title: Sodium nitrite-stimulated metabolic activation of benzo[a]pyrene 7,8-dihydrodiol in human polymorphonuclear leukocytes.
abstract: Sodium nitrite was shown to enhance the metabolism of trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) to 7/8,9,10- and 7,10/8,9-tetrahydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (tetraols) in phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMNs). The production of these tetraols implicates the intermediate formation of the corresponding trans-7,8-dihydroxy-9,10-epoxy-7,8-9,10-tetrahydrobenzo[a]pyrene (anti-BPDE). A 2- to 3-fold increase in the tetraol yield was observed in the presence of nitrite in excess of 1 mM. Sodium azide, an inhibitor of myeloperoxidase and catalase, reduced the nitrite-stimulated metabolism of BP-7,8-diol in PMA-activated leukocytes. Diphenylene iodonium sulphate, a NADPH-oxidase inhibitor, lowered the production of tetraols in PMA-stimulated leukocytes both in the absence and presence of nitrite. Additionally, nitrite markedly enhanced the covalent binding of metabolites derived from [3H](-)-BP-7,8-diol to leukocyte proteins as well as to DNA present extracellularly. The nitrite-stimulated covalent binding to both proteins and DNA was inhibited by the presence of sodium azide. The mechanism underlying the effect of nitrite on the metabolism of BP-7,8-diol to reactive intermediates in PMA-activated human polymorphonuclear leukocytes is not known. However, the results are compatible with a peroxidase-dependent mechanism although other possible pathways may contribute to the enhanced rate of metabolism.
authors.affiliation: Department of Toxicology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: D
authors.initials: D
authors.lastname: Constantin
authors.forename: B
authors.initials: B
authors.lastname: Jernström
authors.forename: I A
authors.initials: IA
authors.lastname: Cotgreave
authors.forename: P
authors.initials: P
authors.lastname: Moldeus
mesh_terms: D001711:Biotransformation; D002273:Carcinogens; D002851:Chromatography, High Pressure Liquid; D004101:Dihydroxydihydrobenzopyrenes / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity; D006801:Humans; D009504:Neutrophils / Q000187:drug effects*; D012977:Sodium Nitrite / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002273:Carcinogens; D004101:Dihydroxydihydrobenzopyrenes; C017228:benzo(a)pyrene 7,8-dihydrodiol; D012977:Sodium Nitrite; D013755:Tetradecanoylphorbol Acetate