Disease modifying drugs targeting β-amyloid

Controversial Past, Splendid Present, Unpredictable Future: A Brief Review of Alzheimer Disease History

Background: The concept of Alzheimer disease (AD)-since its histological discovery by Alzheimer to the present day-has undergone substantial modifications. Methods: We conducted a classical narrative review of this field with a bibliography selection (giving preference to Medline best match). Results: The following subjects are reviewed and discussed: Alzheimer's discovery, Kraepelin's creation of a new disease that was a rare condition until the 1970's, the growing interest and investment in AD as a major killer in a society with a large elderly population in the second half of the 20th century, the consolidation of the AD clinicopathological model, and the modern AD nosology based on the dominant amyloid hypothesis among many others. In the 21st century, the development of AD biomarkers has supported a novel biological definition of AD, although the proposed therapies have failed to cure this disease. The incidence of dementia/AD has shown a decrease in affluent countries (possibly due to control of risk factors), and mixed dementia has been established as the most frequent etiology in the oldest old. Conclusions: The current concept of AD lacks unanimity. Many hypotheses attempt to explain its complex physiopathology entwined with aging, and the dominant amyloid cascade has yielded poor therapeutic results. The reduction in the incidence of dementia/AD appears promising but it should be confirmed in the future. A reevaluation of the AD concept is also necessary.

Attempts to Develop Vaccines Against Alzheimer's Disease: A Systematic Review of Ongoing and Completed Vaccination Trials in Humans

In this systematic review, we evaluate the safety, tolerability, and immunogenicity of vaccination efforts against Alzheimer's disease (AD) in human subjects from both ongoing and completed vaccination trials. Databases like PubMed, Embase, and Scopus were used to identify relevant articles on completed vaccination trials whereas the clinicaltrials.gov database was used for identifying ongoing clinical trials for vaccination against AD in humans until January 2022. Only interventional randomized or non-randomized clinical trials which reported on the safety and immunogenicity of vaccine against AD in humans were included. Cochrane risk of bias tool-2 (RoB-2) or risk of bias in non-randomized studies- of intervention (ROBINS-I) was used for risk of bias assessment as appropriate. A narrative descriptive synthesis of the findings was done. Sixteen randomized/non-randomized clinical trials (phase I: six and phase II: 10) for seven different types of vaccines against AD were identified comprising a total of 2080 participants. Apart from the development of meningoencephalitis in 6% of patients receiving AN1792 in an interrupted phase II trial, the rest of the trial reported promising results on the safety and immunogenicity of vaccines. While only a subset of reported adverse events was treatment related, none of the fatalities reported during the trial were considered related to vaccine administration. The serological response rate ranged from 100% (4/16 trials) to 19.7% in an interrupted trial. Although current trials show promising results, adequately powered phase III studies are needed to conclusively establish the safety, immunogenicity and therapeutic efficacy of vaccines.

Review of Advanced Drug Trials Focusing on the Reduction of Brain Beta-Amyloid to Prevent and Treat Dementia

Alzheimer disease (AD) is the most common neurodegenerative disease and typically affects patients older than age 65. Around this age, the number of neurons begins to gradually decrease in healthy brains, but brains of patients with AD show a marked increase in neuron death, often resulting in a significant loss of cognitive abilities. Cognitive skills affected include information retention, recognition capabilities, and language skills. At present, AD can be definitively diagnosed only through postmortem brain biopsies via the detection of extracellular amyloid beta (Aβ) plaques and intracellular hyperphosphorylated tau neurofibrillary tangles. Because the levels of both Aβ plaques and tau tangles are increased, these 2 proteins are thought to be related to disease progression. Although relatively little is known about the cause of AD and its exact pathobiological development, many forms of treatment have been investigated to determine an effective method for managing AD symptoms by targeting Aβ. These treatments include but are not limited to using small molecules to alter the interactions of Aβ monomers, reducing hyperactivation of neuronal circuits altering Aβ's molecular pathway of synthesis, improving degradation of Aβ, employing passive immunity approaches, and stimulating patients' active immunity to target Aβ. This review summarizes the current therapeutic interventions in Phase II/III of clinical development or higher that are capable of reducing abnormal brain Aβ levels to determine which treatments show the greatest likelihood of clinical efficacy. We conclude that, in the near future, the most promising therapeutic interventions for brain Aβ pathology will likely be passive immunotherapies, with aducanumab and donanemab leading the way, and that these drugs may be combined with antidepressants and acetylcholine esterase inhibitors, which can modulate Aβ synthesis.

Exploring the Potential of Therapeutic Agents Targeted towards Mitigating the Events Associated with Amyloid-β Cascade in Alzheimer's Disease

One of the most commonly occurring neurodegenerative disorders, Alzheimer's disease (AD), encompasses the loss of cognitive and memory potential, impaired learning, dementia and behavioral defects, and has been prevalent since the 1900s. The accelerating occurrence of AD is expected to reach 65.7 million by 2030. The disease results in neural atrophy and disrupted inter-neuronal connections. Amongst multiple AD pathogenesis hypotheses, the amyloid beta (Aβ) cascade is the most relevant and accepted form of the hypothesis, which suggests that Aβ monomers are formed as a result of the cleavage of amyloid precursor protein (APP), followed by the conversion of these monomers to toxic oligomers, which in turn develop β-sheets, fibrils and plaques. The review targets the events in the amyloid hypothesis and elaborates suitable therapeutic agents that function by hindering the steps of plaque formation and lowering Aβ levels in the brain. The authors discuss treatment possibilities, including the inhibition of β- and γ-secretase-mediated enzymatic cleavage of APP, the immune response generating active immunotherapy and passive immunotherapeutic approaches targeting monoclonal antibodies towards Aβ aggregates, the removal of amyloid aggregates by the activation of enzymatic pathways or the regulation of Aβ circulation, glucagon-like peptide-1 (GLP-1)-mediated curbed accumulation and the neurotoxic potential of Aβ aggregates, bapineuzumab-mediated vascular permeability alterations, statin-mediated Aβ peptide degradation, the potential role of ibuprofen and the significance of natural drugs and dyes in hindering the amyloid cascade events. Thus, the authors aim to highlight the treatment perspective, targeting the amyloid hypothesis, while simultaneously emphasizing the need to conduct further investigations, in order to provide an opportunity to neurologists to develop novel and reliable treatment therapies for the retardation of AD progression.

Selected LDLR and APOE Polymorphisms Affect Cognitive and Functional Response to Lipophilic Statins in Alzheimer's Disease

Effects of statins over clinical changes in Alzheimer's disease (AD) are usually non-significant, but epistatic interactions between genetic variants involved in cholesterol metabolism could be important for such effects. We aimed to investigate whether LDLR single-nucleotide polymorphisms rs11669576 (LDLR8), rs5930 (LDLR10), and rs5925 (LDLR13) are associated with cognitive and functional changes in AD, while also considering APOE haplotypes and lipid-lowering treatment with lipophilic statins for stratification. Consecutive outpatients with late-onset AD were screened with cognitive tests, while caregivers scored functionality and caregiver burden, with prospective neurotranslational correlations documented for 1 year. For 179 patients, minor allele frequencies were 0.078 for rs11669576-A (14.5% heterozygotes), 0.346 for rs5930-A (42.5% heterozygotes), and 0.444 for rs5925-C (56.4% heterozygotes), all in Hardy-Weinberg equilibrium; 134 patients had hypercholesterolemia, and 133 used lipophilic statins. Carriers of rs11669576-G had faster cognitive decline, while functional decline was slower for carriers of rs11669576-A who used lipophilic statins. APOE-ε4 carriers who also carried rs5930-AA had improved caregiver burden, while carriers of haplotypes that included rs5930-AG had worse cognitive and functional outcomes, though carriers of the A allele of rs5930 had better cognitive and functional response to lipophilic statins. APOE-ε4 non-carriers who carried rs5925-TT had slower cognitive decline, while lipophilic statins protected carriers of the other genotypes. We preliminarily conclude that reportedly protective variants of LDLR and APOE against risk of AD also slowed cognitive decline, regardless of cholesterol variations, while therapy with lipophilic statins might benefit carriers of specific genetic variants.

Aspirin and other non-steroidal anti-inflammatory drugs for the prevention of dementia

BACKGROUND

Dementia is a worldwide concern. Its global prevalence is increasing. At present, there is no medication licensed to prevent or delay the onset of dementia. Inflammation has been suggested as a key factor in dementia pathogenesis. Therefore, medications with anti-inflammatory properties could be beneficial for dementia prevention.

OBJECTIVES

To evaluate the effectiveness and adverse effects of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) for the primary or secondary prevention of dementia.

SEARCH METHODS

We searched ALOIS, the specialised register of the Cochrane Dementia and Cognitive Improvement Group up to 9 January 2020. ALOIS contains records of clinical trials identified from monthly searches of several major healthcare databases, trial registries and grey literature sources. We ran additional searches across MEDLINE (OvidSP), Embase (OvidSP) and six other databases to ensure that the searches were as comprehensive and up-to-date as possible. We also reviewed citations of reference lists of included studies.

SELECTION CRITERIA

We searched for randomised controlled trials (RCTs) and controlled clinical trials (CCTs) comparing aspirin or other NSAIDs with placebo for the primary or secondary prevention of dementia. We included trials with cognitively healthy participants (primary prevention) or participants with mild cognitive impairment (MCI) or cognitive complaints (secondary prevention).

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures according to the Cochrane Handbook for Systematic Reviews of Interventions. We rated the strength of evidence for each outcome using the GRADE approach.

MAIN RESULTS

We included four RCTs with 23,187 participants. Because of the diversity of these trials, we did not combine data to give summary estimates, but presented a narrative description of the evidence. We identified one trial (19,114 participants) comparing low-dose aspirin (100 mg once daily) to placebo. Participants were aged 70 years or older with no history of dementia, cardiovascular disease or physical disability. Interim analysis indicated no significant treatment effect and the trial was terminated slightly early after a median of 4.7 years' follow-up. There was no evidence of a difference in incidence of dementia between aspirin and placebo groups (risk ratio (RR) 0.98, 95% CI 0.83 to 1.15; high-certainty evidence). Participants allocated aspirin had higher rates of major bleeding (RR 1.37, 95% CI 1.17 to 1.60, high-certainty evidence) and slightly higher mortality (RR 1.14, 95% CI 1.01 to 1.28; high-certainty evidence). There was no evidence of a difference in activities of daily living between groups (RR 0.84, 95% CI 0.70 to 1.02; high-certainty evidence). We identified three trials comparing non-aspirin NSAIDs to placebo. All three trials were terminated early due to adverse events associated with NSAIDs reported in other trials. One trial (2528 participants) investigated the cyclo-oxygenase-2 (COX-2) inhibitor celecoxib (200 mg twice daily) and the non-selective NSAID naproxen (220 mg twice daily) for preventing dementia in cognitively healthy older adults with a family history of Alzheimer's disease (AD). Median follow-up was 734 days. Combining both NSAID treatment arms, there was no evidence of a difference in the incidence of AD between participants allocated NSAIDs and those allocated placebo (RR 1.91, 95% CI 0.89 to 4.10; moderate-certainty evidence). There was also no evidence of a difference in rates of myocardial infarction (RR 1.21, 95% CI 0.61 to 2.40), stroke (RR 1.82, 95% CI 0.76 to 4.37) or mortality (RR 1.37, 95% CI 0.78 to 2.43) between treatment groups (all moderate-certainty evidence). One trial (88 participants) assessed the effectiveness of celecoxib (200 mg or 400 mg daily) in delaying cognitive decline in participants aged 40 to 81 years with mild age-related memory loss but normal memory performance scores. Mean duration of follow-up was 17.6 months in the celecoxib group and 18.1 months in the placebo group. There was no evidence of a difference between groups in test scores in any of six cognitive domains. Participants allocated celecoxib experienced more gastrointestinal adverse events than those allocated placebo (RR 2.66, 95% CI 1.05 to 6.75; low-certainty evidence). One trial (1457 participants) assessed the effectiveness of the COX-2 inhibitor rofecoxib (25 mg once daily) in delaying or preventing a diagnosis of AD in participants with MCI. Median duration of study participation was 115 weeks in the rofecoxib group and 130 weeks in the placebo group. There was a higher incidence of AD in the rofecoxib than the placebo group (RR 1.32, 95% CI 1.01 to 1.72; moderate-certainty evidence). There was no evidence of a difference between groups in cardiovascular adverse events (RR 1.07, 95% CI 0.68 to 1.66; moderate-certainty evidence) or mortality (RR 1.62, 95% CI 0.85 to 3.05; moderate-certainty evidence). Participants allocated rofecoxib had more upper gastrointestinal adverse events (RR 3.53, 95% CI 1.17 to 10.68; moderate-certainty evidence). Reported annual mean difference scores showed no evidence of a difference between groups in activities of daily living (year 1: no data available; year 2: 0.0, 95% CI -0.1 to 0.2; year 3: 0.1, 95% CI -0.1 to 0.3; year 4: 0.1, 95% CI -0.1 to 0.4; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

There is no evidence to support the use of low-dose aspirin or other NSAIDs of any class (celecoxib, rofecoxib or naproxen) for the prevention of dementia, but there was evidence of harm. Although there were limitations in the available evidence, it seems unlikely that there is any need for further trials of low-dose aspirin for dementia prevention. If future studies of NSAIDs for dementia prevention are planned, they will need to be cognisant of the safety concerns arising from the existing studies.

Extracellular Vesicles as a Neprilysin Delivery System Memory Improvement in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative brain disorder which has no effective treatment yet due to the blood barrier in the brain that limits the drugs with the potential of disease improvement. Extracellular vesicles (EVs) are biocompatible nanoparticles with a lipid membrane. These vesicles are secreted from various cells such as mesenchymal stem cells (MSCs) and can pass through biological barriers for transfer of information such as signals or be used as carriers for various proteins like Neprilysin (NEP). NEP is an active enzyme in the clearance of abnormal aggregated beta-amyloid sheets in the brain. In the present study, we used EVs to carry NEP for memory improvement in Alzheimer's disease. For this purpose, bone marrow MSCs were isolated from rat femur. Stemness evaluation of established cells was characterized by differentiation potency and specific markers with flowcytometry. EVs were isolated from MSCs supernatant by ultracentrifugation and analyzed by scanning electron microscopy (SEM), dynamic light scattering (DLS) and western blotting. EVs were loaded with NEP by freeze-thaw cycle and then administrated intranasally in a rat model of the AD for 14 days. Our findings showed EV-loaded NEP caused a decrease in IL-1beta and also BAX but an increase in BCL2 expression level in the rat brain. Altogether, these data showed that EV-loaded NEP can improve brain-related behavioural function which may be mediated through the regulation of inflammation and apoptosis. These findings suggest that EV-loaded NEP can be considered as a potential drug delivery system for the improvement of AD.

Longitudinal lipid profile variations and clinical change in Alzheimer's disease dementia

Hypercholesterolemia and statin use have been unevenly associated with clinical change in Alzheimer's disease dementia. In this longitudinal study, 192 consecutive outpatients with late-onset Alzheimer's disease dementia were stratified according to APOE haplotypes, and followed for one year to investigate associations of lipid profile variations and lipophilic statin therapy with changes in cognition, caregiver burden, basic and instrumental functionality. Overall, 102 patients (53.1%) carried APOE4+ haplotypes and 90 (46.9%) carried APOE4- haplotypes; 189 patients (98.4%) used either a cholinesterase inhibitor, or Memantine, or both; 144 patients had dyslipidemias and 143 of them received statin therapy. Total cholesterol, LDL-cholesterol, Mini-Mental State Examination scores, and functional independence scores were significantly lower at the end of the follow-up, while Clinical Dementia Rating sum-of-boxes scores were higher. Exclusively for APOE4- carriers, rising LDL-cholesterol levels were associated with a trend toward improvements in the Index of Independence in Activities of Daily Living (β=0.010; ρ=0.16), whereas rising HDL-cholesterol levels were associated with lowered scores (β=-0.051; ρ=0.04). Lipophilic statin therapy had non-significant protective effects over Clinical Dementia Rating sum-of-boxes score variations only for APOE4- carriers. APOE4- haplotypes might enhance lipid availability to protect neuronal membranes, thus overcoming their supposed dysfunction in cholesterol metabolism, while APOE4+ carriers have inefficient neural repair mechanisms. In conclusion, APOE haplotypes seem to influence the protective effects of lipid profile variations for patients with Alzheimer's disease dementia, but current evidence is insufficient to propose lipid-lowering drugs as specific anti-dementia therapy.

Amyloid beta modulation of neuronal network activity in vitro

In vitro assays offer a means of screening potential therapeutics and accelerating the drug development process. Here, we utilized neuronal cultures on planar microelectrode arrays (MEA) as a functional assay to assess the neurotoxicity of amyloid-β 1-42 (Aβ42), a biomolecule implicated in the Alzheimer׳s disease (AD). In this approach, neurons harvested from embryonic mice were seeded on the substrate-integrated microelectrode arrays. The cultured neurons form a spontaneously active network, and the spiking activity as a functional endpoint could be detected via the MEA. Aβ42 oligomer, but not monomer, significantly reduced network spike rate. In addition, we demonstrated that the ionotropic glutamate receptors, NMDA and AMPA/kainate, play a role in the effects of Aβ42 on neuronal activity in vitro. To examine the utility of the MEA-based assay for AD drug discovery, we tested two model therapeutics for AD, methylene blue (MB) and memantine. Our results show an almost full recovery in the activity within 24h after administration of Aβ42 in the cultures pre-treated with either MB or memantine. Our findings suggest that cultured neuronal networks may be a useful platform in screening potential therapeutics for Aβ induced changes in neurological function.

Immunotherapeutic approaches for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia worldwide and is an emerging global epidemic. It is characterized by an imbalance between production and clearance of amyloid β (Aβ) and tau proteins. Oligomeric forms of Aβ and tau are believed to be the most toxic. Dramatic results from AD animal models showed great promise for active and passive immune therapies targeting Aβ. However, there is very limited evidence in human studies of the clinical benefits from these approaches. Immunotherapies targeting only tau pathology have had some success but are limited so far to mouse models. The majority of current methods is based on immunological targeting of a self-protein; hence, benefits need to be balanced against risks of stimulating excessive autoimmune toxic inflammation. For greater efficacy the next generation of vaccines needs to focus more on concurrently targeting all the intermediate toxic conformers of oligomeric Aβ and tau species.

Periodontal disease associates with higher brain amyloid load in normal elderly

The accumulation of amyloid-β (Aβ) plaques is a central feature of Alzheimer's disease (AD). First reported in animal models, it remains uncertain if peripheral inflammatory and/or infectious conditions in humans can promote Aβ brain accumulation. Periodontal disease, a common chronic infection, has been previously reported to be associated with AD. Thirty-eight cognitively normal, healthy, and community-residing elderly (mean age, 61 and 68% female) were examined in an Alzheimer's Disease Research Center and a University-Based Dental School. Linear regression models (adjusted for age, apolipoprotein E, and smoking) were used to test the hypothesis that periodontal disease assessed by clinical attachment loss was associated with brain Aβ load using (11)C-Pittsburgh compound B (PIB) positron emission tomography imaging. After adjusting for confounders, clinical attachment loss (≥3 mm), representing a history of periodontal inflammatory/infectious burden, was associated with increased PIB uptake in Aβ vulnerable brain regions (p = 0.002). We show for the first time in humans an association between periodontal disease and brain Aβ load. These data are consistent with the previous animal studies showing that peripheral inflammation/infections are sufficient to produce brain Aβ accumulations.

Activity of P-Glycoprotein, a β-Amyloid Transporter at the Blood-Brain Barrier, Is Compromised in Patients with Mild Alzheimer Disease

Studies in animals and postmortem human brain tissue support a role for P-glycoprotein in clearance of cerebral β-amyloid across the blood-brain barrier (BBB). We tested the hypothesis that BBB P-glycoprotein activity is diminished in Alzheimer disease (AD) by accounting for an AD-related reduction in regional cerebral blood flow (rCBF).

METHODS

We compared P-glycoprotein activity in mild-AD patients (n = 9) and cognitively normal, age-matched controls (n = 9) using PET with a labeled P-glycoprotein substrate, (11)C-verapamil, and (15)O-water to measure rCBF. BBB P-glycoprotein activity was expressed as the (11)C-verapamil radioactivity extraction ratio ((11)C-verapamil brain distributional clearance, K1/rCBF).

RESULTS

Compared with controls, BBB P-glycoprotein activity was significantly lower in the parietotemporal, frontal, and posterior cingulate cortices and hippocampus of mild AD subjects.

CONCLUSION

BBB P-glycoprotein activity in brain regions affected by AD is reduced and is independent of rCBF. This study improves on prior work by eliminating the confounding effect that reduced rCBF has on assessment of BBB P-glycoprotein activity and suggests that impaired P-glycoprotein activity may contribute to cerebral β-amyloid accumulation in AD. P-glycoprotein induction or activation to increase cerebral β-amyloid clearance could constitute a novel preventive or therapeutic strategy for AD.

Immunotherapy for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia worldwide. In AD the normal soluble amyloid β (sAβ) peptide is converted into oligomeric/fibrillar Aβ. The oligomeric forms of Aβ are thought to be the most toxic, while fibrillar Aβ becomes deposited as amyloid plaques and congophilic angiopathy, which serve as neuropathological markers of the disease. In addition the accumulation of abnormally phosphorylated tau as soluble toxic oligomers and as neurofibrillary tangles is a critical part of the pathology. Numerous therapeutic interventions are under investigation to prevent and treat AD. Among the more exciting and advanced of these approaches is vaccination. Active and passive Immunotherapy targeting only Aβ has been successful in many AD model animal trials; however, the more limited human data has shown much less benefit so far, with encephalitis occurring in a minority of patients treated with active immunization and vasogenic edema or amyloid-related imaging abnormalities (ARIA) being a complication in some passive immunization trials. Therapeutic intervention targeting only tau has been tested only in mouse models; and no approaches targeting both pathologies concurrently has been attempted, until very recently. The immune approaches tried so far were targeting a self-protein, albeit in an abnormal conformation; however, effective enhanced clearance of the disease associated conformer has to be balanced with the potential risk of stimulating excessive toxic inflammation. The design of future more effective immunomodulatory approaches will need to target all aspects of AD pathology, as well as specifically targeting pathological oligomeric conformers, without the use of any self-antigen.

Structure based design, synthesis, pharmacophore modeling, virtual screening, and molecular docking studies for identification of novel cyclophilin D inhibitors

Cyclophilin D (CypD) is a peptidyl prolyl isomerase F that resides in the mitochondrial matrix and associates with the inner mitochondrial membrane during the mitochondrial membrane permeability transition. CypD plays a central role in opening the mitochondrial membrane permeability transition pore (mPTP) leading to cell death and has been linked to Alzheimer's disease (AD). Because CypD interacts with amyloid beta (Aβ) to exacerbate mitochondrial and neuronal stress, it is a potential target for drugs to treat AD. Since appropriately designed small organic molecules might bind to CypD and block its interaction with Aβ, 20 trial compounds were designed using known procedures that started with fundamental pyrimidine and sulfonamide scaffolds know to have useful therapeutic effects. Two-dimensional (2D) quantitative structure-activity relationship (QSAR) methods were applied to 40 compounds with known IC50 values. These formed a training set and were followed by a trial set of 20 designed compounds. A correlation analysis was carried out comparing the statistics of the measured IC50 with predicted values for both sets. Selectivity-determining descriptors were interpreted graphically in terms of principle component analyses. These descriptors can be very useful for predicting activity enhancement for lead compounds. A 3D pharmacophore model was also created. Molecular dynamics simulations were carried out for the 20 trial compounds with known IC50 values, and molecular descriptors were determined by 2D QSAR studies using the Lipinski rule-of-five. Fifteen of the 20 molecules satisfied all 5 Lipinski rules, and the remaining 5 satisfied 4 of the 5 Lipinski criteria and nearly satisfied the fifth. Our previous use of 2D QSAR, 3D pharmacophore models, and molecular docking experiments to successfully predict activity indicates that this can be a very powerful technique for screening large numbers of new compounds as active drug candidates. These studies will hopefully provide a basis for efficiently designing and screening large numbers of more potent and selective inhibitors for CypD treatment of AD.

Novel immunological approaches for the treatment of Alzheimer's disease

Alzheimer's disease (AD), the most prevalent form of dementia worldwide, can be deemed as the next global health epidemic. The biochemistry underlying deposition of amyloid beta (A β) and hyperphosphorylated tau aggregates in AD has been extensively studied. The oligomeric forms of A β that are derived from the normal soluble A β peptides are believed to be the most toxic. However, it is the fibrillar Aβ form that aggregates as amyloid plaques and cerebral amyloid angiopathy, which serve as pathological hallmarks of AD. Moreover, deposits of abnormally phosphorylated tau that form soluble toxic oligomers and then accumulate as neurofibrillary tangles are an essential part of AD pathology. Currently, many strategies are being tested that either inhibit, eradicate or prevent the development of plaques in AD. An exciting new approach on the horizon is the immunization approach. Dramatic results from AD animal models have shown promise for active and passive immune therapies targeting A β. However, there is very limited data in humans that suggests a clear benefit. Some hurdles faced with these studies arise from complications noted with therapy. Encephalitis has been reported in trials of active immunization and vasogenic edema or amyloid - related imaging abnormalities (ARIA) has been reported with passive immunization in a minority of patients. As yet, therapies targeting only tau are still limited to mouse models with few studies targeting both pathologies. As the majority of approaches tried so far are based on targeting a self - protein, though in an abnormal conformation, benefits of therapy need to be balanced against the possible risks of stimulating excessive toxic inflammation. For better efficacy, future strategies will need to focus on the toxic oligomers and targeting all aspects of AD pathology.

Immunomodulation targeting of both Aβ and tau pathological conformers ameliorates Alzheimer's disease pathology in TgSwDI and 3xTg mouse models

Background

Central to the pathogenesis of Alzheimer’s disease (AD) and many other neurodegenerative diseases is the conformational change of a normal self-protein into toxic oligomeric species and amyloid deposits. None of these disorders have an effective therapy, but immunization approaches hold great promise. We have previously shown that active immunization with a novel peptide when polymerized into a stable oligomeric conformation, pBri, induced a humoral immune response to toxic Aβ species in an AD model, APP/PS1 transgenic (Tg) mice, reducing plaque deposits. pBri is a glutaraldehyde polymerized form of the carboxyl fragment of an amyloidogenic protein, which is deposited in the brains of patients with a rare autosomal dominant disease due to a missense mutation in a stop codon, resulting in the translation of an intronic sequence, with no known sequence homology to any mammalian protein.

Methods

In the current study we tested whether pBri-peptide-based immunomodulation is effective at reducing both vascular amyloid deposits and tau-related pathology using TgSwDI mice with extensive congophilic angiopathy and 3xTg mice with tau pathology.

Results

Our results indicate that this immunomodulation approach, which produces a humoral response to proteins in a pathological conformation, is effective at reducing both Aβ and tau-related pathologies.

Conclusions

This immunomodulatory approach has the advantage of using a non-self-immunogen that is less likely to be associated with autoimmune toxicity. Furthermore we found that it is able to target all the cardinal features of AD concurrently.

Treating Alzheimer's disease with monoclonal antibodies: current status and outlook for the future

In the past decade, Alzheimer's disease drug discovery has been directed at 'disease modifying drugs' that are able to counteract the progression of Alzheimer's disease by intervening in specific parts of its neuropathological process. Passive immunization with monoclonal antibodies (mAbs) may be able to clear toxic amyloid-β species either directly or through microglia or complement activation, thereby halting the amyloid cascade and preventing neurodegeneration and cognitive and functional decline. Thus far, results from two large phase 3 trial programs with bapineuzumab and solaneuzumab, respectively, have brought rather disappointing results. Possible explanations could be that these compounds were either targeting the wrong amyloid-β species, or were given too late in the disease process. Several new mAbs targeting various amyloid-β epitopes are now being tested in ongoing phase 2 and 3 clinical trials. The present review discusses the various mAbs aimed at amyloid-β, summarizes trial results and provides an outlook for the future.

Modulation of curli assembly and pellicle biofilm formation by chemical and protein chaperones

Enteric bacteria assemble functional amyloid fibers, curli, on their surfaces that share structural and biochemical properties with disease-associated amyloids. Here, we test rationally designed 2-pyridone compounds for their ability to alter amyloid formation of the major curli subunit CsgA. We identified several compounds that discourage CsgA amyloid formation and several compounds that accelerate CsgA amyloid formation. The ability of inhibitor compounds to stop growing CsgA fibers was compared to the same property of the CsgA chaperone, CsgE. CsgE blocked CsgA amyloid assembly and arrested polymerization when added to actively polymerizing fibers. Additionally, CsgE and the 2-pyridone inhibitors prevented biofilm formation by Escherichia coli at the air-liquid interface of a static culture. We demonstrate that curli amyloid assembly and curli-dependent biofilm formation can be modulated not only by protein chaperones, but also by "chemical chaperones."

A score based on screening tests to differentiate mild cognitive impairment from subjective memory complaints

It is not easy to differentiate patients with mild cognitive impairment (MCI) from subjective memory complainers (SMC). Assessments with screening cognitive tools are essential, particularly in primary care where most patients are seen. The objective of this study was to evaluate the diagnostic accuracy of screening cognitive tests and to propose a score derived from screening tests. Elderly subjects with memory complaints were evaluated using the Mini Mental State Examination (MMSE) and the Brief Cognitive Battery (BCB). We added two delayed recalls in the MMSE (a delayed recall and a late-delayed recall, LDR), and also a phonemic fluency test of letter P fluency (LPF). A score was created based on these tests. The diagnoses were made on the basis of clinical consensus and neuropsychological testing. Receiver operating characteristic curve analyses were used to determine area under the curve (AUC), the sensitivity and specificity for each test separately and for the final proposed score. MMSE, LDR, LPF and delayed recall of BCB scores reach statistically significant differences between groups (P=0.000, 0.03, 0.001 and 0.01, respectively). Sensitivity, specificity and AUC were MMSE: 64%, 79% and 0.75 (cut off <29); LDR: 56%, 62% and 0.62 (cut off <3); LPF: 71%, 71% and 0.71 (cut off <14); delayed recall of BCB: 56%, 82% and 0.68 (cut off <9). The proposed score reached a sensitivity of 88% and 76% and specificity of 62% and 75% for cut off over 1 and over 2, respectively. AUC were 0.81. In conclusion, a score created from screening tests is capable of discriminating MCI from SMC with moderate to good accurancy.

Short-term treatment with tolfenamic acid improves cognitive functions in Alzheimer's disease mice

Tolfenamic acid lowers the levels of the amyloid precursor protein (APP) and amyloid beta (Aβ) when administered to C57BL/6 mice by lowering their transcriptional regulator specificity protein 1 (SP1). To determine whether changes upstream in the amyloidogenic pathway that forms Aβ plaques would improve cognitive outcomes, we administered tolfenamic acid for 34 days to hemizygous R1.40 transgenic mice. After the characterization of cognitive deficits in these mice, assessment of spatial learning and memory functions revealed that treatment with tolfenamic acid attenuated long-term memory and working memory deficits, determined using Morris water maze and the Y-maze. These improvements occurred within a shorter period of exposure than that seen with clinically approved drugs. Cognitive enhancement was accompanied by reduction in the levels of the SP1 protein (but not messenger RNA [mRNA]), followed by lowering both the mRNA and the protein levels of APP and subsequent Aβ levels. These findings provide evidence that tolfenamic acid can disrupt the pathologic processes associated with Alzheimer's disease (AD) and are relevant to its scheduled biomarker study in AD patients.

γ-secretase binding sites in aged and Alzheimer's disease human cerebrum: the choroid plexus as a putative origin of CSF Aβ

Deposition of β -amyloid (Aβ) peptides, cleavage products of β-amyloid precursor protein (APP) by β-secretase-1 (BACE1) and γ-secretase, is a neuropathological hallmark of Alzheimer's disease (AD). γ-Secretase inhibition is a therapeutical anti-Aβ approach, although changes in the enzyme's activity in AD brain are unclear. Cerebrospinal fluid (CSF) Aβ peptides are thought to derive from brain parenchyma and thus may serve as biomarkers for assessing cerebral amyloidosis and anti-Aβ efficacy. The present study compared active γ-secretase binding sites with Aβ deposition in aged and AD human cerebrum, and explored the possibility of Aβ production and secretion by the choroid plexus (CP). The specific binding density of [(3) H]-L-685,458, a radiolabeled high-affinity γ-secretase inhibitor, in the temporal neocortex and hippocampal formation was similar for AD and control cases with similar ages and post-mortem delays. The CP in post-mortem samples exhibited exceptionally high [(3) H]-L-685,458 binding density, with the estimated maximal binding sites (Bmax) reduced in the AD relative to control groups. Surgically resected human CP exhibited APP, BACE1 and presenilin-1 immunoreactivity, and β-site APP cleavage enzymatic activity. In primary culture, human CP cells also expressed these amyloidogenic proteins and released Aβ40 and Aβ42 into the medium. Overall, our results suggest that γ-secretase activity appears unaltered in the cerebrum in AD and is not correlated with regional amyloid plaque pathology. The CP appears to be a previously unrecognised non-neuronal contributor to CSF Aβ, probably at reduced levels in AD.