Increase In Number Of Astrocytes Research Articles

The nitrone compound OKN-007 delays motor neuron loss and disease progression in the G93A mouse model of amyotrophic lateral sclerosis.

Our study investigated the therapeutic potential of OKN-007 in the SOD1 G93A mouse model of amyotrophic lateral sclerosis (ALS). The impact of OKN-007, known for its antioxidant, anti-inflammatory, and neuroprotective properties, was tested at two doses (150 mg/kg and 300 mg/kg) at onset and late-stage disease. Results demonstrated a significant delay in disease progression at both doses, with treated mice showing a slower advance to early disease stages compared to untreated controls. Motor neuron counts in the lumbar spinal cord were notably higher in OKN-007 treated mice at the time of disease onset, suggesting neuroprotection. Additionally, OKN-007 reduced microglial activation and preserved reduced neuromuscular junction fragmentation, although it did not significantly alter the increase in astrocyte number or the decline in hindlimb muscle mass. MR spectroscopy (MRS) revealed improved spinal cord perfusion and normalized myo-inositol levels in treated mice, supporting reduced neuroinflammation. While the expression of several proteins associated with inflammation is increased in spinal cord extracts from G93A mice, OKN-007 dampened the expression of IL-1β, IL-1ra and IL-1α. Despite its promising effects on early-stage disease progression, in general, the beneficial effects of OKN-007 diminished over longer treatment durations. Further, we found no improvement in muscle atrophy or weakness phenotypes in OKN-007 treated G93A mice, and no effect on mitochondrial function or lifespan. Overall, our findings suggest that OKN-007 holds potential as a disease-modifying treatment for ALS, although further research is needed to optimize dosing regimens and understand its long-term effects.

Behavior and neuropsychiatric changes in experimental chronic toxoplasmosis: Histopathological and immunohistochemical studies

Background: T. gondii is an intracellular protozoan parasite that can establish a latent infection in thecentral nervous system that may develop into chronic inflammation resulting in neurobehavioral problemsin the host. The processes behind these alterations are still largely mysterious.Objective: Detection of behavioral, histopathological and immunohistochemical changes in mice infectedby T. gondii Me49 strain.Material and Methods: A total of 105 adult male Swiss albino mice were divided into 60 used forexperimental infection, and 45 as control. Assessment of physical appearance was monitored foracute toxoplasmosis daily for three weeks post infection (PI). Correlation between behavior changesand the degree of infection was conducted by measuring histopathological (H&E and silver stain) andimmunohistochemical (presence or absence of CD3, CD138 and caspase-3 immunoreactive cells)parameters weekly starting from 7th week to the 12th week PI.Results: Infected mice had neurobehavioral problems. Variable degrees of perivascular and interstitialinflammatory infiltrates, astrocytosis, deteriorated neurons, and meningitis were demonstrated byhistopathology when compared to uninfected controls. Inflammatory cells (mainly lymphocytes) enteredthe parenchyma at mild, moderate, and severe levels in the brains of infected mice. Immunohistochemicalassessment of CD3, CD138 and caspase-3 revealed a substantial increase in CD3 expression by clusters ofactivated astrocytes in the cerebral parenchyma, suggesting an increase in astrocyte numbers and functionthat was progressive over time. CD138 and caspase-3 immunoreactivity showed decreased expression bythe activated astrocytes.Conclusion: Chronic toxoplasmosis causes deterioration in cognitive and emotional behavior of theinfected host, resulting in neuropsychiatric and behavioral disturbances.

Microglia depletion increase brain injury after acute ischemic stroke in aged mice

Microglia are one of the first responders to ischemic injury. Aged microglia acquire a senescent phenotype and produce more inflammatory cytokines after stroke. Depletion of microglia in young mice worsens post-ischemic damage by increasing inflammation. However, young mice do not have dysfunctional microglia. Hence, we hypothesized that depletion of microglia in older mice will contribute to improved early recovery after ischemic stroke injury. Aged (18–19 month) mice were fed with either control chow diet (CD) or PLX5622 chow diet (PLXD) for 21 days. On day 22, a 60-min middle cerebral artery occlusion (MCAo) surgery or sham surgery was performed. Twenty-four and 72 h after stroke immunohistochemistry and flow cytometry were performed. AFS98, a monoclonal antibody against CSF1R was used to specifically deplete brain macrophages by injection into the right hemisphere. Two days after AFS98 injections, mice underwent one-hour MCAo. Twenty-four hours later mice were euthanized and flow cytometry was performed. An increase in infarct volume (p < 0.05) was seen in the PLXD versus CD after stroke in aged mice at 24 and 72 h. An increase (p < 0.05) in infiltrating monocytes was observed after microglial depletion in aged stroke mice suggesting a differential monocyte response. An increase in astrocyte numbers was evident in the PLXD sham mice compared to CD sham, reflecting the off-target effects of PLX5622 treatment. In conclusion, PLX5622 and AFS98 treatment depleted microglia in aged animals but resulted in increased neuroinflammation after ischemic stroke.

Slc6a3-dependent expression of a CAPS-associated Nlrp3 allele results in progressive behavioral abnormalities and neuroinflammation in aging mice

BackgroundAn association between neuroinflammation and age-related neurologic disorders has been established but the molecular mechanisms and cell types involved have not been thoroughly characterized. Activity of the proinflammatory NLRP3 inflammasome is implicated in Alzheimer’s and Parkinson’s disease and our recent studies in patients suggest that dopaminergic neurons within the degenerating mesencephalon express NLRP3 throughout the progression of PD. Here, we directly test the impact of enhanced inflammasome activity in mesencephalic neurons by characterizing motor function, tissue integrity, and neuroinflammation in aging mice harboring hyperactivating mutations within the endogenous murine Nlrp3 locus, enabled only in cells expressing the dopaminergic neuron-specific Slc6a3 promoter.MethodsWe compared mice harboring inducible alleles encoding the cryopyrin-associated periodic syndrome activating mutations Nlrp3A350V and Nlrp3L351P inserted into the endogenous mouse Nlrp3 locus. Tissue specific expression was driven by breeding these animals with mice expressing Cre recombinase under the control of the dopaminergic neuron-specific Slc6a3 promoter. The experimental mice, designed to express hyperactive NLRP3 only when the endogenous mouse Nlrp3 promotor is active in dopaminergic neurons, were analyzed throughout 18 months of aging using longitudinal motor function assessments. Biochemical and histologic analyses of mesencephalic tissues were conducted in 1- and 18-month-old animals.ResultsWe observed progressive and significant deficits in motor function in animals expressing Nlrp3L351P, compared with animals expressing Nlrp3WT and Nlrp3A350V. Age-dependent neuroinflammatory changes in the mesencephalon were noted in all animals. Analysis of GFAP-immunoreactive astrocytes in the substantia nigra revealed a significant increase in astrocyte number in animals expressing Nlrp3L351P compared with Nlrp3WT and Nlrp3A350V. Further analysis of Nlrp3L351P striatal tissues indicated genotype specific gliosis, elevated Il1b expression, and both morphologic and gene expression indicators of proinflammatory A1 astrocytes.ConclusionsDopaminergic neurons have the potential to accumulate NLRP3 inflammasome activators with age, including reactive oxygen species, dopamine metabolites, and misfolded proteins. Results indicate the Nlrp3 locus is active in dopaminergic neurons in aging mice, and that the hyperactive Nlrp3L351P allele can drive neuroinflammatory changes in association with progressive behavioral deficits. Findings suggest neuronal NLRP3 inflammasome activity may contribute to neuroinflammation observed during normal aging and the progression of neurologic disorders.

A delay in vascularization induces abnormal astrocyte proliferation and migration in the mouse retina.

Astrocytes migrate into the retina through the optic nerve head by means of the axons of retinal ganglion cells, and spread radially toward the peripheral retina. Endothelial cells migrate along the astrocyte cellular network to form the retinal surface vasculature. Here, we examined the effects of a delay in retinal vascularization on the migration and proliferation status of astrocytes in mice. A dose-dependent delay in retinal vascularization was observed in mice that had been treated with KRN633 (1-10 mg/kg), a VEGF receptor inhibitor, on the day of birth and on the following day. Delayed vascularization resulted in a delay in the astrocyte network formation, and an increase in astrocyte number in the optic nerve head and the vascular front. The increase in the number of astrocytes may be attributed to increased proliferation and delayed migration. These abnormalities in astrocyte behavior correlated with the degree of delay in retinal vascularization. The vascularization delay also led to retinal hypoxia, which subsequently stimulated VEGF leading to an increase in vascular density. These findings suggest that a delay in normal vascularization leads to abnormal astrocyte behavior, which results in the formation of abnormal astrocyte and endothelial cell networks in the mouse retina. Developmental Dynamics 246:186-200, 2017. © 2016 Wiley Periodicals, Inc.

Neurodegeneration and Pathology in Epilepsy: Clinical and Basic Perspectives.

Epilepsy is commonly associated with a number of neurodegenerative and pathological alterations in those areas of the brain that are involved in repeated electrographic seizures. These most prominently include neuron loss and an increase in astrocyte number and size but may also include enhanced blood-brain barrier permeability, the formation of new capillaries, axonal sprouting, and central inflammation. In animal models in which seizures are either repeatedly elicited or are self-generated, a similar set of neurodegenerative and pathological alterations in brain anatomy are observed. The primary causal agent responsible for these alterations may be the cascade of events that follow a seizure and lead to an hypoperfusion/hypoxic episode. While epilepsy has long and correctly beenconsidered an electrical disorder, the vascular system likely plays an important causal role in the neurodegeneration and pathology that occur as a consequence of repeated seizures.

Regional Distribution of Copper, Zinc and Iron in Brain of Wistar Rat Model for Non-Wilsonian Brain Copper Toxicosis.

In previous studies, we have reported first in vivo evidence of copper deposition in the choroid plexus, cognitive impairments, astrocytes swelling (Alzheimer type II cells) and astrogliosis (increase in number of astrocytes), and degenerated neurons coupled with significant increase in the hippocampus copper and zinc content in copper-intoxicated Wistar rats. Nonetheless, hippocampus iron levels were not affected by chronic copper-intoxication. Notwithstanding information on distribution of copper, zinc and iron status in different regions of brain due to chronic copper exposure remains fragmentary. In continuation with our previous study, the aim of this study was to investigate the effects of intraperitoneally injected copper lactate (0.15mg Cu/100g body weight) daily for 90days on copper, zinc and iron levels in different regions of the brain using atomic absorption spectrophotometry. Copper-intoxicated group showed significantly increased cortex, cerebellum and striatum copper content (76, 46.8 and 80.7% increase, respectively) compared to control group. However, non-significant changes were observed for the zinc and iron content in cortex, cerebellum and striatum due to chronic copper exposure. In conclusion, the current study demonstrates that chronic copper toxicity causes differential copper buildup in cortex, cerebellum and striatum region of central nervous system of male Wistar rats; signifying the critical requirement to discretely evaluate the effect of copper neurotoxicity in different brain regions, and ensuing neuropathological and cognitive dysfunctions.

Transiently lowering tumor necrosis factor-α synthesis ameliorates neuronal cell loss and cognitive impairments induced by minimal traumatic brain injury in mice.

BackgroundThe treatment of traumatic brain injury (TBI) represents an unmet medical need, as no effective pharmacological treatment currently exists. The development of such a treatment requires a fundamental understanding of the pathophysiological mechanisms that underpin the sequelae resulting from TBI, particularly the ensuing neuronal cell death and cognitive impairments. Tumor necrosis factor-alpha (TNF-α) is a cytokine that is a master regulator of systemic and neuroinflammatory processes. TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.MethodsTo elucidate the role of TNF-α in TBI, particularly as a drug target, the present study evaluated (i) time-dependent TNF-α levels and (ii) markers of apoptosis and gliosis within the brain and related these to behavioral measures of ‘well being’ and cognition in a mouse closed head 50 g weight drop mild TBI (mTBI) model in the presence and absence of post-treatment with an experimental TNF-α synthesis inhibitor, 3,6′-dithiothalidomide.ResultsmTBI elevated brain TNF-α levels, which peaked at 12 h post injury and returned to baseline by 18 h. This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h. Selective impairments in measures of cognition, evaluated by novel object recognition and passive avoidance paradigms - without changes in well being, were evident at 7 days after injury. A single systemic treatment with the TNF-α synthesis inhibitor 3,6′-dithiothalidomide 1 h post injury prevented the mTBI-induced TNF-α elevation and fully ameliorated the neuronal loss (NeuN), elevations in astrocyte number (GFAP) and BID, and cognitive impairments. Cognitive impairments evident at 7 days after injury were prevented by treatment as late as 12 h post mTBI but were not reversed when treatment was delayed until 18 h.ConclusionsThese results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

Histological-MRI correlation in the primary motor cortex of patients with amyotrophic lateral sclerosis.

To establish the relationship between ALS histopathology and quantitative MRI metrics. ALS patients (N = 8) in advanced stages of the disease were enrolled and, immediately after death, the brain of each patient was removed. Freshly excised ALS tissue was imaged at 3.0 Tesla with T1 and T2 mapping protocols and subsequently stained with astrocyte, myelin, and neuronal markers. Measures of ALS histological stains were compared with the internal control (primary visual cortex) and longitudinal parametric maps. Post-mortem T1 -weighted images demonstrate diminished contrast between gray and white matter and alterations in T1 relaxation within the primary motor cortex. An increase in astrocyte number and reactivity as well as evident neuronal loss, a decrease in axonal density, and unraveling of the myelin sheaths in subcortical white matter were found in the ALS primary motor cortex exhibiting significant T1 relaxation and contrast changes. This study provides a histopathological basis for differences in MR T1 contrast and relaxation seen in the ALS brain.

Chronic copper intoxication causes impaired spatial memory and hippocampus copper elevation in wistar rats

Background: Animal models of copper toxicities rarely exhibit neurological impairments and increased brain copper accumulation impeding the development of novel therapeutic approaches to treat neurodegenerative diseases having high brain Cu content. Aims: The aim of this study was to investigate the effects of intraperitoneally injected copper lactate (0.15 mg Cu/100 g b.w.) daily for 90 days on copper and zinc levels in liver, kidney and hippocampus; expression of hepatic metallothionein-I and Atp7b gene, with metallothionein-III and acetylcholine esterase (AChE) gene in brain, biochemical parameters and neurobehavioral functions (by Morris water maze) of male wistar rats. Results: Copper administered animals exhibited significantly decreased serum AChE activity, increased hepatic metallothionein-I gene expression, impaired neuromuscular coordination and spatial memory compared to control rats. Copper intoxicated rats showed significant increase in liver, hippocampus and kidney tissues copper content (99.1, 73 and 74.9 % increase respectively), 40.7 % reduction in hepatic zinc content and interestingly, 77.1% increase in hippocampus zinc content with concomitant increase in copper and zinc levels in serum and urine compared to control rats. Massive copper deposition and copper associated protein in hepatocytes of copper intoxicated rats was substantiated by rhodanine and orcein stains respectively. Copper intoxicated rats demonstrated swelling and increase in number of astrocytes, degenerated neurons having pyknotic nuclei with copper deposition in choroid plexus. Conclusion: Present study shows the first evidence in vivo that chronic copper toxicity causes impaired spatial memory, swelling of astrocytes, decreased serum AChE activity,

Characterization of nestin expression in the spinal cord of GFP transgenic mice after peripheral nerve injury

Many studies have shown that activation and increase in the number of astrocytes and microglia in the spinal cord participate in the initiation and maintenance of neuropathic pain, but little attention has been paid to the responses of neural progenitor cells to peripheral nerve injury. Nestin, a class VI intermediate filament protein, is expressed both in neuronal and glial progenitors as well as in their common precursors; and nestin-positive cells appear in the brain and spinal cord following various forms of damage to these regions. To clarify the responses of neural progenitor cells to nerve injury, we applied L5 spinal nerve transection (L5-SNT) to nestin-promoter GFP (pNestin-GFP) transgenic mice to narrow the target to them. While pNestin-GFP expression was strongly retained in the ependyma lining the central canal of the transgenic spinal cord even in adulthood, it was markedly reduced in the dorsal horn during postnatal development by day 7. Increases in pNestin-GFP expression and labeling by the proliferation marker 5-bromodeoxyuridine were broadly found in the dorsal horn of adult mice on day 3 after L5-SNT. On the other hand, the activation and increase in number of microglia and astrocytes are restricted to the superficial layer of the dorsal horn, the central terminal of injured primary afferent fibers. Purinergic P2X agonist α, β-MeATP increased [Ca2+]i in nestin-positive cells in the superficial layer ipsilateral to nerve injury and P2 receptor antagonists suramin and pyridoxalphosphate-6-azophenyl-2,4-disulphonic acid (PPADS) blocked the expression and elongation of pNestin-GFP fibers in the slice culture of the spinal cord. These results with pNestin-GFP transgenic mice demonstrate that nestin-positive cells proliferate in the dorsal horn in response to peripheral nerve injury and suggest that ATP may contribute to the expression of nestin and activation of neural progenitor cells after nerve injury.

Astrocyte-specific expression of CDK4 is not sufficient for tumor formation, but cooperates with p53 heterozygosity to provide a growth advantage for astrocytes in vivo.

The development of malignant gliomas (astrocytomas) involves the accumulation of multiple genetic changes, including mutations in the p53 and retinoblastoma (Rb) cell cycle regulatory pathways. One Rb pathway alteration seen in high-grade astrocytomas is amplification of cyclin dependent kinase-4 (CDK4). To define the function of CDK4 amplification/overexpression in astrocytoma pathogenesis, we generated three transgenic mouse lines that overexpress human CDK4 (hCDK4) in astrocytes using the human glial fibrillary acidic protein (GFAP) promoter. GFAP-hCDK4 mice do not develop brain tumors, but exhibit a small increase in astrocyte number. Cultured astrocytes from these mice do not demonstrate a cell-autonomous growth advantage in vitro and lack properties of transformed cells. To determine whether cdk4 overexpression provides a cooperative growth advantage in vitro, CDK4-overexpressing C6 glioma cell lines were generated and found to exhibit increased cell growth. In addition, GFAP-hCDK4; p53+/- as well as p53+/-; Rb+/- mice exhibited increased numbers of astrocytes compared to GFAP-hCDK4, p53+/-, or Rb+/- mice in vivo. No cooperative effect was observed with GFAP-hCDK4; Rb+/- mice. These results support the hypothesis that cdk4 overexpression alone is not sufficient for astrocytoma formation, but can provide a cooperative growth advantage in concert with genetic alterations in the p53 pathway.

Retinal pathology in Alzheimer's disease. II. Regional neuron loss and glial changes in GCL

Detailed analyses of neuronal and astrocyte cell numbers in the ganglion cell layer (GCL) of whole-mounted peripheral retinas from 16 Alzheimer's disease (AD) and 11 control eyes (11 and 9 cases, respectively) demonstrate extensive neuronal loss throughout the entire retina in AD as compared to control eyes. The observed neuronal loss is most pronounced in the superior and inferior quadrants, ranging between 40 and 49% throughout the midperipheral regions, and reaching 50–59% in the far peripheral inferior retina, while the overall neuronal loss throughout the entire retina amounts to 36.4% ( p < 0.004). Although the 16% increase in astrocyte numbers is not significant, the ratio of astrocytes to neurons is significantly higher (82%; p < 0.0008) in AD as compared to normal retina (0.238 ± 0.070 vs. 0.131 ± 0.042). These results are strengthened by the close agreement (within ± 15% of respective means) found between fellow eyes. Analysis of glial fibrillary acidic protein immunoreactivity (GFAP-ir) in sections of retinas from an additional 12 AD and 19 control cases show increased GFAP-ir with more extensive labeling astrocytes in the GCL as well as increased labeling of Müller cell end-feet and radial processes in AD as compared to control retinas. The extensive loss of neurons documented in these retinas, accompanied by an increased astrocyte/neuron ratio, provides further support for the substantial involvement of the retina in AD.

Control of astrocytosis by interleukin-1 and transforming growth factor-β1 in human brain

Astrocytosis is a common neurocellular manifestation of brain pathology in individuals with a variety of diseases. It is comprised of astrocytic hyperplasia (an increase in number of astrocytes) and astrocytic hypertrophy (an increase in size of astrocytes). The precise cause (s) of astrocytosis remains unknown. We morphometrically measured the relative extent of astrocytosis in brains of 22 individuals who died with seven different diseases. The relative amounts of interleukin-1 (IL-1) and transforming growth factor-beta 1 (TGF-β1) immunoreactive products (IRPs) were next assessed in sections serial to those in which astrocytosis was measured because these cytokines were shown in animal and in vitro experiments to be associated with astrocytosis. The data demonstrate that astrocytosis and these cytokines were co-localized in all examined human tissues. Relative increase in density of astrocytes was correlated with the increase in total IL-1 but not TGF-β1. In contrast, the increase in size of astrocytes was correlated with TGF-β1 associated only with astrocytes but not with total IL-1. Both IL-1 and TGF-β1 IRPs were present in GFAP IRP-containing and other cells, as assessed by double label immunocytochemistry. These observations suggest that IL-1 acts on astrocytes by both, paracrine and autocrine mechanisms whereas, TGF-β1 only acts by an autocrine mechanism. Because these correlations were statistically significant and also because a change in number and size of astrocytes constitutes the most frequent response of astrocytes to several diseases or injury, we conclude that these cytokines may mediate the most common pathological change in human brain.