Effect of iodine excess on TRAIL and TRAIL-sR1 expression of thyroid in Balb/c and NOD mice / 中国地方病学杂志

ABSTRACT

Objective To investigate the influence of iodine excess on expression of TRAIl/TRAIL-sR1 in NOD and Balb/c mice and to study the effect of TRAIl/TRAIL-sR1 on the pathogenesis of experimental autoimmune thyroiditis(EAT). Methods Both Balb/c and NOD mice were divided randomly into control and iodine excess group by feeding with water containing no NaI or 0.05% Nal. The mice were sacrificed after 8 weeks. TRAIL and TRAIL-sR1 mRNA levels were detected by RT-PCR. The function, morphology and apoptosis of thyroids were also observed by ELISA and Tunnel stain. Results Treated by HI, enlarged follicles and flattened epithelium by accumulation of colloid were found in thyroids of both NOD and Balb/c mice. But significant lymphoid cell infiltration and local fibrosis were only found in thyroids of NOD HI group. The relative weight of thyroids of NOD mice in HI group[(104.8±14.5)mg/kg]was heavier than that of control group [(71.8±20.4)mg/kg]. The level of TT4 declined in HI group[(30.77±3.59)mmol/L]compared with control group[(36.43±2.66)mmol/L], meanwhile, the level of TSH was higher in HI group[(6.98±0.66)μg/L]than that in control group [(5.55±0.56)μg/L]. The difference being statistically significant(t=7.773,-9.526,-4.458, all P < 0.05). The relative weight of thyroids of Balb/c mice of HI group[(155.8±20.8)mg/kg]also heavier than that of control group [(105.1±22.0) mg/kg]. The level of TT4 droped in HI group [(19.75±3.32) mmoL/L]was higher than that in control group[(23.46±6.21)mmoL/L], the level of TSH in HI group[(4.14±1.71)μg/L]was higher than that in control group[(3.55±1.41)μg/L], the difference being statistically significant(t=7.554,-7.239,3.140, all P< 0.05). A great deal of apoptotie ceils observed in NOD (3.97±0.91) and Balb/c mice (1.05±0.45) by Tunnel stain were greater than control groups (0.21±0.15, 0.10±0.03), the difference being statistically significant in beth of the two species(t=-7.167,-17.772, both P < 0.05). The apoptosis index of thyroid follicular epithelium in NOD was obviously higher than Balb/c(t=-7.625, P<0.05). The level of TRAIL mRNA did not remarkably change in Balb/c between control group(0.000 59±0.000 39) and HI group(0.001 24±0.000 46, t=-1.940, P>0.05), but it increased apparently in NOD mice HI group(0.018 88±0.005 77) than that of control group(0.009 61± 0.00591, t=-2.71, P<0.05). The level of the expression of TRAIL-sR1 mRNA increased in HI groups of NOD (0.000 53±0.000 15) and Balb/c mice(0.000 42±0.000 09) than that in control groups of NOD(0.000 28± 0.000 05) and Balb/c mice (0.000 17±0.000 06) and the differences were statistically significant between the two species(t=3.050,3.990, all P<0.05). The differences of the expression of TRAIL and TRAIL-sR1 mRNA between the two species were significant(t=-3.37,-4.76, all P<0.05). Conclusions Iodine excess induces colloid goiter in beth species of mice and thyroiditis in NOD mice. The increase of TRAIL and TRAIL-sR1 influenced by iodine excess is one of the molecular bases of follicular epithelium apoptosis and inflammation in thyroids. Genetic factor is a key factor in the pathogenesis of thyroiditis.