Interleukin-13 Inhibits Lipopolysaccharide-Induced BPIFA1 Expression in Nasal Epithelial Cells

RESEARCH ARTICLE Interleukin-13 Inhibits LipopolysaccharideInduced BPIFA1 Expression in Nasal Epithelial Cells Yung-An Tsou1,2☯, Chia-Der Lin1,3☯*, Hui-Chen Chen3, Hui-Ying Hsu1,3, Lii-Tzu Wu3, Chuan Chiang-Ni4, Chih-Jung Chen4,5, Tsu-Fang Wu6, Min-Chuan Kao4, Yu-An Chen3, Ming-Te Peng3, Ming-Hsui Tsai1, Chuan-Mu Chen2*, Chih-Ho Lai3,4,7* a11111 OPEN ACCESS Citation: Tsou Y-A, Lin C-D, Chen H-C, Hsu H-Y, Wu L-T, Chiang-Ni C, et al. (2015) Interleukin-13 Inhibits Lipopolysaccharide-Induced BPIFA1 Expression in Nasal Epithelial Cells. PLoS ONE 10(12): e0143484. doi:10.1371/journal.pone.0143484 Editor: Yuanpu Peter Di, University of Pittsburgh, UNITED STATES Received: November 19, 2014 Accepted: November 5, 2015 Published: December 8, 2015 Copyright: © 2015 Tsou 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. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by research grants from the Ministry of Science and Technology (103-2633-B-182-001, 104-2320-B-182-040, 1042314-B-039-040); Taiwan Ministry of Health and Welfare Clinical Trial and Research Center of Excellence (MOHW104-TDU-B-212-113002); China Medical University and Hospital (CMU102-ASIA-21, 103-S-15, 103-S-18, and DMR103-025); Chang Gung Memorial Hospital (CMRPD3E0511-3), and the Tomorrow Medicine Foundation (TMF104-01). The funders had no role in study design, data collection 1 Department of Otolaryngology-Head and Neck Surgery, China Medical University and Hospital, Taichung, Taiwan, 2 Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan, 3 Graduate Institute of Basic Medical Science, School of Medicine, China Medical University and Hospital, Taichung, Taiwan, 4 Department of Microbiology and Immunology, Graduate Institute of Biomedical Sciences, Chang Gung University, Taoyuan, Taiwan, 5 Division of Paediatric Infectious Diseases, Department of Paediatrics, Chang Gung Children's Hospital and Chang Gung Memorial Hospital, Taoyuan, Taiwan, 6 Department of Applied Cosmetology, Hung Kuang University, Taichung, Taiwan, 7 Department of Nursing, Asia University, Taichung, Taiwan ☯ These authors contributed equally to this work. * (CDL); (CMC); (CHL) Abstract Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) protein is expressed in human nasopharyngeal and respiratory epithelium and has demonstrated antimicrobial activity. SPLUNC1 is now referred to as bactericidal/permeability-increasing fold containing family A, member 1 (BPIFA1). Reduced BPIFA1 expression is associated with bacterial colonization in patients with chronic rhinosinusitis with nasal polyps (CRSwNP). Interleukin 13 (IL13), predominately secreted by T helper 2 (TH2) cells, has been found to contribute to airway allergies and suppress BPIFA1 expression in nasal epithelial cells. However, the molecular mechanism of IL-13 perturbation of bacterial infection and BPIFA1 expression in host airways remains unclear. In this study, we found that lipopolysaccharide (LPS)-induced BPIFA1 expression in nasal epithelial cells was mediated through the JNK/c-Jun signaling pathway and AP-1 activation. We further demonstrated that IL-13 downregulated the LPSinduced activation of phosphorylated JNK and c-Jun, followed by attenuation of BPIFA1 expression. Moreover, the immunohistochemical analysis showed that IL-13 prominently suppressed BPIFA1 expression in eosinophilic CRSwNP patients with bacterial infection. Taken together, these results suggest that IL-13 plays a critical role in attenuation of bacteria-induced BPIFA1 expression that may result in eosinophilic CRSwNP. Introduction Short palate, lung, and nasal epithelium clone 1 (SPLUNC1) protein, a member of the bactericidal/permeability-increasing protein (BPI) family, is expressed in human nasopharyngeal and PLOS ONE | DOI:10.1371/journal.pone.0143484 December 8, 2015 1 / 16 IL-13 Suppresses LPS-Induced BPIFA1 Expression and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. respiratory epithelium [1,2] and is also referred to as BPI fold containing family A, member 1 (BPIFA1) [3]. Several studies have shown that BPIFA1 possesses antimicrobial activity [4,5]. Additionally, BPIFA1 exhibits surfactant properties of airway secretions [6], and this activity may inhibit biofilm formation of the bacteria [7]. It has also been reported that BPIFA1 plays an important role in the regulation of airway surface liquid volume [8]. Reduced BPIFA1 expression may contribute to the persistent nature of bacterial infections in airways, suggesting that BPIFA1 may serve as a host defense protein against bacterial infection [5,9]. In a recent report, we analyzed patients who underwent sinus surgery for chronic rhinosinusitis with nasal polyps (CRSwNP) and found that reduced BPIFA1 expression was associated with bacterial colonization and negative treatment outcomes in these patients [10]. This evidence indicated that decreased BPIFA1 expression might facilitate bacterial infection in a host, leading to severe disease manifestations. Patients with CRSwNP generally require revision sinus surgery for persistent nasal disease [11,12]. CRSwNP is a disorder characterized by the development of TH2 inflammation and tissue eosinophilia that may be induced by microbial infections [13]. Interleukin 13 (IL-13), a cytokine predominately secreted by TH2, has been found to contribute to airway allergies and to suppress BPIFA1 expression in nasal epithelial cells [14]. Additionally, lipopolysaccharide (LPS), which is secreted from bacterial cell walls and serves as a Toll-like receptor 4 (TLR-4) agonist, has been found to upregulate BPIFA1 expression in polyp epithelial cells from patients with eosinophilic CRSwNP [15]. These findings indicate that IL-13 plays a critical role in regulation of BPIFA1 expression in patients with eosinophilic CRSwNP. However, the molecular mechanisms underlying IL-13 perturbation of bacterial infection and BPIFA1 expression in host airways require further exploration. Considering the potential role of BPIFA1 in host innate immunity, we established an in vitro human nasal cell model and examined patient tissues to determine whether LPS could upregulate BPIFA1 expression. We then demonstrated that IL-13 downregulated LPS-induced activation of phosphorylated JNK and c-Jun, followed by attenuation of BPIFA1 expression. Our results provide insight into the molecular mechanisms underlying the function of BPIFA1, which is modulated by the immune response and can be counteracted in a persistent infection in host airways. Materials and Methods Antibodies and reagents Antibodies against β-actin, BPIFA1 (SPLUNC1 (...truncated)