Mycoplasma fermentans inhibits tumor necrosis factor α-induced apoptosis in the human myelomonocytic U937 cell line

Abstract

Mycoplasma fermentans (M. fermentans) was shown to be involved in the alteration of several eukaryotic cell functions (i.e. cytokine production, gene expression), and was suggested as a causative agent in arthritic diseases involving impaired apoptosis. We investigated whether M. fermentans has a pathogenic potential by affecting tumor necrosis factor (TNF)α-induced apoptosis in the human myelomonocytic U937 cell line. A significant reduction in the TNFα-induced apoptosis (∼60%) was demonstrated upon either infection with live M. fermentans or by stimulation with non-live M. fermentans. To investigate the mechanism of M. termentans antiapoptotic effect, the reduction of mitochondrial transmembrane potential (ΔΨm) and the protease activity of caspase-8 were measured. In the infected cells, the reduction of ΔΨm was inhibited (∼75%), and a ∼60% reduction of caspase-8 activity was measured. In conclusion, M. fermentans significantly inhibits TNFα-induced apoptosis in U937 cells, and its effect is upstream of the mitochondria and upstream of caspase-8. © 2004 Nature Publishing Group All rights reserved.