Bone Marrow Stromal Cells Constitutively Express High Levels of Cytochrome P4501B1 that Metabolize 7,12-Dimethylbenz[a]anthracene
- 1The Center for Environmental Toxicology (S.M.H., C.J.C., C.R.J.),2Department of Pathobiological Sciences (S.M.H., C.J.C.), and3Department of Pharmacology (C.R.J.), University of Wisconsin, Madison, Wisconsin 53706
Abstract
The polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene (DMBA) is a potent carcinogen that produces immunotoxic effects in bone marrow. Here, we show that bone marrow stromal cells metabolize DMBA to such products as 3,4-dihydrodiol, the precursor to the most mutagenic DMBA metabolite. The BMS2 bone marrow stromal cell line constitutively expressed higher levels of CYP1B1 protein and mRNA than C3H10T½ mouse embryo fibroblasts. BMS2 cells also produced a DMBA metabolite profile that was consistent with CYP1B1 activity. Treatment with the potent aryl hydrocarbon receptor (AhR) ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced a ∼2-fold increase in CYP1B1 mRNA, protein, and activity in BMS2 cells. Two forms of the AhR (97 and 104 kDa) and the AhR nuclear translocator were detected in BMS2 cells. The AhR translocated to the nucleus after treatment with TCDD or DMBA but was ∼5 times slower with DMBA. Primary bone marrow stromal (BMS) cell cultures established from AhR−/− mice showed similar basal CYP1B1 expression and activity as cell cultures established from heterozygous littermates or C57BL/6 mice. However, primary BMS cells from AhR−/− mice did not exhibit increased CYP1B1 protein expression after incubation with TCDD. BMS cells therefore constitutively express functional CYP1B1 that is not dependent on the AhR. This contrasts with embryo fibroblasts from the same mouse strain, in which basal CYP1B1 expression is AhR dependent. We therefore conclude that bone marrow toxicity may be mediated by CYP1B1-dependent DMBA metabolism, which is regulated by factors other than the AhR.
Footnotes
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Send reprint requests to: Dr. Colin R. Jefcoate, Department of Pharmacology, Medical Science Center, University of Wisconsin, Madison, 1300 University Avenue, Madison, WI 53706. E-mail:jefcoate{at}facstaff.wisc.edu
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This work was supported by the University of Wisconsin School of Veterinary Medicine, by National Institute of Environmental Health Sciences Training Grants ES07015 and IF32-ES05827 (S.M.H.), and by National Institutes of Health Grant CA16265 (C.R.J.).
- Abbreviations:
- PAH
- polycyclic aromatic hydrocarbon
- AhR−/− BMS
- primary bone marrow stromal cells prepared from AhR null mice
- AhR+/− BMS
- primary bone marrow stromal cells prepared from AhR heterozygote mice
- AhR
- aryl hydrocarbon receptor
- ARNT
- aryl hydrocarbon receptor nuclear translocator
- BMS
- bone marrow stromal
- C57-BMS
- primary bone marrow stromal cells prepared from C57Bl/6 mice
- DMBA
- 7,12-dimethylbenz[a]anthracene
- DMSO
- dimethylsulfoxide
- EGTA
- ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid
- FBS
- fetal bovine serum
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- SDS
- sodium dodecyl sulfate
- TCDD
- 2,3,7,8-tetrachlorodibenzo-p-dioxin
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- Received May 4, 1998.
- Accepted September 9, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
