Src kinase-mediated parallel activation of prostaglandin and constitutive nitric oxide synthase pathways in leptin protection of gastric mucosa against ethanol cytotoxicity.
ABSTRACT Advances in understanding the functional aspects of leptin in the processes affecting peripheral tissues have brought to the forefront the role of this pluripotent cytokine in the processes of gastric mucosal defense and repair. Here, we report that leptin protects the gastric mucosal cells against ethanol cytotoxicity. We show that ethanol cytotoxicity, characterized by a marked drop in the mucosal cells capacity for NO production, arachidonic acid release and prostaglandin generation, was subject to suppression by leptin. The loss in countering capacity of leptin on the ethanol-induced cytotoxicity was attained with cyclooxygenase inhibitor, indomethacin and nitric oxide synthase (cNOS) inhibitor, L-NAME, as well as PP2, an inhibitor of Src kinase. Indomethacin caused the inhibition in PGE(2) generation, pretreatment with L-NAME led to the inhibition in NO production, whereas PP2 exerted the inhibitory effect on leptin-induced changes in NO, arachidonic acid and PGE(2). The leptin-induced changes in arachidonic acid release and PGE(2) generation were blocked by ERK inhibitor, PD98059, but not by PI3K inhibitor, wortmannin. Moreover, the stimulatory effect of leptin on the mucosal cells cNOS activity was inhibited not only by PP2, but also by Akt inhibitor, SH-5. Our findings demonstrate that leptin protection of gastric mucosa against ethanol cytotoxicity involves Src kinase-mediated bifurcated activation of MAPK/ERK and Akt that leads to up-regulation of the respective prostaglandin and nitric oxide synthase pathways.