Tetracycline prevents Aβ oligomer toxicity through an atypical supramolecular interaction

Department of Biotechnology and Biosciences, University of Milano-Bicocca, P.zza della Scienza 2, 20126, Milan, Italy.
Organic & Biomolecular Chemistry (Impact Factor: 3.56). 11/2010; 9(2):463-72. DOI: 10.1039/c0ob00303d
Source: PubMed

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.

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    • "Among the NMR methods based on the ligand observation, one of the most robust and versatile experiments is the saturation transfer difference (STD)-NMR [3]. In the last decade, STD-NMR spectroscopy has been extensively exploited to study receptor-ligand interactions [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]. To the best of our knowledge, only few examples of STDs have been performed by employing HR-MAS techniques with immobilized ligands or receptors. "
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    • "Peptides were never conserved in solution, they were freshly dissolved immediately before use, and residual peptide solutions were always discarded after each experiment. Production and characterization of different aggregative Aβ species (Aβ 1–40 and Aβ 1–42 monomers, oligomers and fibrils) have been carried out as described in a previous publications [7], [8]. Monomers have been produced following a disaggregation protocol based on the use of formic acid and trifluoro acetic acid. "
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