The Effect Of Iodine Excess And Poly(I: C) On Inducing Thyroiditis In AID Sensitive And Non-sensitive Mice

Objective We observed the effect of iodine excess and viral dsRNA analog Poly(I:C) on the thyroid morphous and function of the mice of different strains and performed relative quantitative assay of thyroid function,apoptosis and inflammation related genes,to reveal the influences of environmental factors on inducing individuals with different genetic background to deveolop Autoimmune thyroiditis(AT)and to provide foundation for the national policy of scientific supplement iodine.Methods Autoimmune diseases(AID)sensitive mice(NOD mice)and non-sensitive mice(BALB/c mice)were used and randomly divided into four groups:the control group(C),the iodine excess group(HI),the Poly(I:C)group(P),and iodine excess plus Poly(I:C)group(HI+P).The C group received deionized water and intraperitoneal injection of saline.The HI group drank water with 0.05%NaI and underwent intraperitoneal injection of saline.The P group had deionized water and intraperitoneal injection of Poly(I:C)at 5μg/g.The HI+P group had water with 0.05%NaI and intraperitoneal injection of Poly(I:C).Eight weeks later,we weighed the mice,collected the blood samples,observed the thyroid morphous and measured the weight of the thyroid after the mice were sacrificed.HE staining was employed to observe the histopathology of the thyroid.We used TUNEL to detect the apoptosis of thyroid follicle cells,RIA and ELISA to detect the level of T₄ and TSH,RIA to detect the level of Tg Ab and TPO Ab.SYBR Green real-time PCR was used to select the internal control genes which are required to have a constant expression in different groups in the mice of the two strains and to detect the expression of function related genes(NIS and D1),apoptosis related genes(TRAIL and TRAIL-sR1)and inflammation related genes(ICAM-1 and CXCL10).Results1 The morphous of the thyroid:for the mice of the two strains,enlargement of the thyroid was more obvious in the HI group and the HI+P group than in the C group and the relative weight was higher.In the HI group and the HI+P group,enlarged follicular lumen with colloid accumulation were observed.Besides,obvious infiltration of lymphocytes was seen in NOD mice.For NOD mice,the disorganization was more severe in the HI+P group than in the HI group.2 The apoptosis of thyroid follicle cells:for NOD mice,plenty of cells with positive staining were observed in the HI group and the HI+P group.For BALB/c mice,cells with postive staining was a little more in the HI group and the HI+P group than in the C group.3 The hormone level:for the mice of both strains,the HI group and the HI+P group had a lower level of T₄ and a higher level of TSH compared with the C group.The level of TSH was decreased in the P group.4 The detection of thyroid function,apoptosis and inflammation related genes:18S-rRNA had a contant expression in different groups in the mice of the two strains,and was used as the control gene.The expression of function related genes(NIS and D1):for the mice of the two strains,the expression of NIS and D1 was decreased with different degrees in all treatment groups,especially for NOD mice.The expression of apoptosis related genes(TRAIL and TRAIL-sR1):in the HI group,the expression of TRAIL in NOD mice was increased by 23%but was decreased by 21%in BALB/c mice.In the P group,the expression of TRAIL was decreased in BALB/c mice.In the HI+P group,there are an increase of TRAIL expression by 50%in NOD mice and a decrease of TRAIL-sR1 in both mice.The expression of inflammation related genes(ICAM-1,CXCL10):in the HI group,the expression of ICAM-1 and CXCL10 was increased in NOD mice,and the CXCL10 expression level was more than 7 folds of that in the C group.In BALB/c mice,only the expression of CXCL10 was increased,about two folds of that in the C group.In the P group,the expression of ICAM-1 was inhibited in the mice of the two strains.Compared with the HI group,there is a further increase of CXCL10 expression in the HI+P group,especially for NOD mice,which was 14 folds of that in the C group.Conclusions1 Iodine excess can induce collid accumulation goiter and hypothyroidism in AID sensitive and non-sensitive mice,with the inhibition of the expression of NIS and D1 mRNA.2 Iodine excess can lead to apoptosis of thyroid follicle cells in the mice of the two strains.Apoptosis level in AID sensitive mice is higher than that in non-sensitive mice.3 Iodine excess can induce thyroiditis in AID sensitive mice but not in non-sensitive mice,indicating that environmental factors only play a role as an inducer and it is the genetic background that determines the onset of HT. 4 Poly(I:C)itself doesn't induce thyroiditis in the two strains,but it can aggravate thyroiditis induced by iodine excess in sensitive mice,.The detailed mechanism needs to be further investigated.5 The increase of ICAM-1 and CXCL10 expression may play an important role in the onset and development of thyroiditis.