Mechanical Forces Alter Endothelin-1 Signaling: Comparative Ovine Models of Congenital Heart Disease

Abstract

The risk and progression of pulmonary vascular disease (PVD) in patients with congenital heart disease (CHD) dependent on the hemodynamics associated with different lesions. However, the underlying mechanisms are not understood. Endothelin-1 (ET-1) is a potent vasoconstrictor known to play a role in the pathobiology of PVD. We investigate the hypothesis that the combined effect of high pressure (P) and flow shear stresses (FSS), but not FSS alone, upregulates ET-1 signaling. We used 2 ovine models of CHD: (1) Fetal aortopulmonary graft placement (shunt), resulting in increased FSS and P; and (2) Fetal ligation of the left pulmonary artery (LPA) resulting in increased FSS but normal P to the right lung. Pulmonary arterial endothelial cells (PAEC) and peripheral lung were harvested from control, shunt, and LPA lambs at 3-7 weeks of age. PAECs from control lambs were exposed to high FSS=20dyn/cm2, cyclic stretch CS=18%, and P from 20-50mmHg at constant shear conditions FSS=5dyn/cm2, utilizing a microfluidic device. Lung preproET-1 mRNA were increased in shunt lambs compared to controls. PreproET-1 mRNA expression was unchanged in LPA lambs. In both shunt and LPA lambs, Lung ECE-1 mRNA and protein expression were increased. These changes resulted in increased lung ET-1 levels in shunt lambs, while LPA levels were similar to controls. PAECs exposed to increased FSS decreased ET-1 by 5-fold, while CS increased levels by 1.5-fold. Under physiological FSS=5dyn/cm, the additive effects of P increased preproET-1 mRNA expression, while ECE-1 expression was unchanged. These data suggest that P or the additive effect of P+FSS, rather than increased FSS alone, is the principal driver of increased ET-1 in CHD. Defining the molecular drivers of the pathobiology of PVD resulting from the different mechanical stimuli will allow for a more targeted therapeutic approach.