Tetracycline and its analogues protect Caenorhabditis elegans from β amyloid-induced toxicity by targeting oligomers

The accumulation and deposition of amyloid beta (A beta) peptide in extracellular dense plaques in the brain is a key phase in Alzheimer's disease (AD). Small oligomeric forms of A beta 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 A beta 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 A beta protein, particularly their ability to interact in vivo with the A beta 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 A beta proteotoxicity. The drugs directly interact with the A beta assemblies in vivo and reduce A beta 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 A beta aggregates. (c) 2010 Elsevier Inc. All rights reserved.