Activation of endothelial cells by extracellular vesicles derived from Mycobacterium tuberculosis infected macrophages or mice.

Li Li,Yong Cheng,Jeffrey Schorey,Scott Emrich

doi:10.1371/journal.pone.0198337

Abstract

Endothelial cells play an essential role in regulating an immune response through promoting leukocyte adhesion and cell migration and production of cytokines such as TNFα. Regulation of endothelial cell immune function is tightly regulated and recent studies suggest that extracellular vesicles (EVs) are prominently involved in this process. However, the importance of EVs in regulating endothelial activation in the context of a bacterial infection is poorly understood. To begin addressing this knowledge gap we characterized the endothelial cell response to EVs released from Mycobacterium tuberculosis (Mtb) infected macrophages. Our result showed increased macrophage migration through the monolayer when endothelial cells were pretreated with EVs isolated from Mtb-infected macrophages. Transcriptome analysis showed a significant upregulation of genes involved in cell adhesion and the inflammatory process in endothelial cells treated with EVs. These results were validated by quantitative PCR and flow cytometry. Pathway analysis of these differentially expressed genes indicated that several immune response-related pathways were up-regulated. Endothelial cells were also treated with EVs isolated from the serum of Mtb-infected mice. Interestingly, EVs isolated 14 days but not 7 or 21 days post-infection showed a similar ability to induce endothelial cell activation suggesting a change in EV function during the course of an Mtb infection. Immunofluorescence microscopy result indicated that NF-κB and the Type 1 interferon pathways were involved in endothelial activation by EVs. In summary, our data suggest that EVs can activate endothelial cells and thus may play an important role in modulating host immune responses during an Mtb infection.

Highlights

Extracellular vesicles (EVs) are important mediators of intercellular communication and are known to carry all the different macromolecules: proteins, carbohydrates, lipids and nucleic acids
Our present work indicates that EVs released from Mycobacterium tuberculosis (Mtb)-infected macrophages or isolated from the serum of infected mice can activate endothelial cells leading to increased expression of cell adhesion molecules, chemokines and chemokine receptors as well as promote macrophage migration
To assess cell permeability SVEC4-10 cells were plated on collagen-coated transwells at 3.3x103 cells/well and treated with EVs purified from the condition media of Mtb-infected and uninfected Raw264.7 cells

Summary

Introduction

Extracellular vesicles (EVs) are important mediators of intercellular communication and are known to carry all the different macromolecules: proteins, carbohydrates, lipids and nucleic acids. Their complex composition allows for engagement of multiple receptors and transfer of numerous cellular components resulting in a marked change in the recipient cell. Endothelial cell activation by extracellular vesicles of three major forms: apoptotic bodies, microvesicles, and exosomes. The composition and function of the different EVs varies and depends on the cell of origin and the physiological state at the time of EV release. A significant effort has focused on EVs as potential biomarkers for various diseases [3,4,5,6,7]

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