Abstract P318: INDOLE-3 ACETIC ACID: A NOVEL DUAL-ACTION INHIBITOR OF THE ENDOTHELIN SYSTEM FOR TREATING HYPERTENSION

Elevated levels of endothelin-1 (ET-1) stimulate potent vasoconstriction, free radical production, oxidative stress, and vascular inflammation, which are often present in salt-sensitive hypertension, pulmonary hypertension, drug-resistant hypertension, and hypertension among African Americans. There is currently no known drug that simultaneously targets both ET-1 receptors (ETRs) and the ET-1 synthesizing enzyme ECE-1, even though dual targeting of the ET system could lead to a new generation of drug molecules with improved therapeutic outcome. Using an integrated in vitro, in vivo and in silico approaches, here we report the discovery of indole-3 acetic acid (IAA) as an inhibitor of both ET-1 receptors and ECE-1. IAA is produced in the human body via tryptophan metabolism by gut microbiota. Our data demonstrates that IAA concentration-dependently inhibits ET-1-evoked vasoconstriction in rat resistance mesenteric arteries and ET-1-stimulated reactive oxygen species (ROS) production in smooth muscle cells (SMCs). Furthermore, IAA suppresses ET-1-induced endothelial cell (EC) activation, adhesion molecule overexpression, and leukocyte adhesion. IAA inhibits ET-1-stimulated, ET A R- and ET B R-mediated increases in [Ca 2+ ] i . Intriguingly, IAA produces a concentration-dependent inhibition of purified human ECE-1. Treatment of Dahl salt-sensitive (DSS) hypertensive rats, a model of augmented ET-1 signaling, with an oral extended-release formulation of IAA significantly inhibits blood pressure elevation in high-salt diet-fed (HSD) DSS rats. IAA-treated DSS arteries show intact acetylcholine- and sodium nitroprusside-induced vasodilation, suggesting that IAA preserves endothelial and smooth muscle function, respectively. IAA treatment also prevents arterial remodeling, oxidative stress, and kidney dysfunction in HSD DSS rats. Overall, our study identifies IAA as the first-in-class dual-action inhibitor of ETRs and ECE-1, which produces profound antihypertensive effect in vivo. IAA could also be therapeutically useful for other cardiovascular diseases in which ET-1 signaling is implicated.