[Show abstract][Hide abstract] ABSTRACT: ß-amyloid (Aß1-42) is produced by proteolytic cleavage of the transmembrane type-1 protein, amyloid precursor protein. Under pathological conditions, Aß1-42self-aggregates into oligomers, which cause synaptic dysfunction and neuronal loss, and are considered the culprit of Alzheimer's disease (AD). However, Aß1-42 is mainly monomeric at physiological concentrations, and the precise role of monomeric Aß1-42 in neuronal function is largely unknown. We report that the monomer of Aß1-42 activates type-1 insulin-like growth factor receptors and enhances glucose uptake in neurons and peripheral cells by promoting the translocation of the Glut3 glucose transporter from the cytosol to the plasma membrane. In neurons, activity-dependent glucose uptake was blunted after blocking endogenous Aß production, and re-established in the presence of cerebrospinal fluid Aß. APP-null neurons failed to enhance depolarization-stimulated glucose uptake unless exogenous monomeric Aß1-42 was added. These data suggest that Aß1-42 monomers were critical for maintaining neuronal glucose homeostasis. Accordingly, exogenous Aß1-42 monomers were able to rescue the low levels of glucose consumption observed in brain slices from AD mutant mice.
[Show abstract][Hide abstract] ABSTRACT: A new Cu(i) probe (), bearing an alkyl-pyridinium moiety to get complete water solubility, was synthesized. Fluorescence titrations support copper binding and high selectivity in a water solution whereas formation of aggregates was excluded by DOSY experiments. The detection capability for intracellular Cu(i), especially localized in mitochondria, was demonstrated in differentiated neuroblastoma cells by confocal microscopy.
Chemical Communications 05/2014; 50(96):9835-9838. DOI:10.1039/c4cc02147a · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The human islet polypeptide (hIAPP) or amylin is a 37-residue peptide hormone secreted by β-cells of the islet of Langerhans in the pancreas. Unlike the rat variant of IAPP (rIAPP), human amylin is highly amyloidogenic and is found as amyloid deposits in nearly 95% of patients afflicted with type 2 diabetes mellitus (T2DM). Human and rat IAPP have nearly identical primary sequence differing at only six positions which are encompassed within the 17-29 aminoacid region. Using Circular Dichroism (CD), Dynamic Light Scattering (DLS) and ThT-fluorescence (Th-T), we examined the aggregation properties of both full-length hIAPP1-37 and the related peptide fragment hIAPP17-29. For the sake of comparison, similar experiments were carried out on the respective rat variants rIAPP1-37 and rIAPP17-29. These studies were conducted at physiological pH in buffered solution not containing fluorinated co-solvents as well as in the presence of model membranes (LUV). In addition, the cytotoxic activity of the investigated peptides was determined toward different pancreatic β-cell lines. All the peptide studied in this work resulted cytotoxic despite β-sheet structure being observed, in vitro, for the hIAPP1-37 only. This suggests that β-sheet conformational transition that generally precedes the fibril formation, is not a prerequisite for toxicity towards β-cells. Interestingly, confocal microscopy indicated that the IAPP peptides can enter the cell and might exert their toxic action at an intracellular level.
European Journal of Medicinal Chemistry 05/2014; 81C:442-455. DOI:10.1016/j.ejmech.2014.05.038 · 3.45 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A new turn-on Cu2+ fluorescent sensor (CST) having a trehalose moiety, which confers a relatively large solubility in water, has been synthesized. The chemosensor is therefore suitable for studies in aqueous solution. Full potentiometric and UV-vis characterization evidence that at physiological pH CST forms with Cu2+ a species with a 1:1 stoichiometry allowing for a straightforward correlation between CST response and copper(II) concentration. The presence of the trehalose unit does not negatively affect the selectivity of CST for Cu2+ over a series of metal ions of interest as proven by fluorescence measurements. The novel chemosensor, tested in differentiated neuroblastoma SH-SY5Y cells, is able to detect Cu2+ in the extracellular region, as well as to track copper transfer processes upon cell stimulation induced by cellular depolarization.
[Show abstract][Hide abstract] ABSTRACT: The interaction between lipid vesicles and NGF(1-14) peptide, mimicking nerve growth factor, was addressed to fabricate peptide-associated supported lipid bilayers (SLBs). According to a model of predominant electrostatic interactions, zwitterionic and anionic lipid vesicles were used to optimize the peptide association with the lipid membranes. Both planar silica and core-shell nanoparticles (NPs) were used as polar hydrophilic substrates to form the SLBs functionalized with the NGF peptide. The hybrid biointerface was scrutinized by a multitechnique approach with QCM-D, FRAP and fluorescence spectroscopy in terms of self-assembling kinetics, lipid lateral diffusion, and energy transfer processes in the SLB-wrapped silica NPs dye-doped in the core. The response of neuronal cells to the NGF(1-14)-SLBs highlighted their promising application as a drug delivery nanoplatform for ageing-related diseases.
[Show abstract][Hide abstract] ABSTRACT: A new naphthalimide derivative bearing a tetrathia-azacrown for high affinity and selective binding to Cu(+) was synthesised. Copper recognition properties in solution were evaluated using (1)H NMR and fluorescence spectroscopy. Live cell imaging by confocal microscopy highlighted the capabilities of the new sensor for the two-wavelength detection of intracellular monovalent copper in neuronal cells.
Chemical Communications 05/2013; 49(49). DOI:10.1039/c3cc42069h · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease is the most common form of dementia among older people and is still untreatable. While β-amyloid protein is recognized as the disease determinant with a pivotal role in inducing neuronal loss and dementia, an impaired brain insulin signaling seems to account in part for the cognitive deficit associated with the disease. The origin of this defective signaling is uncertain. Accumulating toxic species of β-amyloid, the so-called oligomers, has been proposed to be responsible for downregulation of neuronal insulin receptors. We have found that the nontoxic form of β-amyloid, the monomer, is able to activate insulin/insulin-like growth factor-1 (IGF-1) receptor signaling and thus behaves as a neuroprotectant agent. Our suggestion is that depletion of β-amyloid monomers, occurring in the preclinical phase of Alzheimer's disease, might be the cause of early insulin/IGF-1 signaling disturbances that anticipate cognitive decline.
[Show abstract][Hide abstract] ABSTRACT: Amyloid-Beta (Aβ) is a major constituent of senile plaques and one of the principle hallmarks of Alzheimer's disease (AD). The peptide is produced by proteolytic cleavage of the larger amyloid precursor protein (APP). Increased production and aggregation of the peptide are associated with pathology. Emerging evidence suggests that the steady-state levels of Aβ are determined by the balance between its production and degradation. For this reason, the tuning of the activity of enzymes that degrade Aβ may be a promising approach in the development of novel therapeutics aimed at reducing Aβ concentration by enhancing its removal. A great part of Aβ degrading enzymes are known to be metalloproteases. In the last decade increasing evidence supported the idea that metal ion homeostasis is affected in several regions of AD brain and metals play an important role in tuning enzyme activity. There are three main different pathways by which metal ions can affect the proteolytic enzymes responsible for Aβ peptides degradation, as metal ions can: (i) form complexes with Aβ peptides that are not easily degraded; (ii) directly bind to degradative enzymes; (iii) produce signalling cascades that alter enzymes activity involved in Aβ catabolism. In the current literature the three points mentioned above are very often puzzled, resulting in a quite fragmentary scenario. The aim of this work is to find a link between metal ion homeostasis and Aβ degradation by separating and analysing the three different pathways proposed.
[Show abstract][Hide abstract] ABSTRACT: 8-Hydroxyquinolines are systems of great interest in the field of inorganic and bioinorganic chemistry. They are metal-binding compounds and are known to exhibit a variety of biological activities, such as antibacterial and anticancer activities. Among these systems, clioquinol has been the focus of a renewed interest in recent years. In this scenario, we synthesized and characterized the new clioquinol glucoconjugate, 5-chloro-7-iodo-8-quinolinyl-β-D-glucopyranoside in order to compare this system to that of clioquinol. We also synthesized, 8-quinolinyl-β-D-glucopyranoside, an 8-hydroxyquinoline glucoconjugate. The reason for the development of glucoconjugates is the glucose avidity, and the over-expression of glucose transporters in cancer cells. Here we demonstrate that glycoconjugates are cleaved in vitro by β-glucosidase and these systems exhibit antiproliferative activity against different tumor cell lines in the presence of copper(II) ions.
[Show abstract][Hide abstract] ABSTRACT: Anabolic-androgenic steroid (AAS) abuse is associated with multiple neurobehavioral disturbances. The sites of action and the neurobiological sequels of AAS abuse are unclear at present. We investigated whether two different AASs, nandrolone and methandrostenolone, could affect neuronal survival in culture. The endogenous androgenic steroid testosterone was used for comparison. Both testosterone and nandrolone were neurotoxic at micromolar concentrations, and their effects were prevented by blockade of androgen receptors (ARs) with flutamide. Neuronal toxicity developed only over a 48-hr exposure to the steroids. The cell-impermeable analogues testosterone-BSA and nandrolone-BSA, which preferentially target membrane-associated ARs, were also neurotoxic in a time-dependent and flutamide-sensitive manner. Testosterone-BSA and nandrolone-BSA were more potent than their parent compounds, suggesting that membrane-associated ARs were the relevant sites for the neurotoxic actions of the steroids. Unlike testosterone and nandrolone, toxicity by methandrostenolone and methandrostenolone-BSA was insensitive to flutamide, but it was prevented by the glucocorticoid receptor (GR) antagonist RU-486. Methandrostenolone-BSA was more potent than the parent compound, suggesting that its toxicity relied on the preferential activation of putative membrane-associated GRs. Consistently with the evidence that membrane-associated GRs can mediate rapid effects, a brief challenge with methandrostenolone-BSA was able to promote neuronal toxicity. Activation of putative membrane steroid receptors by nontoxic (nanomolar) concentrations of either nandrolone-BSA or methandrostenolone-BSA became sufficient to increase neuronal susceptibility to the apoptotic stimulus provided by β-amyloid (the main culprit of AD). We speculate that AAS abuse might facilitate the onset or progression of neurodegenerative diseases not usually linked to drug abuse.
Journal of Neuroscience Research 04/2011; 89(4):592-600. DOI:10.1002/jnr.22578 · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dual orthosteric agonists of metabotropic glutamate 2 (mGlu2) and mGlu3 receptors are being developed as novel antipsychotic agents devoid of the adverse effects of conventional antipsychotics. Therefore, these drugs could be helpful for the treatment of psychotic symptoms associated with Alzheimer's disease (AD). In experimental animals, the antipsychotic activity of mGlu2/3 receptor agonists is largely mediated by the activation of mGlu2 receptors and is mimicked by selective positive allosteric modulators (PAMs) of mGlu2 receptors. We investigated the distinct influence of mGlu2 and mGlu3 receptors in mixed and pure neuronal cultures exposed to synthetic β-amyloid protein (Aβ) to model neurodegeneration occurring in AD. The mGlu2 receptor PAM, N-4'-cyano-biphenyl-3-yl)-N-(3-pyridinylmethyl)-ethanesulfonamide hydrochloride (LY566332), devoid of toxicity per se, amplified Aβ-induced neurodegeneration, and this effect was prevented by the mGlu2/3 receptor antagonist (2S,1'S,2'S)-2-(9-xanthylmethyl)-2-(2'-carboxycyclopropyl)glycine (LY341495). LY566332 potentiated Aβ toxicity regardless of the presence of glial mGlu3 receptors, but it was inactive when neurons lacked mGlu2 receptors. The dual mGlu2/3 receptor agonist, (-)-2-oxa-4-aminobicyclo[3.1.0]exhane-4,6-dicarboxylic acid (LY379268), was neuroprotective in mixed cultures via a paracrine mechanism mediated by transforming growth factor-β1. LY379268 lost its protective activity in neurons grown with astrocytes lacking mGlu3 receptors, indicating that protection against Aβ neurotoxicity was mediated entirely by glial mGlu3 receptors. The selective noncompetitive mGlu3 receptor antagonist, (3S)-1-(5-bromopyrimidin-2-yl)-N-(2,4-dichlorobenzyl)pyrrolidin-3-amine methanesulfonate hydrate (LY2389575), amplified Aβ toxicity on its own, and, interestingly, unmasked a neurotoxic activity of LY379268, which probably was mediated by the activation of mGlu2 receptors. These data indicate that selective potentiation of mGlu2 receptors enhances neuronal vulnerability to Aβ, whereas dual activation of mGlu2 and mGlu3 receptors is protective against Aβ-induced toxicity.
[Show abstract][Hide abstract] ABSTRACT: One hundred years of study have identified beta-Amyloid (A beta) as the most interesting feature of Alzheimer's disease (AD). Since the discovery of A beta as the principal component of amyloid plaques, the central challenge in AD research has been the understanding of A beta involvement in the neurodegenerative process of the disease. The ability of A beta to undergo conformational changes and subsequent aggregation has always been a limiting factor in finding out the activities of the peptide. Extensive research has been carried out to study the molecular mechanisms of amyloid self-assembly. The finding that soluble Abeta concentrations in the brain are correlated with the severity of AD, whereas fibrillar density is not /40,42/, has pointed attention toward the oligomeric forms of Abeta, which are generally considered the most toxic and, therefore, the most important species to be addressed. Despite great efforts in basic AD research, none of the currently available treatments is able to treat the devastating effects of the disease, leading to the consideration that there is more to reason than just A beta production and aggregation. Here we summarize the emerging evidence for the physiological functions of A beta, including our recent demonstration that A beta monomers are endowed with neuroprotective activity, and propose that A beta aggregation might contribute to AD pathology through a "loss-of-function" process. Finally, we discuss the current therapeutics targeting the cerebral load of A beta and possible new ones aimed at preserving the biological functions of A beta.
Reviews in the neurosciences 01/2010; 21(2):83-93. DOI:10.1515/REVNEURO.2010.21.2.83 · 3.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer's disease (AD) is a neurodegenerative disorder that affects more than 37 million people worldwide. Current drugs for AD are only symptomatic, but do not interfere with the underlying pathogenic mechanisms of the disease. AD is characterized by the presence of ß-amyloid (Aβ) plaques, neurofibrillary tangles, and neuronal loss. The identification of the molecular determinants underlying AD pathogenesis is a fundamental step to design new disease-modifying drugs. Recently, a specific impairment of transforming-growth-factor-β1 (TGF-β1) signaling pathway has been demonstrated in AD brain. The deficiency of TGF-β1 signaling has been shown to increase both Aβ accumulation and Aβ-induced neurodegeneration in AD models. The loss of function of TGF-ß1 pathway seems also to contribute to tau pathology and neurofibrillary tangle formation. Growing evidence suggests a neuroprotective role for TGF-β1 against Aβ toxicity both in vitro and in vivo models of AD. Different drugs, such as lithium or group II mGlu receptor agonists are able to increase TGF-β1 levels in the central nervous system (CNS), and might be considered as new neuroprotective tools against Aβ-induced neurodegeneration. In the present review, we examine the evidence for a neuroprotective role of TGF-β1 in AD, and discuss the TGF-β1 signaling pathway as a new pharmacological target for the treatment of AD.
[Show abstract][Hide abstract] ABSTRACT: The 42-aa-long beta-amyloid protein--Abeta(1-42)--is thought to play a central role in the pathogenesis of Alzheimer's disease (AD) (Walsh and Selkoe, 2007). Data from AD brain (Shankar et al., 2008), transgenic APP (amyloid precursor protein)-overexpressing mice (Lesné et al., 2006), and neuronal cultures treated with synthetic Abeta peptides (Lambert et al., 1998) indicate that self-association of Abeta(1-42) monomers into soluble oligomers is required for neurotoxicity. The function of monomeric Abeta(1-42) is unknown. The evidence that Abeta(1-42) is present in the brain and CSF of normal individuals suggests that the peptide is physiologically active (Shoji, 2002). Here we show that synthetic Abeta(1-42) monomers support the survival of developing neurons under conditions of trophic deprivation and protect mature neurons against excitotoxic death, a process that contributes to the overall neurodegeneration associated with AD. The neuroprotective action of Abeta(1-42) monomers was mediated by the activation of the PI-3-K (phosphatidylinositol-3-kinase) pathway, and involved the stimulation of IGF-1 (insulin-like growth factor-1) receptors and/or other receptors of the insulin superfamily. Interestingly, monomers of Abeta(1-42) carrying the Arctic mutation (E22G) associated with familiar AD (Nilsberth et al., 2001) were not neuroprotective. We suggest that pathological aggregation of Abeta(1-42) may also cause neurodegeneration by depriving neurons of the protective activity of Abeta(1-42) monomers. This "loss-of-function" hypothesis of neuronal death should be taken into consideration when designing therapies aimed at reducing Abeta burden.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 09/2009; 29(34):10582-7. DOI:10.1523/JNEUROSCI.1736-09.2009 · 6.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Estrogen receptor alpha (ERalpha) is over-expressed in reactive glia under conditions of neuronal damage. To elucidate the functional significance of ERalpha overexpression, an in vitro model of reactive astrocytes with enhanced expression of ERalpha was obtained by growth in G5 culture supplement. Exposure of cortical neurons to beta-amyloid in the presence of either conditioned medium from reactive astrocytes previously treated with 17beta-estradiol (17betaE2) or transferring of 17betaE2-pretreated astrocytes, caused a greater neuroprotective effect compared to the respective control conditions, although reactive glia resulted being per se neuroprotective. Blockade of ERalpha overexpression by the ER antagonist ICI182,780 was not successful as ICI182,780 behaved as an agonist. However, complete prevention of 17betaE2 effect by ICI182,780 produced an increased sensitivity of neurons to beta-amyloid toxicity. A similar effect was observed when ERalpha knock-down was induced by siRNA. It is suggested that increased ERalpha expression in reactive glia may have a role in limiting neuronal damage.
Neurobiology of Disease 03/2009; 33(3):415-21. DOI:10.1016/j.nbd.2008.11.017 · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aggregation of the amyloid Abeta peptide and its accumulation into insoluble deposits (plaques) are believed to be the main cause of neuronal dysfunction associated with Alzheimer's disease (AD); small molecules that can interfere with the Abeta amyloid fibril formation are therefore of interest for a potential therapeutic strategy. Three new trehalose-conjugated peptides of the well known beta-sheet breaker peptide iAbeta5p, were synthesized. The disaccharide was covalently attached to different sites of the LPFFD peptide chain, i.e. at the N-terminus, C-terminus or at the Asp side chain. CD spectroscopy in different solvents was used to assess changes in the peptide conformation of these compounds. The effects of these glycopeptides on the self-assembly and morphology of Abeta aggregates were investigated by ThT fluorescence assay and dynamic Scanning Force Microscopy, respectively. All the synthesized compounds were tested as inhibitors of Abeta toxicity toward pure cultures of rat cortical neurons.
[Show abstract][Hide abstract] ABSTRACT: The neuropeptide carnosine (beta-amyloid peptide aggregation has been demonstrated. Carnosine protection against peroxynitrite damage is particularly relevant, but until now there has been no evidence of any direct interaction with nitric oxide. In this study we examined the protection that carnosine provides against nitric oxide (NO)-induced cell death in primary rat astroglial cell cultures treated with lipopolysaccharide (LPS) and interferon gamma (INFgamma), a well-known neurotoxic proinflammatory condition. A correlation was found between cell protection and NO free-radical scavenging activity of carnosine. Moreover, by competitive spectrophotometric measurement and electrospray mass spectrometry analysis in cell-free experiments, we demonstrated a direct interaction of the dipeptide with NO. A comparison of carnosine with its homologues or derivatives (homocarnosine and carcinine) as well as with its amino acid constituents (L-histidine and beta-alanine) highlighted that only histidine showed significant scavenging activity. Therefore, carnosine shows direct NO-trapping ability and may be a valuable multifunctional molecule in the treatment of neurodegenerative disorders.
Journal of Neuroscience Research 08/2007; 85(10):2239-45. DOI:10.1002/jnr.21365 · 2.59 Impact Factor