Dithranol-induced down-regulation of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE] receptors in a human epidermal cell line.

The effects of dithranol and its therapeutically inactive oxidation product, danthrone, on 12(S)-HETE binding to the human epidermal cell line SCL-II were studied. Dithranol (0.25-1 microgram/ml), in contrast to danthrone, induced a substantial decrease in 12(S)-HETE binding in a dose-dependent manner. The inhibition occurred after a latency period of 6 h, reached its maximum at 18-24 h and slowly declined thereafter. At a concentration of 1 microgram/ml, the drug led to an approximately 50% decrease in the number of specific high-affinity 12(S)-HEFE receptors (Bmax), whereas receptor affinity (Kd) showed no change. The down-regulation of 12(S)-HETE receptors on epidermal cells by dithranol may contribute to its antipsoriatic action.