Research Article The Antimicrobial Peptide Lysozyme Is Induced after Multiple Trauma Tim Klüter, 1 Stefanie Fitschen-Oestern, 1 Sebastian Lippross, 1 Matthias Weuster, 1 Rolf Mentlein, 2 Nadine Steubesand, 1 Claudia Neunaber, 3 Frank Hildebrand, 4 Thomas Pufe, 5 Mersedeh Tohidnezhad, 5 Andreas Beyer, 6 Andreas Seekamp, 1 and Deike Varoga 1 1 Department of Trauma Surgery, University of Kiel, Arnold-Heller-Straße 3, 24105 Kiel, Germany 2 Department of Anatomy, University of Kiel, Otto-Hahn-Platz 8, 24118 Kiel, Germany 3 Department of Trauma, Hannover Medical School, Carl-Neuberg-Straße 1, 30625 Hannover, Germany 4 Department of Trauma Surgery, University of Aachen, Pauwelsstraße 30, 52074 Aachen, Germany 5 Department of Anatomy and Cell Biology, RWTH Aachen University, Wendlingweg 2, 52074 Aachen, Germany 6 Department of Cardiovascular Surgery, University Medical Center of Schleswig-Holstein, Kiel Campus, Arnold-Heller-Straße 3, 24105 Kiel, Germany Correspondence should be addressed to Tim Kl¨ uter; Tim.Klueter@uksh.de Received 14 May 2014; Revised 21 July 2014; Accepted 4 August 2014; Published 31 August 2014 Academic Editor: Timothy R. Billiar Copyright © 2014 Tim Kl¨ uter et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. he antimicrobial peptide lysozyme is an important factor of innate immunity and exerts high potential of antibacterial activity. In the present study we evaluated the lysozyme expression in serum of multiple injured patients and subsequently analyzed their possible sources and signaling pathways. Expression of lysozyme was examined in blood samples of multiple trauma patients from the day of trauma until 14 days ater trauma by ELISA. To investigate major sources of lysozyme, its expression and regulation in serum samples, diferent blood cells, and tissue samples were analysed by ELISA and real-time PCR. Neutrophils and hepatocytes were stimulated with cytokines and supernatant of Staphylococcus aureus. he present study demonstrates the induction and release of lysozyme in serum of multiple injured patients. he highest lysozyme expression of all tested cells and tissues was detected in neutrophils. Stimulation with trauma-related factors such as interleukin-6 and S. aureus induced lysozyme expression. Liver tissue samples of patients without trauma show little lysozyme expression compared to neutrophils. Ater stimulation with bacterial fragments, lysozyme expression of hepatocytes is upregulated signiicantly. Toll-like receptor 2, a classic receptor of Gram-positive bacterial protein, was detected as a possible target for lysozyme induction. 1. Introduction Multiple trauma is the third most abundant cause of death for all ages, following heart disease and cancer. Generally multiple trauma results in a complex pathophysiological and immunological response. Up to now the molecular mech- anisms are not fully understood. Various immunological alterations known as posttraumatic inlammatory responses depend on the individual injury pattern and the time elapsed ater injury [1]. During the posttraumatic inlammatory reaction multiple cytokines are released by various cells [2]. IL-6 has recently proven to be of outstanding clinical interest and can now be used as a prognostic clinical marker in sepsis [3]. With respect to open wounds and fractures ater multiple trauma, one could regard the overall infection rate as remarkably low [4]. It seems that there are mechanisms in the immune system preventing trauma patients from infections. Several defense mechanisms are activated during the inlammatory reaction. Antimicrobial peptides (AMP) belong to the host defense peptides (HDP) and are key elements of the innate immunity, providing the irst barrier in many epithelial cells against invading microbes. Although Hindawi Publishing Corporation Mediators of Inflammation Volume 2014, Article ID 303106, 7 pages http://dx.doi.org/10.1155/2014/303106