Abstract
The aryl hydrocarbon receptor (AHR) mediates most, if not all, of the many toxicological effects of the environmental pollutant 2,3,7,8-tetrachlorodibenzo- p-dioxin [(TCDD) or dioxin]. The "classical" pathway of AHR action involves dimerization of the liganded AHR with the aryl hydrocarbon nuclear translocator (ARNT) protein, and the AHR-ARNT dimer specifically associates with the enhancer regions of dioxin-responsive genes, leading to their increased transcription. Sutter and coworkers recently reported that epidermal growth factor (EGF) represses the dioxin-mediated induction of CYP1A1 in cultured normal human keratinocytes by inhibiting the recruitment of the transcriptional coactivator protein p300 to the CYP1A1 gene. EGF also inhibits the dioxin-dependent induction of certain parameters in keratinocytes that are reflective of dioxin-induced chloracne. These findings point to the potential usefulness of EGF for the treatment of chloracne and also describe a novel mechanism for repression of dioxin-induced gene transcription.