Ultraviolet irradiation of human skin causes functional vitamin A deficiency, preventable by all-trans retinoic acid pre-treatment

We report here that ultraviolet irradiation substantially reduced the mRNA and protein of the two major nuclear retinoid receptors, RAR-gamma and RXR- alpha, in human skin in vivo. Pre-treatment with retinoic acid mitigated th is loss of nuclear retinoid receptors. Ultraviolet irradiation caused a nea r-total loss of retinoic acid induction of two RAR/RXR target genes, cellul ar retinoic acid binding protein-II and RA 4-hydroxylase, but did not affec t 1,25-dihydroxyvitamin D-3 induction of the vitamin D receptor/RXR-regulat ed gene vitamin D 24-hydroxylase. In effect, ultraviolet irradiation causes a functional vitamin A deficiency that may have deleterious effects on ski n function, contributing to skin photo-aging and carcinogenesis.