Leptin-induced cytosolic phospholipase A₂ activation in gastric mucosal protection against ethanol cytotoxicity involves epidermal growth factor receptor transactivation

A pluripotent cytokine, leptin, released locally within the mucosal tissue is an important mediator of the processes of gastric mucosal defense and repair. Here, we report that leptin protection of gastric mucosal cells against ethanol cytotoxicity requires epidermal growth factor receptor (EGFR) participation. We show that the protective effect of leptin against ethanol cytotoxicity was associated with the increased EGFR and cPLA₂ phosphorylation, and characterized by a marked increase in arachidonic acid (AA) release and prostaglandin (PGE₂) generation. The loss in countering capacity of leptin on the ethanol-induced cytotoxicity was attained with Src kinase inhibitor, PP2, and EGFR kinase inhibitor, AG1478, as well as ERK inhibitor, PD98059. Moreover, all three agents evoked also the inhibition in leptin-induced upregulation in cPLA₂ activity, AA release, and PGE₂ generation. Furthermore, changes caused by leptin in EGFR phosphorylation and cPLA₂ activation were susceptible to suppression by GM6001, a metalloprotease inhibitor of membrane-anchored EGFR ligand cleavage. These findings disclose an important link between leptin-induced and Src kinase-mediated EGFR transactivation and the activation of cytosolic phospholipase A₂ that leads to up-regulation in PGE2 production, thus providing new insights into the mechanism of gastric mucosal protection by leptin.