Inhibition of Alzheimer's amyloid toxicity with a tricyclic pyrone molecule in vitro and in vivo

Nitroxyl Hybrids with Curcumin and Stilbene Scaffolds Display Potent Antioxidant Activity, Remodel the Amyloid Beta Oligomer, and Reverse Amyloid Beta-Induced Cytotoxicity

The disorder and heterogeneity of low-molecular-weight amyloid-beta oligomers (AβOs) underlie their participation in multiple modes of cellular dysfunction associated with the etiology of Alzheimer's disease (AD). The lack of specified conformational states in these species complicates efforts to select or design small molecules to targeting discrete pathogenic states. Furthermore, targeting AβOs alone may be therapeutically insufficient, as AD progresses as a multifactorial, self-amplifying cascade. To address these challenges, we have screened the activity of seven new candidates that serve as Paramagnetic Amyloid Ligand (PAL) candidates. PALs are bifunctional small molecules that both remodel the AβO structure and localize a potent antioxidant that mimics the activity of SOD within live cells. The candidates are built from either a stilbene or curcumin scaffold with nitroxyl moiety to serve as catalytic antioxidants. Measurements of PAL AβO binding and remolding along with assessments of bioactivity allow for the extraction of useful SAR information from screening data. One candidate (HO-4450; PMT-307), with a six-membered nitroxyl ring attached to a stilbene ring, displays the highest potency in protecting against cell-derived Aβ. A preliminary low-dose evaluation in AD model mice provides evidence of modest treatment effects by HO-4450. The results for the curcumin PALs demonstrate that the retention of the native curcumin phenolic groups is advantageous to the design of the hybrid PAL candidates. Finally, the PAL remodeling of AβO secondary structures shows a reasonable correlation between a candidate's bioactivity and its ability to reduce the fraction of antiparallel β-strand.

Morphological and Molecular Profiling of Amyloid-β Species in Alzheimer's Pathogenesis

Alzheimer's disease (AD) is the most common form of dementia around the world (~ 65%). Here, we portray the neuropathology of AD, biomarkers, and classification of amyloid plaques (diffuse, non-cored, dense core, compact). Tau pathology and its involvement with Aβ plaques and cell death are discussed. Amyloid cascade hypotheses, aggregation mechanisms, and molecular species formed in vitro and in vivo (on- and off-pathways) are described. Aβ42/Aβ40 monomers, dimers, trimers, Aβ-derived diffusible ligands, globulomers, dodecamers, amylospheroids, amorphous aggregates, protofibrils, fibrils, and plaques are characterized (structure, size, morphology, solubility, toxicity, mechanistic steps). An update on AD-approved drugs by regulatory agencies, along with new Aβ-based therapies, is presented. Beyond prescribing Aβ plaque disruptors, cholinergic agonists, or NMDA receptor antagonists, other therapeutic strategies (RNAi, glutaminyl cyclase inhibitors, monoclonal antibodies, secretase modulators, Aβ aggregation inhibitors, and anti-amyloid vaccines) are already under clinical trials. New drug discovery approaches based on "designed multiple ligands", "hybrid molecules", or "multitarget-directed ligands" are also being put forward and may contribute to tackling this highly debilitating and fatal form of human dementia.

Mitochondrial disorders leading to Alzheimer's disease-perspectives of diagnosis and treatment

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common cause of dementia globally. The pathogenesis of AD remains still unclear. The three main features of AD are extracellular deposits of amyloid beta (Aβ) plaque, accumulation of abnormal formation hyper-phosphorylated tau protein, and neuronal loss. Mitochondrial impairment plays an important role in the pathogenesis of AD. There are problems with decreased activity of multiple complexes, disturbed mitochondrial fusion, and fission or formation of reactive oxygen species (ROS). Moreover, mitochondrial transport is impaired in AD. Mouse models in many research show disruptions in anterograde and retrograde transport. Both mitochondrial transportation and network impairment have a huge impact on synapse loss and, as a result, cognitive impairment. One of the very serious problems in AD is also disruption of insulin signaling which impairs mitochondrial Aβ removal.Discovering precise mechanisms leading to AD enables us to find new treatment possibilities. Recent studies indicate the positive influence of metformin or antioxidants such as MitoQ, SS-31, SkQ, MitoApo, MitoTEMPO, and MitoVitE on mitochondrial functioning and hence prevent cognitive decline. Impairments in mitochondrial fission may be treated with mitochondrial division inhibitor-1 or ceramide.

Mitochondrial Complex I and β-Amyloid Peptide Interplay in Alzheimer's Disease: A Critical Review of New and Old Little Regarded Findings

Alzheimer's disease (AD) is the most common neurodegenerative disorder and the main cause of dementia which is characterized by a progressive cognitive decline that severely interferes with daily activities of personal life. At a pathological level, it is characterized by the accumulation of abnormal protein structures in the brain-β-amyloid (Aβ) plaques and Tau tangles-which interfere with communication between neurons and lead to their dysfunction and death. In recent years, research on AD has highlighted the critical involvement of mitochondria-the primary energy suppliers for our cells-in the onset and progression of the disease, since mitochondrial bioenergetic deficits precede the beginning of the disease and mitochondria are very sensitive to Aβ toxicity. On the other hand, if it is true that the accumulation of Aβ in the mitochondria leads to mitochondrial malfunctions, it is otherwise proven that mitochondrial dysfunction, through the generation of reactive oxygen species, causes an increase in Aβ production, by initiating a vicious cycle: there is therefore a bidirectional relationship between Aβ aggregation and mitochondrial dysfunction. Here, we focus on the latest news-but also on neglected evidence from the past-concerning the interplay between dysfunctional mitochondrial complex I, oxidative stress, and Aβ, in order to understand how their interplay is implicated in the pathogenesis of the disease.

Phase separation and pathologic transitions of RNP condensates in neurons: implications for amyotrophic lateral sclerosis, frontotemporal dementia and other neurodegenerative disorders

Liquid-liquid phase separation results in the formation of dynamic biomolecular condensates, also known as membrane-less organelles, that allow for the assembly of functional compartments and higher order structures within cells. Multivalent, reversible interactions between RNA-binding proteins (RBPs), including FUS, TDP-43, and hnRNPA1, and/or RNA (e.g., RBP-RBP, RBP-RNA, RNA-RNA), result in the formation of ribonucleoprotein (RNP) condensates, which are critical for RNA processing, mRNA transport, stability, stress granule assembly, and translation. Stress granules, neuronal transport granules, and processing bodies are examples of cytoplasmic RNP condensates, while the nucleolus and Cajal bodies are representative nuclear RNP condensates. In neurons, RNP condensates promote long-range mRNA transport and local translation in the dendrites and axon, and are essential for spatiotemporal regulation of gene expression, axonal integrity and synaptic function. Mutations of RBPs and/or pathologic mislocalization and aggregation of RBPs are hallmarks of several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and Alzheimer's disease. ALS/FTD-linked mutations of RBPs alter the strength and reversibility of multivalent interactions with other RBPs and RNAs, resulting in aberrant phase transitions. These aberrant RNP condensates have detrimental functional consequences on mRNA stability, localization, and translation, and ultimately lead to compromised axonal integrity and synaptic function in disease. Pathogenic protein aggregation is dependent on various factors, and aberrant dynamically arrested RNP condensates may serve as an initial nucleation step for pathologic aggregate formation. Recent studies have focused on identifying mechanisms by which neurons resolve phase transitioned condensates to prevent the formation of pathogenic inclusions/aggregates. The present review focuses on the phase separation of neurodegenerative disease-linked RBPs, physiological functions of RNP condensates, and the pathologic role of aberrant phase transitions in neurodegenerative disease, particularly ALS/FTD. We also examine cellular mechanisms that contribute to the resolution of aberrant condensates in neurons, and potential therapeutic approaches to resolve aberrantly phase transitioned condensates at a molecular level.

Synthesis of Chiral Tricyclic Pyrone Molecules via Palladium(0)-Catalyzed Displacement Reactions of Chiral Tricyclic Pyrone Acetate With Azide or Amine

Tricyclic pyrone (TP) molecules have shown protection of MC65 neuroblastoma cells death induced by amyloid-β proteins through SβC gene, a decrease of amyloid-β peptide levels, and improvement of motor functions and memory in Alzheimer's disease mouse and rat models. Mechanistic studies suggest TP molecules modulate N-methyl-D-aspartate receptor. A short synthesis of chiral TP analogs was sought using a Pd(0)-catalyzed displacement of TP allylic acetate intermediate with sodium azide or substituted benzylamines. A three-step sequence of reactions by the treatment of 2-{(5aS,7S)-3-methyl-1-oxo-1,5a,6,7,8,9-hexahydropyrano[4,3-b]chromen-7-yl}allyl acetate (9) with (Ph3P)4Pd and sodium azide, followed by reduction with Zn-NH4OCHO and coupling with 3-fluoro-4-hydroxybenzaldehyde and NaCNBH3 was found to give TP coupling molecule, (5aS,7S)-7-(1-(3-fluoro-4-hydroxybenzylamino)prop-2-en-2-yl)-3-methyl-6,7,8,9-tetrahydropyrano[4,3-b]chromen-1(5aH)-one (2), in a good yield. An alternative shorter pathway - a two-step sequence of reactions - by the displacement of 9 by 4-(t-butyldimethylsilyloxy)-3-fluoro-benzylamine with a catalytic amount of (Ph3P)4Pd in THF followed by removal of the silyl ether protecting group gave 2, albeit in a lower chemical yield. The described syntheses should provide general procedures for the synthesis of a library of TP molecules for the discovery of anti-Alzheimer drugs.

Mitochondrial complex I as a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD), the most prominent form of dementia in the elderly, has no cure. Strategies focused on the reduction of amyloid beta or hyperphosphorylated Tau protein have largely failed in clinical trials. Novel therapeutic targets and strategies are urgently needed. Emerging data suggest that in response to environmental stress, mitochondria initiate an integrated stress response (ISR) shown to be beneficial for healthy aging and neuroprotection. Here, we review data that implicate mitochondrial electron transport complexes involved in oxidative phosphorylation as a hub for small molecule-targeted therapeutics that could induce beneficial mitochondrial ISR. Specifically, partial inhibition of mitochondrial complex I has been exploited as a novel strategy for multiple human conditions, including AD, with several small molecules being tested in clinical trials. We discuss current understanding of the molecular mechanisms involved in this counterintuitive approach. Since this strategy has also been shown to enhance health and life span, the development of safe and efficacious complex I inhibitors could promote healthy aging, delaying the onset of age-related neurodegenerative diseases.

2-Pyrones from endophytic fungus Diaporthe foeniculina BZM-15

Foeniculins A-C (1-3) together with a pair of enantiomers (±)-foeniculin D (4) were isolated from endophytic fungus Diaporthe foeniculina BZM-15. Their structures including absolute configurations were unambiguously established by extensive interpretation of the NMR and HR-ESI-MS data, ECD measurements powered by molecular calculations, as well as Mo₂(OAc)₄ mediated CD methodology. The cytotoxic activity assay disclosed that these compounds didn't show any noticeable cytotoxic activity.

Partial inhibition of mitochondrial complex I ameliorates Alzheimer's disease pathology and cognition in APP/PS1 female mice

Alzheimer's Disease (AD) is a devastating neurodegenerative disorder without a cure. Here we show that mitochondrial respiratory chain complex I is an important small molecule druggable target in AD. Partial inhibition of complex I triggers the AMP-activated protein kinase-dependent signaling network leading to neuroprotection in symptomatic APP/PS1 female mice, a translational model of AD. Treatment of symptomatic APP/PS1 mice with complex I inhibitor improved energy homeostasis, synaptic activity, long-term potentiation, dendritic spine maturation, cognitive function and proteostasis, and reduced oxidative stress and inflammation in brain and periphery, ultimately blocking the ongoing neurodegeneration. Therapeutic efficacy in vivo was monitored using translational biomarkers FDG-PET, 31P NMR, and metabolomics. Cross-validation of the mouse and the human transcriptomic data from the NIH Accelerating Medicines Partnership-AD database demonstrated that pathways improved by the treatment in APP/PS1 mice, including the immune system response and neurotransmission, represent mechanisms essential for therapeutic efficacy in AD patients.

Partial Inhibition of Mitochondrial Complex I Reduces Tau Pathology and Improves Energy Homeostasis and Synaptic Function in 3xTg-AD Mice

Background:

Accumulation of hyperphosphorylated tau (pTau) protein is associated with synaptic dysfunction in Alzheimer’s disease (AD). We previously demonstrated that neuroprotection in familial mouse models of AD could be achieved by targeting mitochondria complex I (MCI) and activating the adaptive stress response. Efficacy of this strategy on pTau-related pathology remained unknown.

Objective:

To investigate the effect of specific MCI inhibitor tricyclic pyrone compound CP2 on levels of human pTau, memory function, long term potentiation (LTP), and energy homeostasis in 18-month-old 3xTg-AD mice and explore the potential mechanisms.

Methods:

CP2 was administered to male and female 3xTg-AD mice from 3.5–18 months of age. Cognitive function was assessed using the Morris water maze. Glucose metabolism was measured in periphery using a glucose tolerance test and in the brain using fluorodeoxyglucose F18 positron-emission tomography (FDG-PET). LTP was evaluated using electrophysiology in the hippocampus. The expression of key proteins associated with neuroprotective mechanisms were assessed by western blotting.

Results:

Chronic CP2 treatment restored synaptic activity in female 3xTg-AD mice; cognitive function, levels of synaptic proteins, glucose metabolism, and energy homeostasis were improved in male and female 3xTg-AD mice. Significant reduction of human pTau in the brain was associated with increased activity of protein phosphatase of type 2A (PP2A), and reduced activity of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3β (GSK3β).

Conclusion:

CP2 treatment protected against synaptic dysfunction and memory impairment in symptomatic 3xTg-AD mice, and reduced levels of human pTau, indicating that targeting mitochondria with small molecule specific MCI inhibitors represents a promising strategy for treating AD.

A Curcumin Analog Reduces Levels of the Alzheimer's Disease-Associated Amyloid-β Protein by Modulating AβPP Processing and Autophagy

Alzheimer's disease (AD) is a devastating neurodegenerative disease with no cure currently available. A pathological hallmark of AD is accumulation and deposition of amyloid-β protein (Aβ), a ∼4 kDa peptide generated through serial cleavage of the amyloid-β protein precursor (AβPP) by β- and γ-secretases. Curcumin is a natural compound primarily found in the widely used culinary spice, turmeric, which displays therapeutic potential for AD. Recently, we reported the development of curcumin analogs and identified a lead compound, curcumin-like compound-R17 (CLC-R17), that significantly attenuates Aβ deposition in an AD transgenic mouse model. Here, we elucidated the mechanisms of this analog on Aβ levels and AβPP processing using cell models of AD. Using biochemical methods and our recently developed nanoplasmonic fiber tip probe technology, we showed that the lead compound potently lowers Aβ levels in conditioned media and reduces oligomeric amyloid levels in the cells. Furthermore, like curcumin, the lead compound attenuates the maturation of AβPP in the secretory pathway. Interestingly, it upregulated α-secretase processing of AβPP and inhibited β-secretase processing of AβPP by decreasing BACE1 protein levels. Collectively, our data reveal mechanisms of a promising curcumin analog in reducing Aβ levels, which strongly support its development as a potential therapeutic for AD.

Intra-gastrointestinal amyloid-β1-42 oligomers perturb enteric function and induce Alzheimer's disease pathology

KEY POINTS

Alzheimer's disease (AD) patients and transgenic mice have beta-amyloid (Aβ) aggregation in the gastrointestinal (GI) tract. It is possible that Aβ from the periphery contributes to the load of Aβ in the brain, as Aβ has prion-like properties. The present investigations demonstrate that Aβ injected into the GI tract of ICR mice is internalised into enteric cholinergic neurons; at 1 month, administration of Aβ into the body of the stomach and the proximal colon was observed to partly redistribute to the fundus and jejunum; at 1 year, vagal and cerebral β-amyloidosis was present, and mice exhibited GI dysfunction and cognitive deficits. These data reveal a previously undiscovered mechanism that potentially contributes to the development of AD.

ABSTRACT

Alzheimer's disease (AD) is the most common age-related cause of dementia, characterised by extracellular beta-amyloid (Aβ) plaques and intracellular phosphorylated tau tangles in the brain. Aβ deposits have also been observed in the gastrointestinal (GI) tract of AD patients and transgenic mice, with overexpression of amyloid precursor protein. In the present studies, we investigate whether intra-GI administration of Aβ can potentially induce amyloidosis in the central nervous system (CNS) and AD-related pathology such as dementia. We micro-injected Aβ1-42 oligomers (4 μg per site, five sites) or vehicle (saline, 5 μl) into the gastric wall of ICR mice under general anaesthesia. Immunofluorescence staining and in vivo imaging showed that HiLyte Fluor 555-labelled Aβ1-42 had migrated within 3 h via the submucosa to nearby areas and was internalised into cholinergic neurons. At 1 month, HiLyte Fluor 555-labelled Aβ1-42 in the body of the stomach and proximal colon had partly re-distributed to the fundus and jejunum. At 1 year, the jejunum showed functional alterations in neuromuscular coupling (P < 0.001), and Aβ deposits were present in the vagus and brain, with animals exhibiting cognitive impairments in the Y-maze spontaneous alteration test (P < 0.001) and the novel object recognition test (P < 0.001). We found that enteric Aβ oligomers induce an alteration in gastric function, amyloidosis in the CNS, and AD-like dementia via vagal mechanisms. Our results suggest that Aβ load is likely to occur initially in the GI tract and may translocate to the brain, opening the possibility of new strategies for the early diagnosis and prevention of AD.

Intracellular amyloid-β disrupts tight junctions of the retinal pigment epithelium via NF-κB activation

Drusen are focal deposits between the retinal pigment epithelium (RPE) and Bruch's membrane in the retina of patients with age-related macular degeneration. Amyloid-β is one of the important components of drusen, which leads to local inflammation. Furthermore, intracellular amyloid-β disrupts tight junctions of the RPE. However, the intracellular mechanisms linking intracellular amyloid-β and tight-junction disruption are not clear. In this study, intracellular amyloid-β oligomers activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65, leading to the disorganization of tight junctions of the RPE in mice after subretinal injection of amyloid-β. Amyloid-β also triggered NF-κB activation in the RPE cells in confluent culture, which was inhibited by the suppression of the advanced glycosylation end product-specific receptor. NF-κB inhibition by an IκB kinase inhibitor prevented the suppression of expression of tight-junction proteins, zonula occuludens-1 and occludin in RPE cells. In addition, tight-junction complexes remained intact in the RPE of mice with NF-κB inhibition, although there were intracellular amyloid-β oligomers. These data suggested that NF-κB inhibition might be a therapeutic approach to prevent amyloid-β-mediated tight-junction disruption.

Unexpected synthesis of novel 2-pyrone derivatives: crystal structures, Hirshfeld surface analysis and computational studies

Here we report synthesis of three new compounds namely, 1-acetyl-1H-benzimidazolo-2(3H)-one (I), N-(5-acetyl-6-methyl-2-oxo-2H-pyran-4-yl)-N-(2-acetamidophenyl)acetamide (II) and N-(2-acetamidophenyl)-N-2-oxo-2H-pyran-4-yl)acetamide (III) have been synthesized and characterized by single crystal X-ray diffraction. Compounds I and II crystallize in the monoclinic space groups P21/n, and P21/c, respectively, while III crystallizes in the triclinic space group P-1. The theoretical parameters of I-III have been calculated through density functional theory (DFT) by using the hybrid functional B3LYP and basis set 6-311++G**. These theoretical parameters have been compared with the experimental ones obtained by XRD. The significant intermolecular interactions arising in crystal packing are rationalized by means of the Hirshfeld surface analysis method. The major intermolecular contacts in the Hirshfeld surfaces of I-III are from H…H contacts. In addition, binding modes of I-III within Tyrosine-protein kinase JAK2 were investigated using molecular docking and molecular dynamics simulation studies.Communicated by Ramaswamy H. Sarma.

Ginnalin A Inhibits Aggregation, Reverses Fibrillogenesis, and Alleviates Cytotoxicity of Amyloid β(1-42)

Aggregation of misfolded amyloid beta (Aβ) peptides into neurotoxic oligomers and fibrils has been implicated as a key event in the etiopathogenesis of Alzheimer's disease (AD). Ginnalin A (GA), a polyphenolic compound isolated from the red maple (Acer rubrum), has been found to possess anticancer, antiglycation, and antioxidation properties. Using thioflavin T (ThT) fluorescence, surface plasmon resonance (SPR), and atomic force microscopy (AFM), we demonstrate that GA can also effectively inhibit Aβ aggregation by primarily binding to Aβ monomers in a dose-dependent manner. Furthermore, GA can bind to multiple sites of Aβ aggregates to disassemble preformed fibrils and convert them into small aggregates. Circular dichroism (CD) spectra showed that these small aggregates are much less abundant in β-sheets, while cell viability assay confirms that they are essentially innocuous. Molecular dynamics (MD) simulations revealed that GA preferentially contacts with the C- and N-terminal β-sheets and the U-turn region of Aβ(1-42) oligomers through hydrophobic interactions and hydrogen bonding. Compared with other natural compounds that have shown promise in anti-Aβ fibrillogenesis and ameliorating Aβ-induced cytotoxicity, GA is unique in that it exhibits a more efficient inhibition of Aβ aggregation at the very early stage through its strong interaction with Aβ monomers and exerts its inhibitory effect at a lower dosage.

Nature's Derivative(s) as Alternative Anti-Alzheimer's Disease Treatments

Alzheimer's disease (AD), the 'Plague of Twenty-First Century,' is a crippling neurodegenerative disease that affects a majority of the older population globally. By 2050, the incidence of AD is expected to rise to 135 million, while no treatment(s) that can reverse or control the progression of AD are currently available. The treatment(s) in use are limited in their ability to manage the symptoms or slow the progression of the disease and can lead to some severe side effects. The overall care is economically burdensome for the affected individuals as well as the caretakers or family members. Thus, there is a pressing need to identify and develop much safer alternative therapies that can better manage AD. This review discusses a multitude of such treatments borrowed from Ayurveda, traditional Chinese practices, meditation, and exercising for AD treatment. These therapies are in practice since ancient times and reported to be beneficial as anti-AD therapies. Ayurvedic drugs like turmeric, Brahmi, Ashwagandha, etc., management of stress by meditation, regular exercising, and acupuncture have been reported to be efficient in their anti-AD usage. Besides, a combination of vitamins and natural dietary intakes is likely to play a significant role in combating AD. We conclude that the use of such alternative strategies will be a stepping-stone in preventing, treating, curing, or managing the disease.

Kv1.3 inhibition as a potential microglia-targeted therapy for Alzheimer's disease: preclinical proof of concept

Microglia significantly contribute to the pathophysiology of Alzheimer's disease but an effective microglia-targeted therapeutic approach is not yet available clinically. The potassium channels Kv1.3 and Kir2.1 play important roles in regulating immune cell functions and have been implicated by in vitro studies in the 'M1-like pro-inflammatory' or 'M2-like anti-inflammatory' state of microglia, respectively. We here found that amyloid-β oligomer-induced expression of Kv1.3 and Kir2.1 in cultured primary microglia. Likewise, ex vivo microglia acutely isolated from the Alzheimer's model 5xFAD mice co-expressed Kv1.3 and Kir2.1 as well as markers traditionally associated with M1 and M2 activation suggesting that amyloid-β oligomer induces a microglial activation state that is more complex than previously thought. Using the orally available, brain penetrant small molecule Kv1.3 blocker PAP-1 as a tool, we showed that pro-inflammatory and neurotoxic microglial responses induced by amyloid-β oligomer required Kv1.3 activity in vitro and in hippocampal slices. Since we further observed that Kv1.3 was highly expressed in microglia of transgenic Alzheimer's mouse models and human Alzheimer's disease brains, we hypothesized that pharmacological Kv1.3 inhibition could mitigate the pathology induced by amyloid-β aggregates. Indeed, treating APP/PS1 transgenic mice with a 5-month oral regimen of PAP-1, starting at 9 months of age, when the animals already manifest cognitive deficits and amyloid pathology, reduced neuroinflammation, decreased cerebral amyloid load, enhanced hippocampal neuronal plasticity, and improved behavioural deficits. The observed decrease in cerebral amyloid deposition was consistent with the in vitro finding that PAP-1 enhanced amyloid-β uptake by microglia. Collectively, these results provide proof-of-concept data to advance Kv1.3 blockers to Alzheimer's disease clinical trials.

Cu and Zn interactions with Aβ peptides: consequence of coordination on aggregation and formation of neurotoxic soluble Aβ oligomers

The coordination chemistry of transition metal ions (Fe, Cu, Zn) with the amyloid-β (Aβ) peptides has attracted a lot of attention in recent years due to its repercussions in Alzheimer's disease (AD).

Ayurvedic Medicine for the Treatment of Dementia: Mechanistic Aspects

Ayurvedic medicine is a personalized system of traditional medicine native to India and the Indian subcontinent. It is based on a holistic view of treatment which promotes and supports equilibrium in different aspects of human life: the body, mind, and soul. Popular Ayurvedic medicinal plants and formulations that are used to slow down brain aging and enhance memory include Ashwagandha (Withania somnifera), Turmeric (Curcuma longa), Brahmi (Bacopa monnieri), Shankhpushpi (Convolvulus pluricaulis, Evolvulus alsinoides, and other species), gotu kola (Centella asiatica), and guggulu (Commiphora mukul and related species) and a formulation known as Brāhmī Ghṛita, containing Brahmi, Vacā (Acorus calamus), Kuṣṭha (Saussurea lappa), Shankhpushpi, and Purāṇa Ghṛita (old clarified butter/old ghee). The rationale for the utilization of Ayurvedic medicinal plants has depended mostly on traditional usage, with little scientific data on signal transduction processes, efficacy, and safety. However, in recent years, pharmacological and toxicological studies have begun to be published and receive attention from scientists for verification of their claimed pharmacological and therapeutic effects. The purpose of this review is to outline the molecular mechanisms, signal transduction processes, and sites of action of some Ayurvedic medicinal plants. It is hoped that this description can be further explored with modern scientific methods, to reveal new therapeutic leads and jump-start more studies on the use of Ayurvedic medicine for prevention and treatment of dementia.

Microchip Circulation Drastically Accelerates Amyloid Aggregation of 1-42 β-amyloid Peptide from Felis catus

The amyloid aggregation process of amyloid β_1-42 peptide is responsible for Alzheimer's disease, affecting millions of elderly people worldwide. Although there has been a great deal of attention directed toward tackling this disease, still no medicine has been found for this fatal disorder. To address this challenge, it is vital to thoroughly understand the molecular mechanism underlying the amyloid peptide aggregation process, as well as seek substances that could hamper this aggregation. In order to shed light on mechanisms leading to amyloidogenesis, we employed a microfluidic system to determine the possible influence of in vivo-like flow in the microchip channel itself on feline Aβ_1-42 peptide amyloidogenesis. We have shown that shear forces occurring during such flow immensely accelerated peptide aggregation. We also tested the inhibitory influence of 3,3'-[1,6-(2,5-dioxahexane)]bis(1-dodecylimidazolium) dichloride gemini surfactant on peptide amyloidogenesis. Our results suggest that this surfactant may inhibit amyloid β_1-42 fibril formation.

α-pyrones: Small molecules with versatile structural diversity reflected in multiple pharmacological activities-an update

The investigations in the chemistry and biology of α-pyrone (2-pyrone) are of vital importance as they constitute an essential pharmacophore in many naturally occurring and biologically active synthetic agents. They are a promising class of biorenewable platform chemicals that provide access to an array of chemical products and intermediates. Literature survey reveals that a simple change in the substitution pattern on the 2-pyrone ring system often leads to diverse biological activities. In this review, we present a brief overview of 2-pyrone pharmacophore followed by highlighting their pharmacological properties and potential applicability till date. Particular attention is focused on the distinctive chemotherapeutic activities of 2-pyrones as anti-HIV, anti-TB and anti-cancer agents followed by their potential role against neurodegeneration, hypercholesterolemia, microbial infections, chronic obstructive lung disease, inflammation, antinociception and immunomodulation. Since 2005, when 2-pyrones came in limelight, their detailed pharmacological activities have been well documented. This review has mainly been prepared on the basis of original reports published in recent two decades with an aim to attract the attention of researchers towards this versatile scaffold for future endeavors that may lead to the development of potential drug candidates against above diseases.

The Anti-Amyloid-β and Neuroprotective Properties of a Novel Tricyclic Pyrone Molecule

There is an urgent unmet need for new therapeutics for Alzheimer's disease (AD), the most common cause of dementia in the elderly. Therapeutic approaches targeting amyloid-β (Aβ) and its downstream toxicities have become major strategies in AD drug development. We have taken a rational design approach and synthesized a class of tricyclic pyrone (TP) compounds that show anti-Aβ and other neuroprotective actions. The in vivo efficacy of a lead TP named CP2 to ameliorate AD-like pathologies has been shown in mouse models. Here we report the selection and initial characterization of a new lead TP70, which exhibited an anti-Aβ therapeutic index even higher than CP2. Moreover, TP70 was able to reduce oxidative stress, inhibit acyl-coenzyme A:cholesterol acyltransferase (ACAT), and upregulate the expression of ATP-binding cassette subfamily A, member 1 (ABCA1), actions considered neuroprotective in AD. TP70 further showed excellent pharmacokinetic properties, including brain penetration and oral availability. When administered to 5xFAD mice via intraperitoneal or oral route, TP70 enhanced the overall solubility and decreased the level of cerebral Aβ, including both fibrillary and soluble Aβ species. Interestingly, TP70 enhanced N-methyl-D-aspartate (NMDA) receptor-mediated excitatory post-synaptic potential (EPSP) in the hippocampal CA1 area, increased the magnitude of NMDA-dependent hippocampal long-term potentiation (LTP), a cellular model of learning and memory, and prevented the Aβ oligomer-impaired LTP. Significantly, a single dose of TP70 administered to aged 5xFAD mice was effective in mitigating the impaired LTP induction, recorded at 24 h after administration. Our results support a potential of TP70 in clinical development for AD in view of its synergistic neuroprotective actions, ability to positively modulate NMDA receptor-mediated hippocampal plasticity, and favorable pharmacokinetic properties in rodents.

Inhibition of Beta-Amyloid Fibrillation by Luminescent Iridium(III) Complex Probes

We report herein the application of kinetically inert luminescent iridium(III) complexes as dual inhibitors and probes of beta-amyloid fibrillogenesis. These iridium(III) complexes inhibited Aβ_1–40 peptide aggregation in vitro, and protected against Aβ-induced cytotoxicity in neuronal cells. Furthermore, the complexes differentiated between the aggregated and unaggregated forms of Aβ_1–40 peptide on the basis of their emission response.

Protective spin-labeled fluorenes maintain amyloid beta peptide in small oligomers and limit transitions in secondary structure

Alzheimer's disease is characterized by the presence of extracellular plaques comprised of amyloid beta (Aβ) peptides. Soluble oligomers of the Aβ peptide underlie a cascade of neuronal loss and dysfunction associated with Alzheimer's disease. Single particle analyses of Aβ oligomers in solution by fluorescence correlation spectroscopy (FCS) were used to provide real-time descriptions of how spin-labeled fluorenes (SLFs; bi-functional small molecules that block the toxicity of Aβ) prevent and disrupt oligomeric assemblies of Aβ in solution. Furthermore, the circular dichroism (CD) spectrum of untreated Aβ shows a continuous, progressive change over a 24-hour period, while the spectrum of Aβ treated with SLF remains relatively constant following initial incubation. These findings suggest the conformation of Aβ within the oligomer provides a complementary determinant of Aβ toxicity in addition to oligomer growth and size. Although SLF does not produce a dominant state of secondary structure in Aβ, it does induce a net reduction in beta secondary content compared to untreated samples of Aβ. The FCS results, combined with electron paramagnetic resonance spectroscopy and CD spectroscopy, demonstrate SLFs can inhibit the growth of Aβ oligomers and disrupt existing oligomers, while retaining Aβ as a population of smaller, yet largely disordered oligomers.

Modulation of mitochondrial complex I activity averts cognitive decline in multiple animal models of familial Alzheimer's Disease

Development of therapeutic strategies to prevent Alzheimer's Disease (AD) is of great importance. We show that mild inhibition of mitochondrial complex I with small molecule CP2 reduces levels of amyloid beta and phospho-Tau and averts cognitive decline in three animal models of familial AD. Low-mass molecular dynamics simulations and biochemical studies confirmed that CP2 competes with flavin mononucleotide for binding to the redox center of complex I leading to elevated AMP/ATP ratio and activation of AMP-activated protein kinase in neurons and mouse brain without inducing oxidative damage or inflammation. Furthermore, modulation of complex I activity augmented mitochondrial bioenergetics increasing coupling efficiency of respiratory chain and neuronal resistance to stress. Concomitant reduction of glycogen synthase kinase 3β activity and restoration of axonal trafficking resulted in elevated levels of neurotrophic factors and synaptic proteins in adult AD mice. Our results suggest metabolic reprogramming induced by modulation of mitochondrial complex I activity represents promising therapeutic strategy for AD.

Protective effects of curcumin in APPswe transfected SH-SY5Y cells

The APPswe plasmid was transfected into the neuroblastoma cell line SH-SY5Y to establish a cell model of Alzheimer's disease. Graded concentration and time course experiments demonstrate that curcumin significantly upregulates phosphatidylinositol 3-kinase (PI3K), Akt, nuclear factor E2-related factor-2 (Nrf2), heme oxygenase 1 and ferritin expression, and that it significantly downregulates heme oxygenase 2, reactive oxygen species and amyloid-beta 40/42 expression. These effects of curcumin on PI3K, Akt and Nrf2 were blocked by LY294002 (PI3k inhibitor) and NF-E2-related factor-2 siRNA. The results indicate that the cytoprotection conferred by curcumin on APPswe transfected SH-SY5Y cells is mediated by its ability to regulate the balance between heme oxygenase 1 and 2 via the PI3K/Akt/Nrf2 intracellular signaling pathway.

Rationally designed peptidomimetic modulators of aβ toxicity in Alzheimer's disease

Alzheimer's disease is one of the devastating illnesses mankind is facing in the 21st century. The main pathogenic event in Alzheimer's disease is believed to be the aggregation of the β-amyloid (Aβ) peptides into toxic aggregates. Molecules that interfere with this process may act as therapeutic agents for the treatment of the disease. Use of recognition unit based peptidomimetics as inhibitors are a promising approach, as they exhibit greater protease stability compared to natural peptides. Here, we present peptidomimetic inhibitors of Aβ aggregation designed based on the KLVFF (P1) sequence that is known to bind Aβ aggregates. We improved inhibition efficiency of P1 by introducing multiple hydrogen bond donor-acceptor moieties (thymine/barbiturate) at the N-terminal (P2 and P3), and blood serum stability by modifying the backbone by incorporating sarcosine (N-methylglycine) units at alternate positions (P4 and P5). The peptidomimetics showed moderate to good activity in both inhibition and dissolution of Aβ aggregates as depicted by thioflavin assay, circular dichroism (CD) measurements and microscopy (TEM). The activity of P4 and P5 were studied in a yeast cell model showing Aβ toxicity. P4 and P5 could rescue yeast cells from Aβ toxicity and Aβ aggregates were cleared by the process of autophagy.

Alzheimer's therapeutics targeting amyloid beta 1-42 oligomers I: Abeta 42 oligomer binding to specific neuronal receptors is displaced by drug candidates that improve cognitive deficits

Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1-42 oligomers is proposed to underlie cognitive decline in Alzheimer's disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer's disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors--i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD models and sustain improvement long-term, representing a novel mechanism of action for disease-modifying Alzheimer's therapeutics.

Syntheses, neural protective activities, and inhibition of glycogen synthase kinase-3β of substituted quinolines

A new series of fifteen 5-, 6-, and 8-appended 4-methylquinolines were synthesized and evaluated for their neural protective activities. Selected compounds were further examined for their inhibition of glycogen synthase kinase-3β (GSK-3β) and protein kinase C (PKC). Two most potent analogs, compounds 3 and 10, show nanomolar protective activities in amyloid β-induced MC65 cells and enzymatic inhibitory activities against GSK-3β, but poor PKC inhibitory activities. Using normal mouse model, the distribution of the most potent analog 3 in various tissues and possible toxic effects in the locomotors and inhibition of liver transaminases activities were carried out. No apparent decline of locomotor activity and no inhibition of liver transaminases were found. The compound appears to be safe for long-term use in Alzheimer's disease mouse model.

Design, synthesis, and evaluation of bioactive small molecules

Collaborative research projects between chemists, biologists, and medical scientists have inevitably produced many useful drugs, biosensors, and medical instrumentation. Organic chemistry lies at the heart of drug discovery and development. The current range of organic synthetic methodologies allows for the construction of unlimited libraries of small organic molecules for drug screening. In translational research projects, we have focused on the discovery of lead compounds for three major diseases: Alzheimer's disease (AD), breast cancer, and viral infections. In the AD project, we have taken a rational-design approach and synthesized a new class of tricyclic pyrone (TP) compounds that preserve memory and motor functions in amyloid precursor protein (APP)/presenilin-1 (PS1) mice. TPs could protect neuronal death through several possible mechanisms, including their ability to inhibit the formation of both intraneuronal and extracellular amyloid β (Aβ) aggregates, to increase cholesterol efflux, to restore axonal trafficking, and to enhance long-term potentiation (LTP) and restored LTP following treatment with Aβ oligomers. We have also synthesized a new class of gap-junction enhancers, based on substituted quinolines, that possess potent inhibitory activities against breast-cancer cells in vitro and in vivo. Although various antiviral drugs are available, the emergence of viral resistance to existing antiviral drugs and various understudied viral infections, such as norovirus and rotavirus, emphasizes the demand for the development of new antiviral agents against such infections and others. Our laboratories have undertaken these projects for the discovery of new antiviral inhibitors. The discussion of these aforementioned projects may shed light on the future development of drug candidates in the fields of AD, cancer, and viral infections.

Vitamin D-binding protein interacts with Aβ and suppresses Aβ-mediated pathology

The level of vitamin D-binding protein (DBP) is increased in the cerebrospinal fluid of patients with Alzheimer's disease (AD), suggesting a relationship with its pathogenesis. In this study, we investigated whether and how DBP is related to AD using several different approaches. A pull-down assay and a surface plasmon resonance binding assay indicated direct interactions between purified DBP and amyloid beta (Aβ), which was confirmed in the brain of AD patients and transgenic AD model mice by immunoprecipitation assay and immunohistochemical double-staining method. Moreover, atomic force microscopic examination revealed that DBP reduced Aβ aggregation in vitro. DBP also prevented Aβ-mediated death in cultured mouse hippocampal HT22 cell line. Finally, DBP decreased Aβ-induced synaptic loss in the hippocampus and rescued memory deficits in mice after injection of Aβ into the lateral ventricle. These results provide converging evidence that DBP attenuates the harmful effects of Aβ by a direct interaction, and suggest that DBP is a promising therapeutic agent for the treatment of AD.

Dye-binding assays for evaluation of the effects of small molecule inhibitors on amyloid (aβ) self-assembly

Dye-binding assays, such as those utilizing Congo red and thioflavin T, are among the most widely used tools to probe the aggregation of amyloidogenic biomolecules and for the evaluation of small molecule inhibitors of amyloid aggregation and fibrillization. A number of recent reports have indicated that these dye-binding assays could be prone to false positive effects when assessing inhibitors' potential toward Aβ peptides, species involved in Alzheimer's disease. Specifically, this review focuses on the application of thioflavin T for determining the efficiency of small molecule inhibitors of Aβ aggregation and addresses potential reasons that might be associated with the false positive effects in an effort to increase reliability of dye-binding assays.

Inhibition of Acyl-CoA: cholesterol acyltransferase (ACAT), overexpression of cholesterol transporter gene, and protection of amyloid β (Aβ) oligomers-induced neuronal cell death by tricyclic pyrone molecules

A major effort in Alzheimer's disease therapeutic development has targeted Aβ and downstream events. We have synthesized a small library of tricyclic pyrone compounds. Their protective action in MC65 cells and inhibition of ACAT along with the upregulation of cholesterol transporter gene were investigated. Five active compounds exhibited potencies in the nanomolar ranges. The multiple effects of the compounds on Aβ and cellular cholesterol pathways could be potential mechanisms underlying the protective effects in vivo.

Treatment strategies targeting amyloid β-protein

With the advent of the key discovery in the mid-1980s that the amyloid β-protein (Aβ) is the core constituent of the amyloid plaque pathology found in Alzheimer disease (AD), an intensive effort has been underway to attempt to mitigate its role in the hope of treating the disease. This effort fully matured when it was clarified that the Aβ is a normal product of cleavage of the amyloid precursor protein, and well-defined proteases for this process were identified. Further therapeutic options have been developed around the concept of anti-Aβ aggregation inhibitors and the surprising finding that immunization with Aβ itself leads to reduction of pathology in animal models of the disease. Here we review the progress in this field toward the goal of targeting Aβ for treatment and prevention of AD and identify some of the major challenges for the future of this area of medicine.

Effect of Alpinia zerumbet components on antioxidant and skin diseases-related enzymes

Background

The skin is chronically exposed to endogenous and environmental pro-oxidant agents, leading to the harmful generation of reactive oxygen species. Antioxidant is vital substances which possess the ability to protect the body from damage cause by free radicals induce oxidative stress. Alpinia zerumbet, a traditionally important economic plant in Okinawa, contains several interesting bioactive constituents and possesses health promoting properties. In this regard, we carried out to test the inhibitory effect of crude extracts and isolated compounds from A. zerumbet on antioxidant and skin diseases-related enzymes.

Methods

The antioxidant activities were examined by DPPH, ABTS and PMS-NADH radical scavenging. Collagenase, elastase, hyaluronidase and tyrosinase were designed for enzymatic activities to investigate the inhibitory properties of test samples using a continuous spectrophotometric assay. The inhibitory capacity of test samples was presented at half maximal inhibitory concentration (IC₅₀).

Results

The results showed that aqueous extract of the rhizome was found to have greater inhibitory effects than the others on both of antioxidant and skin diseases-related enzymes. Furthermore, 5,6-dehydrokawain (DK), dihydro-5,6-dehydrokawain (DDK) and 8(17),12-labdadiene-15,16-dial (labdadiene), isolated from rhizome, were tested for antioxidant and enzyme inhibitions. We found that DK showed higher inhibitory activities on DPPH, ABTS and PMS-NADH scavenging (IC₅₀ = 122.14 ± 1.40, 110.08 ± 3.34 and 127.78 ± 4.75 μg/ml, respectively). It also had stronger inhibitory activities against collagenase, elastase, hyaluronidase and tyrosinase (IC₅₀ = 24.93 ± 0.97, 19.41 ± 0.61, 19.48 ± 0.24 and 76.67 ± 0.50 μg/ml, respectively) than DDK and labdadiene.

Conclusion

Our results indicate that the rhizome aqueous extract proved to be the source of bioactive compounds against enzymes responsible for causing skin diseases. Moreover, DK could be used as a potent inhibitor and be further exploited to be used in anti-skin disease formulations.

Impaired short-term plasticity in mossy fiber synapses caused by mitochondrial dysfunction of dentate granule cells is the earliest synaptic deficit in a mouse model of Alzheimer's disease

Alzheimer's disease (AD) in the early stages is characterized by memory impairment, which may be attributable to synaptic dysfunction. Oxidative stress, mitochondrial dysfunction, and Ca²⁺ dysregulation are key factors in the pathogenesis of AD, but the causal relationship between these factors and synaptic dysfunction is not clearly understood. We found that in the hippocampus of an AD mouse model (Tg2576), mitochondrial Ca²⁺ handling in dentate granule cells was impaired as early as the second postnatal month, and this Ca²⁺ dysregulation caused an impairment of post-tetanic potentiation in mossy fiber-CA3 synapses. The alteration of cellular Ca²⁺ clearance in Tg2576 mice is region-specific within hippocampus because in another region, CA1 pyramidal neuron, no significant difference in Ca²⁺ clearance was detected between wild-type and Tg2576 mice at this early stage. Impairment of mitochondrial Ca²⁺ uptake was associated with increased mitochondrial reactive oxygen species and depolarization of mitochondrial membrane potential. Mitochondrial dysfunctions in dentate granule cells and impairment of post-tetanic potentiation in mossy fiber-CA3 synapses were fully restored when brain slices obtained from Tg2576 were pretreated with antioxidant, suggesting that mitochondrial oxidative stress initiates other dysfunctions. Reversibility of early dysfunctions by antioxidants at the preclinical stage of AD highlights the importance of early diagnosis and antioxidant therapy to delay or prevent the disease processes.

The influence of spin-labeled fluorene compounds on the assembly and toxicity of the aβ peptide

Background

The deposition and oligomerization of amyloid β (Aβ) peptide plays a key role in the pathogenesis of Alzheimer's disease (AD). Aβ peptide arises from cleavage of the membrane-associated domain of the amyloid precursor protein (APP) by β and γ secretases. Several lines of evidence point to the soluble Aβ oligomer (AβO) as the primary neurotoxic species in the etiology of AD. Recently, we have demonstrated that a class of fluorene molecules specifically disrupts the AβO species.

Methodology/Principal Findings

To achieve a better understanding of the mechanism of action of this disruptive ability, we extend the application of electron paramagnetic resonance (EPR) spectroscopy of site-directed spin labels in the Aβ peptide to investigate the binding and influence of fluorene compounds on AβO structure and dynamics. In addition, we have synthesized a spin-labeled fluorene (SLF) containing a pyrroline nitroxide group that provides both increased cell protection against AβO toxicity and a route to directly observe the binding of the fluorene to the AβO assembly. We also evaluate the ability of fluorenes to target multiple pathological processes involved in the neurodegenerative cascade, such as their ability to block AβO toxicity, scavenge free radicals and diminish the formation of intracellular AβO species.

Conclusions

Fluorene modified with pyrroline nitroxide may be especially useful in counteracting Aβ peptide toxicity, because they posses both antioxidant properties and the ability to disrupt AβO species.

Modulating self-assembly of amyloidogenic proteins as a therapeutic approach for neurodegenerative diseases: strategies and mechanisms

Abnormal protein assembly causes multiple devastating disorders in the central nervous system (CNS), such as Alzheimer's, Parkinson's, Huntington's, and prion diseases. Due to the now extended human lifespan, these diseases have been increasing in prevalence, resulting in major public health problems and the associated financial difficulties worldwide. The wayward proteins that lead to disease self-associate into neurotoxic oligomers and go on to form fibrillar polymers through multiple pathways. Thus, a range of possible targets for pharmacotherapeutic intervention exists along these pathways. Many compounds have shown different levels of effectiveness in inhibiting aberrant self-assembly, dissociating existing aggregates, protecting cells against neurotoxic insults, and in some cases ameliorating disease symptoms in vivo, yet achieving efficient, disease-modifying therapy in humans remains a major unattained goal. To a large degree, this is because the mechanisms of action for these drugs are essentially unknown. For successful design of new effective drugs, it is crucial to elucidate the mechanistic details of their action, including the actual target(s) along the protein aggregation pathways, how the compounds modulate these pathways, and their effect at the cellular, tissue, organ, and organism level. Here, the current knowledge of major mechanisms by which some of the more extensively explored drug candidates work are discussed. In particular, we focus on three prominent strategies: 1) stabilizing the native fold of amyloidogenic proteins, 2) accelerating the aggregation pathways towards the fibrillar endpoint thereby reducing accumulation of toxic oligomers, and 3) modulating the assembly process towards nontoxic oligomers/aggregates. The merit of each strategy is assessed, and the key points to consider when analyzing the efficacy of possible drug candidates and their mechanism of action are discussed.

Polyphenolic glycosides and aglycones utilize opposing pathways to selectively remodel and inactivate toxic oligomers of amyloid β

Substantial evidence suggests that soluble prefibrillar oligomers of the Aβ42 peptide associated with Alzheimer's disease are the most cytotoxic aggregated Aβ isoform. Limited previous work has revealed that aromatic compounds capable of remodeling Aβ oligomers into nontoxic conformers typically do so by converting them into off-pathway aggregates instead of dissociating them into monomers. Towards identifying small-molecule antagonists capable of selectively dissociating toxic Aβ oligomers into soluble peptide at substoichiometric concentrations, we have investigated the pathways used by polyphenol aglycones and their glycosides to remodel Aβ soluble oligomers. We find that eleven polyphenol aglycones of variable size and structure utilize the same remodeling pathway whereby Aβ oligomers are rapidly converted into large, off-pathway aggregates. Strikingly, we find that glycosides of these polyphenols all utilize a distinct remodeling pathway in which Aβ oligomers are rapidly dissociated into soluble, disaggregated peptide. This disaggregation activity is a synergistic combination of the aglycone and glycone moieties because combinations of polyphenols and sugars fail to disaggregate Aβ oligomers. We also find that polyphenolic glycosides and aglycones use the same opposing pathways to remodel Aβ fibrils. Importantly, both classes of polyphenols fail to remodel nontoxic Aβ oligomers (which are indistinguishable in size and morphology to Aβ soluble oligomers) or promote aggregation of freshly disaggregated Aβ peptide; thus revealing that they are specific for remodeling toxic Aβ conformers. We expect that these and related small molecules will be powerful chemical probes for investigating the conformational and cellular underpinnings of Aβ-mediated toxicity.

Gombapyrones E and F, New α-Pyrone Polyenes Produced by Streptomyces sp. KMC-002

Microorganism-derived polyene polyketides have been shown to display a variety of biological activities and have attracted great interest due to their structurally intriguing chemical diversity. Two new polyenes were isolated from a culture broth of Streptomyces sp. KMC-002 obtained from a soil sample in an abandoned mine. The structures of these compounds were determined to be α-pyrone-containing polyene analogues through analyses of HRFABMS, UV and NMR data, and were named Gombapyrones E (1) and F (2). Gombapyrone E (1) showed antibacterial activity against Micrococcus luteus, Enterococcus hirae, Staphylococcus aureus and MRSA.

Curcumin activates Wnt/β-catenin signaling pathway through inhibiting the activity of GSK-3β in APPswe transfected SY5Y cells

Wnt/β-catenin signaling pathway plays an important role in the genesis and development of Alzheimer's disease. The study aims to investigate the effect of Curcumin on the expression of GSK-3β, β-catenin and CyclinD1 in vitro, which are tightly correlated with Wnt/β-catenin signaling pathway, and also to explore the mechanisms, which will provide a novel therapeutic intervention for treatment of Alzheimer's disease. Plasmid APPswe and BACE1-mychis were transiently co-transfected into SHSY5Y cells by Liposfectamin™2000. The cells were treated with Curcumin at 0, 1.25, 5.0, 20.0 μmol/L for 24 h, or with Curcumin at 5.0 μmol/L for 0, and 12, 24 and 48 h for time course assay. Cell lysates were collected for RT-PCR, Western blot assay and immunofluorescent staining were carried out for detecting the effect of Curcumin on the expression of GSK-3β, β-catenin and CyclinD1. RT-PCR and Western blot results showed that the expression of GSK-3β mRNA and protein significantly decreased in the transfected cells treated with Curcumin, and that the changes were in a dose and time-dependent manner (P<0.05); however, the protein expression of GSK-3β-Ser9 was increased (P<0.05). Meanwhile, the expressions of β-catenin and transcriptional factors CyclinD1 mRNA and protein increased and the changes were also in a dose and time-dependent manner (P<0.05). Immunofluorescent staining results not only confirmed the above changes, but also showed that β-catenin had translocated into the nucleus gradually with the increased dosage of Curcumin. Therefore, GSK-3β is a potential target for treatment of AD. Curcumin could activate the Wnt/β-catenin signaling pathway through inhibiting the expression of GSK-3β and inducing the expression of β-catenin and CyclinD1, which will provide a new theory for treatment of neurodegenerative diseases by Curcumin.

Curcumin decreases amyloid-beta peptide levels by attenuating the maturation of amyloid-beta precursor protein

Alzheimer disease (AD) is a devastating neurodegenerative disease with no cure. The pathogenesis of AD is believed to be driven primarily by amyloid-beta (Abeta), the principal component of senile plaques. Abeta is an approximately 4-kDa peptide generated via cleavage of the amyloid-beta precursor protein (APP). Curcumin is a compound in the widely used culinary spice, turmeric, which possesses potent and broad biological activities, including anti-inflammatory and antioxidant activities, chemopreventative effects, and effects on protein trafficking. Recent in vivo studies indicate that curcumin is able to reduce Abeta-related pathology in transgenic AD mouse models via unknown molecular mechanisms. Here, we investigated the effects of curcumin on Abeta levels and APP processing in various cell lines and mouse primary cortical neurons. We show for the first time that curcumin potently lowers Abeta levels by attenuating the maturation of APP in the secretory pathway. These data provide a mechanism of action for the ability of curcumin to attenuate amyloid-beta pathology.

[Neurodegenerative polyglutamine expansion diseases: physiopathology and therapeutic strategies]

Polyglutamine expansion diseases are adult-onset inherited neurodegenerative disorders that lead to death 10 to 20 years after the first symptoms. Currently, there is no therapy to fight against these diseases. They include Huntington's disease, spinobulbar muscular atrophy, dentatorubral-pallido-luysian atrophy and six types of spino-cerebellar ataxia. The diseases are caused by a unique mutational mechanism: an expansion of the CAG trinucleotide in the corresponding genes coding for an expanded tract of glutamine in the mutated proteins. Polyglutamine expansion confers to the mutant proteins toxic properties that cause neuronal cell death in brain regions specific to each disease. Thanks to cellular and animal models (fly, fish, mouse and rat) of these diseases, we have considerably improved our understanding of the toxic nature of polyglutamine expansion and the physiopathology, and we are now in position to design and test therapeutic strategies to prevent or delay the disease process.

Resveratrol inhibits beta-amyloid oligomeric cytotoxicity but does not prevent oligomer formation

Beta-amyloid (Abeta) aggregation has been strongly associated with the neurodegenerative pathology and a cascade of harmful event rated to Alzheimer's disease (AD). Inhibition of Abeta assembly, destabilization of preformed Abeta aggregates and attenuation of the cytotoxicity of Abeta oligomers and fibrils could be valuable therapeutics of patients with AD. Recent studies suggested that moderate consumption of red wine and intake of dietary polyphenols, such as resveratrol, may benefit AD phenotypes in animal models and reduce the relative risk for AD clinical dementia. To understand the mechanism of this neuroprotection, we studied the effects of resveratrol, an active ingredient of polyphenols in wine and many plants, on the polymerization of Abeta42 monomer, the destabilization of Abeta42 fibril and the cell toxicity of Abeta42 in vitro using fluorescence spectroscopic analysis with thioflavin T (ThT), transmission electron microscope (TEM), circular dichroism (CD) and MTT assay. The results showed that resveratrol could dose-dependently inhibit Abeta42 fibril formation and cytotoxicity but could not prevent Abeta42 oligomerization. The studies by Western-blot, dot-blot and ELISA confirmed that the addition of resveratrol resulted in numerous Abeta42 oligomer formation. In conjunction with the concept that Abeta oligomers are linked to Abeta toxicity, we speculate that aside from potential antioxidant activities, resveratrol may directly bind to Abeta42, interfere in Abeta42 aggregation, change the Abeta42 oligomer conformation and attenuate Abeta42 oligomeric cytotoxicity.

Selective and irreversible inhibitors of mosquito acetylcholinesterases for controlling malaria and other mosquito-borne diseases

New insecticides are urgently needed because resistance to current insecticides allows resurgence of disease-transmitting mosquitoes while concerns for human toxicity from current compounds are growing. We previously reported the finding of a free cysteine (Cys) residue at the entrance of the active site of acetylcholinesterase (AChE) in some insects but not in mammals, birds, and fish. These insects have two AChE genes (AP and AO), and only AP-AChE carries the Cys residue. Most of these insects are disease vectors such as the African malaria mosquito (Anopheles gambiae sensu stricto) or crop pests such as aphids. Recently we reported a Cys-targeting small molecule that irreversibly inhibited all AChE activity extracted from aphids while an identical exposure caused no effect on the human AChE. Full inhibition of AChE in aphids indicates that AP-AChE contributes most of the enzymatic activity and suggests that the Cys residue might serve as a target for developing better aphicides. It is therefore worth investigating whether the Cys-targeting strategy is applicable to mosquitocides. Herein, we report that, under conditions that spare the human AChE, a methanethiosulfonate-containing molecule at 6 microM irreversibly inhibited 95% of the AChE activity extracted from An. gambiae s. str. and >80% of the activity from the yellow fever mosquito (Aedes aegypti L.) or the northern house mosquito (Culex pipiens L.) that is a vector of St. Louis encephalitis. This type of inhibition is fast ( approximately 30 min) and due to conjugation of the inhibitor to the active-site Cys of mosquito AP-AChE, according to our observed reactivation of the methanethiosulfonate-inhibited AChE by 2-mercaptoethanol. We also note that our sulfhydryl agents partially and irreversibly inhibited the human AChE after prolonged exposure (>4 hr). This slow inhibition is due to partial enzyme denaturation by the inhibitor and/or micelles of the inhibitor, according to our studies using atomic force microscopy, circular dichroism spectroscopy, X-ray crystallography, time-resolved fluorescence spectroscopy, and liquid chromatography triple quadrupole mass spectrometry. These results support our view that the mosquito-specific Cys is a viable target for developing new mosquitocides to control disease vectors and to alleviate resistance problems with reduced toxicity toward non-target species.