The Research Of Total Glycosides Of Paeony For The Immunomodulatory Mechanism In Rats With Autoimmune Thyroiditis

Objective:In this experiment,based on the experimental autoimmune thyroiditis（EAT）model,we observed the effects and mechanisms of total glucosides of paeony on thyroid function,thyroid autoantibodies,cytokines and thyroid histopathology and expression of Fas and FasL in EAT rats.Compared with selenium yeast tablets,the immunomodulatory mechanism of total glycosides in treatment of autoimmune thyroiditis was analyzed and discussed.Methods:Forty healthy SPF female SD rats weighing 110±10g were selected and randomly divided into 4 groups according to the random number table method:normal group,model group,total glucosides of paeony group,selenium yeast group（10 rats/each group）.At the first week,adaptive feeding of rats in each group was given conventional drinking water and common feed（provided by the Experimental Animal Center）.At 2nd-3rd weeks for primary immunization:thyroglobulin（pTg）antigen was dissolved in PBS solution and fully emulsified with equal volume of complete Freund’s adjuvant（CFA）.Except for normal group,the other groups of rats were given subcutaneous multiple-sites injection（injection of pTg antigen 100μg/each one）.The iodized water was given until the end of the experiment.At the 4th-7th weeks to strengthen immunity:the pTg antigen and incomplete Freund’s adjuvant（IFA）were mixed and emulsified,except for the normal group,the other groupsofratsweregivenmulti-siteimmunization injection（injection of pTg antigen 100μg/each one）,once a week for 4 times.At the 5th week of the experiment,rats were given intragastric administration.The total glucosides of peony（50 mg/kg）were administered daily to the total glucosides of paeony group,and the selenium yeast tablets（200μg/kg）were given daily to the selenium yeast group.The normal and model groups were given the same amount every day.Normal saline was administered continuously for6 weeks.After the rats were killed in the 10th week,serum and thyroid tissues were collected.Serum FT₃,FT₄,TSH,TGAb,TPOAb,IL-10 and IFN-γlevels were detected by ELISA.Thyroid histopathological changes were observed by HE staining,and the expression of Fas and FasL in thyroid tissue were observed by immunohistochemistry.Results:1.Thyroid function:The serum levels of FT₃,FT₄,and TSH in the model group were higher than those in the normal group,with significant differences（P<0.01）.The serum levels of FT₃,FT₄,and TSH in the total glucosides of the peony group and selenium yeast group were lower than those in the model group,with significant differences（P<0.01）.Compared with the selenium yeast group,serum FT₃ and FT₄ levels in the total glucosides of paeony group had no significant changes,and there was no significant difference（P>0.05）.Compared with the selenium yeast group,serum TSH levels in the total glucosides of paeony decreased significantly,with significant differences（P<0.01）.2.Histopathological morphology of the thyroid tissue:HE staining under light microscope showed that normal follicular epithelial cells were seen in the normal group,which was rich in glia,no macrophages and lymphocytes were seen,and no eosinophilia was seen in epithelial cells.In the model group,extensive infiltration of lymphocytes in thyroid tissue was observed.The infiltration of lymphocytes in the thyroid tissue of the peony group and the selenium yeast group significantly decreased compared with the model group.3.Thyroid antibodies:The levels of TGAb and TPOAb in the serum of the model group were higher than those in the normal group,with significant differences（P<0.01）.The serum levels of TGAb and TPOAb in the total glucosides of the white peony and selenium yeast group were lower than those in the model group,with significant differences（P<0.01）.Compared with the selenium yeast group,the levels of serum TGAb and TPOAb in the total glucosides of paeony group had no significant changes,and there was no significant difference（P>0.05）.4.Cytokines:The level of IL-10 in the model group was significantly higher than that of the normal group,with significant difference（P<0.01）.The serum levels of IL-10 in the total glucosides of paeony group and selenium yeast group were lower than those in the model group,with significant differences（P<0.01）.Compared with the selenium yeast group,IL-10 levels in the total glucosides of paeony group had no significant changes,and there was no significant difference（P>0.05）.The level of serum IFN-γin the model group was significantly higher than that in the normal group,with significant difference（P<0.01）.The serum IFN-γlevels in the total glucosides of paeony group and selenium yeast group were lower than those in the model group,with significant differences（P<0.01）.Compared with the selenium yeast group,the serum IFN-γlevels in the total glucosides of paeony group had no significant changes,and there was no significant difference（P>0.05）.5.Fas and FasL:The expression of Fas and FasL in the thyroid tissue of the model group was significantly higher than that in the normal group（P<0.05）.After drug intervention,the expression of Fas and FasL was significantly reduced,and there was a statistically significant difference compared with the model group（P<0.05）.However,compared with the selenium yeast group,the expression of Fas and FasL in the total glucosides of paeony group decreased,the difference was statistically significant（P<0.05）.Conclusion:1.Total glucosides of paeony can reduce lymphocyte infiltration in thyroid tissue of AIT rats,and reduce inflammatory reactions.2.Total glucosides of paeony can reduce the serum TGAb and TPOAb titers in AIT rats.3.Total glucosides of paeony may play a role in the treatment of autoimmune thyroiditis by interfering with the expression level of IL-10/IFN-γ,the Th1/Th2 immune migration pathway.4.Total glucosides of paeony can reduce the expression of Fas and FasL in thyroid tissue of AIT rats and improve the apoptosis of thyroid cells.