Functional study of recombinant Clonorchis sinensis thioredoxin peroxidase on inhibitory effect of macrophage activation

Abstract

Clonorchis sinensis (C. sinensis) estabilishes long term parasitism within bile ducts of humans without notable symptoms. General down-modulated host immune responses in helminth infestation are maintained by excretory-secretory products (ESP), produced by the live parasites and considered as an important immunomodulator in this context. Co-culture experiments with RAW264.7 cells and C. sinensis adults worms through permeable transwell demonstrated that ESP from living C. sinensis functioned as a ligand for TLR4, but effectively attenuated LPS-induced IL-6 and NO production. On the other hands, upsurged secretion of antiinflammatory cytokines IL-10 and TGF-β were observed by C. sinensis ESP treatment. Reference base study found out that thioredoxin peroxidase (TPX) of helminth parasites had an immune-modulating property toward Th2 type through induction of regulatory phenotype of macrophages. Hence, recombinant TPX of C. sinensis was produced and its gene was registered at Genbank (AND65138.1). The CS-TPX reduced LPS-induced expression of TLR4 on cell surface of RAW264.7 cells and LPS-induced secretion of pro-inflammatory mediators NO, TNF-α and IL-6. Moreover, CS-TPX induces IL-10, but not TGF-β. Pull-down assay result revealed the direct interaction between CS-TPX and TLR4 protein. Furthermore, the smallest recombinant fragment of CS-TPX, which is T44, has comparable anti-inflammatory. In conclusion, this study described the macrophage regulatory function of C. sinensis ESP and the smallest fragment of CS-TPX, T44, could function of the negative regulator in LPS treated macrophage cell line RAW264.7 cells. Defined CS-TPX T44 will be one of the best candidates for therapeutic immunosuppressant in allergies and autoimmune diseases.