SKIN-DERIVED ANTILEUKOPROTEINASE (SKALP) AND EPIDERMAL FATTY-ACID-BINDING PROTEIN (E-FABP) - 2 NOVEL MARKERS OF THE PSORIATIC PHENOTYPE THAT RESPOND DIFFERENTIALLY TO TOPICAL STEROID

Recently we have described two novel markers for disturbed epidermal d ifferentiation, which are strongly upregulated in psoriatic epidermis: skin-derived antilenkoproteinase (SKALP) and epidermal fatty acid-bin ding protein (E-FABP). No data are available on the kinetics of SKALP and E-FABP expression in vivo and the relation with epidermal growth a nd differentiation. We used treatment of lesional psoriatic skin with topical steroid as a model to correlate the expression pattern of SKAL P and E-FABP with known cell biological events during regression of th e psoriatic lesion. Expression of these markers was studied using immu nohistochemistry and Northern blot analysis. After 4 weeks of treatmen t a substantial clinical improvement was induced by the topical steroi d, whereas no significant improvement had occurred at the placebo-trea ted sides. The expression of SKALP following treatment with steroid wa s nearly undetectable both at the protein and mRNA level. Mitotic acti vity, as measured by Ki-67 staining, and cytokeratin 16 expression wer e downregulated to normal levels in the steroid-treated epidermis. In contrast, although there was a marked decrease of E-FABP mRNA, the sta ining pattern for E-FABP at the protein level was not affected. After 4 weeks of treatment with steroid the complete suprabasal compartment remained positive, even after considerable clinical improvement of the lesion. We conclude that SKALP and cytokeratin 16 are markers that ar e downregulated even before complete macroscopic clearance of the lesi on. The kinetics of E-FABP expression is distinct from the other molec ules and lags behind the clinical signs of psoriasis.