title: Coordinate activation of intracellular signaling pathways by insulin-like growth factor-1 and platelet-derived growth factor in rat hepatic stellate cells.
abstract: Proliferation of activated hepatic stellate cells (HSC) is an important event in the development of hepatic fibrosis. Insulin-like growth factor-1 (IGF-1) has been shown to be mitogenic for HSC, but the intracellular signaling pathways involved have not been fully characterized. Thus, the aims of the current study were to examine the roles of the extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3-K) and p70-S6 kinase (p70-S6-K) signaling pathways in IGF-1- and platelet-derived growth factor (PDGF)-induced mitogenic signaling of HSC and to examine the potential crosstalk between these pathways. Both IGF-1 and PDGF increased ERK, PI3-K and p70-S6-K activity. When evaluating potential crosstalk between these signaling pathways, we observed that PI3-K is required for p70-S6-K activation by IGF-1 and PDGF, and is partially responsible for PDGF-induced ERK activation. PDGF and IGF-1 also increased the levels of cyclin D1 and phospho-glycogen synthase kinase-3beta. Coordinate activation of ERK, PI3-K and p70-S6-K is important for perpetuating the activated state of HSC during fibrogenesis.
authors.affiliation: Division of Gastroenterology and Hepatology, Saint Louis University Liver Center, Saint Louis University School of Medicine, St. Louis, Missouri 63110-0250, USA.
authors.forename: Kim R
authors.initials: KR
authors.lastname: Bridle
authors.forename: Lin
authors.initials: L
authors.lastname: Li
authors.forename: Rosemary
authors.initials: R
authors.lastname: O'Neill
authors.forename: Robert S
authors.initials: RS
authors.lastname: Britton
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Bacon
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007728:Kupffer Cells / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D019938:Cyclin D1; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D038762:Ribosomal Protein S6 Kinases, 70-kDa; C000605508:Gsk3b protein, rat