Microvesicles Derived from Human Bronchial Epithelial Cells Regulate Macrophage Activation During <i>Mycobacterium abscessus</i> Infection

Intercellular communication is important for host immunity in response to bacterial infections. Nontuberculous mycobacterium (NTM), such as <i>Mycobacterium abscessus</i> (<i>M. ab</i>), is a group of environmental bacteria that can cause severe lung infections in individuals with pre-existing lung conditions, including cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). There is limited knowledge understanding the interaction between airway epithelial cells and immune cells during NTM infections. In this study, we characterized microvesicles (MVs) released from uninfected and <i>M. ab</i>-infected human bronchial epithelial cells and investigated the effect of these MVs on the activation and polarization of THP-1-derived macrophages in cell culture. Our results indicate that MVs released by <i>M. ab</i>-infected human bronchial epithelial cells stimulated the activation of M2-polarized macrophages in cell culture when compared to MVs released by uninfected cells. Additionally, the proteomic analysis for isolated MVs showed that the proteins involved in the cell adhesion pathway were enriched in MVs from <i>M. ab</i>-infected human bronchial epithelial cells compared to MVs from uninfected cells. Among those, the cell surface protein, intercellular adhesion molecule 1 (ICAM-1), regulated the uptake of MVs released by <i>M. ab</i>-infected human bronchial epithelial cells by recipient macrophages in cell culture. In conclusion, our data suggest that in response to <i>M. ab</i> infection, human airway epithelial cells release MVs to modulate the activation of macrophages, which are key cells for mycobacterial intracellular survival in the host.