Bacterial DNA and lipopolysaccharide induce synergistic production of TNF-alpha through a post-transcriptional mechanism.
LPS is well recognized for its potent capacity to activate mouse macrophages to produce TNF-alpha, an important inflammatory mediator in bacterial infection-related diseases such as septic shock. We demonstrate here that while inducing only low levels of TNF-alpha alone, DNA from both Gram-negative and Gram-positive bacteria synergizes with subthreshold concentrations of LPS (0.3 ng/ml) to induce TNF-alpha in the RAW 264.7 macrophage-like cell line. The bacterial DNA effects are mimicked by synthetic CpG-containing oligodeoxynucleotides, but not non-CpG-containing oligodeoxynucleotides. Pretreatment of macrophages with either DNA for 2-8 h inhibits macrophage TNF-alpha production in responses to DNA/LPS. However, when pretreatment was extended to 24 h, DNA/LPS synergy on TNF-alpha is further enhanced. RT-PCR analysis indicates that mRNA levels of the TNF-alpha gene, however, are not synergistically induced by bacterial DNA and LPS. Analyses of the half-life of TNF-alpha mRNA indicate that TNF-alpha message has a longer half-life in bacterial DNA- and LPS-treated macrophages than that in bacterial DNA- or LPS-treated macrophages. These findings indicate that the temporally controlled, synergistic induction of TNF-alpha by bacterial DNA and LPS is not mediated at the transcriptional level. Instead, this synergy may occur via a post-transcriptional mechanism.
Gao
J J
JJ
Department of Basic Medical Sciences, University of Missouri, Kansas City, MO 64111, USA.
Xue
Q
Q
Papasian
C J
CJ
Morrison
D C
DC
D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D018899:CpG Islands / Q000276:immunology; D004269:DNA, Bacterial / Q000494:pharmacology*; D004338:Drug Combinations; D004357:Drug Synergism; D004926:Escherichia coli / Q000235:genetics; D006207:Half-Life; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D051379:Mice; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D012323:RNA Processing, Post-Transcriptional / Q000276:immunology*; D013211:Staphylococcus aureus / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology
D000276:Adjuvants, Immunologic; C408982:CPG-oligonucleotide; D004269:DNA, Bacterial; D004338:Drug Combinations; D008070:Lipopolysaccharides; D009838:Oligodeoxyribonucleotides; D014409:Tumor Necrosis Factor-alpha