Effects Of Selenium On CD4⁺CD25⁺ Regulatory T Cells In NOD.H-2^h4 Mice With Iodine-induced Autoimmune Thyroiditis

ObjectiveThe relationship between iodine intake and thyroid diseases has been continuously paid much attention by endocrinologists in the recent years. It is well known that shortage of iodine intake would induce iodine deficiency disorders (IDD). In addition, excessive iodine may also be harmful to thyroid. Selenium (Se) is an essential trace element of dietary component that, like iodine, influences a number of endocrine processes, most notably, those involved in thyroid hormone synthesis, activation, and metabolism. Furthermore, Se has an important impact on immune function. Se deficiency is accompanied by a loss of immune competence: both cell-mediated and humoral immunity may be impaired. Recent clinical studies have demonstrated the suppressive effect of Se treatment on serum thyroid-specific antibody titers in patients with autoimmune thyroiditis (AIT), suggesting that Se supplementation might be an effective treatment for AIT, but the exact mechanism of this effect is not clear. CD4+CD25+ regulatory T lymphocytes (Treg cells) contribute to the establishment and maintenance of peripheral self-tolerance. Deficits in the numbers and/or function of Treg cells may lead to many kinds of autoimmune diseases. The aim of the present study was to investigate dynamic changes of CD4+CD25+regulatory T cells in NOD.H-2h4 mice with iodine-induced autoimmune thyroiditis, and study whether any effects of Se treatment on CD4+CD25+regulatory T cells exist in NOD.H-2h4 mice with SAT, and explore potential immune mechanism of AIT induced by iodine and the therapeutic effect on AIT.MethodsNOD.H-2h4 mice at 4 weeks of age were randomly divided into control and iodine-treated (HI) groups, mice in HT group were fed with 0.005% NaI (50mg/L NaI, about 100 times of normal daily iodine intake amount), and the contol group received sterile water. Animals were sacrificed at the time point of 4 weeks,8 weeks,12 weeks and 16 weeks after drinking NaI solutions, thyroid tissues were removed and the raletive thyroid weight were measured, the severity of lymphocytic infiltration in thyroids was observed using HE-stained thyroid sections. The serum TgAb titers were measured by ELISA. The percentage of CD4+CD25+Foxp3+T cells in splenic mononuclear cells were detected by multicolor flow cytometry and Foxp3 mRNA expressions in splenocytes were measured by Real-time RT-PCR. Next, we selected NOD.H-2h4 mice at 4 weeks of age and randomly divided into control, SAT without and SAT with Se treatment groups. SAT mice without Se treatment were fed with 0.005% NaI (50mg/L NaI) water for 8 weeks to establish the animal models of AIT. After the eatablishment of SAT, the mice were then supplied with 0.3mg/L Na2SeO3 for 8 weeks. At the experimental end points (8 or 16 weeks), mice were weighed and anesthetize, thyroid tissues, serum and spleens were collected and detected the indicators as above. At the same time, the serum Se concentrations were tested using an inductively coupled plasma mass spectrometry (ICP-MS). Data was analysed using SPSS 16.0 software package.ResultsResults revealed that, compared with control animals, SAT mice without Se treatment have lower numbers of CD4+CD25+Foxp3+ T cells in the splenic mononuclear cells and reduced expressions of Foxp3 mRNA in splenocytes (P< 0.01); raletive thyroid weight and serum TgAb titers increased obviously (P< 0.01), lymphocytic infiltration could be found in thyroids with scores from 1+ to 4+. After Se treatment for 8 weeks, the serum selenium concentration was elevated in the Se treated group as compared with control and SAT without Se treatment groups (P< 0.05). Compared to SAT mice without Se treatment, the percentage of CD4+CD25+Foxp3+T cells and expressions of Foxp3 mRNA increased significantly in SAT/Se treated group (P<0.05). Simultaneously, the relative thyroid weight and serum TgAb titers decreased significantly (P<0.01), histomorphologic appearances of thyroids improved with lower scores of thyroiditis.Conclusion These data indicate that the reduction of CD4+CD25+regulatory T cells play an important role in the development of AIT; Se treatment can increase the percentage of CD4+CD25+regulatory T cells by up-regulating the expression of Foxp3 mRNA, lead to the suppressive effect on TgAb titers and exert therapeutic function on AIT. ObjectiveThe foetus does not completely establish its own thyroid functions in the first trimester, so foetal thyroid hormones are derived mainly from the mother. Maternal hypothyroidism is known to be associated with impaired neurodevelopment in their offspring, but it is controversial whether mild thyroid insufficiency in pregnancy may result in the same outcome in offspring. The aim of this prospective study was to assess the effects of maternal subclinical hypothyroidism (SCH) during the first trimester on neuropsychological development of their offspring at 20-30 months.MethodsWe slected 1761 pregnant women from 10 hospital in Shenyang at about 8 weeks of gestation in this study. Their fasting venous blood (non-anticoagulated) and fasting morning urine specimens were collected, and urinary iodine excretion was detected by the Arsenic-Cerium Catalytic Spectrophotometry based on the Sandell-Kolthoff reaction, and serum thyrotropin (TSH), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb) levels were measured using an super-sensitive immunochemiluminometric assay (ICMA) in all subjects. The entry criteria of study subjects were:1) less than 8 weeks of pregnancy; 2) no history of living in an iodine deficient area; 3) no personal and family thyroid disease history; 4) no personal history of other autoimmune diseases. Pregnant women with SCH (TSH≥2.5 mIU/L, FT4 in the normal range, TPOAb< 50 IU/ml) were divided into two subgroups using trimester-specific thyroid function reference: group A (2.5≤TSH< 3.93 mIU/L,18 cases), and group B (TSH≥3.93 mIU/L,20 cases). Thirty euthyroid and TPOAb-negative women from the same cohort were selected as controls. Intellectual and motor development score evaluations using the Mental Development Index (MDI) and Psychomotor Development Index (PDI) were performed by means of the Bayley Scales of Infant Development (BSID) on the children at 20-30 months of age. Data was analysed using SPSS 16.0 software package.ResultsChildren of women with SCH and subgroup A, B had mean intelligence scores 6.55,3.39 and 9.40 points lower than those of the control group (P= 0.001 P= 0.125 and P< 0.001 respectively); mean motor scores were 6.31,4.35 and 8.07 points lower than those of the controls (P= 0.003 P= 0.070 and P= 0.001 respectively). Mental Development Index (MDI) and Psychomotor Development Index (PDI) of children negatively correlated with maternal serum TSH levels (r=-0.425, P< 0.001 and r=-0.394, P= 0.001 respectively). One-way ANOVA analysis in SCH-A, B and control group revealed that differences of maternal serum TSH affect intelligence and motor scores of their offspring (F= 9.277, P< 0.001 and F= 5.909, P= 0.004 respectively). Ordinal logistic regression analysis showed that, possibilities for the reduction of filial MDI and PDI scores in SCH with maternal TSH levels≥3.93 mIU/L were 8.66,6.27 times to controls(OR= 8.66,95% CI 2.72～27.57; OR= 6.27,95% CI 2.03～19.34 respectively).ConclusionIntellectual and motor development index of children at 20-30 months of age is associated with maternal elevated TSH levels during first trimester. Maternal elevated TSH levels (≥3.93 mIU/L) diagnosed by trimester-specific reference during early gestation are independent associated with lower filial neurodevelopment scores at 20-30 months.