Astrogliosis In Brain Research Articles

Associations of GFAP, NfL, Aβ42/40, and pTau231 with global cognition in LEADS

AbstractBackgroundHistorically, Alzheimer’s disease (AD) biomarkers have been used to identify the presence of pathology and have been shown to change well ahead of symptom onset. While previous research has evaluated plasma pTau231 and its associations with cognition, little to none of this research has focused on early‐onset AD (EOAD) populations. Here we investigate how select plasma biomarkers are associated with global cognitive measures in early‐onset cognitive impairment.MethodThe current sample included 367 Longitudinal Early‐Onset AD Study (LEADS) participants (aged 41 to 65) categorized as amyloid PET‐positive EOAD, amyloid PET‐negative EOnonAD, or cognitively normal (CN). Each participant had baseline global cognitive (Mini‐Mental State Examination [MMSE], Montreal Cognitive Assessment [MoCA], Clinical Dementia Rating Scale sum of boxes [CDR‐SB], and ADAS‐Cog13) and plasma biomarker assessments (Simoa‐HDx N4PE kit: Aβ42/40, phosphorylated Tau [pTau231], Neurofilament light protein [NfL], and glial fibrillary acidic protein [GFAP]). Partial correlations were used to check for associations with cognitive performance controlling for age, sex, and years of education. Fisher r‐to‐z transformations were conducted to compare the performance across diagnostic groups.ResultPartial correlations in the pooled sample showed moderate associations between cognition and plasma pTau231, GFAP and NfL (r = .42‐.50, p<.001) and weaker associations with Aβ42/40 (r = .25‐.33, p<.001). When split into diagnostic groups, the NfL and GFAP correlations were significant in both EOAD and EOnonAD, but not CN. The pTau231 correlations were significant only in EOAD. Aβ42/40 correlations were non‐significant within specific diagnostic groups. No differences were observed in the magnitude of the cognitive and biomarker associations between EOAD and EOnonAD samples (ps>.05).ConclusionAs expected, the neurodegenerative biomarkers pTau231 and NfL showed stronger association with cognition compared to the marker for brain amyloidosis (Aβ42/40). The nonspecific markers for neurodegeneration (NfL) and brain astrogliosis (GFAP) showed associations in both EOAD and EOnonAD while the markers specific to AD were only significant in EOAD. Plasma biomarkers show great promise for AD diagnosis and monitoring.

Inflammatory pathology markers (activated microglia and reactive astrocytes) in early and late onset Alzheimer disease: a post mortem study.

The association between the pathological features of AD and dementia is stronger in younger old persons than in older old persons suggesting that additional factors are involved in the clinical expression of dementia in the oldest old. Cumulative data suggests that neuroinflammation plays a prominent role in Alzheimer's disease (AD) and different studies reported an age-associated dysregulation of the neuroimmune system. Consequently, we sought to characterize the pattern of microglial cell activation and astrogliosis in brain post mortem tissue of pathologically confirmed cases of early and late onset AD (EOAD and LOAD) and determine their relation to age. Immunohistochemistry (CD68 and glial fibrillary acidic protein) with morphometric analysis of astroglial profiles in 36 cases of AD and 28 similarly aged controls. Both EOAD and LOAD groups had higher microglial scores in CA1, entorhinal and temporal cortices, and higher astroglial response in CA1, dentate gyrus, entorhinal and temporal cortices, compared to aged matched controls. Additionally, EOAD had higher microglial scores in subiculum, entorhinal and temporal subcortical white matter, and LOAD higher astrogliosis in CA2 region. Overall, we found that the neuroinflammatory pathological markers in late stage AD human tissue to have a similar pattern in both EOAD and LOAD, though the severity of the pathological markers in the younger group was higher. Understanding the age effect in AD will be important when testing modifying agents that act on the neuroinflammation.

Dose-dependent induction of astrocyte activation and reactive astrogliosis in mouse brain following maternal exposure to carbon black nanoparticle

BackgroundRecent studies indicate that maternal exposure to ambient ultrafine particles and nanoparticles has adverse effects of on the central nervous system. Quantitative dose–response data is required to better understand the developmental neurotoxicity of nanoparticles. The present study investigated dose-dependent effects of maternal exposure to carbon black nanoparticle (CB-NP) on astrocyte in the brains of mouse offspring.MethodsA CB-NP suspension (2.9, 15, or 73 μg/kg) was intranasally administered to pregnant ICR mice on gestational days 5 and 9. Cerebral cortex samples were collected from 6-week-old offspring and examined by Western blotting, immunostaining, microarray analysis, and quantitative reverse transcriptase-polymerase chain reaction. Placentae were collected from pregnant dams on gestational day 13 and examined by microarray analysis.ResultsMaternal exposure to CB-NP induced a dose-dependent increase in glial fibrillary acidic protein (GFAP) expression in the cerebral cortex; this increase was particularly observed in astrocytic end-feet attached to denatured perivascular macrophages. Moreover, maternal CB-NP exposure dose-dependently increased aquaporin-4 expression in the brain parenchyma region around blood vessels. The changes in the expression profiles of GFAP and Aqp4 in offspring after maternal CB-NP exposure were similar to those observed in mice of a more advanced age. The expression levels of mRNAs associated with angiogenesis, cell migration, proliferation, chemotaxis, and growth factor production were also altered in the cerebral cortex of offspring after maternal CB-NP exposure. Differentially expressed genes in placental tissues after CB-NP exposure did not populate any specific gene ontology category.ConclusionsMaternal CB-NP exposure induced long-term activation of astrocytes resulting in reactive astrogliosis in the brains of young mice. Our observations suggest a potentially increased risk of the onset of age-related neurodegenerative diseases by maternal NP exposure. In this study, we report for the first time a quantitative dose–response relationship between maternal NP exposure and phenotypic changes in the central nervous system of the offspring. Moreover, our findings indicate that cortical GFAP and Aqp4 are useful biomarkers that can be employed in further studies aiming to elucidate the underlying mechanism of nanoparticle-mediated developmental neurotoxicity.

Experimental Zika virus infection induces spinal cord injury and encephalitis in newborn Swiss mice

A widespread epidemic of Zika virus (ZIKV) infection was reported in 2015 in South and Central America, with neurological symptons including meningoencephalitis and Guillain-Barré syndrome in adults, besides an apparent increased incidence of microcephaly in infants born to infected mothers. It is becoming a necessity to have a trustworthy animal model to better understand ZIKV infection. In this study we used newborn white Swiss mice as a model to investigate the ZIKV strain recently isolated in Brazil. ZIKV was inoculated via intracerebral and subcutaneous routes and analysed through gross histopathology and immunohistochemistry. Here we demonstrated first that the intracerebral group (ICG) displayed severe cerebral lesions, with neuronal death, presence of apoptotic bodies, white matter degeneration and neutrophil perivascular cuffing. In the subcutaneous group (SCG), we observed moderate cerebral lesions, morphologically similar to that found in ICG and additional myelopathy, with architectural loss, marked by neuronal death and apoptotic bodies. Interestingly, we found an intense astrogliosis in brain of both groups, with increased immunoexpression of GFAP (glial fibrillary acidic protein) and presence of hypertrophic astrocytes. The spinal cord of subcutaneous group (SCG) exhibited reduction of astrocytes, but those positive for GFAP were hypertrophic and presented prolonged cellular processes. Finally significant lesions in the central nervous system (CNS) were present in newborn mice inoculated by both routes, but SCG method led to an important neurological manifestations (including myelopathy), during a longer period of time and appears for us to be a better model for ZIKV infection.

JAK‐STAT signaling pathway mediates astrogliosis in brains of scrapie‐infected mice

Scrapie is characterized histologically, in part, by astrogliosis in brain and spinal cord. However, the mechanisms of astrogliosis in brain injury occurring during prion infection are not well understood. In this study, we investigated the expression levels and cellular localization of Janus kinase (JAK) -signal transducers and activators of transcription (STAT) signaling molecules and growth factors such as leukemia inhibitory factor (LIF) and ciliary neurotropic factor (CNTF) by western blot analysis and immunohistochemistry. We found that expression levels of LIF and CNTF were increased in scrapie-infected brains and phosphorylated (p)-JAK2, p-STAT1 (Ser727 and Tyr701), p-STAT3 (Tyr705), and glial fibrillary acidic protein were expressed strongly in scrapie-infected brains. Moreover, we found that p-STAT1 and p-STAT3 were found mainly in the nucleus in scrapie-infected brains. Immunohistochemically, p-STAT1 was colocalized with LIF and CNTF and p-JAK2 in many reactive astrocytes in scrapie-infected brains. In contrast, immunostaining for p-STAT3 was found in comparatively few astrocytes in limited regions; p-STAT3 staining merged with p-JAK2 in hippocampus sections of scrapie-infected brains. Taken together, our results suggest that activation of JAK2-STAT1 signaling pathway occurred in reactive astrocytes in hippocampus of scrapie-infected brains.

P4-125: JAK-STAT signaling pathway mediates astrogliosis in brains of scrapie-infected mice

P4-125: JAK-STAT signaling pathway mediates astrogliosis in brains of scrapie-infected mice

Glutamine synthetase in cerebrospinal fluid, serum, and brain: a diagnostic marker for Alzheimer disease?

To determine whether the glutamine synthetase (GS) level in cerebrospinal fluid (CSF) is a useful biochemical marker in the diagnosis of Alzheimer disease (AD), and to assess the source of GS (brain vs. blood derived) in CSF. Sandwich enzyme immunoassay and immunoblotting were applied to detect GS in CSF and in serum from neurologically healthy control subjects and patients with neurodegenerative diseases, including AD. The origin of GS was estimated by the concentration gradients of CSF to serum and ventricular to lumbar CSF. In addition, postmortem brain tissue from controls and patients with AD was analyzed using immunohistochemistry for expression of GS. Levels of GS were significantly increased in lumbar CSF from patients with AD (20+/-12 pg/mL; P = .01) and to a lesser extent in patients with vascular dementia and amyotrophic lateral sclerosis. In CSF of controls, GS levels were 4+/-3 pg/mL. The GS concentration gradients were less than 1:10 for CSF to serum and 2:1 for ventricular to lumbar CSF. Immunoreactivity of GS was most prominent in astrocytes from temporal neocortex of patients with AD, suggesting a relationship between astrocyte reactions and increased GS levels in CSF. Level of GS in lumbar CSF of patients with AD is increased significantly but nonspecifically, probably related to the strong astrogliosis in brain. Glutamine synthetase in lumbar CSF is mainly brain derived.

No evidence for astrogliosis in brains of schizophrenic patients. A post-mortem study.

Schizophrenia is clinically and neuropsychologically characterized by severe cognitive and functional impairment suggesting the presence of a neurodegenerative process in the brains of affected individuals. A variety of neuroanatomical changes have been described such as loss and disorientation of neurons in grey and white matter and cortical atrophy. However, the neuropathological basis for schizophrenia is still unclear. In the present study we monitored the density of GFAP-positive astrocytes in brains of 33 schizophrenic patients and 26 healthy controls. Both grey matter (entorhinal cortex and subiculum) and white matter (premotor cortex, subventricular zone of the third ventricle and next to inferior horn) structures were measured bilaterally. The overall finding was that there is no evidence for increased astrogliosis in brains of schizophrenic patients vs healthy controls. Therefore, degeneration is unlikely to be the main neuropathological mechanism in schizophrenic brains.