title: Regulation of pancreatic stellate cell function in vitro: biological and molecular effects of all-trans retinoic acid.
abstract: Pancreatic stellate cells (PSCs) are essentially involved in the development of pancreatic fibrosis, a constant feature of chronic pancreatitis and pancreatic cancer. Profibrogenic mediators, such as ethanol metabolites and cytokines, induce a PSC activation process that involves proliferation, enhanced production of extracellular matrix proteins and a phenotypic transition towards myofibroblasts which includes a loss of the characteristic retinoid-containing fat droplets. Here, we have analysed how exogenous all-trans retinoic acid (ATRA) affects activation of rat PSCs induced by sustained culture. Bromodeoxyuridine-incorporation assays indicated an ATRA-dependent inhibition of DNA synthesis. In contrast, ATRA did not affect expression of alpha-smooth muscle actin, a protein typical for myofibroblasts. Quantification of [3H]proline incorporation revealed a diminished collagen production in ATRA-treated PSCs. Furthermore, zymography experiments showed that supernatants of ATRA-exposed PSC cultures contained higher levels of matrix metalloproteinase-9 but not of matrix metalloproteinase-2 than untreated controls. At the level of intracellular signalling, ATRA had no effect on extracellular signal-regulated kinase activation after incubation of PSCs with the mitogen platelet-derived growth factor (PDGF). In addition, PDGF-induced DNA binding of activator protein-1 (AP-1) transcription factors was not inhibited by ATRA treatment. Luciferase reporter gene assays, however, revealed an ATRA-dependent transrepression of AP-1 in PDGF-stimulated PSCs. Together, the results indicate that exogenous ATRA displays inhibitory effects on PSC proliferation and collagen synthesis but does not block phenotypic transition towards myofibroblasts. We hypothesise that inhibition of AP-1 signalling may be involved in the mediation of biological effects of ATRA on PSCs.
authors.affiliation: Department of Medicine, Division of Gastroenterology, Medical Faculty, University of Rostock, E.-Heydemann-Strasse 6, 18057 Rostock, Germany. jaster@med.uni-rostock.de
authors.forename: Robert
authors.initials: R
authors.lastname: Jaster
authors.forename: Inken
authors.initials: I
authors.lastname: Hilgendorf
authors.forename: Brit
authors.initials: B
authors.lastname: Fitzner
authors.forename: Peter
authors.initials: P
authors.lastname: Brock
authors.forename: Gisela
authors.initials: G
authors.lastname: Sparmann
authors.forename: Jörg
authors.initials: J
authors.lastname: Emmrich
authors.forename: Stefan
authors.initials: S
authors.lastname: Liebe
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000032:analysis; D020780:Matrix Metalloproteinase 9 / Q000032:analysis; D010179:Pancreas / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D018808:Transcription Factor AP-1 / Q000502:physiology; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D000199:Actins; D018808:Transcription Factor AP-1; D014212:Tretinoin; D003094:Collagen; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9