High levels of DNA polymerase ß mRNA corresponding with the high activity in Graves' thyroid tissue.

INTRODUCTION: High DNA polymerase ß activity has been observed in the thyroid tissue of patients with Graves' disease (Nagasaka et al. in Metabolism 37:1051-1054, 1988). This fact aroused our interest in whether the alteration of DNA polymerase ß activity depends on DNA polymerase ß (DNA poly ß) mRNA levels, which may be modulated by thyroid-stimulating hormone (TSH) or thyroid-stimulating substances, i.e. TSH receptor antibody (TRAb). RESULT: Addition of TSH or TRAb to primary cultures of Graves' disease thyroid cells for 4 h led to no increase in DNA poly ß mRNA levels. In contrast, thyroid hormone synthesizing enzyme, peroxidase, mRNA levels increased fivefold after coculture with TSH and TRAb, even though DNA poly ß activity and mRNA levels are already significantly higher in Graves' disease thyroid tissues, compared with normal thyroid tissue. DISCUSSION: These results indicate that DNA poly ß expression in Graves' disease thyroid cells may be maximally activated or plateau in response to thyroid-stimulating immunoglobulins, or that the activation of to poly ß expression may occur via pathways other than the G protein and cyclic AMP system.

Reduced DNASE1 gene expression in thyroid autoimmunity.

The enzyme DNASE1 plays an important role in the hydrolysis of double-stranded DNA and might be related to autoimmunity. Therefore, the authors hypothesized that patients with autoimmune thyroid disease show a reduced expression of the DNASE1 gene. DNASE1 mRNA was quantitatively analyzed in 20 patients (10 with Hashimoto's thyroiditis and 10 with Graves' disease) and 20 age- and sex-matched healthy controls by real-time reverse transcription PCR in a lightcycler using SYBR-Green-format. For relative quantification, the mRNA ratio of the DNASE1 gene to the house keeping gene ß2-MICROGLOBULIN was used. The house keeping gene was proved not to be regulated by autoimmune thyroid disease. The interassay coefficient of variation for patients and controls was 22.2% and 15.6%, respectively, suggesting good reproducibility of measurements. The mean expression of the DNASE1 mRNA in patients was 0.52±0.22 (range 0.18-0.99) and in controls 0.95±0.22 (0.66-1.43). The expression level of the DNASE1 gene was strongly decreased in patients, amounting only 54.7% of that in controls (p<0.001). The lowered expression level in patients was not related to age or sex. This study demonstrated for the first time a downregulation of the DNASE1 mRNA expression in patients with autoimmune thyroid disease. This might result in degrading less DNA from dying cells, thereby promoting the development of thyroid autoimmunity.

Association of polymorphisms in DNMT1, DNMT3A, DNMT3B, MTHFR and MTRR genes with global DNA methylation levels and prognosis of autoimmune thyroid disease.

To clarify the association between factors regulating DNA methylation and the prognosis of autoimmune thyroid diseases (AITDs), we genotyped single nucleotide polymorphisms in genes encoding DNA methyltransferase 1 (DNMT1), DNMT3A, DNMT3B, methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR), which are enzymes essential for DNA methylation. Subjects for this study included 125 patients with Hashimoto's disease (HD), including 48 patients with severe HD and 49 patients with mild HD; 176 patients with Graves' disease (GD), including 79 patients with intractable GD and 47 patients with GD in remission; and 83 healthy volunteers (control subjects). The DNMT1+32204GG genotype was more frequent in patients with intractable GD than in patients with GD in remission. Genomic DNA showed significantly lower levels of global methylation in individuals with the DNMT1+32204GG genotype than in those with the AA genotype. The MTRR+66AA genotype was observed to be more frequent in patients with severe HD than in those with mild HD. The DNMT1+14395A/G, DNMT3B-579G/T, MTHFR+677C/T and +1298A/C polymorphisms were not correlated with the development or prognosis of AITD. Our study indicates that the DNMT1+32204GG genotype correlates with DNA hypomethylation and with the intractability of GD, and that the MTRR+66AA genotype may correlate with the severity of HD.

Thr92Ala polymorphism of human type 2 deiodinase gene (hD2) affects the development of Graves' disease, treatment efficiency, and rate of remission.

Clinical symptoms vary in thyrotoxicosis, and severity of these depends on many factors. Over the last years, impact of genetic factors upon the development and clinical significance of thyrotoxic symptoms became evident. It is known that a production of T3 in various tissues is limited by deiodinase 2 (D2). Recent studies revealed that certain single nucleotide polymorphisms (including threonine (Thr) to alanine (Ala) replacement in D2 gene codon 92, D2 Thr92Ala) affect T3 levels in tissues and in serum. Individuals with Ala92Ala genotype have lower D2 activity in tissues, compared with that in individuals with other genotypes. In our study, we have assessed an association of D2 Thr92Ala polymorphism with (1) frequency of disease development, (2) severity of clinical symptoms of thyrotoxicosis, and (3) rate of remissions, in Graves' disease patients.

Association study between methylenetetrahydrofolate reductase gene polymorphisms and Graves' disease.

5,10-Methylenetetrahydrofolate reductase (MTHFR) catalyzes the metabolism of folate and nucleotides, which are essential for DNA synthesis and methylation. It is highly polymorphic, and its variant genotypes result in lower enzymatic activity and higher plasma homocysteine. Previous studies have provided evidence that a high prevalence of MTHFR gene polymorphisms is frequently detected in patients with autoimmune disease, suggesting a novel genetic association with autoimmune disorders. However, the genetic association between MTHFR and Graves' disease (GD), one of the most common autoimmune diseases, has not been studied. Here, we designed a clinic-based case-control study including 199 GD cases and 235 healthy controls to examine the associations between three common MTHFR polymorphisms (i.e., C677T, A1298C, and G1793A) and GD. Surprisingly, logistic regression analysis shows MTHFR 677CT + TT genotypes are associated with an approximately 42% reduction in the risk of GD in women (adjusted OR = 0.58, 95% CI = 0.3-0.9), compared to the CC genotype, indicating a significant protective effect of 677CT + TT genotypes. Our result provides epidemiological evidence that MTHFR mutation (C677T) protects women from GD. The protective effect, possibly obtained by influencing DNA methylation, should be confirmed in a large number of cohorts.

A long-term follow-up of serum myeloperoxidase antineutrophil cytoplasmic antibodies (MPO-ANCA) in patients with Graves disease treated with propylthiouracil.

Propylthiouracil (PTU) is known to induce myeloperoxidase antineutrophil cytoplasmic antibodies (MPO-ANCA) in patients with Graves disease (GD). Previously, we showed that serum MPO-ANCA were frequently seen in patients with GD treated with PTU. In this study, we analyzed 13 patients with positive MPO-ANCA examining a long-term clinical consequence of these patients as well as antibody titers during 5.6 +/- 3.0 years. PTU therapy was continued in 8 patients and discontinued in 5 patients. Antibody titers decreased in 7 of 8 patients who discontinued PTU therapy but remained positive in 5 patients 5 years after PTU withdrawal. The initial MPO-ANCA levels were significantly higher in those antibody titers remained positive for longer than 5 years (n=5) than in those titers turned to be negative within 5 years after PTU withdrawal (n=3) (203 +/- 256 EU and 22 +/- 2 EU, respectively, P=0.04), but there were no significant differences in age, gender, duration of PTU therapy or dosage of PTU. Among 5 patients who continued PTU therapy, 2 patients with initially low MPO-ANCA titers turned to having negative antibody. No patients had new symptoms or signs of vasculitis throughout the follow-up periods. The long-term follow-up study suggests that higher MPO-ANCA levels remain positive for years after PTU withdrawal but are rarely associated with vasculitis.

Correlation between plasma thyroid hormones and liver enzymes level in thyrotoxic cases and controls in Hazara Division.

BACKGROUND: Thyrotoxicosis is defined as increased synthesis and secretion of thyroid hormones; when associated with defused goitre it is known as grave's disease. Hepatic changes in thyrotoxiosis are fatty changes, cirrhosis and centrilobular necrosis, resulting in elevated serum levels of liver specific enzymes ALT, AST and ALK. Objective of the study was to determine a correlation between plasma levels of 3 liver enzymes, and thyroid hormones in thyrotoxic cases, and matched controls in Hazara Division. METHODS: This study was conducted at Ayub Teaching Hospital Abbottabad from 1st July 2004 to 30th June 2007. The controls were selected from staff and students of Ayub Medial College Abbottabad. Fifty cases of thyrotoxicosis and 50 controls were included in this study by convenience sampling. Their thyroid profile for T3, T4, TSH and liver enzymes profile for ALT, AST, ALK were determined and analysed for a correlation. RESULTS: Mean T3 of cases was 5.23 +/- 1.95 and of controls 1.95 +/- 0.35. Mean T4 of case was 248.88 +/- 62.75, and of controls was 113.40 +/- 19.01. Mean TSH of cases was 0.07 +/- 0.25 and that of controls was 2.24 +/- 0.80. Mean ALT of cases was 38.78 +/- 4.96 while that of controls was 23.98 +/- 5.27. Mean AST of cases was 39.76 +/- 5.05 and of controls was 26.52 +/- 4.49. Mean ALK of cases was 299.68 +/- 22.32 and of controls was 155.10 +/- 37.07. CONCLUSION: Although liver enzymes levels were slightly elevated in many thyrotoxic cases, no significant correlation emerged between any of the thyroid hormones and any of the liver enzymes, either in cases or controls.

Polymorphisms of DNA base-excision repair genes APE/Ref-1 and XRCC1 are not associated with the risk for Graves' disease.

Oxidative stress has been implicated in etiopathogenesis of Graves' disease (GD). Increased lipid peroxidation and oxidative DNA damage have been found in GD patients. Oxidative DNA damage is mainly repaired by the base-excision repair (BER) pathway. Polymorphisms in DNA-repair genes have been associated with the increased risk of various diseases and could also be related to the etiology of GD. Therefore, we conducted a study including 197 patients with GD and age- and sex-matched 303 healthy subjects to examine the role of single-nucleotide polymorphisms of BER genes, APE/Ref-1 (codon 148) and XRCC1 (codons 194 and 399) as a risk factor for GD. These polymorphisms were determined by quantitative real-time PCR and melting curve analysis using LightCycler. No significant association was observed between the variant alleles of APE/Ref-1 codon 148 [odds ratio (OR) = 0.89, 95% confidence interval (CI) = 0.69-1.17], XRCC1 codon 194 (OR = 1.24, 95% CI = 0.79-1.94), and XRCC1 codon 399 (OR = 1.12, 95% CI = 0.86-1.46) and GD. These preliminary results suggest that APE/Ref-1 (codon 148) and XRCC1 (codons 194 and 399) polymorphisms are not significant risk factors for developing GD.

Association between genetic polymorphisms of SLCO1B1 and susceptibility to methimazole-induced liver injury.

Methimazole (MMI) has been used in the therapy of Grave's disease (GD) since 1954, and drug-induced liver injury (DILI) is one of the most deleterious side effects. Genetic polymorphisms of drug-metabolizing enzymes and drug transporters have been associated with drug-induced hepatotoxicity in many cases. The aim of this study was to investigate genetic susceptibility of the drug-metabolizing enzymes and drug transporters to the MMI-DILI. A total of 44 GD patients with MMI-DILI and 118 GD patients without MMI-DILI development were included in the study. Thirty-three single nucleotide polymorphisms (SNPs) in twenty candidate genes were genotyped. We found that rs12422149 of SLCO2B1, rs2032582_AT of ABCB1, rs2306283 of SLCO1B1 and rs4148323 of UGT1A1 exhibited a significant association with MMI-DILI; however, no significant difference existed after Bonferroni correction. Haplotype analysis showed that the frequency of SLCO1B1*1a (388A521T) was significantly higher in MMI-DILI cases than that in the control group (OR = 2.21, 95% CI = 1.11-4.39, P = 0.023), while the frequency of SLCO1B1*1b (388G521T) was significantly higher in the control group (OR = 0.52, 95% CI = 0.29-0.93, P = 0.028). These results suggested that genetic polymorphisms of SLCO1B1 were associated with susceptibility to MMI-DILI. The genetic polymorphism of SLCO1B1 may be important predisposing factors for MMI-induced hepatotoxicity.

Prevalence of pancreatic autoantibodies in non-diabetic patients with autoimmune thyroid disease and its relation to insulin secretion and glucose tolerance.

OBJECTIVE: We evaluated the prevalence of glutamic acid decarboxylase (GADA) and tyrosine phosphatase-protein antibodies (IA2A), their titers and their relation to first phase insulin response (FPIR) and glucose tolerance in autoimmune thyroid diseases (ATDs) patients. SUBJECTS AND METHODS: Graves' disease (GD; n = 181) and Hashimoto's thyroiditis (HT; n = 143) patients in addition to healthy controls (n = 93) were studied. Secondly, FPIR and oral glucose tolerance tests (OGTT) were performed in 11 anti-pancreatic islet-cell (+) and in 20 anti-pancreatic-cell (-) patients. RESULTS: There was a non significant trend for higher prevalence of GADA positivity in GD vs HT (7.2% vs 2% p = 0.06), but the GADA titers were higher in HT. We also did not find a significant difference in IA2 prevalence (0.7% vs 0.0%) between these two groups or compared to the control group. In the subsequent analysis, low FPIR was found in 10% of these patients but without statistical difference for OGTT between pancreatic antibody-positive and -negative patients. CONCLUSION: A trend for greater prevalence of GADA was observed for GD patients than for HT or control. However, the titers of these autoantibodies were higher in HT patients, but there was no significant relation to insulin secretion and glucose tolerance at that moment and stage of autoimmune diseases.

Expression of alpha-amylase isozymes in human thyroid tissues.

Expression of alpha-amylase genes in thyroid tissues was studied by assaying the total amylase activity as well as by using immunohistochemical and Northern blot analysis. The amylase genes expressed were determined by a combination of the polymerase chain reaction (PCR) and blot analysis using synthetic probes specific for the three known amylase isozyme complementary DNAs. The samples consisted of tissues from 18 human thyroid carcinomas (11 well-differentiated carcinomas, 2 poorly differentiated carcinomas, 1 anaplastic carcinoma, and 4 medullary carcinomas) and 9 specimens of nonmalignant thyroid tissue (2 were from nontumorous regions of resected glands and 7 were thyroid tissue from a patient with Graves' disease). Salivary-type amylase was expressed at a relatively high level in nonmalignant thyroid tissue and well-differentiated carcinoma and could be detected by Northern blot analysis. In poorly differentiated carcinoma, it was detected only by the PCR, while in anaplastic or medullary carcinoma, it was not detected even by the PCR. Thus, the expression of salivary-type amylase was characteristic of well-differentiated follicular cells. These observations suggest that salivary-type amylase expression may be a marker for identifying the histogenesis and stage of differentiation of thyroid cancer. In addition, the AMY2B gene product was detected in all different types of cells examined, although its expression was only detectable by the PCR. Pancreatic type amylase was not detected in any of the samples.

[Cytofluorometric analysis of chosen markers of apoptosis CD95/CD95L (Fas/FasL) in thyroid tissues from young patients with Graves' disease and Hashimoto's thyroiditis]. / Cytofluorymetryczna analiza wybranych markerów apoptozy Fas/FasL (CD95/CD95L) w tkance gruczolu tarczowego u mlodocianych pacjentów z choroba Gravesa-Basedowa oraz zapaleniem tarczycy typu Hashimoto.

BACKGROUND: Apoptosis, one of the forms of programmed cell death, is a physiologic process of cell death that is central to normal development and occurs in response to a variety of physiologic and pathophysiologic stimuli. In the thyroid, abnormal apoptotic activity may be involved in a variety of diseases such as Hashimoto thyroiditis and Graves disease. The aim of this study was to estimate the expression of chosen apoptotic molecules CD95 (Fas) and CD95L (FasL) on the surface of thyroid follicular cells in application of mouse monoclonal antibodies #64 which recognized B antigen regions of thyroid peroxidase (TPO) and infiltrating inflammatory cells. MATERIAL AND METHODS: The investigation was performed on thyroid cells isolated from surgically treated thyroid tissues of 15 patients with Graves' disease (GD), 15 patients with a nontoxic multinodular goiter (NTMG) and 15 aspirates obtained by FNAB from patients with Hashimoto thyroiditis (HT). The thyrocytes were identified by an indirect method: in the first stage we added mouse monoclonal autoantibodies specific for TPO (mAb #64) regions and in the second stage we conjugated this complex with rabbit anti-mouse antibodies IgG (Fab')2 with FITC. In the next step the cellular suspension was completed with suitably well-chosen two-colour monoclonal antibodies marked (PE or PerCP) (Becton Dickinson) directed against suitable apoptotic (Fas/FasL) molecules. All investigations were performed by flow cytometry using Coulter EPICS XL apparatus. RESULTS: The percentages of thyroid cells were estimated with expression of region B antigenic TPO in reference to individual apoptotic molecules. The analysis of Fas and FasL expression in thyroid tissues revealed significantly increased percentage of intrathyroidal T cells with CD95+ (p<0.005, p<0.001), CD95L+ (p<0.02, p<0.01) and both CD95/CD95L (ns, p<0.05) expression in comparison to percentages of T cells in patients with HT and NTMG. In addition, on the surface of thyroid follicular cells in patients with GD (p<0.01, p<0.01) and NTMG (p<0.001, p<0.004) we observed a lower percentage of thyrocytes with CD95 and CD95L molecules than in cases with HT. The expression of both apoptotic molecules on thyroid cells was higher (18%) in patients with HT in comparison to the percentages of positive cells in patients with GD (p<0.02, p<0.002) and NTMG, 8% and 1%, respectively. CONCLUSIONS: We conclude that alterations in the expression of death receptors and their ligands on the surface of thyroid follicular cells may play a role in the regulation of apoptosis in thyroid autoimmune disorders.

Paraoxonase and arylesterase levels in autoimmune thyroid diseases.

OBJECTIVE: The aim of this study was to evaluate serum paraoxonase-1 (PON1) activity and its association with oxidative stress in autoimmune thyroid disease (AITD). METHODS: A total of 50 patients with AITD, including 25 with Hashimoto's thyroiditis and 25 with Graves' disease were enrolled. The control group comprised 27 healthy subjects. Blood samples were obtained in the euthyroid period and 3 months after initiation of medical treatment. Serum samples from patients with AITD and the healthy control group were analyzed for basal PON1, salt-stimulated PON1, and arylesterase (ARE) activities, along with lipid hydroperoxide (LOOH) and total free sulfhydryl (-SH) levels. RESULTS: Serum PON1 activities and -SH levels were significantly lower (P < 0.001, for each), whereas LOOH levels were significantly higher (P < 0.001, for each) in patients with AITD, compared to the control group. We observed no significant differences in ARE levels between the patient and healthy control groups (P > 0.05). PON1 activity was positively correlated with -SH (r = 0.522, P < 0.001) and negatively correlated with LOOH (r = -0.487, P < 0.001). PON1 phenotype distribution of the subjects was not significantly different among the three groups (P = 0.961). CONCLUSIONS: Serum PON1 activity is decreased in patients with AITD, and correlated positively with -SH, a well-known antioxidant, and negatively with LOOH, an index of lipid oxidation.

Application of mouse monoclonal antibodies for identification of antigen regions of human thyroid peroxidase in adolescents with Graves' disease and non-toxic multinodular goiter by flow cytometry.

Thyroid peroxidase (TPO) is the major thyroid autoantigen recognized by serum autoantibodies from patients with Graves' disease (GD) or Hashimoto's thyroiditis directed to two immunodominant conformational regions termed A and B. The epitopes of human TPO have been defined using a panel of mouse monoclonal antibodies (mAbs). The aim of this study was to estimate the expression of chosen surface antigen regions of TPO (1, 18, 30, 64 epitopes) on thyroid cells in 15 patients with non-toxic multinodular goiter (NTMG) and 15 patients with GD. The thyrocytes were identified by indirect method: in the first stage we added mouse monoclonal autoantibodies specific for TPO regions and in the second stage we conjugated this complex with rabbit anti-mouse antibodies IgG (Fab')(2) with FITC. All investigations were performed by flow cytometry using Coulter EPICS XL apparatus. The percentages of thyrocytes with expression of epitopes 1, 18, 30, 64 TPO were measured in relation to the respective anti-TPO concentrations: 50-1600 microg/ml. The analysis of epitopes located in immunodominant regions (IDR) of TPO revealed higher percentages of thyrocytes in cases with GD in comparison to NTNG. The most predominant difference was observed for mAb 64 epitope (48 vs 7%, p < 0.019; 39 vs 5%, p < 0.017) at the concentration of 100-200 microg/ml mAbs. The expression of 18 epitope on thyrocytes was also statistically higher in Graves' patients than in the NTMG (14 vs 6%, p < 0.025) at concentration of 400 microg/ml mAbs. However, this expression was much less pronounced. In all the cases, the percentages of thyrocytes with epitopes 1 and 30 were in low detection (8-15% of positive cells). In conclusion, our findings suggest that the elevated expression of TPO epitopes 18 and 64 in young patients with thyroid autoimmune diseases increase stimulation and activation of thyroid cells during inflammatory reaction within the thyroid gland. In addition, predominant expression of 64 TPO epitope that recognizes B domain in GD patients could be a useful marker of the immune process in the thyroid gland.

[Cytofluorymetric evaluation of antigen regions of human thyroid peroxidase in patients with Graves' disease and non-toxic multinodular goiter using mouse monoclonal antibodies]. / Ocena cytofluorymetryczna wybranych regionów antygenowych ludzkiej tyreoperoksydazy u pacjentów z choroba Gravesa-Basedowa oraz z wolem wieloguzkowym nietoksycznym z zastosowaniem mysich przeciwcial monoklonalnych.

The aim of this study was to estimate expression of surface antigen regions of TPO (thyroid peroxidase: #1, #18, #30, #64 epitopes) on thyroid cells in 15 patients with non-toxic multinodular goiter (NTMG) and 15 patients with Graves' disease (GD). The thyrocytes were identified by indirect method: in first stage we added mouse monoclonal autoantibodies specific for TPO regions and in second stage we conjugated this complex with rabbit anti-mouse antibodies IgG (Fab')2 with FITC. All investigations were performed by flow cytometry using apparatus Coulter EPICS XL. The percentages of thyroid cells with expression of antigen regions of TPO 1, 18, 30, 64 were measured in relationship to the responsible anti-TPO concentrations: 50, 100, 200, 400, 800, 1600 microg/ml. The analysis of the expression of epitope #64 TPO revealed insignificantly increased percentages of thyroid cells in patients with GD (73% vs 45%, ns) in comparison to NTMG at anti-TPO antibody concentration of 1600 microg/ml. In addition, we observed that reduction concentration of anti-TPO antibodies leads to the decreased percentage of thyroid cells with antigen region #64 expression. In patients with GD percentage of this cells was significantly higher (48% vs 7% p<0.019, 29% vs 56% p<0.05) in compared to the percentage of thyroid cells from patients with NTMG at concentration of 200-800 microg/ml anti-TPO antibodies. Analysis of epitopes #1 and #18 shown higher percentage of thyroid cells in GD (25% vs 20%, ns for #1 epitope) and (25% vs 13%, ns for #18 epitope) in comparison to the patients with NTMG at concentration 1600 microg/ml of anti-TPO antibodies. The percentages of thyrocytes with epitopes #1 and #18 were decreased in relation to the reduction of anti-TPO concentrations. However, in all our patients epitope #30 TPO was found only in 8% thyroid cells. We conclude that in young patients thyroid immune and nonimmune diseases predispose to elevated expression of TPO epitopes (#1, #18, #64) which suggested increase stimulation and activation of thyroid cells during inflammatory reaction within thyroid gland. Furthermore, dominance expression of #64 TPO epitope in Graves' patients which recognized B domain could be a useful marker of activity of immune process in concentration between 200-800 microg/ml of TPO antibodies.

Relationship between immunological structure and biochemical properties of human thyroid peroxidase.

Although the primary structure of human thyroid peroxidase (hTPO) has been recently deciphered, little is known about its spatial conformation. Such information is of crucial importance in any attempt to relate the structure with the function of hTPO. To probe the antigenic surface of hTPO and to correlate its immunological structure to its biochemical properties, we used 13 monoclonal antibodies (mAb) displaying various affinity for hTPO. Criss-cross experiments showed 7 clusters of reactivity which were interpreted as reflecting 7 epitopes on the surface of the hTPO molecule. Extending our analysis to partial and nonsymmetrical cross-reactivities, these epitopes were shown to be localized in 4 antigenic domains of the hTPO. We further investigated the nature of these 7 hTPO epitopes by testing mAb binding to peroxidases from various origins and chemically modified hTPO; 3 epitopes were shown to be evolutionary conserved, and 5 resistant to reduction and denaturation. We also analyzed the role of the hTPO epitopes in the enzymatic activity and autoimmune targeting of the molecule. Nine epitopes were shown to be localized at the vicinity of both catalytic sites as the binding of their respective mAb modulated the enzyme activity. Autoantibodies from patients presenting with autoimmune thyroid disorders were essentially directed to epitopes similar or adjacent to those recognized by 8 of the 13 mAb and present on only 2 antigenic domains of hTPO. Taken together these data allowed us to propose a tentative map of the surface of the hTPO molecule which associates its epitopic structure with its biochemical functions.

Deficiency of superoxide dismutase in endemic goiter tissue.

Superoxide dismutase (SOD) activity and its concentration were measured in thyroid tissues obtained from patients with Graves' disease, Hashimoto's thyroiditis, differentiated thyroid cancer, and endemic goiter (before and after iodine supplementation) as well as in normal thyroid tissue (paranodular tissue) from patients with follicular adenomas. SOD activity was measured by pyrogallol assay in ethanol-chloroform extracts of the thyroid homogenates. The SOD concentration in the thyroid extract was measured as immunoreactive SOD by electroimmunoassay. Endemic goiter tissues (n = 10) contained significantly lower SOD activity [mean, 1.9 +/- 1.9 (+/- SD) vs. 7.5 +/- 3.9 ng purified SOD/micrograms DNA; P less than 0.02] and concentration (mean, 0.2 +/- 0.1 vs. 0.8 +/- 0.5 ng SOD/microgram DNA; P less than 0.01) compared with those of normal tissues. No other pathological thyroid tissues had such consistently low SOD levels. Lactate dehydrogenase activity, a marker of cytosolic enzyme, was not lower in endemic goiter tissues than in normal tissues, suggesting that both tissues possessed functioning cells capable of producing cytosolic enzyme. Thyroid tissue from endemic goiter patients previously treated with iodized oil injection also had low SOD activity and concentration. Western blot analysis indicated that SOD protein in the endemic goiter tissue did not differ from that in normal thyroid tissue. We conclude that there is deficiency of cytosolic SOD in endemic goiter tissue. Since the deficiency of cytosolic SOD causes more prolonged exposure to oxygen free radicals, the decrease in SOD might contribute to the degenerative changes frequently found in these tissues.

Characterization, by molecular cloning, of smaller forms of thyroid peroxidase messenger ribonucleic acid in human thyroid cells as alternatively spliced transcripts.

The mRNA for human thyroid peroxidase (hTPO) is 3.1 kilobases (kb) in size, coding for a protein of 933 amino acids. However, there is controversy as to whether other hTPO mRNA transcripts exist in thyroid cells. There is one report of the existence of 2.1- and 1.7-kb transcripts (hTPO mRNA species I and II), representing up to half of the hTPO mRNA in TSH-stimulated human thyroid cells. On the other hand, numerous other studies have only observed 3.1-kb hTPO mRNA transcripts. The nature of these putative 2.1- and 1.7-kb mRNA transcripts, if present, is unknown. We now report the isolation and characterization of two smaller hTPO cDNA species, designated hTPO cDNA I and II. cDNA I and II are 1753 and 1044 basepairs (bp) in size, with open reading frames of only 225 and 174 amino acids, respectively. Comparison of the nucleotide sequences of cDNA I and II with available hTPO genomic sequence reveals that cDNA I consists of exons 1-6 (654 bp) and the 5'-end of intron 6 (1099 bp); cDNA II contains exons 1-5 (486 bp) and an unidentified DNA tract of 558 bp further down-stream, presumably an intron. Confirmation that cDNA I and II correspond to mRNA transcripts I and II, respectively, was provided by Northern blot analysis with DNA probes specific for cDNA I and II. hTPO mRNA transcripts I and II are present in TSH-stimulated and TSH-deprived human thyroid cells in culture as well as in intact thyroid tissue. In summary, the present data 1) demonstrate directly that hTPO mRNA transcripts I and II exist in human thyroid cells, 2) explain the discrepant data in the literature regarding their existence, 3) elucidate their molecular structure, 4) indicate that they are generated by alternative splicing, and 5) demonstrate that hTPO mRNA I and II exist in the thyroid gland in vivo as well as in thyroid cells in culture.

Thyroid peroxidase activity-inhibiting immunoglobulins in patients with autoimmune thyroid disease.

The thyroid microsomal antibody (M-Ab) has been found to be an antibody against thyroid peroxidase (TPO), and such antibodies have been reported not only to bind TPO but also to directly inhibit TPO activity. In this study we investigated the relationship between TPO activity-inhibiting immunoglobulin (TPII) and thyroid function in 55 untreated patients with hyperthyroidism due to Graves' disease and 35 untreated patients with Hashimoto's disease. TPO partially purified from the microsomal fraction of Graves' thyroid tissue by Sephacryl S-300 gel filtration was incubated with immunoglobulin (Ig) fractions of serum prepared by precipitation with 15% polyethylene glycol. At the end of incubation, TPO activity was measured by a guaiacol assay. The TPII level was expressed as the TPII index, defined as the inhibition of TPO activity by patient Ig divided by inhibition produced by a known positive Ig. We also measured serum free T4, free T3, and TSH concentrations and anti-M-Ab titers, the latter by a microenzyme-linked immunosorbent assay. When a positive TPII index was defined as more than the mean + 2 SD of the TPII index (0.38) for 15 normal subjects, 13 patients with Graves' disease and 14 patients with Hashimoto's disease had positive TPII index values. There was a positive correlation between the TPII index values and the M-Ab titers in patients with either Graves' disease (r = 0.38; P less than 0.01) or Hashimoto's disease (r = 0.52; P less than 0.01). The mean TPII index in patients with Hashimoto's disease was significantly higher than that in patients with Graves' disease [0.38 +/- 0.42 (+/- SD) vs. 0.19 +/- 0.41; P less than 0.05]. The slope of the regression line between the TPII index values and the M-Ab titers for patients with Hashimoto's disease was steeper than that for patients with Graves' disease. The mean serum free T4 concentration was significantly lower in those patients with Hashimoto's disease who had positive TPII index values than in those with negative TPII index values (14.0 +/- 5.0 vs. 9.6 +/- 3.7 pmol/L; P less than 0.01). There was no significant difference in thyroid function between the patients with Graves' disease with positive and negative TPII index values. TPII appears to inhibit thyroid function in some patients, but no simple relationship between TPII and thyroid function in autoimmune thyroid disease was demonstrated. Understanding the factors that control access of anti-TPO antibody to its antigen may help to elucidate the significance of circulating anti-TPO antibody.

Human thyroid peroxidase (TPO) isoforms, TPO-1 and TPO-2: analysis of protein expression in Graves' thyroid tissue.

Thyroid peroxidase (TPO) is the key enzyme involved in the biosynthesis of thyroid hormones and is an important autoantigen in autoimmune thyroid disease. Different messenger RNA species coding for TPO are present in thyroid tissue, including the species coding for a 933-amino acid protein (termed TPO-1) and a second in which exon 10 is deleted and which is 57 residues shorter (termed TPO-2). However, it is not known whether the smaller, TPO-2 isoform is expressed as a protein in thyroid cells. In SDS-PAGE under reducing conditions, TPO appears in the thyroid microsome and purified protein preparations as a closely migrating double band of approximately 105 (larger form) and 100 kilodaltons (smaller form). We investigated the presence of the isoform TPO-2 polypeptide in Graves' thyroid tissue using rabbit antisera to three different synthetic peptides from exon 10 (specific for TPO-1) and a polyclonal rabbit and monoclonal anti-TPO antibody (both of which are specific for the two forms of TPO). The larger and smaller forms of TPO were purified by electroelution after gel electrophoresis of highly purified natural TPO from Graves' thyroid microsomes. Both of the purified forms of TPO react with all three anti-exon 10 peptide antibodies, the polyclonal anti-TPO and the monoclonal antibody anti-TPO. This shows that both forms of TPO contain exon 10-encoded polypeptide of TPO-1. Interestingly, the proportion of the larger and smaller forms of TPO varied in different Graves' thyroid microsome preparations. To investigate the presence of the smaller TPO-2 isoform in the purified natural TPO preparation, affinity depletion of TPO-1 using the anti-exon 10 peptide antibodies was carried out. The binding of anti-exon 10 peptide antibodies to the immunodepleted TPO-1 fraction was considerably diminished in comparison to binding of polyclonal anti-TPO, suggesting the presence of small amounts (< 10%) of TPO-2 expressed as a protein in thyroid cells. Our results extend previous observations by showing that the alternatively spliced form of TPO, in which exon 10 is excised, is expressed at low levels in Graves' thyroid tissue. Furthermore, we confirm that both the larger and smaller forms of TPO observed on gel electrophoresis contain TPO-1, suggesting that the difference is caused by posttranslational modifications. The presence of small amounts of TPO-2 in Graves' thyroid glands argues for its role in thyroid function, which remains to be clarified.