Tetracycline prevents Aβ oligomer toxicity through an atypical supramolecular interaction.
ABSTRACT The antibiotic tetracycline was reported to possess an anti-amyloidogenic activity on a variety of amyloidogenic proteins both in in vitro and in vivo models. To unveil the mechanism of action of tetracycline on Aβ1-40 and Aβ1-42 at both molecular and supramolecular levels, we carried out a series of experiments using NMR spectroscopy, FTIR spectroscopy, dynamic laser light-scattering (DLS) and atomic force microscopy (AFM). Firstly we showed that the co-incubation of Aβ1-42 oligomers with tetracycline hinders the toxicity towards N2a cell lines in a dose-dependent manner. Therefore, the nature of the interaction between the drug and Aβ oligomers was investigated. To carry out NMR and FTIR studies we have prepared Aβ peptide solutions containing assemblies ranging from monomers to large oligomers. Saturation transfer difference (STD) NMR experiments have shown that tetracycline did not interact with monomers at variance with oligomers. Noteworthy, in this latter case we observed that this interaction was very peculiar since the transfer of magnetization from Aβ oligomers to tetracycline involved all drug protons. In addition, intermolecular cross-peaks between tetracycline and Aβ were not observed in NOESY spectra, indicating the absence of a specific binding site and suggesting the occurrence of a supramolecular interaction. DLS and AFM studies supported this hypothesis since the co-dissolution of Aβ peptides and tetracycline triggered the immediate formation of new aggregates that improved the solubility of Aβ peptides, preventing in this way the progression of the amyloid cascade. Moreover, competitive NMR binding experiments showed for the first time that tetracycline competes with thioflavin T (ThT) in the binding to Aβ peptides. Our data shed light on a novel mechanism of anti-amyloidogenic activity displayed by tetracycline, governed by hydrophobic and charge multiparticle interactions.
- SourceAvailable from: Cristina Airoldi[Show abstract] [Hide abstract]
ABSTRACT: Amyloid peptides, Aβ1-40 and Aβ1-42, represent major molecular targets to develop potential drugs and diagnostic tools for Alzheimer's Disease (AD). In fact, oligomeric and fibrillar aggregates generated by these peptides are amongst the principal components of amyloid plaques found post mortem in patients suffering from AD. Rosmarinic acid has been demonstrated to be effective in preventing the aggregation of amyloid peptides in vitro and to delay the progression of the disease in animal models. Nevertheless, no information is available about its molecular mechanism of action. Herein, we report the NMR characterization of the interaction of Salvia sclareoides extract and that of its major component, rosmarinic acid, with Aβ1-42 peptide, whose oligomers have been described as the most toxic Aβ species in vivo. Our data shed light on the structural determinants of rosmarinic acid-Aβ1-42 oligomers interaction, thus allowing the elucidation of its mechanism of action. They also provide important information for the rational design of new compounds with higher affinity for Aβ peptides to generate new anti-amyloidogenic molecules and/or molecular tools for the specific targeting of amyloid aggregates in vivo. In addition, we identified methyl caffeate, another natural compound present in different plants and human diet, as a good ligand of Aβ1-42 oligomers, which also shows anti-amyloidogenic activity. Finally, we demonstrated the possibility to exploit STD-NMR and trNOESY experiments to screen extracts from natural sources for the presence of Aβ peptide ligands.Chemistry - An Asian Journal 01/2013; · 4.57 Impact Factor
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ABSTRACT: Dye-binding assays that are used to evaluate anti-aggregation ability of small molecule inhibitors towards amyloids are known to be prone to false-positive effects due to spectral overlaps between the dye and the inhibitor. Aza-BODIPY dye, which has both excitation and emission maxima above 600nm, exhibits a significant increase in its fluorescence intensity in the presence of soluble oligomers of Aβ1-42. These results indicate that aza-BODIPY could serve as a near-IR probe for detecting conformational changes of Aβ1-42 soluble oligomers in vitro, and it should eliminate false-positive effects that are associated with currently utilized thioflavin T-based dyes. In addition, a facile synthesis of aza-BODIPY has been developed, which might further expand the applications of this dye.Bioorganic & medicinal chemistry letters 03/2013; 23(6):1732-5. · 2.65 Impact Factor
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ABSTRACT: Smart biomaterials for tissue regeneration need to incorporate molecules able to interact with specific cellular adhesion or morphogenic proteins of the extracellular matrix (ECM).NMR binding studies allow obtaining structural information essential for the comprehension of biological processes and, nowadays, high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy is a well-established tool for the study of heterogeneous systems. Here the generation of a model-system used to explore the possibility to reveal interactions between two molecular entities, one of which linked to a solid support, to mimic a bioactive species immobilized on a biomaterial surface, is presented. The carbohydrate recognition processes that take place in the ECM have a pivotal role in promoting cell adhesion and differentiation and, thus, tissue regeneration. Hence, a pseudo-receptor, that mimics the lectin binding site was prepared and its interaction with a panel of different monosaccharides was characterized. The results obtained support the theoretical model according to which lectins bind carbohydrates exploiting the CH-π interactions occurring in their active site. Moreover the NMR experimental approach here described can be generally applied when the interacting species do not have the same solubility properties in physiological conditions and, in particular, can be exploited for the analysis and characterization of molecular recognition events occurring at biomaterial surface.Journal of Materials Science and Engineering B. 12/2012; 2(12):618-625.