Abstract 302: TRAIL Protects Against Endothelial Dysfunction in vivo and Inhibits Angiotensin-II Induced Oxidative Stress in Vascular Endothelial Cells <i>in vitro</i>

The vascular endothelium is critical for maintenance of cardiovascular homeostasis and vascular oxidative stress is a primary cause of endothelial dysfunction. TNF-related apoptosis-inducing ligand (TRAIL) is increasingly recognised to play a protective role in atherosclerosis, however the molecular mechanisms by which it exerts its beneficial effects are unclear. Our aim was to identify whether TRAIL could protect against atherosclerosis by reducing vascular oxidative stress and improve endothelial cell (EC) function. In vivo , 12 w high fat diet (HFD)-fed Trail -/- Apoe -/- mice had more severe atherosclerosis, with significant impairment in vasorelaxation in response to acetylcholine, but not sodium nitroprusside. HFD Trail -/- Apoe -/- vessels also had increased vascular reactive oxygen species (ROS) as evident by dihydroethidium (DHE) staining compared to HFD Apoe -/- mice. Following injection of Evan’s blue dye, blood vessels from highly vascularised organs of Trail -/- mice demonstrated increased vascular permeability compared to Trail +/+ organs, and altered expression of adhesion molecule and tight junction proteins. In vitro , AngII (50 ng/ml) increased DHE and mitosox staining in ECs within 2 h, which was inhibited by apocynin, rotenone and L-Name, suggesting that NADPH oxidases (NOXs), the mitochondria and eNOS are major producers of ROS. siRNA targeting NOX-4, but not NOX-1, -2, or -5 reduced AngII-induced DHE, whereas siRNA targeting eNOS significantly augmented DHE staining. Importantly, pre-treatment of TRAIL at 1 ng/ml inhibited AngII-inducible DHE and mitosox staining. Functionally, TRAIL reduced eNOS monomer expression and monocyte recruitment in response to AngII. Furthermore, AngII reduced VCAM-1 and PECAM-1 mRNA was no rescued with TRAIL treatment. These findings demonstrate for the first time that TRAIL protects against endothelial dysfunction via its ability to modulate oxidative stress. Understanding the role TRAIL plays in normal physiology and disease, may lead to potential new therapies to improve endothelial function and atherosclerosis.