title: Reactive gamma-ketoaldehydes as novel activators of hepatic stellate cells in vitro.
abstract: Products of lipid oxidation, such as 4-hydroxynonenal (4-HNE), are key activators of hepatic stellate cells (HSC) to a pro-fibrogenic phenotype. Isolevuglandins (IsoLG) are a family of acyclic γ-ketoaldehydes formed through oxidation of arachidonic acid or as by-products of the cyclooxygenase pathway. IsoLGs are highly reactive aldehydes which are efficient at forming protein adducts and cross-links at concentrations 100-fold lower than 4-hydroxynonenal. Since the contribution of IsoLGs to liver injury has not been studied, we synthesized 15-E2-IsoLG and used it to investigate whether IsoLG could induce activation of HSC.
  
  
  
  Primary human HSC were exposed to 15-E2-IsoLG for up to 48h. Exposure to 5μM 15-E2-IsoLG in HSCs promoted cytotoxicity and apoptosis. At non-cytotoxic doses (50 pM-500nM) 15-E2-IsoLG promoted HSC activation, indicated by increased expression of α-SMA, sustained activation of ERK and JNK signaling pathways, and increased mRNA and/or protein expression of cytokines and chemokines, which was blocked by inhibitors of JNK and NF-kB. In addition, IsoLG promoted formation of reactive oxygen species, and induced an early activation of ER stress, followed by autophagy. Inhibition of autophagy partially reduced the pro-inflammatory effects of IsoLG, suggesting that it might serve as a cytoprotective response.
  
  
  
  This study is the first to describe the biological effects of IsoLG in primary HSC, the main drivers of hepatic fibrosis.
  
  
  
  IsoLGs represent a newly identified class of activators of HSC in vitro, which are biologically active at concentrations as low as 500 pM, and are particularly effective at promoting a pro-inflammatory response and autophagy.
authors.affiliation: Regenerative Medicine & Fibrosis Group, Institute for Liver & Digestive Health, University College London, Royal Free, London, UK.
authors.forename: Lisa
authors.initials: L
authors.lastname: Longato
authors.affiliation: Liver Failure Group, Institute for Liver & Digestive Health, University College of London, Royal Free, London, UK.
authors.forename: Fausto
authors.initials: F
authors.lastname: Andreola
authors.affiliation: Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.
authors.forename: Sean S
authors.initials: SS
authors.lastname: Davies
authors.affiliation: Department of Pharmacology, Vanderbilt University, Nashville, TN, USA.
authors.forename: Jackson L
authors.initials: JL
authors.lastname: Roberts
authors.affiliation: Division of Surgery, University College London, Royal Free, London, UK.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Fusai
authors.affiliation: Regenerative Medicine & Fibrosis Group, Institute for Liver & Digestive Health, University College London, Royal Free, London, UK.
authors.forename: Massimo
authors.initials: M
authors.lastname: Pinzani
authors.affiliation: Regenerative Medicine & Fibrosis Group, Institute for Liver & Digestive Health, University College London, Royal Free, London, UK.
authors.forename: Kevin
authors.initials: K
authors.lastname: Moore
authors.affiliation: Regenerative Medicine & Fibrosis Group, Institute for Liver & Digestive Health, University College London, Royal Free, London, UK. Electronic address: k.rombouts@ucl.ac.uk.
authors.forename: Krista
authors.initials: K
authors.lastname: Rombouts
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D055166:Hepatic Stellate Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects*; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008103:Liver Cirrhosis / Q000378:metabolism* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011458:Prostaglandins E / Q000008:administration & dosage* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000447:Aldehydes; D016328:NF-kappa B; D011458:Prostaglandins E; D017382:Reactive Oxygen Species; C047684:levuglandin E2; C027576:4-hydroxy-2-nonenal
keywords: Autophagy; Endoplasmic reticulum stress; Fibrosis; Gamma-ketoaldehydes; Human hepatic stellate cells; Inflammation; Isoketals; Isolevuglandins; Oxidative stress