Human intrahepatic biliary epithelial cells function in innate immunity by producing IL-6 and IL-8 via the TLR4-NF-kappaB and -MAPK signaling pathways.
BACKGROUND
Human intrahepatic biliary epithelial cells (HIBECs) may play active roles in both the innate and adaptive immune responses. Little is known, however, about the role of toll-like receptors (TLRs) on HIBECs in inflammatory cholangiopathies.


METHODS
The expression of TLR1-9 and the biological responses to their ligands, lipopolysaccharide (LPS) or lipoteichoic acid (LTA), were studied in cultured HIBECs by reverse transcription-polymerase chain reaction, immunoblotting, and enzyme-linked immunosorbent assay.


RESULTS
HIBECs constitutively expressed transcripts encoding TLR1-6 and 9, as well as myeloid differentiation factor 88 (MyD88), MD2, and CD14. Stimulation of HIBECs with LPS resulted in translocation of NF-kappaB subunits from the cytoplasmic to the nuclear fraction, followed by increased secretion of a variety of chemokines/cytokines, including interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), and IL-6. Treatment with BAY11-7082 efficiently inhibited the LPS-induced transcription and secretion of these chemokines/cytokines. In HIBECs, the mitogen-activated protein kinases (MAPKs) were also activated by LPS stimulation. These results indicated that LPS activates HIBECs via a TLR4-MyD88-dependent pathway. Stimulation of HIBECs with LTA induced the secretion of a similar profile of cytokines/chemokines via a TLR2-MyD88-dependent pathway.


CONCLUSIONS
In HIBECs, at least TLR2 and 4 are capable of mediating innate immune system function in vitro. This result, in conjunction with our recent finding that TLR4 expression is increased in biliary epithelial cells in primary biliary cirrhosis, suggests the involvement of TLRs in the development of chronic inflammatory cholangiopathies.
Yokoyama
Terufumi
T
Clinical Research Center, National Hospital Organization (NHO) Nagasaki Medical Center, Omura, Nagasaki, Japan.
Komori
Atsumasa
A
Nakamura
Minoru
M
Takii
Yasushi
Y
Kamihira
Takashi
T
Shimoda
Shinji
S
Mori
Tsuyoshi
T
Fujiwara
Shinsuke
S
Koyabu
Makiko
M
Taniguchi
Ken
K
Fujioka
Hikaru
H
Migita
Kiyoshi
K
Yatsuhashi
Hiroshi
H
Ishibashi
Hiromi
H
D001649:Bile Duct Diseases / Q000503:physiopathology; D001653:Bile Ducts, Intrahepatic / Q000166:cytology / Q000276:immunology* / Q000378:metabolism*; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007113:Immunity, Innate / Q000502:physiology*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology*; D009570:Nitriles / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D013450:Sulfones / Q000494:pharmacology; D013682:Teichoic Acids / Q000494:pharmacology; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; C111835:CCL2 protein, human; D018932:Chemokine CCL2; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009570:Nitriles; D012333:RNA, Messenger; D013450:Sulfones; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D013682:Teichoic Acids; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C009900:lipoteichoic acid; D020929:Mitogen-Activated Protein Kinase Kinases