131I诱导甲状腺功能减退大鼠主动脉内皮功能异常相关机制的研究

目的探究放射性131I诱导大鼠甲状腺功能减退（简称甲减）模型中血清一氧化氮（NO）、炎症介质肿瘤坏死因子-α（TNF-α）、白细胞介素6（IL-6）的表达水平及在大鼠甲减模型中主动脉内皮细胞中一氧化氮合酶（NOS）蛋白的表达情况,以期寻找一个较为安全的131I治疗剂量。方法健康雄性SD大鼠45只,其中36只分别腹腔注射2.775、5.550、11.100、16.650 MBq 131I+0.5 mL生理盐水,构建大鼠甲减模型,分为4组,每组9只;剩余9只作为正常对照组,只注射0.5 mL生理盐水。分别于注射后第4、8、16周时每组各处死大鼠3只,用ELISA法检测大鼠血清中NO、TNF-α和IL-6水平,用化学发光免疫分析法检测血清中游离三碘甲状腺原氨酸（FT₃）、游离甲状腺素（FT₄）、促甲状腺激素（TSH）水平,提取主动脉标本检测总的NOS活性,应用Western-blotting分析大鼠主动脉标本中主动脉内皮型NOS（eNOS）、神经型NOS （nNOS）与诱导型NOS（iNOS）蛋白表达水平。组间两两比较采用t检验。结果血清中FT₃、FT₄、TSH水平检测结果发现除2.775 MBq剂量组外的其他3组大鼠均甲减模型构建成功,且5.550 MBq组作为放射性131I治疗的剂量是较为合适的。5.550 MBq组大鼠血清NO水平在注射131I后第4周升高至24.01 μmol/L后逐渐减少;血清中IL-6水平在第4、8、16周时分别为209.23、291.87、302.97 pg/mL,与正常对照组相比,第8、16周差异均有统计学意义（t=8.841、14.224,均P<0.05）。TNF-α水平在第4、8、16周时分别为1441.23、1601.85、1521.51 pg/mL,与正常对照组相比,差异均有统计学意义（t=21.021、17.578、14.498,均P<0.05）。eNOS在不同时间点的表达量为25 985、16 306、6248,各组蛋白水平明显降低,与正常对照组相比,除第4周时蛋白水平差异无统计学意义（t=3.546,P>0.05）外,第8、16周时差异均有统计学意义（t=8.841、14.224,均P<0.05）。nNOS表达量为24 562、36 114、58 211,第4周时下降,第8、16周时逐渐升高,与正常对照组相比,第4、16周时的差异均有统计学意义（t=5.751、7.251,均P<0.05）。iNOS在不同时间点的表达量为55 973、50 575、62 364,与正常对照组相比,各组均明显增加,差异均有统计学意义（t=21.017、16.412、24.981,均P<0.05）。结论放射性131I所致甲减对于心脏具有一定的影响,大剂量的131I可能会刺激合成甲状腺激素减少,从而导致甲减,最终影响其血管内皮NOS基因及蛋白表达,对心血管系统产生影响。

Effect and mechanism of aortic endothelium of hypothyroidism rats induced by 131I

ObjectiveTo investigate the expression of nitric oxide(NO), inflammatory mediators(TNF-a, IL-6) in serum and nitric oxide synthase(NOS) protein in aortic endothelial cells of rats with hypothyroidism induced by radioactive 131I, in order to find a safe dose of 131I for the prevention of hypothyroidism heart disease.MethodsForty-five male rats were selected. The hypothyroidism model was established by intraperitoneal injection of 2.775, 5.550, 11.100, 16.650 MBq 131I + 0.5 mL saline into 36 male rats, with 9 rats in each group. The remaining 9 rats were taken as normal control group and only 0.5 mL saline was injected to each rat. Three rats were sacrificed in each group at 4, 8, and 16 weeks after 131I administration. The serum levels of IL-6, TNF-α and the aortal content of total-NOS activity were determined with chemiluminescence immunoassay. Western blotting was used to analyze the expression of rat aortic specimens of eNOS, nNOS, and iNOS, and count data were analyzed by the t test. A value of P<0.05 was considered statistically significant.ResultsThe serum levels of FT₃, FT₄ and TSH showed that all the groups of hypothyroidism model of rats were successfully constructed except 2.775 MBq group, and 5.550 MBq was regarded as an optimum dosage. The serum level of NO in rats(5.550 MBq) at 4 week increased to 24.01 mol/L and then reduced gradually; the level of serum IL-6 in 4, 8, and 16 were 209.23, 291.87, and 302.97 pg/mL, respectively. Compared with nomal control, statistical differences were observed at 8 and 16 week(t=8.841, 14.224, both P<0.05). The levels of TNF- alpha were 1441.23, 1601.85, and 1521.51 pg/mL, respectively, with statistical differences at different time points(t=21.021, 17.578, 14.498, all P<0.05). The expression of aortic endothelial NOS(eNOS) at different time points was 25 985, 16 306, and 6248. Compared with nomal control, the levels of protein in each group decreased, no statistical significance was observed at 4 week(t=3.546, P>0.05) and statistical differences were observed at 8 and 16 week(t=8.841, 14.224, both P<0.05). The expression of NOS(nNOS) was 24 562, 36 114 and 58 211, down at 4 week(t=3.546, P>0.05), and gradually increased at 8 and 16 week(t=5.751, 7.251, both P>0.05). The expression of inducible nitric oxide synthase(iNOS) was 55 973, 50 575 and 62 364, and all groups increased statistically(t=21.017, 16.412, 24.981, all P<0.05).ConclusionThe hypothyroidism induced by 131I has certain effect on the heart, and our study can provide a new idea for prevention of hypothyroid heart disease for clinical practice and reduction of cardiovascular disease.