title: Lipopolysaccharide enhances transforming growth factor β1-induced platelet-derived growth factor-B expression in bile duct epithelial cells.
abstract: OBJECTIVE
  Platelet-derived growth factor (PDGF)-B is a potent profibrogenic mediator expressed by bile duct epithelial cells (BDECs) that contributes to liver fibrosis after bile duct ligation. However, the mechanism of PDGF-B induction in BDECs during cholestasis is not known. Transforming growth factor β (TGFβ) and lipopolysaccharide (LPS) also contribute to the profibrogenic response after bile duct ligation. We tested the hypothesis that LPS and TGFβ1 synergistically induce PDGF-B expression in BDECs.
  
  
  METHODS
  Transformed human BDECs (MMNK-1 cells) and primary rat BDECs were stimulated with LPS and/or TGFβ1, and signaling pathways through which LPS potentiates TGFβ1-induced PDGF-B mRNA expression were investigated.
  
  
  RESULTS
  Stimulation of MMNK-1 cells with LPS alone did not significantly induce PDGF-B mRNA expression. However, LPS co-treatment enhanced TGFβ1 induction of PDGF-B mRNA in MMNK-1 cells and also in primary rat BDECs. Importantly, co-treatment of MMNK-1 cells with LPS and TGFβ1 also significantly increased PDGF-BB protein expression. Interestingly, LPS did not affect TGFβ1 activation of a SMAD-dependent reporter construct. Rather, stimulation of MMNK-1 cells with LPS, but not TGFβ1, increased JNK1/2 phosphorylation. Expression of dominant negative JNK2, but not dominant negative JNK1, inhibited the LPS potentiation of TGFβ1-induced PDGF-B mRNA expression in MMNK-1 cells. In addition, LPS treatment caused IκBα degradation and activation of a nuclear factor κB (NFκB)-dependent reporter construct. Expression of an IκBα super repressor inhibited activation of NFκB and attenuated LPS potentiation of TGFβ1-induced PDGF-B mRNA.
  
  
  CONCLUSIONS
  The results indicate that LPS activation of NFκB and JNK2 enhances TGFβ1-induced PDGF-B expression in BDECs.
authors: Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
authors: Karen M
authors: KM
authors: Kassel
authors: Bradley P
authors: BP
authors: Sullivan
authors: James P
authors: JP
authors: Luyendyk
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001652:Bile Ducts / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D048056:Mitogen-Activated Protein Kinase 9 / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D020574:Proto-Oncogene Proteins c-sis / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*; D051785:Smad Proteins / Q000378:metabolism; D018709:Statistics, Nonparametric; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D020672:I-kappa B Proteins; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D051785:Smad Proteins; D053773:Transforming Growth Factor beta1; D000072000:NF-KappaB Inhibitor alpha; D048056:Mitogen-Activated Protein Kinase 9