Pivotal advance: The pattern recognition receptor ligands lipopolysaccharide and polyinosine-polycytidylic acid stimulate factor B synthesis by the macrophage through distinct but overlapping mechanisms

David J. Kaczorowski, Amin Afrazi, Melanie J. Scott, Joon H. Kwak, Roop Gill, Rebecca D. Edmonds, Yujian Liu, Jie Fan, Timothy R. Billiar

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

TLRs and complement are critical to the host response in sepsis, trauma, and ischemia/reperfusion. We hypothesize that TLR stimulation leads to synthesis and release of complement components by macrophages, an important source of extrahepatic complement. RAW264.7 macrophages or peritoneal macrophages from WT and TLR4-, TLR3-, TRIF-, or MyD88-deficient mice were cultured under standard conditions. In some experiments, cells were pretreated with inhibitors of MAPKs or a NF-κB inhibitor. Cells were stimulated with TLR ligands at known stimulatory concentrations. Intratracheal and i.p. injections were also performed in mice. RT-PCR, Western blotting, and immunocytochemistry were used for analysis. Using a RT-PCR-based panel, we demonstrate that of 18 complement components tested, factor B of the alternative pathway is the most robustly up-regulated complement component in macrophages in response to LPS. This up-regulation results in release of factor B into the media. Up-regulation of factor B by LPS is dependent on TLR4, TRIF, JNK, and NF-κB. A screen of other TLR ligands demonstrated that stimulation with poly I:C (dsRNA analog) also results in up-regulation of factor B, which is dependent on JNK and NF-κB but independent of TLR3 and TRIF. Up-regulation of factor B is also observed after intratracheal and i.p. injection of LPS or poly I:C in vivo. PRR stimulation profoundly influences production and release of factor B by macrophages. Understanding the mechanisms of PRR-mediated complement production may lead to strategies aimed at preventing tissue damage in diverse settings, including sepsis, trauma, and ischemia/reperfusion.

Original languageEnglish
Pages (from-to)609-618
Number of pages10
JournalJournal of Leukocyte Biology
Volume88
Issue number4
DOIs
StatePublished - Oct 2010
Externally publishedYes

Keywords

  • Complement
  • Inflammation
  • Toll-like receptors

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