Synaptic Dysfunction in Alzheimer's Disease: Aβ, Tau, and Epigenetic Alterations

AMPA receptors in Alzheimer disease: Pathological changes and potential therapeutic targets

Alzheimer disease (AD) is a prevalent neurodegenerative disorder that affects synapses and leads to progressive cognitive decline. The role of N-methyl-D-aspartic acid (NMDA) receptors in the pathogenesis of AD is well-established as they contribute to excitotoxicity and neurodegeneration in the pathological process of extrasynaptic glutamate concentration. However, the therapeutic potential of the NMDA receptor antagonist memantine in rescuing synaptic damage is limited. Research indicates that α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors also play a significant role in AD. Abnormal transcription, expression, and localization of AMPA receptors lead to synaptic dysfunction and damage, contributing to early cognitive impairment in AD patients. Understanding the impact of AMPA receptors on AD pathogenesis and exploring the potential for the development of AMPA receptor-targeting drugs are crucial. This review aims to consolidate recent research findings on AMPA receptors in AD, elucidate the current state of AMPA receptor research and lay the foundation for future basic research and drug development.

Stepwise Structural Simplification of the Dihydroxyanthraquinone Moiety of a Multitarget Rhein-Based Anti-Alzheimer Lead to Improve Drug Metabolism and Pharmacokinetic Properties

Multitarget compounds have emerged as promising drug candidates to cope with complex multifactorial diseases, like Alzheimer's disease (AD). Most multitarget compounds are designed by linking two pharmacophores through a tether chain (linked hybrids), which results in rather large molecules that are particularly useful to hit targets with large binding cavities, but at the expense of suffering from suboptimal physicochemical/pharmacokinetic properties. Molecular size reduction by removal of superfluous structural elements while retaining the key pharmacophoric motifs may represent a compromise solution to achieve both multitargeting and favorable physicochemical/PK properties. Here, we report the stepwise structural simplification of the dihydroxyanthraquinone moiety of a rhein-huprine hybrid lead by hydroxy group removal-ring contraction-ring opening-ring removal, which has led to new analogs that retain or surpass the potency of the lead on its multiple AD targets while exhibiting more favorable drug metabolism and pharmacokinetic (DMPK) properties and safety profile. In particular, the most simplified acetophenone analog displays dual nanomolar inhibition of human acetylcholinesterase and butyrylcholinesterase (IC50 = 6 nM and 13 nM, respectively), moderately potent inhibition of human BACE-1 (48% inhibition at 15 µM) and Aβ42 and tau aggregation (73% and 68% inhibition, respectively, at 10 µM), favorable in vitro brain permeation, higher aqueous solubility (18 µM) and plasma stability (100/96/86% remaining in human/mouse/rat plasma after 6 h incubation), and lower acute toxicity in a model organism (zebrafish embryos; LC50 >> 100 µM) than the initial lead, thereby confirming the successful lead optimization by structural simplification.

Hepatotoxicity assessment of innovative nutritional supplements based on olive-oil formulations enriched with natural antioxidants

Introduction

This study focuses on the assessment of extra virgin olive-oil and olive fruit-based formulations enriched with natural antioxidants as potential nutritional supplements for alleviating symptoms and long-term consequences of illnesses whose molecular pathophysiology is affected by oxidative stress and inflammation, such as Alzheimer's disease (AD).

Methods

Besides evaluating cell viability and proliferation capacity of human hepatocellular carcinoma HepG2 cells exposed to formulations in culture, hepatotoxicity was also considered as an additional safety measure using quantitative real-time PCR on RNA samples isolated from the cell cultures and applying approaches of targeted molecular analysis to uncover potential pathway effects through gene expression profiling. Furthermore, the formulations investigated in this work contrast the addition of natural extract with chemical forms and evaluate the antioxidant delivery mode on cell toxicity.

Results

The results indicate minimal cellular toxicity and a significant beneficial impact on metabolic molecular pathways in HepG2 cell cultures, thus paving the way for innovative therapeutic strategies using olive-oil and antioxidants in dietary supplements to minimize the long-term effects of oxidative stress and inflammatory signals in individuals being suffered by disorders like AD.

Discussion

Overall, the experimental design and the data obtained support the notion of applying innovative molecular methodologies and research techniques to evidently advance the delivery, as well as the scientific impact and validation of nutritional supplements and dietary products to improve public health and healthcare outcomes.

Delivering synaptic protein mRNAs via extracellular vesicles ameliorates cognitive impairment in a mouse model of Alzheimer's disease

BACKGROUND

Synaptic dysfunction with reduced synaptic protein levels is a core feature of Alzheimer's disease (AD). Synaptic proteins play a central role in memory processing, learning, and AD pathogenesis. Evidence suggests that synaptic proteins in plasma neuronal-derived extracellular vesicles (EVs) are reduced in patients with AD. However, it remains unclear whether levels of synaptic proteins in EVs are associated with hippocampal atrophy of AD and whether upregulating the expression of these synaptic proteins has a beneficial effect on AD.

METHODS

In this study, we included 57 patients with AD and 56 healthy controls. We evaluated their brain atrophy through magnetic resonance imaging using the medial temporal lobe atrophy score. We measured the levels of four synaptic proteins, including synaptosome-associated protein 25 (SNAP25), growth-associated protein 43 (GAP43), neurogranin, and synaptotagmin 1 in both plasma neuronal-derived EVs and cerebrospinal fluid (CSF). We further examined the association of synaptic protein levels with brain atrophy. We also evaluated the levels of these synaptic proteins in the brains of 5×FAD mice. Then, we loaded rabies virus glycoprotein-engineered EVs with messenger RNAs (mRNAs) encoding GAP43 and SNAP25 and administered these EVs to 5×FAD mice. After treatment, synaptic proteins, dendritic density, and cognitive function were evaluated.

RESULTS

The results showed that GAP43, SNAP25, neurogranin, and synaptotagmin 1 were decreased in neuronal-derived EVs but increased in CSF in patients with AD, and the changes corresponded to the severity of brain atrophy. GAP43 and SNAP25 were decreased in the brains of 5×FAD mice. The engineered EVs efficiently and stably delivered these synaptic proteins to the brain, where synaptic protein levels were markedly upregulated. Upregulation of synaptic protein expression could ameliorate cognitive impairment in AD by promoting dendritic density. This marks the first successful delivery of synaptic protein mRNAs via EVs in AD mice, yielding remarkable therapeutic effects.

CONCLUSIONS

Synaptic proteins are closely related to AD processes. Delivery of synaptic protein mRNAs via EVs stands as a promising effective precision treatment strategy for AD, which significantly advances the current understanding of therapeutic approaches for the disease.

Supplementation of Medium-Chain Triglycerides Combined with Docosahexaenoic Acid Inhibits Amyloid Beta Protein Deposition by Improving Brain Glucose Metabolism in APP/PS1 Mice

The deterioration of brain glucose metabolism predates the clinical onset of Alzheimer's disease (AD). Medium-chain triglycerides (MCTs) and docosahexaenoic acid (DHA) positively improve brain glucose metabolism and decrease the expression of AD-related proteins. However, the effects of the combined intervention are unclear. The present study explored the effects of the supplementation of MCTs combined with DHA in improving brain glucose metabolism and decreasing AD-related protein expression levels in APP/PS1 mice. The mice were assigned into four dietary treatment groups: the control group, MCTs group, DHA group, and MCTs + DHA group. The corresponding diet of the respective groups was fed to mice from the age of 3 to 11 months. The results showed that the supplementation of MCTs combined with DHA could increase serum octanoic acid (C8:0), decanoic acid (C10:0), DHA, and β-hydroxybutyrate (β-HB) levels; improve glucose metabolism; and reduce nerve cell apoptosis in the brain. Moreover, it also aided with decreasing the expression levels of amyloid beta protein (Aβ), amyloid precursor protein (APP), β-site APP cleaving enzyme-1 (BACE1), and presenilin-1 (PS1) in the brain. Furthermore, the supplementation of MCTs + DHA was significantly more beneficial than that of MCTs or DHA alone. In conclusion, the supplementation of MCTs combined with DHA could improve energy metabolism in the brain of APP/PS1 mice, thus decreasing nerve cell apoptosis and inhibiting the expression of Aβ.

CircLPAR1 Promotes Neuroinflammation and Oxidative Stress in APP/PS1 Mice by Inhibiting SIRT1/Nrf-2/HO-1 Axis Through Destabilizing GDF-15 mRNA

Circular RNA LPAR1 (circLPAR1) was revealed to be elevated in Alzheimer's disease (AD); nevertheless, its role and mechanisms in AD remain unknown. Memory performance of APP/PS1 mice was assessed by Morris water maze test. Expression of circLPAR1 and indicated messenger RNA (mRNA) in mouse brain tissues or/and SH-SY5Y cells were tested by quantitative real-time PCR (qRT-PCR). Protein expression of indicated gene was examined by western blot. Production of proinflammatory cytokines (tumor necrosis factor-α, TNF-α; interleukin-6, IL-6; interleukin-1β, IL-1β; and interleukin-8, IL-8) and oxidative stress-related factors (reactive oxygen species, ROS; malondialdehyde, MDA; superoxide dismutase, SOD; and glutathione, GSH) were assessed by commercial kits. RNA pull down and RNA immunoprecipitation were performed to verify the interplay between up-frameshift protein 1 (UPF1) and circLPAR1 or growth differentiation factor 15 (GDF-15). CircLPAR1 was elevated, while GDF-15 was decreased in both APP/PS1 mice and Aβ-treated SH-SY5Y cells. Knockdown of circLPAR1 and overexpression of GDF-15 protected cells against Aβ-caused inflammation, oxidative stress, and neuronal apoptosis. CircLPAR1 knockdown was also proved to improve AD-related pathological traits and ameliorate cognitive dysfunctions in vivo. In mechanism, we found that circLPAR1 repressed GDF-15 expression by decreasing GDF-15 mRNA stability through UPF1 recruitment. Rescue assays suggested that sirtuin 1 (SIRT1) knockdown reversed GDF-15 overexpression-induced inhibition on Aβ-induced neuronal damage and nuclear factor E2-related factor (Nrf-2)/heme oxygenase-1 (HO-1) pathway inhibition. Moreover, the protective effect of circLPAR1 knockdown against Aβ-induced apoptosis was abolished by GDF-15 knockdown, and SIRT1 overexpression could counteract this effect of GDF-15 knockdown. CircLPAR1 knockdown improved AD-related pathological traits in vitro and in vivo by inhibiting SIRT1/Nrf-2/HO-1 axis through GDF-15.

Phospholipase D1 Attenuation Therapeutics Promotes Resilience against Synaptotoxicity in 12-Month-Old 3xTg-AD Mouse Model of Progressive Neurodegeneration

Abrogating synaptotoxicity in age-related neurodegenerative disorders is an extremely promising area of research with significant neurotherapeutic implications in tauopathies including Alzheimer's disease (AD). Our studies using human clinical samples and mouse models demonstrated that aberrantly elevated phospholipase D1 (PLD1) is associated with amyloid beta (Aβ) and tau-driven synaptic dysfunction and underlying memory deficits. While knocking out the lipolytic PLD1 gene is not detrimental to survival across species, elevated expression is implicated in cancer, cardiovascular conditions and neuropathologies, leading to the successful development of well-tolerated mammalian PLD isoform-specific small molecule inhibitors. Here, we address the importance of PLD1 attenuation, achieved using repeated 1 mg/kg of VU0155069 (VU01) intraperitoneally every alternate day for a month in 3xTg-AD mice beginning only from ~11 months of age (with greater influence of tau-driven insults) compared to age-matched vehicle (0.9% saline)-injected siblings. A multimodal approach involving behavior, electrophysiology and biochemistry corroborate the impact of this pre-clinical therapeutic intervention. VU01 proved efficacious in preventing in later stage AD-like cognitive decline affecting perirhinal cortex-, hippocampal- and amygdala-dependent behaviors. Glutamate-dependent HFS-LTP and LFS-LTD improved. Dendritic spine morphology showed the preservation of mushroom and filamentous spine characteristics. Differential PLD1 immunofluorescence and co-localization with Aβ were noted.

Certification of visinin-like protein-1 (VILIP-1) certified reference material by amino acid-based and sulfur-based liquid chromatography isotope dilution mass spectrometry

As an emerging neurodegenerative disease, Alzheimer's disease (AD) has become a leading cause of dementia in older adults. Visinin-like protein-1 (VILIP-1) is an increasingly used biomarker for AD besides the widely accepted Aβ_1-40, Aβ_1-42, and tau. However, significant variations exist in the commercial immuno-based assays for VILIP-1 quantification, underlining the necessity to establish a traceability chain. Certified reference materials (CRMs) located at the top of the traceability chain are traceability sources for relevant matrix standard materials. In this work, VILIP-1 solution CRM with a certified value and uncertainty of 39.82±1.52 μg·g^-1 was developed and certified using amino acid-based isotope dilution mass spectrometry (AA-ID-MS) and sulfur-based isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Certified values from both strategies showed great consistency, with traceability to SI units. Moreover, the candidate VILIP-1 CRM shows excellent homogeneity and can be stable for at least 7 days at -20°C and 12 months at -70°C. The VILIP-1 CRM developed can be used in value assignment to secondary calibrators and clinical matrix CRMs, showing prospects in early diagnosis and disease monitoring for AD.

Carnosic Acid Attenuates AβOs-Induced Apoptosis and Synaptic Impairment via Regulating NMDAR2B and Its Downstream Cascades in SH-SY5Y Cells

Neuronal death and synaptic loss are principal pathological features of Alzheimer's disease (AD). Amyloid beta oligomers (AβOs) constitute the main neurotoxin underscoring AD pathology. AβOs interact with N-methyl-D-aspartate receptors (NMDARs), resulting in neurotoxic events, including activation of apoptosis and synaptic impairment. Carnosic acid (CA), extracted from Salvia rosmarinus, has been verified its neuroprotective effects in AD. However, the precise mechanisms by which CA induces synaptic protection remain unclear. In this study, we established an in vitro AD model using SH-SY5Y human neuroblastoma cells. We observed that CA improved neuronal survival by suppressing apoptosis. Moreover, CA restored synaptic impairments by increasing expression levels of brain-derived neurotrophic factor (BDNF), postsynaptic density protein-95 (PSD-95), and synaptophysin (Syn). Furthermore, we found these protective effects were dependent on inhibiting the phosphorylation of NMDAR subtype 2B (NMDAR2B), which further suppressed calcium overload and promoted activation of the extracellular signal-regulated kinase (ERK)-cAMP response element-binding protein (CREB) pathway. Administration of N-methyl-D-aspartic acid (NMDA), an agonist of NMDARs, abolished these effects of CA. Our findings demonstrate that CA exerts neuroprotective effects in an in vitro model of AD by regulating NMDAR2B and its downstream cascades, highlighting the therapeutic potential of CA as a NMDARs-targeted candidate in the treatment of AD.

A selective degeneration of cholinergic neurons mediated by NRADD in an Alzheimer's disease mouse model

Cholinergic neurons in the basal forebrain constitute a major source of cholinergic inputs to the forebrain, modulate diverse functions including sensory processing, memory and attention, and are vulnerable to Alzheimer's disease (AD). Recently, we classified cholinergic neurons into two distinct subpopulations; calbindin D28K-expressing (D28K+) versus D28K-lacking (D28K-) neurons. Yet, which of these two cholinergic subpopulations are selectively degenerated in AD and the molecular mechanisms underlying this selective degeneration remain unknown. Here, we reported a discovery that D28K+ neurons are selectively degenerated and this degeneration induces anxiety-like behaviors in the early stage of AD. Neuronal type specific deletion of NRADD effectively rescues D28K+ neuronal degeneration, whereas genetic introduction of exogenous NRADD causes D28K- neuronal loss. This gain- and loss-of-function study reveals a subtype specific degeneration of cholinergic neurons in the disease progression of AD and hence warrants a novel molecular target for AD therapy.

Network pharmacology analysis reveals neuroprotective effects of the Qin-Zhi-Zhu-Dan Formula in Alzheimer’s disease

There is yet no effective drug for Alzheimer’s disease (AD) which is one of the world’s most common neurodegenerative diseases. The Qin-Zhi-Zhu-Dan Formula (QZZD) is derived from a widely used Chinese patent drug–Qing-Kai-Ling Injection. It consists of Radix Scutellariae, Fructus Gardeniae, and Pulvis Fellis Suis. Recent study showed that QZZD and its effective components played important roles in anti-inflammation, antioxidative stress and preventing brain injury. It was noted that QZZD had protective effects on the brain, but the mechanism remained unclear. This study aims to investigate the mechanism of QZZD in the treatment of AD combining network pharmacology approach with experimental validation. In the network pharmacology analysis, a total of 15 active compounds of QZZD and 135 putative targets against AD were first obtained. Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were then applied to clarify the biological mechanism. The anti-inflammatory mechanism of QZZD was proved, and a synthetic pathway–TNFR1-ERK1/2-NF-κBp65 signaling pathway was obtained. On the basis of the above discoveries, we further validated the protective effects QZZD on neurons with an APP/PS1 double transgenic mouse model. Weight change of the mice was monitored to assess QZZD’s influence on the digestive system; water maze experiment was used for evaluating the effects on spatial learning and memory; Western blotting and immunohistochemistry analysis were used to detect the predicted key proteins in network pharmacology analysis, including Aβ, IL-6, NF-κBp65, TNFR1, p-ERK1/2, and ERK1/2. We proved that QZZD could improve neuroinflammation and attenuate neuronal death without influencing the digestive system in APP/PS1 double transgenic mice with dementia. Combining animal pharmacodynamic experiments with network pharmacology analysis, we confirmed the importance of inflammation in pathogenesis of AD, clarified the pharmacodynamic characteristics of QZZD in treating AD, and proved its neuroprotective effects through the regulation of TNFR1-ERK1/2-NF-κBp65 signaling pathway, which might provide reference for studies on treatment of AD in the future.

Sagacious confucius’ pillow elixir ameliorates Dgalactose induced cognitive injury in mice via estrogenic effects and synaptic plasticity

Alzheimer’s disease (AD) is a growing concern in modern society, and there is currently a lack of effective therapeutic drugs. Sagacious Confucius’ Pillow Elixir (SCPE) has been studied for the treatment of neurodegenerative diseases such as AD. This study aimed to reveal the key components and mechanisms of SCPE’s anti-AD effect by combining Ultra-high Performance Liquid Chromatography-electrostatic field Orbitrap combined high-resolution Mass Spectrometry (UPLC-LTQ/Orbitrap-MS) with a network pharmacology approach. And the mechanism was verified by in vivo experiments. Based on UPLC-LTQ/Orbitrap-MS technique identified 9 blood components from rat serum containing SCPE, corresponding to 113 anti-AD targets, and 15 of the 113 targets had high connectivity. KEGG pathway enrichment analysis showed that estrogen signaling pathway and synaptic signaling pathway were the most significantly enriched pathways in SCPE anti-AD, which has been proved by in vivo experiments. SCPE can exert estrogenic effects in the brain by increasing the amount of estrogen in the brain and the expression of ERα receptors. SCPE can enhance the synaptic structure plasticity by promoting the release of brain-derived neurotrophic factor (BDNF) secretion and improving actin polymerization and coordinates cofilin activity. In addition, SCPE also enhances synaptic functional plasticity by increasing the density of postsynaptic densified 95 (PSD95) proteins and the expression of functional receptor AMPA. SCPE is effective for treatment of AD and the mechanism is related to increasing estrogenic effects and improving synaptic plasticity. Our study revealed the synergistic effect of SCPE at the system level and showed that SCPE exhibits anti-AD effects in a multi-component, multi-target and multi-pathway manner. All these provide experimental support for the clinical application and drug development of SCPE in the prevention and treatment of AD.

The Transcranial Light Therapy Improves Synaptic Plasticity in the Alzheimer’s Disease Mouse Model

Alzheimer’s disease (AD) is the main cause of dementia worldwide. Emerging non-invasive treatments such as photobiomodulation target the mitochondria to minimize brain damage, improving cognitive functions. In this work, an experimental design was carried out to evaluate the effect of transcranial light therapy (TLTC) on synaptic plasticity (SP) and cognitive functions in an AD animal model. Twenty-three mice were separated into two general groups: an APP/PS1 (ALZ) transgenic group and a wild-type (WT) group. Each group was randomly subdivided into two subgroups: mice with and without TLTC, depending on whether they would undergo treatment with TLTC. Cognitive function, measured through an object recognition task, showed non-significant improvement after TLTC. SP, on the other hand, was evaluated using four electrophysiological parameters from the Schaffer-CA1 collateral hippocampal synapses: excitatory field potentials (fEPSP), paired pulse facilitation (PPF), long-term depression (LTD), and long-term potentiation (LTP). An improvement was observed in subjects treated with TLTC, showing higher levels of LTP than those transgenic mice that were not exposed to the treatment. Therefore, the results obtained in this work showed that TLTC could be an efficient non-invasive treatment for AD-associated SP deficits.

Screening for Genetic Mutations Associated with Early-Onset Alzheimer's Disease in Han Chinese

BACKGROUND

Early-onset Alzheimer's disease (EOAD) is highly influenced by genetic factors. Numerous mutations in amyloid precursor protein (APP) and presenilin 1 and 2 (PSEN1 and PSEN2) have been identified for EOAD, but they can only account for a small proportion of EOAD cases.

OBJECTIVE

This study aimed to screen genetic mutations and variants associated with EOAD among Han Chinese adults.

METHODS

This study included 34 patients with EOAD and 26 controls from a population-based study and neurological ward. We first sequenced mutations in APP/PSENs and then performed whole-exome sequencing in the remaining patients with negative mutations in APP/PSENs to screen for additional potential genetic variants. Among patients who were negative in genetic screening tests, we further evaluated the risk burden of genes related to the Aβ metabolism-centered network to search for other probable causes of EOAD.

RESULTS

We identified 7 functional variants in APP/PSENs in 8 patients, including 1 APP mutation (p. Val715Met), 3 PSEN1 mutations (p. Phe177Ser; p. Arg377Met; p. Ile416Thr), and 3 PSEN2 mutations (p. Glu24Lys; p. Gly34Ser; p. Met239Thr). Of the remaining 26 EOAD cases without mutations in APP/PSENs, the proportion of carrying rare variants of genes involved in Aβ and APP metabolism was significantly higher than that of controls (84.6% vs. 73.1%, P=0.042). Thirty-one risk genes with 47 variants were identified in 22 patients. However, in 26 normal subjects, only 20 risk genes with 29 variants were identified in 19 subjects.

CONCLUSIONS

Our findings demonstrate the role of APP/PSENs mutations in EOAD, identifying a new PSEN2 missense mutation, and further offer valuable insights into the potential genetic mechanisms of EOAD without APP/PSENs mutations among Han Chinese.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

Downregulation of PIK3CB Involved in Alzheimer's Disease via Apoptosis, Axon Guidance, and FoxO Signaling Pathway

OBJECTIVE

To investigate the molecular function of phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit beta (PIK3CB) underlying Alzheimer's disease (AD).

METHODS

RNA sequencing data were used to filtrate differentially expressed genes (DEGs) in AD/nondementia control and PIK3CB-low/high groups. An unbiased coexpression network was established to evaluate module-trait relationships by using weight gene correlation network analysis (WGCNA). Global regulatory network was constructed to predict the protein-protein interaction. Further cross-talking pathways of PIK3CB were identified by functional enrichment analysis.

RESULTS

The mean expression of PIK3CB in AD patients was significantly lower than those in nondementia controls. We identified 2,385 DEGs from 16,790 background genes in AD/control and PIK3CB-low/high groups. Five coexpression modules were established using WGCNA, which participated in apoptosis, axon guidance, long-term potentiation (LTP), regulation of actin cytoskeleton, synaptic vesicle cycle, FoxO, mitogen-activated protein kinase (MAPK), and vascular endothelial growth factor (VEGF) signaling pathways. DEGs with strong relation to AD and low PIK3CB expression were extracted to construct a global regulatory network, in which cross-talking pathways of PIK3CB were identified, such as apoptosis, axon guidance, and FoxO signaling pathway. The occurrence of AD could be accurately predicted by low PIK3CB based on the area under the curve of 71.7%.

CONCLUSIONS

These findings highlight downregulated PIK3CB as a potential causative factor of AD, possibly mediated via apoptosis, axon guidance, and FoxO signaling pathway.

The Levels of Amyloid β-Protein and P181 in Peripheral Blood of Patients with Alzheimer's Disease Combined with Helicobacter pylori Infection and Their Clinical Significance

OBJECTIVE

To analyze the levels of amyloid β-protein and P181 in peripheral blood of patients with Alzheimer's disease combined with Helicobacter pylori infection and their clinical significance.

METHOD

From January 2019 to June 2020, 59 patients were enrolled in this experiment including the AD group with 27 patients and the normal control group with 32 patients. The patients were divided into two groups: Alzheimer's disease (AD) group (n = 27) and control group (n = 32), collecting the general data of patients, analyzing the diagnostic specificity and sensitivity of serum p-tau181 and Aβ42 and their influence on prognosis, and comparing the serum Aβ42 and p-tau181 concentrations for different HP infection degrees.

RESULT

Single diagnostic sensitivity of Aβ42, p-tau181, and Aβ42 combined p-tau181 was 0.863, 0.854, and 0.972, respectively, and their specificity was 0.048, 0.206, and 0.305, respectively. Compared with the single diagnosis of serum Aβ42 and p-tau181, the combined diagnosis has higher sensitivity and specificity (P < 0.05); age, years of education, serum Aβ42, and p-tau181 are factors affecting the prognosis of patients with Alzheimer's disease combined with Helicobacter pylori infection; the concentration of Aβ42 in the control group was higher than that in the AD group, there was a statistical difference in the Aβ42 concentration between the two groups (P < 0.05), and there was no statistical difference in the concentration of p-tau181 between the two groups (P > 0.05); the HP positive infection rate of the AD group and the control group was 63.0% and 35.7%, respectively. The HP negative infection rate of the AD group and the control group was 37.0% and 64.3%, respectively. Compared with the control group, the positive rate of HP in the AD group was higher, and the difference was statistically significant (P < 0.05); compared with HP-negative patients, HP-positive patients had a higher Aβ42 concentration, and the difference was statistically significant (P < 0.05). The concentration of p-tau181 in the two groups was not statistically significant (P > 0.05); Aβ42 gradually increases with increasing HP infection degree, and there are significant differences in serum Aβ42 levels between different degrees of infection. However, the level of serum p-tau181 does not change significantly with the increase of infection.

CONCLUSION

There are significant alterations in the expression levels of Aβ42 and p-tau181 in peripheral blood of AD patients, and the levels of Aβ42 are related to HP infection; Aβ42 and p-tau181 are potential biomarkers for AD diagnosis and treatment.

iPSC-derived cortical neurons to study sporadic Alzheimer disease: A transcriptome comparison with post-mortem brain samples

Alzheimer's disease (AD) is the most common cause of dementia, characterized by the progressive impairment of cognition and memory loss. Sporadic AD (sAD) represents approximately 95 % of the AD cases and is induced by a complex interplay between genetic and environmental factors called "Alzheimerogens". Heavy metals (e.g. copper) and pesticides (e.g. fipronil) can affect many AD-related processes, including neuroinflammation (considered as AD-inducing factor). Research would benefit from in vitro models to investigate effects of Alzheimerogens. We compared transcriptomics changes in sAD induced pluripotent stem cell (iPSC) derived cortical neurons to differentially expressed genes (DEGs) identified in post-mortem AD brain tissue. These analyses showed that many AD-related processes could be identified in the sAD iPSC-derived neurons, and furthermore, could even identify more DEGs functioning in these processes than post-mortem AD-brain tissue. Thereafter, we exposed the iPSCs to AD-inducing factors (copper(II)chloride, fipronil sulfone and an inflammatory cytokine cocktail). Cytokine exposure induced expression of immune related genes while copper-exposure affected genes involved in lipid and cholesterol metabolism, which are known AD-related processes. Fipronil-exposure did not result in significant transcriptomic changes, although prolonged exposures or higher doses may be necessary. Overall, we show that iPSC-derived cortical neurons can be beneficial in vitro models to identify Alzheimerogens and AD-related molecular mechanisms.

CircLPAR1/miR-212-3p/ZNF217 feedback loop promotes amyloid β-induced neuronal injury in Alzheimer's Disease

BACKGROUND

Alzheimer's Disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognition and language impairment. CircRNA lysophosphatidic acid receptor 1 (circLPAR1) was found to be increased in AD patients, however, the potential role of circLPAR1 in AD process remains unclear.

METHODS

Beta-amyloid (Aβ) 25-35-stimulated CHP-212 and IMR-32 cells were used to perform expression and function analyses. The expression of genes and proteins was determined by qRT-PCR and Western blot. Cell proliferation and apoptosis were analyzed using cell counting kit-8 (CCK-8) assay, flow cytometry, and Western blot, respectively. ELISA analysis was used to detect the levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α). The levels of reactive oxygen species (ROS), lactate dehydrogenase (LDH) and superoxide dismutase (SOD) were detected using commercial kits. The direct interactions between miR-212-3p and ZNF217 (Zinc finger protein 217) or circLPAR1 was verified using dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

RESULTS

CircLPAR1 was highly expressed in AD patients and Aβ25-35-stimulated CHP-212 and IMR-32 cells. Knockdown of circLPAR1 suppressed Aβ25-35-induced neuronal apoptosis, inflammation, and oxidative stress. Mechanistically, circLPAR1 competitively bound to miR-212-3p to elevate its target ZNF217. Rescue experiments suggested that miR-212-3p inhibition reversed circLPAR1 silencing-evoked inhibition on neuronal injury under Aβ25-35 stimulation. Moreover, miR-212-3p re-expression reduced Aβ25-35-induced neuronal apoptosis, inflammation, and oxidative stress, which were abolished by ZNF217 up-regulation.

CONCLUSION

CircLPAR1 promotes Aβ25-35-induced apoptosis, inflammation, and oxidative stress via miR-212-3p/ZNF217 axis, suggesting a new insight into the pathogenesis of AD.

NLRP3 Inflammasome Mediates Neurodegeneration in Rats with Chronic Neuropathic Pain

ABSTRACT

Patients with chronic neuropathic pain (NP) have a significantly increased risk of central nervous degeneration. Trigeminal neuralgia (TN) is a typical NP, and this manifestation is more obvious. In addition to severe pain, patients with TN are often accompanied by cognitive dysfunction and have a higher risk of central nervous system degeneration, but the mechanism is not clear. The NOD-like receptor 3 (NLRP3) inflammasome assembles inside of microglia on activation, which plays an important role in neurodegeneration such as Alzheimer disease. MCC950 is a specific blocker of NLRP3 inflammasome, which can improve the performance of degenerative diseases. Although NLRP3 inflammasome assembles inside of microglia on activation has been shown to be essential for the development and progression of amyloid pathology, its whether it mediates the neurodegeneration caused by NP is currently unclear. By constructing a rat model of chronic TN, we found that as the course of the disease progresses, TN rats have obvious cognitive and memory deficit. In addition, Tau hyperphosphorylation and Aβ expression increase in the cortex and hippocampus of the brain. At the same time, we found that NLRP3 expression increased significantly in model rats. Interestingly, NLRP3 specific blocker MCC950 can alleviate the neurodegeneration of trigeminal neuralgia rats to a certain extent. It is suggested that our NLRP3 inflammasome plays an important role in the neurodegeneration of trigeminal neuralgia rats. And it is related to the activation of central nervous system inflammation.

Exosomes in Alzheimer's Disease: From Being Pathological Players to Potential Diagnostics and Therapeutics

Exosomes (EXOs) were given attention as an extracellular vesicle (EV) with a pivotal pathophysiological role in the development of certain neurodegenerative disorders (NDD), such as Parkinson's and Alzheimer's disease (AD). EXOs have shown the potential to carry pathological and therapeutic cargo; thus, researchers have harnessed EXOs in drug delivery applications. EXOs have shown low immunogenicity as natural drug delivery vehicles, thus ensuring efficient drug delivery without causing significant adverse reactions. Recently, EXOs provided potential drug delivery opportunities in AD and promising future clinical applications with the diagnosis of NDD and were studied for their usefulness in disease detection and prediction prior to the emergence of symptoms. In the future, the microfluidics technique will play an essential role in isolating and detecting EXOs to diagnose AD before the development of advanced symptoms. This review is not reiterative literature but will discuss why EXOs have strong potential in treating AD and how they can be used as a tool to predict and diagnose this disorder.

c-Jun N-Terminal Kinases in Alzheimer's Disease: A Possible Target for the Modulation of the Earliest Alterations

Given the highly multifactorial origin of Alzheimer's disease (AD) neuropathology, disentangling and orderly knowing mechanisms involved in sporadic onset are arduous. Nevertheless, when the elements involved are dissected into smaller pieces, the task becomes more accessible. This review aimed to describe the link between c-Jun N-terminal Kinases (JNKs), master regulators of many cellular functions, and the early alterations of AD: synaptic loss and dysregulation of neuronal transport. Both processes have a role in the posterior cognitive decline observed in AD. The manuscript focuses on the molecular mechanisms of glutamatergic, GABA, and cholinergic synapses altered by the presence of amyloid-β aggregates and hyperphosphorylated tau, as well as on several consequences of the disruption of cellular processes linked to neuronal transport that is controlled by the JNK-JIP (c-jun NH2-terminal kinase (JNK)-interacting proteins (JIPs) complex, including the transport of AβPP or autophagosomes.

Non-Canonical Roles of Tau and Their Contribution to Synaptic Dysfunction

Tau plays a central role in a group of neurodegenerative disorders collectively named tauopathies. Despite the wide range of diverse symptoms at the onset and during the progression of the pathology, all tauopathies share two common hallmarks, namely the misfolding and aggregation of Tau protein and progressive synaptic dysfunctions. Tau aggregation correlates with cognitive decline and behavioural impairment. The mechanistic link between Tau misfolding and the synaptic dysfunction is still unknown, but this correlation is well established in the human brain and also in tauopathy mouse models. At the onset of the pathology, Tau undergoes post-translational modifications (PTMs) inducing the detachment from the cytoskeleton and its release in the cytoplasm as a soluble monomer. In this condition, the physiological enrichment in the axon is definitely disrupted, resulting in Tau relocalization in the cell soma and in dendrites. Subsequently, Tau aggregates into toxic oligomers and amyloidogenic forms that disrupt synaptic homeostasis and function, resulting in neuronal degeneration. The involvement of Tau in synaptic transmission alteration in tauopathies has been extensively reviewed. Here, we will focus on non-canonical Tau functions mediating synapse dysfunction.

Synaptic Dysfunction in Multiple Sclerosis: A Red Thread from Inflammation to Network Disconnection

Multiple sclerosis (MS) has been clinically considered a chronic inflammatory disease of the white matter; however, in the last decade growing evidence supported an important role of gray matter pathology as a major contributor of MS-related disability and the involvement of synaptic structures assumed a key role in the pathophysiology of the disease. Synaptic contacts are considered central units in the information flow, involved in synaptic transmission and plasticity, critical processes for the shaping and functioning of brain networks. During the course of MS, the immune system and its diffusible mediators interact with synaptic structures leading to changes in their structure and function, influencing brain network dynamics. The purpose of this review is to provide an overview of the existing literature on synaptic involvement during experimental and human MS, in order to understand the mechanisms by which synaptic failure eventually leads to brain networks alterations and contributes to disabling MS symptoms and disease progression.

Peony seed oil ameliorates neuroinflammation-mediated cognitive deficits by suppressing microglial activation through inhibition of NF-κB pathway in presenilin 1/2 conditional double knockout mice

Chronic neuroinflammation has been shown to exert adverse influences on the pathology of Alzheimer's disease (AD), associated with the release of abundant proinflammatory mediators by excessively activated microglia, causing synaptic dysfunction, neuronal degeneration, and memory deficits. Thus, the prevention of microglial activation-associated neuroinflammation is important target for deterring neurodegenerative disorders. Peony seed oil (PSO) is a new food resource, rich in α-linolenic acid, the precursor of long chain omega-3 polyunsaturated fatty acids, including docosahexaenoic acid and eicosapentaenoic acid, which exhibit anti-inflammatory properties by altering cell membrane phospholipid fatty acid compositions, disrupting lipid rafts, and inhibiting the activation of the proinflammatory transcription factor NF-κB. However, few studies have examined the anti-neuroinflammatory effects of PSO in AD, and the relevant molecular mechanisms remain unclear. Presenilin1/2 conditional double knockout (PS cDKO) mice display obvious AD-like phenotypes, such as neuroinflammatory responses, synaptic dysfunction, and cognitive deficits. Here, we assessed the potential neuroprotective effects of PSO against neuroinflammation-mediated cognitive deficits in PS cDKO using behavioral tests and molecular biologic analyses. Our study demonstrated that PSO suppressed microglial activation and neuroinflammation through the down-regulation of proinflammatory mediators, such as inducible NOS, COX-2, IL-1β, and TNF-α, in the prefrontal cortex and hippocampus of PS cDKO mice. Further, PSO significantly lessened memory impairment by reversing hyperphosphorylated tau and synaptic proteins deficits in PS cDKO mice. Importantly, PSO's therapeutic effects on cognitive deficits were due to inhibiting neuroinflammatory responses mediated by NF-κB signaling pathway. Taken together, PSO may represent an effective dietary supplementation to restrain the neurodegenerative processes of AD.

Recent Advances on Possible Association Between the Periodontal Infection of Porphyromonas gingivalis and Central Nervous System Injury

Chronic periodontitis caused by Porphyromonas gingivalis (P. gingivalis) infection generally lasts for a lifetime. The long-term existence and development of P. gingivalis infection gradually aggravate the accumulation of inflammatory signals and toxic substances in the body. Recent evidence has revealed that P. gingivalis infection may be relevant to some central nervous system (CNS) diseases. The current work collects information and tries to explore the possible relationship between P. gingivalis infection and CNS diseases, including the interaction or pathways between peripheral infection and CNS injury, and the underlying neurotoxic mechanisms.

The cognitive dysfunction related to Alzheimer disease or cerebral small vessel disease: What's the differences

ABSTRACT

Alzheimer disease (AD) and sporadic cerebral small vessel disease (CSVD) are common cognitive disorders. Both AD and CSVD have mental symptoms including chronic progressive cognitive impairment, dysfunction, and behavioral abnormalities. However, the differences on the cognitive dysfunction of AD and CSVD remain unclear. It is necessary to elucidate the cognitive dysfunction differences of AD and CSVD, and to identify the potential risk factors.AD or sporadic CSVD patients treated in our hospital from December 1, 2018 to May 31, 2019 were included. And we selected healthy participants as controls. The mini-mental state examination and Montreal Cognitive Assessment Scale were used for neuropsychological assessment, and related medical information were collected and compared.A total of 190 patients were included. The total mini-mental state examination scores in AD, CSVD group were significantly less than that of control group, there were significant differences in the domains of directional ability, attention and computing ability, delayed recall, and visual perception (all P < .05); the total Montreal Cognitive Assessment Scale scores in AD, CSVD group were significantly less than that of control group. There were significant differences in the domains of visual space and execution, immediate remember, attention and computing ability, language, delayed recall, and directional ability (all P < .05); diabetes was a risk factor both for AD (hazard ratio = 1.63, 95% confidence interval: 1.35-1.97) and CSVD (hazard ratio = 1.15, 95% confidence interval: 1.08-1.27).The cognitive dysfunctions of AD are difference to that of CSVD patients, and diabetes is the risk factor both for AD and CSVD, future studies are needed to further identify the prevention and treatment of AD and CSVD.

Effects of Naodesheng tablets on amyloid beta-induced dysfunction: A traditional Chinese herbal formula with novel therapeutic potential in Alzheimer's disease revealed by systems pharmacology

Naodesheng (NDS) tablets have been widely used to treat ischemic stroke clinically. NDS relieves neurological function impairment and improve learning and memory in rats with focal cerebral ischemia, suggesting that NDS has potential for Alzheimer's disease (AD) treatment. However, there are no studies about its effective material basis and possible mechanisms. In this study, a systems pharmacology method was applied to reveal the potential molecular mechanism of NDS in the treatment of AD. First, we obtained 360 NDS candidate constituents through ADMET filter analysis. Then, 115 AD-related targets were uncovered by pharmacophore model prediction via mapping the predicted targets against AD-related proteins. In addition, compound-target and target-function networks were established to suggest potential synergistic effects among the candidate constituents. Furthermore, potential targets regulated by NDS were integrated into AD-related pathways to demonstrate the therapeutic mechanism of NDS in AD treatment. Subsequently, a validation experiment proved the therapeutic effect of NDS on cognitive dysfunction in rats with intracerebroventricular injection of Aβ. We found that administration of NDS tablets regulates β-amyloid metabolism, improves synaptic plasticity, inhibits neuroinflammation and improves learning and memory function. In conclusion, this is the first study to provide a comprehensive systems pharmacology approach to elucidate the potential therapeutic mechanism of NDS tablets for AD treatment. We suggest that the protective effects of NDS in neurodegenerative conditions could be partly attributed to its role in improving synaptic plasticity and inhibiting neuroinflammation via NF-κB signaling pathway inhibition and cAMP/PKA/CREB signaling pathway activation.

A network pharmacology approach to uncover the key ingredients in Ginkgo Folium and their anti-Alzheimer's disease mechanisms

This study aimed to identify potential anti-Alzheimer’s disease (AD) targets and action mechanisms of Ginkgo Folium (GF) through a network pharmacology approach. Eighty-four potential targets of 10 active anti-AD ingredients of GF were identified, among which genkwanin (GK) had the greatest number of AD-related targets. KEGG pathway enrichment analysis showed that the most significantly enriched signaling pathway of GF against AD was Alzheimer disease (hsa05010). More importantly, 29 of the 84 targets were significantly correlated with tau, Aβ or both Aβ and tau pathology. In addition, GO analysis suggested that the main biological processes of GF in AD treatment were the regulation of chemical synaptic transmission (GO:0007268), neuron death (GO:0070997), amyloid-beta metabolic process (GO:0050435), etc. We further investigated the anti-AD effects of GK using N2A-APP cells (a classical cellular model of AD). Treatment N2A-APP cells with 100 μM GK for 48 h affected core targets related to tau pathology (such as CDK5 and GSK3β). In conclusion, these findings indicate that GF exerts its therapeutic effects on AD by acting directly on multiple pathological processes of AD.

Dysregulated protein phosphorylation: A determining condition in the continuum of brain aging and Alzheimer's disease

Tau hyperphosphorylation is the first step of neurofibrillary tangle (NFT) formation. In the present study, samples of the entorhinal cortex (EC) and frontal cortex area 8 (FC) of cases with NFT pathology classified as stages I-II, III-IV, and V-VI without comorbidities, and of middle-aged (MA) individuals with no NFT pathology, were analyzed by conventional label-free and SWATH-MS (sequential window acquisition of all theoretical fragment ion spectra mass spectrometry) to assess the (phospho)proteomes. The total number of identified dysregulated phosphoproteins was 214 in the EC, 65 of which were dysregulated at the first stages (I-II) of NFT pathology; 167 phosphoproteins were dysregulated in the FC, 81 of them at stages I-II of NFT pathology. A large percentage of dysregulated phosphoproteins were identified in the two regions and at different stages of NFT progression. The main group of dysregulated phosphoproteins was made up of components of the membranes, cytoskeleton, synapses, proteins linked to membrane transport and ion channels, and kinases. The present results show abnormal phosphorylation of proteins at the first stages of NFT pathology in the elderly (in individuals clinically considered representative of normal aging) and sporadic Alzheimer's disease (sAD). Dysregulated protein phosphorylation in the FC precedes the formation of NFTs and SPs. The most active period of dysregulated phosphorylation is at stages III-IV when a subpopulation of individuals might be clinically categorized as suffering from mild cognitive impairment which is a preceding determinant stage in the progression to dementia. Altered phosphorylation of selected proteins, carried out by activation of several kinases, may alter membrane and cytoskeletal functions, among them synaptic transmission and membrane/cytoskeleton signaling. Besides their implications in sAD, the present observations suggest a molecular substrate for "benign" cognitive deterioration in "normal" brain aging.

DJ-1 in neurodegenerative diseases: Pathogenesis and clinical application

Neurodegenerative diseases (NDs) are one of the major health threats to human characterized by selective and progressive neuronal loss. The mechanisms of NDs are still not fully understood. The study of genetic defects and disease-related proteins offers us a window into the mystery of it, and the extension of knowledge indicates that different NDs share similar features, mechanisms, and even genetic or protein abnormalities. Among these findings, PARK7 and its production DJ-1 protein, which was initially found implicated in PD, have also been found altered in other NDs. PARK7 mutations, altered expression and posttranslational modification (PTM) cause DJ-1 abnormalities, which in turn lead to downstream mechanisms shared by most NDs, such as mitochondrial dysfunction, oxidative stress, protein aggregation, autophagy defects, and so on. The knowledge of DJ-1 derived from PD researches might apply to other NDs in both basic research and clinical application, and might yield novel insights into and alternative approaches for dealing with NDs.

Beneficial Effects of Choline Alphoscerate on Amyloid-β Neurotoxicity in an In vitro Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is the most common form of neurodegenerative disorder characterized by cognitive impairment, which represents an urgent public health concern. Given the worldwide impact of AD, there is a compelling need for effective therapies to slow down or halt this disorder.

OBJECTIVE

Choline alphoscerate (α-GPC) represents a potentially effective cholinergic neurotrans- mission enhancing agent with an interesting clinical profile in cognitive dysfunctions improve- ment, although only scanty data are available about the mechanisms underlying such beneficial ef- fects.

METHOD

The SH-SY5Y neuronal cell line, differentiated for 1 week with 10 μm of all-trans-reti- noic acid (RA), to achieve a switch towards a cholinergic phenotype, was used as an in vitro model of AD. SH-SY5Y cells were pre-treated for 1h with α-GPC (100nM) and treated for 72 h with Aβ25-35 (10μM).

RESULTS

α-GPC was able to antagonize Aβ25-35 mediated neurotoxicity and attenuate the Aβ-in- duced phosphorylation of the Tau protein. Moreover, α-GPC exerted its beneficial effects by em- ploying the NGF/TrkA system, knocked down in AD and, consequently, by sustaining the expres- sion level of synaptic vesicle proteins, such as synaptophysin.

CONCLUSION

Taken together, our data suggest that α-GPC can have a role in neuroprotection in the course of toxic challenges with Aβ. Thus, a deeper understanding of the mechanism underlying its beneficial effect, could provide new insights into potential future pharmacological applications of its functional cholinergic enhancement, with the aim to mitigate AD and could represent the basis for innovative therapy.Recent Advances in Anti-Infective Drug Discovery.

The Association Between Folate and Alzheimer's Disease: A Systematic Review and Meta-Analysis

Alzheimer's disease (AD) is the most common type of neurodegenerative disease leading to dementia in the elderly. Increasing evidence indicates that folate plays an important role in the pathogenesis of AD. To investigate the role of folate deficiency/possible deficiency in the risk of AD and the benefical effect of sufficient folate intake on the prevention of AD, a systematic review and meta-analysis were performed. The Web of Science, PubMed, CENTRAL, EBSCO, CNKI, CQVIP, and Wanfang databases were searched. The analysis of cross-sectional studies showed that the standardized mean difference (SMD) was −0.60 (95% confidence interval (CI): −0.65, −0.55), indicating that plasma/serum folate level is lower in AD patients than that in controls. Moreover, the combined odds ratio (OR) of case-control studies was 0.96 (95% CI: 0.93, 0.99), while the combined ORs were 0.86 (95% CI: 0.46, 1.26) and 1.94 (95% CI: 1.02, 2.86) in populations with normal levels of folate (≥13.5 nmol/L) and folate deficiency/possible deficiency (<13.5 nmol/L), respectively. In addition, the risk ratio (RR) of the cohort studies was 1.88 (95% CI: 1.20, 2.57) in populations with folate deficiency/possible deficiency. Furthermore, when the intake of folate was equal to or higher than the recommended daily allowance, the combined RR and hazard ratio (HR) were 0.44 (95% CI: 0.18, 0.71) and 0.76 (95% CI: 0.52, 0.99), respectively. These results indicate that folate deficiency/possible deficiency increases the risk for AD, while sufficient intake of folate is a protective factor against AD.

Presynaptic protein synthesis and brain plasticity: From physiology to neuropathology

To form and maintain extremely intricate and functional neural circuitry, mammalian neurons are typically endowed with highly arborized dendrites and a long axon. The synapses that link neurons to neurons or to other cells are numerous and often too remote for the cell body to make and deliver new proteins to the right place in time. Moreover, synapses undergo continuous activity-dependent changes in their number and strength, establishing the basis of neural plasticity. The innate dilemma is then how a highly complex neuron provides new proteins for its cytoplasmic periphery and individual synapses to support synaptic plasticity. Here, we review a growing body of evidence that local protein synthesis in discrete sites of the axon and presynaptic terminals plays crucial roles in synaptic plasticity, and that deregulation of this local translation system is implicated in various pathologies of the nervous system.

Impaired pattern separation in Tg2576 mice is associated with hyperexcitable dentate gyrus caused by Kv4.1 downregulation

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that causes memory loss. Most AD researches have focused on neurodegeneration mechanisms. Considering that neurodegenerative changes are not reversible, understanding early functional changes before neurodegeneration is critical to develop new strategies for early detection and treatment of AD. We found that Tg2576 mice exhibited impaired pattern separation at the early preclinical stage. Based on previous studies suggesting a critical role of dentate gyrus (DG) in pattern separation, we investigated functional changes in DG of Tg2576 mice. We found that granule cells in DG (DG-GCs) in Tg2576 mice showed increased action potential firing in response to long depolarizations and reduced 4-AP sensitive K+-currents compared to DG-GCs in wild-type (WT) mice. Among Kv4 family channels, Kv4.1 mRNA expression in DG was significantly lower in Tg2576 mice. We confirmed that Kv4.1 protein expression was reduced in Tg2576, and this reduction was restored by antioxidant treatment. Hyperexcitable DG and impaired pattern separation in Tg2576 mice were also recovered by antioxidant treatment. These results highlight the hyperexcitability of DG-GCs as a pathophysiologic mechanism underlying early cognitive deficits in AD and Kv4.1 as a new target for AD pathogenesis in relation to increased oxidative stress.

Curcumin Reduces Cognitive Deficits by Inhibiting Neuroinflammation through the Endoplasmic Reticulum Stress Pathway in Apolipoprotein E4 Transgenic Mice

Apolipoprotein E4 (ApoE4) is the main genetic risk factor for Alzheimer's disease (AD), but the exact way in which it causes AD remains unclear. Curcumin is considered to have good therapeutic potential for AD, but its mechanism has not been clarified. This study aims to observe the effect of curcumin on ApoE4 transgenic mice and explore its possible molecular mechanism. Eight-month-old ApoE4 transgenic mice were intraperitoneally injected with curcumin for 3 weeks, and the Morris water maze test was used to evaluate the cognitive ability of the mice. Immunofluorescence staining, immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay (ELISA) were used to examine the brain tissues of the mice. Curcumin reduced the high expression of ApoE4 and the excessive release of inflammatory factors in ApoE4 mice. In particular, the expression of marker proteins of endoplasmic reticulum (ER) stress was significantly increased in ApoE4 mice, while curcumin significantly reduced the increase in the expression of these proteins. Collectively, curcumin alleviates neuroinflammation in the brains of ApoE4 mice by inhibiting ER stress, thus improving the learning and cognitive ability of transgenic mice.

Knock-Down of HDAC2 in Human Induced Pluripotent Stem Cell Derived Neurons Improves Neuronal Mitochondrial Dynamics, Neuronal Maturation and Reduces Amyloid Beta Peptides

Histone deacetylase 2 (HDAC2) is a major HDAC protein in the adult brain and has been shown to regulate many neuronal genes. The aberrant expression of HDAC2 and subsequent dysregulation of neuronal gene expression is implicated in neurodegeneration and brain aging. Human induced pluripotent stem cell-derived neurons (hiPSC-Ns) are widely used models for studying neurodegenerative disease mechanisms, but the role of HDAC2 in hiPSC-N differentiation and maturation has not been explored. In this study, we show that levels of HDAC2 progressively decrease as hiPSCs are differentiated towards neurons. This suppression of HDAC2 inversely corresponds to an increase in neuron-specific isoforms of Endophilin-B1, a multifunctional protein involved in mitochondrial dynamics. Expression of neuron-specific isoforms of Endophilin-B1 is accompanied by concomitant expression of a neuron-specific alternative splicing factor, SRRM4. Manipulation of HDAC2 and Endophilin-B1 using lentiviral approaches shows that the knock-down of HDAC2 or the overexpression of a neuron-specific Endophilin-B1 isoform promotes mitochondrial elongation and protects against cytotoxic stress in hiPSC-Ns, while HDAC2 knock-down specifically influences genes regulating mitochondrial dynamics and synaptogenesis. Furthermore, HDAC2 knock-down promotes enhanced mitochondrial respiration and reduces levels of neurotoxic amyloid beta peptides. Collectively, our study demonstrates a role for HDAC2 in hiPSC-neuronal differentiation, highlights neuron-specific isoforms of Endophilin-B1 as a marker of differentiating hiPSC-Ns and demonstrates that HDAC2 regulates key neuronal and mitochondrial pathways in hiPSC-Ns.

Association of CSF proteins with tau and amyloid β levels in asymptomatic 70-year-olds

Background

Increased knowledge of the evolution of molecular changes in neurodegenerative disorders such as Alzheimer’s disease (AD) is important for the understanding of disease pathophysiology and also crucial to be able to identify and validate disease biomarkers. While several biological changes that occur early in the disease development have already been recognized, the need for further characterization of the pathophysiological mechanisms behind AD still remains.

Methods

In this study, we investigated cerebrospinal fluid (CSF) levels of 104 proteins in 307 asymptomatic 70-year-olds from the H70 Gothenburg Birth Cohort Studies using a multiplexed antibody- and bead-based technology.

Results

The protein levels were first correlated with the core AD CSF biomarker concentrations of total tau, phospho-tau and amyloid beta (Aβ42) in all individuals. Sixty-three proteins showed significant correlations to either total tau, phospho-tau or Aβ42. Thereafter, individuals were divided based on CSF Aβ42/Aβ40 ratio and Clinical Dementia Rating (CDR) score to determine if early changes in pathology and cognition had an effect on the correlations. We compared the associations of the analysed proteins with CSF markers between groups and found 33 proteins displaying significantly different associations for amyloid-positive individuals and amyloid-negative individuals, as defined by the CSF Aβ42/Aβ40 ratio. No differences in the associations could be seen for individuals divided by CDR score.

Conclusions

We identified a series of transmembrane proteins, proteins associated with or anchored to the plasma membrane, and proteins involved in or connected to synaptic vesicle transport to be associated with CSF biomarkers of amyloid and tau pathology in AD. Further studies are needed to explore these proteins’ role in AD pathophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00789-5.

Kinase Signaling in Dendritic Development and Disease

Dendrites undergo extensive growth and remodeling during their lifetime. Specification of neurites into dendrites is followed by their arborization, maturation, and functional integration into synaptic networks. Each of these distinct developmental processes is spatially and temporally controlled in an exquisite fashion. Protein kinases through their highly specific substrate phosphorylation regulate dendritic growth and plasticity. Perturbation of kinase function results in aberrant dendritic growth and synaptic function. Not surprisingly, kinase dysfunction is strongly associated with neurodevelopmental and psychiatric disorders. Herein, we review, (a) key kinase pathways that regulate dendrite structure, function and plasticity, (b) how aberrant kinase signaling contributes to dendritic dysfunction in neurological disorders and (c) emergent technologies that can be applied to dissect the role of protein kinases in dendritic structure and function.

Role of miR-211 in a PC12 cell model of Alzheimer's disease via regulation of neurogenin 2

NEW FINDINGS

What is the central question of this study? What is the mechanism of miR-211 in an Alzheimer's disease cell model? What is the main finding and its importance? miR-211 was upregulated in an Alzheimer's disease cell model. It targeted neurogenin 2, reduced the activation of the phosphoinositide 3-kinase-Akt signalling pathway, inhibited the proliferation of the Alzheimer's disease cell model and promoted apoptosis.

ABSTRACT

MicroRNAs (miRs) are aberrantly expressed in Alzheimer's disease (AD) patients. This study was intended to investigate the effect of miR-211 on an AD cell model and the involvement of neurogenin 2 (Ngn2). The appropriate dose and time for the effect of Aβ_1-42 on PC12 cells were determined to establish an AD cell model. An effect of miR-211 expression on cell viability, proliferation and apoptosis was detected after cell transfection. Online prediction and a dual luciferase reporter gene assay were utilized to confirm the binding sequence of miR-211 and Ngn2. qRT-PCR and western blot analysis were applied to measure Ngn2 expression. A gain and loss of function assay of miR-211 and Ngn2 was performed, and activation of the phosphoinositide 3-kinase (PI3K)-Akt signaling pathway was detected. The AD cell model was induced by Aβ_1-42 treatment. miR-211 expression was significantly enhanced after miR-211 transfection, leading to suppressed proliferation and promotion of apoptosis in Aβ_1-42 -treated PC12 cells. In addition, miR-211 could downregulate Ngn2 mRNA and protein expression, while overexpression of Ngn2 could reverse the effects of miR-211 on Aβ_1-42 -treated PC12 cells and significantly enhance the phosphorylated Akt and PI3K protein levels. miR-211 could inhibit growth of PC12 cells by suppressing Ngn2 expression and inactivating the PI3K-Akt signalling pathway.

Resveratrol Supplementation Attenuates Cognitive and Molecular Alterations under Maternal High-Fat Diet Intake: Epigenetic Inheritance over Generations

Environmental factors such as maternal high-fat diet (HFD) intake can increase the risk of age-related cognitive decline in adult offspring. Epigenetic mechanisms are a possible link between diet effect and neurodegeneration across generations. Here, we found a significant decrease in triglyceride levels in a high-fat diet with resveratrol (RSV) HFD + RSV group and the offspring. Firstly, we obtained better cognitive performance in HFD+RSV groups and their offspring. Molecularly, a significant increase in DNA methylation (5-mC) levels, as well as increased gene expression of DNA methyltransferase 1 (Dnmt1) and Dnmt3a in HFD + RSV F1 group, were found. Furthermore, a significant increase of N6-Methyladenosine methylation (m6A) levels in HFD+RSV F1, as well as changes in gene expression of its enzymes Methyltransferase like 3 (Mettl3) and FTO alpha-ketoglutarate dependent dioxygenase (Fto) were found. Moreover, we found a decrease in gene expression levels of pro-inflammatory markers such as Interleukin 1β (Il1-β), Interleukin 6 (Il-6), Tumor necrosis factor-α (Tnf-α), C-X-C motif chemokine ligand 10 (Cxcl-10), the pro-inflammatory factors monocyte chemoattractant protein 1 (Mcp-1) and Tumor growth factor-β1 (Tgf-β1) in HFD+RSV and HFD+RSV F1 groups. Moreover, there was increased gene expression of neurotrophins such as Neural growth factor (Ngf), Neurotrophin-3 (Nt3), and its receptors Tropomyosin receptor kinase TrkA and TrkB. Likewise, an increase in protein levels of brain-derived neurotrophic factor (BDNF) and phospho-protein kinase B (p-Akt) in HFD+RSV F1 was found. These results suggest that maternal RSV supplementation under HFD intake prevents cognitive decline in senescence-accelerated mice prone 8 (SAMP8) adult offspring, promoting a reduction in triglycerides and leptin plasma levels, changes in the pro-inflammatory profile, and restoring the epigenetic landscape as well as synaptic plasticity.

The Cholinergic System, the Adrenergic System and the Neuropathology of Alzheimer's Disease

Neurodegenerative diseases are a major public health problem worldwide with a wide spectrum of symptoms and physiological effects. It has been long reported that the dysregulation of the cholinergic system and the adrenergic system are linked to the etiology of Alzheimer’s disease. Cholinergic neurons are widely distributed in brain regions that play a role in cognitive functions and normal cholinergic signaling related to learning and memory is dependent on acetylcholine. The Locus Coeruleus norepinephrine (LC-NE) is the main noradrenergic nucleus that projects and supplies norepinephrine to different brain regions. Norepinephrine has been shown to be neuroprotective against neurodegeneration and plays a role in behavior and cognition. Cholinergic and adrenergic signaling are dysregulated in Alzheimer’s disease. The degeneration of cholinergic neurons in nucleus basalis of Meynert in the basal forebrain and the degeneration of LC-NE neurons were reported in Alzheimer’s disease. The aim of this review is to describe current literature on the role of the cholinergic system and the adrenergic system (LC-NE) in the pathology of Alzheimer’s disease and potential therapeutic implications.

Does Impairment of Adult Neurogenesis Contribute to Pathophysiology of Alzheimer's Disease? A Still Open Question

Adult hippocampal neurogenesis is a physiological mechanism contributing to hippocampal memory formation. Several studies associated altered hippocampal neurogenesis with aging and Alzheimer's disease (AD). However, whether amyloid-β protein (Aβ)/tau accumulation impairs adult hippocampal neurogenesis and, consequently, the hippocampal circuitry, involved in memory formation, or altered neurogenesis is an epiphenomenon of AD neuropathology contributing negligibly to the AD phenotype, is, especially in humans, still debated. The detrimental effects of Aβ/tau on synaptic function and neuronal viability have been clearly addressed both in in vitro and in vivo experimental models. Until some years ago, studies carried out on in vitro models investigating the action of Aβ/tau on proliferation and differentiation of hippocampal neural stem cells led to contrasting results, mainly due to discrepancies arising from different experimental conditions (e.g., different cellular/animal models, different Aβ and/or tau isoforms, concentrations, and/or aggregation profiles). To date, studies investigating in situ adult hippocampal neurogenesis indicate severe impairment in most of transgenic AD mice; this impairment precedes by several months cognitive dysfunction. Using experimental tools, which only became available in the last few years, research in humans indicated that hippocampal neurogenesis is altered in cognitive declined individuals affected by either mild cognitive impairment or AD as well as in normal cognitive elderly with a significant inverse relationship between the number of newly formed neurons and cognitive impairment. However, despite that such information is available, the question whether impaired neurogenesis contributes to AD pathogenesis or is a mere consequence of Aβ/pTau accumulation is not definitively answered. Herein, we attempted to shed light on this complex and very intriguing topic by reviewing relevant literature on impairment of adult neurogenesis in mouse models of AD and in AD patients analyzing the temporal relationship between the occurrence of altered neurogenesis and the appearance of AD hallmarks and cognitive dysfunctions.

miR-204-3p/Nox4 Mediates Memory Deficits in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder leading to dementia in the elderly, and the mechanisms of AD are not fully defined. MicroRNAs (miRNAs) have been shown to contribute to memory deficits in AD. In this study, we identified that miR-204-3p was downregulated in the hippocampus and plasma of 6-month-old APPswe/PS1dE9 (APP/PS1) mice. miR-204-3p overexpression attenuated memory and synaptic deficits in APP/PS1 mice. The amyloid levels and oxidative stress were decreased in the hippocampus of APP/PS1 mice after miR-204-3p overexpression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (Nox4) was a target of miR-204-3p, and Nox4 inhibition by GLX351322 protected neuronal cells against Aβ1-42-induced neurotoxicity. Furthermore, GLX351322 treatment rescued synaptic and memory deficits, and decreased oxidative stress and amyloid levels in the hippocampus of APP/PS1 mice. These results revealed that miR-204-3p attenuated memory deficits and oxidative stress in APP/PS1 mice by targeting Nox4, and miR-204-3p overexpression and/or Nox4 inhibition might be a potential therapeutic strategy for AD treatment.

The neuroprotective effects of phosphocreatine on Amyloid Beta 25-35-induced differentiated neuronal cell death through inhibition of AKT /GSK-3β /Tau/APP /CDK5 pathways in vivo and vitro

Alzheimer (AD) is a degenerative disease that can lead memory loss and behavioral dysfunction. Aβ protein and phosphorylation of Tau protein are related to the onset of AD. However, at present, its treatment and drugs are limited. The purpose of our study is to evaluate whether phosphocreatine (PCr) could protect neuronal injury induced by Aβ protein in vivo and in vitro through AKT/GSK-3β/Tau/APP/CDK5 pathways. Differentiated PC-12 cells were cultured with Aβ25-35 for 24 h, while the mice were injected with D-Galactose for eight weeks, both of them were pretreated with PCr for 2 h. The results showed PCr could obviously induce cells and hippocampus apoptosis using DAPI and TUNEL. PCr decreased the levels of intercellular reactive oxygen species (ROS) and malondialdehyde (MDA), and increased the activities of superoxide dismutase (SOD). Besides, the apoptosis pathway was detected using Western blot, showing that PCr could significantly reduce caspase-3, caspase-9, Bcl-2/Bax expression in vivo and in vitro. At the same time, PCr could decreased Ca²⁺ and apoptosis by Flow Cytometry in PC-12 cells. We observed that the morphological alteration of hippocampus injury was mitigated with the pretreatment of PCr. Furthermore, PCr pretreatment could decrease Aβ25-35-induced PC-12 cells apoptosis with APP cDNA transfection, which up-regulated AKT/GSK-3β/CDK5 pathways and induced Tau phosphorylation. In summary, PCr could reduce Aβ25-35 toxicity to protect neuronal cells via AKT/GSK-3β/CDK5 pathways.

Phosphatidylcholine Ameliorates LPS-Induced Systemic Inflammation and Cognitive Impairments via Mediating the Gut-Brain Axis Balance

Systemic inflammation will cause an imbalance in the steady state of the gut-brain axis. Phosphatidylcholine (PC) is a phospholipid found in egg yolk that has anti-inflammatory and antioxidant properties. The present research proved that PC supplementation (60 mg/kg body weight) for 35 days prevented inflammatory responses and behavioral disturbances in lipopolysaccharide (LPS)-induced mice. PC could regulate the expression of neurotrophic factors and synaptic proteins, which effectively alleviated the nerve damage and synaptic dysfunction caused by LPS. In addition, PC supplementation ameliorated gut barrier damage, altered gut genes, and improved gut health by modulating the cell adhesion molecule (CAM) pathway. Furthermore, PC remodeled the gut microbiome structure in the mice of the LPS group by increasing the relative abundance of Rikenellaceae and Lachnospiraceae. PC also increased short-chain fatty acid (SCFA) production in LPS-induced mice, which in turn ameliorated brain inflammatory responses. In conclusion, PC supplementation may be a nutritional strategy for the prevention of systemic inflammation via the gut-brain axis.

Pharmacological Activity and Mechanism of Tanshinone IIA in Related Diseases

Salvia miltiorrhiza: (Danshen) is a significant (traditional Chinese medication) natural remedy, enhancing blood circulation and clear blood stasis. In this view, it is widely used against several heart diseases, eg, cardiomyopathy, arrhythmia, and congenital heart defects. Tanshinone IIA (tan-IIA) is the main fat-soluble component of Salvia miltiorrhiza. Modern pharmacological study shows that tan-IIA has anti-inflammatory and anti-oxidant activities. Tan-IIA induces remarkable cardioprotective effects via enhancing angiogenesis which may serve as an effective treatment against cardiovascular diseases (CVD). There is also evidence that tan-IIA has extensive immunomodulatory effects and plays a significant role in the development and function of immune cells. Tan-IIA reduces the production of inflammatory mediators and restores abnormal signaling pathways via regulating the function and activation of immune cells. It can also regulate signal transduction pathways, ie, TLR/NF-κB pathway and MAPKs/NF-κB pathway, thereby tan-IIA has an anti-inflammatory, anticoagulant, antithrombotic and neuroprotective role. It plays a protective role in the pathogenesis of cardiovascular disorders (ie, atherosclerosis, hypertension) and Alzheimer’s disease. It has also been revealed that tan-IIA has an anti-tumor role by killing various tumor cells, inducing differentiation and apoptosis, and has potential activity against carcinoma progression. In the review of this fact, the tan-IIA role in different diseases and its mechanism have been summarized while its clinical applications are also explored to provide a new perspective of Salvia miltiorrhiza. An extensive study on the mechanism of action of tan-IIA is of great significance for the effective use of Chinese herbal medicine and the promotion of its status and influence on the world.

An Isoquinolinium Dual Inhibitor of Cholinesterases and Amyloid β Aggregation Mitigates Neuropathological Changes in a Triple-Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder affecting millions of people worldwide. The underlying pathologic mechanisms of AD are unclear. Over the decades, the development of single target agent did not lead to any successful treatment for AD. A multitarget agent that could tackle more than one AD phenotype may be helpful as a treatment strategy. Cholinesterases (ChEs) including acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), are currently the drug targets with approved treatments. Moreover, amyloid beta (Aβ) deposition is a hallmark of AD that receives considerable attention. Herein, 9Q, a previously reported dual target inhibitor dealing with cholinergic dysfunction and amyloid deposition for AD treatment, has undergone thorough investigations. In vitro studies revealed that 9Q exhibited over 80% inhibition of ChE activity at 100 μM and more than 30% inhibition of Aβ aggregation at 1 mM concentration. Moreover 9Q was able to penetrate the blood-brain barrier (BBB) and enhance the cerebral acetylcholine level in triple transgenic AD (3xTg-AD) mice. Following one month treatment with 9Q, the amyloid burden and the cognitive deficits in 3xTg-AD mice were significantly ameliorated. It was observed that 9Q treatment mitigated synapse dysfunction, decreased amyloidogenic APP processing, and reduced the tau pathology in 3xTg-AD mice. Taken together, our results suggested that dual inhibition of cholinesterases and Aβ aggregation could be a promising approach in AD treatment.

Long genes are more frequently affected by somatic mutations and show reduced expression in Alzheimer's disease: Implications for disease etiology

Aging, the greatest risk factor for Alzheimer's disease (AD), may lead to the accumulation of somatic mutations in neurons. We investigated whether somatic mutations, specifically in longer genes, are implicated in AD etiology. First, we modeled the theoretical likelihood of genes being affected by aging‐induced somatic mutations, dependent on their length. We then tested this model and found that long genes are indeed more affected by somatic mutations and that their expression is more frequently reduced in AD brains. Furthermore, using gene‐set enrichment analysis, we investigated the potential consequences of such long gene disruption. We found that long genes are involved in synaptic adhesion and other synaptic pathways that are predicted to be inhibited in the brains of AD patients. Taken together, our findings indicate that long gene–dependent synaptic impairment may contribute to AD pathogenesis.