Figure 2.

AHR-dependent metabolic activation of PAHs by CYP1 isoforms. Lipophilic PAHs can easily pass the plasma membrane and activate the canonical AHR signaling pathway. The resulting induction of CYP1 isoform expression and enzyme activity accelerates the oxidative metabolism of the invading chemicals. In case a proper detoxification of the resulting reactive PAH metabolites by the conjugating enzyme system (not shown) fails, reactive PAH-diol epoxides may covalently bind to the DNA and form highly mutagenic bulky DNA adducts.