Alzheimer's Disease Mouse Brain Research Articles

Human-mouse proteomics reveals the shared pathways in Alzheimer's disease and delayed protein turnover in the amyloidome.

Murine models of Alzheimer's disease (AD) are crucial for elucidating disease mechanisms but have limitations in fully representing AD molecular complexities. We comprehensively profiled age-dependent brain proteome and phosphoproteome ( n > 10,000 for both) across multiple mouse models of amyloidosis. We identified shared pathways by integrating with human metadata, and prioritized novel components by multi-omics analysis. Collectively, two commonly used models (5xFAD and APP-KI) replicate 30% of the human protein alterations; additional genetic incorporation of tau and splicing pathologies increases this similarity to 42%. We dissected the proteome-transcriptome inconsistency in AD and 5xFAD mouse brains, revealing that inconsistent proteins are enriched within amyloid plaque microenvironment (amyloidome). Determining the 5xFAD proteome turnover demonstrates that amyloid formation delays the degradation of amyloidome components, including Aβ-binding proteins and autophagy/lysosomal proteins. Our proteomic strategy defines shared AD pathways, identify potential new targets, and underscores that protein turnover contributes to proteome-transcriptome discrepancies during AD progression.

Exploration of the pharmacological components and therapeutic mechanisms in treatment of Alzheimer's disease with Polygonati Rhizoma and its processed product using combined analysis of metabolomics, network pharmacology, and gut microbiota

Polygonati Rhizoma (PR, Huangjing in Chinese) and its processed product (PRP), which are used in Traditional Chinese medicine (TCM) for cognitive enhancement and treatment of Alzheimer's disease (AD), have not been fully explored in terms of the different mechanisms underlying their anti-AD effects. Therefore, we used APP/PS1 mice as an AD model to assess the effects of PR and PRP on anxiety-like behaviors, cognitive function, memory performance, and pathological changes in the murine brain. UPLC-HRMS was applied to identify the components of PR and PRP that entered into the blood and brain. Network pharmacology was used to elucidate potential mechanisms underlying the improvement of AD. Differences in the intestinal flora composition between mice treated with PR and PRP were investigated using 16S rRNA sequencing, establishing a correlation between pharmacological components and distinct flora profiles. The results revealed that both PR and PRP interventions ameliorated cognitive deficits and attenuated Amyloid β (Aβ) plaque deposition in the brains of AD mice. Seven specific blood-entering components, namely glutamic acid, Phe-Phe, and uridine, etc., were associated with PR intervention, whereas ten specific blood-entering components including (2R,3S)-3-isopropylmalate, 3-methylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione, and 3-methoxytyrosine were related to PRP intervention. Uridine was identified as a common brain-penetrating component in both PR and PRP interventions. Network pharmacology analysis suggested that the NOD-like receptor signaling pathway, Calcium signaling pathway and Alzheimer's disease were specific pathways targeted in AD treatment using PR intervention. Moreover, the apoptosis pathway was specifically linked to AD treatment during PRP intervention. Furthermore, the administration of both PR and PRP enhanced the abundance and diversity of the intestinal flora in APP/PS1 mice. Western blotting confirmed that PR excels in regulates inflammation, whereas PRP balances autophagy and apoptosis to alleviate the progression of AD. This study offers valuable insights and establishes a robust foundation for further comprehensive exploration of the intrinsic correlation between TCM and AD.

Suppressing UBE2N ameliorates Alzheimer's disease pathology through the clearance of amyloid beta.

Aging is one of the risk factors for the early onset of Alzheimer's disease (AD). We previously discovered that the age-dependent increase in Ubiquitin Conjugating Enzyme E2 N (UBE2N) plays a role in the accumulation of misfolded proteins through K63 ubiquitination, which has been linked to AD pathogenesis. However, the impact of UBE2N on amyloid pathology and clearance has remained unknown. We observed the elevated UBE2N during the amyloid beta (Aβ) generation in the brains of 5×FAD, APP/PS1 mice, and patients with AD, in comparison to healthy individuals. UBE2N overexpression exacerbated amyloid deposition in 5×FAD mice and senescent monkeys, whereas knocking down UBE2N via CRISPR/Cas9 reduced Aβ generation and cognitive deficiency. Moreover, pharmacological inhibition of UBE2N ameliorated Aβ pathology and subsequent transcript defects in 5×FAD mice. We have discovered that age-dependent expression of UBE2N is a critical regulator of AD pathology. Our findings suggest that UBE2N could serve as a potential pharmacological target for the advancement of AD therapeutics. Ubiquitin Conjugating Enzyme E2 N (UBE2N) levelwas elevated during amyloid beta (Aβ) deposition in AD mouse and patients' brains. UBE2N exacerbated Aβ generation in the AD mouse and senescent monkey. Drug inhibition of UBE2N ameliorated Aβ pathology and cognitive deficiency.

Direct and Rapid Visualization of the Spatial Distribution of Cholesterol in Alzheimer's and Cancer Tissue via MALDI Mass Spectrometry Imaging.

Cholesterol is a vital component of the central nervous system and tissues, and understanding its spatial distribution is crucial for biology, pathophysiology, and diagnostics. However, direct imaging of cholesterol using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) remains challenging and time-consuming due to the difficulty in ionizing the sterol molecule. To tackle this issue, a MALDI-MSI method is established for direct and rapid analysis of the spatial distribution of cholesterol in Alzheimer's disease (AD), different cancer tissues and organs via MALDI-MSI. This excellent imaging performance depends on the study and systemic optimization of various conditions that affect the imaging of MALDI-MSI. In this case, we report the distribution and levels of cholesterol across specific structures of the AD mouse brain and different tumor tissue and organs. According to the results, the content of cholesterol in the AD mouse cerebellum, especially in the arborvitae, was significantly higher than that in the wild type (WT) model. Furthermore, we successfully visualize the distribution of cholesterol in other organs, such as the heart, liver, spleen, kidney, pancreas, as well as tumor tissues parenchyma and interstitium using MALDI-MSI. Notably, the attribution of cholesterol MS/MS hydrocarbon fragments was systematically investigated. Our presented optimization strategy and established MALDI-MSI method can be easily generalized for different animal tissues or live samples, thereby facilitating the potential for applications of MALDI-MSI in clinical, medical and biological research.

TGR5 deficiency in excitatory neurons ameliorates Alzheimer's pathology by regulating APP processing.

Bile acids (BAs) metabolism has a significant impact on the pathogenesis of Alzheimer's disease (AD). We found that deoxycholic acid (DCA) increased in brains of AD mice at an early stage. The enhanced production of DCA induces the up-regulation of the bile acid receptor Takeda G protein-coupled receptor (TGR5), which is also specifically increased in neurons of AD mouse brains at an early stage. The accumulation of exogenous DCA impairs cognitive function in wild-type mice, but not in TGR5 knockout mice. This suggests that TGR5 is the primary receptor mediating these effects of DCA. Furthermore, excitatory neuron-specific knockout of TGR5 ameliorates Aβ pathology and cognition impairments in AD mice. The underlying mechanism linking TGR5 and AD pathology relies on the downstream effectors of TGR5 and the APP production, which is succinctly concluded as a "p-STAT3-APH1-γ-secretase" signaling pathway. Our studies identified the critical role of TGR5 in the pathological development of AD.

NMN synbiotics intervention modulates gut microbiota and metabolism in APP/PS1 Alzheimer's disease mouse models

Alzheimer's disease (AD) is a complex neurodegenerative condition with growing evidence implicating the gut microbiota in its pathogenesis. This study aimed to investigate the effects of NMN synbiotics, a combination of β-nicotinamide mononucleotide (NMN), Lactobacillus plantarum, and lactulose, on the gut microbiota composition and metabolic profiles in APP/PS1 transgenic mice. Results demonstrated that NMN synbiotics led to a notable restructuring of the gut microbiota, with a decreased Firmicutes/Bacteroidetes ratio in the AD mice, suggesting a potential amelioration of gut dysbiosis. Alpha diversity indices indicated a reduction in microbial diversity following NMN synbiotics supplementation, while beta diversity analyses revealed a shift towards a more balanced microbial community structure. Functional predictions based on the 16S rRNA data highlighted alterations in metabolic pathways, particularly those related to amino acid and energy metabolism, which are crucial for neuronal health. The metabolomic analysis uncovered a significant impact of NMN synbiotics on the gut metabolome, with normalization of metabolic composition in AD mice. Differential metabolite functions were enriched in pathways associated with neurotransmitter synthesis and energy metabolism, pointing to the potential therapeutic effects of NMN synbiotics in modulating the gut-brain axis and synaptic function in AD. Immunohistochemical staining observed a significant reduction of amyloid plaques formed by Aβ deposition in the brain of AD mice after NMN synbiotics intervention. The findings underscore the potential of using synbiotics to ameliorate the neurodegenerative processes associated with Alzheimer's disease, opening new avenues for therapeutic interventions.

Iterative Design of Near-Infrared Fluorescent Probes for Early Diagnosis of Alzheimer's Disease by Targeting Aβ Oligomers.

Amyloid-β oligomers (AβOs), crucial toxic proteins in early Alzheimer's disease (AD), precede the formation of Aβ plaques and cognitive impairment. In this context, we present our iterative process for developing novel near-infrared fluorescent (NIRF) probes specifically targeting AβOs, aimed at early AD diagnosis. An initial screening identified compound 18 as being highly selective for AβOs. Subsequent analysis revealed that compound 20 improved serum stability while retaining affinity for AβOs. The most promising iteration, compound 37, demonstrated exceptional qualities: a high affinity for AβOs, emission in the near-infrared region, and good biocompatibility. Significantly, ex vivo double staining indicated that compound 37 detected AβOs in AD mouse brain and in vivo imaging experiments showed that compound 37 could differentiate between 4-month-old AD mice and age-matched wild-type mice. Therefore, compound 37 has emerged as a valuable NIRF probe for early detection of AD and a useful tool in exploring AD's pathological mechanisms.

Structural identification and anti-neuroinflammatory effect of a heteropolysaccharide ATP50-3 from Acorus tatarinowii rhizome

Acorus tatarinowii, a famous traditional Chinese medicine, is used for the clinical treatment of memory impairment and dementia. In this research, AT50, the crude polysaccharide extracted from A. tatarinowii rhizome, significantly improved the memory and learning ability of mice with Alzheimer's disease (AD) and exerted excellent anti-neuroinflammatory effects. More importantly, AT50 returned the levels of NO, TNF-α, IL-1β, PGE-2, and IL-6 in AD mouse brains to normal levels. To identify the active ingredients in AT50, a heteropolysaccharide ATP50–3 was obtained from AT50. Structural analysis indicated ATP50–3 consisted of α-L-Araf-(1→, →2)-α-L-Araf-(1→, →3)-α-L-Araf-(1→, →5)-α-L-Araf-(1→, α-D-Xylp-(1→, →3,4)-β-D-Xylp-(1→, →3)-α-D-Galp-(1→, →3,6)-α-D-Galp-(1→, →6)-4-OAc-α-D-Galp-(1→, →3,4,6)-α-D-Galp-(1→, →4)-α-D-Glcp-(1→, →2,3,6)-β-D-Glcp-(1→, →4,6)-α-D-Manp-(1→, →3,4)-α-L-Rhap-(1→, →4)-α-D-GalpA-(1→, and →4)-α-D-GlcpA-(1 → residues and terminated with Xyl and Ara. Additionally, ATP50–3 significantly inhibited the release of proinflammatory factors in lipopolysaccharide-stimulated BV2 cells. ATP50–3 may be an active constituent of AT50, responsible for its anti-neuroinflammatory effects, with great potential to treat AD.

HDAC9-mediated calmodulin deacetylation induces memory impairment in Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive dysfunction and memory impairment. AD pathology involves protein acetylation. Previous studies have mainly focused on histone acetylation in AD, however, the roles of nonhistone acetylation in AD are less explored. The protein acetylation and expression levels were detected by western blotting and co-immunoprecipitation. The stoichiometry of acetylation was measured by home-made and site-specific antibodies against acetylated-CaM (Ac-CaM) at K22, K95, and K116. Hippocampus-dependent learning and memory were evaluated by using the Morris water maze, novel object recognition, and contextual fear conditioning tests. We showed that calmodulin (CaM) acetylation is reduced in plasma of AD patients and mice. CaM acetylation and its target Ca2+ /CaM-dependent kinase II α (CaMKIIα) activity were severely impaired in AD mouse brain. The stoichiometry showed that Ac-K22, K95-CaM acetylation were decreased in AD patients and mice. Moreover, we screened and identified that lysine deacetylase 9 (HDAC9) was the main deacetylase for CaM. In addition, HDAC9 inhibition increased CaM acetylation and CaMKIIα activity, and hippocampus-dependent memory in AD mice. HDAC9-mediated CaM deacetylation induces memory impairment in AD, HDAC9, or CaM acetylation may become potential therapeutic targets for AD.

Impact of aging on copper isotopic composition in the murine brain.

Aging is the main risk factor for Alzheimer's disease (AD). AD is linked to alterations in metal homeostasis and changes in stable metal isotopic composition can occur, possibly allowing the latter to serve as relevant biomarkers for potential AD diagnosis. Copper stable isotopes are used to investigate changes in Cu homeostasis associated with various diseases. Prior work has shown that in AD mouse models, the accumulation of 63Cu in the brain is associated with the disease's progression. However, our understanding of how the normal aging process influences the brain's isotopic composition of copper remains limited. In order to determine the utility and predictive power of Cu isotopes in AD diagnostics, we aim-in this study-to develop a baseline trajectory of Cu isotopic composition in the normally aging mouse brain. We determined the copper concentration and isotopic composition in brains of 30 healthy mice (WT) ranging in age from 6 to 12 mo, and further incorporate prior data obtained for 3-mo-old healthy mice; this range approximately equates to 20-50yr in human equivalency. A significant 65Cu enrichment has been observed in the 12-mo-old mice compared to the youngest group, concomitant with an increase in Cu concentration with age. Meanwhile, literature data for brains of AD mice display an enrichment in 63Cu isotope compared to WT. It is acutely important that this baseline enrichment in 65Cu is fully constrained and normalized against if any coherent diagnostic observations regarding 63Cu enrichment as a biomarker for AD are to be developed.

Ratiometric fluorescence imaging of lysosomal NO in living cells and mice brains with Alzheimer's disease.

We report an integrated ratiometric lysosomal nitric oxide (NO) nanoprobe based on engineered semiconducting polymer dots (Pdots), LyNO-Pdots, which consist of a newly designed NO-responsive dye, a fluorescent conjugated polymer and two functional polymers. The developed probe LyNO-Pdots exhibit high specificity and stability, good photostability and favorable blood-brain barrier (BBB) penetration ability. The LyNO-Pdots are successfully applied to ratiometric imaging of lysosomal NO variations in brain-derived endothelial cells, brain tissues and mice brains with Alzheimer's disease (AD). The results demonstrate that the NO content in the brains of AD mice is considerably higher than that in normal mice.

2-Phenylbenzothiazolyl iridium complexes as inhibitors and probes of amyloid β aggregation.

The aggregation of amyloid β (Aβ) peptides is a significant hallmark of Alzheimer's disease (AD), and the detection of Aβ aggregates and the inhibition of their formation are important for the diagnosis and treatment of AD, respectively. Herein, we report a series of benzothiazole-based Ir(III) complexes HN-1 to HN-8 that exhibit appreciable inhibition of Aβ aggregation in vitro and in living cells. These Ir(III) complexes can induce a significant fluorescence increase when binding to Aβ fibrils and Aβ oligomers, while their measured log D values suggest these compounds could have enhanced blood-brain barrier (BBB) permeability. In vivo studies show that HN-1, HN-2, HN-3, and HN-8 successfully penetrate the BBB and stain the amyloid plaques in AD mouse brains after a 10-day treatment, suggesting that these Ir(III) complexes could act as lead compounds for AD therapeutic and diagnostic agent development.

Terahertz Irradiation Improves Cognitive Impairments and Attenuates Alzheimer’s Neuropathology in the APPSWE/PS1DE9 Mouse: A Novel Therapeutic Intervention for Alzheimer’s Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the deposition of amyloid-β (Aβ), neurofibrillary tangles, neuroinflammation, and neurodegeneration in the brain. In recent years, considering the unsatisfied benefits of pharmacological therapies, non-pharmacological therapy has become a research hotspot for AD intervention. Terahertz (THz) waves with a range between microwave and infrared regions in the electromagnetic spectrum and high permeability to a wide range of materials have great potential in the bioengineering field. However, its biological impacts on the central nervous system, under either physiological or pathological conditions, are poorly investigated. In this study, we first measured the 0.14 THz waves penetration across the skull of a C57BL/6 mouse and found the percentage of THz penetration to be ~70%, guaranteeing that THz waves can reach the relevant brain regions. We then exposed the APPSWE/PS1DE9 mouse model of AD to repeated low-frequency THz waves on the head. We demonstrated that THz waves treatment significantly improved the cognitive impairment and alleviated AD neuropathology including Aβ deposition and tau hyperphosphorylation in the AD mice. Moreover, THz waves treatment effectively attenuated mitochondrial impairment, neuroinflammation, and neuronal loss in the AD mouse brain. Our findings reveal previously unappreciated beneficial effects of THz waves treatment in AD and suggest that THz waves may have the potential to be used as a novel therapeutic intervention for this devastating disease.

Alzheimer's disease-induced phagocytic microglia express a specific profile of coding and non-coding RNAs.

Alzheimer's disease (AD) is a neurodegenerative disease and the main cause of dementia in the elderly. AD pathology is characterized by accumulation of microglia around the beta-amyloid (Aβ) plaques which assumes disease-specific transcriptional signatures, as for the disease-associated microglia (DAM). However, the regulators of microglial phagocytosis are still unknown. We isolated Aβ-laden microglia from the brain of 5xFAD mice for RNA sequencing to characterize the transcriptional signature in phagocytic microglia and to identify the key non-coding RNAs capable of regulating microglial phagocytosis. Through spatial sequencing, we show the transcriptional changes of microglia in the AD mouse brain in relation to Aβ proximity. Finally, we show that phagocytic messenger RNAs are regulated by miR-7a-5p, miR-29a-3p and miR-146a-5p microRNAs and segregate the DAM population into phagocytic and non-phagocytic states. Our study pinpoints key regulators of microglial Aβ clearing capacity suggesting new targets for future therapeutic approaches.

Combination of deep learning and 2D CARS figures for identification of amyloid-β plaques.

In vivo imaging and accurate identification of amyloid-β (Aβ) plaque are crucial in Alzheimer's disease (AD) research. In this work, we propose to combine the coherent anti-Stokes Raman scattering (CARS) microscopy, a powerful detection technology for providing Raman spectra and label-free imaging, with deep learning to distinguish Aβ from non-Aβ regions in AD mice brains in vivo. The 1D CARS spectra is firstly converted to 2D CARS figures by using two different methods: spectral recurrence plot (SRP) and spectral Gramian angular field (SGAF). This can provide more learnable information to the network, improving the classification precision. We then devise a cross-stage attention network (CSAN) that automatically learns the features of Aβ plaques and non-Aβ regions by taking advantage of the computational advances in deep learning. Our algorithm yields higher accuracy, precision, sensitivity and specificity than the results of conventional multivariate statistical analysis method and 1D CARS spectra combined with deep learning, demonstrating its competence in identifying Aβ plaques. Last but not least, the CSAN framework requires no prior information on the imaging modality and may be applicable to other spectroscopy analytical fields.

Interactions of Cellular Energetic Gene Clusters in the Alzheimer's Mouse Brain.

Alzheimer's disease (AD) is the most common cause of dementia in the aging population. The pathological characteristics include extracellular senile plaques and intracellular neurofibrillary tangles. In addition, mitochondrial dysfunction, oxidative stress, and neuroinflammation contribute to AD pathogenesis. In this study, we sought to determine the crosstalk between different pathways in the brain of 5XFAD mice, a mouse model for amyloid pathology, by RNA-seq analysis. We observed significant changes in the expression of genes (1288 genes; adj p value < 0.05; log2-fold > 1 and < 1) related to pathways including oxidation-reduction, oxidative phosphorylation, innate immune response, ribosomal protein synthesis, and ubiquitin proteosome system. The most striking feature was the downregulation of genes related to oxidation-reduction process with changes in the expression of a large number of mitochondrial genes. We also observed an upregulation of several immune response genes. Gene interaction network of oxidation-reduction related genes further confirmed a tight cluster of mitochondrial genes. Furthermore, gene interaction analysis of all the 1288 genes showed at least three distinct interaction clusters, with the predominant one relating to cellular energetics. In summary, we identified 1288 genes distinctly different in the 5XFAD brain compared to the WT brain and found cellular energetics to be the most distinct gene cluster in the AD mouse brain.

Zein-Based Nanoparticles Improve the Therapeutic Efficacy of a TrkB Agonist toward Alzheimer's Disease.

The brain-derived neurotrophic factor (BDNF)/TrkB pathway plays a crucial role in neural plasticity and neuronal survival but is often deficient in neurodegenerative diseases like Alzheimer's disease (AD). CF3CN acts as a specific TrkB agonist that displays therapeutic effects in the AD mouse model, but its brain/plasma ratio (B/P ratio) distribution is not satisfactory. To increase its brain exposure, we synthesized several derivatives and employed nanoparticle (NP) formulation to optimize the most potent #2 derivative's in vivo PK profiles. We generated stable #2-loaded zein/lactoferrin composite NPs (#2/zein/LF) using the antisolvent co-precipitation method. In vivo PK studies revealed that nanoencapsulation improved #2's oral bioavailability by approximately 2-fold and significantly enhanced its plasma Cmax and t1/2, but the brain profiles were comparable. Pharmacodynamics showed that #2/zein/LF activates TrkB signaling that phosphorylates asparagine endopeptidase (AEP) T322 and decreases its enzymatic activity, resulting in reduced AEP-cleaved amyloid precursor protein and Tau fragments in the brains of AD mice, correlating with its PK profiles. After 3 months of treatment in 3xTg mice, #2/zein/LF decreased AD pathologies and alleviated cognitive dysfunction. Hence, zein/LF composite nanoencapsulation is a promising drug delivery method for improving the PK profiles of a potential preclinical candidate for treating neurodegenerative diseases.

Whey protein powder with milk fat globule membrane attenuates Alzheimer's disease pathology in 3×Tg-AD mice by modulating neuroinflammation through the peroxisome proliferator-activated receptor γ signaling pathway

Whey protein powder (PP), which is mainly derived from bovine milk, is rich in milk fat globule membrane (MFGM). The MGFM has been shown to play a role in promoting neuronal development and cognition in the infant brain. However, its role in Alzheimer's disease (AD) has not been elucidated. Here, we showed that the cognitive ability of 3×Tg-AD mice (a triple-transgenic mouse model of AD) could be improved by feeding PP to mice for 3 mo. In addition, PP ameliorated amyloid peptide deposition and tau hyperphosphorylation in the brains of AD mice. We found that PP could alleviate AD pathology by inhibiting neuroinflammation through the peroxisome proliferator-activated receptor γ (PPARγ)-nuclear factor-κB signaling pathway in the brains of AD mice. Our study revealed an unexpected role of PP in regulating the neuroinflammatory pathology of AD in a mouse model.

O-GlcNAcylation regulates extracellular signal-regulated kinase (ERK) activation in Alzheimer's disease.

Aberrant activation of Extracellular Signal-Regulated Kinase (ERK) signaling is associated with Alzheimer's disease (AD) pathogenesis. For example, enhanced ERK signal activation mediated by Apolipoprotein E4 (APOE4), which is a critical genetic risk factor for AD, increases the transcription of amyloid precursor protein (APP). We hypothesize that O-linked N-acetylglucosamine (O-GlcNAc) regulates the phosphorylation and activation of ERK. O-GlcNAc is a single sugar post-translational modification that dynamically cycles on and off proteins in response to nutrient changes by the action of the enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), respectively. However, O-GlcNAc quickly returns to a baseline level after stimulus removal (called O-GlcNAc homeostasis). We did a serum reactivation time-course followed by western blot in SH-SY5Y neuroblastoma cells after long-term O-GlcNAcase (OGA) inhibition by Thiamet-G (TMG) treatment, O-GlcNAc transferase (OGT) knock-down (KD) and OGA KD. Brain tissues of C57BL6/J mice and 5XFAD Alzheimer's disease mice intra-peritoneally injected with TMG for 1 month and C57BL6/J mice intra-peritoneally injected with TMG for 6 months were also used for western blot. We found that ERK1/2 phosphorylation at Thr 202/Tyr204 and Thr183/Tyr185 (p-ERK) are amplified and hence ERK1/2 are activated after long-term OGA inhibition in SH-SY5Y cells. In addition to pharmacological treatment, genetic disruption of O-GlcNAc by OGT KD and OGA KD also increased p-ERK in SH-SY5Y cells suggesting O-GlcNAc homeostasis controls ERK signaling. To determine how O-GlcNAc regulates p-ERK, we probed the expression of phosphorylated mitogen-activated protein kinase-kinase (p-MEK) which phosphorylates and activates ERK and Dual specificity phosphatase-4 (DUSP4) which dephosphorylates and inactivates ERK in SH-SY5Y cells. p-MEK increases in TMG treated and OGT KD cells whereas total DUSP4 decreases in OGT KD and OGA KD cells with serum reactivation time course. Next, we probed the role of OGA inhibition in regulating ERK activation using mice brain-tissue samples. Interestingly, 6-month intra-peritoneal TMG injection in C57BL/6J mice showed an increase in amplitude of p-ERK and APP protein levels, indicating long-term OGA inhibition potentially contributes to AD progression. Furthermore, 1-month TMG injection was sufficient to increase the amplitude of p-ERK in 5XFAD AD mice brains suggesting AD phenotype contributes to the acceleration of ERK activation mediated by OGA inhibition. Together, these results indicate that disruptions to O-GlcNAc homeostasis amplify ERK signal activation in AD.

Micheliolide attenuates neuroinflammation to improve cognitive impairment of Alzheimer's disease by inhibiting NF-κB and PI3K/Akt signaling pathways

Inflammatory reaction in the brain activates glial cells, and over-activated glial cells secrete inflammatory mediators, which aggravates the inflammatory response in the brain and accelerates the development of Alzheimer's disease (AD) in turn. Numerous natural compounds from herbs can alleviate inflammation, and it is very promising to find anti-neuroinflammatory natural compounds. Micheliolide (MCL) is an asesquiterpene lactone. Studies have proved that MCL showed an obvious anti-inflammatory property. Nevertheless, whether MCL can treat AD has not been determined. In this research, AD model mice were fed with a diet supplemented MCL for 3 months, the cognitive ability and inflammatory state of mice were detected. We found that MCL raised the frequency of touching novel objects, cut down the escape latency, raised the number of crossing platform, inhibited the infiltration of inflammatory cells and the secretion of interleukin-1α (IL-1α), IL-12p40, IL-13, IL-17A, tumor necrosis factor-α (TNF-α), granulocyte colony stimulating factor (G-CSF), macrophage inflammatory protein-1α (MIP-1α) and monocyte chemotactic protein-1 (MCP-1) in peripheral blood samples, inhibited the hyperplasia of glial cells and the production of IL-1α, IL-4, G-CSF, granulocyte-macrophage colony stimulating factor (GM-CSF), MIP-1α and MIP-1β, and reduced the deposition of Aβ peptides in the brain of AD mice. We also concluded that MCL dropped the expression of IL-1β, TNF-α, cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and the phosphorylation of IκB, p65 and Akt in BV-2 cells. In conclusion, MCL alleviates the intensity of systemic inflammatory reaction via inhibiting nuclear transcription factor κ gene binding (NF-κB) and phosphoinositide-3-kinase/serine/threonine kinase (PI3K/Akt) pathways in glial cells, and improves the cognitive impairment of AD mice. Therefore, MCL could be a therapeutic candidate for AD.