Effect of adenosine triphosphate on amiodarone-induced optic neuropathy in rats: biochemical and histopathological evaluation.

OBJECTIVE: This study aims to investigate possible preventive effect of ATP on optic nerve damage caused by amiodarone in rats. MATERIAL AND METHOD: Thirty albino male Wistar rats weighing between 265 and 278 g were used in the study. Before the experiment, the rats were housed at 22 °C in a 12-h light/dark cycle under appropriate condition. The rats were equally divided into five groups of six animals each: healthy group, 50 mg/kg amiodarone (AMD-50), 100 mg/kg amiodarone (AMD-100), 25 mg/kg ATP + 50 mg/kg amiodarone (ATAD-50), and 25 mg/kg ATP + 100 mg/kg amiodarone (ATAD-100). At the end of 14th day, the animals were sacrificed using cardiac puncture under deep thiopental anaesthesia, and optic nerve tissues were harvested to measure superoxide dismutase (SOD), total glutathione (tGSH), malondialdehyde (MDA), and catalase (CAT) levels. RESULTS: The MDA levels were found to be significantly higher in the AMD-50 and AMD-100 groups compared to the healthy group (p ˂ 0.001). There was also a significant difference between the AMD-50 and ATAD-50 groups, and between the AMD-100 and ATAD-100 groups regarding MDA levels (p ˂ 0.001). tGSH, SOD, and CAT levels were significantly lower in the AMD-50 and AMD-100 groups compared to the healthy group (p ˂ 0.001). ATP was found to partially inhibit amiodarone-induced optic neuropathy. CONCLUSION: The biochemical and histopathological results of this study demonstrated that amiodarone at high doses caused more severe optic neuropathy inducing oxidative damage, but ATP could relatively antagonise these negative effects on the optic nerve. Therefore, we believe that ATP may be beneficial in preventing amiodarone-induced optic neuropathy.

Optic Neuropathies: Current and Future Strategies for Optic Nerve Protection and Repair.

Processes that damage the optic nerve, including elevated intraocular pressure, trauma, ischemia, and compression, often cause visual loss for which there is no current treatment [...].

Continuous Hypoxia Reduces Retinal Ganglion Cell Degeneration in a Mouse Model of Mitochondrial Optic Neuropathy.

Purpose: To test whether continuous hypoxia is neuroprotective to retinal ganglion cells (RGCs) in a mouse model of mitochondrial optic neuropathy. Methods: RGC degeneration was assessed in genetically modified mice in which the floxed gene for the complex I subunit NDUFS4 is deleted from RGCs using Vlgut2-driven Cre recombinase. Beginning at postnatal day 25 (P25), Vglut2-Cre;ndufs4loxP/loxP mice and control littermates were housed under hypoxia (11% oxygen) or kept under normoxia (21% oxygen). Survival of RGC somas and axons was assessed at P60 and P90 via histological analysis of retinal flatmounts and optic nerve cross-sections, respectively. Retinal tissue was also assessed for gliosis and neuroinflammation using western blot and immunofluorescence. Results: Consistent with our previous characterization of this model, at least one-third of RGCs had degenerated by P60 in Vglut2-Cre;ndufs4loxP/loxP mice remaining under normoxia. However, continuous hypoxia resulted in complete rescue of RGC somas and axons at this time point, with normal axonal myelination observed on electron microscopy. Though only partial, hypoxia-mediated rescue of complex I-deficient RGC somas and axons remained significant at P90. Hypoxia prevented reactive gliosis at P60, but the retinal accumulation of Iba1+ mononuclear phagocytic cells was not substantially reduced. Conclusions: Continuous hypoxia achieved dramatic rescue of early RGC degeneration in mice with severe mitochondrial dysfunction. Although complete rescue was not durable to P90, our observations suggest that investigating the mechanisms underlying hypoxia-mediated neuroprotection of RGCs may identify useful therapeutic strategies for optic neuropathies resulting from less profound mitochondrial impairment, such as Leber hereditary optic neuropathy.

Advanced Therapy and Clinical Trials to Treat Patients with Optic Nerve Diseases.

Optic nerve diseases include a wide variety of pathogenic conditions triggering injury or dysfunction of the optic nerves that lead to visual impairment or blindness in one or both eyes. Despite their pathogenic variety, most of them proceed through common mechanisms that allow them to investigate together. Nevertheless, roles of the cells, tissues, genes, growth factors, and proteins, and all underlying pathophysiological mechanisms need to be studied fully for better management of each optic nerve disease. This review presents a collection of information regarding ongoing and completed clinical trials (CT) of advanced therapies that deliver stem cell and gene therapy treatments as drugs to patients with optic nerve diseases as well as successes and failures achieved in treating these patients in the last few years. These drugs seem safe from creating neurotoxicity. It describes outcomes of a bibliographic search for stem cell therapy, gene therapy, and neuroprotection-based CT registered in the International ClinicalTrials.gov, the European EudraCT, and the Spanish REEC database, and related papers published in the PUBMED database by applying different search terminologies. This review overall informs the patients of optic neurodiseases that advanced therapies are progressing successfully in search of effective and safe treatments for them.

A Review on the Application of Stem Cell Secretome in the Protection and Regeneration of Retinal Ganglion Cells; a Clinical Prospect in the Treatment of Optic Neuropathies.

PURPOSE: Retinal ganglion cells (RGCs) are one the most specialized neural tissues in the body. They transmit (and further process) chemoelectrical information originating in outer retinal layers to the central nervous system. In fact, the optic nerve is composed of RGC axons. Like other neural cells, RGCs will not completely heal after the injury, leading to irreversible vision loss from disorders such as glaucoma that primarily affect these cells. Several methods have been developed to protect or regenerate RGCs during or after the insult has occurred. This study aims to review the most recent clinical, animal and laboratory experiments designed for the regeneration of RGC that apply the stem cell-derived secretome. METHODS: We extracted the studies from Web of Science (ISI), Medline (PubMed), Scopus, Embase, and Google scholar from the first record to the last report registered in 2022, using the following keywords; "secretome" OR "conditioned medium" OR "exosome" OR "extracellular vesicle" AND "stem cell" AND "RGC" OR "optic neuropathy". Any registered clinical trials related to the subject were also extracted from clinicaltrial.gov. All published original studies that express the effect of stem cell secretome on RGC cells in optic neuropathy, whether in vitro, in animal studies, or in clinical trials were included in this survey. RESULTS: In this review, we provided an update on the existing reports, and a brief description of the details applied in the procedure. Compared to cell transplant, applying stem cell-derived secretome has the advantage of minimized immunogenicity yet preserving efficacy via its rich content of growth factors. CONCLUSIONS: Different sources of stem cell secretomes have distinct implications in the management of RGC injury, which is the main subject of the present article.

Ethambutol toxicity: Expert panel consensus for the primary prevention, diagnosis and management of ethambutol-induced optic neuropathy.

Ethambutol use may lead to permanent vision loss by inducing a dose- and duration-dependent optic neuropathy. This has been of concern to ophthalmologists and physicians both; however, ethambutol continues to be used because of its anti-mycobacterial action with relative systemic safety. Recently, the guidelines of the Revised National Tuberculosis Control Programme of India have been revised to allow for fixed dose and longer duration of ethambutol use; this is likely to result in an increase in vision-threatening adverse effects. Taking cognizance of this, neuro-ophthalmologists, infectious disease specialists, and scientists met under the aegis of the Indian Neuro-Ophthalmology Society to deliberate on prevention, early diagnosis, and management of ethambutol-related toxic optic neuropathy. The recommendations made by the expert group focus on early suspicion of ethambutol toxicity through screening at the physician's office and opportunistic screening by the ophthalmologist. Further, they focus on an early diagnosis through identification of specific clinical biomarkers and on management in way of early stoppage of the drug and supportive therapy. This statement also describes the mechanism of reporting a case of toxic optic neuropathy through the Pharmacovigilance Programme of India and emphasizes the need for spreading awareness regarding vision-threatening adverse effects among patients and healthcare workers.

Presumed neuroprotective therapies prescribed by veterinary ophthalmologists for canine degenerative retinal and optic nerve diseases.

OBJECTIVE: To investigate veterinary ophthalmologists' use of presumed neuroprotective therapies for degenerative retinal and optic nerve diseases in dogs. PROCEDURES: An online survey was sent to 663 board-certified veterinary ophthalmologists who were Diplomates of the American College of Veterinary Ophthalmologists (ACVO), Asian College of Veterinary Ophthalmologists (AiCVO), Latin American College of Veterinary Ophthalmologists (Colegio Latinoamericano de Oftalmólogos Veterinarios, CLOVE), or European College of Veterinary Ophthalmologists (ECVO). The survey was created using Qualtrics® software and focused on the prescription of presumed neuroprotective treatments for canine glaucoma, sudden acquired retinal degeneration syndrome (SARDS), progressive retinal atrophy (PRA), and retinal detachment (RD). RESULTS: A total of 165 completed surveys were received, representing an overall response rate of 25%, which was comparable across the four specialty colleges. Of all respondents, 140/165 (85%) prescribed some form of presumed neuroprotective therapies at least once in the last five years: 114/165 (69%) for glaucoma, 51/165 (31%) for SARDS, 116/165 (70%) for PRA, and 50/165 (30%) for RD. The three most recommended neuroprotective reagents were the commercial Ocu-GLO™ Vision Supplement for animals, amlodipine, and human eye supplements. CONCLUSIONS: Despite lack of published clinical efficacy data, the majority of surveyed board-certified veterinary ophthalmologists previously prescribed a presumed neuroprotective therapy at least once in the last five years in dogs with degenerative retinal and optic nerve diseases.

Protection of retinal ganglion cells in glaucoma: Current status and future.

Glaucoma is a neuropathic disease that causes optic nerve damage, loss of retinal ganglion cells (RGCs), and visual field defects. Most glaucoma patients have no early signs or symptoms. Conventional pharmacological glaucoma medications and surgeries that focus on lowering intraocular pressure are not sufficient; RGCs continue to die, and the patient's vision continues to decline. Recent evidence has demonstrated that neuroprotective approaches could be a promising strategy for protecting against glaucoma. In the case of glaucoma, neuroprotection aims to prevent or slow down disease progression by mitigating RGCs death and optic nerve degeneration. Notably, new pharmacologic medications such as antiglaucomatous agents, antibiotics, dietary supplementation, novel neuroprotective molecules, neurotrophic factors, translational methods such as gene therapy and cell therapy, and electrical stimulation-based physiotherapy are emerging to attenuate the death of RGCs, or to make RGCs resilient to attacks. Understanding the roles of these interventions in RGC protection may offer benefits over traditional pharmacological medications and surgeries. In this review, we summarize the recent neuroprotective strategy for glaucoma, both in clinical trials and in laboratory research.

Ethambutol Optic Neuropathy: Vigilance and Screening, the Keys to Prevent Blindness with the Revised Anti-tuberculous Therapy Regimen.

There has been change in the guidelines for the management of tuberculosis in India. The new guidelines advocate the daily use of Ethambutol for both intensive and continuation phase of the treatment. This may be a matter of concern as increased cumulative dose may lead to increase in incidence of toxic optic neuropathy due to ethambutol. Indian Neuro-Ophthalmology Society has taken cognizance of the issue and has come-up with guidelines for prevention and early detection of the toxic optic neuropathy.

ROCK inhibitors beneficially alter the spatial configuration of TGFß2-treated 3D organoids from a human trabecular meshwork (HTM).

To elucidate molecular pharmacology of Rho-associated coiled-coil containing protein kinase inhibitors (ROCK-i, Ripasudil and Y27632) on their efficiency for aqueous outflow, 2D or 3D cultures of a human trabecular meshwork (HTM) were prepared in the presence of TGFß2. Those were examined by transendothelial electrical resistance (TEER, 2D), electronic microscopy (EM, 2D and 3D), expression of the extracellular matrix (ECM) including collagen1 (COL1), COL4 and COL6, and fibronectin (FN) by immunolabeling and/or quantitative PCR (3D), and solidity of 3D organoids by a micro-squeezer. TGFß2 significantly increased the TEER values in 2D cultures, and the ECM expression indicated that the 3D organoids assumed a more densely packed shape. ROCK-i greatly reduced the TGFß2-induced enhancement of TEER and the immunolabeled ECM expression of the 3D organoids. In contrast, the mRNA expression of COL1 was increased, and those of COL4 and FN were unchanged. EM revealed that TGFß2 caused the HTM cells to become more compact and abundant ECM deposits within the 3D organoids were observed. These were significantly inhibited by ROCK-i. The dense solids caused by the presence of TGFß2 were significantly suppressed by ROCK-i. Current study indicates that ROCK-i cause beneficial effects toward the spatial configuration of TGFß2-induced HTM 3D organoids.

Axonal protection by a small molecule SIRT1 activator, SRT2104, with alteration of autophagy in TNF-induced optic nerve degeneration.

PURPOSE: To examine the effects of SRT2104, an SIRT1 activator, in optic nerve degeneration induced by TNF and to investigate whether it affects the autophagic status after induction of axonal degeneration. STUDY DESIGN: Experimental. METHODS: Adult male Wistar rats received intravitreal injection of TNF alone, concomitant injection of SRT2104 and TNF, or injection of SRT2104 alone. The autophagic status in the optic nerve was evaluated to examine p62 and LC3-II expression by immunoblot analysis. The effect of SRT2104 on TNF-induced axon loss was determined by counting the number of axons. RESULTS: Intravitreal injection of SRT2104 showed a modest protective tendency in the 2-pmol-treated groups against TNF-induced axon loss, although the tendency was not significant on quantitative analysis. However, significant protective effects were found in the 20- or 200-pmol-treated groups. Injection of SRT2104 alone significantly decreased the p62 levels and increased the LC3-II levels as compared with the basal levels. Similarly, concomitant injection of SRT2104 and TNF significantly decreased the p62 levels and increased the LC3-II levels as compared with the TNF-treated group. Upregulation of SIRT1 expression was observed in the optic nerve after SRT2104 treatment. CONCLUSION: The SIRT1 activator SRT2104 exerts axonal protection in TNF-induced optic nerve degeneration. This effect may be associated with upregulated autophagic status in the optic nerve.

Does TRABECULECTOMY meet the 10-10-10 challenge in PACG, POAG, JOAG and Secondary glaucomas?

PURPOSE: Evaluation of the intraocular pressure (IOP) lowering efficacy of trabeculectomies over > 10 years and their ability to stabilize glaucomatous optic neuropathy. METHODS: In total, 181 eyes (136 patients), which underwent trabeculectomy (10 min surgery) at least 10 years prior and were on regular follow-up, were evaluated. Qualified/complete success was taken as criteria A: IOP ≤ 12 mmHg, B: IOP ≤ 15 mmHg and C: IOP ≤ 18 mmHg, with all > 5 mmHg, with/without medications. Target IOP in advanced glaucoma is about 10 mmHg, therefore trabeculectomy 10-10-10 challenge! RESULTS: The mean age of patients was 46.32 ± 11.50 years. Absolute success was 50.27%, 54.14% and 59.66% according to criteria A, B and C at last follow-up, while qualified success was 70.11%, 81.77% and 96.13%. An IOP of ≤ 12 mmHg was noted in 34, 64.15%, PACG eyes, 14, 73.68%, POAG, 15, 65.22%, JOAG and 64, 74.42%, secondary glaucoma eyes. The reduction in IOP overall was 64.83 ± 16.80% at last review and was 59.47 ± 16.07% in PACG, 62.40 ± 17.72% in POAG, 71.89 ± 8.50% in JOAG and 67.74 ± 18.10% in secondary glaucoma eyes. "Target" IOP was achieved in 97.29% of early glaucoma, 85.71% moderate glaucoma and 70% severe glaucoma eyes. 97.24% of patients were perimetrically stable. 2.21% of eyes post-trabeculectomy had a shallow anterior chamber needing surgical intervention. Visual acuity was maintained or better in 93.92% of patients, with a cataract surgery performed in 6.63% eyes. A repeat trabeculectomy was performed in 3.31% of eyes. CONCLUSION: Trabeculectomy 10-10-10 is achievable in the long term, with few complications or repeat surgical interventions in the majority of POAG, PACG, JOAG and secondary glaucomas. Therefore, trabeculectomy should not be relegated to a last resort, but should be undertaken as soon as possible, if medical therapy is inadequate, unaffordable or compliance is an issue.

The neuroprotective role of citicoline treatment in glaucoma - 6 months results of a prospective therapeutic trial.

Objectives. Neuroprotective treatment, including citicoline, is a new perspective in glaucoma management, having the role of progression delay. The purpose of the present study was to observe the evolution of the different parameters in patients with glaucoma treated with citicoline. Methods. 22 patients with GPUD were enrolled in the study, and they received oral citicoline in addition to the ocular hypotensive therapy. Investigations were performed at the beginning of the current study, then at 3 months and 6 months, and included, besides full ophthalmologic checkup and IOP determination, optic nerve and RGCs OCT, and visual evoked potentials, pattern and flash. The data we obtained were statistically analyzed with the SPSS (Microsoft) program. Results. The outcomes of the study following VEP wave analysis indicated variations in P100 wave amplitude, but after 6 months period, an increase was found. Also, the P2 wave amplitude recorded statistically insignificant variations. The increase in P2 latency at 6 months was noted as statistically significant. Negative correlations were also met between the thickness of the RGC layer and the P100 latency, but also between the amplitude and the latency of this wave. At 6 months, a positive correlation between the RGC layer and the P100 amplitude was observed. The RNFL thickness at the optical disc had higher values at the 6 months visit, it was statistically significant, and a slight increase in the thickness of the RGC layer between successive visits was noted. These might be an examination artifact because clinically they are not possible. The RNFL thickness showed a positive correlation with the amplitude of P100 and P2 waves. Conclusions. The study of the parameters and their correlations demonstrated that citicoline had positive effects in glaucoma on certain aspects, data confirmed by literature.

Axonal Protection by Tacrolimus with Inhibition of NFATc1 in TNF-Induced Optic Nerve Degeneration.

Tacrolimus, a calcineurin (CaN) inhibitor, has been used for treatment of refractory allergic ocular disease, although its role in optic nerve degeneration remains to be elucidated. In this study, we investigated whether tacrolimus modulates tumor necrosis factor (TNF)-mediated axonal degeneration and whether it alters nuclear factor of activated T cells (NFATc), a downstream effector of CaN signaling. Immunoblot analysis showed no significant difference in CaNAα protein levels in optic nerve on day 3, 7, or 14 after TNF injection compared with PBS injection. However, a significant increase in NFATc1 protein level was observed in optic nerve 7 days after TNF injection. This increase was negated by simultaneous administration of tacrolimus. Administration of tacrolimus alone did not change the NFATc1 protein level in comparison to that observed after PBS injection. A significant increase in TNF protein level was observed in optic nerve 14 days after TNF injection and this increase was prevented by tacrolimus. Immunohistochemical analysis showed the immunoreactivity of NFATc1 to be increased in optic nerve after TNF injection. This increased immunoreactivity was colocalized with glial fibrillary acidic protein and was suppressed by tacrolimus. Treatment of tacrolimus significantly ameliorated the TNF-mediated axonal loss. These results suggest that tacrolimus is neuroprotective against axon loss in TNF-induced optic neuropathy and that the effect arises from suppression of the CaN/NFATc1 pathway.

Physiological motion of the optic chiasm and its impact on stereotactic radiosurgery dose.

OBJECTIVE: Avoidance of radiation-induced optic neuropathy (RION) from stereotactic radiosurgery (SRS) requires precise anatomical localization; however, no prior studies have characterized the physiologic motion of the optic chiasm. We measured the extent of chiasm motion and its impact on SRS dose. METHODS: In this cross-sectional study, serial MRI was performed in multiple planes in 11 human subjects without optic pathway abnormalities to determine chiasm motion across time. Subsequently, the measured displacement was applied to the hypothetical chiasm dose received in 11 patients treated with SRS to a perichiasmatic lesion. RESULTS: On sagittal images, the average anteroposterior chiasm displacement was 0.51 mm [95% confidence interval (CI) 0.27 - 0.75 mm], and the average superior-inferior displacement was 0.48 mm (95% CI 0.22 - 0.74 mm). On coronal images, the average superior-inferior displacement was 0.42 mm (95% CI 0.13 - 0.71 mm), and the average lateral displacement was 0.75 mm (95% CI 0.42 - 1.08 mm). In 11 patients who underwent SRS to a perichiasmatic lesion, the average displacements increased the maximum chiasm dose (Dmax) by a mean of 14 % (range 6-23 %; p < 0.001). CONCLUSION: Average motion of the optic chiasm was approximately 0.50-0.75 mm, which increased chiasm Dmax by a mean of 14%. In the occasional patient with higher-than-average chiasm motion in a region of steep dose gradient, the increase in chiasm Dmax and risk of RION could be even larger. Similarly, previously reported chiasm dose constraints may underestimate the true dose received during radiosurgery. ADVANCES IN KNOWLEDGE: To limit the risk of RION, clinicians may consider adding a 0.50-0.75 mm expansion to the chiasm avoidance structure.

Mesenchymal Stem Cell-Derived Small Extracellular Vesicles Promote Neuroprotection in a Genetic DBA/2J Mouse Model of Glaucoma.

Purpose: To determine if bone marrow-derived stem cell (BMSC) small extracellular vesicles (sEV) promote retinal ganglion cell (RGC) neuroprotection in the genetic DBA/2J mouse model of glaucoma for 12 months. Methods: BMSC sEV and control fibroblast-derived sEV were intravitreally injected into 3-month-old DBA/2J mice once a month for 9 months. IOP and positive scotopic threshold responses were measured from 3 months: IOP was measured monthly and positive scotopic threshold responses were measured every 3 months. RGC neuroprotection was determined in wholemounts stained with RNA binding protein with multiple splicing (RBPMS), whereas axonal damage was assessed using paraphenylenediamine staining. Results: As expected, DBA/2J mice developed chronic ocular hypertension beginning at 6 months. The delivery of BMSC sEV, but not fibroblast sEV, provided significant neuroprotective effects for RBPMS+ RGC while significantly reducing the number of degenerating axons seen in the optic nerve. BMSC sEV significantly preserved RGC function in 6-month-old mice, but provided no benefit at 9 and 12 months. Conclusions: BMSC sEV are an effective neuroprotective treatment in a chronic model of ocular hypertension for 1 year, preserving RGC numbers and protecting against axonal degeneration.