Exosomes derived from Schistosoma japonicum Cystatin treated macrophages attenuated CLP-induced sepsis in mice

Abstract

Abstract Background Sepsis is a disease caused by multiple microbial infections resulting in excessive immune activation and multiple organ failure. Schistosoma japonicum cystatin (Sj-Cys) is a cysteine protease inhibitor and strong immunomodulator that stimulates M2 macrophages and alleviates inflammatory damage caused by sepsis. We would like to investigate whether exosomes derived from Sj-Cys treated macrophages convey the anti-inflammatory responses to mice with sepsis. Methods RAW264.7 macrophages were treated with rSj-Cys (2 µg/mL) for 48 h, the exosomes were obtained from the cell culture supernatant by ultracentrifugation and identified by transmission electron microscope, flow cytometry and Western blot assay. Sepsis was induced in BALB/c mice by cecal ligation and puncture (CLP). The mice with CLP-induced sepsis were treated with exosomes via intraperitoneal injection (10 µg/mouse). The therapeutic effect of exosomes on sepsis was assessed by observing the survival rate of mice up to 72 hours after CLP surgery and by measuring serum levels of inflammatory cytokines, liver/kidney damage biomarkers alanine aminotransferase (ALT), aspartate aminotransferase (AST)/urea nitrogen (BUN) and creatinine (Cr) in sera and observing pathological changes in tissue sections. The tissue levels of M1(iNOS), M2 (Arg-1) macrophage surface markers and TRL2/MyD88 were measured to explore possible mechanisms. Results Exosomes derived from Sj-Cys-treated macrophages exhibited significant therapeutic effect on CLP-induced sepsis in mice with prolonged survival rate and less damage of critical organs by down-regulating the pro-inflammatory factors TNF-α and IL-6 and up-regulating the anti-inflammatory factor TGF-β. The therapeutic effect of exosomes is associated with macrophage polarization from M1 (iNOS+) to M2 (Arg-1+) in infected tissues via down-regulating TRL2/MyD88 inflammatory pathway. Conclusions Exosomes derived from Sj-Cys-treated macrophages attenuated sepsis in mice through promoting macrophage polarization from M1 to M2 and reducing inflammatory responses, possibly via down-regulating TLR2/MyD88 inflammatory signaling pathway.