Treatment and Relapse Prevention of Typical and Atypical Optic Neuritis.

Optic neuritis (ON) is an inflammatory condition involving the optic nerve. Several important typical and atypical ON variants are now recognized. Typical ON has a more favorable prognosis; it can be idiopathic or represent an early manifestation of demyelinating diseases, mostly multiple sclerosis (MS). The atypical spectrum includes entities such as antibody-driven ON associated with neuromyelitis optica spectrum disorder (NMOSD) and myelin oligodendrocyte glycoprotein antibody disease (MOGAD), chronic/relapsing inflammatory optic neuropathy (CRION), and sarcoidosis-associated ON. Appropriate and timely diagnosis is essential to rapidly decide on the appropriate treatment, maximize visual recovery, and minimize recurrences. This review paper aims at presenting the currently available state-of-the-art treatment strategies for typical and atypical ON, both in the acute phase and in the long-term. Moreover, emerging therapeutic approaches and novel steps in the direction of achieving remyelination are discussed.

The background occurrence of selected clinical conditions prior to the start of an extensive national vaccination program in Japan.

INTRODUCTION: The COVID-19 pandemic caused by SARS-CoV-2 has now affected tens of millions of people globally. It is the hope that vaccines against SARS-CoV-2 will deliver a comprehensive solution to this global pandemic; however, this will require extensive national vaccination programs. Ultimately, clinical conditions and even sudden unexplained death will occur around the time of vaccination, thus a distinction needs to be made between events that are causally related to the vaccine or temporally related to vaccination. This study aimed to estimate the background occurrence of 43 clinical conditions in the Japanese population. METHODS: A retrospective cohort study was conducted from 2013 to 2019 using data from two large healthcare claims databases (MDV and JMDC) in Japan. The estimated number of new cases and incidence were calculated based on the actual number of new cases identified in the databases. The PubMed and Ichushi-web databases, as well as grey literature such as guidelines and government statistics, were also searched to identify any publications related to incidence of these conditions in Japan. RESULTS AND CONCLUSION: The estimates of the number of total cases and incidence were similar for the MDV and JMDC databases for some diseases. In addition, some estimates were similar to those in the scientific literature. For example, from the MDV and JMDC databases, estimates of incidence of confirmed Bell's palsy in 2019 were 41.7 and 47.9 cases per 100,000 population per year, respectively. These estimates were of the same order from the scientific publication. Determining whether clinical conditions occurring around the time of vaccination are causally or only temporally related to vaccination will be critical for public health decision makers as well as for the general public. Comparison of background occurrence at the population level may provide some additional objective evidence for the evaluation of temporality or causality.

Dexras1 Deletion and Iron Chelation Promote Neuroprotection in Experimental Optic Neuritis.

Dysregulation of iron metabolism, and resultant cytotoxicity, has been implicated in the pathogenesis of multiple sclerosis (MS) and other neurodegenerative processes. Iron accumulation promotes cytotoxicity through various mechanisms including oxidative stress and glutamate toxicity, and occurs in both MS patients and in the experimental autoimmune encephalomyelitis (EAE) model of MS. Divalent Metal Transporter1, a major iron importer in cells, is stimulated by signaling of Dexras1, a small G protein member of the Ras family. Dexras1 is activated by S-nitrosylation by nitric oxide (NO) produced by either inducible nitric oxide synthase in activated microglia/macrophages or neuronal nitric oxide synthase in neurons. Here we show Dexras1 exacerbates oxidative stress-induced neurodegeneration in experimental optic neuritis, an inflammatory demyelinating optic nerve condition that occurs in MS and EAE. Dexras1 deletion, as well as treatment with the iron chelator deferiprone, preserves vision and attenuates retinal ganglion cell (RGC) and axonal loss during EAE optic neuritis. These results suggest that iron entry triggered by NO-activated Dexras1 signaling is a potential mechanism of neuronal death in experimental optic neuritis. The current data suggest modulation of Dexras1 signaling and iron chelation are potential novel treatment strategies for optic neuritis and MS, and possibly other optic neuropathies as well.

Effects of Varying Intranasal Treatment Regimens in ST266-Mediated Retinal Ganglion Cell Neuroprotection.

INTRODUCTION: Previous studies have shown that intranasally administered ST266, a novel biological secretome of amnion-derived multipotent progenitor cells containing multiple growth factors and anti-inflammatory cytokines, attenuated visual dysfunction and prevented retinal ganglion cell (RGC) loss in experimental optic neuritis. Long-term effects and dose escalation studies examined here have not been reported previously. METHODS: Optic neuritis was induced in the multiple sclerosis model experimental autoimmune encephalomyelitis (EAE). EAE and control mice were treated once or twice daily with intranasal placebo/vehicle or ST266 beginning after onset of optic neuritis for either 15 days or continuously until sacrifice. Visual function was assessed by optokinetic responses (OKRs). RGC survival and optic nerve inflammation and demyelination were measured. RESULTS: Both once and twice daily continuous intranasal ST266 treatment from disease onset to 56 days after EAE induction significantly increased OKR scores, decreased RGC loss, and reduced optic nerve inflammation and demyelination compared with placebo (saline, nonspecific protein solution, or cell culture media)-treated EAE mice. ST266 treatment given for just 15 days after disease onset, then discontinued, only delayed OKR decreases, and had limited effects on RGC survival and optic nerve inflammation 56 days after disease induction. CONCLUSIONS: ST266 is a potential neuroprotective therapy to prevent RGC damage, and intranasal delivery warrants further study as a novel mechanism to deliver protein therapies for optic neuropathies. Results suggest that once daily ST266 treatment is sufficient to sustain maximal benefits and demonstrate that neuroprotective effects promoted by ST266 are specific to the combination of factors present in this complex biologic therapy.

Prophylactic Treatment with Intravenous Immunoglobulin Attenuates Experimental Optic Neuritis in Mice.

Optic neuritis is characterized by optic nerve inflammation, demyelination and axonal loss. Intravenous immunoglobulin (IVIg) has been reported to be effective for steroid-resistant patients. However, there is no report investigating the histopathological efficacy of IVIg in optic neuritis models. In this study, we examined the effects of IVIg on optic neuritis of experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune optic neuritis (EAON). Inflammation, demyelination and axonal loss were assessed in the optic nerve sections. IVIg showed dose-dependent prevention of clinical symptoms in EAON. IVIg provided an anti-inflammatory effect in both EAE and EAON, associated with improved demyelination. Axonal loss in EAE was also significantly attenuated. These results suggest that IVIg has neuroprotective properties in experimental optic neuritis, and is a promising new treatment for optic neuritis.

The retinoprotective role of phenytoin.

Phenytoin is a non-sedative barbiturate derivate and has been recently rediscovered as a neuroprotective and retinoprotective compound in patients affected by optic neuritis secondary to multiple sclerosis. However, currently there are still no neuroprotective compounds registered and available in the clinic. We reviewed the literature supporting the retinoprotective properties of phenytoin and analyzed the various approaches and definitions from the first research periods onwards. The retinoprotective role of phenytoin was already known in the 1970s, but only recently has this effect been rediscovered, confirming that it could indeed provide structural protection of the retinal cells.

Neuroprotection by eIF2α-CHOP inhibition and XBP-1 activation in EAE/optic neuritiss.

No therapies exist to prevent neuronal deficits in multiple sclerosis (MS), because the molecular mechanism responsible for the progressive neurodegeneration is unknown. We previously showed that axon injury-induced neuronal endoplasmic reticulum (ER) stress plays an important role in retinal ganglion cell (RGC) death and optic nerve degeneration in traumatic and glaucomatous optic neuropathies. Optic neuritis, one of the most common clinical manifestations of MS, is readily modeled by experimental autoimmune encephalomyelitis (EAE) in mouse. Using this in vivo model, we now show that ER stress is induced early in EAE and that modulation of ER stress by inhibition of eIF2α-CHOP and activation of XBP-1 in RGC specifically, protects RGC somata and axons and preserves visual function. This finding adds to the evidence that ER stress is a general upstream mechanism for neurodegeneration and suggests that targeting ER stress molecules is a promising therapeutic strategy for neuroprotection in MS.

Oligodendrocyte death, neuroinflammation, and the effects of minocycline in a rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION).

Purpose: Optic nerve (ON) damage following nonarteritic anterior ischemic optic neuropathy (NAION) and its models is associated with neurodegenerative inflammation. Minocycline is a tetracycline derivative antibiotic believed to exert a neuroprotective effect by selective alteration and activation of the neuroinflammatory response. We evaluated minocycline's post-induction ability to modify early and late post-ischemic inflammatory responses and its retinal ganglion cell (RGC)-neuroprotective ability. Methods: We used the rodent NAION (rNAION) model in male Sprague-Dawley rats. Animals received either vehicle or minocycline (33 mg/kg) daily intraperitoneally for 28 days. Early (3 days) ON-cytokine responses were evaluated, and oligodendrocyte death was temporally evaluated using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis. Cellular inflammation was evaluated with immunohistochemistry, and RGC preservation was compared with stereology of Brn3a-positive cells in flat mounted retinas. Results: Post-rNAION, oligodendrocytes exhibit a delayed pattern of apoptosis extending over a month, with extrinsic monocyte infiltration occurring only in the primary rNAION lesion and progressive distal microglial activation. Post-induction minocycline failed to improve retinal ganglion cell survival compared with the vehicle treated (893.14 vs. 920.72; p>0.9). Cytokine analysis of the rNAION lesion 3 days post-induction revealed that minocycline exert general inflammatory suppression without selective upregulation of cytokines associated with the proposed alternative or neuroprotective M2 inflammatory pathway. Conclusions: The pattern of cytokine release, extended temporal window of oligodendrocyte death, and progressive microglial activation suggests that selective neuroimmunomodulation, rather than general inflammatory suppression, may be required for effective repair strategies in ischemic optic neuropathies.

A Case of Optic Neuritis Concomitant with Pituitary Tumor During Pregnancy.

BACKGROUND: Optic neuritis (ON) is unilateral painful optic nerve inflammation in a young healthy female diagnosed by excluding glaucoma. ON onset during pregnancy is rare, with only 2 cases reported to date. CASE DESCRIPTION: A 35-year-old previously healthy parous woman who was pregnant with her second child suffered rapidly progressive visual acuity loss. Magnetic resonance imaging (MRI) revealed a pituitary tumor. Emergency surgery was performed for optic nerve compression; however, her visual impairment worsened. Postoperative diffusion-weighted MRI showed high intensity in the bilateral optic nerves, and ON was diagnosed. Administration of methylprednisolone was effective, and her visual acuity recovered over 6 months. CONCLUSIONS: Associated pituitary macroadenoma complicated the true diagnosis of ON, because contrast medium cannot be used in pregnant women. The diffusion-weighted MRI findings were useful for diagnosing this complex clinical condition.

Neuroprotective effect of melatonin in experimental optic neuritis in rats.

Optic neuritis (ON) is an inflammatory, demyelinating, and neurodegenerative condition of the optic nerve, which might induce permanent vision loss. Currently, there are no effective therapies for this disorder. We have developed an experimental model of primary ON in rats through a single microinjection of 4.5 µg of bacterial lipopolysaccharide (LPS) into the optic nerve. Since melatonin acts as a pleiotropic therapeutic agent in various neurodegenerative diseases, we analyzed the effect of melatonin on LPS-induced ON. For this purpose, LPS or vehicle were injected into the optic nerve from adult male Wistar rats. One group of animals received a subcutaneous pellet of 20 mg melatonin at 24 hr before vehicle or LPS injection, and another group was submitted to a sham procedure. Melatonin completely prevented the decrease in visual evoked potentials (VEPs), and pupil light reflex (PLR), and preserved anterograde transport of cholera toxin ß-subunit from the retina to the superior colliculus. Moreover, melatonin prevented microglial reactivity (ED1-immunoreactivity, P < 0.01), astrocytosis (glial fibrillary acid protein-immunostaining, P < 0.05), demyelination (luxol fast blue staining, P < 0.01), and axon (toluidine blue staining, P < 0.01) and retinal ganglion cell (Brn3a-immunoreactivity, P < 0.01) loss, induced by LPS. Melatonin completely prevented the increase in nitric oxide synthase 2, cyclooxygenase-2 levels (Western blot) and TNFα levels, and partly prevented lipid peroxidation induced by experimental ON. When the pellet of melatonin was implanted at 4 days postinjection of LPS, it completely reversed the decrease in VEPs and PLR. These data suggest that melatonin could be a promising candidate for ON treatment.

Retinoic acid receptor stimulation ameliorates experimental autoimmune optic neuritis.

BACKGROUND: To determine whether all-trans retinoic acid or a synthetic retinoic acid receptor-α/ß-specific agonist, Am80, can reduce the degree of experimental autoimmune optic neuritis in mice with experimental autoimmune encephalomyelitis. METHODS: Optic neuritis was induced in C57BL/6 mice by immunizing them with myelin oligodendrocyte glycoprotein35-55 . All-trans retinoic acid (350 µg/mouse/time point) or Am80 (5 mg/kg/time point) was administered every other day from day 0 to day 20. The degree of experimental autoimmune encephalomyelitis was scored and histopathological analysis of the optic neuritis was performed on day 22 after the immunization. In vivo-primed draining lymph node cells obtained from vehicle-treated or all-trans retinoic acid-treated mice were stimulated with myelin oligodendrocyte glycoprotein35-55 , and the culture supernatant was collected for assays of interferon-γ and interleukin-17. RESULTS: All-trans retinoic acid treatment significantly reduced the clinical score of experimental autoimmune encephalomyelitis and the severity of the optic neuritis by histopathological analysis. The production of interferon-γ and interleukin-17 was significantly reduced in all-trans retinoic acid-treated mice compared with vehicle-treated mice. Am80 treatment also significantly decreased the severity of the optic neuritis in mice with experimental autoimmune encephalomyelitis. CONCLUSIONS: These findings demonstrate that all-trans retinoic acid and Am80 treatment were able to reduce the severity of optic neuritis in mice with experimental autoimmune encephalomyelitis. Activation of retinoic acid receptor-α/ß may be a molecular target for the treatment of autoimmune optic neuritis induced by Th1 or Th17-dominated immune responses.

Relación entre el test de sensibilidad al contraste y el nivel de gravedad en pacientes con esclerosis múltiple / Relationship between contrast sensitivity test and disease severity in multiple sclerosis patients

OBJETIVO: Evaluar la utilidad de la prueba de sensibilidad al contraste Pelli-Robson en pacientes con esclerosis múltiple, dependiendo de la escala expandida del estado de discapacidad (EDSS). MATERIAL Y MÉTODOS: Estudio retrospectivo de 62 pacientes diagnosticados de esclerosis múltiple y remitidos desde el Servicio de Neurología a la Unidad de Neurooftalmología del Hospital Virgen de la Victoria. Los pacientes fueron clasificados según la escala EDSS en 3 grupos: A) inferior a 1,5; B) entre 1,5 y 3,5 y C) superior a 3,5. Se determinó la agudeza visual y la sensibilidad al contraste monocular y binocular mediante las pruebas de Snellen y Pelli-Robson, respectivamente. Un total de 12 pacientes libres de enfermedad fueron reclutados como grupo control. Se analizaron estadísticamente los resultados obtenidos. RESULTADOS: El tiempo medio de evolución de la enfermedad fue de 81,54 ± 35,32 meses. Los valores medios del Pelli-Robson monocular y binocular en el grupo control fueron 1,82 ± 0,10 y 1,93 ± 0,43, mientras que en los pacientes con esclerosis múltiple fueron 1,61 ± 0,29 y 1,83 ± 0,19 respectivamente, siendo estas diferencias estadísticamente significativas en el análisis monocular para un nivel de significación de p < 0,05. Respecto al nivel de gravedad, los valores medios monoculares y binoculares de la prueba de Pelli-Robson fueron en el grupo A: 1,66 ± 0,24 y 1,90 ± 0,98; en el grupo B: 1,64 ± 0,21 y 1,82 ± 0,16 y en el grupo C: 1,47 ± 0,45 y 1,73 ± 0,32, respectivamente. Las diferencias entre grupos mostraron una significación estadística para ambas pruebas: p = 0,05 y p = 0,027. CONCLUSIONES: La sensibilidad al contraste, monocular y binocular, analizada mediante la prueba de Pelli-Robson disminuye significativamente según aumenta el nivel de gravedad medida con la escala EDSS en pacientes con esclerosis múltiple

OBJECTIVE: To assess the importance of the Pelli-Robson contrast sensitivity test in multiple sclerosis patients according to the Expanded Disability Status Scale (EDSS). MATERIAL AND METHODS: A total of 62 patients with multiple sclerosis were included in a retrospective study. Patients were enrolled from the Neurology Department to Neuroophthalmology at Virgen de la Victoria Hospital. Patients were classified into 3 groups according to EDSS: group A) lower than 1.5, group B) between 1.5 and 3.5 and group C) greater than 3.5. Visual acuity and monocular and binocular contrast sensitivity were performed with Snellen and Pelli-Robson tests respectively. Twelve disease-free control participants were also recruited. Correlations between parameter changes were analyzed. RESULTS: The mean duration of the disease was 81.54 ± 35.32 months. Monocular and binocular Pelli-Robson mean values in the control group were 1.82 ± 0.10 and 1.93 ± 0.43 respectively, and 1.61 ± 0.29 and 1.83 ± 0.19 in multiple sclerosis patients. There were statistically significant differences in the monocular analysis for a level of significance P<0.05. Mean monocular and binocular Pelli-Robson values in relation to gravity level were, in group A: 1.66 ± 0.24 and 1.90 ± 0.98, group B: 1.64 ± 0.21 and 1.82 ± 0.16, and group C: 1.47 ± 0.45 and 1.73 ± 0.32 respectively. Group differences were statistically significant in both tests: P=0.05 and P=0.027. CONCLUSIONS: Monocular and binocular contrast discrimination analyzed using the Pelli-Robson test was found to be significantly lower when the severity level, according EDSS, increases in multiple sclerosis patients

Pediatric optic neuritis: does a prolonged course of steroids reduce relapses? A preliminary study.

BACKGROUND: Optic neuritis is an important pediatric disorder causing visual impairment. Because of the absence of pediatric-specific studies, data extrapolated from the adult-based optic neuritis treatment trial are used to guide management of pediatric patients. Recent literature promotes a prolonged course of oral steroids to prevent relapses. However, there are no published data to support this view. Patients who were recently treated in our hospital received a longer course of steroids, relative to those treated several years ago. We hypothesized that a longer course of steroids results in fewer relapses and better final visual acuity. METHODS: A retrospective analysis of 26 consecutive patients (age 4.5-19 years) treated for optic neuritis within the past 10 years was conducted. Patients received either a short course (2 weeks) or a prolonged course (more than 2 weeks) of steroids. Some patients were not treated. Mean follow-up was 70 weeks (3 weeks-10 years). Comparisons were made among the groups receiving 2 weeks of steroid treatment (16 of 26 patients) and greater than 2 weeks of steroid treatment (seven of 26 patients) to evaluate relapse rate, eventual visual acuity, and reported side effects. RESULTS: There were no significant differences in the relapse rates, reported side effects, and final visual acuity in the two treatment groups. CONCLUSIONS: In this cohort, a prolonged course of steroids was not associated with reduced relapse rate, increased side effects, or improved visual outcome. This cohort was small, but the results do not identify any reason to deviate from the common approach of optic neuritis treatment, which is 2 weeks of steroids.

Gypenosides might have neuroprotective and immunomodulatory effects on optic neuritis.

Optic neuritis is a common disease in young adults, inducing apoptosis of retinal ganglion cells, which leads to varying degree of visual function damages, even blindness. As the standard treatment, methylprednisolone pulse therapy can only promote the recovery of visual acuity but not prevent retinal ganglion cell degeneration. It cannot help improve the ultimate visual outcome. Both inflammatory response and endogenous oxidative stress play crucial roles in the progression of optic neuritis. The combination of immunomodulatory and antioxidant is expected to improve the prognosis of the disease by preventing the apoptosis of retinal ganglion cells. Triterpenoids (oleanolic acid derived) were reported to have the dual capacity of simultaneously repressing production of pro-inflammatory mediators and exerting neuroprotective effects through induction of anti-oxidant genes in experimental optic neuritis. Gypenosides with an aglycone mainly of dammarane-type tetracyclic triterpenoids, also has the dual capacity of immune regulation and antioxidation. Both gypenosides and oleanolic acid were reported to have similar roles in hepatoprotection. Beside, gypenosides were reported to have the capacity of modulating the activation of immune cells and the expression of cytokines. In addition, gypenosides showed neuroprotective effect against oxidative injury in dopaminergic neurons and mouse model of Parkinson's disease. Accordingly, we propose that gypenosides have potential neuroprotective and immunomodulatory effects on optic neuritis through antioxidation and immune regulation. The application of gypenosides might prevent the apoptosis of retinal ganglion cells and improve the ultimate visual outcome in patients with optic neuritis.

An unusual case of bilateral multifocal retinal pigment epithelial detachment with methanol-induced optic neuritis.

PURPOSE: To describe an unusual case of methanol-induced optic neuritis with bilateral multifocal extrafoveal serous retinal pigment epithelial (RPE) detachment. METHODS: Single case report. CASE REPORT: A 40-year-old male presented with acute bilateral loss of vision and history of consumption of adulterated alcohol. On examination, his vision was perception of light in the right eye and finger counting at 1-ft distance in the left eye. Pupillary reactions were sluggish. The optic discs were normal. An elevated lesion with subretinal serous fluid was present over macula adjacent to superior major vessel arcade in the right eye, which was confirmed as a large extrafoveal RPE detachment on fluorescein angiography. There were two more small RPE detachments in the right eye as well as in the left eye. All RPE detachments were extrafoveal in location. The patient was managed medically with intravenous methylprednisolone (1 g) in 500 ml of ringer lactate for three consecutive days. After three doses, visual acuity of both eyes was recorded as 20/20. CONCLUSION: We herein report an unusual case of bilateral multifocal extrafoveal serous RPE detachment in a patient of methanol-induced optic neuritis. RPE detachments may be due to the toxic effect of methanol metabolites.

Suppression of murine experimental autoimmune optic neuritis by mature dendritic cells transfected with calcitonin gene-related Peptide gene.

PURPOSE: Calcitonin gene-related peptide (CGRP) exhibits prominent anti-inflammatory actions. We examined whether CGRP-transfected dendritic cells (DC) prevent the development of experimental autoimmune optic neuritis (EAON) and experimental autoimmune encephalomyelitis (EAE). METHODS: A human CGRP-expressing plasmid was constructed, and used to transfect C57BL/6 mouse bone marrow-derived matured DC (mDC) by electroporation METHODS: Transfection efficiency was 50% with 80% cell viability. C57BL/6 mice were immunized with myelo-oligodendrocyte glycoprotein 35-55, and injected intravenously with CGRP-expressing mDC (CGRP gene-transfected group) or mock-transfected mDC (mock-transfected group) at the induction or effector phase. EAE was diagnosed clinically and EAON was assessed histopathologically. Delayed hypersensitivity was measured. Supernatants of spleen cell cultures were assayed for cytokines using ELISA. The CD4(+)CD25(+)Foxp3(+) fraction in spleen cells was analyzed using flow cytometry. RESULTS: For gene therapy in the induction phase, EAE developed in 50% of mice in the CGRP-transfected group compared with 80% in the mock-transfected group, and the mean pathological score for EAON was 1 in the CGRP-transfected group compared with 2 in the mock-transfected group (P < 0.05). For gene therapy in the effector phase, the mean EAE clinical score (1.5 vs. 3.0) and mean EAON pathological score (1.0 vs. 2.0) were both lower in the CGRP-transfected group compared with the mock-transfected group (P < 0.05). Delayed hypersensitivity was suppressed significantly in the CGRP-transfected group. IL-10 production by spleen cells in the CGRP-transfected group increased independent of MOG concentration, compared with the mock-transfected group. Interestingly, the proportion of CD4(+)CD25(+)Foxp3(+) cells increased significantly (P < 0.05) in the CGRP-transfected group compared with the mock-transfected group. CONCLUSIONS: Gene therapy with CGRP-expressing mDC was effective in suppressing the development of EAON and EAE.

Evaluation of sirtuin role in neuroprotection of retinal ganglion cells in hypoxia.

PURPOSE. Hypoxia-induced apoptosis is responsible for reduced retinal ganglion cell (RGC) viability in a variety of chronic ocular disorders. Sirtuin 1 (SIRT1) plays an important role in preserving cell viability during hypoxia. We investigated the role of SIRT1 in sustaining RGC viability in an in vitro model of hypoxia. METHODS. Staurosphorine-differentiated RGCs (RGC-5) received varying hypoxic concentrations (100-500 µM) of cobalt chloride (CoCl2) for 24 hours. Hypoxia-induced cell viability was assessed by WST-1 assay. The role of SIRT1 in promoting viability was determined indirectly via sirtinol (SIRT1 inhibitor). Hypoxia-induced apoptosis was evaluated by measuring stress-activated protein kinase/c-jun N-terminal kinase (SAPK/JNK) and caspase 3 activity. Vascular endothelial growth factor (VEGF) was measured to ascertain the influence of SIRT1. RESULTS. CoCl2 concentrations greater than 100 µM resulted in significantly reduced RGC viability (P=0.01). CoCl2 treatment increased SIRT1 levels significantly (P<0.01): 100 (6.5-fold), 200 (6-fold), 300 (3.5-fold), and 400 µM (4.5-fold). Phosphorylated SAPK/JNK increased 36-fold (200 µM CoCl2 concentration), then plateaued at the 300- (25-fold) and 400-µM (27.8-fold) CoCl2 concentrations (P<0.01). CoCl2 and sirtinol treatment increased Caspase 3 activity (P<0.05). VEGF release was significantly higher than control at the 100-µM CoCl2 concentrations (P<0.01). Sirtinol reduced RGC viability, SIRT1 levels, and VEGF release (P<0.01) while having greater effect on SAPK/JNK phosphorylation. CONCLUSIONS. SIRT1 significantly influences RGC viability. Sirtinol's effect reflects the interaction SIRT1 has with apoptotic signaling proteins. This investigation demonstrated SIRT1 importance in forestalling the effects of hypoxia-induced apoptosis.

Blocking endothelin-B receptors rescues retinal ganglion cells from optic nerve injury through suppression of neuroinflammation.

PURPOSE: The endothelins (ETs) cause reactive astrogliosis, which involves neuroinflammation and neurodegeneration in the central nervous system. The purpose of this study was to determine whether blocking the ET signals will protect retinal ganglion cells (RGCs) from optic nerve injury. METHODS: We studied the effect of pretreatment with BQ-123, an antagonist of ETA receptors, and BQ-788, an antagonist of ETB receptors, on the survival of RGCs after the optic nerve of rats was crushed. We also performed immunohistological evaluations and real-time PCR of the crushed site to determine the expressions of the ET-1, CD68, GFAP, TNF-α, and iNOS genes in the neuroinflammation of the optic nerves. RESULTS: The mRNA levels of the ETB receptors were upregulated (5.6-fold) on day 7 after crushing the optic nerves. Cells expressing ETB receptors were recruited mainly to the crushed site where the immunoreactivity to GFAP was weak. These cells were also immuunoreactive to ETs and CD68, a constitutive marker of microglia/macrophages. In the adjacent areas, immunoreactivity to GFAP was intense. Crushing the optic nerve increased the mRNA levels of ET-1 (4.5-fold), CD68 (87.5-fold), GFAP (2-fold), TNF-α (480-fold), and iNOS (6-fold) on day 7. Pretreatment with BQ-788 significantly suppressed the upregulation of these genes and loss of RGCs on day 7, whereas BQ-123 failed to protect the RGCs. CONCLUSIONS: These results suggest that the microglia/macrophages recruited to the crushed site are the possible cellular sources of the ETs, which caused reciprocal activation of astrocytes. Blocking the ETB receptors by BQ-788 rescued RGCs, most likely by attenuating neuroinflammatory events.