title: Platelet-derived growth factor receptor tyrosine kinase inhibitor AG1295 attenuates rat hepatic stellate cell growth.
abstract: Enhanced activity of receptor tyrosine kinases such as the platelet-derived growth factor-receptorbeta (PDGF-Rbeta) has been implicated as a contributing factor in the development of hepatic fibrosis. In this study we have used tyrosine kinase inhibitors of the tyrphostin class (AG1295) to specifically block autophosphorylation of PDGF-Rbeta and proliferation of rat hepatic stellate cells. We also examined the effect of AG1295 on the PDGF-BB-induced activation of the 44 kd and 42 kd mitogen-activated protein (MAP) kinase isoforms (p44mapk/p42mapk). Rat hepatic stellate cells were treated with AG1295 (10 micromol/L) for 24 hours and stimulated with PDGF-BB for 5 minutes. AG1295 specifically inhibited autophosphorylation of PDGF-Rbeta and caused a 20% decrease in PDGF-BB-stimulated bromodeoxyuridine incorporation by rat hepatic stellate cells. Treatment of rat hepatic stellate cells with AG1295 resulted in an inhibition of the PDGF-BB-induced activation of MAP kinase isoforms. Quantification of the immunoprecipitated tyrosine-phosphorylated phosphatidylinositol 3-kinase, phospholipase C-gamma, and p21ras guanosine triphosphatase-activating protein by Western blotting revealed that AG1295 treatment effectively inhibits tyrosine phosphorylation of these kinases in hepatic stellate cells. Our findings demonstrate that AG1295 is a selective inhibitor of the tyrosine phosphorylation of PDGF-Rbeta and its downstream signaling pathway, and this compound could offer a strategy for the treatment of fibrotic liver diseases.
authors.affiliation: Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Iwamoto
authors.forename: M
authors.initials: M
authors.lastname: Nakamuta
authors.forename: S
authors.initials: S
authors.lastname: Tada
authors.forename: R
authors.initials: R
authors.lastname: Sugimoto
authors.forename: M
authors.initials: M
authors.lastname: Enjoji
authors.forename: H
authors.initials: H
authors.lastname: Nawata
mesh_terms: D000818:Animals; D000077214:Becaplermin; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000378:metabolism; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D007527:Isoenzymes / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology*
chemical_list: C407689:6,7-dimethoxy-2-phenylquinoxaline; D007527:Isoenzymes; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D020032:Tyrphostins; D000077214:Becaplermin; D004247:DNA; D019869:Phosphatidylinositol 3-Kinases; D020797:Receptor, Platelet-Derived Growth Factor beta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D016283:Proto-Oncogene Proteins p21(ras); D001973:Bromodeoxyuridine