Macrophage-Orbital Fibroblast Interaction and Hypoxia Promote Inflammation and Adipogenesis in Graves' Orbitopathy

The role of adiponectin and its receptor signaling in ocular inflammation-associated diseases

Ocular inflammation-associated diseases are leading causes of global visual impairment, with limited treatment options. Adiponectin, a hormone primarily secreted by adipose tissue, binds to its receptors, which are widely distributed throughout the body, exerting powerful physiological regulatory effects. The protective role of adiponectin in various inflammatory diseases has gained increasing attention in recent years. Previous studies have confirmed the presence of adiponectin and its receptors in the eyes. Furthermore, adiponectin and its analogs have shown potential as novel drugs for the treatment of inflammatory eye diseases. This article summarizes the evidence for the interplay between adiponectin and inflammatory eye diseases and provides new perspectives on the diagnostic and therapeutic possibilities of adiponectin.

Plasma exosomes from patients with active thyroid-associated orbitopathy induce inflammation and fibrosis in orbital fibroblasts

BACKGROUND

The pathogenesis of thyroid-associated orbitopathy (TAO) remains incompletely understand. The interaction between immunocytes and orbital fibroblasts (OFs) play a critical role in orbital inflammatory and fibrosis. Accumulating reports indicate that a significant portion of plasma exosomes (Pla-Exos) are derived from immune cells; however, their impact upon OFs function is unclear.

METHODS

OFs were primary cultured from inactive TAO patients. Exosomes isolated from plasma samples of patients with active TAO and healthy controls (HCs) were utilized for functional and RNA cargo analysis. Functional analysis in thymocyte differentiation antigen-1+ (Thy-1+) OFs measured expression of inflammatory and fibrotic markers (mRNAs and proteins) and cell activity in response to Pla-Exos. RNA cargo analysis was performed by RNA sequencing and RT-qPCR. Thy-1+ OFs were transfected with miR-144-3p mimics/inhibitors to evaluate its regulation of inflammation, fibrosis, and proliferation.

RESULTS

Pla-Exos derived from active TAO patients (Pla-ExosTAO-A) induced stronger production of inflammatory cytokines and hyaluronic acid (HA) in Thy-1+ OFs while inhibiting their proliferation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and single sample gene set enrichment analysis (ssGSEA) suggested that the difference in mRNA expression levels between Pla-ExosTAO-A and Pla-ExosHC was closely related to immune cells. Differential expression analysis revealed that 62 upregulated and 45 downregulated miRNAs in Pla-ExosTAO-A, with the elevation of miR-144-3p in both Pla-Exos and PBMCs in active TAO group. KEGG analysis revealed that the target genes of differentially expressed miRNA and miR-144-3p enriched in immune-related signaling pathways. Overexpression of the miR-144-3p mimic significantly upregulated the secretion of inflammatory cytokines and HA in Thy-1+ OFs while inhibiting their proliferation.

CONCLUSION

Pla-Exos derived from patients with active TAO were immune-active, which may be a long-term stimulus casual for inflammatory and fibrotic progression of TAO. Our finding suggests that Pla-Exos could be used as biomarkers or treatment targets in TAO patients.

Redox mechanisms in autoimmune thyroid eye disease

Thyroid eye disease (TED) is an autoimmune condition affecting the orbit and the eye with its adnexa, often occurring as an extrathyroidal complication of Graves' disease (GD). Orbital inflammatory infiltration and the stimulation of orbital fibroblasts, triggering de novo adipogenesis, an overproduction of hyaluronan, myofibroblast differentiation, and eventual tissue fibrosis are hallmarks of the disease. Notably, several redox signaling pathways have been shown to intensify inflammation and to promote adipogenesis, myofibroblast differentiation, and fibrogenesis by upregulating potent cytokines, such as interleukin (IL)-1β, IL-6, and transforming growth factor (TGF)-β. While existing treatment options can manage symptoms and potentially halt disease progression, they come with drawbacks such as relapses, side effects, and chronic adverse effects on the optic nerve. Currently, several studies shed light on the pathogenetic contributions of emerging factors within immunological cascades and chronic oxidative stress. This review article provides an overview on the latest advancements in understanding the pathophysiology of TED, with a special focus of the interplay between oxidative stress, immunological mechanisms and environmental factors. Furthermore, cutting-edge therapeutic approaches targeting redox mechanisms will be presented and discussed.

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.

Influence of biological sex, age and smoking on Graves’ orbitopathy – a ten-year tertiary referral center analysis

Purpose

Severity of Graves’ orbitopathy (GO) shows wide individual differences. For optimal treatment, it is important to be able to predict the natural course of the disease as accurate as possible to counteract with anti-inflammatory and surgical treatment. Therefore, we aimed to further elucidate the impact of sex, age and smoking on GO.

Methods

We collected the clinical and demographic data of all patients of our tertiary referral center from January 2008 till December 2018 and analyzed it with descriptive statistics. Only patients with a complete data set were included in the further analysis. Odds ratio’s for moderate-to-severe and sight-threatening GO in relation to age, sex and smoking were calculated by means of multivariate logistic regression models.

Results

We evaluated the data of 4260 patient with GO and complete data sets. Most of these were women (83%). There were no significant differences between male and female patients regarding smoking habits and thyroid treatment. Men were significantly older at initial manifestation of TED (51.8 vs. 49.9y, p<0.01) and showed significant more often severe stages (61% vs. 53%, p<0.0001). Therefore, they needed significantly more intense treatment with steroids, irradiation, orbital decompression and muscle surgery. In multivariate logistic regression analyses age (OR 0.97, 95% CI:0.97-0.98, p<0.0001), male sex (OR 1.64, 95% CI:1.38-1.9, p<0.0001), smoking (OR 1.19, 95% CI:1.04-1.36, p=0.01), Grave’s disease (OR 1.55, 95% CI:1.26-1.90, p<0.0001) and history of radioiodine treatment (RAI) (OR 2.44, 95% CI:2.10-2.86, p<0.0001) showed an significant association with severe stages of GO.

Discussion

Our retrospective analysis showed once more that women are more often afflicted by GO. In contrast, men seem to be more severely afflicted and in need of anti-inflammatory and surgical treatments. This might be due to a different approach to the health system and resilience to GO specific symptoms, as well as previously described worse thyroid control. Estrogen mediated effects might also play a role as in other autoimmune diseases and should be subject of further trials. Besides the biological sex, smoking could again be confirmed as serious risk factor for severe GO. Of note, RAI was associated with more severe stages of GO, which should be subject to further investigation.

Chemokines in thyroid autoimmunity

The chemokine receptor CXCR3 and its chemokines CXCL9, CXCL10, and CXCL11 are involved in the pathogenesis of autoimmune diseases. Th1 lymphocytes are recruited by Th1 chemokines, secreted by damaged cells. In inflamed tissues, the attracted Th1 lymphocytes induce the IFN-gamma and TNF-alpha release, that stimulates the secretion of Th1 chemokines, initiating and reiterating an amplification feedback loop. Autoimmune thyroid disorders (AITD) are the most recurrent autoimmune diseases, including Graves' disease (GD) and autoimmune thyroiditis, clinically defined by thyrotoxicosis and hypothyroidism, respectively. Graves' ophthalmopathy is one of GD extrathyroidal manifestations, occurring in ~30-50% of GD patients. In the early phase of AITD, the Th1 immune response is prevalent, and a following switch to a Th2 immune response has been shown in the late, inactive, phase. The reviewed data underline the importance of chemokines in thyroid autoimmunity and suggest CXCR3-receptor and its chemokines as potential targets of novel drugs for these disorders.

Sphingolipids in thyroid eye disease

Graves' disease (GD) is caused by an autoimmune formation of autoantibodies and autoreactive T-cells against the thyroid stimulating hormone receptor (TSHR). The autoimmune reaction does not only lead to overstimulation of the thyroid gland, but very often also to an immune reaction against antigens within the orbital tissue leading to thyroid eye disease, which is characterized by activation of orbital fibroblasts, orbital generation of adipocytes and myofibroblasts and increased hyaluronan production in the orbit. Thyroid eye disease is the most common extra-thyroidal manifestation of the autoimmune Graves' disease. Several studies indicate an important role of sphingolipids, in particular the acid sphingomyelinase/ceramide system and sphingosine 1-phosphate in thyroid eye disease. Here, we discuss how the biophysical properties of sphingolipids contribute to cell signaling, in particular in the context of thyroid eye disease. We further review the role of the acid sphingomyelinase/ceramide system in autoimmune diseases and its function in T lymphocytes to provide some novel hypotheses for the pathogenesis of thyroid eye disease and potentially allowing the development of novel treatments.

TSG6 Plays a Role in Improving Orbital Inflammatory Infiltration and Extracellular Matrix Accumulation in TAO Model Mice

Introduction

TSG-6 plays a wide anti-inflammatory and therapeutic role in a variety of autoimmune diseases as the key mediator of mesenchymal stem cells (MSCs).

Purpose

We aimed to test whether TSG-6 could exert similar effects as MSCS in TAO via establishing TAO animal model immunized by hTSHR-A subunit plasmid.

Material and Methods

We tested the expression level of TSG-6 on intraconal orbital fat from controls and patients with TAO. We established a stable thyroid-associated ophthalmopathy animal model by immunizing 6-week-old female Balb/c mice with recombination hTSHR-A subunit plasmid. After four immunizations, TSG-6 or dexamethasone was injected through the tail vein. The effects of the drugs on body weight, thyroid function, orbital inflammation, fibrosis and lipogenesis were observed.

Results

The expression of TSG-6 in the orbital tissues of TAO patient is lower than that of normal people. In our animal model, mice showed weight loss, higher TT4 and TSHR antibody levels, and ocular symptoms such as inflammation and proptosis. TSG-6 can reduce ocular fibrosis and lipogenesis by inhibiting the infiltration of CD3+ T lymphocytes and macrophages in the mouse model of thyroid associated ophthalmopathy. Compared with dexamethasone, TSG-6 showed comparable anti-inflammatory effect, moreover, it has given a better performance in inhibiting adipogenesis.

Conclusion

It was demonstrated that TSG-6 has a considerable positive impact on improving eye symptoms of TAO mice, which could be a novel candidate for the early treatment of TAO.