Arylhydrocarbon receptor

Evolutionarily old, highly conserved cytoplasmic protein that is expressed by all cells of the epidermis. UVB rays lead to activation of the aryl hydrocarbon receptor via FICZ, a photoproduct generated by photooxidation from the amino acid tryptophan. The system operates like steroid hormones; AhR is located in the cytoplasm, migrates into the cell nucleus after binding the low-molecular agonist, complexes with another protein and binds to target genes. The consecutive AhR signaling cascade can apparently also induce skin aging via a dysregulation of clock genes. This cascade can also interact with the estrogen receptor (ER) signaling cascade (estrogen-induced pigmentation!). Furthermore, the disruption of this signaling cascade can be associated with premature skin aging. The AhR is known as the "dioxin receptor" and is also a known sensor for a number of low-molecular environmental substances (dioxin leads to a strong hyperactivation of AhR).

It is noteworthy that Malazessia furfur is able to alter skin pimagenization via malazessin, a natural ligand of the AhR.

1. Esser C et al (2010) UV radiation and pigmentation. dermatologist 61: 561-565
2. Fritsche E et al (2007): Lightening up the UV response: The AhR is a cytoplasmic photosensor. Proc Natl Acad Sci 104:8851-8856.