Programmed cell death of retinal ganglion cells during experimental glaucoma
The death of retinal ganglion cells during glaucoma is thought to result from damage to their axons as they exit the eye through the lamina cribrosa. In this study, intraocular pressure in the rat was increased to twice the normal averge by cauterizing two limbal-derived veins. To investigate whether retinal ganglion cells in the glaucomatous eye follow an apoptotic type of death, DNA breaks in nuclei were labeled in situ, using a method that specifically incorporates biotinylated deoxynucleotides by exogenous terminal deoxynucleotidyl transferase to the 3′-OH ends of DNA. The active nature of the death mechanism was demonstrated by the reduction in numbers of biotin-labeled nuclei after administration of the protein synthesis inhibitor, cycloheximide. Our results suggest that retinal ganglion cells of the adult rat die through apoptosis when the intraocular pressure is markedly increased. This raises new possibilities in the treatment of glaucomatous damage to the retina, by the potential interruptibility of a program for neuronal death.
References (4)
- AbramsL. et al.
Comparison of three tonometers for measuring intraocular pressure in rabbits
Invest. Ophthalmol. Vis. Sci.
(1994) - ArmalyM.F. et al.
Biostatistical analysis of the Collaborative Glaucoma Study, I: summary report of the risk factors for glaucomatous visual-field defects
ARch. Ophthalmol.
(1980)
Cited by (433)
Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments
2024, Progress in Retinal and Eye ResearchGlaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.
Timolol-loaded ethosomes for ophthalmic delivery: Reduction of high intraocular pressure in vivo
2023, International Journal of PharmaceuticsThe beta-adrenoceptor blocker timolol maleate (TML) is a commonly used pharmaceutical agent for the management of glaucoma. Conventional eye drops have limitations due to biological or pharmaceutical factors. Therefore, TML-loaded ethosomes have been designed to mitigate these restrictions and give a viable solution for reducing elevated intraocular pressure (IOP). The ethosomes were prepared using the thin film hydration method. Integrating the Box-Behnken experimental strategy, the optimal formulation was identified. The physicochemical characterization studies were performed on the optimal formulation. Then, in vitro release and ex vivo permeation studies were conducted. The irritation assessment was also carried out with Hen's Egg Test–Chorioallantoic Membrane model (HET-CAM), and in vivo evaluation of the IOP lowering effect was also performed on rats. The physicochemical characterization studies demonstrated that the components of the formulation were compatible with each other. The particle size, zeta potential, and encapsulation efficiency (EE%) were found as 88.23 ± 1.25 nm, −28.7 ± 2.03 mV, and 89.73 ± 0.42 %, respectively. The in vitro drug release mechanism was found as Korsmeyer-Peppas kinetics (R2 = 0.9923). The HET-CAM findings verified the formulation's eligibility for biological applications. The IOP measurements revealed no statistical difference (p > 0.05) between the once-a-day application of the optimal formulation and the three-times-a-day application of the conventional eye drop. A similar pharmacological response was observed at lowered application frequencies. Therefore, it was concluded that the novel TML-loaded ethosomes could be a safe and efficient alternative for glaucoma treatment.
Mitochondrial Dysfunction in Primary Open-Angle Glaucoma Characterized by Flavoprotein Fluorescence at the Optic Nerve Head
2022, Ophthalmology GlaucomaTo investigate the presence of flavoprotein fluorescence (FPF) at the optic nerve head (ONH) rim as a marker of mitochondrial dysfunction in primary open-angle glaucoma (POAG) and control eyes.
Retrospective cross-sectional study of patients recruited from the New York Eye and Ear Infirmary of Mount Sinai.
A total of 86 eyes (50 eyes of 30 patients with POAG and 36 eyes of 20 control participants) were enrolled. The presence of POAG was defined by circumpapillary retinal nerve fiber layer thickness (cpRNFLT) of less than the bottom fifth percentile of the normative database, glaucomatous ONH changes, and visual field defects on 24-2 tests.
Primary open-angle glaucoma and control eyes were imaged using the OcuMet Beacon. A 23° × 23° infrared scan was obtained, and an FPF scan was performed within a capture field spanning 13° in diameter. The ONH margins on the infrared image were identified by software algorithms. Then, FPF was measured within an elliptical annulus around the ONH rim, with the inner and outer boundaries corresponding to 0.5 to 1.1 times the ONH rim size.
Flavoprotein fluorescence at the OHN rim in POAG and control eyes.
Differences in FPF between POAG and control eyes were characterized through mixed-effects logistic regression, adjusted for age and interocular pressure. Flavoprotein fluorescence was significantly higher in POAG versus control eyes, with a mean ± SD of 46.4 ± 27.9 versus 28.0 ± 11.7 (P < 0.001), respectively. Among POAG eyes, FPF showed correlation to visual field mean deviation (P < 0.001), visual field pattern standard deviation (P = 0.003), and cpRNFLT (P = 0.001) on linear mixed-effects models.
Higher FPF in POAG versus control eyes suggests the presence of mitochondrial dysfunction at the ONH rim in eyes with glaucomatous damage. The degree of FPF corresponds to disease severity, as measured by visual field and nerve fiber layer thickness metrics. Thus, FPF may represent a metabolic indicator of disease status that reveals the extent of injury in glaucoma.
Age and intraocular pressure in murine experimental glaucoma
2022, Progress in Retinal and Eye ResearchAge and intraocular pressure (IOP) are the two most important risk factors for the development and progression of open-angle glaucoma. While IOP is commonly considered in models of experimental glaucoma (EG), most studies use juvenile or adult animals and seldom older animals which are representative of the human disease. This paper provides a concise review of how retinal ganglion cell (RGC) loss, the hallmark of glaucoma, can be evaluated in EG with a special emphasis on serial in vivo imaging, a parallel approach used in clinical practice. It appraises the suitability of EG models for the purpose of in vivo imaging and argues for the use of models that provide a sustained elevation of IOP, without compromise of the ocular media. In a study with parallel cohorts of adult (3-month-old, equivalent to 20 human years) and old (2-year-old, equivalent to 70 human years) mice, we compare the effects of elevated IOP on serial ganglion cell complex thickness and individual RGC dendritic morphology changes obtained in vivo. We also evaluate how age modulates the impact of elevated IOP on RGC somal and axonal density in histological analysis as well the density of melanopsin RGCs. We discuss the challenges of using old animals and emphasize the potential of single RGC imaging for understanding the pathobiology of RGC loss and evaluating new therapeutic avenues.
A network pharmacology-based strategy for predicting the protective mechanism of Ginkgo biloba on damaged retinal ganglion cells
2022, Chinese Journal of Natural MedicinesHallmarks of the pathophysiology of glaucoma are oxidative stress and apoptotic death of retinal ganglion cells (RGCs). Ginkgo biloba extract (EGb) with multi-target, multi-pathway functions has been reported to exert positive pharmacological effects on oxidative stress and damaged RGCs. However, the ingredients and anti-apoptotic targets of EGb in the treatment of open-angle glaucoma (OAG) have not been fully elucidated. Therefore, in-depth analysis is necessary for further research. Ginkgo biloba-related and anti-apoptotic targets were identified and then combined to obtain the intersection, representing the potential anti-apoptotic targets of Ginkgo biloba. In addition, compound-anti-apoptotic target and OAG-target protein-protein interaction network were merged to obtain five core genes and compound-OAG-anti-apoptotic target protein-protein interaction network. Consequently, the active compounds and anti-apoptotic targets of Ginkgo biloba in the treatment of OAG were identified, namely luteolin, β-sitosterol, kaempferol, stigmasterol, quercetin, and p53, Bax, Bcl-2, Caspase-3 and Caspase-9, respectively. For the anti-apoptotic targets of Ginkgo biloba in the treatment of OAG, Gene Ontology (GO) and pathway analysis were executed to confirm the gene functions of Ginkgo biloba in antagonizing apoptosis of RGCs. The pathway enrichment was mainly involved in transcriptional activation of p53 responsive genes, activation of caspases and apoptotic processes. Finally, we confirmed the results of the network analysis by H2O2 treated RGC-5 cells in vitro. The results demonstrated that EGb protection can effectively diminish H2O2-induced apoptosis by inhibiting p53 acetylation, reducing the ratio of Bax/Bcl-2 and suppressing the expression of specific cleavage of Caspase-9 and Caspase-3.
Detecting retinal cell stress and apoptosis with DARC: Progression from lab to clinic
2022, Progress in Retinal and Eye ResearchDARC (Detection of Apoptosing Retinal Cells) is a retinal imaging technology that has been developed within the last 2 decades from basic laboratory science to Phase 2 clinical trials. It uses ANX776 (fluorescently labelled Annexin A5) to identify stressed and apoptotic cells in the living eye. During its development, DARC has undergone biochemistry optimisation, scale-up and GMP manufacture and extensive preclinical evaluation. Initially tested in preclinical glaucoma and optic neuropathy models, it has also been investigated in AMD, Alzheimer's, Parkinson's and Diabetic models, and used to assess efficacy of therapies. Progression to clinical trials has not been speedy. Intravenous ANX776 has to date been found to be safe and well-tolerated in 129 patients, including 16 from Phase 1 and 113 from Phase 2. Results on glaucoma and AMD patients have been recently published, and suggest DARC with an AI-aided algorithm can be used to predict disease activity. New analyses of DARC in GA (Geographic Atrophy) prediction are reported here. Although further studies are needed to validate these findings, it appears there is potential for the technology to be used as a biomarker. Much larger clinical studies will be needed before it can be considered as a diagnostic, although the relatively non-invasive nature of the nasal as opposed to intravenous administration would widen its acceptability in the future as a screening tool.
This review describes DARC development and its progression into Phase 2 clinical trials from lab-based research. It discusses hypotheses, potential challenges, and regulatory hurdles in translating technology.