title: Oxidative stress modulates KLF6Full and its splice variants.
abstract: BACKGROUND
  Induction of reactive oxygen species (ROS) is a central mechanism in alcohol hepatotoxicity. Krüppel-like factor 6 (KLF6), a transcription factor and a tumor-suppressor gene, is an early-responsive gene to injury; however, the effect of ROS and alcohol on KLF6 induction is unknown. The aim of this study is to investigate the contribution of 2 sources of ROS, cytochrome P450 2E1 (CYP2E1), NAD(P)H quinone oxidoreductase (NQO1), and alcohol on the modulation of KLF6(Full)  expression, splicing to KLF6_V1 and KLF6_V2, and the effect on TNFα, a downstream target.
  
  
  RESULTS
  Endogenous ROS production in CYP2E1-expressing HepG2 cells induced mRNA and protein expression of KLF6(Full)  and its splice variants compared to control cells. Incubation with pro-oxidants such as arachidonic acid (AA), β-naphtoflavone, and H(2) O(2)  further enhanced KLF6(Full)  and its splice variants. The AA effects on KLF6(Full)  and its splice forms were blocked by vitamin E-which prevents lipid peroxidation-and by diallylsulfide-a CYP2E1 inhibitor. Menadione and paraquat, 2 pro-oxidants metabolized via NQO1, induced KLF6(Full)  mRNA in a thiol-dependent manner. Antioxidants and an NQO1 inhibitor suppressed the menadione-dependent increase in KLF6(Full)  and its splice variants mRNA. Furthermore, primary hepatocytes and livers from chronic alcohol-fed rats, with elevated lipid peroxidation, H(2) O(2)  and CYP2E1 but with low GSH, showed a ~2-fold increase in KLF6(Full)  mRNA compared to controls. Inhibition of p38 phosphorylation further up-regulated the CYP2E1 and the AA effects on KLF6(Full)  mRNA, whereas inhibition JNK and ERK1/2 phosphorylation decreased both. KLF6_V1 but not KLF6(Full)  ablation markedly increased TNFα levels in macrophages; thus, TNFα emerges as a downstream target of KLF6_V1.
  
  
  CONCLUSIONS
  The novel effect of ROS on modulating KLF6(Full)  expression and its splice variants could play a relevant role in liver injury and in TNFα regulation.
authors.affiliation: Department of Medicine, Division of Liver Diseases, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Raquel
authors.initials: R
authors.lastname: Urtasun
authors.forename: Francisco Javier
authors.initials: FJ
authors.lastname: Cubero
authors.forename: Natalia
authors.initials: N
authors.lastname: Nieto
mesh_terms: D000818:Animals; D019392:Cytochrome P-450 CYP2E1 / Q000096:biosynthesis / Q000235:genetics; D045325:HCT116 Cells; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051379:Mice; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: C105465:KLF6 protein, human; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; D019392:Cytochrome P-450 CYP2E1