The Effect Of Methimazole On Experimental Autoimmune Thyroiditis

Objective:To study the effect of methimazole on experimental autoimmune thyroiditis(EAT),and initially discuss the immuno-regulatory mechanism from Th1/Th2 cytokine disequilibrium aspect.Methods:80 KM mice were randomly divided into 5 groups,each has 16 mice.A:Normal control group;B:EAT control group;C:Prednisone treatment group;D:Methimazole treatment group;E:Methimazole early treatment group.The groups of B,C,D,E immunized with thyroglobulin(Tg)to establish the model of EAT.Meanwhile,each group was intragastric administration one time every day.A,B group were given distilled water as control groups.C,D groups were administered respectively Prednisone and Methimazole from ten days after primary immunity.Methimazole Were administered at the same time with primary immunity(0th days)in E group.All mice were administered drugs 28 days continuely and were killed at 38th days after primary immunity.We used radio-immunoassay(RIA)to test the levels of serum thyroglobulin antibody(TgAb)and thyroid peroxidase antibody(TPOAb).Separate thyroid glands,ten of them were used to histological analysis and the other were used to assay the levels of cytokines,IFN-γand IL-10 mRNA through the methods of reverse transcription-polymerase chain reaction(RT-PCR).Results:(1)EAT models:EAT mice had inflammation cell infiltration in thyroid follicle matrix.The levels of serum TGAb and TPOAb were increased.(2)EAT incidence:The incidence of B group was 70%.Those of severe disease were 20%. The incidence of EAT was decreased to 20%,40%,40%in C,D and E groups.The severity of infiltration was reduced.The incidence of C group was decreased by 20%,but not statistically significant as compared with D group(P＞0.05).(3)The level of serum antibody:the level of TGAb,TPOAb in B group were 5-6 times of A group.Compared with B group,the levels of TGAb and TPOAb in C and D groups significantly decreased(P＜0.05).The down degree of the level of TGAb in D group is lower than C group(P＜0.05).There were no significant difference between D and E group(P＞0.05).(4)The expression of cytokines mRNA in thyroid gland:There were no IFN-γ,IL-10 mRNA expression in A group,but expressed in B,C,D and E groups.Compared with B group, the expression of IFN-γmRNA in C,D groups was significantly downregulated and the expression of IL-10 mRNA was significantly upregulated.(P＜0.05).The down degree of the level of IFN-γmRNA expression in D group is lower than C group(P＜0.01).There were no significant difference between the expression of IFN-γin D and E group(P＜0.05).Conclusions:(1)Methimazole has some effects on EAT but weaker than prednisone. (2)The protective function of methimazole and prednisone may be related to downregulating Th1 cytokine and upregulating Th2 cytokine.