Roles of prostaglandin production and mitogen-activated protein kinase activation in hepatocyte growth factor—mediated rat hepatocyte proliferation

Abstract

Hepatocyte growth factor (HGF) and epidermal growth factor (EGF)-stimulated DNA synthesis in primary cultured rat hepatocytes. HGF-induced DNA synthesis was concentration-dependently inhibited by a cyclooxygenase inhibitor, indomethacin. BW755C, a dual inhibitor for cyclooxygenase and lipoxygenase activities, also inhibited hepatocyte growth. Prostaglandin E1 (PGE1), PGE2, and PGF2 alpha induced DNA synthesis even at such a low concentration as 5 nmol/L and potentiated [3H]thymidine incorporation induced by HGF in an additive manner. HGF caused arachidonic acid (AA) release and eicosanoid production. These events were detectable within 10 minutes after stimulation and lasted for at least 60 minutes. Furthermore, two proteins with approximately 40 kd were tyrosine phosphorylated by HGF. These proteins were identified as p42/p44 mitogen-activated protein (MAP) kinases by anti-MAP kinase immunoblots, which were known to activate cytosolic phospholipase A2 (cPLA2), a key enzyme in AA release. Activation of MAP kinases was detectable within 5 minutes after stimulation with HGF and lasted for at least 60 minutes. EGF-mediated DNA synthesis was also inhibited by the above cyclooxygenase inhibitors. EGF caused AA release and tyrosine phosphorylation of MAP kinases. These results suggest that HGF as well as EGF causes AA release, probably through activation of cPLA2 mediated by MAP kinases, and that PGs, metabolites of AA, might play a pivotal role in hepatocyte proliferation in an autocrine mechanism.

Phospholipase D activation in hepatocyte growth factor-stimulated rat hepatocytes mediates the expressions of c-jun and c-fos: Involvement of protein tyrosine kinase, protein kinase C, and Ca2+

“…In HGF-stimulated hepatoported following HGF receptor activation. [17][18][19][20][21][22][23] In the previous cytes, butanol prevented the formation of PA and DG.reports, 19,23 we showed that HGF stimulated inisitol 1,4,5-A PAP inhibitor, propranolol, inhibited DG production trisphosphate formation and increased in intracellular Ca 2/ with a reciprocal increase of PA, implying that PLD concentration. In contrast to rapid and transient change of played a role in the formation of not only PA but DG.…”

“…In contrast, daidzein 41 which lacks the hydroxyl group of genistein and has minimal effect on tyrosine kinase activity, was without inhibitory effect on HGF-induced PLD activation. A cyclooxygenase inhibitor, indomethacin (50 mmol/L), which suppressed HGF-induced [ 3 H]thymidine incorporation in rat hepatocytes, 21 did not affect HGF-stimulated PLD activation. Effects of Ca 2/ on HGF-Induced PLD Activation.…”

“…In HGF-stimulated hepatoported following HGF receptor activation. [17][18][19][20][21][22][23] In the previous cytes, butanol prevented the formation of PA and DG.…”

“…Hepatocytes were isolated from male Wistar rats (150-170 g) by perfusion of the liver with 0.05% collagenase and 0.05% hyaluronidase as previously described. 21 The isolated hepatocytes (3 1 10 4 cells/cm 2 ) were incubated in plastic dishes coated with rat tail collagen for 4 hours in Williams' medium E containing 5% calf serum, 10 09 mol/L insulin, 10 09 mol/L dexamethasone in a humidified atomosphere of 5% CO 2 , and 95% air at 37ЊC. The cells were further incubated in serum-starved Williams' medium E for 20 hours.…”

“…DNA synthesis was measured by [ 3 H]thymidine incorporation. 21 After incubation in serum-free Williams' medium E for 20 hours, hepatocytes were stimulated with 10 ng/mL HGF and cultured for an additional 36 hours. For the last 24 hours, [ 3 H]thymidine (1.0 mCi/mL) was included.…”