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      Role of aryl hydrocarbon receptor-mediated induction of the CYP1 enzymes in environmental toxicity and cancer.

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          Abstract

          The mammalian CYP1A1, CYP1A2, and CYP1B1 genes (encoding cytochromes P450 1A1, 1A2, and 1B1, respectively) are regulated by the aromatic hydrocarbon receptor (AHR). The CYP1 enzymes are responsible for both metabolically activating and detoxifying numerous polycyclic aromatic hydrocarbons (PAHs) and aromatic amines present in combustion products. Many substrates for CYP1 enzymes are AHR ligands. Differences in AHR affinity between inbred mouse strains reflect variations in CYP1 inducibility and clearly have been shown to be associated with differences in risk of toxicity or cancer caused by PAHs and arylamines. Variability in the human AHR affinity exists, but differences in human risk of toxicity or cancer related to AHR activation remain unproven. Mouse lines having one or another of the Cyp1 genes disrupted have shown paradoxical effects; in the test tube or in cell culture these enzymes show metabolic activation of PAHs or arylamines, whereas in the intact animal these enzymes are sometimes more important in the role of detoxification than metabolic potentiation. Intact animal data contradict pharmaceutical company policies that routinely test drugs under development; if a candidate drug shows CYP1 inducibility, further testing is generally discontinued for fear of possible toxic or carcinogenic effects. In the future, use of "humanized" mouse lines, containing a human AHR or CYP1 allele in place of the orthologous mouse gene, is one likely approach to show that the AHR and the CYP1 enzymes in human behave similarly to that in mouse.

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          Author and article information

          Journal
          J Biol Chem
          The Journal of biological chemistry
          American Society for Biochemistry & Molecular Biology (ASBMB)
          0021-9258
          0021-9258
          Jun 04 2004
          : 279
          : 23
          Affiliations
          [1 ] Department of Environmental Health and Center for Environmental Genetics, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0056, USA. dan.nebert@uc.edu
          Article
          S0021-9258(20)66509-7
          10.1074/jbc.R400004200
          15028720
          1ca2f7ee-c9b2-4d60-866e-834a57f68bca
          History

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