Abstract 369: D5 Dopamine Receptor Decreases Reactive Oxygen Species via Heme Oxygenase-1

Abstract

D5 dopamine receptor (D5R) knock-out mice (D5-/-) have higher blood pressure and reactive oxygen species (ROS) production than their D5R wild-type littermates (D5+/+), related in part to increased NADPH oxidase expression and activity. We tested the hypothesis that the high blood pressure and increased ROS production in D5-/- mice may also be related to decreased heme oxygenase-1 (HO-1) expression and activity. We found that renal HO-1 protein expression and HO enzyme activity were decreased (by 65% and 50%, respectively) in D5-/- relative to D5+/+ mice. A 24 h of administration of hemin, an HO-1 inducer, increased HO-1 protein expression and HO activity (6.8-fold and 1.9-fold, respectively) in D5-/- but not D5+/+ mice and normalized the increased blood pressure and ROS production in D5-/- mice. Expression of HO-1 protein and HO activity were increased (2.3-fold and 1.5-fold, respectively) in HEK cells which heterologously expressed human wild-type D5R (HEK-hD5R) but not empty vector-transfected HEK-293 cells. Fenoldopam (Fen) treatment increased HO-1 protein expression and HO activity and HO-1 and D5R co-localization and co-immunoprecipitation in HEK-hD5R cells. Basal cellular ROS production was decreased by 35% in HEK-hD5R that was abrogated with silencing of the HO-1 gene. HO-1 siRNA also decreased the ability of Fen to decrease ROS production in HEK-hD5R cells. In summary, the D5R positively regulates HO-1 activity through direct protein/protein interaction in the short-term and by increasing HO-1 protein expression, in the long-term. Impaired D5R regulation of HO-1 may be involved in the pathogenesis and maintenance of hypertension in D5-/- mice.