Emerging Alzheimer's disease therapies: inhibition of beta-secretase

Targeting CaN/NFAT in Alzheimer's brain degeneration

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a progressive loss of cognitive functions. While the exact causes of this debilitating disorder remain elusive, numerous investigations have characterized its two core pathologies: the presence of β-amyloid plaques and tau tangles. Additionally, multiple studies of postmortem brain tissue, as well as results from AD preclinical models, have consistently demonstrated the presence of a sustained inflammatory response. As the persistent immune response is associated with neurodegeneration, it became clear that it may also exacerbate other AD pathologies, providing a link between the initial deposition of β-amyloid plaques and the later development of neurofibrillary tangles. Initially discovered in T cells, the nuclear factor of activated T-cells (NFAT) is one of the main transcription factors driving the expression of inflammatory genes and thus regulating immune responses. NFAT-dependent production of inflammatory mediators is controlled by Ca2+-dependent protein phosphatase calcineurin (CaN), which dephosphorylates NFAT and promotes its transcriptional activity. A substantial body of evidence has demonstrated that aberrant CaN/NFAT signaling is linked to several pathologies observed in AD, including neuronal apoptosis, synaptic deficits, and glia activation. In view of this, the role of NFAT isoforms in AD has been linked to disease progression at different stages, some of which are paralleled to diminished cognitive status. The use of classical inhibitors of CaN/NFAT signaling, such as tacrolimus or cyclosporine, or adeno-associated viruses to specifically inhibit astrocytic NFAT activation, has alleviated some symptoms of AD by diminishing β-amyloid neurotoxicity and neuroinflammation. In this article, we discuss the recent findings related to the contribution of CaN/NFAT signaling to the progression of AD and highlight the possible benefits of targeting this pathway in AD treatment.

BACE-1 Inhibitors Targeting Alzheimer's Disease

The accumulation of amyloid-β (Aβ) is the main event related to Alzheimer's disease (AD) progression. Over the years, several disease-modulating approaches have been reported, but without clinical success. The amyloid cascade hypothesis evolved and proposed essential targets such as tau protein aggregation and modulation of β-secretase (β-site amyloid precursor protein cleaving enzyme 1 - BACE-1) and γ-secretase proteases. BACE-1 cuts the amyloid precursor protein (APP) to release the C99 fragment, giving rise to several Aβ peptide species during the subsequent γ-secretase cleavage. In this way, BACE-1 has emerged as a clinically validated and attractive target in medicinal chemistry, as it plays a crucial role in the rate of Aβ generation. In this review, we report the main results of candidates in clinical trials such as E2609, MK8931, and AZD-3293, in addition to highlighting the pharmacokinetic and pharmacodynamic-related effects of the inhibitors already reported. The current status of developing new peptidomimetic, non-peptidomimetic, naturally occurring, and other class inhibitors are demonstrated, considering their main limitations and lessons learned. The goal is to provide a broad and complete approach to the subject, exploring new chemical classes and perspectives.

In Silico Molecular Docking Analysis of Karanjin against Alzheimer's and Parkinson's Diseases as a Potential Natural Lead Molecule for New Drug Design, Development and Therapy

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders that have emerged as among the serious health problems of the 21st century. The medications currently available to treat AD and PD have limited efficacy and are associated with side effects. Natural products are one of the most vital and conservative sources of medicines for treating neurological problems. Karanjin is a furanoflavonoid, isolated mainly from Pongamia pinnata with several medicinal plants, and has been reported for numerous health benefits. However, the effect of karanjin on AD and PD has not yet been systematically investigated. To evaluate the neuroprotective effect of karanjin, extensive in silico studies starting with molecular docking against five putative targets for AD and four targets for PD were conducted. The findings were compared with three standard drugs using Auto Dock 4.1 and Molegro Virtual Docker software. Additionally, the physiochemical properties (Lipinski rule of five), drug-likeness and parameters including absorption, distribution, metabolism, elimination and toxicity (ADMET) profiles of karanjin were also studied. The molecular dynamics (MD) simulations were performed with two selective karanjin docking complexes to analyze the dynamic behaviors and binding free energy at 100 ns time scale. In addition, frontier molecular orbitals (FMOs) and density-functional theory (DFT) were also investigated from computational quantum mechanism perspectives using the Avogadro-ORCA 1.2.0 platform. Karanjin complies with all five of Lipinski's drug-likeness rules with suitable ADMET profiles for therapeutic use. The docking scores (kcal/mol) showed comparatively higher potency against AD and PD associated targets than currently used standard drugs. Overall, the potential binding affinity from molecular docking, static thermodynamics feature from MD-simulation and other multiparametric drug-ability profiles suggest that karanjin could be considered as a suitable therapeutic lead for AD and PD treatment. Furthermore, the present results were strongly correlated with the earlier study on karanjin in an Alzheimer's animal model. However, necessary in vivo studies, clinical trials, bioavailability, permeability and safe dose administration, etc. must be required to use karanjin as a potential drug against AD and PD treatment, where the in silico results are more helpful to accelerate the drug development.

Deficiency in MT5-MMP Supports Branching of Human iPSCs-Derived Neurons and Reduces Expression of GLAST/S100 in iPSCs-Derived Astrocytes

For some time, it has been accepted that the β-site APP cleaving enzyme 1 (BACE1) and the γ-secretase are two main players in the amyloidogenic processing of the β-amyloid precursor protein (APP). Recently, the membrane-type 5 matrix metalloproteinase (MT5-MMP/MMP-24), mainly expressed in the nervous system, has been highlighted as a new key player in APP-processing, able to stimulate amyloidogenesis and also to generate a neurotoxic APP derivative. In addition, the loss of MT5-MMP has been demonstrated to abrogate pathological hallmarks in a mouse model of Alzheimer’s disease (AD), thus shedding light on MT5-MMP as an attractive new therapeutic target. However, a more comprehensive analysis of the role of MT5-MMP is necessary to evaluate how its targeting affects neurons and glia in pathological and physiological situations. In this study, leveraging on CRISPR-Cas9 genome editing strategy, we established cultures of human-induced pluripotent stem cells (hiPSC)-derived neurons and astrocytes to investigate the impact of MT5-MMP deficiency on their phenotypes. We found that MT5-MMP-deficient neurons exhibited an increased number of primary and secondary neurites, as compared to isogenic hiPSC-derived neurons. Moreover, MT5-MMP-deficient astrocytes displayed higher surface area and volume compared to control astrocytes. The MT5-MMP-deficient astrocytes also exhibited decreased GLAST and S100β expression. These findings provide novel insights into the physiological role of MT5-MMP in human neurons and astrocytes, suggesting that therapeutic strategies targeting MT5-MMP should be controlled for potential side effects on astrocytic physiology and neuronal morphology.

Recent Developments in New Therapeutic Agents against Alzheimer and Parkinson Diseases: In-Silico Approaches

Neurodegenerative diseases (ND), including Alzheimer's (AD) and Parkinson's Disease (PD), are becoming increasingly more common and are recognized as a social problem in modern societies. These disorders are characterized by a progressive neurodegeneration and are considered one of the main causes of disability and mortality worldwide. Currently, there is no existing cure for AD nor PD and the clinically used drugs aim only at symptomatic relief, and are not capable of stopping neurodegeneration. Over the last years, several drug candidates reached clinical trials phases, but they were suspended, mainly because of the unsatisfactory pharmacological benefits. Recently, the number of compounds developed using in silico approaches has been increasing at a promising rate, mainly evaluating the affinity for several macromolecular targets and applying filters to exclude compounds with potentially unfavorable pharmacokinetics. Thus, in this review, an overview of the current therapeutics in use for these two ND, the main targets in drug development, and the primary studies published in the last five years that used in silico approaches to design novel drug candidates for AD and PD treatment will be presented. In addition, future perspectives for the treatment of these ND will also be briefly discussed.

In Silico Molecular Docking Analysis of Potential Anti-Alzheimer's Compounds Present in Chloroform Extract of Carissa carandas Leaf Using Gas Chromatography MS/MS

Background: The current treatment of Alzheimer's disease (AD) is far from adequate. AD can be treated by inhibiting either β-amyloid protein deposition or acetylcholinesterase enzyme activity. Many treatments for AD are directed at these 2 targets. In the present study, the phytoconstituents of Carissa carandas chloroform leaf extract were identified by gas chromatography-MS/MS analysis, and in silico molecular docking studies were performed to evaluate their potential against AD. Objectives: The present study aimed to identify the possible anti-Alzheimer's activity of novel phytoconstituents isolated from C carandas. Methods: The powdered leafy material was subjected to successive Soxhlet extraction using 3 different solvents: n-hexane, chloroform, and methanol. The chloroform extract was subjected to gas chromatography-MS/MS analysis, and the observed chromatogram revealed the presence of 48 chemical constituents. Among them, 42 new phytoconstituents are reported in this plant for the first time. The gas chromatography-MS/MS-identified phytoconstituents were evaluated by iGEMDOCK software against AD targets of β-amyloid fibril (protein data bank ID: 2LMN) and recombinant human acetylcholinesterase (protein data bank ID: 3LII) ligands, and their anti-AD potential were compared with those of known inhibitors of galantamine and curcumin. Results: On the basis of results from both docking assays, the 5 compounds with the highest docking energy were further analyzed using in silico admetSAR web portal modeling for the evaluation of parameters such as intestinal absorption, blood-brain barrier permeation, carcinogenicity, and acute oral toxicity. Conclusions: The chloroform leaf extract of C carandas was found to contain constituents that have affinities for the 2 targets tested; that is, amyloid β and acetylcholinesterase. The best docking scores were found for 7 compounds: 1-heneicosanol; N-nonadecanol-1; cholesta-4,6-dien-3-ol, (3beta); di-n-octyl phthalate; 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione; 6-undecyl-5,6-dihydro-2H-pyran-2-one, and phenol, 2,4-di-t-butyl-6-nitro compounds, and these compounds were therefore suggested to be promising anti-AD lead compounds. Further, the target leads were subjected to ligplot analysis for their 2-dimensional representation of hydrogen bonding and hydrophobic interactions. Thus, the results obtained from the in silico study of C carandas leaf extract using these computational approaches indicate the presence of phytoconstituents that have affinities for the selected 2 targets of AD. (Curr Ther Res Clin Exp. 2020; 81:XXX-XXX).

BACE1 inhibitors: Current status and future directions in treating Alzheimer's disease

Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative brain disorder with no current cure. One of the important therapeutic approaches of AD is the inhibition of β-site APP cleaving enzyme-1 (BACE1), which is involved in the rate-limiting step of the cleavage process of the amyloid precursor protein (APP) leading to the generation of the neurotoxic amyloid β (Aβ) protein after the γ-secretase completes its function. The produced insoluble Aβ aggregates lead to plaques deposition and neurodegeneration. BACE1 is, therefore, one of the attractive targets for the treatment of AD. This approach led to the development of potent BACE1 inhibitors, many of which were advanced to late stages in clinical trials. Nonetheless, the high failure rate of lead drug candidates targeting BACE1 brought to the forefront the need for finding new targets to uncover the mystery behind AD. In this review, we aim to discuss the most promising classes of BACE1 inhibitors with a description and analysis of their pharmacodynamic and pharmacokinetic parameters, with more focus on the lead drug candidates that reached late stages of clinical trials, such as MK8931, AZD-3293, JNJ-54861911, E2609, and CNP520. In addition, the manuscript discusses the safety concerns and insignificant physiological effects, which were highlighted for the most successful BACE1 inhibitors. Furthermore, the review demonstrates with increasing evidence that despite tremendous efforts and promising results conceived with BACE1 inhibitors, the latest studies suggest that their clinical use for treating Alzheimer's disease should be reconsidered. Finally, the review sheds light on alternative therapeutic options for targeting AD.

Tripchlorolide Attenuates β-amyloid Generation via Suppressing PPARγ-Regulated BACE1 Activity in N2a/APP695 Cells

Due to its apparent rate-limiting function, BACE1 (β-secretase) appears to be a prime target for prevention of amyloid-β (Aβ) generation in brains with Alzheimer's disease (AD). The activity of BACE1 is regulated by peroxisome proliferator-activated receptor-γ (PPARγ), a transcription factor binding site of the BACE1 promoter, indicating that PPARγ may be a potential target for AD treatment. Several studies have demonstrated that PPARγ activation is involved in the immunostimulation of amyloid-β precursor protein processing by nonsteroidal anti-inflammatory drugs (NSAIDs). The present study found that tripchlorolide (T₄), with a similar chemical structure to that of NSAIDs, decreased the levels of Aβ secreted in N2a-APP695 cells. T₄ treatment reduced the mRNA and protein levels of BACE1 and the protein level of sAPPβ, a cleaved N-terminal fragment of APP by BACE1. The treatment also translocated PPARγ from cytoplasm to nuclear. Intriguingly, T₄, like pioglitazone (a PPARγ agonist), suppressed the BACE1 activity in N2a-APP695 cells, which was attenuated by GW9662 (a PPARγ antagonist). These results indicate that T₄ may be a PPARγ agonist to enhance the binding of nuclear PPARγ to the BACE1 promoter, which may in turn inhibit the transcription and translation of BACE1, suppress the activity of BACE1, and ultimately attenuate the generation of Aβ. Due to its capability to alter Aβ generation and to protect central neural system against the neurotoxicity of Aβ, T₄ may serve as a promising agent in modulating Aβ-related pathology in Alzheimer's disease.

Electroacupuncture Reduces Aβ Production and BACE1 Expression in SAMP8 Mice

Electroacupuncture (EA) has been reported to have beneficial effects on Alzheimer’s disease (AD). BACE1 (β-site amyloid precursor protein-cleaving enzyme 1) is involved in the abnormal production of amyloid-β plaque (Aβ), a hallmark of AD pathophysiology. Thus, the present study investigated the effects of EA on memory impairment, Aβ production, and BACE1 expression in senescence-accelerated mouse prone 8 (SAMP8) mice. We found that EA improved spatial learning and memory impairment of SAMP8 mice. Furthermore, EA attenuated Aβ production and repressed the expression of BACE1 in the hippocampus of SAMP8 mice. Taken together, our results suggest that EA could have a potential therapeutic application in AD and that BACE1 may be an important target of EA in the treatment of AD.

Combined treatment with a BACE inhibitor and anti-Aβ antibody gantenerumab enhances amyloid reduction in APPLondon mice

Therapeutic approaches for prevention or reduction of amyloidosis are currently a main objective in basic and clinical research on Alzheimer's disease. Among the agents explored in clinical trials are anti-Aβ peptide antibodies and secretase inhibitors. Most anti-Aβ antibodies are considered to act via inhibition of amyloidosis and enhanced clearance of existing amyloid, although secretase inhibitors reduce the de novo production of Aβ. Limited information is currently available on the efficacy and potential advantages of combinatorial antiamyloid treatment. We performed a chronic study in APPLondon transgenic mice that received treatment with anti-Aβ antibody gantenerumab and BACE inhibitor RO5508887, either as mono- or combination treatment. Treatment aimed to evaluate efficacy on amyloid progression, similar to preexisting amyloidosis as present in Alzheimer's disease patients. Mono-treatments with either compound caused a dose-dependent reduction of total brain Aβ and amyloid burden. Combination treatment with both compounds significantly enhanced the antiamyloid effect. The observed combination effect was most pronounced for lowering of amyloid plaque load and plaque number, which suggests effective inhibition of de novo plaque formation. Moreover, significantly enhanced clearance of pre-existing amyloid plaques was observed when gantenerumab was coadministered with RO5508887. BACE inhibition led to a significant time- and dose-dependent decrease in CSF Aβ, which was not observed for gantenerumab treatment. Our results demonstrate that combining these two antiamyloid agents enhances overall efficacy and suggests that combination treatments may be of clinical relevance.

Beneficial effect of antibodies against β- secretase cleavage site of APP on Alzheimer's-like pathology in triple-transgenic mice

The toxicity of amyloid β and tau, the two hallmark proteins in Alzheimer's disease (AD), has been extensively studied individually. Recently new data suggest their possible interactions and synergistic effects in the disease. In this study, we investigate the ability of antibodies against the β secretase cleavage site on APP, named BBS1, to affect tau pathology, besides their well established effect on intracellular Aβ and amyloid load. For this purpose we treated the triple transgenic mice model of AD (3x Tg-AD) with mAb BBS1 intracerebroventricularly, using mini osmotic pumps for one month. The experimental data demonstrated reduction in total and phosphorylated tau levels, explained by significant reduction in GSK3β which phosphorylates tau on sites recognized by antibodies against PHF1 and AT-8. The treatment increased the cognitive capabilities and reduced the brain inflammation levels which accompany AD pathology. The data showing that tau pathology was significantly reduced by BBS1 antibodies suggest a close interaction between tau and Aβ in the development of AD, and may serve as an efficient novel immunotherapy against both hallmarks of this disease.

Immunotherapy for Alzheimer's disease

Alzheimer's disease (AD) is characterized by β-amyloid (Aβ) plaques consisted primarily of aggregated Aβ proteins and neurofibrillary tangles formed by hyperphosphorylated tau protein. Both Aβ and hyperphosphorylated tau are toxic both in vivo and in vitro. Immunotherapy targeting Aβ seems to provide a promising approach to reduce the toxic species in the brain. However, there is little evidence from clinical trials so far indicating the efficacy of Aβ immunotherapy in cognitive improvement. Immunization with tau peptides or anti-tau antibodies could remove the tau aggregates and improve the cognitive function in preclinical study, which provides a novel strategy of AD therapy. In this article, we will summarize the immunotherapeutic strategies targeting either Aβ or tau.

Alzheimer's therapeutics: translation of preclinical science to clinical drug development

Over the past three decades, significant progress has been made in understanding the neurobiology of Alzheimer's disease. In recent years, the first attempts to implement novel mechanism-based treatments brought rather disappointing results, with low, if any, drug efficacy and significant side effects. A discrepancy between our expectations based on preclinical models and the results of clinical trials calls for a revision of our theoretical views and questions every stage of translation-from how we model the disease to how we run clinical trials. In the following sections, we will use some specific examples of the therapeutics from acetylcholinesterase inhibitors to recent anti-Aβ immunization and γ-secretase inhibition to discuss whether preclinical studies could predict the limitations in efficacy and side effects that we were so disappointed to observe in recent clinical trials. We discuss ways to improve both the predictive validity of mouse models and the translation of knowledge between preclinical and clinical stages of drug development.

Is BACE1 a suitable therapeutic target for the treatment of Alzheimer's disease? Current strategies and future directions

Alzheimer's disease (AD) is characterized by the extracellular deposition of the β-amyloid protein (Aβ). Aβ is a fragment of a much larger precursor protein, the amyloid precursor protein (APP). Sequential proteolytic cleavage of APP by β-secretase and γ-secretase liberates Aβ from APP. The aspartyl protease BACE1 (β-site APP-cleaving enzyme 1) catalyses the rate-limiting step in the production of Aβ, and as such it is considered to be a major target for drug development in Alzheimer's disease. However, the development of a BACE1 inhibitor therapy is problematic for two reasons. First, BACE1 has been found to have important physiological roles. Therefore, inhibition of the enzyme could have toxic consequences. Second, the active site of BACE1 is relatively large, and many of the bulky compounds that are needed to inhibit BACE1 activity are unlikely to cross the blood-brain barrier. This review focuses on the structure BACE1, current therapeutic strategies based on developing active-site inhibitors, and new approaches to therapy involving targeting the expression or post-translational regulation of BACE1.

Regulatory role of cytosolic phospholipase A2alpha in NADPH oxidase activity and in inducible nitric oxide synthase induction by aggregated Abeta1-42 in microglia

In Alzheimer's disease, extracellular deposits of amyloid beta(1-42) (Abeta(1-42)) may induce activation of microglial cells by releasing proinflammatory factors that contribute to the neurodegeneration process. Since the activation of cytosolic phospholipase A(2)alpha (cPLA(2)alpha) has been reported in inflammatory conditions, its role in primary rat microglial cell activated by aggregated Abeta(1-42) was elucidated. The results of the present study show that activation of microglia by 5 microM aggregated Abeta(1-42) (as evident by the amoeboid morphology and increased CD68 immunofluorescence reactivity) caused an immediate activation of cPLA(2)alpha, measured by its phosphorylated form and its specific activity, followed by a gradual elevation of its expression and activity during 24 h. Inhibition of cPLA(2)alpha expression and activity by the presence of 1 microM specific antisense resulted in a significant decrease in NADPH oxidase activity that releases superoxides, PGE(2) formation, iNOS expression, and NO production, indicating a major role for cPLA(2)alpha in the regulation of these inflammatory processes. NADPH oxidase activity, which is under cPLA(2)alpha regulation, was found to upregulate cPLA(2)alpha and COX-2 protein expression through the redox-sensitive NFkappaB activation as evident by its phosphorylation on Ser-536, resulting in increased PGE(2) formation. The secreted PGE(2) induced the synthesis of iNOS and the production of NO through the PKA-CREB pathway. Taken together, our results suggest that the response of cPLA(2)alpha to aggregated Abeta(1-42) is probably a key player in the oxidative stress present in AD, regulating potent oxidative agents: the production of superoxides by NADPH oxidase and NO formation by iNOS.

Existing plaques and neuritic abnormalities in APP:PS1 mice are not affected by administration of the gamma-secretase inhibitor LY-411575

The gamma-secretase complex is a major therapeutic target for the prevention and treatment of Alzheimer's disease. Previous studies have shown that treatment of young APP mice with specific inhibitors of gamma-secretase prevented formation of new plaques. It has not yet been shown directly whether existing plaques would be affected by gamma-secretase inhibitor treatment. Similarly, alterations in neuronal morphology in the immediate vicinity of plaques represent a plaque-specific neurotoxic effect. Reversal of these alterations is an important endpoint of successful therapy whether or not a treatment affects plaque size. In the present study we used longitudinal imaging in vivo with multiphoton microscopy to study the effects of the orally active gamma-secretase inhibitor LY-411575 in 10-11 month old APP:PS1 mice with established amyloid pathology and neuritic abnormalities. Neurons expressed YFP allowing fluorescent detection of morphology whereas plaques were labelled with methoxy-XO4. The same identified neurites and plaques were followed in weekly imaging sessions in living mice treated daily (5 mg/kg) for 3 weeks with the compound. Although LY-411575 reduced Abeta levels in plasma and brain, it did not have an effect on the size of existing plaques. There was also no effect on the abnormal neuritic curvature near plaques, or the dystrophies in very close proximity to senile plaques. Our results suggest that therapeutics aimed at inhibition of Abeta generation are less effective for reversal of existing plaques than for prevention of new plaque formation and have no effect on the plaque-mediated neuritic abnormalities, at least under these conditions where Abeta production is suppressed but not completely blocked. Therefore, a combination therapy of Abeta suppression with agents that increase clearance of amyloid and/or prevent neurotoxicity might be needed for a more effective treatment in patients with pre-existing pathology.

Ensemble-docking approach on BACE-1: pharmacophore perception and guidelines for drug design

Beta-secretase (BACE-1), a key enzyme in the etiopathogenesis and progression of Alzheimer disease, is the focus of medicinal chemistry efforts both in the pharmaceutical industry and in academia. Despite the availability of diverse peptidomimetic BACE-1 inhibitors, nonpeptidic compounds suitable for oral delivery and transport across the blood brain barrier are in great demand. Herein, a number of active and structurally diverse inhibitors were selected and subjected to an ensemble-docking process into five BACE-1 X-ray structures. The calculated bioactive conformations of these inhibitors allowed us to build an exhaustive pharmacophore model, which captures both the common geometric and electronic features essential for enzyme inhibition. The model is intended to aid the rational design of new BACE-1 inhibitors. Furthermore, a comparison of BACE/cathepsin D X-ray structures was made to provide guidelines for the design of BACE-selective inhibitors.

Biotechnology applications of amino acids in protein purification and formulations

Amino acids are widely used in biotechnology applications. Since amino acids are natural compounds, they can be safely used in pharmaceutical applications, e.g., as a solvent additive for protein purification and as an excipient for protein formulations. At high concentrations, certain amino acids are found to raise intra-cellular osmotic pressure and adjust to the high salt concentrations of the surrounding medium. They are called "compatible solutes", since they do not affect macromolecular function. Not only are they needed to increase the osmotic pressure, they are known to increase the stability of the proteins. Sucrose, glycerol and certain amino acids were used to enhance the stability of unstable proteins after isolation from natural environments. The mechanism of the action of these protein-stabilizing amino acids is relatively well understood. On the contrary, arginine was accidentally discovered as a useful reagent for assisting in the refolding of recombinant proteins. This effect of arginine was ascribed to its ability to suppress aggregation of the proteins during refolding, thereby increasing refolding efficiency. By the same mechanism, arginine now finds much wider applications than previously anticipated in the research and development of proteins, in particular in pharmaceutical applications. For example, arginine solubilizes proteins from loose inclusion bodies, resulting in efficient production of active proteins. Arginine suppresses protein-protein interactions in solution and also non-specific adsorption to gel permeation chromatography columns. Arginine facilitates elution of bound proteins from various column resins, including Protein-A or dye affinity columns and hydrophobic interaction columns. This review covers various biotechnology applications of amino acids, in particular arginine.

Identification of inhibitors using a cell-based assay for monitoring Golgi-resident protease activity

Noninvasive real-time quantification of cellular protease activity allows monitoring of enzymatic activity and identification of activity modulators within the protease's natural milieu. We developed a protease activity assay based on differential localization of a recombinant reporter consisting of a Golgi retention signal and a protease cleavage sequence fused to alkaline phosphatase (AP). When expressed in mammalian cells, this protein localizes to Golgi bodies and, on protease-mediated cleavage, AP translocates to the extracellular medium where its activity is measured. We used this system to monitor the Golgi-associated protease furin, a pluripotent enzyme with a key role in tumorigenesis, viral propagation of avian influenza, ebola, and HIV as well as in activation of anthrax, pseudomonas, and diphtheria toxins. This technology was adapted for high-throughput screening of 39,000-compound small molecule libraries, leading to identification of furin inhibitors. Furthermore, this strategy was used to identify inhibitors of another Golgi protease, the beta-site amyloid precursor protein (APP)-cleaving enzyme (BACE). BACE cleavage of the APP leads to formation of the Abeta peptide, a key event that leads to Alzheimer's disease. In conclusion, we describe a customizable noninvasive technology for real-time assessment of Golgi protease activity used to identify inhibitors of furin and BACE.

The Primary Care of Alzheimer Disease

Alzheimer disease is the most common cause of progressive irreversible intellectual loss in aging humans. The number of individuals and families affected by this disorder will continue to grow as society ages worldwide. Our understanding of the biology, underlying pathophysiology, and diagnosis of Alzheimer disease has greatly expanded over the past few years and much has been published in these areas. This review focuses on the primary care of this disorder and addresses the "now what" question. Topics examined include limiting excess disability, responding to commonly raised questions of family members, pharmacologic and nonpharmacologic therapeutic options, long-term planning, and caregiver issues.

A method for induced-fit docking, scoring, and ranking of flexible ligands. Application to peptidic and pseudopeptidic beta-secretase (BACE 1) inhibitors

Inhibition of beta-secretase (BACE 1) has recently been investigated as a promising therapeutic approach in the treatment of Alzheimer's disease, and a growing number of BACE 1 inhibitors and crystal structures of BACE 1/inhibitors complexes have been reported. We report herein a predictive computational method and its application to potential BACE 1 inhibitors. Using a training set of 50 known highly flexible inhibitors, we developed a docking method that accounts for the flexibility of both the protein and the inhibitors. Protein flexibility is accounted for using a specifically designed genetic algorithm. We next developed a scoring function consisting of force field evaluation of the inhibitor/protein interactions and two additional terms for hydrogen bonding and entropy change upon binding. Discarding three outliers from the training set, our protocol was found to perform well with an rmsd of 1.19 kcal/mol. Evaluation of the predictive power was next carried out by virtual screening of 80 synthetic compounds. The significant enrichment at the top of the ranking list in active compounds demonstrated the ability of the docking and scoring protocol to rank the compounds relative to their activities.

Evaluating scoring functions for docking and designing beta-secretase inhibitors

Several simple scoring methods were examined for 2 series of beta-secretase (BACE-1) inhibitors to identify a docking/scoring protocol which could be used to design BACE-1 inhibitors in a drug discovery program. Both the PLP1 score and MMFFs interaction energy (E(inter)) performed as well or better than more computationally intensive methods for a set of substrate-based inhibitors, while the latter performed well for both sets of inhibitors.

Detection of a soluble form of BACE-1 in human cerebrospinal fluid by a sensitive activity assay

BACKGROUND

Formation of deposits of the insoluble amyloid beta-peptide is believed to be causally related with neurodegeneration in Alzheimer disease (AD). The beta-peptide originates from a larger amyloid precursor protein (APP) by the action of proteolytic enzymes. The first proteolytic event leading to amyloid formation is the cleavage of APP by the membrane-bound aspartyl protease BACE-1, also known as memapsin-2. Inhibition of BACE-1 is thought to be a therapeutic approach to AD. Measuring BACE-1 activity in biological samples would be useful to elucidate the mechanism of AD and for development of AD drugs.

METHODS

We developed a sensitive and specific activity assay for BACE-1. The assay is based on a genetically engineered proenzyme that is specifically activated by BACE-1. The resulting active enzyme is measured with a chromogenic substrate. The use of 2 coupled reactions produces a detection limit as low as 0.4 pmol/L.

RESULTS

The assay detected BACE-1 activity in extracts of human brain tissue as well as, unexpectedly, in human cerebrospinal fluid (CSF). Gel electrophoresis and Western blotting identified the BACE-1 present in CSF as a truncated soluble form of the originally membrane-bound BACE-1.

CONCLUSION

Detection of the soluble form of BACE-1 in CSF, a relatively easily accessible biological fluid, may be useful for monitoring the effects of drug candidates in vivo and may have diagnostic or prognostic applications.

Neuroprotection and neurodegenerative diseases: from biology to clinical practice

Neurodegenerative diseases and, in particular, Alzheimer disease, are characterized by progressive neuronal loss correlated in time with the symptoms of the disease considered. Whereas the symptoms of those incapacitating diseases are beginning to be managed with a relative efficacy, the ultimate objective of therapy nonetheless remains preventing cell (neuronal and/or astrocytic) death in a neurocytoprotective approach. In biologic terms, in the light of progress at basic research level, three strategies may be envisaged: (1) antagonizing the cytotoxic causal events (excess intracellular calcium, accumulation of abnormal proteins, excitotoxic effects of amino acids, oxidative stress, processes related to inflammation, etc.); (2) stimulating the endogenous protective processes (anti-free radical or DNA repair systems, production of neurotrophic factors, potential cytoprotective action of steroids, etc.); (3) promoting damaged structure repair strategies (grafts) or deep brain or cortical neurostimulation with a view to triggering (beyond the symptomatic actions) potential 'protective' cell mechanisms. The clinical transition of the various strategies whose efficacy is being tested in animal and/or cell models, experimental analogs of the diseases, and thus the objective demonstration in humans of pharmacological and/or surgical neurocytoprotection, is currently the subject of considerable methodological debate (What are the right psychometric assessment criteria? What are the most pertinent laboratory or neuroradiological markers, etc.?). A number of clinical trials have been completed or are ongoing with drugs that are reputed to be neuroprotective. Thus, elements of the response are beginning to be generated with a view to determining whether it will soon be possible to effectively slow or even stop the neurodegenerative process whose etiology, in most cases, remains obscure.

Current Status and Future Promise of Pharmacotherapeutic Strategies for Alzheimer’s Disease

BACKGROUND AND OBJECTIVE

The pharmacotherapy of Alzheimer's disease (AD) is evolving rapidly. Unless new discoveries continue to emerge to facilitate prevention and effective treatment of the disease, the anticipated burden of this disease on caregivers and society at large will overwhelm resources. The objective of this paper is to review the state of development of approaches likely to yield effective interventional measures with regard to AD in the future.

DESIGN

A comprehensive systematic search of MEDLINE using focused search criteria, a search of reference lists from these studies and reviews, a review of the Cochrane Database of Systematic Reviews, and a hand search of relevant journals was conducted. Selection of articles was based on the clinical focus. Additional inclusion criteria preferentially selected key articles that contained higher-level evidence in accordance with explicit, validated criteria.

RESULTS

Pharmaceutical interventions are being developed and tested that confer neuroprotective benefits by targeting causative mechanisms.

CONCLUSION

The paradigm that AD is pharmacologically unresponsive is shifting. Our understanding of the molecular mechanisms of neurodegeneration will soon allow us to more specifically target and interrupt the processes that contribute to this dementia.

IFN-γ-induced BACE1 expression is mediated by activation of JAK2 and ERK1/2 signaling pathways and direct binding of STAT1 to BACE1 promoter in astrocytes

Beta-site APP cleaving enzyme 1 (BACE1) is an essential enzyme for the production of beta amyloid. Since we found that injection of interferon-gamma (IFN-gamma) into young mouse brains increased BACE1 expression in astrocytes, we investigated molecular mechanisms underlying this process by cloning a putative BACE1 promoter. BACE1 promoter activity was differentially regulated by IFN-gamma in a region specific manner and down-regulated by an inhibitor of Janus kinase 2 (JAK2). A dominant negative mutant of signal transducer and activator of transcription 1 (STAT1) expression suppressed BACE1 promoter activity, and this was rescued by transfecting wild type STAT1. Electrophoretic mobility shift assay and promoter activity assays indicated that STAT1 binds directly to the putative STAT1 binding sequence of BACE1 promoter. Because IFN-gamma treatment induced STAT1 phosphorylation, we examined whether the expression of a suppressor of cytokine signaling (SOCS), negative regulator of JAK2, suppresses BACE1 promoter activity. The results show that SOCS1 or SOCS3 expression suppressed BACE1 promoter by blocking phosphorylation of Tyr701 residue in STAT1. Also, because IFN-gamma treatment specifically potentiated extracellular signal regulated MAP kinase (ERK) 1/2 activation, pretreatment of mitogen-activated or extracellular signal-regulated protein kinase (MEK) inhibitor, PD98059, significantly attenuated IFN-gamma-induced BACE1 promoter activity and protein expression through blocking phosphorylation of Ser727 residue in STAT1, suggesting that ERK1/2 is associated with IFN-gamma-induced STAT1 signaling cascade. Taken together, our results suggest that IFN-gamma activates JAK2 and ERK1/2 and then phosphorylated STAT1 binds to the putative STAT1 binding sequences in BACE1 promoter region to modulate BACE1 protein expression in astrocytes.

Pharmacology of Alzheimer's disease: appraisal and prospects

Ten years after the introduction of the first drug, tacrine, in the treatment of Alzheimer's disease, it seems appropriate to re-appraise the pharmacological processes of innovation in the research field of dementia. The aim of this review is to pinpoint concrete improvements achieved in this field, regarding experimental methods and clinical evaluation of the compounds, as well as the neurochemistry of the disease and cellular targets to consider in priority. This review deals with this objective in three parts: (1) assessment of current therapeutics, (2) discussion of the experimental models and clinical practices and (3) prospective drugs of the future. The implementation of considered strategies will require the involvement and close cooperation between political decisions, pharmaceutical companies and the scientific community.

Targeting BACE1 with siRNAs ameliorates Alzheimer disease neuropathology in a transgenic model

In Alzheimer disease, increased beta-secretase (BACE1) activity has been associated with neurodegeneration and accumulation of amyloid precursor protein (APP) products. Thus, inactivation of BACE1 could be important in the treatment of Alzheimer disease. In this study, we found that lowering BACE1 levels using lentiviral vectors expressing siRNAs targeting BACE1 reduced amyloid production and the neurodegenerative and behavioral deficits in APP transgenic mice, a model of Alzheimer disease. Our results suggest that lentiviral vector delivery of BACE1 siRNA can specifically reduce the cleavage of APP and neurodegeneration in vivo and indicate that this approach could have potential therapeutic value for treatment of Alzheimer disease.

High beta-secretase activity elicits neurodegeneration in transgenic mice despite reductions in amyloid-beta levels: implications for the treatment of Alzheimer disease

Amyloid-beta peptides (Abeta) are widely presumed to play a causal role in Alzheimer disease. Release of Abeta from the amyloid precursor protein (APP) requires proteolysis by the beta-site APP-cleaving enzyme (BACE1). Although increased BACE1 activity in Alzheimer disease brains and human (h) BACE1 transgenic (tg) mice results in altered APP cleavage, the contribution of these molecular alterations to neurodegeneration is unclear. We therefore used the murine Thy1 promoter to express high levels of hBACE1, with or without hAPP, in neurons of tg mice. Compared with hAPP mice, hBACE1/hAPP doubly tg mice had increased levels of APP C-terminal fragments (C89, C83) and decreased levels of full-length APP and Abeta. In contrast to non-tg controls and hAPP mice, hBACE1 mice and hBACE1/hAPP mice showed degeneration of neurons in the neocortex and hippocampus and degradation of myelin. Neurological deficits were also more severe in hBACE1 and hBACE1/hAPP mice than in hAPP mice. These results demonstrate that high levels of BACE1 activity are sufficient to elicit neurodegeneration and neurological decline in vivo. This pathogenic pathway involves the accumulation of APP C-terminal fragments but does not depend on increased production of human Abeta. Thus, inhibiting BACE1 may block not only Abeta-dependent but also Abeta-independent pathogenic mechanisms.

Current Status and Future Promise of Pharmacotherapeutic Strategies for Alzheimer’s Disease

BACKGROUND AND OBJECTIVE

The pharmacotherapy of Alzheimer's disease (AD) is evolving rapidly. Unless new discoveries continue to emerge to facilitate prevention and effective treatment of the disease, the anticipated burden of this disease on caregivers and society at large will overwhelm resources. The objective of this paper is to review the state of development of approaches likely to yield effective interventional measures with regard to AD in the future.

DESIGN

A comprehensive systematic search of MEDLINE using focused search criteria, a search of reference lists from these studies and reviews, a review of the Cochrane Database of Systematic Reviews, and a hand search of relevant journals was conducted. Selection of articles was based on the clinical focus. Additional inclusion criteria preferentially selected key articles that contained higher-level evidence in accordance with explicit, validated criteria.

RESULTS

Pharmaceutical interventions are being developed and tested that confer neuroprotective benefits by targeting causative mechanisms.

CONCLUSION

The paradigm that AD is pharmacologically unresponsive is shifting. Our understanding of the molecular mechanisms of neurodegeneration will soon allow us to more specifically target and interrupt the processes that contribute to this dementia.

Pharmacologie de la maladie d’Alzheimer : vision du futur

Ten years after the introduction of the first drug for the treatment of Alzheimer's disease, tacrine, it seems appropriate to reappraise the pharmacological processes of innovation in the field of research in dementia. The aim of this review is to pinpoint concrete improvements achieved in this field, in terms of experimental methods and clinical evaluation of the compounds, as well as the neurochemistry of the disease and cellular targets deserving of initial consideration. * The article first considers the use of animal models of Alzheimer's disease, which are classified according to two categories: animals with lesions of some neuronal pathways specifically implicated in clinical symptoms (i.e. lesions of the nucleus basalis of Meynert, the origin of cholinergic projections to the cortex underlying memory processes); and transgenic models, which are intended to reproduce some of the neuropathological hallmarks of Alzheimer's disease. Drugs can be tested in animals with such alterations for their effect on neuropathology, neurochemistry and behavioural disturbances. More recently, in silico models have been developed, which offer the possibility of simulating the pharmacodynamic effects of drugs in specific areas of the brain. These experiments are helpful in distinguishing purely symptomatic effects from disease-modifying effects, the latter being the ultimate goal of the modern pharmacology of dementia. * The second breakthrough considered in this article is the codification and standardisation of clinical methods for obtaining a more accurate and earlier diagnosis (the recent introduction of the concept of "Mild Cognitive Impairment", which includes patients who will later develop a true clinical dementia syndrome). In that respect, the determination of the biological markers of Alzheimer's disease (apolipoprotein E, amyloid substance, protein-tau, isoprostane) as well as progress in neuroimaging (functional positron emission tomography [fPET]-scan, single photon emission-computed tomography [SPECT], functional nuclear magnetic resonance [fNMR]) are discussed in terms of their potential as new tools in the early stages of drug development (surrogate markers). The methods used during the comparative clinical trials (phase III) have been elaborated and internationally standardised during the assessment of the different acetylcholinesterase inhibitors (AChE-I), with the knowledge that, since 1994, four of these have been officially approved: tacrine, donepezil, rivastigmine and galantamine; the same methods have been used for developing memantine, a recently-launched modulator of glutamatergic neurotransmission. The validated scales now take into consideration not only the cognitive dimensions of Alzheimer's disease but also the behavioural symptoms, with the introduction of the concept of BPSD (behavioural psychological symptoms of dementia). Some proposals to improve this clinical assessment of anti-dementia drugs are presented here. * The section of this article dealing with prospective issues considers the main pathways of interest in drug innovation and the elucidation of new targets for the future compounds. As well as their symptomatic effects on the different components of cognition, drugs should be neuroprotective and limit the lesions documented in Alzheimer's disease, with the aim of progressing far beyond the amyloid hypothesis (immunisation, beta-sheet breakers, secretase inhibitors). The field of excitotoxicity (which is mainly glutamate dependent) appears fruitful, because of the possibility of pharmacological intervention at the different steps in the excitotoxic process. All the new directions presented in this article support the concept of true disease-modifying agents. In conclusion, this prospective review should be considered as a guide in fostering drug innovation in Alzheimer's disease and related disorders and should help to decrease the gap existing between neuroscience and therapeutics.

Modeling the protonation states of the catalytic aspartates in beta-secretase

Beta-secretase (BACE) is a critical enzyme in the production of beta-amyloid, a protein that has been implicated as a potential cause of Alzheimer's disease (AD). There are two aspartic acid residues (Asp 32 and Asp 228) present in the catalytic region of BACE that can adopt multiple protonation states. The protonation state and precise location of the protons for these two residues, particularly in the presence of an inhibitor, are subjects of great interest since they have a direct bearing on the mechanism of aspartyl proteases and efforts to model beta-secretase. We have carried out full liner-scaling quantum mechanical (QM) calculations that include Poisson-Boltzmann solvation in order to identify the preferred protonation state and proton location in the presence and absence of an inhibitor. These calculations favor the monoprotonated state in the presence of ligand, and di-deprotonated state in the absence of ligand. Further the proton in the monoprotonated state is located on the inner oxygen of Asp 228. These results have implications for the catalytic mechanism of BACE and related aspartyl proteases. They also provide a reference state for the protein in structure-based modeling studies of this therapeutically important target.

Harnessing chaperones to generate small-molecule inhibitors of amyloid beta aggregation

Protein aggregation is involved in the pathogenesis of neurodegenerative diseases and hence is considered an attractive target for therapeutic intervention. However, protein-protein interactions are exceedingly difficult to inhibit. Small molecules lack sufficient steric bulk to prevent interactions between large peptide surfaces. To yield potent inhibitors of beta-amyloid (Abeta) aggregation, we synthesized small molecules that increase their steric bulk by binding to chaperones but also have a moiety available for interaction with Abeta. This strategy yields potent inhibitors of Abeta aggregation and could lead to therapeutics for Alzheimer's disease and other forms of neurodegeneration.

Pharmacotherapeutic approaches to the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), a progressive degenerative disorder of the brain, is the most common cause of cognitive impairment in the elderly. The pharmacotherapy of AD is evolving rapidly. Cholinergic stabilization with cholinesterase-inhibitor (ChEI) therapy implies neuroprotection and a resultant slowing of disability and disease progression. The moderate-affinity N-methyl-d-aspartate (NMDA)-receptor antagonist memantine may block neural excitotoxicity.

OBJECTIVE

The purpose of this review was to examine the evidence for the responsiveness to pharmacotherapy of established AD; specifically, the extent to which the benefits of therapy have been proved, the extent to which currently available ChEIs support cholinergic neurotransmission, and the extent to which currently available ChEIs and memantine provide neuroprotection.

METHODS

Relevant studies were identified through a comprehensive search of MEDLINE for articles published between January 1999 and February 2004 using the terms Alzheimer's pharmacotherapy, cholinesterase inhibitor therapy, Alzheimer's disease, donepezil, rivastigmine, galantamine, glutamatergic system modifiers, and memantine; a search of the reference lists of identified articles; and a manual search of pertinent journals. Articles were selected that contained higher-level evidence, based on explicit validated criteria.

RESULTS

ChEI therapy was associated with quality-of-life improvements that included enhanced performance of activities of daily living, reduced behavioral disturbances, stabilized cognitive impairment, decreased caregiver stress, and delay in the first dementia-related nursing home placement. In large clinical trials in moderate to severe AD (a stage that is associated with distress for patients and caregiver burden, and for which other treatments are not available), memantine showed an ability to delay cognitive and functional deterioration. The combination of memantine and ChEI therapy was significantly more efficacious than ChEI therapy alone (P < 0.001) and was well tolerated.

CONCLUSIONS

The idea that AD is pharmacologically unresponsive appears to be changing. With the use of ChEI and NMDA-receptor antagonist therapy, the symptoms and outcomes of this devastating neurodegenerative disease can be improved and its course altered.

Membrane permeability related physicochemical properties of a novel γ-secretase inhibitor

Pharmaceutical profiling studies were conducted on a novel prototype gamma-secretase inhibitor, to determine the potential of its oral absorption. Such compounds can be of use in the treatment of Alzheimer's disease (AD). The studies included determination of solubility, dissociation constant (pK(a)), octanol/water partition coefficient (log P) and the capacity factor (k'(IAM)) on immobilized artificial membrane (IAM) chromatographic columns. The compound is very slightly solubility in water (120 +/- 50 microg/mL) but the solubility increased considerably in basic medium (270 +/- 60 microg/mL). The compound exhibited pK(a) of (10.36 +/- 0.11); and log P of (3.36 +/- 0.16) determined by shake-flask method and (3.31 +/- 0.01) determined by high performance liquid chromatography (HPLC). The experimentally determined log P values correlated well with the calculated one of 3.44. The observed log k'(IAM) value of (2.79 +/- 0.04) indicates that the compound can reasonably be expected to have high membrane permeability, and therefore, good absorption profile if taken orally. This conclusion is also supported by other parameters determined.

Soluble Arctic amyloid beta protein inhibits hippocampal long-term potentiation in vivo

Mutations in the amyloid precursor protein that result in substitutions of glutamic acid at residue 22 of the amyloid beta protein (A beta) with glutamine (Q22, Dutch) or glycine (G22, Arctic) cause aggressive familial neurological diseases characterized by cerebrovascular haemorrhages or Alzheimer's-type dementia, respectively. The present study compared the ability of these peptides to block long-term potentiation (LTP) of glutamatergic transmission in the hippocampus in vivo. The effects of intracerebroventricular injection of wild-type, Q22 and G22 A beta(1-40) peptides were examined in the CA1 area of urethane-anaesthetized rats. Both mutant peptides were approximately 100-fold more potent than wild-type A beta at inhibiting LTP induced by high-frequency stimulation when solutions of A beta were freshly prepared. Fibrillar material, as determined by electron microscopy, was obvious in all these peptide solutions and exhibited appreciable Congo Red binding, particularly for A beta(1-40)G22 and A beta(1-40)Q22. A soluble fraction of A beta(1-40)G22, obtained following high-speed centrifugation, retained full activity of the peptide solution to inhibit LTP, providing strong evidence that in the case of the Arctic disease a soluble nonfibrillar form of A beta may represent the primary mediator of A beta-related cognitive deficits, particularly early in the disease. In contrast, nonfibrillar soluble A beta(1-40)Q22 supernatant solution was approximately 10-fold less potent at inhibiting LTP than A beta(1-40)G22, a finding consistent with fibrillar A beta contributing to the inhibition of LTP by the Dutch peptide.

BACE (β-secretase) modulates the processing of APLP2 in vivo

BACE is an aspartyl protease that cleaves the amyloid precursor protein (APP) at the beta-secretase cleavage site and is involved in Alzheimer's disease. The aim of our study was to determine whether BACE affects the processing of the APP homolog APLP2. To this end, we developed BACE knockout mice with a targeted insertion of the gene for beta-galactosidase. BACE appeared to be exclusively expressed in neurons as determined by differential staining. BACE was expressed in specific areas in the cortex, hippocampus, cerebellum, pons, and spinal cord. APP processing was altered in the BACE knockouts with Abeta levels decreasing. The levels of APLP2 proteolytic products were decreased in BACE KO mice, but increased in BACE transgenic mice. Overexpression of BACE in cultured cells led to increased APLP2 processing. Our results strongly suggest that BACE is a neuronal protein that modulates the processing of both APP and APLP2.

Adaptor protein interactions: modulators of amyloid precursor protein metabolism and Alzheimer's disease risk?

The cytoplasmic C-terminus of APP plays critical roles in its cellular trafficking and delivery to proteases. Adaptor proteins with phosphotyrosine-binding (PTB) domains, including those in the X11, Fe65, and c-Jun N-terminal kinase (JNK)-interacting protein (JIP) families, bind specifically to the absolutely conserved -YENPTY- motif in the APP C-terminus to regulate its trafficking and processing. Compounds that modulate APP-adaptor protein interactions may inhibit Abeta generation by specifically targeting the substrate (APP) instead of the enzyme (beta- or gamma-secretase). Genetic polymorphisms in (or near) adaptor proteins may influence risk of sporadic AD by interacting with APP in vivo to modulate its trafficking and processing to Abeta.

Altered kallikrein 7 and 10 concentrations in cerebrospinal fluid of patients with Alzheimer's disease and frontotemporal dementia

BACKGROUND

The role of various proteases in the pathogenesis of Alzheimer's disease is well documented. Recently, many members of the human tissue kallikrein family, a group of 15 secreted serine proteases, were found to be highly expressed in the central nervous system (CNS). Some of these enzymes can be measured in cerebrospinal fluid (CSF) by using ELISA-type methodologies.

METHODS

We quantified various kallikreins in CSF of 20 patients with Alzheimer's disease (AD), 16 patients with frontotemporal dementia (FTD), and 15 controls. We then correlated the levels of various kallikreins with presence of AD or FTD. Among all kallikreins measured, detectable levels in CSF were identified for kallikreins hK6, hK7, and hK10. Other tested kallikreins (hK5, hK8, hK11, and hK13) were unmeasurable. The most notable differences between kallikrein levels in CSF and the three groups of subjects were seen between controls and FTD patients for hK6 (decrease in FTD; P = 0.017), controls and FTD patients for hK7 (decrease in FTD; P < 0.001), and controls and AD patients for hK7 (decrease in AD; P = 0.019). In addition, significant differences were seen between FTD patients or control subjects and patients with AD patients for hK10 (increase in AD; P < 0.02). Approximately half of the AD patients had CSF hK10 levels that were higher than all patients with FTD except one and all control subjects except two. Various kallikrein concentrations in CSF were correlated, the strongest correlation seen between hK6 and hK7 (r(s) = 0.58). We also observed a statistically significant association between decreasing hK7 concentration in CSF and possession of one or two ApoE4 alleles (P = 0.014).

CONCLUSIONS

We demonstrate for the first time significant alterations of hK6, hK7, and hK10 concentration in CSF of patients with AD and FTD. Notably, all three kallikreins (hK6, hK7, and hK10) are decreased in CSF of FTD patients and hK10 is increased in CSF of AD patients, in comparison to control subjects. The possible connection between these enzymes and the pathogenesis and progression of AD and FTD needs to be further investigated.

Gleevec inhibits beta-amyloid production but not Notch cleavage

Amyloid-beta (Abeta) peptides, consisting mainly of 40 and 42 aa (Abeta40 and Abeta42, respectively), are metabolites of the amyloid precursor protein and are believed to be major pathological determinants of Alzheimer's disease. The proteolytic cleavages that form the Abeta N and C termini are catalyzed by beta-secretase and gamma-secretase, respectively. Here we demonstrate that gamma-secretase generation of Abeta in an N2a cell-free system is ATP dependent. In addition, the Abl kinase inhibitor imatinib mesylate (Gleevec, or STI571), which targets the ATP-binding site of Abl and several other tyrosine kinases, potently reduces Abeta production in the N2a cell-free system and in intact N2a cells. Both STI571 and a related compound, inhibitor 2, also reduce Abeta production in rat primary neuronal cultures and in vivo in guinea pig brain. STI571 does not inhibit the gamma-secretase-catalyzed S3 cleavage of Notch-1. Furthermore, production of Abeta and its inhibition by STI571 were demonstrated to occur to similar extents in both Abl-/- and WT mouse fibroblasts, indicating that the effect of STI571 on Abeta production does not involve Abl kinase. The efficacy of STI571 in reducing Abeta without affecting Notch-1 cleavage may prove useful as a basis for developing novel therapies for Alzheimer's disease.

Attack on amyloid

International Titisee Conference on Alzheimer's and Parkinson's Disease: From Basic Science to Therapeutic Treatment