title: Inhibitory effects of digoxin and ouabain on aldosterone synthesis in human adrenocortical NCI-H295 cells.
abstract: The present study was to investigate the effects and action mechanisms of digoxin and ouabain on steroidogenesis in human adrenocortical NCI-H295 cells. Administration of digoxin or ouabain for 24 h decreased the basal and angiotensin II (Ang II)-stimulated release of aldosterone by NCI-H295 cells. The conversions of corticosterone (substrate of cytochrome P450 aldosterone synthase, P450c11AS) to aldosterone or deoxycortisol (substrate of cytochrome P450 11beta-hydroxylase, P450c11beta) to cortisol were reduced by digoxin or ouabain. The basal and 22-hydroxy-cholesterol (a membrane-permeable cholesterol, substrate of cytochrome P450 side-chain cleavage enzyme, P450scc)-stimulated pregnenolone release in mitochondria was inhibited by digoxin or ouabain. Digoxin or ouabain suppressed the basal and Ang II-stimulated protein expression of steroidogenic acute regulatory (StAR) protein and P450scc. Incubation of digoxin or ouabain for 24 h reduced P450c11AS mRNA expression in NCI-H295 cells. Digoxin or ouabain (10(-6) M, 24 h)-treated cells showed a lower resting intracellular Ca2+ concentration ([Ca2+]i) and an attenuated response of [Ca2+]i to Ang II. Since no significant cytotoxicity was observed at 10(-6) M digoxin or ouabain, the digoxin- or ouabain-induced decrease of aldosterone or cortisol release was not associated with cytotoxicity. These results demonstrate that digoxin or ouabain inhibits the aldosterone or cortisol release via reduction of P450c11AS or P450c11beta and P450scc activities, inhibition of StAR and P450scc protein expression, suppression of P450c11AS mRNA expression, and attenuation of Ca2+ mobilization in NCI-H295 cells.
authors.affiliation: National Taipei College of Nursing, Taipei, Taiwan, Republic of China.
authors.forename: Mei-Mei
authors.initials: MM
authors.lastname: Kau
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Kan
authors.forename: Jiing-Rong
authors.initials: JR
authors.lastname: Wang
authors.forename: Paulus S
authors.initials: PS
authors.lastname: Wang
mesh_terms: D000306:Adrenal Cortex Neoplasms / Q000378:metabolism* / Q000473:pathology; D000450:Aldosterone / Q000096:biosynthesis*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D045744:Cell Line, Tumor; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000037:antagonists & inhibitors; D019405:Cytochrome P-450 CYP11B2 / Q000037:antagonists & inhibitors / Q000235:genetics; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D004077:Digoxin / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D006854:Hydrocortisone / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D000451:Mineralocorticoid Receptor Antagonists / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology*; D010750:Phosphoproteins / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000037:antagonists & inhibitors; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors / Q000235:genetics; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D002121:Calcium Channel Blockers; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D000451:Mineralocorticoid Receptor Antagonists; D010750:Phosphoproteins; D012333:RNA, Messenger; D000098682:Steroidogenic Acute Regulatory Protein; D000450:Aldosterone; D010042:Ouabain; D004077:Digoxin; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C120361:Cyp11b3 protein, rat; D019405:Cytochrome P-450 CYP11B2; D002786:Cholesterol Side-Chain Cleavage Enzyme; D006854:Hydrocortisone