Phosphatidylinositol-3 kinase and extracellular signal-regulated kinase mediate the chemotactic and mitogenic effects of insulin-like growth factor-I in human hepatic stellate cells.
OBJECTIVE
Several studies have shown that proliferation of hepatic stellate cells is stimulated by insulin-like growth factor-I. The aim of this study was to investigate the effect of insulin-like growth factor-I on human hepatic stellate cells chemotaxis and the intracellular pathways involved in both mitogenic and chemotactic effects.


RESULTS
Insulin-like growth factor-I, at the concentration of 100 ng/ml, was able to induce a 2- to 3-fold increase in human hepatic stellate cells migration in a modified Boyden chamber system. This effect was associated with a marked activation of phosphatidylinositol 3-kinase by insulin-like growth factor-I, as evaluated by measurement of phosphatidylinositol 3-kinase activity in phosphotyrosine immunoprecipitates In order to establish a functional link between these observations, we then performed experiments employing two selective phosphatidylinositol 3-kinase inhibitors, namely wortmannin and LY294002. These compounds blocked activation of phosphatidylinositol 3-kinase and inhibited insulin-like growth factor-I-induced hepatic stellate cells migration. Since phosphatidylinositol 3-kinase activation has been shown to be necessary for platelet-derived growth factor-induced mitogenesis in hepatic stellate cells, we verified the effects of phosphatidylinositol 3-kinase inhibition on insulin-like growth factor-I-induced DNA synthesis. Incubation with either wortmannin or LY294002, dose-dependently reduced the mitogenic potential of insulin-like growth factor-I. Since phosphatidylinositol 3-kinase is involved, at least in part, in the activation of the Ras/extracellular signal-regulated kinase pathway in hepatic stellate cells, the role of extracellular signal-regulated kinase activation in mediating the biological effects of insulin-like growth factor-I was explored. Insulin-like growth factor-I induced mitogenesis and chemotaxis were markedly reduced by pre-incubation of hepatic stellate cells with PD-98059, a selective inhibitor of MEK.


CONCLUSIONS
Activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase is required for both insulin-like growth factor-I-dependent hepatic stellate cells proliferation and chemotaxis. Insulin-like growth factor-I, together with other soluble mediators, may contribute to the hepatic wound-healing response by modulating hepatic stellate cells migration and proliferation.
Gentilini
A
A
Dipartimento di Medicina Interna, Università degli Studi di Firenze, Florence, Italy.
Marra
F
F
Gentilini
P
P
Pinzani
M
M
D000730:Androstadienes / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology*; D002867:Chromones / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D008934:Mitogens / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin
D000730:Androstadienes; D002630:Chemotactic Factors; D002867:Chromones; D004247:DNA; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007334:Insulin-Like Growth Factor I; D020928:Mitogen-Activated Protein Kinases; D008934:Mitogens; D009025:Morpholines; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000077191:Wortmannin; C058957:insulin-like growth factor 1, des-(1-3)-; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one