Alzheimer's Disease Mouse Brain Research Articles

Emodin inhibits aggregation of amyloid-β peptide 1-42 and improves cognitive deficits in Alzheimer's disease transgenic mice.

Aggregation of amyloid-β peptide 1-42 (Aβ42) initiates the onset of Alzheimer's disease (AD), and all the drugs designed to attenuate AD have failed in clinical trials. Emodin reduces levels of β-amyloid, tau aggregation, oxidative stress, and inflammatory response, demonstrating AD therapeutic potential, whereas its effect on the accumulation of the amyloid-β protein is not well understood. In this work, we investigated emodin activity on Aβ aggregation using a range of biochemical, biophysical, and cell-based approaches. We provide evidence to suggest that emodin blocks Aβ42 fibrillogenesis and Aβ-induced cytotoxicity, displaying a greater effect than that of curcumin. Through adopting three short peptides (Aβ1-16, Aβ17-33, and Aβ28-42), it was proven that emodin interacts with the Leu17-Gly33 sequence. Furthermore, our findings indicated that Val18 and Phe19 in Aβ42 are the target residues with which emodin interacts according amino acid mutation experiments. When fed to 8-month-old B6C3-Tg mice for 2months, high-dose emodin ameliorates cognitive impairment by 60%-70%. Pathological results revealed that levels of Aβ deposition in the brains of AD mice treated with a high dose of emodin decreased by 50%-70%. Therefore, our study indicates that emodin may represent a promising drug for AD treatment.

The Chemokine-like Receptor 1 Deficiency Improves Cognitive Deficits of AD Mice and Attenuates Tau Hyperphosphorylation via Regulating Tau Seeding.

Pathologic features of Alzheimer's disease (AD) include accumulation of amyloid β (Aβ) and hyperphosphorylated tau protein. We have shown previously that the chemokine-like receptor 1 (CMKLR1) is a functional receptor for Aβ, and CMKLR1 contributes to the uptake of Aβ. However, it is unclear whether CMKLR1 ameliorates or aggravates the process of AD. Here, we show that deletion of the gene coding for CMKLR1 significantly increased Aβ deposits in brains of both male and female amyloid β precursor protein/presenilin-1 mice. However, it markedly decreased the mortality of these mice. Behavioral studies found that CMKLR1 deficiency improved cognitive impairment of male and female amyloid β precursor protein/presenilin-1 mice and intracerebroventricular-streptozotocin injection AD mice. We further explored the effect of CMKLR1 on tau pathology. We found that CMKLR1 deficiency or inhibition attenuated the hyperphosphorylation of tau in brains of AD mice in vivo and in the neuronal cells in vitro The expression of CMKLR1 on the neurons affected tau phosphorylation by participating in tau seeding. Together, these results uncover a novel mechanism of CMKLR1 in the pathologic process of AD and suggest that inhibiting the promotion effect of CMKLR1 on tau seeding may provide a new strategy for the treatment of AD.SIGNIFICANCE STATEMENT Evidence suggests that inflammation is involved in the pathologic progression of AD. The chemokine-like receptor 1 (CMKLR1), belonging to the family of GPCRs, is able to bind and uptake amyloid β. We show here, for the first time, that, although CMKLR1 deficiency increased amyloid β deposits in AD mice, it reduced the mortality and improved the cognitive deficits of AD mice. We furthermore show that CMKLR1 deficiency or inhibition attenuated tau hyperphosphorylation in brains of AD model mice in vivo and in neuronal cells in vitro Finally, we first discovered that the expression of CMKLR1 on neurons affected tau phosphorylation by participating in tau seeding. These findings suggest that inhibition of CMKLR1 may provide a new strategy for the treatment of AD.

Brain Dicer1 Is Down-Regulated in a Mouse Model of Alzheimer's Disease Via Aβ42-Induced Repression of Nuclear Factor Erythroid 2-Related Factor 2.

Dicer1 is a microRNA-processing enzyme which plays critical roles in neuronal survival and neuritogenesis. Dicer1 deletion induces neurodegeneration or degeneration in retinal pigment epithelium, which is associated with oxidative stress. Oxidative stress is thought to be central in the pathogenesis of Alzheimer's disease (AD). Therefore, we hypothesize that Dicer1 may play roles in AD. Using immunoblotting and quantitative real-time PCR, Dicer1 protein and mRNA were reduced in the hippocampi of the AD mouse model APPswe/PSEN1dE9 compared with littermate controls. SiRNA-mediated Dicer1 knockdown induced oxidative stress and apoptosis and reduced mitochondrial membrane potential in cultured neurons. Chronic Aβ42 exposure decreased Dicer1 and nuclear factor erythroid 2-related factor 2 (Nrf2) which were reversed by N-acetyl-cystein. Nrf2 overexpression increased Dicer1 mRNA and protein and reverted the Aβ42-induced Dicer1 reduction. We further cloned Dicer1 promoter variants harboring the Nrf2-binding site, the antioxidant response elements (ARE), into a luciferase reporter and found that simultaneous transfection of Nrf2-expressing plasmid increased luciferase expression from these promoter constructs. ChIP assays indicated that Nrf2 directly interacted with the ARE motifs in the Dicer1 promoter. Furthermore, Dicer1 overexpression in cultured neurons reverted Aβ42-induced neurite deficits. Notably, injection of Dicer1-expressing adenovirus into the hippocampus of the mice significantly improved spatial learning. Altogether, we found novel roles of Dicer1 in AD and a novel regulatory pathway for Dicer1. These results suggest that Dicer1 is a target in AD therapy, especially at the early stage of this disorder. In this study, we found that Dicer1 was reduced in the brain of AD mice which is the first report to examine Dicer1 in AD. We further found (i) that Aβ42 exposure decreased Dicer1 via attenuating Nrf2-ARE signaling and (ii) injection of Dicer1-expressing adenovirus into the hippocampus of the AD mice significantly improved spatial learning. Altogether, we found novel roles of Dicer1 in AD and a novel regulatory pathway for Dicer1. This study may open new avenues for investigating potential pathognomonics and pathogenesis in AD.

Mitophagy regulates integrity of mitochondria at synapses and is critical for synaptic maintenance.

Synaptic mitochondria are particularly vulnerable to physiological insults, and defects in synaptic mitochondria are linked to early pathophysiology of Alzheimer's disease (AD). Mitophagy, a cargo-specific autophagy for elimination of dysfunctional mitochondria, constitutes a key quality control mechanism. However, how mitophagy ensures synaptic mitochondrial integrity remains largely unknown. Here, we reveal Rheb and Snapin as key players regulating mitochondrial homeostasis at synapses. Rheb initiates mitophagy to target damaged mitochondria for autophagy, whereas dynein-Snapin-mediated retrograde transport promotes clearance of mitophagosomes from synaptic terminals. We demonstrate that synaptic accumulation of mitophagosomes is a feature in AD-related mutant hAPP mouse brains, which is attributed to increased mitophagy initiation coupled with impaired removal of mitophagosomes from AD synapses due to defective retrograde transport. Furthermore, while deficiency in dynein-Snapin-mediated retrograde transport recapitulates synaptic mitophagy stress and induces synaptic degeneration, elevated Snapin expression attenuates mitochondrial defects and ameliorates synapse loss in AD mouse brains. Taken together, our study provides new insights into mitophagy regulation of synaptic mitochondrial integrity, establishing a foundation for mitigating AD-associated mitochondria deficits and synaptic damage through mitophagy enhancement.

Hippocampus Proteomics and Brain Lipidomics Reveal Network Dysfunction and Lipid Molecular Abnormalities in APP/PS1 Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is closely associated with protein dysfunction and aberrant lipid metabolism in the brain. Our study could be conducive to the discovery of lipid and protein biomarkers for early diagnosis and therapy. In our current work, novel quantitative proteomic and lipidomic methods were developed for the characterization of molecular perturbation occurring in the brain in early stage AD mice. For this purpose, we performed a proteomic and lipidomic screening by liquid chromatography with mass spectrometry. Significant changes were detected, including 231 proteins and 11 lipid compounds in the AD mouse brain. Early stage AD disturbed biological pathways implicated in neuroactive ligand-receptor, complement and coagulation cascades, PI3K-Akt signaling and metabolic pathways, and glycerophospholipid metabolism. The results in the current study suggest that these significantly altered proteins and lipids may be implicated in early stage AD. Our work raises the possibility of AD diagnosis and therapy by providing new protein targets and lipid biomarkers.

Piezoelectric materials for ultrasound-driven dissociation of Alzheimer's β-amyloid aggregate structure

Piezoelectric materials can evoke electrochemical reactions by transferring charge carriers to reactants upon receiving mechanical stimuli. We report a newly discovered function of piezoelectric bismuth oxychloride (BiOCl) nanosheets for dissociating Alzheimer's β-amyloid (Aβ) aggregates through ultrasound-induced redox reactions. The accumulation of Aβ aggregates (e.g., Aβ fibrils, plaques) in the central nervous system is a major pathological hallmark of Alzheimer's disease (AD). Thus, clearing Aβ aggregates is considered a key for treating AD, but the dissociation of Aβ aggregates is challenging due to their extremely robust structure consisting of β-sheets. BiOCl nanosheets are a biocompatible piezoelectric material with piezocatalytic activity in response to ultrasound. Our analyses using multiple spectroscopic and microscopic tools have revealed that BiOCl nanosheets effectively disassemble Aβ fibrils under ultrasound stimulation. Sono-activated BiOCl nanosheets produce piezo-induced oxidative stress, which effectively destabilizes the β-sheets in Aβ fibrils. In vitro evolution has also shown that sono-activated BiOCl nanosheets can effectively alleviate the neuro-toxicity of Aβ fibrils. Furthermore, ex vivo evolution demonstrated that amount of Aβ plaques in AD mouse's brain slices was drastically reduced by treatment with sono-activated BiOCl nanosheets.

A Conditionally Releasable “Do not Eat Me” CD47 Signal Facilitates Microglia‐Targeted Drug Delivery for the Treatment of Alzheimer's Disease

AbstractEfficient brain drug delivery has been a challenge in the treatment of Alzheimer's disease (AD) and other brain disorders as blood‐brain barrier (BBB) impedes most drugs to reach brain. To overcome this obstacle, a novel poly(lactic‐co‐glycolic acid) (PLGA) nanoparticle conjugated with CD47 extracellular domain via reactive oxygen species (ROS)‐responsive phenylborate ester bond exhibiting “do not eat me” signal and BBB penetrating peptide CRTIGPSVC (CRT) and microglia modulation agent Nec‐1s encapsulated in it is developed. The experimental results show that the designed nanoparticle efficiently increases its half‐life in blood circulation by preventing engulfment via phagocytes, and enhances its brain distribution by synergistic effect of CD47 and CRT. The high level of ROS in mouse brain releases CD47 from the nanoparticles and the resultant particles are effectively phagocytized by resident microglia. The engulfed Nec‐1s modulates pathological microglia to a beneficial state, which reduces Aβ burden, microgliosis and astrocytosis, decreases cytokine production and oxidative stress in the brains of AD mice, and finally attenuates cognition deficits and synapse loss. The results first demonstrate that the conditionally releasable “do not eat me” CD47 signal remarkably facilitates microglia‐targeted drug delivery and warrants further study to develop therapeutic agent for AD treatment.

RETRACTED: A new Zn(II)-coordination polymer based on m-terphenyl pentacarboxylic acid ligand for photocatalytic methylene blue degradation and protective effect against Alzheimer’s disease by reducing the inflammatory response and oxidative stress in the nerve cells

Abstract In this work, a novel two-dimensional coordination polymer was prepared via reaction of 4,4′-dipyridyl (4,4′-bipy) with Zn(NO3)2·6H2O and m-terphenyl pentacarboxylic acid (H5L) within water and DMA mixed solvent, and its chemical formula is [Zn2(HL)(4,4′-bipy)(H2O)](DMA) (1). Due to its good framework stability in water, complex 1 was studied as a catalyst for photocatalytic degradation of methylene blue (MB) in water under the ultraviolet light. Both of the remarkable efficiency and good catalytic stability could be achieved in the complex 1. Furthermore, to evaluate the treatment activity of the compound on the Alzheimer's disease (AD), AD mice model was established and treated with the compound. And then, AD mice brain tissues were weighted and the cognitive function of AD mice was determined. Then, the content of amyloid β peptides (Aβ) in the hippocampus was measured with western blot; the inflammatory cytokines TNF-α along with IL-1β within CSF was detected via ELISA detection kit; oxidative stress level within the cells of nerve was determined via ROS test kit. CCK-8 assay was performed to detect the toxicity of the compound on normal human cells.

An activatable near-infrared fluorescent probe for methylglyoxal imaging in Alzheimer's disease mice

Visual detection of the methylglyoxal (MGO) level in the brain is critical for understanding its role in the onset and progression of AD. Herein, we disclosed a NIR fluorescent probe, DBTPP, for detecting MGO by utilizing a thiadiazole-fused o-phenylenediamine moiety as a MGO-specific sensing unit. DBTPP exhibits a series of distinct advantages, such as NIR emission, high selectivity and sensitivity, excellent acid-stability, and a huge off-on ratio. The probe could accurately monitor both exogenous and endogenous MGO variations in SH-SY5Y cells. Besides, it was able to image the endogenous MGO in a transgenic AD mouse model successfully, suggesting the great potential of MGO as a biomarker for early AD diagnosis.

Unambiguous Detection of Elevated Levels of Hypochlorous Acid in Double Transgenic AD Mouse Brain.

Alzheimer's disease (AD) is one of the most prevalent forms of dementia. The current diagnosis methods based on the behavior and cognitive decline or imaging of core biomarkers, namely, amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs), in the brain offer poor to moderate success. Detection and imaging of biomarkers that cause additional traits of pathophysiological aberrations in the brain are invaluable to monitor early disease onset and progression of AD pathology. The pathological hallmark of AD is associated with generation of excessive reactive oxygen species (ROS) in the brain, which aggravate oxidative stress and inflammation. ROS production involves elevated levels of hypochlorous acid (HOCl) and can serve as one of the potential biomarkers for the diagnosis of AD. We report the design, synthesis, and characterization of switchable coumarin-morpholine (CM) conjugates as off-on fluorescence probes for the specific detection of HOCl produced and proximally localized with amyloid plaques. The nonfluorescent thioamide probe CM2 undergoes regioselective transformation to fluorescent amide probe CM1 in the presence of HOCl (∼90-fold fluorescence enhancement and 0.32 quantum yield) with high selectivity and sensitivity (detection limit: 0.17 μM). The excellent cellular uptake and blood-brain barrier (BBB) crossing ability of CM2 allowed unambiguous and differential detection, imaging, and quantification of HOCl in cellular milieu and in the wild type (WT) and AD mouse brains. This study demonstrates the elevated level of HOCl in the AD mouse brain and the potential to expand the repertoire of biomarkers for the diagnosis of AD.

Multilayered N-Glycoproteome Profiling Reveals Highly Heterogeneous and Dysregulated Protein N-Glycosylation Related to Alzheimer's Disease.

Protein N-glycosylation is ubiquitous in the brain and is closely related to cognition and memory. Alzheimer's disease (AD) is a multifactorial disorder that lacks a clear pathogenesis and treatment. Aberrant N-glycosylation has been suggested to be involved in AD pathology. However, the systematic variations in protein N-glycosylation and their roles in AD have not been thoroughly investigated due to technical challenges. Here, we applied multilayered N-glycoproteomics to quantify the global protein expression levels, N-glycosylation sites, N-glycans, and site-specific N-glycopeptides in AD (APP/PS1 transgenic) and wild-type mouse brains. The N-glycoproteomic landscape exhibited highly complex site-specific heterogeneity in AD mouse brains. The generally dysregulated N-glycosylation in AD, which involved proteins such as glutamate receptors as well as fucosylated and oligomannose glycans, were explored by quantitative analyses. Furthermore, functional studies revealed the crucial effects of N-glycosylation on proteins and neurons. Our work provides a systematic multilayered N-glycoproteomic strategy for AD and can be applied to diverse biological systems.

Application of in Vivo Fluorescence Imaging and Metal Ion Detection for Investigation of Bis(ethylmaltolato) Oxidovanadium (IV) on Alzheimer's Disease

Alzheimer's disease (AD) is a major type of dementia in the elderly. Clinical medication at present can only relieve symptoms but has no therapeutical effect. Thus, it is urgent to develop an effective drug for the treatment of AD. In this study, 2-month-old triple transgenic AD model mice (3 × Tg-AD) was treated with 0.2 and 1.0 mM bis(ethylmaltolato) oxidovanadium IV (BEOV) in drinking water for 2 months respectively. The results of open field test, elevated plus-maze test and Y maze test showed that BEOV could significantly improve the exploratory ability, memory capacity and exercise ability and relieve the anxiety of 4-month-old 3 × Tg-AD mice. The dendritic spines of pyramidal neuron in neocortex were detected by in vivo two-photon imaging of YFP and AD-YFP mice (the offspring of 3 × Tg-AD and YFP mice). The numbers of dendritic spines increased in YFP mice but decreased in AD-YFP mice from 2.5-month-old to 3.5-month-old. Treatment with BEOV (1.0 mM) in the AD-YFP mice significantly increased the numbers of total dendritic spines, mushroom spines and thin spines, which suggested that BEOV could protect cortical neurons and reduce the loss of dendritic spines. The contents of metal ions in the brain of mice were further measured by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that BEOV (1.0 mM) could significantly increase the contents of V and Se and decrease the contents of Fe, Zn, Hg, Pb, Bi and Ni in AD brains, implying that vanadium might synergize with selenium to regulate the contents of metal ions in AD mice. Summarily, BEOV could mediate the homeostasis of multiple metal ions in AD brain and protect cortical neurons by reducing the loss of dendritic spines, thus to interfere with the pathological process of AD. BEOV could alleviate the anxiety of AD mice and improve their exploratory ability and memory capacity. Pathogenic study revealed that BEOV could regulate the homeostasis of multiple metal ions and inhibit the loss of dendritic spines in the brain of AD mice, thus interfering with the pathological process of AD.

Multimodal Imaging of Amyloid Plaques: Fusion of the Single-Probe Mass Spectrometry Image and Fluorescence Microscopy Image.

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. The formation of amyloid plaques by aggregated amyloid beta (Aβ) peptides is a primary event in AD pathology. Understanding the metabolomic features and related pathways is critical for studying plaque-related pathological events (e.g., cell death and neuron dysfunction). Mass spectrometry imaging (MSI), due to its high sensitivity and ability to obtain the spatial distribution of metabolites, has been applied to AD studies. However, limited studies of metabolites in amyloid plaques have been performed due to the drawbacks of the commonly used techniques such as matrix-assisted laser desorption/ionization MSI. In the current study, we obtained high spatial resolution (∼17 μm) MS images of the AD mouse brain using the Single-probe, a microscale sampling and ionization device, coupled to a mass spectrometer under ambient conditions. The adjacent slices were used to obtain fluorescence microscopy images to locate amyloid plaques. The MS image and the fluorescence microscopy image were fused to spatially correlate histological protein hallmarks with metabolomic features. The fused images produced significantly improved spatial resolution (∼5 μm), allowing for the determination of fine structures in MS images and metabolomic biomarkers representing amyloid plaques.

SNX8 Enhances Non-amyloidogenic APP Trafficking and Attenuates Aβ Accumulation and Memory Deficits in an AD Mouse.

Dysregulation of various APP trafficking components in the endosome has been previously implicated in Alzheimer’s disease (AD). Although single nucleotide polymorphisms within the gene locus encoding the endosomal component, SNX8 have been previously associated with AD, how SNX8 levels are altered and its contribution to AD onset is currently unknown. Here, we observe decreased expression of SNX8 in human AD and AD mouse brain. SNX8 predominantly localized to early and late endosomes, where SNX8 overexpression enhanced total APP levels, cell surface APP distribution and consequent soluble APPα cleavage. SNX8 depletion resulted in elevated β-amyloid (Aβ) levels, while SNX8 overexpression reduced Aβ levels in cells and in an APP/PS1 AD mouse model. Importantly, SNX8 overexpression rescued cognitive impairment in APP/PS1 mice. Together, these results implicate a neuroprotective role for SNX8 in enhancing non-amyloidogenic APP trafficking and processing pathways. Given that endosomal dysfunction is an early event in AD, restoration of dysfunctional endosomal components such as SNX8 may be beneficial in future therapeutic strategies.

Development of a novel amyloid specific gadolinium contrast agent for MR imaging modality in alzheimer's disease mouse brain

Development of a novel amyloid specific gadolinium contrast agent for MR imaging modality in alzheimer's disease mouse brain

Activatable Small-Molecule Photoacoustic Probes that Cross the Blood-Brain Barrier for Visualization of Copper(II) in Mice with Alzheimer's Disease.

Copper enrichment in the brain is highly related to Alzheimer's disease (AD) pathogenesis, but in vivo tracing of Cu2+ in the brain by imaging techniques is still a great challenge. In this work, we developed a series of activatable photoacoustic (PA) probes with low molecular weights (less than 438 Da), RPS1-RPS4, which can specifically chelate with Cu2+ to form radicals with turn-on PA signals in the near-infrared (NIR) region. Introducing the electron-donating group N,N-dimethylaniline into the probe was found to significantly enhance the radical stability and PA intensity. The best probe in the series, RPS1, showed a fast response (within seconds) to Cu2+ with high selectivity and a low PA detection limit of 90.9 nm. Owing to the low molecular weight and amphiphilic structure, RPS1 could effectively cross the blood-brain barrier (BBB) and thus allowed us, for the first time, to visualize Cu2+ in vivo via PA imaging in the brains of AD mice.

Activatable Small‐Molecule Photoacoustic Probes that Cross the Blood–Brain Barrier for Visualization of Copper(II) in Mice with Alzheimer's Disease

AbstractCopper enrichment in the brain is highly related to Alzheimer's disease (AD) pathogenesis, but in vivo tracing of Cu2+ in the brain by imaging techniques is still a great challenge. In this work, we developed a series of activatable photoacoustic (PA) probes with low molecular weights (less than 438 Da), RPS1–RPS4, which can specifically chelate with Cu2+ to form radicals with turn‐on PA signals in the near‐infrared (NIR) region. Introducing the electron‐donating group N,N‐dimethylaniline into the probe was found to significantly enhance the radical stability and PA intensity. The best probe in the series, RPS1, showed a fast response (within seconds) to Cu2+ with high selectivity and a low PA detection limit of 90.9 nm. Owing to the low molecular weight and amphiphilic structure, RPS1 could effectively cross the blood–brain barrier (BBB) and thus allowed us, for the first time, to visualize Cu2+ in vivo via PA imaging in the brains of AD mice.

Glutaminyl cyclase inhibitor exhibits anti-inflammatory effects in both AD and LPS-induced inflammatory model mice

Up-regulated glutaminyl cyclase (QC) plays crucial roles in the initiation of Alzheimer's disease (AD) and kinds of chronic diseases mediated by inflammation. QC is supposed as a novel target for the therapeutics of these diseases. Here, we explored the anti-inflammation effects of diphenyl conjugated imidazole (DPCI) derivatives which were previously designed, synthesized and evaluated as novel QC inhibitors for AD treatment in our lab. Behavioral tests, QC activity assay, histology and ELISA analysis were conducted on both AD and lipopolysaccharides (LPS)-induced inflammatory model mice. It was shown that behavioral and cognitive performance in AD mice treated with the selected compound DPCI-23 were enhanced notably. QC activity, the formation of pE-Aβ and Aβ plaques and the activation of astrocytes and microglia cells in AD mice brains were inhibited, and the levels of inflammatory factors such as IL-6, IL-1β and TNF-α in serum were reduced remarkably. Furthermore, elevated QC activity in inflammatory mice brains was also inhibited, and levels of IL-1β, IL-1ra, TNF-α and CCL2 in serum, kidneys and brains together with the activated astrocytes and microglia cells in brains were all repressed significantly after the treatment of DPCI-23. These findings observed in this research demonstrated the anti-inflammation potency of DPCI-23 in modal of AD and inflammation by inhibiting QC activity, and may contribute to the employment of QC inhibitors for the prevention and treatment of AD and other inflammatory diseases.

High Aβ load may cause microglial cell dysfunction and reduced nuclear repressor element-1 silencing transcription factor (REST) expression which might be ascribed to its degradation by ubiquitination.

This study aimed to investigate the effects of high Aβ load on the microglial function, neuronal activity, and repressor element-1 silencing transcription factor (REST) expression and nuclear localization and further explore the mechanism underlying nuclear REST deficiency and the correlation between pathology and symptoms in Alzheimer's disease (AD). BV2 cells and N2A cells were treated with Aβ at different concentrations, and the viability, apoptosis and autophagy of these cells were further evaluated. The expression of major histocompatibility complex class II (MHC-II, a marker of microglial activation), REST in the neurons and REST specific phosphorylase casein kinase 1 (CK1) were detected. Aβ at a low concentration (2.5 µmol/L) could alter the microglial morphology, and the proportion of amoebic microglia and protein expression of MHC-II increased in a Aβ concentration dependent manner. Aβ at a high concentration (10 µmol/L) was able to reduce REST expression, elevate the expression of pro-apoptotic and pro-autophagic genes, inhibit the expression of anti-apoptotic gene, and reduce the neuronal activity. REST expression reduced, but CK1 increased in neurons, and CK1 inhibitor significantly increased REST expression. there was co-expression of REST and CK1 in the brain of AD mice, which was characterized by reduced nuclear REST expression and elevated CK1 expression. High Aβ load may cause microglial cell dysfunction and loss of REST expression in the neurons, resulting in dementia. The reduced nuclear REST might be ascribed to its degradation by ubiquitination. This supports the hypothesis that high plaque load may increase the risk for dementia.

Glutaminase C Regulates Microglial Activation and Pro-inflammatory Exosome Release: Relevance to the Pathogenesis of Alzheimer's Disease.

Microglial activation is a key pathogenic process at the onset of Alzheimer’s disease (AD). Identifying regulators of microglial activation bears great potential in elucidating causes and mechanisms of AD and determining candidates for early intervention. Previous studies demonstrate abnormal elevation of glutaminase C (GAC) in HIV-infected or immune-activated microglia. However, whether GAC elevation causes microglial activation remains unknown. In this study, we found heightened expression levels of GAC in early AD mouse brain tissues compared with those in control littermates. Investigations on an in vitro neuroinflammation model revealed that GAC is increased in primary mouse microglia following pro-inflammatory stimulation. To model GAC elevation we overexpressed GAC by plasmid transfection and observed that GAC-overexpression shift the microglial phenotype to a pro-inflammatory state. Treatment with BPTES, a glutaminase inhibitor, reversed LPS-induced microglial activation and inflammation. Furthermore, we discovered that GAC overexpression in mouse microglia increased exosome release and changed exosome content, which includes specific packaging of pro-inflammatory miRNAs that activate microglia. Together, our results demonstrate a causal effect of GAC elevation on microglial activation and exosome release, both of which promote the establishment of a pro-inflammatory microenvironment. Therefore, GAC may have important relevance to the pathogenesis of AD.