VITAMIN-D(3) AND CALCIPOTRIOL DECREASE EXTRACELLULAR PLASMINOGEN-ACTIVATOR ACTIVITY IN CULTURED KERATINOCYTES

Vitamin D3, 1alpha,25(OH)2D3, and its metabolites regulate the growth and differentiation of several cell types. Vitamin D3 and its analogue , calcipotriol (MC 903), inhibit the proliferation of cultured human a nd mouse keratinocytes and induce keratinocyte differentiation. Calcip otriol is effective in the treatment of psoriasis in which increased p lasminogen activator activity has been reported. We analyzed therefore the effects of calcipotriol and vitamin D3 on the production of plasm inogen activator (PA) activity in human keratinocytes and a mouse kera tinocyte cell line. Caseinolysis-in-agarose assays indicated that vita min D3 decreases total PA activity in both keratinocyte culture system s. Zymographic analyses of the medium indicated that the secreted acti vator was of the urokinase type (u-PA). A decrease was observed also i n extracellular matrix and membrane-associated u-PA activity of vitami n D3 and calcipotriol treated cells. Immunoblotting analysis of the co nditioned medium from human keratinocytes revealed a decrease in the u -PA protein levels. Accordingly, Northern hybridization analysis of th e respective mRNAs indicated a rapid decrease in urokinase mRNA levels . Calcipotriol decreased u-PA activity also in the presence of inducer s of u-PA activity like transforming growth factor-beta, epidermal gro wth factor, and phorbol-12-myristate-13-acetate. Calcipotriol also cau sed a decrease in tissue type PA (t-PA) activity of the keratinocytes. Most t-PA activity was associated with the extracellular matrices and cell membranes as revealed by zymographic analysis. Paradoxically, th e secretion and deposition to the matrix of plasminogen activator inhi bitor type 1 decreased in calcipotriol-treated cells. The results indi cate that a major effect of vitamin D3 on cultured keratinocytes is a decrease of plasminogen activator activity.