Mediation by Arachidonic Acid Metabolites of the H₂O₂‐Induced Stimulation of Mitogen‐Activated Protein Kinases (Extracellular‐Signal‐Regulated Kinase and c‐Jun NH₂‐Terminal Kinase)

Abstract

Reactive oxygen species modulate major cellular functions by mechanisms which are still poorly understood. Recently, H,O, has been reported to stimulate the activity of the mitogen-activated protein kinases (MAPKs) ERK and JNK, and the expression of the proto-oncogenes c-fos and c-jun. As their expression is enhanced by H,O, in astrocytes, we studied whether these MAPKs were stimulated by H,O, in primary cultured astrocytes. The result was positive, a maximum of stimulation being reached with 200 pM H,O, (0.3 pmol H,O,/cell) for both ERK and JNK. ERK was previously reported to stimulate cytosolic phospholipase A, phosphorylation and activity. H,O, stimulated the release of arachidonic acid in astrocytes, as already reported in other cell types. We found also that cPLA, phosphorylation was increased by H,O,. Moreover, the stimulation by H,O, of ERK and JNK was decreased by phospholipase A, activity inhibitors. When astrocytes were incubated first with eicosatetraynoic acid, a structural analogue competing in arachidonic acid metabolism, the stimulation of JNK by H,O, was also inhibited, suggesting the involvement of arachidonic acid metabolites. Cyclooxygenase or cytochrome P450 nionooxygenase inhibitors failed in decreasing the MAPK stimulation by HZ02, whereas lipoxygenase inhibitors completely abolished that of JNK. Mitogenicity has been reported to be stimulated by H,O, in other cell types. Although ERK was strongly and durably stimulated by 200 pM H,O, in astrocytes, at the same extent as by mitogenic growth factors, basal thymidine incorporation rate was decreased by more than 80% after 12-15 h. Moreover, the stimulation of thymidine incorporation induced by basic fibroblast growth factor was transiently abolished by H,O,. Furthermore, H,O, likely induced the expression of CLIOO/PACl/MKP-l, a dual specificity phosphatase which has been implicated in ERK and JNK inactivation in the nucleus. Finally, the prior treatment of astrocytes with MK886, a 5-lipoxygenaseactivating protein inhibitor, prevented JNK from stimulation, but did not prevent thymidine incorporation from inhibition, both induced by H,O,. These results strongly suggest an involvement of arachidonic acid and/or its metabolites in the stimulation of both ERK and JNK following the oxidative stress evoked by H,O,, which induced a cell cycle arrest probably independent of the stimulation of JNK.

Dexamethasone-mediated regulation of death and differentiation of muscle cells. Is hydrogen peroxide involved in the process?

“…Nevertheless, our observations were in agreement with the data presented by Tournier et al [45] unmasked glucocorticoid-dependent myogenesis. Our results provide evidence that at low concentrations, glucocorticoids are able to shorten the time gap to the onset of terminal differentiation (fusion).…”

Cross-talk between Cytosolic Phospholipase A2α (cPLA2α) and Secretory Phospholipase A2 (sPLA2) in Hydrogen Peroxide-induced Arachidonic Acid Release in Murine Mesangial Cells

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Bioactive substances of plant origin in food - impact on genomics

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