Amyloid-beta peptide degradation in cell cultures by mycoplasma contaminants.

BACKGROUND

Cell cultures have become an indispensable tool in Alzheimer's disease research for studying amyloid-beta (Abeta) 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 Abeta. As a result, we observed no accumulation of Abeta in the conditioned medium of mycoplasma-positive cells stably transfected with the amyloid-beta precursor protein (APP). Importantly, eradication of the mycoplasma contaminant - identified as M. hyorhinis - by treatments with a quinolone-based antibiotic, restored extracellular Abeta accumulation in the APP-transfected cells.

CONCLUSION

These data show that mycoplasmas degrade Abeta and thus may represent a significant source of variability when comparing extracellular Abeta levels in different cell lines. On the basis of these results, we recommend assessment of mycoplasma contaminations prior to extracellular Abeta level measurements in cultured cells.