Profound Endothelial Dysfunction and Inflammation in Fabry Disease: Responses to Exercise Training

Abstract

Cardiovascular disease is the leading cause of death in the United States and globally. Atherosclerosis is an important basis for coronary heart disease and stroke, the two major types of cardiovascular disorders. Fabry disease promotes accelerated atherogenesis and thrombogenesis by loss of activity of the lysosomal hydrolase, α-Galactosidase A (GLA), resulting in the accumulation of globotriaosylceramide (Gb3) in vascular endothelial cells. Although endothelial dysfunction, characterized by decreased nitric oxide bioavailability, is believed to be the basis for the vasculopathy in Fabry disease, the pathophysiological mechanisms underlying GLA deficiency remain elusive. Using Fabry disease as a model to study accelerated vascular disease, the overall purpose of my dissertation was to further characterize endothelial dysfunction and inflammation using murine and in vitro endothelial cell models of Fabry disease, and to examine the effects of 12 weeks of voluntary exercise on endothelial function in the setting of eNOS dysregulation. The major findings of my dissertation studies include that: 1) GLA deficiency in mice resulted in early, profound endothelial dysfunction in the mesenteric artery, which was associated with eNOS uncoupling and changes in eNOS activating and inhibitory phosphorylation sites; 2) the in vitro disruption of GLA in endothelial cells with siRNA or CRISPR/Cas9 directly promoted a decrease in eNOS activity and robustly elevated the secretion of von Willebrand factor (VWF), which plays an important role in thrombi formation; 3) pharmacological approaches that improve exogenous or endogenous NO availability or reduce reactive oxygen species (ROS) completely normalized the elevated VWF secretion in the setting of GLA deficiency; and 4) 12 weeks of voluntary wheel exercise did not significantly improve endothelium-mediated vasodilation or the oxidative stress profile despite increased p-Akt (Ser473), AMPK (Thr172), and eNOS (Ser1177) signaling cascades in the aorta of 12-14 month old GLA deficient mice. Overall, the findings from these dissertation projects suggest that in Fabry disease: 1) decreased NO availability due to eNOS uncoupling and elevated ROS may exacerbate endothelial dysfunction and inflammation; 2) VWF release from the endothelium appears to be mediated by the profound endothelial dysfunction present in GLA deficiency; 3) strategies that increase NO bioavailability and/or decrease ROS, such as sepiapterin, tempol, and ebselen lead to an attenuation in VWF secretion; and 4) exercise mediated activation of Akt/AMPK/eNOS signaling cascades without significant improvement in aortic endothelial function in 12-14 month old GLA deficient mice. In summary, this dissertation compliments the prior hypothesis that GLA deficiency-mediated eNOS dysregulation is an important basis for endothelial inflammation and questions whether current treatment strategies for Fabry disease are optimal for improving the underlying vasculopathy.