Date of Award
2007
Degree Type
Thesis
Degree Name
Doctor of Philosophy
Program
Pharmacology and Toxicology
Supervisor
Dr. Karel Tyml
Abstract
The microcirculation regulates blood flow through the coordinated vasodilation or vasoconstriction of resistance vessels over a relatively long length. Endogenous mediators of sepsis may compromise this coordination, by inhibiting gap junction intercellular communication between vascular cells. I hypothesized that an increase in the septic mediator nitric oxide (NO) may be responsible for the sepsis-induced attenuation of arteriolar conducted vasoconstriction. Using an in vivo model of arteriolar conducted vasoconstriction in the mouse cremaster muscle, sepsis was found to reduce arteriolar conduction. This deficit in arteriolar conduction was prevented by genetic deletion of the nNOS protein, restored by pharmacological inhibition of nNOS, and not affected by inhibition of soluble guanylyl cyclase. Genetic deletion of the gap junction protein connexin37 (Cx37) resulted in attenuated conduction in control mice. Ascorbate prevented the sepsis-induced reduction in arteriolar conduction by inhibiting the increase in nNOS activity. To better understand the mechanism by which NO reduces vascular cell coupling, we used an in vitro model to examine the effect of exogenous NO on electrical coupling in endothelial cell (EC) monolayers. Coupling was assessed by measuring the spread of electrical current injected into the monolayer and calculating the monolayer intercellular resistance (inverse measure of coupling). NO rapidly and reversibly reduced electrical coupling in a Cx37-dependent manner. The decrease in coupling was not affected by inhibition of soluble guanylyl cyclase or by scavenging peroxynitrite. The findings presented in this thesis demonstrate that increased nNOS activity and the resultant increased NO production in the septic mouse cremaster muscle are the key factors responsible for the deficit in conducted vasoconstriction along the arteriole. Since NO reduces electrical coupling between cultured ECs by targeting Cx37, we propose that NO in sepsis impairs arteriolar conducted vasoconstriction through a Cx37 dependent mechanism. Ascorbate may represent a new strategy in the prevention of microvascular dysfunction in sepsis by inhibiting the excessive production of nNOS- derived NO
Recommended Citation
McKinnon, Rebecca Lynn, "EFFECT OF SEPSIS AND NITRIC OXIDE ON VASCULAR CELL COUPLING: CRITICAL ROLE OF CONNEXIN37" (2007). Digitized Theses. 5055.
https://ir.lib.uwo.ca/digitizedtheses/5055