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A1318 - Chitin Induced Production of Prostaglandin E2 in Alveolar Macrophages and Bronchial Epithelial Cells
Author Block: T. Takeshige1, N. Harada1, K. Matsuno1, A. Ishimori1, Y. Tanabe1, H. Sasano1, A. Nakamura1, S. Harada1, Y. Katsura1, F. Makino1, J. Ito1, R. Atsuta1, H. Akiba2, K. Takahashi1; 1Department of Respiratory Medicine, Juntendo University Faculty of Medicine and Graduate School of Medicine, Tokyo, Japan, 2Department of Immunology, Juntendo University Faculty of Medicine and Graduate School of Medicine, Tokyo, Japan.
Background: Allergy is acknowledged as a major risk factor for asthma, and allergen sensitization by specific allergen, such as insects, mites or fungi is fundamental to the development of asthma. These antigens known as pathogen-associated patterns (PAMPs) are recognized by dendritic cells (DC) and macrophages through pattern-recognition receptors. Chitin is a second-most-abundant polysaccharide in nature after cellulose and is found in the cell walls of fungi and the exoskeleton of crustaceans and insects. PAMPs induced to produce interleukin (IL)-1β, IL-18 and IL-33 by a mechanism dependent on activation of NLR family, pyrin domain-containing 3 (NLRP3) in macrophages. Our previous study showed that chitin induced IL-1β production in alveolar macrophages. On the other hand, previous studies have shown that PAMPs induced prostaglandin E2 (PGE2) production was independent of the NLRP3 inflammasome. PGE2 is commonly considered a potent proinflammatory mediator and is involved in several inflammatory diseases. Several studies found higher levels of PGE2 in BALF, sputum and bronchial secretions from asthmatic patients. Bronchial epithelial cells, smooth muscle cells and alveolar macrophages could be produced PGE2. In this study, we investigated whether chitin induces the PGE2 production in alveolar macrophages and bronchial epithelial cells.
Methods: Mice were intranasally injected chitin on consecutive 3 days, and after 24 hours from last injection bronchoalveolar lavage (BAL) fluids were collected. After alveolar macrophage preparation, total cellular RNA was isolated from alveolar macrophages and the supernates of the alveolar macrophage cultures were collected. The expression mRNA levels of PGE2 synthases in mouse alveolar macrophages, MH-S cells (mouse alveolar macrophages cell line), and BEAS-2B cells (human bronchial epithelial cell line) after treatment with chitin were evaluated by quantitative real-time reverse transcription-PCR.
Results: The murine model of chitin-induced airway inflammation showed the inflammatory cell infiltration into BAL fluids and higher concentrations of PGE2 in BAL fluids, as compared to control mice. Levels of cyclooxygenase (COX) 2 and microsomal PGE2 synthase (mPGES)-2 mRNA expression and PGE2 in culture supernatants of alveolar macrophages were significantly increased after the treatment with chitin. Moreover, we also showed that chitin induced mRNA expression levels of PGE2 synthases in MH-S cells and BEAS-2B cells.
Conclusion: These results suggested that chitin has the potential to induce airway inflammation and PGE2 production in alveolar macrophages and bronchial epithelial cells. The functions of PGE2 in the chitin-induced airway inflammation still require further investigation.