title: Serum and extracellular calcium modulate induction of cytochrome P-450IA1 in human keratinocytes.
abstract: Culture conditions allowing for cytochrome P-450IA1 induction by 2,3,7,8-tetrachlorodibenzofuran (TCDF) in normal human keratinocytes (HK) were investigated. HK grown in serum-free low extracellular Ca2+ (0.1 mM) medium did not accumulate P-450IA1 mRNA in response to TCDF. If, however, the cultures were pretreated for more than 24 h with either serum or elevated extracellular Ca2+ (2.0 mM), induction of P-450IA1 was obtained by TCDF. Serum and elevated Ca2+ concentrations were found to be additive in this respect. When analyzing HK derived from five individuals, no apparent difference was found in the relative induction of P-450IA1 by increasing concentrations of TCDF, giving an EC50 of approximately 2 nM. The permissive effect of serum and elevated Ca2+ could be conferred to a reporter gene by the -1140 to +2435 part of the human CYPIA1 gene. Culture conditions allowing for P-450IA1 induction correlated with conditions that induced mRNA corresponding to the differentiation specific enzyme epidermal transglutaminase. This finding, together with the known differentiation promoting effects of serum and elevated Ca2+, suggest that terminal differentiation is necessary for P-450IA1 induction in HK by Ah receptor ligands.
authors.affiliation: Center for Biotechnology, Karolinska Institute, NOVUM, Huddinge, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Berghard
authors.forename: K
authors.initials: K
authors.lastname: Gradin
authors.forename: R
authors.initials: R
authors.lastname: Toftgård
mesh_terms: D001769:Blood; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D003470:Culture Media; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004790:Enzyme Induction; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics*; D011503:Transglutaminases / Q000096:biosynthesis / Q000235:genetics
chemical_list: D003470:Culture Media; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D011503:Transglutaminases; D002118:Calcium