Current drug targets for Alzheimer's disease treatment

Electrochemical impedance spectroscopy for study of amyloid β-peptide interactions with (−) nicotine ditartrate and (−) cotinine

Immobilization of amyloid beta (Abeta) (1-40) peptide on Au-colloid modified gold electrodes has been studied. Colloidal Au was self-assembled onto gold electrodes through the thiol groups of 1,6-hexanedithiol monolayer. Next, buffered aqueous solution of Abeta (1-40) peptide existing in the beta-sheet structure in the acidic media was dropped on the electrode surface. Each step of electrode modification has been confirmed with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The changes of the resistance of the layer with deposited Abeta (1-40) peptide, occurred under stimulation by different concentration of (-) nicotine ditartrate and (-) cotinine were measured with EIS and were used for the calculation of association constants. The gentle measuring conditions applied in electrochemical impedance spectroscopy, together with suitable environment for biomolecules immobilization created by Au-colloid, might be recommended as the analytical tool for assessing the effectiveness of potential drugs used in Alzheimer's disease (AD) therapy.

Analysis of electroencephalograms in Alzheimer's disease patients with multiscale entropy

The aim of this study was to analyse the electroencephalogram (EEG) background activity of Alzheimer's disease (AD) patients using multiscale entropy (MSE). MSE is a recently developed method that quantifies the regularity of a signal on different time scales. These time scales are inspected by means of several coarse-grained sequences formed from the analysed signals. We recorded the EEGs from 19 scalp electrodes in 11 AD patients and 11 age-matched controls and estimated the MSE profile for each epoch of the EEG recordings. The shape of the MSE profiles reveals the EEG complexity, and it suggests that the EEG contains information in deeper scales than the smallest one. Moreover, the results showed that the EEG background activity is less complex in AD patients than control subjects. We found significant differences between both subject groups at electrodes F3, F7, Fp1, Fp2, T5, T6, P3, P4, O1 and O2 (p-value < 0.01, Student's t-test). These findings indicate that the EEG complexity analysis performed on deeper time scales by MSE may be a useful tool in order to increase our knowledge of AD.

Ex situ atomic force microscopy analysis of beta-amyloid self-assembly and deposition on a synthetic template

The beta-amyloid (Abeta) deposition, which is the conversion of soluble Abeta peptides to insoluble plaques on a surface, is an essential pathological process in Alzheimer's disease (AD). The identification and characterization of possible environmental factors that may influence amyloid deposition in vivo are important to unveil the underlying etiology of AD. According to the amyloid cascade hypothesis, diffuse plaques are initial and visual deposits in the early event of AD, leading to amyloid plaques. To study amyloid deposition and growth in vitro, we prepared a synthetic template by immobilizing Abeta seeds on an N-hydroxysuccinimide ester-activated solid surface. According to our analysis with an ex situ atomic force microscope, the formation of amyloid plaque-like aggregates was mediated by the interaction between Abeta in a solution and on a synthetic template, suggesting that Abeta oligomers function well as seeds for amyloid deposition. It was observed that insoluble amyloid aggregates formed on the template surface serve as a sink of soluble Abeta in a solution as well as mediate the formation of intermediates in the pathway of amyloid fibrillization in a solution. Relative seeding efficiencies of fresh monomers, oligomers, and fully grown fibrils were analyzed by measuring the deposited plaque volume and its height distribution through atomic force microscopy. The result revealed that oligomeric forms of Abeta act more efficiently as seeds than monomers or fibrils do. Fluorescence spectroscopy with thioflavin T confirmed that amyloid aggregate formation proceeds in a concentration-dependent manner. Analysis with Fourier transform infrared spectroscopy indicated a progressive transition of soluble Abeta42 monomer to amyloid fibrils having antiparallel beta-sheet structure on the template. Furthermore, studies on the interaction between Abeta40 and 42, two major variants of Abeta derived from the amyloid precursor protein, showed that amyloid aggregate formation on the surface was accelerated further by the homogeneous association of soluble Abeta42 onto Abeta42 seeds than by other combinations. A slightly acidic condition was found to be unfavorable for amyloid formation. This study gives insight into understanding the effects of environmental factors on amyloid formation via the use of a synthetic template system.

Screening of plants used in Danish folk medicine to treat memory dysfunction for acetylcholinesterase inhibitory activity

Aqueous and methanolic extracts of 11 plants, used in Danish folk medicine for improvement of memory and cognition, and 3 Corydalis species were tested for acetylcholinesterase inhibitory activity using the Ellman colorimetric method. Significant inhibitory activity in dose-dependent manner was observed for extracts of Corydalis cava, Corydalis intermedia, Corydalis solida ssp. laxa and Corydalis solida ssp. slivenensis. Extracts of Ruta graveolens, Lavandula angustifolia, Rosmarinus officinalis, Petroselinum crispum and Mentha spicata exhibited moderate inhibition of the enzyme, defined as more than 15% at 0.1 mg/ml.

Noncovalent interaction between amyloid-beta-peptide (1-40) and oleuropein studied by electrospray ionization mass spectrometry

Beta amyloid peptide (Abeta) is the major proteinaceous component of senile plaques formed in Alzheimer's disease (AD) brain. The aggregation of Abeta is associated with neurodegeneration, loss of cognitive ability, and premature death. It has been suggested that oxidative stress and generation of free radical species have implications in the fibrillation of Abeta and its subsequent neurotoxicity. For this reason, it is proposed that antioxidants may offer a protective or therapeutic alternative against amyloidosis. This study is the first report of the formation of the noncovalent complex between Abeta or its oxidized form and the natural derived antioxidant oleuropein (OE) by electrospray ionization mass spectrometry (ESI MS). ESI MS allowed the real time monitoring of the complex formation between Abeta, OE, and variants thereof. Several experimental conditions, such as elevated orifice potential, low pH values, presence of organic modifier, and ligand concentration were examined, to assess the specificity and the stability of the formed noncovalent complexes.

(+)-N-Deoxymilitarinone A, a neuritogenic pyridone alkaloid from the insect pathogenic fungus Paecilomyces farinosus

A new pyridone alkaloid, (+)-N-deoxymilitarinone A (1), was isolated from Paecilomyces farinosus RCEF 0097 along with the related metabolites, militarinone D and militarinone B. The sterol 22E,4R-ergosta-7,22-diene-3beta,5alpha,6beta,9alpha-tetraol was also identified. The structures were established by spectroscopic methods, in particular with the aid of extensive NMR experiments. Compound 1 induced neurite sprouting in PC 12 cells when tested at 33 and 100 microM concentrations. A cytotoxic effect was observed in human neurons (IMR-32) at a concentration of 100 microM.

Acteoside of Callicarpa dichotoma Attenuates Scopolamine-Induced Memory Impairments

We previously reported that ten phenylethanoid glycosides including acteoside isolated from the leaves and twigs of Callicarpa dichotoma significantly attenuated glutamate-induced neurotoxicity. In the present study, we examined anti-amnesic activity of acteoside using scopolamine-induced (1 mg/kg body weight, s.c.) amnesic mice with both passive avoidance and Morris water maze tests. Acute oral treatment (single administration prior to scopolamine treatment) of mice with acteoside (1.0, 2.5 mg/kg body weight) significantly mitigated scopolamine-induced memory deficits in the passive avoidance test. It is interesting to note that prolonged oral daily treatment of mice with much lower amount (0.1 mg/kg body weight) of acteoside for 10 d reversed the scopolamine-induced memory deficits. In the Morris water maze, prolonged oral treatment with acteoside (prolonged daily administration of 1.0 mg/kg body weight for 10 d) significantly ameliorated scopolamine-induced memory deficits showing the formation of long-term and/or short-term spatial memory. We suggest, therefore, that acteoside has anti-amnesic activity that may ultimately hold significant therapeutic value in alleviating certain memory impairment observed in Alzheimer's disease.

Design, synthesis, and evaluation of 2-phenoxy-indan-1-one derivatives as acetylcholinesterase inhibitors

A series of 2-phenoxy-indan-1-one derivatives have been designed, synthesized, and tested as acetylcholinesterase inhibitors. The most potent compound exhibited high AChE inhibitory activity (IC50 = 50 nM), and the molecular docking study indicated that it was nicely accommodated by AChE.

ESP-102, a standardized combined extract of Angelica gigas, Saururus chinensis and Schizandra chinensis, significantly improved scopolamine-induced memory impairment in mice

We assessed the effects of oral treatments of ESP-102, a standardized combined extract of Angelica gigas, Saururus chinensis and Schizandra chinensis, on learning and memory deficit. The cognition-enhancing effect of ESP-102 was investigated in scopolamine-induced (1 mg/kg body weight, s.c.) amnesic mice with both passive avoidance and Morris water maze performance tests. Acute oral treatment (single administration prior to scopolamine treatment) of mice with ESP-102 (doses in the range of 10 to 100 mg/kg body weight) significantly reduced scopolamine-induced memory deficits in the passive avoidance performance test. Another noteworthy result included the fact that prolonged oral daily treatments of mice with much lower amounts of ESP-102 (1 and 10 mg/kg body weight) for ten days reversed scopolamine-induced memory deficits. In the Morris water maze performance test, both acute and prolonged oral treatments with ESP-102 (single administration of 100 mg/kg body weight or prolonged daily administration of 1 and 10 mg/kg body weight for ten days, respectively, significantly ameliorated scopolamine-induced memory deficits as indicated by the formation of long-term and/or short-term spatial memory. In addition, we investigated the effects of ESP-102 on neurotoxicity induced by amyloid-beta peptide (Abeta25-35) or glutamate in primary cultured cortical neurons of rats. Pretreatment of cultures with ESP-102 (0.001, 0.01 and 0.1 mug/ml) significantly protected neurons from neurotoxicity induced by either glutamate or Abeta25-35. These results suggest that ESP-102 may have some protective characteristics against neuronal cell death and cognitive impairments often observed in Alzheimer's disease, stroke, ischemic injury and other neurodegenerative diseases.

P3 cap modified Phe*-Ala series BACE inhibitors

With the aim of reducing molecular weight and adjusting log D value of BACE inhibitors to more favorable range for BBB penetration and better bioavailability, we synthesized and evaluated several series of P3 cap modified BACE inhibitors obtained via replacement of the P3NHBoc moiety as seen in 3 with other polar functional groups such as amino, hydroxyl and fluorine. Several promising inhibitors emerging from this P3 cap SAR study (e.g., 15 and 19) demonstrated good enzyme inhibitory potencies (BACE-1 IC(50) <50 nM) and whole cell activities (IC(50) approximately 1 microM).

EEG dynamics in patients with Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder characterized by cognitive and intellectual deficits and behavior disturbance. The electroencephalogram (EEG) has been used as a tool for diagnosing AD for several decades. The hallmark of EEG abnormalities in AD patients is a shift of the power spectrum to lower frequencies and a decrease in coherence of fast rhythms. These abnormalities are thought to be associated with functional disconnections among cortical areas resulting from death of cortical neurons, axonal pathology, cholinergic deficits, etc. This article reviews main findings of EEG abnormalities in AD patients obtained from conventional spectral analysis and nonlinear dynamical methods. In particular, nonlinear alterations in the EEG of AD patients, i.e. a decreased complexity of EEG patterns and reduced information transmission among cortical areas, and their clinical implications are discussed. For future studies, improvement of the accuracy of differential diagnosis and early detection of AD based on multimodal approaches, longitudinal studies on nonlinear dynamics of the EEG, drug effects on the EEG dynamics, and linear and nonlinear functional connectivity among cortical regions in AD are proposed to be investigated. EEG abnormalities of AD patients are characterized by slowed mean frequency, less complex activity, and reduced coherences among cortical regions. These abnormalities suggest that the EEG has utility as a valuable tool for differential and early diagnosis of AD.

A proximal gene promoter region for the beta-amyloid precursor protein provides a link between development, apoptosis, and Alzheimer's disease

Abnormalities in regulation of the beta-amyloid precursor protein (APP) gene might be a crucial factor in Alzheimer's disease (AD). Our aim is to study the role of a specific proximal APP promoter element under the apoptotic condition. Our transfection studies with APP promoter deletion constructs indicate that each cell type differently regulates promoter activity. The minimum region that was sufficient to drive basal promoter activity in neuronal PC12 and neuroblastoma SK-N-SH cells was -75/+104 and -47/+104 bp, respectively. In SK-N-SH cells, the -47/+104 construct displayed the highest promoter activity, and the -75/-46 region acted as a negative regulatory element. Results from the gel electrophoretic mobility shift assay (EMSA) indicate that the -75/-46 region binds to a distinct DNA-protein complex with nuclear protein(s) from HeLa, PC12, NIH-3T3, and neuroblastoma cells. EMSA results from HeLa cells, which were stimulated by serum starvation (SR), indicate a significant induction in the signal of the DNA-protein complex from controls. EMSA results from PC12 cells, which were subjected to hypoxia, indicate a significant reduction in the signal. Our results suggest that the -75/-46 region binds to a protein that is upregulated in serum starvation, and downregulated in hypoxia. Because serum starvation contributes to the induction of apoptosis, these results suggest a role of the 30-bp proximal APP promoter element in enhanced apoptotic neuronal cell death.

Does nitric oxide synthase contribute to the pathogenesis of Alzheimer's disease?: effects of beta-amyloid deposition on NOS in transgenic mouse brain with AD pathology

Oxidative stress is a risk factor for Alzheimer's disease (AD) whose major hallmark includes brain depositions of the amyloid beta peptide (Abeta) derived from the beta-amyloid precursor protein (APP). Our aim was to determine whether or not excessive Abeta deposition would alter nitric oxide synthase (NOS) activity, and thereby affect NOS-mediated superoxide formation. We compared NOS activity in brain extracts between Tg mice (expressing APP Swedish double mutation plus presenilin [PS-1] and nontransgenic [nTg] mice. Five brain regions, including cerebral cortex, hippocampus, cerebellum, and striatum from both nTg and Tg mice showed a detectable level of neuronal (n) NOS activity. Cerebellar extracts from both nTg and Tg mice displayed the highest level of nNOS activity, which was fourfold higher than cortical extracts. Although there was an increase in nNOS activity in Tg brain extracts, this did not attain statistical significance. A similar result was obtained for inducible NOS levels. Our results suggest that excess levels of Abeta failed to both trigger NOS activity and change NOS levels.

Future considerations for the medical management of nerve-agent intoxication

The use of chemical warfare agents against civilians and unprotected troops in international conflicts or by terrorists against civilians is considered to be a real threat, particularly following the terrorist attacks on 11 September 2001 against the World Trade Center in New York and against the Pentagon in Washington, DC. Over the past 10 years, terrorists have been planning to use or have used chemical warfare agents on several occasions around the world, and the attacks in 2001 illustrate their willingness to use any means of warfare to cause death and destruction among civilians. In spite of new international treaties with strong verification measures and with an aim to prohibit and prevent the use of weapons of mass destruction, nevertheless, some countries and terrorist groups have been able to develop, produce, and use such weapons, particularly nerve agents, in domestic terrorist attacks or during warfare in international conflicts. This article reviews current medical therapy for nerve-agent intoxication and discusses possible future improvement of medical therapies. Present medical counter-measures against nerve agents are not sufficiently effective particularly in protecting the brain. Therefore, new and more effective countermeasures must be developed to enable better medical treatment of civilians and military personnel following exposure to nerve agents. Therefore, it is important with an enhanced effort by all countries, to improve and increase research in medical countermeasures, in the development of protective equipment, and in carrying out regular training of medical and emergency personnel as well as of military nuclear, biological, or chemical (NBC) units. Only then will nations be able to reduce the risk from and prevent the use of such weapons of mass destruction (WMD).

APH1, PEN2, and Nicastrin increase Abeta levels and gamma-secretase activity

A major component of the amyloid plaque core in Alzheimer's disease (AD) is the 40-42-residue amyloid beta peptide (Abeta). Mutations linked to AD such as those in presenilins 1 (PS1) and 2 (PS2) invariably increase the longer Abeta42 species that forms neurotoxic oligomers. It is believed that PS1/2 constitute the catalytic subunit of the gamma-secretase responsible for the final step in Abeta biogenesis. Recent genetic studies have identified a number of additional genes encoding APH1a, APH1b, PEN2, and Nicastrin proteins, which are part of the gamma-secretase complex with PS1. Further, knockout studies using RNAi showed that these components are essential for gamma-secretase activity. However, the nature of gamma-secretase and how the aforementioned proteins regulate its activity are still incompletely understood. Here we present evidence that unlike PS1, overexpression of these proteins can increase the levels of Abeta, suggesting that these proteins are limiting for gamma-secretase activity. In addition, our studies also suggest that the presenilin partners regulate the relative levels of Abeta40 and Abeta42.

The role of the carboxyl-terminal fragments of amyloid precursor protein in Alzheimer's disease

Two major pathological hallmarks of Alzheimer's disease (AD) are the senile plaques that are primarily composed of amyloid beta-peptide (Abeta) and neurofibrillary tangles consisting of tau aggregates. Abeta is generated proteolytically from a family of Abeta-containing precursor proteins (APP; 695-770 amino acid) by secretase enzymes to different specific carboxyl-terminal fragments (CTFs). Herein we examined APP and its products in autopsied brain sections from 10 AD and 10 non-AD control subjects immunochemically using an antibody that was raised against APP751-770 residue (O443). The O443 antibody was initially characterized by Western blot analysis and immunoprecipitation. In this study, we used this antibody for immunohistochemical analysis to determine the distribution of APP and its CTF species. In 10 brain regions showing different levels of plaques and tangles, antibody O443 stained the perinuclear region of the nucleus, plaques, and neurites. Tangle-bearing neurons also appeared to stain with the antibody, suggesting that these dysfunctional neurons continue to synthesize APP/CTF. Alternatively, the normally short-lived APP/CTF can be stabilized and persist in these neurons. Taken together, these results suggest that, in addition to the widely believed role of Abeta, CTFs may play a key role in the pathogenesis of AD. Studying their localization and biogenesis may reveal the biological activities of CTFs of APP. The present study may pave the way for possible antiamyloidogenic therapy in the treatment of AD.

Regulation of promoter activity of the APP gene by cytokines and growth factors: implications in Alzheimer's disease

One of the major pathological hallmarks of Alzheimer's disease (AD) is the presence of brain depositions of senile plaques that are primarily composed of potentially toxic amyloid beta-peptide (Abeta), which is generated from a family of Abeta-containing precursor proteins (APP; 695-770 amino acids). The role of inflammatory cytokines and growth factors has been implicated in the pathogenesis of AD. Our goal is to study the effects of these factors on the regulation of APP gene expression. Here we compared APP promoter activity in the presence of different growth factors and cytokines such as brain-derived neurotrophic factor (BDNF), interleukin (IL-1), nerve growth factor (NGF), neurotrofin-3 (NT-3), transforming growth factor (TGF-beta1), and tumor necrosis factor (TNF-alpha1). PC12 neuronal cells, which were treated separately with these agents, were transfected with the construct containing either 190 bp APP proximal promoter region (-46 to 144 bp with respect to the transcription start site [+1]), 94 bp APP 5'-untranslated region (UTR, +50 to 144) or other 5'-UTR-deleted regions. Each construct was cloned upstream of a reporter chloramphenicol acetyl transferase gene (CAT). The treatment of PC12 cells with NGF stimulated reporter activity in all constructs tested. The treatment of cells with BDNF, NT3, TGF-beta1, or TNF-alpha stimulated reporter activity in a promoter/UTR-specific manner. Transfection with the complete -46 to 144 region retained the maximum stimulatory activity for any treatment tested in PC12 cells. These results suggest that the regulatory elements of the APP gene respond to the stimulation of different growth factors, cytokines, and interleukins. This is consistent with the effects of the different growth factors, cytokines, and interleukins on APP message and protein levels.

Functional characterization of the 5'-regulatory region of the murine apolipoprotein gene

The apolipoprotein E (APOE) gene causes a major risk factor for the development of Alzheimer's disease (AD). To study the transcription control of the mouse (m) APOE gene, we first tested the promoter activity of a 721-base-pair (bp) 5'-flanking region, which is located 771 bp upstream from the translation initiation codon. We cloned the 721-bp region upstream of the reporter chloramphenicol acetyl transferase (CAT) gene into a promoterless vector (pBLCAT3). The mAPOE promoter and vector DNA were separately transfected in rat glial C6 and neuronal PC12 cell lines. The 721-bp APOE region (from position 329 to 1050) is functionally active in different cell lines tested. The serial deletion analysis indicates that the 266-bp promoter region (from 784 to 1050) has the highest and the 67-bp region (from 983 to 1050) the lowest activity on the reporter gene in neuronal and astrocytic cell lines. These studies suggest that the 147-bp region (from 637 to 784) has a negative regulatory effect on the reporter gene. In the gel shift assay, the 67-bp region binds to a specific transcription factor(s) in PC12 nuclear extracts. Our results suggest that mAPOE can also be expressed in neuronal cells in addition to the astrocytic cells. Characterization of mAPOE promoter is important for the AD drug development discovery and APOE transgenic mice studies.