The Human Aryl Hydrocarbon Receptor (AHR) and its Role in Skin Homeostasis

The aryl hydrocarbon receptor (AhR) is a transcription factor activated by the binding of low molecular weight molecules that could be environmental chemicals, molecules of plant origin or endogenous compounds. AhR is strongly expressed in tissue barriers, such as lungs, intestinal gut, and skin. It was identified as the key regulator of certain xenobiotic metabolism enzymes. The signaling pathway regulated by AhR is thus considered an adaptive response to these xenobiotics. More recently, several studies have highlighted the AhR involvement in inflammatory processes, which can lead to the development of chronic inflammatory pathologies and skin cancers. Given the growing importance of environmental pollution, AhR's involvement in xenobiotic metabolism and inflammation gives it a crucial role in skin homeostasis. During this review, we will discuss about different AhR ligands families, its activation/repression mechanisms, and its target genes. Subsequently, we will focus on interactions between AhR and other signaling pathways and its involvement in inflammatory skin pathologies. Taken together, it strongly suggests that AhR is an emerging suitable target to handle inflammatory skin diseases.