Lipopolysaccharide (LPS)-Induced Biliary Epithelial Cell NRas Activation Requires Epidermal Growth Factor Receptor (EGFR).
Cholangiocytes (biliary epithelial cells) actively participate in microbe-induced proinflammatory responses in the liver and contribute to inflammatory and infectious cholangiopathies. We previously demonstrated that cholangiocyte TLR-dependent NRas activation contributes to proinflammatory/ proliferative responses. We test the hypothesis that LPS-induced activation of NRas requires the EGFR. SV40-transformed human cholangiocytes (H69 cells), or low passage normal human cholangiocytes (NHC), were treated with LPS in the presence or absence of EGFR or ADAM metallopeptidase domain 17 (TACE) inhibitors. Ras activation assays, quantitative RT-PCR, and proliferation assays were performed in cells cultured with or without inhibitors or an siRNA to Grb2. Immunofluorescence for phospho-EGFR was performed on LPS-treated mouse samples and specimens from patients with primary sclerosing cholangitis, primary biliary cirrhosis, hepatitis C, and normal livers. LPS-treatment induced an association between the TLR/MyD88 and EGFR/Grb2 signaling apparatus, NRas activation, and EGFR phosphorylation. NRas activation was sensitive to EGFR and TACE inhibitors and correlated with EGFR phosphorylation. The TACE inhibitor and Grb2 depletion prevented LPS-induced IL6 expression (p<0.05) and proliferation (p<0.01). Additionally, cholangiocytes from LPS-treated mouse livers and human primary sclerosing cholangitis (PSC) livers exhibited increased phospho-EGFR (p<0.01). Moreover, LPS-induced mouse cholangiocyte proliferation was inhibited by concurrent treatment with the EGFR inhibitor, Erlotinib. Our results suggest that EGFR is essential for LPS-induced, TLR4/MyD88-mediated NRas activation and induction of a robust proinflammatory cholangiocyte response. These findings have implications not only for revealing the signaling potential of TLRs, but also implicate EGFR as an integral component of cholangiocyte TLR-induced proinflammatory processes.
Division of Gastroenterology and Hepatology, and the Mayo Clinic Center for Cell Signaling in Gastroenterology, Mayo Clinic, Rochester, Minnesota, 55905, United States of America.
Christy E
CE
Trussoni
Division of Gastroenterology and Hepatology, and the Mayo Clinic Center for Cell Signaling in Gastroenterology, Mayo Clinic, Rochester, Minnesota, 55905, United States of America.
James H
JH
Tabibian
Division of Gastroenterology and Hepatology, and the Mayo Clinic Center for Cell Signaling in Gastroenterology, Mayo Clinic, Rochester, Minnesota, 55905, United States of America.
Patrick L
PL
Splinter
Division of Gastroenterology and Hepatology, and the Mayo Clinic Center for Cell Signaling in Gastroenterology, Mayo Clinic, Rochester, Minnesota, 55905, United States of America.
Steven P
SP
O'Hara
D051722:ADAM Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000072198:ADAM17 Protein; D000818:Animals; D001652:Bile Ducts / Q000166:cytology* / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004066:Digestive System Diseases / Q000378:metabolism / Q000473:pathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000009:adverse effects / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects
D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D008565:Membrane Proteins; C512478:EGFR protein, human; C541485:EGFR protein, mouse; D066246:ErbB Receptors; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human