Date of Graduation

2017

Document Type

Dissertation

Degree Type

PhD

College

College of Physical Activity and Sport Sciences

Department

Sport and Exercise Psychology

Committee Chair

I M Olfert

Committee Co-Chair

Paul D Chantler

Committee Member

Timothy R Nurkiewicz

Committee Member

Emidio Pistilli

Committee Member

Dale W Porter

Abstract

Pulmonary exposure to multi-walled carbon nanotubes (MWCNT) has been shown to disrupt endothelium-dependent arteriolar dilation in the peripheral microcirculation. The molecular mechanisms behind these arteriolar disruptions have yet to be fully elucidated. The secreted matricellular matrix protein thrombospondin-1 (TSP-1) is capable of moderating arteriolar vasodilation by inhibiting NO signaling at several points, including the inhibition soluble guanylate cyclase activity and eNOS activation. The central hypothesis was that TSP-1, following pulmonary exposure to MWCNT, mediates peripheral changes in dilatory capacity. To test this hypothesis, wild-type C57B6J (WT), TSP-1 knockout (TSP-1 KO) and CD47 knockout (CD47 KO) mice were exposed via lung aspiration to 50 microg MWCNT or a sham dispersion medium control. Following exposure (24hrs), arteriolar characteristics and reactivity were measured in the gluteus maximus muscle using intravital microscopy (IVM) coupled with microiontophoretic delivery of acetylcholine (ACh) or sodium nitroprusside (SNP). In WT mice exposed to MWCNT, skeletal muscle TSP-1 protein increased (p < 0.05) 517.9 +/- 112.5 % compared to sham exposed, and exhibited a 38.5 +/- 2.5 % and 47.9 +/- 7.3 % decrease (p < 0.05) in endothelium-dependent and independent vasodilation, respectively. In contrast, TSP-1 protein was not increased following MWCNT exposure in TSP-1 KO mice and KO were protected from losses in dilatory capacity. Microvascular leukocyte-endothelium interactions were measured by leukocyte adhesion and rolling activity in third order venules. The WT+MWCNT group demonstrated 223.8 +/- 7.6 % higher (p < 0.05) leukocyte rolling compared to WT+SHAM controls. TSP-1 KO and CD47 animals exposed to MWCNT showed no differences from WT+SHAM control. Total tissue total nitrite (NO-2) and nitrate (NO-3) a measure of nitric oxide status, was decreased (p < 0.05) in WT+MWCNT lung by 47.4 +/- 13.8 % and plasma by 32.3 +/- 4.0 %, while not different from sham controls in the KO groups. Finally, several inflammatory cytokines, as quantified by Meso Scale Discovery, were upregulated in tissues of both TSP-1 and CD47 KO animals, but not in either of the WT groups. Taken together, these data provide the first evidence that TSP-1 is likely a central mediator of the systemic microvascular dysfunction that follows pulmonary MWCNT exposure.

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