Advisory Committee Chair
Victor J Thannickal
Advisory Committee Members
Trent E Tipple
Date of Award
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
The oxidative tyrosine modification, o,o′-dityrosine, has been identified in various pathologic conditions associated with oxidative stress in mammalian systems, and demonstrated to be important in physiologic processes in invertebrate organisms. The formation of o,o’-dityrosine is catalyzed by a heme peroxidase (hPx) in the presence of hydrogen peroxide (H2O2). The understanding of this stable, covalent tyrosine modifica-tion in lung biology is limited. Oxidative stress has been implicated in the pathogenesis of various lung diseases, including interstitial lung disease (ILD) and cystic fibrosis (CF). We observed that the oxidative protein modification, o,o’-dityrosine, was markedly ele-vated in the circulating plasma of ILD patients with an almost complete separation in lev-els between ILD and healthy control human subjects. The increase in o,o’-dityrosine lev-els was replicated in a fibrotic lung injury mouse model with increases observed in both lung tissue and circulating plasma. We then demonstrate that the tyrosine-rich extracel-lular matrix protein, fibronectin, is susceptible to hPx-catalyzed o,o’-dityrosine crosslink-ing. The modification of fibronectin is increased in the circulating plasma of human sub-jects with ILD, and is increased in lung tissue and plasma of mice subjected to fibrotic lung injury. The crosslinking of fibronectin by o,o’-dityrosine could have both physio-logic and/or pathophysiologic consequences; we find that proteolysis is decreased and fibroblast migration signaling is altered. In CF, o,o’-dityrosine has been shown to be ele-vated in the sputum of patients with the obstructive airway disease. Therefore, we sought to determine if o,o’-dityrosine crosslinking of mucus proteins alters mucus viscoelastic properties and mucociliary clearance. We determined that mucus proteins are modified by hPx-mediated oxidative crosslinking. This crosslinking mediated by myeloperoxi-dase, a hPx that is elevated in the CF airway, decreases mucociliary transport that can be abrogated by the addition of competitive inhibitor, L-tyrosine. Together, these findings further the understanding of the role of the oxidative protein modification, o,o’-dityrosine, in lung biology and mammalian systems. The work has identified novel po-tential prognostic and therapeutic targets for ILD and CF, and provides the impetus to study this biochemistry in other lung diseases.
Locy, Morgan, "The Oxidative Tyrosine Modification, O,O’-Dityrosine, In Lung Disease" (2018). All ETDs from UAB. 2323.