Polarized Secretion of Interleukin (IL)-6 and IL-8 by Human Airway Epithelia 16HBE14o- Cells in Response to Cationic Polypeptide Challenge Alison Wai-ming Chow1, Jocelyn Feng-ting Liang1, Janice Siu-chong Wong1, Yan Fu2, Nelson Leung-sang Tang2,3, Wing-hung Ko1,3* 1 School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong, Special Administrative Region, People’s Republic of China, 2 Department of Chemical Pathology, The Chinese University of Hong Kong, Shatin, Hong Kong, Special Administrative Region, People’s Republic of China, 3 KIZ/CUHK Joint Laboratory of Bioresource and Molecular Research of Common Diseases, The Chinese University of Hong Kong, Shatin, Hong Kong, Special Administrative Region, People’s Republic of China Abstract Background: The airway epithelium participates in asthmatic inflammation in many ways. Target cells of the epithelium can respond to a variety of inflammatory mediators and cytokines. Damage to the surface epithelium occurs following the secretion of eosinophil-derived, highly toxic cationic proteins. Moreover, the surface epithelium itself is responsible for the synthesis and release of cytokines that cause the selective recruitment, retention, and accumulation of various inflammatory cells. To mimic the damage seen during asthmatic inflammation, the bronchial epithelium can be challenged with highly charged cationic polypeptides such as poly-L-arginine. Methodology/Principal Findings: In this study, human bronchial epithelial cells, 16HBE14o- cells, were ‘‘chemically injured’’ by exposing them to poly-L-arginine as a surrogate of the eosinophil cationic protein. Cytokine antibody array data showed that seven inflammatory mediators were elevated out of the 40 tested, including marked elevation in interleukin (IL)-6 and IL-8 secretion. IL-6 and IL-8 mRNA expression levels were elevated as measured with real-time PCR. Cell culture supernatants from apical and basolateral compartments were collected, and the IL-6 and IL-8 production was quantified with ELISA. IL-6 and IL-8 secretion by 16HBE14o- epithelia into the apical compartment was significantly higher than that from the basolateral compartment. Using specific inhibitors, the production of IL-6 and IL-8 was found to be dependent on p38 MAPK, ERK1/2 MAPK, and NF-kB pathways. Conclusions/Significance: The results clearly demonstrate that damage to the bronchial epithelia by poly-L-arginine stimulates polarized IL-6 and IL-8 secretion. This apically directed secretion of cytokines may play an important role in orchestrating epithelial cell responses to inflammation. Citation: Chow AW-m, Liang JF-t, Wong JS-c, Fu Y, Tang NL-s, et al. (2010) Polarized Secretion of Interleukin (IL)-6 and IL-8 by Human Airway Epithelia 16HBE14o- Cells in Response to Cationic Polypeptide Challenge. PLoS ONE 5(8): e12091. doi:10.1371/journal.pone.0012091 Editor: Wen-Liang Zhou, Sun Yat-Sen University, China Received March 19, 2010; Accepted July 11, 2010; Published August 12, 2010 Copyright: 2010 Chow et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was supported by a Direct Grant for Research, The Chinese University of Hong Kong (#2041451), and Research Grant Council General Research Fund (#2140595) awarded to W. H. Ko. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: whko@cuhk.edu.hk Introduction Human airways are lined by a layer of surface epithelium, which are essential to the integrated function (e.g., effective mucus clearance) of the respiratory tract in health and disease [1,2]. Asthma is now considered to be an inflammatory disorder of the airways [3]. Eosinophils are believed to play a more important role than other inflammatory cells. There is an association between tissue eosinophilia and the airway hyper-responsiveness of asthma. The release of pro-inflammatory cytokines such as IL-4 and IL-5 that leads to the recruitment and infiltration of eosinophils is thus a hallmark of asthma [4]. The eosinophils degranulate, releasing a range of highly charged molecules (e.g., toxic cationic proteins) that damage the respiratory epithelium and account for many of the histopathologic abnormalities of asthma [5]. The airway epithelium participates in inflammation in many ways. The cells can act as target cells that respond to exposure to a variety of inflammatory mediators and cytokines by altering one or several of their functions, such as mucin secretion or ion transport [6]. Damage to the surface epithelium is due to the secretion of eosinophil-derived, highly toxic cationic proteins, such as major basic protein (MBP) [7]. To mimic the damage seen in asthma inflammation, the bronchial epithelium can be challenged with highly charged cationic polypeptides such as poly-L-arginine, which is similar in structure and function to the biologically active moiety of MBP [8–10]. Moreover, the surface epithelium itself is responsible for the synthesis and release of cytokines that cause the selective recruitment, retention, and accumulation of various inflammatory cells [3]. IL-6 and IL-8 are two classic proin- flammatory cytokines that play important roles in bronchial PLoS ONE | www.plosone.org 1 August 2010 | Volume 5 | Issue 8 | e12091