Abstract: Objective To establish an ultra-filtration centrifugation method to purify the outer membrane vesicles (OMVs) of Acinetobacter baumannii(A.baumannii), and to investigate the ability of OMVs to induce inflamma-tion in human monocyte-derired macrophages THP-1. Methods A.baumannii was cultured, and the OMVs were purified from the supernatant of culture medium by ultra-filtration centrifuge,the morphology was observed by transmission electron microscopy. THP-1 cells were incubated with OMVs at the concentration of 5 and 50 μg/mL respectively. The expression of NOD-like receptor protein 3(NLRP3) and caspase-1 were determined by RT-qPCR. The concentration of IL-1β in culture medium supernatant was measured by ELISA. The expression of LC-3Ⅱ and Beclin-1 was examined by Western blot. The activity of caspase-3 was determined by enzyme dynamics assay. The expression of reactive oxygen species (ROS) was determined by flow cytometry. Results A.baumannii OMVs was purified successfully. The OMVs could activate NLRP3 inflammasome, increase the expression of LC-3Ⅱ and Beclin-1 and up-regulate the activity of caspase-3 (P<0.05). The OMVs significantly up-regulated the expression of ROS in THP-1 cells after 1 h co-culture (P<0.05). Conclusions OMVs of A.baumannii can significantly activate macrophages NLRP3 inflammasome and induce cell autophagy and apoptosis.

Key words: Acinetobacter baumannii, outer membrane vesicles, inflammation, autophagy, apoptosis