Immunobiology 217 (2012) 761–767 Contents lists available at SciVerse ScienceDirect Immunobiology jou rnal h om epage: www.elsevier.com/locate/imbio Deficiency of the CGRP receptor component RAMP1 attenuates immunosuppression during the early phase of septic peritonitis Gabriela Jusek a , Daniel Reim a , Kazutake Tsujikawa b , Bernhard Holzmann a,∗ a Department of Surgery, Technical University Munich, Ismaninger Strasse 22, 81675 Munich, Germany b Department of Immunology, Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamadaoka, Suita, Osaka 565-0871, Japan a r t i c l e i n f o Article history: Received 27 April 2012 Accepted 27 April 2012 Keywords: CGRP Host defense Immunosuppression IL-10 Sepsis Defensins a b s t r a c t The neuropeptide CGRP contributes to the control of excessive cytokine production in endotoxemia models. However, the function of CGRP in sepsis caused by infection with viable pathogens is unknown. Here, we show that mice deficient for the CGRP receptor component RAMP1 have an improved anti- bacterial defense during the early, but not late, phase of polymicrobial septic peritonitis. The protective effect of Ramp1-deficiency was associated with reduced levels of IL-10 in plasma and peritoneal lavage fluid. Consistent with these findings, CGRP markedly increased IL-10 production of peritoneal and bone marrow-derived macrophages in response to short term stimulation with LPS in vitro. In addition, the lack of an intact CGRP receptor resulted in an increased recruitment and activation of neutrophils and caused an enhanced release of defensin-1 in the peritoneal cavity. Considered together, our results identify the neuropeptide CGRP as a crucial immunosuppressive mediator impairing host defense during the early, but not late, phase of septic peritonitis. © 2012 Elsevier GmbH. All rights reserved. Introduction Sensory nerves containing the neuropeptide CGRP are abundant in lymphoid organs and contact tissue mast cells and macrophages as well as Langerhans cells in the skin (Hosoi et al. 1993; Metcalfe et al. 1997; Naukkarinen et al. 1996; Stead et al. 1987; Weihe et al. 1991). During inflammation, CGRP is released from sensory nerves in response to tryptase, which is secreted by activated mast cells (Steinhoff et al. 2000). CGRP binds to a receptor complex consisting of the seven-transmembrane domain protein CLR and the type-1 transmembrane protein RAMP1 (Foord and Marshall 1999; Hay et al. 2006; Parameswaran and Spielman 2006; Walker et al. 2010). The membrane-bound RAMP1/CLR complex is linked to the cytosolic CGRP receptor component protein, which is required for receptor function (Evans et al. 2000). In immune cells, signal transduction through the CGRP receptor involves activation of G S proteins, leading to the elevation of cellular cAMP levels and activa- tion of PKA (Walker et al. 2010). In other cell types, CGRP may also Abbreviations: CASP, colon ascendens stent peritonitis; CGRP, calcitonin gene- related peptide; CLR, calcitonin receptor-like receptor; ICER, inducible cAMP early repressor; RAMP1, receptor activity-modifying protein 1. ∗ Corresponding author at: Technische Universität München, Klinikum rechts der Isar, Department of Surgery, Ismaninger Strasse 22, 81675 Munich, Germany. Tel.: +49 89 4140 2033; fax: +49 89 4140 6605. E-mail addresses: holzmann@chir.med.tu-muenchen.de, bernhard.holzmann@tum.de (B. Holzmann). activate phospholipase C1 via G q/11 proteins, causing calcium mobilization. The CGRP receptor is expressed on most immune cells and mediates potent anti-inflammatory activities. Treatment of den- dritic cells or macrophages with CGRP reduces the expression of MHC class II antigens and CD86, thereby inhibiting the antigen- presenting capacity of these cells, and impairs production of inflammatory cytokines such as TNF, IL-12, IL-1 and CCL4 (Carucci et al. 2000; Fox et al. 1997; Harzenetter et al. 2007; Hosoi et al. 1993; Torii et al. 1997). Upon administration to experimental animals, CGRP inhibits delayed-type and contact hypersensitivity responses and mediates immunosuppressive effects of ultraviolet irradiation of the skin (Asahina et al. 1995; Garssen et al. 1998; Gillardon et al. 1995; Hosoi et al. 1993; Legat et al. 2004; Niizeki et al. 1997). Moreover, inflammation and organ injury in models of chronic colitis were found to be attenuated by CGRP treatment (Reinshagen et al. 1998, 2000). Several studies suggested that CGRP also has potent anti- inflammatory activities in murine models of endotoxemia. Administration of CGRP was found to reduce systemic levels of TNF, increase the production of IL-10 and improve outcome in mice treated with a combination of LPS and d-galactosamine or with high doses of LPS (Gomes et al. 2005; Kroeger et al. 2009). In addition to augmenting IL-10 release, the mechanisms underly- ing the anti-inflammatory effects of CGRP involve up-regulation of the transcriptional repressor ICER (Harzenetter et al. 2007; Kroeger et al. 2009). ICER mediates IL-10-independent anti-inflammatory 0171-2985/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.imbio.2012.04.009