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TLR Expression on Neutrophils at the Pulmonary Site of Infection: TLR1/TLR2-Mediated Up-Regulation of TLR5 Expression in Cystic Fibrosis Lung Disease¹

Barbara Koller^*, Matthias Kappler^*, Phillip Latzin, Amit Gaggar, Marcus Schreiner^*, Sherkin Takyar, Michael Kormann^*, Michael Kabesch^*, Dirk Roos^¶, Matthias Griese^* and Dominik Hartl^2,*

^* Children's Hospital of the Ludwig-Maximilians-University, Munich, Germany; Children’s Hospital, University of Bern, Bern, Switzerland; Department of Pediatrics and Department of Physiology/Biophysics, University of Alabama, Birmingham, AL 35294; Department of Pulmonary and Critical Care Medicine, Yale University School of Medicine, New Haven, CT 06510; and ^¶ Sanquin Research and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands

Cystic fibrosis (CF) lung disease is characterized by infection with Pseudomonas aeruginosa and a sustained accumulation of neutrophils. In this study, we analyzed 1) the expression of MyD88-dependent TLRs on circulating and airway neutrophils in P. aeruginosa-infected CF patients, P. aeruginosa-infected non-CF bronchiectasis patients, and noninfected healthy control subjects and 2) studied the regulation of TLR expression and functionality on neutrophils in vitro. TLR2, TLR4, TLR5, and TLR9 expression was increased on airway neutrophils compared with circulating neutrophils in CF and bronchiectasis patients. On airway neutrophils, TLR5 was the only TLR that was significantly higher expressed in CF patients compared with bronchiectasis patients and healthy controls. Studies using confocal microscopy and flow cytometry revealed that TLR5 was stored intracellularly in neutrophils and was mobilized to the cell surface in a protein synthesis-independent manner through protein kinase C activation or after stimulation with TLR ligands and cytokines characteristic of the CF airway microenvironment. The most potent stimulator of TLR5 expression was the bacterial lipoprotein Pam₃CSK₄. Ab-blocking experiments revealed that the effect of Pam₃CSK₄ was mediated through cooperation of TLR1 and TLR2 signaling. TLR5 activation enhanced the phagocytic capacity and the respiratory burst activity of neutrophils, which was mediated, at least partially, via a stimulation of IL-8 production and CXCR1 signaling. This study demonstrates a novel mechanism of TLR regulation in neutrophils and suggests a critical role for TLR5 in neutrophil-P. aeruginosa interactions in CF lung disease.

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 the Society for Pediatric Pneumology (to D.H.) and the Cystic Fibrosis Foundation (Grant GAGGA07A0 to A.G.).

² Address correspondence and reprint requests to Dr. Dominik Hartl, Ludwig-Maximilians-University, Children’s Hospital Research Center, Lindwurmstrasse 2a, D-80337 Munich, Germany. E-mail address: dominic.hartl{at}med.uni-muenchen.de

³ Abbreviations used in this paper: CF, cystic fibrosis; BAL, bronchoalveolar lavage; BALF, BAL fluid; CHX, cycloheximide; FEV₁, forced expiratory volume in 1 s; LTA, lipoteichoic acid; MFI, mean fluorescence intensity; Pam₃CSK₄ tripalmitoyl, CysSerLys₄; PI, propidium iodide; LY, lucifer yellow; TIRAP, Toll/IL-1R domain-containing adaptor protein.