The Immune Effects And Mechanisms Of Glucocorticoid Receptor Signal On Myeloid-Derived Suppressor Cells In Immunological Liver Injury

Background:Glucocoticoid receptor (GR), belonging to a kind of nucleus transcription factor, could be activated by its ligand and regulate immune cell activation or function to inhibit immune inflammation by binding with specific DNA sequence of its target genes and then regulating gene transcription. However, it remains unknown about the regulatory roles of GR in myeloid derived-suppressor cells (MDSCs), a kind of newly discovered immunosuppressive cells.Part I The change of GR expression and MDSCs percentage in immunological liver injuryAims:To study the changes of GR expression and MDSC percentage in immunological liver injury.Methods:The change of splenic MDSCs and the GR expression of splenic MDSCs in the LPS-induced liver injury model and LPS tolerance model are determined by cell surface staining and intracellular staining, respectively.Results:1. Compared with control group, the number of splenic MDSCs in LPS-induced liver injury group is decreased, while that in LPS tolerance group increasing.2. GR expression of splenic MDSCs from LPS-induced liver injury model is lower than that in control group, while GR expression of splenic MDSCs from LPS tolerance group is higher than that in control group and LPS-induced liver injury group.Conclusion:MDSC and GR signals probably play an important role in regulating inflammatory liver injury.Part ? The effect of GR on MDSCs in inflammatory liver injuryAims:To study the effect of GR on MDSCs in inflammatory liver injury.Methods:1. The mice are divided into model group and experimental group, and the later one are injected GR activator dexamethasone (Dex). The survival rate, serum TNF-? level and MDSCs function are determined.2. The mice are divided into model group and experimental group:one group injected GR inhibitor RU-486 alone, one group injected GR activitor Dex alone, and another group injected RU-486 and Dex. Serum TNF-a level and MDSCs function are determined.3. The mice are divided into LPS-induced liver injury group, LPS tolerance group, LPS tolerance and Dex group, LPS tolerance and RU-486 group and LPS tolerance and RU-486 and Dex group. Serum TNF-a level and MDSCs function are determined.Results:1. GR activator Dex improves the survival rate of LPS-induced liver injury and enhances the function of MDSCs, which plays an important role in Dex protecting mice against LPS-induced liver injury.2. The inhibition effect of serum TNF-? and ALT and the enhancement of MDSCs function induced by Dex are rescued by GR inhibitor RU-486.3. Compared with LPS-induced liver injury group, GR activator Dex can further decrease serum TNF-? and ALT level from LPS tolerance mice, and MDSCs function is enhanced further by Dex in LPS tolerance model.Conclusion:GR activation inhibits LPS-induced liver injury development and promotes the protective effect of LPS tolerance on mice by enhancing MDSCs immunosuppressive function.Part ? The regulatory mechanism of MDSCs in inflammatory liver injuryAims:To study the regulatory mechanisms of MDSCs in protecting inflammatory liver injury.Methods:1. Serum NO level, together with iNOS and Argniase I mRNA level of splenic MDSCs is determined.2. Isolate splenic MDSCs treated by L-NMMA in vitro, and the effect of MDSCs inhibiting T cell proliferation and secreting TNF-a is determined.Results:1. Serum NO level is increased in mice treated by GR activator Dex, together with the mRNA level of iNOS from isolated MDSCs.2. The immunosuppressive function of MDSCs is decreased obviously when treated by L-NMMA in vitro.Conclusion:MDSCs take an important part in protecting mice against inflammatory liver injury through NO pathway to inhibit T cell proliferation and TNF-a secretion and promote IL-10 secretion.