title: Potentiation of proopiomelanocortin gene expression in cultured pituitary cells by benzodiazepines.
abstract: BACKGROUND
  Benzodiazepines are frequently used not only as a part of general anesthesia but also for the purpose of sedation during regional anesthesia. Effects of these drugs on the hypothalamic-pituitary-adrenal axis activity have been studied, but are still controversial. It is not known whether benzodiazepines affect expression of proopiomelanocortin, precursor protein of adrenocorticotropic hormone and related peptides.
  
  
  METHODS
  AtT20PL cell line, a clone of AtT20/D16v mouse corticotroph tumor cells stably transfected with approximately 0.7 kilobases (kb) of the rat proopiomelanocortin 5' promoter-luciferase fusion gene, was used. In the presence or absence of diazepam or midazolam, cells were stimulated by corticotropin-releasing hormone (CRH) or forskolin. Proopiomelanocortin gene expression was estimated by measurement of luciferase activity. Furthermore, to study the mechanism of benzodiazepine effects, cyclic adenosine 3',5'-monophosphate (cyclic AMP) efflux was measured by enzyme immunoassay.
  
  
  RESULTS
  Diazepam and midazolam dose-dependently increased the proopiomelanocortin gene expression induced by CRH or forskolin. The potentiating effect was not affected by benzodiazepine receptor antagonists flumazenil and PK11195, but was abolished by a cyclic AMP-dependent protein kinase inhibitor H89. Cyclic AMP efflux induced by CRH or forskolin was also enhanced by diazepam and midazolam. In the presence of isobutylmethylxanthine, a nonspecific phosphodiesterase inhibitor, potentiation of proopiomelanocortin gene expression and enhancement of cyclic AMP efflux by benzodiazepines were not observed.
  
  
  CONCLUSIONS
  Benzodiazepines potentiate the effect of CRH or forskolin on proopiomelanocortin gene expression. The potentiating effect is not mediated by the benzodiazepine receptors, but its mechanism probably involves inhibition of phosphodiesterase.
authors.affiliation: Department of Anesthesia, Kyoto University Hospital, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan. kfukuda@kuhp.kyoto-u.ac.jp
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Fukuda
authors.forename: Nobuo
authors.initials: N
authors.lastname: Uetsuki
authors.forename: Hisatoshi
authors.initials: H
authors.lastname: Uga
authors.forename: Mitsuko
authors.initials: M
authors.lastname: Hashiguchi
authors.forename: Masami
authors.initials: M
authors.lastname: Sato
authors.forename: Taizo
authors.initials: T
authors.lastname: Hisano
authors.forename: Hajime
authors.initials: H
authors.lastname: Segawa
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Iwasaki
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003975:Diazepam / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D017930:Genes, Reporter; D007700:Kinetics; D008156:Luciferases / Q000235:genetics; D051379:Mice; D008874:Midazolam / Q000494:pharmacology; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D014162:Transfection
chemical_list: D014151:Anti-Anxiety Agents; D005576:Colforsin; D011333:Pro-Opiomelanocortin; D008156:Luciferases; D003975:Diazepam; D008874:Midazolam; D015056:1-Methyl-3-isobutylxanthine