Microglial Marker Research Articles

Mesencephalic astrocyte-derived neurotrophic factor (MANF) alleviates cerebral ischemia/reperfusion injury in mice by regulating microglia polarization via A20/NF-κB pathway

Microglia, resident brain immune cells, is critical in inflammation, apoptosis, neurogenesis and neurological recovery during cerebral ischemia/reperfusion (I/R) injury. Mesencephalic astrocyte-derived neurotrophic factor (MANF), a novel identified endoplasmic reticulum stress-inducible neurotrophic factor, can alleviate I/R injury by reducing the inflammatory reaction, but its specific regulatory mechanism on microglia after ischemic stroke has not been fully clarified. To mimic the process of ischemia/reperfusion in vivo and in vitro, middle cerebral artery occlusion/reperfusion (MCAO/R) was induced in C57BL/6J mice and oxygen glucose deprivation/reoxygenation (OGD/R) model was established in BV-2 cells. Moreover, MANF small interfering RNA (siRNA) was used to silence the expression of endogenous MANF, while recombination human MANF protein (rhMANF) acted as an exogenous supplement. Seventy-two hours after MCAO/R, 2,3,5-triphenyltetrazolium staining, neurological scores, brain water content, immunohistochemical staining, immunofluorescent staining, flow cytometry, hematoxylin and eosin staining, quantitative real-time PCR and western blot are applied to evaluate the protective effect and possible mechanism of MANF on cerebral I/R injury. In vitro, cell viability, inflammatory cytokines and the expression of MANF, A20, NF-κB and the markers of microglia were analyzed. The results showed that MANF decreased brain infarct volume, neurological scores, and brain water content. In addition, MANF promoted the polarization of microglia to an anti-inflammatory phenotype both in vivo and in vitro, which are related to A20/NF-κB pathway. In summary, MANF may offer novel therapeutic approaches for ischemic stroke in the process of microglia polarization.

Central activation of the fatty acid sensor GPR120 suppresses microglia reactivity and alleviates sickness- and anxiety-like behaviors

G protein-coupled receptor 120 (GPR120, Ffar4) is a sensor for long-chain fatty acids including omega-3 polyunsaturated fatty acids (n-3 PUFAs) known for beneficial effects on inflammation, metabolism, and mood. GPR120 mediates the anti-inflammatory and insulin-sensitizing effects of n-3 PUFAs in peripheral tissues. The aim of this study was to determine the impact of GPR120 stimulation on microglial reactivity, neuroinflammation and sickness- and anxiety-like behaviors by acute proinflammatory insults. We found GPR120 mRNA to be enriched in both murine and human microglia, and in situ hybridization revealed GPR120 expression in microglia of the nucleus accumbens (NAc) in mice. In a manner similar to or exceeding n-3 PUFAs, GPR120 agonism (Compound A, CpdA) strongly attenuated lipopolysaccharide (LPS)-induced proinflammatory marker expression in primary mouse microglia, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and inhibited nuclear factor-ĸB translocation to the nucleus. Central administration of CpdA to adult mice blunted LPS-induced hypolocomotion and anxiety-like behavior and reduced TNF-α, IL-1β and IBA-1 (microglia marker) mRNA in the NAc, a brain region modulating anxiety and motivation and implicated in neuroinflammation-induced mood deficits. GPR120 agonist pre-treatment attenuated NAc microglia reactivity and alleviated sickness-like behaviors elicited by central injection TNF-α and IL-1β. These findings suggest that microglial GPR120 contributes to neuroimmune regulation and behavioral changes in response to acute infection and elevated brain cytokines. GPR120 may participate in the protective action of n-3 PUFAs at the neural and behavioral level and offers potential as treatment target for neuroinflammatory conditions.

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.

Electroacupuncture stimulation ameliorates cognitive impairment induced by long-term high-fat diet by regulating microglial BDNF

Long-term high-fat diet (HFD) in adolescents leads to impaired hippocampal function and increases the risk of cognitive impairment. Studies have shown that HFD activates hippocampal microglia and induces hippocampal inflammation, which is an important factor for cognitive impairment. Electroacupuncture stimulation (ES), a nerve stimulation therapy, is anti-inflammatory. This study explored its therapeutic potential and mechanism of action in obesity-related cognitive impairment. 4-week-old C57 mice were given either normal or HFD for 22 weeks. At 19 weeks, some of the HFD mice were treated with ES and nigericin sodium salt. The cognitive behavior was assessed through Morris water maze test at 23 weeks. Western blotting was used to detect the expression levels of pro-inflammatory molecules IL-1β and IL-1R, synaptic plasticity related proteins synaptophysin and Postsynaptic Density-95 (PSD-95), and apoptotic molecules (Caspase-3 and Bcl-2), in the hippocampus. The number, morphology, and status of microglia, along with the brain-derived neurotrophic factor（BDNF） content, were analyzed using immunofluorescence. ES treatment improved cognitive deficits in HFD model mice, and decreased the expressions of microglial activation marker, CD68, and microglial BDNF. Inhibition of proinflammatory cytokine, IL-1β, and IL-1R promoted PSD-95 and synaptophysin expressions. Peripheral NLRP3 inflammasome agonist injections exacerbated the cognitive deficits in HFD mice and promoted the expressions of IL-1β and IL-1R in the hippocampus. The microglia showed obvious morphological damage and apoptosis. Collectively, our findings suggest that ES inhibits inflammation, regulates microglial BDNF, and causes remodeling of hippocampal function in mice to counteract obesity-like induced cognitive impairment. Overexcitation of peripheral inflammasome complexes induces hippocampal microglia apoptosis, which hinders the effects of ES.

Endogenous Sox8 is a critical factor for timely remyelination and oligodendroglial cell repletion in the cuprizone model

Genome-wide association studies identified a single nucleotide polymorphism (SNP) downstream of the transcription factor Sox8, associated with an increased risk of multiple sclerosis (MS). Sox8 is known to influence oligodendrocyte terminal differentiation and is involved in myelin maintenance by mature oligodendrocytes. The possible link of a Sox8 related SNP and MS risk, along with the role of Sox8 in oligodendrocyte physiology prompted us to investigate its relevance during de- and remyelination using the cuprizone model. Sox8−/− mice and wildtype littermates received a cuprizone diet for 5 weeks (wk). Sox8−/− mice showed reduced motor performance and weight compared to wildtype controls. Brains were histologically analysed at the maximum of demyelination (wk 5) and on two time points during remyelination (wk 5.5 and wk 6) for oligodendroglial, astroglial, microglial and myelin markers. We identified reduced proliferation of oligodendrocyte precursor cells at wk 5 as well as reduced numbers of mature oligodendrocytes in Sox8−/− mice at wk 6. Moreover, analysis of myelin markers revealed a delay in remyelination in the Sox8−/− group, demonstrating the potential importance of Sox8 in remyelination processes. Our findings present, for the first time, compelling evidence of a significant role of Sox8 in the context of a disease model.

Acute ischemia induces spatially and transcriptionally distinct microglial subclusters

BackgroundDamage in the ischemic core and penumbra after stroke affects patient prognosis. Microglia immediately respond to ischemic insult and initiate immune inflammation, playing an important role in the cellular injury after stroke. However, the microglial heterogeneity and the mechanisms involved remain unclear.MethodsWe first performed single-cell RNA-sequencing (scRNA-seq) and spatial transcriptomics (ST) on middle cerebral artery occlusion (MCAO) mice from three time points to determine stroke-associated microglial subclusters and their spatial distributions. Furthermore, the expression of microglial subcluster-specific marker genes and the localization of different microglial subclusters were verified on MCAO mice through RNAscope and immunofluorescence. Gene set variation analysis (GSVA) was performed to reveal functional characteristics of microglia sub-clusters. Additionally, ingenuity pathway analysis (IPA) was used to explore upstream regulators of microglial subclusters, which was confirmed by immunofluorescence, RT-qPCR, shRNA-mediated knockdown, and targeted metabolomics. Finally, the infarct size, neurological deficits, and neuronal apoptosis were evaluated in MCAO mice after manipulation of specific microglial subcluster.ResultsWe discovered stroke-associated microglial subclusters in the brains of MCAO mice. We also identified novel marker genes of these microglial subclusters and defined these cells as ischemic core-associated (ICAM) and ischemic penumbra-associated (IPAM) microglia, according to their spatial distribution. ICAM, induced by damage-associated molecular patterns, are probably fueled by glycolysis, and exhibit increased pro-inflammatory cytokines and chemokines production. BACH1 is a key transcription factor driving ICAM generation. In contrast, glucocorticoids, which are enriched in the penumbra, likely trigger IPAM formation, which are presumably powered by the citrate cycle and oxidative phosphorylation and are characterized by moderate pro-inflammatory responses, inflammation-alleviating metabolic features, and myelinotrophic properties.ConclusionsICAM could induce excessive neuroinflammation, aggravating brain injury, whereas IPAM probably exhibit neuroprotective features, which could be essential for the homeostasis and survival of cells in the penumbra. Our findings provide a biological basis for targeting specific microglial subclusters as a potential therapeutic strategy for ischemic stroke.

Examining the microglial TSPO phenotype in Alzheimer’s disease

AbstractBackgroundNeuroinflammation is a key pathological feature of Alzheimer’s disease (AD), with microglia being the main inflammatory cell type in the CNS. In order to examine these cells in vivo, PET ligands targeting the microglial translocator protein (TSPO) have been developed. However, it remains unclear the specific target of these ligands, whether this is all microglia or a subset of cells. We aim to elucidate this by identifying the microglial phenotype most associated with TSPO in humans.MethodHuman post‐mortem sections of temporal lobe (TL) and cerebellum (Cb) from cases classified by Braak stage (0‐II, III‐IV, V‐VI; each n = 10) were immunostained for pan‐Aß, pTau, and microglial markers TSPO, Iba1 and HLA‐DR with protein load quantified. Double immunofluorescent staining was performed with TSPO and microglial markers HLA‐DR and CD68 with positive cells counted.ResultTL showed an increase in Aβ (P<0.0001), pTau (P<0.0001) and TSPO (P<0.0001) protein load, but not Iba1 or HLA‐DR, with progressing Braak stage. Aβ (P = 0.0008) and Iba1 (P = 0.012) load increased in the Cb, but not pTau, TSPO or HLA‐DR. Of note, TSPO load in TL was associated with pTau. In both areas, no difference was found in number of HLA+ or CD68+ cells, though TL TSPO+ cell number increased significantly (P = 0.0347). There was no difference in the number of HLA‐DR+/TSPO+ or CD68+/TSPO+ cells with progressing Braak stage. However, significantly more CD68+/TSPO+ than HLA‐DR+/TSPO+ cells were detected in both the TL (P<0.0001) and Cb (P = 0.009) regions.ConclusionThe results suggest that TSPO expression is related to late stage disease (pTau) and microglial phagocytosis (CD68), a function we have previously identified associated with the presence of dementia, cognitive decline and tau pathology. Further additional analysis with other microglial markers is currently ongoing.

Microglial phenotype and proinflammatory gene induction in human prefrontal cortex in Alcohol Use Disorder overlap with Alzheimer’s Disease

AbstractBackgroundAlcohol Use Disorder (AUD) and heavy alcohol abuse are associated with dementia. However, studies focused on Alzheimer’s disease (AD) tend to exclude heavy alcohol drinking patients. We hypothesize microglial phenotype changes in AUD contribute to degeneration that parallels AD.MethodOrbital frontal cortex (OFC) from moderate drinking controls and heavy drinking AUD individuals paired by age were obtained from the New South Wales Tissue Resource Center in Sydney Australia. Tissue blocks were used for RTPCR gene mRNA and paraffin sections for immunohistochemistry assessment of microglial and proinflammatory genes and proteins, respectively. Fluoro‐Jade B, TUNEL stain and neuron marker NeuN were used to assess degeneration.ResultAUD OFC expressed increased levels of proinflammatory HMGB1, RAGE, and multiple Toll‐like receptors (TLR). In addition, AUD OFC increased expression of the TLR adaptor protein myeloid differentiation primary response 88 (MyD88), NFκB, and proinflammatory cytokines, chemokines, and their corresponding receptors. Iba1, a marker of monocytes and microglia, is increased in AUD, but not mRNA levels. Macrophage‐1 antigen, a complement receptor, is increased in AUD cortex as is CX3C chemokine receptor 1 (CX3CR1), the fractalkine receptor. OX42 staining (CD11b) in also increased. Microglial markers P2ry12, and CSF1R also show greater cellular staining in human AUD. The lysosomal scavenger receptor marker CD68 is also increased in AUD cortex. CX3CR1 and CD11b mRNA are increased in AUD cortex, but not CD68. Interestingly, TMEM119, a specific microglial marker, is decreased in AUD, both mRNA and protein staining in contrast to other markers increasing. Assessment of DNA oxidation using 8‐hydroxy‐2'‐deoxyguanosine (8‐OHdG) a biomarker of oxidative DNA/RNA damage 8‐OHdG+IR indicated AUD more than doubled cortical cells with this marker. Induction of HMGB1‐TLR‐MyD88‐NFκB proinflammatory signaling pathways, oxidative stress and microglial activation correlate with markers of neurodegeneration.ConclusionThe increased expression of TLR receptors, MyD88 and NFkB and increased proinflammatory cytokines are consistent with increased microglial activation and oxidative stress induced degeneration. Studies support alcohol activated microglia‐monocytes as driving loss of NeuN and other neurodegeneration markers. The reduced TMEM119 level with other markers increasing may indicate monocytes are replacing microglia in AUD cortex.

Toxoplasma gondii‐induced amyloid reduction and neuroimmune responses in Alzheimer’s disease

AbstractBackgroundToxoplasma gondii is a foodborne parasite that induces monocyte recruitment and microglial activation during infection of the brain. Similarly, in Alzheimer’s disease (AD), activated immune cells are often found in the brain and these localize near amyloid beta plaques. However, after infection with T. gondii in AD mouse models, there are fewer amyloid beta plaques in the brain, increased microglial activation, and decreased severity of AD symptoms. We hypothesize that T. gondii infection activates and enhances the phagocytic ability of microglia to clear amyloid beta.MethodFemale 5xFAD mice were infected with T. gondii or PBS treated, and their brains harvested after 6 weeks of infection. Brain tissue from these animals was analyzed for amyloid (Amyloglo) and immune cell markers for microglia, monocytes, and T cells (IBA1, CD68, CD11c, CD11b, CD45, CD3) by light sheet imaging, confocal microscopy, or flow cytometry. Mice were also fitted with headplates and cranial windows and injected with methoxy‐X04 (10 mg/kg) to enable longitudinal imaging of amyloid over the span of infection.ResultConfocal microscopy of brain sections and light sheet imaging of intact brains from infected and uninfected 5xFAD mice have shown increased microglial activation markers (IBA1 and CD68) and decreased amyloid surface area and volume throughout infected brains in infected animals. Infected mouse brains also have increased co‐localization of amyloid and CD68 compared to uninfected mouse brains. Two‐photon imaging reveals that amyloid plaque area in vivo no longer increases in infected mouse brains as early as three weeks post‐infection and lasts as long as thirteen weeks post‐infection. Additionally, after six weeks of infection, we see an increase in Disease Associate Microglia (DAM) by flow cytometry, as well as an influx of other immune cells in the brain of infected mice as compared to PBS treated control mice.ConclusionOur data show that infection with T. gondii increases microglial markers associated with the DAM profile and these cells likely increase phagocytosis of amyloid beta. Infection with T. gondii appears to modulate the neuroimmune environment, including responding microglial cells, resulting in a neuroprotective phenotype.

Basic Science and Pathogenesis - Part 2.

Genetic studies of Alzheimer's disease (AD) have shown association with microglia in the brain. We probed microglia with markers against amyloid-associated (Clec7a, Axl), inflammatory M1 (CD86), alternatively activated M2 (CD206, CD163), and homeostatic (P2ry12, TMEM119) phenotypes in low plaque/tangle pathology controls (A-T-), high plaque/low tangle pathology controls (A+,T-), high plaque/high tangle pathology controls (HPCs) and late AD samples. We sought to determine how these microglial markers changed with clinical and neuropathological AD. APOE status was also explored as its associated with increased inflammation (suggesting M1 effects) and APOE is highly expressed by amyloid-associated microglia. Samples of parietal cortex from AD patients were cryopreserved in 0.32M sucrose + inhibitors and obtained from the UC Irvine ADRC. The tissue was later thawed, homogenized in 0.32M sucrose + inhibitors and then slow frozen to -80°C. These samples were then processed and probed against targets of interest by western blotting. Preliminary data shows a 64.7% decrease in P2ry12 signal in late AD compared to A-T- controls that approaches significance, although TMEM119 shows no changes. A similar pattern is seen in APOE4+(APOE3/4 and 4/4) samples compared to ones that are APOE3/3, with P2ry12 showing a significant decrease while TMEM119 showing no change. CD206 shows a 44.8% decrease in late AD samples relative to A-T- controls, though CD163 shows no difference. CD206 and CD163 do not differ between HPC and late AD samples, nor are they modulated by APOE genotype. Preliminary data suggests a decrease of homeostatic microglial signature with the presence of neuropathological, not clinical, AD, although one of the markers, TMEM119, showed no change. TMEM119 and P2ry12 are interesting markers of homeostasis that were characterized in mouse models of AD yet may have a more complicated connection to human disease (Zhou et. al., 2020). M2 microglial marker CD206 shows an increase with neuropathological, but not clinical, AD. Again, a complicated picture of M2 markers is seen, with CD206 showing change but not CD163. APOE genotype differences modulated the P2ry12 homeostatic signal, although no M2 changes were seen.

Association between brain [18F]FDG‐PET signal and genetic cell markers in the brain tissue

AbstractBackgroundBrain glucose hypometabolism, indexed by [18F]FDG‐PET, is considered a biomarker of neurodegeneration in Alzheimer’s disease (AD). However, other brain cells, such as astrocytes and microglia, also consume considerable amounts of glucose and may contribute to the [18F]FDG‐PET signal in the brain. Thus, the cellular source of the [18F]FDG‐PET signal remains controversial. Here, we aimed to evaluate whether canonical markers of different brain cell types (neuron, oligodendrocyte, astrocyte, and microglia) associate with brain [18F]FDG‐PET signal in humans and a rat model of human amyloidosis.Method[18F]FDG‐PET images were acquired in ten‐month‐old APP/PS1 (TgF344‐AD, n = 8) and wild‐type (WT, n = 6) rats. Next, we evaluated the gene expression of NeuN, Olig2, GFAP, S100B, and IBA1 in the frontal and temporoparietal cortices and cerebellum. Association maps integrating mRNA with brain [18F]FDG‐PET signal were conducted at the voxel level using RMINC. [18F]FDG‐PET and brain tissue mRNA (GFAP, ACSA2, S100B, GLAST, IBA1, CSF1R, TREM2, Olig2, Cldn11, NeuN) of cognitively unimpaired patients were obtained from ADNI and Allen Brain Atlas database, respectively. In humans, mean regional [18F]FDG‐PET SUVr (reference region: pons) and mRNA expression were used to evaluate their association using a gaussian model. Differences were considered statistically significant at p<0.05 (t>2).ResultGFAP and S100B mRNA levels in the temporoparietal and frontal cortices positively correlated with brain [18F]FDG‐PET signal (local maxima, GFAPt(13) = 9.4, S100Bt(13) = 6.6; Fig1B‐C). No associations were found with TREM2, Olig2 and NeuN (t(13)<2; Fig1D‐F). We expanded our analysis by comparing gene astrocyte markers and astrocyte gene cell markers in humans. At the regional level, we found that FDG‐PET SUVr and astrocyte mRNA were positively associated: S100B (R‐squared = 0.34), GFAP (R‐squared = 0.33), GLAST (R‐squared = 0.31) and ACSA‐2 (R‐squared = 0.31; Fig1G).ConclusionOur findings suggest astrocyte mRNA markers are more closely associated with brain [18F]FDG‐PET signal than neuronal, oligodendrocyte, and microglial mRNA markers.

Etiological contributions of adolescent binge alcohol on onset of Alzheimer’s disease‐associated basal forebrain neuropathology in 5xFAD mice and post‐mortem human AUD brain

AbstractBackgroundHeavy alcohol use is an etiological factor for development of dementia and may contribute to onset of Alzheimer’s disease (AD). Both alcohol use disorder (AUD) and AD share common underlying neuropathology, including basal forebrain cholinergic neuron degeneration and proinflammatory neuroimmune activation, and evidence suggest these systems are particularly sensitive to adolescent alcohol exposure. Using the 5xFAD mouse model of AD, we tested the hypothesis that adolescent intermittent ethanol (AIE), which models human adolescent binge drinking, would accelerate onset of AD‐associated pathology in the adult basal forebrain.MethodIn Experiment 1, non‐transgenic and 5xFAD male and female mice received AIE treatment (5.0 g/kg, i.g. 2‐days on/2‐days off; postnatal day [P]30 – P55) and basal forebrain tissue collected for immunohistochemistry and gene expression analysis on P100. In Experiment 2, 5xFAD female mice received AIE treatment as described above followed by glycyrrhizic acid (GA; 150 mg/L), a high mobility group box 1 (HMGB1) inhibitor, in drinking water from P56 – P100. At study conclusion, basal forebrain tissue was collected for immunohistochemistry and gene expression analysis on P100. In Experiment 3, AD‐associated neuropathology was assessed in the post‐mortem human basal forebrain of individuals with AUD relative to age‐matched moderate drinking CONs.ResultIn Experiment 1, AIE accelerated loss of basal forebrain cholinergic neurons and heterogeneous nuclear ribonucleoprotein (hnRNP) expression in 5xFAD females, but not males, relative to age‐matched 5xFAD CONs. This was accompanied by a female‐specific accelerated accumulation of plaque markers (e.g., Aβ1‐42, Thioflavin‐S, HMGB1) as well as microglial activation and proinflammatory neuroimmune signaling genes (e.g., HMGB1, RAGE) in the adult basal forebrain. In Experiment 2, post‐AIE treatment with the HMGB1 inhibitor GA reversed AIE‐induced accelerated loss of cholinergic neurons, accumulation of plaque markers, and upregulation of microglial activation markers and proinflammatory signaling molecules. In Experiment 3, AUD individuals exhibited decreased cholinergic and hnRNP markers and increased Aβ1‐42 immunoreactivity as well as cholinergic neuron co‐expression with Aβ1‐42 that negatively correlated with an adolescent age of drinking onset.ConclusionThese data reveal that adolescent binge ethanol exposure may be an etiological factor contributing to onset of AD‐associated neuropathology in the adult basal forebrain through HMGB1‐neuroimmune signaling.

Distinct immune signatures associated with sex and genotype in the 15m novel hAPP+hAPOE mouse risk model of Alzheimer’s disease

AbstractBackgroundAlzheimer’s disease research continues to struggle with the translatability of animal models to human patients. Exploring whole systems is integral to early AD biomarker discovery in the pursuit of therapeutics to delay or prevent AD. Previous finds in our lab indicate sex differences in immune transcription levels in human AD brain and in the humanized apolipoprotein E (APOE) mouse model. Herein we investigated the impact of the APOE genotype in a novel mouse model, humanized amyloid precursor protein (APP), and humanized APOE transgenes (Jackson Laboratory).MethodsTo identify immunophenotypes at late‐midlife (15 months: late 40s – early 50s human correlative) a novel hAPP+hAPOE mouse model was utilized: hAPP (5M:5F), hAPP+hAPOE ε3/3 (16M:16F), & hAPP+hAPOE ε4/4 (16M:16F). The brain was hemisected. The left side was processed for multi‐color flow cytometry analysis. Peripheral blood was taken via cardiac puncture. The plasma was isolated and ELISA was used to detect levels of Aβ 40‐42 and pro‐inflammatory cytokines. PBMCs were isolated from the peripheral blood for multi‐color flow cytometry analysis. Microglia (CD45, CD11b), microglia reactivity (MHCII, CD68), phagocytosis (pHrodo), and oxidative stress (CellRox) levels were determined in the brain. Lymphocytes (CD3, CD4, CD8, CD19), lymphocyte activity (CD69), and oxidative stress (CellRox) levels were determined in both the brain and peripheral blood. Midlife endocrine status was determined for the female mice by daily lavage.ResultshAPP+hAPOE ε4/4 animals exhibited accelerated endocrine aging evidence by increased proportion of irregular cycling mice, compared to hAPP hAPOE ε3/3 animals. Microglial activation marker by MHCII was significantly impacted by sex (p<0.0001) and less so by genotype (p = 0.0551). Microglial function measured by pHrodo was impacted by sex (p<0.0001) with hAPP+hAPOE ε3/3 males exhibiting greater phagocytosis in MHCII+ microglia relative to their female counterpart.ConclusionThe interaction between the genotypes APP and APOE in combination with sex has a significant impact on immune phenotypes in the late‐midlife brain. These indications offer unique insights for future targeted therapeutics. Our findings support further investigation into neuroimmune activation in mid‐life to delay or prevent AD.

Association between brain [18F]FDG‐PET signal and genetic cell markers in the brain tissue

AbstractBackgroundBrain glucose hypometabolism, indexed by [18F]FDG‐PET, is considered a biomarker of neurodegeneration in Alzheimer’s disease (AD). However, other brain cells, such as astrocytes and microglia, also consume considerable amounts of glucose and may contribute to the [18F]FDG‐PET signal in the brain. Thus, the cellular source of the [18F]FDG‐PET signal remains controversial. Here, we aimed to evaluate whether canonical markers of different brain cell types (neuron, oligodendrocyte, astrocyte, and microglia) associate with brain [18F]FDG‐PET signal in humans and a rat model of human amyloidosis.Method[18F]FDG‐PET images were acquired in ten‐month‐old APP/PS1 (TgF344‐AD, n = 8) and wild‐type (WT, n = 6) rats. Next, we evaluated the gene expression of NeuN, Olig2, GFAP, S100B, and IBA1 in the frontal and temporoparietal cortices and cerebellum. Association maps integrating mRNA with brain [18F]FDG‐PET signal were conducted at the voxel level using RMINC. [18F]FDG‐PET and brain tissue mRNA (GFAP, ACSA2, S100B, GLAST, IBA1, CSF1R, TREM2, Olig2, Cldn11, NeuN) of cognitively unimpaired patients were obtained from ADNI and Allen Brain Atlas database, respectively. In humans, mean regional [18F]FDG‐PET SUVr (reference region: pons) and mRNA expression were used to evaluate their association using a gaussian model. Differences were considered statistically significant at p<0.05 (t>2).ResultGFAP and S100B mRNA levels in the temporoparietal and frontal cortices positively correlated with brain [18F]FDG‐PET signal (local maxima, GFAPt(13) = 9.4, S100Bt(13) = 6.6; Fig1B‐C). No associations were found with TREM2, Olig2 and NeuN (t(13)<2; Fig1D‐F). We expanded our analysis by comparing gene astrocyte markers and astrocyte gene cell markers in humans. At the regional level, we found that FDG‐PET SUVr and astrocyte mRNA were positively associated: S100B (R‐squared = 0.34), GFAP (R‐squared = 0.33), GLAST (R‐squared = 0.31) and ACSA‐2 (R‐squared = 0.31; Fig1G).ConclusionOur findings suggest astrocyte mRNA markers are more closely associated with brain [18F]FDG‐PET signal than neuronal, oligodendrocyte, and microglial mRNA markers.

Targeting Microglia/Macrophages Notch1 Protects Neurons from Pyroptosis in Ischemic Stroke.

The immune-inflammatory cascade and pyroptosis play an important role in the pathogenesis of cerebral ischemia-reperfusion injury (CIRI). The maintenance of immune homeostasis is inextricably linked to the Notch signaling pathway, but whether myeloid Notch1 affects microglia polarization as well as neuronal pyroptosis in CIRI is not fully understood. This study was designed to clarify the role of myeloid Notch1 in CIRI, providing new therapeutic strategies for ischemic stroke. Myeloid-specific Notch1 knockout (Notch1M-KO) mice and the floxed Notch1 (Notch1FL/FL) mice were subjected to middle cerebral artery occlusion (MCAO). After 3 days of CIRI, we evaluated the neurological deficit score and cerebral infarction volume. Immunofluorescence staining was used to detect the expression of Notch1 and microglial subtype markers. Cerebral infiltrating macrophages were detected by flow cytometry. RT-qPCR was used to detect pro-inflammatory cytokines. Western blot was used to detect the expression of pyroptosis related proteins. The Notch1-siRNA transfected BV2 cells were co-cultured with HT22 cells to investigate the potential mechanisms by which microglial Notch1 affects neuronal pyroptosis induced by anoxia/reoxygenation in vitro. We found that Notch1 was activated in cerebral microglia/macrophages after CIRI. Myeloid Notch1 deficiency decreased the cerebral infarct volume (24.17 ± 3.29 vs. 36.17 ± 2.27, p < 0.001), neurological function scores (2.33 ± 0.47 vs. 3.17 ± 0.37, p < 0.001) and the infiltration of peripheral monocytes/macrophages (3.26 ± 0.53 vs. 5.67 ± 0.57, p < 0.01). Strikingly, myeloid-specific Notch1 knockout alleviated pyroptosis. Compared with microglia M1, increased microglia M2 were detected in the ischemic penumbra. In parallel in vitro co-culture experiments, we found that Notch1 knockdown in microglial BV2 cells inhibited anoxia/reoxygenation-induced JAK2/STAT3 activation and pyroptosis in hippocampal neuron HT22 cells. Our findings elucidate the underlying mechanism of the myeloid Notch1 signaling pathway in regulating neuronal pyroptosis in CIRI, suggesting that targeting myeloid-specific Notch1 is an effective strategy for the treatment of ischemic stroke.

Electroacupuncture improves cognitive dysfunction in rats with Alzheimer's disease by regulating microglial cells.

To observe the effect of electroacupuncture (EA) on microglia (MG), Janus kinase-2 (JAK2) and signal transducer and activator of transcription-3 (STAT3) in hippocampal CA1 region of Alzheimer's di-sease (AD) rats, so as to explore its mechanisms in the treatment of AD. Thirty-six male SD rats were randomly divided into sham operation, model and EA groups, with 12 rats in each group. The AD rat model was established by intraperitoneal injection of D-galactose combined with intrahippocampal injection of aggregated Aβ25-35. The rats in the EA group were given EA (2 Hz/20 Hz, 2 mA) at "Baihui"(GV20) and"Shenting"(GV24) for 30 min, once daily, 6 days a week for 4 weeks. Morris water maze test was used to detect the learning and memory ability and spatial exploration ability of rats. HE staining was used to observe the pathological changes of hippocampus. The ultrastructure of hippocampal neurons was observed by transmission electron microscopy. The positive expression of MG marker io-nized calcium adaptor protein (Iba-1) in hippocampus was observed by immunofluorescence staining. The expression levels of serum inflammatory factor interferon-γ (IFN-γ) and transforming growth factor beta 1 (TGF-β1) were detected by ELISA. The mRNA expression levels of JAK2, STAT3, inducible nitric oxide synthase (iNOS) and arginase-1 (Arg-1) in hippocampal CA1 region were detected by real-time quantitative PCR. The protein and phosphorylation levels of JAK2 and STAT3 in hippocampal CA1 region were detected by Western blot. Compared with the sham operation group, the escape latency of the model group was significantly prolonged (P<0.01), and the number of crossing the original platform was significantly reduced (P<0.01), the positive expression of Iba-1 in CA1 region, the content of serum IFN-γ, the relative mRNA expressions of JAK2, STAT3 and iNOS, and the protein and phosphorylation levels of JAK2 and STAT3 were significantly increased (P<0.01), while the content of serum TGF-β1 and the relative expression of Arg-1 mRNA were significantly decreased (P<0.01). Compared with the model group, the escape latency of rats in the EA group was significantly shortened (P<0.01), the number of crossing the original platform was significantly increased (P<0.01), the positive expression of Iba1, the content of serum IFN-γ, the mRNA expressions of JAK2, STAT3 and iNOS, and the protein and phosphorylation levels of JAK2 and STAT3 were significantly decreased (P<0.05, P<0.01), while the content of serum TGF-β1 and the expression of Arg-1 mRNA were significantly increased (P<0.01). Moreover, pathological and ultrastructural observation showed a reduction in the number of hippocampal neurons, changement of nuclear morphology, dilation of intercellular space, and decreased number of mitochondria in the model group；these situations were relatively milder in the EA group. EA can improve the learning and memory function of AD rats, which may be associated with its functions in decreasing MG activities, and inhibiting the JAK2 / STAT3 signaling pathway in the hippocampus.

Atorvastatin Promotes Pro/anti-inflammatory Phenotypic Transformation of Microglia via Wnt/β-catenin Pathway in Hypoxic-Ischemic Neonatal Rats.

Inflammatory reaction plays a key role in the pathogenesis of hypoxic-ischemic encephalopathy (HIE) in neonates. Microglia are resident innate immune cells in the central nervous system and are profoundly involved in neuroinflammation. Studies have revealed that atorvastatin exerts a neuroprotective effect by regulating neuroinflammation in adult animal models of brain stroke and traumatic brain injury, but its role regarding damage to the developing brain remains unclear. This study aimed to clarify the effect and mechanism of atorvastatin on the regulation of microglia function in neonatal hypoxic-ischemic brain damage (HIBD). The oxygen glucose deprivation (OGD) of microglia and neonatal rat HIBD model was established. Atorvastatin, recombinant sclerostin protein (SOST), and XAV939 (degradation of β-catenin) were administered to OGD microglia and HIBD rats. The pathological changes of brain tissue, cerebral infarction volume, learning and memory ability of rats, pro-inflammatory (CD16+/Iba1+) and anti-inflammatory (CD206+/Iba1+) microglia markers, inflammation-related indicators (Inos, Tnfα, Il6, Arg1, Tgfb, and Mrc1), and Wnt/β-catenin signaling molecules were examined. Atorvastatin reduced OGD-induced pro-inflammatory microglia and pro-inflammatory factors, while increasing anti-inflammatory microglia and anti-inflammatory factors. In vivo, atorvastatin attenuated hypoxia-ischemia (HI)-induced neuroinflammation and brain damage. Mechanistically, atorvastatin decreased SOST expression and activated the Wnt/β-catenin signaling pathway, and the administration of recombinant SOST protein or XAV939 inhibited Wnt/β-catenin signaling and attenuated the anti-inflammatory effect of atorvastatin. Atorvastatin promotes the pro/anti-inflammatory phenotypic transformation of microglia via the Wnt/β-catenin pathway in HI neonatal rats. Atorvastatin may be developed as a potent agent for the treatment of HIE in neonates.

Increased activity of IRE1 improves the clinical presentation of EAE.

Activation of the endoplasmic reticulum (ER)stress sensor inositol-requiring enzyme-1α (IRE1α) contributes to neuronal development and is known to induce neuronal remodeling invitro and invivo. On the contrary, excessive IRE1 activity is often detrimental and may contribute to neurodegeneration. To determine the consequences of increased activation of IRE1α, we used a mouse model expressing a C148S variant of IRE1α with increased and sustained activation. Surprisingly, the mutation did not affect the differentiation of highly secretory antibody-producing cells but exhibited a beneficial effect in a mouse model of experimental autoimmune encephalomyelitis (EAE). Although mechanical allodynia was unaffected, significant improvement in motor function was found in IRE1C148S mice with EAE relative to wild type (WT) mice. Coincident with this improvement, there was reduced microgliosis in the spinal cord of IRE1C148S mice, with reduced expression of proinflammatory cytokine genes. This was accompanied by reduced axonal degeneration and enhanced 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) levels, suggesting improved myelin integrity. Interestingly, while the IRE1C148S mutation is expressed in all cells, the reduction in proinflammatory cytokines and in the microglial activation marker ionized calcium-binding adapter molecule (IBA1), along with preservation of phagocytic gene expression, all point to microglia as the cell type contributing to the clinical improvement in IRE1C148S animals. Our data suggest that sustained increase in IRE1α activity can be beneficial invivo, and that this protection is cell type and context dependent. Considering the overwhelming but conflicting evidence for the role of ER stress in neurological diseases, a better understanding of the function of ER stress sensors in physiological contexts is clearly needed.

Brazilian green propolis prevent Alzheimer’s disease-like cognitive impairment induced by amyloid beta in mice

BackgroundThe increasing incidence of cognitive impairment has become a health problem in the aging society. Owing to its antioxidant and anti-inflammatory properties, Brazilian green propolis—derived from Baccharis dracunculifolia—is anticipated to possess anticognitive properties. However, the preventive effect of Brazilian green propolis on cognitive impairment remains unexplained. This study aimed to investigate the effect of Brazilian green propolis on cognitive impairment using a mouse model of Alzheimer’s disease (AD) induced by intracerebroventricular injection of amyloid beta (Aβ)25‒35.MethodsFive-week-old male Slc:ddY mice were randomly divided into five groups (n = 8). The groups were pretreated with vehicle and propolis at a dose of 100, 300 and 900 mg/kg body weight for 8 days, then AD-like phenotypes were induced by intracerebroventricular (ICV) injection of Aβ25‒35. A sham operation group was set as the control. Memory and learning ability were measured at 7 to 8 days after ICV injection. Gene expression and histological studies were performed at the endpoint of the study.ResultsIn a passive avoidance test, the administration of Brazilian green propolis prevented the impairment of learning and memory function. Furthermore, comprehensive gene expression analysis in the hippocampus and forebrain cortex revealed that Brazilian green propolis suppressed Aβ25–35-induced inflammatory and immune responses. In particular, Brazilian green propolis prevented alterations in gene expressions of microglial and astrocytic markers such as Trem2 and Lcn2 induced by Aβ25‒35 injection, suggesting the suppression of excessive activation of glial cells in the brain. In addition, Brazilian green propolis suppressed the elevation of plasma interleukin (IL)-6 levels induced by Aβ25‒35 injection.ConclusionsThe results suggest that the prophylactic administration of Brazilian green propolis has a preventive effect against AD by suppressing excessive inflammation and immune response in glial cells. To our knowledge, this study is the first to demonstrate that Brazilian green propolis may inhibit the hyperactivation of microglia and astrocytes as a mechanism of action to prevent AD. Thus, it is a promising ingredient for preventing AD-type dementia.

Melatonin-mediated mitophagy protects against long-term impairments after repeated neonatal sevoflurane exposures

BackgroundMelatonin is known to have protective effects in aging, neurodegenerative disorders and mitochondria-related diseases, while there is a poor understanding of the effects of melatonin treatment on mitophagy in neonatal cognitive dysfunction after repeated sevoflurane exposures. This study explores the protective effects of melatonin on mitophagy and cognition in developing rats exposed to sevoflurane. MethodsPostnatal day six (P6) neonatal rats were exposed to 3 % sevoflurane for 2 h daily from P6 to P8. In the intervention groups, rats received 3-Methyladenine (3-MA) intracerebroventricularly from P6 to P8 and melatonin intraperitoneally from P6 to P8 following water drinking once daily from P21 to P41, respectively. Behavioral tests, including open field (OF), novel object recognition (NOR), and fear conditioning (FC) tests, were performed to assess cognitive function during young adulthood. In another experiment, rat brains were harvested for biochemical, histopathological, and electron microscopy studies. ResultsRats exposed to sevoflurane showed disordered mitophagy and mitochondrial dysfunction as revealed by increased mitophagy marker proteins (microtubule-associated protein 1 light chain 3 (LC3) II/I, and parkin), decreased autophagy marker protein (sequestosome 1 (P62/SQSTM1)), electron transport chain (ETC) proteins and ATP levels. Immunofluorescent staining of LC3 was co-localized mostly with a neuronal marker and microglial marker but was not co-localized with a marker for astrocytes in rats exposed to sevoflurane. These rats had poorer performance in the NOR and FC tests than control rats during young adulthood. Melatonin treatment reversed the abnormal expression of mitophagy proteins, mitochondrial energy metabolism, the activity of microglia, and impaired cognition. These ameliorations were blocked by an autophagy inhibitor, 3-MA, except for the activation of microglia. ConclusionWe have demonstrated that melatonin inhibits microglial activation by enhancing mitophagy and finally significantly reduces sevoflurane-induced deficits in cognition in neonatal rats. These results suggest that melatonin might be beneficial if considered when the anesthesia must be administered at a very young age.