Treatment of MCs with IL-1 alpha induced a time-dependent increase in JNK1/SAPK kinase activity, assessed by phosphorylation of the activating transcription factor-2 (ATF-2).     ///    "Furthermore, stimulation of MCs with the exogenous cyclooxygenase-, lipoxygenase-, phosphodiesterase-, and epoxygenase-derived arachidonate metabolites, in contrast to AA itself, did not activate JNK1/SAPK. "    ///    "MCs were grown from collagenase-treated glomeruli, and JNK/SAPK activity in MC lysates was determined using an immunocomplex kinase assay. "    ///    "This effect was AA specific, as only AA and its precursor linoleic acid stimulated JNK1/SAPK activity. "    ///    Other fatty acids failed to activate JNK1/SAPK.     ///    "Pretreatment of MCs with specific inhibitors of AA oxidation by cyclooxygenase, lipoxygenase, and cytochrome P-450 epoxygenase had no effect on either IL-1- or AA-induced JNK1/SAPK activation. "    ///    "We conclude that IL-1-stimulated AA release, in part, mediates stimulation of JNK1/SAPK activity and that AA activates JNK1/SAPK by a mechanism that does not require enzymatic oxygenation. "    ///    "The JNK1 pathway has been implicated in cell fate decisions, and IL-1 stimulates the Jun N-terminal/stress-activated protein kinases (JNK1/SAPK). "    ///    "Pretreatment of MCs with aristolochic acid, a PLA2 inhibitor, concordantly reduced IL-1-regulated [3H]AA release and JNK1/SAPK activity, suggesting that cytosolic AA in part mediates IL-1-induced JNK1/SAPK activation. "    ///    "Free arachidonic acid (AA) activates several protein kinases, and because IL-1 rapidly stimulates phospholipase A2 (PLA2) activity release AA, IL-1-induced activation of JNK1/SAPK may be mediated by AA release. "    ///    Addition of AA stimulated JNK1/SAPK activity in a time- and concentration-dependent manner. 