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 μM) was added to the cells which were then stimulated with 1 μM 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.