Age-related changes in hippocampal AD pathology, actin remodeling proteins and spatial memory behavior of male APP/PS1 mice

The Kv7 channel opener Retigabine reduces neuropathology and alleviates behavioral deficits in APP/PS1 transgenic mice

Hyperexcitability of neuronal networks is central to the pathogenesis of Alzheimer's disease (AD). Pharmacological activation of Kv7 channels is an effective way to reduce neuronal firing. Our results showed that that pharmacologically activating the Kv7 channel with Retigabine (RTG) can alleviate cognitive impairment in mice without affecting spontaneous activity. RTG could also ameliorate damage to the Nissl bodies in cortex and hippocampal CA and DG regions in 9-month-old APP/PS1 mice. Additionally, RTG could reduce the Aβ plaque number in the hippocampus and cortex of both 6-month-old and 9-month-old mice. By recordings of electroencephalogram, we showed that a decrease in the number of abnormal discharges in the brains of the AD model mice when the Kv7 channel was opened. Moreover, Western blot analysis revealed a reduction in the expression of the p-Tau protein in both the hippocampus and cortex upon Kv7 channel opening. These findings suggest that Kv7 channel opener RTG may ameliorate cognitive impairment in AD, most likely by reducing brain excitability.

Selenium alleviates modafinil-induced neurobehavioral toxicity in rat via PI3K/Akt/mTOR/GSK3B signaling pathway and suppression of oxidative stress and apoptosis: in vivo and in silico study

Nonmedical use of modafinil (MOD) led to increased rates of overdose toxicity, road accidents, addiction, withdrawal, suicide, and mental illnesses. The current study aims to determine the probable MOD brain toxicity and elucidate the possible role of selenium (Se) in ameliorating the neurotoxicity in rat models. Fifty-four male Albino rats were randomly assigned into nine groups. The groups were G1 (control negative), G2 (Se0.1), G3 (Se0.2), G4 (MOD300), G5 (MOD600), G6 (Se0.1 + MOD300), G7 (Se0.2 + MOD300), G8 (Se0.1 + MOD600), and G9 (Se0.2 + MOD600). After finishing the experiment, blood and brain tissue were harvested for biochemical and histological investigation. Neurobehavior parameters were assessed. Tissue neurotransmitter levels and oxidative stress markers were assessed. Gene expression of PI3K/Akt/mTOR-GSK3B, orexin, and orexin receptor2 was measured by qRT-PCR. Histological and immunohistochemistry assessments, as well as molecular docking, were carried out. MOD-induced neurobehavioral toxicity exhibited by behavioral and cognitive function impairments, which are associated with decreased antioxidant activities, increased MDA levels, and decreases in neurotransmitter levels. Brain levels of mRNA expression of PI3K, Akt, and mTOR were decreased, while GS3K, orexin, and orexin receptors were significantly elevated. These disturbances were confirmed by histopathological brain changes with increased silver and Bax immunostaining and decreased crystal violet levels. MOD induced neurotoxic effects in a dose-dependent manner. Compared with the MOD groups, SE coadministration significantly attenuates MOD-induced toxic changes. Docking study shows the protective role of Se as an apoptosis inhibitor and inflammation inhibitor. In conclusion, Se could be used as a biologically effective antioxidant compound to protect from MOD neurobehavioral toxicity in Wistar rats by reversing behavioral alterations, inflammation, apoptosis, and oxidative injury.

The effect of hyperthyroidism on cognitive function, neuroinflammation, and necroptosis in APP/PS1 mice

BACKGROUND

Increasing evidence has linked the thyroid dysfunction to the pathogenesis of dementia. Evidence from clinical studies has demonstrated that hypothyroidism is related to an increased risk of dementia. But the association of hyperthyroidism with dementia is largely unknown.

METHODS

We used the adenovirus containing thyrotropin receptor (TSHR) amino acid residues 1-289 (Ad-TSHR289)-induced Graves' disease (GD) phenotype in Alzheimer's disease (AD) model mice (APP/PS1 mice) to evaluate the effect of hyperthyroidism on the cognitive function and β-amyloid (Aβ) accumulation.

RESULTS

GD mice exhibited a stable long-term hyperthyroidism and cognitive deficits. Single Cell RNA-sequencing analysis indicated that microglia function played a critical role in the pathophysiological processes in GD mice. Neuroinflammation and polarization of microglia (M1/M2 phenotype) and activated receptor-interacting serine/threonine protein kinase 3 (RIPK3)/mixed lineage kinase domain-like pseudo-kinase (MLKL)-mediated necroptosis contributed to the pathological process, including Aβ deposition and neuronal loss. RIPK3 inhibitor could inhibit GD-mediated Aβ accumulation and neuronal loss.

CONCLUSIONS

Our findings reveal that GD hyperthyroidism aggravates cognitive deficits in AD mice and induces Aβ deposition and neuronal loss by inducing neuroinflammation and RIPK3/MLKL-mediated necroptosis.

Inhibition of Nogo-A rescues synaptic plasticity and associativity in APP/PS1 animal model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and cognitive decline. Synaptic impairment is one of the first events to occur in the progression of this disease. Synaptic plasticity and cellular association of various plastic events have been shown to be affected in AD models. Nogo-A, a well-known axonal growth inhibitor with a recently discovered role as a plasticity suppressor, and its main receptor Nogo-66 receptor 1 (NGR1) have been found to be overexpressed in the hippocampus of Alzheimer's patients. However, the role of Nogo-A and its receptor in the pathology of AD is still widely unknown. In this work we set out to investigate whether Nogo-A is working as a plasticity suppressor in AD. Our results show that inhibition of the Nogo-A pathway via the Nogo-R antibody in an Alzheimer's mouse model, APP/PS1, leads to the restoration of both synaptic plasticity and associativity in a protein synthesis and NMDR-dependent manner. We also show that inhibition of the p75^NTR pathway, which is strongly associated with NGR1, restores synaptic plasticity as well. Mechanistically, we propose that the restoration of synaptic plasticity in APP/PS1 via inhibition of the Nogo-A pathway is due to the modulation of the RhoA-ROCK2 pathway and increase in plasticity related proteins. Our study identifies Nogo-A as a plasticity suppressor in AD models hence targeting Nogo-A could be a promising strategy to understanding AD pathology.

Dynamic network modeling of gut microbiota during Alzheimer's disease progression in mice

The intimate association between the gut microbiota (GM) and the central nervous system points to potential intervention strategies for neurological diseases. Nevertheless, there is currently no theoretical framework for selecting the window period and target bacteria for GM interventions owing to the complexity of the gut microecosystem. In this study, we constructed a complex network-based modeling approach to evaluate the topological features of the GM and infer the window period and bacterial candidates for GM interventions. We used Alzheimer's disease (AD) as an example and traced the GM dynamic changes in AD and wild-type mice at one, two, three, six, and nine months of age. The results revealed alterations of the topological features of the GM from a scale-free network into a random network during AD progression, indicating severe GM disequilibrium at the late stage of AD. Through stability and vulnerability assessments of the GM networks, we identified the third month after birth as the optimal window period for GM interventions in AD mice. Further computational simulations and robustness evaluations determined that the hub bacteria were potential candidates for GM interventions. Moreover, our GM functional analysis suggested that Lachnospiraceae UCG-001 - the hub and enriched bacterium in AD mice - was the keystone bacterium for GM interventions owing to its contributions to quinolinic acid synthesis. In conclusion, this study established a complex network-based modeling approach as a practical strategy for disease interventions from the perspective of the gut microecosystem.

Neural Oscillation Disorder in the Hippocampal CA1 Region of Different Alzheimer's Disease Mice

BACKGROUND

Alzheimer's disease (AD) is a well-known neurodegenerative disease that gradually induces neural network dysfunction and progressive memory deficits. Neural network activity is represented by rhythmic oscillations that influence local field potentials (LFPs). However, changes in hippocampal neural rhythmic oscillations in the early stage of AD remain largely unexplored.

OBJECTIVE

This study investigated neural rhythmic oscillations in 3-month-old APP/PS1 and 5x- FAD mice to assess early neural connectivity in AD.

METHODS

LFPs were recorded from the hippocampal CA1 region with implanted microelectrode arrays while the mice were in the awake resting stage. Welch fast Fourier transforms, continuous wavelet transforms, and phase-amplitude coupling analyses were used to compute the power density of different frequency bands and phase-amplitude modulation indices in the LFPs.

RESULTS

Our results showed impaired theta, low gamma, and high gamma frequency band power in APP/PS1 and 5xFAD mice during the awake resting stage. AD mice also showed decreased delta, alpha, and beta frequency band power. Impaired theta-low gamma and theta-high gamma phaseamplitude coupling were observed in 5xFAD mice.

CONCLUSION

This study revealed neural network activity differences in oscillation power and cross-frequency coupling in the early stage of AD, providing a new perspective for developing biomarkers for early AD diagnosis.

Anodal transcranial direct current stimulation alleviates cognitive impairment in an APP/PS1 model of Alzheimer's disease in the preclinical stage

Anodal transcranial direct current stimulation (AtDCS) has been shown to alleviate cognitive impairment in an APP/PS1 model of Alzheimer's disease in the preclinical stage. However, this enhancement was only observed immediately after AtDCS, and the long-term effect of AtDCS remains unknown. In this study, we treated 26-week-old mouse models of Alzheimer's disease in the preclinical stage with 10 AtDCS sessions or sham stimulation. The Morris water maze, novel object recognition task, and novel object location test were implemented to evaluate spatial learning memory and recognition memory of mice. Western blotting was used to detect the relevant protein content. Morphological changes were observed using immunohistochemistry and immunofluorescence staining. Six weeks after treatment, the mice subjected to AtDCS sessions had a shorter escape latency, a shorter path length, more platform area crossings, and spent more time in the target quadrant than sham-stimulated mice. The mice subjected to AtDCS sessions also performed better in the novel object recognition and novel object location tests than sham-stimulated mice. Furthermore, AtDCS reduced the levels of amyloid-β42 and glial fibrillary acidic protein, a marker of astrocyte activation, and increased the level of neuronal marker NeuN in hippocampal tissue. These findings suggest that AtDCS can improve the spatial learning and memory abilities and pathological state of an APP/PS1 mouse model of Alzheimer's disease in the preclinical stage, with improvements that last for at least 6 weeks.

Transcranial Direct Current Stimulation Alleviates Neurovascular Unit Dysfunction in Mice With Preclinical Alzheimer’s Disease

Neurons, glial cells and blood vessels are collectively referred to as the neurovascular unit (NVU). In the Alzheimer’s disease (AD) brain, the main components of the NVU undergo pathological changes. Transcranial direct current stimulation (tDCS) can protect neurons, induce changes in glial cells, regulate cerebral blood flow, and exert long-term neuroprotection. However, the mechanism by which tDCS improves NVU function is unclear. In this study, we explored the effect of tDCS on the NVU in mice with preclinical AD and the related mechanisms. 10 sessions of tDCS were given to six-month-old male APP/PS1 mice in the preclinical stage. The model group, sham stimulation group, and control group were made up of APP/PS1 mice and C57 mice of the same age. All mice were histologically evaluated two months after receiving tDCS. Protein content was measured using Western blotting and an enzyme-linked immunosorbent assay (ELISA). The link between glial cells and blood vessels was studied using immunofluorescence staining and lectin staining. The results showed that tDCS affected the metabolism of Aβ; the levels of Aβ, amyloid precursor protein (APP) and BACE1 were significantly reduced, and the levels of ADAM10 were significantly increased in the frontal cortex and hippocampus in the stimulation group. In the stimulation group, tDCS reduced the protein levels of Iba1 and GFAP and increased the protein levels of NeuN, LRP1 and PDGRFβ. This suggests that tDCS can improve NVU function in APP/PS1 mice in the preclinical stage. Increased blood vessel density and blood vessel length, decreased IgG extravasation, and increased the protein levels of occludin and coverage of astrocyte foot processes with blood vessels suggested that tDCS had a protective effect on the blood-brain barrier. Furthermore, the increased numbers of Vimentin, S100 expression and blood vessels (lectin-positive) around Aβ indicated that the effect of tDCS was mediated by astrocytes and blood vessels. There was no significant difference in these parameters between the model group and the sham stimulation group. In conclusion, our results show that tDCS can improve NVU function in APP/PS1 mice in the preclinical stage, providing further support for the use of tDCS as a treatment for AD.

Tangeretin Inhibits BACE1 Activity and Attenuates Cognitive Impairments in AD Model Mice

Tangeretin (TAN) exhibits many bioactivities, including neuroprotective effects. However, the efficacy of TAN in Alzheimer's disease (AD) has not been sufficiently investigated. In the present study, we integrated behavioral tests, pathology assessment, and biochemical analyses to elucidate the antidementia activity of TAN in APPswe/PSEN1dE9 transgenic (Tg) mice. At supplementation levels of 100 mg/kg body weight per day, TAN significantly attenuated the cognitive impairment of Tg mice in behavioral tests. These effects were associated with less synaptic impairments and fewer β-amyloid accumulations after TAN administration. Furthermore, our study revealed that TAN possessed powerful inhibitory activity against β-secretase both in vitro and in vivo, which played a crucial role in the process of Aβ generation. These findings indicate that TAN is a potential drug for preventing AD pathology. The key mechanism underlying the antidementia effect of TAN may include its inhibitory activity against β-secretase.

Sex-specific accelerated decay in time/activity-dependent plasticity and associative memory in an animal model of Alzheimer's disease

Clinical studies have shown that female brains are more predisposed to neurodegenerative diseases such as Alzheimer's disease (AD), but the cellular and molecular mechanisms behind this disparity remain unknown. In several mouse models of AD, synaptic plasticity dysfunction is an early event and appears before significant accumulation of amyloid plaques and neuronal degeneration. However, it is unclear whether sexual dimorphism at the synaptic level contributes to the higher risk and prevalence of AD in females. Our studies on APP/PS1 (APPSwe/PS1dE9) mouse model show that AD impacts hippocampal long‐term plasticity in a sex‐specific manner. Long‐term potentiation (LTP) induced by strong tetanic stimulation (STET), theta burst stimulation (TBS) and population spike timing‐dependent plasticity (pSTDP) show a faster decay in AD females compared with age‐matched AD males. In addition, behavioural tagging (BT), a model of associative memory, is specifically impaired in AD females with a faster decay in memory compared with males. Together with the plasticity and behavioural data, we also observed an upregulation of neuroinflammatory markers, along with downregulation of transcripts that regulate cellular processes associated with synaptic plasticity and memory in females. Immunohistochemistry of AD brains confirms that female APP/PS1 mice carry a higher amyloid plaque burden and have enhanced microglial activation compared with male APP/PS1 mice. Their presence in the diseased mice also suggests a link between the impairment of LTP and the upregulation of the inflammatory response. Overall, our data show that synaptic plasticity and associative memory impairments are more prominent in females and this might account for the faster progression of AD in females.

A dual-targeted multifunctional nanoformulation for potential prevention and therapy of Alzheimer's disease

Antioxidation and adjustable treatment strategies are critical for the effective treatment of Alzheimer's disease (AD). Here, we design a dual-targeted Prussian blue nanoformulation (PTCN) that can cross the blood-brain barrier and target amyloid beta aggregates further exert antioxidant effects. An adjustable gradient dosing strategy with PTCN is used for the first time to design the preventive and therapeutic trials based on the severity of oxidative stress at different AD stages. The results show that PTCN could effectively ameliorate AD-related pathological processes, improve the cognitive decline, and rescue hippocampal atrophy of APP/PS1 mice in both preventive and therapeutic trials. Altogether, PTCN provided here is a successful combination of three traditional biomaterials with good biosafety, which has broad prospects for the early prevention, mild remission, and late treatment of AD, and is expected to be developed into personalized therapeutic drugs and healthcare products for clinical AD in the future.

Dietary lactoferrin has differential effects on gut microbiota in young versus middle-aged APPswe/PS1dE9 transgenic mice but no effects on cognitive function

Background

Existing evidence suggest that lactoferrin might be beneficial for Alzheimer’s disease, while precise mechanisms are not fully elucidated.

Objective

To determine the effects of lactoferrin intervention on cognitive function from APPswe/PS1dE9 (APP/PS1) mice, and potential mechanisms involved.

Design

Both the young and middle-aged male APP/PS1 mice were divided into the control and lactoferrin intervention groups with 16 weeks’ intervention.

Results

Lactoferrin had no effects on cognitive function for both the young and middle-aged mice, and no key markers involved in Aβ, tau pathology, neuro-inflammation and synaptic plasticity were altered after lactoferrin intervention. With regards to gut microbiota profiles, in the young APP/PS1 mice, lactoferrin elevated the α diversity index including ACE and Chao 1, and reduced the relative abundance of the genera Bacteroides and Alistipes and elevated Oscillibacter; in addition, Oscillibacter, Anaerotruncus, EF096579_g, EU454405_g, Mollicutes_RF39, EU474361_g, EU774448_g, and EF096976_g were specifically abundant via linear discriminant analysis with effect size (LEfSe) analysis. In the middle-aged APP/PS1 mice, the relative abundance of the phylum Proteobacteria, as well as the genera Oscillospira, Coprococcus, and Ruminococcus was significantly reduced post lactoferrin; additionally, S24_7, Bacteroidia, Bacteroidetes, and Methylobacterium were specific via LEfSe analysis in the lactoferrin group.

Conclusions

Dietary lactoferrin might be beneficial for gut microbiota homeostasis although it might have no effects on cognition.

Unwanted Exacerbation of the Immune Response in Neurodegenerative Disease: A Time to Review the Impact

The COVID-19 pandemic imposed a series of behavioral changes that resulted in increased social isolation and a more sedentary life for many across all age groups, but, above all, for the elderly population who are the most vulnerable to infections and chronic neurodegenerative diseases. Systemic inflammatory responses are known to accelerate neurodegenerative disease progression, which leads to permanent damage, loss of brain function, and the loss of autonomy for many aged people. During the COVID-19 pandemic, a spectrum of inflammatory responses was generated in affected individuals, and it is expected that the elderly patients with chronic neurodegenerative diseases who survived SARSCoV-2 infection, it will be found, sooner or later, that there is a worsening of their neurodegenerative conditions. Using mouse prion disease as a model for chronic neurodegeneration, we review the effects of social isolation, sedentary living, and viral infection on the disease progression with a focus on sickness behavior and on the responses of microglia and astrocytes. Focusing on aging, we discuss the cellular and molecular mechanisms related to immunosenescence in chronic neurodegenerative diseases and how infections may accelerate their progression.

Thymosin β4 reverses phenotypic polarization of glial cells and cognitive impairment via negative regulation of NF-κB signaling axis in APP/PS1 mice

Background

Thymosin β4 (Tβ4) is the most abundant member of the β-thymosins and plays an important role in the control of actin polymerization in eukaryotic cells. While its effects in multiple organs and diseases are being widely investigated, the safety profile has been established in animals and humans, currently, little is known about its influence on Alzheimer’s disease (AD) and the possible mechanisms. Thus, we aimed to evaluate the effects and mechanisms of Tβ4 on glial polarization and cognitive performance in APP/PS1 transgenic mice.

Methods

Behavior tests were conducted to assess the learning and memory, anxiety and depression in APP/PS1 mice. Thioflavin S staining, Nissl staining, immunohistochemistry/immunofluorescence, ELISA, qRT-PCR, and immunoblotting were performed to explore Aβ accumulation, phenotypic polarization of glial cells, neuronal loss and function, and TLR4/NF-κB axis in APP/PS1 mice.

Results

We demonstrated that Tβ4 protein level elevated in all APP/PS1 mice. Over-expression of Tβ4 alone alleviated AD-like phenotypes of APP/PS1 mice, showed less brain Aβ accumulation and more Insulin-degrading enzyme (IDE), reversed phenotypic polarization of microglia and astrocyte to a healthy state, improved neuronal function and cognitive behavior performance, and accidentally displayed antidepressant-like effect. Besides, Tβ4 could downregulate both TLR4/MyD88/NF-κB p65 and p52-dependent inflammatory pathways in the APP/PS1 mice. While combination drug of TLR4 antagonist TAK242 or NF-κB p65 inhibitor PDTC exerted no further effects.

Conclusions

These results suggest that Tβ4 may exert its function by regulating both classical and non-canonical NF-κB signaling and is restoring its function as a potential therapeutic target against AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02166-3.

Fe65: A Scaffolding Protein of Actin Regulators

The scaffolding protein family Fe65, composed of Fe65, Fe65L1, and Fe65L2, was identified as an interaction partner of the amyloid precursor protein (APP), which plays a key function in Alzheimer’s disease. All three Fe65 family members possess three highly conserved interaction domains, forming complexes with diverse binding partners that can be assigned to different cellular functions, such as transactivation of genes in the nucleus, modulation of calcium homeostasis and lipid metabolism, and regulation of the actin cytoskeleton. In this article, we rule out putative new intracellular signaling mechanisms of the APP-interacting protein Fe65 in the regulation of actin cytoskeleton dynamics in the context of various neuronal functions, such as cell migration, neurite outgrowth, and synaptic plasticity.

System-Level Analysis of Alzheimer's Disease Prioritizes Candidate Genes for Neurodegeneration

Alzheimer’s disease (AD) is a debilitating neurodegenerative disorder. Since the advent of the genome-wide association study (GWAS) we have come to understand much about the genes involved in AD heritability and pathophysiology. Large case-control meta-GWAS studies have increased our ability to prioritize weaker effect alleles, while the recent development of network-based functional prediction has provided a mechanism by which we can use machine learning to reprioritize GWAS hits in the functional context of relevant brain tissues like the hippocampus and amygdala. In parallel with these developments, groups like the Alzheimer’s Disease Neuroimaging Initiative (ADNI) have compiled rich compendia of AD patient data including genotype and biomarker information, including derived volume measures for relevant structures like the hippocampus and the amygdala. In this study we wanted to identify genes involved in AD-related atrophy of these two structures, which are often critically impaired over the course of the disease. To do this we developed a combined score prioritization method which uses the cumulative distribution function of a gene’s functional and positional score, to prioritize top genes that not only segregate with disease status, but also with hippocampal and amygdalar atrophy. Our method identified a mix of genes that had previously been identified in AD GWAS including APOE, TOMM40, and NECTIN2(PVRL2) and several others that have not been identified in AD genetic studies, but play integral roles in AD-effected functional pathways including IQSEC1, PFN1, and PAK2. Our findings support the viability of our novel combined score as a method for prioritizing region- and even cell-specific AD risk genes.

Enhanced Autolysosomal Function Ameliorates the Inflammatory Response Mediated by the NLRP3 Inflammasome in Alzheimer's Disease

The pathogenesis of Alzheimer’s disease (AD) involves activation of many NLRP3 inflammatory bodies, which may be related to amyloid β peptide and aggregation of misfolded proteins. Autophagy is an important regulator of inflammatory bodies. However, autophagy shows dynamic changes in the development of AD, and its role in inflammation remains controversial. In this study, the key link between autophagic disorders and the NLRP3 inflammasome in AD was investigated. APP/PS1 double transgenic mice and C57 mice with Aβ_25–35 injected into the lateral ventricle were used as two animal models of AD. Immunofluorescence staining and Western blot analysis showed that NLRP3 inflammasome-related proteins and inflammatory cytokines, such as IL-1α, IL-1β, IL-6, IL-12, and TNF-α, were increased and microglia were activated in the brains of both AD animal models. Endogenous overexpression of the APPswe gene and exogenous addition of Aβ_25–35 increased the expression of NLRP3 inflammasome-related proteins, while exogenous Aβ_25–35 intervention more significantly activated inflammation. Furthermore, LC3 was increased in the AD animal and cell models, and the level of Lamp1 decreased. After overexpression of the primary regulator of lysosomal biogenesis, TFEB, the lysosome protein Lamp1 was increased, and LC3 and inflammatory protein expression were decreased. These results suggest that the NLRP3 inflammasome-mediated inflammatory response is activated in AD animal and cell models, which may be related to the decline in autolysosome function. Overexpression of the TFEB protein can reduce the inflammatory response by improving autolysosome function in AD model cells.

MicroRNA and mRNA profiling of cerebral cortex in a transgenic mouse model of Alzheimer's disease by RNA sequencing

In a previous study, we found that long non-coding genes in Alzheimer’s disease (AD) are a result of endogenous gene disorders caused by the recruitment of microRNA (miRNA) and mRNA, and that miR-200a-3p and other representative miRNAs can mediate cognitive impairment and thus serve as new biomarkers for AD. In this study, we investigated the abnormal expression of miRNA and mRNA and the pathogenesis of AD at the epigenetic level. To this aim, we performed RNA sequencing and an integrative analysis of the cerebral cortex of the widely used amyloid precursor protein and presenilin-1 double transgenic mouse model of AD. Overall, 129 mRNAs and 68 miRNAs were aberrantly expressed. Among these, eight down-regulated miRNAs and seven up-regulated miRNAs appeared as promising noninvasive biomarkers and therapeutic targets. The main enriched signaling pathways involved mitogen-activated kinase protein, phosphatidylinositol 3-kinase-protein kinase B, mechanistic target of rapamycin kinase, forkhead box O, and autophagy. An miRNA-mRNA network between dysregulated miRNAs and corresponding target genes connected with AD progression was also constructed. These miRNAs and mRNAs are potential biomarkers and therapeutic targets for new treatment strategies, early diagnosis, and prevention of AD. The present results provide a novel perspective on the role of miRNAs and mRNAs in AD. This study was approved by the Experimental Animal Care and Use Committee of Institute of Medicinal Biotechnology of Beijing, China (approval No. IMB-201909-D6) on September 6, 2019.

Acetylation of AMPA Receptors Regulates Receptor Trafficking and Rescues Memory Deficits in Alzheimer's Disease

In Alzheimer's disease (AD), decreases in the amount and synaptic localization of AMPA receptors (AMPARs) result in weakened synaptic activity and dysfunction in synaptic plasticity, leading to impairments in cognitive functions. We have previously found that AMPARs are subject to lysine acetylation, resulting in higher AMPAR stability and protein accumulation. Here we report that AMPAR acetylation was significantly reduced in AD and neurons with Aβ incubation. We identified p300 as the acetyltransferase responsible for AMPAR acetylation and found that enhancing GluA1 acetylation ameliorated Aβ-induced reductions in total and cell-surface AMPARs. Importantly, expression of acetylation mimetic GluA1 (GluA1-4KQ) in APP/PS1 mice rescued impairments in synaptic plasticity and memory. These findings indicate that Aβ-induced reduction in AMPAR acetylation and stability contributes to synaptopathy and memory deficiency in AD, suggesting that AMPAR acetylation may be an effective molecular target for AD therapeutics.

Lychee seed polyphenol protects the blood-brain barrier through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy in bEnd.3 cells and APP/PS1 mice

Blood-brain barrier (BBB) dysfunction has been implicated in Alzheimer's disease (AD) and is closely linked to the release of proinflammatory cytokines in brain capillary endothelial cells. We have previously reported that lychee seed polyphenols (LSP) exerted anti-neuroinflammatory effect. In this study, we aimed to explore the protective effect of LSP on BBB integrity. The monolayer permeability of bEnd.3 cells, and the mRNA level and protein expression of tight junction proteins (TJs), including Claudin 5, Occludin, and ZO-1, were examined. In addition, the inhibition of Aβ(25-35)-induced NLRP3 inflammasome activation, and the autophagy induced by LSP were investigated by detecting the expression of NLRP3, caspase-1, ASC, LC3, AMPK, mTOR, and ULK1. Furthermore, the cognitive function and the expression of TJs, NLRP3, caspase-1, IL-1β, and p62 were determined in APP/PS1 mice. The results showed that LSP significantly decreased the monolayer permeability and inhibited the NLRP3 inflammasome in Aβ(25-35)-induced bEnd3 cells. In addition, LSP induced autophagy via the AMPK/mTOR/ULK1 pathway in bEnd.3 cells, and improved the spatial learning and memory function, increased the TJs expression, and inhibited the expression of NLRP3, caspase-1, IL-1β, and p62 in APP/PS1 mice. Therefore, LSP protects BBB integrity in AD through inhibiting Aβ(25-35)-induced NLRP3 inflammasome activation via the AMPK/mTOR/ULK1-mediated autophagy.

Anodal Transcranial Direct Current Stimulation Can Improve Spatial Learning and Memory and Attenuate Aβ42 Burden at the Early Stage of Alzheimer's Disease in APP/PS1 Transgenic Mice

Alzheimer’s disease (AD) is an irreversible progressive neurodegenerative disease. Intervention in the early stage of AD is a new path for AD treatment that is being explored. The behavioral and pathological effects of anodal transcranial direct current stimulation (AtDCS) at the early stage of AD in the mouse model, amyloid precursor protein (APP)/presenilin-1 (PS1) transgenic mice, were investigated based on our previous studies. Thirty-three 6-month-old male APP/PS1 mice were randomly divided into the model group (AD group), model + sham stimulation group (ADST group) and stimulation group (ADT group). Eleven 6-month-old male C57 wild-type mice were randomly selected as a control group (CTL group). The ADT group received 10 AtDCS sessions. The Morris water maze (MWM) task and novel object recognition (NOR) task were used to test mouse memory. Nissl staining, Western blot (WB), immunohistochemistry and immunofluorescence staining of β-amyloid (Aβ₄₂), glial fibrillary acidic protein (GFAP) and NF200 were conducted for pathological analysis. The ADT group and the CTL group had a shorter escape latency and more platform-region crossings than the AD group and ADST group in the MWM. There was no significant difference in the discrimination index among the groups in the NOR task. Pathological analysis showed visible differences between the AD group and ADT group. This study revealed that early-stage APP/PS1 transgenic mice did not show recognition memory impairment. AtDCS effectively improved spatial learning and memory in the early-stage APP/PS1 transgenic mouse model of AD, alleviating Aβ burden and having a protective effect on neurons. AtDCS could improve AD-related symptoms by activating many glial cells to promote the degradation and clearance of Aβ or directly affecting production and degradation of Aβ to reduce glial activation. AtDCS is an effective means of early intervention in the early stage of AD.

Hippocampal overexpression of SGK1 ameliorates spatial memory, rescues Aβ pathology and actin cytoskeleton polymerization in middle-aged APP/PS1 mice

The increasing occurrence and ineffective treatment of Alzheimer's disease (AD) has become one of the major challenges of the world. Limited studies have shown that serum- and glucocorticoid-inducible kinase 1 (SGK1) is involved in spatial memory formation and consolidation, but its role in AD-like spatial memory impairment and the related mechanisms are not clear. In this study, we first examined the age-related changes of SGK1 in the hippocampus of female APP/PS1 (AD) mice. Based on the finding and our previous finding that significant spatial memory impairment was detected in 8-month old AD mice, SGK1-overexpressing AAV (oSGK1) was constructed and injected into the hippocampus of 9-month old AD mice. One month later, the behavior alterations, Aβ production and deposit as well as changes of CA1 spine density and selected actin polymerization remodeling proteins were examined. The results showed that significant decrease of SGK1 was detected in 10-month old AD mice. The spatial memory impairment, the production and deposit of Aβ were reversed by oSGK1. Levels of hippocampal ADAM10 (α-secretase) and IDE (Aβ degradase), actin remodeling related proteins Rictor, Rac1, Cdc42 and Profilin-1 were significantly increased after oSGK1 treatment while hippocampal BACE1 (γ-secretase) and Cofilin remained unchanged. Taken together, our findings demonstrated a pivotal role of SGK1 in the treatment of AD-related memory impairment through upregulation of non- amyloidogenic processing of APP and degradation of Aβ, increase in spine plasticity related proteins, indicating increase in hippocampal SGK1 may be a potent therapeutic target against AD.