Graves' immunoglobulins and cytokines stimulate the expression of intercellular adhesion molecule-1 (ICAM-1) in cultured Graves' orbital fibroblasts

DNA Methylation in Autoimmune Thyroid Disease

Graves disease and Hashimoto disease form part of the spectrum of autoimmune thyroid disease (AITD), to which genetic and environmental factors are recognized contributors. Epigenetics provides a potential link between environmental influences, gene expression, and thyroid autoimmunity. DNA methylation (DNAm) is the best studied epigenetic process, and global hypomethylation of leukocyte DNA is reported in several autoimmune disorders. This review summarizes the current understanding of DNAm in AITD. Targeted DNAm studies of blood samples from AITD patients have reported differential DNAm in the promoter regions of several genes implicated in AITD, including TNF, IFNG, IL2RA, IL6, ICAM1, and PTPN22. In many cases, however, the findings await replication and are unsupported by functional studies to support causal roles in AITD pathogenesis. Furthermore, thyroid hormones affect DNAm, and in many studies confounding by reverse causation has not been considered. Recent studies have shown that DNAm patterns in candidate genes including ITGA6, PRKAA2, and DAPK1 differ between AITD patients from regions with different iodine status, providing a potential mechanism for associations between iodine and AITD. Research focus in the field is moving from candidate gene studies to an epigenome-wide approach. Genome-wide methylation studies of AITD patients have demonstrated multiple differentially methylated positions, including some in immunoregulatory genes such as NOTCH1, HLA-DRB1, TNF, and ICAM1. Large, epigenome-wide studies are required to elucidate the pathophysiological role of DNAm in AITD, with the potential to provide novel diagnostic and prognostic biomarkers as well as therapeutic targets.

Long non-coding RNA MALAT1 exacerbates acute respiratory distress syndrome by upregulating ICAM-1 expression via microRNA-150-5p downregulation

Acute respiratory distress syndrome (ARDS) is a severe form of acute lung injury in which severe inflammatory responses induce cell apoptosis, necrosis, and fibrosis. This study investigated the role of lung adenocarcinoma transcript 1 (MALAT1) in ARDS and the underlying mechanism involved. The expression of MALAT1, microRNA-150-5p (miR-150-5p), and intercellular adhesion molecule-1 (ICAM-1) was determined in ARDS patients and lipopolysaccharide (LPS)-treated human pulmonary microvascular endothelial cells (HPMECs). Next, the interactions among MALAT1, miR-150-5p, and ICAM-1 were explored. Gain- or loss-of-function experiments in HPMECs were employed to determine cell apoptosis and inflammation. Furthermore, a mouse xenograft model of ARDS was established in order to verify the function of MALAT1 in vivo. MALAT1 and ICAM-1 were upregulated, while miR-150-5p was downregulated in both ARDS patients and LPS-treated HPMECs. MALAT1 upregulated ICAM-1 expression by competitively binding to miR-150-5p. MALAT1 silencing or miR-150-5p overexpression was shown to suppress HPMEC apoptosis, decrease the expressions of pro-inflammatory cytokines (IL-6, IL-1β and TNF-α) and E-selectin in HPMECs, as well as alleviated lung injury in nude mice. These findings demonstrated that MALAT1 silencing can potentially suppress HPMEC apoptosis and alleviate lung injury in ARDS via miR-150-5p-targeted ICAM-1, suggestive of a novel therapeutic target for ARDS.

The role of cell mediated immunopathogenesis in thyroid-associated ophthalmopathy

Currently, thyroid-associated ophthalmopathy (TAO) lacks effective treatment due to our lack of clarity in its immunopathogenesis. Orbital fibroblasts play a key role in altering inflammation and immune response in TAO, and are considered as the key target and effector cells in its pathogenesis. The orbit infiltrating CD34+ fibrocytes add on to the process by expressing high levels of autoantigens and inflammatory cytokines, while also differentiating into myofibroblasts or adipocytes. This review focuses on the role of orbital fibroblasts and CD34+ fibrocytes in the pathogenesis of TAO, highlighting the basis of emerging treatments.

High circulating levels of sICAM-1 and sVCAM-1 in the patients with Hashimoto's thyroiditis

OBJECTIVE

To investigate whether soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) levels are increased in euthyroid patients with Hashimoto's thyroiditis (HT) and whether they are associated with thyroid autoimmunity and metabolic parameters.

DESIGN

Cross-sectional.

SUBJECTS AND METHODS

In total, 80 euthyroid patients with HT and 80 age- and body mass index (BMI)-matched control participants were included. Serum sICAM-1, sVCAM-1, free triiodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (anti-TPO), thyroglobulin antibody (anti-TG), fasting blood glucose (FBG), insulin, and lipid levels and homeostasis model assessment for insulin resistance (HOMA-IR) were assessed in all participants.

RESULTS

The patients with HT had significantly higher levels of sICAM-1 and sVCAM-1 than controls (both p < 0.001). The difference was sustained after adjustment for TSH and levothyroxine use. Regression analysis demonstrated that sICAM-1 was related to anti-TPO (p < 0.001), and sVCAM-1 was related to both anti-TPO and-TG (p < 0.001 and p = 0.03, respectively); this relationship was sustained after adjustment for age and BMI. Although FBG and HOMA-IR were higher in the HT group, logistic regression analysis revealed that there was no effect of anti-TPO, anti-TG, sICAM-1, sVCAM-1, and C-reactive protein (CRP) on the occurrence of high FBG and high HOMA-IR.

CONCLUSION

sICAM-1 and sVCAM-1 levels were significantly elevated in the patients with euthyroid HT and correlated closely with thyroid autoimmunity. However, soluble adhesion molecules had no relation with glucose metabolism parameters in the HT patients.

Current perspectives on the role of orbital fibroblasts in the pathogenesis of Graves' ophthalmopathy

Graves' ophthalmopathy (GO) is an extra-thyroidal complication of Graves' disease (GD; Graves' hyperthyroidism) characterized by orbital tissue inflammation, expansion, remodeling and fibrosis. Although the initiating trigger of GO is still indistinct, excessive orbital fibroblast activity is at the heart of its pathogenesis. Orbital fibroblasts are activated by cellular interactions with immune cells and the soluble factors they secrete. Orbital fibroblasts, especially from GO patients, express the thyrotropin receptor (TSH-receptor; TSHR), and activation of the orbital fibroblast population by stimulatory autoantibodies directed against the TSHR may provide an important link between GD and GO. Furthermore, stimulatory autoantibodies directed against the insulin-like growth factor-1 receptor have been proposed to contribute to orbital fibroblast activation in GO. Activated orbital fibroblasts produce inflammatory mediators thereby contributing to the orbital inflammatory process in GO. Moreover, orbital fibroblasts exhibit robust proliferative activity and extracellular matrix (especially hyaluronan) synthesizing capacity and can differentiate into adipocytes and myofibroblasts with disease progression, thereby contributing to tissue expansion/remodeling and fibrosis in GO. Orbital fibroblasts, especially those from GO patients, exhibit a hyper-responsive phenotype when compared to fibroblasts from other anatomical regions, which may further contribute to GO pathogenesis. Fibrocytes have been identified as additional source of orbital fibroblasts in GO, where they may contribute to orbital tissue inflammation, adipogenesis and remodeling/fibrosis. This review addresses our current view on the role that orbital fibroblasts fulfill in GO pathogenesis and both established as well as less established not fully crystallized concepts that need future studies will be discussed.

Development of a Novel Thyroid Function Fluctuated Animal Model for Thyroid-Associated Ophthalmopathy

Background

The establishment of a suitable and stable animal model is critical for research on thyroid-associated ophthalmopathy (TAO). In clinical practice, we found that patients treated with I-131 often exhibit TAO; therefore, we aimed to establish a novel thyroid function fluctuated animal model of TAO by simulating the clinical treatment process.

Methods

We treated SD rats with I-131 to damage the thyroid and then used sodium levothyroxine (L-T4) to supplement the thyroid hormone (TH) levels every seven days, leading to a fluctuating level of thyroid hormones that simulated the status of clinical TAO patients. Rats administered normal saline were considered as a control. The weight, intraocular pressure, and serum T3, T4, TSH and TRAb levels of the rats were measured, and the pathological changes were analyzed by H&E staining and transmission electron microscopy (TEM).

Results

The experimental rats (TAO group) exhibited significantly reduced weight and elevated intraocular pressure compared with the control rats. Meanwhile, the serum levels of T3 and T4 were up-regulated in the TAO group, but the TSH level decreased during the 10-week study. Moreover, increased numbers of blood vessels and inflammatory cell infiltrations were observed in the orbital tissues of the TAO rats, while no abnormal changes occurred in the control rats. The orbital myofibrils in the TAO rats appeared fractured and dissolved, with twisted structures. Mitochondrial swelling and vacuoles within the endoplasmic reticulum, swelling nerve fibers, shedding nerve myelin, and macrophages were found in the TAO group.

Conclusion

Rats treated with I-131 and sodium levothyroxine exhibited characteristics similar to those of TAO patients in the clinic, providing an effective and simple method for the establishment of a stable animal model for research on the pathogenesis and treatment of TAO.

Quercetin inhibits IL-1β-induced inflammation, hyaluronan production and adipogenesis in orbital fibroblasts from Graves' orbitopathy

Management of Graves' orbitopathy (GO) is challenging, as no reliable, specific, and safe medical therapeutic agents have yet been developed. We investigated the effect of quercetin in primary cultured orbital fibroblasts from GO, targeting pathways of inflammation, aberrant accumulation of extracellular matrix macromolecules, and adipose tissue expansion. Quercetin significantly attenuated intercellular adhesion molecule-1 (ICAM-1), interleukin (IL) -6, IL-8, and cyclooxygenase (COX) -2 mRNA expression, and inhibited IL-1β-induced increases in ICAM-1, IL-6, and IL-8 mRNA. Increased hyaluronan production induced by IL-1β or tumor necrosis factor-α was suppressed by quercetin in a dose- and time-dependent manner. Treatment with noncytotoxic doses of quercetin inhibited accumulation of intracytoplasmic lipid droplets and resulted in a dose-dependent decrease in expression of peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein (C/EBP) α, and C/EBPβ proteins. In conclusion, inhibition of inflammation, hyaluronan production, and adipogenesis by the natural plant product quercetin in vitro provides the basis for further study of its potential use in the treatment of GO.

Peroxisome proliferator-activated receptor gamma ligands inhibit transforming growth factor-beta-induced, hyaluronan-dependent, T cell adhesion to orbital fibroblasts

Thyroid eye disease is characterized by the infiltration of leukocytes and accumulation of hyaluronan (HA) in orbital tissue. Inflamed orbital tissue expands in size due to excessive HA and to the formation of scar tissue (fibrosis) and/or adipose accumulation. Transforming growth factor β (TGF-β) acts as a key inducer of fibrosis by enhancing extracellular matrix production. Treatment of primary human orbital fibroblasts with TGF-β led to significant increases in both HA synthesis and secretion. TGF-β also strongly induced hyaluronan synthase 1 (HAS1) and HAS2 mRNA levels, which increased 50- and 6-fold, respectively. Remarkably, the addition of the peroxisome proliferator-activated receptor (PPARγ) ligands pioglitazone (Pio) or rosiglitazone (Rosi) to TGF-β-treated orbital fibroblasts attenuated HA synthesis and reduced HAS1 and HAS2 mRNA levels. The attenuation of TGF-β function by Pio and Rosi was independent of PPARγ activity. Furthermore, Pio and Rosi treatment inhibited TGF-β-induced T cell adhesion to orbital fibroblasts. Our findings demonstrate that TGF-β plays an important role in HA synthesis and in the inflammatory response by enhancing or facilitating inflammatory cell infiltration and adhesion to orbital tissue. Pio and Rosi exhibit anti-fibrotic and anti-inflammatory activity and may be useful in treating thyroid eye disease.

Apoptosis in orbital fibroadipose tissue and its association with clinical features in Graves' ophthalmopathy

PURPOSE

To evaluate the rate of apoptosis in orbital fibroadipose tissue in Graves' ophthalmopathy (GO) patients and investigate its associations with disease characteristics.

METHODS

Orbital tissue samples were obtained during decompression surgery from 25 GO patients. Disease activity was evaluated using the Clinical Activity Score, while the clinical features of GO were evaluated using the Total Eye Score (TES). Tissue samples of 12 patients without any thyroid or autoimmune disease were studied as controls. The rate of apoptosis was evaluated with a terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling (TUNEL) assay, and ultrastructural features of apoptosis were evaluated with electron microscopy.

RESULTS

The rate of apoptosis in orbital fibroadipose tissue was significantly higher in GO cases than in the control group (p < 0.001) and significantly correlated with TES (r: 0.545; p = 0.005). The rate of apoptosis was 7.9% +/- 6.5%, and 22.0% +/- 7.8% in type 1 and type 2 cases, respectively (p = 0.001). The rate of apoptosis was 21.6% +/- 7.5% in eyes showing dysthyroid optic neuropathy (DON) and 6.7% +/- 5.4% in eyes without DON (p = 0.005).

CONCLUSIONS

The rate of apoptosis was high in the orbital fibroadipose tissue of GO cases and was related to the clinical features of the disease.

The effects of tumour necrosis factor-alpha and interleukin1 on an in vitro model of thyroid-associated ophthalmopathy; contrasting effects on adipogenesis

OBJECTIVE

Cytokines are likely to play a key pathogenic role in thyroid-associated ophthalmopathy (TAO). Anti-cytokine therapy has been proposed to be a possible treatment for active TAO. We aimed to establish the effects of selected cytokines on intercellular adhesion molecule 1 (ICAM1) expression, glycosaminoglycan (GAG) production and adipogenesis in orbital fibroblasts (OFs) from patients with TAO.

METHODS

Orbital tissue was taken during surgery from eight patients with TAO and five control subjects. OFs were cultured and ICAM1 expression measured by flow cytometry. GAG production was measured by hyaluronic acid ELISA. OFs were grown in adipogenic media and the degree of adipogenesis quantified.

RESULTS

Responses were similar in OFs from patients with and without TAO. Tumour necrosis factor-alpha (TNFalpha) and interleukin1 (IL1) (0.1 ng/ml) stimulated ICAM1 expression by eight- to ten-fold. Anti-cytokine agents inhibited the cytokine-upregulated ICAM1 expression by 90-99% (P<0.01). TNFalpha and IL1 (0.1 ng/ml) increased hyaluronic acid production by 44 and 95% (P<0.01) respectively. Anti-cytokine agents inhibited these responses by 79-138% (P<0.04).0.013 AU and -1.0; P<0.03) whilst IL1 (0.1 ng/ml) stimulated adipogenesis (+0.05 AU and +5.7; P<0.02) measured by oil-red-O extraction and visual assessment respectively. The anti-IL1 agent inhibited IL1-mediated adipogenesis by 69-106% (P<0.04).

CONCLUSION

TNFalpha and IL1 stimulate ICAM1 expression and GAG production, but have opposite effects on adipogenesis in OFs in vitro. IL1 promotes adipogenesis and its effects can be blocked by anti-IL1 agents in vitro. These agents may be the anti-cytokine treatment of choice for clinical trials in active TAO.

Inhibitory effects of Triptolide on interferon-gamma-induced human leucocyte antigen-DR, intercellular adhesion molecule-1, CD40 expression on retro-ocular fibroblasts derived from patients with Graves' ophthalmopathy

PURPOSE

To explore the effects of Triptolide, the principal active diterpenoid from the Chinese Medicinal Herb Tripterygium Wilfordii Hook F that has immunosuppressive and anti-inflammatory properties, on cell proliferation, hyaluronic acid (HA) synthesis, and the expressions of human leucocyte antigen-DR (HLA-DR), intercellular adhesion molecule-1 (ICAM-1) and CD40 on cultured retro-ocular fibroblasts (RFs) from patients with Graves' ophthalmopathy.

METHODS

After two to five passages, cultured RFs were incubated for 48 h within a medium alone or in the presence of recombinant human interferon-gamma (IFN-gamma) and various concentrations of Triptolide. Cell viability was assessed by MTT (3-[4.5-dimethylahiazol-2-yl]-2,5-diphenyltetrazolium Bromide). RFs proliferation was assessed by [(3)H]-thymidine incorporation assay. Flow cytometry was used to investigate the amount of HLA-DR, ICAM-1 and CD40. HA synthesis was measured by radioimmunoassay.

RESULTS

Cell viability was not detrimentally affected when incubated with Triptolide from 0.01 microg/L to 10 microg/L for 48 h, and decreased with 20 microg/L Triptolide. The incorporation of [(3)H]-thymidine of RFs was 55 476 +/- 15 842 cpm incubated with medium alone or 18 352 +/- 3568 cpm with 10 microg/L Triptolide (t = 5.600, P < 0.01). Initially, the percentage of positive cells of HLA-DR, ICAM-1 and CD40 on RFs were 4.75 +/- 2.13%, 17.53 +/- 10.12% and 6.38 +/- 2.23%, respectively, and the synthesis of HA was 100 +/- 12%. Compared with basal values, 48-h incubation with IFN-gamma (100 U/mL) significantly enhanced the amount of HLA-DR, ICAM-1 and CD40, and HA synthesis. The values were 60.58 +/- 10.12% (t = 13.224, P < 0.01), 62.66 +/- 18.17% (t = 5.315, P < 0.01), 57.67 +/- 13.61% (t = 9.110, P < 0.01) and 164 +/- 22% (t = 9.238, P < 0.01), respectively. Triptolide 0.01 microg/L had little effect on IFN-gamma-induced HLA-DR, ICAM-1 and CD40 amounts, as well as HA synthesis. When the concentration ranged from 0.1 microg/L to 10 microg/L, Triptolide inhibited IFN-gamma-induced RFs activation in a dose-dependent manner. It was also found that Triptolide had the same inhibiting effects on IFN-gamma-induced RFs and skin fibroblasts from patients with normal individual conditions.

CONCLUSIONS

Triptolide could inhibit IFN-gamma-induced activation of RFs derived from patients with Graves' ophthalmopathy.

Insights into the role of fibroblasts in human autoimmune diseases

Traditional wisdom has considered fibroblasts as contributing to the structural integrity of tissues rather than playing a dynamic role in physiological or pathological processes. It is only recently that they have been recognized as comprising diverse populations of cells exhibiting complex patterns of biosynthetic activity. They represent determinants that react to stimuli and help define tissue remodelling through the expression of molecules imposing constraints on their cellular neighbourhood. Moreover, fibroblasts can initiate the earliest molecular events leading to inflammatory responses. Thus they must now be viewed as active participants in tissue reactivity. In this short review, I will provide an overview of contemporary thought about the contribution of fibroblasts to the pathogenesis of autoimmune processes through their expression of, and responses to, mediators of inflammation and tissue remodelling.

Synovial fibroblasts from patients with rheumatoid arthritis, like fibroblasts from Graves' disease, express high levels of IL-16 when treated with Igs against insulin-like growth factor-1 receptor

We have reported recently that IgG from patients with Graves' disease (GD) can induce the expression of the CD4-specific T lymphocyte chemoattractant, IL-16, and RANTES, a C-C chemokine, in their fibroblasts. This induction is mediated through the insulin-like growth factor-1 receptor (IGF-1R) pathway. We now report that Abs from individuals with active rheumatoid arthritis (RA-IgG) stimulate in their synovial fibroblasts the expression of these same cytokines. IgG from individuals without known autoimmune disease fails to elicit this chemoattractant production. Furthermore, RA-IgG fails to induce IL-16 or RANTES expression in synovial fibroblasts from donors with osteoarthritis. RA-IgG-provoked IL-16 and RANTES production also appears to involve the IGF-1R because receptor-blocking Abs prevent the response. RA fibroblasts transfected with a dominant-negative mutant IGF-1R fail to respond to RA-IgG. IGF-1 and the IGF-1R-specific analog Des(1-3) also induce cytokine production in RA fibroblasts. RA-IgG-provoked IL-16 expression is inhibited by rapamycin, a specific macrolide inhibitor of the Akt/FRAP/mammalian target of rapamycin/p70(s6k) pathway, and by dexamethasone. GD-IgG can also induce IL-16 in RA fibroblasts, and RA-IgG shows similar activity in GD fibroblasts. Thus, IgGs from patients with RA, like those associated with GD, activate IGF-1R, and in so doing provoke T cell chemoattraction expression in fibroblasts, suggesting a potential common pathway in the two diseases. Immune-competent cell trafficking to synovial tissue is integral to the pathogenesis of RA. Recognition of this novel RA-IgG/fibroblast interaction and its functional consequences may help identify therapeutic targets.

Thyroid associated ophthalmopathy: evidence for CD4(+) gammadelta T cells; de novo differentiation of RFD7(+) macrophages, but not of RFD1(+) dendritic cells; and loss of gammadelta and alphabeta T cell receptor expression

AIM

To characterise periorbital immune cells (stages, kinetics) in active and inactive thyroid associated ophthalmopathy (A-TAO; I-TAO).

METHODS

In orbital tissue cryosections of patients with A-TAO (n = 15), I-TAO (n = 11), and healthy controls (n = 14), adipose and fibrovascular areas were evaluated for MHC II(+) cells, CD45(+) total leukocytes, myeloid cells (CD33(+) monocytes; CD14(+) macrophages; mature RFD7(+) macrophages; RFD1(+) dendritic cells (DCs)), and lymphoid cells (CD4(+) T cells; alphabeta and gammadelta T cells; CD20(+) B cells). Results are expressed as medians and 5% confidence intervals.

RESULTS

In fibrovascular septae, a surge of CD33(+) immigrants clearly correlating with disease activity generated significantly increased (p<0.05) percentages of CD14(+) and RFD7(+) macrophages. Intriguingly, CD4(+) cells were mostly gammadelta T cells, while alphabeta T helper cells were much less frequent. Successful treatment rendering TAO inactive apparently downregulates monocyte influx, macrophage differentiation, and T cell receptor expression. Similar trends were recorded for adipose tissue. Interestingly, RFD1(+) DCs were completely absent from all conditions examined.

CONCLUSION

A-TAO coincides with periorbital monocyte infiltration and de novo differentiation of macrophages, but not DCs. The authors discuss a novel potential role for inflammatory CD4(+) gammadelta T cells in TAO. Successful treatment apparently downregulates orbital monocyte recruitment and effects functional T cell knockout.

The putative role of fibroblasts in the pathogenesis of Graves' disease: evidence for the involvement of the insulin-like growth factor-1 receptor in fibroblast activation

Graves' disease when fully expressed affects the thyroid gland and connective tissues of the orbit and pretibium. While the glandular disease is relatively well-characterized, the pathogenesis of the orbital and dermal components remains enigmatic. In the following article, we review some of the evidence suggesting that fibroblast activation in Graves' disease might play an integral role in the tissue remodeling associated with ophthalmopathy. The thyrotropin receptor (TSHR) is expressed at low levels in several connective tissue depots and by their derivative fibroblasts, including those from the orbit. Little direct evidence currently links extra-thyroidal TSHR expression with Graves' disease. Very recent observations now implicate the insulin-like growth factor-1 receptor (IGF-1R) as a fibroblast activating antigen. When immunoglobulins from patients with the disease, with or without clinical ophthalmopathy, bind IGF-1R on the surface of fibroblasts, the receptor becomes activated and upregulates the expression of two T lymphocyte chemoattractants, IL-16 and RANTES. Thus, IGF-1R may represent a second self-antigen with a pathogenic role in extra-thyroidal Graves' disease.

Novel aspects of orbital fibroblast pathology

Orbital fibroblasts exhibit a unique phenotype including exaggerated responses to proinflammatory cytokines. We hypothesize that the unusual susceptability of these fibroblasts to molecular cues underlies the involvement of the orbit in Graves' ophthalmopathy. A number of attributes of orbital fibroblasts are reviewed in this article. In addition, we have found IgG circulating in patients with Graves' disease that binds and activates the insulin-like growth factor-1 receptor displayed on fibroblasts from many anatomic regions. Activation of this receptor leads to the expression of T-cell chemoattractants. Thus, fibroblast activation, and the resulting T-cell trafficking to connective tissue in Graves' disease may be systemic. The consequences of lymphocyte-derived cytokine action may differ vastly in the orbit and other tissues manifesting clinically obvious disease.

Current perspective on the pathogenesis of Graves' disease and ophthalmopathy

Graves' disease (GD) is a very common autoimmune disorder of the thyroid in which stimulatory antibodies bind to the thyrotropin receptor and activate glandular function, resulting in hyperthyroidism. In addition, some patients with GD develop localized manifestations including ophthalmopathy (GO) and dermopathy. Since the cloning of the receptor cDNA, significant progress has been made in understanding the structure-function relationship of the receptor, which has been discussed in a number of earlier reviews. In this paper, we have focused our discussion on studies related to the molecular mechanisms of the disease pathogenesis and the development of animal models for GD. It has become apparent that multiple factors contribute to the etiology of GD, including host genetic as well as environmental factors. Studies in experimental animals indicate that GD is a slowly progressing disease that involves activation and recruitment of thyrotropin receptor-specific T and B cells. This activation eventually results in the production of stimulatory antibodies that can cause hyperthyroidism. Similarly, significant new insights have been gained in our understanding of GO that occurs in a subset of patients with GD. As in GD, both environmental and genetic factors play important roles in the development of GO. Although a number of putative ocular autoantigens have been identified, their role in the pathogenesis of GO awaits confirmation. Extensive analyses of orbital tissues obtained from patients with GO have provided a clearer understanding of the roles of T and B cells, cytokines and chemokines, and various ocular tissues including ocular muscles and fibroblasts. Equally impressive is the progress made in understanding why connective tissues of the orbit and the skin in GO are singled out for activation and undergo extensive remodeling. Results to date indicate that fibroblasts can act as sentinel cells and initiate lymphocyte recruitment and tissue remodeling. Moreover, these fibroblasts can be readily activated by Ig in the sera of patients with GD, suggesting a central role for them in the pathogenesis. Collectively, recent studies have led to a better understanding of the pathogenesis of GD and GO and have opened up potential new avenues for developing novel treatments for GD and GO.

T-cell-mediated immunity in thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is considered to be an autoimmune inflammatory disorder of the extraocular muscles and the orbital fat/connective tissue. Recent studies analyzing T cells infiltrating retrobulbar tissues generated important insights into the immunopathogenesis of TAO. The present review focuses on advances in our understanding of mechanisms responsible for the autoimmune inflammation in TAO, especially T cell migration to the inflammatory site, T cell activation by autoantigens and costimulatory signals and their cytokine profile. The elucidation of these processes might lead to the development of novel therapeutic strategies directed against autoreactive T cells.

Role of cytokines in the pathogenesis of thyroid-associated ophthalmopathy

Thyroid-associated ophthalmopathy (TAO) is generally considered to be an autoimmune disorder associated with Graves' disease. However, the nature of autoantigen or mechanism of the development of ophthalmopathy remains unclear. In the present review we focus the accumulating evidence on roles of cytokines in the orbital tissues from patients with TAO and animal models. From the analysis of T-cell clones, T helper 1 (T(H)1)-like clones were predominant in cultures from patients with recent onset hyperthyroidism and T(H)2-like clones were predominant in culture form patients with more remote onset hyperthyroidism. T(H)1-like cytokine profiles are predominant in eye muscle tissue and related to the eye muscle enlargement, while T(H)2-like cytokine profiles are predominant in orbital fat tissue from patients with TAO and negatively related to orbital volume. Therefore, T(H)1-like cytokines, proinflammatory cytokines, may play a role on the development of eye muscle component of TAO in the acute stage. T(H)2-like cytokines, anti-inflammatory cytokines, may play protective role in the chronic stage of TAO. The studies using animal models suggest the genetic background is involved in the pathogenesis of TAO. The studies on polymorphism of the cytokine genes support the proinflammatory role of T(H)1-like cytokines and protective role of T(H)2-like cytokines.

Smoking and disease severity are independent determinants of serum adhesion molecule levels in Graves' ophthalmopathy

Adhesion molecules play a key role in autoimmune disorders, and serum concentrations of soluble adhesion molecules are increased in Graves' ophthalmopathy (GO). Whether this is due to the strong association with smoking is unknown. It is also not known if the severity or activity of GO determine the serum levels of adhesion molecules. We measured serum concentrations of sICAM-1, sVCAM-1 and sELAM-1 in 62 euthyroid Graves' patients with untreated GO, in 62 healthy controls matched for sex, age and smoking habits, and in 26 euthyroid Graves' patients without GO. GO severity was assessed by the Total Eye Score and the activity by the Clinical Activity Score. Adhesion molecules were measured by highly sensitive ELISAs. GO patients had higher levels than controls (median values in ng/ml with range): sICAM-1 300 [171--575] versus 244 [119--674], P < 0.001; sVCAM-1 457 [317--1060] versus 410 [238--562], P < 0.001; and sELAM-1 61 [19--174] versus 53 [23--118], P = 0.021. Euthyroid Graves' disease patients without GO had levels similar to controls: sICAM-1 273 138--453), sVCAM-1 386 [260--1041] and sELAM-1 46 [22--118]. Smoking had an independent effect and was associated with higher levels of sICAM-1 and lower levels of sVCAM-1 in both GO patients and controls; sELAM-1 levels were comparable. In the 62 GO patients, sICAM-1 correlated significantly with severity of eye disease (r = 0.40, P = 0.002). No correlation was found with the duration of GO, the Clinical Activity Score or TBII levels. Multivariate analysis of all 150 subjects showed that the presence of GO and smoking are independent determinants of sICAM-1 and sVCAM-1 concentrations. In GO patients, the Total Eye Score was a stronger determinant than smoking. It is concluded that (i) smoking is associated with increased sICAM-1 and decreased sVCAM-1 levels; (ii) independent from smoking, euthyroid GO patients have higher levels of sICAM-1, sVCAM-1 and sELAM-1 than patients with euthyroid Graves' disease or healthy controls; (iii) the major determinant of sICAM-1 in GO patients is the severity of their eye disease.

Igs from patients with Graves' disease induce the expression of T cell chemoattractants in their fibroblasts

Thyroid-associated ophthalmopathy and dermopathy are connective tissue manifestations of Graves' disease (GD). Tissue remodeling is a prominent feature of both and is apparently driven by recruited T cells. In this study, we report that IgG isolated from patients with GD (GD-IgG) up-regulates T lymphocyte chemoattractant activity in GD-derived fibroblasts from orbit, thyroid, and several regions of skin. This chemoattractant activity, absent in fibroblasts from donors without known thyroid disease, is partially susceptible to neutralization by anti-IL-16 and anti-RANTES Abs. IL-16 is a CD4(+)-specific chemoattractant and RANTES is a C-C-type chemokine. IL-16 and RANTES protein levels, as determined by specific ELISAs, are substantially increased by GD-IgG in GD fibroblasts. Addition of the macrolide, rapamycin, to fibroblast culture medium blocked the up-regulation by GD-IgG of IL-16, implicating the FRAP/mTOR/p70(s6k) pathway in the induction of IL-16 expression. These findings suggest a specific mechanism for activation of fibroblasts in GD resulting in the recruitment of T cells. They may provide insight into a missing link between the glandular and extrathyroidal manifestations of GD.

Serum levels of tumor necrosis factor-alpha, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and soluble interleukin-1 receptor antagonist in patients with thyroid eye disease undergoing treatment with somatostatin analogues

The aim of this prospective, randomized study was to investigate the serum levels of tumor necrosis factor-alpha (TNF-alpha), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), and soluble interleukin-1 receptor antagonist (sIL-1RA) in patients with thyroid eye disease (TED) before and 1 and 3 months after treatment with somatostatin analogues (SM-a). Thirty patients, all with signs and symptoms of TED, were studied. Twenty-two patients (13 females) had active eye disease with a clinical activity score (CAS) > or = 4 (patients with active disease [PA]) and 8 patients (5 females) had inactive TED with CAS < or = 3 (patients with inactive disease [PI]). All PA patients had a positive orbital octreoscan, whereas PI patients had a negative one. Fifteen patients from the PA group were selected randomly and received SM-a (PA-S subgroup), while the remaining 7 patients were used as control subgroup (PA-C), received neither therapy, nor placebo. From the 15 patients who received SM-a (PA-S), 6 received octreotide (OCT) and 9 lanreotide (LRT). TED was reevaluated using the CAS 1 and 3 months after the initiation of SM-a treatment. Ten healthy individuals (6 females) were used as controls (group C). We found an increase in the basal levels of TNF-alpha (14.2 +/- 7.1 pg/mL), sICAM-1 (809.1 +/- 167.0 ng/mL), and sIL-1RA (542.1 +/- 259.0 pg/mL) in PA patients as a total group compared with the PI (1.6 +/- 1.9, 676.8 +/- 73.4, 267.6 +/- 152.8, respectively) group and C (1.9 +/- 1.4, 598.0 +/- 126.2, 258.6 +/- 155.1, respectively). The basal levels of TNF-alpha (13.3 +/- 8.3 pg/mL) and sIL-1RA (533.7 +/- 308.9 pg/mL) in PA-S as well as in PA-C (16.0 +/- 2.9, 560.2 +/- 107.3, respectively) subgroups were also increased compared with PI patients and C (1.9 +/- 1.4 and 258.6 +/- 155.1, respectively). The same was true for sICAM-1 when baseline levels compared with C (817.1 +/- 187.3 and 791.9 +/- 123.5, respectively vs. 598.0 +/- 126.2 ng/mL). After SM-a, serum levels of sICAM-1 and sVCAM-1 were decreased significantly 1 (781.2 +/- 205.9, 1,193.5 +/- 511.8 ng/mL) and 3 months (786.8 +/- 199.6, 1,122.1 +/- 225.3 ng/mL) after the initiation of treatment. In conclusion, serum levels of TNF-a, sICAM-1, and sIL-1RA were elevated in patients with active TED compared to controls. Furthermore, sICAM-1 and sVICAM-1 levels declined during the treatment with SM-a in patients with active TED.

Thyroid-associated ophthalmopathy: clinical features, pathogenesis, and management

Thyroid-associated ophthalmopathy (TAO) is a progressive eye disorder characterized by immune-mediated inflammation of the extraocular muscles and orbital connective tissue. TAO is linked, in a unique way, with thyroid autoimmunity, in particular Graves' hyperthyroidism. Our working hypothesis for the pathogenesis of TAO is that recognition of a thyrotropin receptor (TSHR)-like protein in the orbital preadipocytes by antibodies may be the initial event leading to homing of lymphocytes into the orbital tissues. In the course of thyroid inflammation, antibodies and T cells reactive against G2s expressed in thyroid membranes cross-react with the protein in the eye muscle fiber, leading to eye muscle damage and dysfunction. Those patients with anti-G2s antibodies develop ocular myopathy. Antibodies against flavoprotein, the 64-kDa protein, which are produced in the context of eye muscle fiber damage and mitochondrial rupture, are sensitive markers of immune-mediated fiber necrosis in patients with ophthalmopathy but do not directly damage the eye muscle. Antibodies against type XIII collagen, which is localized in the plasma membranes of orbital fibroblast, may be a new marker for the congestive ophthalmopathy subtype of TAO. The measurement of antibodies against key eye muscle and orbital connective tissue autoantigens may have a role in the management of active ophthalmopathy and its prediction in patients with Graves' hyperthyroidism.

Both Th1- and Th2-derived cytokines in serum are elevated in Graves' ophthalmopathy

Increased serum cytokine levels have been reported in patients with autoimmune thyroid disease, but less is known about their levels in patients with Graves' ophthalmopathy (GO). It is not known whether GO is a cell-mediated or humoral autoimmune disease. We investigated whether serum cytokines are elevated in GO patients and whether the cytokines were Th1- or Th2-derived. In addition, elevated cytokines might reflect the activity of GO, and thus we investigated whether cytokine levels could predict the clinical response to orbital radiotherapy. We studied 62 consecutive patients with moderately severe untreated GO and 62 healthy controls, matched for sex, age and smoking habits. Serum concentrations of IL-1RA, sIL-2R, IL-6, sIL-6R, tumour necrosis factor-alpha (TNF-alpha) RI and II and sCD30 were measured using highly sensitive ELISAs, in the patients before and 3 and 6 months after radiotherapy. All patients were euthyroid, with anti-thyroid drugs, before and during the entire study period. All baseline cytokine and cytokine receptor levels were significantly elevated in GO patients compared with healthy controls, except for IL-1RA. The levels did not correlate with parameters of the thyroid disease, nor with the duration, activity or severity of GO. However, backward logistic regression analysis showed that IL-6, sCD30 and TNFalphaRI were able to predict a beneficial response to orbital radiotherapy. We therefore conclude that both Th1- and Th2-derived cytokines are elevated in GO patients compared with its controls. IL-6, sCD30 and TNFalphaRI had some value for predicting therapeutic outcome to orbital irradiation, and may thus reflect active eye disease.

Association of thyrotrophin receptor antibodies with the clinical features of Graves' ophthalmopathy

OBJECTIVE

Graves' ophthalmopathy (GO) and Graves' hyperthyroidism are closely associated diseases and thought to be caused by the same autoimmune process. An obvious explanation for this would be the presence of autoantibodies reacting with an autoantigen present in the orbit and the thyroid gland. The TSH-Receptor (TSH-R) antibodies are a likely candidate, because they cause Graves' hyperthyroidism and the TSH-R appears to be present also in orbital tissues. If TSH-R antibodies are responsible for the ophthalmopathy one would expect their titres to correlate with clinical characteristics of the eye disease. The aim of the present study is to see whether TSH-R antibodies are related to the activity and severity of the thyroid-associated ophthalmopathy.

DESIGN AND PATIENTS

TSH-R antibody levels were measured as TBII (TRAK assay), and TSI (cAMP response of a TSH-R transfected cell line) in serum of 63 patients with untreated moderately severe GO, accompanying Graves' thyroid disease; all patients had been euthyroid for > 2 months.

RESULTS

TBII and TSI titres were strongly related to each other. TBII or TSI titres did not correlate with thyroidal or orbital disease duration, nor with TPO antibody levels. In contrast, we found a striking and highly significant correlation between the Clinical Activity Score (CAS) of the eye disease, and both TBII (r = 0.54; P < 0.0001) and TSI (r = 0.50; P < 0.0001). In addition, a weaker but significant relation was found between proptosis (in mm) and TBII (r = 0.36; P = 0.004) and TSI (r = 0.49; P = 0.0001). No correlation was found with eye muscle motility.

CONCLUSION

TSH-R antibody levels correlate directly with clinical features of Graves' ophthalmopathy. The results support the hypothesis of a pathogenetic role of TSH-R antibodies and the TSH-R in the orbit of Graves' ophthalmopathy patients.

Thyrocyte proliferation by cellular adhesion to infiltrating lymphocytes through the intercellular adhesion molecule-1/lymphocyte function-associated antigen-1 pathway in Graves' disease

Graves' disease (GD) is an autoimmune thyroid disease characterized by infiltration of lymphocytes into the thyroid, and intrathyroid lymphocytes are known to play an important role in the pathogenesis of GD. However, it remains to be understood how lymphocytes adhere to thyrocytes and regulate the thyrocyte function through cellular adhesion. We studied the mechanisms of T cell adhesion to thyrocytes using intrathyroid mononuclear cells (ITMC) and thyrocytes purified from the thyroids of patients with GD. The following novel features of cellular adhesion of ITMC to thyrocytes in the regulation of the thyrocyte function in GD were observed: 1) GD-ITMC expressed lymphocyte function-associated antigen (LFA)-1, which became an active adhesive configuration much higher than peripheral blood mononuclear cells (PBMC) from normal volunteers and GD patients; 2) GD-thyrocytes expressed a high quantity of intercellular adhesion molecule (ICAM)-1; 3) GD-ITMC adhered to GD-thyrocytes, whereas normal PBMC required activation stimuli by phorbol myriacetate, a pharmacological integrin-trigger, to adhere to GD- thyrocytes; 4) monoclonal antibody-blocking studies showed that the adhesion of the activated PBMC and ITMC to thyrocytes was mainly mediated by the LFA-1/ICAM-1 pathway; 5) the adhesion of GD-thyrocytes to the activated-PBMC or ITMC induced the proliferation of the thyrocytes, which was blocked by the addition of ICAM-1 and/or LFA-1 monoclonal antibodies; and 6) in GD thyrocytes of early cultures, ICAM-1 expression on GD-thyrocytes and its adhesion to LFA-1 on phorbol myriacetate-activated PBMC or ITMC were not modulated by the addition of interleukin-1beta or interferon-gamma, and proliferation of thyrocytes by the cellular adhesion via the ICAM-1/LFA-1 pathway was independent of the proliferative response of these cytokines. Taken together, these results suggest that lymphocytes infiltrating GD thyroid induce proliferation of GD-thyrocyte by the cellular adhesion to thyrocytes via ICAM-1/LFA-1, which may lead to the development of a goiter.

Pathogenesis of ophthalmopathy in autoimmune thyroid disease

What causes GO is still a mystery, but the disease process results from a complex interplay of genetic and environmental factors. Genes such as those for HLA genes may determine a patient's susceptibility to the disease and its severity, but environmental factors, often unknown, may determine its course. Once established, the chronic inflammatory process within the orbital tissues appears to take on a momentum of its own. Given our current state of knowledge, the following working scheme for the pathogenesis of GO can be proposed (Fig. 1): On the background of a permissive immunogenetic milieu, circulating T cells in patients with GD, directed against certain antigens on thyroid follicular cells, recognize antigenic epitopes that are shared by tissues contained in the orbital space. Of the cell types residing in these tissues, preadipocytes and fibroblasts, most likely act as target and effector cells of the orbital immune process, respectively. This includes preadipocyte fibroblasts present in the perimysium of extraocular muscles, which do not appear to be immunologically different from those located in the orbital connective tissue. Orbital preadipocyte fibroblasts may be stimulated by unknown circulating or locally produced factors to differentiate into mature adipocytes that express increased levels of TSHr. How autoreactive T cells escape deletion and control by the immune system and come to be directed against a self-antigen presented by cells residing in the thyroid gland and extrathyroidal locations, is still unknown. Proliferation and expansion of autoreactive T cell clones may be due to mimicry of a host antigen by a microorganism, but this remains speculative. T cell recruitment into the orbital tissues is facilitated by certain chemokines and cytokines, which help to attract T cells by stimulating the expression of certain adhesion molecules (e.g., ICAM-1, VCAM-1, CD44) in vascular endothelium and connective tissue cells. These adhesion receptors are known to also play an important costimulatory role by activating T cells and facilitating antigen recognition, which amplifies the cellular immune process. Analysis of variable region genes of T cell antigen receptors in orbital T cells of patients with active GO has revealed their restricted TcR V gene usage, suggesting that antigen-driven selection and/or expansion of specific T cells may occur early in the evolution of GO. T cells and macrophages populating the orbital space are known to synthesize and release a [figure: see text] number of cytokines (most likely a Th1-type spectrum) into the surrounding tissue. Cytokines, oxygen free radicals and fibrogenic growth factors, released both from infiltrating inflammatory and residential cells, act upon orbital preadipocytes in a paracrine and autocrine manner to stimulate adipogenesis, fibroblast proliferation, glycosaminoglycan synthesis, and the expression of immunomodulatory molecules. Smoking, a well-known aggravating factor in GO, may aggravate tissue hypoxia and exert important immunomodulatory effects. The long held hypothesis of a thyroid cross-reactive antigen within the orbital tissues has recently gained significant support by an animal model of GO, and by in vitro and ex vivo studies. If confirmed in immunological studies, these data may well explain the localized infiltration of the orbital tissues by autoreactive lymphocytes that share intriguing molecular features with intrathyroidal lymphocytes. Local release of particular cytokines, TSHr-directed antibodies, or other factors might further enhance adipogenesis, glycosaminoglycan synthesis and expression of immunomodulatory proteins within the orbit. Other factors, including inflammatory cytokines, might act as counterbalancing inhibitors of these effects. However, if the net effect of these changes is to increase the volume of the fatty connective tissues within the orbit, then proptosis, extraocular muscle dysfunction, and periorbital congestion will ensue. Whether this hypothetical sequence of events will finally explain the involvement of the orbit in GD is unknown. Future studies will be aimed at identifying factors that might modulate adipogenesis in orbital cells and clarifying the link between adipogenesis and TSHr expression in the orbit. Taken together, a number of important details in the complex pathogenesis of GO have been resolved in recent years, but many challenges are still ahead. Elucidation of the primary antigen and how it is recognized by the immune system will be key issues.

Oxygen free radicals in interleukin-1beta-induced glycosaminoglycan production by retro-ocular fibroblasts from normal subjects and Graves' ophthalmopathy patients

Graves' ophthalmopathy (GO) is attributed to an autoimmune process that results in the accumulation in retro-ocular tissue of glycosaminoglycans (GAG) that are in turn responsible for the development of clinical signs and symptoms. Retro-ocular fibroblasts are thought to be the source of GAG production and deposition in GO. In the present study, we investigated interleukin (IL)-1beta-induced oxygen free radical production and the role of oxygen free radicals in IL-1beta-induced GAG production in retro-ocular fibroblasts from both normal subjects and patients with GO. Normal retro-ocular fibroblasts demonstrated no measurable oxygen free radicals whereas GO retro-ocular fibroblasts showed detectable signals by electron paramagnetic resonance (EPR) spectroscopy. IL-1beta increased the free radical production in both cells. Superoxide dismutase (SOD) activity in GO retroocular fibroblasts was higher than that in normal cells. IL-1beta dose- and time-dependently stimulated the SOD activity in both cells, with GO retro-ocular fibroblasts showing less responsiveness. IL-1beta dose-dependently increased [3H]glucosamine incorporation into GAG by both cells. An exogenous oxygen free radical-generating system failed to increase GAG. Scavenging oxygen free radicals by the use of SOD (100 U/mL) and catalase (300 U/mL) partially blocked the IL-1beta-induced GAG production in both cells. These results suggest that stress related oxygen free radicals are present in the retro-ocular tissue in GO and that oxygen free radicals are involved in GAG accumulation induced by cytokine IL-1beta.

Cytokines in the evolution of Graves' ophthalmopathy

Infiltration of the retroocular space by inflammatory cells and the accumulation of glycosaminoglycans are histological characteristics of Graves' ophthalmopathy. Various cytokines, released by infiltrating immunocompetent cells and resident connective tissue cells, play a pivotal role in the evolution of this disease. The predominant cytokines secreted by orbital T cells during the course of the disease may govern the activity and stage of the local autoimmune process. Cytokine effects of potential relevance to the pathogenesis of Graves' ophthalmopathy include their ability to stimulate orbital fibroblasts to proliferate and secrete excess quantities of glycosaminoglycans. The edema associated with these hydrophilic macromolecules is directly responsible for many of the characteristic clinical features of the disease. In addition, certain cytokines induce or enhance the expression on orbital fibroblasts of immunomodulatory proteins. We review current evidence supporting the notion that cytokines are central to the development and evolution of Graves' ophthalmopathy.

Soluble intercellular adhesion molecule-1 (sICAM-1) concentrations in Graves' disease patients followed up for development of ophthalmopathy

It is commonly recognized that a few patients with Graves' disease (GD) develop an overt ophthalmopathy, although most of them show subclinical extraocular muscle enlargement by appropriate imaging techniques. At present, it is not possible to identify the subgroup of GD patients with subclinical retroorbital connective involvement. Recently, it has been shown that increase of soluble intercellular adhesion molecule-1 (sICAM-1) serum levels is correlated to clinical activity score in active Graves' ophthalmopathy (GO) patients with or without hyperthyroidism, suggesting that sICAM-1 serum values could reflect the degree of ocular inflammatory activity. The aim of this longitudinal study was to evaluate sICAM-1 serum levels in GD patients without clinical ophthalmopathy and to assess their possible relationship with occurrence of GO. We measured sICAM-1 serum levels in 103 initially hyperthyroid GD patients without clinical ophthalmopathy and in 100 healthy subjects. All patients were treated with methimazole for 2 yr. Sera were collected from all patients before treatment and then monthly for the first 6 months of therapy, every 2 months in the following 6 months, and finally at the end of the follow-up study. Patients developing GO were excluded from the follow-up at the onset of ophthalmopathy. During the follow-up 17 GD patients (16.5%, group 1) developed overt eye involvement (14 as active inflammatory ophthalmopathy and 3 as ophthalmopathy without clinical retroorbital connective inflammation) and 86 (83.5%, group 2) did not. At start of the study, the mean of sICAM-1 serum concentrations did not differ significantly between the 2 groups, but it was significantly higher than in controls in both groups. No significant correlation between serum sICAM-1 concentrations and free thyroid hormone levels was found in the 2 groups of patients. During the follow-up study, a further increase of sICAM-1 serum levels was observed in 12 of the 14 patients (85.7%) of group 1 who developed active inflammatory ophthalmopathy not only at the onset but also before clinical GO appearance. On the contrary, the 3 patients of group 1 that developed ophthalmopathy without clinical retroorbital inflammation did not show any further increase of sICAM-1 levels at every time of follow-up in comparison with the starting values, even if their sICAM-1 levels were always higher than in normal controls. Finally, group 2 patients showed significantly decreased sICAM-1 levels throughout the follow-up period when compared with the starting values, although they were still significantly higher than in controls. These results indicate that a further increase of sICAM-1 serum levels before the onset of clinical ophthalmopathy may be a marker of subclinical retroorbital connective inflammation in GD patients. Therefore, our study suggests that serial determinations of sICAM-1 serum levels could help to identify and trace at the right time those GD patients prone to developing active inflammatory ophthalmopathy.

Orbital fibroblast chemokine modulation: effects of dexamethasone and cyclosporin A

AIM

Orbital inflammation is common, but the mechanisms underlying leucocytic infiltration of orbital tissue are poorly understood. Human orbital fibroblasts (OF) express chemokines, interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1), when exposed to proinflammatory cytokines. The effect of dexamethasone (DEX) and cyclosporin A (CSA) on OF IL-8 and MCP-1 were examined.

METHODS

Cultured human OF were incubated with recombinant interleukin 1 beta (rIL-1 beta; 0.2, 2.0, 20 ng/ml) alone or incubated with rIL-1 beta and DEX (10(-8), 10(-7), 10(-6) M) or CSA (3, 30, 300 ng/ml) for 24 hours. ELISA and northern blot analyses were performed to determine OF IL-8 and MCP-1 protein secretion and mRNA expression, respectively.

RESULTS

OF lacked constitutive IL-8 or MCP-1 expression, but secreted significant amounts of these chemokines and expressed substantial steady state mRNA for both chemokines upon rIL-1 beta stimulation. DEX caused dose dependent inhibition of IL-1 induced IL-8 (p < 0.001) and MCP-1 (p < 0.05) secretion and mRNA expression at all concentrations of rIL-1 beta. CSA enhanced IL-1 induced OF IL-8 (p < 0.001) and suppressed rIL-1 beta induced OF MCP-1 (p < 0.05) secretion when lower doses of rIL-1 beta were used. These effects on secreted chemokines at different concentrations of rIL-1 beta and immunomodulating agents were corroborated by steady state OF IL-8 and MCP-1 mRNA expression.

CONCLUSIONS

DEX is a potent inhibitor of OF IL-8 and MCP-1. In contrast, CSA enhances IL-1 induced OF IL-8 and suppresses OF MCP-1. These observations may explain the relative lack of CSA effectiveness in human orbital diseases that respond to corticosteroids.

Retro-orbital autoimmunity

What causes Graves' ophthalmopathy is still a mystery, but the disease process results from a complex interplay of genetic and environmental factors. Genes such as those encoding for human leukocyte antigens, cytokines or putative target antigens may determine a patient's susceptibility to the disease and the disease severity, but environmental factors may determine its course. During the last 5 years, significant progress has been made towards a more in-depth understanding of the initiating events of the orbital immune process which occur in the context of autoimmune thyroid disease. Once established, the chronic inflammatory process within the orbital tissues appears to take on a momentum of its own. The work of many investigators has recently helped to extend our knowledge about the effector and target cells, and their reciprocal interaction, in the evolution and perpetuation of the orbital immune process. This chapter's focus is on the more recent aspects of retro-orbital autoimmunity, discussing new developments concerning orbital T-cell repertoires, candidate orbital antigens, potential target and effector cells, and their role in the extrathyroidal manifestations of autoimmune thyroid disease.

Superoxide radical production stimulates retroocular fibroblast proliferation in Graves' ophthalmopathy

Retroocular fibroblast proliferation is believed to be a key component in the pathogenesis of Graves' ophthalmopathy. In the present study, we assessed the ability of superoxide radicals, generated using the xanthine oxidase/hypoxanthine system to induce cellular proliferation in cultured human retroocular fibroblasts obtained from two patients with severe Graves' ophthalmopathy and two control patients undergoing corrective eye surgery. In tissue obtained from patients with Graves' ophthalmopathy, fibroblast proliferation, as assessed by [3H]-thymidine incorporation, was induced by superoxide radicals in a dose-dependent manner. Xanthine oxidase or hypoxanthine alone had no proliferative effect, and control retroocular fibroblasts showed no proliferation in response to superoxide generation. Preincubation with the antithyroid drug methimazole, at concentrations ranging from 0-25 microM, prevented superoxide-induced fibroblast proliferation in a dose-response pattern. Preincubation with the xanthine oxidase inhibitor, allopurinol (1.0 mM) or the antioxidant nicotinamide (10 microM) also inhibited superoxide-induced fibroblast proliferation, whereas propylthiouracil (10 microM) had little effect. These studies suggest a pathway through which oxygen free radicals may contribute to the retroocular fibroblast proliferation observed in patients with Graves' ophthalmopathy.

TSH receptor transcripts and TSH receptor-like immunoreactivity in orbital and pretibial fibroblasts of patients with Graves' ophthalmopathy and pretibial myxedema

Several lines of experimental and clinical evidence favor a close etiologic link between Graves' disease and its associated extrathyroidal manifestations, ophthalmopathy and pretibial dermopathy. The human TSHR represents a candidate antigen shared between the thyroid gland and the involved extrathyroidal sites in Graves' disease. Here, we demonstrate that ribonucleic acid encoding exons 1-10 of human TSHR can be detected in fibroblasts derived from the affected orbital and pretibial space in patients with Graves' ophthalmopathy and pretibial dermopathy. RNA prepared from cultured fibroblasts was reverse transcribed and the resulting cDNA amplified by the polymerase chain reaction using primers spanning exons 1 through 10 of TSHR. The predicted transcripts (1890 and 2092 bp, respectively) were obtained with cDNA derived from orbital and pretibial fibroblasts of all patients with GO and PTM, and orbital fibroblasts of one healthy individual, and confirmed by southern hybridization. Sequencing of TSHR transcripts confirmed their identity with the reported nucleotide sequence of the human TSHR. Immunostaining using both monoclonal and polyclonal antibodies directed against the recombinant human TSHR revealed specific TSHR-like immunoreactivity in fibroblasts and adipose/connective tissue derived from the orbital and pretibial space of patients with GO and PTD, but not in normal individuals or control tissues. Detection, within the orbital and pretibial tissues, of RNA encoding nonvariant hTSHR and of immunoreactivity for this important autoantigen in Graves' disease suggests that the pathogenic role of the TSHR may extend beyond the thyroid gland, and may include the associated extrathyroidal manifestations.

Adhesion molecules in autoimmune disease

Leukocyte activation, circulation, and localization to inflammatory sites are dependent on adherence to molecules on other cells or to extracellular matrix ligands. Adhesion molecule expression and interactions are probably involved in initiation and propagation of autoimmune diseases. Adhesion molecules pertinent to the development of autoimmunity are the subject of this review. Material in this review was generated by a manual and a computerized search of medical literature pertaining to adhesion molecules and specific autoimmune diseases. Topics covered include adhesion molecule classification, regulation of adhesion, and characterization of adhesion receptors in specific autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus, Sjögren's syndrome, autoimmune thyroid disease, multiple sclerosis, and diabetes mellitus. Adhesion molecules are classified into selectin, integrin, and immunoglobulin supergene family groups. Increased adhesion molecule expression and avidity changes occurring with cellular activation are the principal methods regulating leukocyte adhesion. Tumor necrosis factor-alpha (TNF alpha), interferon-gamma (IFN-gamma), and interleukin-1 (IL-1) stimulate adhesion receptor expression on lymphoid and nonlymphoid tissues. Although differences between specific autoimmune diseases exist, key interactions facilitating the development of autoimmune inflammation appear to include L-selectin/P-selectin/E-selectin, lymphocyte function-associated antigen-1 (LFA-1)/intercellular adhesion molecule-1 (ICAM-1), very late antigen-4 (VLA-4)/vascular cell adhesion molecule-1 (VCAM-1), and alpha 4B7/MadCAM or VCAM-1 adhesion. Administration of anti-adhesion molecule antibodies in experimental animal models of autoimmunity and in a preliminary trial with RA patients has been successful in preventing or reducing autoimmune disease severity. A vast array of adhesive interactions occurs between immunocompetent cells, endothelium, extracellular matrix, and target tissues during the evolution of an autoimmune disease. Further characterization of leukocyte migration patterns and adherence should clarify pathogenic processes in specific autoimmune diseases and identify potential therapeutic targets for their treatment.

Cytokines and thyroid function

Cytokines play a crucial role in autoimmune thyroid disease (ATD) through various mechanisms. They are produced in the thyroid by intrathyroidal inflammatory cells, in particular lymphocytes, as well as by the thyroid follicular cells (TFC) themselves and may thus act in a cascade to enhance the autoimmune process (Fig. 1). Cytokines upregulate the inflammatory reaction through stimulation of both T and B cells, resulting in antibody production and tissue injury. In addition, intrathyroidal cytokines induce immunological changes in TFC including enhancement of both major histocompatibility complex (MHC) class I and class II molecule expression, and upregulation of adhesion and complement regulatory molecule expression. Cytokines can also modulate both growth and function of TFC and have a role in extrathyroidal complications of ATD, most importantly thyroid-associated ophthalmopathy (TAO), where they induce fibroblast proliferation and enhance the production of glycosaminoglycans (GAG), resulting in proptosis and the other clinical features of the disease. In addition to these effects, exogenous administration of cytokines has been associated with impairment of thyroid function ranging from the appearance of autoantibodies alone to the development of frank thyroid dysfunction. Cytokines have also been implicated in subacute thyroiditis (SAT) and amiodarone-induced thyroid dysfunction, as well as in thyroid function abnormalities occurring in patients with non-thyroidal illnesses (NTI). Genetic variations in cytokine genes represent potential risk factors for ATD, and disease associations have been described for polymorphisms in IL-1ra and TNF beta genes. Recent experimental evidence suggests the possibility of novel cytokine-based therapeutic approaches for ATD and its complications, in particular TAO.

The TSH receptor and thyroid diseases

Recent advances in the understanding of the molecular biology of the TSH receptor have had a considerable impact on several aspects of thyroidology. The identification and functional characterization of mutations in the TSH receptor gene which constitutively activate the TSH receptor in the absence of its ligand provide an explanation for the molecular mechanism which is most likely responsible for the majority of the hyperfunctioning thyroid adenomas. Moreover, these constitutively activating mutations also cause a new form of familial hyperthyroidism: non-autoimmune autosomal dominant hyperthyroidism and also sporadic cases of congenital non-autoimmune hyperthyroidism. TSH receptor mutations which cause a reduced sensitivity to TSH have been identified as the cause of non-autoimmune congenital hypothyroidism. TSH receptor mRNA variants have been found in thyroid associated ophthalmopathy. If protein expression for these variants can be demonstrated, this finding could advance our understanding of thyroid associated ophthalmopathy. The ability to produce large quantities of TSH receptor protein in bacteria has led to the generation of more sophisticated assays for TSH receptor antibodies and enabled the generation of an animal model for thyroid autoimmunity.

Analysis of T-cell antigen receptor variable region gene usage in patients with thyroid-related pretibial dermopathy

It is unknown whether T cells infiltrating the pretibial skin of patients with thyroid-related pretibial dermopathy represent a primary immune response or participate in a nonspecific inflammatory process. To characterize these T cells at the molecular level, we examined the T-cell antigen receptor variable region gene usage in pretibial skin biopsy specimens obtained from patients with early and late stages of pretibial dermopathy and from individuals with unrelated inflammatory conditions of the pretibial skin. RNA extracted from pretibial biopsy specimens and peripheral blood lymphocytes was reverse transcribed and amplified with the polymerase chain reaction and 22 V alpha and 23 V beta gene-specific oligonucleotide primers. The resulting T-cell receptor (TcR) V alpha and V beta transcripts were verified by Southern hybridization analysis using TcR C-region-specific, digoxigenin-labeled oligonucleotide probes. Compared with matched peripheral blood lymphocytes, the pretibial TcR V alpha and V beta gene repertoire expressed was heterogeneous but revealed marked restriction of V alpha and V beta gene usage in samples derived from patients with active inflammatory pretibial dermopathy of recent onset. In contrast, greater diversity of the TcR V alpha gene repertoire and loss of TcR V beta gene restriction were noted in patients with long-standing, clinically inactive pretibial dermopathy. TcR V gene usage in pretibial tissue and peripheral blood lymphocyte samples obtained from control subjects was unrestricted. Limited variability of TcR V gene usage in early pretibial dermopathy may reflect a primary immune response of antigen-specific T lymphocytes infiltrating the pretibial skin in thyroid-related pretibial dermopathy.

Involvement of the orbital fibroblast and TSH receptor in the pathogenesis of Graves' ophthalmopathy

Our concepts and understanding of the etiology, evolution, and propagation of Graves' ophthalmopathy have become much more sophisticated that they were 10 years ago. Given our current state of knowledge, the following scheme for the pathogenesis of Graves' ophthalmopathy can be proposed. Circulating T cells in patients with Graves' disease, directed against an antigen on thyroid follicular cells, recognize antigenic epitopes that are shared by tissues contained in the retroorbital space. Of the cell types residing in these tissues, fibroblasts are most likely to act as both target and effector cells of the retroorbital immune process. This includes those fibroblasts present in the perimysium of extraocular muscles, which do not appear to be immunologically different from fibroblasts located in the retroorbital connective tissue. By contrast, convincing evidence implicating the human extraocular myocyte itself (rather than the tissue conglomerate of extraocular muscle) as a primary target in GO remains to be demonstrated. Together with adipocytes, fibroblasts may also serve as target and effector cells in pretibial myxedema. How autoreactive T cells escape deletion by the immune system and come to be directed against a self-antigen presented by cells residing in the thyroid gland and extrathyroidal locations is unknown. T cells are recruited to and infiltrate the orbit via certain adhesion receptors, which may also play a costimulatory role in T cell activation and facilitate antigen recognition. Analysis of variable region gene usage of the T cell antigen receptors in retroorbital T cells of patients with active GO reveals limited variability, suggesting that antigen-driven selection and/or expansion of specific T cells may occur early in the evolution of GO.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum laminin in Graves' disease

We determined serum levels of laminin in 23 patients with Graves' disease (GD) and in 24 patients with toxic nodular goiter (TNG). Elevated levels of soluble laminin were observed in patients with GD prior to treatment (median concentration 1376 ng mL-1 [range 712-2402]), compared to patients with TNG (median 442 ng mL-1 [284-891]), and normal controls (median 492 ng mL-1 [range 235-675], n = 26), respectively. In GD patients serum laminin levels decreased during thiamazole treatment and normalized within 8 weeks of therapy. There was no correlation between serum laminin levels and serum levels of thyroid hormones and/or auto-antibodies, respectively. Whether serum laminin is a marker for alterations of extracellular matrix during GD and release of basement membrane components in the circulation and/or reflects an impaired clearance remains to be elucidated.

Extraocular muscles: basic and clinical aspects of structure and function

Although extraocular muscle is perhaps the least understood component of the oculomotor system, these muscles represent the most common site of surgical intervention in the treatment of strabismus and other ocular motility disorders. This review synthesizes information derived from both basic and clinical studies in order to develop a better understanding of how these muscles may respond to surgical or pharmacological interventions and in disease states. In addition, a detailed knowledge of the structural and functional properties of extraocular muscle, that would allow some degree of prediction of the adaptive responses of these muscles, is vital as a basis to guide the development of new treatments for eye movement disorders.

Assessment and Management of the Patient with Graves’ Ophthalmopathy

The appropriate management of a patient with Graves' ophthalmopathy (GO) can be determined only following a careful assessment of the signs and symptoms of the disease. A detailed examination and discussion allows the clinician to determine which components of the disease are most troublesome to that particular patient. The advantages and disadvantages of the various treatment options for each disease component can be best understood in light of current concepts of the pathogenesis of GO. This paper will begin with a discussion of the histologic and gross pathologic features of the disease, followed by a brief review of pathogenic mechanisms responsible for their development. The assessment of a patient with GO will be discussed and the modes of therapy available to address each of the signs and symptoms will be reviewed. Readers interested in a more detailed discussion of the management of GO are encouraged to read the excellent recent review by Drs. Burch and Wartofsky.