title: Hexose-6-phosphate dehydrogenase modulates 11beta-hydroxysteroid dehydrogenase type 1-dependent metabolism of 7-keto- and 7beta-hydroxy-neurosteroids.
abstract: BACKGROUND
  The role of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in the regulation of energy metabolism and immune system by locally reactivating glucocorticoids has been extensively studied. Experiments determining initial rates of enzyme activity revealed that 11beta-HSD1 can catalyze both the reductase and the dehydrogenase reaction in cell lysates, whereas it predominantly catalyzes the reduction of cortisone to cortisol in intact cells that also express hexose-6-phosphate dehydrogenase (H6PDH), which provides cofactor NADPH. Besides its role in glucocorticoid metabolism, there is evidence that 11beta-HSD1 is involved in the metabolism of 7-keto- and 7-hydroxy-steroids; however the impact of H6PDH on this alternative function of 11beta-HSD1 has not been assessed.
  
  
  METHODS
  We investigated the 11beta-HSD1-dependent metabolism of the neurosteroids 7-keto-, 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) and 7-keto- and 7beta-hydroxy-pregnenolone, respectively, in the absence or presence of H6PDH in intact cells. 3D-structural modeling was applied to study the binding of ligands in 11beta-HSD1.
  
  
  RESULTS
  We demonstrated that 11beta-HSD1 functions in a reversible way and efficiently catalyzed the interconversion of these 7-keto- and 7-hydroxy-neurosteroids in intact cells. In the presence of H6PDH, 11beta-HSD1 predominantly converted 7-keto-DHEA and 7-ketopregnenolone into their corresponding 7beta-hydroxy metabolites, indicating a role for H6PDH and 11beta-HSD1 in the local generation of 7beta-hydroxy-neurosteroids. 3D-structural modeling offered an explanation for the preferred formation of 7beta-hydroxy-neurosteroids.
  
  
  CONCLUSIONS
  Our results from experiments determining the steady state concentrations of glucocorticoids or 7-oxygenated neurosteroids suggested that the equilibrium between cortisone and cortisol and between 7-keto- and 7-hydroxy-neurosteroids is regulated by 11beta-HSD1 and greatly depends on the coexpression with H6PDH. Thus, the impact of H6PDH on 11beta-HSD1 activity has to be considered for understanding both glucocorticoid and neurosteroid action in different tissues.
authors.affiliation: Institute of Molecular and Systems Toxicology, University of Basel, Basel, Switzerland; Department of Nephrology and Hypertension, University of Berne, Berne, Switzerland.
authors.forename: Lyubomir G
authors.initials: LG
authors.lastname: Nashev
authors.forename: Charlie
authors.initials: C
authors.lastname: Chandsawangbhuwana
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Balazs
authors.forename: Atanas G
authors.initials: AG
authors.lastname: Atanasov
authors.forename: Bernhard
authors.initials: B
authors.lastname: Dick
authors.forename: Felix J
authors.initials: FJ
authors.lastname: Frey
authors.forename: Michael E
authors.initials: ME
authors.lastname: Baker
authors.forename: Alex
authors.initials: A
authors.lastname: Odermatt
mesh_terms: D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1 / Q000737:chemistry / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000378:metabolism*; D002478:Cells, Cultured; D003348:Cortisone / Q000378:metabolism; D003687:Dehydroepiandrosterone / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D008958:Models, Molecular; D018377:Neurotransmitter Agents / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D018377:Neurotransmitter Agents; D003687:Dehydroepiandrosterone; D002237:Carbohydrate Dehydrogenases; C020552:galactose-6-phosphate dehydrogenase; D043205:11-beta-Hydroxysteroid Dehydrogenase Type 1; C468386:HSD11B1 protein, human; D003348:Cortisone; D006854:Hydrocortisone