[Echinococcus granulosus cyst fluid(EgCF) inhibits the migration and phagocytic function of mouse macrophages induced by LPS via inducing cytoskeletal rearrangement].

Objective To investigate the effect of Echinococcus granulosus cyst fluid(EgCF) on the cytoskeletal rearrangement and phagocytosis and the migration of macrophages induced by lipopolysaccharide(LPS). Methods Peritoneal macrophages of C57BL/6 mice were isolated and cultured in vitro, and divided into control group and LPS group and LPS combined with EgCF group. After 48 hours of treatment, filamentous actin (F-actin) changes were observed with rhodamine-labelled phalloidin staining and fluorescence microscopy; TranswellTM chamber was used to test cell migration ability and flow cytometry to test cell phagocytosis. After 1 hour of treatment, PI3K and AKT, phosphorylated AKT (p-AKT), Rac1, guanosine triphospho-Rac1 (GTP-Rac1), WASP and Arp2 protein expressions were detected with Western blot analysis. Results Compared with the control group, after LPS stimulation, macrophages were deformed significantly; pseudopodia increased; actin cytoskeleton increased and was more distributed in pseudopodia; the ability of migration and phagocytosis were significantly improved, and the expression of PI3K, p-AKT, GTP-Rac1, WASP and Arp2 proteins significantly increased. EgCF treatment caused cell shrinkage and disappearance of pseudopodia protrusions of LPS-activated cells, and led to the reduced phagocytic and migratory of cells; the protein expression of PI3K, p-AKT, GTP-Rac1, WASP and Arp2 decreased significantly compared with the LPS group. Conclusion LPS induces the migration and enhances phagocytosis of macrophages while EgCF inhibits these effects, which is related to actin cytoskeleton rearrangement.

Echinococcus granulosus cyst fluid suppresses inflammatory responses by inhibiting TRAF6 signalling in macrophages.

Echinococcus granulosus sensu lato has complex defence mechanisms that protect it from the anti-parasitic immune response for long periods. Echinococcus granulosus cyst fluid (EgCF) is involved in the immune escape. Nevertheless, whether and how EgCF modulates the inflammatory response in macrophages remains poorly understood. Here, real-time polymerase chain reaction and enzyme-linked immunosorbent assay revealed that EgCF could markedly attenuate the lipopolysaccharide (LPS)-induced production of pro-inflammatory factors including tumour necrosis factor-α, interleukin (IL)-12 and IL-6 but increase the expression of IL-10 at mRNA and protein levels in mouse peritoneal macrophages and RAW 264.7 cells. Mechanically, western blotting and immunofluorescence assay showed that EgCF abolished the activation of nuclear factor (NF)-κB p65, p38 mitogen-activated protein kinase (MAPK) and ERK1/2 signalling pathways by LPS stimulation in mouse macrophages. EgCF's anti-inflammatory role was at least partly contributed by promoting proteasomal degradation of the critical adaptor TRAF6. Moreover, the EgCF-promoted anti-inflammatory response and TRAF6 proteasomal degradation were conserved in human THP-1 macrophages. These findings collectively reveal a novel mechanism by which EgCF suppresses inflammatory responses by inhibiting TRAF6 and the downstream activation of NF-κB and MAPK signalling in both human and mouse macrophages, providing new insights into the molecular mechanisms underlying the E. granulosus-induced immune evasion.