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Dehydroepiandrosterone Sulfate and Allopregnanolone Directly Stimulate Catecholamine Production via Induction of Tyrosine Hydroxylase and Secretion by Affecting Actin Polymerization

Departments of Pharmacology (I.C., A.G.), Clinical Chemistry (E.D., C.T., A.N.M.), and Biochemistry (L.V., C.S.), School of Medicine, University of Crete, Heraklion GR-711 10, Greece

Address all correspondence and requests for reprints to: Achille Gravanis, Department of Pharmacology, School of Medicine, University of Crete, Heraklion GR-711 10, Crete, Greece. E-mail: gravanis{at}med.uoc.gr.

Adrenal cortical cells of zona reticularis produce the neuroactive steroids dehydroepiandrosterone (DHEA), its sulfate ester dehydroepiandrosterone sulfate (DHEAS), and allopregnanolone (ALLO). An interaction between zona reticularis and adrenal medulla has been postulated based on their close proximity and their interwoven borders. The aim of this paper was to examine in vitro the possible paracrine effects of these steroids on catecholamine production from adrenomedullary chromaffin cells, using an established in vitro model of chromaffin cells, the PC12 rat pheochromocytoma cell line. We have found the following: 1) DHEA, DHEAS, and ALLO increased acutely (peak effect between 10–30 min) and dose-dependently (EC₅₀ in the nanomolar range) catecholamine levels (norepinephrine and dopamine). 2) It appears that the acute effect of these steroids involved actin depolymerization/actin filament disassembly, a fast-response cellular system regulating trafficking of catecholamine vesicles. Specifically, 10^–6 M phallacidin, an actin filament stabilizer, completely prevented steroid-induced catecholamine secretion. 3) DHEAS and ALLO, but not DHEA, also affected catecholamine synthesis. Indeed, DHEAS and ALLO increased catecholamine levels at 24 h, an effect blocked by L-2-methyl-3-(-4hydroxyphenyl)alanine and 3-(hydrazinomethyl)phenol hydrochloride, inhibitors of tyrosine hydroxylase and L-aromatic amino acid decarboxylase, respectively, suggesting that this effect involved catecholamine synthesis. The latter hypothesis was confirmed by finding that DHEAS and ALLO increased both the mRNA and protein levels of tyrosine hydroxylase. In conclusion, our findings suggest that neuroactive steroids exert a direct tonic effect on adrenal catecholamine synthesis and secretion. These data associate the adrenomedullary malfunction observed in old age and neuroactive steroids.

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