Schistosoma japonicum Cystatin Alleviates Sepsis Through Activating Regulatory Macrophages

Abstract

Multi-organ failure caused by the inflammatory cytokine storm induced by severe infection is the major cause of death for sepsis. Sj-Cys is a cysteine protease inhibitor secreted by Schistosoma japonicum with strong immunomodulatory functions on host immune system. Our previous studies have shown that treatment with Sj-Cys recombinant protein (rSj-Cys) attenuated inflammation caused by sepsis. However, the immunological mechanism underlying the immunomodulation of Sj-Cys for regulating inflammatory diseases is not yet known. In this study, we investigated the effect of Sj-Cys on the macrophage M2 polarization and subsequent therapeutic effect on sepsis. The rSj-Cys was expressed in yeast Pichia pastoris. Incubation of mouse bone marrow-derived macrophages (BMDMs) with yeast-expressed rSj-Cys significantly activated the polarization of macrophages to M2 subtype characterized by the expression of F4/80+ CD206+ with the elated secretion of IL-10 and TGF-β. Adoptive transfer of rSj-Cys treated BMDMs to mice with sepsis induced by cecal ligation and puncture (CLP) significantly improved their survival rates and the systemic clinical manifestations of sepsis compared with mice receiving non-treated normal BMDMs. The therapeutic effect of Sj-Cys-induced M2 macrophages on sepsis was also reflected by the reduced pathological damages in organs of heart, lung, liver and kidney and reduced serological levels of tissue damage-related ALT, AST, BUN and Cr, associated with downregulated pro-inflammatory cytokines (IFN-gamma and IL-6) and upregulated regulatory anti-inflammatory cytokines (IL-10 and TGF-β). Our results demonstrated that Sj-Cys is a strong immunomodulatory protein with anti-inflammatory features through activating M2 macrophage polarization. The findings of this study suggested that Sj-Cys itself or Sj-Cys-induced M2 macrophages could be used as therapeutic agents in the treatment of sepsis or other inflammatory diseases.

Therapeutic Effect of Schistosoma japonicum Cystatin on Atherosclerotic Renal Damage

“…Further investigation found that CD4 + CD25 + Foxp3 + Tregs were significantly decreased in HFD-induced atherosclerosis, and the treatment with r Sj -Cys significantly stimulated the proliferation of Tregs in splenocytes ( Figures 11A,B ). The results are consistent with the findings by Chen et al (2017) that infection of S. japonicum stimulated the differentiation of Tregs and our previous findings of the therapeutic effects of r Sj -Cys on sepsis related to the increased levels of IL-10 and TGF-β ( Li et al, 2017 ; Xie et al, 2021 ). Our results strongly suggest that r Sj -Cys plays a role in inhibiting inflammation and prevention of atherosclerosis mainly through stimulating T regulatory response.…”

“…DNA-encoding Sj -Cys (GenBank: FJ617450) was amplified from S. japonicum total cDNA and cloned into yeast expression vector pPIC9k. Recombinant Sj -Cys (r Sj -Cys) with His-tag at C-terminus was expressed in Pichia pastoris GS115 using the method described previously ( Xie et al, 2021 ). The contaminated endotoxin in the purified r Sj -Cys was removed by using a ToxOut TM High Capacity Endotoxin Removal Kit (BioVision, Palo Alto, CA, United States) and confirmed by Pierce TM LAL Chromogenic Endotoxin Quantitation Kit (Thermo Fisher Scientific Inc., Waltham, MA, United States).…”

“…Infection of S. mansoni reduced 50% atherosclerotic lesions in the aortic arch associated with reduced cholesterol level in blood of mice ( Doenhoff et al, 2002 ). Schistosoma japonicum –secreted cystatin ( Sj -Cys) is a strong immunomodulatory protein to regulate macrophage activation and inhibit host inflammatory cytokines ( Vray et al, 2002 ) and has been successfully used to treat murine collagen-induced arthritis ( Liu et al, 2016 ), type 1 diabetes ( Yan et al, 2020 ), trinitrobenzene sulfonic acid (TNBS)-induced experimental colitis ( Wang et al, 2016 ), and bacterial sepsis ( Li et al, 2017 ; Gao et al, 2020 ; Xie et al, 2021 ). Whether r Sj -Cys has therapeutic effect on atherosclerosis and its complications has not yet been reported.…”

Ferroptosis in Macrophage Impairment in Sepsis

“…M1 and M2 types of macrophages can be converted to each other under certain conditions, so that differentiated macrophages can “repolarize” and play corresponding functions [ 15 ]. Macrophages continuously monitor the body's immune defense, which requires continuous energy supply [ 16 ]. Under normal physiological conditions, macrophages take oxidative phosphorylation of glucose as their main metabolic pathway for energy demand.…”

The Fight Against Severe COVID-19: Can Parasitic Worms Contribute?

“…To date, a number of helminth-derived molecular products have resulted in improved sepsis outcomes in animal models. Several studies have investigated the role of Schistosoma japonicum cystatin (rSj-Cys) in regulating the inflammatory response in the cecal ligation and puncture (CLP)-induced mouse sepsis model (33)(34)(35). Administration of rSj-Cys to mice provided significant therapeutic effects on CLP-induced sepsis characterized by increased survival rates, alleviated overall disease severity with reduced tissue injury in the kidney, lung and liver (33) and cardiomyopathy (34).…”