Title

Chemical, biochemical, and physiological aspects of nitric oxide, S-nitrosothiols, and protein disulfide isomerase.

Date of Award

2005

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Chemistry and Biochemistry

Keywords

Chemistry, Biochemistry.

Rights

CC BY-NC-ND 4.0

Abstract

Nitric oxide (NO•), S-nitrosothiols (RSNO), and cell surface protein disulfide isomerase (csPDI) are involved in many cellular processes. In this work, we investigate the participation of NO• and RSNO with respect to csPDI physiology. Omapatrilat (Omap) is developed by Bristol-Meyers Squibb for the treatment of hypertension. The effect of Omap treatment on two aspects of endothelial cell NO• metabolism was examined. Incubation with Omap resulted in an increase in the relative efficiency of L-arginine uptake (Vmax/K m), a precursor for NO• synthesis. Upon nitrosating the free sulthydryl group on Omap, we demonstrated its ability to deliver NO• to the cytosol via csPDI. In addition, treatment with Omap increased the affinity of csPDI for S-nitroso-albumin. We introduce O-aminobenzoyl-S-nitrosohomocysteine (AbzHcysNO) as a novel probe for use in cell surface thiol quantification. The chemical properties of AbzHcysNO allow for the detection of thiols with a limit of 30 pmol, using a fluorescence plate reader. Furthermore, it will be shown that this sensitivity is sufficient for determining the cell-surface thiol levels of cultured mammalian cells. PDI exhibits both disulfide exchange and denitrosation activities and has been recently located on the surface of platelets. The disulfide exchange activity of csPDI has been shown to regulate platelet adhesion, activation, and aggregation. Herein we have shown the denitrosation activity of csPDI catalyses the release of NO• from GSNO which inhibits platelet aggregation through the GC/PKG pathway. Additionally, the presence of extracellular RSNOs occupied the active site of PDI, thus preventing the integrin-ligand disulfide exchange required for platelet adhesion. The presence of NADPH oxidase (NOX) on the surface of platelets alludes to the possibility that NOX activity may play a role in switching csPDI between its disulfide exchange and denitrosation activities. Monitoring the activities of NOX and csPDI in an animal model of early insulin resistance, as well as in NIDDM humans, indicated that platelet NOX activity was enhanced while csPDI activity was diminished compared to controls. This suggested that, in NIDDM, elevated NOX activity turns off the denitrosation activity of csPDI and promotes the pro-aggregatory disulfide integrin-ligand coupling, thus resulting in platelet hyperactivity.Dept. of Chemistry and Biochemistry. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .R66. Source: Dissertation Abstracts International, Volume: 66-07, Section: B, page: 3697. Thesis (Ph.D.)--University of Windsor (Canada), 2005.