Amyloid Beta

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.

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.

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.

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.

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

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.

The local heat delivered by metallic nanoparticles selectively attached to their target can be used as a molecular surgery to safely remove toxic and clogging aggregates. We apply this principle to protein aggregates, in particular to the amyloid beta protein (A ) involved in Alzheimer's disease (AD), a neurodegenerative disease where unnaturally folded A proteins self-assemble and deposit forming amyloid fibrils and plaques. We show the possibility to remotely redissolve these deposits and to interfere with their growth, using the local heat dissipated by gold nanoparticles (AuNP) selectively attached to the aggregates and irradiated with low gigahertz electromagnetic fields. Simultaneous tagging and manipulation by AuNP of A at different stages of aggregation allow both, noninvasive exploration and dissolution of molecular aggregates.

To investigate potential dietary risk factors of Alzheimer's disease (AD), triple transgenic (3xTg-AD) mice were exposed from 4 to 13 months of age to diets with a low n-3:n-6 polyunsaturated fatty acid (PUFA) ratio incorporated in either low-fat (5% w/w) or high-fat (35% w/w) formulas and compared with a control diet. The n-3:n-6 PUFA ratio was decreased independently of the dietary treatments in the frontal cortex of 3xTg-AD mice compared to non-transgenic littermates. Consumption of a high-fat diet with a low n-3:n-6 PUFA ratio increased amyloid-␤ (A␤) 40 and 42 concentrations in detergent-insoluble extracts of parieto-temporal cortex homogenates from 3xTg-AD mice. Low n-3:n-6 PUFA intake ratio increased insoluble tau regardless of total fat consumption, whereas high-fat diet incorporating a low n-3:n-6 PUFA ratio also increased soluble tau compared to controls. Moreover, the high-fat diet decreased cortical levels of the postsynaptic marker drebrin, while leaving presynaptic proteins synaptophysin, SNAP-25 and syntaxin 3 unchanged. Overall, these results suggest that high-fat consumption combined with low n-3 PUFA intake promote AD-like neuropathology.

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.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder primarily characterized by excessive deposition of amyloid-␤ (A␤) peptides in the brain. One of the earliest neuropathological changes in AD is the presence of a high number of reactive astrocytes at sites of A␤ deposition. Disturbance of glutamatergic neurotransmission and consequent excitotoxicity is also believed as implicated in the progression of this dementia. Therefore, the study of astrocyte responses to A␤, the main cellular type involved in the maintenance of synaptic glutamate concentrations, is crucial for understanding the pathogenesis of AD. This study aims to investigate the effect of A␤ on the astrocytic glutamate transporters, glutamate transporter-1 (GLT-1) and glutamate-aspartate transporter (GLAST), and their relative participation to glutamate clearance. In addition we have also investigated the involvement of mitogen-activated protein (MAP) kinases in the modulation of GLT-1 and GLAST levels and activity and the putative contribution of oxidative stress induced by A␤ to the astrocytic glutamate transport function. Therefore, we used primary cultures of rat brain astrocytes exposed to A␤ synthetic peptides. The data obtained show that A␤ 1-40 peptide decreased astroglial glutamate uptake capacity in a non-competitive mode of inhibition, assessed in terms of tritium radiolabeled D-aspartate (D-[ 3 H]aspartate) transport. The activity of GLT-1 seemed to be more affected than that of GLAST, and the levels of both transporters were decreased in A␤ 1-40 -treated astrocytes. We demonstrated that MAP kinases, extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase, were activated in an early phase of A␤ 1-40 treatment and the whole pathways differentially modulated the glutamate transporters activity/lev-els. Moreover it was shown that oxidative stress induced by A␤ 1-40 may lead to the glutamate uptake impairment observed. Taken together, our results suggest that A␤ peptide downregulates the astrocytic glutamate uptake capacity and this effect may be in part mediated by oxidative stress and the differential activity and complex balance between the MAP kinase signaling pathways.

Aluminium, an environmentally abundant non-redox trivalent cation has long been implicated in the pathogenesis of Alzheimer’s disease (AD). However, the definite mechanism of aluminium toxicity in AD is not known. Evidence suggests that trace metal homeostasis plays a crucial role in the normal functioning of the brain, and any disturbance in it can exacerbate events associated with AD. The present paper reviews the scientific literature linking aluminium with AD. The focus is on aluminium levels in brain, region-specific and subcellular distribution, its relation to neurofibrillary tangles, amyloid beta, and other metals. A detailed mechanism of the role of aluminium in oxidative stress and cell death is highlighted. The importance of complex speciation chemistry of aluminium in relation to biology has been emphasized. The debatable role of aluminium in AD and the cross-talk between aluminium and genetic susceptibility are also discussed. Finally, it is concluded based on extensive literature that the neurotoxic effects of aluminium are beyond any doubt, and aluminium as a factor in AD cannot be discarded. However, whether aluminium is a sole factor in AD and whether it is a factor in all AD cases still needs to be understood.

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.

Recently, silibinin, a clinically used hepatoprotectant, has been reported to prevent amyloid beta induced memory impairment by reducing oxidative stress and inflammation in mice brain. However, the exact mechanism of neuroprotective effect of silibinin has not been properly studied especially in context of brain energy metabolism and cholinergic functions, the essential factors that undergo impairment in Alzheimer's disease. Therefore, the present study investigated the effect of silibinin on impairment in memory, brain energy metabolism and cholinergic function following intracerebral (IC) streptozotocin (STZ) administration in mice. STZ (0.5 mg/kg), administered twice at an interval of 48 h, caused significant memory impairment tested by Morris water maze. Further, STZ significantly decreased ATP and increased synaptosomal calcium level in mice brain. Increased oxidative and nitrosative stress was also observed in IC STZ injected mice brain. STZ IC induced memory impairment is associated with increased activity and mRNA expression of acetylcholinesterase (AChE) and decreased α-7 nicotinic acetylcholine receptor (α-7-nAChR) mRNA expression in mice brain. Pretreatment with silibinin (100 and 200 mg/kg, po) attenuated STZ induced memory impairment by reducing oxidative and nitrosative stress and synaptosomal calcium ion level. Further, silibinin dose dependently restored ATP level indicating improvement in brain energy metabolism. The activity and mRNA expression of AChE was restored by silibinin. Moreover, α-7-nAChR mRNA expression was significantly increased by silibinin in STZ treated mice brain. The present study clearly demonstrates that beneficial effects of silibinin in STZ induced memory impairment in mice is due to improvement in brain energy metabolism and cholinergic function.► Intracerebral STZ administration. ► Increased oxidative and nitrosative stress. ► Mitochondrial dysfunction and impairment in energy metabolism. ► Cholinergic dysfunction. ► Memory impairment.

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.

The accumulation and deposition of amyloid beta (Aβ) peptide in extracellular dense plaques in the brain is a key phase in Alzheimer's disease (AD). Small oligomeric forms of Aβ are responsible for the toxicity and the early cognitive impairment observed in patients before the amyloid plaque deposits appear. It is essential for the development of an efficient cure for AD to identify compounds that interfere with Aβ aggregation, counteracting the molecular mechanisms involved in conversion of the monomeric amyloid protein into oligomeric and fibrillar forms. Tetracyclines have been proposed for AD therapy, although their effects on the aggregation of Aβ protein, particularly their ability to interact in vivo with the Aβ oligomers and/or aggregates, remain to be understood. Using transgenic Caenorhabditis elegans as a simplified invertebrate model of AD, we evaluated the ability of tetracyclines to interfere with the sequence of events leading to Aβ proteotoxicity. The drugs directly interact with the Aβ assemblies in vivo and reduce Aβ oligomer deposition, protecting C. elegans from oxidative stress and the onset of the paralysis phenotype. These effects were specific, dose-related and not linked to any antibiotic activity, suggesting that the drugs might offer an effective therapeutic strategy to target soluble Aβ aggregates.

Metal ions like Cu(II) and Zn(II) are accumulated in Alzheimer’s disease amyloid plaques. The amyloid-β (Aβ) peptide involved in the disease interacts with these metal ions at neutral pH via ligands provided by the N-terminal histidines and the N-terminus. The present study uses high-resolution NMR spectroscopy to monitor the residue-specific interactions of Cu(II) and Zn(II) with 15N- and 13C,15N-labeled Aβ(1–40) peptides at varying pH levels. At pH 7.4 both ions bind to the specific ligands, competing with one another. At pH 5.5 Cu(II) retains its specific histidine ligands, while Zn(II) seems to lack residue-specific interactions. The low pH mimics acidosis which is linked to inflammatory processes in vivo. The results suggest that the cell toxic effects of redox active Cu(II) binding to Aβ may be reversed by the protective activity of non-redox active Zn(II) binding to the same major binding site under non-acidic conditions. Under acidic conditions, the protective effect of Zn(II) may be decreased or changed, since Zn(II) is less able to compete with Cu(II) for the specific binding site on the Aβ peptide under these conditions.

show 6-to 60-fold Nova-dependent effects on alternative splicing. The magnitude of Nova's effect on alternative splicing of these transcripts is unprecedented in mammals (26). Moreover, each of these genes are expressed both within and outside the brain, and previous work has identified exons preferentially used (or excluded) in the brain. Our results indicate that Nova is the primary, if not sole, determinant of brainspecific alternative splicing of these and perhaps other transcripts.

The amyloid beta (Abeta) peptide is responsible for toxic amyloid plaque formation and is central to the aetiology of Alzheimer's disease (AD). It is generated by proteolytic processing of the amyloid precursor protein (APP) by beta-secretase (BACE-1) and gamma-secretase. Consequently, inhibition of BACE-1, a rate-limiting enzyme in the production of Abeta, is an attractive therapeutic approach to the treatment of Alzheimer's disease. This paper reports on improved microtiter plate-based fluorescence and colorimetric assays for the high-throughput screening (HTS) of BACE-1 inhibitors achieved by employing, for the first time, casein fluorescein isothiocyanate (casein-FITC) and N-α-benzoyl-D,L-arginine p-nitroanilide (BAPNA) as substrates, since they are known to be readily available and convenient substrates for proteases. The methods are based on the fluorescence enhancement following casein-FITC proteolysis and the visible absorbance of the p-nitroaniline (pNA) produced by BAPNA hydrolysis, with both reactions catalysed by BACE-1. Casein-FITC is a high-affinity substrate (K m =110 nM) for BACE-1, more so than the Swedish (SW) type peptide (a peptide containing the Swedish mutant of APP, a familiar mutation that enhances Abeta production). BACE-1 catalysis of casein-FITC proteolysis exhibited Michaelis-Menten kinetic. Therefore, it was found that BACE-1 was saturable with casein-FITC that was processed in a time-and pHdependent manner with greater catalytic efficiency than observed for the SW peptide. The enantioselective hydroly-sis of L-BAPNA by BACE-1 was observed. L-BAPNA was hydrolysed ten times more efficiently by BACE-1 than the WT (wild-type peptide). The novel methods were validated using a FRET assay as an independent reference method. Therefore, in order to select new leads endowed with multifunctional activities, drugs for Alzheimer's disease (AD)-potent acetylcholinesterase (AChE) inhibitorswere tested for BACE-1 inhibition using the proposed validated assays. Among these, donepezil, besides being an acetylcholinesterase inhibitor, was also found to be a BACE-1 inhibitor that displayed submicromolar potency (170 nM).

The beta amyloid (A␤) protein is a key molecule in the pathogenesis of Alzheimer's disease (AD). The tendency of the A␤ peptide to aggregate, its reported neurotoxicity, and genetic linkage studies, have led to a hypothesis of AD pathogenesis that many AD researchers term the amyloid cascade hypothesis. In this hypothesis, an increased production of A␤ results in neurodegeneration and ultimately dementia through a cascade of events. In the past 15 years, debate amongst AD researchers has arisen as to whether A␤ is a cause or an effect of the pathogenic process. Recent in vitro and in vivo research has consolidated the theory that A␤ is the primary cause, initiating secondary events, culminating in the neuropathological hallmarks associated with AD. This research has led to the development of therapeutic agents, currently in human clinical trials, which target A␤.

The receptor for advanced glycation end products (RAGE) is thought to be a primary transporter of -amyloid across the blood-brain barrier (BBB) into the brain from the systemic circulation, while the low-density lipoprotein receptor-related protein (LRP)-1 mediates transport of -amyloid out of the brain. To determine whether there are Alzhei-mer's disease (AD)-related changes in these BBBassociated -amyloid receptors, we studied RAGE, LRP-1, and -amyloid in human elderly control and AD hippocampi. In control hippocampi, there was robust RAGE immunoreactivity in neurons, whereas microvascular staining was barely detectable. LRP-1 staining, in contrast, was clearly evident within microvessels but only weakly stained neurons. In AD cases, neuronal RAGE immunoreactivity was signiWcantly decreased. An unexpected Wnding was the strongly positive microvascular RAGE immunoreactivity. No evidence for colocalization of RAGE and -amyloid was seen within either microvessels or senile plaques. A reversed pattern was evident for LRP-1 in AD. There was very strong staining for LRP-1 in neurons, with minimal microvascular staining. Unlike RAGE, colocalization of LRP-1 and -amyloid was clearly present within senile plaques but not microvessels. Western blot analysis revealed a much higher concentration of RAGE protein in AD hippocampi as compared with controls. Concentration of LRP-1 was increased in AD hippocampi, likely secondary to its colocalization with senile plaques. These data conWrm that AD is associated with changes in the relative distribution of RAGE and LRP-1 receptors in human hippocampus. They also suggest that the proportion of amyloid within the brains of AD patients that is derived from the systemic circulation may be signiWcant.

The present study assessed the influence of dietary lipids on accumulation of amyloid beta-peptide (AB) in the brain. Seven experimental diets with varying n-6/n-3-ratio, saturated and polyunsaturated fatty acid and cholesterol contents were fed to transgenic APPswe/PS1dE9 mice for 3 -4 months beginning at a young adult age (6 months). Hippocampal AB levels were determined with ELISA and plaque load by using immunocytochemistry. A typical Western diet with 40% saturated fatty acids and 1% of cholesterol increased, while diets supplemented with docosahexaenoic acid (DHA) decreased AB levels compared to regular (soy oil based) diet. DHA diet also decreased the number of activated microglia in hippocampus and increased exploratory activity of transgenic mice, but did not improve their spatial learning in the water maze. The favorable effect of DHA on AB production was verified in two different cell lines. Regulation of dietary lipid intake may offer a new tool to reduce the risk of Alzheimer's disease at the population level. D

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.

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.

In the last decade surface plasmon resonance (SPR) biosensors have made great strides both in terms of technology and its applications. SPR biosensors have become a central tool for study of molecular interactions and have been widely used for detection of chemical and biological analytes. Food analysis belongs to major areas of potential applications of SPR biosensors. Therefore, numerous SPR biosensors for detection of analytes implicated in food safety (e.g. pathogens, toxins, drug residues, vitamins, hormones, chemical contaminants, and allergens) have been developed. This paper reviews recent developments in the field of SPR biosensors for food safety, in particular, for detection of foodborne pathogens and toxins.

The present review focuses on the utility of a canine model in evaluating nutritional interventions for age-related cognitive dysfunction. Aged dogs demonstrate progressive cognitive decline with concurrent amyloid-beta pathology that parallels the pathology observed in aging humans. Dogs, therefore, provide a natural model of human pathological aging. We have and are in the process of evaluating several nutritional-based interventions aimed at preventing cognitive decline and brain aging. In a three-year longitudinal study, we examined the effects of a diet enriched with antioxidants and mitochondrial cofactors on several measures of cognition and brain aging. Compared to controls, aged dogs on the enriched diet demonstrated both short-and long-term cognitive benefits, as well decreased deposition of amyloid-beta protein. The diet also reduced behavioral signs associated with canine Cognitive Dysfunction Syndrome when assessed in veterinary clinical trials. We also have preliminary evidence suggesting a beneficial effect of a proprietary blend of docosahexaenoic acid and phospholipids on both cognitive and physiological measures. Collectively, our data indicate (1) that the dog, either in the laboratory or in the clinic, provides an important tool for assessing nutritional interventions and (2) that combination interventions aimed at several mechanisms of pathological aging may prove more effective than single nutritive components in human trials.

Hippocampal atrophy as assessed by magnetic resonance imaging (MRI) and abnormal cerebrospinal fluid (CSF) biomarkers are supportive features for the diagnosis of Alzheimer's disease (AD) and are assumed to be indirect pathological markers of the disease. In AD patients, antemortem MRI hippocampal volumes (HVs) correlate with the density of neurofibrillary tangles (but not with senile plaques) at autopsy suggesting that HVs may better correlate with CSF tau and hyperphosphorylated tau (P-tau) levels than CSF amyloid beta protein (A␤) 42 level. Here, we tested this hypothesis in a well-defined AD group. Patients were selected according to the New Research Criteria for AD, including specific episodic memory deficit and CSF AD profile (defined as abnormal ratio of A␤ 42 :tau). MRI was performed within 6 months of lumbar puncture. HVs were obtained using automated segmentation software. Thirty-six patients were included. Left HV correlated with CSF tau (R ϭ Ϫ0.53) and P-tau (R ϭ Ϫ0.56) levels. Mean HVs correlated with the CSF P-tau level (R ϭ Ϫ0.52). No correlation was found between any brain measurement and CSF A␤ 42 level. The CSF tau and P-tau levels, but not the CSF A␤ 42 level, correlated with HV, suggesting that CSF tau markers reflect the neuronal loss associated with the physiopathological process of AD.

Alzheimer's disease (AD) is a neurodegenerative disorder occurring in the elderly. It is widely accepted that the amyloid beta peptide (Ab) aggregation and especially the oligomeric states rather than fibrils are involved in AD onset. We used infrared spectroscopy to provide structural information on the entire aggregation pathway of Ab(1-40), starting from monomeric Ab to the end of the process, fibrils. Our structural study suggests that conversion of oligomers into fibrils results from a transition from antiparallel to parallel b-sheet. These structural changes are described in terms of H-bonding rupture/formation, b-strands reorientation and b-sheet elongation. As antiparallel b-sheet structure is also observed for other amyloidogenic proteins forming oligomers, reorganization of the b-sheet implicating a reorientation of b-strands could be a generic mechanism determining the kinetics of protein misfolding. Elucidation of the process driving aggregation, including structural transitions, could be essential in a search for therapies inhibiting aggregation or disrupting aggregates.

The beta-amyloid hypothesis of Alzheimer's Disease (AD) has dominated the thinking and research in this area for over a decade and a half. While there has been a great deal of effort in attempting to prove its centrality in this devastating disease, and while an enormous amount has been learned about its properties (e.g., putative toxicity, processing and signaling), A␤ has not proven to be both necessary and sufficient for the development, neurotoxicity, and cognitive deficits associated with this disease. Instead, the few treatments that are available have emerged from aging research and are primarily directed toward modification of acetylcholine levels. Clearly, it is time to rethink this position and to propose instead that future approaches should focus upon altering the age-related sensitivity of the neuronal environment to insults involving such factors as inflammation and oxidative stress. In other words "solve the problems of aging and by extension those of AD will also be reduced." This review is being submitted as a rather Lutherian attempt to "nail an alternative thesis" to the gate of the Church of the Holy Amyloid to open its doors to the idea that aging is the most pervasive element in this disease and A␤ is merely one of the planets.

Transthyretin (TTR), a carrier protein for thyroxine and retinol in plasma and cerebrospinal fluid (CSF), has been shown to bind the amyloid beta peptide. Accordingly, TTR has been suggested to protect against amyloid beta deposition, a key pathological feature in Alzheimer's disease (AD). Supporting this view are the reduced TTR levels found in CSF of patients with AD, as well as reports of altered TTR expression in the cortex and hippocampus of AD rodent models. Importantly, early characterization of TTR distribution revealed the choroid plexus as the site of TTR synthesis within the brain. To resolve this controversy we used precise laser microdissection technology to assay for TTR mRNA expression. Our results clearly demonstrate that TTR is not produced in the brain parenchyma of wild-type mice nor in two different transgenic mouse models of AD, suggesting that contamination by choroid plexus contributed to the recent results indicating TTR production in various brain regions. The relevance of TTR to AD should now take into consideration TTR production by the choroid plexus and its ability, in the CSF, to sequester the amyloid beta peptide.

The local heat delivered by metallic nanoparticles selectively attached to their target can be used as a molecular surgery to safely remove toxic and clogging aggregates. We apply this principle to protein aggregates, in particular to the amyloid beta protein (A ) involved in Alzheimer's disease (AD), a neurodegenerative disease where unnaturally folded A proteins self-assemble and deposit forming amyloid fibrils and plaques. We show the possibility to remotely redissolve these deposits and to interfere with their growth, using the local heat dissipated by gold nanoparticles (AuNP) selectively attached to the aggregates and irradiated with low gigahertz electromagnetic fields. Simultaneous tagging and manipulation by AuNP of A at different stages of aggregation allow both, noninvasive exploration and dissolution of molecular aggregates.

A vaccine targeting the amyloid-beta (A␤) peptide is a promising potential immunotherapy for Alzheimer's disease patients. However, experience from a recent clinical trial of a candidate A␤ vaccine has suggested that it is important to develop techniques to induce high titer antibodies against A␤ associated with vaccine efficacy while reducing the T cell responses against A␤ 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 Q␤ bacteriophage-based A␤ vaccines. Immunization with A␤ conjugated to VLPs or Q␤ elicited anti-A␤ antibody responses at low doses and without the use of adjuvants. The flexibility of these virus-based display systems allowed us to link and induce antibodies against short A␤-derived peptides from the amino-and carboxyl-termini of the peptide. Immunization of mice with A␤ peptide in combination with Freund's adjuvant elicited predominantly IgG2c antibodies and strong T cell proliferative responses against A␤. In contrast, VLP-conjugated A␤ peptides elicited more balanced isotype responses, dominated by IgG1. Both VLP and Q␤-based A␤ vaccines induced weak or negligible T cell responses against A␤. T cell responses were largely directed against linked viral epitopes. Taken together, virus-based vaccines that allow the presentation of A␤ in a repetitive dense array are new and potentially more effective vaccine candidates for Alzheimer's disease.

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.

Cerebral amyloid beta (Aβ) deposition occurs in a substantial fraction of cognitively normal (CN) older individuals. However, it has been difficult to reliably detect evidence of amyloid-related cognitive alterations in CN using standard neuropsychological measures. We sought to determine whether a highly demanding face-name associative memory exam (FNAME) could detect evidence of Aβ-related memory impairment in CN. We studied 45 CN subjects (mean age = 71.7 ± 8.8) with Clinical Dementia Rating (CDR) scores = 0 and MMSE ≥ 28, using Positron Emission Tomography with Pittsburgh Compound B (PiB PET). Memory factor scores were derived from a principal components analysis for FNAME name retrieval (FN-N), FNAME occupation retrieval (FN-O) and the 6-Trial Selective Reminding Test (SRT). Using multiple linear and logistic regression analyses, we related the memory factor scores to PiB distribution volume ratios (DVR, cerebellar reference) as either a continuous or a dichotomous variable in frontal cortex and a posterior cortical region representing the precuneus, posterior cingulate and lateral parietal cortices (PPCLP), co-varying for age and AMNART IQ (a proxy of cognitive reserve (CR)). A significant inverse relationship for FN-N was found with Aβ deposition in frontal (R 2 = .29, β = −2.2, p = 0.02) and PPCLP cortices (R 2 = .26, β = −2.4, p = 0.05). In contrast, neither FN-O nor the SRT were significantly related to Aβ deposition. Performance on a demanding test of face-name associative memory was related to Aβ burden in brain regions associated with memory systems. Associative memory for faces and names, a common complaint among older adults, may be a sensitive marker of early Aβ-related impairment.

Amyloid b (Ab) aggregates are considered as possible targets for therapy and/or diagnosis of Alzheimer disease (AD). It has been previously shown that curcumin targets Ab plaques and interferes with their formation, suggesting a potential role for prevention or treatment of AD. Herein, a click chemistry method was used to generate nanoliposomes decorated with a curcumin derivative, designed to maintain the planar structure required for interaction with Ab, as directly confirmed by Surface Plasmon Resonance experiments. Another type of liposomes was formed starting from curcumin-phospholipid conjugate, in which the planar structure of curcumin is disrupted. Both types of generated curcumindecorated vesicles had mean diameters in the nano range (131e207 nm) and slightly negative z-potential values according to their lipid composition, and were stable for periods up to 20 days. They also demonstrated high integrity during incubation in presence of plasma proteins. Surface Plasmon Resonance experiments, measuring the binding of flowing liposomes to immobilized Ab1-42, indicated that the liposomes exposing the curcumin derivative (maintaining the planarity) have extremely high affinity for Ab1-42 fibrils (1e5 nM), likely because of the occurrence of multivalent interactions, whereas those exposing non-planar curcumin did not bind to Ab1-42. In summary, we describe here the preparation and characterization of new nanoparticles with a very high affinity for Ab1-42 fibrils, to be exploited as vectors for the targeted delivery of new diagnostic and therapeutic molecules for AD.