title: Mixed Lineage Kinase 3 Mediates the Induction of CXCL10 by a STAT1-Dependent Mechanism During Hepatocyte Lipotoxicity.
abstract: Saturated fatty acids (SFA) and their toxic metabolites contribute to hepatocyte lipotoxicity in nonalcoholic steatohepatitis (NASH). We previously reported that hepatocytes, under lipotoxic stress, express the potent macrophage chemotactic ligand C-X-C motif chemokine 10 (CXCL10), and release CXCL10-enriched extracellular vesicles (EV) by a mixed lineage kinase (MLK) 3-dependent mechanism. In the current study, we sought to examine the signaling pathway responsible for CXCL10 induction during hepatocyte lipotoxicity. Here, we demonstrate a role for signal transducer and activator of transcription (STAT) 1 in regulating CXCL10 expression. Huh7 and HepG2 cells were treated with lysophosphatidylcholine (LPC), the toxic metabolite of the SFA palmitate. In LPC-treated hepatocytes, CXCL10 induction is mediated by a mitogen activated protein kinase (MAPK) signaling cascade consisting of a relay kinase module of MLK3, MKK3/6, and p38. P38 in turn induces STAT1 Ser727 phosphorylation and CXCL10 upregulation in hepatocytes, which is reduced by genetic or pharmacological inhibition of this MAPK signaling cascade. The binding and activity of STAT1 at the CXCL10 gene promoter were identified by chromatin immunoprecipitation and luciferase gene expression assays. Promoter activation was attenuated by MLK3/STAT1 inhibition or by deletion of the consensus STAT1 binding sites within the CXCL10 promoter. In lipotoxic hepatocytes, MLK3 activates a MAPK signaling cascade, resulting in the activating phosphorylation of STAT1, and CXCL10 transcriptional upregulation. Hence, this kinase relay module and/or STAT1 inhibition may serve as a therapeutic target to reduce CXCL10 release, thereby attenuating NASH pathogenesis. J. Cell. Biochem. 118: 3249-3259, 2017. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tomita
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Ayano
authors.initials: A
authors.lastname: Kabashima
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Brittany L
authors.initials: BL
authors.lastname: Freeman
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Steven F
authors.initials: SF
authors.lastname: Bronk
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Petra
authors.initials: P
authors.lastname: Hirsova
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.|Division of Pediatric Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Samar H
authors.identifier: 0000-0001-8470-8337
authors.initials: SH
authors.lastname: Ibrahim
mesh_terms: D054357:Chemokine CXCL10 / Q000378:metabolism*; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008244:Lysophosphatidylcholines / Q000633:toxicity; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D065626:Non-alcoholic Fatty Liver Disease / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D019308:Palmitic Acid / Q000633:toxicity; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D002721:omega-Chloroacetophenone; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
chemical_list: D054357:Chemokine CXCL10; D008244:Lysophosphatidylcholines; D020930:MAP Kinase Kinase Kinases; D019308:Palmitic Acid; D050794:STAT1 Transcription Factor; D002721:omega-Chloroacetophenone; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C114753:CXCL10 protein, human; C485433:Cxcl10 protein, mouse; C494079:STAT1 protein, human; C494080:Stat1 protein, mouse
keywords: CXCL10; LIPOTOXICITY; MLK3; NASH; STAT1; p38 MAPK