Effects of antipsoriatic drugs on biosynthesis of platelet activating factor by human keratinocytes.

Human keratinocytes in primary culture stimulated by Ca2+ ionophore A23187(Io) could synthesize and release a material which might aggregate aspirin-treated washed rabbit platelets and was identified as platelet activating factor (PAF) by four methods. Io stimulated the production of PAF by keratinocytes in a time- and dose-dependent manner. The PAF precursors, i.e., AAGPC and Lyso-PAF, were detected in keratinocytes. Nitrogen mustard and dexamethasone could time- and dose-dependently inhibit PAF biosynthesis from Io to induce human keratinocytes in culture. The IC50 of nitrogen mustard and dexamethasone were 6.34 x 10(-9) M and 1.005 x 10(-8) M respectively. The results showed that the synthesis and release of PAF by normal human keratinocytes may be accounted for the development of cutaneous inflammation and the pathogenesis of some skin disorders and application of drugs that inhibit PAF synthesis may be a new and effective approach to the management of some inflammatory skin diseases such as psoriasis.