EFFECTS OF CALCIPOTRIOL AND CLOBETASOL-17-PROPIONATE ON UVB-IRRADIATED HUMAN SKIN - AN IMMUNOHISTOCHEMICAL STUDY

Corticosteroids and vitamin D-3 analogues inhibit proliferation, enhan ce normal keratinisation and interfere with cutaneous inflammation in in vitro systems. Both treatments are effective in psoriasis, although several reports suggest that vitamin D-3 is less effective in reducin g the inflammatory changes compared to its potent effect on keratinocy te growth and differentiation. The aim of the present study was to com pare and contrast the effects of the vitamin D-3 analogue calcipotriol , clobetasol-17-propionate and a placebo on immunohistochemical marker s for epidermal growth, keratinisation and inflammation induced by a s tandardised single challenge with ultraviolet B (UVB) radiation in nor mal human skin. Clobetasol proved to inhibit UVB-induced proliferation of epidermal cells, tenascin induction, keratin 16 induction and the accumulation of T lymphocytes and CD1a-positive cells. Epidermal thinn ing due to clobetasol was also observed. No effect of clobetasol was s hown on the enhanced terminal differentiation following UVB challenge. In contrast, calcipotriol reduced the member of transglutaminase-posi tive cells following UVB challenge but increased the thickness of the epidermis without a significant effect on other markers for keratinisa tion, epidermal proliferation and inflammation. The present study reco nfirms the potent effect of topical corticosteroids on various aspects of UVB-challenged skin. In contrast, calcipotriol interfered especial ly with one differentiation pathway (transglutaminase) without modulat ion of other UVB-induced changes.