The Mechanism Of Poly(I:C) Aggravating Thyroiditis Induced By Iodine Excess Of NOD Mouse

Objective:Epidemiological research showed that iodine excessively intaken as an important essence which can cause autoimmune thyroiditis clinically,but the mechanism has not been well known.The clinical information indicated viral infection also involved in the morbidity of the autoimmune thyroiditis.The recently research discovered that EBV and HSV infection can cause autoimmune thyroiditis. poly(I:C) can aggregate the degree of the thyroiditis caused by iodine excess have been displayed in previous experiment in our lab.We will explain this phenomenon through this experiment and seek the pathway which poly(I:C) aggravate the degree of the thyroiditis caused by iodide excess.Methods:The different genetic background mice:NOD mice is genetic sensitivity in autoimmune disease and BALB/c mice is not sensitive,were used to build the thyroiditis model by drinking water plus iodine and injecting poly(I:C).To observe the effect of the viral infection to the models,the functional related items,identifying lymphocytes,cytokins and TLR3 were test by corresponding methods.26 nod and 31 BALB/c female mice,7-8 weeks old,were divided randomly into four groups:1.Control group(C):mice were on a regular diet and injected intra peritoneally (i.p.) with physiological saline(5.0μg/g body weight each day on the first week and 1 time/2days on the last week)2.Iodide excess group(HI):mice were on a high iodide diet(0.05%NaI-supplemented water) and injected intra peritoneally with physiological saline.3.poly(I:C)(P):7 mice were on a regular diet and injected intra peritoneally (i.p.) with poly(I:C) like HI group.4.iodide excess plus poly(I:C) group(I+P):7mice in I+P group were on a high iodide diet and injected intra peritoneally(i.p.) with poly(I:C)8 weeks later,all the mice were weighted alive then sacrificed,thyroids were weighted and the blood and spleens in whole were taken.Morphological change of thyroids was observed after HE dye.The hormone level of TT4,TSH in serum were tested respectively by RIA and ELISA.The immunofluorescence was used to assess the level of TLR3 in the thyroids.The expression of IFN-α,IFN-γand IL-4 mRNA were detected by real time PCR.The way of processing method of BALB/c was the same as the NOD.Results:The relative weight of the thyroids in HI and I+P group became heavier than the C group(P＜0.05).This was happened in both of the two species.The TT4 level in serus in I+P group decreased compared with the C group and the TSH became higher than C group(P＜0.05).The HE dye of the thyroids showed that the enlarged follicles and flattened epithelium by accumulation of colloid in HI and I+P groups in both species mice. CD3 positive cells infiltration were found in HI and I+P mice's thyroids in NOD but it didn't show in BALB/c mice's thyroids.The level of the inflammation in thyroid is different in the two species.NOD mice:the degree of destructed follicles:Ⅱ(12.5%),Ⅲ(50.0%),Ⅳ(37.5%),local fibrosis was also found.TLR3 positive cells were only found in NOD mice in HI group and I+P group.The expression of IL-4 mRNA increased in P group both of the two species' thyroids.It raised in HI group of NOD mice.In spleens the expression increased in P and I+P groups of BALB/c mice but it droped in P group of NOD mice.The expression of IFN-γmRNA in thyroids of BALB/c mice increased in HI and I+P group and the NOD mice(P＜0.05).In spleens it didn't change in BALB/c mice, while it increased in HI,P and I+P groups of NOD mice(P＜0.05).The IFN-αwere increased in HI,P,I+P groups in thyroids and spleenss of the two species except in the P group in spleenss of BALB/c mice.Conclusions:1.Iodine excess initiate the expression of TLR3 of NOD mice's thyroid follicular epithelium.The innate immunal reaction is stimulated through TLR3 pathway.This is an important mechanism of the HT taking place.2.poly(I:C) can stimulate the expression of TLR3 slightly and inhibit thyroid function,but poly(I:C) cannot induce thyroiditis solo.3.TLR3,which expresses caused by iodine excess can combine with poly(I:C) and activate the TLR3 pathway.It cause the expression of IFN I increase and cause the target orgens damaged and inflamation deteriorated. 4.There is a delicate regulation of the balance of Th1/Th2.The expression of IFN-γmRNA increased in thyroids when thyroidtitis occurred.It indicate that IFN-γis a key factor in the course of thyroiditis.