Dopamine D 5 receptor-mediated decreases in mitochondrial reactive oxygen species production are cAMP and autophagy dependent.

Overproduction of reactive oxygen species (ROS) plays an important role in the pathogenesis of hypertension. The dopamine D5 receptor (D5 R) is known to decrease ROS production, but the mechanism is not completely understood. In HEK293 cells overexpressing D5 R, fenoldopam, an agonist of the two D1 -like receptors, D1 R and D5 R, decreased the production of mitochondria-derived ROS (mito-ROS). The fenoldopam-mediated decrease in mito-ROS production was mimicked by Sp-cAMPS but blocked by Rp-cAMPS. In human renal proximal tubule cells with DRD1 gene silencing to eliminate the confounding effect of D1 R, fenoldopam still decreased mito-ROS production. By contrast, Sch23390, a D1 R and D5 R antagonist, increased mito-ROS production in the absence of D1 R, D5 R is constitutively active. The fenoldopam-mediated inhibition of mito-ROS production may have been related to autophagy because fenoldopam increased the expression of the autophagy hallmark proteins, autophagy protein 5 (ATG5), and the microtubule-associated protein 1 light chain (LC)3-II. In the presence of chloroquine or spautin-1, inhibitors of autophagy, fenoldopam further increased ATG5 and LC3-II expression, indicating an important role of D5 R in the positive regulation of autophagy. However, when autophagy was inhibited, fenoldopam was unable to inhibit ROS production. Indeed, the levels of these autophagy hallmark proteins were decreased in the kidney cortices of Drd5-/- mice. Moreover, ROS production was increased in mitochondria isolated from the kidney cortices of Drd5-/- mice, relative to Drd5+/+ littermates. In conclusion, D5 R-mediated activation of autophagy plays a role in the D5 R-mediated inhibition of mito-ROS production in the kidneys.