title: Potent mutagenicity of 3-methylindole requires pulmonary cytochrome P450-mediated bioactivation: a comparison to the prototype cigarette smoke mutagens B(a)P and NNK.
abstract: 3-Methylindole (3MI) is a preferential pneumotoxicant found in cigarette smoke. A number of lung-expressed human cytochrome P450 enzymes, including 1A1, 2F1, and 2A13, catalyze the metabolism of 3MI to reactive intermediates that fragment DNA, measured with the Comet assay to assess DNA damage, in a cytochrome P450-dependent manner in primary normal human lung cells in culture, but the mutagenesis of 3MI has been controversial. In the present study, the mutagenic potential of 3MI was compared to the prototypical cigarette smoke carcinogens benzo(a)pyrene (B(a)P) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). 3MI, B(a)P, and NNK were incubated with the Salmonella typhimurium strain TA98, which is known to detect the most common subtype of cigarette smoke-induced mutagenicity, frameshift mutations in DNA, and with Salmonella typhimurium strain TA100, which detects base pair substitution mutants, with five sources of P450-mediated bioactivation: rat liver S9, human lung microsomes, recombinant CYP2A13, purified CYP2F3, and recombinant CYP1A1. Only B(a)P was mutagenic in TA100, and it was bioactivated by human lung microsomes and rat liver S9 sources of P450s. However, with the TA98 strain, CYP1A1, CYP2A13, CYP2F3, and human lung microsomes bioactivated 3MI to highly mutagenic intermediates, whereas neither human nor rat liver S9 subcellular fractions formed mutagenic intermediates from 3MI. Quantitative Western blot analysis verified that all three respiratory enzymes were present in human lung microsomes in widely varying amounts. These results indicate that metabolism of 3MI by human lung-expressed cytochrome P450 enzymes but not hepatic P450s elicits equivalent or higher mutagenicity than the prototype cigarette smoke mutagens B(a)P and NNK and indicates that 3MI is a likely human pulmonary carcinogen.
authors.affiliation: Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112-5820, USA.
authors.forename: Jessica M
authors.initials: JM
authors.lastname: Weems
authors.forename: John G
authors.initials: JG
authors.lastname: Lamb
authors.forename: Jaime
authors.initials: J
authors.lastname: D'Agostino
authors.forename: Xinxin
authors.initials: X
authors.lastname: Ding
authors.forename: Garold S
authors.initials: GS
authors.lastname: Yost
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000737:chemistry / Q000633:toxicity; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D006801:Humans; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D009152:Mutagenicity Tests; D009153:Mutagens / Q000737:chemistry / Q000633:toxicity*; D009602:Nitrosamines / Q000737:chemistry / Q000633:toxicity; D051381:Rats; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects; D012862:Skatole / Q000737:chemistry / Q000633:toxicity*; D012907:Smoking
chemical_list: D009153:Mutagens; D009602:Nitrosamines; D000091243:Ribosomal Protein S9; D012269:Ribosomal Proteins; D001564:Benzo(a)pyrene; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; D003577:Cytochrome P-450 Enzyme System; D012862:Skatole; D001189:Aryl Hydrocarbon Hydroxylases; C414206:CYP2A13 protein, human
references.citation: Drug Metab Dispos. 1985 Nov-Dec;13(6):690-4
references.pmid: 2867872
references.citation: Cancer Res. 2000 Sep 15;60(18):5074-9
references.pmid: 11016631
references.citation: Oncogene. 2002 Oct 21;21(48):7298-306
references.pmid: 12379874
references.citation: Biochemistry. 2008 Sep 16;47(37):9756-70
references.pmid: 18717595
references.citation: Carcinogenesis. 2005 Mar;26(3):621-9
references.pmid: 15579482
references.citation: Am J Public Health. 1992 Jul;82(7):1023-6
references.pmid: 1609904
references.citation: Chem Res Toxicol. 2001 Jul;14(7):767-90
references.pmid: 11453723
references.citation: Mutat Res. 2001 May 31;492(1-2):13-27
references.pmid: 11377240
references.citation: Toxicol Appl Pharmacol. 1991 May;108(3):531-7
references.pmid: 2020974
references.citation: Carcinogenesis. 2005 Nov;26(11):1947-55
references.pmid: 15958517
references.citation: Toxicol Sci. 2009 Nov;112(1):59-67
references.pmid: 19700606
references.citation: Chem Res Toxicol. 1996 Jan-Feb;9(1):291-7
references.pmid: 8924606
references.citation: Proc Natl Acad Sci U S A. 1975 Dec;72(12):5135-9
references.pmid: 1061098
references.citation: J Pharmacol Exp Ther. 1996 Jan;276(1):21-9
references.pmid: 8558432
references.citation: Toxicol Appl Pharmacol. 1993 Oct;122(2):182-90
references.pmid: 8212000
references.citation: Cancer Res. 1995 Dec 1;55(23):5566-73
references.pmid: 7585636
references.citation: Chem Res Toxicol. 2001 Aug;14(8):1014-24
references.pmid: 11511175
references.citation: Chem Res Toxicol. 1998 Nov;11(11):1326-31
references.pmid: 9815193
references.citation: Chem Res Toxicol. 2010 Mar 15;23(3):696-704
references.pmid: 20187624
references.citation: Food Chem Toxicol. 2003 Jun;41(6):807-17
references.pmid: 12738186
references.citation: J Biol Chem. 2003 May 2;278(18):15473-83
references.pmid: 12598524
references.citation: Drug Metab Dispos. 2006 Oct;34(10):1672-6
references.pmid: 16815959
references.citation: Drug Metab Dispos. 1999 Jul;27(7):798-803
references.pmid: 10383923
references.citation: Chem Res Toxicol. 1998 Jul;11(7):741-9
references.pmid: 9671536
references.citation: Tob Control. 2004 Mar;13(1):13-6
references.pmid: 14985588
references.citation: Proc Natl Acad Sci U S A. 1975 Mar;72(3):979-83
references.pmid: 165497
references.citation: Chem Res Toxicol. 1992 Sep-Oct;5(5):713-9
references.pmid: 1446013
references.citation: Environ Mol Mutagen. 2002;40(1):1-17
references.pmid: 12211071
references.citation: Carcinogenesis. 2002 Dec;23(12):1969-77
references.pmid: 12507920
references.citation: Biochimie. 2010 Mar;92(3):292-306
references.pmid: 20034539
references.citation: Drug Metab Dispos. 2009 Oct;37(10):2018-27
references.pmid: 19608696
references.citation: J Pharmacol Exp Ther. 1998 Jun;285(3):1287-95
references.pmid: 9618435
references.citation: Drug Metab Dispos. 2008 Jan;36(1):155-62
references.pmid: 17962375
references.citation: Annu Rev Pharmacol Toxicol. 2003;43:149-73
references.pmid: 12171978
references.citation: Mutat Res. 2008 Jan 31;650(1):15-29
references.pmid: 18006367
references.citation: Chem Res Toxicol. 1989 Sep-Oct;2(5):273-9
references.pmid: 2519817
references.citation: Toxicol Appl Pharmacol. 1987 Aug;90(1):60-8
references.pmid: 3629592
references.citation: Toxicol Sci. 2003 Feb;71(2):229-36
references.pmid: 12563108
references.citation: J Natl Cancer Inst. 1999 Jul 21;91(14):1194-210
references.pmid: 10413421
references.citation: J Pharmacol Exp Ther. 2007 Nov;323(2):570-8
references.pmid: 17671098
references.citation: Drug Metab Dispos. 2001 Jul;29(7):950-3
references.pmid: 11408359
references.citation: Chem Res Toxicol. 2009 Aug;22(8):1406-14
references.pmid: 19947653
references.citation: Chem Res Toxicol. 2007 Jan;20(1):140-8
references.pmid: 17226936
references.citation: Cancer Res. 2003 Nov 15;63(22):7581-3
references.pmid: 14633670