Showing papers by "Jeroen Buters published in 1999"
TL;DR: CYP1B1-null mice, created by targeted gene disruption in embryonic stem cells, were born at the expected frequency from heterozygous matings with no observable phenotype as discussed by the authors.
Abstract: CYP1B1-null mice, created by targeted gene disruption in embryonic stem cells, were born at the expected frequency from heterozygous matings with no observable phenotype, thus establishing that CYP1B1 is not required for mouse development. CYP1B1 was not detectable in cultured embryonic fibroblast (EF) or in different tissues, such as lung, of the CYP1B1-null mouse treated with the aryl hydrocarbon receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin whereas the equivalent wild-type EF cells express basal and substantial inducible CYP1B1 and lung expresses inducible CYP1B1. CYP1A1 is induced to far higher levels than CYP1B1 in liver, kidney, and lung in wild-type mice and is induced to a similar extent in CYP1B1-null mice. 7,12-dimethylbenz[a]anthracene (DMBA) was toxic in wild-type EFs that express CYP1B1 but not CYP1A1. These cells effectively metabolized DMBA, consistent with CYP1B1 involvement in producing the procarcinogenic 3,4-dihydrodiol as a major metabolite, whereas CYP1B1-null EF showed no significant metabolism and were resistant to DMBA-mediated toxicity. When wild-type mice were administered high levels of DMBA intragastrically, 70% developed highly malignant lymphomas whereas only 7.5% of CYP1B1-null mice had lymphomas. Skin hyperplasia and tumors were also more frequent in wild-type mice. These results establish that CYP1B1, located exclusively at extrahepatic sites, mediates the carcinogenicity of DMBA. Surprisingly, CYP1A1, which has a high rate of DMBA metabolism in vitro, is not sufficient for this carcinogenesis, which demonstrates the importance of extrahepatic P450s in determining susceptibility to chemical carcinogens and validates the search for associations between P450 expression and cancer risk in humans.
369 citations
TL;DR: Findings provide convincing evidence that bone marrow stromal cell CYP1B1 metabolism of DMBA, but not AhR activation, is required for DMBA-induced pre-B-cell apoptosis.
Abstract: We previously demonstrated that murine bone marrow stromal cells express high levels of cytochrome P4501B1 (CYP1B1) that metabolizes 7,12-dimethylbenza[a]anthracene (DMBA), and that DMBA activates the Ah receptor (AhR) in these cells in vitro. More recently, we reported that CYP1B1 is required for DMBA-induced lymphoblastoma formation in vivo. In this study, we addressed the hypothesis that bone marrow stromal cell CYP1B1, and not AhR activation, is required for DMBA-induced pre-B-cell apoptosis. Although DMBA did not directly cause apoptosis in pre-B cells, dose-dependent apoptosis of pre-B cells was observed when they were cocultured with a bone marrow stromal cell line. The DMBA 3,4-dihydrodiol metabolite was more potent in effecting pre-B-cell apoptosis than DMBA, whereas the potent AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin was inactive. Both pre-B cells and bone marrow stromal cells contained DMBA-diol-epoxide DNA adducts, indicating that reactive metabolites were transferred from stromal cells to pre-B cells. DMBA caused apoptosis when cocultured with primary bone marrow stromal cells isolated from AhR-null mice but not CYP1B1-null mice. When cocultured with AhR-null primary bone marrow stromal cells, DMBA induced approximately 50% of the pre-B-cell apoptosis seen with stromal cells from AhR-heterozygous mice. This reduced level of apoptosis parallels the decreased CYP1B1 expression in AhR-null mouse bone marrow stromal cells. These findings provide convincing evidence that bone marrow stromal cell CYP1B1 metabolism of DMBA, but not AhR activation, is required for DMBA-induced pre-B-cell apoptosis.
49 citations
TL;DR: The first report on the establishment of a cytochrome P450 (P450)-null mouse line appeared in 1995 and several other mouse lines lacking P450s have been produced since then.
Abstract: In 1995, the first report on the establishment of a cytochrome P450 (P450)-null mouse line appeared [1]. Since then, several other mouse lines lacking P450s have been produced. The total number of ...
31 citations
TL;DR: After almost two decades, it is now evident that methodology based on molecular biology and gene technology has dramatically changed the way basic and applied toxicology is being performed as discussed by the authors, and it star...
Abstract: After almost two decades, it is now evident that methodology based on molecular biology and gene technology has dramatically changed the way basic and applied toxicology is being performed. It star...
23 citations