11?-Hydroxysteroid dehydrogenases control access of 7?,27-dihydroxycholesterol to retinoid-related orphan receptor ?.

ABSTRACT: Oxysterols previously were considered intermediates of bile acid and steroid hormone biosynthetic pathways. However, recent research has emphasized the roles of oxysterols in essential physiologic processes and in various diseases. Despite these discoveries, the metabolic pathways leading to the different oxysterols are still largely unknown and the biosynthetic origin of several oxysterols remains unidentified. Earlier studies demonstrated that the glucocorticoid metabolizing enzymes, 11?-hydroxysteroid dehydrogenase (11?-HSD) types 1 and 2, interconvert 7-ketocholesterol (7kC) and 7?-hydroxycholesterol (7?OHC). We examined the role of 11?-HSDs in the enzymatic control of the intracellular availability of 7?,27-dihydroxycholesterol (7?27OHC), a retinoid-related orphan receptor ? (ROR?) ligand. We used microsomal preparations of cells expressing recombinant 11?-HSD1 and 11?-HSD2 to assess whether 7?27OHC and 7-keto,27-hydroxycholesterol (7k27OHC) are substrates of these enzymes. Binding of 7?27OHC and 7k27OHC to 11?-HSDs was studied by molecular modeling. To our knowledge, the stereospecific oxoreduction of 7k27OHC to 7?27OHC by human 11?-HSD1 and the reverse oxidation reaction of 7?27OHC to 7k27OHC by human 11?-HSD2 were demonstrated for the first time. Apparent enzyme affinities of 11?-HSDs for these novel substrates were equal to or higher than those of the glucocorticoids. This is supported by the fact that 7k27OHC and 7?27OHC are potent inhibitors of the 11?-HSD1-dependent oxoreduction of cortisone and the 11?-HSD2-dependent oxidation of cortisol, respectively. Furthermore, molecular docking calculations explained stereospecific enzyme activities. Finally, using an inducible ROR? reporter system, we showed that 11?-HSD1 and 11?-HSD2 controlled ROR? activity. These findings revealed a novel glucocorticoid-independent prereceptor regulation mechanism by 11?-HSDs that warrants further investigation.

SUBMITTER: Beck KR 

PROVIDER: S-EPMC6718442 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature