Abstract
Polycyclic aromatic hydrocarbons (PAHs) are major carcinogenic environmental contaminants known to exert bone marrow toxicity and to induce leukemias, suggesting that these chemicals target hematopoietic stem cells. To investigate this hypothesis, we studied the effects of PAHs on cell proliferation and differentiation in human hematopoietic CD34+ cell cultures. Benzo(a)pyrene (BP), a prototypical PAH, was shown to markedly impair CD34+ cell expansion and to inhibit CD34+ cell differentiation into various hematological cell lineages, including erythroid, granulomacrophagic, and megakaryocytic lineages. This was associated with the induction of a caspase- and mitochondrion-related apoptosis process. CD34+ progenitor cells were found to exhibit functional expression of the aryl hydrocarbon receptor (AhR), and the use of the pure AhR antagonist 3′-methoxy-4′-nitroflavone partially counteracted the deleterious effects of BP in CD34+ cell cultures, underlining the involvement of AhR in BP toxicity. Additional events such as CYP1A1/1B1-dependent PAH metabolism and adduct formation were also required since 1) 2,3,7,8-tetrachlorodibenzo-p-dioxin, a very potent ligand of the AhR that is poorly metabolized and therefore does not generate reactive metabolites in contrast to PAHs, failed to affect CD34+ cell expansion; 2) the CYP1A1/1B1 inhibitor α-naphthoflavone blocked both BP adduct formation and BP toxicity; and 3) benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide, a highly reactive BP metabolite, exerted a marked toxicity toward CD34+ cell cultures. Overall, these data indicate that human hematopoietic CD34+ cells can bioactivate chemical carcinogens such as PAHs and, in this way, constitute targets for such carcinogenic environmental contaminants.
Footnotes
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This work was supported by Agence Française de Sécurité Sanitaire et Environnementale and the Fondation de France. J.v.G. is a recipient of a fellowship from the Ligue contre le Cancer (Comité des Côtes d'Armor).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.105.084780.
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ABBREVIATIONS: PAH, polycyclic aromatic hydrocarbon; BP, benzo(a)pyrene; BPDE, benzo(a)pyrene-trans-7,8-dihydrodiol-9,10-epoxide; P450, cytochrome P450; AhR, aryl hydrocarbon receptor; ARNT, AhR nuclear translocator; DMBA, 7-12 dimethylbenzanthracene; NAC, N-acetylcysteine; NF, naphthoflavone; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin; Ab, antibody; mAb, monoclonal antibody; 3′M4′NF, 3′-methoxy-4′-nitroflavone; CFU, colony-forming unit(s); BFU-E, burst-forming units-erythroid; CFU-GM, CFU-granulocyte-macrophage; CFU-M, CFU-macrophage; FITC, fluorescein isothiocyanate; Ac-DEVD-AMC, N-acetyl-Asp-Glu-Val-Asp-amino-4-methylcoumarin; PIPES, 1,4-piperazinediethanesulfonic acid; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid; DiOC6(3), 3-3′-dihexyl-oxocarbocyanine; RT-PCR, reverse transcriptase-polymerase chain reaction; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; ROS, reactive oxygen species.
- Received February 9, 2005.
- Accepted April 26, 2005.
- The American Society for Pharmacology and Experimental Therapeutics
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