STIMULATION OF P38 PHOSPHORYLATION AND ACTIVITY BY ARACHIDONIC-ACID IN HELA-CELLS, HL60 PROMYELOCYTIC LEUKEMIC-CELLS, AND HUMAN NEUTROPHILS- EVIDENCE FOR CELL-TYPE-SPECIFIC ACTIVATION OF MITOGEN-ACTIVATED PROTEIN-KINASES

Although it is well appreciated that arachidonic acid, a second messen ger molecule that is released by ligand-stimulated phospholipase A(2), stimulates a wide range of cell types, the mechanisms that mediate th e actions of arachidonic acid are still poorly understood, We now repo rt that arachidonic acid stimulated the appearance of dual-phosphoryla ted (active) p38 mitogen-activated protein kinase as detected by Weste rn blotting in HeLa cells, HL60 cells, human neutrophils, and human um bilical vein endothelial cells but not Jurkat cells. An increase in p3 8 kinase activity caused by arachidonic acid was also observed. Furthe r studies with neutrophils show that the stimulation of p38 dual phosp horylation by arachidonic acid was transient, peaking;at 5 min, and wa s concentration-dependent. The effect of arachidonic acid was not affe cted by either nordihydroguaiaretic acid, an inhibitor of the 5-, 12-, and 15-lipoxygenases or by indomethacin, an inhibitor of cyclooxygena se, Arachidonic acid also stimulated the phosphorylation and/or activi ty of the extracellular signal-regulated protein kinase and of c-jun N -terminal. kinase in a cell-type-specific manner. An examination of th e mechanisms through which arachidonic acid stimulated the phosphoryla tion/activity of p38 and extracellular signal-regulated protein kinase in neutrophils revealed an involvement of protein kinase C, Thus, ara chidonic acid stimulated the translocation of protein kinase C alpha; beta I, and beta II to a particulate fraction, and the effects of arac hidonic acid on mitogen-activated protein kin;ase phosphorylation/acti vity were partially inhibited by GF109203X, an inhibitor of protein ki nase C, This study Is the first to demonstrate that a polyunsaturated fatty acid causes the dual phosphorylation and activation of p38.