title: Nitric oxide potently inhibits the rate-limiting enzymatic step in steroidogenesis.
abstract: This study tested the hypothesis that nitric oxide (NO) inhibits the rate-limiting catalytic step in steroidogenesis, cytochrome P450 cholesterol side-chain cleaving enzyme (CYP11A1), independent of soluble guanylyl cyclase (GC-S) stimulation. To assess CYP11A1 activity, pregnenolone levels were quantified in murine adrenocortical Y1 cells in the presence of the 3beta-hydroxy-Delta(5)-steroid dehydrogenase inhibitor, 2alpha-cyano-17beta-hydroxy-4,4',17alpha-trimethylandrost-5-ene-3-one. The NO donor, (Z)-1-[2-(2-aminoethyl-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate(deta nonoate), inhibited vasoactive intestinal peptide-, forskolin- and 22alpha-hydroxycholesterol (22HC)-facilitated pregnenolonogenesis in the absence of GC-S activation and in the presence of a GC-S inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). CYP11A1 was also heterologously expressed in monkey COS7 cells. Deta nonoate inhibited 22HC-facilitated activity of the over-expressed enzyme in the absence of GC-S activation and in the presence of ODQ. The NO-independent, GC-S agonist, 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole did not inhibit steroidogenesis. The IC(50) for effects of free NO on CYP11A1 was potent and in the 0.4-2 microM range. These results support the hypothesis that NO inhibits the rate-limiting enzyme in steroidogenesis independent of GC-S activation.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics, University of North Dakota School of Medicine and Health Sciences, 501 North Columbia Road, 58203, Grand Forks, ND 58203, USA. james.drewett@uc.edu
authors.forename: James G
authors.initials: JG
authors.lastname: Drewett
authors.forename: Robin L
authors.initials: RL
authors.lastname: Adams-Hays
authors.forename: Begonia Y
authors.initials: BY
authors.lastname: Ho
authors.forename: David J
authors.initials: DJ
authors.lastname: Hegge
mesh_terms: D000818:Animals; D019556:COS Cells; D002384:Catalysis / Q000187:drug effects; D002786:Cholesterol Side-Chain Cleavage Enzyme / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006152:Cyclic GMP / Q000032:analysis; D006162:Guanylate Cyclase / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006834:Hydrazines / Q000494:pharmacology; D051379:Mice; D024101:Mitochondrial Proteins; D009569:Nitric Oxide / Q000502:physiology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009603:Nitroso Compounds; D016716:PC12 Cells; D011284:Pregnenolone / Q000096:biosynthesis; D051381:Rats; D013256:Steroids / Q000096:biosynthesis*; D014162:Transfection
chemical_list: D006834:Hydrazines; D024101:Mitochondrial Proteins; D020030:Nitric Oxide Donors; D009603:Nitroso Compounds; D013256:Steroids; C094210:2,2'-(hydroxynitrosohydrazono)bis-ethanamine; D009569:Nitric Oxide; D011284:Pregnenolone; D002786:Cholesterol Side-Chain Cleavage Enzyme; D006162:Guanylate Cyclase; D006152:Cyclic GMP