Suppression of TNF-alpha mRNA expression in LPS-primed macrophages occurs at the level of nuclear factor-kappa B activation, but not at the level of protein kinase C or CD14 expression.
Previously, we reported that preexposure of proteose peptone-elicited murine peritoneal exudate macrophages (P-PEM) to a low dose of LPS suppressed the expression of TNF-alpha mRNA, but not of IL-1 beta mRNA, induced by a second round of LPS exposure. To elucidate the mechanisms underlying this hyporesponsiveness to LPS, we focused on two molecules: nuclear factor (NF)-kappa B and CD14. Activation of NF-kappa B induced by a second round of LPS was suppressed in LPS-primed P-PEM much like the suppression of TNF-alpha mRNA expression. However, protein kinase C (PKC), a candidate as an activator of NF-kappa B, was not desensitized by LPS priming. LPS-induced TNF-alpha production was not affected by depletion of PKC, and LPS could not induce translocation of PKC. CD14 expression showed no significant difference between control and primed P-PEM. In contrast with J774.1 cells and thioglycolate medium-elicited macrophages (T-PEM), P-PEM exhibited serum-independent TNF-alpha production, and a polyclonal Ab to murine CD14 had no inhibitory effect on the LPS-induced TNF-alpha production by P-PEM. These results suggest that priming by LPS causes blockage at an early step, at least before the activation of NF-kappa B, in the LPS signal transduction pathway, but not at the expression of CD14. Our results also suggest that, in P-PEM, in contrast to J774.1 cells and T-PEM, neither PKC nor CD14 is involved in the LPS-induced activation and suppression of TNF-alpha gene expression.
Takasuka
N
N
Department of Immunology, National Institute of Health Science, Tokyo, Japan.
Matsuura
K
K
Yamamoto
S
S
Akagawa
K S
KS
D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis*; D015214:Antigens, Differentiation, Myelomonocytic / Q000096:biosynthesis*; D001483:Base Sequence; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005260:Female; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008809:Mice, Inbred C3H; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000096:biosynthesis*; D011493:Protein Kinase C / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D011493:Protein Kinase C