| Toll-like receptors, serve as pattern recognition receptors (PRRs), activate specific signaling pathways that initiate the production of cytokines through recognizing different microbial components. Among the10known human TLRs, TLR3is responsible for sensing dsRNA-a common byproduct or intermediate in viral genome replication. DCs are the most potent professional antigen presenting cells (APCs) and play a crucial role at the cross-talk of innate and adaptive immune systems. DCs are capable of producing IFN-β in response to viral infection and viral dsRNA mimicking polyinosinic:polycytidylic acid (pIC). On the other hand, IFN-β is known to have the effect of DC function and maturation. Moreover, previous studies showed that TLR3pathway also takes part in many disease progressions, so it is a promising therapeutic target for the treatment of these diseases. Researches on small molecules which could be new drugs will offer more therapeutic potentials against such diseases.Chaeoglobosin Fex (Cha Fex) is a cytochalasin isolated from Chaetomium globosum QEN-14. Our recent study showed that Cha Fex has inhibitory effects on LPS-induced TNF-α, IL-6and MCP-1production through blocking the degradation of IκB-a and the phosphorylation of JNK, ERK1/2, and p38. These results suggest that Cha Fex has the potential to repress TLR4signaling in macrophages activated directly by LPS stimulation. However, it is still unclear whether Cha Fex possesses the effect on the professional antigen presenting cells for antigen detection and its stimulation function to other effector lymphocytes.Aim:(1) To evaluate the effect of Cha Fex on poly(I:C)-induced bone marrow-derived DCs.(2) To investigate regulatory mechanism of Cha Fex on DCs.Methods:Dendritic cells were generated from mouse bone marrow progenitor cells. The effect of Chaeoglobosin Fex on the cell viability of BMDCs was examined by CCK-8. The effect of Chaeoglobosin Fex on the cell apoptosis was analyzed by Annexin V/PI staining.The production of IFN-β on BMDCs was detected by ELISA. The mRNA levels for target gene were quantified by real-time quantitative polymerase chain reaction (qPCR). The expression of surface markers on BMDCs was detected by flow cytometry. Stimulatory capacity of DCs to T cells was reflected in the allogenic MLR assay. Endocytotic activity of DCs was measured as cellular uptake of FITC-dextran and was quantified by flow cytometry. The uptake of poly(I:C) by DCs was monitored by flow cytometry using poly(I:C) conjugated to rhodamine. The effect of Cha Fex on the activation of IRF-3, NF-κB and MAPKs in poly(I:C)-activated BMDCs was examined by Western blottingResults:Cha Fex attenuated the production of IFN-β both at the mRNA and protein level in poly(I:C)-induced DCs. Moreover, Cha Fex also decreased the levels of IL-6, IL-12, TNF-a and MCP-1mRNA in poly(I:C)-induced DCs. Cha Fex markedly inhibited the maturation and function of the DCs with a reduced capacity to uptake antigens and low level of expression of surface molecules, such as CD40, CD80, CD86and MHCⅡ. Moreover, Cha Fex abrogated the ability of poly(I:C)-induced DCs to promotion of T cell proliferation. DCs pretreated with Cha Fex did not exhibit a remarkable reduction in endocytic capacity in exposure to poly(I:C)-rhodamine. Furthermore, Cha Fex inhibited the phosphorylation of IκB-α and IRF-3in poly(I:C)-induced DCs. Cha Fex also reduced the phosphorylation of p38and JNK, without affecting ERK1/2.Conclusion:Cha Fex can inhibit the maturation and function of poly(I:C)-induced DCs and exhibit an immunosuppressive effect on mouse bone marrow-derived DCs via TLR3signaling, which suggests potential application of Cha Fex in the treatment of autoimmune inflammatory diseases. |
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