Abstract: Objective To observe the effect of exosomes secreted by lipopolysaccharides (LPS)-stimulated macrophages on hepatic stellate cell activation and migration and explore the underlying molecular mechanism. Methods Human monocyte THP-1 cells were induced to differentiate into macrophages using propylene glycol methyl ether acetic acid (PMA, 100 ng/mL, 24 h) followed by stimulation with LPS, and the culture supernatant of macrophages was collected for extraction of the exosomes by ultracentrifugation. The expression of miR-155-5p in the exosomes was detected using qRT-PCR. A Transwell co-culture system was used to observe the effects of the macrophage-derived exosomes on LX2 cell (a hepatic stellate cell line) proliferation, migration, oxidative stress and the expression of fibrosis biomarkers, which were also observed in LX2 cells transfected with miR-155-5p-mimics or miR-155-5p-inhibitors. Western blotting was used to detect the expressions of SOCS1 and its downstream signal pathway proteins. Results Treatment with the exosomes from LPS-stimulated macrophages significantly enhanced the proliferation and migration ability of LX2 cells and increased the levels of oxidative stress and expressions of the fibrosis markers such as type I collagen (P<0.05). The expression of miR-155-5p in the exosomes secreted by macrophages was significantly increased after LPS treatment (P<0.01). LX2 cells overexpressing miR-155-5p also exhibited significantly enhanced proliferation and migration with increased oxidative stress levels and expression of type I collagen (P<0.05), and interference of miR-155-5p expression produced the opposite effects. Western blotting showed that miR-155-5p overexpression obviously inhibited SOCS1 expression and promoted p-Smad2/3, Smad2/3 and RhoA protein expressions in LX2 cells (P<0.05). Conclusion LPS stimulation of the macrophages increases miR-155-5p expression in the exosomes to promote activation and migration and increase oxidative stress and collagen production in hepatic stellate cells.

Key words: lipopolysaccharide; macrophage; exosome; microRNA-155-5p; hepatic stellate cells; liver fibrosis