The Aryl hydrocarbon Receptor System

One of the best known detoxication system is the Arylhydrocarbon receptor (AhR) system. The AhR has been initially described as the dioxin and polyaromatic hydrocarbons receptor which, when activated by its ligands, induces a number of enzymes and transporters leading to the metabolism and elimination of the xenobiotics. Recently, the mammalian AhR has been shown to have a number of different functions in addition to xenobiotic detection and elimination. Furthermore, in non vertebrates, the AhR orthologs appear not to bind xenochemicals and to elicit different functions. Recent evidence indicates that this receptor has important endogenous functions subsequent to activation by natural dietary compounds and/or endogenous metabolites. Thus, this receptor has physiological functions that extend beyond specific instances of detoxification. Understanding of the roles played by this receptor might be enhanced by a systems biology approach. A thorough description of the effects of this receptor in different species will help us understand their multiple functions and their evolution.