Bioactivation of N-hydroxy-2-acetylaminofluorenes by N,O-acyltransferase: substituent effects on covalent binding to DNA.
N-Acetoxyarylamines are reactive metabolites that lead to arylamine adduct formation with biological macromolecules. A series of 7-substituted-N-hydroxy-2-acetylaminofluorenes were converted to reactive N-acetoxyarylamines by enzymatic N,O-acyltransfer in the presence of DNA. The N-arylhydroxamic acid substrates that contained electronegative 7-substituents formed greater amounts of DNA adducts than either the unsubstituted compound (N-OH-AAF) or those analogs that contained electron-donating groups in the 7-position. Glutathione did not decrease the rates of DNA adduct formation, but other nucleophiles, such as potassium O-ethylxanthate, thiourea and N-acetylmethionine, inhibited adduct formation by the 7-Br-substituted compound (7-Br-N-OH-AAF) and the unsubstituted parent compound (N-OH-AAF). Nucleophiles, reducing agents (e.g. ascorbic acid) and spin-trapping agents had minimal effect on DNA adduct formation by the bioactivated form of 7-acetyl-2-(N-hydroxy-acetylamino)fluorene (7-Ac-N-OH-AAF). Triethylphosphite, an agent that reacts with aryl nitrenes, caused a concentration-dependent reduction in the amount of DNA adduct formed subsequent to bioactivation of 7-Ac-N-OH-AAF, but did not influence adduct formation when N-OH-AAF and 7-Br-N-OH-AAF were the substrates. The results indicate that a change in the reaction mechanism(s) responsible for DNA adduct formation occurred when the strongly electronegative acetyl group was incorporated into the 7-position of N-OH-AAF. It is proposed that a nitrene intermediate is involved in the formation of covalent adducts with DNA when 7-Ac-N-OH-AAF is activated by N,O-acyltransfer.
Boteju
L W
LW
Department of Medicinal Chemistry, University of Minnesota, Minneapolis 55455.
Hanna
P E
PE
D000123:Acetyltransferases; D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001711:Biotransformation; D002273:Carcinogens / Q000493:pharmacokinetics*; D006224:Cricetinae; D003497:Cyclic N-Oxides; D004247:DNA / Q000187:drug effects / Q000378:metabolism*; D004249:DNA Damage; D005609:Free Radicals; D005978:Glutathione / Q000494:pharmacology; D006881:Hydroxyacetylaminofluorene / Q000031:analogs & derivatives* / Q000493:pharmacokinetics*; D008297:Male; D008647:Mesocricetus; D009589:Nitrogen Oxides; D013113:Spin Labels; D013329:Structure-Activity Relationship
D002273:Carcinogens; D003497:Cyclic N-Oxides; D005609:Free Radicals; D009589:Nitrogen Oxides; D013113:Spin Labels; C029217:phenyl-N-tert-butylnitrone; D006881:Hydroxyacetylaminofluorene; D004247:DNA; D000217:Acyltransferases; D000123:Acetyltransferases; C019736:N-hydroxyarylamine O-acetyltransferase; D005978:Glutathione; D001205:Ascorbic Acid