The significance of immune-related molecule expression profiles in an animal model of Graves' disease

Peptidomic profiling of endogenous peptides in the spleens of mouse models of Graves' disease

Background

Graves' disease (GD) is a common autoimmune thyroid disorder. The pathogenesis of GD involves an autoimmune response to the A subunit of the human thyrotropin receptor (hTSHR), although the specific mechanisms are not fully elucidated.

Methods

This study established a GD model by immunizing BALB/c mice with a recombinant adenovirus expressing the hTSHR A subunit. Spleen tissues were collected and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify differentially expressed peptides (DEPs). Gene Ontology (GO) analysis and KEGG pathway analysis were further utilized to annotate the functions of these DEPs. Additionally, peptide bioactivity prediction and molecular docking studies were conducted using Alphafold and Pymol software, respectively, to assess the binding affinity of specific peptides to the hTSHR A subunit.

Results

The GD mouse model was successfully established, and 1,428 DEPs were identified in the spleen, with 368 upregulated and 1,060 downregulated. Functional analysis indicated that these DEPs are mainly involved in cellular endocytosis, regulation of gene expression, and nucleocytoplasmic transport. Notably, molecular docking studies revealed that the abnormally highly expressed peptide HG2A-24aa demonstrated potential bioactivity and strong binding affinity with hTSHR-289aa.

Conclusion

The specific bioactive peptides may play key roles in the pathogenesis of GD, particularly HG2A-24aa, which may have a significant role in the MHC II antigen presentation pathway mediated by the hTSHR A subunit.

Development and application of animal models to study thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO), also known as Graves' ophthalmopathy, is an autoimmune disease that is usually accompanied by hyperthyroidism. Its pathogenesis involves the activation of autoimmune T lymphocytes by a cross-antigen reaction of thyroid and orbital tissues. The thyroid-stimulating hormone receptor (TSHR) is known to play an important role in the development of TAO. Because of the difficulty of orbital tissue biopsy, the establishment of an ideal animal model is important for developing novel clinical therapies of TAO. To date, TAO animal modeling methods are mainly based on inducing experimental animals to produce anti-thyroid-stimulating hormone receptor antibodies (TRAbs) and then recruit autoimmune T lymphocytes. Currently, the most common methods are hTSHR-A subunit plasmid electroporation and hTSHR-A subunit adenovirus transfection. These animal models provide a powerful tool for exploring the internal relationship between local and systemic immune microenvironment disorders of the TAO orbit, facilitating the development of new drugs. However, existing TAO modeling methods still have some defects, such as low modeling rate, long modeling cycles, low repetition rate, and considerable differences from human histology. Hence, the modeling methods require further innovation, improvement, and in-depth exploration.

Dihydrotestosterone regulates oxidative stress and immunosuppressive cytokines in a female BALB/c mouse model of Graves' disease

Background: Graves' disease (GD) is an autoimmune disease that affects more women than men. In our previous study, a potent bioactive androgen, 5α-dihydrotestosterone (DHT) showed a protective effect against GD in female BALB/c mice. Evidence indicates that abnormal oxidative stress and immunosuppressive cytokines (TGF-β, IL-35) play critical roles in the pathogenesis and development of GD. The purpose of this research is to measure these cytokines and oxidative stress markers to explore potential protective mechanisms of DHT in a BALB/c mouse model of GD. Methods: GD was induced in female BALB/c mice by intramuscular injection of an adenovirus expressing the A-subunit of the TSH receptor (Ad-TSHR289). DHT or a matching placebo was injected every 3 days. Mice were sacrificed four weeks after the third virus immunization to obtain blood, thyroid and spleen for further analysis. Results: Thyroid hormones were significantly reduced in DHT treated GD mice. In addition, DHT attenuated thyroid oxidative injuries in GD mice, as shown by decreased total antioxidation capability (TAOC), superoxide dismutase (SOD) and the level of malondialdehyde (MDA). The levels of immunosuppressive cytokines (TGF-β, IL-35) in DHT group were significant higher compared with the GD group. Conclusions: The results demonstrated that DHT could reduce the severity of GD in female BALB/c mice by regulating oxidative stress. The upregulation of immunosuppressive cytokines might be another important protective mechanism.

Animal models of Graves' disease and Graves' orbitopathy

PURPOSE OF REVIEW

The purpose of this article is to summarize the recent advances on experimental Graves' hyperthyroidism and orbitopathy as studied in two widely used mouse models, which involve repetitive genetic vaccinations using either adenovirus or in-vivo electroporation of the eukaryotic expression plasmid expressing the thyrotropin receptor (TSHR) as a vector.

RECENT FINDINGS

The models have been improved by using different types of antigens, including the holo receptor, the receptor A-subunit, an alternatively spliced form of variant receptor lacking a single leucine-rich repeat in the codomain, the receptors of human or mouse origin; different mice such as wild-type, TSHR knockout, TSHR transgenic and different inbred mice; and different immunization protocols. They are now useful for elucidating the pathogenic mechanisms of not only Graves' hyperthyroidism but also Graves' orbitopathy.

SUMMARY

This review summarizes the literature of mouse models of Graves' hyperthyroidism and orbitopathy published over the last 3 years.

Modeling Graves' Orbitopathy in Experimental Graves' Disease

Graves' orbitopathy (GO), also known as thyroid eye disease is an inflammatory disease of the orbital tissue of the eye that arises as a consequence of autoimmune thyroid disease. The central feature of the disease is the production of antibodies to the thyrotropin hormone receptor (TSHR) that modulate the function of the receptor leading to autoimmune hyperthyroidism and GO. Over the years, all viable preclinical models of Graves' disease have been incomplete and singularly failed to progress in the treatment of orbital complications. A new mouse model of GO based upon immunogenic presentation of human TSHR A-subunit plasmid by close field electroporation is shown to lead to induction of prolonged functional antibodies to TSHR resulting in chronic disease with subsequent progression to GO. The stable preclinical GO model exhibited pathologies reminiscent of human disease characterized by orbital remodeling by inflammation and adipogenesis. Inflammatory lesions characterized by CD3+ T cells and macrophages were localized in the orbital muscle tissue. This was accompanied by extensive adipogenesis of orbital fat in some immune animals. Surprisingly, other signs of orbital involvement were reminiscent of eyelid inflammation involving chemosis, with dilated and congested orbital blood vessels. More recently, the model is replicated in the author's independent laboratories. The pre-clinical model will provide the basis to study the pathogenic and regulatory roles of immune T and B cells and their subpopulations to understand the initiation, pathophysiology, and progression of GO.

Disturbances of modulating molecules (FOXP3, CTLA-4/CD28/B7, and CD40/CD40L) mRNA expressions in the orbital tissue from patients with severe graves' ophthalmopathy

Purpose. To evaluate the relationship between the expression of orbital tissue mRNA for FOXP3, CTLA-4/CD28/CD80/CD86, and CD40/CD40 and the severity of Graves' orbitopathy (GO). Material and Methods. Orbital tissue was obtained from 26 patients with GO, with mild (n = 6) or severe GO (n = 20), and 7 healthy controls. The expression of mRNA of FOXP3, CTLA-4/CD28/CD80/CD86, CD40/CD40L was measured by RT-PCR. TCR and CD3 were evaluated by immunohistochemistry. Results. Higher mRNA for FoxP3 (relative expression: 1.4) and CD40 (1.27) and lower expression of CTLA-4 (0.61) were found in the GO tissues versus controls. In severe GO as compared to mild GO higher mRNA expression for FoxP3 (1.35) and CD40 (1.4) and lower expression for CTLA-4 (0.78), CD28 (0.62), and CD40L (0.56) were found. A positive correlation was found between FOXP3 mRNA and CD3 infiltration (R = 0.796, P = 0.0000001). Conclusions. The enhanced FOXP3 mRNA expression in GO samples may suggest the dysfunction of FOXP3 cells in the severe GO. The diminished mRNA expression of CTLA-4 in severe GO may indicate inadequate T regulatory function. The enhanced mRNA expression of CD40 in severe GO and negative correlation to CRP mRNA may suggest their role in the active and inactive GO.

CTLA-4 CT60 (rs3087243) polymorphism and autoimmune thyroid diseases susceptibility: a comprehensive meta-analysis

OBJECTIVE

To determine whether the cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) CT60 polymorphism (rs3087243) confers susceptibility to autoimmune thyroid disease (AITDs).

METHODS

A meta-analysis was performed using: (1) allelic contrast, (2) recessive model and (3) dominant model. Electronic search of PubMed, Medline and Chinese National Knowledge Infrastructure (CNKI) was conducted to select studies.

RESULTS

Finally, a total of 20 separate studies were available for the current meta-analysis: Graves' disease (GD): 18 studies including 1 Iranian, 6 Caucasian and 11 Asian populations; Hashimoto's thyroiditis (HT): seven studies including one Iranian, three Caucasian and three Asian populations. A significant association was found between the CTLA-4 CT60 polymorphism (rs3087243) and GD, with regard to comparisons between allele and genotype frequencies (all p < 0.001). After stratification by ethnicity, significant relationships were consistently identified both in Caucasian and Asian populations. Furthermore, the association between this allelic variant and HT risk was also found in overall and Asian populations (OR: 1.26, 95% CI: 1.10-1.44; OR: 1.45, 95% CI: 1.19-1.76, respectively).

CONCLUSION

Taken together, our study suggested that the CT60 polymorphism (rs3087243) in CTLA-4 gene might confer susceptibility to the AITDs (GD/HT).