Endotoxin-induced chemokine expression in murine peritoneal mesothelial cells: the role of toll-like receptor 4.
Acute peritonitis, in which peritoneal mesothelial cells are directly exposed to bacterial components, is a major cause of peritoneal dysfunction in continuous ambulatory peritoneal dialysis patients. We have previously shown that Toll-like receptors (TLR) are expressed in kidney cells, and LPS induces TLR4-dependent chemokine production in tubular epithelial cells. The present work was designed to investigate the involvement of TLR, especially TLR4, in the lipid A-mediated chemokine production by murine peritoneal mesothelial cells (MPMC). A primary cell culture of MPMC from C3H/HeN mice (wild-type mice; LPS sensitive) and from C3H/HeJ mice (containing a point mutation of TLR4; LPS hyposensitive) was established. The expression profile of the TLR family and their accessory molecules, CD14 and MD-2, which are requisite for the LPS signaling pathway, was examined by RT-PCR, Northern blot test, and immunohistochemical staining. Synthetic lipid A-mediated chemokine production by MPMC was studied. The involvement of MAP kinase family (ERK, JNK, and p38 mitogen-activated protein kinase) and nuclear factor (NF)-kappaB in these processes was also studied. MPMC constitutively express TLR4, CD14, and MD-2. A prominent induction of monocyte chemotactic protein-1 (MCP-1) and macrophage inflammatory protein (MIP)-2 by MPMC was detected after lipid A stimulation and was strictly dependent on TLR4. Furthermore, TLR4-dependent chemokine production followed by leukocyte influx into the peritoneal cavity was also confirmed in vivo after stimulation with LPS. mRNA expression of MCP-1 was abolished by NF-kappaB inhibition, but were not affected by the inhibition of ERK, JNK, or p38. As compared with MCP-1, MIP-2 mRNA expression was inhibited by a high dose of curcumin but not by NF-kappaB decoy oligodeoxynucleotide and individual inhibitions of MAP kinase, suggesting that the additional signaling pathway with NF-kappaB might be involved in mRNA expression of MIP-2. These show that TLR4 is directly involved in the production of MCP-1 and MIP-2 by MPMC in a NF-kappaB-dependent manner, but the process does not require any MAP kinase activation. The results provide a candidate molecular target in prevention of it.
Kato
Sawako
S
Division of Clinical Immunology, Department of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan.
Yuzawa
Yukio
Y
Tsuboi
Naotake
N
Maruyama
Shoichi
S
Morita
Yoshiki
Y
Matsuguchi
Tetsuya
T
Matsuo
Seiichi
S
D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000276:immunology; D018932:Chemokine CCL2 / Q000235:genetics; D054426:Chemokine CXCL2; D018925:Chemokines / Q000235:genetics*; D004848:Epithelium; D015870:Gene Expression / Q000187:drug effects / Q000276:immunology; D008050:Lipid A / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D008817:Mice, Mutant Strains; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010537:Peritoneum / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D010538:Peritonitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D015854:Up-Regulation
D018932:Chemokine CCL2; D054426:Chemokine CXCL2; D018925:Chemokines; C404915:Cxcl2 protein, mouse; D008050:Lipid A; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D020928:Mitogen-Activated Protein Kinases