title: Alternaria extract activates autophagy that induces IL-18 release from airway epithelial cells.
abstract: Alternaria alternata is a major outdoor allergen that causes allergic airway diseases. Alternaria extract (ALT-E) has been shown to induce airway epithelial cells to release IL-18 and thereby initiate Th2-type responses. We investigated the underlying mechanisms involved in IL-18 release from ALT-E-stimulated airway epithelial cells. Normal human bronchial epithelial cells and A549 human lung adenocarcinoma cells were stimulated with ALT-E in the presence of different inhibitors of autophagy or caspases. IL-18 levels in culture supernatants were measured by ELISA. The numbers of autophagosomes, an LC3-I to LC3-II conversion, and p62 degradation were determined by immunofluorescence staining and immunoblotting. 3-methyladenine and bafilomycin, which inhibit the formation of preautophagosomal structures and autolysosomes, respectively, suppressed ALT-E-induced IL-18 release by cells, whereas caspase 1 and 8 inhibitors did not. ALT-E-stimulation increased autophagosome formation, LC-3 conversion, and p62 degradation in airway epithelial cells. LPS-stimulation induced the LC3 conversion in A549 cells, but did not induce IL-18 release or p62 degradation. Unlike LPS, ALT-E induced airway epithelial cells to release IL-18 via an autophagy dependent, caspase 1 and 8 independent pathway. Although autophagy has been shown to negatively regulate canonical inflammasome activity in TLR-stimulated macrophages, our data indicates that this process is an unconventional mechanism of IL-18 secretion by airway epithelial cells.
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan; Department of Internal Medicine, University of Texas Medical Branch at Galveston, 301 University Blvd, Galveston, TX 77555, USA.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Murai
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan.
authors.forename: Shintaro
authors.initials: S
authors.lastname: Okazaki
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Hayashi
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kawakita
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch at Galveston, 301 University Blvd, Galveston, TX 77555, USA.
authors.forename: Koa
authors.initials: K
authors.lastname: Hosoki
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan.
authors.forename: Motoko
authors.initials: M
authors.lastname: Yasutomi
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch at Galveston, 301 University Blvd, Galveston, TX 77555, USA.
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Sur
authors.affiliation: Department of Pediatrics, University of Fukui, 23-3 Matsuoka Shimo-Aizuki, Eiheiji-cho, Yoshida-gun, Fukui, 911-1193, Japan. Electronic address: yohshima@u-fukui.ac.jp.
authors.forename: Yusei
authors.initials: Y
authors.lastname: Ohshima
mesh_terms: D000485:Allergens / Q000302:isolation & purification / Q000633:toxicity*; D000528:Alternaria / Q000276:immunology* / Q000472:pathogenicity*; D001249:Asthma / Q000209:etiology / Q000276:immunology / Q000473:pathology; D001343:Autophagy / Q000187:drug effects* / Q000276:immunology*; D020170:Caspase 1 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D058847:Inflammasomes / Q000187:drug effects / Q000276:immunology; D020382:Interleukin-18 / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000633:toxicity; D020545:Respiratory Mucosa / Q000187:drug effects* / Q000276:immunology* / Q000473:pathology
chemical_list: D000485:Allergens; D058847:Inflammasomes; D020382:Interleukin-18; D008070:Lipopolysaccharides; C505530:CASP8 protein, human; D053181:Caspase 8; D020170:Caspase 1
keywords: Airway epithelial cells; Allergy; Alternaria; Asthma; Autophagy; Interleukin-18