All ETDs from UAB

Advisory Committee Chair

Jessy S Deshane

Advisory Committee Members

Steven R Duncan

Anita B Hjelmeland

Peter D Burrows

Chad H Steele

Document Type

Dissertation

Date of Award

2019

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

T helper type 2 (Th2) cells and more recently IL-17-producing Th17 cells are implicated in disease pathogenesis of asthma; however other immune subsets including cells of the myeloid-lineage are being appreciated as drivers of airway inflammation. Our laboratory has demonstrated that a reactive oxygen species (ROS) producing subset of myeloid-derived regulatory cells (MDRCs) can drive inflammation in the airways of asthmatics. Recently, immune modulation by nano-sized vesicles called exosomes has also been reported. Herein, we characterize the composition of airway exosomes by lipidomics, flow cytometry, and ImageStream analyses. Furthermore, we explore the potential for airway MDRC-derived exosomes to promote T cell activation and Th polarization in asthmatics. We also investigate the potential of mitochondrial signaling by exosomes that have packaged functional mitochondria. Characterization of exosomes from bron-choalveolar lavage fluid (BAL) revealed higher concentration of exosomes in the airways of asthmatics that positively correlated with blood IgE titer and eosinophil frequencies. Lipidomics of BAL exosomes revealed unique airway lipid signatures involved in in-flammation. Flow cytometry and ImageStream analyses showed increased frequencies of HLA-DR+ and CD54+ exosomes in asthmatics. We demonstrate the presence of mito-chondrial DNA and functional mitochondria with membrane potential inside the exo-somes. Furthermore, our studies show that exosomes package mitochondria through mi-tochondrial fission. Functional analyses of these exosomes revealed their ability to drive proliferation and polarization of Th2, Th17 and Th2/17 hybrid populations. This activa-tion is seen only in T cells that internalized exosomes with mitochondria, and T cell acti-vation is abrogated by blocking the MHCII-TCR interaction. These studies suggested that exosomal mitochondrial signaling is important in driving T cell responses. Internali-zation of exosomes occurred through membrane fusion, and mitochondria transferred by exosomes co-localized with the polarized cytoskeleton and mitochondria of recipient T cells, suggesting that exosomes are internalized at the site of the immune synapse. Inhi-bition of mitochondrial complexes inside exosomes resulted in abrogation of lymphocyte activation, however complex I inhibition resulted in enhanced activation in both healthy and asthmatic T cells. These data suggest a novel role for exosomes to promote inflam-mation in asthmatics that may require the transfer of mitochondria, alteration of T cell metabolism and reverse electron transport.

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