title: Unfolded protein response induced by Brefeldin A increases collagen type I levels in hepatic stellate cells through an IRE1α, p38 MAPK and Smad-dependent pathway.
abstract: Unfolded protein response (UPR) triggered as a consequence of ER stress has been shown to be involved in the development of different pathologies, including fibrotic disorders. In the present paper we explore the role played by UPR on a key fibrogenic parameter in the liver: collagen type I levels in activated hepatic stellate cells (HSC). Using Brefeldin A (BFA) as an ER stress inducer we found that UPR correlated with enhanced mRNA and protein levels of collagen type I in a cell line of immortalized non-tumoral rat HSC. Analysis of the three branches of UPR revealed the activation of IRE1α, PERK and ATF6 in response to BFA, although PERK activation was shown not to be involved in the fibrogenic action of BFA. BFA also activated p38 MAPK in an IRE1α-dependent way and the p38 MAPK inhibitor SB203580 prevented the increase in collagen type I mRNA and protein levels caused by BFA, suggesting the involvement of this kinase on this effect. Analysis of Smad activation showed that phosphorylated nuclear levels of Smad2 and 3 were increased in response to BFA treatment. Inhibition of Smad3 phosphorylation by SIS3 prevented the enhancement of collagen type I levels caused by BFA. Pretreatment with IRE1α and p38 MAPK inhibitors also prevented the increased p-Smad3 accumulation in the nucleus, suggesting an IRE1α-p38 MAPK-Smad pathway to be responsible for the fibrogenic action of BFA on HSC.
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Marina Ruiz
authors.initials: MR
authors.lastname: de Galarreta
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Amaia
authors.initials: A
authors.lastname: Navarro
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Ansorena
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Antonia García
authors.initials: AG
authors.lastname: Garzón
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Teresa
authors.initials: T
authors.lastname: Mòdol
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: María J
authors.initials: MJ
authors.lastname: López-Zabalza
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Martínez-Irujo
authors.affiliation: Department of Biochemistry and Genetics, University of Navarra, 31008 Pamplona, Spain. Electronic address: miraburu@unav.es.
authors.forename: María J
authors.initials: MJ
authors.lastname: Iraburu
mesh_terms: D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology*; D002460:Cell Line; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects* / Q000502:physiology; D004722:Endoribonucleases / Q000037:antagonists & inhibitors / Q000502:physiology*; D005355:Fibrosis; D005786:Gene Expression Regulation / Q000187:drug effects; D055166:Hepatic Stellate Cells / Q000187:drug effects* / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000502:physiology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D051900:Smad3 Protein / Q000502:physiology*; D056811:Unfolded Protein Response / Q000187:drug effects* / Q000502:physiology; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D024042:Collagen Type I; C575026:Ern1 protein, rat; D007093:Imidazoles; D009097:Multienzyme Complexes; D011725:Pyridines; D012333:RNA, Messenger; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D020126:Brefeldin A; D017346:Protein Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D004722:Endoribonucleases; C093642:SB 203580
keywords: Collagen type I; Hepatic stellate cells; Unfolded protein response