Extracellular ATP determines 11beta-hydroxysteroid dehydrogenase type 2 activity via purinergic receptors

Abstract

Hypertension and sodium retention are features of a diminished 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2). The activity of this enzyme is reduced in various disease states with abnormal renal sodium retention and hypertension, including preeclampsia. ATP release to the extracellular compartment is observed with shear stress, inflammation, and placental ischemia. It was hypothesized that ATP downregulates 11beta-HSD2 activity. For that purpose, cell lines from different tissues that previously were used to study the regulation of 11beta-HSD2 were investigated: JEG-3, a vascular trophoblastic; LLCPK1, a renal tubular; and SW620, a colonic epithelial cell line. The 11beta-HSD2 activity, assessed by the conversion of 3H-cortisol to cortisone, was reversibly reduced during incubation with ATP or its stable analogue ATPgammaS in intact JEG-3 and LLCPK1, but not in SW620 cells. In JEG-3 cells, the purinergic antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid but not suramin reversed the inhibition. Incubation with UTP and ADP and their degradation products including adenosine and alpha,beta-methylene-ATP did not inhibit 11beta-HSD2 activity. In contrast, 11beta-HSD2 activity increased almost 2.5-fold after incubation with 2'-methylthio-ATP. This indicates a bidirectional regulation by nucleotides via purinergic receptors. In JEG-3 cells, ATP/ATPgammaS did not alter 11beta-HSD2 promoter activity but reduced 11beta-HSD2 protein and mRNA concentration and half-life, suggesting a posttranscriptional regulation. In conclusion, ATP inhibits cell type specifically via purinergic receptors the expression and activity of the 11beta-HSD2 by a posttranscriptional mechanism.