Aß1-6A2V(D) peptide, effective on Aß aggregation, inhibits tau misfolding and protects the brain after traumatic brain injury.

Alzheimer's disease (AD), the leading cause of dementia in older adults, is a double proteinopathy characterized by amyloid-ß (Aß) and tau pathology. Despite enormous efforts that have been spent in the last decades to find effective therapies, late pharmacological interventions along the course of the disease, inaccurate clinical methodologies in the enrollment of patients, and inadequate biomarkers for evaluating drug efficacy have not allowed the development of an effective therapeutic strategy. The approaches followed so far for developing drugs or antibodies focused solely on targeting Aß or tau protein. This paper explores the potential therapeutic capacity of an all-D-isomer synthetic peptide limited to the first six amino acids of the N-terminal sequence of the A2V-mutated Aß, Aß1-6A2V(D), that was developed following the observation of a clinical case that provided the background for its development. We first performed an in-depth biochemical characterization documenting the capacity of Aß1-6A2V(D) to interfere with the aggregation and stability of tau protein. To tackle Aß1-6A2V(D) in vivo effects against a neurological decline in genetically predisposed or acquired high AD risk mice, we tested its effects in triple transgenic animals harboring human PS1(M146 V), APP(SW), and MAPT(P301L) transgenes and aged wild-type mice exposed to experimental traumatic brain injury (TBI), a recognized risk factor for AD. We found that Aß1-6A2V(D) treatment in TBI mice improved neurological outcomes and reduced blood markers of axonal damage. Exploiting the C. elegans model as a biosensor of amyloidogenic proteins' toxicity, we observed a rescue of locomotor defects in nematodes exposed to the brain homogenates from TBI mice treated with Aß1-6A2V(D) compared to TBI controls. By this integrated approach, we demonstrate that Aß1-6A2V(D) not only impedes tau aggregation but also favors its degradation by tissue proteases, confirming that this peptide interferes with both Aß and tau aggregation propensity and proteotoxicity.

A novel bio-inspired strategy to prevent amyloidogenesis and synaptic damage in Alzheimer's disease.

Alzheimer's disease (AD) is an irreversible neurodegenerative disorder that affects millions of people worldwide. AD pathogenesis is intricate. It primarily involves two main molecular players-amyloid-ß (Aß) and tau-which actually have an intrinsic trend to generate molecular assemblies that are toxic to neurons. Incomplete knowledge of the molecular mechanisms inducing the onset and sustaining the progression of the disease, as well as the lack of valid models to fully recapitulate the pathogenesis of human disease, have until now hampered the development of a successful therapy for AD. The overall experience with clinical trials with a number of potential drugs-including the recent outcomes of studies with monoclonal antibodies against Aß-seems to indicate that Aß-targeting is not effective if it is not accompanied by an efficient challenge of Aß neurotoxic properties. We took advantage from the discovery of a naturally-occurring variant of Aß (AßA2V) that has anti-amyloidogenic properties, and designed a novel bio-inspired strategy for AD based on the intranasal delivery of a six-mer peptide (Aß1-6A2V) retaining the anti-amyloidogenic abilities of the full-length AßA2V variant. This approach turned out to be effective in preventing the aggregation of wild type Aß and averting the synaptic damage associated with amyloidogenesis in a mouse model of AD. The results of our preclinical studies inspired by a protective model already existing in nature, that is the human heterozygous AßA2V carriers which seem to be protected from AD, open the way to an unprecedented and promising approach for the prevention of the disease in humans.

Selenoprotein N is an endoplasmic reticulum calcium sensor that links luminal calcium levels to a redox activity.

The endoplasmic reticulum (ER) is the reservoir for calcium in cells. Luminal calcium levels are determined by calcium-sensing proteins that trigger calcium dynamics in response to calcium fluctuations. Here we report that Selenoprotein N (SEPN1) is a type II transmembrane protein that senses ER calcium fluctuations by binding this ion through a luminal EF-hand domain. In vitro and in vivo experiments show that via this domain, SEPN1 responds to diminished luminal calcium levels, dynamically changing its oligomeric state and enhancing its redox-dependent interaction with cellular partners, including the ER calcium pump sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA). Importantly, single amino acid substitutions in the EF-hand domain of SEPN1 identified as clinical variations are shown to impair its calcium-binding and calcium-dependent structural changes, suggesting a key role of the EF-hand domain in SEPN1 function. In conclusion, SEPN1 is a ER calcium sensor that responds to luminal calcium depletion, changing its oligomeric state and acting as a reductase to refill ER calcium stores.

A Comprehensive Technology Platform for the Rapid Discovery of Peptide Inhibitors against SARS-CoV-2 Pseudovirus Infection.

We developed and validated a technology platform for designing and testing peptides inhibiting the infectivity of SARS-CoV-2 spike protein-based pseudoviruses. This platform integrates target evaluation, in silico inhibitor design, peptide synthesis, and efficacy screening. We generated a cyclic peptide library derived from the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein and the angiotensin-converting enzyme 2 (ACE2) receptor. The cell-free validation process by ELISA competition assays and Surface Plasmon Resonance (SPR) studies revealed that the cyclic peptide c9_05, but not its linear form, binds well to ACE2. Moreover, it effectively inhibited the transduction in HEK293, stably expressing the human ACE2 receptor of pseudovirus particles displaying the SARS-CoV-2 spike in the Wuhan or UK variants. However, the inhibitory efficacy of c9_05 was negligible against the Omicron variant, and it failed to impede the entry of pseudoviruses carrying the B.1.351 (South African) spike. These variants contain three or more mutations known to increase affinity to ACE2. This suggests further refinement is needed for potential SARS-CoV-2 inhibition. Our study hints at a promising approach to develop inhibitors targeting viral infectivity receptors, including SARS-CoV-2's. This platform also promises swift identification and evaluation of inhibitors for other emergent viruses.

Nonphosphorylated tau slows down Aß1-42 aggregation, binds to Aß1-42 oligomers, and reduces Aß1-42 toxicity.

The formation of neurofibrillary tangles and amyloid plaques accompanies the progression of Alzheimer's disease. Tangles are made of fibrillar aggregates formed by the microtubule-associated protein tau, whereas plaques comprise fibrillar forms of amyloid-beta (Aß). Both form toxic oligomers during aggregation and are thought to interact synergistically to each promote the accumulation of the other. Recent in vitro studies have suggested that the monomeric nonphosphorylated full-length tau protein hinders the aggregation of Aß1-40 peptide, but whether the same is true for the more aggregation-prone Aß1-42 was not determined. We used in vitro and in vivo techniques to explore this question. We have monitored the aggregation kinetics of Aß1-42 by thioflavine T fluorescence in the presence or the absence of different concentrations of nonphosphorylated tau. We observed that elongation of Aß1-42 fibrils was inhibited by tau in a dose-dependent manner. Interestingly, the fibrils were structurally different in the presence of tau but did not incorporate tau. Surface plasmon resonance indicated that tau monomers bound to Aß1-42 oligomers (but not monomers) and hindered their interaction with the anti-Aß antibody 4G8, suggesting that tau binds to the hydrophobic central core of Aß recognized by 4G8. Tau monomers also antagonized the toxic effects of Aß oligomers in Caenorhabditis elegans. This suggests that nonphosphorylated tau might have a neuroprotective effect by binding Aß1-42 oligomers formed during the aggregation and shielding their hydrophobic patches.

Cytoskeleton Elements Contribute to Prion Peptide-Induced Endothelial Barrier Breakdown in a Blood-Brain Barrier In Vitro System.

The mechanisms involved in the interaction of PrP 106-126, a peptide corresponding to the prion protein amyloidogenic region, with the blood-brain barrier (BBB) were studied. PrP 106-126 treatment that was previously shown to impair BBB function, reduced cAMP levels in cultured brain endothelial cells, increased nitric oxide (NO) levels, and changed the activation mode of the small GTPases Rac1 (inactivation) and RhoA (activation). The latter are well established regulators of endothelial barrier properties that act via cytoskeletal elements. Indeed, liquid chromatography-mass spectrometry (LC-MS)-based proteomic profiling study revealed extensive changes in expression of cytoskeleton-related proteins. These results shed light on the nature of the interaction between the prion peptide PrP 106-126 and the BBB and emphasize the importance of the cytoskeleton in endothelium response to prion- induced stress.

Micro- and Nanoplastics' Effects on Protein Folding and Amyloidosis.

A significant portion of the world's plastic is not properly disposed of and, through various processes, is degraded into microscopic particles termed micro- and nanoplastics. Marine and terrestrial faunae, including humans, inevitably get in contact and may inhale and ingest these microscopic plastics which can deposit throughout the body, potentially altering cellular and molecular functions in the nervous and other systems. For instance, at the cellular level, studies in animal models have shown that plastic particles can cross the blood-brain barrier and interact with neurons, and thus affect cognition. At the molecular level, plastics may specifically influence the folding of proteins, induce the formation of aberrant amyloid proteins, and therefore potentially trigger the development of systemic and local amyloidosis. In this review, we discuss the general issue of plastic micro- and nanoparticle generation, with a focus on their effects on protein folding, misfolding, and their possible clinical implications.

Synthesis and Molecular Modelling Studies of New 1,3-Diaryl-5-Oxo-Proline Derivatives as Endothelin Receptor Ligands.

The synthesis of seventeen new 1,3-diaryl-5-oxo-proline derivatives as endothelin receptor (ETR) ligands is described. The structural configuration of the new molecules was determined by analyzing selected signals in proton NMR spectra. In vitro binding assays of the human ETA and ETB receptors allowed us to identify compound 31h as a selective ETAR ligand. The molecular docking of the selected compounds and the ETA antagonist atrasentan in the ETAR homology model provided insight into the structural elements required for the affinity and the selectivity of the ETAR subtype.

Clusterin Binds to Aß1-42 Oligomers with High Affinity and Interferes with Peptide Aggregation by Inhibiting Primary and Secondary Nucleation.

The aggregation of amyloid ß protein (Aß) is a fundamental pathogenic mechanism leading to the neuronal damage present in Alzheimer disease, and soluble Aß oligomers are thought to be a major toxic culprit. Thus, better knowledge and specific targeting of the pathways that lead to these noxious species may result in valuable therapeutic strategies. We characterized some effects of the molecular chaperone clusterin, providing new and more detailed evidence of its potential neuroprotective effects. Using a classical thioflavin T assay, we observed a dose-dependent inhibition of the aggregation process. The global analysis of time courses under different conditions demonstrated that clusterin has no effect on the elongation rate but mainly interferes with the nucleation processes (both primary and secondary), reducing the number of nuclei available for further fibril growth. Then, using a recently developed immunoassay based on surface plasmon resonance, we obtained direct evidence of a high-affinity (KD= 1 nm) interaction of clusterin with biologically relevant Aß1-42oligomers, selectively captured on the sensor chip. Moreover, with the same technology, we observed that substoichiometric concentrations of clusterin prevent oligomer interaction with the antibody 4G8, suggesting that the chaperone shields hydrophobic residues exposed on the oligomeric assemblies. Finally, we found that preincubation with clusterin antagonizes the toxic effects of Aß1-42oligomers, as evaluated in a recently developedin vivomodel inCaenorhabditis elegans.These data substantiate the interaction of clusterin with biologically active regions exposed on nuclei/oligomers of Aß1-42, providing a molecular basis for the neuroprotective effects of the chaperone.

New N- and O-arylpiperazinylalkyl pyrimidines and 2-methylquinazolines derivatives as 5-HT7 and 5-HT1A receptor ligands: Synthesis, structure-activity relationships, and molecular modeling studies.

Based on our earlier studies of structure activity relationships on 4-substituted piperazine derivatives, in this work we synthesized a novel set of long-chain arylpiperazines with the purpose of elucidating if some structural modifications in the terminal fragment could affect the binding affinity for the 5-HT7 and 5-HT1A receptors. In this new series, the quinazolinone system of the previous derivatives was replaced by a 6-phenylpyrimidine or a 2-methylquinazoline, which were used as versatile building blocks for the preparation of new compounds. A 4-arylpiperazine moiety through a five methylene chain was anchored at the nitrogen or oxygen atom of the heterocyclic scaffolds. The substituents borne by the piperazine nucleus were phenyl, phenylmethyl, 3- or 4-chlorophenyl, and 2-ethoxyphenyl. Binding tests, performed on human cloned 5-HT7 and 5-HT1A receptors, showed that, among the newly synthesized derivatives, 4-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentoxy]-6-phenyl-pyrimidine (13) and 3-[5-[4-(2-ethoxyphenyl)-1-piperazinyl]pentyl]-2-methyl-4(3H)-quinazolinone (20) displayed the best affinity values, Ki=23.5 and 8.42nM for 5-HT7 and 6.96 and 2.99nM for 5-HT1A receptors, respectively. Moreover, the functional properties for both compounds were further evaluated using the cAMP assay. Finally, a molecular modeling study has been performed for 5-HT7 and 5-HT1A receptor homology models to investigate the binding mode of N- and O-alkylated pyrimidinones/pyrimidines 4-13, 2-methylquinazolinones/quinazolines 17-22, and previously reported 2- and 3-substituted quinazolinones 23-30.

The cell-permeable Aß1-6A2VTAT(D) peptide reverts synaptopathy induced by Aß1-42wt.

Alzheimer disease (AD) is the most prevalent form of dementia. Loss of hippocampal synapses is the first neurodegenerative event in AD. Synaptic loss has been associated with the accumulation in the brain parenchyma of soluble oligomeric forms of amyloid ß peptide (Aß1-42wt). Clinical observations have shown that a mutation in the APP protein (A673V) causes an early onset AD-type dementia in homozygous carriers while heterozygous carriers are unaffected. This mutation leads to the formation of mutated Aß peptides (Aß1-42A2V) in homozygous patients, while in heterozygous subjects both Aß1-42wt and Aß1-42A2V are present. To better understand the impact of the A673V mutation in AD, we analyzed the synaptotoxic effect of oligomers formed by aggregation of different Aß peptides (Aß1-42wt or Aß1-42A2V) and the combination of the two Aß1-42MIX (Aß1-42wt and Aß1-42A2V) in an in vitro model of synaptic injury. We showed that Aß1-42A2V oligomers are more toxic than Aß1-42wt oligomers in hippocampal neurons, confirming the results previously obtained in cell lines. Furthermore, we reported that oligomers obtained by the combination of both wild type and mutated peptides (Aß1-42MIX) did not exert synaptic toxicity. We concluded that the combination of Aß1-42wt and Aß1-42A2V peptides hinders the toxicity of Aß1-42A2V and counteracts the manifestation of synaptopathy in vitro. Finally we took advantage of this finding to generate a cell-permeable peptide for clinical application, by fusing the first six residues of the Aß1-42A2V to the TAT cargo sequence (Aß1-6A2VTAT(D)). Noteworthy, the treatment with Aß1-6A2VTAT(D) confers neuroprotection against both in vitro and in vivo synaptopathy models. Therefore Aß1-6A2VTAT(D) may represent an innovative therapeutic tool to prevent synaptic degeneration in AD.

The new ß amyloid-derived peptide Aß1-6A2V-TAT(D) prevents Aß oligomer formation and protects transgenic C. elegans from Aß toxicity.

One attractive pharmacological strategy for Alzheimer's disease (AD) is to design small peptides to interact with amyloid-ß (Aß) protein reducing its aggregation and toxicity. Starting from clinical observations indicating that patients coding a mutated Aß variant (AßA2V) in the heterozygous state do not develop AD, we developed AßA2V synthetic peptides, as well as a small peptide homologous to residues 1-6. These hindered the amyloidogenesis of Aß and its neurotoxicity in vitro, suggesting a basis for the design of a new small peptide in D-isomeric form, linked to the arginine-rich TAT sequence [Aß1-6A2V-TAT(D)], to allow translocation across biological membranes and the blood-brain barrier. Aß1-6A2V-TAT(D) was resistant to protease degradation, stable in serum and specifically able to interfere with Aß aggregation in vitro, reducing the appearance of toxic soluble species and protecting transgenic C. elegans from toxicity related to the muscular expression of human Aß. These observations offer a proof of concept for future pharmacological studies in mouse models of AD, providing a foundation for the design of AßA2V-based peptidomimetic molecules for therapeutic purposes.

Design and synthesis of new homo and hetero bis-piperazinyl-1-propanone derivatives as 5-HT7R selective ligands over 5-HT1AR.

In this work we report the discovery of new homo and hetero bis-piperazinyl-1-propanone derivatives as selective ligands for 5-HT7 over 5-HT1A receptor. These newly synthesized compounds possess a 4-arylpiperazine linked through an acyl spacer to another substituted piperazine system and were tested for their binding properties on human cloned 5-HT1A and 5-HT7 serotonin receptors. Among these, phenyl, 4- and 2-chlorophenyl, 2-methoxyphenyl, 2-pyridyl, and 2-pyrimidyl derivatives 15, 24, 25, and 27-29 displayed nanomolar affinity values for the 5-HT7 receptor (Ki 23.5-52.0nM) and no affinity for the 5-HT1A receptor.

The hunt for brain Aß oligomers by peripherally circulating multi-functional nanoparticles: Potential therapeutic approach for Alzheimer disease.

We previously showed the ability of liposomes bi-functionalized with phosphatidic acid and an ApoE-derived peptide (mApoE-PA-LIP) to reduce brain Aß in transgenic Alzheimer mice. Herein we investigated the efficacy of mApoE-PA-LIP to withdraw Aß peptide in different aggregation forms from the brain, using a transwell cellular model of the blood-brain barrier and APP/PS1 mice. The spontaneous efflux of Aß oligomers (Aßo), but not of Aß fibrils, from the 'brain' side of the transwell was strongly enhanced (5-fold) in presence of mApoE-PA-LIP in the 'blood' compartment. This effect is due to a withdrawal of Aßo exerted by peripheral mApoE-PA-LIP by sink effect, because, when present in the brain side, they did not act as Aßo carrier and limit the oligomer efflux. In vivo peripheral administration of mApoE-PA-LIP significantly increased the plasma Aß level, suggesting that Aß-binding particles exploiting the sink effect can be used as a therapeutic strategy for Alzheimer disease. From the Clinical Editor: Alzheimer disease (AD) at present is an incurable disease, which is thought to be caused by an accumulation of amyloid-ß (Aß) peptides in the brain. Many strategies in combating this disease have been focused on either the prevention or dissolving these peptides. In this article, the authors showed the ability of liposomes bi-functionalized with phosphatidic acid and with an ApoE- derived peptide to withdraw amyloid peptides from the brain. The data would help the future design of more novel treatment for Alzheimer disease.

Multifunctional liposomes reduce brain ß-amyloid burden and ameliorate memory impairment in Alzheimer's disease mouse models.

Alzheimer's disease is characterized by the accumulation and deposition of plaques of ß-amyloid (Aß) peptide in the brain. Given its pivotal role, new therapies targeting Aß are in demand. We rationally designed liposomes targeting the brain and promoting the disaggregation of Aß assemblies and evaluated their efficiency in reducing the Aß burden in Alzheimer's disease mouse models. Liposomes were bifunctionalized with a peptide derived from the apolipoprotein-E receptor-binding domain for blood-brain barrier targeting and with phosphatidic acid for Aß binding. Bifunctionalized liposomes display the unique ability to hinder the formation of, and disaggregate, Aß assemblies in vitro (EM experiments). Administration of bifunctionalized liposomes to APP/presenilin 1 transgenic mice (aged 10 months) for 3 weeks (three injections per week) decreased total brain-insoluble Aß1-42 (-33%), assessed by ELISA, and the number and total area of plaques (-34%) detected histologically. Also, brain Aß oligomers were reduced (-70.5%), as assessed by SDS-PAGE. Plaque reduction was confirmed in APP23 transgenic mice (aged 15 months) either histologically or by PET imaging with [(11)C]Pittsburgh compound B (PIB). The reduction of brain Aß was associated with its increase in liver (+18%) and spleen (+20%). Notably, the novel-object recognition test showed that the treatment ameliorated mouse impaired memory. Finally, liposomes reached the brain in an intact form, as determined by confocal microscopy experiments with fluorescently labeled liposomes. These data suggest that bifunctionalized liposomes destabilize brain Aß aggregates and promote peptide removal across the blood-brain barrier and its peripheral clearance. This all-in-one multitask therapeutic device can be considered as a candidate for the treatment of Alzheimer's disease.

The peculiar role of the A2V mutation in amyloid-ß (Aß) 1-42 molecular assembly.

We recently reported a novel Aß precursor protein mutation (A673V), corresponding to position 2 of Aß1-42 peptides (Aß1-42A2V), that caused an early onset AD-type dementia in a homozygous individual. The heterozygous relatives were not affected as an indication of autosomal recessive inheritance of this mutation. We investigated the folding kinetics of native unfolded Aß1-42A2V in comparison with the wild type sequence (Aß1-42WT) and the equimolar solution of both peptides (Aß1-42MIX) to characterize the oligomers that are produced in the early phases. We carried out the structural characterization of the three preparations using electron and atomic force microscopy, fluorescence emission, and x-ray diffraction and described the soluble oligomer formation kinetics by laser light scattering. The mutation promoted a peculiar pathway of oligomerization, forming a connected system similar to a polymer network with hydrophobic residues on the external surface. Aß1-42MIX generated assemblies very similar to those produced by Aß1-42WT, albeit with slower kinetics due to the difficulties of Aß1-42WT and Aß1-42A2V peptides in building up of stable intermolecular interaction.

Synthesis and binding properties of new long-chain 4-substituted piperazine derivatives as 5-HT1A and 5-HT7 receptor ligands.

New long-chain 4-substituted piperazines linked to a thienopyrimidine or a quinazoline system were synthesized and tested for their binding properties on human cloned 5-HT1A and 5-HT7 serotonin receptors. Some structural modifications, concerning tree main portions, that is, terminal fragment, chain length, and aryl substituents, were examined. The 2- and 3-substituted thienopyrimidinone and quinazolinone systems were selected as terminal fragment and a chain length of four or five methylene units was set. Explored aryl substituents were phenyl, phenylmethyl, 3- or 4-chlorophenyl, and 2-ethoxyphenyl. Title compounds showed affinity for 5-HT1A and 5-HT7 receptors. In particular, 2-ethoxyphenyl derivatives 40 and 45 displayed Ki values in the nanomolar range on both receptors, acting as dual ligands.

Liposomes bi-functionalized with phosphatidic acid and an ApoE-derived peptide affect Aß aggregation features and cross the blood-brain-barrier: implications for therapy of Alzheimer disease.

Targeting amyloid-ß peptide (Aß) within the brain is a strategy actively sought for therapy of Alzheimer's disease (AD). We investigated the ability of liposomes bi-functionalized with phosphatidic acid and with a modified ApoE-derived peptide (mApoE-PA-LIP) to affect Aß aggregation/disaggregation features and to cross in vitro and in vivo the blood-brain barrier (BBB). Surface plasmon resonance showed that bi-functionalized liposomes strongly bind Aß (kD=0.6 µM), while Thioflavin-T and SDS-PAGE/WB assays show that liposomes inhibit peptide aggregation (70% inhibition after 72 h) and trigger the disaggregation of preformed aggregates (60% decrease after 120 h incubation). Moreover, experiments with dually radiolabelled LIP suggest that bi-functionalization enhances the passage of radioactivity across the BBB either in vitro (permeability=2.5×10(-5) cm/min, 5-fold higher with respect to mono-functionalized liposomes) or in vivo in healthy mice. Taken together, our results suggest that mApoE-PA-LIP are valuable nanodevices with a potential applicability in vivo for the treatment of AD. From the clinical editor: Bi-functionalized liposomes with phosphatidic acid and a modified ApoE-derived peptide were demonstrated to influence Aß aggregation/disaggregation as a potential treatment in an Alzheimer's model. The liposomes were able to cross the blood-brain barrier in vitro and in vivo. Similar liposomes may become clinically valuable nanodevices with a potential applicability for the treatment of Alzheimer's disease.

Specific recognition of biologically active amyloid-ß oligomers by a new surface plasmon resonance-based immunoassay and an in vivo assay in Caenorhabditis elegans.

Soluble oligomers of the amyloid-ß (Aß) peptide play a key role in the pathogenesis of Alzheimer's disease, but their elusive nature makes their detection challenging. Here we describe a novel immunoassay based on surface plasmon resonance (SPR) that specifically recognizes biologically active Aß oligomers. As a capturing agent, we immobilized on the sensor chip the monoclonal antibody 4G8, which targets a central hydrophobic region of Aß. This SPR assay allows specific recognition of oligomeric intermediates that rapidly appear and disappear during the incubation of synthetic Aß(1-42), discriminating them from monomers and higher order aggregates. The species recognized by SPR generate ionic currents in artificial lipid bilayers and inhibit the physiological pharyngeal contractions in Caenorhabditis elegans, a new method for testing the toxic potential of Aß oligomers. With these assays we found that the formation of biologically relevant Aß oligomers is inhibited by epigallocatechin gallate and increased by the A2V mutation, previously reported to induce early onset dementia. The SPR-based immunoassay provides new opportunities for detection of toxic Aß oligomers in biological samples and could be adapted to study misfolding proteins in other neurodegenerative disorders.

Tetrahydro-ß-carboline-based spirocyclic lactam as type II' ß-turn: application to the synthesis and biological evaluation of somatostatine mimetics.

The synthesis of novel spirocyclic lactams, embodying D-tryptophan (Trp) amino acid as the central core and acting as peptidomimetics, is presented. It relies on the strategic combination of Seebach's self-reproduction of chirality chemistry and Pictet-Spengler condensation as key steps. Investigation of the conformational behavior by molecular modeling, X-ray crystallography, and NMR and IR spectroscopies suggests very stable and highly predictable type II' ß-turn conformations for all compounds. Relying on this feature, we also pursued their application to two potential mimetics of the hormone somatostatin, a pharmaceutically relevant natural peptide, which contains a Trp-based type II' ß-turn pharmacophore.