It Takes Two to Tango: IGF-I and TSH Receptors in Thyroid Eye Disease

Targeting the Aryl Hydrocarbon Receptor to Attenuate IGF1R Signaling in Thyroid Eye Disease

Background: Thyroid eye disease (TED) is an autoimmune disorder characterized by proptosis, inflammation, and fibrosis. Elevated insulin-like growth factor 1 receptor (IGF1R) signaling in TED orbital fibroblasts (OFs) drives the proliferation and biosynthesis of hyaluronan, which causes enlargement of orbital tissue volume. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates cellular stress responses, metabolism, and inflammation. Given its important role in regulating cellular responses, we hypothesized that activation of the AHR could limit excessive IGF1R signaling in TED OFs, offering therapeutic potential. Methods: We measured IGF1R and AHR expression levels in TED, non-TED, and non-OF controls. OF activation was analyzed using proliferation, hyaluronan accumulation, and migration assays. RNA sequencing was used to detect transcriptome-wide changes in IGF1-treated TED OFs. After gene set enrichment analysis, select gene expression changes were validated by quantitative polymerase chain reaction. OFs were treated with the AHR ligands 6-formylindolo[3,2-b]carbazole (FICZ) or tapinarof with or without IGF1. Western blotting evaluated signaling pathways impacted by AHR and IGF1R signaling. Results: TED OFs showed elevated IGF1R and AHR expression levels compared to controls. IGF1 significantly increased hyaluronan accumulation, proliferation, and migration in TED OFs compared to non-TED OFs. IGF1R signaling altered the expression of hundreds of genes controlling cell migration, proliferation, and metabolism in TED OFs. These genes included TUBA1B, TUBA1C, CRABP2 (upregulated), and IRS2 and SOD3 (downregulated). AHR activation blocked proliferation, migration, hyaluronan production, and gene expression mediated through IGF1R signaling. The AHR inhibited these pathways by reducing phosphorylation of GSK3β, an important mediator of IGF1R/β-catenin mediated signaling. Conclusions: AHR activation represents a promising therapeutic strategy for mitigating TED progression by inhibiting IGF1R signaling. Through modulation of GSK3β-mediated pathways, AHR activation may target additional pathologically relevant pathways beyond those affected by direct IGF1R inhibitors. This research provides novel insights into TED pathophysiology and offers a potential avenue for developing therapies to improve patient outcomes.

Development and validation of potential molecular subtypes and signatures of thyroid eye disease based on angiogenesis-related gene analysis

BACKGROUND

Thyroid eye disease (TED) is an autoimmune inflammatory disorder of the orbit, associated with a range of potential clinical sequelae. Tumor cells in TED overexpress pro-angiogenic factors, driving the formation of heterogeneous and immature neovascularization. This dysregulated angiogenesis often leads to a hypoxic microenvironment due to insufficient perfusion. Despite its importance, the role of angiogenesis-related genes (ARGs) in TED pathophysiology remains poorly understood.

METHODS

To bridge this knowledge gap, our study aimed to identify and validate ARGs implicated in TED using a comprehensive bioinformatics strategy. By intersecting differential gene expression analyses with a curated list of 103 known ARGs, we aimed to pinpoint those with potential roles in TED. Advanced methodologies, including GSEA and GSVA, facilitated an in-depth exploration of the biological functions and pathways associated with these ARGs. Further refinement through Lasso regression and SVM-RFE enabled the identification of key hub genes and the evaluation of their diagnostic potential for TED. Additionally, we investigated the relationship between these hub ARGs and relevant clinical parameters. To corroborate our findings, we analyzed expression data from datasets GSE58331 and GSE105149, focusing on the six ARGs identified as potentially crucial to TED pathology.

RESULTS

Our investigation unveiled six ARGs (CRIP2, DUSP1, CTSL, DOCK5, ERAP1, SCG2) as intimately connected to TED. Functional analyses highlighted their involvement in processes such as response to ameboidal-type cell migration, epithelial cell migration, epithelium migration. Importantly, the diagnostic capabilities of these ARGs demonstrated promising efficacy in distinguishing TED from non-affected states.

CONCLUSIONS

This study identifies six ARGs as novel biomarker candidates for TED, elucidating their potential roles in the disease's pathogenesis.

Controversies Surrounding IGF-I Receptor Involvement in Thyroid-Associated Ophthalmopathy

Background: Thyroid-associated ophthalmopathy (TAO, aka thyroid eye disease [TED], Graves' orbitopathy) remains poorly understood and inadequately treated since its initial description. It is disfiguring, can threaten vision, and represents an autoimmune process closely associated with thyroid disease. Unambiguous connections linking TAO to the glandular maladies of Graves' disease (GD) remain incompletely clarified. Detecting the thyrotropin receptor (TSHR) in periocular tissues suggests that this cell-surface protein represents a shared autoantigen with the thyroid gland, but we now know that its expression is ubiquitous. Most patients with TAO have relatively high circulating levels of activating anti-TSHR autoantibodies. Emerging more recently is the importance of insulin-like growth factor I receptor (IGF-IR) in the pathogenesis of TAO. The TSHR/IGF-IR signaling complex apparently drives circulating fibrocytes and the unique phenotypes of fibroblasts inhabiting the TAO orbit (GD-OF). Methods: The PubMed database was scanned for articles dating back to the earliest time periods covered. Keywords used for primary searches included thyroid-associated ophthalmopathy, Graves' orbitopathy, TED, orbit, TSH receptor, IGF-I receptor, and autoimmune thyroid disease. Secondary searches used numerous other search terms. Results: GD-OF have been characterized extensively as being particularly responsive to the immunological factors and key effectors in TAO pathogenesis. Both TSHR and IGF-IR are overexpressed by GD-OF and CD34+ fibrocytes and form a signaling complex. They are activated through this TSHR/IGF-IR complex to produce large amounts of hyaluronan and express multiple cytokines. This complex mediates cellular responses to pathogenic IgGs in TAO. CD34+ fibrocytes and CD34+ OF also express relatively high levels of multiple thyroid autoantigens. Identifying IGF-IR as a key component of a receptor complex and its intertwining signaling activities with those of TSHR has led to a targeted medical therapy for TAO. This therapy involves the selective systemic inhibition of IGF-IR. Conclusions: Much has been learned over the preceding decades about the pathogenesis of TAO. Among these is the identification of IGF-IR as a pivotal component underpinning the disease. This has led directly to development of an effective targeted therapy. Important gaps in our understanding persist, and current therapies have limitations. Thus, despite these advancements, considerably more remains to be achieved.

The relationship between cholesterol levels and thyroid eye disease

Background

Thyroid eye disease (TED) is the most prevalent extrathyroidal manifestation of Graves' disease (GD). Emerging evidence suggests a relationship between elevated total and low-density lipoprotein (LDL) cholesterol levels and TED. This study aimed to investigate this correlation in the Brazilian population by analyzing data from two tertiary care centers.

Methods

Data were collected from GD patients treated with methimazole between 1999 and 2021, excluding those receiving other treatments. Laboratory results and information on smoking habits, statin use and medications affecting lipid profiles during the euthyroid state were analyzed.

Results

Smoking and elevated LDL cholesterol levels were significantly associated with TED activity and severity. Logistic regression revealed correlations between higher LDL cholesterol, total cholesterol and increased clinical activity score (P < 0.01, OR: 1.012, 95% CI: 1.003-1.021; P < 0.01, OR: 1.010, 95% CI: 1.002-1.018). These were also associated with more severe disease forms as defined by EUGOGO (P < 0.01, OR: 1.015, 95% CI: 1.006-1.024; P < 0.005, OR: 1.011, 95% CI: 1.004-1.019). Multiple regression confirmed that TED activity was significantly correlated with LDL cholesterol (P < 0.01) and smoking status (P < 0.01). Disease severity was associated with reduced HDL cholesterol (P < 0.05, OR: 0.973, 95% CI: 0.948-0.999), elevated LDL cholesterol (P < 0.005, OR: 1.013, 95% CI: 1.004-1.023) and active smoking (P < 0.05, OR: 2.881, 95% CI: 1.190-6.971).

Conclusion

Elevated LDL cholesterol may serve as a potential indicator of TED. Further research is needed to determine whether lipid-lowering interventions could reduce TED risk or improve its management.

Thyroid eye disease and ocular myasthenia gravis

PURPOSE OF REVIEW

An overview of two ocular diseases, which significantly impact quality of life: thyroid eye disease (TED) and ocular myasthenia gravis (OMG). Additionally, we describe the clinical challenge when they occur simultaneously. We will describe the pathophysiology of both conditions, the currently available diagnostic tools, and the therapies available.

RECENT FINDINGS

Recent literature has described newer diagnostic modalities, predictors of disease severity and co-occurrence of TED and OMG, and novel therapies. There is also critical analysis of current therapeutics and risk factors.

SUMMARY

The findings from this review suggest a need for heightened clinical awareness and early detection strategies for TED and OMG due to their overlapping clinical presentation. Emerging therapies and diagnostic techniques should be integrated into practice. Further research is warranted to explore the long-term safety and efficacy of novel treatments and the potential genetic links between these conditions.

Characteristics of Hyaluronan Metabolism During Myofibroblast Differentiation in Orbital Fibroblasts

Purpose

To study the impact of myofibroblast differentiation (MD) on hyaluronan (HA) turnover in orbital fibroblasts (OFs) focusing on the expression of its key enzymes and their potential implications in the pathogenesis of thyroid eye disease (TED).

Methods

Primary cultures of OFs were established from tissue samples (TED OFs, n = 4; non-TED OFs, n = 5). MD was induced by TGF-β1 (5 ng/mL). Measurements were performed after 24- and 72-hour treatments. The proliferation rate was determined by 5-bromo-2'-deoxyuridine (BrdU) incorporation. HA level and size were measured using an aggrecan-based ELISA-like method and agarose gel electrophoresis, respectively. mRNA expressions of myofibroblast markers and enzymes with a role in HA metabolism were determined using real-time PCR.

Results

Upregulation of type I collagen alpha1 chain, alpha-smooth muscle actin, and fibronectin indicated that OFs underwent MD after stimulation by TGF-β. After 72 hours, proliferation of untreated cultures declined, but it remained higher in myofibroblasts. Pericellular HA content, but not HA in the supernatant of myofibroblasts, increased compared to untreated cells. TGF-β was a potent stimulator of hyaluronan synthase 1 (HAS1) expression. The expression of hyaluronidase-1 and cell migration-inducing protein (CEMIP) diminished following MD, whereas the expression of transmembrane protein 2, the regulator of HA catabolism through CEMIP, was elevated. The size distribution of HA shifted toward a high-molecular-weight form following treatment with TGF-β.

Conclusions

OFs undergoing MD are characterized by decreased HA turnover as a consequence of the inhibition of hyaluronidases and HAS1 induction. Our results suggest that hyaluronidases could be potential targets in the treatment of TED.

A Comprehensive Review of Thyroid Eye Disease Pathogenesis: From Immune Dysregulations to Novel Diagnostic and Therapeutic Approaches

Thyroid eye disease is a complex inflammatory disorder of the orbit that has gained tremendous interest over the past years, and numerous scientific efforts have been deployed to elucidate its pathophysiology for novel drug development. Our manuscript will delve into the molecular dysregulations involved in the pathogenesis of thyroid eye disease that led to its clinical manifestations. Abnormalities within the apoptotic pathway, inflammatory cascade, and autoimmune regulatory systems will be covered. We will further discuss the challenges involved in its diagnosis and management and provide a summary of the current diagnostic tools (i.e., molecular biomarkers, diagnostic scores) from the perspective of clinicians. Finally, our comprehensive literature review will provide a thorough summary of most recent preclinical and clinical studies around the topic of thyroid eye disease, with an emphasis on the manuscripts published within the last five years. We believe our manuscript will bring novelty within the field by bridging the fundamental sciences with the clinical aspect of this disease. This review will be a great tool for clinicians in better understanding the pathogenesis of thyroid eye disease while providing an outlook on future perspectives (i.e., liquid biopsies, artificial intelligence).

TSHR-IGF-IR complex drives orbital fibroblast misbehavior in thyroid eye disease

PURPOSE OF REVIEW

Evolving understanding of thyroid eye disease (TED) has led to rapidly advancing therapeutic options. Most new treatments under development or recently available to patients are predicated on insights into disease mechanism.

RECENT FINDINGS

TED, a disfiguring process, involves inflammation and remodeling of the connective tissues around the eye. TED most frequently presents as a component of Graves' disease. Advances in our understanding of cells involved in TED and their molecular interactions have led to novel therapeutic targets. Among these cell types are orbital fibroblasts and a subset comprising monocyte progenitor cells, known as CD34 + CXCR4 + fibrocytes. Among the attributes of fibrocytes is their expression of several autoantigens associated with Graves' disease, including TSHR, thyroglobulin and thyroperoxidase. Fibrocytes also express high levels of the insulin-like growth factor-I (IGF-I) receptor, thought to mediate fibroblast activation. Therapeutically targeting the TSHR/IGF-IR receptor complex using an IGF-I receptor antagonist, teprotumumab, has resulted in substantial clinical benefit for patients with TED. The neural axon repellent, Slit2, and its cognate receptor, ROBO1, appear to modulate the inflammatory phenotype of these orbit-infiltrating fibrocytes.

SUMMARY

More detailed understanding of orbital fibroblasts and the distinctions between cell subsets comprising them should lead to more effective therapies with fewer side effects.

Teprotumumab versus intravenous methylprednisolone in thyroid eye disease: A systematic review

Thyroid eye disease (TED), also known as thyroid-associated ophthalmopathy, is an autoimmune disorder caused due to a complex interplay between autoantigens including the thyroid-stimulating hormone receptor and the insulin-like growth factor-I receptor. TED is characterized by progressive proptosis or diplopia. This systematic review aimed to compare the efficacy of the newer monoclonal antibody - teprotumumab and intravenous methylprednisolone (IVMP) in TED patients. We performed a systematic review of previously published studies from 2013 to June 2023. A total of 329 articles were screened; among them, 111 non-duplicate publications were identified. After the screening of titles and abstracts, 156 publications were excluded; then, another 47 published papers were excluded after the full-text screening. The remaining 15 eligible studies were included in this systematic review. The majority of studies used either teprotumumab alone or in combination with others. Among 15 studies, eight studies used teprotumumab in TED patients, whereas remaining 7 studies used a standard treatment regimen. This systematic review provides an overview of the existing treatment options using monoclonal antibody - teprotumumab and IVMP in TED patients. The overall assessment provides a finding that antibody - teprotumumab is is a good choice compared to conventional IVMP for providing better outcomes in patients with TED.

Epidemiology of thyroid-stimulating immunoglobulin in recent-onset symptomatic thyroid eye disease

Purpose

This study aims to report correlations between thyroid-stimulating immunoglobulin (TSI) and both clinical and radiological parameters in recent-onset symptomatic thyroid eye disease (TED) patients.

Methods

A prospective cohort study of TED patients managed at the Chinese University of Hong Kong from January 2014 to May 2022. Serum TSI levels were determined with the functional assay. Outcomes included the Clinical Activity Score (CAS), marginal reflex distance1 (MRD1), extraocular muscle motility restriction (EOMy), exophthalmos, and diplopia. The radiological assessment included cross-sectional areas and signal of extraocular muscles on STIR-sequence MRI.

Results

A total of 255 (197 female) treatment-naive patients, with an average onset age of 50 ± 14 years (mean ± s.d.), were included. Elevated pre-treatment TSI level was observed in 223 (88%) patients. There was a weak positive correlation between TSI and CAS (r = 0.28, P = 0.000031), MRD1 (r = 0.17, P = 0.0080), and the size of the levator palpebrae superioris/superior rectus complex (r = 0.25, P = 0.018). No significant correlation existed between TSI and STIR signals. The AUC and optimal cut-off value for clinical active TED were 0.67 (95% CI: 0.60-0.75) and 284% (specificity: 50%, sensitivity: 85%). In total, 64 patients received intravenous methylprednisolone (IVMP) during the study interval, and they had a higher baseline TSI level than those who did not have IVMP (P = 0.000044). Serial post-IVMP TSI among the 62 patients showed a significant reduction compared to the baseline level (P < 0.001). Both the baseline and post-IVMP TSI levels, and percentages of TSI changes were comparable between patients who responded and did not respond to the first course of IVMP.

Conclusion

TSI can be a serum biomarker for the diagnosis, prognosis, and treatment response of TED. Further validation should be warranted.

Exploring gut microbiota and metabolite alterations in patients with thyroid-associated ophthalmopathy using high-throughput sequencing and untargeted metabolomics

Introduction

Thyroid-associated ophthalmopathy (TAO) is an autoimmune-driven orbital inflammatory disease. Despite research efforts, its exact pathogenesis remains unclear. This study aimed to characterize the intestinal flora and metabolic changes in patients with TAO to identify the flora and metabolites associated with disease development.

Methods

Thirty patients with TAO and 29 healthy controls were included in the study. The intestinal flora and metabolites were analyzed using high-throughput sequencing of the 16S rRNA gene and non-targeted metabolomics technology, respectively. Fresh fecal samples were collected from both populations for analysis.

Results

Reduced gut richness and diversity were observed in patients with TAO. Compared to healthy controls, significant differences in relative abundance were observed in patients with TAO at the order level Clostridiales, family level Staphylococcaceae, genus level Staphylococcus, Fournierella, Eubacterium siraeum, CAG-56, Ruminococcus gnavus, Intestinibacter, Actinomyces, and Erysipelotrichaceae UCG-003 (logFC>1 and P<0.05). Veillonella and Megamonas were closely associated with clinical symptoms in patients with TAO. Among the 184 significantly different metabolites, 63 were upregulated, and 121 were downregulated in patients with TAO compared to healthy controls. The biosynthesis of unsaturated fatty acids was the significantly enriched metabolic pathway. Correlation analysis revealed Actinomyces was positively correlated with NAGlySer 15:0/16:0, FAHFA 3:0/20:0, and Lignoceric Acid, while Ruminococcus gnavu was positively correlated with Cer 18:0;2O/16:0; (3OH) and ST 24:1;O4/18:2.

Conclusion

Specific intestinal flora and metabolites are closely associated with TAO development. Further investigation into the functional associations between these flora and metabolites will enhance our understanding of TAO pathogenesis.

Reverse repurposing: Potential utility of cancer drugs in nonmalignant illnesses

Growth and immune process dysregulation can result in both cancer and nonmalignant disease (hereditary or acquired, with and without predisposition to malignancy). Moreover, perhaps unexpectedly, many nonmalignant illnesses harbor genomic alterations indistinguishable from druggable oncogenic drivers. Therefore, targeted compounds used successfully to treat cancer may have therapeutic potential for nonmalignant conditions harboring the same target. MEK, PI3K/AKT/mTOR, fibroblast growth factor receptor (FGFR), and NRG1/ERBB pathway genes have all been implicated in both cancer and noncancerous conditions, and several cognate antagonists, as well as Bruton's tyrosine kinase inhibitors, JAK inhibitors, and CD20-directed antibodies, have established or theoretical therapeutic potential to bridge cancer and benign diseases. Intriguingly, pharmacologically tractable cancer drivers characterize a wide spectrum of disorders without malignant potential, including but not limited to Alzheimer's disease and a variety of other neurodegenerative conditions, rheumatoid arthritis, achondroplastic dwarfism, and endometriosis. Expanded repositioning of oncology agents in order to benefit benign but serious medical illnesses is warranted.

Immune checkpoints: new insights into the pathogenesis of thyroid eye disease

Thyroid eye disease (TED) is a disfiguring autoimmune disease characterized by changes in the orbital tissues and is caused by abnormal thyroid function or thyroid-related antibodies. It is the ocular manifestation of Graves' disease. The expression of thyroid-stimulating hormone receptor (TSHR) and the insulin-like growth factor-1 receptor (IGF-1 R) on the cell membrane of orbital fibroblasts (OFs) is responsible for TED pathology. Excessive inflammation is caused when these receptors in the orbit are stimulated by autoantibodies. CD34+ fibrocytes, found in the peripheral blood and orbital tissues of patients with TED, express immune checkpoints (ICs) like MHC II, B7, and PD-L1, indicating their potential role in presenting antigens and regulating the immune response in TED pathogenesis. Immune checkpoint inhibitors (ICIs) have significantly transformed cancer treatment. However, it can also lead to the occurrence of TED in some instances, suggesting the abnormality of ICs in TED. This review will examine the overall pathogenic mechanism linked to the immune cells of TED and then discuss the latest research findings on the immunomodulatory role of ICs in the development and pathogenesis of TED. This will offer fresh perspectives on the study of pathogenesis and the identification of potential therapeutic targets.

Comparison of orbital fibroblasts from Graves' ophthalmopathy and healthy control

Graves' ophthalmopathy (GO) is an extrathyroidal manifestation of Graves' disease, Orbital fibroblasts (OFs) are recognized as key players in GO pathogenesis, involved in orbital inflammation, tissue remodeling, and fibrosis. This study offers a primary exploration of cell behavior and characteristics on OFs from GO (GO-OFs), and compared to OFs from healthy control (HC-OFs). Results reveal that GO-OFs exhibit delayed migration from tissue fragments, while no significant difference in cell proliferation is observed between GO-OFs and HC-OFs. Aberrant expression pattern of surface proteins Thy-1, TSHR, and IGF-1R suggests shared autoantigens and pathways between GO and GD, contributing to inflammation and fibrosis. Investigations into cytokine responses unveil elevated secretion of hyaluronic acid (HA) and prostaglandin E2 (PGE2) in GO-OFs, emphasizing their role in tissue remodeling. These findings deepen our understanding of OFs in GO pathogenesis, offering potential therapeutic avenues.

A comparison of proptosis reduction with teprotumumab versus surgical decompression based on fat-to-muscle ratio in thyroid eye disease

PURPOSE

To explore if orbital fat-to-muscle ratio (FMR) is predictive of whether surgical decompression or teprotumumab leads to greater proptosis reduction in thyroid eye disease (TED).

METHODS

A single-center retrospective cohort study comparing surgical decompression with teprotumumab according to FMR. All TED patients completing an 8-dose course of teprotumumab between January 2020 and September 2022 and all patients undergoing bony orbital decompression from January 2017 to December 2019 were included. Subjects were excluded if they were <18 years, received both surgical decompression and teprotumumab, or lacked orbital imaging. The primary exposure variable was teprotumumab or surgical decompression. The secondary exposure variable was baseline FMR. The primary outcome measure was change in proptosis (mm).

RESULTS

Thirty-eight patients, mean age 53.5 years (±11.4), were included in the teprotumumab group and 160 patients, mean age 48 years (±11.1), in the surgical group. Average proptosis reduction after teprotumumab and surgical decompression was 3 mm (±1.44) and 5 mm (±1.75), respectively. The FMR was stratified at the median of 1.80. In subjects with FMR < 1.80, teprotumumab showed equivalent proptosis reduction compared to surgical decompression, -0.33 mm (SE 1.32) p = .802. In subjects with FMR ≥ 1.80, surgical decompression led to significantly more proptosis reduction than teprotumumab, 3.01 mm (SE 0.54), p < .001.

CONCLUSIONS

Baseline FMR can be used to counsel patients as to proptosis reduction with teprotumumab versus surgery. Subjects with low FMR obtain comparable proptosis reduction with teprotumumab or surgery, whereas high FMR is associated with more significant proptosis reduction following surgery over teprotumumab.

Ocular surface and meibomian gland evaluation in euthyroid Graves' ophthalmopathy

PURPOSE

Euthyroid Graves' ophthalmology (EGO) refers to the subgroup of thyroid eye disease patients with distinct clinical presentations. This study evaluated the ocular surface and meibomian gland changes in EGO patients.

METHODS

A cross-sectional study was conducted at The Chinese University of Hong Kong including 34 EGO patients and 34 age-and sex- matched healthy controls. Outcome measures include anterior segment examination, keratographic and meibographic imaging.

RESULTS

Between 34 EGO patients and 34 age and sex-matched healthy controls, EGO was associated with a higher ocular surface disease index (P < 0.01), higher severity of meibomian gland dropout (upper: P < 0.001, lower: P < 0.00001) and higher percentage of partial blinking (P = 0.0036). The worse affected eyes of the EGO patients were associated with corneal staining (P = 0.0019), eyelid telangiectasia (P = 0.0009), eyelid thickening (P = 0.0013), eyelid irregularity (P = 0.0054), meibomian gland plugging (P < 0.00001), expressibility (P < 0.00001), and meibum quality (P < 0.00001). When the two eyes of the same EGO patient were compared, the degree of meibomian gland dropout was higher among the worse affected eyes (upper: P < 0.00001, and lower: P < 0.00001). Tear meniscus height, lipid layer thickness, and noninvasive break-up time were comparable between the two eyes of EGO patients and also between EGO patients and healthy controls. TMH was positively correlated with the degree of exophthalmos (r = 0.383, P < 0.05).

CONCLUSION

EGO patients have more ocular surface complications and meibomian gland dropouts than healthy controls. Almost 60% of them had dry eye symptoms, but aqueous deficiency was not apparent. Further studies are warranted to clarify the mechanism of dry eye in EGO. (249 words).

Non-canonical G protein signaling

The original paradigm of classical - also referred to as canonical - cellular signal transduction of heterotrimeric G proteins (G protein) is defined by a hierarchical, orthograde interaction of three players: the agonist-activated G protein-coupled receptor (GPCR), which activates the transducing G protein, that in turn regulates its intracellular effectors. This receptor-transducer-effector concept was extended by the identification of regulators and adapters such as the regulators of G protein signaling (RGS), receptor kinases like βARK, or GPCR-interacting arrestin adapters that are integrated into this canonical signaling process at different levels to enable fine-tuning. Finally, the identification of atypical signaling mechanisms of classical regulators, together with the discovery of novel modulators, added a new and fascinating dimension to the cellular G protein signal transduction. This heterogeneous group of accessory G protein modulators was coined "activators of G protein signaling" (AGS) proteins and plays distinct roles in canonical and non-canonical G protein signaling pathways. AGS proteins contribute to the control of essential cellular functions such as cell development and division, intracellular transport processes, secretion, autophagy or cell movements. As such, they are involved in numerous biological processes that are crucial for diseases, like diabetes mellitus, cancer, and stroke, which represent major health burdens. Although the identification of a large number of non-canonical G protein signaling pathways has broadened the spectrum of this cellular communication system, their underlying mechanisms, functions, and biological effects are poorly understood. In this review, we highlight and discuss atypical G protein-dependent signaling mechanisms with a focus on inhibitory G proteins (Gi) involved in canonical and non-canonical signal transduction, review recent developments and open questions, address the potential of new approaches for targeted pharmacological interventions.

Current Therapeutic Approaches for Graves' Orbitopathy - are Targeted Therapies the Future?

Graves' orbitopathy is an autoimmune disease of the orbit that most frequently occurs with Graves' hyperthyroidism. The occurrence of autoantibodies directed against the TSH receptor (TRAb) is of central importance for the diagnosis and pathogenesis. These autoantibodies are mostly stimulating, and induce uncontrolled hyperthyroidism and tissue remodelling in the orbit and more or less pronounced inflammation. Consequently, patients suffer to a variable extent from periocular swelling, exophthalmos, and fibrosis of the eye muscles and thus restrictive motility impairment with double vision. In recent decades, therapeutic approaches have mainly comprised immunosuppressive treatments and antithyroid drug therapy for hyperthyroidism to inhibit thyroid hormone production. With the recognition that TRAb also activates an important growth factor receptor, IGF1R (insulin-like growth factor 1 receptor), biological agents have been developed. Teprotumumab (an inhibitory IGF1R antibody) has already been approved in the USA and the therapeutic effects are enormous, especially with regard to the reduction of exophthalmos. Side effects are to be considered, especially hyperglycaemia and hearing loss. It is not yet clear whether the autoimmune reaction (development of the TRAb/attraction of immunocompetent cells) is also influenced by anti-IGF1R inhibiting agents. Recurrences after therapy show that the inhibition of antibody development must be included in the therapeutic concept, especially in severe cases.

Fibrocyte Participation in Thyroid-Associated Ophthalmopathy Suggests New Approaches to Therapy

PURPOSE

Review the historical context of research and changing therapeutic landscape of thyroid-associated ophthalmopathy (TAO) by focusing on the relationship between TAO, CD34+ fibrocytes, thyrotropin receptor (TSHR), and insulin-like growth factor-I receptor (IGF-IR).

METHODS

A literature review using search terms, including fibrocytes, IGF-IR, TSHR, TAO, and thyroid eye disease.

RESULTS

The mechanisms involved in TAO have been partially identified. Substantial progress has been made over several decades, including 1) recognizing the interplay between the professional immune system and orbital tissues; 2) TSHR and IGF-IR act interdependently in mediating the pathogenesis of TAO; 3) Multiple cytokines and specific immune cells are involved in activating and remodeling orbital tissue; 4) Recognition of these mechanisms is allowing the development of target therapies such as teprotumumab, a monoclonal antibody IGF-IR inhibitor approved by the US Food and drug administration for treatment of TAO; and 5) It appears that teprotumumab acts on the systemic immune system peripheral to the orbit.

CONCLUSION

Additional molecules targeting IGF-IR and other plausible disease mechanisms are currently under development. This activity in the TAO therapeutic space portends even greater improvements in patient care.

Purine metabolism-related genes and immunization in thyroid eye disease were validated using bioinformatics and machine learning

Thyroid eye disease (TED), an autoimmune inflammatory disorder affecting the orbit, exhibits a range of clinical manifestations. While the disease presentation can vary, cases that adhere to a prototypical pattern typically commence with mild symptoms that subsequently escalate in severity before entering a phase of stabilization. Notably, the metabolic activity of cells implicated in the disease substantially deviates from that of healthy cells, with purine metabolism representing a critical facet of cellular material metabolism by supplying components essential for DNA and RNA synthesis. Nevertheless, the precise involvement of Purine Metabolism Genes (PMGs) in the defensive mechanism against TED remains largely unexplored. The present study employed a bioinformatics approach to identify and validate potential PMGs associated with TED. A curated set of 65 candidate PMGs was utilized to uncover novel PMGs through a combination of differential expression analysis and a PMG dataset. Furthermore, GSEA and GSVA were employed to explore the biological functions and pathways associated with the newly identified PMGs. Subsequently, the Lasso regression and SVM-RFE algorithms were applied to identify hub genes and assess the diagnostic efficacy of the top 10 PMGs in distinguishing TED. Additionally, the relationship between hub PMGs and clinical characteristics was investigated. Finally, the expression levels of the identified ten PMGs were validated using the GSE58331 and GSE105149 datasets. This study revealed ten PMGs related with TED. PRPS2, PFAS, ATIC, NT5C1A, POLR2E, POLR2F, POLR3B, PDE3A, ADSS, and NTPCR are among the PMGs. The biological function investigation revealed their participation in processes such as RNA splicing, purine-containing chemical metabolism, and purine nucleotide metabolism. Furthermore, the diagnostic performance of the 10 PMGs in differentiating TED was encouraging. This study was effective in identifying ten PMGs linked to TED. These findings provide light on potential new biomarkers for TED and open up possibilities for tracking disease development.

Teprotumumab-trbw as a Novel Monoclonal Antibody for Thyroid Eye Disease: A Literature Review

Thyroid eye disease (TED) can cause disfigurement and vision loss, most commonly in patients with Graves' disease. These symptoms are related to orbital inflammation subsequently cause proptosis and limited eye movement. Traditionally, TED is treated with corticosteroids to decrease inflammation and surgery once the disease stabilizes. However, multiple medications that play a role in immune modulation have been tested and found to be beneficial in treating TED, either as an adjuvant to steroids or in severe disease resistant to steroids. Teprotumumab-trbw, a novel monoclonal antibody sold under the trade name Tepezza®, is the first immune modulator to be approved by the Unites States Food and Drug Administration (FDA) for TED. Teprotumumab-trbw targets the insulin-like growth factor-1 receptor, which is upregulated on orbital fibroblasts and decreases activation in patients with TED. The FDA approved this drug for patients with less than nine months of disease duration and high levels of disease activity. Multiple studies have shown significant positive results in disease modulation, as well as limited side effects.

Teprotumumab in thyroid eye disease: wonder drug or great divider?

Progress in the management of thyroid eye disease (TED) has been slow for many decades. The recent introduction of teprotumumab (TEP) in the therapeutic arena for TED has had a major impact in view of its efficacy, particularly with respect to its ability to reduce proptosis. However, the high cost of TEP, limited availability to patients outside the USA, and the lack of data on cost-effectiveness are significant barriers to improving the care of patients with TED globally. Recent guidance from authoritative professional organisations deliver different perspectives on the role of TEP in the routine management of patients with TED, underscoring the complexities of interpreting the evidence. The advance that TEP undoubtedly represents in managing TED effectively has highlighted inequities faced by patients and uncertainties about appropriate metrics of efficacy. Professional organisations have an important role addressing these problems. Future studies need to focus on optimising the measurement of outcomes and on assessing cost-effectiveness.

Efficacy and Safety of 6-Weekly versus 12-Weekly Intravenous Methylprednisolone in Moderate-to-Severe Active Thyroid-Associated Ophthalmopathy

PURPOSE

To compare the efficacy and safety of 6-weekly and 12-weekly intravenous methylprednisolone (IVMP) regimens in moderate-to-severe, active thyroid-associated orbitopathy (TAO) patients.

BASIC PROCEDURES

Retrospective comparative study of patients who received IVMP between January 2011 and July 2021 at the Thyroid Eye Clinic, the Chinese University of Hong Kong. Outcome measures included the 7-item clinical activity score (CAS), exophthalmos, extraocular muscle motility (EOMy), marginal reflex distance (MRD), best corrected visual acuity (BCVA), intraocular pressure (IOP), the requirement of additional treatment, and complications.

MAIN FINDINGS

A total of 65 (63% (41/65) females) moderate-to-severe, active TAO patients aged 50 ± 13 (25-74) years received 6-weekly (n = 22) or 12-weekly (n = 43) IVMP. Sex, age, smoking status, and Graves' disease status were comparable in the two groups (all p > 0.05). CAS at week 6 (p = 0.0279), 12 (p = 0.00228), and 52 (p = 0.0228) were lower at each time for the 12-weekly group. Exophthalmos improved more at week 6 (p = 0.0453) and 12 (p = 0.0347) in the 12-weekly group. The improvement of diplopia, MRD1, MRD2, and EOMy were comparable between the two groups. More patients in the 6-weekly group (p = 0.00169) required additional treatments including IVMP+/-ORT. Patients in the 6-weekly group who did not require additional treatment had a lower presenting CAS (p = 0.0193) than those who required additional treatment. The total numbers of adverse events were comparable between the two groups.

Bone marrow fibrocytes: villain or white knight in thyroid-associated ophthalmopathy?

PURPOSE OF REVIEW

We attempt to provide an historical perspective on progress made in understanding the pathogenesis of thyroid-associated ophthalmopathy (TAO), focusing on the roles of orbital fibroblasts (OF) in the diseased orbit (termed GD-OF) and how these cells differ from those residing in the healthy orbit. GD-OF comprise both residential OF and those apparently derived from CD34 + fibrocytes.

RECENT FINDINGS

CD34 + fibrocytes of the monocyte lineage putatively traffic to the TAO orbit from bone marrow. We believe that these fibroblastic cell populations dictate the activity and severity of TAO. Their impact on disease may be moderated by Slit2, a neuron axon guidance repellent synthesized by and released from residential CD34 - OF. Approximately 50% of patients with GD develop clinically meaningful TAO. Relatively few require systemic medical and surgical therapies, while milder disease can be managed with conservative, local care. Determining the intrinsic properties of GD-OF and their expression of Slit2 may explain why some patients with GD develop severe, vision-threatening TAO while others virtually escape any of its manifestations. Such insights should allow for improved and better-tolerated therapies.

SUMMARY

Identifying unique characteristics of fibrocytes and GD-OF subsets reveals their apparent roles in tissue activation, inflammation, and remodeling associated with TAO. Better understanding of these cells, their origins, behavior, and factors modulating their activities remains necessary for the development of more targeted, effective, and safe treatments.

Teprotumumab Divergently Alters Fibrocyte Gene Expression: Implications for Thyroid-associated Ophthalmopathy

CONTEXT

Teprotumumab, an IGF-I receptor (IGF-IR) inhibitor, is effective in thyroid-associated ophthalmopathy (TAO). The drug can modulate induction by TSH of IL-6 and IL-8 in CD34+ fibrocytes and their putative derivatives, CD34+ orbital fibroblasts (CD34+ OF). Fibrocytes express multiple thyroid autoantigens and cytokines implicated in TAO, which are downregulated by Slit2. Inflammation and disordered hyaluronan (HA) accumulation occur in TAO. Whether teprotumumab alters these processes directly in fibrocytes/CD34+ OF remains uncertain.

OBJECTIVE

Determine teprotumumab effects on expression/synthesis of several TAO-relevant molecules in fibrocytes and GD-OF.

DESIGN/SETTING/PARTICIPANTS

Patients with TAO and healthy donors were recruited from an academic endocrine and oculoplastic practice.

MAIN OUTCOME MEASURES

Real-time PCR, specific immunoassays.

RESULTS

Teprotumumab attenuates basal and TSH-inducible autoimmune regulator protein, thyroglobulin, sodium iodide symporter, thyroperoxidase, IL-10, and B-cell activating factor levels in fibrocytes. It downregulates IL-23p19 expression/induction while enhancing IL-12p35, intracellular and secreted IL-1 receptor antagonists, and Slit2. These effects are mirrored by linsitinib. HA production is marginally enhanced by teprotumumab, the consequence of enhanced HAS2 expression.

CONCLUSION

Teprotumumab affects specific gene expression in fibrocytes and GD-OF in a target-specific, nonmonolithic manner, whereas IGF-IR control of these cells appears complex. The current results suggest that the drug may act on cytokine expression and HA production systemically and locally, within the TAO orbit. These findings extend our insights into the mechanisms through which IGF-IR inhibition might elicit clinical responses in TAO, including a potential role of Slit2 in attenuating inflammation and tissue remodeling.

Understanding Pathogenesis Intersects With Effective Treatment for Thyroid Eye Disease

CONTEXT

Thyroid eye disease (TED), a vision-threatening and disfiguring autoimmune process, has thwarted our efforts to understand its pathogenesis and develop effective and safe treatments. Recent scientific advances have facilitated improved treatment options.

OBJECTIVE

Review historically remote and recent advances in understanding TED.

DESIGN/SETTING/PARTICIPANTS

PubMed was scanned using search terms including thyroid-associated ophthalmopathy, thyroid eye disease, Graves' orbitopathy, autoimmune thyroid disease, and orbital inflammation.

MAIN OUTCOME MEASURES

Strength of scientific evidence, size, scope, and controls of clinical trials/observations.

RESULTS

Glucocorticoid steroids are widely prescribed systemic medical therapy. They can lessen inflammation-related manifestations of TED but fail to reliably reduce proptosis and diplopia, 2 major causes of morbidity. Other current therapies include mycophenolate, rituximab (anti-CD20 B cell-depleting monoclonal antibody), tocilizumab (interleukin-6 receptor antagonist), and teprotumumab (IGF-I receptor inhibitor). Several new therapeutic approaches have been proposed including targeting prostaglandin receptors, vascular endothelial growth factor, mTOR, and cholesterol pathways. Of potentially greater long-term importance are attempts to restore immune tolerance.

CONCLUSION

Despite their current wide use, steroids may no longer enjoy first-tier status for TED as more effective and better tolerated medical options become available. Multiple current and emerging therapies, the rationales for which are rooted in theoretical and experimental science, promise better options. These include teprotumumab, rituximab, and tocilizumab. Restoration of immune tolerance could ultimately become the most effective and safe medical management for TED.

The Mysterious Universe of the TSH Receptor

The thyroid-stimulating hormone receptor (TSH-R) is predominantly expressed in the basolateral membrane of thyrocytes, where it stimulates almost every aspect of their metabolism. Several extrathyroidal locations of the receptor have been found including: the pituitary, the hypothalamus, and other areas of the central nervous system; the periorbital tissue; the skin; the kidney; the adrenal; the liver; the immune system cells; blood cells and vascular tissues; the adipose tissue; the cardiac and skeletal muscles, and the bone. Although the functionality of the receptor has been demonstrated in most of these tissues, its physiological importance is still a matter of debate. A contribution to several pathological processes is evident in some cases, as is the case of Grave's disease in its multiple presentations. Conversely, in the context of other thyroid abnormalities, the contribution of the TSH-R and its ligand is still a matter of debate. This article reviews the several different sites of expression of the TSH-R and its potential role in both physiological and pathological processes.