Interleukin 27 Inhibits Mast Cell Mediated Immune Response

This doctoral thesis includes two parts:(1) The role of TAB2 mRNA in regulation of endotoxin tolerance viamicroRNA-155 in macrophages;(2) Interleukin 27 inhibits mast cell mediated immune response.Part1The role of TAB2 mRNA in regulation of endotoxin tolerance via microRNA-155Competing endogenous RNA (ceRNA) is a new regulation pattern, reviewed recently. All types of RNA transcripts, sharing common microRNAs, can regulate each other through competing for those common microRNAs via microRNA response sites (MRE).To date, there has been some evidence supporting this new hyphosis.Published data have demonstrated that ceRNA regulation network have function of tumorigenesis and other pathological processes.In the present study, we found that miRNA-155 (miR-155) is up-regulated in primary macrophages and RAW264.7 cells upon LPS stimulation. And RAW264.7 cellswith miR-155 knockdown are less susceptible to endotoxin tolerance compared with RAW264.7 control cells, which suggested that miR-155 may function in endotoxin tolerance. Considering its ability to target both TAB2 and SOCS1, two important molecules involved in LPS-TLR4 signaling, thus we hypothesized that TAB2 and SOCS1 may regulate each other through competing for miR-155 in endotoxin tolerance. We constructed TAB23’UTR stably-overpressed RAW264.7 cell lines. TAB2 3’UTR stably-overexpressed RAW264.7 cells express enhanced SOCS1 protein when induced endotoxin tolerance, accompanied by decreased proinflammatory cytokines IL-6 and TNF-a. In RAW264.7 cells that TAB2 mRNA was knocked down by siRNA, SOCS1 protein was reversely dampened, accompanied by decreased IL-6 and TNF-a when endotoxin tolerance was induced. In RAW264.7 cells with miR-155 knockdown, which lack miR-155 expression, there was no significant change in SOCS1 protein level when interfere TAB2 mRNA expression in RAW264.7 cells.These results indicated that TAB2 mRNA regulates SOCS1 expression in a miR-155 dependent pattern. Thus, here we clarified a novelregulatory mechanism for fine-tuning of endotoxin tolerance during innate immune response.Part 2Interleukin 27 inhibits mast cell mediated immune responseInterleukin 27(IL-27) is known as a positive regulator for Thl response firstly. And some studies indicate that IL-27 also has an immunosuppressive function and suppresses production of inflammatory cytokines later.Mast cell is an important subset of immune cells involved inallergic responses. Antigen-mediated cross-linking of IgE on mast cells triggers a signaling cascade that results in mast cell degranulation and pro-inflammatory cytokine production, which are key effectors in allergic reactions. Here we show that the activation of mast cells is negatively regulated by IL-27. We found that Mice lacking wsx-1 also displayed increased sensitivity to IgE-mediated skin allergic responses and chronic airway inflammation. IL-27 protein expression is detected by in skin and lung of mice. Loss of wsx-1 in mouse bone marrow derived mast cells led the cells to be hyperresponsive to the stimulation via FcεRI. The dysregulated signaling in wsx-1-/-mast cells is associated with increased activation of "Grb2-PLC-γl-SLP-76" signaling within LAT signalosome and "PI3K/Akt/IεBα" signaling within NTAL signalosome.Collectively, our findings reveal that IL-27 negtively regulates mast cells mediated immune response.