The aryl hydrocarbon receptor (AHR) belongs to the family of Per-Arnt-Sim (PAS) transcription factors, which are evolutionarily conserved and participate in the sensing of environmental stimuli. They encompass molecules that are involved in chemical sensing, such as AHR, in the regulation of circadian rhythm, such as BMAL1 and BMAL2, and in the detection of oxygen concentrations, such as HIF-1a, HIF-2a and HIF-3a [1–۳]. AHR is widely expressed in different tissues [4] and its activity is tightly controlled. It is normally present in the cell cytoplasm in an inactive state bound to proteins, including the chaperone Hsp90 [5], AHR interacting protein (AIP) [6,7] and the cochaperone p23 [8], that enhance the ability of AHR to bind ligands and prevent its migration to the nucleus. Upon ligand binding, AHR is released from the chaperones, translocates to the nucleus and binds to the AHR-nuclear translocator (ARNT) [9]. This heterodimer binds to dioxin responsive elements (DRE) of various enhancers and promoters to induce transcription of target genes [10]. Typically, these include the microsomal cytochrome P450-dependent monooxygenases CYP1A1 and CYP1A2, which participate in the metabolism of AHR ligands [1]. The AHR signaling pathway has been recently reviewed in detail [11].