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Raby, A.C., Holst, B., Davies, J., Colmont, C., Laumonnier, Y., Coles, B., Shah, S., Hall, J., Topley, N., Kohl, J., Morgan, B.P. and Labeta, M.O. (2011) TLR activation enhances C5a-induced pro-inflammatory responses by negatively modulating the second C5a receptor, C5L2. European Journal of Immunology, 41, 2741-2752. doi:10.1002/eji.201041350

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• TITLE: Synergistic interaction between C5a and NOD2 signaling in the regulation of chemokine expression in RAW 264.7 macrophages

  AUTHORS: Hui Tang, Umme Amara, Dora Tang, Mark A. Barnes, Christine McDonald, Laura E. Nagy

  KEYWORDS: Anaphylatoxin; C5L2; C5a Receptor; Complement; NOD2

  JOURNAL NAME: Advances in Bioscience and Biotechnology, Vol.4 No.8C, August 19, 2013

  ABSTRACT: The innate immune response is a complex process involving multiple pathogen-recognition receptors, including toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors. Complement is also a critical component of innate immunity. While complement is known to interact with TLR-mediated signals, the interactions between NOD-like receptors and complement are not well understood. Here we report a synergistic interaction between C5a and Nod2 signaling in RAW 264.7 marophages. Long-term treatment with muramyl dipeptide (MDP), a NOD2 ligand, enhanced C5a-mediated expression of chemokine mRNAs in RAW 264.7 cells. This response was dependent on NOD2 expression and was associated with a decrease in expression of C5L2, a receptor for C5a which acts as a negative modulator of C5a receptor (C5aR) activity. MDP amplified C5a-mediated phosphorylation of p38 MAPK. Treatment of RAW264.7 cells with an inhibitor of p38 attenuated the synergistic effects of C5aon MDP-primed cells on MIP-2, but not MCP-1, mRNA. In contrast, inhibition of AKT prevented C5a stimulation of MCP-1, but not MIP-2, mRNA, in MDP-primed cells. Taken together, these data demonstrated a synergistic interaction between C5a and NOD2 in the regulation of chemokine expression in macrophages, associated with a down-regulation of C5L2, a negative regulator of C5a receptor activity.