title: Induction of CYP1A1 and CYP1B1 in T-47D human breast cancer cells by benzo[a]pyrene is diminished by arsenite.
abstract: Polycyclic aromatic hydrocarbons (PAHs) and metals are often environmental cocontaminants, yet there have been relatively few studies of combined effects of PAHs and metals on cytochrome P450 (P450)-catalyzed metabolism. We examined the effects of NaAsO(2) in combination with benzo[a]pyrene (BAP) on CYP1A1 and CYP1B1 in T-47D human breast cancer cells by using estrogen metabolism as a probe of their activities. Exposure to BAP caused elevated rates of the 2- and 4-hydroxylation pathways of estrogen metabolism, indicating induction of both CYP1A1, an estradiol 2-hydroxylase, and CYP1B1, an estradiol 4-hydroxylase. BAP-induced metabolism peaked 9 to 16 h after exposure and returned to near-basal levels by 48 h. Concentration-response studies showed maximal induction of the 2- and 4-hydroxylation pathways at 3 microM BAP; higher levels caused reduced rates of metabolism due to inhibition of CYP1A1 and CYP1B1. NaAsO(2) caused pronounced decreases in the induction of CYP1A1 and CYP1B1 by 3 microM BAP because cotreatment with 10 microM NaAsO(2) inhibited the rates of the 2- and 4-hydroxylation pathways by 86 and 92%, respectively. Western immunoblots showed diminished levels of BAP-induced CYP1A1 by coexposure to NaAsO(2). The levels of the CYP1A1 and CYP1B1 mRNAs induced by BAP were not significantly affected by coexposure to NaAsO(2); however, heme oxygenase 1 mRNA levels were markedly induced by coexposure to BAP and NaAsO(2). These results indicate a post-transcriptional inhibitory effect of arsenite on the expression of CYP1A1 and CYP1B1 in T-47D cells, possibly resulting from reduced heme availability.
authors.affiliation: Laboratory of Human Toxicology and Molecular Epidemiology, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA. spink@wadsworth.org
authors.forename: David C
authors.initials: DC
authors.lastname: Spink
authors.forename: Barbara H
authors.initials: BH
authors.lastname: Katz
authors.forename: Mirza M
authors.initials: MM
authors.lastname: Hussain
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Spink
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Wu
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.forename: Ronald
authors.initials: R
authors.lastname: Pause
authors.forename: Laurence S
authors.initials: LS
authors.lastname: Kaminsky
mesh_terms: D018053:Arsenites / Q000633:toxicity*; D001189:Aryl Hydrocarbon Hydroxylases; D001564:Benzo(a)pyrene / Q000633:toxicity*; D015153:Blotting, Western; D001943:Breast Neoplasms; D002851:Chromatography, High Pressure Liquid; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D004785:Environmental Pollutants / Q000633:toxicity*; D004790:Enzyme Induction / Q000187:drug effects; D004958:Estradiol / Q000378:metabolism; D047628:Estrogen Receptor alpha; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism; D051547:Heme Oxygenase-1; D006801:Humans; D006900:Hydroxylation; D008565:Membrane Proteins; D006899:Mixed Function Oxygenases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000819:agonists; D011960:Receptors, Estrogen / Q000378:metabolism; D017670:Sodium Compounds / Q000633:toxicity*; D014407:Tumor Cells, Cultured
chemical_list: D018053:Arsenites; D004785:Environmental Pollutants; D047628:Estrogen Receptor alpha; D008565:Membrane Proteins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D011960:Receptors, Estrogen; D017670:Sodium Compounds; D001564:Benzo(a)pyrene; C017947:sodium arsenite; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1