Oxidative stress induces arachidonate release from human lung cells through the epithelial growth factor receptor pathway.

Oxidative stress is thought to be a factor influencing many inflammatory responses, including arachidonic acid (AA) release. We have studied the effect of hydrogen peroxide on AA and prostaglandin E2 release, cytosolic phospholipase (cPLA2) steady-state mRNA, cPLA2 protein levels, cPLA2 enzyme activity, and cPLA2 phosphorylation in a human lung epithelial cell line: A549 cells. Hydrogen peroxide caused a dose-dependent increase of A23187-stimulated AA and prostaglandin E2 release, with a maximum effect at 1 h. This effect is associated with a maximum specific cPLA2 activity at 1 h, and with a significant increase in cPLA2 Serine 505 phosphorylation. All these effects were abolished, in a dose-related manner, by the epithelial growth factor receptor kinase inhibitor, AG 1478. To further investigate the pathway leading to the increase cPLA2 phosphorylation, we used cells transfected with a Ras dominant negative vector and mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) and p38 k...