Demonstration of innate immune responses in the thyroid gland: potential to sense danger and a possible trigger for autoimmune reactions

Vitamin D: An Essential Nutrient in the Dual Relationship between Autoimmune Thyroid Diseases and Celiac Disease-A Comprehensive Review

Autoimmune thyroid diseases (AITD) are among the most frequent autoimmune disorders, with a multifactorial etiology in which both genetic and environmental determinants are probably involved. Celiac disease (CeD) also represents a public concern, given its increasing prevalence due to the recent improvement of screening programs, leading to the detection of silent subtypes. The two conditions may be closely associated due to common risk factors, including genetic setting, changes in the composition and diversity of the gut microbiota, and deficiency of nutrients like vitamin D. This comprehensive review discussed the current evidence on the pivotal role of vitamin D in modulating both gut microbiota dysbiosis and immune system dysfunction, shedding light on the possible relevance of an adequate intake of this nutrient in the primary prevention of AITD and CeD. While future technology-based strategies for proper vitamin D supplementation could be attractive in the context of personalized medicine, several issues remain to be defined, including standardized assays for vitamin D determination, timely recommendations on vitamin D intake for immune system functioning, and longitudinal studies and randomized controlled trials to definitely establish a causal relationship between serum vitamin D levels and the onset of AITD and CeD.

Intestinal microbiota regulates the gut-thyroid axis: the new dawn of improving Hashimoto thyroiditis

Intestinal microbiota plays an indispensable role in the host's innate immune system, which may be related to the occurrence of many autoimmune diseases. Hashimoto thyroiditis (HT) is one of the most common autoimmune diseases, and there is plenty of evidence indicating that HT may be related to genetics and environmental triggers, but the specific mechanism has not been proven clearly. Significantly, the composition and abundance of intestinal microbiota in patients with HT have an obvious difference. This phenomenon led us to think about whether intestinal microbiota can affect the progress of HT through some mechanisms. By summarizing the potential mechanism of intestinal microflora in regulating Hashimoto thyroiditis, this article explores the possibility of improving HT by regulating intestinal microbiota and summarizes relevant biomarkers as therapeutic targets, which provide new ideas for the clinical diagnosis and treatment of Hashimoto thyroiditis.

Identification of Shared Biomarkers and Immune Infiltration Signatures between Vitiligo and Hashimoto's Thyroiditis

Background

Vitiligo and Hashimoto's thyroiditis (HT) are concomitant autoimmune diseases characterized by the destruction of melanocytes or thyrocytes. We aimed to explore the immunological mechanism of this comorbidity and screen their potential biomarkers.

Methods

We downloaded the microarray datasets from the GEO database. Differentially expressed genes (DEGs) and immune-related genes (IRGs) were selected. The immune-related differentially expressed genes (IRDEGs) were obtained by taking the intersection. Candidate biomarkers were elected by Cytoscape software. CIBERSORT was used to depict immune cell infiltration prospects. Correlation analysis was conducted between infiltrating cells and several indicators. The results were validated by real-time quantitative PCR (RT-qPCR).

Results

Three datasets and 60 IRDEGs were obtained in total. Pathway enrichment analysis showed that the T cell receptor signaling pathway, IL-17 signaling pathway, receptor-ligand activity, and signaling receptor activator activity were significantly enriched. We screened out four hub genes, including IFNG, STAT1, IL1B, and CXCL10. The ROC curve indicated the highest diagnostic value of CXCL10 in both vitiligo and HT. Immuno-infiltration analysis revealed significant changes in T cell subsets and macrophage subtypes, which were correlated with four hub genes, melanocyte markers, and thyroid-specific antigens. qPCR validated the hub genes in peripheral blood mononuclear cells from patients with comorbidity.

Conclusion

IFNG, STAT1, IL1B, and CXCL10, were the key IRDEGs to vitiligo and HT. These genes may participate in the comorbidity by remodeling the immune cell infiltration pattern, and cross-expressed antigens may mediate the common damage of melanocytes and thyroid tissues.

DBP exposure induces thyroid inflammatory impairment through activating AKT/NF-κB/NLRP3 signaling

Previous studies exhibited reproductive and neurodevelopmental toxicity in rats exposed to Di-n-butyl phthalate (DBP). However, the effects of DBP exposure on the other endocrine organ are still unclear. This study aimed to assess the impact of DBP exposure on the thyroid of male rats and the associated mechanisms. Here, rats were respectively treated with DBP at 0 (control), 50 (low dose), 250 (medium dose), or 500 (high dose) mg/kg/day dissolved in 1 ml quantity of corn oil by intragastrical administration for two weeks. The results demonstrated that the proliferation and inflammatory response changes were significantly different compared to the control. In vivo DBP is mainly converted to mono-n-butyl phthalate (MBP), an active form producing untoward reactions of DBP exposure. Therefore, for in vitro experiments, we treated the thyroid follicular epithelial cell line (Nthy-ori 3-1) in a temporal gradient using 1 mM MBP. Further in vitro studies showed that MBP exposure upregulated tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), as well as interleukin-1β (IL-1β) by activating AKT/NF-κB/NLRP3 signaling. Meanwhile, we detected that Pellino2 (Peli2) played an essential role in promoting the activation of NLRP3 inflammasome. Briefly speaking, this study confirmed that DBP exposure caused impaired thyroid structure and thyroid inflammation in male rats, which offered new views into the harm of DBP exposure on the endocrine organ.

The Role of Toll-like Receptor 2 (TLR2) in the Development and Progression of Hashimoto’s Disease (HD): A Case Study on Female Patients in Poland

Chronic lymphocytic thyroiditis, commonly known as HD, is one of the most common thyroid disorders. Due to the diverse factors affecting the etiopathogenesis of this disease (hormonal disorders and genetic and environmental factors), as well as the direct involvement of the immune system, scientists are increasingly willing to undertake research aimed at explaining the impact of the loss of immune tolerance and reactivity of autoantigens on the development of the disease. One of the directions of research in recent years is the role of the innate immune response, particularly Toll-like receptors (TLRs), in the pathogenesis of HD. The purpose of this study was to determine the importance of Toll-like receptor 2 (TLR2) expression on selected populations of immune cells, namely, monocytes (MONs) and dendritic cells (DCs), in the course of HD. Particular attention was paid to the analysis of TLR2’s correlation with clinical parameters and the possibility its use as a potential biomarker molecule in the diagnostic process. Based on the obtained results, we found a statistically significant increase in the percentage of all analyzed populations of immune cells, i.e., mDC BDCA-1+CD19−, pDC BDCA-1+CD123, classical MONs CD14+CD16−, and non-classical MONs CD14+CD16+ showing on their surface TLR2 expression in patients diagnosed with HD compared to the healthy volunteers. Moreover, in the study group, we noted a more than 6-fold increase in the concentration of the soluble form of TLR2 in plasma compared to healthy patients. In addition, the correlation analysis showed significant positive correlations between the level of TLR2 expression on selected subpopulations of immune cells and biochemical indicators of thyroid function. Based on the obtained results, we can assume that TLR2 may be involved in the immunopathogenesis of HD.

Thyroid stimulating hormone suppresses the expression and activity of cytosolic sulfotransferase 1a1 in thyrocytes

Sulfonation is an important step in the metabolism of dopamine, estrogens, dehydroepiandrosterone, as well as thyroid hormones. However, the regulation of cytosolic sulfotransferases in the thyroid is not well understood. In a DNA microarray analysis of rat thyroid FRTL-5 cells, we found that the mRNA expression of 10 of 48 sulfotransferases was significantly altered by thyroid stimulating hormone (TSH), with that of sulfotransferase family 1A member 1 (SULT1A1) being the most significantly affected. Real-time PCR and Western blot analyses revealed that TSH, forskolin and dibutyryl cyclic AMP significantly suppressed SULT1A1 mRNA and protein levels in a time- and concentration-dependent manner. Moreover, immunofluorescence staining of FRTL-5 cells showed that SULT1A1 is localized in the perinuclear area in the absence of TSH but is spread throughout the cytoplasm with reduced fluorescence intensity in the presence of TSH. Sulfotransferase activity in FRTL-5 cells, measured using 3'-phosphoadenosine-5'-phosphosulfate as a donner and p-nitrophenol as an acceptor substrate, was significantly reduced by TSH. These findings suggest that the expression and activity of SULT1A1 are modulated by TSH in thyrocytes.

Hashimoto's Thyroiditis Encephalopathy Induced by COVID-19 Infection

Various factors can lead to thyroiditis, including any acute inflammatory process, especially viral illness. While coronavirus disease 2019 (COVID-19) has been linked to disorders of various systems, there is a lack of literature showing an association of coronavirus with the cause of Hashimoto's thyroiditis. Several possible mechanisms for this outcome have been proposed; chief among them is molecular mimicry. Here, we are reporting a case of Hashimoto's thyroiditis incited by COVID-19 in a 34-year-old obese female who presented with anxiety, behavioral changes, and repeated head movements. The patient had an elevated thyroid stimulating hormone (TSH) level, a low thyroxine (T4) level, and a positive anti-microsomal antibody screen. The patient also tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Ultrasound of the patient's neck showed an enlarged heterogeneous thyroid gland. Thyroid replacement therapy with intravenous levothyroxine was started with the subsequent oral transition. Concurrently, she received antibiotics, steroids, and low-molecular-weight heparin for COVID-19. The patient exhibited significant improvement in her mental status, with an eventual return to baseline. The results of the thyroid panel obtained at the outpatient follow-up were normal. Although there is a paucity of data to show COVID-19 as a cause of this painless thyroiditis, this case demonstrates such causality between these two.

Thyrotoxicosis occurrence in SARS-CoV-2 infection: A case report

Introduction

Coronavirus Disease 2019 (COVID-19) is predominantly manifested as respiratory distress. There are growing reports of extrapulmonary clinical manifestations of COVID-19 in addition to the respiratory symptoms. COVID-19 has been associated with the thyroid function through Angiotensin-converting enzyme 2 (ACE2), the central mechanism through Thyroid Stimulating Hormone (TSH), and direct replication of the virus.

Case presentation

A 26-year-old woman presented with complaints of palpitation and abdominal pain for three days. Because the symptoms were worsening, she was brought to the emergency room. Her temperature was 37.9 °C without any symptoms of cough, coryza, sneezing, nor headache. Physical examination revealed tremor, tachycardia with 162 beats per minute (bpm), excessive sweating, hyperreflexia of patellar reflex, and no prominent lump in the neck. Electrocardiography (ECG) showed supraventricular tachycardic rhythm (SVT) and 150 J cardioversions were performed. The ECG converted to sinus rhythm, regular, with 120 bpm. Thyroid function tests showed an elevated fT4 level (>7.77 ng/dL) and low TSH level (<0.005 μIU/mL). Chest X-ray showed slight cardiomegaly without prominent abnormality in the lungs that was confirmed with thoracic computerized tomography. The result of the rapid antigen test for COVID-19 was positive and confirmed with polymerase chain reaction testing. She was then treated in the intensive isolation room with remdesivir, anti-hyperthyroid, and supportive therapy. As her condition improved, she was shifted to a non-intensive isolation room and was discharged from the hospital at day 7.

Discussion

COVID-19 could present as a thyroid crisis as the initial clinical manifestation. Clinicians should be aware that presentation of thyroid dysfunction in a patient without previous endocrine disease could be due to COVID-19 infection. Early recognition, anti-hyperthyroid therapy, and following isolation procedures for COVID-19 are required in the emergency condition.

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Thyroid crisis could be associated with COVID-19 infection.

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Extra-respiratory manifestations of COVID-19 infection vary among patients.

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Clinicians should be aware of thyroid crisis as a COVID-19 infection manifestation.

Inflammasome activation as a link between obesity and thyroid disorders: Implications for an integrated clinical management

Obesity is strongly associated with chronic low-grade inflammation. Obese patients have an increased risk to develop thyroid autoimmunity and to became hypothyroid, suggesting a pathogenetic link between obesity, inflammation and autoimmunity. Moreover, type 2 diabetes and dyslipidemia, also characterized by low-grade inflammation, were recently associated with more aggressive forms of Graves' ophthalmopathy. The association between obesity and autoimmune thyroid disorders may also go in the opposite direction, as treating autoimmune hyper and hypothyroidism can lead to weight gain. In addition, restoration of euthyroidism by L-T4 replacement therapy is more challenging in obese athyreotic patients, as it is difficult to maintain thyrotropin stimulation hormone (TSH) values within the normal range. Intriguingly, pro-inflammatory cytokines decrease in obese patients after bariatric surgery along with TSH levels. Moreover, the risk of thyroid cancer is increased in patients with thyroid autoimmune disorders, and is also related to the degree of obesity and inflammation. Molecular studies have shown a relationship between the low-grade inflammation of obesity and the activity of intracellular multiprotein complexes typical of immune cells (inflammasomes). We will now highlight some clinical implications of inflammasome activation in the relationship between obesity and thyroid disease.

Association of IL-1β, NLRP3, and COX-2 Gene Polymorphisms with Autoimmune Thyroid Disease Risk and Clinical Features in the Iranian Population

Background

Grave's disease (GD) and Hashimoto's thyroiditis (HT) are autoimmune diseases of the thyroid gland in which genetic predisposition plays a major role in their development. Currently, the role of NLRP3 inflammasome and COX-2 has been documented in many autoimmune diseases. The purpose of the study is to delineate the impact of IL-1β (rs1143634), NLRP3 (rs3806265), and COX-2 (rs2745557) gene polymorphisms in the development of GD and HT.

Methods

A total of 256 newly diagnosed patients with autoimmune thyroid disease (135 patients with HT and 121 GD patients) as case groups and 145 controls were included in the study.

Results

Recessive and overdominant models showed a significant association between IL-1β rs1143634 SNP and HT development risk. The frequency of TT genotype and T allele of IL-1β rs1143634 SNP in the control group was significantly higher than the GD group. There was no significant association between NLRP3 rs3806265 polymorphism and HT and GD development. The frequency of GA genotype of COX-2 (rs2745557) in the control group was significantly higher than that in the HT group. There was no significant association between COX-2 rs2745557 genotypic and allelic distribution and GD development risk. The results revealed a significant relationship between some clinical features of HT and GD groups and SNPs studied.

Conclusion

The results manifest the significant impact of IL-1β rs1143634 and COX-2 (rs2745557) SNPs and HT development and IL-1β rs1143634 SNP on GD occurrence risk. Furthermore, a significant relationship was observed between some clinical features of HT and GD groups and studied SNPs.

Network Pharmacology to Explore the Molecular Mechanisms of Prunella vulgaris for Treating Hashimoto's Thyroiditis

Purpose:Prunella vulgaris (PV), a traditional Chinese medicine, has been used to treat patients with thyroid disease for centuries in China. The purpose of the present study was to investigate its bioactive ingredients and mechanisms against Hashimoto’s thyroiditis (HT) using network pharmacology and molecular docking technology to provide some basis for experimental research.

Methods: Ingredients of the PV formula were retrieved from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Additionally, HT-related genes were retrieved from the UniProt and GeneCards databases. Cytoscape constructed networks for visualization. A protein–protein interaction (PPI) network analysis was constructed, and a PPI network was built using the Search Tool for the Retrieval of Interacting Genes (STRING) database. These key targets of PV were enriched and analyzed by molecular docking verification, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment.

Results: The compound–target network included 11 compounds and 66 target genes. Key targets contained Jun proto-oncogene (JUN), hsp90aa1.1 (AKI), mitogen-activated protein kinase 1 (MAPK1), and tumor protein p53 (TP53). The main pathways included the AGE-RAGE signaling pathway, the TNF signaling pathway, the PI3K–Akt signaling pathway, and the mitogen-activated protein kinase signaling pathway. The molecular docking results revealed that the main compound identified in the Prunella vulgaris was luteolin, followed by kaempferol, which had a strong affinity for HT.

Conclusion: Molecular docking studies indicated that luteolin and kaempferol were bioactive compounds of PV and might play an essential role in treating HT by regulating multiple signaling pathways.

Thyroid and COVID-19: a review on pathophysiological, clinical and organizational aspects

BACKGROUND

Thyroid dysfunction has been observed in patients with COVID-19, and endocrinologists are requested to understand this clinical issue. Pandemic-related restrictions and reorganization of healthcare services may affect thyroid disease management.

OBJECTIVE AND METHODS

To analyze and discuss the relationship between COVID-19 and thyroid diseases from several perspectives. PubMed/MEDLINE, Google Scholar, Scopus, ClinicalTrial.gov were searched for this purpose by using free text words and medical subject headings as follows: "sars cov 2", "covid 19", "subacute thyroiditis", "atypical thyroiditis", "chronic thyroiditis", "hashimoto's thyroiditis", "graves' disease", "thyroid nodule", "differentiated thyroid cancer", "medullary thyroid cancer", "methimazole", "levothyroxine", "multikinase inhibitor", "remdesivir", "tocilizumab". Data were collected, analyzed, and discussed to answer the following clinical questions: "What evidence suggests that COVID-19 may induce detrimental consequences on thyroid function?"; "Could previous or concomitant thyroid diseases deteriorate the prognosis of COVID-19 once the infection has occurred?"; "Could medical management of thyroid diseases influence the clinical course of COVID-19?"; "Does medical management of COVID-19 interfere with thyroid function?"; "Are there defined strategies to better manage endocrine diseases despite restrictive measures and in-hospital and ambulatory activities reorganizations?".

RESULTS

SARS-CoV-2 may induce thyroid dysfunction that is usually reversible, including subclinical and atypical thyroiditis. Patients with baseline thyroid diseases are not at higher risk of contracting or transmitting SARS-CoV-2, and baseline thyroid dysfunction does not foster a worse progression of COVID-19. However, it is unclear whether low levels of free triiodothyronine, observed in seriously ill patients with COVID-19, may worsen the disease's clinical progression and, consequently, if triiodothyronine supplementation could be a tool for reducing this burden. Glucocorticoids and heparin may affect thyroid hormone secretion and measurement, respectively, leading to possible misdiagnosis of thyroid dysfunction in severe cases of COVID-19. High-risk thyroid nodules require a fine-needle aspiration without relevant delay, whereas other non-urgent diagnostic procedures and therapeutic interventions should be postponed.

DISCUSSION

Currently, we know that SARS-CoV-2 could lead to short-term and reversible thyroid dysfunction, but thyroid diseases seem not to affect the progression of COVID-19. Adequate management of patients with thyroid diseases remains essential during the pandemic, but it could be compromised because of healthcare service restrictions. Endocrine care centers should continuously recognize and classify priority cases for in-person visits and therapeutic procedures. Telemedicine may be a useful tool for managing patients not requiring in-person visits.

The 4G/5G Polymorphism of Plasminogen Activator Inhibitor Type 1 is a Predictor of Moderate-to-Severe Thyroid Eye Disease

Introduction

Thyroid eye disease (TED) is an autoimmune disease of the orbits. Once developed, complete cure is rare. Plasminogen activator inhibitor type 1 (PAI-1) contributes to remodeling of connective tissue and has a central role in the pathogenesis of TED. We aimed to test if the 4G/5G polymorphism of PAI-1 is a predictor of the development of moderate-to-severe TED.

Methods

A total of 185 patients with Graves’ disease, 87 of them with TED, 98 without TED, as well as 201 healthy controls, were studied. Genomic DNA was isolated from peripheral blood samples. The 4G/5G polymorphism of the PAI-1 gene was analyzed by allele-specific PCR, and the distribution of genotypes was calculated in each group. Plasma PAI-1 and thyroid hormone levels were measured by ELISA and ECLIA, respectively.

Results

The 4G/4G genotype was associated with the development of moderate-to-severe TED (OR = 2.54; 95% CI: 1.26–5.14; p < 0.01). The 4G/5G polymorphism of PAI-1 was not a predictor of plasma PAI-1 levels.

Conclusion

The 4G/4G genotype of PAI-1 is a risk factor for the development of moderate-to-severe TED. Patients with Graves’ disease who harbor this genotype may be candidates for special attention towards the development of TED.

The Transcription Factor NF-κB Mediates Thyrotropin-Stimulated Expression of Thyroid Differentiation Markers

Background: The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor is a key regulator of cell survival, proliferation, and gene expression. Although activation of NF-κB signaling in thyroid follicular cells after thyrotropin (TSH) receptor (TSHR) engagement has been reported, the downstream signaling leading to NF-κB activation remains unexplored. Here, we sought to elucidate the mechanisms that regulate NF-κB signaling activation in response to TSH stimulation. Methods: Fisher rat-derived thyroid cell lines and primary cultures of NF-κB essential modulator (NEMO)-deficient mice thyrocytes were used as models. Signaling pathways leading to the activation of NF-κB were investigated by using chemical inhibitors and phospho-specific antibodies. Luciferase reporter gene assays and site-directed mutagenesis were used to monitor NF-κB-dependent gene transcriptional activity and the expression of thyroid differentiation markers was assessed by reverse transcription quantitative polymerase chain reaction and Western blot, respectively. Chromatin immunoprecipitation (ChIP) was carried out to investigate NF-κB subunit p65 DNA binding, and small interfering RNA (siRNA)-mediated gene knockdown approaches were used for studying gene function. Results: Using thyroid cell lines, we observed that TSH treatment leads to protein kinase C (PKC)-mediated canonical NF-κB p65 subunit nuclear expression. Moreover, TSH stimulation phosphorylated the kinase TAK-1, and its knockdown abolished TSH-induced NF-κB transcriptional activity. TSH induced the transcriptional activity of the NF-κB subunit p65 in a protein kinase A (PKA)-dependent phosphorylation at Ser-276. In addition, p65 phosphorylation at Ser-276 induced acetyl transferase p300 recruitment, leading to its acetylation on Lys-310 and thereby enhancing its transcriptional activity. Evaluation of the role played by NF-κB in thyroid physiology demonstrated that the canonical NF-κB inhibitor BAY 11-7082 reduced TSH-induced expression of thyroid differentiation markers. The involvement of NF-κB signaling in thyroid physiology was confirmed by assessing the TSH-induced gene expression in primary cultures of NEMO-deficient mice thyrocytes. ChIP and the knockdown experiments revealed that p65 is a nuclear effector of TSH actions, inducing the transcripcional expression of thyroid differentiation markers. Conclusions: Taken together, our results point to NF-κB being a pivotal mediator in the TSH-induced thyroid follicular cell differentiation, a relevant finding with potential physiological and pathophysiological implications.

Hormonal Regulation of the MHC Class I Gene in Thyroid Cells: Role of the Promoter "Tissue-Specific" Region

In previous studies we have demonstrated that the expression of the Major Histocompatibility Complex (MHC) class I gene in thyrocytes is controlled by several hormones, growth factors, and drugs. These substances mainly act on two regions of the MHC class I promoter a "tissue-specific" region (-800 to -676 bp) and a "hormone/cytokines-sensitive" region (-500 to -68 bp). In a previous study, we have shown that the role of the "tissue-specific" region in the MHC class I gene expression is dominant compared to that of the "hormone/cytokines-sensitive" region. In the present report we further investigate the dominant role of the "tissue-specific" region evaluating the effect of thyroid stimulating hormone (TSH), methimazole (MMI), phenylmethimazole (C10), glucose and thymosin-α1. By performing experiments of electrophoretic mobility shift assays (EMSAs) we show that TSH, MMI and C10, which inhibit MHC class I expression, act on the "tissue-specific" region increasing the formation of a silencer complex. Glucose and thymosin-α1, which stimulate MHC class I expression, act decreasing the formation of this complex. We further show that the silencer complex is formed by two distinct members of the transcription factors families activator protein-1 (AP-1) and nuclear factor-kB (NF-kB), c-jun and p65, respectively. These observations are important in order to understand the regulation of MHC class I gene expression in thyroid cells and its involvement in the development of thyroid autoimmunity.

Higher Levels of Serum TLR2 and TLR4 in Patients with Hashimoto's Thyroiditis

OBJECTIVE

Hashimoto's thyroiditis (HT) is an autoimmune disorder caused by the interaction between genes and environmental triggers. HT is the most common endocrine disorder, as well as the most common cause of hypothyroidism. Autoimmunity plays a crucial role in the pathogenesis of HT and recent studies suggest that Toll-like receptor (TLR) signals lead to increased inflammatory response. The aim of our study is to investigate whether TLR-2 and TLR-4 levels and gene polymorphisms contribute to the damaged immune response leading to HT.

METHODS

Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, single-nucleotide polymorphisms (SNPs) of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile were studied in 100 patients with HT and 100 healthy controls. Also, we investigated serum levels of TLR-2 and TLR-4 in the immunopathogenesis of HT. TLR-2 and TLR-4 serum levels were found to be significantly higher in HT patients than the control group. However, no statistical significance was found between patient and control groups in terms of genotype frequencies and allele frequency distribution of TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphisms.

RESULT

TLR2 gene Arg677Trp, Arg753Gln, 196-174 del and TLR4 gene Asp299Gly, Thr399Ile polymorphism do not appear to have a role in the development of HT disease. However, in our study, serum levels of TLR-2 and TLR-4 were found to be higher in HT patients than control groups.

CONCLUSION

These findings suggest that TLR-2 and TLR-4 play an important role in the immunopathologic mechanism of disease by causing an increase in proinflammatory response.

Associations between NLRC4 Gene Polymorphisms and Autoimmune Thyroid Disease

Background

Many studies have shown that NLRC4 inflammasome polymorphisms are associated with a variety of autoimmune diseases, but the associations between NLRC4 polymorphisms and autoimmune thyroid diseases (AITDs) are unclear. Our research was aimed at identifying the correlations between NLRC4 polymorphisms and AITDs.

Methods

Hi-SNP high-throughput genotyping technology was used for detecting four single-nucleotide polymorphisms (SNPs) of NLRC4 in 1005 AITDs patients (including 629 Graves' disease and 376 Hashimoto's thyroiditis) and 781 healthy controls.

Results

Compared with healthy controls, the allele frequencies and genotype distribution of rs385076 were statistically related to AITDs (P = 0.016 and P = 0.048, respectively) and Hashimoto's thyroiditis (P = 0.022 and P = 0.046, respectively). Before adjusting for age and gender, rs385076 and AITDs had a significant association in three models of allele model, dominant model, and homozygous model. After adjusting for age and gender, in the above three models, there is still a clear relationship between them. Before adjusting for age and gender, there were prominent discrepancy between rs385076 and Hashimoto's thyroiditis in the allele model (OR = 0.81, 95% CI 0.67-0.97; P = 0.021) and the dominant model (OR = 0.73, 95% CI 0.57-0.94; P = 0.014), after adjusting for age and gender, rs385076 and Hashimoto's thyroiditis were significantly related to allele model, dominant model, and homozygous model. However, rs455060, rs212704, and rs675712 were not related to AITDs in our study.

Conclusion

NLRC4 rs385076 was found to have a significant association with Hashimoto's thyroiditis for the first time. It laid a foundation for the disclosure of the pathogenesis of AITDs, and provided a possible treatment prospect for HT.

Current Iodine Nutrition Status and Prevalence of Thyroid Disorders in Tibetan Adults in an Oxygen-Deficient Plateau, Tibet, China: A Population-Based Study

Background: Iodine deficiency (ID) is a global problem in individuals living in an iodine-deficient environment, specifically in mountainous regions. However, data regarding the iodine nutritional status of Tibetan people in the plateau are limited. Methods: A population-based survey was conducted from July 2016 to July 2017 in Lhasa, Tibet, including 12 communities in Lhasa city and 10 surrounding rural areas. The iodine nutritional status of Tibetan people was evaluated using the traditional iodine nutrition indexes: urinary iodine concentration (UIC), thyroid size, serum thyroxine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody (TPOAb). Results: A total of 2295 healthy participants were screened, and 2160 participants who had completed all the required examinations were enrolled in this study (response rate, 94.1%). Urinary iodine showed a skewed distribution, with a median (upper and lower quartiles) of 154 (99-229) μg/L. The percentages of low iodine (UIC <100 μg/L), adequate iodine (UIC, 100-199 μg/L), and high iodine (UIC ≥200 μg/L) were 25.6%, 42.0%, and 32.4%, respectively. The urinary iodine level in the urban region was higher than that in the rural region (p < 0.05). Urinary iodine levels were lower with increasing age (p < 0.05). The prevalence of hyperthyroidism, hypothyroidism, goiter, TPOAb positivity, and thyroglobulin antibody positivity was 1.0%, 21.8%, 4.7%, 6.6%, and 10.4%, respectively. Logistic regression analysis found that urinary iodine was an independent risk factor for TPOAb positivity (odds ratio = 0.997 [95% confidence interval, 0.995-0.999]; p < 0.001). Conclusions: Compared with individuals living in the plains of China, Tibetan adults have a higher rate of ID. UIC was an independent risk factor for TPOAb positivity. This public health issue should be further investigated.

Innate Immune-Modulatory Activity of Prunella vulgaris in Thyrocytes Functions as a Potential Mechanism for Treating Hashimoto's Thyroiditis

Prunella vulgaris (PV), a perennial herb, has been used to treat thyroid diseases in China for over 2,000 years. In particular, its therapeutic effect has been described for Hashimoto's thyroiditis, including reducing titers autoantibodies against thyroid peroxidase and thyroglobulin of and T helper 17 (Th17) cells. However, the underlying mechanism for how PV exerts such effects has not been investigated. We examined the effects of PV on innate immune activation, which is thought to be one of the triggers for the development of autoimmune diseases, including Hashimoto's thyroiditis. In cultured thyrocytes, PV reduced mRNA levels of inflammatory cytokines that were originally induced as a result of innate immune activation initiated by transfection of double-stranded DNA (dsDNA) or dsRNA. PV suppressed activation of nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF3), and suppressed corresponding promoter activation, which were initially activated by dsDNA or dsRNA. PV also suppressed the mRNA levels of molecules responsible for antigen processing and presentation, and PV protected thyrocytes from apoptosis induced by dsDNA and dsRNA. Additionally, PV suppressed the expression of genes involved in iodide uptake and oxidation. Taken together, these results suggest that PV exerts its protective effect on thyrocytes by suppressing both innate and adaptive immune responses and cell death. PV may also protect cells from iodide-associated oxidative injury. This report is among the first to identify the mechanisms to explain PV's beneficial effects in Hashimoto's thyroiditis.

Cytokine Secretion and Pyroptosis of Thyroid Follicular Cells Mediated by Enhanced NLRP3, NLRP1, NLRC4, and AIM2 Inflammasomes Are Associated With Autoimmune Thyroiditis

Background

Inflammasomes, which mediate maturation of interleukin-1β (IL-β) and interleukin-18 (IL-18) and lead to pyroptosis, have been linked to various autoimmune disorders. This study investigated whether they are involved in the pathogenesis of autoimmune thyroiditis (AIT).

Methods

We collected thyroid tissues from 50 patients with AIT and 50 sex- and age-matched controls. Serum levels of free T3, free T4, thyrotropin, thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured by electrochemiluminescent immunoassays. Expression of several inflammasome components, the NOD-like receptor (NLR) family pyrin domain containing 1 (NLRP1), NLRP3, CARD-domain containing 4 (NLRC4), absent in melanoma 2 (AIM2), the apoptosis-associated speck-like protein that contains a caspase recruitment domain (ASC), caspase-1, IL-1β, and IL-18 was determined by real-time PCR and western blot. Immunohistochemistry was used to localize the expression of NLRP1, NLRP3, NLRC4, and AIM2. The Nthy-ori 3-1 thyroid cell line was stimulated with tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-17A, interleukin-6, and poly(dA:dT). The levels of IL-18 and IL-1β in the cell supernatant were measured by enzyme-linked immunosorbent assay, and lactate dehydrogenase was quantified by absorptiometry. ASC specks were examined by confocal immunofluorescence microscopic analysis. Cell death was examined by flow cytometry, and the N-terminal domain of gasdermin D was detected by western blot analysis.

Results

Expression of NLRP1, NLRP3, NLRC4, AIM2, ASC, caspase-1, pro IL-1β, pro IL-18, mRNA, and protein was significantly increased in thyroid tissues from patients with AIT, and enhanced posttranslational maturation of caspase-1, IL-18 and IL-1β was also observed. Expression of NLRP1, NLRP3, NLRC4, and AIM2 was localized mainly in thyroid follicular cells adjacent to areas of lymphatic infiltration. The thyroid mRNA level of NLRP1 and ASC was correlated to the serum TPOAb and TgAb levels in the AIT group. TNF-α and IFN-γ had a priming effect on the expression of multiple inflammasome components in thyroid cells. IFN-γ was found to strengthen poly(dA:dT)-induced cell pyroptosis and bioactive IL-18 release.

Conclusion

Our work has demonstrated for the first time that multiple inflammasomes are associated with AIT pathogenesis. The identified NLRP3, NLRP1, NLRC4, AIM2 inflammasomes and their downstream cytokines may represent potential therapeutic targets and biomarkers of AIT.

The Role of the Transcription Factor Nuclear Factor-kappa B in Thyroid Autoimmunity and Cancer

Nuclear factor-kappa B (NF-κB) is a ubiquitous transcription factor that is involved in inflammatory and immune responses, as well as in regulation of expression of many other genes related to cell survival, proliferation, and differentiation. In mammals, NF-κB comprises five subunits that can bind to promoter regions of target genes as homodimers or heterodimers. The most common dimer is the p50/p65 heterodimer. The several combinations of dimers that can be formed contribute to the heterogeneous regulation of NF-κB target genes, and this heterogeneity is further increased by interactions of the NF-κB dimers with other transcription factors, such as steroid hormone receptors, activator protein-1 (AP-1), and cAMP response element binding protein (CREB). In the thyroid, several studies have demonstrated the involvement of NF-κB in thyroid autoimmunity, thyroid cancer, and thyroid-specific gene regulation. The role of NF-κB in thyroid autoimmunity was hypothesized more than 20 years ago, after the finding that the binding of distinct NF-κB heterodimers to the major histocompatibility complex class I gene is hormonally regulated. Further studies have shown increased activity of NF-κB in thyroid autoimmune diseases and in thyroid orbitopathy. Increased activity of NF-κB has also been observed in thyroid cancer, where it correlates with a more aggressive pattern. Of particular interest, mutation of some oncogenes or tumor suppressor genes involved in thyroid carcinogenesis results in constitutive activation of the NF-κB pathway. More recently, it has been shown that NF-κB also has a role in thyroid physiology, as it is fundamental for the expression of the main thyroid-specific genes, such as sodium iodide symporter, thyroid peroxidase, thyroglobulin, Pax8, and TTF-1 (NKX2-1).

Increased Toll-Like Receptors Activity and TLR Ligands in Patients with Autoimmune Thyroid Diseases

OBJECTIVE

Autoimmune thyroid disease (AITD) is an organ-specific disorder due to the interplay between environmental and genetic factors. Toll-like receptors (TLRs) are pattern recognition receptors expressed abundantly on monocytes. There is a paucity of data on TLR expression in AITD. The aim of this study was to examine TLR expression, activation, ligands, and downstream signaling adaptors in peripheral blood mononuclear cells (PBMCs) extracted from untreated AITD patients and healthy controls.

METHOD

We isolated PBMC of 30 healthy controls, 36 patients with untreated Hashimoto's thyroiditis, and 30 patients with newly onset Graves' disease. TLR mRNA, protein expression, TLR ligands, and TLR adaptor molecules were measured using real-time PCR, Western blot, flow cytometry, and enzyme-linked immunosorbent assay (ELISA). PBMC was simulated with TLR agonists. The effects of TLR agonists on the viability of human PBMC were evaluated using the MTT assay. The supernatants of cell cultures were measured for the pro-inflammatory cytokines, interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), and IL-10 by ELISA.

RESULTS

TLR2, TLR3, TLR9, and TLR10 mRNA were significantly increased in AITD patients compared with controls. TLR2, TLR3, TLR9, high mobility group box 1 (HMGB1), and RAGE expression on monocytes was higher in patients than control at baseline and TLR agonists' stimulation. The release of TNF-α and IL-6 was significantly increased in PBMCs from AITD patients with TLR agonists, while IL-10 was significantly decreased. Downstream targets of TLR, myeloid differentiation factor 88 (MyD88), and myeloid toll/IL-1 receptor-domain containing adaptor-inducing interferon-β were significantly elevated in AITD patients. Levels of TLR2 ligands, HMGB1, and heat shock protein 60 were significantly elevated in AITD patients compared with those in controls and positively correlated with TgAb and TPOAb, while sRAGE concentration was significantly decreased in AITD patients.

CONCLUSION

This work is the first to show that TLR2, TLR3, and TLR9 expression and activation are elevated in the PBMCs of patients with AITD and TLRs may participate in the pathogenesis of AITD.

Naked DNA in cells: An inducer of major histocompatibility complex molecules to evoke autoimmune responses?

The major histocompatibility complex (MHC) is the exclusive chaperone that presents intracellular antigens, either self or foreign to T cells. Interestingly, aberrant expression of MHC molecules has been reported in various autoimmune target tissues such as thyroid follicular cells in Grave’s disease. Herein, we review the discovery of an unexpected effect of cytosolic double-stranded DNA (dsDNA), despite its origins, to induce antigen processing and presenting genes, including MHC molecules, in non-immune cells. Moreover, we highlight several recent studies that suggest cell injury endows thyroid epithelial cells with a phenotype of mature antigen presenting cells by inducing multiple antigen processing and presenting genes via releasing genomic DNA fragments into the cytosol. We discuss the possibility that such cytosolic dsDNA, in naked form without binding to histone proteins, might be involved in the development of cell damage-triggered autoimmune responses. We also discuss the possible molecular mechanism by which cytosolic dsDNA can induce MHC molecules. It is reasonable to speculate that cytosolic dsDNA-induced MHC class I is partially due to an autocrine/paracrine effect of type I interferon (IFN). While the mechanism of cytosolic dsDNA-induced MHC class II expression appears, at least partially, distinct from that mediated by IFN-γ. Further in-depth are required to clarify this picture.

Thyrotropin Receptor Epitope and Human Leukocyte Antigen in Graves' Disease

Graves' disease (GD) is an organ-specific autoimmune disease, and thyrotropin (TSH) receptor (TSHR) is a major autoantigen in this condition. Since the extracellular domain of human TSHR (TSHR-ECD) is shed into the circulation, TSHR-ECD is a preferentially immunogenic portion of TSHR. Both genetic factors and environmental factors contribute to development of GD. Inheritance of human leukocyte antigen (HLA) genes, especially HLA-DR3, is associated with GD. TSHR-ECD protein is endocytosed into antigen-presenting cells (APCs), and processed to TSHR-ECD peptides. These peptide epitopes bind to HLA-class II molecules, and subsequently the complex of HLA-class II and TSHR-ECD epitope is presented to CD4+ T cells. The activated CD4+ T cells secrete cytokines/chemokines that stimulate B-cells to produce TSAb, and in turn hyperthyroidism occurs. Numerous studies have been done to identify T- and B-cell epitopes in TSHR-ECD, including (1) in silico, (2) in vitro, (3) in vivo, and (4) clinical experiments. Murine models of GD and HLA-transgenic mice have played a pivotal role in elucidating the immunological mechanisms. To date, linear or conformational epitopes of TSHR-ECD, as well as the molecular structure of the epitope-binding groove in HLA-DR, were reported to be related to the pathogenesis in GD. Dysfunction of central tolerance in the thymus, or in peripheral tolerance, such as regulatory T cells, could allow development of GD. Novel treatments using TSHR antagonists or mutated TSHR peptides have been reported to be effective. We review and update the role of immunogenic TSHR epitopes and HLA in GD, and offer perspectives on TSHR epitope specific treatments.

The prevalence of thyroid autoimmunity in patients with urticaria: a systematic review and meta-analysis

Thyroid autoimmunity is the most common organ-specific autoimmune disorder, which is characterized by the production of thyroid autoantibodies and lymphocytic infiltration into the thyroid. The majority cases of chronic urticaria have unknown (idiopathic) causes, with about 30-40 % possibly having an autoimmune substrate. Considering that autoimmune factors may be the common features of both thyroid autoimmunity and urticaria, it is likely that both entities may coexist within the same patient. A number of studies have investigated the association between thyroid autoimmunity and urticaria. However, most of these studies are relatively small sample size, the power achieved in those studies was not sufficient to detect whether there is an association between urticaria and thyroid autoimmunity. The aim of this study is to combine primary data from all relevant studies to produce reliable estimates of the associations between thyroid autoantibodies and urticaria. Literature databases were searched including Medline, Embase, Web of Science, Chinese Wanfang, and CBM databases from January 1980 to December 2013. A total of 14,203 urticaria cases and 12,339 non-urticaria controls were included in this study. From these data, the odds ratio (OR) with 95% confidence interval (95% CI) was calculated. The meta-analysis results showed that the prevalence of positive thyroid autoantibodies in patients with urticaria was higher than non-urticaria controls (TgAb: OR 6.55, 95% CI 3.19-13.42, P<0.00001, I2=67%; TmAb: OR 4.51, 95% CI 2.78-7.33, P<0.00001, I2=47%; TPOAb: OR 8.71, 95% CI 6.89-11.01, P<0.00001, I2=20%, respectively). The results of this meta-analysis suggested that patients with urticaria were more likely to have thyroid autoimmunity than the control groups.

Thyroid autoimmunity as a window to autoimmunity: An explanation for sex differences in the prevalence of thyroid autoimmunity

Autoimmune thyroid diseases (AITDs), predominately Graves׳ disease and Hashimoto׳s thyroiditis, comprise the most common autoimmune diseases in humans. Both have the production of anti-thyroid antibody as an important aspect and both are much more prevalent in females, being at least 10 times more common than in males. Using these two clues, a hypothesis for the initiation of thyroid autoimmunity is proposed that helps to make the case that the thyroid is one of the most sensitive sites for autoimmunity and helps account for the prevalence and the observed sex differences in AITDs and associated diseases, such as type 1 diabetes and Latent Autoimmune Diabetes in Adults (LADA). The primary mechanisms proposed involve the underlying state of inflammation as a result of the adipokines, especially leptin, TNF-α, and IL-6, and the receptors able to recognize pathogen-associated molecular patterns (PAMP׳s) and damage-associated molecular patterns (DAMP׳s) through Toll-like receptors (TLR) and others receptors present on thyrocytes. The adipokines are produced by adipose tissue, but have hormone-like and immune modulating properties. As the levels of leptin are significantly higher in females, an explanation for the sex difference in thyroid autoimmunity emerges. The ability of the thyrocytes to participate in innate immunity through the TLR provides an adjuvant-like signal and allows for the action of other agents, such as environmental factors, viruses, bacteria, and even stress to provide the initiation step to break tolerance to thyroid self-antigens. Seeing the thyroid as one of the most sensitive sites for autoimmunity, means that for many autoimmune disorders, if autoimmunity is present, it is likely to also be present in the thyroid - and that that condition in the thyroid was probably earlier. The evidence is seen in multiple autoimmune syndrome.

Human anaplastic thyroid carcinoma cells are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract NK cells

PURPOSE

Anaplastic thyroid carcinoma (ATC) is one of the most aggressive forms of cancer with no curative therapies available. To date, strategies to target ATC by immunotherapy have not been evaluated. We investigated whether ATC would be a suitable target for natural killer (NK) cell-based immunotherapy.

EXPERIMENTAL DESIGN

We first established seven new cell lines from ATC tumors, three from papillary thyroid carcinoma tumors and analyzed them together with eight additional ATC cell lines. Cells were analyzed for sensitivity to lysis by NK cells and their ability to chemoattract and regulate the activity of NK cells. In addition, fresh tumor samples and peripheral blood from six patients with ATC were analyzed for NK cell infiltration and phenotype.

RESULTS

We observed that ATC cell lines are sensitive to lysis by ex vivo expanded NK cells and that the lysis was abrogated upon blockade of NKG2D. Sensitivity of thyroid cancer cell lines to NK cell-mediated lysis correlated with surface expression of UL16-binding protein 2 on tumor cells. Moreover, ATC cell lines produced high levels of CXCL10 and stimulated migration of expanded NK cells and ATC tumors were enriched for NK cells expressing the cognate chemokine receptor CXCR3. However, compared with NK cells in peripheral blood, ATC tumor-derived NK cells displayed a suppressed phenotype with a downregulated expression of NKG2D. In vitro, suppression of NK cell-mediated lysis and NKG2D expression by ATC cells was restored upon neutralization of prostaglandin-E2.

CONCLUSIONS

ATC cell lines are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract CXCR3-positive NK cells. Patients with ATC may benefit from NK cell-based immunotherapy.

Iodine excess as an environmental risk factor for autoimmune thyroid disease

The global effort to prevent iodine deficiency disorders through iodine supplementation, such as universal salt iodization, has achieved impressive progress during the last few decades. However, iodine excess, due to extensive environmental iodine exposure in addition to poor monitoring, is currently a more frequent occurrence than iodine deficiency. Iodine excess is a precipitating environmental factor in the development of autoimmune thyroid disease. Excessive amounts of iodide have been linked to the development of autoimmune thyroiditis in humans and animals, while intrathyroidal depletion of iodine prevents disease in animal strains susceptible to severe thyroiditis. Although the mechanisms by which iodide induces thyroiditis are still unclear, several mechanisms have been proposed: (1) excess iodine induces the production of cytokines and chemokines that can recruit immunocompetent cells to the thyroid; (2) processing excess iodine in thyroid epithelial cells may result in elevated levels of oxidative stress, leading to harmful lipid oxidation and thyroid tissue injuries; and (3) iodine incorporation in the protein chain of thyroglobulin may augment the antigenicity of this molecule. This review will summarize the current knowledge regarding excess iodide as an environmental toxicant and relate it to the development of autoimmune thyroid disease.

Apoptosis of NOD.H2 h4 thyrocytes by low concentrations of iodide is associated with impaired control of oxidative stress

BACKGROUND

Enhanced iodide intake in NOD.H2(h4) mice accelerates the incidence and severity of spontaneous autoimmune thyroiditis (SAT) via an unknown mechanism. A plausible hypothesis is that iodide-induced apoptosis of thyrocytes can create imbalances in antigenic load and/or disruption of immunoregulatory mechanisms that facilitate activation of autoreactive T cells in cervical lymph nodes draining the thyroid.

METHODS

We examined whether NOD.H2(h4) thyrocytes, exposed to low NaI concentrations in vitro, are more susceptible to apoptosis compared to thyrocytes from CBA/J mice, which are resistant to iodide-accelerated SAT (ISAT). We also looked, at the transcriptional level, for differential activation of genes involved in apoptosis or oxidative stress pathways that may account for potential differences in iodide-mediated apoptosis between NOD.H2(h4) and CBA/J thyrocytes.

RESULTS

We report that NOD.H2(h4) thyrocytes, cultured for 24 h at very low (4-8 μM) concentrations of NaI, exhibit high levels (40-55%) of apoptosis, as assessed microscopically following staining with fluorescent caspase inhibitors. Similar treatment of thyrocytes from CBA/J mice, which are resistant to ISAT, yielded significantly lower (10-20%) apoptotic rates. Expression analysis by real-time polymerase chain reaction using arrays of apoptosis- and oxidative stress-related genes showed that NaI intake upregulates the expression of 22 genes involved in ROS metabolism and/or antioxidant function in CBA/J thyrocytes, whereas only two of these genes were upregulated in NOD.H2(h4) thyrocytes. Among the set of overexpressed genes were those encoding thyroid peroxidase (Tpo; 5.77-fold), glutathione peroxidases (Gpx2, Gpx4, Gpx7; 2.03-3.14-fold), peroxiredoxins (Prdx1, Prdx2, Prdx5; 2.27-2.97-fold), superoxide dismutase 1 (Sod1; 3.57-fold), thioredoxin 1 (Txn1; 2.13-fold), and the uncoupling proteins 2 and 3 (Ucp2, Ucp3; 2.01-2.15-fold).

CONCLUSIONS

The results demonstrate that an impaired control of oxidative stress mechanisms is associated with the observed high susceptibility of NOD.H2(h4) thyrocytes to NaI-mediated apoptosis, and suggest a contributing factor for the development of ISAT in this strain.

Roles of DUOX-mediated hydrogen peroxide in metabolism, host defense, and signaling

SIGNIFICANCE

Among the NADPH oxidases, the dual oxidases, DUOX1 and DUOX2, constitute a distinct subfamily initially called thyroid oxidases, based on their high level of expression in thyroid tissue. Genetic alterations causing inherited hypothyroidism clearly demonstrate their physiological implication in thyroid hormonogenesis. However, a growing list of biological functions triggered by DUOX-dependent reactive oxygen species (ROS) in highly differentiated mucosae have recently emerged.

RECENT ADVANCES

A role of DUOX enzymes as ROS providers for lactoperoxidase-mediated killing of invading pathogens has been well established and a role in bacteria chemorepulsion has been proposed. Control of DUOX expression and activity by inflammatory molecules and immune receptor activation consolidates their contributions to innate immune defense of mucosal surfaces. Recent studies conducted in ancestral organisms have identified effectors of DUOX redox signaling involved in wound healing including epithelium regeneration and leukocyte recruitment. Moreover, local generation of hydrogen peroxide (H2O2) by DUOX has also been suggested to constitute a positive feedback loop to promote receptor signaling activation.

CRITICAL ISSUES

A correct balance between H2O2 generation and detoxification mechanisms must be properly maintained to avoid oxidative damages. Overexpression of DUOX genes has been associated with an increasing number of chronic inflammatory diseases. Furthermore, H2O2-mediated DNA damage supports a mutagenic function promoting tumor development.

FUTURE DIRECTIONS

Despite the high sequence similarity shared between DUOX1 and DUOX2, the two isoforms present distinct regulations, tissue expression and catalytic functions. The phenotypic characterization of novel DUOX/DUOXA invalidated animal models will be very useful for defining their medical importance in pathological conditions.

Enhanced iodine supplementation alters the immune process in a transgenic mouse model for autoimmune thyroiditis

BACKGROUND

The impact of excessive iodine intake on the development of autoimmune thyroiditis (AIT) is still under debate. Transgenic, antibody-devoid TAZ10 mice spontaneously develop AIT due to autoreactive thyroperoxidase-specific T cells. In this model, development of AIT is determined by a T cell infiltration of the thyroid gland leading to an elevation of serum thyrotropin (TSH) levels and significant weight gain. In the present study we investigated the impact of moderate and high iodine supplementation on the course of disease in these mice, which are immunologically prone to AIT.

METHODS

In addition to normal nutrition, mice were supplemented for 20 weeks with 2.5 μg versus 5 μg iodine per milliliter drinking water, which corresponds to a human daily iodine supplementation of 150 μg, 315 μg, and 615 μg iodine. AIT-defining parameters (weight gain, elevation of serum TSH levels, cellular infiltration of the thyroid) and immunologic effects were analyzed.

RESULTS

No significant differences were displayed when comparing weight and serum TSH levels in the iodine-supplemented versus control groups. Increased thyroid infiltrates with CD8⁺ T cells were detected by fluorescein-activated cell sorter (FACS) and immunofluorescence staining in mice supplemented with elevated iodine amounts (315 μg and 615 μg iodine per day, respectively). Immunologic monitoring revealed selective changes in immune cell frequencies (CD8⁺ and regulatory T cells, natural killer [NK] cells) and cytokine production (interferon-γ, interleukin-1α, and interleukin-17), however, without affecting the overall immune balance.

CONCLUSION

Our results demonstrate that elevated iodine supplementation has no physical impact on the course of disease in transgenic, antibody-devoid TAZ10 mice, which are immunologically prone to AIT.

Mechanisms of therapeutic resistance in cancer (stem) cells with emphasis on thyroid cancer cells

The two main reasons for death of cancer patients, tumor recurrence and metastasis, are multi-stage cellular processes that involve increased cell plasticity and coincide with elevated resistance to anti-cancer treatments. Epithelial-to-mesenchymal transition (EMT) is a key contributor to metastasis in many cancer types, including thyroid cancer and is known to confer stem cell-like properties onto cancer cells. This review provides an overview of molecular mechanisms and factors known to contribute to cancer cell plasticity and capable of enhancing cancer cell resistance to radio- and chemotherapy. We elucidate the role of DNA repair mechanisms in contributing to therapeutic resistance, with a special emphasis on thyroid cancer. Next, we explore the emerging roles of autophagy and damage-associated molecular pattern responses in EMT and chemoresistance in tumor cells. Finally, we demonstrate how cancer cells, including thyroid cancer cells, can highjack the oncofetal nucleoprotein high-mobility group A2 to gain increased transformative cell plasticity, prevent apoptosis, and enhance metastasis of chemoresistant tumor cells.

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.

Increased serum type I interferon activity in organ-specific autoimmune disorders: clinical, imaging, and serological associations

Background: Activation of the type I interferon (IFN) pathway has been implicated in the pathogenesis of systemic autoimmune disorders but its role in the pathogenesis of organ-specific autoimmunity is limited. We tested the hypothesis that endogenous expression of type I IFN functional activity contributes to the pathogenesis of autoimmune thyroid disease (ATD) and type I diabetes (T1DM).

Methods: We studied 39 patients with ATD and 39 age and sex matched controls along with 88 T1DM patients and 46 healthy matched controls respectively. Available clinical and serological parameters were recorded by chart review, and thyroid ultrasound was performed in 17 ATD patients. Type I IFN serum activity was determined in all subjects using a reporter cell assay. The rs1990760 SNP of the interferon-induced helicase 1 gene was genotyped in ATD patients.

Results: Serum type I IFN activity was increased in patients with ATD and T1DM compared to controls (p-values: 0.002 and 0.04, respectively). ATD patients with high type I IFN serum activity had increased prevalence of antibodies against thyroglobulin (anti-Tg) and cardiopulmonary manifestations compared to those with low IFN activity. Additionally, the presence of micronodules on thyroid ultrasound was associated with higher type I IFN levels. In patients with T1DM, high IFN levels were associated with increased apolipoprotein-B levels.

Conclusion: Serum type I IFN activity is increased in ATD and T1DM and is associated with specific clinical, serological, and imaging features. These findings may implicate type I IFN pathway in the pathogenesis of specific features of organ-specific autoimmunity.