Comparison of eicosanoid generation by highly purified human Langerhans cells and keratinocytes

The present study was conducted to investigate the eicosanoid metabolism of highly enriched human Langerhans cells and keratinocytes. Arachidonic acid (100 microM) was added to the cells which were then stimulated with 1 microM calcium ionophore A 23187 for 10 and 30 min. The supernatants were examined for cyclooxygenase and lipoxygenase products using different chromatographic systems and radioimmunoassays. Compounds were identified by comparison with authentic standards. The major cyclooxygenase product of both cell types was prostaglandin D2, with minor amounts of prostaglandin E2. The main products of the lipoxygenase pathway were 5-hydroxyeicosatetraenoic acid (5-HETE), 12-HETE, 15-HETE, and their corresponding hydroperoxy derivatives, with small amounts of leukotrienes B4 and C4. The major differences in the metabolism of the two cell types were related to faster kinetics of generation of the mediators and a more complete conversion of arachidonic acid by the LC. Because eicosanoids have been implicated to be potent mediators of inflammation and immunomodulators, the present data underline the potential contributory role of epidermal cells to eicosanoid-associated pathologic processes.