New insights into the molecular mechanisms of chemical carcinogenesis: In vivo adduction of histone H2B by a reactive metabolite of the chemical carcinogen furan.
Furan is a rodent hepatocarcinogen ubiquitously found in the environment and heat-processed foods. Furan undergoes cytochrome P450 2E1-catalyzed bioactivation to cis-2-butene-1,4-dial (BDA), which has been shown to form an electrophilic conjugate (GSH-BDA) with glutathione. Both BDA and GSH-BDA yield covalent adducts with lysine residues in proteins. Dose- and time-dependent epigenetic histone alterations have been observed in furan-treated rats. While the covalent modification of histones by chemical carcinogens has long been proposed, histone-carcinogen adducts have eluded detection in vivo. In this study, we investigated if the covalent modification of histones by furan may occur in vivo prior to epigenetic histone alterations. Using a "bottom-up" methodology, involving the analysis of tryptic peptides by liquid chromatography - high resolution mass spectrometry, we obtained evidence for a cross-link between GSH-BDA and lysine 107 of histone H2B isolated from the livers of male F344 rats treated with tumorigenic doses of furan. This cross-link was detected at the shortest treatment period (90 days) in the lowest dose group (0.92mg/kg body weight/day), prior to the identification of epigenetic changes, and occurred at a lysine residue that is a target for epigenetic modifications and crucial for nucleosome stability. Our results represent the first unequivocal proof of the occurrence of carcinogen-modified histones in vivo and suggest that such modification happens at the initial stages of furan-induced carcinogenesis. This type of alteration may be general in scope, opening new insights into the mechanisms of chemical carcinogenesis/toxicity and new opportunities for the development of early compound-specific biomarkers of exposure.
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
João
J
Nunes
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
Inês L
IL
Martins
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
Catarina
C
Charneira
Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Igor P
IP
Pogribny
Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Aline
A
de Conti
Division of Biochemical Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA.
Frederick A
FA
Beland
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
M Matilde
MM
Marques
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
Cristina C
CC
Jacob
Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. Electronic address: alexandra.antunes@tecnico.ulisboa.pt.
Alexandra M M
AMM
Antunes
D000818:Animals; D063646:Carcinogenesis / Q000187:drug effects*; D015197:Carcinogenicity Tests; D002273:Carcinogens / Q000633:toxicity*; D005663:Furans / Q000378:metabolism / Q000633:toxicity*; D005978:Glutathione / Q000737:chemistry; D006657:Histones / Q000633:toxicity*; D008099:Liver / Q000737:chemistry / Q000378:metabolism; D008297:Male; D010455:Peptides / Q000737:chemistry; D051381:Rats; D011916:Rats, Inbred F344; D014357:Trypsin / Q000737:chemistry
D002273:Carcinogens; D005663:Furans; D006657:Histones; D010455:Peptides; D014357:Trypsin; D005978:Glutathione
Biomarkers; Chemically induced cancers; Furan; Histone adducts