Corticosterone and 11-dehydrocorticosterone stimulate Na,K-ATPase gene expression in vascular smooth muscle cells

Abstract

Background. In mineralocorticoid target tissues such as kidney and colon, the enzyme 11β-hydroxysteroid dehydrogenase (11βOHSD) catalizes the reversible conversion of corticosterone (cs) to inactive 11- dehydrocorticosterone (DHCS) in rats, and cortisol to inactive cortisone in humans. This enzyme is also expressed in vascular smooth muscle cells (VSMC). Methods. In cultured VSMC from rat thoracic aortae, we examined the effects of CS and DHCS on Na,K-ATPase α1- and β1-mRNA accumulation by Northern blot analysis, on α1- and β1-subunit protein accumulation by Western blot analysis, and on Na,K-ATPase activity by the coupled assay method. Results. In VSMC, CS and DHCS (10-6 M) increased α1-mRNA level 2.6- and 2.5-fold at 48 hours and β1-mRNA level 9.2- and 9.1-fold at 12 hours, respectively. The RNA transcription inhibitor (actinomycin D) abolished both CS- and DHCS- mediated α1- and β1-mRNA induction. The glucocorticoid receptor antagonist (RU38486) and the mineralocorticoid receptor antagonists (ZK91587) inhibited both CS- and DHCS-mediated α1- and β1-mRNA induction. The 11βOHSD inhibitor (carbenoxolone) inhibited DHCS-mediated α1- and β1-mRNA induction, whereas it caused no effect on CS-mediated α1- or β1-mRNA induction. The addition of CS or DHCS to VSMC significantly increased α1- and β1-subunit protein levels and Na,K-ATPase activity. When adrenalectomized rats were treated with CS or DHCS for 12 hours, aorta α1- and β1-mRNA levels increased 3.0- and 8.7-fold or 3.4- and 8.4-fold, respectively. Conclusions. In VSMC, both CS and DHCS stimulate Na,KATPase α1- and β1-mRNA accumulation, α1- and β1-subunit protein accumulation, and Na,K-ATPase activity. The CS-mediated α1- and β1-mRNA induction occurs independently of 11βOHSD, whereas the DHCS-mediated α1- and β1-mRNA induction occurs through 11βOHSD-dependent mechanisms, possibly via conversion of inactive DHCS into active CS.