碘过量对NOD和Balb/c鼠甲状腺TRAIL和TRAIL-sR1表达的影响

目的 观察碘过量对自身免疫性疾病敏感品系NOD鼠和非敏感品系Balb/c鼠甲状腺细胞凋亡相关基因肿瘤坏死因子的相关凋亡诱导配体(tumor necrosis factor-related apoptosis-inducing ligand, TRAIL)和其受体TRAIL刺激性受体1(TRAIL-sR1)表达的影响,了解碘过量诱导实验性自身免疫性甲状腺炎(EAT)发病过程中TRAIL和TRAIL-sR1的作用机制.方法 6～7周龄雌性NOD鼠和Balb/c鼠各16只,按体质量各随机分为对照组和碘过量(HI)组,每组8只.对照组饮高压灭菌水,HI组饮0.05%NaI添加水,饲养8周后处死.测量甲状腺相对质量,进行甲状腺组织形态学观察,测量血清甲状腺素(TT4)和甲状腺刺激激素(TSH),检测甲状腺滤泡上皮细胞凋亡情况,应用实时定量PcR(real time PCR)方法检测TRAIL和TRAIL-sR1 mRNA表达情况.结果 NOD鼠HI组甲状腺相对质量(104.8±14.5)mg/kg]高于对照组(71.8±20.4)mg/kg],血清TT4水平(30.77±3.59)mmol/L]低于对照组(36.43±2.66)mmol/L],TSH水平(6.98±0.66)μg/L]高于对照组(5.55±0.56)μg/L],组间比较差异均有统计学意义(t值分别为7.773、-9.526、-4.458,P均<0.05).HI组甲状腺出现滤泡扩张、胶质潴留及明显的淋巴细胞浸润伴灶性纤维化.Balb/c鼠川组甲状腺相对质量(155.8±20.8)mg/kg]高于对照组(105.1±22.0)mg/kg],血清TT4水平(19.75±3.32)mmol/L]低于对照组(23.46±6.21)mmol/L],TSH水平(4.14±1.71)μg/L]高于对照组(3.55±1.41)μg/L],组间比较差异均有统计学意义(t值分别为7.554、-7.239、3.140,P均<0.05);HI组甲状腺仅有甲状腺滤泡扩张,胶质潴留,而未见明显的淋巴细胞浸润.HI组NOD鼠和Balb/c鼠甲状腺滤泡上皮细胞的凋亡指数(3.97±0.91、1.05±0.45)分别高于对照组(0.21±0.15、0.10±0.03),组间比较差异均有统计学意义(t值分别为-7.167、-17.772,P均<0.05),Balb/c鼠HI组的甲状腺滤泡上皮细胞的凋亡指数低于NOD鼠HI组,组间比较差异有统计学意义(t=-7.625,P<0.05).NOD鼠HI组TRAIL mRNA表达水平(0.018 88±0.005 77)高于对照组(0.00961±0.005 91),组间比较差异有统计学意义(t=-2.710,P<0.05);Balb/c鼠HI组TRAIL表达水平(0.001 24±0.000 46)与对照组(0.000 59±0.000 39)比较,差异无统计学意义(t=-1.940,P>0.05);NOD鼠和Balb/c鼠HI组的TRAIL-sR1 mRNA表达水平(0.000 53±0.000 15、0.000 42±0.000 09)均高于对照组(0.000 28±0.000 05、0.000 17±0.000 06),组间比较差异有统计学意义(t值分别为3.050,3.990,P均<0.05),Balb/c鼠HI组的TRAIL和TRAIL-sR1的mRNA表达水平均低于NOD鼠HI组,组间比较差异均有统计学意义(t值分别为-3.370、-4.760,P均<0.05).结论 碘过量可使NOD和Balb/c鼠发生胶质潴留性甲状腺肿,并可造成NOD鼠甲状腺发生明显的炎症反应.TRAIL和TRAIL-sR1表达水平升高是碘过量导致甲状腺滤泡上皮凋亡和炎症发生的分子基础之一.遗传在甲状腺炎的发病过程中起到至关重要的作用.

Effect of iodine excess on TRAIL and TRAIL-sR1 expression of thyroid in Balb/c and NOD mice

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.