Phosphoinositide 3-kinase, but not mitogen-activated protein kinase, pathway is involved in hepatocyte growth factor-mediated protection against bileacid-induced apoptosis in cultured rat hepatocytes

We have previously shown that cAMP protects against hydrophobic bile acid-i nduced apoptosis in cultured rat hepatocytes through pathways dependent on activation of phosphoinositide 3-kinase and inhibition of mitogen activated protein kinase. Hepatocyte growth factor protects epithelial cells against apoptosis and activates both of these kinases in hepatocytes. We studied t he effect of hepatocyte growth factor on glycochenodeoxycholate-induced apo ptosis to determine whether hepatocyte growth factor protects hepatocytes a gainst bile acid-induced apoptosis and whether the protective effect is med iated via phosphoinositide S-kinase and/or mitogen-activated protein kinase pathways. Two-hour exposure of cultured rat hepatocytes to glycochenodeoxy cholate resulted in apoptosis in 12.5 +/- 0.49% of the cells. Pretreatment with hepatocyte-growth factor (50 ng/mL) decreased apoptosis by 50% to 70%. Hepatocyte growth factor cytoprotection was prevented by pretreatment with the phosphoinositide 3-kinase inhibitors, wortmannin (50 nmol/L) or Ly 294 002 (40 mu mol/L). Hepatocyte growth factor activated phosphoinositide 3-ki nase dependent protein kinase B and mitogen-activated protein kinase. Pretr eatment of hepatocytes with a mitogen-activated protein kinase inhibitor, U 0126 (40 mu mol/L) or an inhibitor of pp70(S6) kinase, rapamycin (100 nmol/ L), had no effect on the growth factor's anti-apopotic effect. Treatment wi th hepatocyte growth factor resulted in mitogen-activated protein kinase-de pendent phosphorylation of BAD on serine(112) In summary, hepatocyte growth factor protection against bile acid-induced apoptosis occurs via a phospho inositide 3-kinase pathway and is not dependent on the mitogen-activated pr otein kinase pathway, phosphorylation of BAD on serine(112), or activation of p70(S6) kinase.