The effects of excessive iodine intake on mRNA expressions of interleukin-23, interleukin-17 and gamma interferon in BABL/c mice

Abstract

Objective To observe the effects of excessive iodine intake on autoimmune thyroiditis and mRNA expressions of interleukin-17 (IL-17),interleukin-23 (IL-23) and gamma interferon (IFN-γ) in thyroid gland and spleen of mice and to further explore the pathogenesis of iodine overdose induced autoimmune thyroiditis.Methods According to body mass,seven to eight weeks old BALB/c mice (body mass 20-25 g,half male and half female) were selected and divided into 4 groups (12 mice in each group,half male and half female) by random number table.Control group(CG) drank deionized water; thyroglobulin group(TG) drank deionized water,and were immunized with 0.1 mg thyroglobulin(Tg) subcutaneously at the age of 8 weeks and with two booster immunization at the age of 11 and 15 weeks,respectively; iodine excess group (HI) drank water containing 0.05％ sodium iodide (NaI); thyroglobulin + iodine excess(TG + HI) group drank water containing 0.05％ NaI,and were immunized the same way as TG group did.The 4 groups were fed with normal diet.After 8 weeks,hematoxylin-eosin (HE) staining was employed to observe the histopathology of thyroid; chemiluminescence immunoassay (CIA) was used to observe the level of thyroid hormone and real-time PCR (RT-PCR) was used to detect the level of inflammation related genes(IL-17,IL-23 and IFN-γ) in thyroid and spleen.Results Compared with CG group,goiter,follicular expansion and glial retention were observed in HI and TG + HI groups,but thyroid follicular was consistent in TG group.There was rare lymphocyte infiltration in HI group,but single scattered lymphocyte infiltration was detected in TG group,and local lymphocyte infiltration and destructed tissue were observed in TG + HI group.Among the 4 groups,the content of free triiodothyronine (FT3),total thyroxine (TT4) and free thyroxine (FT4) were significantly different between groups(F =12.54,4.00,10.62,all P ＜ 0.05).RT-PCR results showed that in thyroid,the relative expressions of IL-23,IL-17 and IFN-γ in the 4 groups were significantly different between groups(F =9.01,9.19,4.79,all P ＜ 0.01).The mRNA expressions of IL-23(0.257 6 + 0.169 3,0.262 0 + 0.126 3) and IFN-γ(0.185 0 + 0.170 1,0.144 8 ± 0.078 4) in TG and TG + HI groups were significantly increased compared with those of CG group (0.114 5 ± 0.073 2,0.057 4 + 0.032 9,all P ＜ 0.05) ; the expression of IL-17(0.017 4 ± 0.017 8) in TG + HI group was higher than that of CG group(0.000 6 ± 0.00 3,P＜ 0.05).In spleen,the expressions of IL-23,IL-17 and IFN-γ in the 4 groups were significantly different between groups (F =9.01,9.14,3.56,all P ＜ 0.05).In TG and TG + HI groups,the mRNA expressions of IL-17(0.007 8 ± 0.006 6,0.009 6 + 0.010 0) and IFN-γ(0.219 3 + 0.061 1,0.222 8 + 0.208 0) were higher than those of CG group(0.001 8 ± 0.001 1,0.076 1 ± 0.046 0,all P ＜ 0.05); the mRNA expressions of IL-23(0.050 7 ± 0.042 6,0.117 5 ± 0.083 1) in HI and TG + HI groups were higher than that of CG group(0.004 8 ± 0.005 2,all P ＜ 0.05).Conclusions Excessive iodine intake can lead to mice goiter; in TG-induced autoimmune thyroid inflammation,iodine excess can lead to increased mRNA expressions of IL-23,IL-17 and IFN-γ in thyroid gland and spleen of mice. Key words: Iodine ; Thyroiditis, Autoimmune; Interleukin-17 ; Interleukin-23; Gamma interferon