Host Cell-Derived Extracellular Vesicles Regulate Iron Uptake in Recipient Macrophages during Mycobacterium abscessus Infection

The role of host cell-derived extracellular vesicles
(EVs) in host–pathogen
interactions remains to be defined during mycobacterial infection.
In this study, we characterized EVs from mouse RAW 264.7 cells uninfected
or infected with Mycobacterium abscessus (M.ab), one of the most common
nontuberculous mycobacterial (NTM) pathogens in humans. Our results
show that M.ab infection increased
the release of EVs but had no effect on the size distribution and
total protein abundance of EVs from RAW 264.7 cells. Interestingly,
EVs released by M.ab-infected RAW
264.7 cells significantly enhanced M.ab growth within recipient macrophages in cell culture. The proteomic
analysis found that transferrin receptor was enriched in EVs from M.ab-infected RAW 264.7 cells compared
to EVs from uninfected cells. Iron assay further indicates that EVs
from M.ab-infected RAW 264.7 cells
increased total iron level in recipient macrophages but not EVs from
uninfected RAW 264.7 cells. However, iron abundance within EVs remained
similar across both conditions. Finally, EVs from M.ab-infected RAW 264.7 cells failed to improve M.ab growth within recipient macrophages
in the presence of an iron-chelating agent, deferoxamine, in cell
culture. Therefore, our data suggest that M.ab-infected mouse macrophages likely regulate M.ab growth by upregulating iron uptake in recipient
cells via released EVs.