Induction of CYP1A1 and CYP1B1 in T-47D human breast cancer cells by benzo[a]pyrene is diminished by arsenite.
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.
Spink
David C
DC
Laboratory of Human Toxicology and Molecular Epidemiology, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA. spink@wadsworth.org
Katz
Barbara H
BH
Hussain
Mirza M
MM
Spink
Barbara C
BC
Wu
Susan J
SJ
Liu
Ning
N
Pause
Ronald
R
Kaminsky
Laurence S
LS
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
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