Deciphering the role of regulatory T cell derived Mmp12 in lung injury resolution

About This Grant

ABSTRACT Acute Respiratory Distress Syndrome (ARDS) is characterized by heightened lung inflammation and edema in the alveoli and interstitium, affecting the lung's primary function of gas exchange. The treatment for ARDS has improved over the years, but the mortality of 20-40% is still associated with ARDS, and the residual defects in lung function in survivors create a critical need for additional therapies. T regulatory cells (Tregs) are emerging as a therapeutic area of interest to facilitate lung resolution due to their reparative and anti-inflammatory properties. Previous work of my sponsor, Dr. Jason Mock, has associated a higher percentage of Tregs in the CD4+ lymphocyte population in the bronchoalveolar lavage fluid (BALF) of patients with ARDS with time to liberation from mechanical ventilation; moreover, in recent years, clinical trials for Treg cell therapy for ARDS have been initiated. However, to realize the full potential of these therapies, we must understand the specific mechanisms by which Tregs facilitate and promote resolution and repair. Our previous work identified the transcript Mmp12 as upregulated more than twenty-fold in Tregs in lungs resolving from LPS-induced ALI compared to Tregs from uninjured lungs. Mmp12's pleiotropic effects extend to the resolution of inflammation by dampening neutrophil infiltration, clearing neutrophil extracellular traps (NETs), terminating complement activation, and accelerating coagulation; however, Treg-derived Mmp12 has been largely unexplored. I hypothesize that Treg-expressed Mmp12 promotes lung resolution by cleaving proinflammatory soluble mediators and reducing the proinflammatory immune cell populations, thereby promoting optimal resolution from lung injury. Aim 1 will determine the function of Treg-derived Mmp12 in the resolution of inflammation during ALI induced by LPS or influenza. Parameters of inflammation and repair will be compared in mice with Tregs lacking Mmp12 (TregMmp12-/- mice) to mice with Tregs expressing wild-type Mmp12. Aim 2 will determine the substrates of extracellular Treg-derived Mmp12. These substrates will be identified by comparison of cleaved substrates in TregMmp12-/- and control lungs during LPS- or influenza-induced ALI using N-TAIL proteomics. Total Mmp12 protein concentration will be measured to determine the fraction of Mmp12 that Tregs contribute. The kinetics of Treg-derived Mmp12 mRNA and protein expression and of substrate cleavage by Treg-generated Mmp12 will be determined. The heterogeneity of Mmp12 expression by known Treg subsets will be assessed. These studies will not only determine the role of Treg-derived Mmp12 by identifying specific substrates that facilitate resolution but also elucidate the effects of Treg-derived Mmp12 in Treg biology and function during lung injury and repair. Through this proposal, I will (1) develop laboratory skills, (2) improve my scientific communication skills through presentations, manuscript preparation, and dissemination to the public, (3) broaden my scientific background, as well as seminars series and workshops about lung disease, the ethical conduct of research and career development.