Dopamine D₁ and D₅ receptors differentially regulate oxidative stress through paraoxonase 2 in kidney cells

Abstract

Background. The renal dopaminergic system plays an important role in the pathogenesis of hypertension. Dopamine D₁-like receptors (D₁R and D₅R) decrease reactive oxygen species (ROS) production via inhibition of pro-oxidant enzymes such as NADPH oxidase. Paraoxonase 2 (PON2) is also involved in the inhibition of NADPH oxidase activity. Therefore, we tested the hypothesis that D₁R and D₅R inhibit ROS production by increasing the expression of PON2, including those in membrane microdomains. Methods and results. PON2 colocalized with D₁R and D₅R in mouse renal proximal tubules (RPTs), human RPT (hRPT) cells, and HEK293 cells heterologously expressing human D₁R (HEK-hD₁R) or D₅R (HEK-hD₅R). Fenoldopam, an agonist for both D₁R and D₅R, increased PON2 co-immunoprecipitation with D₁R and D₅R in HEK-hD₁R and HEK-hD₅R cells, respectively. Silencing PON2 increased ROS production and NADPH oxidase activity, and impaired the inhibitory effect of fenoldopam. Fenoldopam increased PON2 protein in both lipid rafts (LRs) and non-LRs in HEK-hD₁R cells, but only in non-LRs in HEK-hD₅R and hRPT cells. Long-term (hrs) fenoldopam stimulation increased PON2 protein in a time-dependent manner in HEK-hD₅R, but not in HEK-hD₁R cells. Because the effects of fenoldopam on non-LR and total PON2 expressions were similar in HEK-hD₅R and hRPT cells, additional studies were performed to determine the relationship between D₅R and PON2. Renal PON2 protein was decreased in D₅^−/− mice. In hRPT cells, silencing D₅R decreased PON2 expression and increased ROS production. Conclusions. We conclude that D₁-like receptors inhibit ROS production by altering PON2 distribution in membrane microdomains in the short-term, and by increasing PON2 expression in the long-term.

Keywords::

• dopamine receptors
• paraoxonase 2
• reactive oxygen species
• NADPH oxidase
• lipid rafts

Acknowledgments

These studies were supported in part by grants from the National Natural Science Foundation of China (31130029, 81100500), and grant from the US National Institutes of Health, 5P01HL074940.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.