Defense Date

2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Clinical and Translational Sciences

First Advisor

Judith A. Voynow

Second Advisor

Daniel H. Conrad

Third Advisor

Bruce K. Rubin

Fourth Advisor

Charles E. Chalfant

Fifth Advisor

Devanand Sarkar

Abstract

Alterations to sphingolipid metabolism are associated with increased pulmonary inflammation, but the impact of inflammatory mediators, such as neutrophil elastase (NE), on airway sphingolipid homeostasis remains unknown. NE is a protease associated CF lung disease progression, and can be found in up to micromolar concentrations in patient airways. While sphingolipids have been investigated in the context of CF, the focus has been on loss of cystic fibrosis transmembrane conductance regulator (CFTR) function. Here, we present a novel observation: oropharyngeal aspiration of NE increases airway ceramides in mice. Using a previously characterized mouse model of NE-induced inflammation, we demonstrate that NE increases de novo ceramide production, which is likely mediated via increased SPTLC2 levels. Inhibition of de novo sphingolipid synthesis using myriocin, an SPT inhibitor, decreases airway ceramide as well as the release of pro-inflammatory signaling molecules induced by NE. Furthermore, in a retrospective study of the sphingolipid content of CF sputum—the largest of its type in this patient cohort to date, we investigated the association between NE and sphingolipids. There were linear correlations between the concentration of active NE and ceramide, sphingomyelin, and monohexosylceramide moieties as well as sphingosine-1-phosphate. The presence of Methicillin-resistant Staphylococcus aureus (MRSA) positive culture and female gender both strengthened the association of NE and sphingolipids, but higher FEV1 % predicted weakened the association, and Pseudomonas aeruginosa had no effect on the association between NE and sphingolipids. These data suggest that NE may increase sphingolipids in CF airways as it did in our in vivo model, and that this association is stronger in patients that have worse lung function, are female, and whose lungs are colonized with MRSA. Modulating sphingolipid homeostasis could provide novel pharmacological approaches for alleviating pulmonary inflammation.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

2-28-2018

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