Several methods were used to detect changes in thyroid activity and in degradation of thyroxine (T4) in exercising and sedentary control rats. Rats were run in a motor-driven exercise wheel over a three-week period at progressively increasing work loads and then were run 1.5-2 hours per day for 10-14 days before sacrifice. Disappearance of injected T4-125I from plasma was considerably enhanced by exercise. As determined by isotopic equilibration and paper chromatographic methods, T4 concentration was depressed in plasma and elevated in liver of exercised rats. No significant changes in T4 concentration were observed in heart, kidney, or gastrocnemius muscle. Thyroidal iodotyrosine levels were elevated immediately following but not 24 hours after exercise. Serum free T4 was higher in exercised rats. In vitro deiodinating activity in liver, muscle or kidney homogenates was not affected by exercise. The elevated T4 degradation rate accompanying exercise is thus likely due to the elevated free T4. The liver is apparently the tissue site responsible for the increased T4 uptake and degradation.

Thyroid hormones, which are secreted by the thyroid gland, are one of the most important halogenated compounds in the body. Thyroid hormones control almost every processes in the body including growth, body temperature, protein synthesis, carbohydrate and fat metabolism, heart rate, and cardiovascular, renal and brain function. Thyroid gland secretes L-thyroxine or 3,3',5,5'-tetraiodothyronine (T4) as a prohormone. While the biologically active hormone 3,3',5-triiodothyronine (T3) is produced by selective phenolic ring deiodination of T4, selective tyrosyl ring deiodination of T4 produces a biologically less active metabolite 3,3',5'-triiodothyronine (rT3). Tyrosyl and phenolic ring deiodination of T3 and rT3, respectively, also produces a biologically inactive metabolite 3,3'-diiodothyronine (3,3'-T2). Regioselective deiodinations of thyroid hormones are catalysed by three isoforms of a selenoenzyme iodothyronine deiodinase (DIO1, DIO2, DIO3). DIO1 can remove iodine from both the tyrosyl and phenolic rings of thyroid hormones, whereas DIO2 and DIO3 are selective towards phenolic and tyrosyl ring, respectively. Although the Figure 1. (A) Deiodination of thyroid hormones by iodothyronine deiodinases (DIOs) (A) and naphthyl-based selenium and/or sulphur compounds (B). mystery behind the origin of regioselectivity of deiodination by DIOs remains unsolved, formation of halogen bonding between selenium in the active site of DIOs and iodine of thyroid hormones has been widely accepted as the mechanism of deiodination. Halogen bonding, a noncovalent interaction between halogen and an electron donor such as nitrogen, oxygen, sulphur, selenium etc., elongates the C-I bond and impart a carbanionic character on the carbon atom that gets protonated after the removal of iodide. Apart from the deiodination, thyroid hormones also undergo decarboxylation, oxidative deamination, sulphate-conjugation to form iodothyronamines, iodothyroaetic acids and sulphated thyroid hormones, respectively. Figure 2. (A) Proposed mechanism of deiodination of thyroid hormones by deiodinase mimics. (B) Halogenation of uracil- and cytosine-containing nucleosides by hypohalous acid (HOX). Recently, naphthyl-based selenium/sulphur-containing compounds, such as compound 1 (Figure 1B), have been reported to mediate the selective tyrosyl ring deiodination of T4 and T3 to form rT3 and 3,3'-T2, respectively. Interestingly, replacement of the selenol moiety in compound 1 with a thiol decreases the activity, whereas replacement of the thiol moiety with another selenol dramatically increases the deiodination activity. Based on the detailed experimental and theoretical investigations, a mechanism involving the Se···I halogen bonding was proposed (Figure 2A). In addition to the halogen bonding between selenium and iodine atom, chalcogen bonding between two nearby chalcogen atoms was also shown to be important for the deiodination activity. Another important class of halogenated compounds in the body are the halogenated nucleosides. Myeloperoxidase and eosinophil peroxidase are heme-containing enzymes, which can convert halide ions (X¯) into a toxic reactive halogen species hypohalous acid (HOX) in presence of hydrogen peroxide (H2O2). Uracil- and cytosine-containing nucleosides are known to undergo halogenation at the 5-position of the nucleobase to form the halogenated nucleosides (Figure 2B). Interestingly, halogenated nucleosides such as 5-halo-2'-deoxyuridine are known to be incorporated in the DNA of dividing cells essentially substituting for thymidine. Incorporation of halogenated nucleosides into the DNA leads to mutagenesis, carcinogenesis and loss of genome integrity. Thymidylate synthase (TSase), the key enzyme involved in the biosynthesis of 2'-deoxythmidine-5'-monophosphate (dTMP) from 2'-deoxyuridine-5'-monophosphate (dUMP), can catalyse the dehalogenation of halogenated nucleotides in presence of external thiols. This thesis consists of five chapters. The first chapter provides a general introduction to halogen bonding, thyroid hormones and halogenated nucleosides. This chapter also briefly describes the halogen bond-mediated biochemical and biomimetic deiodinations of thyroid hormones by iodothyronine deiodinases and naphthyl-based organoselenium compounds. Dehalogenation of halogenated nucleotides by thymidylate synthase and thiol-based small molecules has also been discussed in this chapter. The second chapter of this thesis contains the regioselective deiodination of iodothyronamines (TAMs) by deiodinases mimics. TAMs are the endogenous metabolites produced by the decarboxylation of β-alanine side chain of thyroid hormones (THs). 3,3',5-triiodothyronamine (T3AM) and 3,5-diiodothyronamine (3,5-T2AM) undergoes selective tyrosyl ring deiodination by deiodinase mimics to form 3,3'-diiodothyronamine (3,3'-T2AM) and 3-iodothyronamine (3-T1AM), respectively. Interestingly, when the initial rates of deiodinations of T3 and T3AM were compared, deiodination of T3 was found to be several fold faster than that of T3AM under identical reaction conditions. To understand the ability of the iodine atoms to form Figure 3. (A) HPLC chromatogram of deiodination of T3. (B) Proposed mode of interaction of dimeric T3 and monomeric T3AM with organoselenium compounds. halogen bonding, a model selenolate (MeSe¯) was optimized with the T3 and T3AM. Although both T3 and T3AM forms the expected Se···I halogen bonding with MeSe¯, the strength of halogen bonding was found to be less for T3AM than T3. Furthermore, detailed kinetic and spectroscopic studies indicate that T3 and T3AM exist as dimeric and monomeric species in solution. The dimerization of T3 in solution was shown to have remarkable impact on the activation energy and pre-exponential factor of the deiodination reactions. Single crystal X-Ray crystallography and theoretical calculations indicated that in addition to Se···I halogen bonding, I···I halogen bonding may play an important role in the deodination of thyroid hormones by deiodinase mimics. Furthermore, the presence of heteroatoms such as nitrogen, oxygen and sulphur in the close proximity of one of the selenium atoms of deiodinase mimics was shown to have significant effect on the rate of deiodination reactions. The third chapter of the thesis focusses on the conformational polymorphism and conformation-dependent halogen bonding of L-thyroxine. Synthetic version of L-thyroxine (T4) is a life-saver for millions of people who are suffering from hypothyroidism, a thyroidal disorder recognised by low levels of T4 and elevated levels of TSH in blood plasma. Synthetic version of L-thyroxine is available in the Figure 4. Ball and stick model of the single crystal X-Ray structure of the conformational polymorphs of L-thyroxine. Form I and Form II was exclusively crystallized from methanol and acetonitrile, respectively. Water molecules are omitted for clarity. market with various brand names. However, adverse effects have been observed in the patients when they switch their brand of thyroxine. Based on these observations, the American Thyroid Association (ATA), the Endocrine Society (TES), and the American Association of Clinical Endocrinologists (AACE) declared that the different brands of T4 are not bioequivalent, thus leading to differences in the bioavailability of the drug. We have shown that the commercially available thyroxine exists in at least two stable forms (Form I and Form II) with different three-dimensional structures (Figure 4). These two forms exhibit different intermolecular interactions in crystal packing, spectral behaviours, thermal stabilities, optical activity and very interestingly, different solubility in acidic and basic pH. At pH 4, solubility of Form I is about 42% and 45% greater than that of Form II and bulk T4, respectively, whereas at pH 9, the solubility of Form II is about 38% and 42% higher than that of Form I and bulk T4, respectively. As T4 is a narrow therapeutic index drug, these differences in solubility may have remarkable impact on the bioavailability of the drug. In addition to this, we have shown that the ability of the iodine atoms in the C-I bonds to form halogen bond with donor atoms can be altered by changing the relative orientation of tyrosyl and phenolic rings in T4. In the fourth chapter, the three-dimensional structures and conformations of thyroid hormones (THs) and iodothyronamines (TAMs) are discussed. TAMs, the endogenous decarboxylated metabolites of THs, exhibit different binding affinities to the transport proteins and iodothyronine deiodinases (DIOs) compared to the THs. Figure 5. Change in the structure and conformations of thyroid hormones and iodothyronamines with the decarboxylation of amino acid side chain and deiodination of phenolic and tyrosyl ring. Furthermore, the substrate specificities of DIOs have been found to be dependent on the position of iodine atoms on the phenolic and tyrosyl ring of TAMs and THs. Single crystal X-ray structures of TAMs indicate that decarboxylation of amino acid side chain of THs induces significant changes in the structure and conformation. Furthermore, the positional isomers of THs and TAMs exhibit remarkably different conformations, which may have significant effect on the binding of these metabolites to the active site of DIOs. In addition to the structure and conformations, different categories of the intermolecular halogen···halogen (X···X) interactions in the crystal packing of THs and TAMs have also been discussed. Natural bond orbital (NBO) analysis have been done on the halogen-bonded geometries to understand the electronic nature of these interactions. In the fifth chapter, the dehalogenation of halogenated nucleosides and nucleobases by naphthyl-based sulphur/selenium compounds is discussed. Purine and pyrimidine nucleosides are halogenated at various positions of the aromatic ring by different peroxidases such as myeloperoxidase and eosinophil peroxidase present in the white blood cells. Incorporation of the halogenated nucleosides into the DNA of replicating cells leads to DNA-strand breaks, mutagenesis, carcinogenesis and loss of Figure 6. (A) Dehalogenation of halogenated nucleosides. Effect of base-pairing wih adenine and guanine on the deiodination of IU (B) and debromination of BrU (C) by compound 2. genome integrity. We have shown that the naphthalene-based organoselenium compounds such as compound 2 can mediate the dehalogenation of 5-iodo-2'-deoxyuridine (5-IdUd) and 5-bromo-2'-deoxyuridine (5-BrdUd) to produce 2'-deoxyuridine (dUd) (Figure 6A). The deiodination of 5-IdUd was found to be faster than the debromination of 5-BrdUd by compound 2. The mechanism of dehalogenation of halogenated nucleosides by compound 2 was found to be dependent on the nature of halogen. While the deiodination of 5-IdUd by compound 2 follow halogen bond-mediated pathway like thyroid hormones, debromination of 5-BrdUd follow a Michael addition-elimination pathway. Similar results were obtained when 5-iodo-2'-deoxycytidine (5-IdCd) or 5-bromo-2'-deoxycytidine (5-BrdCd) was used as substrate for dehalogenation reaction. Base-pairing of 5-iodouracil (IU) and 5-bromouracil (5-BrU) with adenine and guanine has a significant effect on the rate of dehalogenations of IU and BrU by compound 2 (Figure 6B and 6C).

Call number: LD2668 .T4 1985 P34 / Master of Science

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

INTRODUÇÃO: Os efeitos deletérios do mercúrio (Hg) no sistema nervoso central, em diferentes formas químicas, têm sido descritos em diversos estudos, entretanto, a ação tóxica sobre a tireoide ainda é pouco compreendida. Experimentos em animais, expostos ao Hg, em diversas formas, mostraram evidências de alterações do parênquima e dos hormônios tireoidianos. A elevada deposição do metal na tireoide e a alta afinidade pelo selênio das desiodases podem ser fatores relevantes para a explicação dos seus efeitos tóxicos. OBJETIVOS: avaliar se a exposição crônica ocupacional ao Hg metálico pode estar associada a alterações da função hormonal tireoidiana, bem como do parênquima da glândula, mesmo depois de cessar a exposição. MÉTODOS: Realizado estudo seccional em 55 expostos ao Hg e 55 controles, do sexo masculino, pareados por idade. Analisadas as concentrações dos hormônios: T3 total e livre (T3T e T3L), T4 livre (T4L) e TSH por eletroquimioluminescência, T3 Reverso (T3R) por cromatografia líquida acoplada à espectrometria de massas em tandem, selênio (no sangue) e Hg na urina (HgU) por espectrofotometria de absorção atômica, iodo urinário por detecção indireta pela Reação de Sandell - Kolthoff, anticorpos anti-tireoperoxidase por ensaio imunoquimioluminométrico. A Ultrassonografia (US) Modo B e Dúplex-doppler da tireoide avaliou as dimensões, ecogenicidade, ecotextura, vascularização e nódulos. Os nódulos com aspecto suspeito de malignidade foram submetidos à punção aspirativa por agulha fina (PAAF) e a análise citológica seguiu a classificação de Bethesda. A análise das variáveis contínuas utilizou os testes t ou U de Mann-Whitney e o Qui-quadrado para associação das variáveis categóricas. A correlação de Spearman utilizada para avaliar a relação entre as variáveis de exposição e as concentrações hormonais. O modelo de regressão logística univariada e múltipla foram empregados para análise do risco. O nível de significância dos testes foi Alfa = 0,05. RESULTADOS: a média de idade dos expostos ao Hg foi 55,2 anos (±6,6 anos) e dos controles 53,4 anos (±6,8 anos). Não houve diferença estatisticamente significativa entre as médias de idade dos grupos (p=0,158). A média das concentrações de Hg urinário, durante o período laboral, foi significativamente mais elevada em expostos (51,9 Microg/L versus 1,79 Micrpg/L; p < 0,01). A média de duração do período laboral foi de 14,5 anos (dp=±7,26). A média das concentrações de TSH foi mais elevada em expostos (3,31 MicroIU/ml versus 2,31MicroIU/ml), com diferença estatisticamente significante entre os grupos (p=0,030). As concentrações de TSH excederam o limite de normalidade (4,20 MicroIU/ml) em 13 indivíduos expostos (27,3%) e em quatro controles (7,3%), com associação estatisticamente significativa entre a elevação de TSH e a exposição ao mercúrio (p =0,018). No modelo de regressão logística, a exposição ao mercúrio mostrou uma razão de chances estatisticamente significativa para elevação das concentrações de TSH (OR=4,86; p=0,038). Não houve diferença estatisticamente significativa da relação T4L:T3L entre os indivíduos expostos e o grupo controle (p=0,791). As médias das concentrações dos hormônios T3, T3L e T4L não apresentaram diferença estatisticamente significativa entre os grupos (p > 0,05). A comparação de médias das concentrações de T3 Reverso mostrou um valor de p próximo do nível de significância do teste (p = 0,06). As proporções de alterações da ecogenicidade foram maiores em expostos (27,3% versus 9,1 %; p=0,026), com associação estatisticamente significativa à exposição ao Hg. Não foi observada associação, estatisticamente significativa, entre a exposição ao Hg e o padrão heterogêneo de ecotextura, ou o aumento de vascularização do parênquima (p > 0,05). A presença de nódulos foi similar entre os grupos. O exame citológico identificou a presença de carcinoma papilífero de tireoide em três indivíduos expostos e um controle. O anatomopatológico confirmou a presença de carcinoma papilífero em quatro indivíduos e identificou o carcinoma folicular em um dos controles. CONCLUSÕES: Os resultados deste estudo mostraram a presença de elevação das concentrações de TSH, e alterações do parênquima tireoidiano, mais frequentes entre os trabalhadores expostos ao Hg, mesmo depois de cessar a atividade laboral, indicando a importância do monitoramento da tireoide / INTRODUCTION: The deleterious effects of mercury (Hg) on the central nervous system, in different chemical forms, have been described in several studies, however, the toxic action on the thyroid is still little understood. Experiments in animals exposed to mercury (Hg), in different states, showed parenchymal and thyroid hormones alterations. The accumulation of metal on thyroid and high affinity for selenium of deiodinases can be a relevant factor for the explanation of his toxic effects. OBJECTIVE: Evaluate the occupational exposure of metallic Hg and its association with the hormones and thyroid parenchyma alterations, even after the labor exposure was discontinued. METHODS: A sectional study in 55 exposed and 55 control males, paired by age was conducted. Serum dosages of total triiodothyronine (T3), free T3 (TT3 and FT3), free T4 (FT4) and TSH were obtained by electrochemical luminescence, the reverse T3 (RT3) by chromatography, selenium (blood), urinary Hg (U-Hg) by atomic absorption spectrophotometry, anti-thyroid peroxidase antibody by immunochemiluminometric assay, urinary iodine by Sandell-Kolthoff reaction. The thyroid parenchyma was evaluated by B-mode ultrasonography with Doppler. The nodules with suspicious aspect of malignancy were submitted to aspiration puncture with a thin needle. The t-test, or Mann-Whitney, chi-square and Spearman correlation were performed. For the risk analysis a univariate and multivariate logistic regression model was used (Alfa = 0.05). RESULTS: The mean age of the exposed to Hg was 55.2 years (SD± 6.6 years) and controls was 53.4 years (SD± 6.8 years). The U-Hg average was significantly higher in exposed (51.9 Microg/L versus 1.79 Microg/L; p=0.000). The longer work duration was 14.5 years (SD ±7.26 years). TSH concentrations exceeded the normality limit (4.20 MicroIU/ml) in 13 exposed individuals (27.3%) and four controls (7.3%), with a statistical significant association between the increase in serum TSH and exposure to mercury (p = 0.018). In the logistic regression model, the exposure to mercury (yes or no) showed a predictive value to the increase of TSH concentrations (OR=4.86; p=0.038). There was no statistical significant difference in the T4L:T3L ratio between the exposed individuals and the control group (p=0.791). The mean concentrations of the hormones T3, T3L and T4L showed no statistically significant difference between the groups (p > 0.05). The comparison of means of the Reverse T3 concentrations showed a p value borderline (p = 0.06). The proportions of the echogenicity alterations were higher at the exposed group (27.3% versus 9.1 %; p=0.026). There was no statistical significant association between the exposure to Hg and the thyroid echotexture pattern or parenchyma increased vascularization (p > 0.05). It was observed a papillary carcinoma in three exposed and one control individual and a follicular in one control. CONCLUSIONS: The results of this study showed the higher serum TSH concentration and prevalence of parenchyma alteration in the Hg exposed group, after cessation of exposure, and indicate the importance of the thyroid monitoring

Ames dwarf (df/df) mice are deficient in anterior pituitary hormones: growth hormone (GH), thyroid stimulating hormone (TSH), and prolactin (PRL) due to a spontaneous, homozygous mutation of prop1[superscript df] gene. These dwarf mice exhibit characteristics such as delayed growth and development coupled with delayed aging, increased lifespan, overall increased insulin sensitivity, as well as resistance to certain diseases and cancers. The mutant mice possess low blood glucose, low serum insulin, and lower body temperature. Their enhanced longevity (about 40-60% longer lifespan than normal mice) is associated with their GH deficiency and disruption in the somatotropic axis (GH/IGF-1 hormonal pathway) as well as increased insulin sensitivity, which is supported by other mutant mouse models for longevity like Snell dwarfs and growth hormone receptor knock-out (GHRKO) mice. When young male Ames dwarf mice were treated with GH replacement therapy, they showed increased body growth to nearly match the normal mouse phenotype. In conjunction to an increase in physical growth, however, GH treatment also decreases the longevity and insulin sensitivity that are characteristic of these mice to levels seen in normal mice. Because of the lack of TSH, they also have undetectable levels of Thyroxine (T4). While T4 treatment didn't increase bodyweight of dwarfs to the same extent as GH treatment, the T4 treated mice retained their enhanced lifespan. Although df/df mice have enhanced whole-body insulin sensitivity, the male skeletal muscle was previously shown to be less responsive to insulin than their liver. In our study we analyzed the insulin signaling pathway in skeletal muscle from female mice after treatment with GH or GH combined with T4. Gene expression and protein expression were investigated in the skeletal muscle of female Ames dwarf mice that were treated with GH or GH and T4 therapy. Real Time Polymerase Chain Reaction (RT-PCR) was used to analyze the expression of mRNA involved with insulin and GH signaling, while western blots were used to analyze protein expression. This project found that female Ames skeletal muscle didn't respond to GH treatment to the same extent as males, and that GH and T4 treatment tends to neutralize the effects seen in GH-only treatment.

INTRODUÇÃO: Manifestações auto-imunes são frequentes na infecção pelo vírus da hepatite C (VHC). Apesar da associação com doenças auto-imunes de tireóide (DAIT) ser controversa, sabe-se que distúrbios tireoidianos podem surgir ou piorar com tratamento com IFN e ribavirina. Os objetivos deste estudo foram avaliar a função tireoidiana em pacientes infectados pelo VHC, caracterizar distúrbios tireoidianos antes, durante e após tratamento com IFN e estudar as frequências dos genótipos dos polimorfismos do gene CTLA4, correlacionando-os com características clínicas e laboratoriais, presença de disfunção tireoidiana e evolução durante tratamento com IFN. MÉTODOS: Avaliação prospectiva de 112 indivíduos com infecção crônica pelo VHC, 30 tratados com IFN, e 183 controles. Realizaram-se avaliações clínica, hormonal e de auto-imunidade tireoidiana e ultra-sonografia de tireóide no início e durante tratamento. Avaliações de globulina transportadora de hormônios tireoidianos (TBG), de CXCL10 e de biópsia hepática foram feitas pré-tratamento. Análises dos polimorfismos do gene CTLA4 -318C>T, A49G e CT60 foram realizadas por PCR-RFLP e de AT(n) por análise de fragmento através de eletroforese capilar. RESULTADOS: A frequência de DAIT entre infectados por VHC não diferiu dos controles (10,7 vs 13,5%, p=0,585). Os limites de distribuição dos níveis de T3 (T3T) e T4 (T4T) totais foram superiores aos de referência (T3T 112-246 ng/dL; T4T 7,8-15,2 g/dL), assim como de TBG (17-47 mg/L). TBG correlacionou-se com T3T (r=0,654, p<0,001) e T4T (r=0,741, p<0,001). Heterogeneidade (p=0,027) e hipoecogenicidade de parênquima (p=0,002) foram mais frequentes nos pacientes com DAIT. Aumento de vascularização esteve presente em 49,2% dos infectados sem distúrbio tireoidiano. CXCL10 esteve aumentada nos infectados (p=0,006), mas não se relacionou com disfunção tireoidiana. Sua elevação correspondeu ao grau de atividade necro-inflamatória na biópsia hepática (p=0,006) e correlacionou-se com T3T (r=0,388, p=0,003), T4T (r=0,444, p=0,001) e TBG (r=0,551, p<0,001). Dezenove por cento dos pacientes desenvolveram tireoidites auto-imunes por IFN e 16% não auto-imunes. Em 14 pacientes sem alteração tireoidiana durante o uso de IFN, T3T diminuiu ao longo de 12 meses (p=0,038) concomitante à queda de ALT (p=0,055). T4T diminuiu com 3 (p=0,039) e 12 meses (p=0,008), T4 livre e TSH permaneceram estáveis. Encontrou-se maior frequência de oito repetições AT na região 3UTR do gene CTLA4 nos infectados por VHC (p=0,019). O alelo C do polimorfismo -318C>T esteve relacionado com infecção pelos genótipos 1 (p=0,020, OR 0,19) e 3 (p=0,008, OR 9,13), assim como o alelo G do polimorfismo A49G (p=0,002, OR 0,38 e p=0,004, OR 2,49, respectivamente). Não se identificou relação dos polimorfismos do gene CTLA4 com distúrbios tireoidianos, antes ou após tratamento com IFN. CONCLUSÕES: Não foi encontrada associação entre infecção por VHC e doenças tireoidianas. Indivíduos infectados por VHC têm maiores níveis de T3T e T4T, correlacionados com TBG. Aumento de CXCL10 não se associou com disfunção tireoidiana, mas se correlacionou com TBG, T3T e T4T. IFN provocou tireoidites auto-imunes e não auto-imunes, além de reduzir T3T e T4T coincidente com melhora de lesão hepática. Não se encontrou relação dos polimorfismos do gene CTLA4 com características clínicas e laboratoriais ou presença de disfunção tireoidiana prévia ou induzida por IFN / INTRODUCTION: Autoimmune disorders are frequent in patients infected by the hepatitis C virus (HCV). Although the association with autoimmune thyroid diseases (AITD) is controversial, thyroid disturbance could occur or worsen with IFN and ribavirin treatment. The aims of the study were evaluate thyroid function in HCV-infected patients, characterize thyroid disturbance prior and after IFN treatment and analyze the frequency of the genotypes of the polymorphisms of CTLA4 gene, and their relation to clinical and laboratorial features, presence of thyroid dysfunction and disturbance along IFN treatment. METHODS: Prospective evaluation of 112 chronically HCV-infected subjects, 30 treated with IFN, and 183 controls. Clinical, hormonal, thyroid autoimmunity and ultrasound exams were performed before and during treatment. Thyroxine-binding globulin (TBG), CXCL10 and hepatic biopsies were also evaluated before treatment. Analysis of polymorphisms of CTLA4 gene -318C>T, A49G and CT60 were made by PCR-RFLP and AT(n) polymorphism analysis by capillary electrophoresis in automatic sequencer. RESULTS: The frequency of AITD among HCV-infected subjects was similar to the rate among controls (10.7 vs 13.5%, p=0.585). Total T3 (T3T) and T4 (T4T) distributions were right shifted (T3T 112-246 ng/dL; T4T 7.8-15.2 g/dL), as was TBG (17-47 mg/L). TBG correlated to both T3T (r=0.654, p<0.001) and T4T (r=0.741, p<0.001). Thyroid heterogeneity (p=0.027) and hipoechogenicity (p=0.002) were associated with AITD and, most notably, increased vascularization was present in 49.2% of HCV-infected patients without thyroid disturbance. CXCL10 was higher in HCV-infected group (p=0.006) but was not related to thyroid dysfunction. Increase in CXCL10 levels were consistent with hepatic necroinflammatory activity (p=0.006) and correlated to T3T (r=0.388, p=0.003), T4T (r=0.444, p=0.001) and TBG (r=0.551, p<0.001). Nineteen percent of subjects treated with IFN presented autoimmune thyroiditis and 16% had non-autoimmune thyroiditis. In 14 subjects without IFN-induced thyroid dysfunction, T3T decreased along 12 months of follow-up (p=0.038) concomitant to ALT decrease (p=0.055). T4T decreased within 3 (p=0.039) and 12 months (p=0.008), while both free T4 and TSH remained stable. Eight AT repetitions in 3UTR site of the CTLA4 gene were more frequent among HCV-infected subjects. The C allele of -318C>T polymorphism was associated with genotype 1 (p=0.020, OR 0.19) and 3 infections (p=0.008, OR 9.13), similar to allele G of A49G polymorphism (p=0.002, OR 0.38 and p=0.004, OR 2.49, respectively). No association of the polymorphisms of CTLA4 gene and thyroid disorders, prior or induced by IFN treatment, was found. CONCLUSIONS: No association between HCV-infection and thyroid diseases was found. HCV-infected subjects had higher T3T and T4T which were correlated to TBG. Increased CXCL10 was not associated to thyroid dysfunction, but correlated to TBG, T3T and T4T. IFN induced autoimmune and non-autoimmune thyroiditis. IFN also reduced T3T and T4T levels commensurately with liver improvement. The polymorphisms of CTLA4 gene were not associated with clinical and laboratorial features or presence of thyroid dysfunction, prior or induced by IFN

Recém-nascidos com sepse apresentam sintomas clínicos e alterações laboratoriais por tempo e gravidade variáveis. A sepse neonatal pode comprometer diversos tecidos e modificar a ação das enzimas, incluindo a desiodase tipo 1, responsável pela formação do T3 plasmático a partir do T4 nos tecidos periféricos. Além disso, em certos períodos da doença, pode haver uma ação reduzida do T4 em níveis teciduais. Estas alterações são identificadas como Doença Não Tireoidiana, e pouco se conhece sobre ela no período neonatal. Os objetivos deste estudo foram determinar os níveis séricos dos hormônios tireoidianos em recém-nascidos a termo durante a sepse e a convalescença, verificando a presença da Doença Não Tireoidiana e determinando seus padrões na sepse de curta duração, na sepse prolongada e no choque séptico. Foram estudados 28 recém-nascidos a termo com sepse, 12 com duração prolongada por mais de oito dias e 15 com choque séptico. Os recém-nascidos que tiveram sepse prolongada foram os que apresentaram maior perda de peso desde o nascimento até o início da doença, média de 21 dias, e que tiveram culturas positivas para fungos. Doença Não Tireoidiana foi encontrada em 60,7% dos casos, prevalente nos recém-nascidos com sepse de prolongada duração, dentre os quais a prevalência foi inversamente relacionada ao tempo do prolongamento da sepse. A Doença Não Tireoidiana não apresentou correlação com o choque séptico. A síndrome do T3 baixo, caracterizada por T3 baixo, TSH normal e T3 reverso geralmente aumentado, foi encontrada em 58,8% dos casos, sem diferença com a duração da sepse. O nível sérico de T3 foi mais baixo na sepse do que na convalescença sem diferença com o tempo de duração da doença. Não foi encontrada elevação de T3 reverso. A síndrome do T4 e T3 baixo, caracterizada por T4 e T3 baixo e TSH normal, foi encontrada em 29,5%, sem diferença com o tempo de duração da doença, apenas no choque séptico, retornando aos níveis normais na convalescença em ambos os grupos. A síndrome Mista que resulta da combinação de anormalidades foi encontrada em 11,7% dos casos, sem diferença com a duração da doença ou choque séptico. Doença Não Tireoidiana esteve presente nos recém-nascidos a termo com sepse, mais freqüente nos de prolongada duração. Síndrome do T3 baixo foi o padrão mais freqüente, porém sem elevação do T3 reverso; e a síndrome do T4 e T3 baixo só foi encontrada no choque séptico, embora sem relação com o mesmo. / Newborn infants with sepsis present clinical symptoms and laboratory alterations of varying lengths of time and degrees of severity. Neonatal sepsis may harm certain kinds of tissue and change the function of enzymes including Type 1 Deiodinase, which is responsible for the creation of Plasmatic T3 from T4 in peripheral tissues. Additionally, in certain periods of the illness there might be a reduced action of the T4 in tissue levels. These alterations are known as Nonthyroidal Illnesses. Little is known about Nonthyroidal Illnesses regarding these alterations during the neonatal period. The objective of this study was to determine the thyroidal hormone serum levels in full-term newborn infants during sepsis and convalescence, verifying the presence and determining the standards of the Nonthyroidal Illness in short-term sepsis, in prolonged sepsis and septic shock. 28 full-term newborn infants with sepsis were studied, along with 12 full-term newborn infants with prolonged sepsis in excess of eight days, and 15 with septic shock. The newborn infants who had prolonged sepsis were those who presented the greatest weight loss from birth through the start of the illness, 21 days on average, and whose cultures tested positive for bacteria. Nonthyroidal Illness was found in 60.7% of the cases; being most prevalent in newborn infants with prolonged sepsis, amongst whom the prevalence was inversely related to the prolonged time with sepsis. There was no correlation between Nonthyroidal Illness with septic shock. Low T3 syndrome, characterized by low T3, normal TSH and generally increased reverse T3, was found in 58.8% of the cases, with there being no difference in the length of the sepsis. The T3 serum level was lower in sepsis than in convalescence, with there being no difference in the duration of the illness. Elevated reverse T3 was not found. Low T4 and T3 syndrome, characterized by low T3 and T4, normal TSH was found in 29.5% of the cases, with there being no difference with the length of the illness duration and only found in septic shock, returning to normal levels in convalescence in both groups. The Mixed Syndrome, which results from the combination of abnormalities, was found in 11.7% of the cases, and there was no difference regarding length of illness or septic shock. Nonthyroidal Illness was present in full-term newborn infants with sepsis, and was most common in those of prolonged duration sepsis. Low T3 Syndrome was the most common standard. However, in the absence of elevated reverse T3 and T4 and T3 syndrome, it was only found during septic shock; even though it was unrelated to the same.

Recém-nascidos com sepse apresentam sintomas clínicos e alterações laboratoriais por tempo e gravidade variáveis. A sepse neonatal pode comprometer diversos tecidos e modificar a ação das enzimas, incluindo a desiodase tipo 1, responsável pela formação do T3 plasmático a partir do T4 nos tecidos periféricos. Além disso, em certos períodos da doença, pode haver uma ação reduzida do T4 em níveis teciduais. Estas alterações são identificadas como Doença Não Tireoidiana, e pouco se conhece sobre ela no período neonatal. Os objetivos deste estudo foram determinar os níveis séricos dos hormônios tireoidianos em recém-nascidos a termo durante a sepse e a convalescença, verificando a presença da Doença Não Tireoidiana e determinando seus padrões na sepse de curta duração, na sepse prolongada e no choque séptico. Foram estudados 28 recém-nascidos a termo com sepse, 12 com duração prolongada por mais de oito dias e 15 com choque séptico. Os recém-nascidos que tiveram sepse prolongada foram os que apresentaram maior perda de peso desde o nascimento até o início da doença, média de 21 dias, e que tiveram culturas positivas para fungos. Doença Não Tireoidiana foi encontrada em 60,7% dos casos, prevalente nos recém-nascidos com sepse de prolongada duração, dentre os quais a prevalência foi inversamente relacionada ao tempo do prolongamento da sepse. A Doença Não Tireoidiana não apresentou correlação com o choque séptico. A síndrome do T3 baixo, caracterizada por T3 baixo, TSH normal e T3 reverso geralmente aumentado, foi encontrada em 58,8% dos casos, sem diferença com a duração da sepse. O nível sérico de T3 foi mais baixo na sepse do que na convalescença sem diferença com o tempo de duração da doença. Não foi encontrada elevação de T3 reverso. A síndrome do T4 e T3 baixo, caracterizada por T4 e T3 baixo e TSH normal, foi encontrada em 29,5%, sem diferença com o tempo de duração da doença, apenas no choque séptico, retornando aos níveis normais na convalescença em ambos os grupos. A síndrome Mista que resulta da combinação de anormalidades foi encontrada em 11,7% dos casos, sem diferença com a duração da doença ou choque séptico. Doença Não Tireoidiana esteve presente nos recém-nascidos a termo com sepse, mais freqüente nos de prolongada duração. Síndrome do T3 baixo foi o padrão mais freqüente, porém sem elevação do T3 reverso; e a síndrome do T4 e T3 baixo só foi encontrada no choque séptico, embora sem relação com o mesmo. / Newborn infants with sepsis present clinical symptoms and laboratory alterations of varying lengths of time and degrees of severity. Neonatal sepsis may harm certain kinds of tissue and change the function of enzymes including Type 1 Deiodinase, which is responsible for the creation of Plasmatic T3 from T4 in peripheral tissues. Additionally, in certain periods of the illness there might be a reduced action of the T4 in tissue levels. These alterations are known as Nonthyroidal Illnesses. Little is known about Nonthyroidal Illnesses regarding these alterations during the neonatal period. The objective of this study was to determine the thyroidal hormone serum levels in full-term newborn infants during sepsis and convalescence, verifying the presence and determining the standards of the Nonthyroidal Illness in short-term sepsis, in prolonged sepsis and septic shock. 28 full-term newborn infants with sepsis were studied, along with 12 full-term newborn infants with prolonged sepsis in excess of eight days, and 15 with septic shock. The newborn infants who had prolonged sepsis were those who presented the greatest weight loss from birth through the start of the illness, 21 days on average, and whose cultures tested positive for bacteria. Nonthyroidal Illness was found in 60.7% of the cases; being most prevalent in newborn infants with prolonged sepsis, amongst whom the prevalence was inversely related to the prolonged time with sepsis. There was no correlation between Nonthyroidal Illness with septic shock. Low T3 syndrome, characterized by low T3, normal TSH and generally increased reverse T3, was found in 58.8% of the cases, with there being no difference in the length of the sepsis. The T3 serum level was lower in sepsis than in convalescence, with there being no difference in the duration of the illness. Elevated reverse T3 was not found. Low T4 and T3 syndrome, characterized by low T3 and T4, normal TSH was found in 29.5% of the cases, with there being no difference with the length of the illness duration and only found in septic shock, returning to normal levels in convalescence in both groups. The Mixed Syndrome, which results from the combination of abnormalities, was found in 11.7% of the cases, and there was no difference regarding length of illness or septic shock. Nonthyroidal Illness was present in full-term newborn infants with sepsis, and was most common in those of prolonged duration sepsis. Low T3 Syndrome was the most common standard. However, in the absence of elevated reverse T3 and T4 and T3 syndrome, it was only found during septic shock; even though it was unrelated to the same.

Thyroxine (T4), the main secretory hormone of the thyroid gland, is produced on thyroglobulin by thyroid peroxidase (TPO)/hydrogen peroxide/iodide system. The synthesis of T4 by TPO involves two independent steps: iodination of tyrosine and phenolic coupling of the resulting iodotyrosine residues. The prohormone T4 is then converted to its biologically active form T3 by a selenocysteine-containing iodothyronine deiodinase (ID-I), which is present in highest amounts in liver, kidney, thyroid and pituitary. The 5'-deiodination catalyzed by ID-I is a ping-pong, bisubstrate reaction in which the selenol (or selenolate) group of the enzyme (E-SeH or E-Se-) first reacts with thyroxine (T4) to form a selenenyl iodide (E-SeI) intermediate. Subsequent reaction of the selenenyl iodide with an as yet unidentified intracellular cofactor completes the catalytic cycle and regenerates the selenol. Although the deiodination reactions are essential for the function of thyroid gland, the activation of thyroid stimulating hormone (TSH) receptor by auto-antibodies leads to an overproduction of thyroid hormones. In addition, these antibodies stimulate ID-I and probably other deiodinases to produce relatively more amount of T3. Figure 1. Synthesis of thyroid hormones by heme-containing Thyroid Peroxidase(TPO)(Refer PDF File) As these antibodies are not under pituitary feedback control system, there is no negative influence on the thyroid activity and, therefore, the uncontrolled production of thyroid hormones leads to a condition called “hyperthyroidism”. Under these conditions, the overproduction of T4 and T3 can be controlled by specific inhibitors, which either block the thyroid hormone biosynthesis or reduce the conversion of T4 to T3. A unique class of such inhibitors is the thiourea drugs, methimazole (1, MMI), 6-n-propyl-2-thiouracil (3, PTU), and 6-methyl-2-thiouracil (5, MTU). Although these compounds are the most commonly employed drugs in the treatment of hyperthyroidism, the detailed mechanism of their action is still not clear. According to the initially proposed mechanism, these drugs may divert oxidized iodides away from thyroglobulin by forming stable electron donor-acceptor complexes with diiodine, which can effectively reduce the thyroid hormone biosynthesis. It has also been proposed that these drugs may block the thyroid hormone synthesis by coordinating to the metal center of thyroid peroxidase (TPO). After the discovery that the ID-I is responsible for the activation of thyroxine, it has been reported that PTU, but not MMI, reacts with the selenenyl iodide intermediate (E-SeI) of ID-I to form a selenenyl sulfide as a dead end product, thereby blocking the conversion of T4 to T3 during the monodeiodination reaction. The mechanism of anti-thyroid activity is further complicated by the fact that the gold-containing drugs such as gold thioglucose (GTG) inhibit the deiodinase activity by reacting with the selenol group of the native enzyme. Recently, the selenium analogues 2 (MSeI), 4 (PSeU) and 6 (MSeU) attracted considerable attention because these compounds are expected to be more nucleophilic than their sulfur analogues and the formation of an –Se–Se– bond may occur more readily than the formation of an –Se–S– bond with the ID-I enzyme. However, the data derived from the inhibition of TPO by selenium compounds show that these compounds may inhibit the TPO activity by a different mechanism. Therefore, further studies are required to understand the mechanism by which the selenium compounds exert their inhibitory action. Our initial attempts to isolate 2 were unsuccessful and the final stable compound in the synthesis was characterized to be the diselenide (8). In view of the current interest in anti-thyroid drugs and their mechanism, we extended our approach to the synthesis and biological activities of a number of sulfur and selenium derivatives bearing the methimazole pharmacophore. The thesis consists of five chapters. The first chapter gives a general introduction to thyroid hormone synthesis and anti-thyroid drugs. In this chapter, the biosynthesis of thyroid hormones, structure and function of heme peroxidases, activation of thyroid hormones by iodothyronine deiodinases are discussed. This chapter also gives a brief introduction to some common problems associated with the thyroid gland, with a particular emphasis on hyperthyroidism. The structure and activity of some commonly used anti-thyroid drugs and the role of selenium in thyroid are discussed. The literature references related to this work are provided at the end of the chapter. The second chapter deals with the synthesis and characterization of the selenium analogue (MSeI) of anti-thyroid drug methimazole and a series of organoselenium compounds bearing N-methylimidazole pharmacophore are described. The clinically employed anti-thyroid drug, methimazole (MMI), exists predominantly in its thione form, which is responsible for its anti-thyroidal activity. The selenium analogue MSeI, on the other hand, is not stable in air and spontaneously oxidizes to the corresponding diselenide (MSeIox). Experimental and theoretical studies on MSeI suggest that this compound exists in a zwitterionic form in which the selenium atom carries a large negative charge. The structure of MSeI was studied in solution by NMR spectroscopy and the 77Se NMR chemical shift shows a large upfield shift (-5 ppm) in the signal as compared to the true selones for which the signals normally appear in the downfield range (500-2500 ppm). This confirms that MSeI exists predominantly in its zwitterionic form in solution. Our theoretical studies show that the formation of the diselenide (MSeIox) from selenol tautomer is energetically more favored than the formation of the disulfide (MMIox) from the thiol tautomer of MMI. This study also shows that the replacement of the N−H group in MSeI by an N-methyl or N-benzyl substituent does not affect the nature of C−Se bond. In the third chapter, the inhibition of lactoperoxidase-catalyzed oxidation of ABTS by anti-thyroid drugs and related derivatives is described. The commonly used anti-thyroid agent methemazole (MMI) inhibits the lactoperoxidase (LPO) with an IC50 value of 7.0 µM which is much lower than that of the other two anti-thyroid drugs, PTU and MTU. The selenium analogue of methimazole (MSeI) also inhibits LPO with an IC50 value of 16.4 µM, which is about 4-5 times lower than that of PTU and MTU. In contrast to thiones and selones, the S- and Se-protected compounds do not show any noticeable inhibition under identical experimental conditions. While the inhibition of LPO by MMI cannot be reversed by increasing the hydrogen peroxide concentration, the inhibition by MSeI can be completely reversed by increasing the peroxide concentration. Some of the selenium compounds in the present study show interesting anti-oxidant activity in addition to their inhibition propertities. In the presence of glutathione (GSH), MSeI constitutes a redox cycle involving a catalytic reduction of H2O2 and thereby mimics the glutathione peroxidase (GPx) activity in vitro. These studies reveal that the degradation of the intracellular H2O2 by the selenium analogues of anti-thyroid drugs may be beneficial to the thyroid gland as these compounds may act as antioxidants and protect thyroid cells from oxidative damage. Because the drugs with an action essentially on H2O2 can reversibly inhibit thyroid peroxidase, such drugs with a more controlled action could be of great importance in the treatment of hyperthyroidism. Figure 2. (A) Concentration-inhibition curves for the inhibition of LPO-catalyzed oxidation of ABTS by MMI and MSeI at pH 7.0 and 30 °C. (B) Plot of initial rates (vo) for the LPO-catalyzed oxidation of ABTS vs concentration of H2O2. (a) Control activity, (b) 40 µM of MSeI, (c) 40 µM of MSeIox, (d) 80 µM of PTU, (e) 80 µM of MTU, (f) 40 µM of MMI. The incubation mixture contained 6.5 nM LPO, 1.4 mM ABTS, 0.067 M phosphatebuffer(pH7).(Refer PDF File) The fourth chapter describes the inhibition of lactoperoxidase (LPO)-catalyzed iodination of L-tyrosine by anti-thyroid drug methimazole (MMI) and its selenium analogue (MSeI). These inhibition studies show that MSeI inhibits LPO with an IC50 value of 12.4 µM, which is higher than that of MMI (5.2 µM). The effect of hydrogen peroxide on the inhibition of LPO by MMI and MSeI is also discussed. These studies also reveal that the inhibition of LPO-catalyzed iodination by MSeI can be completely reversed by increasing the peroxide concentration. On the other hand, the inhibition by MMI cannot be reversed by increasing the concentration of the peroxide. To under stand the nature of compounds formed in the reactions between anti-thyroid drugs and iodine, the reactions of MSeI with molecular iodine is described. MSeI reacts with I2 to produce novel ionic diselenides, and the nature of the species formed in this reaction appears to be solvent dependent. The formation of ionic species (mono and dications) in the reaction is confirmed by UV-Vis, FT-IR and FT-Raman spectroscopic investigations and single crystal x-ray studies. The major conclusion drawn from this study is that MSeI reacts with iodine, even in its oxidized form, to form ionic diselenides containing iodide or polyiodide anions, which might be possible intermediates in the inhibition of thyroid hormones. Dication X-ray crystal structure of the monocation X-ray crystal structure of the dication In the fifth chapter, the synthesis and characterization of several thiones and selones having N,N-disubstituted imidazole moiety are described. Experimental and theoretical studies were performed on a number of selones, which suggest that these compounds exist as zwitterions in which the selenium atom carries a large negative charge. The structures of selones were studied in solution by NMR spectroscopy and the 77Se NMR chemical shifts for the selones show large upfield shifts in the signals, confirming the zwitterionic structure of the selones in solution. The thermal isomerization of some S- and Se-substituted methyl and benzyl imidazole derivatives to produce the thermodynamically more stable N-substituted derivatives is described. A structure–activity correlation was attempted on the inhibition of LPO-catalyzed oxidation and iodination reactions by several thiouracil compounds, which indicates that the presence of an n-propyl group in PTU is important for an efficient inhibition. In contrast to the S- and Se-substituted derivatives, the selones produced by thermal isomerization exhibited efficient inhibition, indicating the importance of reactive selone (zwitterionic) moiety in the inhibition. The inhibition data on another well-known anti-thyroid agent carbimazole (CBZ) support the assumption that CBZ acts as a prodrug, requiring a conversion to methimazole (MMI) for its inhibitory action on thyroid peroxidase. (Refer pdf file/original thesis)