Abstract: Objective To investigate the effect of 3-oxo-C12-HSL on autophagy in mouse alveolar macrophages MH-S cells. Methods: MH-S cells were treated with culture supernatants of the mutant and wild type PA strains of LasI gene (3-oxo-C12-HSL synthetic gene) and chemically synthesized 3-oxo-C12-HSL signaling molecules. GFP puncta was observed by Laser confocal fluorescence microscopy and the ratio of LC3II/LC3I was detected by western blotting to detect the formation of autophagic. Autophagic Flux was also detected by monitoring the degradation of p62 and the change of chloroquine to LC3II/LC3I ratio. Results The supernatant of the culture medium of the wild type PA strain increased the GFP puncta of the MH-S cells (P<0.05) and the ratio of LC3II/LC3I (P<0.01), The mutant PA strain of LasI gene cannot cause the above changes related to autophagy. The chemically synthesized 3-oxo-C12-HSL signal molecules can increase the number of autophagic bodies and the expression of LC3II (P<0.01). Autophagic substrate p62 is degraded by 3-oxo-C12-HSL. Chloroquine, a lysosomal inhibitor, enhanced LC3II accumulation caused by 3-oxo-C12-HSL (P<0.05, P<0.01). Conclusions 3-oxo-C12-HSL increases the level of autophagy in MH-S cells.

Key words: autophagy, 3-oxo-C12-HSL, alveolar macrophages, Pseudomonas aeruginosa