Nano-hesperetin enhances the functional recovery and endogenous remyelination of the optic pathway in focal demyelination model.

Our recent report demonstrated that hesperetin (Hst) as a citrus flavonoid, significantly reduces the levels of demyelination in optic chiasm of rats. Previous evidence also indicated that nano-hesperetin (nano-Hst) possesses beneficial impacts in experimental models of Alzheimer's disease and autism. In this study, the effects of nano-Hst on latency of visual signals, demyelination levels, glial activation, and expression of Olig2 and MBP were evaluated in lysolecithin (LPC)-induced demyelination model. Focal demyelination was induced by injection of LPC (1%, 2 µL) into the rat optic chiasm. Animals received oral administration of nano-Hst at dose of 20 mg/kg for 14 or 21 days post LPC injection. Visual evoked potential (VEP) recording showed that nano-Hst reduces the latency of visual signals and ameliorates the extent of demyelination areas and glial activation. Expression levels of the Olig2 and MBP were also significantly increased in nano-Hst treated rats. Overall, our data suggest that nano-Hst reduces the latency of visual signals through its protective effects on myelin sheath, amelioration of glial activation, and enhancement of endogenous remyelination.

Arbutin Improves Functional Recovery and Attenuates Glial Activation in Lysolecethin-Induced Demyelination Model in Rat Optic Chiasm.

Neuroinflammation, glial activation, and oxidative injury are the main pathological mechanisms of demyelination in multiple sclerosis (MS). Arbutin, a natural polyphenol compound, possesses antioxidant, anti-inflammatory, and neuroprotective properties whose therapeutic potential has not been studied in the experimental animal models of MS. In the present study, the efficiency of arbutin on lysolecthin (LPC)-induced local demyelination model was investigated. Demyelination was induced by micro-injection of 2 µl LPC (1%) into the rat optic chiasm and the treated group received daily injection of arbutin (50 mg/kg, i.p) during 2 weeks. Visual-evoked potential (VEP) recordings were used to functionally assess the visual pathway. Gene expression analysis was done to evaluate the arbutin effect on the inflammatory, stress oxidative-related mediators, and myelin markers. The myelin-specific staining was performed to assess demyelination and GFAP staining as an astrocyte marker. We found that arbutin significantly reduced P1-latency of VEPs waves and demyelination at 7 and 14 days post-demyelination. Arbutin decreased inflammatory cytokines (IL-1B, IL-17, TNF-α) and iNOS mRNA expression level. In addition, the expression level of anti-inflammatory cytokine (IL-10) and antioxidant mediators (Nrf-2 and HO-1) was enhanced by arbutin treatment. Arbutin increased MBP and Olig2 expression levels in demyelination context. Finally, arbutin attenuated GFAP as an astrocyte marker. Finally, this study demonstrates that arbutin improves functional recovery and myelin repair in the demyelinated optic chiasm through attenuation of inflammation, astrocyte activation, and oxidative stress. These findings might open new promising avenues for treating demyelinating disorders such as multiple sclerosis. Graphical abstract.

Fingolimod (FTY720) improves the functional recovery and myelin preservation of the optic pathway in focal demyelination model of rat optic chiasm.

It has been shown that fingolimod (FTY720) possesses beneficial effects on remyelination in the central nervous system (CNS). In this study, the effects of FTY720 and sodium valproate (VPA) as histone deacetylase inhibitor (HDAC) on the conductivity of visual signals, extent of demyelination area, glial activation, and expression levels of HDAC1and S1PR1 have been evaluated in the optic chiasm of lysolecithin (LPC)-induced demyelination model. In order to produce this demyelination model, LPC (1%, 2 µL) was injected into the rat optic chiasm. Latency of visual waves was measured by visual evoked potential (VEP) recording. The extent of demyelination area and level of glial activation were assessed using immunostaining. Gene expression analysis was performed to evaluate the expression levels of HDAC1, S1PR1, Olig2, and MBP in the optic chiasm. Analysis of electrophysiological data showed that LPC administration increased the latency of visual signals. FTY720 improved the functional recovery of the visual pathway and reduced the level of glial activation in the optic chiasm. FTY720 enhanced myelin repair and up-regulated the expression levels of Olig2 and MBP. Additionally, the expression levels of HDAC1 and S1PR1 were significantly reduced in animals treated with FTY720. In contrast to FTY720 treated animals, administration of VPA could not significantly improve the functional recovery of optic pathway following LPC injection. Cumulatively, the results of the present study demonstrate that FTY720 application improves the functional recovery of the optic pathway by reducing demyelination levels, amelioration of glial activation, and down-regulating of S1PR1 and HDAC1.

Modulating proteoglycan receptor PTPσ using intracellular sigma peptide improves remyelination and functional recovery in mice with demyelinated optic chiasm.

Multiple sclerosis (MS) is an autoimmune disease characterized by myelin and axonal damage in the central nervous system (CNS). Glial scar which is a hallmark of MS contains repair inhibitory molecules including chondroitin sulfate proteoglycans (CSPGs). CSPGs inhibit repair of damaged area through various receptors including protein tyrosine phosphatase sigma (PTPσ). In the current study we use intracellular sigma peptide (ISP), an inhibitor of PTPσ signaling, in LPC-induced focal demyelination of mouse optic chiasm. ISP treatment resulted in decreased demyelination, reduced astrogliosis, and increased newly generated oligodendrocytes which subsequently led to enhanced remyelination. Analyzing of electrophysiological (as performed by visual evoked potential recording) and behavioral (performed by visual cliff test) outcomes showed that ISP-treatment improved the integrity of optic pathway as well as the visual acuity. When ISP was administrated only during the repair phase, histological, electrophysiological and behavioral studies showed its regenerative effect. Our results demonstrated the possibility of using ISP as a new strategy to inhibit PTPσ for myelin protection, myelin repair in demyelinated axons, and functional neural pathway conductivity restoration in patients suffering from MS.

Querectin improves myelin repair of optic chiasm in lyolecithin-induced focal demyelination model.

Although the beneficial effects of quercetin on oligodendrocyte precursor cell (OPCs) population has been evaluated in-vitro, there are few studies about the effects of quercetin on myelin repair in the context of demyelination. The aim of this study was to investigate the effects of querectin on functional recovery and myelin repair of optic chiasm in lysolecithin (LPC)-induced demyelination model. Demyelination was induced by local injection of LPC 1% (2 µl) into rat optic chiasm. Querectin at doses 25 or 50 mg/kg was administrated daily by oral gavage for 7 or 14 days post LPC. Visual evoked potential (VEPs) recordings were used to assess the functional property of the optic pathway. Immunostaining and myelin staining were performed on brain sections 7 or 14 days post lesion. Electrophysiological data indicated that LPC injection increased the latency of VEPs waves and quercetin effectively reduced the delay of visual signals. The level of glial activation was alleviated in animals under treatment of quercetin compared to vehicle group. Furthermore, quercetin treatment decreased the extent of demyelination areas and increased the remyelination process following LPC injection. Overall, our findings indicate that quercetin could remarkably improve the functional recovery of the optic pathway by its protective effects on myelin sheath and attenuation of glial activation.

Pregabalin enhances myelin repair and attenuates glial activation in lysolecithin-induced demyelination model of rat optic chiasm.

Multiple sclerosis (MS) is an autoimmune disease in which more than 70% of patients experience visual disturbance as the earliest symptoms. Lysolecithin (LPC)-induced focal demyelination model has been developed to evaluate the effects of different therapies on myelin repair improvement. In this study, the effects of pregabalin administration on myelin repair and glial activation were investigated. Local demyelination was induced by administration of LPC (1%, 2µL) into the rat optic chiasm. Rats underwent daily injection of pregabalin (30mg/kg, i.p) or vehicle. Visual-evoked potentials (VEPs) recordings were performed for evaluating the function of optic pathway on days 3, 7, 14 and 28 post lesions. Myelin specific staining and immunostaining against GFAP and Iba1 were also carried out for assessment of myelination and glial activation respectively. Electrophysiological data indicated that pregabalin administration could significantly reduce the P1-N1 latency and increase the amplitude of VEPs waves compared to saline group. Luxol fast blue staining and immunostaining against PLP, as mature myelin marker, showed that myelin repair was improved in animals received pregabalin treatment. In addition, pregabalin effectively reduced the expression of GFAP and Iba1 as activated glial markers in optic chiasm. The present study indicates that pregabalin administration enhances myelin repair and ameliorates glial activation of optic chiasm following local injection of LPC.

Oct4 transcription factor in conjunction with valproic acid accelerates myelin repair in demyelinated optic chiasm in mice.

Multiple sclerosis is a demyelinating disease with severe neurological symptoms due to blockage of signal conduction in affected axons. Spontaneous remyelination via endogenous progenitors is limited and eventually fails. Recent reports showed that forced expression of some transcription factors within the brain converted somatic cells to neural progenitors and neuroblasts. Here, we report the effect of valproic acid (VPA) along with forced expression of Oct4 transcription factor on lysolecithin (LPC)-induced experimental demyelination. Mice were gavaged with VPA for one week, and then inducible Oct4 expressing lentiviral particles were injected into the lateral ventricle. After one-week induction of Oct4, LPC was injected into the optic chiasm. Functional remyelination was assessed by visual-evoked potential (VEP) recording. Myelination level was studied using FluoroMyelin staining and immunohistofluorescent (IHF) against proteolipid protein (PLP). IHF was also performed to detect Oct4 and SSEA1 as pluripotency markers and Olig2, Sox10, CNPase and PDGFRα as oligodendrocyte lineage markers. One week after injection of Oct4 expressing vector, pluripotency markers SSEA1 and Oct4 were detected in the rims of the 3rd ventricle. LPC injection caused extensive demyelination and significantly delayed the latency of VEP wave. Animals pre-treated with VPA+Oct4 expressing vector, showed faster recovery in the VEP latency and enhanced myelination. Immunostaining against oligodendrocyte lineage markers showed an increased number of Sox10+ and myelinating cells. Moreover, transdifferentiation of some Oct4-transfected cells (GFP+ cells) to Olig2+ and CNPase+ cells was confirmed by immunostaining. One-week administration of VPA followed by one-week forced expression of Oct4 enhanced myelination by converting transduced cells to myelinating oligodendrocytes. This finding seems promising for enhancing myelin repair within the adult brains.

Astaxanthin offers neuroprotection and reduces neuroinflammation in experimental subarachnoid hemorrhage.

BACKGROUND: Neuroinflammation has been proven to play a crucial role in early brain injury pathogenesis and represents a target for treatment of subarachnoid hemorrhage (SAH). Astaxanthin (ATX), a dietary carotenoid, has been shown to have powerful anti-inflammation property in various models of tissue injury. However, the potential effects of ATX on neuroinflammation in SAH remain uninvestigated. The goal of this study was to investigate the protective effects of ATX on neuroinflammation in a rat prechiasmatic cistern SAH model. METHODS: Rats were randomly distributed into multiple groups undergoing the sham surgery or SAH procedures, and ATX (25 mg/kg or 75 mg/kg) or equal volume of vehicle was given by oral gavage at 30 min after SAH. All rats were sacrificed at 24 h after SAH. Neurologic scores, brain water content, blood-brain barrier permeability, and neuronal cell death were examined. Brain inflammation was evaluated by means of expression changes in myeloperoxidase, cytokines (interleukin-1ß, tumor necrosis factor-α), adhesion molecules (intercellular adhesion molecule-1), and nuclear factor kappa B DNA-binding activity. RESULTS: Our data indicated that post-SAH treatment with high dose of ATX could significantly downregulate the increased nuclear factor kappa B activity and the expression of inflammatory cytokines and intercellular adhesion molecule-1 in both messenger RNA transcription and protein synthesis. Moreover, these beneficial effects lead to the amelioration of the secondary brain injury cascades including cerebral edema, blood-brain barrier disruption, neurological dysfunction, and neuronal degeneration. CONCLUSIONS: These results indicate that ATX treatment is neuroprotective against SAH, possibly through suppression of cerebral inflammation.

Management of paradoxical response in pediatric tubercular meningitis with methylprednisolone.

Paradoxical response to anti-tubercular drugs remains a diagnostic dilemma. In India where tuberculosis is quite prevalent, paradoxical response to anti-tubercular treatment (ATT) is either misdiagnosed or under-diagnosed. We report two cases of optochiasmatic arachnoiditis due to paradoxical response in children suffering from tuberculous meningitis. Visual acuity was recorded as no light perception in all eyes of both patients while they were taking 4-drug ATT (isoniazid, rifampicin, pyrazinamide and ethambutol). However their systemic conditions did not worsen. They were treated with intravenous methylprednisolone for five days followed by systemic corticosteroids on a tapering dose for four weeks along with ATT. This case report highlights the importance of early recognition of this sight-threatening complication and timely, effective treatment to prevent permanent blindness.

Brain and optic chiasmal herniation following cabergoline treatment for a giant prolactinoma: wait or intervene?

OBJECTIVE: Dopamine agonists (DA) are the treatment of choice in patients with macroprolactinomas. Brain and optic chiasm herniation are unusual complications following treatment with DA. REPORT: We present a case of a giant prolactinoma complicated by visual deterioration following cabergoline treatment. A 42-year-old man was admitted with seizures, right visual loss and visual defect in the upper left temporal quadrant. Magnetic resonance imaging (MRI) identified a giant adenoma, which proved to be a prolactinoma, compressing the optic chiasm and extending into the suprasellar region. Treatment with cabergoline was initiated resulting in improvement in visual fields, tumor shrinkage and prolactin level decrease. Five months later and despite tumor reduction, a deterioration of his visual fields was observed. The second MRI revealed brain and optic chiasmal herniation into the pituitary sella. Cabergoline dose was reduced and surgical resection of the adenoma along with untethering of the optic nerve was performed leading to improvement of the visual defects. CONCLUSIONS: This report describes a rare case of brain and optic chiasmal herniation attributed to DA therapy for a macroprolactinoma. It is important for clinicians to examine visual fields and promptly identify any visual deterioration in patients with macroprolactinomas receiving DA treatment.

Marked recovery of vision in children with optic pathway gliomas treated with bevacizumab.

IMPORTANCE: Children with optic pathway gliomas (OPGs) frequently experience vision loss from their tumors. Standard front-line treatment using carboplatin-based chemotherapy typically produces only a modest benefit (eg, stabilization or 0.2 logMAR improvement) in visual acuity (VA). Bevacizumab is a monoclonal antibody that targets vascular endothelial growth factor and acts primarily as an anti-angiogenic agent. Recent reports suggest a qualitative improvement in vision after bevacizumab-based treatment in children with OPGs. OBSERVATIONS: We report 4 cases of pediatric OPGs (2 neurofibromatosis type 1-related and 2 sporadic cases) that received treatment with bevacizumab due to progressive VA or visual field (VF) loss despite prior treatment with chemotherapy or proton-beam radiation. All 4 subjects demonstrated a marked improvement in their VA, VF, or both while receiving bevacizumab-based therapy. Three patients had complete resolution of their VA or VF loss in at least 1 eye-2 of whom had previously received bevacizumab therapy. CONCLUSIONS AND RELEVANCE: Given that most patients with OPG-related visual impairment will show modest or no visual improvement with standard treatment, the incorporation of bevacizumab in these cases may greatly improve visual outcomes and should be considered in appropriate clinical situations.

Optic nerve and visual pathways primary glioblastoma treated with radiotherapy and temozolomide chemotherapy.

PURPOSE: Primary malignant gliomas of the optic nerves are rare tumors of adulthood, progressing rapidly to blindness and to death within several months, regardless of the type of treatment. Recently, treatments associating radiotherapy and temozolomide have been used in other types of glioblastomas, but their impact on optic nerve malignant gliomas is not known. METHODS: This was a retrospective case series of 2 patients diagnosed with primary optic nerve and chiasm glioblastoma (GBM), treated with radiotherapy and concomitant temozolomide. RESULTS: A 74-year-old man presented with visual loss caused by an infiltrative and enhancing lesion, affecting the left optic nerve and the chiasm, subsequently confirmed as GBM World Health Organization (WHO) grade IV. The patient was treated with external conformal radiotherapy (54 Gy over 42 days) and concomitant chemotherapy with temozolomide (75 mg/m2/day), followed by 6 monthly cycles of adjuvant treatment (250 mg/day for 5 days). The second patient was a 74-year-old woman diagnosed with bilateral visual loss due to pathologically confirmed GBM (WHO grade IV). She was treated with temozolomide (220 mg/day) for 1 month, followed by radiotherapy (54 Gy over 42 days) and temozolomide chemotherapy (75 mg/m2/day). There was no adjuvant regimen. This treatment resulted in disease stabilization and partial preservation of vision during 12 months for patient 1, 8 months for patient 2. Survival after first examination was 15 and 11 months, respectively. CONCLUSIONS: Combined radiotherapy and temozolomide may be an alternative treatment in optic nerve and visual pathways primary GBM, potentially providing a longer survival.

Adenosine A1 receptor agonist, N6-cyclohexyladenosine, protects myelin and induces remyelination in an experimental model of rat optic chiasm demyelination; electrophysiological and histopathological studies.

Chronic demyelinated lesions and subsequent functional impairment are resulted from eventual failure of remyelination process as seen in multiple sclerosis. Activation of adenosine A1 receptor is reported to be effective on neural stem cells (NSCs) proliferation and oligodendrocytes differentiation. Therefore, this study attempted to investigate the effect of A1 receptor agonist N6-cyclohexyladenosine (CHA), on lysolecithin (LPC) induced demyelination and remyelination in rat optic chiasm. The experiments were carried out on male Wistar rats using visual evoked potential recording, myelin staining by Luxol fast blue and histological evaluation of demyelinated and remyelinated axons within the area of lesion. CHA was administrated i.c.v. during demyelination or remyelination phases. As revealed by myelin staining, the most extent of demyelination occurred at 7th day post-lesion (dpl 7), but gradually myelination was restored toward control during days 14-28. VEP P1-latency and P1-N1 amplitude showed widespread demyelination on dpl 7 and 14 which consequently was reversed during days 14-28 post lesion. I.c.v. treatment of animals with CHA during demyelination phase (days 0-13) reduced the extent of demyelination. During remyelination phase (days 14-28), CHA was able to increase remyelination in both electrophysiological and histopathological studies. The effects of CHA seem to be due to its protective effect on myelinating cells and its regenerative effect through potentiating endogenous neural progenitors.

Longitudinal measures of visual function, tumor volume, and prediction of visual outcomes after treatment of optic pathway gliomas.

PURPOSE: To examine longitudinal changes in visual acuity, tumor volume, and visual evoked potentials (VEP) before and after treatment in children with optic pathway gliomas. DESIGN: Retrospective cohort study. PARTICIPANTS: Twenty-one patients (0.7-9 years of age). METHODS: Patients initially were treated either by chemotherapy (n = 18) or radiotherapy (n = 3). Patients were followed up with serial magnetic resonance imaging, age-corrected visual acuity measurements in logarithm of the minimum angle of resolution (logMAR) units, and pattern VEP. Longitudinal visual outcome data were obtained on average for 9 years (range, 4-16 years). Tumor volumes before and after treatment were estimated in 15 patients. Multivariate regression was used to predict visual outcomes. MAIN OUTCOME MEASURES: Visual acuity, relative tumor volumes, and VEP. RESULTS: Before treatment, 81% of patients had reduced visual acuity and 81% had optic nerve pallor, whereas all had a reduced VEP in 1 or both eyes. After initial treatment, tumor volume decreased in 53%, stabilized in 27%, and progressively increased in 20%. Treatment arrested the rapid decline in visual acuity loss and stabilized visual acuity for 4 to 5 years. The rate of visual acuity decline was not correlated with tumor shrinkage. Sixty-two percent of patients required additional treatment with either chemotherapy or radiation because of tumor growth or progressive loss of visual function. Visual acuity at last examination was stable or improved in 33% of patients, but on average declined 0.4 logMAR units. Visual acuity was 20/200 or better in 1 eye of 62% of patients. The rate of visual acuity decline was predicted weakly by tumor volume at presentation (R(2) = 0.19; P<0.009). Visual acuity at last examination was predicted best by visual acuity and tumor volume at presentation (R(2) = 0.66; P<0.001). CONCLUSIONS: Systemic chemotherapy arrested the decline in visual acuity and stabilized vision on average for 5 years. At presentation, VEPs were a more sensitive indicator of optic pathway damage than visual acuity or optic nerve appearance. Although tumor reduction or stabilization was achieved in 80% of patients, pre-existing visual damage, indexed by objective measures of tumor volume and visual function, limited visual outcomes. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Tuberculous optochiasmatic arachnoiditis: a devastating form of tuberculous meningitis.

Tuberculous meningitis is primarily a disease of the meninges of brain and spinal cord along with adjacent brain parenchyma. The characteristic pathological changes are meningeal inflammation, basal exudates, vasculitis and hydrocephalus. Tuberculous meningitis has a strong predilection for basal parts of the brain. Exudates, if dominantly present in the interpeduncular, suprasellar and Sylvian cisterns, result in optochiasmatic arachnoiditis and tuberculoma. Optochiasmatic arachnoiditis and tuberculoma are devastating forms of tuberculous meningitis and often associated with profound vision loss. This clinical entity more frequently affects young adults. In a recent study, on the multivariate logistic regression analysis, female sex, younger age and raised cerebrospinal fluid protein content were identified as predictors for developing optochiasmatic arachnoiditis. Frequently, optochiasmatic tuberculoma and optochiasmatic arachnoiditis develop paradoxically while a patient is being treated with anti-TB drugs. MRI reveals confluent enhancing lesions that are present in the interpeduncular fossa, pontine cistern, and the perimesencephalic and suprasellar cisterns. Management of tuberculous optochiasmatic arachnoiditis and optochiasmatic arachnoiditis tuberculoma has been variable. Treatment of optochiasmatic arachnoiditis continues to be a challenge and the response is generally unsatisfactory. In isolated case reports and in small series, corticosteroids, methyl prednisolone, thalidomide and hyaluronidase have been used with variable success. The benefit from neurosurgery is controversial and deterioration may follow the initial temporary improvement. Management of paradoxical optochiasmatic arachnoiditis is also controversial. Some patients regain vision following treatment with anti-TB drugs and continued usage of corticosteroids. Neurosurgery may be considered in the patients with either treatment failure or when diagnosis is in doubt. In conclusion, presence of optochiasmatic arachnoiditis or tuberculoma has important therapeutic and prognostic implications for patients of tuberculous meningitis.

VEGF signaling through neuropilin 1 guides commissural axon crossing at the optic chiasm.

During development, the axons of retinal ganglion cell (RGC) neurons must decide whether to cross or avoid the midline at the optic chiasm to project to targets on both sides of the brain. By combining genetic analyses with in vitro assays, we show that neuropilin 1 (NRP1) promotes contralateral RGC projection in mammals. Unexpectedly, the NRP1 ligand involved is not an axon guidance cue of the class 3 semaphorin family, but VEGF164, the neuropilin-binding isoform of the classical vascular growth factor VEGF-A. VEGF164 is expressed at the chiasm midline and is required for normal contralateral growth in vivo. In outgrowth and growth cone turning assays, VEGF164 acts directly on NRP1-expressing contralateral RGCs to provide growth-promoting and chemoattractive signals. These findings have identified a permissive midline signal for axons at the chiasm midline and provide in vivo evidence that VEGF-A is an essential axon guidance cue.

Brain and optic chiasmal herniations into sella after cabergoline therapy of giant prolactinoma.

Optic chiasmal herniation following dopamine agonist therapy is a rare complication in patients with giant prolactinomas. But there are a few case reports of brain and chiasmal herniation following medical therapy in such cases. We report a young man who developed secondary visual loss and seizures after 6 months of medical treatment with cabergoline for giant prolactinoma. Magnetic resonance imaging of hypothalamic pituitary region revealed optic chiasmal and frontal lobe herniation into sella. There was marginal improvement in his vision after cabergoline dose reduction. The present case report highlights frontal lobe herniation in conjunction with optic chiasmal herniation as a very rare complication of medical therapy of giant prolactinoma. Different treatment options of this condition are being discussed.