Interleukin-1 increases 15-hydroxyeicosatetraenoic acid production in human dermal fibroblasts

Inhibition of the formation of pro-inflammatory eicosanoids such as leukotrienes and 12-hydroxyeicosatetraenoic acid by 15-hydroxyeicosatetraenoic acid (15-HETE) has been reported. Psoriatic dermis synthesizes reduced levels of 15-HETE and it has been postulated to play a role in the pathophysiology of this disease. Interleukin-1 stimulates the production of prostaglandin E2 in fibroblasts, but its effect on the synthesis of 15-HETE is at present unknown. The aim of this study was to investigate the modulation of 15-HETE formation by interleukin-1 in dermal fibroblasts. Cells were treated with recombinant interleukin-1 alpha or beta prior to incubation with exogenous 14C-arachidonic acid, and eicosanoids were analyzed by HPLC. Interleukin-1 significantly increased the production of 15-HETE, but also 12-hydroxy-heptadecatrienoic acid, 11-hydroxyeicosatetraenoic acid, and prostaglandins, in a concentration- and time-dependent fashion. No significant differences between the two types of interleukin-1 were found. Dexamethasone (10 nM), and the protein synthesis inhibitors actinomycin D (1 microM) and cycloheximide (3 micrograms/ml) completely abolished the effect of interleukin-1 on 15-HETE formation. Whereas indomethacin (0.5-25 microM) strongly inhibited the synthesis of 15-HETE, aspirin (100-1000 microM) was unable to significantly inhibit its formation in both untreated and interleukin-treated fibroblasts. Aspirin inhibited the 15-HETE produced by cyclooxygenase from ram seminal vesicles, although to a lesser extent than indomethacin. In cell-free extracts, the activity concerning the synthesis of 15-HETE was associated with the microsomal fraction (100,000 x g pellet). Overall, these results strongly suggest that interleukin-1 increases 15-HETE formation mainly through the expression of new cyclooxygenase.