Interleukin-1 stimulates Jun N-terminal/stress-activated protein kinase by an arachidonate-dependent mechanism in mesangial cells.
BACKGROUND
We have studied interleukin-1 (IL-1)-stimulated signals and gene expression in mesangial cells (MCs) to identify molecular mechanisms of MC activation, a process characteristic of glomerular inflammation. The JNK1 pathway has been implicated in cell fate decisions, and IL-1 stimulates the Jun N-terminal/stress-activated protein kinases (JNK1/SAPK). However, early postreceptor mechanisms by which IL-1 activates these enzymes remain unclear. 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.


METHODS
MCs were grown from collagenase-treated glomeruli, and JNK/SAPK activity in MC lysates was determined using an immunocomplex kinase assay.


RESULTS
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). Using similar incubation conditions, IL-1 also increased [3H]AA release from MCs. 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. Addition of AA stimulated JNK1/SAPK activity in a time- and concentration-dependent manner. 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. 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.


CONCLUSIONS
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. JNK1 signaling pathway components may provide molecular switches that mediate structural rearrangements and biochemical processes characteristic of MC activation and could provide a novel target(s) for therapeutic intervention.
Huang
S
S
Department of Medicine, School of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
Konieczkowski
M
M
Schelling
J R
JR
Sedor
J R
JR
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism* / Q000494:pharmacology; D034341:Aristolochic Acids; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D007375:Interleukin-1 / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases; D015289:Leukotrienes / Q000494:pharmacology; D008054:Lipid Peroxides / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases; D009393:Nephritis / Q000201:enzymology; D010616:Phenanthrenes / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013229:Stearic Acids / Q000494:pharmacology; D014316:Tritium; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D034341:Aristolochic Acids; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D007375:Interleukin-1; D015289:Leukotrienes; D008054:Lipid Peroxides; D010616:Phenanthrenes; D010726:Phosphodiesterase Inhibitors; D013229:Stearic Acids; D014662:Vasoconstrictor Agents; D014316:Tritium; D016718:Arachidonic Acid; C031183:stearic acid; C021201:12-HPETE; C025086:15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C046782:14,15-epoxy-5,8,11-eicosatrienoic acid; C059778:7,7-dimethyl-5,8-eicosadienoic acid; C000228:aristolochic acid I; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D015126:8,11,14-Eicosatrienoic Acid; D015232:Dinoprostone