Secretory and cytosolic phospholipase A(2) regulate the long-term cytokine-induced eicosanoid production in human keratinocytes

The involvement of cytosolic phospholipase A(2) (cPLA(2)) and secretory non -pancreatic PLA(2) (npPLA(2)) in release of arachidonic acid (AA) preceding eicosanoid formation in the human keratinocyte cell line HaCaT was examine d, Interleukin 1 beta (IL-1 beta) and tumour necrosis factor-alpha (TNF), p horbol myristate acetate (PMA) and calcium ionophore A(23187) increased the extracellular AA release, and stimulated eicosanoid synthesis as determine d by HPLC analysis. The main metabolites after stimulation with IL-1 beta, PMA or A(23187) were PGE(2), an unidentified PG and LTB4, while TNF stimula ted METE-production. Both cPLA(2) and npPLA(2) message and enzyme activity were detected in unstimulated HaCaT cells. IL-1 beta, PMA and TNF increased both cPLA(2) enzyme activity and expression, but did not lead to any incre ase in npPLA(2) expression or activity. The selective npPLA(2) inhibitors L Y311727 and 12-epi-scalaradial, or the cPLA(2) inhibitor arachidonyl triflu oro methyl ketone (AACOCF(3)) reduced IL-1 beta-induced eicosanoid producti on in a concentration dependent manner. The results presented strongly sugg est that both cPLA(2) and npPLA(2) contribute to the long-term generation o f AA preceding eicosanoid production in differentiated, human keratinocytes , Inhibitors against npPLA(2) or cPLA(2) enzymes should be useful in treati ng inflammatory skin diseases, such as psoriasis, (C) 2000 Academic Press.