ARACHIDONIC-ACID ACTIVATES C-JUN N-TERMINAL KINASE THROUGH NADPH OXIDASE IN RABBIT PROXIMAL TUBULAR EPITHELIAL-CELLS

In kidney epithelial cells, arachidonic acid and other fatty acids are important signal transduction molecules for G protein-coupled recepto rs. We now demonstrate that arachidonic acid induced a time- and dose- dependent activation of JNK, a member of the mitogen-activated protein kinase family, as assessed by phosphorylation of the transcription fa ctor ATF-2. Increments in JNK activity were detectable at 5 mu M arach idonic acid and plateaued at 30 mu M. Activation was specific to arach idonic acid and linoleic acid, since other fatty acids of the n - 3 an d n - 6 series and/or various degrees of saturation were without effec t. Specific inhibitors of cyclooxygenase-, lipoxygenase-, and cytochro me P450-dependent metabolism did not affect arachidonic acid induced J NK activity. We further demon strated that the free radical scavenger N-acetylcysteine blocked arachidonic acid-induced JNK activation, whil e H2O2, a reactive oxidative molecule, activated JNK in a dose-depende nt manner, providing additional support for a redox mechanism. Moreove r, arachidonic acid activated NADPH oxidase (EC 1.6.-.-, EC 1.6.99.-) in a dose-dependent manner, and the potency of superoxide generation p aralleled that of JNK activation by other fatty acids. We conclude tha t in kidney epithelial cells arachidonic acid activates JNK by means o f NADPH oxidase and superoxide generation, independent of eicosanoid b iosynthesis.