Amyloid-beta peptide degradation in cell cultures by mycoplasma contaminants

Abstract

Background. Cell cultures have become an indispensable tool in Alzheimer's disease research for studying amyloid- (A) metabolism. It is estimated that up to 35% of cell cultures in current use are infected with various mycoplasma species. In contrast with common bacterial and fungal infections, contaminations of cell cultures with mycoplasmas represent a challenging issue in terms of detectability and prevention. Mycoplasmas are the smallest and simplest self-replicating bacteria and the consequences of an infection for the host cells are variable, ranging from no apparent effect to induction of apoptosis. Findings. Here we present evidence that mycoplasmas from a cell culture contamination are able to efficiently and rapidly degrade extracellular A. As a result, we observed no accumulation of A in the conditioned medium of mycoplasma-positive cells stably transfected with the amyloid- precursor protein (APP). Importantly, eradication of the mycoplasma contaminant - identified as M. hyorhinis - by treatments with a quinolone-based antibiotic, restored extracellular A accumulation in the APP-transfected cells. Conclusion. These data show that mycoplasmas degrade A and thus may represent a significant source of variability when comparing extracellular A levels in different cell lines. On the basis of these results, we recommend assessment of mycoplasma contaminations prior to extracellular A level measurements in cultured cells. © 2008 Zhao et al; licensee BioMed Central Ltd.