title: Synergistic interaction between C5a and NOD2 signaling in the regulation of chemokine expression in RAW 264.7 macrophages.
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 macrophages. 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 C5a on 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.
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Tang
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA.
authors.forename: Umme
authors.initials: U
authors.lastname: Amara
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA.
authors.forename: Dora
authors.initials: D
authors.lastname: Tang
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA ; Department of Molecular Medicine, Case Western Reserve University, Cleveland, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Barnes
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA ; Department of Molecular Medicine, Case Western Reserve University, Cleveland, USA.
authors.forename: Christine
authors.initials: C
authors.lastname: McDonald
authors.affiliation: Departments of Pathobiology Cleveland Clinic, Cleveland, USA ; Department of Molecular Medicine, Case Western Reserve University, Cleveland, USA ; Department of Gastroenterology Cleveland Clinic, Cleveland, USA.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Nagy
keywords: Anaphylatoxin; C5L2; C5a Receptor; Complement; NOD2