Constitutive knockout of interleukin-6 ameliorates memory deficits and entorhinal astrocytosis in the MRL/lpr mouse model of neuropsychiatric lupus.

BACKGROUND: Neuropsychiatric lupus (NPSLE) describes the cognitive, memory, and affective emotional burdens faced by many lupus patients. While NPSLE's pathogenesis has not been fully elucidated, clinical imaging studies and cerebrospinal fluid (CSF) findings, namely elevated interleukin-6 (IL-6) levels, point to ongoing neuroinflammation in affected patients. Not only linked to systemic autoimmunity, IL-6 can also activate neurotoxic glial cells the brain. A prior pre-clinical study demonstrated that IL-6 can acutely induce a loss of sucrose preference; the present study sought to assess the necessity of chronic IL-6 exposure in the NPSLE-like disease of MRL/lpr lupus mice. METHODS: We quantified 1308 proteins in individual serum or pooled CSF samples from MRL/lpr and control MRL/mpj mice using protein microarrays. Serum IL-6 levels were plotted against characteristic NPSLE neurobehavioral deficits. Next, IL-6 knockout MRL/lpr (IL-6 KO; n = 15) and IL-6 wildtype MRL/lpr mice (IL-6 WT; n = 15) underwent behavioral testing, focusing on murine correlates of learning and memory deficits, depression, and anxiety. Using qPCR, we quantified the expression of inflammatory genes in the cortex and hippocampus of MRL/lpr IL-6 KO and WT mice. Immunofluorescent staining was performed to quantify numbers of microglia (Iba1 +) and astrocytes (GFAP +) in multiple cortical regions, the hippocampus, and the amygdala. RESULTS: MRL/lpr CSF analyses revealed increases in IL-17, MCP-1, TNF-α, and IL-6 (a priori p-value < 0.1). Serum levels of IL-6 correlated with learning and memory performance (R2 = 0.58; p = 0.03), but not motivated behavior, in MRL/lpr mice. Compared to MRL/lpr IL-6 WT, IL-6 KO mice exhibited improved novelty preference on object placement (45.4% vs 60.2%, p < 0.0001) and object recognition (48.9% vs 67.9%, p = 0.002) but equivalent performance in tests for anxiety-like disease and depression-like behavior. IL-6 KO mice displayed decreased cortical expression of aif1 (microglia; p = 0.049) and gfap (astrocytes; p = 0.044). Correspondingly, IL-6 KO mice exhibited decreased density of GFAP + cells compared to IL-6 WT in the entorhinal cortex (89 vs 148 cells/mm2, p = 0.037), an area vital to memory. CONCLUSIONS: The inflammatory composition of MRL/lpr CSF resembles that of human NPSLE patients. Increased in the CNS, IL-6 is necessary to the development of learning and memory deficits in the MRL/lpr model of NPSLE. Furthermore, the stimulation of entorhinal astrocytosis appears to be a key mechanism by which IL-6 promotes these behavioral deficits.

Lysyl oxidase like-1 deficiency in optic nerve head astrocytes elicits reactive astrocytosis and alters functional effects of astrocyte derived exosomes.

Glaucoma is a multifactorial progressive ocular pathology that manifests clinically with damage to the optic nerve (ON) and the retina, ultimately leading to blindness. The optic nerve head (ONH) shows the earliest signs of glaucoma pathology, and therefore, is an attractive target for drug discovery. The goal of this study was to elucidate the effects of reactive astrocytosis on the elastin metabolism pathway in primary rat optic nerve head astrocytes (ONHA), the primary glial cell type in the unmyelinated ONH. Following exposure to static equibiaxial mechanical strain, we observed prototypic molecular and biochemical signatures of reactive astrocytosis that were associated with a decrease in lysyl oxidase like 1 (Loxl1) expression and a concomitant decrease in elastin (Eln) gene expression. We subsequently investigated the role of Loxl1 in reactive astrocytosis by generating primary rat ONHA cultures with ∼50% decreased Loxl1 expression. Our results suggest that reduced Loxl1 expression is sufficient to elicit molecular signatures of elastinopathy in ONHA. Astrocyte derived exosomes (ADE) significantly increased the length of primary neurites of primary neurons in vitro. In contrast, ADE from Loxl1-deficient ONHA were deficient of trophic effects on neurite outgrowth in vitro, positing that Loxl1 dysfunction and the ensuing impaired elastin synthesis during reactive astrocytosis in the ONH may contribute to impaired neuron-glia signaling in glaucoma. Our data support a role of dysregulated Loxl1 function in eliciting reactive astrocytosis in glaucoma subtypes associated with increased IOP, even in the absence of genetic polymorphisms in LOXL1 typically associated with exfoliation glaucoma. This suggests the need for a paradigm shift toward considering lysyl oxidase activity and elastin metabolism and signaling as contributors to an altered secretome of the ONH that may lead to the progression of glaucomatous changes. Future research is needed to investigate cargo of exosomes in the context of reactive astrocytosis and identify the pathways leading to the observed transcriptome changes during reactive astrocytosis.

The novel estrogen receptor modulator STX attenuates Amyloid-ß neurotoxicity in the 5XFAD mouse model of Alzheimer's disease.

Based on previous evidence that the non-steroidal estrogen receptor modulator STX mitigates the effects of neurotoxic Amyloid-ß (Aß) in vitro, we have evaluated its neuroprotective benefits in a mouse model of Alzheimer's disease. Cohorts of 5XFAD mice, which begin to accumulate cerebral Aß at two months of age, were treated with orally-administered STX starting at 6 months of age for two months. After behavioral testing to evaluate cognitive function, biochemical and immunohistochemical assays were used to analyze key markers of mitochondrial function and synaptic integrity. Oral STX treatment attenuated Aß-associated mitochondrial toxicity and synaptic toxicity in the brain, as previously documented in cultured neurons. STX also moderately improved spatial memory in 5XFAD mice. In addition, STX reduced markers for reactive astrocytosis and microgliosis surrounding amyloid plaques, and also unexpectedly reduced overall levels of cerebral Aß in the brain. The neuroprotective effects of STX were more robust in females than in males. These results suggest that STX may have therapeutic potential in Alzheimer's Disease.

Plasma GFAP is an early marker of amyloid-ß but not tau pathology in Alzheimer's disease.

Although recent clinical trials targeting amyloid-ß in Alzheimer's disease have shown promising results, there is increasing evidence suggesting that understanding alternative disease pathways that interact with amyloid-ß metabolism and amyloid pathology might be important to halt the clinical deterioration. In particular, there is evidence supporting a critical role of astroglial activation and astrocytosis in Alzheimer's disease. However, so far, no studies have assessed whether astrocytosis is independently related to either amyloid-ß or tau pathology in vivo. To address this question, we determined the levels of the astrocytic marker GFAP in plasma and CSF of 217 amyloid-ß-negative cognitively unimpaired individuals, 71 amyloid-ß-positive cognitively unimpaired individuals, 78 amyloid-ß-positive cognitively impaired individuals, 63 amyloid-ß-negative cognitively impaired individuals and 75 patients with a non-Alzheimer's disease neurodegenerative disorder from the Swedish BioFINDER-2 study. Participants underwent longitudinal amyloid-ß (18F-flutemetamol) and tau (18F-RO948) PET as well as cognitive testing. We found that plasma GFAP concentration was significantly increased in all amyloid-ß-positive groups compared with participants without amyloid-ß pathology (P < 0.01). In addition, there were significant associations between plasma GFAP with higher amyloid-ß-PET signal in all amyloid-ß-positive groups, but also in cognitively normal individuals with normal amyloid-ß values (P < 0.001), which remained significant after controlling for tau-PET signal. Furthermore, plasma GFAP could predict amyloid-ß-PET positivity with an area under the curve of 0.76, which was greater than the performance achieved by CSF GFAP (0.69) and other glial markers (CSF YKL-40: 0.64, soluble TREM2: 0.71). Although correlations were also observed between tau-PET and plasma GFAP, these were no longer significant after controlling for amyloid-ß-PET. In contrast to plasma GFAP, CSF GFAP concentration was significantly increased in non-Alzheimer's disease patients compared to other groups (P < 0.05) and correlated with amyloid-ß-PET only in amyloid-ß-positive cognitively impaired individuals (P = 0.005). Finally, plasma GFAP was associated with both longitudinal amyloid-ß-PET and cognitive decline, and mediated the effect of amyloid-ß-PET on tau-PET burden, suggesting that astrocytosis secondary to amyloid-ß aggregation might promote tau accumulation. Altogether, these findings indicate that plasma GFAP is an early marker associated with brain amyloid-ß pathology but not tau aggregation, even in cognitively normal individuals with a normal amyloid-ß status. This suggests that plasma GFAP should be incorporated in current hypothetical models of Alzheimer's disease pathogenesis and be used as a non-invasive and accessible tool to detect early astrocytosis secondary to amyloid-ß pathology.

Inflammatory Response and Secondary White Matter Damage to the Corpus Callosum after Focal Striatal Stroke in Rats.

Stroke is one of the leading causes of death and long-term disabilities worldwide, resulting in a debilitating condition occasioned by disturbances in the cerebral vasculature. Primary damage due to metabolic collapse is a quick outcome following stroke, but a multitude of secondary events, including excitotoxicity, inflammatory response, and oxidative stress cause further cell death and functional impairment. In the present work, we investigated whether a primary ischemic damage into the dorsal striatum may cause secondary damage in the circumjacent corpus callosum (CC). Animals were injected with endothelin-1 and perfused at 3, 7, 14, and 30 post-lesion days (PLD). Sections were stained with Cresyl violet for basic histopathology and immunolabeled by antibodies against astrocytes (anti-GFAP), macrophages/microglia (anti-IBA1/anti MHC-II), oligodendrocytes (anti-TAU) and myelin (anti-MBP), and Anti-Nogo. There were conspicuous microgliosis and astrocytosis in the CC, followed by later oligodendrocyte death and myelin impairment. Our results suggest that secondary white matter damage in the CC follows a primary focal striatal ischemia in adult rats.

Healthy Properties of a New Formulation of Pomegranate-Peel Extract in Mice Suffering from Experimental Autoimmune Encephalomyelitis.

A new formulation of a pomegranate-peel extract (PEm) obtained by PUAE (Pulsed Ultrasound-Assisted Extraction) and titrated in both ellagic acid (EA) and punicalagin is proposed, characterized and then analyzed for potential health properties in mice suffering from the experimental autoimmune encephalomyelitis (EAE). PEm effects were compared to those elicited by a formulation containing EA (EAm). Control and EAE mice were chronically administered EAm and Pem dissolved in the drinking water, starting from the day 10 post-immunization (d.p.i.), with a "therapeutic" protocol to deliver daily 50 mg/kg of EA. Treated EAE mice did not limit their daily access to the beverage, nor did they show changes in body weight, but they displayed a significant amelioration of "in vivo" clinical symptoms. "Ex vivo" histochemical analysis showed that spinal-cord demyelination and inflammation in PEm and EAm-treated EAE mice at 23 ± 1 d.p.i. were comparable to those in the untreated EAE animals, while microglia activation (measured as Ionized Calcium Binding Adaptor 1, Iba1 staining) and astrocytosis (quantified as glial fibrillar acid protein, GFAP immunopositivity) significantly recovered, particularly in the gray matter. EAm and PEm displayed comparable efficiencies in controlling the spinal pathological cellular hallmarks in EAE mice, and this would support their delivery as dietary supplementation in patients suffering from multiple sclerosis (MS).

Intermittent Fasting Alleviates Cognitive Impairments and Hippocampal Neuronal Loss but Enhances Astrocytosis in Mice with Subcortical Vascular Dementia.

BACKGROUND: Intermittent fasting (IF) is found to exhibit neuroprotection against various insults, including ischemia; however, IF has been mainly applied before disease onset. It remains unknown whether IF implementation alleviates the long-term detrimental effects of a disease after its establishment. OBJECTIVES: To investigate the IF effects on cognitive impairments and cerebrovascular pathologies in a subcortical vascular dementia (SVaD) mouse model. METHODS: The SVaD model was developed by inducing hypoperfusion and hyperlipidemia in apoE-deficient (apoE-/-) mice. We subjected 10-week-old apoE-/- mice to bilateral common carotid artery stenosis using micro-coils after they were fed a high-fat diet (HFD; 45% energy) for 6 weeks to induce hyperlipidemia. Age-matched wild-type C57BL/6J mice received sham surgery after undergoing an identical HFD treatment. Both the SVaD model and wild-type mice either started a 1-month IF regimen (time-restricted feeding for 6 hours per day) or continued the standard diet ad libitum (6.2% fat energy) at 8 weeks post-surgery. We assessed mice weight, food intake, and outcomes in a behavioral test battery before, during, and after the IF regimen, prior to histopathological analyses (microvessel density, neuronal density, white matter damage, astrocytosis) of their brains. RESULTS: SVaD model mice on the IF regimen (SVaD-IF) exhibited higher mean recognition and spatial working memory performance compared to SVaD mice fed ad libitum (SVaD-AL; P < 0.01). Additionally, SVaD-IF mice had ∼5% higher hippocampal neuronal density in the dentate gyrus (DG) and cornu ammonis 1 regions than SVaD-AL mice (P < 0.001), which paralleled their post-IF cognitive enhancements. However, SVaD-IF mice showed an ∼50% increase in hippocampal DG astrocytosis compared to SVaD-AL mice (P < 0.05), with no significant differences in microvessel densities among the 2 groups. CONCLUSIONS: The improvements in SVaD-IF mice suggest that IF could be a potential nonpharmacological remedy for SVaD. This finding could stimulate future investigations on IF's neuroprotective potential across many neurovascular diseases.

Aspirin and N-acetylcysteine co-administration markedly inhibit chronic ethanol intake and block relapse binge drinking: Role of neuroinflammation-oxidative stress self-perpetuation.

Chronic alcohol intake leads to neuroinflammation and cell injury, proposed to result in alterations that perpetuate alcohol intake and cued relapse. Studies show that brain oxidative stress is consistently associated with alcohol-induced neuroinflammation, and literature implies that oxidative stress and neuroinflammation perpetuate each other. In line with a self-perpetuating mechanism, it is hypothesized that inhibition of either oxidative stress or neuroinflammation could reduce chronic alcohol intake and relapse. The present study conducted on alcohol-preferring rats shows that chronic ethanol intake was inhibited by 50% to 55% by the oral administration of low doses of either the antioxidant N-acetylcysteine (40 mg/kg/d) or the anti-inflammatory aspirin (ASA; 15 mg/kg/d), while the co-administration of both dugs led to a 70% to 75% (P < .001) inhibition of chronic alcohol intake. Following chronic alcohol intake, a prolonged alcohol deprivation, and subsequent alcohol re-access, relapse drinking resulted in blood alcohol levels of 95 to 100 mg/dL in 60 minutes, which were reduced by 60% by either N-acetylcysteine or aspirin and by 85% by the co-administration of both drugs (blood alcohol: 10 to 15 mg/dL; P < .001). Alcohol intake either on the chronic phase or following deprivation and re-access led to a 50% reduction of cortical glutamate transporter GLT-1 levels, while aspirin administration fully returned GLT-1 to normal levels. N-acetylcysteine administration did not alter GLT-1 levels, while N-acetylcysteine may activate the cystine/glutamate transport xCT, presynaptically inhibiting relapse. Overall, the study suggests that a neuroinflammation/oxidative stress self-perpetuation cycle maintains chronic alcohol intake and relapse drinking. The co-administration of anti-inflammatory and antioxidant agents may have translational value in alcohol-use disorders.

Bmal1-deficiency affects glial synaptic coverage of the hippocampal mossy fiber synapse and the actin cytoskeleton in astrocytes.

Bmal1 is an essential component of the molecular clockwork, which drives circadian rhythms in cell function. In Bmal1-deficient (Bmal1-/-) mice, chronodisruption is associated with cognitive deficits and progressive brain pathology including astrocytosis indicated by increased expression of glial fibrillary acidic protein (GFAP). However, relatively little is known about the impact of Bmal1-deficiency on astrocyte morphology prior to astrocytosis. Therefore, in this study we analysed astrocyte morphology in young (6-8 weeks old) adult Bmal1-/- mice. At this age, overall GFAP immunoreactivity was not increased in Bmal1-deficient mice. At the ultrastructural level, we found a decrease in the volume fraction of the fine astrocytic processes that cover the hippocampal mossy fiber synapse, suggesting an impairment of perisynaptic processes and their contribution to neurotransmission. For further analyses of actin cytoskeleton, which is essential for distal process formation, we used cultured Bmal1-/- astrocytes. Bmal1-/- astrocytes showed an impaired formation of actin stress fibers. Moreover, Bmal1-/- astrocytes showed reduced levels of the actin-binding protein cortactin (CTTN). Cttn promoter region contains an E-Box like element and chromatin immunoprecipitation revealed that Cttn is a potential Bmal1 target gene. In addition, the level of GTP-bound (active) Rho-GTPase (Rho-GTP) was reduced in Bmal1-/- astrocytes. In summary, our data demonstrate that Bmal1-deficiency affects morphology of the fine astrocyte processes prior to strong upregulation of GFAP, presumably because of impaired Cttn expression and reduced Rho-GTP activation. These morphological changes might result in altered synaptic function and, thereby, relate to cognitive deficits in chronodisruption.

TDP-43 mediated blood-brain barrier permeability and leukocyte infiltration promote neurodegeneration in a low-grade systemic inflammation mouse model.

BACKGROUND: Neuronal cytoplasmic inclusions containing TAR DNA-binding protein 43 (TDP-43) are a neuropathological feature of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's Disease (AD). Emerging evidence also indicates that systemic inflammation may be a contributor to the pathology progression of these neurodegenerative diseases. METHODS: To investigate the role of systemic inflammation in the progression of neuronal TDP-43 pathology, AAV9 particles driven by the UCHL1 promoter were delivered to the frontal cortex of wild-type aged mice via intracranial injections to overexpress TDP-43 or green fluorescent protein (GFP) in corticospinal motor neurons. Animals were then subjected to a low-dose (500 µg/kg) intraperitoneal E. coli lipopolysaccharide (LPS) administration challenge for 2 weeks to mimic a chronically altered low-grade systemic inflammatory state. Mice were then subjected to neurobehavioral studies, followed by biochemical and immunohistochemical analyses of the brain tissue. RESULTS: In the present study, we report that elevated neuronal TDP-43 levels induced microglial and astrocytic activation in the cortex of injected mice followed by increased RANTES signaling. Moreover, overexpression of TDP-43 exerted abundant mouse immunoglobulin G (IgG), CD3, and CD4+ T cell infiltration as well as endothelial and pericyte activation suggesting increased blood-brain barrier permeability. The BBB permeability in TDP-43 overexpressing brains yielded the frontal cortex vulnerable to the systemic inflammatory response following LPS treatment, leading to marked neutrophil infiltration, neuronal loss, reduced synaptosome-associated protein 25 (SNAP-25) levels, and behavioral impairments in the radial arm water maze (RAWM) task. CONCLUSIONS: These results reveal a novel role for TDP-43 in BBB permeability and leukocyte recruitment, indicating complex intermolecular interactions between an altered systemic inflammatory state and pathologically prone TDP-43 protein to promote disease progression.

Longitudinal association between astrocyte function and glucose metabolism in autosomal dominant Alzheimer's disease.

PURPOSE: The spatial resolution of 18F-fluorodeoxyglucose PET does not allow the specific cellular origin of its signal to be determined, but it is commonly accepted that transport and trapping of 18F-fluorodeoxyglucose reflects neuronal glucose metabolism. The main frameworks for the diagnosis of Alzheimer's disease suggest that hypometabolism measured with 18F-fluorodeoxyglucose PET is a biomarker of neuronal injury and neurodegeneration. There is preclinical evidence to suggest that astrocytes contribute, at least partially, to the in vivo 18F-fluorodeoxyglucose PET signal. However, due to a paucity of PET tracers for imaging astrocytic processes, the relationship between astrocyte function and glucose metabolism in human brain is not fully understood. The aim of this study was to investigate the longitudinal association between astrocyte function and glucose metabolism in Alzheimer's disease. METHODS: The current investigation combined longitudinal PET data from patients with autosomal dominant Alzheimer's disease, including data on astrocyte function (11C-deuterium-L-deprenyl binding) and glucose metabolism (18F-fluorodeoxyglucose uptake). Research participants included 7 presymptomatic and 4 symptomatic mutation carriers (age 44.9 ± 9.8 years and 58.0 ± 3.7 years, respectively) and 16 noncarriers (age 51.1 ± 14.2 years). Eight carriers and eight noncarriers underwent longitudinal follow-up PET imaging at an average of 2.8 ± 0.2 and 3.0 ± 0.5 years from baseline, respectively. RESULTS: Longitudinal decline in astrocyte function as measured using 11C-deuterium-L-deprenyl PET was significantly associated with progressive hypometabolism (18F-fluorodeoxyglucose uptake) in mutation carriers; no significant association was observed in noncarriers. CONCLUSION: The emerging data shift the accepted wisdom that decreases in cerebral metabolism measured with 18F-fluorodeoxyglucose solely reflect neuronal injury, and places astrocytes more centrally in the development of Alzheimer's disease.

Calcineurin A beta deficiency ameliorates HFD-induced hypothalamic astrocytosis in mice.

ᅟ: Astrocytosis is a reactive process involving cellular, molecular, and functional changes to facilitate neuronal survival, myelin preservation, blood brain barrier function and protective glial scar formation upon brain insult. The overall pro- or anti-inflammatory impact of reactive astrocytes appears to be driven in a context- and disease-driven manner by modulation of astrocytic Ca2+ homeostasis and activation of Ca2+/calmodulin-activated serine/threonine phosphatase calcineurin. Here, we aimed to assess whether calcineurin is dispensable for astrocytosis in the hypothalamus driven by prolonged high fat diet (HFD) feeding. Global deletion of calcineurin A beta (gene name: Ppp3cb) led to a decrease of glial fibrillary acidic protein (GFAP)-positive cells in the ventromedial hypothalamus (VMH), dorsomedial hypothalamus (DMH), and arcuate nucleus (ARC) of mice exposed chronically to HFD. The concomitant decrease in Iba1-positive microglia in the VMH further suggests a modest impact of Ppp3cb deletion on microgliosis. Pharmacological inhibition of calcineurin activity by Fk506 had no impact on IBA1-positive microglia in hypothalami of mice acutely exposed to HFD for 1 week. However, Fk506-treated mice displayed a decrease in GFAP levels in the ARC. In vivo effects could not be replicated in cell culture, where calcineurin inhibition by Fk506 had no effect on astrocytic morphology, astrocytic cell death, GFAP, and vimentin protein levels or microglia numbers in primary hypothalamic astrocytes and microglia co-cultures. Further, adenoviral overexpression of calcineurin subunit Ppp3r1 in primary glia culture did not lead to an increase in GFAP fluorescence intensity. Overall, our results point to a prominent role of calcineurin in mediating hypothalamic astrocytosis as response to acute and chronic HFD exposure. Moreover, discrepant findings in vivo and in cell culture indicate the necessity of studying astrocytes in their "natural" environment, i.e., preserving an intact hypothalamic microenvironment with neurons and non-neuronal cells in close proximity.

Permeability changes and effect of chemotherapy in brain adjacent to tumor in an experimental model of metastatic brain tumor from breast cancer.

BACKGROUND: Brain tumor vasculature can be significantly compromised and leakier than that of normal brain blood vessels. Little is known if there are vascular permeability alterations in the brain adjacent to tumor (BAT). Changes in BAT permeability may also lead to increased drug permeation in the BAT, which may exert toxicity on cells of the central nervous system. Herein, we studied permeation changes in BAT using quantitative fluorescent microscopy and autoradiography, while the effect of chemotherapy within the BAT region was determined by staining for activated astrocytes. METHODS: Human metastatic breast cancer cells (MDA-MB-231Br) were injected into left ventricle of female NuNu mice. Metastases were allowed to grow for 28 days, after which animals were injected fluorescent tracers Texas Red (625 Da) or Texas Red dextran (3 kDa) or a chemotherapeutic agent 14C-paclitaxel. The accumulation of tracers and 14C-paclitaxel in BAT were determined by using quantitative fluorescent microscopy and autoradiography respectively. The effect of chemotherapy in BAT was determined by staining for activated astrocytes. RESULTS: The mean permeability of texas Red (625 Da) within BAT region increased 1.0 to 2.5-fold when compared to normal brain, whereas, Texas Red dextran (3 kDa) demonstrated mean permeability increase ranging from 1.0 to 1.8-fold compared to normal brain. The Kin values in the BAT for both Texas Red (625 Da) and Texas Red dextran (3 kDa) were found to be 4.32 ± 0.2 × 105 mL/s/g and 1.6 ± 1.4 × 105 mL/s/g respectively and found to be significantly higher than the normal brain. We also found that there is significant increase in accumulation of 14C-Paclitaxel in BAT compared to the normal brain. We also observed animals treated with chemotherapy (paclitaxel (10 mg/kg), erubilin (1.5 mg/kg) and docetaxel (10 mg/kg)) showed activated astrocytes in BAT. CONCLUSIONS: Our data showed increased permeation of fluorescent tracers and 14C-paclitaxel in the BAT. This increased permeation lead to elevated levels of activated astrocytes in BAT region in the animals treated with chemotherapy.

Diverging longitudinal changes in astrocytosis and amyloid PET in autosomal dominant Alzheimer's disease.

Alzheimer's disease is a multifactorial dementia disorder characterized by early amyloid-ß, tau deposition, glial activation and neurodegeneration, where the interrelationships between the different pathophysiological events are not yet well characterized. In this study, longitudinal multitracer positron emission tomography imaging of individuals with autosomal dominant or sporadic Alzheimer's disease was used to quantify the changes in regional distribution of brain astrocytosis (tracer (11)C-deuterium-L-deprenyl), fibrillar amyloid-ß plaque deposition ((11)C-Pittsburgh compound B), and glucose metabolism ((18)F-fluorodeoxyglucose) from early presymptomatic stages over an extended period to clinical symptoms. The 52 baseline participants comprised autosomal dominant Alzheimer's disease mutation carriers (n = 11; 49.6 ± 10.3 years old) and non-carriers (n = 16; 51.1 ± 14.2 years old; 10 male), and patients with sporadic mild cognitive impairment (n = 17; 61.9 ± 6.4 years old; nine male) and sporadic Alzheimer's disease (n = 8; 63.0 ± 6.5 years old; five male); for confidentiality reasons, the gender of mutation carriers is not revealed. The autosomal dominant Alzheimer's disease participants belonged to families with known mutations in either presenilin 1 (PSEN1) or amyloid precursor protein (APPswe or APParc) genes. Sporadic mild cognitive impairment patients were further divided into (11)C-Pittsburgh compound B-positive (n = 13; 62.0 ± 6.4; seven male) and (11)C-Pittsburgh compound B-negative (n = 4; 61.8 ± 7.5 years old; two male) groups using a neocortical standardized uptake value ratio cut-off value of 1.41, which was calculated with respect to the cerebellar grey matter. All baseline participants underwent multitracer positron emission tomography scans, cerebrospinal fluid biomarker analysis and neuropsychological assessment. Twenty-six of the participants underwent clinical and imaging follow-up examinations after 2.8 ± 0.6 years. By using linear mixed-effects models, fibrillar amyloid-ß plaque deposition was first observed in the striatum of presymptomatic autosomal dominant Alzheimer's disease carriers from 17 years before expected symptom onset; at about the same time, astrocytosis was significantly elevated and then steadily declined. Diverging from the astrocytosis pattern, amyloid-ß plaque deposition increased with disease progression. Glucose metabolism steadily declined from 10 years after initial amyloid-ß plaque deposition. Patients with sporadic mild cognitive impairment who were (11)C-Pittsburgh compound B-positive at baseline showed increasing amyloid-ß plaque deposition and decreasing glucose metabolism but, in contrast to autosomal dominant Alzheimer's disease carriers, there was no significant longitudinal decline in astrocytosis over time. The prominent initially high and then declining astrocytosis in autosomal dominant Alzheimer's disease carriers, contrasting with the increasing amyloid-ß plaque load during disease progression, suggests astrocyte activation is implicated in the early stages of Alzheimer's disease pathology.

Molecular Imaging of Neuroinflammation in Neurodegenerative Dementias: The Role of In Vivo PET Imaging.

Neurodegeneration elicits neuroinflammatory responses to kill pathogens, clear debris and support tissue repair. Neuroinflammation is a dynamic biological response characterized by the recruitment of innate and adaptive immune system cells in the site of tissue damage. Resident microglia and infiltrating immune cells partake in the restoration of central nervous system homeostasis. Nevertheless, their activation may shift to chronic and aggressive responses, which jeopardize neuron survival and may contribute to the disease process itself. Positron Emission Tomography (PET) molecular imaging represents a unique tool contributing to in vivo investigating of neuroinflammatory processes in patients. In the present review, we first provide an overview on the molecular basis of neuroinflammation in neurodegenerative diseases with emphasis on microglia activation, astrocytosis and the molecular targets for PET imaging. Then, we review the state-of-the-art of in vivo PET imaging for neuroinflammation in dementia conditions associated with different proteinopathies, such as Alzheimer's disease, frontotemporal lobar degeneration and Parkinsonian spectrum.

Frequent mild head injury promotes trigeminal sensitivity concomitant with microglial proliferation, astrocytosis, and increased neuropeptide levels in the trigeminal pain system.

BACKGROUND: Frequent mild head injuries or concussion along with the presence of headache may contribute to the persistence of concussion symptoms. METHODS: In this study, the acute effects of recovery between mild head injuries and the frequency of injuries on a headache behavior, trigeminal allodynia, was assessed using von Frey testing up to one week after injury, while histopathological changes in the trigeminal pain pathway were evaluated using western blot, ELISA and immunohistochemistry.  RESULTS: A decreased recovery time combined with an increased mild closed head injury (CHI) frequency results in reduced trigeminal allodynia thresholds compared to controls. The repetitive CHI group with the highest injury frequency showed the greatest reduction in trigeminal thresholds along with greatest increased levels of calcitonin gene-related peptide (CGRP) in the trigeminal nucleus caudalis. Repetitive CHI resulted in astrogliosis in the central trigeminal system, increased GFAP protein levels in the sensory barrel cortex, and an increased number of microglia cells in the trigeminal nucleus caudalis. CONCLUSIONS: Headache behavior in rats is dependent on the injury frequency and recovery interval between mild head injuries. A worsening of headache behavior after repetitive mild head injuries was concomitant with increases in CGRP levels, the presence of astrocytosis, and microglia proliferation in the central trigeminal pathway. Signaling between neurons and proliferating microglia in the trigeminal pain system may contribute to the initiation of acute headache after concussion or other traumatic brain injuries.

Granulocyte colony-stimulating factor promotes behavioral recovery in a mouse model of traumatic brain injury.

Hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) represent a novel approach for treatment of traumatic brain injury (TBI). After mild controlled cortical impact (CCI), mice were treated with G-CSF (100 µg/kg) for 3 consecutive days. The primary behavioral endpoint was performance on the radial arm water maze (RAWM), assessed 7 and 14 days after CCI. Secondary endpoints included 1) motor performance on a rotating cylinder (rotarod), 2) measurement of microglial and astroglial response, 3) hippocampal neurogenesis, and 4) measures of neurotrophic factors (brain-derived neurotrophic factor [BDNF] and glial cell line-derived neurotrophic factor [GDNF]) and cytokines in brain homogenates. G-CSF-treated animals performed significantly better than vehicle-treated mice in the RAWM at 1 and 2 weeks but not on the rotarod. Cellular changes found in the G-CSF group included increased hippocampal neurogenesis as well as astrocytosis and microgliosis in both the striatum and the hippocampus. Neurotrophic factors GDNF and BDNF, elaborated by activated microglia and astrocytes, were increased in G-CSF-treated mice. These factors along with G-CSF itself are known to promote hippocampal neurogenesis and inhibit apoptosis and likely contributed to improvement in the hippocampal-dependent learning task. Six cytokines that were modulated by G-CSF treatment following CCI were elevated on day 3, but only one of them remained altered by day 7, and all of them were no different from vehicle controls by day 14. The pro- and anti-inflammatory cytokines modulated by G-CSF administration interact in a complex and incompletely understood network involving both damage and recovery processes, underscoring the dual role of inflammation after TBI.

Astrocytes in neurodegenerative diseases (I): function and molecular description.

INTRODUCTION: Astrocytes have been considered mere supporting cells in the CNS. However, we now know that astrocytes are actively involved in many of the functions of the CNS and may play an important role in neurodegenerative diseases. DEVELOPMENT: This article reviews the roles astrocytes play in CNS development and plasticity; control of synaptic transmission; regulation of blood flow, energy, and metabolism; formation of the blood-brain barrier; regulation of the circadian rhythms, lipid metabolism and secretion of lipoproteins; and in neurogenesis. Astrocyte markers and the functions of astrogliosis are also described. CONCLUSION: Astrocytes play an active role in the CNS. A good knowledge of astrocytes is essential to understanding the mechanisms of neurodegenerative diseases.

Pathophysiology of brain dysfunction in hyperammonemic syndromes: The many faces of glutamine.

Ineffective hepatic clearance of excess ammonia in the form of urea, as occurs in urea cycle enzymopathies (UCDs) and in liver failure, leads to increases in circulating and tissue concentrations of glutamine and a positive correlation between brain glutamine and the severity of neurological symptoms. Studies using 1H/13C Nuclear Magnetic Resonance (NMR) spectroscopy reveal increased de novo synthesis of glutamine in the brain in acute liver failure (ALF) but increases of synthesis rates per se do not correlate with either the severity of encephalopathy or brain edema. Skeletal muscle becomes primarily responsible for removal of excess ammonia in liver failure and in UCDs, an adaptation that results from a post-translational induction of the glutamine synthetase (GS) gene. The importance of muscle in ammonia removal in hyperammonemia accounts for the resurgence of interest in maintaining adequate dietary protein and the use of agents aimed at the stimulation of muscle GS. Alternative or additional metabolic and regulatory pathways that impact on brain glutamine homeostasis in hyperammonemia include (i) glutamine deamination by the two isoforms of glutaminase, (ii) glutamine transamination leading to the production of the putative neurotoxin alpha-ketoglutaramate and (iii) alterations of high affinity astrocytic glutamine transporters (SNATs). Findings of reduced expression of the glutamine transporter SNAT-5 (responsible for glutamine clearance from the astrocyte) in ALF raise the possibility of "glutamine trapping" within these cells. Such a trapping mechanism could contribute to cytotoxic brain edema and to the imbalance between excitatory and inhibitory neurotransmission in this disorder.

Leukoencephalomyelopathy of mature captive cheetahs and other large felids: a novel neurodegenerative disease that came and went?

A novel leukoencephalomyelopathy was identified in 73 mature male and female large captive felids between 1994 and 2005. While the majority of identified cases occurred in cheetahs (Acinonyx jubatus), the disease was also found in members of 2 other subfamilies of Felidae: 1 generic tiger (Panthera tigris) and 2 Florida panthers (Puma concolor coryi). The median age at time of death was 12 years, and all but 1 cheetah were housed in the United States. Characteristic clinical history included progressive loss of vision leading to blindness, disorientation, and/or difficulty eating. Neurologic deficits progressed at a variable rate over days to years. Mild to severe bilateral degenerative lesions were present in the cerebral white matter and variably and to a lesser degree in the white matter of the brain stem and spinal cord. Astrocytosis and swelling of myelin sheaths progressed to total white matter degeneration and cavitation. Large, bizarre reactive astrocytes are a consistent histopathologic feature of this condition. The cause of the severe white matter degeneration in these captive felids remains unknown; the lesions were not typical of any known neurotoxicoses, direct effects of or reactions to infectious diseases, or nutritional deficiencies. Leukoencephalomyelopathy was identified in 70 cheetahs, 1 tiger, and 2 panthers over an 11-year period, and to our knowledge, cases have ceased without planned intervention. Given what is known about the epidemiology of the disease and morphology of the lesions, an environmental or husbandry-associated source of neurotoxicity is suspected.