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Autolysosomal Formation Is Required for Autophagy-Dependent IL-18 Release from Airway Epithelial Cells.
Saturday, March 5, 2016
South Exhibit Hall H (Convention Center)
Hiroki Murai, MD, PhD, Shintaro Okazaki, MD, Hisako Hayashi, MD, PhD, Akiko Kawakita, MD, Motoko Yasutomi, MD, PhD, Sanjiv Sur, MD, Yusei Ohshima, MD,PhD
Rationale:   We have previously reported that IL-18 release from airway epithelial cells in response to Alternaria extract (ALT-E) is depend on autophagy activation but not on caspase 1 activation. LPS has been shown to activate caspase 1 and autophagy and to induce oxidative stress in macrophages through TLR4. Here, we compared LPS- and ALT-E-stimuli, and analyzed the precise roles of activating processes of autophagy in IL-18 release from airway epithelial cells.

Methods: After A549 or NHBE cells were stimulated with ALT-E or LPS, IL-18 release was measured by ELISA. Autophagosome and autolysosome formations were measured by western blotting analysis using LC3 and p62 antibodies, respectively. To assess the involvement of oxidative stress in the IL-18 release, the cells were pre-treated with antioxidants, N-acetyl cysteine (NAC) and MG132 for 1 h prior to stimulation with ALT-E.

Results: Stimulation with ALT-E but not with LPS induced IL-18 release from AECs. NAC and MG132 ameliorated the ALT-E-induced IL-18 release. Both ALT-E and LPS provoked the formation of LC3-II, which occurred in early phase of autophagy activation. ALT-E stimulation facilitated the degradation of p62, which arose in the late phase of autophagy activation, whereas LPS did not affects p62 degradation.

Conclusions: Stimulation with ALT-E induced oxidative stress, which was involved in IL-18 release as well as autophagy activation. The autolysosomal formation during autophagy activation seems essential for the IL-18 release from airway epithelial cells.