Update on Disease-Modifying/Preventive Therapies in Alzheimer's Disease

Genetic dependency of Alzheimer's disease-associated genes across cells and tissue types

Effective treatments targeting disease etiology are urgently needed for Alzheimer's disease (AD). Although candidate AD genes have been identified and altering their levels may serve as therapeutic strategies, the consequence of such alterations remain largely unknown. Herein, we analyzed CRISPR knockout/RNAi knockdown screen data for over 700 cell lines and evaluated cellular dependencies of 104 AD-associated genes previously identified by genome-wide association studies (GWAS) and gene expression network studies. Multiple genes showed widespread cell dependencies across tissue lineages, suggesting their inhibition may yield off-target effects. Meanwhile, several genes including SPI1, MEF2C, GAB2, ABCC11, ATCG1 were identified as genes of interest since their genetic knockouts specifically affected high-expressing cells whose tissue lineages are relevant to cell types found in AD. Overall, analyses of genetic screen data identified AD-associated genes whose knockout or knockdown selectively affected cell lines of relevant tissue lineages, prioritizing targets for potential AD treatments.

The Alzheimer's Prevention Initiative Generation Program: Study design of two randomized controlled trials for individuals at risk for clinical onset of Alzheimer's disease

Introduction

Alzheimer's disease (AD) pathology, including the accumulation of amyloid beta (Aβ) species and tau pathology, begins decades before the onset of cognitive impairment. This long preclinical period provides an opportunity for clinical trials designed to prevent or delay the onset of cognitive impairment due to AD. Under the umbrella of the Alzheimer's Prevention Initiative Generation Program, therapies targeting Aβ, including CNP520 (umibecestat), a β-site-amyloid precursor protein cleaving enzyme-1 (BACE-1) inhibitor, and CAD106, an active Aβ immunotherapy, are in clinical development in preclinical AD.

Methods

The Alzheimer's Prevention Initiative Generation Program comprises two pivotal (phase 2/3) studies that assess the efficacy and safety of umibecestat and CAD106 in cognitively unimpaired individuals with high risk for developing symptoms of AD based on their age (60-75 years), APOE4 genotype, and, for heterozygotes (APOE ε2/ε4 or ε3/ε4), elevated brain amyloid. Approximately, 3500 individuals will be enrolled in either Generation Study 1 (randomized to cohort 1 [CAD106 injection or placebo, 5:3] or cohort 2 [oral umibecestat 50 mg or placebo, 3:2]) or Generation Study 2 (randomized to oral umibecestat 50 mg and 15 mg, or placebo [2:1:2]). Participants receive treatment for at least 60 months and up to a maximum of 96 months. Primary outcomes include time to event, with event defined as diagnosis of mild cognitive impairment due to AD and/or dementia due to AD, and the Alzheimer's Prevention Initiative preclinical composite cognitive test battery. Secondary endpoints include the Clinical Dementia Rating Sum of Boxes, Repeatable Battery for the Assessment of Neuropsychological Status total score, Everyday Cognition Scale, biomarkers, and brain imaging.

Discussion

The Generation Program is designed to assess the efficacy, safety, and biomarker effects of the two treatments in individuals at high risk for AD. It may also provide a plausible test of the amyloid hypothesis and further accelerate the evaluation of AD prevention therapies.

Zanthoxylum alatum ameliorates scopolamine-induced amnesia in rats: Behavioral, biochemical, and molecular evidence

OBJECTIVE:

Hydroethanolic extract of Zanthoxylum alatum seeds (HEZA) in scopolamine-induced amnesia was investigated for memory enhancing activity.

MATERIALS AND METHODS:

Radial arm maze (RAM) test was performed to evaluate the behavioral activity. Rats were treated with HEZA (50, 100, and 200 mg/kg, p. o.) and tacrine (3 mg/kg. i. p.) for 14 days. Scopolamine (0.4 mg/kg) was injected i. p. into rats after 45 min of drug administration on the 14^th day. The messenger RNA (mRNA)/protein profile of few markers (acetylcholinesterase [AChE], heme oxygenase-1 [HO-1], nuclear factor-kappa B [NFκB], nuclear factor erythroid 2–related factor 2 [Nrf2], protein phosphatase 2A[PP2A], Tau, brain-derived neurotrophic factor [BDNF], tropomyosin-related kinase B [TrkB], Bcl-2-associated X protein [Bax], and Caspase-3) were also measured by polymerase chain reaction (PCR) and immunoblotting assay. Brain cytokines (tumor necrosis factor alpha [TNF-α], interleukin [IL]-1 β, and IL-10) in hippocampus were evaluated using commercially available enzyme-linked immunosorbent assay kits.

RESULTS:

HEZA exhibited anti-amnesic activity as indicated by a significant reduction in the working memory error and reference memory error in RAM. Pretreatment with HEZA significantly down-regulated the expression of AChE, NFκB, Tau, Bax, and Caspase-3 with simultaneous up-regulation of Nrf2, HO-1, PP2A, BDNF, and TrkB genes in the hippocampal tissues similar to tacrine when compared with scopolamine-treated rats. Pretreatment with HEZA attenuated scopolamine-induced elevation of TNF-α, IL-1 β, levels in hippocampus and reversed diminished IL-10 concentrations towards normal levels in the brain.

CONCLUSION:

Zanthoxylum alatum seeds could probably counteract amnesia. Since its use is mainly reported as a stimulant and tonic, this novel activity could be a boon for the scientists to explore more in this direction.

Isorhynchophylline alleviates learning and memory impairments induced by aluminum chloride in mice

BACKGROUND

To evaluate the effect of Isorhynchophylline (IRN) on the learning and memory impairments induced by aluminum chloride (AlCl3) in mice.

METHODS

Fifty male Balb-c mice (4-month-old) were randomly divided into five groups: control, AlCl3 plus vehicle, AlCl3 plus IRN (20 mg/kg), AlCl3 plus IRN (40 mg/kg) and AlCl3 plus donepezil (5 mg/kg). Learning and memory impairments were induced in mice by subcutaneously injecting with AlCl3 (50 mg/kg) once a day for 8 consecutive weeks. At the same time, mice were intragastrically given vehicle or IRN (20 and 40 mg/kg) or donepezil (5 mg/kg) 30 min before each AlCl3 injection. The spatial learning and memory function was assessed using radial arm maze. After sacrificed, the parameters of oxidative stress and cholinergic system in the brain tissues were examined with ELISA kits. Moreover, the expression of nuclear factor kappa B (NF-κB) signaling pathway was analyzed with western blotting.

RESULTS

The results showed that treatment with IRN could significantly ameliorate the cognitive deficits induced by AlCl3 in mice. In addition, treatment with IRN was found to reduce the level of malondialdehyde, enhance the activities of superoxide dismutases and catalase, increase the level of glutathione, and markedly inhibit the activity of acetylcholinesterase (AChE) in the brain tissues of the AlCl3-treated mice. Moreover, IRN significantly suppressed the phosphorylation of NF-κB p65 and IκBα in the brain tissues of AlCl3-treated mice. However, IRN did not show significant effect on the activity of butyrylcholinesterase.

CONCLUSION

Our findings demonstrated for the first time that IRN could alleviate learning and memory impairments induced by AlCl3 in mice. The neuroprotective effect of IRN against AlCl3-induced AD is probably mediated, at least in part, through inhibiting the AChE activity and reducing the oxidative damage of brain tissue via suppress the NF-κB signaling pathway. These results contributed to a better understanding of the in vivo anti-AD mechanism of IRN. It was concluded that IRN could protect the learning and memory function.

Retinal oxygen metabolism in patients with mild cognitive impairment

Introduction

We have previously reported that retinal vessel oxygen saturation is increased in mild-to-moderate dementia of Alzheimer's type when compared with healthy individuals. Mild cognitive impairment (MCI) is the predementia stage of the disease. The main purpose was to investigate if these changes are seen in MCI.

Methods

Retinal vessel oxygen saturation was measured in 42 patients with MCI and 42 healthy individuals with a noninvasive retinal oximeter, Oxymap T1. The groups were paired according to age.

Results

Arteriolar and venular oxygen saturation was increased in MCI patients compared to healthy individuals (arterioles: 93.1 ± 3.7% vs. 91.1 ± 3.4%, P = .01; venules: 59.6 ± 6.1% vs. 54.9 ± 6.4%, P = .001). Arteriovenous difference was decreased in MCI compared to healthy individuals (33.5 ± 4.5% vs. 36.2 ± 5.2%, P = .01).

Discussion

Increased retinal vessel oxygen saturation and decreased arteriovenous difference in MCI could reflect less oxygen extraction by retinal tissue. This indicates that retinal oxygen metabolism may be affected in patients with MCI.

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The need for reliable, noninvasive techniques for diagnosis of dementia is widely recognized.

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This research indicates that retinal metabolism is decreased in patients in the predementia stage of mild cognitive impairment.

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Retinal oximetry is a novel noninvasive method that could help as a diagnostic tool in dementia.

[Alzheimer's disease from Auguste Deter to the present : Progress, disappointments and open questions]

AIM

The present article aims to provide a short overview of the discovery history, conceptual development, as well as on current neurobiological and pharmacological research questions in the field of Alzheimer's disease (AD). In view of the long hoped for but so far unachieved therapeutic breakthrough, this also includes a critical reflection of current research paradigms.

MATERIAL AND METHODS

Starting from the first case report described by Alois Alzheimer in 1906, the historical impact of his seminal discovery is reconstructed. Neurobiological research paradigms central to AD are discussed with respect to their relevance for modern biomarker-based diagnostic approaches as well as to the development of innovative disease-modifying drug therapies.

RESULTS

Originally conceived as a rare presenile form of dementia it was not until the 1970s that AD was granted an orphan disease status. The biomedical deconstruction of senility and the introduction of new research methods enabled the nosological unification of AD with the concept of senile dementia which, in turn led to a global flowering of AD research. In the 1990s the amyloid cascade hypothesis was introduced as the leading research paradigm of AD. In the following years this stimulated the development of a huge variety of innovative biomarker-based diagnostic and disease-modifying pharmacological approaches.

CONCLUSION

Against the background of the recent failures of many clinical drug trials, the relevance of the amyloid cascade hypothesis to explain the etiology of sporadic AD is increasingly being questioned. On the one hand, this leaves the question of the central etiological paradigm unresolved and on the other hand it stimulated a debate on alternative etiological models which might lead to fruitful consequences for future research strategies.

Novel strategies for Alzheimer's disease treatment: An overview of anti-amyloid beta monoclonal antibodies

Alzheimer's disease (AD) is a multifactorial, progressive neurodegenerative disorder with a poor prognosis, and thus, novel therapies for AD are certainly needed in a growing population of elderly patients or asymptomatic individuals, who are at risk for AD, worldwide. It has been established that some AD biomarkers such as amyloid-beta load in the brain, precede the onset of the disease, by approximately 20 years. Therefore, the therapy to prevent or effectively treat AD has to be initiated before the emergence of symptoms. A goal of this review is to present the results of recent clinical trials on monoclonal antibodies against amyloid beta, used for the treatment of AD and also to address some of the current challenges and emerging strategies to prevent AD. In recent trials, a monoclonal antibody, i.e. solanezumab has shown some beneficial cognitive effects among mild AD patients. Ongoing studies with gantenerumab and crenezumab will examine when exactly the AD treatment, aimed at modifying the disease course has to be started. This review was based on Medline database search for trials on passive anti-AD immunotherapy, for which the main timeframe was set from 2012 to 2015.

Drug Development in Alzheimer's Disease: The Contribution of PET and SPECT

Clinical trials aiming to develop disease-altering drugs for Alzheimer’s disease (AD), a neurodegenerative disorder with devastating consequences, are failing at an alarming rate. Poorly defined inclusion-and outcome criteria, due to a limited amount of objective biomarkers, is one of the major concerns. Non-invasive molecular imaging techniques, positron emission tomography and single photon emission (computed) tomography (PET and SPE(C)T), allow visualization and quantification of a wide variety of (patho)physiological processes and allow early (differential) diagnosis in many disorders. PET and SPECT have the ability to provide biomarkers that permit spatial assessment of pathophysiological molecular changes and therefore objectively evaluate and follow up therapeutic response, especially in the brain. A number of specific PET/SPECT biomarkers used in support of emerging clinical therapies in AD are discussed in this review.