Glial Changes Research Articles

THE STUDY OF ASSOCIATIONS BETWEEN IL1Β C3953T GENE POLYMORPHISM AND CLINICAL-NEUROLOGICAL, NEUROIMAGING, HEMODYNAMIC CHARACTERISTICS AND COGNITIVE DYSFUNCTION IN PATIENTS WITH POST-INFECTIOUS ENCEPHALOPATHY

The aim: To investigate potential associations between the C3953T polymorphic variant of the interleukin-one beta (IL1β) gene and clinical-neurological, neuroimaging, hemodynamic characteristics, as well as cognitive dysfunction in patients with post-infectious encephalopathy (PIE).
 Materials and methods: A total of 128 patients with post-infectious encephalopathy (PIE) who were receiving inpatient treatment in the neurological departments of the Communal Non-commercial Enterprise “Ternopil Regional Clinical Psychoneurological Hospital” of Ternopil Regional Council,” Ternopil, Ukraine, were examined and included in the retrospective analysis in 2021–2022. The molecular-genetic testing was performed for 26 patients in the molecular genetics laboratory of the State Institution “Reference Centre for Molecular Diagnostics of the Ministry of Health of Ukraine,” Kyiv. The control group consisted of 12 people, who were representative in age and gender. Statistical processing of the results was performed using the STATISTICA 10.0 software.
 Results: Analysis of the dependence of neuroimaging changes on the frequency of genotypes of the C3953T polymorphic variant of the IL1β gene in patients with PIE showed a significant relationship between their frequency distribution and the presence/absence of gliosis phenomena (p=0.009). Thus, gliosis was detected in all carriers of the T/T genotype C3953T polymorphic variant of the IL1β gene. Analyzing the dependence of changes obtained during the transcranial Doppler ultrasound scanning of cerebral vessels on the polymorphic variant C3953T of the IL1β gene in patients with PIE, all carriers of the T/T genotype were diagnosed with angiospasm (p=0.038) and vertebrobasilar insufficiency (p=0.010).
 Conclusions: Results suggest the reasonability of further researching the interaction between IL1β and glial cells and changes in the cognitive functioning of cytokine genotypes with larger sample sizes that may help explain the pathophysiological mechanisms leading to cognitive impairment in patients with PIE.

Glial cell changes in the corpus callosum in chronically-starved mice

Anorexia nervosa (AN) is characterized by emaciation, hyperactivity, and amenorrhea. Imaging studies in AN patients have revealed reductions in grey and white matter volume, which correlate with the severity of neuropsychological deficits. However, the cellular basis for the observed brain atrophy is poorly understood. Although distinct hypothalamic centers, including the arcuate nucleus (ARC) are critically involved in regulating feeding behavior, little is known about potential hypothalamic modifications in this disorder. Since glia e.g. astrocytes and microglia influence neuronal circuits, we investigated the glial changes underlying pathophysiology of starvation in the corpus callosum (CC) and hypothalamus. Female mice were given a limited amount of food once a day and had unlimited access to a running wheel until a 20% weight reduction was achieved (acute starvation). This weight reduction was maintained for two weeks to mimic chronic starvation. Immunohistochemistry was used to quantify the density of astrocytes, microglia, oligodendrocytes, and the staining intensity of neuropeptide Y (NPY), a potent orexigenic peptide. Chronic starvation induced a decreased density of OLIG2+ oligodendrocytes, GFAP+ astrocytes, and IBA1+ microglia in the CC. However, the densities of glial cells remained unchanged in the ARC following starvation. Additionally, the staining intensity of NPY increased after both acute and chronic starvation, indicating an increased orexigenic signaling. Chronic starvation induced glial cell changes in the CC in a mouse model of AN suggesting that glia pathophysiology may play a role in the disease.

Single Cell RNASeq Analysis of AD and Control Post Mortem Brain Samples

Alzheimer’s disease (AD) is a devastative late life disease, molecularly characterized by biochemical lesions of amyloid β plaques and Tau tangles. the 2nd most frequent one worldwide with no early detection methods/cure. I have applied single cell sequencing and analysed post mortem brain samples (using a Chromium machine) from 2 AD and 2 control frontal cortex samples. All the samples had ethics approval, and the RNA was tested for quality. The samples were obtained from the Edenborough MRC brain bank. Very few genes have been linked to far to AD (mainly through GWAS studies [1]). Overall, I quantified about 24,000 nuclei. Using statistical, bioinformatics and computational analyses I have detected significant differential expression changes in astrocyte, neuronal and microglial marker genes. I also conducted network analyses. The percentage of reads passing filter was slightly low (68%). Overall output was a bit lower than optimal. There was still over 1.6Bn clusters generated though, which is within the specification for an S1 flow-cell, and base call quality (quality control) was excellent: 97% >Q30. The read counts mapping to genome occupancy rate was also fairy low (63-81%). The number of barcodes is as follows: sample 1 (AD, Braak I-II) - 6,223 sample 2 (control) 6,262 sample 3 (AD Braak I-II) 5,332 sample 4 (AD, Braak I-II) 5,332 as well. The data is available for download under the GEO (accession number GSE175814). to assess global and cell-type specific gene expression impacts in Alzheimer’s versus control brain samples, we performed a holistic comparison of matching cell populations in AD and controls with the software cell Harmony. To identify possible gene regulatory network underlying transcriptional regulation in these distinct populations, we further explored prior evidenced transcription factor targets relationships from cell Harmony. Importantly, we observe both common and cell-type specific core transcription factors regulators, with both enriched downstream targets and regulated transcription factors. Upregulated networks in Astrocytes were associated with broad regulation by HIF1A, SOX2, NRF1, and RB1. the proportion of endothelial cells was higher in the Alzheimer’s disease samples than the neurological control samples. results reveal that the cell type-specific transcriptomic changes in Alzheimer’s disease are associated with 4 molecular pathways: angiogenesis in endothelial cells, immune response in endothelial cells and microglia, myelination in oligodendrocytes, and synaptic signalling in astrocytes and neurons. I also compared the results with microarray data from large cohort studies that examined samples from the prefrontal cortex (Alzheimer’s disease: n = 310; Neurological controls: n = 157) or temporal cortex (Alzheimer’s disease: n = 106; Neurological controls: n = 135). Among the DEGs identified in our snRNA-seq analysis, 1,113 and 764 genes were significantly differentially expressed in the microarray data from the prefrontal cortex and temporal cortex, respectively. subcluster analysis of microglia identified 13 subpopulations; VGF signalling was also found as changed. In the future, imaging of post mortem Alzheimer’s patients may verify brain cellular morphology/cell volume of vascular changes in the Alzheimer’s compared to control samples. My study findings [2] may open new venues to our understanding of the disease underlying molecular processes and cellular signaling. Regarding the glial cell changes, our main conclusion is that the glial cells may be reactive in the disease and not causal.

Glial changes are associated with cerebrovascular integrity in hyperhomocysteinemia‐induced VCID in mouse and human brain

AbstractBackgroundWith the aged population estimated to double by 2050 and the rate of dementia expected to triple, it is critical to identify treatments for dementia. One of the leading causes of dementia is vascular contributions to cognitive impairment and dementia (VCID), and is frequently found co‐morbidly with Alzheimer’s disease, the other leading cause of dementia. A modifiable risk factor for VCID is hyperhomocysteinemia (HHcy), which is defined as elevated levels of plasma homocysteine (a non‐protein‐forming amino acid), and most late‐life HHcy is caused by impaired B vitamin absorption. Although HHcy is a risk factor for VCID, the mechanism through which it induces cognitive impairment remains unclear.MethodWe used human and mouse brain tissue to determine glial and vascular changes associated with HHcy. Wild‐type (C57Bl6J) mice were placed on a HHcy or control diet for 6, 10, 14, or 18 weeks. Using qPCR, we investigated pro‐ and anti‐inflammatory cytokines. We also determined changes in microglia (IBA‐1) and identified the number of microhemorrhages and cognitive changes. In humans, we identified 31 autopsied research volunteers with antemortem homocysteine levels; 13 cases had normal plasma homocysteine levels (<14µmol/L) and 18 had high plasma homocysteine levels (>14µmol/L). We determined whether the level of plasma homocysteine was associated with microglia (IBA‐1) and astrocytes (GFAP) as well as microhemorrhages and atherosclerosis severity in the frontal and occipital cortices. Both gene expression and protein inflammatory markers were measured to determine associations with plasma homocysteine.ResultIn our mouse model of HHcy, we identified a time course of glial changes that first begins with an increase in pro‐inflammatory cytokines and increases in microglial staining at 6 weeks on diet. This is followed by cognitive changes at 10 weeks on diet. Finally, at 14 weeks on diet, we see significant cognitive deficits due to HHcy. In human tissue, HHcy was associated with more microglia but fewer astrocytes, a significant decrease in inflammation and increased microhemorrhages in the frontal cortex.ConclusionTaken together, this data shows that in both mouse and human tissue, HHcy induces significant glial and vascular pathology that could be driven by inflammatory effects.

Memory dysfunction in mild cognitive impairment (MCI) and early Alzheimer disease (AD) dementia is closely associated with synapse loss, and shows significant correlation with pathological tau in synapses and inflammatory glial cell responses in postmortem human brain

AbstractBackgroundSynapse density loss is among the strongest histopathological correlates of dementia in AD. Prodromal stages of AD, comprising amnestic MCI and mild AD dementia, represent the most promising timepoints for interventions aimed at attaining efficacious neurobiological and clinical effects. Yet, the understanding of other contributing neuropathologic changes in these prodromal disease stages and their impact on early cognitive dysfunction remains limited.MethodsWe studied the visual cortex of 28 demented and non‐demented human brains who had died at Braak III‐IV stages of NFT pathology, and who showed a comparable β‐amyloid plaque burden and absence of NFT deposits in the studied brain region, and a group of age‐matched healthy controls. We used immunohistochemical analyses with artificial intelligence quantifications, expansion microscopy, synaptosome extractions, and Western blotting, to assess associations between antemortem MMSE scores and synapse densities, glial cell phenotypes, and pathological tau.ResultsWe found a significant loss of presynapses (Synapsin 1+), excitatory postsynapses (PSD95+), and colocalized synapses (Synapsin1‐PSD95+) in the brains of demented compared to non‐demented and controls. Moreover, we observed an association between excitatory synapse loss and memory dysfunction (MMSE score) as well as rate of disease progression (MMSE loss/time). MMSE scores were further associated with increase in tau oligomers (TOC1+) and phospho‐tau (AT270+) in synaptosomes, but not with 4G8+ β‐amyloid burden. Additionally, disease severity and rate of progression were significantly correlated with inflammatory glial changes.ConclusionsOur data suggest that excitatory synapse loss could serve as an early and robust neuropathologic correlate of disease severity and rate of progression from MCI stages of the disease, and be a closer and better determinant of cognitive decline than β‐amyloid and tau deposits. Moreover, early increases in soluble tau in synapses together with local inflammatory glial cell responses could drive development of incipient changes in memory function and serve as potential early biomarkers. Our results point to the importance of early detection and interventions aimed at synapse preservation from prodromal stages of AD, and suggest soluble tau and inflammatory glial cell changes as key targets in the early AD phases.

Neuronal transcriptome, tau and synapse loss in Alzheimer’s knock-in mice require prion protein

BackgroundProgression of Alzheimer’s disease leads to synapse loss, neural network dysfunction and cognitive failure. Accumulation of protein aggregates and brain immune activation have triggering roles in synaptic failure but the neuronal mechanisms underlying synapse loss are unclear. On the neuronal surface, cellular prion protein (PrPC) is known to be a high-affinity binding site for Amyloid-β oligomers (Aβo). However, PrPC’s dependence in knock-in AD models for tau accumulation, transcriptomic alterations and imaging biomarkers is unknown.MethodsThe necessity of PrPC was examined as a function of age in homozygous AppNL−G−F/hMapt double knock-in mice (DKI). Phenotypes of AppNL−G−F/hMapt mice with a deletion of Prnp expression (DKI; Prnp−/−) were compared with DKI mice with intact Prnp, mice with a targeted deletion of Prnp (Prnp−/−), and mice with intact Prnp (WT). Phenotypes examined included behavioral deficits, synapse loss by PET imaging, synapse loss by immunohistology, tau pathology, gliosis, inflammatory markers, and snRNA-seq transcriptomic profiling.ResultsBy 9 months age, DKI mice showed learning and memory impairment, but DKI; Prnp−/− and Prnp−/− groups were indistinguishable from WT. Synapse loss in DKI brain, measured by [18F]SynVesT-1 SV2A PET or anti-SV2A immunohistology, was prevented by Prnp deletion. Accumulation of Tau phosphorylated at aa 217 and 202/205, C1q tagging of synapses, and dystrophic neurites were all increased in DKI mice but each decreased to WT levels with Prnp deletion. In contrast, astrogliosis, microgliosis and Aβ levels were unchanged between DKI and DKI; Prnp−/− groups. Single-nuclei transcriptomics revealed differential expression in neurons and glia of DKI mice relative to WT. For DKI; Prnp−/− mice, the majority of neuronal genes differentially expressed in DKI mice were no longer significantly altered relative to WT, but most glial DKI-dependent gene expression changes persisted. The DKI-dependent neuronal genes corrected by Prnp deletion associated bioinformatically with synaptic function. Additional genes were uniquely altered only in the Prnp−/− or the DKI; Prnp−/− groups.ConclusionsThus, PrPC-dependent synapse loss, phospho-tau accumulation and neuronal gene expression in AD mice can be reversed without clearing Aβ plaque or preventing gliotic reaction. This supports targeting the Aβo-PrPC interaction to prevent Aβo-neurotoxicity and pathologic tau accumulation in AD.

Resveratrol improves the prognosis of rats after spinal cord injury by inhibiting mitogen-activated protein kinases signaling pathway

Spinal cord injury (SCI) is a serious condition that results in irreparable nerve damage and severe loss of motor or sensory function. Resveratrol (3,4′,5-trihy- droxystilbene) is a naturally occurring plant-based polyphenol that has demonstrated powerful antioxidative, anti-inflammatory, and anti-carcinogenic pharmaceutical properties in previous studies. In the central nervous system, it promotes neuronal recovery and protects residual function. However, the role of resveratrol in SCI recovery remains elusive. In this study, the potential mechanisms by which resveratrol affect SCI in rats were assessed by constructing a contusion model of SCI. Resveratrol was intraperitoneally administered to rats. Behavioral scores and electrophysiological examinations were performed to assess functional recovery. After magnetic resonance imaging and staining with hematoxylin and eosin (HE) and Luxor Fast Blue (LFB), tissue recovery was analyzed. Immunofluorescence with NeuN and glial fibrillary acidic protein (GFAP) was employed to evaluate neuronal survival and glial changes. TdT-mediated dUTP nick end labeling (TUNEL) assay was performed to examine apoptotic rates. Moreover, network pharmacology was performed to identify relevant pathways of resveratrol for the treatment of SCI. Lastly, ELISA was performed to detect the expression levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6. Our findings revealed that resveratrol dramatically improved the hindlimb locomotor function and their electrophysiological outcomes. Notably, lesion size was significantly reduced on magnetic resonance imaging. HE and LFB staining exposed increased sparseness of tissue and myelin. GFAP and NeuN immunofluorescence assays at the lesion site determined that resveratrol boosted neuronal survival and attenuated glial cell overgrowth. In addition, resveratrol reduced the density and number of TUNEL-positive cells in rats after injury. Additionally, gene ontology analysis revealed that the enriched differentially expressed protein was associated with the JNK/p38MAPK (c-jun N-terminal kinase/p38 mitogen-activated protein kinase) signaling pathway. Following resveratrol treatment, the expression levels of IL-1β, TNF-α, and IL-6 were decreased. In summary, the administration of resveratrol protects motor function and neuronal survival in rats after SCI. Furthermore, resveratrol exerts an anti-inflammatory effect by blocking the JNK/p38MAPK signaling pathway.

Cross species systems biology discovers glial DDR2, STOM, and KANK2 as therapeutic targets in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a neurodegenerative parkinsonian disorder characterized by cell-type-specific tau lesions in neurons and glia. Prior work uncovered transcriptome changes in human PSP brains, although their cell-specificity is unknown. Further, systematic data integration and experimental validation platforms to prioritize brain transcriptional perturbations as therapeutic targets in PSP are currently lacking. In this study, we combine bulk tissue (n = 408) and single nucleus RNAseq (n = 34) data from PSP and control brains with transcriptome data from a mouse tauopathy and experimental validations in Drosophila tau models for systematic discovery of high-confidence expression changes in PSP with therapeutic potential. We discover, replicate, and annotate thousands of differentially expressed genes in PSP, many of which reside in glia-enriched co-expression modules and cells. We prioritize DDR2, STOM, and KANK2 as promising therapeutic targets in PSP with striking cross-species validations. We share our findings and data via our interactive application tool PSP RNAseq Atlas (https://rtools.mayo.edu/PSP_RNAseq_Atlas/). Our findings reveal robust glial transcriptome changes in PSP, provide a cross-species systems biology approach, and a tool for therapeutic target discoveries in PSP with potential application in other neurodegenerative diseases.

TNF-α blockage by etanercept restores spatial learning and reduces cellular degeneration in the hippocampus during liver cirrhosis

Hepatic encephalopathy (HE) is one of the most debilitating cerebral complications of liver cirrhosis. The one-year survival of patients with liver cirrhosis and severe encephalopathy is less than 50%. Recent studies have indicated that neuroinflammation is a new player in the pathogenesis of HE, which seems to be involved in the development of cognitive impairment. In this study, we demonstrated neurobehavioral and neuropathological consequences of liver cirrhosis and tested the therapeutic potential of the tumor necrosis factor-α (TNF-α) inhibitor, etanercept. Sixty male adult Wistar albino rats (120–190 g) were allocated into four groups, where groups I and IV served as controls. Thioacetamide (TAA; 300 mg/kg) was intraperitoneally injected twice a week for five months to induce liver cirrhosis in group II (n = 20). Both TAA and etanercept (2 mg/kg) were administered to group III (n = 20). At the end of the experiment, spatial learning was assessed using Morris water maze. TNF-α was detected in both serum and hippocampus. The excised brains were also immunohistochemically stained with glial fibrillary acidic protein (GFAP) to estimate both the number and integrity of hippocampal astrocytes. Ultrastructural changes in the hippocampus were characterized by transmission electron microscopy. The results showed that blocking TNF-α by etanercept was accompanied by a lower TNF-α expression and a higher number of GFAP-positive astrocytes in the hippocampus. Etanercept intervention alleviated the neuronal and glial degenerative changes and impeded the deterioration of spatial learning ability. In conclusion, TNF-α is strongly involved in the development of liver cirrhosis and the associated encephalopathy. TNF-α blockers may be a promising approach for management of hepatic cirrhosis and its cerebral complications.

TDP-43 pathology in Drosophila induces glial-cell type specific toxicity that can be ameliorated by knock-down of SF2/SRSF1.

Accumulation of cytoplasmic inclusions of TAR-DNA binding protein 43 (TDP-43) is seen in both neurons and glia in a range of neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD) and Alzheimer's disease (AD). Disease progression involves non-cell autonomous interactions among multiple cell types, including neurons, microglia and astrocytes. We investigated the effects in Drosophila of inducible, glial cell type-specific TDP-43 overexpression, a model that causes TDP-43 protein pathology including loss of nuclear TDP-43 and accumulation of cytoplasmic inclusions. We report that TDP-43 pathology in Drosophila is sufficient to cause progressive loss of each of the 5 glial sub-types. But the effects on organismal survival were most pronounced when TDP-43 pathology was induced in the perineural glia (PNG) or astrocytes. In the case of PNG, this effect is not attributable to loss of the glial population, because ablation of these glia by expression of pro-apoptotic reaper expression has relatively little impact on survival. To uncover underlying mechanisms, we used cell-type-specific nuclear RNA sequencing to characterize the transcriptional changes induced by pathological TDP-43 expression. We identified numerous glial cell-type specific transcriptional changes. Notably, SF2/SRSF1 levels were found to be decreased in both PNG and in astrocytes. We found that further knockdown of SF2/SRSF1 in either PNG or astrocytes lessens the detrimental effects of TDP-43 pathology on lifespan, but extends survival of the glial cells. Thus TDP-43 pathology in astrocytes or PNG causes systemic effects that shorten lifespan and SF2/SRSF1 knockdown rescues the loss of these glia, and also reduces their systemic toxicity to the organism.

Dysregulated glial genes in Alzheimer's disease are essential for homeostatic plasticity: Evidence from integrative epigenetic and single cell analyses.

Synaptic homeostatic plasticity is a foundational regulatory mechanism that maintains the stability of synaptic and neural functions within the nervous system. Impairment of homeostatic regulation has been linked to synapse destabilization during the progression of Alzheimer's disease (AD). Recent epigenetic and transcriptomic characterizations of the nervous system have revealed intricate molecular details about the aging brain and the pathogenesis of neurodegenerative diseases. Yet, how abnormal epigenetic and transcriptomic alterations in different cell types in AD affect synaptic homeostatic plasticity remains to be elucidated. Various glial cell types play critical roles in modulating synaptic functions both during the aging process and in the context of AD. Here, we investigated the impact of glial dysregulation of histone acetylation and transcriptome in AD on synaptic homeostatic plasticity, using computational analysis combined with electrophysiological methods in Drosophila. By integrating snRNA-seq and H3K9ac ChIP-seq data from the same AD patient cohort, we pinpointed cell type-specific signature genes that were transcriptionally altered by histone acetylation. We subsequently investigated the role of these glial genes in regulating presynaptic homeostatic potentiation in Drosophila. Remarkably, nine glial-specific genes, which were identified through our computational method as targets of H3K9ac and transcriptional dysregulation, were found to be crucial for the regulation of synaptic homeostatic plasticity in Drosophila. Our genetic evidence connects abnormal glial transcriptomic changes in AD with the impairment of homeostatic plasticity in the nervous system. In summary, our integrative computational and genetic studies highlight specific glial genes as potential key players in the homeostatic imbalance observed in AD.

Atorvastatin rescues hyperhomocysteinemia-induced cognitive deficits and neuroinflammatory gene changes

BackgroundEpidemiological data suggests statins could reduce the risk of dementia, and more specifically, Alzheimer’s disease (AD). Pre-clinical data suggests statins reduce the risk of dementia through their pleiotropic effects rather than their cholesterol lowering effects. While AD is a leading cause of dementia, it is frequently found co-morbidly with cerebral small vessel disease and other vascular contributions to cognitive impairment and dementia (VCID), which are another leading cause of dementia. In this study, we determined if atorvastatin ameliorated hyperhomocysteinemia (HHcy)-induced VCID.MethodsWild-type (C57Bl6/J) mice were placed on a diet to induce HHcy or a control diet each with or without atorvastatin for 14 weeks. Mice underwent novel object recognition testing before tissue collection. Plasma total cholesterol and total homocysteine as well as related metabolites were measured. Using qPCR and NanoString technology, we profiled glial cell-associated gene expression changes. Finally, microglial morphology, astrocyte end feet, and microhemorrhages were analyzed using histological methods.ResultsAtorvastatin treatment of HHcy in mice led to no changes in total cholesterol but decreases in total homocysteine in plasma. While HHcy decreased expression of many glial genes, atorvastatin rescued these gene changes, which mostly occurred in oligodendrocytes and microglia. Microglia in HHcy mice with atorvastatin were trending towards fewer processes compared to control with atorvastatin, but there were no atorvastatin effects on astrocyte end feet. While atorvastatin treatment was trending towards increasing the area of microhemorrhages in HHcy mice in the frontal cortex, it only slightly (non-significantly) reduced the number of microhemorrhages. Finally, atorvastatin treatment in HHcy mice led to improved cognition on the novel object recognition task.ConclusionsThese data suggest that atorvastatin rescued cognitive changes induced by HHcy most likely through lowering plasma total homocysteine and rescuing gene expression changes rather than impacts on vascular integrity or microglial changes.

Microglial and Astrocytic Responses in the Human Midcingulate Cortex in Huntington's Disease.

Patients with Huntington's disease can present with variable difficulties of motor functioning, mood, and cognition. Neurodegeneration occurs in the anterior cingulate cortex of some patients with Huntington's disease and is linked to the presentation of mood symptomatology. Neuroinflammation, perpetrated by activated microglia and astrocytes, has been reported in Huntington's disease and may contribute to disease progression and presentation. This study sought to quantify the density of mutant huntingtin protein and neuroinflammatory glial changes in the midcingulate cortex of postmortem patients with Huntington's disease and determine if either correlates with the presentation of mood, motor, or mixed symptomatology. Free-floating immunohistochemistry quantified 1C2 immunolabeling density as an indicative marker of mutant huntingtin protein, and protein and morphological markers of astrocyte (EAAT2, Cx43, and GFAP), and microglial (Iba1 and HLA-DP/DQ/DR) activation. Relationships among the level of microglial activation, mutant huntingtin burden, and case characteristics were explored using correlative analysis. We report alterations in activated microglia number and morphology in the midcingulate cortex of Huntington's disease cases with predominant mood symptomatology. An increased proportion of activated microglia was observed in the midcingulate of all Huntington's disease cases and positively correlated with 1C2 burden. Alterations in the astrocytic glutamate transporter EAAT2 were observed in the midcingulate cortex of patients associated with mood symptoms. This study presents pathological changes in microglia and astrocytes in the midcingulate cortex in Huntington's disease, which coincide with mood symptom presentation. These findings further the understanding of neuroinflammation in Huntington's disease, a necessary step for developing inflammation-targeted therapeutics. ANN NEUROL 2023;94:895-910.

Biological agents and the aging brain: glial inflammation and neurotoxic signaling.

Neuroinflammation is a universal characteristic of brain aging and neurological disorders, irrespective of the disease state. Glial inflammation mediates this signaling, through astrocyte and microglial polarization from neuroprotective to neurotoxic phenotypes. Glial reactivity results in the loss of homeostasis, as these cells no longer provide support to neurons, in addition to the production of chronically toxic pro-inflammatory mediators. These glial changes initiate an inflammatory brain state that injures the central nervous system (CNS) over time. As the brain ages, glia are altered, including increased glial cell numbers, morphological changes, and either a pre-disposition or inability to become reactive. These alterations induce age-related neuropathologies, ultimately leading to neuronal degradation and irreversible damage associated with disorders of the aged brain, including Alzheimer's Disease (AD) and other related diseases. While the complex interactions of these glial cells and the brain are well studied, the role additional stressors, such as infectious agents, play on age-related neuropathology has not been fully elucidated. Both biological agents in the periphery, such as bacterial infections, or in the CNS, including viral infections like SARS-CoV-2, push glia into neuroinflammatory phenotypes that can exacerbate pathology within the aging brain. These biological agents release pattern associated molecular patterns (PAMPs) that bind to pattern recognition receptors (PRRs) on glial cells, beginning an inflammatory cascade. In this review, we will summarize the evidence that biological agents induce reactive glia, which worsens age-related neuropathology.

Molecular Changes in the Brain of the Wintering Calidris pusilla in the Mangroves of the Amazon River Estuary.

Migrant birds prepare differently to fly north for breeding in the spring and for the flight to lower latitudes during autumn, avoiding the cold and food shortages of the Northern Hemisphere's harsh winter. The molecular events associated with these fundamental stages in the life history of migrants include the differential gene expression in different tissues. Semipalmated sandpipers (Calidris pusilla) are Arctic-breeding shorebirds that migrate to the coast of South America during the non-breeding season. In a previous study, we demonstrated that between the beginning and the end of the wintering period, substantial glial changes and neurogenesis occur in the brain of C. pusilla. These changes follow the epic journey of the autumn migration when a 5-day non-stop transatlantic flight towards the coast of South America and the subsequent preparation for the long-distance flight of the spring migration takes place. Here, we tested the hypothesis that the differential gene expressions observed in the brains of individuals captured in the autumn and spring windows are consistent with the previously described cellular changes. We searched for differential gene expressions in the brain of the semipalmated sandpiper, of recently arrived birds (RA) from the autumnal migration, and that of individuals in the premigratory period (PM) in the spring. All individuals were collected in the tropical coastal of northern Brazil in the mangrove region of the Amazon River estuary. We generated a de novo neurotranscriptome for C. pusilla individuals and compared the gene expressions across libraries. To that end, we mapped an RNA-Seq that reads to the C. pusilla neurotranscriptome in four brain samples of each group and found that the differential gene expressions in newly arrived and premigratory birds were related with neurogenesis, metabolic pathways (ketone body biosynthetic and the catabolic and lipid biosynthetic processes), and glial changes (astrocyte-dopaminergic neuron signaling, astrocyte differentiation, astrocyte cell migration, and astrocyte activation involved in immune response), as well as genes related to the immune response to virus infections (Type I Interferons), inflammatory cytokines (IL-6, IL-1β, TNF, and NF-κB), NLRP3 inflammasome, anti-inflammatory cytokines (IL-10), and cell death pathways (pyroptosis- and caspase-related changes).

Effects of Probiotics on Colitis-Induced Exacerbation of Alzheimer's Disease in AppNL-G-F Mice.

Alzheimer's disease (AD) is characterized by progressive cognitive decline and is a leading cause of death in the United States. Neuroinflammation has been implicated in the progression of AD, and several recent studies suggest that peripheral immune dysfunction may influence the disease. Continuing evidence indicates that intestinal dysbiosis is an attribute of AD, and inflammatory bowel disease (IBD) has been shown to aggravate cognitive impairment. Previously, we separately demonstrated that an IBD-like condition exacerbates AD-related changes in the brains of the AppNL-G-F mouse model of AD, while probiotic intervention has an attenuating effect. In this study, we investigated the combination of a dietary probiotic and an IBD-like condition for effects on the brains of mice. Male C57BL/6 wild type (WT) and AppNL-G-F mice were randomly divided into four groups: vehicle control, oral probiotic, dextran sulfate sodium (DSS), and DSS given with probiotics. As anticipated, probiotic treatment attenuated the DSS-induced colitis disease activity index in WT and AppNL-G-F mice. Although probiotic feeding significantly attenuated the DSS-mediated increase in WT colonic lipocalin levels, it was less protective in the AppNL-G-F DSS-treated group. In parallel with the intestinal changes, combined probiotic and DSS treatment increased microglial, neutrophil elastase, and 5hmC immunoreactivity while decreasing c-Fos staining compared to DSS treatment alone in the brains of WT mice. Although less abundant, probiotic combined with DSS treatment demonstrated a few similar changes in AppNL-G-F brains with increased microglial and decreased c-Fos immunoreactivity in addition to a slight increase in Aβ plaque staining. Both probiotic and DSS treatment also altered the levels of several cytokines in WT and AppNL-G-F brains, with a unique increase in the levels of TNFα and IL-2 being observed in only AppNL-G-F mice following combined DSS and probiotic treatment. Our data indicate that, while dietary probiotic intervention provides protection against the colitis-like condition, it also influences numerous glial, cytokine, and neuronal changes in the brain that may regulate brain function and the progression of AD.

Brain-specific regulatory T cell expansion limits cognitive decline.

Recent work from Lemaitre and colleagues leveraged a central nervous system (CNS)-specific gene delivery approach to expand regulatory T cells (Treg) in aged mice. CNS-restricted Treg expansion reversed age-related glial cell transcriptomic changes and prevented aspects of cognitive decline, unveiling immune modulation as a potential approach to protect cognitive function with age.

THU-364 - Glial transcriptional changes in experimental HE arise early and show similarities with established neuroinflammatory disorders

THU-364 - Glial transcriptional changes in experimental HE arise early and show similarities with established neuroinflammatory disorders

Experimental hepatic encephalopathy causes early but sustained glial transcriptional changes

Hepatic encephalopathy (HE) is a common complication of liver cirrhosis, associated with high morbidity and mortality, for which no brain-targeted therapies exist at present. The interplay between hyperammonemia and inflammation is thought to drive HE development. As such, astrocytes, the most important ammonia-metabolizing cells in the brain, and microglia, the main immunomodulatory cells in the brain, have been heavily implicated in HE development. As insight into cellular perturbations driving brain pathology remains largely elusive, we aimed to investigate cell-type specific transcriptomic changes in the HE brain. In the recently established mouse bile duct ligation (BDL) model of HE, we performed RNA-Seq of sorted astrocytes and microglia at 14 and 28 days after induction. This revealed a marked transcriptional response in both cell types which was most pronounced in microglia. In both cell types, pathways related to inflammation and hypoxia, mechanisms commonly implicated in HE, were enriched. Additionally, astrocytes exhibited increased corticoid receptor and oxidative stress signaling, whereas microglial transcriptome changes were linked to immune cell attraction. Accordingly, both monocytes and neutrophils accumulated in the BDL mouse brain. Time-dependent changes were limited in both cell types, suggesting early establishment of a pathological phenotype. While HE is often considered a unique form of encephalopathy, astrocytic and microglial transcriptomes showed significant overlap with previously established gene expression signatures in other neuroinflammatory diseases like septic encephalopathy and stroke, suggesting common pathophysiological mechanisms. Our dataset identifies key molecular mechanisms involved in preclinical HE and provides a valuable resource for development of novel glial-directed therapeutic strategies.Graphical

Whole-body vibration ameliorates glial pathological changes in the hippocampus of hAPP transgenic mice, but does not affect plaque load

BackgroundAlzheimer’s disease (AD) is the core cause of dementia in elderly populations. One of the main hallmarks of AD is extracellular amyloid beta (Aβ) accumulation (APP-pathology) associated with glial-mediated neuroinflammation. Whole-Body Vibration (WBV) is a passive form of exercise, but its effects on AD pathology are still unknown.MethodsFive months old male J20 mice (n = 26) and their wild type (WT) littermates (n = 24) were used to investigate the effect of WBV on amyloid pathology and the healthy brain. Both J20 and WT mice underwent WBV on a vibration platform or pseudo vibration treatment. The vibration intervention consisted of 2 WBV sessions of 10 min per day, five days per week for five consecutive weeks. After five weeks of WBV, the balance beam test was used to assess motor performance. Brain tissue was collected to quantify Aβ deposition and immunomarkers of astrocytes and microglia.ResultsJ20 mice have a limited number of plaques at this relatively young age. Amyloid plaque load was not affected by WBV. Microglia activation based on IBA1-immunostaining was significantly increased in the J20 animals compared to the WT littermates, whereas CD68 expression was not significantly altered. WBV treatment was effective to ameliorate microglia activation based on morphology in both J20 and WT animals in the Dentate Gyrus, but not so in the other subregions. Furthermore, GFAP expression based on coverage was reduced in J20 pseudo-treated mice compared to the WT littermates and it was significantly reserved in the J20 WBV vs. pseudo-treated animals. Further, only for the WT animals a tendency of improved motor performance was observed in the WBV group compared to the pseudo vibration group.ConclusionIn accordance with the literature, we detected an early plaque load, reduced GFAP expression and increased microglia activity in J20 mice at the age of ~ 6 months. Our findings indicate that WBV has beneficial effects on the early progression of brain pathology. WBV restored, above all, the morphology of GFAP positive astrocytes to the WT level that could be considered the non-pathological and hence “healthy” level. Next experiments need to be performed to determine whether WBV is also affective in J20 mice of older age or other AD mouse models.