Targeting Beta-Amyloid at the CSF: A New Therapeutic Strategy in Alzheimer's Disease

Perivascular brain clearance as a therapeutic target in cerebral amyloid angiopathy and Alzheimer's disease

Although distinct diseases, both cerebral amyloid angiopathy (CAA) and Alzheimer's disease (AD) are characterized by the aggregation and accumulation of amyloid-β (Aβ). This is thought to be due, in part, to impaired perivascular Aβ clearance from the brain. This shared failure in both diseases presents a common opportunity for therapeutic intervention. In this review we discuss the idea that promoting perivascular brain clearance could be an effective strategy for safely reducing Aβ levels in CAA and AD thereby improving clinical outcomes, most notably hemorrhagic stroke and cognitive decline. We will explore the evidence for the different forces that are thought to drive perivascular brain clearance, review the literature on potential strategies for potentiating these driving forces, and finally we will discuss the substantial translational challenges and considerations that would accompany such an intervention.

Targeting Soluble Amyloid Oligomers in Alzheimer's Disease: A Hypothetical Model Study Comparing Intrathecal Pseudodelivery of mAbs Against Intravenous Administration

BACKGROUND/OBJECTIVE

Neurotoxic soluble amyloid-β (Aβ) oligomers are key drivers of Alzheimer's pathology, with evidence suggesting that early targeting of these soluble forms may slow disease progression. Traditional intravenous (IV) monoclonal antibodies (mAbs) face challenges, including limited brain penetration and risks such as amyloid-related imaging abnormalities (ARIA). This hypothetical study aimed to model amyloid dynamics in early-to-moderate Alzheimer's disease (AD) and compare the efficacy of IV mAn with intrathecal pseudodelivery, a novel method that confines mAbs in a subcutaneous reservoir for selective amyloid clearance in cerebrospinal fluid (CSF) without systemic exposure.

METHODS

A mathematical framework was employed to simulate Aβ dynamics in patients with early-to-moderate AD. Two therapeutic approaches were compared: IV mAb and intrathecal pseudodelivery of mAb. The model incorporated amyloid kinetics, mAb affinity, protofibril size, and therapy-induced clearance rates to evaluate the impact of both methods on amyloid reduction, PET negativity timelines, and the risk of ARIA.

RESULTS

Intrathecal pseudodelivery significantly accelerated Aβ clearance compared to IV administration, achieving amyloid PET scan negativity by month 132, as opposed to month 150 with IV mAb. This method demonstrated no ARIA risk and reduced amyloid reaccumulation. By targeting soluble Aβ species more effectively, intrathecal pseudodelivery emerged as a safer and more efficient strategy for early AD intervention.

CONCLUSIONS

Intrathecal pseudodelivery offers a promising alternative to IV mAbs, overcoming challenges associated with blood-brain barrier penetration and systemic side effects. Further research should focus on optimizing this approach and exploring combination therapies to enhance clinical outcomes in AD.

Intrathecal Immunoselective Nanopheresis for Alzheimer's Disease: What and How? Why and When?

Nanotechnology is transforming therapeutics for brain disorders, especially in developing drug delivery systems. Intrathecal immunoselective nanopheresis with soluble monoclonal antibodies represents an innovative approach in the realm of drug delivery systems for Central Nervous System conditions, especially for targeting soluble beta-amyloid in Alzheimer's disease. This review delves into the concept of intrathecal immunoselective nanopheresis. It provides an overall description of devices to perform this technique while discussing the nanotechnology behind its mechanism of action, its potential advantages, and clinical implications. By exploring current research and advancements, we aim to provide a comprehensive understanding of this novel method, addressing the critical questions of what it is, how it works, why it is needed, and when it should be applied. Special attention is given to patient selection and the optimal timing for therapy initiation in Alzheimer's, coinciding with the peak accumulation of amyloid oligomers in the early stages. Potential limitations and alternative targets beyond beta-amyloid and future perspectives for immunoselective nanopheresis are also described.

The use of plasma exchange with albumin replacement in the management of Alzheimer's disease: a scoping review

Introduction

AD is a progressive neurodegenerative disorder causing significant cognitive decline and impaired daily functioning. Current treatments offer only modest relief, and many amyloid-targeting therapies have failed, prompting exploration of alternative approaches such as PE with albumin replacement.

Objectives

This scoping review systematically maps the literature on PE with albumin replacement in AD management, focusing on outcomes, methodologies, and reported benefits and risks.

Methods

A comprehensive search in PubMed, supplemented by reference scanning and hand-searching, identified studies involving PE with albumin replacement in AD patients. Data charting and critical appraisal were conducted using standardized tools.

Results

Seven primary studies from the AMBAR (Alzheimer Management by Albumin Replacement) trial met the inclusion criteria, consistently reporting improvements in cognitive function, positive neuroimaging results, and favorable neuropsychiatric outcomes. For instance, one study found a significant slowing of cognitive decline (p < 0.05) among patients receiving PE with albumin replacement. Another study showed better preservation of hippocampal volume and improved brain perfusion metrics in the treatment group (p < 0.05). The intervention was generally well-tolerated with manageable side effects.

Conclusion

PE with albumin replacement is a promising therapeutic approach for AD, warranting further investigation to confirm its efficacy and safety across broader settings.

Scoping review registration

https://osf.io/v6dez/?view_only=1cd9637e7e0347d39713bf19aac0dfe8.

Engineered Antibodies to Improve Efficacy against Neurodegenerative Disorders

Antibodies that can selectively remove rogue proteins in the brain are an obvious choice to treat neurodegenerative disorders (NDs), but after decades of efforts, only two antibodies to treat Alzheimer's disease are approved, dozens are in the testing phase, and one was withdrawn, and the other halted, likely due to efficacy issues. However, these outcomes should have been evident since these antibodies cannot enter the brain sufficiently due to the blood-brain barrier (BBB) protectant. However, all products can be rejuvenated by binding them with transferrin, preferably as smaller fragments. This model can be tested quickly and at a low cost and should be applied to bapineuzumab, solanezumab, crenezumab, gantenerumab, aducanumab, lecanemab, donanemab, cinpanemab, and gantenerumab, and their fragments. This paper demonstrates that conjugating with transferrin does not alter the binding to brain proteins such as amyloid-β (Aβ) and α-synuclein. We also present a selection of conjugate designs that will allow cleavage upon entering the brain to prevent their exocytosis while keeping the fragments connected to enable optimal binding to proteins. The identified products can be readily tested and returned to patients with the lowest regulatory cost and delays. These engineered antibodies can be manufactured by recombinant engineering, preferably by mRNA technology, as a more affordable solution to meet the dire need to treat neurodegenerative disorders effectively.

Effect and Potential Mechanism of Immunotherapy on Cognitive Deficits in Animal Models of Alzheimer's Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Immunotherapy has been reported to ameliorate Alzheimer's disease (AD) in the animal model; however, the immunologic approaches and mechanisms have not been specifically described. Thus, the systematic review and meta-analysis were conducted to explore the effect and potential mechanism of immunotherapy on AD animal experiments based on behavioral indicators.

METHODS

According to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and the Cochrane Collaboration guidelines and the inclusion/exclusion criteria of immunotherapy in animal studies, 15 studies were systematically reviewed after extraction from a collected database of 3,742 publications. Finally, the effect and mechanism of immunotherapy on AD models were described by performing multiple subgroup analyses.

RESULTS

After immunotherapy, the escape latency was reduced by 18.15 seconds and the number of crossings over the platform location was increased by 1.60 times in the Morris Water Maze. Furthermore, compared to the control group, active and passive immunization could markedly ameliorate learning and memory impairment in 3 × Tg AD animal models, and active immunization could ameliorate the learning and memory ability of the APPswe/PS1ΔE9 AD animal model. Meanwhile, it could be speculated that cognitive dysfunction was improved by immunotherapy, perhaps mainly via reducing Aβ40, Aβ42, and Tau levels, as well as increasing IL-4 levels.

CONCLUSION

Immunotherapy significantly ameliorated the cognitive dysfunction of AD animal models by assessing behavioral indicators.

A Nanostructured Protein Filtration Device for Possible Use in the Treatment of Alzheimer's Disease-Concept and Feasibility after In Vivo Tests

BACKGROUND

Alzheimer's disease (AD), along with other neurodegenerative disorders, remains a challenge for clinicians, mainly because of the incomplete knowledge surrounding its etiology and inefficient therapeutic options. Considering the central role of amyloid beta (Aβ) in the onset and evolution of AD, Aβ-targeted therapies are among the most promising research directions. In the context of decreased Aβ elimination from the central nervous system in the AD patient, the authors propose a novel therapeutic approach based on the "Cerebrospinal Fluid Sink Therapeutic Strategy" presented in previous works. This article aims to demonstrate the laborious process of the development and testing of an effective nanoporous ceramic filter, which is the main component of an experimental device capable of filtrating Aβ from the cerebrospinal fluid in an AD mouse model.

METHODS

First, the authors present the main steps needed to create a functional filtrating nanoporous ceramic filter, which represents the central part of the experimental filtration device. This process included synthesis, functionalization, and quality control of the functionalization, which were performed via various spectroscopy methods and thermal analysis, selectivity measurements, and a biocompatibility assessment. Subsequently, the prototype was implanted in APP/PS1 mice for four weeks, then removed, and the nanoporous ceramic filter was tested for its filtration capacity and potential structural damages.

RESULTS

In applying the multi-step protocol, the authors developed a functional Aβ-selective filtration nanoporous ceramic filter that was used within the prototype. All animal models survived the implantation procedure and had no significant adverse effects during the 4-week trial period. Post-treatment analysis of the nanoporous ceramic filter showed significant protein loading, but no complete clogging of the pores.

CONCLUSIONS

We demonstrated that a nanoporous ceramic filter-based system that filtrates Aβ from the cerebrospinal fluid is a feasible and safe treatment modality in the AD mouse model. The presented prototype has a functional lifespan of around four weeks, highlighting the need to develop advanced nanoporous ceramic filters with anti-biofouling properties to ensure the long-term action of this therapy.

Cerebrospinal fluid biomarkers for cerebral amyloid angiopathy

Integrating cerebrospinal fluid-biomarkers into diagnostic workup of patients with sporadic cerebral amyloid angiopathy may support early and correct identification. We aimed to identify and validate clinical- and cerebrospinal fluid-biomarkers for in vivo diagnosis of cerebral amyloid angiopathy. This observational cohort study screened 2795 consecutive patients admitted for cognitive complaints to the academic departments of neurology and psychiatry over a 10-year period (2009-2018). We included 372 patients with available hemosiderin-sensitive MR imaging and cerebrospinal fluid-based neurochemical dementia diagnostics, i.e. Aβ40, Aβ42, t-tau, p-tau. We investigated the association of clinical- and cerebrospinal fluid-biomarkers with the MRI-based diagnosis of cerebral amyloid angiopathy, applying confounder-adjusted modelling, receiver operating characteristic and unsupervised cluster analyses. We identified 67 patients with cerebral amyloid angiopathy, 76 patients with Alzheimer's disease, 75 patients with mild cognitive impairment due to Alzheimer's disease, 76 patients with mild cognitive impairment with unlikely Alzheimer's disease and 78 healthy controls. Patients with cerebral amyloid angiopathy showed a specific cerebrospinal fluid pattern: average concentration of Aß40 [13 792 pg/ml (10 081-18 063)] was decreased compared to all controls (P < 0.05); Aß42 [634 pg/ml (492-834)] was comparable to Alzheimer's disease and mild cognitive impairment due to Alzheimer's disease (P = 0.10, P = 0.93) but decreased compared to mild cognitive impairment and healthy controls (both P < 0.001); p-tau [67.3 pg/ml (42.9-91.9)] and t-tau [468 pg/ml (275-698)] were decreased compared to Alzheimer's disease (P < 0.001, P = 0.001) and mild cognitive impairment due to Alzheimer's disease (P = 0.001, P = 0.07), but elevated compared to mild cognitive impairment and healthy controls (both P < 0.001). Multivariate modelling validated independent clinical association of cerebral amyloid angiopathy with older age [odds-ratio: 1.06, 95% confidence interval (1.02-1.10), P < 0.01], prior lobar intracerebral haemorrhage [14.00 (2.64-74.19), P < 0.01], prior ischaemic stroke [3.36 (1.58-7.11), P < 0.01], transient focal neurologic episodes (TFNEs) [4.19 (1.06-16.64), P = 0.04] and gait disturbance [2.82 (1.11-7.15), P = 0.03]. For cerebrospinal fluid-biomarkers per 1 pg/ml, both lower Aß40 [0.9999 (0.9998-1.0000), P < 0.01] and lower Aß42 levels [0.9989 (0.9980-0.9998), P = 0.01] provided an independent association with cerebral amyloid angiopathy controlled for all aforementioned clinical confounders. Both amyloid biomarkers showed good discrimination for diagnosis of cerebral amyloid angiopathy among adjusted receiver operating characteristic analyses (area under the receiver operating characteristic curves, Aß40: 0.80 (0.73-0.86), P < 0.001; Aß42: 0.81 (0.75-0.88), P < 0.001). Unsupervised Euclidian clustering of all cerebrospinal fluid-biomarker-profiles resulted in distinct segregation of cerebral amyloid angiopathy patients from all controls. Together, we demonstrate that a distinctive set of cerebrospinal fluid-biomarkers effectively differentiate cerebral amyloid angiopathy patients from patients with Alzheimer's disease, mild cognitive impairment with or without underlying Alzheimer's disease, and healthy controls. Integrating our findings into a multiparametric approach may facilitate diagnosing cerebral amyloid angiopathy, and may aid clinical decision-making, but warrants future prospective validation.

Mechanical filtration of the cerebrospinal fluid: procedures, systems, and applications

INTRODUCTION

Mechanical methods aimed at the filtration of the cerebrospinal fluid (CSF) are a group of therapies that have been proposed to treat neurological conditions where pathogens are present in the CSF. Even though the industry of medical devices has not been very active in this field, there is a lack of systematization of the different systems and procedures that can be applied.

AREAS COVERED

First, we systematize the classification and definitions of procedures and systems for mechanical filtration of the CSF. Then, we made a literature review in search of clinical or preclinical studies where any system of mechanical CSF clearance was proposed or applied.

EXPERT OPINION

We found mechanical filtration of the CSF has been explored in subarachnoid hemorrhage, CNS infections (bacterial, viral, and fungal), meningeal carcinomatosis, multiple sclerosis, autoimmune encephalitis, and polyradiculomyelitis. Brain aging and neurodegenerative diseases are additional potential conditions of interest. While there is some preliminary positive evidence for many of these conditions, more advanced systems, detailed descriptions of procedures, and rigorous validations are needed to make these therapies a reality in the next decades.

Intrathecal Pseudodelivery of Drugs in the Therapy of Neurodegenerative Diseases: Rationale, Basis and Potential Applications

Intrathecal pseudodelivery of drugs is a novel route to administer medications to treat neurodegenerative diseases based on the CSF-sink therapeutic strategy by means of implantable devices. While the development of this therapy is still in the preclinical stage, it offers promising advantages over traditional routes of drug delivery. In this paper, we describe the rationale of this system and provide a technical report on the mechanism of action, that relies on the use of nanoporous membranes enabling selective molecular permeability. On one side, the membranes do not permit the crossing of certain drugs; whereas, on the other side, they permit the crossing of target molecules present in the CSF. Target molecules, by binding drugs inside the system, are retained or cleaved and subsequently eliminated from the central nervous system. Finally, we provide a list of potential indications, the respective molecular targets, and the proposed therapeutic agents.

Nanoporous Membranes for the Filtration of Proteins from Biological Fluids: Biocompatibility Tests on Cell Cultures and Suggested Applications for the Treatment of Alzheimer's Disease

BACKGROUND

Alzheimer's disease has a significant epidemiological and socioeconomic impact, and, unfortunately, the extensive research focused on potential curative therapies has not yet proven to be successful. However, in recent years, important steps have been made in the development and functionalization of nanoporous alumina membranes, which might be of great interest for medical use, including the treatment of neurodegenerative diseases. In this context, the aim of this article is to present the synthesis and biocompatibility testing of a special filtrating nano-membrane, which is planned to be used in an experimental device for Alzheimer's disease treatment.

METHODS

Firstly, the alumina nanoporous membrane was synthesized via the two-step anodizing process in oxalic acid-based electrolytes and functionalized via the atomic layer deposition technique. Subsequently, quality control tests (spectrophotometry and potential measurements), toxicity, and biocompatibility tests (cell viability assays) were conducted.

RESULTS

The proposed alumina nanoporous membrane proved to be efficient for amyloid-beta filtration according to the permeability studies conducted for 72 h. The proposed membrane has proven to be fully compatible with the tested cell cultures.

CONCLUSIONS

The proposed alumina nanoporous membrane model is safe and could be incorporated into implantable devices for further in vivo experiments and might be an efficient therapeutic approach for Alzheimer's disease.

New, Fully Implantable Device for Selective Clearance of CSF-Target Molecules: Proof of Concept in a Murine Model of Alzheimer’s Disease

We have previously proposed a radical change in the current strategy to clear pathogenic proteins from the central nervous system (CNS) based on the cerebrospinal fluid (CSF)-sink therapeutic strategy, whereby pathogenic proteins can be removed directly from the CNS via CSF. To this aim, we designed and manufactured an implantable device for selective and continuous apheresis of CSF enabling, in combination with anti-amyloid-beta (Aβ) monoclonal antibodies (mAb), the clearance of Aβ from the CSF. Here, we provide the first proof of concept in the APP/PS1 mouse model of Alzheimer’s disease (AD). Devices were implanted in twenty-four mice (seventeen APP/PS1 and seven Wt) with low rates of complications. We confirmed that the apheresis module is permeable to the Aβ peptide and impermeable to mAb. Moreover, our results showed that continuous clearance of soluble Aβ from the CSF for a few weeks decreases cortical Aβ plaques. Thus, we conclude that this intervention is feasible and may provide important advantages in terms of safety and efficacy.

The "Cerebrospinal Fluid Sink Therapeutic Strategy" in Alzheimer's Disease-From Theory to Design of Applied Systems

Alzheimer’s disease (AD) is a global health problem, with incidence and prevalence considered to increase during the next decades. However, no currently available effective treatment exists despite numerous clinical trials in progress. Moreover, although many hypotheses are accepted regarding the pathophysiological mechanisms of AD onset and evolution, there are still many unknowns about the disorder. A relatively new approach, based on the amyloid-beta dynamics among different biological compartments, is currently intensely discussed, as it seems to offer a promising solution with significant therapeutic impact. Known as the “cerebrospinal-fluid-sink therapeutic strategy”, part of the “three-sink therapeutic strategy”, this theoretical model focuses on the dynamics of amyloid-beta among the three main liquid compartments of the human body, namely blood, cerebrospinal fluid, and the (brain) interstitial fluid. In this context, this article aims to describe in detail the abovementioned hypothesis, by reviewing in the first part the most relevant anatomical and physiological aspects of amyloid-beta dynamics. Subsequently, explored therapeutic strategies based on the clearance of amyloid-beta from the cerebrospinal fluid level are presented, additionally highlighting their limitations. Finally, the originality and novelty of this work rely on the research experience of the authors, who focus on implantable devices and their utility in AD treatment.

Association of Superficial White Matter Alterations with Cerebrospinal Fluid Biomarkers and Cognitive Decline in Neurodegenerative Dementia

BACKGROUND

Superficial white matter (SWM) alterations correlated with cognitive decline have been described in Alzheimer's disease (AD).

OBJECTIVE

The study aims to extend the investigation of the SWM alterations to AD and non-AD neurodegenerative dementia (ND) and explore the relationship with cerebrospinal fluid (CSF) biomarkers and clinical data.

METHODS

From a database of 323 suspected dementia cases, we retrospectively recruited 55 ND with abnormal amyloid-β42 (AD) and 38 ND with normal amyloid-β42 (non-AD) and collected clinical data, CSF biomarkers, and magnetic resonance images. Ten healthy controls (HC) were recruited for imaging and Mini-Mental State Examination (MMSE). Diffusion tensor imaging (DTI) measurements were performed in the lobar SWM regions and Kruskal Wallis tests were used for among-group comparison. Spearman's correlation tests were performed between DTI measures, CSF biomarkers, and clinical data.

RESULTS

AD and non-AD showed significant differences in the DTI measures across the SWM compared to HC. Significant differences between AD and non-AD were detected in the left parietal lobe. DTI measures correlated with amyloid-β42 and MMSE diffusely in the SWM, less extensively with total-tau and phosphorylated tau, and with disease duration in the parietal lobe bilaterally.

CONCLUSION

Widespread SWM alterations occur in both AD and non-AD ND and AD shows appreciably more severe alterations in the parietal SWM. Notably, the alterations in the SWM are strongly linked not only to the cognitive decline but also to the diagnostic CSF biomarkers. Further studies are encouraged to evaluate the DTI measures in the SWM as in vivo non-invasive biomarkers in the preclinical phase.

Effectiveness of idebenone nanorod formulations in the treatment of Alzheimer's disease

Idebenone (IDB) has demonstrated the potential to treat mitochondrial and neurodegenerative diseases, including Alzheimer's disease (AD). However, its therapeutic effects are compromised by poor compliance due to low bioavailability. The objective of this study is to fabricate IDB nanorods (IDBNRs) to improve oral bioavailability and increase concentrations in the brain in order to enhance therapeutic effects of IDB in the treatment of AD. IDBNRs showed desired sizes and rod-shaped morphologies. The release rate and the antioxidant activity of IDBNRs were improved relative to other delivery routes. The plasma and brain concentrations were enhanced due to rapid release into the systemic circulation. In behavioral tests, mice treated orally with IDBNRs showed amelioration of AD-induced impairment of learning and memory. Thus, because of improved efficiency of drug delivery, doses can be reduced, and the compliance and therapeutic experience of patients can be improved. IDBNRs may provide effective and convenient treatments for AD patients in the future.

Relationship Between Amyloid-β Deposition and Blood-Brain Barrier Dysfunction in Alzheimer's Disease

Amyloid-β (Aβ) is the predominant pathologic protein in Alzheimer's disease (AD). The production and deposition of Aβ are important factors affecting AD progression and prognosis. The deposition of neurotoxic Aβ contributes to damage of the blood-brain barrier. However, the BBB is also crucial in maintaining the normal metabolism of Aβ, and dysfunction of the BBB aggravates Aβ deposition. This review characterizes Aβ deposition and BBB damage in AD, summarizes their interactions, and details their respective mechanisms.

Interplay between stress-related genes may influence Alzheimer's disease development: The results of genetic interaction analyses of human data

Emerging evidence from experimental and clinical research suggests that stress-related genes may play key roles in AD development. The fact that genome-wide association studies were not able to detect a contribution of such genes to AD indicates the possibility that these genes may influence AD non-linearly, through interactions of their products. In this paper, we selected two stress-related genes (GCN2/EIF2AK4 and APP) based on recent findings from experimental studies which suggest that the interplay between these genes might influence AD in humans. To test this hypothesis, we evaluated the effects of interactions between SNPs in these two genes on AD occurrence, using the Health and Retirement Study data on white indidividuals. We found several interacting SNP-pairs whose associations with AD remained statistically significant after correction for multiple testing. These findings emphasize the importance of nonlinear mechanisms of polygenic AD regulation that cannot be detected in traditional association studies. To estimate collective effects of multiple interacting SNP-pairs on AD, we constructed a new composite index, called Interaction Polygenic Risk Score, and showed that its association with AD is highly statistically significant. These results open a new avenue in the analyses of mechanisms of complex multigenic AD regulation.

Anti-Aβ agents for mild to moderate Alzheimer's disease: systematic review and meta-analysis

OBJECTIVE

To assess the efficacy and safety of Aβ-targeting agents for mild to moderate Alzheimer's disease.

METHODS

The MEDLINE, Embase, Cochrane Central Register of Controlled Trials, PsycINFO, ClinicalTrials.gov and the WHO's International Clinical Trials Registry Platform search portal were searched from their inception to April 2020. We generated pooled estimates using random effects meta-analyses.

RESULTS

Nineteen randomised controlled trials, of which 17 had a low risk of bias, included 12 903 participants. The meta-analysis showed no difference in the cognitive subscale of Alzheimer's Disease Assessment Scale (ADAS-Cog) between anti-Aβ drugs and placebo (mean difference (MD): 0.20, 95% CI -0.40 to 0.81; I ²=99.8%; minimal important difference 3.1-3.8 points, moderate-certainty evidence). For ADAS-Cog, results suggested that one drug that increases Aβ clearance may differ in effect (MD: -0.96, 95% CI -0.99 to -0.92) from drugs that reduce Aβ production (MD: 0.78, 95% CI 0.25 to 1.32) (interaction p<0.000001); this difference also existed in the outcome of MMSE and CDR-SOB. Compared with placebo, anti-Aβ drug-related adverse events were as follows: anxiety, depression, diarrhoea, fatigue, rash, syncope and vomit.

DISCUSSION

From current evidence, anti-Aβ interventions are unlikely to have an important impact on slowing cognitive or functional decline. Although the subgroup analysis suggested possible benefits from Aβ clearance drugs, the analysis has limited credibility, and a benefit from drugs that increase clearance, if real, is very small.

TRIAL REGISTRATION NUMBER

PROSPERO registration number CRD42019126272.

Bridging the Gap Between Fluid Biomarkers for Alzheimer's Disease, Model Systems, and Patients

Alzheimer’s disease (AD) is a debilitating neurodegenerative disease characterized by the accumulation of two proteins in fibrillar form: amyloid-β (Aβ) and tau. Despite decades of intensive research, we cannot yet pinpoint the exact cause of the disease or unequivocally determine the exact mechanism(s) underlying its progression. This confounds early diagnosis and treatment of the disease. Cerebrospinal fluid (CSF) biomarkers, which can reveal ongoing biochemical changes in the brain, can help monitor developing AD pathology prior to clinical diagnosis. Here we review preclinical and clinical investigations of commonly used biomarkers in animals and patients with AD, which can bridge translation from model systems into the clinic. The core AD biomarkers have been found to translate well across species, whereas biomarkers of neuroinflammation translate to a lesser extent. Nevertheless, there is no absolute equivalence between biomarkers in human AD patients and those examined in preclinical models in terms of revealing key pathological hallmarks of the disease. In this review, we provide an overview of current but also novel AD biomarkers and how they relate to key constituents of the pathological cascade, highlighting confounding factors and pitfalls in interpretation, and also provide recommendations for standardized procedures during sample collection to enhance the translational validity of preclinical AD models.

Mangosteen Pericarp and Its Bioactive Xanthones: Potential Therapeutic Value in Alzheimer's Disease, Parkinson's Disease, and Depression with Pharmacokinetic and Safety Profiles

Alzheimer's disease (AD), Parkinson's disease (PD), and depression are growing burdens for society globally, partly due to a lack of effective treatments. Mangosteen (Garcinia mangostana L.,) pericarp (MP) and its xanthones may provide therapeutic advantages for these disorders. In this review, we discuss potential therapeutic value of MP-derived agents in AD, PD, and depression with their pharmacokinetic and safety profiles. MP-derived agents have shown multifunctional effects including neuroprotective, antioxidant, and anti-neuroinflammatory actions. In addition, they target specific disease pathologies, such as amyloid beta production and deposition as well as cholinergic dysfunction in AD; α-synuclein aggregation in PD; and modulation of monoamine disturbance in depression. Particularly, the xanthone derivatives, including α-mangostin and γ-mangostin, exhibit potent pharmacological actions. However, low oral bioavailability and poor brain penetration may limit their therapeutic applications. These challenges can be overcome in part by administering as a form of MP extract (MPE) or using specific carrier systems. MPE and α-mangostin are generally safe and well-tolerated in animals. Furthermore, mangosteen-based products are safe for humans. Therefore, MPE and its bioactive xanthones are promising candidates for the treatment of AD, PD, and depression. Further studies including clinical trials are essential to decipher their efficacy, and pharmacokinetic and safety profiles in these disorders.

Angiopoietin-1 accelerates Alzheimer's disease via FOXA2/PEN2/APP pathway in APP/PS1 mice

Angiopoietin-1 (Ang-1), a regulatory angiogenesis protein and it has been found to be involved in the occurrence and progression of Alzheimer's disease. However, it was still to be addressed the distinctly role and the molecular mechanisms of Ang-1 affects Alzheimer's disease. Our data suggest that Ang-1 aggravated the accumulation of Aβ₄₂ and cognitive decline in APP/PS1 mice. The upregulation of APPβ is essential for Aβ₄₂ production in N2a cells overexpressing the mutational human APP gene (N2a/APP695 cells), while downregulation of PEN2 could reduce APP expression. Silencing of FOXA2 lead to inhibition of APP expression, as well as decrease of Aβ₄₂ contents. In conclusion, Ang-1 has an accelerative effect on Alzheimer's disease by increasing the secretion of Aβ₄₂ via FOXA2/PEN2/APP pathway.

Therapeutic Potential of Direct Clearance of the Amyloid-β in Alzheimer's Disease

Alzheimer’s disease (AD) is characterized by deposition and accumulation of amyloid-β (Aβ) and its corresponding plaques within the brain. Although much debate exists whether these plaques are the cause or the effect of AD, the accumulation of Aβ is linked with the imbalance between the production and clearance of Aβ. The receptor for advanced glycation endproducts (RAGE) facilitates entry of free Aβ from the peripheral stream. Conversely, lipoprotein receptor-related protein 1 (LRP1), located in the abluminal side at the blood–brain barrier mediates the efflux of Aβ. Research on altering the rates of clearance of Aβ by targeting these two pathways has been extensively study. Additionally, a cerebrospinal fluid (CSF) circulation assistant device has also been evaluated as an approach to increase solute concentration in the CSF via mechanical drainage, to allow for removal of Aβ from the brain. Herein, we provide a brief review of these approaches that are designed to re-establish a homeostatic Aβ balance in the brain.

In vivo evaluation and atom-based 3D-QSAR studies on saponins from shells of Xanthoceras sorbifolium Bunge as anti-AD agents

A series of oleanane type of glycosides (1-19), including nine undescribed ones (1-9), were isolated and identified from Xanthoceras sorbifolium. Subsequently, an atom-based 3D-QSAR model was constructed based on results of the in vivo anti-AD evaluation of the isolates (2-3, 10-17) and nine literature-reported anti-AD oleanane type of glycosides to clarify the structure-anti-AD activity, and under the guidance of which 19 was predicted and proved to elicit a nearly equivalent in vivo anti-AD effect as xanthoceraside and donepezil that were used as positive drugs in the Y maze and Morris water maze test.

Exosomes: The next generation of endogenous nanomaterials for advanced drug delivery and therapy

Development of functional nanomaterials is of great importance and significance for advanced drug delivery and therapy. Nevertheless, exogenous nanomaterials have a great ability to induce undesired immune responses and nano-protein interactions, which may result in toxicity and failure of therapy. Exosomes, a kind of endogenous extracellular vesicle (40-100 nm in diameter), are considered as a new generation of a natural nanoscale delivery system. Exosomes secreted by different types of cells carry different signal molecules (such as RNAs and proteins) and thus have a great potential for targeted drug delivery and therapy. Herein, we provide comprehensive understanding of the properties and applications of exosomes, including their biogenesis, biofunctions, isolation, purification, and drug loading, and typical examples in drug delivery and therapy. Furthermore, their advantages compared to other nanoparticles and potential in tumor immunotherapy are also discussed. STATEMENT OF SIGNIFICANCE: Exosomes, a kind of endogenous extracellular vesicle, have emerged as a novel and attractive endogenous nanomaterial for advanced drug delivery and targeted therapy. Exosomes are secreted by many types of cells and carry some unique signals obtained from their parental cells. Furthermore, the liposome-like structure allows exosomes to load various drugs. Hence, the potential of exosomes in drug delivery, tumor targeted therapy, and immunotherapy has been investigated in recent years. On the basis of their endogenous features and multifunctional properties, exosomes are of great significance and interest for the development of future medicine and pharmaceuticals.

Recent advancements toward therapeutic vaccines against Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by protein aggregates of amyloid β (Aβ) and tau. These proteins have normal physiological functions, but in AD, they undergo a conformational change and aggregate as toxic oligomeric and fibrillar species with a high β-sheet content.

AREAS COVERED

Active and passive immunotherapeutic approaches are among the most attractive methods for targeting misfolded Aβ and tau. Promising preclinical testing of various immunotherapeutic approaches has yet to translate to cognitive benefits in human clinical trials. Knowledge gained from these past failures has led to the development of second-generation Aβ-active immunotherapies, anti-Aβ monoclonal antibodies targeting a wide array of Aβ conformations, and to a number of immunotherapies targeting pathological tau. This review covers the more recent advances in vaccine development for AD from 2016 to present.

EXPERT COMMENTARY

Due to the complex pathophysiology of AD, greatest clinical efficacy will most likely be achieved by concurrently targeting the most toxic forms of both Aβ and tau.