Adenovirus-delivered DKK3/WNT4 and Steroidogenesis in Primary Cultures of Adrenocortical Cells

Abstract

The Wnt family molecules Dickkopf-3 (DKK3) and WNT4 are present at higher concentrations in the zona glomerulosa than in the rest of the adrenal cortex. In order to study direct effects of these proteins on adrenocortical cell function, we created adenoviruses encoding human DKK3 and WNT4. When added to cultured human adrenocortical cells, DKK3 inhibited aldosterone and cortisol biosynthesis, either alone or together with cyclic AMP. WNT4 increased steroidogenesis when added alone but decreased it in the presence of cyclic AMP. A control adenovirus encoding GFP had no effect. RNA was prepared from cultured cells and was assayed by real-time PCR. CYP11A1 (cholesterol side-chain cleavage enzyme), HSD3B2 (3β-hydroxysteroid dehydrogenase type II), CYP17 (17α-hydroxylase), CYP21 (21-hydroxylase) and CYP11B1 (11β-hydroxylase) mRNAs were all increased by cyclic AMP, whereas CYP11B2 (aldosterone synthase) was unaffected. DKK3 decreased cyclic AMP-stimulated CYP17. WNT4 increased both CYP17 and CYP21 in the absence of cyclic AMP. Both DKK3 and WNT4 increased the level of CYP11B2. These data show that these Wnt signaling molecules have multiple actions on steroidogenesis in adrenocortical cells, including effects on overall steroidogenesis (aldosterone and cortisol biosynthesis) and distinct effects on steroidogenic enzyme mRNA levels. The co-localization of DKK3 and WNT4 in the glomerulosa and their stimulation of CYP11B2 imply an action on glomerulosa-specific function.

Key words

Adrenal cortex - Wnt signaling - Dickkopf proteins - CYP11B2 (aldosterone synthase) - real-time PCR

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