S1PR1 signaling attenuates apoptosis of retinal ganglion cells via modulation of cJun/Bim cascade and Bad phosphorylation in a mouse model of glaucoma.

Glaucoma is a complex neurodegenerative disease characterized by optic nerve damage and apoptotic retinal ganglion cell (RGC) death, and is the leading cause of irreversible blindness worldwide. Among the sphingosine 1-phosphate receptors (S1PRs) family, S1PR1 is a highly expressed subtype in the central nervous system and has gained rapid attention as an important mediator of pathophysiological processes in the brain and the retina. Our recent study showed that mice treated orally with siponimod drug exerted neuroprotection via modulation of neuronal S1PR1 in experimental glaucoma. This study identified the molecular signaling pathway modulated by S1PR1 activation with siponimod treatment in RGCs in glaucomatous injury. We investigated the critical neuroprotective signaling pathway in vivo using mice deleted for S1PR1 in RGCs. Our results showed marked upregulation of the apoptotic pathway was associated with decreased Akt and Erk1/2 activation levels in the retina in glaucoma conditions. Activation of S1PR1 with siponimod treatment significantly increased neuroprotective Akt and Erk1/2 activation and attenuated the apoptotic signaling via suppression of c-Jun/Bim cascade and by increasing Bad phosphorylation. Conversely, deletion of S1PR1 in RGCs significantly increased the apoptotic cells in the ganglion cell layer in glaucoma and diminished the neuroprotective effects of siponimod treatment on Akt/Erk1/2 activation, c-Jun/Bim cascade, and Bad phosphorylation. Our data demonstrated that activation of S1PR1 in RGCs induces crucial neuroprotective signaling that suppresses the proapoptotic c-Jun/Bim cascade and increases antiapoptotic Bad phosphorylation. Our findings suggest that S1PR1 is a potential therapeutic target for neuroprotection of RGCs in glaucoma.

Neuroserpin gene therapy inhibits retinal ganglion cell apoptosis and promotes functional preservation in glaucoma.

Our research has proven that the inhibitory activity of the serine protease inhibitor neuroserpin (NS) is impaired because of its oxidation deactivation in glaucoma. Using genetic NS knockout (NS-/-) and NS overexpression (NS+/+ Tg) animal models and antibody-based neutralization approaches, we demonstrate that NS loss is detrimental to retinal structure and function. NS ablation was associated with perturbations in autophagy and microglial and synaptic markers, leading to significantly enhanced IBA1, PSD95, beclin-1, and LC3-II/LC3-I ratio and reduced phosphorylated neurofilament heavy chain (pNFH) levels. On the other hand, NS upregulation promoted retinal ganglion cell (RGC) survival in wild-type and NS-/- glaucomatous mice and increased pNFH expression. NS+/+Tg mice demonstrated decreased PSD95, beclin-1, LC3-II/LC3-I ratio, and IBA1 following glaucoma induction, highlighting its protective role. We generated a novel reactive site NS variant (M363R-NS) resistant to oxidative deactivation. Intravitreal administration of M363R-NS was observed to rescue the RGC degenerative phenotype in NS-/- mice. These findings demonstrate that NS dysfunction plays a key role in the glaucoma inner retinal degenerative phenotype and that modulating NS imparts significant protection to the retina. NS upregulation protected RGC function and restored biochemical networks associated with autophagy and microglial and synaptic function in glaucoma.

Neuroserpin, a crucial regulator for axogenesis, synaptic modelling and cell-cell interactions in the pathophysiology of neurological disease.

Neuroserpin is an axonally secreted serpin that is involved in regulating plasminogen and its enzyme activators, such as tissue plasminogen activator (tPA). The protein has been increasingly shown to play key roles in neuronal development, plasticity, maturation and synaptic refinement. The proteinase inhibitor may function both independently and through tPA-dependent mechanisms. Herein, we discuss the recent evidence regarding the role of neuroserpin in healthy and diseased conditions and highlight the participation of the serpin in various cellular signalling pathways. Several polymorphisms and mutations have also been identified in the protein that may affect the serpin conformation, leading to polymer formation and its intracellular accumulation. The current understanding of the involvement of neuroserpin in Alzheimer's disease, cancer, glaucoma, stroke, neuropsychiatric disorders and familial encephalopathy with neuroserpin inclusion bodies (FENIB) is presented. To truly understand the detrimental consequences of neuroserpin dysfunction and the effective therapeutic targeting of this molecule in pathological conditions, a cross-disciplinary understanding of neuroserpin alterations and its cellular signaling networks is essential.

Fingolimod effects on the brain are mediated through biochemical modulation of bioenergetics, autophagy, and neuroinflammatory networks.

Fingolimod (FTY720) is an oral drug approved by the Food and Drug Administration (FDA) for management of multiple sclerosis (MS) symptoms, which has also shown beneficial effects against Alzheimer's (AD) and Parkinson's (PD) diseases pathologies. Although an extensive effort has been made to identify mechanisms underpinning its therapeutic effects, much remains unknown. Here, we investigated Fingolimod induced proteome changes in the cerebellum (CB) and frontal cortex (FC) regions of the brain which are known to be severely affected in MS, using a tandem mass tag (TMT) isobaric labeling-based quantitative mass-spectrometric approach to investigate the mechanism of action of Fingolimod. This study identified 6749 and 6319 proteins in CB and FC, respectively, and returned 2609 and 3086 differentially expressed proteins in mouse CB and FC, respectively, between Fingolimod treated and control groups. Subsequent bioinformatics analyses indicated a metabolic reprogramming in both brain regions of the Fingolimod treated group, where oxidative phosphorylation was upregulated while glycolysis and pentose phosphate pathway were downregulated. In addition, modulation of neuroinflammation in the Fingolimod treated group was indicated by upregulation of retrograde endocannabinoid signaling and autophagy pathways, and downregulation of neuroinflammation related pathways including neutrophil degranulation and the IL-12 mediated signaling pathway. Our findings suggest that Fingolimod may exert its protective effects on the brain by inducing metabolic reprogramming and neuroinflammation pathway modulation.

Expansion of chronic MS lesions is associated with an increase of radial diffusivity in periplaque white matter.

BACKGROUND: Expansion of chronic multiple sclerosis (MS) lesion is associated with slow-burning inflammation at lesion rim. However, the underlying mechanisms leading to expansion are not fully understood. OBJECTIVE: To investigate the relationship between diffusivity markers of demyelination and axonal loss in perilesional white matter and lesion expansion in relapsing-remitting MS (RRMS). METHODS: T1, FLAIR and diffusion tensor images were acquired from 30 patients. Novel single-streamline technique was used to estimate diffusivity in lesions, perilesional white matter and normal-appearing white matter (NAWM). RESULTS: Significant association was found between baseline periplaque radial diffusivity (RD) and subsequent lesion expansion. Conversely, periplaque axial diffusivity (AD) did not correlate with lesion growth. Baseline RD (but not AD) in periplaque white matter of expanding lesions was significantly higher compared with non-expanding lesions. Correlation between increase of both RD and AD in the periplaque area during follow-up period and lesion expansion was noticeably stronger for RD. Increase of RD in periplaque area was also much higher compared to AD. There was significant increase of AD and RD in the periplaque area of expanding, but not in non-expanding, lesions. CONCLUSION: Periplaque demyelination is likely to be an initial step in a process of lesion expansion and, as such, potentially represents a suitable target for remyelinating therapies.

The effect of systemic and topical ophthalmic medications on choroidal thickness: A review.

The choroid plays an important role in various ocular pathologies and retinal blood supply. There is a knowledge gap on how the choroid is affected by systemic and topical medications. Systemic medications that affect microvasculature elsewhere in the body can also affect the microvasculature of the choroid. This review summarizes current knowledge on associations between systemic and topical medications and changes in choroidal thickness (CT). This review included 71 studies on mydriatics/cycloplegics, intraocular pressure (IOP)-lowering therapies, antihypertensives, adrenergic antagonists, statins, corticosteroids, hydroxychloroquine, isotretinoin, hormonal contraceptives, phosphodiesterase inhibitors, antipsychotics, antineoplastic agents, ethanol, caffeine and nicotine. IOP-lowering therapies, atropine eye drops, and systemic administration of ß blockers and ethanol are associated with a significant increase in CT. Cyclopentolate and phenylephrine are associated with a CT reduction. Systemic medications that decrease CT include caffeine and nicotine. Tropicamide, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, statins, corticosteroids, hydroxychloroquine and hormonal contraceptives have mixed findings. CT increase associated with IOP-lowering therapies is possibly achieved by enhancing aqueous humour flow to the choroid thus elevating choroidal blood flow and thickness. CT changes appear to be independent from systemic blood pressure changes, suggesting that a significant association with an antihypertensive could be due to an idiosyncratic drug property. Statins and candesartan decrease macrophage accumulation and intercellular adhesion molecule 1 expression in the choroid. The choroid and its response to various disease processes and systemic medication can be further investigated to improve patient care, particularly in patients with choroid and retina pathologies.

Mitochondrial dysfunction in Alzheimer's disease - a proteomics perspective.

Mitochondrial dysfunction is involved in Alzheimer's disease (AD) pathogenesis. Mitochondria have their own genetic material; however, most of their proteins (∼99%) are synthesized as precursors on cytosolic ribosomes, and then imported into the mitochondria. Therefore, exploring proteome changes in these organelles can yield valuable information and shed light on the molecular mechanisms underlying mitochondrial dysfunction in AD. Here, we review AD-associated mitochondrial changes including the effects of amyloid beta and tau protein accumulation on the mitochondrial proteome. We also discuss the relationship of ApoE genetic polymorphism with mitochondrial changes, and present a meta-analysis of various differentially expressed proteins in the mitochondria in AD.Area covered: Proteomics studies and their contribution to our understanding of mitochondrial dysfunction in AD pathogenesis.Expert opinion: Proteomics has proven to be an efficient tool to uncover various aspects of this complex organelle, which will broaden our understanding of mitochondrial dysfunction in AD. Evidently, mitochondrial dysfunction is an early biochemical event that might play a central role in driving AD pathogenesis.

Expansion of chronic lesions is linked to disease progression in relapsing-remitting multiple sclerosis patients.

BACKGROUND: Slow-burning inflammation is putatively associated with lesion expansion and leads to progressive loss of axons and disability worsening. OBJECTIVE: To investigate the incidence and extent of chronic white matter lesion expansion in relapsing-remitting multiple sclerosis (RRMS) patients and to evaluate its relationship with biomarkers of disease progression. METHODS: Pre- and post-gadolinium T1, fluid-attenuated inversion recovery (FLAIR) and diffusion tensor images were acquired from 33 patients. Lesional activity were analysed between baseline and 48 months using custom-designed software. RESULTS: A total of 569 lesions were identified as chronic at baseline, of which 261 were expanding, 236 were stable and 72 were shrinking. In addition, 139 new lesions (both confluent and free-standing) were observed. Chronic lesion expansion was associated with patient's age and accounted for the bulk (67.3%) of total brain lesion volume increase, while only 32.7% was attributable to new lesion formation. Change in chronic lesion volume correlated with the rate of brain atrophy (r = -0.57, p = 0.001), change of Expanded Disability Status Scale (EDSS; r = 0.38, p = 0.03) and an increase of isotropic diffusivity inside the lesions (r = 0.75, p < 0.001). CONCLUSION: Expansion of chronic lesions in RRMS patients is the primary determinant of increased T2 total lesion load. It significantly contributes to disease progression and partially driving axonal loss inside the lesions and brain damage outside of lesional tissue.

TAP AND INJECT VERSUS PARS PLANA VITRECTOMY FOR POSTPROCEDURAL ENDOPHTHALMITIS: A Meta-analysis.

PURPOSE: To compare the visual outcomes after prompt pars plana vitrectomy (PPV) with tap biopsy and intravitreal antimicrobial injection to treat postinjection and postsurgery endophthalmitis. METHODS: The Cochrane Central Register of Controlled Trials, Ovid MEDLINE, and Ovid Embase databases were searched for articles published between January 2010 and November 2020. Two independent reviewers selected articles and extracted data. We analyzed data in RevMan 5.3 and assessed methodological quality using the Cochrane ROBINS-I tool. The mean improvement in visual outcome was compared between PPV and intravitreal antimicrobial injection as a relative risk of improving ≥2 lines and a mean logarithm of the minimal angle of resolution difference in improvement. RESULTS: Fifteen retrospective case series (1,355 eyes), of which 739 eyes (55%) received intravitreal antimicrobial injection and 616 (45%) received PPV as initial treatment, were included. The overall relative risk of improving 2 or more lines in PPV in comparison with intravitreal antimicrobial injection was 1.04 (95% CI 0.88-1.23; P = 0.61; I2 = 0%) with a mean difference of 0.04 (95% CI -0.18 to 0.27; P = 0.69; I2 = 0%). The results stayed robust when subgroup analysis based on causative procedure for endophthalmitis was performed. CONCLUSION: Intravitreal antimicrobial injection is noninferior to PPV for the treatment of postcataract operation, postinjection, and post-PPV endophthalmitis.

Evolving geographic diversity in SARS-CoV2 and in silico analysis of replicating enzyme 3CLpro targeting repurposed drug candidates.

BACKGROUND: Severe acute respiratory syndrome (SARS) has been initiating pandemics since the beginning of the century. In December 2019, the world was hit again by a devastating SARS episode that has so far infected almost four million individuals worldwide, with over 200,000 fatalities having already occurred by mid-April 2020, and the infection rate continues to grow exponentially. SARS coronavirus 2 (SARS-CoV-2) is a single stranded RNA pathogen which is characterised by a high mutation rate. It is vital to explore the mutagenic capability of the viral genome that enables SARS-CoV-2 to rapidly jump from one host immunity to another and adapt to the genetic pool of local populations. METHODS: For this study, we analysed 2301 complete viral sequences reported from SARS-CoV-2 infected patients. SARS-CoV-2 host genomes were collected from The Global Initiative on Sharing All Influenza Data (GISAID) database containing 9 genomes from pangolin-CoV origin and 3 genomes from bat-CoV origin, Wuhan SARS-CoV2 reference genome was collected from GeneBank database. The Multiple sequence alignment tool, Clustal Omega was used for genomic sequence alignment. The viral replicating enzyme, 3-chymotrypsin-like cysteine protease (3CLpro) that plays a key role in its pathogenicity was used to assess its affinity with pharmacological inhibitors and repurposed drugs such as anti-viral flavones, biflavanoids, anti-malarial drugs and vitamin supplements. RESULTS: Our results demonstrate that bat-CoV shares > 96% similar identity, while pangolin-CoV shares 85.98% identity with Wuhan SARS-CoV-2 genome. This in-depth analysis has identified 12 novel recurrent mutations in South American and African viral genomes out of which 3 were unique in South America, 4 unique in Africa and 5 were present in-patient isolates from both populations. Using state of the art in silico approaches, this study further investigates the interaction of repurposed drugs with the SARS-CoV-2 3CLpro enzyme, which regulates viral replication machinery. CONCLUSIONS: Overall, this study provides insights into the evolving mutations, with implications to understand viral pathogenicity and possible new strategies for repurposing compounds to combat the nCovid-19 pandemic.

Demyelination precedes axonal loss in the transneuronal spread of human neurodegenerative disease.

The spread of neurodegeneration through the human brain network is reported as underlying the progression of neurodegenerative disorders. However, the exact mechanisms remain unknown. The human visual pathway is characterized by its unique hierarchical architecture and, therefore, represents an ideal model to study trans-synaptic degeneration, in contrast to the complexity in neural connectivity of the whole brain. Here we show in two specifically selected patient cohorts, including (i) glaucoma patients with symmetrical bilateral hemifield defects respecting the horizontal meridian (n = 25, 14 females, 64.8 ± 10.1 years; versus 13 normal controls with similar age/sex distributions); and (ii) multiple sclerosis patients without optic radiation lesions (to avoid potential effects of lesions on diffusivity measures) (n = 30, 25 females, 37.9 ± 10.8 years; versus 20 controls), that there are measurable topographic changes in the posterior visual pathways corresponding to the primary optic nerve defects. A significant anisotropic increase of water diffusion was detected in both patient cohorts in the optic radiations, characterized by changes in perpendicular (radial) diffusivity (a measure of myelin integrity) that extended more posteriorly than those observed in parallel (axial) diffusivity (reflecting axonal integrity). In glaucoma, which is not considered a demyelinating disease, the observed increase in radial diffusivity within the optic radiations was validated by topographically linked delay of visual evoked potential latency, a functional measure of demyelination. Radial diffusivity change in the optic radiations was also associated with an asymmetrical reduction in the thickness of the calcarine cortex in glaucoma. In addition, 3 years longitudinal observation of the multiple sclerosis patient cohort revealed an anterograde increase of radial diffusivity in the anterior part of optic radiations which again was retinotopically associated with the primary damage caused by optic neuritis. Finally, in an animal model of optic nerve injury, we observed early glial activation and demyelination in the posterior visual projections, evidenced by the presence of myelin-laden macrophages. This occurred prior to the appearance of amyloid precursor protein accumulation, an indicator of disrupted fast axonal transport. This study demonstrated strong topographical spread of neurodegeneration along recognized neural projections and showed that myelin and glial pathology precedes axonal loss in the process, suggesting that the mechanism of trans-synaptic damage may be at least partially mediated by glial components at the cellular level. The findings may have broad biological and therapeutic implications for other neurodegenerative disorders.

Loss of Shp2 Rescues BDNF/TrkB Signaling and Contributes to Improved Retinal Ganglion Cell Neuroprotection.

Glaucoma is characterized by the loss of retinal ganglion cells (RGC), and accordingly the preservation of RGCs and their axons has recently attracted significant attention to improve therapeutic outcomes in the disease. Here, we report that Src homology region 2-containing protein tyrosine phosphatase 2 (Shp2) undergoes activation in the RGCs, in animal model of glaucoma as well as in the human glaucoma tissues and that Shp2 dephosphorylates tropomyosin receptor kinase B (TrkB) receptor, leading to reduced BDNF/TrkB neuroprotective survival signaling. This was elucidated by specifically modulating Shp2 expression in the RGCs in vivo, using adeno-associated virus serotype 2 (AAV2) constructs. Shp2 upregulation promoted endoplasmic reticulum (ER) stress and apoptosis, along with functional and structural deficits in the inner retina. In contrast, loss of Shp2 decelerated the loss of RGCs, preserved their function, and suppressed ER stress and apoptosis in glaucoma. This report constitutes the first identification of Shp2-mediated TrkB regulatory mechanisms in the RGCs that can become a potential therapeutic target in both glaucoma and other neurodegenerative disorders.

Differing Structural and Functional Patterns of Optic Nerve Damage in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder.

PURPOSE: To assess differential patterns of axonal loss and demyelination in the optic nerve in multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD). DESIGN: Cross-sectional study. PARTICIPANTS: One hundred ninety-two participants, including 136 MS patients (272 eyes), 19 NMOSD patients (38 eyes), and 37 healthy control participants (74 eyes). METHODS: All participants underwent spectral-domain OCT scans and multifocal visual evoked potential (mfVEP) recordings. High-resolution magnetic resonance imaging (MRI) with the diffusion protocol also was performed in all patients. MAIN OUTCOME MEASURES: Ganglion cell-inner plexiform layer (GCIPL) thickness and mfVEP amplitude and latency at 5 eccentricities; global and temporal retinal nerve fiber layer thickness. RESULTS: In optic neuritis (ON) eyes, the NMOSD patients had more severe GCIPL loss (P < 0.001) and mfVEP amplitude reduction (P < 0.001) compared with MS patients, whereas in contrast, mfVEP latency delay was more evident in MS patients (P < 0.001). The NMOSD patients showed more morphologic and functional loss at the foveal to parafoveal region, whereas the MS patients showed evenly distributed damage at the macula. Correlation analysis demonstrated a strong structure-function (OCT-mfVEP) association in the NMOSD patients, which was only moderate in the MS patients. In non-ON (NON) eyes, the MS patients showed significantly thinner GCIPL than controls (P < 0.001), whereas no GCIPL loss was observed in NON eyes in NMOSD. In addition, a significant correlation was found between all OCT and mfVEP measures in MS patients, but not in NMOSD patients. MRI demonstrated significant lesional load in the optic radiation in MS compared to NMOSD eyes (P = 0.002), which was related to the above OCT and mfVEP changes in NON eyes. CONCLUSIONS: Our study demonstrated different patterns of ON damage in NMOSD and MS. In MS, the ON damage was less severe, with demyelination as the main pathologic component, whereas in NMOSD, axonal loss was more severe compared with myelin loss. The disproportional mfVEP amplitude and latency changes suggested predominant axonal damage within the anterior visual pathway as the main clinical feature of NMOSD, in contrast to MS, where demyelination spreads along the entire visual pathway.

Evidence of Müller Glial Dysfunction in Patients with Aquaporin-4 Immunoglobulin G-Positive Neuromyelitis Optica Spectrum Disorder.

PURPOSE: To compare functional and structural changes in the retina in patients with aquaporin-4 immunoglobulin G (AQP4-IgG)-positive neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS). DESIGN: Cross-sectional study; biochemical study of human retinas. PARTICIPANTS: A total of 181 participants, including 22 consecutive patients (44 eyes) with NMOSD, 131 patients (262 eyes) with multiple sclerosis (MS), and 28 normal subjects (56 eyes). In addition, 8 eyeballs from healthy donors were used for biochemical analysis. METHODS: Full-field electroretinography (ERG) and spectral-domain OCT were performed in all the subjects. Topography of AQP4 expression and Müller glial distribution were analyzed using Western blotting and immunohistochemistry. MAIN OUTCOME MEASURES: Full-field ERG parameters, including amplitudes and peak times. Tissue volume of each of the retinal layers at the fovea by OCT segmentation. Levels of AQP4 expression at different retinal regions. RESULTS: The b-wave amplitude was significantly reduced in patients with AQP4-IgG+ NMOSD in scotopic ERGs (compared with AQP4-IgG- subjects, patients with MS, and normal controls) but not in photopic ERGs. Further analysis showed that this b-wave change was mainly caused by reduction of the slow PII component, suggesting specific Müller cell dysfunction. We also found thinning of specific retinal layers at the fovea in patients with AQP4-IgG+ NMOSD, in the Henle fiber outer nuclear layer (HFONL) and the inner segment (IS) layer, but not in the inner nuclear layer (INL), outer plexiform layer (OPL), or outer segment (OS) layer. Furthermore, there was a significant association between foveal HFONL-IS complex thinning and scotopic b-wave amplitude reduction (P = 0.005∼0.01, fixed-effects model). Western blotting demonstrated that Müller cell-specific AQP4 was expressed at a higher level at the fovea than the peripheral retina. Immunohistochemical studies revealed that the specific foveal thinning reflected the topography of AQP4 expression and Müller glial distribution in the human macula. CONCLUSIONS: This study provides in vivo structural and functional evidence of Müller glial dysfunction in eyes of patients with AQP4-IgG+ NMOSD. Topography of retinal structural change is supported by distribution of Müller cells and patterns of AQP4 expression. The study suggests that visual electrophysiology and retinal imaging could be useful biomarkers to assess the potential retinal astrocytopathy in NMOSD.

Performance of iPad-based threshold perimetry in glaucoma and controls.

IMPORTANCE: Independent validation of iPad visual field testing software Melbourne Rapid Fields (MRF). BACKGROUND: To examine the functionality of MRF and compare its performance with Humphrey SITA 24-2 (HVF). DESIGN: Prospective, cross-sectional validation study. PARICIPANTS: Sixty glaucomas mean deviation (MD:-5.08±5.22); 17 pre-perimetric, 43 HVF field defects and 25 controls. METHODS: The MRF was compared with HVF for scotoma detection, global indices, regional mean threshold values and sensitivity/specificity. Long-term test-retest variability was assessed after 6 months. MAIN OUTCOME MEASURES: Linear regression and Bland Altman analyses of global indices sensitivity/specificity using (ROC) curves, intraclass correlations. RESULTS: Using a cluster definition of three points at <1% or two at 0.5% to define a scotoma on HVF, MRF detected 39/54 abnormal hemifields with a similar threshold-based criteria. Global indices were highly correlated between MRF and HVF: MD r2 = 0.80, PSD r2 = 0.77, VFI r2 = 0.85 (all P < 0.0001). For manifest glaucoma patients, correlations of regional mean thresholds ranged from r2 = 0.45-0.78, despite differing array of tested points between devices. ROC analysis of global indices showed reasonable sensitivity/specificity with (AUC) values of MD:0.89, (PSD:0.85) and (VFI:0.88). MRF retest variability was low with (ICC) values at 0.95 (MD and VFI), 0.94 (PSD). However, individual test point variability for mid-range thresholds was higher. CONCLUSIONS AND RELEVANCE: MRF perimetry, despite using a completely different test paradigm, shows good performance characteristics compared to HVF for detection of defects, correlation of global indices and regional mean threshold values. Reproducibility for individual points may limit application for monitoring change over time, and fixation monitoring needs improvement.

BDNF impairment is associated with age-related changes in the inner retina and exacerbates experimental glaucoma.

Brain-derived neurotrophic factor (BDNF) stimulation of its high-affinity receptor TrkB results in activation of pro-survival cell-signalling pathways that can afford neuroprotection to the retina. Reduction in retrograde axonal transport of neurotrophic factors such as BDNF from the brain to the neuronal cell bodies in the retina has been suggested as a critical factor underlying progressive and selective degeneration of ganglion cell layer and optic nerve in glaucoma. We investigated the role of BDNF in preserving inner retinal homeostasis in normal and glaucoma states using BDNF(+/-) mice and compared it with wild type controls. This study demonstrated that BDNF(+/-) animals were more susceptible to functional, morphological and molecular degenerative changes in the inner retina caused by age as well as upon exposure to experimental glaucoma caused by increased intraocular pressure. Glaucoma induced a down regulation of BDNF/TrkB signalling and an increase in levels of neurotoxic amyloid ß 1-42 in the optic nerve head which were exacerbated in BDNF(+/-) mice. Similar results were obtained upon analysing the human optic nerve head tissues. Our data highlighted the role of BDNF in maintaining the inner retinal integrity under normal conditions and the detrimental effects of its insufficiency on the retina and optic nerve in glaucoma.

Brain derived neurotrophic factor is involved in the regulation of glycogen synthase kinase 3ß (GSK3ß) signalling.

Glycogen synthase kinase 3ß (GSK3ß) is involved in several biochemical processes in neurons regulating cellular survival, gene expression, cell fate determination, metabolism and proliferation. GSK3ß activity is inhibited through the phosphorylation of its Ser-9 residue. In this study we sought to investigate the role of BDNF/TrkB signalling in the modulation of GSK3ß activity. BDNF/TrkB signalling regulates the GSK3ß activity both in vivo in the retinal tissue as well as in the neuronal cells under culture conditions. We report here for the first time that BDNF can also regulate GSK3ß activity independent of its effects through the TrkB receptor signalling. Knockdown of BDNF lead to a decline in GSK3ß phosphorylation without having a detectable effect on the TrkB activity or its downstream effectors Akt and Erk1/2. Treatment with TrkB receptor agonist had a stimulating effect on the GSK3ß phosphorylation, but the effect was significantly less pronounced in the cells in which BDNF was knocked down. The use of TrkB receptor antagonist similarly, manifested itself in the form of downregulation of GSK3ß phosphorylation, but a combined TrkB inhibition and BDNF knockdown exhibited a much stronger negative effect. In vivo, we observed reduced levels of GSK3ß phosphorylation in the retinal tissues of the BDNF(+/-) animals implicating critical role of BDNF in the regulation of the GSK3ß activity. Concluding, BDNF/TrkB axis strongly regulates the GSK3ß activity and BDNF also exhibits GSK3ß regulatory effect independent of its actions through the TrkB receptor signalling.

The role of myelin in neurodegeneration: implications for drug targets and neuroprotection strategies.

Myelination of axons in the central nervous system offers numerous advantages, including decreased energy expenditure for signal transmission and enhanced signal speed. The myelin sheaths surrounding an axon consist of a multi-layered membrane that is formed by oligodendrocytes, while specific glycoproteins and lipids play various roles in this formation process. As beneficial as myelin can be, its dysregulation and degeneration can prove detrimental. Inflammation, oxidative stress, and changes in cellular metabolism and the extracellular matrix can lead to demyelination of these axons. These factors are hallmark characteristics of certain demyelinating diseases including multiple sclerosis. The effects of demyelination are also implicated in primary degeneration in diseases such as glaucoma and Alzheimer's disease, as well as in processes of secondary degeneration. This reveals a relationship between myelin and secondary processes of neurodegeneration, including resultant degeneration following traumatic injury and transsynaptic degeneration. The role of myelin in primary and secondary degeneration is also of interest in the exploration of strategies and targets for remyelination, including the use of anti-inflammatory molecules or nanoparticles to deliver drugs. Although the use of these methods in animal models of diseases have shown to be effective in promoting remyelination, very few clinical trials in patients have met primary end points. This may be due to shortcomings or considerations that are not met while designing a clinical trial that targets remyelination. Potential solutions include diversifying disease targets and requiring concomitant interventions to promote rehabilitation.