remains ill-understood. Previous studies on cortical neuroplasticity primarily focused on the consequences of foveal visual field defects (VFD), yet these findings may not generalize to peripheral defects such as occur in glaucoma. Moreover, recent findings on neuroplasticity are often based on population receptive field (pRF) mapping, but interpreting these results is complicated in the absence of appropriate control conditions. Here, we used fMRI-based neural modeling to assess putative changes in pRFs associated with glaucomatous VFD. We compared the fMRI-signals and pRF in glaucoma participants to those of controls with case-matched simulated VFD. We found that the amplitude of the fMRI-signal is reduced in glaucoma compared to control participants and correlated with disease severity. Furthermore, while coarse retinotopic structure is maintained in all participants with glaucoma, we observed local pRF shifts and enlargements in early visual areas, relative to control participants. These differences suggest that the adult brain retains some degree of local neuroplasticity. This finding has translational relevance, as it is consistent with VFD masking, which prevents glaucoma patients from noticing their VFD and seeking timely treatment.

Combined use of coenzyme Q10 and citicoline: A new possibility for patients with glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Several risk factors have been involved in the pathogenesis of the disease. By now, the main treatable risk factor is elevated intraocular pressure. Nevertheless, some patients, whose intraocular pressure is considered in the target level, still experience a progression of the disease. Glaucoma is a form of multifactorial ocular neurodegeneration with complex etiology, pathogenesis, and pathology. New evidence strongly suggests brain involvement in all aspects of this disease. This hypothesis and the need to prevent glaucomatous progression led to a growing interest in the pharmacological research of new neuroprotective, non-IOP-lowering, agents. The aim of this paper is to report evidence of the usefulness of Coenzyme Q10 and Citicoline, eventually combined, in the prevention of glaucomatous neurodegeneration.

Nanoparticles for the treatment of glaucoma-associated neuroinflammation

Recently, a considerable amount of literature has emerged around the theme of neuroinflammation linked to neurodegeneration. Glaucoma is a neurodegenerative disease characterized by visual impairment. Understanding the complex neuroinflammatory processes underlying retinal ganglion cell loss has the potential to improve conventional therapeutic approaches in glaucoma. Due to the presence of multiple barriers that a systemically administered drug has to cross to reach the intraocular space, ocular drug delivery has always been a challenge. Nowadays, studies are focused on improving the current therapies for glaucoma by utilizing nanoparticles as the modes of drug transport across the ocular anatomical and physiological barriers. This review offers some important insights on the therapeutic advancements made in this direction, focusing on the use of nanoparticles loaded with anti-inflammatory and neuroprotective agents in the treatment of glaucoma. The prospect of these novel therapies is discussed in relation to the current therapies to alleviate inflammation in glaucoma, which are being reviewed as well, along with the detailed molecular and cellular mechanisms governing the onset and the progression of the disease.

Peptains block retinal ganglion cell death in animal models of ocular hypertension: implications for neuroprotection in glaucoma

Ocular hypertension is a significant risk factor for vision loss in glaucoma due to the death of retinal ganglion cells (RGCs). This study investigated the effects of the antiapoptotic peptides peptain-1 and peptain-3a on RGC death in vitro in rat primary RGCs and in mouse models of ocular hypertension. Apoptosis was induced in primary rat RGCs by trophic factor deprivation for 48 h in the presence or absence of peptains. The effects of intravitreally injected peptains on RGC death were investigated in mice subjected to retinal ischemic/reperfusion (I/R) injury and elevated intraocular pressure (IOP). I/R injury was induced in mice by elevating the IOP to 120 mm Hg for 1 h, followed by rapid reperfusion. Ocular hypertension was induced in mice by injecting microbeads (MB) or silicone oil (SO) into the anterior chamber of the eye. Retinal flatmounts were immunostained with RGC and activated glial markers. Effects on anterograde axonal transport were determined by intravitreal injection of cholera toxin-B. Peptain-1 and peptain-3a inhibited neurotrophic factor deprivation-mediated RGC apoptosis by 29% and 35%, respectively. I/R injury caused 52% RGC loss, but peptain-1 and peptain-3a restricted RGC loss to 13% and 16%, respectively. MB and SO injections resulted in 31% and 36% loss in RGCs following 6 weeks and 4 weeks of IOP elevation, respectively. Peptain-1 and peptain-3a inhibited RGC death; the loss was only 4% and 12% in MB-injected eyes and 16% and 15% in SO-injected eyes, respectively. Anterograde transport was defective in eyes with ocular hypertension, but this defect was substantially ameliorated in peptain-injected eyes. Peptains suppressed ocular hypertension-mediated retinal glial activation. In summary, our results showed that peptains block RGC somal and axonal damage and neuroinflammation in animal models of glaucoma. We propose that peptains have the potential to be developed as therapeutics against neurodegeneration in glaucoma.

Optic Nerve Head Myelin-Related Protein, GFAP, and Iba1 Alterations in Non-Human Primates With Early to Moderate Experimental Glaucoma

Purpose

The purpose of this study was to test if optic nerve head (ONH) myelin basic protein (MBP), 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), glial fibrillary acidic protein (GFAP), and ionized calcium binding adaptor molecule 1 (Iba1) proteins are altered in non-human primate (NHP) early/moderate experimental glaucoma (EG).

Methods

Following paraformaldehyde perfusion, control and EG eye ONH tissues from four NHPs were paraffin embedded and serially (5 µm) vertically sectioned. Anti-MBP, CNPase, GFAP, Iba1, and nuclear dye-stained sections were imaged using sub-saturating light intensities. Whole-section images were segmented creating anatomically consistent laminar (L) and retrolaminar (RL) regions/sub-regions. EG versus control eye intensity/pixel-cluster density data within L and two RL regions (RL1 [1-250 µm]/RL2 [251-500 µm] from L) were compared using random effects models within the statistical program “R.”

Results

EG eye retinal nerve fiber loss ranged from 0% to 20%. EG eyes’ MBP and CNPase intensity were decreased within the RL1 (MBP = 31.4%, P < 0.001; CNPase =62.3%, P < 0.001) and RL2 (MBP = 19.6%, P < 0.001; CNPase = 56.1%, P = 0.0004) regions. EG eye GFAP intensity was decreased in the L (41.6%, P < 0.001) and RL regions (26.7% for RL1, and 28.4% for RL2, both P < 0.001). Iba1+ and NucBlue pixel-cluster density were increased in the laminar (28.2%, P = 0.03 and 16.6%, P = 0.008) and both RL regions (RL1 = 37.3%, P = 0.01 and 23.7%, P = 0.0002; RL2 = 53.7%, P = 0.002 and 33.2%, P < 0.001).

Conclusions

Retrolaminar myelin disruption occurs early in NHP EG and may be accompanied by laminar and retrolaminar decreases in astrocyte process labeling and increases in microglial/ macrophage density. The mechanistic and therapeutic implications of these findings warrant further study.

Rho Kinase Inhibitors as a Neuroprotective Pharmacological Intervention for the Treatment of Glaucoma

Glaucoma is a leading cause of irreversible blindness, and its prevalence has led to research into treatment modalities for glaucoma to prevent the progression of the disease. The primary treatment for glaucoma that has been extensively used is ocular hypotensives to reduce raised intraocular pressure. This treatment has its drawbacks due to the existence of other variants of glaucoma, such as normal-tension glaucoma, where the intraocular pressure is measured to be within regular levels. Hence, there is a need for new treatment interventions which can deliver a better prognosis for glaucoma. Neuroprotection is a new concept studied recently, and neuroprotective agents are being developed for glaucoma therapy. Rho kinase inhibitors are one such neuroprotective agent, and the most recent addition to the class of ocular hypotensives, where they function by reducing raised intraocular pressure. Its neuroprotective capabilities, such as cell survival and axon regeneration, are yet to be determined in detail. This literature review article aims to look into the need for new treatments such as neuroprotection to prevent the progression of glaucoma and the efficacy of rho kinase inhibitors in the treatment of glaucoma, with particular emphasis on its neuroprotective abilities. It also aims to identify the limitations that can occur while approaching neuroprotective therapy, as well as how it can enable future treatment modalities. By exploring this field, blindness caused by progressive glaucoma can be halted and managed by glaucoma therapy.

Screening of primary open-angle glaucoma diagnostic markers based on immune-related genes and immune infiltration

Purpose

Primary open-angle glaucoma (POAG) continues to be a poorly understood disease. Although there were multiple researches on the identification of POAG biomarkers, few studies systematically revealed the immune-related cells and immune infiltration of POAG. Bioinformatics analyses of optic nerve (ON) and trabecular meshwork (TM) gene expression data were performed to further elucidate the immune-related genes of POAG and identify candidate target genes for treatment.

Methods

We performed a gene analysis of publicly available microarray data, namely, the GSE27276-GPL2507, GSE2378-GPL8300, GSE9944-GPL8300, and GSE9944-GPL571 datasets from the Gene Expression Omnibus database. The obtained datasets were used as input for parallel pathway analyses. Based on random forest and support vector machine (SVM) analysis to screen the key genes, significantly changed pathways were clustered into functional categories, and the results were further investigated. CIBERSORT was used to evaluate the infiltration of immune cells in POAG tissues. A network visualizing the differences between the data in the POAG and normal groups was created. GO and KEGG enrichment analyses were performed using the Metascape database. We divided the differentially expressed mRNAs into upregulated and downregulated groups and predicted the drug targets of the differentially expressed genes through the Connectivity Map (CMap) database.

Results

A total of 49 differentially expressed genes, including 19 downregulated genes and 30 upregulated genes, were detected. Five genes ((Keratin 14) KRT14, (Hemoglobin subunit beta) HBB, (Acyl-CoA Oxidase 2) ACOX2, (Hephaestin) HEPH and Keratin 13 (KRT13)) were significantly changed. The results showed that the expression profiles of drug disturbances, including those for avrainvillamide-analysis-3, cytochalasin-D, NPI-2358, oxymethylone and vinorelbine, were negatively correlated with the expression profiles of disease disturbances. This finding indicated that these drugs may reduce or even reverse the POAG disease state.

Conclusion

This study provides an overview of the processes involved in the molecular pathogenesis of POAG in the ON and TM. The findings provide a new understanding of the molecular mechanism of POAG from the perspective of immunology.

Neuroprotection in neurodegenerations of the brain and eye: Lessons from the past and directions for the future

Background

Neurological and ophthalmological neurodegenerative diseases in large part share underlying biology and pathophysiology. Despite extensive preclinical research on neuroprotection that in many cases bridges and unifies both fields, only a handful of neuroprotective therapies have succeeded clinically in either.

Main body

Understanding the commonalities among brain and neuroretinal neurodegenerations can help develop innovative ways to improve translational success in neuroprotection research and emerging therapies. To do this, analysis of why translational research in neuroprotection fails necessitates addressing roadblocks at basic research and clinical trial levels. These include optimizing translational approaches with respect to biomarkers, therapeutic targets, treatments, animal models, and regulatory pathways.

Conclusion

The common features of neurological and ophthalmological neurodegenerations are useful for outlining a path forward that should increase the likelihood of translational success in neuroprotective therapies.

Protective Effect of Curcuma Extract in an Ex Vivo Model of Retinal Degeneration via Antioxidant Activity and Targeting the SUMOylation

Retinal degeneration is the major and principal cause behind many incurable blindness diseases. Several studies indicated the neuroprotective effect of Curcuma longa in eye pathologies, specifically retinopathy. However, the molecular mechanism behind its effect has not been completely elucidated. Using an ex vivo model of retinal degeneration obtained from an ex vivo optic nerve cut (ONC), we demonstrated that Curcuma extract (Cur) exerted a neuroprotective effect. Importantly, Cur was able to modulate apoptosis and MAPK signaling pathway activation and prevent retinal ganglion cell (RGC) loss. Other well-known neuroprotective pharmacological tools, including memantine (Mem), citicoline (Cit), and ginkgolic acid (GA), were used to compare the potential mechanisms of Cur. The antioxidant activity of retinas treated with Cur following optic nerve cut was significantly higher than control, but Cur failed to change the retina glutamate content. Considering the antioxidant effect of Cur and taking advantage of our recent findings on the crosstalk between oxidative stress and post-translational protein modifiers, in particular, small ubiquitin-related modifier (SUMO), we were interested in exploring the effect of Cur on SUMOylation. We found that Cur significantly prevented the increase of protein SUMOylation, confirming our previous in vitro data indicating the cytoprotective effect of curcumin through modulating the oxidative stress and SUMO-JNK axis. Altogether, these results suggest that Curcuma protects the retina from degeneration via antioxidant activity and targets SUMOylation. Therefore, it might be considered for the combination therapy with other neuroprotective agents with different mechanisms in preclinical studies on retinal degeneration.

CircXPO5 Plays a Neuroprotective Function in the Lateral Geniculate Nucleus of Glaucoma by Regulating GRIN2A

PURPOSE

Previous studies have found the neurodegeneration and atrophy of glaucomatous lateral geniculate nucleus (LGN), but the mechanism is still unknown. Circular RNA (circRNA) plays some important roles in physiological and pathological progression of the disease. In this study, we focused on the differentially expressed circRNAs and the mechanism for circXPO5 in LGN degeneration in a macaque glaucoma model.

METHODS

Using RNA-seq, we analyzed the differentially expressed circRNAs in a macaque glaucoma model. An RT-QPCR was used to check the expression of selected differentially expressed circRNAs, candidate miRNAs and mRNAs. A competing endogenous RNA (ceRNA) network analysis was performed to examine the mechanism of circXPO5 action.

RESULTS

circXPO5 significantly decreased in the glaucoma model and a ceRNA network analysis revealed that circXPO5 can bind to miR-330-5p, which also binds to GRIN2A (ionotropic receptor NMDA type subunit 2A). QPCR detection showed a decrease in GRIN2A and an increase in miR-330-5p.

CONCLUSIONS

Our earlier studies revealed that the GRIN2A gene regulates the calcium signal pathway. Decreasing of GRIN2A related with neuron apoptosis and neurodegeneration. These findings indicate that the reduction in circXPO5 may have a protective effect on neuronal apoptosis in the visual central system of glaucoma.

Imaging biomarkers for Alzheimer's disease and glaucoma: Current and future practices

Glaucoma is a leading cause of blindness worldwide. Although intraocular pressure is the main risk factor for glaucoma, several intraocular pressure independent factors have been associated with the risk of developing the disease and its progression. The diagnosis of glaucoma relies on clinical features of the optic nerve, visual field test, and optical coherence tomography. However, the multidisciplinary aspect of the disease suggests that other biomarkers may be useful for the diagnosis, thus underling the importance of novel imaging techniques supporting clinicians. This review analyzes the common pathogenic mechanisms between glaucoma and Alzheimer's disease and the possible novel approaches for diagnosis and follow up.

Evaluation of putative differences in vessel density and flow area in normal tension and high-pressure glaucoma using OCT-angiography

PURPOSE

To evaluate the putative differences in terms of vessel density and flow area between control (CTRL), high-pressure glaucoma (HPG) and normal tension glaucoma (NTG) subjects at macular and peripapillary level. To assess the correlation between Visual Field Index (VFI), the stage of glaucoma, and optical coherence tomography angiography (OCT-A) parameters.

MATERIAL AND METHODS

In this pilot, prospective study 46 eyes of 46 glaucomatous patients (19 NTG+27 HPG) and 25 control eyes (CTRL) of 25 subjects were recruited. All patients underwent a complete ophthalmologic examination and visual field testing. A 3×3mm volumetric macular scan (Angio Retina [3.0]) and a 4.5×4.5mm diameter peripapillary scan (Angio Disc [4.5]) were performed in the right eye using RTVue-XR Avanti (Optovue, Inc.) OCT-A.

RESULTS

Groups were homogeneous for age (P=0.784) and gender (P=0.623). Among the evaluated optic nerve head (ONH) and macular OCT-A parameters, ONH whole image (P<0.001), inside disc (P=0.021), peripapillary (P<0.001), ONH flow area (P<0.026), macula whole image (P<0.001), fovea (P<0.001), parafovea (P<0.001) showed a significant difference when CTRL group was compared to HPG group at the post hoc test. Similarly, ONH whole image (P<0.001), inside disc (P=0.005), peripapillary (P<0.001), ONH flow area (P<0.026), macula whole image (P<0.001), FOVEA (P<0.001), parafovea (P<0.001) showed a significant difference were CTRL were compared to NTG group. On the contrary, no significant difference was found when NTG and HPG groups were compared. Age was not significantly correlated with any of the OCT-A parameters. The stage of the disease showed a high, significant, correlation with ONH whole image (r=-0.81; P<0.0001), inside disc (r=-0.42; P<0.0001), peripapillary (r=-0.81; P<0.0001), RNFL (r=-0.79; P<0.0001), macula whole image (r=0.56; P<0.0001), fovea (r=-0.78; P<0.0001) and parafovea (r=0.67; P<0.0001). On the contrary, VFI showed a high, significant, correlation with ONH whole image (r=0.77; P<0.0001), inside disc (r=0.39; P=0.0018), peripapillary (r=0.713; P<0.0001), RNFL (r=0.63; P<0.0001), macula whole image (r=-0.39; P=0.0007), fovea (r=0.60; P<0.0001) and parafovea (r=-0.52; P<0.0001).

CONCLUSIONS

Our data support the usefulness of the OCT-A in the common clinical practice for diagnosis, staging, evaluating the progression of the disease as well as for better understanding of its pathogenic mechanisms.

Functional Availability of ON-Bipolar Cells in the Degenerated Retina: Timing and Longevity of an Optogenetic Gene Therapy

Degenerative diseases of the retina are responsible for the death of photoreceptors and subsequent loss of vision in patients. Nevertheless, the inner retinal layers remain intact over an extended period of time, enabling the restoration of light sensitivity in blind retinas via the expression of optogenetic tools in the remaining retinal cells. The chimeric Opto-mGluR6 protein represents such a tool. With exclusive ON-bipolar cell expression, it combines the light-sensitive domains of melanopsin and the intracellular domains of the metabotropic glutamate receptor 6 (mGluR6), which naturally mediates light responses in these cells. Albeit vision restoration in blind mice by Opto-mGluR6 delivery was previously shown, much is left to be explored in regard to the effects of the timing of the treatment in the degenerated retina. We performed a functional evaluation of Opto-mGluR6-treated murine blind retinas using multi-electrode arrays (MEAs) and observed long-term functional preservation in the treated retinas, as well as successful therapeutical intervention in later stages of degeneration. Moreover, the treatment decreased the inherent retinal hyperactivity of the degenerated retinas to levels undistinguishable from healthy controls. Finally, we observed for the first time micro electroretinograms (mERGs) in optogenetically treated animals, corroborating the origin of Opto-mGluR6 signalling at the level of mGluR6 of ON-bipolar cells.

The Future of Stem Cells and Their Derivates in the Treatment of Glaucoma. A Critical Point of View

This review focuses on the clinical translation of preclinical studies, especially those that have used stem cells in the treatment of glaucoma, with an emphasis on optic nerve regeneration. The studies referred to in the review aim to treat optic nerve atrophy, while cell therapies targeting other sites in the eye, such as the trabecular meshwork, have not been addressed. Such complex and varied pathophysiological mechanisms that lead to glaucoma may explain the fact that although stem cells have a high capacity of neuronal regeneration, the treatments performed did not have the expected results and the promise offered by animal studies was not achieved. By analyzing the facts associated with failure, important lessons are to be learned: the type of stem cells that are used, the route of administration, the selection of patients eligible for these treatments, additional therapies that support stem cells transplantation and their mode of action, methods of avoiding the host’s immune response. Many of these problems could be solved using exosomes (EV), but also miRNA, which allows more targeted approaches with minimal side effects.

Immune responses to injury and their links to eye disease

The eye is regarded as an immune privileged site. Since the presence of a vasculature would impair vision, the vasculature of the eye is located outside of the central light path. As a result, many regions of the eye evolved mechanisms to deliver immune cells to sites of dysgenesis, injury, or in response to the many age-related pathologies. While the purpose of these immune responses is reparative or protective, cytokines released by immune cells compromise visual acuity by inducing inflammation and fibrosis. The response to traumatic or pathological injury is distinct in different regions of the eye. Age-related diseases impact both the anterior and posterior segment and lead to reduced quality of life and blindness. Here we focus attention on the role that inflammation and fibrosis play in the progression of age-related pathologies of the cornea and the lens as well as in glaucoma, the formation of epiretinal membranes, and in proliferative vitreoretinopathy.

Risk Factors for Retinal Ganglion Cell Distress in Glaucoma and Neuroprotective Potential Intervention

Retinal ganglion cells (RGCs) are a population of neurons of the central nervous system (CNS) extending with their soma to the inner retina and with their axons to the optic nerve. Glaucoma represents a group of neurodegenerative diseases where the slow progressive death of RGCs results in a permanent loss of vision. To date, although Intra Ocular Pressure (IOP) is considered the main therapeutic target, the precise mechanisms by which RGCs die in glaucoma have not yet been clarified. In fact, Primary Open Angle Glaucoma (POAG), which is the most common glaucoma form, also occurs without elevated IOP. This present review provides a summary of some pathological conditions, i.e., axonal transport blockade, glutamate excitotoxicity and changes in pro-inflammatory cytokines along the RGC projection, all involved in the glaucoma cascade. Moreover, neuro-protective therapeutic approaches, which aim to improve RGC degeneration, have also been taken into consideration.

Muscarinic Acetylcholine Receptors in the Retina-Therapeutic Implications

Muscarinic acetylcholine receptors (mAChRs) belong to the superfamily of G-protein-coupled receptors (GPCRs). The family of mAChRs is composed of five subtypes, M1, M2, M3, M4 and M5, which have distinct expression patterns and functions. In the eye and its adnexa, mAChRs are widely expressed and exert multiple functions, such as modulation of tear secretion, regulation of pupil size, modulation of intraocular pressure, participation in cell-to-cell signaling and modula-tion of vascular diameter in the retina. Due to this variety of functions, it is reasonable to assume that abnormalities in mAChR signaling may contribute to the development of various ocular diseases. On the other hand, mAChRs may offer an attractive therapeutic target to treat ocular diseases. Thus far, non-subtype-selective mAChR ligands have been used in ophthalmology to treat dry eye disease, myopia and glaucoma. However, these drugs were shown to cause various side-effects. Thus, the use of subtype-selective ligands would be useful to circumvent this problem. In this review, we give an overview on the localization and on the functional role of mAChR subtypes in the eye and its adnexa with a special focus on the retina. Moreover, we describe the pathophysiological role of mAChRs in retinal diseases and discuss potential therapeutic approaches.

Ion-Complex Microcrystal Formulation Provides Sustained Delivery of a Multimodal Kinase Inhibitor from the Subconjunctival Space for Protection of Retinal Ganglion Cells

Glaucoma is the leading cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP) is one of the major risk factors for glaucoma onset and progression, and available pharmaceutical interventions are exclusively targeted at IOP lowering. However, degeneration of retinal ganglion cells (RGCs) may continue to progress despite extensive lowering of IOP. A complementary strategy to IOP reduction is the use of neuroprotective agents that interrupt the process of cell death by mechanisms independent of IOP. Here, we describe an ion complexation approach for formulating microcrystals containing ~50% loading of a protein kinase inhibitor, sunitinib, to enhance survival of RGCs with subconjunctival injection. A single subconjunctival injection of sunitinib-pamoate complex (SPC) microcrystals provided 20 weeks of sustained retina drug levels, leading to neuroprotection in a rat model of optic nerve injury. Furthermore, subconjunctival injection of SPC microcrystals also led to therapeutic effects in a rat model of corneal neovascularization. Importantly, therapeutically relevant retina drug concentrations were achieved with subconjunctival injection of SPC microcrystals in pigs. For a chronic disease such as glaucoma, a formulation that provides sustained therapeutic effects to complement IOP lowering therapies could provide improved disease management and promote patient quality of life.

A Review on Newer Ocular Drug Delivery Systems with an Emphasis on Glaucoma

Glaucoma is an irreversible condition resulting from the increase in intraocular pressure (IOP); which leads to permanent loss of vision with the destruction of retinal ganglion cells (RGCs). The IOP elevations are controlled in normal by the physiological flow of aqueous humour. A population with age above 40 is more susceptible to glaucoma. Other factors like gender, genetics, race etc. plays major roles in the development of the disease. Current treatment methods available for the disease includes drugs come under the classes of beta receptor blockers, carbonic anhydrase inhibitors, cholinergic agonists, prostaglandins etc. N-methyl-D-aspartate (NMDA) antagonists, inducible nitric oxide synthase (iNOS) inhibition, cytoskeletal agents, Rho-kinase inhibitors etc are few novel targets sites which are in research focus for the treatment of the disease. Developments in nanomedicine are also being evaluated for their potential in treating the growing glaucomatous population. Nanosystems are suggested to avoid the difficulties in tackling the various ocular barriers to a limit, help to decrease the instillation frequency of topical medication and can provide drug delivery in a sustained or controlled manner. This review focuses on the current and emerging treatment methods for glaucoma along with some of the nanoformulations for ocular drug delivery.

Sympathetic context of the disease - a new era in glaucoma management

Primary open angle glaucoma (POAG) is a multifactorial optic neuropathy, which progresses in a chronic manner. Several etiological factors are involved, including genetic factors, race, age, IOP or vascular, systemic factors. IOP has an established role in the initiation and evolution of glaucoma, but its interactions with additional risk factors are complex. We propose the notion of the Glaucoma Etiological Area (GEA), as a representation of all the elements acting in collaboration in the physiopathology of each glaucoma case. When combined in different proportions, these elements may trigger the typical glaucomatous optic neuropathy (GON). We know that the statistical values of IOP are valid for normal eyes, but the glaucoma eye is not a normal eye. The notion of GEA can open a new perspective to interpret IOP values and to assess the true value of IOP control as a treatment for glaucoma. Applying the GEA theory allows us to tune the role of IOP. Additional factors, such as ocular properties (RGCL status, CCT, IOP fluctuation curve), ocular comorbidities (PEX, PDS), systemic comorbidities (arterial hypertension, vasospastic diseases such as migraines or Reynaud’s syndrome) or patient’s attitude towards glaucoma management (treatment compliance, access to follow-up and treatment) may greatly influence the evolution of GON and should be viewed holistically when developing a management plan for each patient. Applying the notion of GEA in clinical practice allows a more realistic approach of the pathophysiology of the disease and for a glaucoma treatment that is tailored to each patient.

Abbreviations: AG = advanced glaucoma, BP = blood pressure, CCT = central corneal thickness, CIGTS = Collaborative Initial Glaucoma Treatment Study, CNTGS = Collaborative Normal-Tension Glaucoma Study, EMGT = Early Manifest Glaucoma Trial, GEA = glaucoma etiological area, GON = glaucomatous optic neuropathy, IOP = intraocular pressure, NTG = Normal Tension Glaucoma, OHTS = Ocular Hypertension Study, PDS = Pigmentary dispersion syndrome, PEX = Pseudoexfoliation syndrome, POAG - primary open-angle glaucoma, RGCL = retinal ganglion cell layer, VFL = visual field loss

Long Noncoding RNA Maternally Expressed Gene 3 Targets miR-30b and Regulates the AKT Serine/Threonine Kinase 1/Phosphoinositide 3-Kinase Signaling Pathway of H2O2-Induced Proliferation, Apoptosis, and Oxidative Stress in Retinal Ganglion Cells

Oxidative stress is an important factor affecting retinal ganglion cell (RGC) apoptosis. RGC apoptosis is the main pathophysiological feature of visual impairment as a result of glaucoma. Recently, it has been found that long noncoding RNA (lncRNA) and microRNAs are involved in RGC apoptosis. Here, the function of lncRNA maternally expressed gene 3 (MEG3) and miR-30b in H2 O2-induced RGC proliferation, apoptosis, and oxidative stress was investigated. The expression levels of MEG3 and miR-30b were detected by RT-PCR; the effects of MEG3 and miR-30b on the proliferation and apoptosis of RGCs were observed by flow cytometry; the levels of apoptosis-related proteins and AKT/PI3K signal pathway proteins were detected by protein immunoassay; and the regulation of miR-34a by pvt1 was verified by in vivo and in vitro experiments. The expression of MEG3 and miR-30b increased and decreased significantly in RGCs treated by H2O2. MEG3 expression decreased, apoptosis level-related proteins decreased, the apoptosis rate reduced, and the activity of MDA and SOD decreased. When the expression of miR-34a was inhibited, the proliferation rate of RGCs increased, the apoptosis rate decreased, and the level of apoptosis-related proteins decreased, which reversed MEG3’s effect on RGC apoptosis and proliferation. Furthermore, pvt1 could bind the miR-30b promoter and regulate it with in vitro expression and in vivo expression. Besides, we found that miR-30b can regulate the AKT/PI3K signaling pathway and participate in cell apoptosis and hyperplasia in stress response. LncRNA MEG3 targets miR-30b and regulates the AKT/PI3K signaling pathway on H2 O2-induced cell apoptosis, hyperplasia, and oxidative stress of RGCs.

Novel Drug Delivery Systems Fighting Glaucoma: Formulation Obstacles and Solutions

Glaucoma is considered to be one of the biggest health problems in the world. It is the main cause of preventable blindness due to its asymptomatic nature in the early stages on the one hand and patients' non-adherence on the other. There are several approaches in glaucoma treatment, whereby this has to be individually designed for each patient. The first-line treatment is medication therapy. However, taking into account numerous disadvantages of conventional ophthalmic dosage forms, intensive work has been carried out on the development of novel drug delivery systems for glaucoma. This review aims to provide an overview of formulation solutions and strategies in the development of in situ gel systems, nanosystems, ocular inserts, contact lenses, collagen corneal shields, ocular implants, microneedles, and iontophoretic devices. The results of studies confirming the effectiveness of the aforementioned drug delivery systems were also briefly presented.

Evaluating the neuroprotective impact of senolytic drugs on human vision

Glaucoma, a chronic neurodegenerative disease of retinal ganglion cells (RGCs), is a leading cause of irreversible blindness worldwide. Its management currently focuses on lowering intraocular pressure to slow disease progression. However, disease-modifying, neuroprotective treatments for glaucoma remain a major unmet need. Recently, senescent cells have been observed in glaucomatous eyes, exposing a potential pathway for alternative glaucoma therapies. Prior studies demonstrated that targeting senescent RGCs for removal (i.e., a senolytic approach) protected healthy RGCs and preserved visual function in a mouse ocular hypertension model. However, the effects of senolytic drugs on vision in human patients are unknown. Here, we used existing clinical data to conduct a retrospective cohort study in 28 human glaucoma patients who had been exposed to senolytics. Senolytic exposure was not associated with decreased visual acuity, elevated intraocular pressure, or documentation of senolytic-related adverse ocular effects by treating ophthalmologists. Additionally, patients exposed to senolytics (n = 9) did not exhibit faster progression of glaucomatous visual field damage compared to matched glaucoma patients (n = 26) without senolytic exposure. These results suggest that senolytic drugs do not carry significant ocular toxicity and provide further support for additional evaluation of the potential neuroprotective effects of senolytics on glaucoma and other neurodegenerative diseases.

Effects of Citicoline, Homotaurine, and Vitamin E on Contrast Sensitivity and Visual-Related Quality of Life in Patients with Primary Open-Angle Glaucoma: A Preliminary Study

The aim of the present study was to evaluate the effects of supplementation with a fixed combination of citicoline 500 mg, homotaurine 50 mg, and vitamin E 12 mg (CIT/HOMO/VITE) on contrast sensitivity and visual-related quality of life in patients with primary open-angle glaucoma (POAG) in mild stage. This was a multicenter, observational, cross-over, short-term, pilot study on POAG patients with stable controlled intraocular pressure (IOP). Patients were randomly assigned to Group 1 (current topical therapy for 4 months and then current topical therapy plus CIT/HOMO/VITE for 4 months) or Group 2 (CIT/HOMO/VITE in addition to current topical therapy for 4 months and then topical therapy alone for 4 months). Best-corrected visual acuity, IOP, visual field, and the Spaeth/Richman contrast sensitivity (SPARCS) test score were recorded at baseline and after 4 and 8 months. The Glaucoma Quality of Life-15 (GQL-15) questionnaire was administered at each check time. Forty-four patients were assigned to Group 1 and 65 to Group 2. Over the follow-up period, there were no significant changes in IOP or visual field findings, whereas SPARCS and GQL-15 findings significantly varied from baseline, both being improved in subjects treated with CIT/HOMO/VITE fixed combination. These results demonstrate that a daily intake of a fixed combination of citicoline, homotaurine, and vitamin E in addition to the topical medical treatment significantly increased the total score of the contrast sensitivity test and the quality of life in patients with POAG.

Coenzyme Q and its role in glaucoma

Presently the management of glaucoma is limited to lowering of intra-ocular pressure (IOP). Since this modality does not appear to be successful in all cases there is increasing focus on non-IOP lowering medications. Coenzyme Q is a naturally occurring compound similar to vitamins. There are a few reports suggesting the neuroprotective efficacy of this agent in glaucoma models. The present systematic review was undertaken to study the pharmacology, physiology, metabolism and role of Coenzyme Q in glaucoma. An English-language search for relevant items was undertaken using PubMed, Google Scholar, Scopus and other databases. The present review found a positive outcome of Coenzyme Q as a neuroprotectant being reported in all studies. However, the review also found that the majority of studies on Coenzyme Q have been reported by a single group of researchers. In order to have a more wide-ranging impact regarding the efficacy of Coenzyme Q in glaucoma, it would be useful to undertake further multi- center trials.

Treatment with GDF15, a TGFβ superfamily protein, induces protective effect on retinal ganglion cells

Growth differentiation factor 15 (GDF15) is a protein belonging to the transforming growth factor beta (TGF-β) superfamily. The precursor GDF15 is cleaved and activated as a mature GDF15 by protease. GDF15 has been detected in the aqueous humor of the primary open angle glaucoma patients, however the localization and the effect on the retinal ganglion cells (RGCs) are still unknown. Thus, the purpose of this study was to elucidate the effect of GDF15 on mouse optic nerve crush (ONC) model and primary culture of rat RGCs. Immunostaining showed that the GDF15 was in the ganglion cell layer (GCL), and colocalized with GFAP-positive cells in the GCL and the optic nerve. Western blotting analysis showed that the mature GDF15 was upregulated in the retina and the optic nerve after the ONC. Intravitreal injection of GDF15 suppressed RGCs loss of the ONC model mice in vivo. The neurites length of the primary culture of rat RGCs were increased by mature GDF15 treatment. In addition, the neurotrophic effect of GDF15 was canceled by RET inhibitor treatment. These findings indicate that GDF15 has neuroprotective effect on RGCs via GFRAL-RET pathway. Therefore, GDF15 may be one of novel therapeutic targets in RGC degenerative diseases.

Computational Analysis of Clinical and Molecular Markers and New Theranostic Possibilities in Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is a paramount cause of irreversible visual disability worldwide. We focus on identifying clinical and molecular facts that may help elucidating the pathogenic mechanisms of the disease. By using ophthalmological approaches (biomicroscopy, ocular fundus, optical coherence tomography, and perimetry) and experimental tests (enzyme-linked immunosorbent assay (ELISA), high performance liquid chromatography (HPLC), and Western blot/immunoblotting) directed to evaluate the oxidative stress, inflammation, apoptosis, and neurodegeneration processes, we gather information to build a network of data to perform a computational bioinformatics analysis. Our results showed strong interaction of the above players and its downstream effectors in POAG pathogenesis. In conclusion, specific risk factors were identified, and molecules involved in multiple pathways were found in relation to anterior and posterior eye segment glaucoma changes, pointing to new theranostic challenges for better managing POAG progression.

Prophylactic anti-glaucoma therapy in dogs with primary glaucoma: A practitioner survey of current medical protocols

AIM

To examine the use of prophylactic anti-glaucoma medications in the normotensive fellow eye in dogs with unilateral overt primary glaucoma by veterinary ophthalmology clinicians.

METHODS

A survey of veterinary ophthalmology clinicians was distributed over two international list serves servicing veterinary ophthalmologists, trainees, and individuals whose practice consisted primarily of ophthalmic patients. The survey was developed following analysis of historical and currently available medical options for control of intraocular pressure and for neuroprotection.

RESULTS

Responses from 199 veterinary ophthalmology clinicians were evaluated. While a large variety of topical anti-hypertensive drugs and protocols were used, the most commonly used medications were aqueous humor production suppressors such as dorzolamide 2.0% ophthalmic solution, timolol 0.5% ophthalmic solution, and a combination product containing both drugs. Latanoprost 0.005% ophthalmic solution was used infrequently for prophylaxis by comparison. The majority of respondents do not use concurrent anti-inflammatory medications (61.22%), although a sizeable minority used prednisolone acetate, dexamethasone, or ketorolac as prophylactic treatment. Systemically administered ocular anti-hypertensive agents were rarely used. Only 40% of respondents used neuroprotectant agents; the most commonly prescribed were the calcium channel blocker amlodipine and the nutraceutical Ocu-Glo™. Recommended intervals between re-examination by the clinician ranged from one month to one year, with most re-evaluations occurring every 3 to 6 months. The majority of respondents recommended more frequent assessments of IOP at intervals between once monthly and once every 3 months.

CONCLUSIONS

Data analysis of medical therapy for the normotensive fellow eye of dogs previously diagnosed with primary glaucoma suggests that there is a great need for well-designed, prospective, controlled, multi-center studies to determine which protocols have the greatest efficacy in delaying an overt attack in the previously normotensive eye in dogs with a genetic predisposition to glaucoma. Prospective studies utilizing a carbonic anhydrase inhibitor such as dorzolamide and a prostaglandin analogue such as latanoprost would be reasonable as these two drugs are widely used in the treatment of overt glaucoma and would allow for an exploration of the impact of different mechanisms of action of lowering IOP on the pathophysiology of primary glaucoma.

Intravitreal Co-Administration of GDNF and CNTF Confers Synergistic and Long-Lasting Protection against Injury-Induced Cell Death of Retinal Ganglion Cells in Mice

We have recently demonstrated that neural stem cell-based intravitreal co-administration of glial cell line-derived neurotrophic factor (GDNF) and ciliary neurotrophic factor (CNTF) confers profound protection to injured retinal ganglion cells (RGCs) in a mouse optic nerve crush model, resulting in the survival of ~38% RGCs two months after the nerve lesion. Here, we analyzed whether this neuroprotective effect is long-lasting and studied the impact of the pronounced RGC rescue on axonal regeneration. To this aim, we co-injected a GDNF- and a CNTF-overexpressing neural stem cell line into the vitreous cavity of adult mice one day after an optic nerve crush and determined the number of surviving RGCs 4, 6 and 8 months after the lesion. Remarkably, we found no significant decrease in the number of surviving RGCs between the successive analysis time points, indicating that the combined administration of GDNF and CNTF conferred lifelong protection to injured RGCs. While the simultaneous administration of GDNF and CNTF stimulated pronounced intraretinal axon growth when compared to retinas treated with either factor alone, numbers of regenerating axons in the distal optic nerve stumps were similar in animals co-treated with both factors and animals treated with CNTF only.

The role of neuroinflammation in the pathogenesis of glaucoma neurodegeneration

The chapter is a review enclosed in the volume "Glaucoma: A pancitopatia of the retina and beyond." No cure exists for glaucoma. Knowledge on the molecular and cellular alterations underlying glaucoma neurodegeneration (GL-ND) includes innovative and path-breaking research on neuroinflammation and neuroprotection. A series of events involving immune response (IR), oxidative stress and gene expression are occurring during the glaucoma course. Uveitic glaucoma (UG) is a prevalent acute/chronic complication, in the setting of chronic anterior chamber inflammation. Managing the disease requires a team approach to guarantee better results for eyes and vision. Advances in biomedicine/biotechnology are driving a tremendous revolution in ophthalmology and ophthalmic research. New diagnostic and imaging modalities, constantly refined, enable outstanding criteria for delimiting glaucomatous neurodegeneration. Moreover, biotherapies that may modulate or inhibit the IR must be considered among the first-line for glaucoma neuroprotection. This review offers the readers useful and practical information on the latest updates in this regard.

The Antiglaucoma Agent and EP2 Receptor Agonist Omidenepag Does Not Affect Eyelash Growth in Mice

Purpose: The present study investigated the effects of the antiglaucoma agent and selective E2 receptor agonist omidenepag isopropyl (OMDI) on eyelash growth in comparison with a prostaglandin analog (prostamide receptor agonist) in mice.

Methods: Four-week-old female mice (C57BL/6J) were divided into 3 groups of n = 10 each. The groups were administered 3 μL of 0.003% OMDI solution, the vehicle (negative control), or a 0.03% bimatoprost solution (positive control) on the upper eyelids of the right eyes once daily for 14 days. On the 15th day, all animals were euthanized, and the upper eyelids with eyelashes were fixed with 10% neutral formalin. Eyelashes were evaluated for number, length, and thickness using a stereomicroscope. Specimens were then paraffin-embedded and stained with hematoxylin and eosin, followed by microscopic examination to assess eyelash morphology and growth cycle.

Results: Eyelash number (143.5 ± 6.7/eyelid), thickness, and percentage of dermal papilla in the anagen phase in the OMDI group were similar to those observed in the vehicle group (eyelash number, 144.2 ± 5.7/eyelid). In contrast, eyelash number (166.7 ± 7.0/eyelid), thickness, and the percentage of dermal papilla in the anagen phase were significantly greater in the bimatoprost group compared with those of the vehicle group.

Conclusions: Unlike existing prostaglandin analogs, our findings indicate that OMDI has no effect on eyelash growth in mice, suggesting that it may be a promising antiglaucoma agent with a reduced number of adverse effects.

Cytidine 5'-Diphosphocholine (Citicoline): Evidence for a Neuroprotective Role in Glaucoma

Glaucoma, a heterogeneous set of progressively degenerative optic neuropathies characterized by a loss of retinal ganglion cells (RGCs) and typical visual field deficits that can progress to blindness, is a neurodegenerative disease involving both ocular and visual brain structures. Although elevated intraocular pressure (IOP) remains the most important modifiable risk factor of primary open-angle glaucoma (POAG) and is the main therapeutic target in treating glaucoma, other factors that influence the disease course are involved and reaching the optimal IOP target does not stop the progression of glaucoma, as the visual field continues to narrow. In addition to a managed IOP, neuroprotection may be beneficial by slowing the progression of glaucoma and improving the visual defects. Citicoline (cytidine 5'-diphosphocholine) is a naturally occurring endogenous compound that has been investigated as a novel therapeutic agent for the management of glaucoma. Citicoline has demonstrated activity in a range of central neurodegenerative diseases, and experimental evidence suggests a it performs a neuromodulator and neuroprotective role on neuronal cells, including RGCs, associated with improvement in visual function, extension of the visual field and central benefits for the patient. This review aims to critically summarize the current evidence for the neuroprotective properties of citicoline in glaucoma.

Norrin Protects Retinal Ganglion Cells from Excitotoxic Damage via the Induction of Leukemia Inhibitory Factor

PURPOSE

To investigate whether and how leukemia inhibitory factor (Lif) is involved in mediating the neuroprotective effects of Norrin on retinal ganglion cells (RGC) following excitotoxic damage. Norrin is a secreted protein that protects RGC from N-methyl-d-aspartate (NMDA)-mediated excitotoxic damage, which is accompanied by increased expression of protective factors such as Lif, Edn2 and Fgf2.

METHODS

Lif-deficient mice were injected with NMDA in one eye and NMDA plus Norrin into the other eye. RGC damage was investigated and quantified by TUNEL labeling 24 h after injection. Retinal mRNA expression was analyzed by quantitative real-time polymerase chain reaction following retinal treatment.

RESULTS

After intravitreal injection of NMDA and Norrin in wild-type mice approximately 50% less TUNEL positive cells were observed in the RGC layer when compared to NMDA-treated littermates, an effect which was lost in Lif-deficient mice. The mRNA expression for Gfap, a marker for Müller cell gliosis, as well as Edn2 and Fgf2 was induced in wild-type mice following NMDA/Norrin treatment but substantially blocked in Lif-deficient mice.

CONCLUSIONS

Norrin mediates its protective properties on RGC via Lif, which is required to enhance Müller cell gliosis and to induce protective factors such as Edn2 or Fgf2.

Assessing the Performance of Daily Intake of a Homotaurine, Carnosine, Forskolin, Vitamin B2, Vitamin B6, and Magnesium Based Food Supplement for the Maintenance of Visual Function in Patients with Primary Open Angle Glaucoma

Background

Glaucoma is a multifactorial optic neuropathy, which causes a continuous loss of retinal ganglion cells. Given the neurodegenerative nature of glaucoma, the necessity for neuroprotective intervention still arises, to be added alongside hypotonic therapy.

Objective

The objective of this study was to assess the effect of daily intake of a homotaurine, carnosine, forskolin, vitamins B1, B2, and B6, folic acid, and magnesium based supplement (GANGLIOLIFE®) on the progression rates of the visual field in patients with progressive POAG despite good tonometric compensation and to assess the most suitable dosage.

Methods

This is a monocentric nonrandomized experimental clinical study. Patients with mean deviation (MD) ranging from -2 dB to -15 dB with MD progression ≥1 dB in the previous year and IOP values of ≤18 mm Hg were included. All the patients underwent supplement therapy for a period of 6 months. For the first 2 months, they took 2 tablets a day, and for the following 4 months, 1 tablet a day. The patients were assessed before the start of treatment, time 0 (T ₀), after 2 months (T ₁), and after 6 months (T ₂) of therapy. At each check-up, patients were given a full eye test including perimetry, RNFL, and GCC using FD-OCT, PERG, contrast sensitivity, and QoL evaluation using the Glaucoma Symptom Scale questionnaire and National Eye Institute Visual Function Questionnaire 25.

Results

31 patients with a mean age of 70.80 ± 8.77 were included. At T ₁ and T ₂, the mean values of MD were lessened (MD = -5.37 ± -2.91, P < 0.01, and MD = -5.48 ± 3.15, P < 0.05, respectively) compared to T ₀ (MD = -5.98 ± 2.83). Patients also demonstrated a significant reduction in IOP (P < 0.01), improved light sensitivity (P < 0.01) and contrast sensitivity (P < 0.05), and a better quality of life (P < 0.05).

Conclusions

Treatment with a supplement which includes homotaurine, carnosine, forskolin, vitamins B1, B2, and B6, folic acid, and magnesium has been shown to be able to slow down the rate of progression of functional damage and improve visual function after 2 and 6 months of daily intake. Quality of life showed significant improvement.

Effects of the Selective EP2 Receptor Agonist Omidenepag on Adipocyte Differentiation in 3T3-L1 Cells

Purpose: We aimed at comparing the effects of omidenepag (OMD) with those of prostaglandin F (FP) receptor agonists (FP agonists) on adipogenesis in mouse 3T3-L1 cells. Methods: To evaluate the agonistic activities of OMD against the mouse EP2 (mEP2) receptor, we determined cAMP contents in mEP2 receptor-expressing CHO cells by using radioimmunoassays. Overall, 3T3-L1 cells were cultured in differentiation medium for 10 days and adipocyte differentiation was assessed according to Oil Red O-stained cell areas. Changes in expression levels of the adipogenic transcription factors Pparg, Cebpa, and Cebpb were determined by using real-time polymerase chain reaction (PCR). OMD at 0.1, 1, 10, and 40 μmol/L, latanoprost free acid (LAT-A) at 0.1 μmol/L, or prostaglandin F_2α (PGF_2α), at 0.1 μmol/L were added to cell culture media during adipogenesis. Oil Red O-stained areas and expression patterns of transcription factor targets of OMD or FP agonists were compared with those of untreated controls. Results: The 50% effective concentration (EC₅₀) of OMD against the mEP2 receptor was 3.9 nmol/L. Accumulations of Oil Red O-stained lipid droplets were observed inside control cells on day 10. LAT-A and PGF_2α significantly inhibited the accumulation of lipid droplets; however, OMD had no effect on this process even at concentrations up to 40 μmol/L. LAT-A and PGF_2α significantly suppressed Pparg, Cebpa, and Cebpb gene expression levels during adipocyte differentiation. Conversely, OMD had no obvious effects on the expression levels of these genes. Conclusions: A selective EP2 receptor agonist, OMD, did not affect the adipocyte differentiation in 3T3-L1 cells, whereas FP agonists significantly inhibited this process.

Is there a relationship between dopamine and rhegmatogenous retinal detachment?

Dopamine and its receptors have been widely studied in the neurological conditions and in the retina. In this study, we evaluated the possible role of dopamine in rhegmatogenous retinal detachment (RRD) by comparing the amount of 3,4-dihydroxyphenylacetic acid (DOPAC), a surrogate index of retinal dopamine levels, in the vitreous sample of patients affected by RRD with those affected by macular pucker and vitreous hemorrhage. Our results showed that significantly higher levels of DOPAC were found in the vitreous sample of patients affected by RRD compared with those affected by vitreous hemorrhage and macular pucker (P = 0.002). Specifically, no trace of the substance was found in vitreous hemorrhage and macular pucker samples. A slightly significant positive correlation was found among DOPAC and post-operative best corrected visual acuity (r = 0.470, P = 0.049). No correlation was found between DOPAC and the days elapsed between diagnosis and surgery (P = 0.317). For the first time our findings suggest that DOPAC is released in RRD, but not in other retinal diseases such as vitreous hemorrhage and macular pucker. Moreover, we showed a correlation between visual acuity outcome and the amount of DOPAC in the vitreous. This might have a potential, although still unknown, implication in the pathogenesis of the disease and/or in the associated photoreceptors loss. This study was approved by the Ethics Committee of Rome Tor Vergata University Hospital (R.S.92.10) on September 24, 2010.

Primary Open Angle Glaucoma Is Associated With Functional Brain Network Reorganization

Background: Resting-state functional magnetic resonance imaging (rs-fMRI) is commonly employed to study changes in functional brain connectivity. The recent hypothesis of a brain involvement in primary open angle Glaucoma has sprung interest for neuroimaging studies in this classically ophthalmological pathology.

Object: We explored a putative reorganization of functional brain networks in Glaucomatous patients, and evaluated the potential of functional network disruption indices as biomarkers of disease severity in terms of their relationship to clinical variables as well as select retinal layer thicknesses.

Methods: Nineteen Glaucoma patients and 16 healthy control subjects (age: 50–76, mean 61.0 ± 8.2 years) underwent rs-fMRI examination at 3T. After preprocessing, rs-fMRI time series were parcellated into 116 regions using the Automated Anatomical Labeling atlas and adjacency matrices were computed based on partial correlations. Graph-theoretical measures of integration, segregation and centrality as well as group-wise and subject-wise disruption index estimates (which use regression of graph-theoretical metrics across subjects to quantify overall network changes) were then generated for all subjects. All subjects also underwent Optical Coherence Tomography (OCT) and visual field index (VFI) quantification. We then examined associations between brain network measures and VFI, as well as thickness of retinal nerve fiber layer (RNFL) and macular ganglion cell layer (MaculaGCL).

Results: In Glaucoma, group-wise disruption indices were negative for all graph theoretical metrics. Also, we found statistically significant group-wise differences in subject-wise disruption indexes in all local metrics. Two brain regions serving as hubs in healthy controls were not present in the Glaucoma group. Instead, three hub regions were present in Glaucoma patients but not in controls. We found significant associations between all disruption indices and VFI, RNFL as well as MaculaGCL. The disruption index based on the clustering coefficient yielded the best discriminative power for differentiating Glaucoma patients from healthy controls [Area Under the ROC curve (AUC) 0.91, sensitivity, 100%; specificity, 78.95%].

Conclusions: Our findings support a possible relationship between functional brain changes and disease severity in Glaucoma, as well as alternative explanations for motor and cognitive symptoms in Glaucoma, possibly pointing toward an inclusion of this pathology in the heterogeneous group of disconnection syndromes.

Enriched environment provides neuroprotection against experimental glaucoma

Glaucoma is one of the most frequent causes of visual impairment worldwide, and involves selective damage to retinal ganglion cells (RGCs) and their axons. We analyzed the effect of enriched environment (EE) housing on the optic nerve, and retinal alterations in an induced model of ocular hypertension. For this purpose, male Wistar rats were weekly injected with vehicle or chondroitin sulfate (CS) into the eye anterior chamber for 10 weeks and housed in standard environment or EE. EE housing prevented the effect of experimental glaucoma on visual evoked potentials, retinal anterograde transport, phosphorylated neurofilament-immunoreactivity, axon number, microglial/macrophage reactivity (ionized calcium binding adaptor molecule 1-immunoreactivity), and astrocytosis (glial fibrillary acidic protein-immunostaining), as well as oligodendrocytes alterations (luxol fast blue staining, and myelin basic protein-immunoreactivity) in the proximal portion of the optic nerve. Moreover EE prevented the increase in ionized calcium binding adaptor molecule-1 levels, and RGC loss (Brn3a-immunoreactivity) in the retina from hypertensive eyes. EE increased retinal brain-derived neurotrophic factor levels. When EE housing started after 6 weeks of ocular hypertension, a preservation of visual evoked potentials amplitude, axon, and Brn3a(+) RGC number was observed. Taken together, these results suggest that EE preserved visual functions, reduced optic nerve axoglial alterations, and protected RGCs against glaucomatous damage.