Induction of TNF-alpha and MnSOD by endotoxin: role of membrane CD14 and Toll-like receptor-4.
Endotoxin (LPS) is a potent inducer of tumor necrosis factor-alpha (TNF-alpha) and manganese superoxide dismutase (MnSOD). Recent evidence suggests that LPS induction of TNF-alpha and MnSOD mRNAs is mediated through distinct intracellular signal transduction pathways. Membrane CD14 (mCD14) and Toll-like receptor-4 (TLR4) mediate LPS induction of TNF-alpha in macrophages. In the current study, we evaluated the role of mCD14 and TLR4 in LPS induction of MnSOD using peritoneal macrophages from CD14 knockout (CD14-KO) mice and mice with the Tlr4 gene point mutation (C3H/HeJ) or deletion (C57BL/10ScCr). We studied mCD14-dependent (1 and 10 ng/ml) and mCD14-independent (1,000 ng/ml) concentrations of LPS. Compared with control (BALB/c) macrophages, LPS at 1 and 10 ng/ml failed to induce TNF-alpha or MnSOD mRNA in CD14-KO macrophages. However, LPS at 1,000 ng/ml induced TNF-alpha and MnSOD mRNAs equally in macrophages from CD14-KO and control mice. LPS (1, 10, or 1,000 ng/ml) failed to induce TNF-alpha or MnSOD mRNA and failed to activate nuclear factor-kappaB in C3H/HeJ or C57BL/10ScCr macrophages. Measurements of TNF-alpha and MnSOD enzyme activity paralleled TNF-alpha and MnSOD mRNA levels. These data demonstrate that, like TNF-alpha, induction of MnSOD by LPS is mediated by mCD14 and TLR4 in murine macrophages.
Tsan
M F
MF
Research Service, Stratton Veterans Affairs Medical Center, Albany, NY 12208, USA. min-fu.tsan2@med.va.gov
Clark
R N
RN
Goyert
S M
SM
White
J E
JE
D000818:Animals; D029721:Drosophila Proteins; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology; D018950:Lipopolysaccharide Receptors / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000201:enzymology*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000235:genetics* / Q000378:metabolism; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000378:metabolism
D029721:Drosophila Proteins; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D013482:Superoxide Dismutase