Publication Date

2019-03-04

Availability

Open access

Embargo Period

2019-03-04

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Neuroscience (Medicine)

Date of Defense

2018-12-04

First Committee Member

Robert W. Keane

Second Committee Member

W. Dalton Dietrich

Third Committee Member

Ellen F. Barrett

Fourth Committee Member

Gregory E. Conner

Fifth Committee Member

Daniel J. Liebl

Sixth Committee Member

Kristine O'Phelan

Abstract

Approximately 20-25 percent of Traumatic Brain Injury (TBI) subjects develop Acute Lung Injury (ALI), but the pathomechanisms of TBI-induced ALI remain poorly defined. In my thesis, I investigated whether (Extracellular Vesicle) EV-mediated inflammasome signalling contributed to the etiology of TBI-induced ALI. C57/BL6 male mice were subjected to Controlled Cortical Impact, and the brains and lungs were examined for inflammasome activation and ALI at 4 hours and 24 hours after TBI. I show that TBI releases EV containing inflammasome proteins into serum that target the lung to cause ALI. Administration of a Low Molecular Weight Heparin (Enoxaparin, a blocker of EV uptake) or treatment with a monoclonal antibody against apoptosis speck-like staining protein containing a caspase recruitment domain (anti-ASC) after adoptive transfer of EV isolated from TBI-injured mice significantly inhibited inflammasome activation in the lungs of recipient mice resulting in improved ALI scores. In addition, treatment with Enoxaparin reduced inflammasome activation and lung injury in TBI-injured mice and anti-ASC reduced inflammasome activation after TBI in the brain of injured mice. Furthermore, serum-derived EVs from severe TBI patients were isolated and analyzed for particle size, concentration, origin, and levels of ASC. Severe TBI patients with lung injury had a significantly higher level of ASC in serum and serum-derived EVs compared to individuals without lung injury. EVs were co-cultured with lung human microvascular endothelial cells (HMVEC-L) and induced inflammasome activation and endothelial cell pyroptosis. My results demonstrate that serum-derived EVs and inflammasome proteins play a critical role in the pathogenesis of TBI-induced lung injury, and provide evidence for activation of an EV-mediated Neural-Respiratory Inflammasome Axis in TBI-induced lung injury.

Keywords

Traumatic Brain Injury; Inflammasome; Extracellular Vesicles; Neuroinflammation; Acute Lung Injury; Pyroptosis

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