Extensive Gliosis Research Articles

First Report of Viral Nervous Necrosis in Asian Sea Bass, Lates Calcarifer Cultured in Sri Lanka

Viral Nervous Necrosis (VNN) caused by Betanodavirus is a devastating disease in aquatic animals. The virus infects both marine and freshwater fish worldwide. Vacuolating necrosis of neural cells of the brain, the retina of the eye, and the spinal cord of the infected fish are the primary histological lesions of the condition. It causes up to 100% mortality in larvae and juvenile fish and can cause significant death in adult fish. The present study detected viral nervous necrosis in larvae and fry of Asian sea bass (Lates calcarifer) with progressive mortality of up to 95% in one week during the Northeast monsoon when the mean water temperature was 27 to 29°C. Histopathological examination of the moribund fish revealed extensive vacuolation and gliosis in the olfactory bulb, the optic lobe of the forebrain, and the inner and outer layer of the retina. Furthermore, tissues of the brain and the retina had intracellular inclusion bodies suggesting viral etiology, further justified by the negative results of the bacterial and parasitic examinations. The Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) test additionally confirms the etiology diagnosis using specific primers designed previously. The histopathology and RT-PCR results suggest that the mortalities of Asian sea bass were due to the VNN. The present finding is the first report of the VNN associated with mass mortalities in Asian seabass cultured in Sri Lanka. These crucial findings emphasize the need for quarantine and control strategies to prevent the spread of the virus and outbreak of the disease.

Study of the histopathological and hematological changes due to dimtethoate toxicity in rabbis

The dimethoate is considered as one of most important organophosphorus pesticides that vastly used in agriculture in many countries especially in Iraq which caused different diseases in plants, animals and man. In present study we investigated the histopathological and hematological changes in rabbits resulting from chronic dimethoate intoxication. The treated groups (G2, G3 and G4) received dimethoate orally (10, 25 and 50 mg/kg of B.W.) respectively for two months while the control group (G1) was given water for the same period. The hematological results showed significant decrease in red blood cells counts and hemoglobin values (P< 0.05) in treated groups especially G3 and G4 compared to G1 control group. While the total W.B.Cs counts showed variables values without significant differences between treated groups and control group. The histopathological lesions in organs are dose concerning and include mild hepatocellular degeneration and hepatic necrosis ,hemorrhage with extensive periportal fibrosis, chronic inflammatory cells infiltrations mainly lymphocytes and macrophages in addition to liver fibrosis and cirrhosis and biliary hyperplasia with cholangitis occurred only with toxic doses of dimethoate especially G4, also there degenerative changes and necrosis in kidney and heart, hemosiderosis and hemorrhage with lymphoid depletion in spleen , In brain, there is extensive demyelination and perineruonal edema and perivascular leukocytes cuffing and extensive focal gliosis and the lungs showed congestion with thickened alveolar walls because of slight infiltrations of inflammatory cells mainly lymphocytes and macrophages also there is severe pulmonary hemorrhage and edema with severe emphysematous area and atelectasis in pulmonary tissue. It was concluded that dimethoate induces different histopathological lesions in different organs in rabbits especially in liver which causes hepatocellular degeneration, biliary hyperplasia and cholangitis with hepatic fibrosis and cirrhosis and causes significant decrease in red blood cells counts and hemoglobin values in treated groups compared to the control.

The heterogeneity of microglial activation and its epigenetic and non-coding RNA regulations in the immunopathogenesis of neurodegenerative diseases.

Microglia are resident immune cells in the brain and play a central role in the development and surveillance of the nervous system. Extensive gliosis is a common pathological feature of several neurodegenerative diseases, such as Alzheimer's disease (AD), the most common cause of dementia. Microglia can respond to multiple inflammatory insults and later transform into different phenotypes, such as pro- and anti-inflammatory phenotypes, thereby exerting different functions. In recent years, an increasing number of studies based on both traditional bulk sequencing and novel single-cell/nuclear sequencing and multi-omics analysis, have shown that microglial phenotypes are highly heterogeneous and dynamic, depending on the severity and stage of the disease as well as the particular inflammatory milieu. Thus, redirecting microglial activation to beneficial and neuroprotective phenotypes promises to halt the progression of neurodegenerative diseases. To this end, an increasing number of studies have focused on unraveling heterogeneous microglial phenotypes and their underlying molecular mechanisms, including those due to epigenetic and non-coding RNA modulations. In this review, we summarize the epigenetic mechanisms in the form of DNA and histone modifications, as well as the general non-coding RNA regulations that modulate microglial activation during immunopathogenesis of neurodegenerative diseases and discuss promising research approaches in the microglial era.

Accurate and stable chronic in vivo voltammetry enabled by a replaceable subcutaneous reference electrode

SummaryIn vivo sensing of neurotransmitters has provided valuable insight into both healthy and diseased brain. However, chronically implanted Ag/AgCl reference electrodes suffer from degradationgradation, resulting in errors in the potential at the working electrode. Here, we report a simple, effective way to protect in vivo sensing measurements from reference polarization with a replaceable subcutaneously implanted reference. We compared a brain-implanted reference and a subcutaneous reference and observed no difference in impedance or dopamine redox peak separation in an acute preparation. Chronically, peak background potential and dopamine oxidation potential shifts were eliminated for three weeks. Scanning electron microscopy shows changes in surface morphology and composition of chronically implanted Ag/AgCl electrodes, and postmortem histology reveals extensive cell death and gliosis in the surrounding tissue. As accurate reference potentials are critical to in vivo electrochemistry applications, this simple technique can improve a wide and diverse assortment of in vivo preparations.

Spinal cord occupation ratio (SCOR) and its application in the diagnosis of cervical spinal cord compression in Mucopolysaccharidoses

Introduction Mucopolysaccharidoses (MPS) can lead to cervical spinal cord compression (SCC). Diagnostic scores for SCC in MPS use the obliteration of the passage of cerebrospinal fluid in the anterior and posterior spinal cord in the sagittal section of magnetic resonance imaging (MRI). The spinal cord occupation ratio (SCOR) published, by Nouri et al (2018), establishes the spinal cord filling index for the spinal cord, identifying disproportionate spinal cord occupation in the canal. When evaluating congenital canal stenosis, the risk of spinal cord injury has been considered increased when the SCOR is ≥70% in the median sagittal plane or ≥ 80% in the axial plane. Although these values ​​have not been validated for MPS populations, they could be useful. Objective To verify the SCOR in MPS patients with diagnosis of cervical SCC comparing the SCOR with other markers proposed in the existing MPS SCC scores, such as the extent of gliosis, clinical impact and the SCC assessment as represented by the obliteration of CSF flow. Methods We reviewed imaging tests of the cervical spine from MPS patients with previously confirmed SCC, using the SCOR measure in the median sagittal plane, evaluation of the presence and extent of spinal gliosis on MRI, evaluation of the clinical impact using a clinical score and evaluation of the images for the obliteration of cerebral spinal fluid (CSF) flow. Results Thirty-one MRI of 24 different patients were included. The average SCOR was 87.1%. This was lower (81.6%) in patients without gliosis, when compared to those with focal (90.5%) and extensive (97%) gliosis. The only patient with gliosis associated with a lacunar lesion, resulting from an acute compressive injury, had a 68% SCOR, due to the atrophic spinal cord injury. As expected, SCOR was higher in patients with total or partial CSF obliteration, but one among the 3 patients without CSF flow obliteration, with a 76% SCOR, had already developed focal gliosis and mild clinical abnormalities. Patients with more extensive gliosis had higher clinical scores. Four patients had more than one imaging scan evaluated. SCOR upward trend showed an annual average increase of 3.8%. Discussion & Conclusions The use of SCOR allows the diagnosis of cervical spinal canal stenosis in an objective way. It is possible that the cut-off values used by Nouri et al in patients with congenital stenosis could be useful to diagnose cervical stenosis in MPS patients, preceding the finding of CSF flow obstruction, presence of gliosis or clinical abnormalities. Furthermore, the use of SCOR may assist in the longitudinal evaluation of disease progression. Better follow-up and timely diagnosis allows for scheduling of surgery at the best clinical moment, minimizing complications.

Metabolic Enzyme Alterations and Astrocyte Dysfunction in a Murine Model of Alexander Disease With Severe Reactive Gliosis

Alexander disease (AxD) is a rare and fatal neurodegenerative disorder caused by mutations in the gene encoding glial fibrillary acidic protein (GFAP). In this report, a mouse model of AxD (GFAPTg;Gfap+/R236H) was analyzed that contains a heterozygous R236H point mutation in murine Gfap as well as a transgene with a GFAP promoter to overexpress human GFAP. Using label-free quantitative proteomic comparisons of brain tissue from GFAPTg;Gfap+/R236H versus wild-type mice confirmed upregulation of the glutathione metabolism pathway and indicated proteins were elevated in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, which had not been reported previously in AxD. Relative protein-level differences were confirmed by a targeted proteomics assay, including proteins related to astrocytes and oligodendrocytes. Of particular interest was the decreased level of the oligodendrocyte protein, 2-hydroxyacylsphingosine 1-beta-galactosyltransferase (Ugt8), since Ugt8-deficient mice exhibit a phenotype similar to GFAPTg;Gfap+/R236H mice (e.g., tremors, ataxia, hind-limb paralysis). In addition, decreased levels of myelin-associated proteins were found in the GFAPTg;Gfap+/R236H mice, consistent with the role of Ugt8 in myelin synthesis. Fabp7 upregulation in GFAPTg;Gfap+/R236H mice was also selected for further investigation due to its uncharacterized association to AxD, critical function in astrocyte proliferation, and functional ability to inhibit the anti-inflammatory PPAR signaling pathway in models of amyotrophic lateral sclerosis (ALS). Within Gfap+ astrocytes, Fabp7 was markedly increased in the hippocampus, a brain region subjected to extensive pathology and chronic reactive gliosis in GFAPTg;Gfap+/R236H mice. Last, to determine whether the findings in GFAPTg;Gfap+/R236H mice are present in the human condition, AxD patient and control samples were analyzed by Western blot, which indicated that Type I AxD patients have a significant fourfold upregulation of FABP7. However, immunohistochemistry analysis showed that UGT8 accumulates in AxD patient subpial brain regions where abundant amounts of Rosenthal fibers are located, which was not observed in the GFAPTg;Gfap+/R236H mice.

Kv1.1 subunits localize to cardiorespiratory brain networks in mice where their absence induces astrogliosis and microgliosis

Cardiorespiratory collapse following a seizure is a suspected cause of sudden unexpected death in epilepsy (SUDEP), the leading cause of epilepsy-related mortality. In the commonly used Kcna1 gene knockout (Kcna1−/−) mouse model of SUDEP, cardiorespiratory profiling reveals an array of aberrant breathing patterns that could contribute to risk of seizure-related mortality. However, the brain structures mediating these respiratory abnormalities remain unknown. We hypothesize that Kv1.1 deficiency in respiratory control centers of the brain contribute to respiratory dysfunction in Kcna1−/− mice leading to increased SUDEP risk. Thus, in this study, we first used immunohistochemistry to map expression of Kv1.1 protein in cardiorespiratory brain regions of wild-type Kcna1+/+ (WT) mice. Next, GFAP and Iba1 immunostaining was used to test for the presence of astrogliosis and microgliosis, respectively, in the cardiorespiratory centers of Kcna1−/− mice, which could be indicative of seizure-related brain injury that could impair breathing. In WT mice, we detected Kv1.1 protein in all cardiorespiratory centers examined, including the basolateral amygdala, dorsal respiratory group, dorsal motor nucleus of vagus, nucleus ambiguus, ventral respiratory column, and pontine respiratory group, as well as chemosensory centers including the retrotrapezoid and median raphae nuclei. Extensive gliosis was observed in the same areas in Kcna1−/− mice suggesting that seizure-associated brain injury could contribute to respiratory abnormalities.

Tau Protein Phosphorylated at Threonine-231 is Expressed Abundantly in the Cerebellum in Prion Encephalopathies.

Background:Transmissible spongiform encephalopathies (TSEs) are rare neurodegenerative disorders that affect animals and humans. Bovine spongiform encephalopathy (BSE) in cattle, and Creutzfeld-Jakob Disease (CJD) in humans belong to this group. The causative agent of TSEs is called “prion”, which corresponds to a pathological form (PrPSc) of a normal cellular protein (PrPC) expressed in nerve cells. PrPSc is resistant to degradation and can induce abnormal folding of PrPC, and TSEs are characterized by extensive spongiosis and gliosis and the presence of PrPSc amyloid plaques. CJD presents initially with clinical symptoms similar to Alzheimer’s disease (AD). In AD, tau aggregates and amyloid-β protein plaques are associated with memory loss and cognitive impairment in patients.Objective:In this work, we study the role of tau and its relationship with PrPSc plaques in CJD.Methods:Multiple immunostainings with specific antibodies were carried out and analyzed by confocal microscopy.Results:We found increased expression of the glial fibrillary acidic protein (GFAP) and matrix metalloproteinase (MMP-9), and an exacerbated apoptosis in the granular layer in cases with prion disease. In these cases, tau protein phosphorylated at Thr-231 was overexpressed in the axons and dendrites of Purkinje cells and the extensions of parallel fibers in the cerebellum.Conclusion:We conclude that phosphorylation of tau may be a response to a toxic and inflammatory environment generated by the pathological form of prion.

Turner syndrome associated with cerebellar abnormalities

We present an autopsied fetus with Turner syndrome (TS), obtained after a therapeutic abortion at the Clinic of Obstetrics and Gynecology at the University Hospital, Plovdiv, Bulgaria. It was a female fetus weighing 75 g. The chorionic villus sampling followed by karyotyping established monosomy XO. The fetal autopsy confirmed agenesis of the cerebellar vermis and cerebellar hypoplasia. The immunohistochemical study of the brain with S100 protein (S100), glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), and cluster of differentiation 68 was taken into consideration. The presence of extensive gliosis reaction is proved in the cerebellar structures of TS by the positivity of glial markers: (GFAP) and S100 protein. The quantity of neurons proved by NSE marker is probably associated with the deficiency of differentiation and cell migration caused by inhibition in the development of young cells. The presented case of TS found a new phenotype with cerebellar abnormalities described for the first time.

Calming Down Mast Cells with Ketotifen: A Potential Strategy for Multiple Sclerosis Therapy?

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) characterized by extensive inflammation, demyelination, axonal loss and gliosis. Evidence indicates that mast cells contribute to immunopathogenesis of both MS and experimental autoimmune encephalomyelitis (EAE), which is the most employed animal model to study this disease. Considering the inflammatory potential of mast cells, their presence at the CNS and their stabilization by certain drugs, we investigated the effect of ketotifen fumarate (Ket) on EAE development. EAE was induced in C57BL/6 mice by immunization with MOG35-55 and the animals were injected daily with Ket from the seventh to the 17th day after disease induction. This early intervention with Ket significantly reduced disease prevalence and severity. The protective effect was concomitant with less NLRP3 inflammasome activation, rebalanced oxidative stress and also reduced T cell infiltration at the CNS. Even though Ket administration did not alter mast cell percentage at the CNS, it decreased the local CPA3 and CMA1 mRNA expression that are enzymes typically produced by these cells. Evaluation of the CNS-barrier permeability indicated that Ket clearly restored the permeability levels of this barrier. Ket also triggered an evident lymphadenomegaly due to accumulation of T cells that produced higher levels of encephalitogenic cytokines in response to in vitro stimulation with MOG. Altogether these findings reinforce the concept that mast cells are particularly relevant in MS immunopathogenesis and that Ket, a known stabilizer of their activity, has the potential to be used in MS control.

Reactive gliosis mimicking tumor recurrence - a case series documenting MRI abnormalities and neuropathological correlates.

. The aim of this study is to identify, in our center, all cases of foreign-body reactions to hemostatic agents or other prostheses resulting in a radiological suspicion of tumor recurrence. We interrogated our internal database to identify all such cases and systematically evaluated the MRI brain scans of patients: (i) at the time of initial tumor diagnosis, (ii) postoperatively, (iii) and at the time of suspected tumor recurrence. In addition, we reviewed each patient’s operative notes and reviewed the histology of all cases following a second surgical intervention. In total, we identified 8 patients, 7 of whom had a WHO grade II glioma at initial surgery. We did not identify any distinguishing radiological abnormalities from the initial diagnostic brain scan to the suspected recurrence, and histologically all cases were characterized by extensive gliosis; with both macrophages and reactive astrocytes present throughout. The cause of gliosis was identified as being relating to hemostatic agents in 4 cases; in the other 4 cases, the foreign-body reaction was presumed to be caused be materials used in a craniotomy or cranioplasty. This study highlights the difficulty in radiologically diagnosing a foreign-body reaction and also identifies that such a gliotic reaction may occur as a consequence of exogenous materials used in a craniotomy or cranioplasty.

Focal Transplantation of Aberrant Glial Cells Carrying the SOD1G93A Mutation into Rat Spinal Cord Induces Extensive Gliosis

Objective: We aimed to determine the potential of aberrant glial cells (AbAs) isolated from the spinal cord of adult SOD1^G93A symptomatic rats to induce gliosis and neuronal damage following focal transplantation into the lumbar spinal cord of wild-type rats. Methods: AbAs were obtained from the spinal cords of SOD1^G93A symptomatic rats. One hundred thousand cells were injected using a glass micropipette into the lumbar spinal cords (L3-L5) of syngeneic wild-type adult rats. Equal volumes of culture medium or wild-type neonatal microglia were used as controls. Seven days after transplantation, immunohistochemistry analysis was carried out using astrocytic and microglia cell markers. Transplanted SOD1^G93A AbAs were recognized by specific antibodies to human SOD1 (hSOD1) or misfolded human SOD1. Results: Seven days after transplantation, AbAs were mainly detected in the medial region of the lumbar ventral horn as a well-limited cell cluster formed at the site of injection by their immunoreactivity to either misfolded SOD1 or normally folded hSOD1. Compared with controls, transplanted AbAs were surrounded by marked microgliosis and reactive astrocytes. Marked microgliosis was observed to extend bilaterally up to the cervical cord. Motor neurons close to AbA transplants were surrounded by activated glial cells and displayed ubiquitin aggregation. Conclusions: AbAs bearing mutant SOD1^G93A have the potential to induce neuroinflammation along the spinal cord and incipient damage to the motor neurons. The emergence of AbAs during amyotrophic lateral sclerosis pathogenesis may therefore be a mechanism to boost neuroinflammation and spread motor neuron damage along the neuroaxis.

Peripheral Tumor Necrosis Factor-Alpha (TNF-α) Modulates Amyloid Pathology by Regulating Blood-Derived Immune Cells and Glial Response in the Brain of AD/TNF Transgenic Mice.

Increasing evidence has suggested that systemic inflammation along with local brain inflammation can play a significant role in Alzheimer's disease (AD) pathogenesis. Identifying key molecules that regulate the crosstalk between the immune and the CNS can provide potential therapeutic targets. TNF-α is a proinflammatory cytokine implicated in the pathogenesis of systemic inflammatory and neurodegenerative diseases, such as rheumatoid arthritis (RA) and AD. Recent studies have reported that anti-TNF-α therapy or RA itself can modulate AD pathology, although the underlying mechanism is unclear. To investigate the role of peripheral TNF-α as a mediator of RA in the pathogenesis of AD, we generated double-transgenic 5XFAD/Tg197 AD/TNF mice that develop amyloid deposits and inflammatory arthritis induced by human TNF-α (huTNF-α) expression. We found that 5XFAD/Tg197 mice display decreased amyloid deposition, compromised neuronal integrity, and robust brain inflammation characterized by extensive gliosis and elevated blood-derived immune cell populations, including phagocytic macrophages and microglia. To evaluate the contribution of peripheral huTNF-α in the observed brain phenotype, we treated 5XFAD/Tg197 mice systemically with infliximab, an anti-huTNF-α antibody that does not penetrate the blood-brain barrier and prevents arthritis. Peripheral inhibition of huTNF-α increases amyloid deposition, rescues neuronal impairment, and suppresses gliosis and recruitment of blood-derived immune cells, without affecting brain huTNF-α levels. Our data report, for the first time, a distinctive role for peripheral TNF-α in the modulation of the amyloid phenotype in mice by regulating blood-derived and local brain inflammatory cell populations involved in β-amyloid clearance.SIGNIFICANCE STATEMENT Mounting evidence supports the active involvement of systemic inflammation, in addition to local brain inflammation, in Alzheimer's disease (AD) progression. TNF-α is a pluripotent cytokine that has been independently involved in the pathogenesis of systemic inflammatory rheumatoid arthritis (RA) and AD. Here we first demonstrate that manipulation of peripheral TNF-α in the context of arthritis modulates the amyloid phenotype by regulating immune cell trafficking in the mouse brain. Our study suggests that additionally to its local actions in the AD brain, TNF-α can also indirectly modulate amyloid pathology as a regulator of peripheral inflammation. Our findings may have significant implications in the treatment of RA patients with anti-TNF-α drugs and in the potential use of TNF-targeted therapies for AD.

L2hgdh Deficiency Accumulates l-2-Hydroxyglutarate with Progressive Leukoencephalopathy and Neurodegeneration.

l-2-Hydroxyglutarate aciduria (L-2-HGA) is an autosomal recessive neurometabolic disorder caused by a mutation in the l-2-hydroxyglutarate dehydrogenase (L2HGDH) gene. In this study, we generated L2hgdh knockout (KO) mice and observed a robust increase of l-2-hydroxyglutarate (L-2-HG) levels in multiple tissues. The highest levels of L-2-HG were observed in the brain and testis, with a corresponding increase in histone methylation in these tissues. L2hgdh KO mice exhibit white matter abnormalities, extensive gliosis, microglia-mediated neuroinflammation, and an expansion of oligodendrocyte progenitor cells (OPCs). Moreover, L2hgdh deficiency leads to impaired adult hippocampal neurogenesis and late-onset neurodegeneration in mouse brains. Our data provide in vivo evidence that L2hgdh mutation leads to L-2-HG accumulation, leukoencephalopathy, and neurodegeneration in mice, thereby offering new insights into the pathophysiology of L-2-HGA in humans.

Effects of Mucuna pruriens on Free Fatty Acid Levels and Histopathological Changes in the Brains of Rats Fed a High Fructose Diet

Objective: To investigate free fatty acid levels and histopathological changes in the brain of rats fed a high fructose diet (HFrD) and to evaluate the effects of Mucuna pruriens, known to have antidiabetic activity, on these changes. Materials and Methods: The study comprised 28 mature female Wistar rats. The rats were divided into 4 groups, each included 7 rats. Group 1: control; group 2: fed an HFrD; group 3: fed normal rat chow and M. pruriens; group 4: fed an HFrD and M. pruriens for 6 weeks. At the end of 6 weeks, the rats were decapitated, blood and brain tissues were obtained. Serum glucose and triglyceride levels were measured. Free fatty acid levels were measured in 1 cerebral hemisphere of each rat and histopathological changes in the other. The Mann-Whitney U test was used to compare quantitative continuous data between 2 independent groups, and the Kruskal-Wallis test was used to compare quantitative continuous data between more than 2 independent groups. Results: Arachidonic acid and docosahexaenoic acid levels were significantly higher in group 2 than in group 1 (p < 0.05). Free arachidonic acid and docosahexaenoic acid levels in group 4 were significantly less than in group 2 (p < 0.05). Histopathological examination of group 2 revealed extensive gliosis, neuronal hydropic degeneration, and edema. In group 4, gliosis was much lighter than in group 2, and edema was not observed. Neuronal structures in group 4 were similar to those in group 1. Conclusions: The HFrD increased the levels of free arachidonic acid and docosahexaenoic acid probably due to membrane degradation resulting from possible oxidative stress and inflammation in the brain. The HFrD also caused extensive gliosis, neuronal hydropic degeneration, and edema. Hence, M. pruriens could have therapeutic effects on free fatty acid metabolism and local inflammatory responses in the brains of rats fed an HFrD.

Temporal and spatial characteristics of RGC death and axon degeneration in the rat model of nonarteritic anterior ischemic optic neuropathy

Objective: To investigate the temporal and spatial characteristics of retinal ganglion cell (RGC) death and axon degeneration in the rat model of nonarteritic anterior ischemic optic neuropathy (rNAION). Methods: Experimental study. The model of rNAION was induced by directly illuminating the optic nerve head with laser, after intravenous infusion with the photosensitizing agent rose Bengal. Seventy-one SD rats were randomly divided into five groups: 1-week (n=14), 2-week (n=14), 4-week (n=15) , 8-week (n=16) model group and the normal control group (n=12). Hematoxylin and eosin (H&E) staining and morphometric measurement with FG labeling were performed to assess rNAION-indeced histologic changes in the retina at different time points. RGCs were counted on retinal flat mounts in a masked fashion. Semithin sections stained with toluidine blue and transmission electron microscopy were performed to evaluate axonal degeneration. The differences of RGC density among multiple groups were tested with one-way ANOVA while the survival rate of RGC with kruskal-Wallis. Results: H&E-stained retina sections of rNAION revealed RGC loss. The density of labeled RGC was (2 273±219) cells/mm2 in the control group, (2 075±120) cells/mm2 in the 1-week group, (1 783±143) cells/mm2 in the 2-week group, (1 330±169) cells/mm2 in the 4-week group and (869±301) cells/mm2 in the 8-week group. There were significant differences between all pairs of groups (F=80.98, P<0.01). The impairment of RGC was aggravatedprogressively, which mainly in the upper quadrant. The survival rate of RGC was 99.9%±3.4%, 91.8%±2.9%, 72.6%±5.7%, 54.4%±7.0% and 37.5%±13.0%, respectively. There were significant differences between the 1-week and 2-week group(Z=-3.78, P<0.01), the 2-week and 4-week group(Z=-3.89, P<0.01), and the 4-week and 8-week group(Z=-3.23, P<0.01). Toluidine blue staining of the ON revealed significant demyelination 1 week after ischemic damage. Progressive axonal degeneration existed for several weeks, which mainly affected the central region of the optic nerve with extensive reactive gliosis. Ultrastructural study showed axonal edema and collapsed sheaths in the ischemic optic. Four weeks later, there were extensive axonal loss and severe glial scars. Conclusions: rNAION results in regional and later RGC death. The extended period of RGC death after rNAION induction is much more longer than previously recognized. (Chin J Ophthalmol, 2016, 52: 918-923).

Hypomyelination following deletion of Tsc2 in oligodendrocyte precursors.

While abnormalities in myelin in tuberous sclerosis complex (TSC) have been known for some time, recent imaging-based data suggest myelin abnormalities may be independent of the pathognomonic cortical lesions ("tubers"). Multiple mouse models of TSC exhibit myelination deficits, though the cell types responsible and the mechanisms underlying the myelin abnormalities remain unclear. To determine the role of alterations in mTOR signaling in myelination, we generated a conditional knockout (CKO) mouse model using Cre-recombinase and the Olig2 promoter to inactivate the Tsc2 gene in oligodendrocyte precursor cells. Characterization of myelin and myelin constituent proteins demonstrated a marked hypomyelination phenotype. Diffusion-based magnetic resonance imaging studies were likewise consistent with hypomyelination. Hypomyelination was due in part to decreased myelinated axon density and myelin thickness as well as decreased oligodendrocyte numbers. Coincident with hypomyelination, an extensive gliosis was seen in both the cortex and white matter tracks, suggesting alterations in cell fate due to changes in mTOR activity in oligodendrocyte precursors. Despite a high-frequency appendicular tremor and altered gait in CKO mice, no significant changes in activity, vocalizations, or anxiety-like phenotypes were seen. Our findings support a known role of mTOR signaling in regulation of myelination and demonstrate that increased mTORC1 activity early in development within oligodendrocytes results in hypomyelination and not hypermyelination. Our data further support a dissociation between decreased Akt activity and increased mTORC1 activity toward hypomyelination. Thus, therapies promoting activation of Akt-dependent pathways while reducing mTORC1 activity may prove beneficial in treatment of human disease.

Tau deposition drives neuropathological, inflammatory and behavioral abnormalities independently of neuronal loss in a novel mouse model.

Aberrant tau protein accumulation drives neurofibrillary tangle (NFT) formation in several neurodegenerative diseases. Currently, efforts to elucidate pathogenic mechanisms and assess the efficacy of therapeutic targets are limited by constraints of existing models of tauopathy. In order to generate a more versatile mouse model of tauopathy, somatic brain transgenesis was utilized to deliver adeno-associated virus serotype 1 (AAV1) encoding human mutant P301L-tau compared with GFP control. At 6 months of age, we observed widespread human tau expression with concomitant accumulation of hyperphosphorylated and abnormally folded proteinase K resistant tau. However, no overt neuronal loss was observed, though significant abnormalities were noted in the postsynaptic scaffolding protein PSD95. Neurofibrillary pathology was also detected with Gallyas silver stain and Thioflavin-S, and electron microscopy revealed the deposition of closely packed filaments. In addition to classic markers of tauopathy, significant neuroinflammation and extensive gliosis were detected in AAV1-TauP301L mice. This model also recapitulates the behavioral phenotype characteristic of mouse models of tauopathy, including abnormalities in exploration, anxiety, and learning and memory. These findings indicate that biochemical and neuropathological hallmarks of tauopathies are accurately conserved and are independent of cell death in this novel AAV-based model of tauopathy, which offers exceptional versatility and speed in comparison with existing transgenic models. Therefore, we anticipate this approach will facilitate the identification and validation of genetic modifiers of disease, as well as accelerate preclinical assessment of potential therapeutic targets.

Astrogliosis is a possible player in preventing delayed neuronal death.

Mitigating secondary delayed neuronal injury has been a therapeutic strategy for minimizing neurological symptoms after several types of brain injury. Interestingly, secondary neuronal loss appeared to be closely related to functional loss and/or death of astrocytes. In the brain damage induced by agonists of two glutamate receptors, N-ethyl-D-aspartic acid (NMDA) and kainic acid (KA), NMDA induced neuronal death within 3 h, but did not increase further thereafter. However, in the KA-injected brain, neuronal death was not obviously detectable even at injection sites at 3 h, but extensively increased to encompass the entire hemisphere at 7 days. Brain inflammation, a possible cause of secondary neuronal damage, showed little differences between the two models. Importantly, however, astrocyte behavior was completely different. In the NMDA-injected cortex, the loss of glial fibrillary acidic protein-expressing (GFAP+) astrocytes was confined to the injection site until 7 days after the injection, and astrocytes around the damage sites showed extensive gliosis and appeared to isolate the damage sites. In contrast, in the KA-injected brain, GFAP+ astrocytes, like neurons, slowly, but progressively, disappeared across the entire hemisphere. Other markers of astrocytes, including S100β, glutamate transporter EAAT2, the potassium channel Kir4.1 and glutamine synthase, showed patterns similar to that of GFAP in both NMDA- and KA-injected cortexes. More importantly, astrocyte disappearance and/or functional loss preceded neuronal death in the KA-injected brain. Taken together, these results suggest that loss of astrocyte support to neurons may be a critical cause of delayed neuronal death in the injured brain.

Lipid Integration in Neurodegeneration: An Overview of Alzheimer’s Disease

Various types of lipids and their metabolic products associated with the biological membrane play a crucial role in signal transduction, modulation, and activation of receptors and as precursors of bioactive lipid mediators. Dysfunction in the lipid homeostasis in the brain could be a risk factor for the many types of neurodegenerative disorders, including Alzheimer's disease, Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. These neurodegenerative disorders are marked by extensive neuronal apoptosis, gliosis, and alteration in the differentiation, proliferation, and development of neurons. Sphingomyelin, a constituent of plasma membrane, as well as its primary metabolite ceramide acts as a potential lipid second messenger molecule linked with the modulation of various cellular signaling pathways. Excessive production of reactive oxygen species associated with enhanced oxidative stress has been implicated with these molecules and involved in the regulation of a variety of different neurodegenerative and neuroinflammatory disorders. Studies have shown that alterations in the levels of plasma lipid/cholesterol concentration may result to neurodegenerative diseases. Alteration in the levels of inflammatory cytokines and mediators in the brain has also been found to be implicated in the pathophysiology of neurodegenerative diseases. Although several mechanisms involved in neuronal apoptosis have been described, the molecular mechanisms underlying the correlation between lipid metabolism and the neurological deficits are not clearly understood. In the present review, an attempt has been made to provide detailed information about the association of lipids in neurodegeneration especially in Alzheimer's disease.