Amyloid Beta

Previous studies suggest membrane binding is a key determinant of amyloid β (Aβ) neurotoxicity. However, it is unclear whether this interaction is receptor driven. To address this issue, a D-handed enantiomer of Aβ42 (D-Aβ42) was synthesized and its biophysical and neurotoxic properties were compared to the wild-type Aβ42 (L-Aβ42). The results showed D- and L-Aβ42 are chemically equivalent with respect to copper binding, generation of reactive oxygen species and aggregation profiles. Cell binding studies show both peptides bound to cultured cortical neurons. However, only L-Aβ42 was neurotoxic and inhibited long term potentiation indicating L-Aβ42 requires a stereospecific target to mediate toxicity. We identified the lipid phosphatidylserine, as a potential target. Annexin V, which has very high affinity for externalized phosphatidylserine, significantly inhibited L-Aβ42 but not D-Aβ42 binding to the cultured cortical neurons and significantly rescued L-Aβ42 neurotoxicity. This suggests that Aβ mediated toxicity in Alzheimer disease is dependent upon Aβ binding to phosphatidylserine on neuronal cells.

One of the theories involved in the etiology of Alzheimer's disease (AD) is the oxidative stress hypothesis. The amyloid bpeptide (Ab), a hallmark in the pathogenesis of AD and the main component of senile plaques, generates free radicals in a metal-catalyzed reaction inducing neuronal cell death by a reactive oxygen species mediated process which damage neuronal membrane lipids, proteins and nucleic acids. Therefore, the interest in the protective role of dierent antioxidants in AD such as vitamin E, melatonin and estrogens is growing up. In this review we summarize data that support the involvement of oxidative stress as an active factor in Ab-mediated neuropathology, by triggering or facilitating neurodegeneration, through a wide range of molecular events that disturb neuronal cell homeostasis. 7

Valeriana officinalis have been used in traditional medicine for its sedative, hypnotic, and anticonvulsant effects. There are several eports in the literature supporting a GABAergic mechanism of action for valerian. The rationale of the present work is based on the concept that by decreasing neuronal network excitability valerian consumption may contribute to neuroprotection. The aim of our investigation was to evaluate the neuroprotective effects ofV. officinalis against the toxicity induced by amyloid beta peptide 25–35 [Aβ(25–35)]. Cultured rat hip-pocampal neurons were exposed to Aβ(25–35)(25 μM) for 24–48 h,after which morphological and biochemical properties were evaluated. The neuronal injury evoked by Aβ, which includes a decrease in cell educing capacity and associated neuronal degeneration, was prevented by valerian extract. Analysis of intracellular free calcium ([Ca2+]i)indicated that the neuroprotective mechanisms may involve the inhibition of excess influx of Ca2+ following neuronal injury. Moreover, membrane peroxidation in rat hippocampal synaptosomes was evaluated, and our data indicate that valerian extract partially inhibited ascorbate/iron-induced peroxidation. In conclusion we show evidence that the signalling pathways involving [Ca2+]i and the redox state of the cells may play a central ole in the neuroprotective properties ofV. officinalis extract against Aβ toxicity. The novelty of the findings of the present work, indicating neuroprotective properties of valerian against Aβ toxicity may, at the long-term, contribute to introduction of a new elevant use of valerian alcoholic extract to prevent neuronal degeneration in aging or neurodegenerative disorders.

Nicastrin is a protein recently discovered associated to presenilins and involved in the production of amyloid beta peptide that accumulates in Alzheimer's disease (AD) brain. In this study the nicastrin gene was examined for unknown mutations and polymorphisms in 104 patients with familial AD (52 early-onset and 52 late-onset), 174 sporadic AD and 191 healthy neurological controls of Italian origin. The scanning of the nicastrin gene identified a missense mutation (N417Y) in two patients with sporadic AD, in an early-onset familial AD and in a young control subject. Furthermore, we found two silent mutations and four intronic polymorphisms, three of them co-segregating in a single haplotype. We found some differences in the distribution of genotype alterations in the AD population compared to the controls. However, our data together with other evidence did not support the pathological role of missense mutation N417Y.

We describe the genetic analysis of an Alzheimer's disease (AD) sample derived from a genetically isolated population. Genetic assessment included the analysis of genes involved in AD, such as the genes for amyloid precursor protein (APP), presenilin 1 (PSEN1) and presenilin 2 (PSEN2). We also assessed genes for some proteins that constitute the ␥-secretase complex: nicastrin (NCSTN), presenilin enhancer-2 (PEN2), in addition to the AD risk factor apolipoprotein E (APOE). Using polymerase chain reaction and single strand conformational polymorphism method, screens for APP, PSEN1 and PSEN2 genes revealed one mutation in PSEN1. Furthermore, we found an intronic +17G > C polymorphism in PEN2 which, in homozygous form, was greater in early onset Alzheimer's disease (EOAD) compared to controls, and one haplotype in the NCSTN gene which was linked to EOAD and familial AD (FAD). Finally, the genotyping of APOE confirmed that the 4 allele could be a risk factor for the onset of AD, in particular for FAD subjects. In conclusion, these results show the existence of Sardinian genetic peculiarities, essential in studies regarding genetically inherited and multifactorial disorders, as AD.

Alzheimer's disease (AD) brains are characterized by extensive oxidative stress. Additionally, large depositions of amyloid beta-peptide (Abeta) are observed, and many researchers opine that Abeta is central to the pathogenesis of AD. Our laboratory combined these two observations in a comprehensive model for neurodegeneration in AD brains centered around Abeta-induced oxidative stress. Given the oxidative stress in AD and its potentially important role in neurodegeneration, considerable research has been conducted on the use of antioxidants to slow or reverse the pathology and course of AD. One source of antioxidants is the diet. This review examines the literature of the effects of endogenous and exogenous, nutritionally-derived antioxidants in relation to AD. In particular, studies of glutathione and other SH-containing antioxidants, vitamins, and polyphenolic compounds and their use in AD and modulation of Abeta-induced oxidative stress and neurotoxicity are reviewed.

Dysregulated lipid and cholesterol homeostasis in the body, and particularly in the brain,has been demonstrated in neurodegenerative diseases such as Alzheimer’s disease (AD), as well as Parkinson’s disease (PD) and Huntington’s disease (HD). These changes in
lipidmetabolismmay be a consequence of the disease process, or part of the pathogenic mechanism, or both. More importantly perhaps, with respect to AD, is the mounting evidence that dyslipidaemia helps to drive production or reduce clearance of Aβ, the amyloidogenic peptide believed to be central in AD pathogenesis. Furthermore, other
dyslipidaemia-related conditions have also been linked to AD pathogenesis, including obesity, hypertension, inflammation, insulin resistance, and type 2 diabetes. Apart from advancing age, the carriage of one or two copies of the APOE 𝜀4 alleles is one of the
biggest risk factors for developing late-onset (sporadic) AD. The product of this gene is apoE, a protein involved in the transport of lipids. Possession of APOE 𝜀4 alleles also predisposes individuals to a higher risk of cardiovascular disease. Here we discuss lipid
and cholesterol metabolism, and we give an overview of the various lipid and cholesterol metabolic pathways and changes that have been linked toAD, particularly the influence of the different forms of apoE on lipid, cholesterol, and Aβ metabolism.

Lipids play an important part as risk or protective factors for Alzheimer's disease. This review summarizes the current findings in which lipids influence Alzheimer's disease and introduces the molecular mechanism how these lipids are linked to amyloid production. Besides the pathological impact of amyloid in Alzheimer's disease, amyloid has a physiological function in regulating lipid homeostasis in return. The understanding of the resulting regulatory cycles between amyloid precursor protein processing and lipids provides a platform for the development of new causal therapeutic approaches for Alzheimer's disease.

The b-amyloid peptide (Ab) is widely considered to be the molecule that causes Alzheimer's disease (AD). Besides this pathological function of Ab, recently published data reveal that Ab also has an essential physiological role in lipid homeostasis. Cholesterol increases Ab production, and conversely Ab production causes a decrease in cholesterol synthesis. The latter appears to be mediated by the inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), a key enzyme in cholesterol synthesis, in an action similar to that of statins. Moreover, Ab regulates sphingolipid metabolism by directly activating sphingomyelinases (SMases). This review summarizes the molecular basis for the known physiological functions of Ab and amyloid precursor protein (APP), the roles of Ab and APP in lipid homeostasis and the medical implications of addressing lipid homeostasis in respect to AD. This knowledge might provide new insights for current and future therapeutic approaches to AD.

Extensive evidence suggests that the self-assembly of amyloid-beta peptide (Ab) is a nucleation-dependent process that involves the formation of several oligomeric intermediates. Despite neuronal toxicity being recently related to Ab soluble oligomers, results from aggregation studies are often controversial, mainly because of the low reproducibility of several experimental protocols. Here a multimethodological study that included atomic force microscopy (AFM), transmission electron microscopy (TEM), fluorescence microscopy (FLM), mass spectrometry techniques (matrix-assisted laser desorption/ionization time-of-flight [MALDI-TOF] and electrospray ionization quadrupole time-of-flight [ESI-QTOF]), and direct thioflavin T (ThT) fluorescence spectroscopy were enabled to set up a reliable and highly reproducible experimental protocol for the characterization of the morphology and dimension of Ab 1-42 (Ab42) aggregates along the self-assembly pathway. This multimethodological approach allowed elucidating the diverse assembly species formed during the Ab aggregation process and was applied to the detailed investigation of the mechanism of Ab42 inhibition by myricetin. In particular, a very striking result was the molecular weight determination of the initial oligomeric nuclei by MALDI-TOF, composed of up to 10 monomers, and their morphology by AFM.

Alzheimer's disease (AD), the most common neurodegenerative disorder, which affects more than 35 million people worldwide, is characterized by a massive accumulation of tangles and amyloid plaques. Several risk factors linked to lipid homeostasis have been identified. Apolipoprotein E (ApoE), which also has a strong impact in coronary artery disease, is besides aging the most prominent risk factor in sporadic AD. High levels of lipoproteins and cholesterol increase the risk of AD and some cholesterol lowering drugs like statins seem to correlate with a reduced risk for dementia. Moreover, cholesterol increases amyloid β (Aβ) production, which is derived from amyloid precursor protein (APP) by proteolytic processing. Beside cholesterol, other lipids that strongly modulate APP processing could be identified and interestingly the APP cleavage products itself regulate lipid homeostasis resulting in complex regulatory feedback cycles. Here, we review the mechanistic link of cholesterol and sphingolipid homeostasis and APP processing and the consequence of this bidirectional link for and in AD. Although cholesterol is the best studied brain lipid in AD, many other lipids are involved in the Aβ-lipid regulatory system and some of these lipids exceed the cholesterol effect on Aβ production [1][2]. This involvement is bidirectional. On the one hand, lipids control APP processing and, on the other hand, APP processing controls the levels of several key lipids . Beside the physiological function of APP processing in lipid homeostasis, under pathological conditions like AD, these regulating (feedback-) cycles are dysfunctional. Additionally, mutual influence of lipids and APP processing raises the question if altered lipid homeostasis is the cause or consequence of AD.

There is a growing body of evidence to support a role for oxidative stress in Alzheimer's disease (AD), with increased levels of lipid peroxidation, DNA and protein oxidation products (HNE, 8-HO-guanidine and protein carbonyls respectively) in AD brains. The brain is a highly oxidative organ consuming 20% of the body's oxygen despite accounting for only 2% of the total body weight. With normal ageing the brain accumulates metals ions such iron (Fe), zinc (Zn) and copper (Cu). Consequently the brain is abundant in antioxidants to control and prevent the detrimental formation of reactive oxygen species (ROS) generated via Fenton chemistry involving redox active metal ion reduction and activation of molecular oxygen. In AD there is an over accumulation of the Amyloid β peptide (Aβ), this is the result of either an elevated generation from amyloid precursor protein (APP) or inefficient clearance of Aβ from the brain. Aβ can efficiently generate reactive oxygen species in the presence of the transition metals copper and iron in vitro. Under oxidative conditions Aβ will form stable dityrosine cross-linked dimers which are generated from free radical attack on the tyrosine residue at position 10. There are elevated levels of urea and SDS resistant stable linked Aβ oligomers as well as dityrosine cross-linked peptides and proteins in AD brain. Since soluble Aβ levels correlate best with the degree of degeneration [C.A. McLean, R.A. Cherny, F.W. Fraser, S.J. Fuller, M.J. Smith, K. Beyreuther, A.I. Bush, C.L. Masters, Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer's disease, Ann. Neurol. 46 (1999) 860–866] we suggest that the toxic Aβ species corresponds to a soluble dityrosine cross-linked oligomer. Current therapeutic strategies using metal chelators such as clioquinol and desferrioxamine have had some success in altering the progression of AD symptoms. Similarly, natural antioxidants curcumin and ginkgo extract have modest but positive effects in slowing AD development. Therefore, drugs that target the oxidative pathways in AD could have genuine therapeutic efficacy.

Mounting evidence is demonstrating roles for the amyloid precursor protein (APP) and its proteolytic product Ab in metal homeostasis. Furthermore, aberrant metal homeostasis is observed in patients with Alzheimer's disease (AD), and this may contribute to AD pathogenesis, by enhancing the formation of reactive oxygen species and toxic Ab oligomers and facilitating the formation of the hallmark amyloid deposits in AD brain. Indeed, zinc released from synaptic activity has been shown to induce parenchymal and cerebrovascular amyloid in transgenic mice. On the other hand, abnormal metabolism of APP and Ab may impair brain metal homeostasis as part of the AD pathogenic process. Ab and APP expression have both been shown to decrease brain copper (Cu) levels, whereas increasing brain Cu availability results in decreased levels of Ab and amyloid plaque formation in transgenic mice. Lowering Cu concentrations can downregulate the transcription of APP, strengthening the hypothesis that APP and Ab form part of the Cu homeostatic machinery in the brain. This is a complex pathway, and it appears that when the sensitive metal balance in the brain is sufficiently disrupted, it can lead to the self-perpetuating pathogenesis of AD. Clinical trials are currently studying agents that can remedy abnormal Ab-metal interactions.

Alzheimer's disease (AD) is the principal cause of dementia in older people, and accumulation of amyloidbeta (Aβ) peptide is a crucial event in AD pathogenesis. Despite opposite results found in literature, increased evidence posits that high cholesterol levels enhance the risk to develop AD. In fact, cholesterol metabolism and catabolism are affected in this neurodegenerative disorder. Since amyloid precursor protein (APP) processing and subsequent Aβ production are dependent on membrane cholesterol content and on levels of isoprenoid intermediates in the cholesterol biosynthesis pathway, changes in cholesterol might have different consequences on Aβ formation. These pieces of evidence support that inhibitors of cholesterol synthesis, like statins, could have a therapeutic role in AD. Many studies about the effect of statins use in AD show conflicting results; however, some authors explain it by the differences in administrated doses. Recent studies demonstrate that statins can efficiently decrease Aβ formation from APP and be neuroprotective against the peptide toxicity. Because of the high number of pleiotropic effects of statins, novel molecular mechanisms that account for the beneficial effect of these drugs on AD might be discovered in a near future.

FK506 binding proteins (FKBPs), also called immunophilins, are prolyl-isomerases (PPIases) that participate in a wide variety of cellular functions including hormone signaling and protein folding. Recent studies indicate that proteins that contain PPIase activity can also alter the processing of Alzheimer's Amyloid Precursor Protein (APP). Originally identified in hematopoietic cells, FKBP52 is much more abundantly expressed in neurons, including the hippocampus, frontal cortex, and basal ganglia. Given the fact that the high molecular weight immunophilin FKBP52 is highly expressed in CNS regions susceptible to Alzheimer's, we investigated its role in Ab toxicity. Towards this goal, we generated Ab transgenic Drosophila that harbor gain of function or loss of function mutations of FKBP52. FKBP52 overexpression reduced the toxicity of Ab and increased lifespan in Ab flies, whereas loss of function of FKBP52 exacerbated these Ab phenotypes. Interestingly, the Ab pathology was enhanced by mutations in the copper transporters Atox1, which interacts with FKBP52, and Ctr1A and was suppressed in FKBP52 mutant flies raised on a copper chelator diet. Using mammalian cultures, we show that FKBP52 (2/2) cells have increased intracellular copper and higher levels of Ab. This effect is reversed by reconstitution of FKBP52. Finally, we also found that FKBP52 formed stable complexes with APP through its FK506 interacting domain. Taken together, these studies identify a novel role for FKBP52 in modulating toxicity of Ab peptides. Citation: Sanokawa-Akakura R, Cao W, Allan K, Patel K, Ganesh A, et al. (2010) Control of Alzheimer's Amyloid Beta Toxicity by the High Molecular Weight Immunophilin FKBP52 and Copper Homeostasis in Drosophila. PLoS ONE 5(1): e8626.

We reviewed the literature for disease-specific markers in cerebrospinal fluid (CSF) and evaluated their diagnostic and prognostic relevance in neurological diseases. High tau protein in combination with low amyloid b levels has a high sensitivity (80%) and specificity (90%) for AlzheimerÕs disease (AD) against normal aging and can predict conversion of mild cognitive impairment to AD. The detection of 14-3-3 has a high sensitivity (80-90%) and specificity (90%) for the diagnosis of CJD. Low or undetectable CSF hypocretin-1 (orexin-1) levels constitute a diagnostic biomarker for narcolepsy with cataplexy. Detection of beta-2-transferrin indicates CSF contamination in oto-and rhinorrhoe with a sensitivity of >79% at a specificity of 95% similar to the beta-trace protein (sensitivity >90%, specificity 100%). However, beta-trace protein is faster and cheaper to perform. Possible future biomarkers are: elevated levels of vascular endothelial growth factor are relatively sensitive (51-100%) and specific (73-100%) for leptomeningeal metastases from solid tumors and are associated with a poor prognosis in this condition. Elevated CSF neurofilament (Nf) levels probably reflect acute neuronal degeneration. The prognostic value of CSF Nf levels is highest in acute conditions such as subarachnoid hemorrhage, acute optic neuritis and neuromyelitis optica.

Since the discovery of the significance of the cholesterol-carrying apolipoprotein E and cholesterolaemia as major risk factors for Alzheimer's Disease (AD) there has been a mounting interest in the role of this lipid as a possible pathogenic agent. In this review we analyse the current evidence linking cholesterol metabolism and regulation in the CNS with the known mechanisms underlying the development of Alzheimer's Disease. Cholesterol is known to affect amyloid-b generation and toxicity, although it must be considered that the results studies using the statin class of drugs to lower plasma cholesterol may be affected by other effects associated with these drugs. Finally, we report some of our results pointing at the interplay between neurons and astrocytes and NADPH oxidase activation as a new candidate mechanism linking cholesterol and AD pathology.

A vaccine targeting the amyloid-beta (Abeta) peptide is a promising potential immunotherapy for Alzheimer's disease patients. However, experience from a recent clinical trial of a candidate Abeta vaccine has suggested that it is important to develop techniques to induce high titer antibodies against Abeta associated with vaccine efficacy while reducing the T cell responses against Abeta that were potentially responsible for serious side effects. We have previously demonstrated that immunization with self- and foreign antigens arrayed in a repetitive fashion on the surface of virus-like particles (VLPs) induces high titer antibody responses at low doses and in the absence of potentially inflammatory adjuvants. In this study, we examined the antibody and T cell responses upon immunization with human papillomavirus VLP- and Qbeta bacteriophage-based Abeta vaccines. Immunization with Abeta conjugated to VLPs or Qbeta elicited anti-Abeta antibody responses at low doses and without th...

Amyloid b (Ab) aggregates are considered as possible targets for therapy and/or diagnosis of Alzheimer disease (AD), and nanoparticles functionalized with Ab-specific ligands are considered promising vehicles for imaging probes and therapeutic agents. Herein, we characterized the binding properties of nanoliposomes decorated with an anti-Ab monoclonal antibody (Ab-MAb). The Ab-MAb was obtained in mice by immunization with Ab antigen followed by hybridoma fusion. Surface Plasmon Resonance (SPR) studies confirmed the very high affinity of purified Ab-MAb for both Ab monomers and fibrils (K D ¼ 0.08 and 0.13 nM, respectively). The affinity of the biotinylated Ab-MAb, used thereafter for liposome decoration, was lower although still in the low nanomolar range (K D ¼ 2.1 and 1.6 nM, respectively). Biotin-streptavidin ligation method was used to decorate nanoliposomes with Ab-MAb, at different densities. IgG-decorated liposomes were generated by the same methodology, as control. Vesicles were monodisperse with mean diameters 124e134 nm and demonstrated good colloidal stability and integrity when incubated with serum proteins. When studied by SPR, Ab-MAb-liposomes, but not IgG-liposomes, markedly bound to Ab monomers and fibrils, immobilized on the chip. K D values (calculated on Ab-MAb content) were about 0.5 and 2 nM with liposomes at high and low Ab-MAb density, respectively. Ab-MAbliposome binding to Ab fibrils was additionally confirmed by ultracentrifugation technique, in which interactions occur in solution under physiological conditions. Moreover, Ab-MAb-liposomes bound amyloid deposits in post-mortem AD brain samples, confirming the potential of these nanoparticles for the diagnosis and therapy of AD.

Huntington’s disease (HD) is a progressive neurodegenerative disorder associated with selective neuronal cell death. Abnormal aggregation of huntingtin protein with polyQ expansion has been shown to be causally linked to HD. Grape seed polyphenolic extract (GSPE) is a natural compound that has previously been shown to interfere with aggregations of proteins involved in neurological disorders, such as amyloid beta peptides (Aβ) and Tau protein. In this study we found that GSPE treatment significantly inhibits polyQ aggregation in phaeochromocytoma (PC)-12 cell line containing an ecdysone-inducible protein comprising the first 17 amino acid of huntingtin plus 103 glutamines fused with enhanced GFP. In vivo feasibility studies using the Q93httexon1 drosophila model of HD, we extended our in vitro evidence and found that flies fed with GSPE had a significantly improved lifespan compared to the control flies. Using the R6/2 rodent model of HD, we found that oral administration of 100 mg/kg/day GSPE (equivalent to 500mg per day in human) significantly attenuated the motor skill decay as well as extended the lifespan in the R6/2 mice relative to vehicle-control mice. Collectively, our studies strongly suggest that GSPE might be able to modulate the onset and/or progression of HD.

Age has a powerful effect on enhanced susceptibility to neurodegenerative diseases, including susceptibility to stroke and cognitive impairment (CI) even in optimally healthy individuals. We critically evaluated the notion that oxidative stress increases in aging brain. Rigorous studies show logarithmic age-dependent increases in oxidized proteins and oxidized DNA lesions. Decreased activity of antioxidant protective enzymes does not account for the observed increases. The reactivity of the lipid oxidation product 4-hydroxy-2-nonenal (HNE) with key mitochondria enzymes may be important in the age-dependent loss in energy generation and enhanced susceptibility of neurons to apoptosis. Age-dependent enhanced neuroinflammatory processes may play an important role in toxin generation that causes death or dysfunction of neurons in neurodegenerative diseases. Non-steroidal anti-inflammatory drugs (NSAIDs) show significant promise. Vitamin E supplementation did not show major beneficial ef...

A point mutation of G to C at codon 693 of the amyloid-beta (A␤) precursor protein gene results in Glu to Gln substitution at position 22 of the A␤ (A␤Q22) associated with hereditary cerebrovascular amyloidosis with hemorrhage Dutch type. Factors that regulate A␤Q22 levels in the central nervous system (CNS) are largely unknown. By using ventriculo-cisternal perfusion technique in guinea pigs, we demonstrated that clearance from the cerebrospinal fluid and transport from the CNS to blood of [ 125 I]-A␤Q22 (1 nM) were reduced by 36% and 52%, respectively, in comparison to the wild type A␤ 1-40 peptide. In contrast to significant uptake and transport of A␤ 1-40 across the brain capillaries and leptomeningeal vessels, A␤Q22 was not taken up at these CNS vascular transport sites, which was associated with its 53% greater accumulation in the brain. The CNS clearance of A␤ 1-40 was half-saturated at 23.6 nM; A␤Q22 had about 6.8-fold less affinity for the CNS efflux transporters and its elimination relied mainly on transport across the choroid plexus. Thus, the Dutch mutation impairs elimination of A␤ from brain by reducing its rapid transport across the blood-brain barrier and the vascular drainage pathways, which in turn may result in accumulation of the peptide around the blood vessels and in brain.

Alzheimer's disease is a multifactorial neurodegenerative disorder characterized by the pathological brain deposition of neurofibrillary tangles and senile plaques. The latter consist mainly of insoluble b-amyloid (Ab) fibril deposition. Ab aggregation and deposition can be increased by several factors, including metal ions. In this study we investigated the role played by metal ions in affecting Ab oligomerization in the presence and in the absence of its hydrophobic fragment Ab 17-28 . This was done not as a physiological investigation, but as a paradigmatic study to confirm the key role of Ab superficial hydrophobicity as a relevant aggravating factor that contributes to the toxicity of Ab and Ab-metal complexes. The structural conformations of Ab-metal complexes were monitored through fluorescence and turbidity measurements as well as transmission electron microscopy. Results reported herein indicate that various metals differentially influence Ab conformation, with aluminum being the only metal ion for which we are able to determine a dramatic enhancement of peptide oligomer formation with a consequent toxic effect. This scenario was further enhanced by the presence of Ab 17-28 , which resulted in a marked toxicity in a neuroblastoma cell culture as a consequence of the enhancement of the hydrophobicity of the amyloid and amyloid-metal complexes.

Objectives: The aim of this study was to investigate transthyretin (prealbumin) effects on Aβ 25-35 -induced cytotoxicity. Design and methods: In view of the well-recognized literature data demonstrating that Aβ 25-35 fibrillar aggregates cause in vitro cytotoxicity to human red blood cells and apoptotic changes to SK-N-BE neuroblastoma cells in cultures (ultrastructural evidence), we tested transthyretin effects on these two experimental models.

Alzheimer's disease (AD) is the most common type of dementia in the elderly. Products of oxidative and nitrosative stress (OS and NS, respectively) accumulate with aging, which is the main risk factor for AD. This provides the basis for the involvement of OS and NS in AD pathogenesis. OS and NS occur in biological systems due to the dysregulation of the redox balance, caused by a deficiency of antioxidants and/or the overproduction of free radicals. Free radical attack against lipids, proteins, sugars and nucleic acids leads to the formation of bioproducts whose detection in fluids and tissues represents the currently available method for assessing oxidative/nitrosative damage. Post-mortem and in-vivo studies have demonstrated an accumulation of products of free radical damage in the central nervous system and in the peripheral tissues of subjects with AD or mild cognitive impairment (MCI). In addition to their individual role, biomarkers for OS and NS in AD are associated with altered bioenergetics and amyloidbeta (Ab) metabolism. In this review we discuss the main results obtained in the field of biomarkers of oxidative/nitrosative stress in AD and MCI in humans, in addition to their potential role as a tool for diagnosis, prognosis and treatment efficacy in AD. ß

Oxidative stress may have an important role in the progression of neurodegenerative disorders such as Alzheimer's disease (AD) and prion diseases. Oxidative damage could result from interactions between highly reactive transition metals such as copper (Cu) and endogenous reducing and/or oxidizing molecules in the brain. One such molecule, homocysteine, a thiol-containing amino acid, has previously been shown to modulate Cu toxicity in HeLa and endothelial cells in vitro. Due to a possible link between hyperhomocysteinemia and AD, we examined whether interaction between homocysteine and Cu could potentiate Cu neurotoxicity. Primary mouse neuronal cultures were treated with homocysteine and either Cu (II), Fe (II or III) or Zn (II). Homocysteine was shown to selectively potentiate toxicity from low micromolar concentrations of Cu. The toxicity of homocysteine/Cu coincubation was dependent on the ability of homocysteine to reduce Cu (II) as re¯ected by the inhibition of toxicity with the Cu (I)-speci®c chelator, bathocuproine disulphonate. This was supported by data showing that homocysteine reduced Cu (II) more effectively than cysteine or methionine but did not reduce Fe (III) to Fe (II). Homocysteine also generated high levels of hydrogen peroxide in the presence of Cu (II) and promoted Ab/Cu-mediated hydrogen peroxide production and neurotoxicity. The potentiation of metal toxicity did not involve excitotoxicity as ionotropic glutamate receptor antagonists had no effect on neurotoxicity. Homocysteine alone also had no effect on neuronal glutathione levels. These studies suggest that increased copper and/or homocysteine levels in the elderly could promote signi®cant oxidant damage to neurons and may represent additional risk factor pathways which conspire to produce AD or related neurodegenerative conditions.

Dehydroepiandrosterone sulfate (DHEAS) has been reported to improve memory in aged animals and suggested as a treatment for age-related dementias. The SAMP8 mouse, a model of Alzheimer's disease, has an age-related impairment in learning and memory and an increase in brain levels of amyloid precursor protein (APP) and amyloid beta protein (Ah). Male SAMP8 mice also have a decrease in testosterone, to which DHEA is a precursor. Diabetes has been suggested as a model of aging and to be linked to Alzheimer's disease. Diabetics can have memory deficits and lower DHEAS levels. Here, we examined the effects of chronic oral DHEAS on acquisition and retention for T-maze footshock avoidance in 12 mo male SAMP8 mice and in CD-1 mice with streptozocin-induced diabetes. Learning and memory were improved in aged SAMP8 mice, but not in CD-1 mice with streptozocin-induced diabetes. These findings suggest that DHEAS is more effective in reversing the cognitive impairments associated with overexpression of Ah than with diabetes. Published by Elsevier Inc.

Aggregation of proteins in tissues is associated with several diseases, including Alzheimer's disease. It is characterized by the accumulation of amyloid β peptide (Aβ) in the extracellular spaces of the brain cells, resulting in neuronal death and other pathological changes. α-Crystallin, a small heat-shock protein in lens, and a peptide chaperone having the functional site sequence DFVIFLDVKHFSPEDLTVK of αA-crystallin may inhibit Aβ fibrillogenesis and toxicity. The peptide chaperone (mini-αA-crystallin), having an Aβ interacting domain and a complex solubilizing domain, was shown in previous studies to prevent aggregation of several proteins under denaturing conditions. In this in vitro study, using transmission electron microscopy and thioflavin T binding assay, we show that mini-αA-crystallin arrests the fibril formation of Aβ peptides. Mini-αA-crystallin also suppresses the toxic action of Aβ on rat pheochromocytoma (PC12) cells. The wide chaperoning capability of the peptide and its ability to inhibit amyloid fibril formation and suppress toxicity suggest that mini-αA-crystallin may serve as a universal chaperone in controlling diseases of protein aggregation, including Alzheimer's disease. (Mol Cell Biochem 267: [147][148][149][150][151][152][153][154][155] 2004)

The reliable diagnostic identification of neuropsychiatric disorders such as schizophrenia, bipolar disease, and depression has been associated with some biological markers (genomics, proteomics, metabolomics) but to date, these markers do not have the sensitivity/specificity of a diagnostic test. Biomarker tests that are relevant to global chronic disease are now applicable to neuropsychiatric diseases to prevent autoimmune disease, endoplasmic reticulum stress associated mitophagy with relevance to neuron apoptosis. Metabolic abnormalities has been linked to neuropsychiatric disorder with the careful nutritional assessment of patients reported in many published studies. Early interventions with genomic medicine now assist in the prevention of autoimmune disease associated with global chronic disease and neuropsychiatric disorders. Functional foods that contain appropriate doses of activators will allow modulation of neuropsychiatric diseases at the nuclear receptor level with the maintenance of neuron endoplasmic reticulum stress and the prevention of mitophagy associated with accelerated neurodegeneration.

Nutritional therapy has become important to drug metabolism and treatment with the calorie sensitive gene Sirtuin 1 (Sirt 1) shown to be critical to the prevention of non alcoholic fatty liver disease (NAFLD) with the activation of hepatic drug metabolism. Indian spices have been used extensively in healthy diets in the developing and developed countries for the prevention of NAFLD, diabetes and Alzheimer's disease. Experimental evidence with relevance to ingestion of Indian spices (mg/day) is limited in various countries. Curcumin intake (mg/ day) an amyloid beta aggregation inhibitor for the treatment of Alzheimer's disease should be carefully controlled to prevent mitophagy and NAFLD. Indian spices that contain Sirt 1 activators such as cinnamon should be consumed to maintain hepatic drug and spice metabolism with the prevention of insulin resistance. Excessive intake of various Indian spices should be avoided to maintain the therapeutic properties of curcumin and cinnamon and to prevent spice-drug or drug-drug interactions. Data on safety and toxicity of Indian spices may indicate that toxic curcumin effects may be related to over ingestion of various Indian spices relevant to drug induced mitochondrial toxicity in NAFLD, diabetes and neurodegenerative diseases.

We demonstrate that A␤ 1-42 but not the reverse protein A␤ 42-1 or A␤ 1-40 stimulated cAMP formation and this stimulation was inhibited by selective ␤AR antagonists in mouse primary cortical astrocytes. A␤ 1-42 significantly increased apoE levels which were significantly inhibited by the ␤AR selective antagonists with the greatest inhibition observed with the ␤ 2 antagonist. Separate lines of evidence have suggested that agonist-induced stimulation of ␤ARs and increases in apoE abundance may serve a neuroprotective role in astrocytes. Our results indicate a potential interaction between ␤ARs and apoE which may contribute to reducing A␤ 1-42 neurotoxicity.

The interaction between PD1 on T lymphocytes and PD-L1 on antigen presenting cells (APC) modulates the balance between inflammation and tolerance by inducing IL-10 production and apoptosis of antigen-specific cells. We analyzed the PD1/PD-L1 pathway, annexin V (AV)-expression, and proliferation in amyloid-beta (A␤)-stimulated PBMC of patients with Alzheimer's disease (AD) (N ϭ 35) or mild cognitive impairment (MCI) (N ϭ 30) and of age-matched healthy controls (HC; N ϭ 30). Results showed that PD1-expressing CD4 ϩ T cells, density of PD-L1 on CD14 ϩ APC, IL-10 production, and PD-L1-expressing/IL-10-producing CD14 ϩ APC were significantly reduced in AD and MCI patients compared to HC. A␤-stimulated PD1/AV-expressing (apoptotic) CD4 ϩ T cells were also diminished, whereas proliferation was augmented in AD and MCI patients compared to controls. Finally, incubation of cells with PD-L1-neutralizing antibodies significantly decreased apoptosis of A␤-specific CD4 ϩ T lymphocytes. An impairment of the PD-L1/PD1 pathway is present in AD and MCI. Such alteration results in reduced IL-10 production and diminished apoptosis of A␤-specific CD4 ϩ T lymphocytes; these phenomena could play a role in the neuroinflammation accompanying AD.

Oxidative stress plays a significant role in the pathogenesis of Alzheimer's disease (AD), a devastating disease of the elderly. The brain is more vulnerable than other organs to oxidative stress, and most of the components of neurons (lipids, proteins, and nucleic acids) can be oxidized in AD due to mitochondrial dysfunction, increased metal levels, infl ammation, and β-amyloid (Aβ) peptides. Oxidative stress participates in the development of AD by promoting Aβ deposition, tau hyperphosphorylation, and the subsequent loss of synapses and neurons. The relationship between oxidative stress and AD suggests that oxidative stress is an essential part of the pathological process, and antioxidants may be useful for AD treatment.

The pathologic lesions of Alzheimer's disease (AD) are characterized by accumulation of protein aggregates consisting of intracellular or extracellular misfolded proteins. The amyloid-β (Aβ) protein accumulates extracellularly in senile plaques and cerebral amyloid angiopathy, whereas the hyperphosphorylated tau protein accumulates intracellularly as neurofibrillary tangles. "Professional chaperones", such as the heat shock protein family, have a function in the prevention of protein misfolding and subsequent aggregation. "Amateur" chaperones, such as apolipoproteins and heparan sulfate proteoglycans, bind amyloidogenic proteins and may affect their aggregation process. Professional and amateur chaperones not only colocalize with the pathological lesions of AD, but may also be involved in conformational changes of Aβ, and in the clearance of Aβ from the brain via phagocytosis or active transport across the blood-brain barrier. Thus, both professional and amateur chaperones may be involved in the aggregation, accumulation, persistence, and clearance of Aβ and tau and in other Aβ-associated reactions such as inflammation associated with AD lesions, and may, therefore, serve as potential targets for therapeutic intervention.

Huntington’s disease (HD) is a progressive neurodegenerative disorder associated with selective neuronal cell death. Abnormal aggregation of huntingtin protein with polyQ expansion has been shown to be causally linked to HD. Grape seed polyphenolic extract (GSPE) is a natural compound that has previously been shown to interfere with aggregations of proteins involved in neurological disorders, such as amyloid beta peptides (Aβ) and Tau protein. In this study we found that GSPE treatment significantly inhibits polyQ aggregation in phaeochromocytoma (PC)-12 cell line containing an ecdysone-inducible protein comprising the first 17 amino acid of huntingtin plus 103 glutamines fused with enhanced GFP. In vivo feasibility studies using the Q93httexon1 drosophila model of HD, we extended our in vitro evidence and found that flies fed with GSPE had a significantly improved lifespan compared to the control flies. Using the R6/2 rodent model of HD, we found that oral administration of 100 mg/kg/day GSPE (equivalent to 500mg per day in human) significantly attenuated the motor skill decay as well as extended the lifespan in the R6/2 mice relative to vehicle-control mice. Collectively, our studies strongly suggest that GSPE might be able to modulate the onset and/or progression of HD.

Amyloid-β peptide (Aβ) is considered a triggering agent of Alzheimer's disease. In relation to a therapeutic treatment of the disease, the interaction of Aβ with the cell membrane has to be elucidated at the molecular level to understand its mechanism of action. In previous works, we had ascertained by neutron diffraction on stacked lipid multilayers that a toxic fragment of Aβ is able to penetrate and perturb the lipid bilayer. Here, the influence of Aβ(1-42), the most abundant Aβ form in senile plaques, on unilamellar lipid vesicles of phospholipids is investigated by small-angle neutron scattering. We have used the recently proposed separated form factor method to fit the data and to obtain information about the vesicle diameter and structure of the lipid bilayer and its change upon peptide administration. The lipid membrane parameters were obtained with different models of the bilayer profile. As a result, we obtained an increase in the vesicle radii, indicating vesicle fusion. This effect was particularly enhanced at pH 7.0 and at a high peptide/lipid ratio. At the same time, a thinning of the lipid bilayer occurred. A fusogenic activity of the peptide may have very important consequences and may contribute to cytotoxicity by destabilizing the cell membrane. The perturbation of the bilayer structure suggests a strong interaction and/or insertion of the peptide into the membrane, although its localization remains beyond the limit of the experimental resolution.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

Understanding the pathogenicity of amyloid-beta (Aβ) peptides constitutes a major goal in research on Alzheimer’s disease (AD). One hypothesis entails that Aβ peptides induce uncontrolled, neurotoxic ion flux through cellular membranes. The exact biophysical mechanism of this ion flux is, however, a subject of an ongoing controversy which has attenuated progress toward understanding the importance of Aβ-induced ion flux in AD. The work presented here addresses two prevalent controversies regarding the nature of transmembrane ion flux induced by Αβ peptides. First, the results clarify that Αβ can induce stepwise ion flux across planar lipid bilayers as opposed to a gradual increase in transmembrane current; they show that the previously reported gradual thinning of membranes with concomitant increase in transmembrane current arises from residues of the solvent hexafluoroisopropanol, which is commonly used for the preparation of amyloid samples. Second, the results provide additional evidence suggesting that Aβ peptides can induce ion channel-like ion flux in cellular membranes that is independent from the postulated ability of Αβ to modulate intrinsic cellular ion channels or transporter proteins.

We evaluated pathomechanisms and systemic manifestations of Alzheimer disease (AD), an aging-related dementing neurodegenerative disorder, by expression profiling. Blood mononuclear cell (BMC) transcriptomes of sporadic AD subjects and aged-matched normal elderly controls (NEC) were compared using the human NIA microarray.