Response of psoriatic lesions to multiple applications of leukotriene B4 and 12-HETE.

Single topical application of the neutrophil chemoattractant arachidonic acid metabolites leukotriene B4 (LTB4) and 12-R,S-hydroxy-5,8,10,14-eicosatetraenoic acid [corrected] (12-HETE) to normal skin elicits a histological response similar to early psoriasis. This effect diminishes following repeated application indicating the development of local tolerance. In order to assess whether induction of tolerance could be exploited as a treatment for psoriasis we studied the clinical effects of topical application of LTB4 (n = 6) and 12-HETE (n = 3) under occlusion to small psoriatic lesions for 12 consecutive days. The area of the control lesions decreased significantly over the study period while the areas of lesions to which LTB4 and 12-HETE were applied remained unchanged. No other difference between responses of the three groups was detected. We have shown that, in the doses used, multiple applications of these substances to established stable psoriatic lesions do not produce a therapeutically useful response.