COPD is a chronic inflammatory pulmonary condition which the 3rd leading cause of death in the United States and has significant impact on the US Veteran and active military population. Despite its prevalence and increased attributable morbidity/mortality, there are no specific COPD therapeutics which alter the natural history of the disorder. Our group and others have provided extensive evidence of the importance of proteolytic damage as a critical component to the progression of COPD. However, our ability to understand how proteases bypass the robust antiprotease shield within the lung is poorly understood. Here, we examine a new pathogenic entity, the neutrophil-derived exosome, which expresses the protease neutrophil elastase (NE) on its surface. We provide preliminary data demonstrating these exosomes have active NE enzymatic activity, capable of degrading components of the lung extracellular matrix (ECM). Importantly, we highlight that exosome-associated NE is resistant to its naturally occurring antiprotease, alpha-1 antitrypsin (A1AT), and can lead to fulminant emphysema when intratracheally administered in vivo. For this proposal, we will build on these seminal observations, first by examining the impact of smoke to induce the release of these proteolytic exosomes from PMNs (Specific Aim 1a) and then examining the antiprotease resistance of exosomes isolated from COPD and non-COPD subjects, with a focus of inducing NE disassociation from these exosomes to enhance endogenous antiprotease sensitivity (Specific Aim 1b). Next, we will use bronchoalveolar lavage (BAL) samples from 6-month smoking mouse model, isolate PMN-derived exosomes, and intratracheally deliver these into naïve mice to induce emphysema, inhibiting these effects via NE disassociation (Specific Aim 2). Finally, we will examine a cohort of COPD subjects (current or former smokers) and non-COPD subjects (smokers and never smokers) to determine the expression of NE-associated exosomes in these cohorts and stability of these measurements over time (Specific Aim 3). The successful completion of these aims will lead to an increased understanding of the PMN exosome as a critical pathogenic entity in COPD, with improved understanding of the downstream effects of its unfettered protease activity. Importantly, these studies will likely result in the development of a new biomarker and potential new therapeutic approaches for the treatment of Veterans who are diagnosed with COPD.