Topical glucocorticosteroids modulate the expression of CRABP I and II in human skin differently.

Epidermal cells express two retinotic acid-binding proteins (CRABP I and II). Because CRABP II protein is strongly induced by topical retinoic acid, the respective roles of the two proteins in the pharmacological activity and toxicity of topical retinoids deserve particular attention. Since topical steroids diminish the irritation induced by retinoic acid (RA), whereas retinoic acid may counteract the atrophogenic effects of steroids, the possible interplay of both compounds in the expression of CRABP I and II appeared worth studying. We have analyzed the effects of topical application of triamcinolone acetonide (TA) on the retinoic acid-induced altered expression of CRABP I and II in normal human skin, at the protein and mRNA levels. We found that CRABP II protein and mRNA were strongly increased upon retinoic acid application: this induction was significantly inhibited by concomitant application of triamcinolone acetonide; a more potent steroid, difluocortolone valerate, was also found to diminish normal endogenous expression of CRABP II. In contrast, CRABP I protein was decreased by topical retinoic acid, and the down modulating effect of retinoic acid was counteracted by triamcinolone acetonide.