Maturation of dendritic cells by necrotic thyrocytes facilitates induction of experimental autoimmune thyroiditis

Experimental rat models for Hashimoto's thyroiditis

PURPOSE

Hashimoto's thyroiditis (HT) is an autoimmune thyroid disease characterized by T lymphocyte-mediated destruction of thyroid follicles. To study the pathogenesis of HT and the efficacy of new substances for its treatment, an easily obtained and adequate to the human disease experimental model is needed. The aim of our study was to find out whether it is possible to induce experimental autoimmune thyroiditis (EAT) similar to Hashimoto's thyroiditis by injecting with thyroglobulin (Tg) without using agents that enhance its thyroiditogenicity and without taking into account the genetic sensitivity of animals.

METHODS

Wistar rats were immunized with freshly isolated rat Tg or porcine Tg. In 8 weeks, histological studies of the thyroid and parathyroid glands were performed. Thyroid function and total serum calcium level were also evaluated.

RESULTS

Immunization with both rat and porcine freshly isolated Tg caused T lymphocytic infiltration of the thyroid gland, thyroid follicle atrophy and degradation in Wistar rats. EAT caused by porcine Tg was characterized by greater severity than EAT induced with rat Tg. In 55% of rats with porcine Tg-induced EAT, oxyphilic metaplasia was detected in the parathyroid glands. In addition, low total serum calcium was observed in these rats.

CONCLUSION

Two rat models of autoimmune thyroiditis were obtained. EAT caused in Wistar rats by immunization with rat Tg is similar to Hashimoto's thyroiditis. EAT induced with porcine Tg was accompanied by oxyphil cell metaplasia in the parathyroids and hypocalcemia.

Fever of unknown origin following parathyroidectomy prior to onset of typical polymyalgia rheumatica symptoms: a case report

Polymyalgia rheumatica (PMR) is a disease commonly seen in elderly individuals, however, the etiology has not been reported. Typical clinical features include bilateral shoulder pain and morning stiffness, while serologic autoantibody test findings are negative. Approximately 40%–50% of affected patients present with low-grade fever, fatigue, and appetite loss, which we often experience in the field of general medicine, and thus, the condition should not be given low priority. However, knowledge regarding such constitutional manifestations is also limited. We encountered an elderly woman with a fever of unknown origin that developed following a parathyroidectomy for a single parathyroid adenoma, after which severe shoulder pain and morning stiffness emerged, leading to a diagnosis of PMR. The fever developed several days prior to appearance of severe pain, which is an uncommon presentation in PMR cases. Our patient had low-grade inflammation without pyrexia prior to the surgery, which might have been an important reason for the accelerated immoderate immune activation leading to PMR induced by surgery in this case. Furthermore, she was infected with the influenza A virus 3 weeks before coming to us. Some reports have suggested a relationship between the influenza virus or vaccine and PMR. It is difficult to conclude regarding the definite trigger in our patient, though the details of this case should be helpful for a better understanding of the disease.

Isolated vitamin D deficiency is not associated with nonthyroidal illness syndrome, but with thyroid autoimmunity

AIM

This study aimed to compare thyroid functions, thyroid autoantibodies, and the existence of nonthyroidal illness syndrome (NTIS) according to vitamin D level.

MATERIALS AND METHODS

The study included age- and BMI-matched healthy volunteers with and without vitamin D deficiency. In addition, the nonthyroidal illness syndrome status was evaluated.

RESULTS

Anti-TPO positivity was significantly more common in those with severe and moderate vitamin D deficiency, as compared to those with a normal 25(OH)D level. Furthermore, TSH levels were significantly lower in those with severe and moderate vitamin D deficiency than in those with a normal 25(OH)D level. In addition, there was a significant weak inverse correlation between anti-TPO positivity and the 25(OH)D level and a positive correlation between the TSH level and 25(OH)D level. Only 1 thyroid function test result was compatible with NTIS among the participants with moderate vitamin D deficiency; therefore the difference was not significant.

CONCLUSIONS

The prevalence of thyroid autoantibody positivity was higher in those with severe and moderate vitamin D deficiency than in those with a normal 25(OH)D level. Additional large-scale studies must be conducted to determine if vitamin D deficiency plays a causal role in the pathogenesis of Hashimoto's thyroiditis and NTIS.

Vitamin D deficiency is related to thyroid antibodies in autoimmune thyroiditis

INTRODUCTION

It has been known that vitamin D has some immunomodulatory effects and in autoimmune thyroid diseases, vitamin D deficiency was more prevalent. In this study, our aim was to investigate the relationship between thyroid autoantibodies and vitamin D.

MATERIAL AND METHODS

Group 1 and 2 consisted of 254 and 27 newly diagnosed Hashimoto's thyroiditis (HT) and Graves' disease (GD) cases, respectively; age-matched 124 healthy subjects were enrolled as controls (group 3). All subjects (n = 405) were evaluated for 25OHD and thyroid autoantibody [anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-tg)] levels.

RESULTS

Group 2 and group 1 patients had lower 25OHD levels than group 3 subjects 14.9 ±8.6 ng/ml, 19.4 ±10.1 ng/ml and 22.5 ±15.4 ng/ml, respectively (p < 0.001). Serum 25OHD levels inversely correlated with anti-tg (r = -0.136, p = 0.025), anti-TPO (r = -0.176, p = 0.003) and parathormone (PTH) (r = -0.240, p < 0.001). Group 2 patients had higher anti-tg and anti-TPO levels than group 1 and 3 (p < 0.001).

CONCLUSIONS

In this study, we found that patients with autoimmune thyroid disease (AITD) present with lower vitamin D levels and GD patients have higher prevalence. Since we found an inverse correlation between vitamin D levels and thyroid antibody levels, we may suggest that vitamin D deficiency is one of the potential factors in pathogenesis of autoimmune thyroid disorders.

Breaking tolerance to thyroid antigens: changing concepts in thyroid autoimmunity

Thyroid autoimmunity involves loss of tolerance to thyroid proteins in genetically susceptible individuals in association with environmental factors. In central tolerance, intrathymic autoantigen presentation deletes immature T cells with high affinity for autoantigen-derived peptides. Regulatory T cells provide an alternative mechanism to silence autoimmune T cells in the periphery. The TSH receptor (TSHR), thyroid peroxidase (TPO), and thyroglobulin (Tg) have unusual properties ("immunogenicity") that contribute to breaking tolerance, including size, abundance, membrane association, glycosylation, and polymorphisms. Insight into loss of tolerance to thyroid proteins comes from spontaneous and induced animal models: 1) intrathymic expression controls self-tolerance to the TSHR, not TPO or Tg; 2) regulatory T cells are not involved in TSHR self-tolerance and instead control the balance between Graves' disease and thyroiditis; 3) breaking TSHR tolerance involves contributions from major histocompatibility complex molecules (humans and induced mouse models), TSHR polymorphism(s) (humans), and alternative splicing (mice); 4) loss of tolerance to Tg before TPO indicates that greater Tg immunogenicity vs TPO dominates central tolerance expectations; 5) tolerance is induced by thyroid autoantigen administration before autoimmunity is established; 6) interferon-α therapy for hepatitis C infection enhances thyroid autoimmunity in patients with intact immunity; Graves' disease developing after T-cell depletion reflects reconstitution autoimmunity; and 7) most environmental factors (including excess iodine) "reveal," but do not induce, thyroid autoimmunity. Micro-organisms likely exert their effects via bystander stimulation. Finally, no single mechanism explains the loss of tolerance to thyroid proteins. The goal of inducing self-tolerance to prevent autoimmune thyroid disease will require accurate prediction of at-risk individuals together with an antigen-specific, not blanket, therapeutic approach.

Iodine increases and predicts incidence of thyroiditis in NOD mice: Histopathological and ultrastructural study

Prolonged intake of large amounts of iodine has been reported to increase the incidence of hypothyroidism in humans, as well as in animals which are prone to spontaneously developing autoimmune thyroiditis. We sought to investigate the histopathological consequences of large amounts of dietary iodine on the thyroid gland and observe the occurrence of lymphocytic infiltration associated with the time of exposure to iodine. An experimental model using non-obese diabetic (NOD) mice was analyzed. A potassium iodide intake of 0.2 mg/animal/day was administered via drinking water, in experimental groups of 60 and 90 days (EG60 and EG90). Distended rough endoplasmic reticulum, degenerated mitochondria, debris and amorphous spaces or ‘ill-defined’ spaces were observed with electron microscopy (EM). Lymphocyte infiltration was observed in the two groups and the time of exposure to iodine did not increase the appearance of lymphocyte infiltration but significantly associated with the development of necrosis. The results of the present study demonstrated that the NOD mouse is a feasible experimental model for thyroiditis induced by iodine administration and may represent an opportunity to analyze the steps and factors associated with genetic autoimmune thyroiditis. High doses of ingested iodine were observed to precdict and increase the incidence of the thyroiditis process.

Dendritic cells and aging: consequences for autoimmunity

The immune system has evolved to mount immune responses against foreign pathogens and to remain silent against self-antigens. A balance between immunity and tolerance is required as any disturbance may result in chronic inflammation or autoimmunity. Dendritic cells (DCs) actively participate in maintaining this balance. Under steady-state conditions, DCs remain in an immature state and do not mount an immune response against circulating self-antigens in the periphery, which maintains a state of tolerance. By contrast, foreign antigens result in DC maturation and DC-induced T-cell activation. Inappropriate maturation of DCs due to infections or tissue injury may cause alterations in the balance between the tolerogenic and immunogenic functions of DCs and instigate the development of autoimmune diseases. This article provides an overview of the effects of advancing age on DC functions and their implications in autoimmunity.

Relative vitamin D insufficiency in Hashimoto's thyroiditis

BACKGROUND

Vitamin D insufficiency, defined as serum levels of 25-hydroxyvitamin D [25(OH)D3] lower than 30 ng/mL, has been reported to be prevalent in several autoimmune diseases such as multiple sclerosis and type 1 diabetes mellitus. The goal of the present study was to assess whether vitamin D insufficiency is also a feature of Hashimoto's thyroiditis (HT).

METHODS

We performed a prevalence case-control study that included 161 cases with HT and 162 healthy controls. Serum levels of 25(OH)D3, calcium, phosphorus, and parathyroid hormone were measured in all 323 subjects.

RESULTS

The prevalence of vitamin D insufficiency in HT cases (148 of 161, 92%) was significantly higher than that observed in healthy controls (102 of 162, 63%, p < 0.0001). Among HT cases, the prevalence rate of vitamin D insufficiency showed a trend to be higher in patients with overt hypothyroidism (47 of 50, 94%) or subclinical hypothyroidism (44 of 45, 98%) than in those with euthyroidism (57 of 66, 86%), but the differences were not significant (p = 0.083).

CONCLUSION

Vitamin D insufficiency is associated with HT. Further studies are needed to determine whether vitamin D insufficiency is a casual factor in the pathogenesis of HT or rather a consequence of the disease.

Toll-like receptor 3 signaling enables human esophageal epithelial cells to sense endogenous danger signals released by necrotic cells

The mechanisms by which gastroesophageal reflux disease esophagitis develops are controversial. Although many support the notion that caustic injury leads to reflux esophagitis, others have proposed that reflux esophagitis is caused by esophageal epithelial cytokine-mediated inflammation. We previously demonstrated that Toll-like receptor 3 (TLR3) is highly expressed and functional in the nontransformed human esophageal epithelial cell line EPC2-hTERT. In addition to activation by viral double-stranded RNA, TLR3 can be activated by endogenous mRNA released by necrotic cells. In the present study, we investigated the role of esophageal epithelial TLR3 to sense danger signals released by necrotic esophageal epithelial cells in vitro. Following induction of freeze-thaw necrosis, necrotic EPC2-hTERT cell supernatants (NCS) were used to stimulate EPC2-hTERT monolayers, leading to NF-κB-dependent induction of IL-8 mRNA expression. Responses to self-derived NCS were not observed in transformed gastrointestinal epithelial cell lines, including TE-1 and Caco-2 cells, suggesting that the ability to sense endogenous danger signals is unique to nontransformed esophageal epithelial cells. To determine the immunostimulatory role of epithelial RNA, EPC2-hTERT cells were stimulated with self-derived mRNA, which significantly induced IL-8 mRNA expression. Finally, suppression of TLR3 signaling in a DN-TLR3 cell line, hTERT-ΔTIR-TLR3, led to reduced NCS-induced IL-8 induction by both NCS and mRNA stimulation. Our results demonstrate that human esophageal epithelial cells can sense endogenous danger signals, in part through TLR3 signaling. This supports the concept that epithelial injury plays an inciting role in the pathogenesis of reflux-induced esophagitis, providing important insights into the mechanisms by which epithelial injury leads to inflammation.

[The effect of selenium therapy on autoimmune thyroiditis]

Selenium as an essential trace element is capable of exerting complex effects on the endocrine and immune system by its antioxidant capacity. The role of selenium is important because the level of free oxygen radicals is elevated in the physiological thyroid hormone synthesis.

THE AIM OF STUDY

was to determine whether selenium therapy can influence the level of antithyroid peroxidase and antithyroglobulin antibodies or whether there is a correlation between antioxidant capacity and the titer of autoantibodies.

METHOD

132 patient with autoimmune thyroiditis were investigated in a prospective, blind and placebo-controlled study. L-thyroxine substitution therapy was made in both groups and the level of TSH remained in the normal range. The selenium-treated group (n = 70 patients, 68 female, mean age 41,4 +/- 9,5 year) was compared with the placebo-treated group (n = 62 patients, 61 female, mean age 42,7 +/- 8,3 year). Selenium therapy was continued by L-seleno-methionine (per os 2 x 100 microg/day) for one year. Determination of TSH, fT4, fT3 and autoantibodies was carried out by chemiluminescence method. Total antioxidant capacity was determined by Randox kit, the level of selenium in the sera by atomic absorption technique was measured. In the follow-up study, patients were controlled every third month and at the end of a one-year observation period.

RESULTS

The level of selenium in the untreated patients was significantly lower than in treated patients and controls. The fT3/fT4 ration proved to be higher in patients after selenium therapy. The titer of antithyroid antibodies (mostly the antithyroid peroxidase) significantly decreased at the end of the study. An inverse correlation was found between antioxidant capacity and the level of antithyroid peroxidase antibodies. The volume of thyroid gland slightly diminished in treated patients. Side effects were not observed.

CONCLUSIONS

Selenium completed with L-thyroxine is a suitable therapy for patients with autoimmune thyroiditis.

Cultured murine thyroid epithelial cells expressing transgenic Fas-associated death domain-like interleukin-1beta converting enzyme inhibitory protein are protected from fas-mediated apoptosis

The antiapoptotic molecule Fas-associated death domain-like IL-1beta-converting enzyme inhibitory protein (FLIP) inhibits Fas-mediated apoptosis by blocking activation of caspase-8. We previously showed that expression of transgenic FLIP on thyroid epithelial cells (TECs) of DBA/1 and CBA/J mice promoted earlier resolution of granulomatous experimental autoimmune thyroiditis in vivo. This study was undertaken to directly determine whether transgenic FLIP expressed on cultured TECs can protect TECs from Fas-mediated apoptosis in vitro. The results indicate that cultured TECs from DBA/1 and CBA/J mice can be sensitized in vitro by interferon-gamma and TNF-alpha to undergo Fas-mediated apoptosis. Transgenic overexpression of FLIP protected cultured TECs of FLIP transgene (Tg)+ DBA/1 and CBA/J mice from Fas-mediated apoptosis, and FLIP small interfering RNA transfection of cultured TECs of FLIP Tg+ DBA/1 and CBA/J mice abolished the protective effect. These in vitro results are consistent with our previous in vivo studies using DBA/1 and CBA/J FLIP Tg+ mice and provide direct support for the hypothesis that transgenic expression of FLIP promotes resolution of granulomatous experimental autoimmune thyroiditis by protecting TECs from apoptosis.

Increased pressure stimulates aberrant dendritic cell maturation

Patients with malignancy typically exhibit abnormal dendritic cell profiles. Interstitial tumor pressure is increased 20-50mmHg over that in normal tissue. We hypothesized that elevated pressure in the tumor microenvironment may influence dendritic cell (DC) phenotype and function. Monocyte-derived immature and mature DC isolated from healthy human donors were exposed to either ambient or 40 mmHg increased pressure at 37°C for 12 hours, then assessed for expression of CD80, CD86, CD83, CD40, MHC-I and MHC-II. IL-12 production and phagocytosis of CFSE-labeled tumor lysate were assessed in parallel. Elevated pressure significantly increased expression of all co-stimulatory and MHC molecules on mature DC. Immature DC significantly increased expression of CD80, CD86, CD83 and MHC-II, but not MHC-I and CD40, versus ambient pressure controls. Pressure-treated immature DC phenotypically resembled mature DC controls, but produced low IL-12. Phenotypic maturation correlated with decreased phagocytic capacity. These results suggest increased extracellular pressure may cause aberrant DC maturation and impair tumor immunosurveillance.

Recognition of thyroglobulin by T cells: the role of iodine

Among known autoantigens, thyroglobulin (Tg) is unique in its capacity to store iodine, an element provided in our daily diet. Evolutionary pressure has sculpted Tg into a large molecular scaffolding to allow organification of iodide and its incorporation into thyroid hormones. The increase in molecular size and the posttranslational modification by iodine had to exact immunological consequences. Over the last 15 years, numerous Tg peptides-targets of thyroiditogenic T cells-have been mapped, raising questions regarding the mechanisms that maintain or abrogate immune tolerance against this large autoantigen. This review summarizes the work in this area and discusses the role iodine may play in these processes.