Advances in developing novel therapeutic strategies for Alzheimer's disease

Mitochondrial Fusion Suppresses Tau Pathology-Induced Neurodegeneration and Cognitive Decline

BACKGROUND

Abnormalities of mitochondrial fission and fusion, dynamic processes known to be essential for various aspects of mitochondrial function, have repeatedly been reported to be altered in Alzheimer's disease (AD). Neurofibrillary tangles are known as a hallmark feature of AD and are commonly considered a likely cause of neurodegeneration in this devastating disease.

OBJECTIVE

To understand the pathological role of mitochondrial dynamics in the context of tauopathy.

METHODS

The widely used P301S transgenic mice of tauopathy (P301S mice) were crossed with transgenic TMFN mice with the forced expression of Mfn2 specifically in neurons to obtain double transgenic P301S/TMFN mice. Brain tissues from 11-month-old non-transgenic (NTG), TMFN, P301S, and P301S/TMFN mice were analyzed by electron microscopy, confocal microscopy, immunoblot, histological staining, and immunostaining for mitochondria, tau pathology, and tau pathology-induced neurodegeneration and gliosis. The cognitive function was assessed by the Barnes maze.

RESULTS

P301S mice exhibited mitochondrial fragmentation and a consistent decrease in Mfn2 compared to age-matched NTG mice. When P301S mice were crossed with TMFN mice (P301S/TMFN mice), neuronal loss, as well as mitochondria fragmentation were significantly attenuated. Greatly alleviated tau hyperphosphorylation, filamentous aggregates, and thioflavin-S positive tangles were also noted in P301S/TMFN mice. Furthermore, P301S/TMFN mice showed marked suppression of neuroinflammation and improved cognitive performance in contrast to P301S mice.

CONCLUSION

These in vivo findings suggest that promoted mitochondrial fusion suppresses toxic tau accumulation and associated neurodegeneration, which may protect against the progression of AD and related tauopathies.

Dysregulated Wnt Signalling in the Alzheimer's Brain

The Wnt signalling system is essential for both the developing and adult central nervous system. It regulates numerous cellular functions ranging from neurogenesis to blood brain barrier biology. Dysregulated Wnt signalling can thus have significant consequences for normal brain function, which is becoming increasingly clear in Alzheimer's disease (AD), an age-related neurodegenerative disorder that is the most prevalent form of dementia. AD exhibits a range of pathophysiological manifestations including aberrant amyloid precursor protein processing, tau pathology, synapse loss, neuroinflammation and blood brain barrier breakdown, which have been associated to a greater or lesser degree with abnormal Wnt signalling. Here we provide a comprehensive overview of the role of Wnt signalling in the CNS, and the research that implicates dysregulated Wnt signalling in the ageing brain and in AD pathogenesis. We also discuss the opportunities for therapeutic intervention in AD via modulation of the Wnt signalling pathway, and highlight some of the challenges and the gaps in our current understanding that need to be met to enable that goal.

Emerging role of AMPA receptor subunit GluA1 in synaptic plasticity: Implications for Alzheimer's disease

It is well established that GluA1 mediated synaptic plasticity plays a central role in the early development of AD. The complex cellular and molecular mechanisms that enable GluA1‐related synaptic regulation remain to fully understood. Particularly, understanding the mechanisms that disrupt GluA1 related synaptic plasticity is central to the development of disease‐modifying therapies which are sorely needed as the incidence of AD rises. We surmise that the published evidence establishes deficits in synaptic plasticity as a central factor of AD aetiology. We additionally highlight potential therapeutic strategies for the treatment of AD, and we delve into the roles of GluA1 in learning and memory. Particularly, we review the current understanding of the molecular interactions that confer the actions of this ubiquitous excitatory receptor subunit including post‐translational modification and accessory protein recruitment of the GluA1 subunit. These are proposed to regulate receptor trafficking, recycling, channel conductance and synaptic transmission and plasticity.

A Community-Based Study Identifying Metabolic Biomarkers of Mild Cognitive Impairment and Alzheimer's Disease Using Artificial Intelligence and Machine Learning

BACKGROUND

Currently, there is no objective, clinically available tool for the accurate diagnosis of Alzheimer's disease (AD). There is a pressing need for a novel, minimally invasive, cost friendly, and easily accessible tool to diagnose AD, assess disease severity, and prognosticate course. Metabolomics is a promising tool for discovery of new, biologically, and clinically relevant biomarkers for AD detection and classification.

OBJECTIVE

Utilizing artificial intelligence and machine learning, we aim to assess whether a panel of metabolites as detected in plasma can be used as an objective and clinically feasible tool for the diagnosis of mild cognitive impairment (MCI) and AD.

METHODS

Using a community-based sample cohort acquired from different sites across the US, we adopted an approach combining Proton Nuclear Magnetic Resonance Spectroscopy (1H NMR), Liquid Chromatography coupled with Mass Spectrometry (LC-MS) and various machine learning statistical approaches to identify a biomarker panel capable of identifying those patients with AD and MCI from healthy controls.

RESULTS

Of the 212 measured metabolites, 5 were identified as optimal to discriminate between controls, and individuals with MCI or AD. Our models performed with AUC values in the range of 0.72-0.76, with the sensitivity and specificity values ranging from 0.75-0.85 and 0.69-0.81, respectively. Univariate and pathway analysis identified lipid metabolism as the most perturbed biochemical pathway in MCI and AD.

CONCLUSION

A comprehensive method of acquiring metabolomics data, coupled with machine learning techniques, has identified a strong panel of diagnostic biomarkers capable of identifying individuals with MCI and AD. Further, our data confirm what other groups have reported, that lipid metabolism is significantly perturbed in those individuals suffering with dementia. This work may provide additional insight into AD pathogenesis and encourage more in-depth analysis of the AD lipidome.

APOE2: protective mechanism and therapeutic implications for Alzheimer's disease

Investigations of apolipoprotein E (APOE) gene, the major genetic risk modifier for Alzheimer's disease (AD), have yielded significant insights into the pathogenic mechanism. Among the three common coding variants, APOE*ε4 increases, whereas APOE*ε2 decreases the risk of late-onset AD compared with APOE*ε3. Despite increased understanding of the detrimental effect of APOE*ε4, it remains unclear how APOE*ε2 confers protection against AD. Accumulating evidence suggests that APOE*ε2 protects against AD through both amyloid-β (Aβ)-dependent and independent mechanisms. In addition, APOE*ε2 has been identified as a longevity gene, suggesting a systemic effect of APOE*ε2 on the aging process. However, APOE*ε2 is not entirely benign; APOE*ε2 carriers exhibit increased risk of certain cerebrovascular diseases and neurological disorders. Here, we review evidence from both human and animal studies demonstrating the protective effect of APOE*ε2 against AD and propose a working model depicting potential underlying mechanisms. Finally, we discuss potential therapeutic strategies designed to leverage the protective effect of APOE2 to treat AD.

Forsythoside B attenuates memory impairment and neuroinflammation via inhibition on NF-κB signaling in Alzheimer's disease

Background

Neuroinflammation is a principal element in Alzheimer’s disease (AD) pathogenesis, so anti-inflammation may be a promising therapeutic strategy. Forsythoside B (FTS•B), a phenylethanoid glycoside isolated from Forsythiae fructus, has been reported to exert anti-inflammatory effects. However, no studies have reported whether the anti-inflammatory properties of FTS•B have a neuroprotective effect in AD. In the present study, these effects of FTS•B were investigated using amyloid precursor protein/presenilin 1 (APP/PS1) mice, BV-2 cells, and HT22 cells.

Methods

APP/PS1 mice were administered FTS•B intragastrically for 36 days. Behavioral tests were then carried out to examine cognitive functions, including the Morris water maze, Y maze, and open field experiment. Immunohistochemistry was used to analyze the deposition of amyloid-beta (Aβ), the phosphorylation of tau protein, and the levels of 4-hydroxynonenal, glial fibrillary acidic protein, and ionized calcium-binding adapter molecule 1 in the hippocampus. Proteins that showed marked changes in levels related to neuroinflammation were identified using proteomics and verified using enzyme-linked immunosorbent assay and western blot. BV-2 and HT22 cells were also used to confirm the anti-neuroinflammatory effects of FTS•B.

Results

In APP/PS1 mice, FTS•B counteracted cognitive decline, ameliorated the deposition of Aβ and the phosphorylation of tau protein, and attenuated the activation of microglia and astrocytes in the cortex and hippocampus. FTS•B affected vital signaling, particularly by decreasing the activation of JNK-interacting protein 3/C-Jun NH2-terminal kinase and suppressing WD-repeat and FYVE-domain-containing protein 1/toll-like receptor 3 (WDFY1/TLR3), further suppressing the activation of nuclear factor-κB (NF-κB) signaling. In BV-2 and HT22 cells, FTS•B prevented lipopolysaccharide-induced neuroinflammation and reduced the microglia-mediated neurotoxicity.

Conclusions

FTS•B effectively counteracted cognitive decline by regulating neuroinflammation via NF-κB signaling in APP/PS1 mice, providing preliminary experimental evidence that FTS•B is a promising therapeutic agent in AD treatment.

The neutrophil-to-lymphocyte ratio in Alzheimer's disease: Current understanding and potential applications

Alzheimer's disease (AD) is a chronic neurodegenerative disorder affecting millions of people, and its prevalence is expected to continue to grow in the older age population. It is characterized by cognitive impairment and dementia on the long term leading to a wide spectrum of social and financial burdens. Due to these burdens, there is a need to have a better understanding of the disease pathophysiology as well as to come up with more readily available and cost-effective screening tools to provide an acceptable estimate of the disease risk/diagnosis in the early years of the disease before dementia develops as it is in these early years that lifestyle modifications can be more effective in protecting against and delaying the frank cognitive impairment associated with AD. Recently, there has been a more detailed, yet incomplete, comprehension of the inflammatory component of the AD pathophysiology. The inflammatory response in AD entails hyperactivation of neutrophils with noticeable changes in their subsets and increased migration of lymphocytes into the central nervous system (CNS) across the compromised blood-brain barrier (BBB). These changes in the counts of the different immune cells in AD allowed for pursuing a new cost-effective, and more widely accessible diagnostic tool, which is the neutrophil-to-lymphocyte ratio (NLR). In this review, we aimed to discuss the inflammatory response in AD, and how this response is reflected in the counts of different immune cells, mainly neutrophils and lymphocytes which can be implemented in the utility of NLR as a diagnostic tool in AD patients.

Inhibition of Calpain Protects Against Tauopathy in Transgenic P301S Tau Mice

Alzheimer's disease (AD) and other tauopathies are characterized by intracellular accumulation of microtubule-associated tau protein leading to neurodegeneration. Calpastatin is the endogenous inhibitor of calpain, a calcium-dependent cysteine protease that has been increasingly implicated in tauopathies. In this study, we generated a neuron specific calpastatin overexpressing knock-in transgenic mouse model and crossed it with the PS19 tauopathy mouse model expressing human P301S mutant tau protein. The forced expression of calpastatin in neurons significantly alleviated tau hyperphosphorylation measured by immunocytochemistry and immunoblot. The genetic inhibition of calpain by calpastatin also greatly suppressed characteristic hippocampal neuron loss and widespread astrogliosis and microgliosis in PS19 mice. Consistently, PS19 mice with neuronal calpastatin overexpression exhibited remarkably alleviated cognitive deficits, muscle weakness, skeletal muscle atrophy, and neuromuscular denervation, together implying the neuroprotective effects of neuronal calpastatin in PS19 mice of tauopathy. In sum, this study provides additional evidence supporting the pathological role of calpain in neurodegenerative diseases associated with tau pathology, and suggests that targeting calpain is likely a promising therapeutic approach for these devastating diseases.

Shenzao jiannao oral liquid, an herbal formula, ameliorates cognitive impairments by rescuing neuronal death and triggering endogenous neurogenesis in AD-like mice induced by a combination of Aβ42 and scopolamine

ETHNOPHARMACOLOGICAL RELEVANCE

According to the theory of traditional Chinese medicine (TCM), Alzheimer's disease (AD) is identified as "forgetfulness" or "dementia", and is mainly caused by "kidney essence deficiency" which ultimately induces "encephala reduction". Therefore, herbal formulas possessing the efficacy of nourishing kidney essence or replenishing brain marrow are commonly served as effective strategies for AD treatment. Shenzao jiannao oral liquid (SZJN), a traditional Chinese preparation approved by the China Food and Drug Administration (CFDA), is used for the treatment of insomnia and mind fatigue at present for its efficacy of nourishing kidneys. In present study, we found that SZJN could improve cognitive function of AD-like mice.

AIMS OF STUDY

This study aims to investigate the effects of SJZN on ameliorating cognitive deficits of AD-like mouse model, and to illuminate the underlying mechanisms from the perspective of neuroprotection and neurogenesis.

MATERIALS AND METHODS

Kunming mice (28 ± 2 g) were randomly allocated into seven groups: control, sham, model, donepezil and SZJN groups (low, middle and high). The AD mouse model was established by Aβ42 combined with scopolamine. SZJN were intragastrically administrated at doses of 0.3, 1.5 and 7.5 g/kg for 28 days. Morris water maze (MWM) test was applied to determine the cognitive function. Hematoxylin eosin (HE) and Nissl staining were carried out to evaluate pathological damages in the cortex and hippocampal tissues. To explore the protective effects of SZJN on multiple pathogenic factors of AD, protein levels of Aβ42, glial fibrillary acidic protein (GFAP), Bax, Bcl-2, Caspase-3, synaptophysin (SYP), brain-derived neurotrophic factor (BDNF), and neurogenesis related proteins were assessed using Immunofluorescence (IF) and western blot analysis. In vitro, the AD cell model was established by transduction of APP_695swe genes into Neural stem cells (NSCs) isolated from the hippocampal tissues of neonatal C57BL/6 mice. Cell viability assay and neurosphere formation assay were carried out to verify the efficacy of SZJN on proliferation of NSCs.

RESULTS

Our results demonstrated that SZJN (1.5 g/kg and 7.5 g/kg) treatment significantly ameliorated cognitive deficits of AD-like mice. SZJN (7.5 g/kg) treatment significantly retarded the pathological damages including neuronal degeneration, neuronal apoptosis, Aβ peptides aggregation and reaction of astrocytes in AD-like mice. In addition, SZJN (7.5 g/kg) increased the expression of BDNF and SYP, and restored the abnormal level of MDA and SOD in the brain of AD-like mice. Furthermore, SZJN treatment for 28 days remarkably increased the proliferation of NSCs evidenced by more Nestin⁺ and BrdU⁺ cells in the hippocampal DG regions, and increased the amount of mature neurons marked by NeuN both in the cortex and hippocampal DG regions. In vitro, SZJN treatement (16, 32, 64 mg/ml) promoted the proliferation of NSCs evidenced by the increased amount and enlarged size of the neurospheres (p < 0.05).

CONCLUSIONS

Our findings indicated that SZJN could ameliorate cognitive deficits by protecting neurons from death and triggering endogenous neurogenesis. Therefore, SZJN may be considered as a promising agent to restore neuronal loss and deter the deterioration in AD patients.

Upregulation of Prickle2 Ameliorates Alzheimer's Disease-Like Pathology in a Transgenic Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD) is a devastating neurodegenerative disorder that has no effective therapies. Prickle planar cell polarity protein 2 (Prickle2), is an important cytoplasmic regulator of Wnt/PCP signaling. It has been reported that Prickle2 deficiency reduced neurite outgrowth levels in mouse N2a cells and led to autism-like behaviors and hippocampal synaptic dysfunction in mice. However, much less is known about the relationship of Prickle2 to AD pathogenesis. RT-qPCR, Western blot and IHC results showed that the mRNA and protein levels of Prickle2 were reduced in APP/PS1/Tau transgenic (3xTg) mice. Intravenous injection of Prickle2-overexpressing AAV-PHP.eB vectors improved the cognitive deficits in 3xTg mice. We also demonstrated that Prickle2 could repress oxidative stress and neuroinflammation, ameliorate the amyloid β (Aβ) plaque pathology and reduce Tau hyperphosphorylation in APP/PS1 mice. Further investigation of the mechanism of Prickle2 in AD revealed that Prickle2 inhibited Wnt/PCP/JNK pathway in vivo and in vitro. Our results suggest that Prickle2 might be a potential candidate for the diagnosis and treatment of AD.

Recent developments of small molecule γ-secretase modulators for Alzheimer's disease

Alzheimer's disease (AD) is the most common form of progressive neurodegenerative disorder, marked by memory loss and a decline in cognitive function. The major hallmarks of AD are the presence of intracellular neurofibrillary tau tangles (NFTs) composed of hyperphosphorylated tau proteins and extracellular plaques composed of amyloid beta peptides (Aβ). The amyloid (Aβ) cascade hypothesis proposes that the AD pathogenesis is initiated by the accumulation of Aβ peptides in the parenchyma of the brain. An aspartyl intramembranal protease called γ-secretase is responsible for the production of Aβ by the cleavage of the amyloid precursor protein (APP). Clinical studies of γ-secretase inhibitors (GSIs) for AD failed due to the lack of substrate specificity. Therefore, γ-secretase modulators (GSMs) have been developed as potential disease modifying agents to modulate the γ-secretase cleavage activity towards the production of toxic Aβ42 peptides. Following the first-generation 'nonsteroidal anti-inflammatory drug' (NSAID) based GSMs, second-generation GSMs (carboxylic acid based NSAID derivatives and non-NSAID derived heterocyclic analogues), as well as natural product-based GSMs, have been developed. In this review, we focus on the recent developments of small molecule-based GSMs that show potential improvements in terms of drug-like properties as well as their current status in human clinical trials and the future perspectives of GSM research.

Therapeutic Strategies Targeting Amyloid-β in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder linked to protein misfolding and aggregation. AD is pathologically characterized by senile plaques formed by extracellular Amyloid-β (Aβ) peptide and Intracellular Neurofibrillary Tangles (NFT) formed by hyperphosphorylated tau protein. Extensive synaptic loss and neuronal degeneration are responsible for memory impairment, cognitive decline and behavioral dysfunctions typical of AD. Amyloidosis has been implicated in the depression of acetylcholine synthesis and release, overactivation of N-methyl-D-aspartate (NMDA) receptors and increased intracellular calcium levels that result in excitotoxic neuronal degeneration. Current drugs used in AD treatment are either cholinesterase inhibitors or NMDA receptor antagonists; however, they provide only symptomatic relief and do not alter the progression of the disease. Aβ is the product of Amyloid Precursor Protein (APP) processing after successive cleavage by β- and γ-secretases while APP proteolysis by α-secretase results in non-amyloidogenic products. According to the amyloid cascade hypothesis, Aβ dyshomeostasis results in the accumulation and aggregation of Aβ into soluble oligomers and insoluble fibrils. The former are synaptotoxic and can induce tau hyperphosphorylation while the latter deposit in senile plaques and elicit proinflammatory responses, contributing to oxidative stress, neuronal degeneration and neuroinflammation. Aβ-protein-targeted therapeutic strategies are thus a promising disease-modifying approach for the treatment and prevention of AD. This review summarizes recent findings on Aβ-protein targeted AD drugs, including β-secretase inhibitors, γ-secretase inhibitors and modulators, α-secretase activators, direct inhibitors of Aβ aggregation and immunotherapy targeting Aβ, focusing mainly on those currently under clinical trials.

Stem cell therapy for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory loss and cognitive impairment. It is caused by synaptic failure and excessive accumulation of misfolded proteins. To date, almost all advanced clinical trials on specific AD-related pathways have failed mostly due to a large number of neurons lost in the brain of patients with AD. Also, currently available drug candidates intervene too late. Stem cells have improved characteristics of self-renewal, proliferation, differentiation, and recombination with the advent of stem cell technology and the transformation of these cells into different types of central nervous system neurons and glial cells. Stem cell treatment has been successful in AD animal models. Recent preclinical studies on stem cell therapy for AD have proved to be promising. Cell replacement therapies, such as human embryonic stem cells or induced pluripotent stem cell-derived neural cells, have the potential to treat patients with AD, and human clinical trials are ongoing in this regard. However, many steps still need to be taken before stem cell therapy becomes a clinically feasible treatment for human AD and related diseases. This paper reviews the pathophysiology of AD and the application prospects of related stem cells based on cell type.

Deciphering Alzheimer's disease: predicting new therapeutic strategies via improved understanding of biology and pathogenesis

INTRODUCTION

There is no cure for Alzheimer's disease (AD). One explanation may pertain to the need to intervene as early as possible upstream from the accumulation of β-amyloid plaques and tau tangles.

AREAS COVERED

A PUBMED literature search was completed to review the biological or pathological changes at the basis of disease initiation; this includes neuroinflammation, oxidative stress, microbiome changes and glymphatic system dysfunction. Innovative therapeutic strategies based on these mechanisms are also discussed.

EXPERT OPINION

Improved understanding of the pathophysiological mechanisms that underly AD would assist in the identification of drug targets for clinical trials. Furthermore, pharmacokinetic and pharmacodynamic studies are key for the characterization of the properties of disease-modifying drugs and the improvement of their penetration of the blood-brain barrier. Drug targets can be examined at different stages of the disease, hence the importance of selecting and recruiting the appropriate participants, preferably at the earliest stage of AD. New trial designs should be established which primarily involve combination therapies that can work synergistically on common pathways. Going forward, innovative treatment strategies involving nanotechnology, young blood products transfusion and photobiomodulation also offer promise for the future.

MicroRNAs Related to Cognitive Impairment After Hearing Loss

Objectives

Our research group has previously demonstrated that hearing loss might be a risk factor for synaptic loss within the hippocampus and impairment of cognition using an animal model of Alzheimer disease. In this study, after inducing hearing loss in a rat model of Alzheimer disease, the associations of various microRNAs (miRNAs) with cognitive impairment were investigated.

Methods

Rats were divided randomly into two experimental groups: the control group, which underwent sham surgery and subthreshold amyloid-β infusion and the deaf group, which underwent bilateral cochlear ablation and subthreshold amyloid-β infusion. All rats completed several cognitive function assessments 11 weeks after surgery, including the object-in-place task (OPT), the novel object recognition task (NOR), the object location task (OLT), and the Y-maze test. After the rats completed these tests, hippocampus tissue samples were assessed using miRNA microarrays. Candidate miRNAs were selected based on the results and then validated with quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analyses.

Results

The deaf group showed considerably lower scores on the OPT, OLT, and Y-maze test than the control group. The microarray analysis revealed that miR-29b-3p, -30e-5p, -153-3p, -376a-3p, -598-3p, -652-5p, and -873-3p were candidate miRNAs, and qRT-PCR showed significantly higher levels of miR-376a-3p and miR-598-3p in the deaf group.

Conclusion

These results indicate that miR-376a-3p and miR-598-3p were related to cognitive impairment after hearing loss.

Brain-Derived Neurotrophic Factor (BDNF) Preserves the Functional Integrity of Neural Networks in the β-Amyloidopathy Model in vitro

Alzheimer’s disease (AD) is a widespread chronic neurodegenerative pathology characterized by synaptic dysfunction, partial neuronal death, cognitive decline and memory impairments. The major hallmarks of AD are extracellular senile amyloid plaques formed by various types of amyloid proteins (Aβ) and the formation and accumulation of intracellular neurofibrillary tangles. However, there is a lack of relevant experimental models for studying changes in neural network activity, the features of intercellular signaling or the effects of drugs on the functional activity of nervous cells during AD development. In this work, we examined two experimental models of amyloidopathy using primary hippocampal cultures. The first model involves the embryonic brains of 5xFAD mice; the second uses chronic application of amyloid beta 1-42 (Aβ1-42). The model based on primary hippocampal cells obtained from 5xFAD mice demonstrated changes in spontaneous network calcium activity characterized by a decrease in the number of cells exhibiting Ca²⁺ activity, a decrease in the number of Ca²⁺ oscillations and an increase in the duration of Ca²⁺ events from day 21 of culture development in vitro. Chronic application of Aβ1-42 resulted in the rapid establishment of significant neurodegenerative changes in primary hippocampal cultures, leading to marked impairments in neural network calcium activity and increased cell death. Using this model and multielectrode arrays, we studied the influence of amyloidopathy on spontaneous bioelectrical neural network activity in primary hippocampal cultures. It was shown that chronic Aβ application decreased the number of network bursts and spikes in a burst. The spatial structure of neural networks was also disturbed that characterized by reduction in both the number of key network elements (hubs) and connections between network elements. Moreover, application of brain-derived neurotrophic factor (BDNF) recombinant protein and BDNF hyperexpression by an adeno-associated virus vector partially prevented these amyloidopathy-induced neurodegenerative phenomena. BDNF maintained cell viability and spontaneous bioelectrical and calcium network activity in primary hippocampal cultures.

Periodontal Disease and Periodontal Disease-Related Bacteria Involved in the Pathogenesis of Alzheimer's Disease

Alzheimer’s disease (AD) is the most common cause of dementia, and it exhibits pathological properties such as deposition of extracellular amyloid β (Aβ) and abnormally phosphorylated Tau in nerve cells and a decrease of synapses. Conventionally, drugs targeting Aβ and its related molecules have been developed on the basis of the amyloid cascade hypothesis, but sufficient effects on the disease have not been obtained in past clinical trials. On the other hand, it has been pointed out that chronic inflammation and microbial infection in the brain may be involved in the pathogenesis of AD. Recently, attention has been focused on the relationship between the periodontopathic bacterium Porphylomonas gingivalis and AD. P. gingivalis and its toxins have been detected in autopsy brain tissues from patients with AD. In addition, pathological conditions of AD are formed or exacerbated in mice infected with P. gingivalis. Compounds that target the toxins of P. gingivalis ameliorate the pathogenesis of AD triggered by P. gingivalis infection. These findings indicate that the pathological condition of AD may be regulated by controlling the bacteria in the oral cavity and the body. In the current aging society, the importance of oral and periodontal care for preventing the onset of AD will increase.

Soluble SORLA Enhances Neurite Outgrowth and Regeneration through Activation of the EGF Receptor/ERK Signaling Axis

SORLA is a transmembrane trafficking protein associated with Alzheimer's disease risk. Although SORLA is abundantly expressed in neurons, physiological roles for SORLA remain unclear. Here, we show that cultured transgenic neurons overexpressing SORLA feature longer neurites, and accelerated neurite regeneration with wounding. Enhanced release of a soluble form of SORLA (sSORLA) is observed in transgenic mouse neurons overexpressing human SORLA, while purified sSORLA promotes neurite extension and regeneration. Phosphoproteomic analyses demonstrate enrichment of phosphoproteins related to the epidermal growth factor (EGFR)/ERK pathway in SORLA transgenic mouse hippocampus from both genders. sSORLA coprecipitates with EGFR in vitro, and sSORLA treatment increases EGFR Y1173 phosphorylation, which is involved in ERK activation in cultured neurons. Furthermore, sSORLA triggers ERK activation, whereas pharmacological EGFR or ERK inhibition reverses sSORLA-dependent enhancement of neurite outgrowth. In search for downstream ERK effectors activated by sSORLA, we identified upregulation of Fos expression in hippocampus from male mice overexpressing SORLA by RNAseq analysis. We also found that Fos is upregulated and translocates to the nucleus in an ERK-dependent manner in neurons treated with sSORLA. Together, these results demonstrate that sSORLA is an EGFR-interacting protein that activates EGFR/ERK/Fos signaling to enhance neurite outgrowth and regeneration.SIGNIFICANCE STATEMENT SORLA is a transmembrane trafficking protein previously known to reduce the levels of amyloid-β, which is critical in the pathogenesis of Alzheimer's disease. In addition, SORLA mutations are a risk factor for Alzheimer's disease. Interestingly, the SORLA ectodomain is cleaved into a soluble form, sSORLA, which has been shown to regulate cytoskeletal signaling pathways and cell motility in cells outside the nervous system. We show here that sSORLA binds and activates the EGF receptor to induce downstream signaling through the ERK serine/threonine kinase and the Fos transcription factor, thereby enhancing neurite outgrowth. These findings reveal a novel role for sSORLA in promoting neurite regeneration through the EGF receptor/ERK/Fos pathway, thereby demonstrating a potential neuroprotective mechanism involving SORLA.

Loss of β-catenin via activated GSK3β causes diabetic retinal neurodegeneration by instigating a vicious cycle of oxidative stress-driven mitochondrial impairment

Synaptic neurodegeneration of retinal ganglion cells (RGCs) is the earliest event in the pathogenesis of diabetic retinopathy. Our previous study proposed that impairment of mitochondrial trafficking by hyperphosphorylated tau is a potential contributor to RGCs synapse degeneration. However, other molecular mechanisms underlying mitochondrial defect in diabetic retinal neurodegeneration remain to be elucidated. Here, using a high-fat diet (HFD)-induced diabetic mouse model, we showed for the first time that downregulation of active β-catenin due to abnormal GSK3β activation caused synaptic neurodegeneration of RGCs by inhibiting ROS scavenging enzymes, thus triggering oxidative stress-driven mitochondrial impairment in HFD-induced diabetes. Rescue of β-catenin via ectopic expression of β-catenin with a recombinant adenoviral vector, or via GSK3β inhibition by a targeted si-GSK3β, through intravitreal administration, abrogated the oxidative stress-derived mitochondrial defect and synaptic neurodegeneration in diabetic RGCs. By contrast, ablation of β-catenin by si-β-catenin abolished the protective effect of GSK3β inhibition on diabetic RGCs by suppression of antioxidant scavengers and augmentation of oxidative stress-driven mitochondrial lesion. Thus, our data identify β-catenin as a part of an endogenous protective system in diabetic RGCs and a promising target to develop intervention strategies that protect RGCs from neurodegeneration at early onset of diabetic retinopathy.

Testing whether the progression of Alzheimer's disease changes with the year of publication, additional design, and geographical area: a modeling analysis of literature aggregate data

BACKGROUND

Our objectives were to develop a disease progression model for cognitive decline in Alzheimer's disease (AD) and to determine whether disease progression of AD is related to the year of publication, add-on trial design, and geographical regions.

METHODS

Placebo-controlled randomized AD clinical trials were systemically searched in public databases. Longitudinal placebo response (mean change from baseline in the cognitive subscale of the Alzheimer's Disease Assessment Scale [ADAS-cog]) and the corresponding demographic information were extracted to establish a disease progression model. Covariate screening and subgroup analyses were performed to identify potential factors affecting the disease progression rate.

RESULTS

A total of 134 publications (140 trials) were included in this model-based meta-analysis. The typical disease progression rate was 5.82 points per year. The baseline ADAS-cog score was included in the final model using an inverse U-type function. Age was found to be negatively correlated with disease progression rate. After correcting the baseline ADAS-cog score and the age effect, no significant difference in the disease progression rate was found between trials published before and after 2008 and between trials using an add-on design and those that did not use an add-on design. However, a significant difference was found among different trial regions. Trials in East Asian countries showed the slowest decline rate and the largest placebo effect.

CONCLUSIONS

Our model successfully quantified AD disease progression by integrating baseline ADAS-cog score and age as important predictors. These factors and geographic location should be considered when optimizing future trial designs and conducting indirect comparisons of clinical outcomes.

A Perspective on Multi-target Drugs for Alzheimer's Disease

Alzheimer's disease (AD) has a complex pathophysiology that includes aggregation of pathological proteins, impaired neurotransmission, increased oxidative stress, or microglia-mediated neuroinflammation. Therapeutics targeting only one of these AD-related subpathologies have not yet been successful in the search for a disease-modifying treatment. Therefore, multi-target drugs (MTDs) aiming simultaneously at several subpathologies are expected to be a better approach. However, the concept of MTD is inherently connected with several limitations, which are often ignored during MTD design and development. Here, we provide an overview of the MTD approach and discuss its potential pitfalls in the context of AD treatment. We also put forward ideas to be used in the rational design of MTDs to obtain drugs that are effective against AD.

Extract of Danggui-Shaoyao-San ameliorates cognition deficits by regulating DHA metabolism in APP/PS1 mice

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional Chinese medicine formula Danggui-Shaoyao-San (DSS) has been reported to show therapeutic effect on alleviating the symptoms of Alzheimer's disease (AD).

AIM OF THE STUDY

The present study aims to investigate the relation between DSS treatment of AD and DHA metabolism and evaluates its neuroprotective effect on cognitive in APP/PS1 mice.

MATERIAL AND METHODS

DSS (1.6, 3.2, 6.4 g/kg/day) or Aricept (3 mg/kg/day) was orally administered (i.g.) to APP/PS1 mice, and saline was orally administered to Wild-type (WT) male mice as control group. Then, the Morris water maze (MWM) test, Y-maze spontaneous alternation test, open filed test and fear conditioning test were conducted for evaluation of learning and memory abilities. The DHA content was assessed by HPLC-MS/MS. Physiological indices were determined, including triglyceride (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), ROS level, activity of superoxide dismutase (SOD), glutathione (GSH), malondialdehyde (MDA), PEG2, TXB2 and LTB4. The expressions of COX-1, COX-2, cPLA2, iPLA2, 15-LOX, and were assessed by Western blot.

RESULTS

APP/PS1 mice showed serious cognitive impairment in behavioral tests. However, treatment of DSS extract significantly ameliorated the cognitive deficits of APP/PS1 mice. Biochemical measurements showed the increases in TG, TC, LDL-c and the decrease in HDL-c in APP/PS1 mice compared with WT mice, and DSS extract significantly retarded these changes. Low content of DHA, low expression of iPLA2 and 15-LOX were observed both in hippocampus and cortex of APP/PS1 mice, while DSS extract significantly restored these changes. Additionally, the abnormal activity of SOD and ROS level, the decreased levels of MDA and GSH were observed in APP/PS1 mice, while DSS extract prominently lessened these changes. Moreover, DSS extract decreased the level of PEG2, TXB2 and LTB4 and also attenuated the expression of cPLA2, COX-1 and COX-2 in hippocampus as well as cortex of APP/PS1 mice.

CONCLUSIONS

Based on these results, we suggest that DSS play a positive effective role in increasing DHA content by up-regulating iPLA2 and 15-LOX, resulting in ameliorating oxidative stress and inflammation and finally ameliorating cognition deficits in APP/PS1 mice.

The role of cell type-specific mitochondrial dysfunction in the pathogenesis of Alzheimer's disease

The decrease of metabolism in the brain has been observed as the important lesions of Alzheimer’s disease (AD) from the early stages of diagnosis. The cumulative evidence has reported that the failure of mitochondria, an organelle involved in diverse biological processes as well as energy production, maybe the cause or effect of the pathogenesis of AD. Both amyloid and tau pathologies have an impact upon mitochondria through physical interaction or indirect signaling pathways, resulting in the disruption of mitochondrial function and dynamics which can trigger AD. In addition, mitochondria are involved in different biological processes depending on the specific functions of each cell type in the brain. Thus, it is necessary to understand mitochondrial dysfunction as part of the pathological phenotypes of AD according to each cell type. In this review, we summarize that 1) the effects of AD pathology inducing mitochondrial dysfunction and 2) the contribution of mitochondrial dysfunction in each cell type to AD pathogenesis.

Targeting the Wnt/β-catenin pathway in neurodegenerative diseases: recent approaches and current challenges

INTRODUCTION

Wnt/β-catenin signaling is an evolutionarily conserved pathway having a crucial role in embryonic and adult life. Specifically, the Wnt/β-catenin axis is pivotal to the development and homeostasis of the nervous system, and its dysregulation has been associated with various neurological disorders, including neurodegenerative diseases. Therefore, this signaling pathway has been proposed as a potential therapeutic target against neurodegeneration.

AREAS COVERED

This review focuses on the role of Wnt/β-catenin pathway in the pathogenesis of neurodegenerative diseases, including Parkinson's, Alzheimer's Diseases and Amyotrophic Lateral Sclerosis. The evidence showing that defects in the signaling might be involved in the development of these diseases, and the pharmacological approaches tested so far, are discussed. The possibilities that this pathway offers in terms of new therapeutic opportunities are also considered.

EXPERT OPINION

The increasing interest paid to the role of Wnt/β-catenin pathway in the onset of neurodegenerative diseases demonstrates how targeting this signaling for therapeutic purposes could be a great opportunity for both neuroprotection and neurorepair. Without overlooking some licit concerns about drug safety and delivery to the brain, there is growing and more convincing evidence that restoring this signaling in neurodegenerative diseases may strongly increase the chance to develop disease-modifying treatments for these brain pathologies.

Systems Pharmacology Approach to Investigate the Mechanism of Kai-Xin-San in Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disease characterized by cognitive dysfunction. Kai-Xin-San (KXS) is a traditional Chinese medicine (TCM) formula that has been used to treat AD patients for over a thousand years in China. However, the therapeutic mechanisms of KXS for treating AD have not been fully explored. Herein, we used a comprehensive network pharmacology approach to investigate the mechanism of action of KXS in the treatment of AD. This approach consists of construction of multiple networks and Gene Ontology enrichment and pathway analyses. Furthermore, animal experiments were performed to validate the predicted molecular mechanisms obtained from the systems pharmacology-based analysis. As a result, 50 chemicals in KXS and 39 AD-associated proteins were identified as major active compounds and targets, respectively. The therapeutic mechanisms of KXS in treating AD were primarily related to the regulation of four pathology modules, including amyloid beta metabolism, tau protein hyperphosphorylation process, cholinergic dysfunction, and inflammation. In scopolamine-induced cognitive dysfunction mice, we validated the anti-inflammatory effects of KXS on AD by determining the levels of inflammation cytokines including interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α. We also found cholinergic system dysfunction amelioration of KXS is correlated with upregulation of the cholinergic receptor CHRNB2. In conclusion, our work proposes a comprehensive systems pharmacology approach to explore the underlying therapeutic mechanism of KXS for the treatment of AD.

Combining Virtual Screening Protocol and In Vitro Evaluation towards the Discovery of BACE1 Inhibitors

The treatment options for a patient diagnosed with Alzheimer’s disease (AD) are currently limited. The cerebral accumulation of amyloid-β (Aβ) is a critical molecular event in the pathogenesis of AD. When the amyloidogenic β-secretase (BACE1) is inhibited, the production of Aβ peptide is reduced. Henceforth, the main goal of this study is the discovery of new small bioactive molecules that potentially reach the brain and inhibit BACE1. The work was conducted by a customized molecular modelling protocol, including pharmacophore-based and molecular docking-based virtual screening (VS). Structure-based (SB) and ligand-based (LB) pharmacophore models were designed to accurately screen several drug-like compound databases. The retrieved hits were subjected to molecular docking and in silico filtered to predict their ability to cross the blood–brain barrier (BBB). Additionally, 34 high-scoring compounds structurally distinct from known BACE1 inhibitors were selected for in vitro screening assay, which resulted in 13 novel hit-compounds for this relevant therapeutic target. This study disclosed new BACE1 inhibitors, proving the utility of combining computational and in vitro approaches for effectively predicting anti-BACE1 agents in the early drug discovery process.

Research Progress on Alzheimer's Disease and Resveratrol

Alzheimer's disease (AD), a common irreversible neurodegenerative disease characterized by amyloid-β plaques, neurofibrillary tangles, and changes in tau phosphorylation, is accompanied by memory loss and symptoms of cognitive dysfunction. Increases in disease incidence due to the ageing of the population have placed a great burden on society. To date, the mechanism of AD and the identities of adequate drugs for AD prevention and treatment have eluded the medical community. It has been confirmed that phytochemicals have certain neuroprotective effects against AD. For example, some progress has been made in research on the use of resveratrol, a natural polyphenolic phytochemical, for the prevention and treatment of AD in recent years. Elucidation of the pathogenesis of AD will create a solid foundation for drug treatment. In addition, research on resveratrol, including its mechanism of action, the roles of signalling pathways and its therapeutic targets, will provide new ideas for AD treatment, which is of great significance. In this review, we discuss the possible relationships between AD and the following factors: synapses, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors (AMPARs), silent information regulator 1 (SIRT1), and estrogens. We also discuss the findings of previous studies regarding these relationships in the context of AD treatment and further summarize research progress related to resveratrol treatment.

Therapeutic Potential of Diosgenin and Its Major Derivatives against Neurological Diseases: Recent Advances

Diosgenin (DG), a well-known steroidal sapogenin, is present abundantly in medicinal herbs such as Dioscorea rhizome, Dioscorea villosa, Trigonella foenum-graecum, Smilax China, and Rhizoma polgonati. DG is utilized as a major starting material for the production of steroidal drugs in the pharmaceutical industry. Due to its wide range of pharmacological activities and medicinal properties, it has been used in the treatment of cancers, hyperlipidemia, inflammation, and infections. Numerous studies have reported that DG is useful in the prevention and treatment of neurological diseases. Its therapeutic mechanisms are based on the mediation of different signaling pathways, and targeting these pathways might lead to the development of effective therapeutic agents for neurological diseases. The present review mainly summarizes recent progress using DG and its derivatives as therapeutic agents for multiple neurological disorders along with their various mechanisms in the central nervous system. In particular, those related to therapeutic efficacy for Parkinson's disease, Alzheimer's disease, brain injury, neuroinflammation, and ischemia are discussed. This review article also critically evaluates existing limitations associated with the solubility and bioavailability of DG and discusses imperatives for translational clinical research. It briefly recapitulates recent advances in structural modification and novel formulations to increase the therapeutic efficacy and brain levels of DG. In the present review, databases of PubMed, Web of Science, and Scopus were used for studies of DG and its derivatives in the treatment of central nervous system diseases published in English until December 10, 2019. Three independent researchers examined articles for eligibility. A total of 150 articles were screened from the above scientific literature databases. Finally, a total of 46 articles were extracted and included in this review. Keywords related to glioma, ischemia, memory, aging, cognitive impairment, Alzheimer, Parkinson, and neurodegenerative disorders were searched in the databases based on DG and its derivatives.

A Network-Based Approach to Explore the Mechanisms of Uncaria Alkaloids in Treating Hypertension and Alleviating Alzheimer's Disease

Uncaria alkaloids are the major bioactive chemicals found in the Uncaria genus, which have a long history of clinical application in treating cardiovascular and mental diseases in traditional Chinese medicine (TCM). However, there are gaps in understanding the multiple targets, pathways, and biological activities of Uncaria alkaloids. By constructing the interactions among drug-targets-diseases, network pharmacology provides a systemic methodology and a novel perspective to present the intricate connections among drugs, potential targets, and related pathways. It is a valuable tool for studying TCM drugs with multiple indications, and how these multi-indication drugs are affected by complex interactions in the biological system. To better understand the mechanisms and targets of Uncaria alkaloids, we built an integrated analytical platform based on network pharmacology, including target prediction, protein-protein interaction (PPI) network, topology analysis, gene enrichment analysis, and molecular docking. Using this platform, we revealed the underlying mechanisms of Uncaria alkaloids' anti-hypertensive effects and explored the possible application of Uncaria alkaloids in preventing Alzheimer's disease. These results were further evaluated and refined using biological experiments. Our study provides a novel strategy for understanding the holistic pharmacology of TCM, as well as for exploring the multi-indication properties of TCM beyond its traditional applications.

Endogenous 3-Iodothyronamine (T1AM) and Synthetic Thyronamine-like Analog SG-2 Act as Novel Pleiotropic Neuroprotective Agents Through the Modulation of SIRT6

3-iodothyronamine (T1AM) and the recently developed analog SG-2 are rapidly emerging as promising multi-target neuroprotective ligands able to reprogram lipid metabolism and to produce memory enhancement in mice. To elucidate the molecular mechanisms underlying the multi-target effects of these novel drug candidates, here we investigated whether the modulation of SIRT6, known to play a key role in reprogramming energy metabolism, might also drive the activation of clearing pathways, such as autophagy and ubiquitine-proteasome (UP), as further mechanisms against neurodegeneration. We show that both T1AM and SG-2 increase autophagy in U87MG cells by inducing the expression of SIRT6, which suppresses Akt activity thus leading to mTOR inhibition. This effect was concomitant with down-regulation of autophagy-related genes, including Hif1α, p53 and mTOR. Remarkably, when mTOR was inhibited a concomitant activation of autophagy and UP took place in U87MG cells. Since both compounds activate autophagy, which is known to sustain long term potentiation (LTP) in the entorhinal cortex (EC) and counteracting AD pathology, further electrophysiological studies were carried out in a transgenic mouse model of AD. We found that SG-2 was able to rescue LTP with an efficacy comparable to T1AM, further underlying its potential as a novel pleiotropic agent for neurodegenerative disorders treatment.

Plasma levels of Interleukin 18 but not amyloid-β or Tau are elevated in female depressive patients

BACKGROUND

Depression is associated with inflammation and Alzheimer's disease (AD). However, detailed molecular mechanisms linking mood, neuroinflammation and AD remain unclear. Although changes in peripheral inflammatory factors such as Interleukin 18 (IL18), and AD-associated amyloid-β (Aβ) peptides have been linked to depression, a solid relationship between these factors in depressive disorder has yet to be established. This study aims to further determine whether plasma IL18, Aβ40, Aβ42, and the AD-associated tangle component Tau, as well as IL18 single nucleotide polymorphisms (SNPs) may be biomarkers for depression.

METHODS

We measured plasma IL18, Aβ40, Aβ42, and Tau in 64 depressive patients and 75 healthy controls, and characterized genotypes of three IL18 SNPs (rs187238, rs1946518 and rs1946519) in these subjects. Comparisons between depressive patients and controls were carried out in males, in females or in combination. Regression analyses were conducted to examine the correlation between these parameters.

RESULTS

We found that none of the plasma levels of IL18, Aβ40, Aβ42, and Tau, the ratio of Aβ42/Aβ40, and the genotypes of IL18 SNPs were significantly different between combined depressive patients and combined healthy controls, or between male depressive patients and male controls. However, IL18 levels were less in females than in males in healthy people and were significantly increased in female depressive patients compared to female controls. Moreover, IL18 and standardized IL18 were correlated with standardized Aβ42/Aβ40 ratio and standardized Tau in depressive patients.

CONCLUSIONS

Plasma IL18 may be a potential biomarker for depression in women.

β-amyloid redirects norepinephrine signaling to activate the pathogenic GSK3β/tau cascade

The brain noradrenergic system is critical for normal cognition and is affected at early stages in Alzheimer's disease (AD). Here, we reveal a previously unappreciated direct role of norepinephrine signaling in connecting β-amyloid (Aβ) and tau, two key pathological components of AD pathogenesis. Our results show that Aβ oligomers bind to an allosteric site on α2A adrenergic receptor (α2AAR) to redirect norepinephrine-elicited signaling to glycogen synthase kinase 3β (GSK3β) activation and tau hyperphosphorylation. This norepinephrine-dependent mechanism sensitizes pathological GSK3β/tau activation in response to nanomolar accumulations of extracellular Aβ, which is 50- to 100-fold lower than the amount required to activate GSK3β by Aβ alone. The significance of our findings is supported by in vivo evidence in two mouse models, human tissue sample analysis, and longitudinal clinical data. Our study provides translational insights into mechanisms underlying Aβ proteotoxicity, which might have strong implications for the interpretation of Aβ clearance trial results and future drug design and for understanding the selective vulnerability of noradrenergic neurons in AD.

Current Status of Drug Targets and Emerging Therapeutic Strategies in the Management of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease affecting the elderly. AD is associated with a progressive decline in memory and cognitive abilities, drastic changes in behavioural patterns and other psychiatric manifestations. It leads to a significant decline in the quality of life at personal, household as well as national level. Although AD was described about hundred years back and multiple theories have been proposed, its exact pathophysiology is unknown. There is no cure for AD and the life expectancy of AD patients remains low at 3-9 years. An accurate understanding of the molecular mechanism(s) involved in the pathogenesis of AD is imperative to devise a successful treatment strategy. This review explains and summarises the current understanding of different therapeutic strategies based on various molecular pathways known to date. Different strategies based on anti-amyloid pathology, glutamatergic pathway, anti-tau, neuroprotection through neurotrophic factors and cholinergic neurotransmission have been discussed. Further, the use of anti-inflammatory drugs, nutraceuticals, and dietary interventions has also been explained in the management of AD. It further describes different pharmacological and dietary interventions being used in treating and/or managing AD. Additionally, this article provides a thorough review of the literature for improving the therapeutic paradigm of AD.

Destabilization potential of phenolics on Aβ fibrils: mechanistic insights from molecular dynamics simulation

Ellagic acid from pomegranate and walnuts is found to destabilize Aβ fibrils. It can be a potential drug to treat AD.

Study on the Multitarget Synergistic Effects of Kai-Xin-San against Alzheimer's Disease Based on Systems Biology

Kai-Xin-San (KXS), a classical Chinese traditional prescription, was widely applied in the treatment of Alzheimer's disease (AD), while its functional mechanisms still remain unclear. By using systems biology approaches at animal, cellular, and molecular levels, the improvement of KXS on cognitive impairment was achieved by inhibiting abnormal acetylcholinesterase. The function on the nerve skeleton was performed by regulating the Tau phosphorylation pathway. Its antioxidant, anti-inflammatory, and antiapoptotic effects by modulating the aberrant upregulation of ROS, proinflammatory factors, and apoptosis-related proteins in the brain were studied to reveal the synergistic therapeutic efficacy of KXS. Then, formula dismantling in vitro indicated that ginseng was the principal herb, whereas three other herbs served adjuvant roles to achieve the best effect. After that, the in vivo analysis of components into plasma and brain of AD rats showed that 8 of 23 components in blood and 4 of 10 components in brain were from ginseng, respectively, further verifying the principal status of ginseng and the synergistic effects of the formula. Thus, the anti-AD effects of KXS were achieved by multitargets and multichannels. The systems biology approaches presented here provide a novel way in traditional herbal medicine research.

Alzheimer's Disease Pharmacotherapy in Relation to Cholinergic System Involvement

Alzheimer’s disease, a major and increasing global health challenge, is an irreversible, progressive form of dementia, associated with an ongoing decline of brain functioning. The etiology of this disease is not completely understood, and no safe and effective anti-Alzheimer’s disease drug to prevent, stop, or reverse its evolution is currently available. Current pharmacotherapy concentrated on drugs that aimed to improve the cerebral acetylcholine levels by facilitating cholinergic neurotransmission through inhibiting cholinesterase. These compounds, recognized as cholinesterase inhibitors, offer a viable target across key sign domains of Alzheimer’s disease, but have a modest influence on improving the progression of this condition. In this paper, we sought to highlight the current understanding of the cholinergic system involvement in Alzheimer’s disease progression in relation to the recent status of the available cholinesterase inhibitors as effective therapeutics.

Friend, Foe or Both? Immune Activity in Alzheimer's Disease

Alzheimer's disease (AD) is marked by the presence of amyloid beta (Aβ) plaques, neurofibrillary tangles (NFT), neuronal death and synaptic loss, and inflammation in the brain. AD research has, in large part, been dedicated to the understanding of Aβ and NFT deposition as well as to the pharmacological reduction of these hallmarks. However, recent GWAS data indicates neuroinflammation plays a critical role in AD development, thereby redirecting research efforts toward unveiling the complexities of AD-associated neuroinflammation. It is clear that the innate immune system is intimately associated with AD progression, however, the specific roles of glia and neuroinflammation in AD pathology remain to be described. Moreover, inflammatory processes have largely been painted as detrimental to AD pathology, when in fact, many immune mechanisms such as phagocytosis aid in the reduction of AD pathologies. In this review, we aim to outline the delicate balance between the beneficial and detrimental aspects of immune activation in AD as a more thorough understanding of these processes is critical to development of effective therapeutics for AD.

Plasma Clusterin as a Potential Biomarker for Alzheimer’s Disease-A Systematic Review and Meta-analysis

Background:

Plasma clusterin has been reported to be associated with the pathology, prevalence, severity, and rapid clinical progress of Alzheimer’s Disease (AD). However, whether plasma clusterin can be used as a biomarker of AD is inconsistent and even conflicting.

Objective:

We conducted this study to evaluate the potential of plasma clusterin as the biomarker of AD.

Method:

PubMed, Embase, and Cochrane databases were systematically searched for studies on the relationship between plasma clusterin levels and AD diagnosis, risk and disease severity. We also compared the difference in Cerebrospinal Fluid (CSF) clusterin levels between AD and control groups. We converted and pooled data using standardized mean difference, Pearson linear regression model and the Cox regression model.

Results:

A total of 17 articles and 7228 individuals, including 1936 AD were included. The quality ranged from moderate to high. There was no difference in plasma clusterin between AD and control groups (SMD= 0.19 [-0.10, 0.48], p=0.20). Plasma clusterin levels were not correlated with the risk (RR=1.03 [0.97-1.09], p=0.31), the MMSE scores (R=0.33 [-0.06, 0.71], p= 0.09), and the integrated neuropsychological measurements (R=0.21 [-0.20, 0.63], p=0.31) of AD. Additionally, there was no difference in CSF clusterin between AD and control groups (SMD=1.94 [ -0.49, 4.37], p=0.12).

Conclusion:

Our meta-analysis suggested no relationship between plasma clusterin levels and the diagnosis, risk, and disease severity of AD and no difference in the CSF clusterin between AD and the control groups. Overall, there is no evidence to support plasma clusterin as a biomarker of AD based on the pooled results.

Restoring Wnt/β-catenin signaling is a promising therapeutic strategy for Alzheimer's disease

Alzheimer’s disease (AD) is an aging-related neurological disorder characterized by synaptic loss and dementia. Wnt/β-catenin signaling is an essential signal transduction pathway that regulates numerous cellular processes including cell survival. In brain, Wnt/β-catenin signaling is not only crucial for neuronal survival and neurogenesis, but it plays important roles in regulating synaptic plasticity and blood-brain barrier integrity and function. Moreover, activation of Wnt/β-catenin signaling inhibits amyloid-β production and tau protein hyperphosphorylation in the brain. Critically, Wnt/β-catenin signaling is greatly suppressed in AD brain via multiple pathogenic mechanisms. As such, restoring Wnt/β-catenin signaling represents a unique opportunity for the rational design of novel AD therapies.

The Brain-Heart Axis: Alzheimer's, Diabetes, and Hypertension

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder affecting millions worldwide. Currently, there are only four approved treatments for AD, which improve symptoms modestly. AD is believed to be caused by the formation of intercellular plaques and intracellular tangles in the brain, but thus far all new drugs which target these pathologies have failed clinical trials. New research highlights the link between AD and Type II Diabetes (T2D), and some believe that AD is actually a brain specific form of it termed Type III Diabetes (T3D). Drugs which are currently approved for the treatment of T2D, such as metformin, have shown promising results in improving cognitive function and even preventing the development of AD in diabetic patients. Recent studies shed light on the relationship between the brain and cardiovascular system in which the brain and heart communicate with one another via the vasculature to regulate fluid and nutrient homeostasis. This line of research reveals how the brain-heart axis regulates hypertension and diabetes, both of which can impact cognitive function. In this review we survey past and ongoing research and clinical trials for AD, and argue that AD is a complex and systemic disorder which requires comprehensive approaches beyond the brain for effective prevention and/or treatment.

Next Generation Precision Medicine: CRISPR-mediated Genome Editing for the Treatment of Neurodegenerative Disorders

Despite significant advancements in the field of molecular neurobiology especially neuroinflammation and neurodegeneration, the highly complex molecular mechanisms underlying neurodegenerative diseases remain elusive. As a result, the development of the next generation neurotherapeutics has experienced a considerable lag phase. Recent advancements in the field of genome editing offer a new template for dissecting the precise molecular pathways underlying the complex neurodegenerative disorders. We believe that the innovative genome and transcriptome editing strategies offer an excellent opportunity to decipher novel therapeutic targets, develop novel neurodegenerative disease models, develop neuroimaging modalities, develop next-generation diagnostics as well as develop patient-specific precision-targeted personalized therapies to effectively treat neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic lateral sclerosis, Frontotemporal dementia etc. Here, we review the latest developments in the field of CRISPR-mediated genome editing and provide unbiased futuristic insights regarding its translational potential to improve the treatment outcomes and minimize financial burden. However, despite significant advancements, we would caution the scientific community that since the CRISPR field is still evolving, currently we do not know the full spectrum of CRISPR-mediated side effects. In the wake of the recent news regarding CRISPR-edited human babies being born in China, we urge the scientific community to maintain high scientific and ethical standards and utilize CRISPR for developing in vitro disease in a dish model, in vivo testing in nonhuman primates and lower vertebrates and for the development of neurotherapeutics for the currently incurable neurodegenerative disorders. Graphical Abstract.

Bazhu Decoction, a Traditional Chinese Medical Formula, Ameliorates Cognitive Deficits in the 5xFAD Mouse Model of Alzheimer's Disease

Alzheimer’s disease (AD) is the most common neurodegenerative disorder associated with aging. There are currently no effective treatments for AD. Bazhu decoction (BZD), a traditional Chinese medicine (TCM) formula, has been employed clinically to alleviate AD. However, the underlying molecular mechanisms are still unclear. Here we found that middle- and high-doses of BZD ameliorated the behavioral aspects of 5xFAD transgenic mice in elevated plus maze, Y maze and Morris water maze tests. Moreover, BZD reduced the protein levels of BACE1 and PS1, resulting in a reduction of Aβ plaques. We also identified a beneficial effect of BZD on oxidative stress by attenuating MDA levels and SOD activity in the brains of 5xFAD mice. Together, these results indicate that BZD produces a dose-dependent positive effect on 5xFAD transgenic mouse model by decreasing APP processing and Aβ plaques, and by ameliorating oxidative damage. BZD may play a protective role in the cognitive and anxiety impairments and may be a complementary therapeutic option for AD.

The Emerging Roles and Therapeutic Potential of Soluble TREM2 in Alzheimer's Disease

Alzheimer’s disease (AD) is the most common form of dementia characterized by the deposition of extracellular amyloid-β (Aβ)-containing plaques, the formation of intraneuronal neurofibrillary tangles as well as neuroinflammatory changes. As the key player in the brain innate immune system, microglia has now taken a center stage in AD research. A large number of AD risk loci identified by genome-wide association studies are located in or near the genes highly expressed in microglia. Among them, the triggering receptor expressed on myeloid cells 2 (TREM2) has drawn much attention. A rare variant in TREM2 increases AD risk with an odds ratio comparable to the strongest genetic risk factor apolipoprotein ε4 allele. In the past 6 years, extensive studies have dissected the mechanisms by which TREM2 and its variants modulate microglial functions impacting amyloid and tau pathologies in both animal models and human studies. In addition to the full-length TREM2, research on the soluble form of TREM2 (sTREM2) has facilitated the translation of preclinical findings on TREM2. In this review, we summarize our current understanding of the biology and pathobiology of sTREM2 including its origin, its emergence as a disease biomarker, and its potential neuroprotective functions. These aspects are important for understanding the involvement of sTREM2 in AD pathogenesis and may provide novel insights into applying sTREM2 for AD diagnosis and therapy.

Dreaming of a New World Where Alzheimer's Is a Treatable Disorder

Alzheimer’s disease (AD) is the most common form of dementia. It’s a chronic and untreatable neurodegenerative disease with irreversible progression and has important social and economic implications in terms of direct medical and social care costs. Despite prolonged and expensive efforts employed by the scientific community over the last few decades, no effective treatments are still available for patients, and the development of disease-modifying drugs is now a really urgent need. The recent failure of clinical trials based on the immunotherapeutic approach against amyloid-β(Aβ) protein questioned the validity of the “amyloid cascade hypothesis” as the molecular machinery causing the disease. Indeed, most attempts to design effective treatments for AD have been based until now on molecular targets suggested to be implicated in AD pathogenesis by the amyloid cascade hypothesis. However, mounting evidence from scientific literature supports the view of AD as a multifactorial disease that results from the concomitant action of multiple molecular players. This view, together with the lack of success of the disease-modifying single-target approaches, strongly suggests that AD drug design needs to be shifted towards multi-targeted compounds or drug combinations acting synergistically on the main core features of disease pathogenesis. The discovery of drug candidates targeting multiple factors involved in AD would greatly improve drug development. So, it is reasonable that upcoming strategies for the design of preventive and/or therapeutic agents for AD point to a multi-pronged approach including more than one druggable target to definitely defeat the disease.

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

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

Rebalancing metal dyshomeostasis for Alzheimer's disease therapy

Alzheimer's disease (AD) is a type of neurodegenerative malady that is associated with the accumulation of amyloid plaques. Metal ions are critical for the development and upkeep of brain activity, but metal dyshomeostasis can contribute to the development of neurodegenerative diseases, including AD. This review highlights the association between metal dyshomeostasis and AD pathology, the feasibility of rebalancing metal homeostasis as a therapeutic strategy for AD, and a survey of current drugs that action via rebalancing metal homeostasis. Finally, we discuss the challenges that should be overcome by researchers in the future to enable the practical use of metal homeostasis rebalancing agents for clinical application.

Appoptosin Mediates Lesions Induced by Oxidative Stress Through the JNK-FoxO1 Pathway

Oxidative stress is a common feature of neurodegenerative diseases and plays an important role in disease progression. Appoptosin is a pro-apoptotic protein that contributes to the pathogenesis of neurodegenerative diseases such as Alzheimer's disease and progressive supranuclear palsy. However, whether appoptosin mediates oxidative stress-induced neurotoxicity has yet to be determined. Here, we observe that appoptosin protein levels are induced by hydrogen peroxide (H₂O₂) exposure through the inhibition of proteasomal appoptosin degradation. Furthermore, we demonstrate that overexpression of appoptosin induces apoptosis through the JNK-FoxO1 pathway. Importantly, knockdown of appoptosin can ameliorate H₂O₂-induced JNK activation and apoptosis in primary neurons. Thus, we propose that appoptosin functions as an upstream regulator of the JNK-FoxO1 pathway, contributing to cell death in response to oxidative stress during neurodegeneration.

High-resolution mapping of brain vasculature and its impairment in the hippocampus of Alzheimer's disease mice

Accumulating evidence indicates the critical importance of cerebrovascular dysfunction in the pathogenesis of Alzheimer's disease (AD). However, systematic comparative studies on the precise brain vasculature of wild-type and AD model mice are still rare. Using an image-optimization method for analysing Micro-Optical Sectioning Tomography (MOST) data, we generated cross-scale whole-brain 3D atlases that cover the entire vascular system from large vessels down to smallest capillaries at submicron resolution, for both wild-type mice and a transgenic (APP/PS1) mouse model of AD. In addition to distinct vascular patterns in different brain regions, we found that the main vessels of the molecular layer of the hippocampal dentate gyrus (DG-ml) undergo abrupt changes in both diameter and branch angle, spreading a unique comb-like pattern of capillaries. By using a quantitative analysis workflow, we identified in the hippocampus of AD mice an overall reduction of the mean vascular diameter, volume fraction and branch angle, with most significant impairment in the DG-ml. In addition, virtual endoscopy revealed irregular morphological features in the vessel lumen of the AD mice, potentially contributing to the impairment of blood flow. Our results demonstrate the capability of high-resolution cross-scale evaluation of brain vasculature and underscore the importance of studying hippocampal microcirculation for understanding AD pathogenesis.

Rapid Identification of Tanshinone IIA Metabolites in an Amyloid-β1-42 Induced Alzherimer's Disease Rat Model using UHPLC-Q-Exactive Qrbitrap Mass Spectrometry

Alzheimer’s disease (AD) is a neurodegenerative disorder that damages health and welfare of the elderly, and there has been no effective therapy for AD until now. It has been proved that tanshinone IIA (tan IIA) could alleviate pathological symptoms of AD via improving non-amyloidogenic cleavage of amyloid precursor protein, decreasing the accumulations of p-tau and amyloid-β_1–42 (Aβ_1–42), and so forth. However, the further biochemical mechanisms of tan IIA are not clear. The experiment was undertaken to explore metabolites of tan IIA in AD rats induced by microinjecting Aβ_1-42 in the CA1 region of hippocampus. AD rats were orally administrated with tan IIA at 100 mg/kg weight, and plasma, urine, faeces, kidney, liver and brain were then collected for metabolites analysis by UHPLC-Q-Exactive Qrbitrap mass spectrometry. Consequently, a total of 37 metabolites were positively or putatively identified on the basis of mass fragmentation behavior, accurate mass measurements and retention times. As a result, methylation, hydroxylation, dehydration, decarbonylation, reduction reaction, glucuronidation, glycine linking and their composite reactions were characterized to illuminate metabolic pathways of tan IIA in vivo. Several metabolites presented differences in the distribution of tan IIA between the sham control and the AD model group. Overall, these results provided valuable references for research on metabolites of tan IIA in vivo and its probable active structure for exerting neuroprotection.