G Protein-Coupled Receptor 43 Is Essential for Neutrophil Recruitment during Intestinal Inflammation 1 Christian Sina,* ‡ Olga Gavrilova,* Matti Fo ¨rster,* Andreas Till,* Stefanie Derer,* Friederike Hildebrand,* Bjo ¨ rn Raabe, † Athena Chalaris, † Ju ¨ rgen Scheller, † Ateequr Rehmann,* Andre Franke,* Stephan Ott,* ‡ Robert Ha ¨sler,* Susanna Nikolaus,* ‡ Ulrich R. Fo ¨lsch, ‡ Stefan Rose-John, † Hui-Ping Jiang, § Jun Li, ¶ Stefan Schreiber, 2 * ‡ and Philip Rosenstiel 2,3 * Molecular danger signals attract neutrophilic granulocytes (polymorphonuclear leukocytes (PMNs)) to sites of infection. The G protein-coupled receptor (GPR) 43 recognizes propionate and butyrate and is abundantly expressed on PMNs. The functional role of GPR43 activation for in vivo orchestration of immune response is unclear. We examined dextrane sodium sulfate (DSS)-induced acute and chronic intestinal inflammatory response in wild-type and Gpr43-deficient mice. The severity of colonic inflammation was assessed by clinical signs, histological scoring, and cytokine production. Chemotaxis of wild-type and Gpr43-deficient PMNs was assessed through transwell cell chemotactic assay. A reduced invasion of PMNs and increased mortality due to septic com- plications were observed in acute DSS colitis. In chronic DSS colitis, Gpr43 / animals showed diminished PMN intestinal migration, but protection against inflammatory tissue destruction. No significant difference in PMN migration and cytokine secretion was detected in a sterile inflammatory model. Ex vivo experiments show that GPR43-induced migration is dependent on activation of the protein kinase p38, and that this signal acts in cooperation with the chemotactic cytokine keratinocyte che- moattractant. Interestingly, shedding of L-selectin in response to propionate and butyrate was compromised in Gpr43 / mice. These results indicate a critical role for GPR43-mediated recruitment of PMNs in containing intestinal bacterial translocation, yet also emphasize the bipotential role of PMNs in mediating tissue destruction in chronic intestinal inflammation. The Journal of Immunology, 2009, 183: 7514 –7522. I nflammatory bowel diseases (IBD), 4 Crohn’s disease (CD) and ulcerative colitis, are disorders of unknown etiology characterized by chronic relapsing-remitting inflammation of the gastrointestinal tract. Pathophysiological and genetic evidence points to an important role of intestinal barrier function in the initiation and perpetuation of the disease (1–7). Impaired epithelial permeability and loss of the integrity of the primary immunolog- ical barrier may lead to an increase of physiological and patho- genic bacteria and their components, which in turn may trigger intestinal inflammation (8). A pathological hallmark of active IBD is a strong migration of neutrophilic granulocytes (polymorpho- nuclear leukocytes (PMNs)) into the mucosa, which can be char- acteristically found in the lamina propria and in the epithelial layer in IBD patients (9, 10). Physiologically, phagocytic cells, including PMNs, build up an evolutionary ancient first line of mesenchymal defense. The cells migrate to sites of invaded pathogens guided by a variety of che- motactic molecules exerting an important role in the containment and eradication of pathogens. Genetic deficiency in neutrophil ox- idative defense has been discovered as the cause of chronic gran- ulomatous diseases, rendering the affected individuals susceptible to bacterial and fungal infections (11, 12). Conversely, increased and deregulated PMN recruitment and overactivation have been accused to pivotally contribute to tissue damage in chronic inflam- matory disorders and are key pathological features of both human IBD and experimental colitis models (13–15). It has been shown that migration of PMNs into inflamed tissues in general depends on several factors, including the presence of various chemokines, up-regulation of integrins, and reorganization of the cellular cytoskeleton (16 –18). Recently, short chain fatty acids (SCFA) that are mainly produced by the commensal flora of the gut have been described as potent activator molecules of PMNs by binding to the membrane-associated Gq/Gi protein-coupled receptor (GPR) 43 (19 –22). In vitro experiments revealed a SCFA-dependent induction of chemotaxis in human PMNs in a *Institute of Clinical Molecular Biology, University Hospital Schleswig-Holstein, Kiel, Germany; † Institute of Biochemistry, Medical Faculty, Christian-Albrechts Uni- versity, Kiel, Germany; ‡ Department of General Internal Medicine, University Hos- pital Schleswig-Holstein, Kiel, Germany; § Department of Translational Sciences, Boehringer Ingelheim Pharmaceuticals, Ridgefield, CT 06877; and ¶ Department of Immunology and Inflammation, Boehringer Ingelheim Pharmaceuticals, Ridgefield, CT 06877 Received for publication January 8, 2009. Accepted for publication September 28, 2009. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 This work was supported by Deutsche Forschungsgemeinschaft Excellence Cluster Inflammation at Interfaces, the Sonderforschungsbereich 617 and 415, the Bundesministerium fu ¨r Bildung, Wissenschaft, Forschung und Technologie National Genome Research Network plus Network on Inflammatory Disorders, and the Bundesministerium fu ¨r Bildung, Wissenschaft, Forschung und Technologie Infection Network Metagenomics of Intestinal Inflammation. 2 S.S. and P.R. share senior authorship. 3 Address correspondence and reprint requests to Dr. Philip Rosenstiel and Dr. Stefan Schreiber, Institute of Clinical Molecular Biology, University Hospital Schleswig- Holstein, Campus Kiel, Schittenhelmstr. 12, D-24105 Kiel, Germany. E-mail ad- dresses: p.rosenstiel@mucosa.de or s.schreiber@mucosa.de 4 Abbreviations used in this paper: IBD, inflammatory bowel disease; CD, Crohn’s disease; COC, colonic organ culture; DAI, disease activity index; DSS, dextran sul- fate sodium; GPR43, G protein-coupled receptor 43; KC, keratinocyte chemoattrac- tant; MPO, myeloperoxidase; PMN, polymorphonuclear leukocyte; SCFA, short chain fatty acid; TACE, TNF- converting enzyme; WT, wild type. Copyright © 2009 by The American Association of Immunologists, Inc. 0022-1767/09/$2.00 The Journal of Immunology www.jimmunol.org/cgi/doi/10.4049/jimmunol.0900063