title: The biphasic nature of hypoxia-induced directional migration of activated human hepatic stellate cells.
abstract: Liver fibrogenesis is sustained by pro-fibrogenic myofibroblast-like cells (MFs), mainly originating from activated hepatic stellate cells (HSC/MFs) or portal (myo)fibroblasts, and is favoured by hypoxia-dependent angiogenesis. Human HSC/MFs were reported to express vascular-endothelial growth factor (VEGF) and VEGF-receptor type 2 and to migrate under hypoxic conditions. This study was designed to investigate early and delayed signalling mechanisms involved in hypoxia-induced migration of human HSC/MFs. Signal transduction pathways and intracellular generation of reactive oxygen species (ROS) were evaluated by integrating morphological, cell, and molecular biology techniques. Non-oriented and oriented migration were evaluated by using wound healing assay and the modified Boyden's chamber assay, respectively. The data indicate that hypoxia-induced migration of HSC/MFs is a biphasic process characterized by the following sequence of events: (a) an early (15 min) and mitochondria-related increased generation of intracellular ROS which (b) was sufficient to switch on activation of ERK1/2 and JNK1/2 that were responsible for the early phase of oriented migration; (c) a delayed and HIF-1α-dependent increase in VEGF expression (facilitated by ROS) and its progressive, time-dependent release in the extracellular medium that (d) was mainly responsible for sustained migration of HSC/MFs. Finally, immunohistochemistry performed on HCV-related fibrotic/cirrhotic livers revealed HIF-2α and haem-oxygenase-1 positivity in hepatocytes and α-SMA-positive MFs, indicating that MFs were likely to be exposed in vivo to both hypoxia and oxidative stress. In conclusion, hypoxia-induced migration of HSC/MFs involves an early, mitochondrial-dependent ROS-mediated activation of ERK and JNK, followed by a delayed- and HIF-1α-dependent up-regulation and release of VEGF.
authors.affiliation: Dip. Medicina e Oncologia Sperimentale-Centro Interuniversitario di Fisiopatologia Epatica, University of Torino, Torino, Italy.
authors.forename: Erica
authors.initials: E
authors.lastname: Novo
authors.forename: Davide
authors.initials: D
authors.lastname: Povero
authors.forename: Chiara
authors.initials: C
authors.lastname: Busletta
authors.forename: Claudia
authors.initials: C
authors.lastname: Paternostro
authors.forename: Lorenzo Valfrè
authors.initials: LV
authors.lastname: di Bonzo
authors.forename: Stefania
authors.initials: S
authors.lastname: Cannito
authors.forename: Alessandra
authors.initials: A
authors.lastname: Compagnone
authors.forename: Andrea
authors.initials: A
authors.lastname: Bandino
authors.forename: Fabio
authors.initials: F
authors.lastname: Marra
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Colombatto
authors.forename: Ezio
authors.initials: E
authors.lastname: David
authors.forename: Massimo
authors.initials: M
authors.lastname: Pinzani
authors.forename: Maurizio
authors.initials: M
authors.lastname: Parola
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D015687:Cell Hypoxia; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D015194:Diffusion Chambers, Culture; D020868:Gene Silencing; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000502:physiology*; D006526:Hepatitis C / Q000378:metabolism / Q000473:pathology / Q000821:virology; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology / Q000821:virology; D006801:Humans; D008103:Liver Cirrhosis / Q000378:metabolism / Q000473:pathology; D008928:Mitochondria / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics* / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics* / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D014945:Wound Healing / Q000502:physiology; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D051547:Heme Oxygenase-1; D019950:Mitogen-Activated Protein Kinase 1; D048055:Mitogen-Activated Protein Kinase 8; D016283:Proto-Oncogene Proteins p21(ras); D017382:Reactive Oxygen Species; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1; C535150:MAPK1 protein, human