Macrophage Activation in Acute Exacerbation of Idiopathic Pulmonary Fibrosis

January Macrophage Activation in Acute Exacerbation of Idiopathic Pulmonary Fibrosis Jonas Christian Schupp 0 1 2 Harald Binder 0 1 2 Benedikt Jger 0 1 2 Giuseppe Cillis 0 1 2 Gernot Zissel 0 1 2 Joachim Mller-Quernheim 0 1 2 Antje Prasse 0 1 2 0 1 Department of Pneumology, University Medical Centre , Freiburg, Germany , 2 Institute of Medical Biostatistics, Epidemiology and Informatics, University Medical Center, Johannes Gutenberg University , Mainz, Germany , 3 Faculty of Biology, University of Freiburg , Freiburg, Germany , 4 Respiratory Diseases Section, Department of Clinical Medicine and Immunological Sciences, University of Siena , Siena , Italy 1 Funding: This study was supported by E-RARE proj- ect, JRC 2011 IPF-AE (DLR 01GM1210A), (http:// www.erare.eu), AP. The article processing charge was funded by the open access publication fund of the Albert Ludwigs University Freiburg. The funders had no role in study design, data collection and analy- sis, decision to publish, or preparation of the manuscript 2 Academic Editor: Bernhard Ryffel, French National Centre for Scientific Research , FRANCE - Acute exacerbation (AE) of idiopathic pulmonary fibrosis (IPF) is a common cause of disease acceleration in IPF and has a major impact on mortality. The role of macrophage activation in AE of IPF has never been addressed before. We evaluated BAL cell cytokine profiles and BAL differential cell counts in 71 IPF patients w/wo AE and in 20 healthy volunteers. Twelve patients suffered from AE at initial diagnosis while sixteen patients developed AE in the 24 months of follow-up. The levels of IL-1ra, CCL2, CCL17, CCL18, CCL22, TNF-, IL-1, CXCL1 and IL-8 spontaneously produced by BAL-cells were analysed by ELISA. In patients with AE, the percentage of BAL neutrophils was significantly increased compared to stable patients. We found an increase in the production rate of the proinflammatory cytokines CXCL1 and IL-8 combined with an increase in all tested M2 cytokines by BAL-cells. An increase in CCL18 levels and neutrophil counts during AE was observed in BAL cells from patients from whom serial lavages were obtained. Furthermore, high baseline levels of CCL18 production by BAL cells were significantly predictive for the development of future AE. BAL cell cytokine production levels at acute exacerbation show up-regulation of pro-inflammatory as well as anti-inflammatory/ M2 cytokines. Our data suggest that AE in IPF is not an incidental event but rather driven by cellular mechanisms including M2 macrophage activation. Competing Interests: JMQ, AP and GZ have a patent EP 2011/060641 24.06.2011 Blockade of CCL18 signalling via CCR6 as a therapeutic option in fibrotic diseases and cancer pending. AP received lecture fees from Intermune, Boehringer Ingelheim and consultancy fees for Novartis, Aventis-Sanofi. Antje Prasse and Gernot Zissel are PLOS ONE Editorial Board members. This does not alter the authors' adherence to PLOS ONE Editorial policies and criteria. All other authors report no conflicts of interest. Idiopathic pulmonary fibrosis (IPF) is a fatal disease with limited treatment options [1]. Although IPF has an overall poor prognosis, it is now recognized that its clinical course varies from slow progression to acute exacerbation with subsequent respiratory deterioration and death [24]. Independent of the status of pulmonary function, an accelerated progression of respiratory symptoms and deterioration of pulmonary function may occur at any stage in the course of the disease. These episodes are called acute exacerbations (AE) of IPF [5]. Martinez and colleagues [4] reported that in their IPF cohort 47% of deaths followed an acute deterioration in respiratory symptoms. Recently, two studies [6, 7] reported the 1-year incidence of AE as 8.5% and 14.2%, respectively. Song and colleagues [6] also showed that AE was the most common cause of rapid deterioration in IPF. After the initial diagnosis, the median survival of patients with AE was much shorter than that of patients without any episode of rapid deterioration. Thus, AE is thought to be an important factor affecting mortality in IPF. The mechanisms and causes of AE in IPF are poorly understood and have only partially been studied so far [8]. Currently, it is debated whether AE is an externally induced, incidental event or a result of underlying cellular mechanisms [9]. Lung pathology of IPF patients with AE is very similar to that of acute respiratory distress syndrome (ARDS) including diffuse alveolar damage and hyaline membranes [10, 11]. Hence, a diffuse injury to alveolar epithelial cells was postulated. Gene expression studies of lung tissues indicated that AE of IPF is characterized by enhanced epithelial injury and proliferation as compared to stable IPF; reflected by increases in Cyclin A2, alpha-defensins and apoptosis of epithelium [12]. Fibrotic lung diseases including IPF are associated with a distinct type of macrophage activation called M2 or alternative activation [13, 14]. Classical/M1 macrophage activation by microbial agents and/or Th1 cytokines, in particular by interferon gamma (IFN-), induces the production of interleukin 12 (IL-12). On the other hand, macrophages stimulated by Th2 cytokines disclose a different activation pathway called alternative activation or M2 which plays a critical role in tumour progression and wound healing [15]. A profibrotic role of alternativelyactivated alveolar macrophages in IPF was demonstrated in humans [16] as well as in mouse models [13, 1719]. We reported recently, that collagen induces a profibrotic M2 type of alveolar macrophages [20] via CCL18 [16]. Based on these findings, we became interested in investigating the activation type of alveolar macrophages from IPF patients with acute exacerbation. Therefore, a comprehensive panel of chemokines produced by classically (IL-1, TNF-, CXCL1, IL-8) and by alternatively (CCL2, CCL17, CCL18, CCL22, IL-1ra) activated macrophages [21] was evaluated. Over a period of seven years, seventy-one consecutive, therapy-naive patients with IPF, who were administered to our tertiary referral centre to undergo a standardized bronchoscopy with bronchoalveolar lavage (BAL) (as previously described [22, 23]) during routine diagnostic work-up, and twenty healthy volunteers were included in the study after obtaining their written informed consent. The patients were diagnosed according to the consensus statement criteria by clinical evaluation, high resolution computed tomography, histologic and laboratory findings [2]. Patients with underlying collagen vascular disease, occupational diseases or other identifiable causes of usual interstitial pneumonitis were excluded. Acute exacerbation in IPF was defined as a sudden aggravation of dyspnea within 30 days, in which any other identifiable causes have been excluded and new ground glass opacity and/or consolidation in HR-CT have been documented [3]. BAL microscopy, microbiologica (...truncated)