Superoxide radical production stimulates retroocular fibroblast proliferation in Graves' ophthalmopathy

Effects of pulse methylprednisolone and oral methylprednisolone treatments on serum levels of oxidative stress markers in Graves' ophthalmopathy

BACKGROUND

Recent evidence has shown that oxidative stress may play a role in the pathogenesis of autoimmune diseases, and this is an issue of considerable research interest in the field of infiltrative ophthalmopathy. Therefore, we evaluated both the relationship between Graves' ophthalmopathy (GO) and serum levels of certain indicators of oxidative stress, and the effects of methylprednisolone treatment on serum malondialdehyde (MDA) and glutathione (GSH) levels in patients with euthyroid GO.

MATERIALS AND METHODS

We compared GO patients to both Graves' patients without ophthalmopathy and healthy controls. Ultimately, we assessed four subject groups. Graves' patients with ophthalmopathy (GO) were subcategorized into two groups: Group A subjects (n = 18) were given intravenous glucocorticoid and Group B patients (n = 15) were given oral glucocorticoid. Graves' patients without ophthalmopathy comprised Group C (n = 20), and healthy controls comprised Group D (n = 15). Serum levels of MDA and GSH were measured at baseline and after 4 and 24 weeks of observation via spectrophotometric methods.

RESULTS

We found that serum MDA levels were significantly higher in the two GO groups (Groups A and B) than in GO patients without ophthalmopathy or healthy controls. Conversely, GSH levels were significantly lower in the two GO groups than in Groups C and D. MDA and GSH levels were not different between the latter two groups. MDA levels were strongly and positively correlated with a clinical activity score (CAS). In Group A, MDA levels and the CAS were significantly lower than in Group B at 4 weeks. After 24 weeks, however, MDA levels and the CAS were similar in these two groups.

CONCLUSION

Oxidative stress appears to be involved in the pathophysiology of GO. Relative to oral dosing, the intravenous administration of a glucocorticoid seems to yield more rapid improvement in disease activity. MDA might be useful as an indicator of clinical activity.

Oxidative stress profile in graves' ophthalmopathy in Indian patients

PURPOSE

To report the oxidative stress profile in patient of Graves' ophthalmopathy and to study the effect of hormone level normalization on oxidative stress profile.

METHODS

All first time reporting patients with Graves' ophthalmopathy to Department of ophthalmology CSM Medical University (erstwhile King George's Medical University) Lucknow during the period January 2006 to December 2008 formed the cohort. Before initiating treatment a proforma directed detailed history, complete ophthalmological examination and investigations were done. Blood sample for pro/antioxidant enzyme were withdrawn for study after taking an informed consent. Patients were treated with antithyroid drugs alone to achieve a stable euthyroid status for at least 6 months following which a blood sample was again withdrawn to study the pro/anti oxidant enzyme status following treatment.

RESULTS

On normalization of thyroid status the values of reactive oxygen species decreased significantly (p<0.05) and levels of antioxidants also got corrected significantly (p<0.05). However both these values remained significantly (p<0.05) altered as compared to normal persons.

CONCLUSION

We demonstrated that even after normalization of thyroid hormone level, the oxidative stress levels remain elevated. Moreover, activity of Superoxide Dismutase (SOD), Catalase (CAT), Glutathione reductase (GSHR), Glutathione peroxidise (GPx) showed decrease which could be attributed to altered metabolism and already prevalent deficiency of essential micronutrients like zinc, copper, mercury, and selenium in the Indian population. Hence, this gives way to the thought that the supplementation of these nutrients may have a role as an adjuvant to hormonal therapy in patients with Graves' ophthalmopathy.

Immunopathogenesis of thyroid eye disease: emerging paradigms

Graves disease represents a systemic autoimmune process targeting the thyroid, orbit, and pretibial skin. The thyroid dysfunction is treatable, but no consistently effective medical therapy has yet been described for the orbital manifestations of Graves disease, also known as thyroid-associated ophthalmopathy or thyroid eye disease. Several autoantigens are potentially relevant to the pathogenesis of thyroid eye disease. Activating antibodies generated against the thyrotropin receptor can be detected in a majority of patients, and these drive hyperthyroidism. However, stimulating antibodies against the insulin-like growth factor-1 receptor (IGF-1R) may also play a role in the extra-thyroid manifestations of Graves disease. IGF-1R is overexpressed by orbital fibroblasts derived from patients with thyroid eye disease, whereas IGF-1R(+) T and IGF-1R(+) B cells are considerably more frequent in Graves disease. Actions of several cytokines and the molecular interplay peculiar to the orbit appear to provoke the inflammation, fat expansion, and deposition of excessive extracellular matrix molecules in thyroid eye disease. Based upon these new insights, several therapeutic strategies can now be proposed that, for the first time, might specifically interrupt its pathogenesis.

Update on the medical treatment of Graves' ophthalmopathy

PURPOSE

To review recent advances in the understanding of Graves' ophthalmopathy (GO) pathogenesis as well as discuss current and future medical management strategies.

DESIGN

Interpretive essay.

METHODS

Literature review and interpretation.

RESULTS

Medical treatment of GO has slowly evolved during the past few decades and has been hampered by a poor understanding of the disease at a cellular and molecular level. Current treatment recommendations and guidelines therefore focus on nonspecific immuno-suppression. Newer classes of treatment agents hold promise to more selectively target underlying cellular and molecular alterations in GO.

CONCLUSION

Cooperation between individual patients, physicians and between differing medical centers, together with a refined understanding of the pathogenesis of GO, will lead to newer more-effective treatments for the disease and improve patient quality of life.

Oxidative stress in patients with Graves' ophthalmopathy: relationship between oxidative DNA damage and clinical evolution

PURPOSE

To evaluate the relationship between oxidative stress and clinical evolution in patients with Graves' ophthalmopathy (GO).

METHODS

Thirty-one euthyroid GO patients and 25 healthy subjects participated in this study. Oxidative DNA damage was assessed by determination of the 8-hydroxy-2'-deoxyguanosine (8-OHdG) level in urine by ELISA. The relationship of oxidative DNA damage to the clinical evolutions of GO, especially the smoking status, clinical activity scores (CAS), and ophthalmopathy index was examined.

RESULTS

The mean 8-OHdG was significantly higher in GO patients than that of normal controls (12.6+/-5.7 vs 6.7+/-2.5 ng/mg creatinine, P<0.001). Smokers had significant higher 8-OHdG than did never smokers in GO patients (P=0.029), but not in healthy controls (P=0.374). Among GO patients, only CAS remained significantly correlated with 8-OHdG (P=0.001) after adjusting for age, sex, disease duration, the status of antithyroid drug and smoking, and thyroid-stimulating hormone level. Patients with active GO (CAS>3) had higher 8-OHdG than did the patients with CAS <or=3 (16.3+/-4.9 vs 8.6+/-3.0 ng/mg creatinine).

CONCLUSIONS

Our findings suggest that urinary 8-OHdG is increased in GO patients and is correlated with the disease activity. Smoking had a higher impact on the increased 8-OHdG among GO patients.

Oxidative stress and antioxidant activity in orbital fibroadipose tissue in Graves' ophthalmopathy

PURPOSE

To investigate the oxidative stress and antioxidant activity in the orbit in Graves' ophthalmopathy (GO).

MATERIALS AND METHODS

Orbital fibroadipose tissue samples were obtained from 13 cases during orbital fat decompression surgery. All cases demonstrated features of moderate or severe GO according to the European Group on Graves' Orbitopathy classification. The disease activity was evaluated with the Clinical Activity Score, and the clinical features of GO were evaluated with the Ophthalmopathy Index. Orbital fibroadipose tissue samples of 8 patients without any thyroid or autoimmune disease were studied as controls. In the tissue samples, lipid hydroperoxide level was examined to determine the level of oxidative stress; glutathione level to determine antioxidant level; superoxide dismutase, glutathione reductase, and glutathione peroxidase activities to determine antioxidant activity.

RESULTS

Lipid hydroperoxide level and all three antioxidant enzyme activities were found to be significantly elevated, while glutathione level significantly diminished in tissue samples from GO cases compared to controls (p < 0.05). Glutathione levels in tissue samples of GO cases showed negative correlation with Ophthalmopathy Index (r = -0.59, p < 0.05).

CONCLUSIONS

The antioxidant activity in the orbit is enhanced in GO. However, the oxidative stress appears to be severe enough to deplete the tissue antioxidants and leads to oxidative tissue damage. This study may support the possible value of antioxidant treatment in GO.

Association of Graves' disease and Graves' ophthalmopathy with the polymorphisms in promoter and exon 1 of cytotoxic T lymphocyte associated antigen-4 gene

OBJECTIVE

To investigate the association of Graves' disease and Graves' ophthalmopathy with the C/T transition polymorphism at position -318 of promoter and the A/G transition polymorphism at position 49 of exon 1 within cytotoxic T lymphocyte associated antigen-4 (CTLA-4) gene.

METHODS

Thirty-three patients with ophthalmopathy of Graves' disease, fifty-six Graves' patients without ophthalmopathy and sixty normal subjects as control were involved in the present case-control study. The polymorphisms were evaluated by polymerase chain reaction fragment length polymorphism (PCR-RFLP). Comparisons were made of gene frequencies and allele frequencies between the groups.

RESULTS

The gene frequencies of CT and allele frequencies of T were much higher in Graves' patients with ophthalmopathy than that in the group without ophthalmopathy (P=0.020, P=0.019). The gene frequencies of GG and allele frequencies of G in patients with Graves' disease were significantly increased as compared with control group (P=0.008, P=0.007). The data suggest that smokers with Graves' disease seemed to be more predisposed to ophthalmopathy than non-smokers (P=0.018).

CONCLUSION

Our results suggest that an allele of T at position -318 of promoter is associated with genetic susceptibility to Graves' ophthalmopathy while an allele of G at position 49 of exon 1 is associated with genetic susceptibility to Graves' disease instead. Smoking is believed to be a major risk factor for ophthalmopathy.

Smoking and thyroid-associated ophthalmopathy: A novel explanation of the biological link

INTRODUCTION

Cigarette smoking is the strongest modifiable risk factor for developing thyroid-associated ophthalmopathy (TAO), and the severity of TAO is related to the current number of cigarettes smoked per day. We aimed to establish the effects of cigarette smoke extract (CSE) on an in vitro model of TAO.

METHODS

Orbital tissue was taken during surgery from 10 patients with TAO and nine control subjects. Orbital fibroblasts were cultured and exposed to CSE, and intercellular adhesion molecule 1 (ICAM1) expression was measured by flow cytometry. Glycosaminoglycan production was measured by hyaluronic acid ELISA. Orbital fibroblasts were grown in adipogenic media with or without CSE and/or IL-1, and the degree of adipogenesis was quantified.

RESULTS

Fibroblasts from patients with TAO and controls showed similar responses. ICAM1 expression was not affected by CSE. Hyaluronic acid production was stimulated by CSE in a dose-dependent manner (correlation coefficient, 0.978; P = 0.022), with 5% CSE causing an increase of 44% (P = 0.001). CSE increased adipogenesis in a dose-related manner, as did IL-1. The effects of CSE and IL-1 on adipogenesis were synergistic, with the degree of adipogenesis in the well containing both 5% CSE and 0.1 ng/ml IL-1 being double the magnitude of the sum of the values obtained from either stimulus alone (P < 0.001). Addition of an anti-IL-1 antibody to the well containing both 5% CSE and 0.1 ng/ml IL-1 reduced the degree of adipogenesis by 82% (P < 0.001).

CONCLUSION

These findings may help explain how cigarette smoking has a detrimental effect in TAO and suggests that IL-1 may be an attractive therapeutic target in TAO.

Pathogenesis of graves ophthalmopathy: implications for prediction, prevention, and treatment

PURPOSE

To review current concepts regarding the pathogenesis of Graves ophthalmopathy (GO). We have presented this information in the context of potential target sites for novel disease therapies.

DESIGN

Review of recent literature.

METHODS

Synthesis of recent literature.

RESULTS

Enlargement of the extraocular muscle bodies and expansion of the orbital fatty connective tissues is apparent in patients with GO. These changes result from abnormal hyaluronic acid accumulation and edema within these tissues and expanded volume of the orbital adipose tissues. Recent studies have suggested that the increase in orbital fat volume is caused by stimulation of adipogenesis within these tissues. The orbital fibroblast appears to be the major target cell of the autoimmune process in GO. A subset of these cells is capable of producing hyaluronic acid and differentiating into mature adipocytes, given appropriate stimulation. In addition, orbital fibroblasts from patients with GO have been shown to display immunoregulatory molecules and to express both thyrotropin receptors (TSHRs) and insulin-like growth factor 1 receptors (IGF-1Rs). Increased TSHR expression in the GO orbit appears to be the result of stimulated adipocyte differentiation. The activation of IGF-1R on orbital fibroblasts by immunoglobulins from GO patients results in increased production of both hyaluronic acid and molecules that stimulate the infiltration of activated T cells into areas of inflammation.

CONCLUSIONS

Potential targets for novel therapeutic agents to be used in GO include blocking T-cell costimulation, depleting B cells, inhibiting cytokine action, targeting the IGF-1R or the TSHR, and preventing connective tissue remodeling.

Pharmacological Treatments for Thyroid Eye Disease

Thyroid eye disease (TED), which affects the majority of patients with Grave's disease, is associated with significant ophthalmic morbidity. In patients with mild disease, supportive treatment with lubricating medication can be sufficient. However, in patients with severe TED and disfiguring proptosis or sight-threatening neuropathy, more aggressive medical or surgical interventions are necessary. Corticosteroids remain the preferred pharmacological treatment modality in the majority of patients with an active inflammatory component. Other immunosuppressive drugs in combination with corticosteroids may be helpful in patients with corticosteroid-resistant TED. Newer agents such as somatostatin analogues have not shown to be of significant clinical benefit; however, initial studies on the use of antioxidants and cytokine antagonists are encouraging.

Peripheral parameters of oxidative stress in patients with infiltrative Graves' ophthalmopathy treated with corticosteroids

Infiltrative ophthalmopathy, which may develop in patients with Graves' disease, is considered an inflammatory disorder of autoimmune background. There is growing evidence that changed reactive oxygen species (ROS) metabolism plays an important role in pathogenesis of autoimmune diseases. Corticotherapy is a principal method of ophthalmopathy treatment, and its therapeutic effect is partially connected with influence on ROS generation systems. This study was undertaken to investigate corticosteroids treatment influence on blood extracellular indices of ROS metabolism in Graves' ophthalmopathy patients. Plasma indices of free radical generation and scavenging were determined in 22 euthyroid patients with active infiltrative Graves' ophthalmopathy initially, after intensive corticotherapy and after completing of steroid treatment. Age- and sex-matched 24 healthy volunteers and 25 euthyroid Graves' patients without overt ophthalmopathy served as controls. In the ophthalmopathy patients hydrogen peroxide (H(2)O(2)), lipid hydroperoxides (ROOH), thiobarbituric acid-reacting substances (TBARS) and ceruloplasmin (CP) levels and superoxide dismutase (SOD) and catalase (CAT) activities were increased, whereas glutathione peroxidase (GPx) and glutathione reductase (GR) activities were reduced. Intensive corticotherapy resulted in normalization (partial for ROOH) of ROS metabolism peripheral markers. After the withdrawal of corticosteroids a reduction of ophthalmopathy clinical activity was present, yet a marked restoration of increased oxidative stress indices was observed, along with activation of antioxidant defence systems (not significant for CAT activity). These data demonstrate that corticosteroids are effective in reduction of peripheral oxidative stress present in infiltrative Graves' ophthalmopathy, but this effect tends to be transient.

Oxidative stress peripheral parameters in Graves' disease: the effect of methimazole treatment in patients with and without infiltrative ophthalmopathy

OBJECTIVES

The study was designed to estimate the influence of hyperthyroidism and antithyroid treatment on oxidative stress peripheral parameters in Graves' disease patients with and without infiltrative ophthalmopathy.

DESIGN AND METHODS

Free radical generation and scavenging plasma indices were determined in 47 patients with hyperthyroidism due to Graves' disease (22 with and 25 without infiltrative ophthalmopathy), as well as in 24 healthy volunteers after euthyroidism achievement with methimazole.

RESULTS

In the hyperthyroid patients, hydrogen peroxide, lipid hydroperoxides, thiobarbituric acid-reacting substances, ceruloplasmin, superoxide dismutase, and catalase were increased. Glutathione peroxidase and glutathione reductase, however, were reduced. Methimazole treatment resulted in all markers being normalized in the patients without infiltrative ophthalmopathy, yet oxidative stress was still present in the ophthalmopathy group.

CONCLUSION

We suggest that apart from the thyroid metabolic status influence, it is orbital inflammation that triggers changes in blood extracellular indices of reactive oxygen species metabolism.

Graves' ophthalmopathy: state of the art and perspectives

Graves' ophthalmopathy (GO) is an autoimmune orbital disorder most commonly associated with Graves' disease. Recent studies have underscored the role that orbital cells, particularly fibroblasts and adipocytes, play in causing the increase in orbital content responsible for clinical manifestations of the disease. GO seems to be related to autoimmune reactions triggered by autoreactive T lymphocytes of thyroid origin, which recognize antigen(s) shared by thyroid and orbit. The nature of the antigen (or antigens) involved is not fully understood, but TSH receptor is likely to be involved. Cytokines secreted by T lymphocytes, macrophages and fibroblasts play an essential role in perpetuating the disease. Animal models of GO have been developed, but results have not clarified GO pathogenesis yet. Progress in the management of the ophthalmopathy has been very limited, and glucocorticoids, orbital radiotherapy and orbital decompression remain the mainstays in GO treatment. Novel treatments, such as somatostatin analogues, antioxidants, cytokine antagonists are currently under investigation, as well as the effects of total thyroid ablation. Cessation of smoking currently represents the only form of GO (secondary and tertiary) prevention.

Oxidative stress and Graves' ophthalmopathy: in vitro studies and therapeutic implications

Graves' ophthalmopathy (GO) is a disorder of autoimmune origin caused by a complex interplay of endogenous and environmental factors. After recognition of one or more antigens shared by thyroid and orbit, activated T lymphocytes infiltrating the orbit trigger a cascade of events leading to production of cytokines, growth factors and oxygen reactive species. Proliferation of adipocytes and fibroblasts then follows, with an increased synthesis of glycosaminoglycans (GAG), which attract water and cause edema of orbital structures and venous congestion. Proliferation of orbital fibroblasts and adipocytes, both in the retroocular tissue and in the perimysium of extraocular muscles, are among the most important events leading to the increased volume of orbital structures (fibroadipose tissue and extraocular muscles). The contribution of oxygen reactive species to the changes occurring in the orbit is underscored by in vitro studies. Superoxide radical stimulates orbital fibroblasts to proliferate and to produce GAG. Furthermore, hydrogen peroxide induces expression of HLA-DR and heat shock protein-72, involved in antigen recognition and T-lymphocyte recruitment. Cigarette smoking, which is probably the most important environmental factor associated with GO occurrence and maintenance, might also act, among other mechanisms, by enhancing generation of oxygen reactive species and reducing antioxidant production. Substances such as nicotinamide, allopurinol and pentoxifylline reduce superoxide- or hydrogen peroxide-induced proliferation of fibroblasts, GAG production and HLA-DR or HSP-72 expression by GO orbital fibroblasts, possibly through scavenging oxygen free radicals. Two small, non-randomized and/or uncontrolled studies investigated the effects of nicotinamide, allopurinol or pentoxifylline on GO. Favorable results were reported, but data are not fully convincing and the true effectiveness of these agents needs to be verified in randomized, controlled trials enrolling a larger number of patients. It currently seems unlikely that they may find a relevant place in the limited armamentarium available for the management of severe GO.

Free radical activity and antioxidant defense mechanisms in patients with hyperthyroidism due to Graves' disease during therapy

Free radical-mediated oxidative stress has been implicated in the etiopathogenesis of several autoimmune disorders. We investigated the prooxidant-antioxidant status in order to evaluate the possible deleterious role of oxidative phenomena in patients with Graves' disease. Thirty patients with hyperthyroidism due to Graves' disease were investigated. Thirty age-matched healthy subjects were studied as a control group. Free radical activity indices, antioxidant defense systems, and thyroid and pituitary hormone levels were measured in fasting blood samples. Blood samples were taken before initiation of therapy and after attainment of euthyroid state. A significant increase in lipid peroxidation activity indices, i.e., conjugated dienes and thiobarbituric acid-reacting substances, was found in blood serum of the patients with untreated Graves' disease. These changes were accompanied by a decrease in plasma thiol and erythrocyte lysate thiol groups concentrations. Hyperthyroidism resulted in a marked increase in intracellular antioxidant enzymes, i.e., superoxide dismutase, catalase and glutathione peroxidase activities as compared to the controls. Extracellular anti-free radical scavenging systems potential, measured by glutathione reductase activity and total antioxidant status level, was found to be significantly decreased in untreated Graves' patients. Treatment with thiamazole resulted in normalization of the free radical and antioxidant activity indices. The obtained results indicate an enhanced generation of reactive oxygen species and impairment of cellular and extracellular antioxidant systems potential in patients with Graves' disease. The attainment of euthyroid state led to an improvement in oxidative stress indices and antioxidant potential parameters.

Antioxidant agents in the treatment of Graves' ophthalmopathy

PURPOSE

To report the effect of antioxidant agents in the treatment of mild and moderately severe Graves' ophthalmopathy.

METHODS

Prospective, nonrandomized, comparative study performed at a referral center. A series of 11 patients with mild or moderately severe, active, newly diagnosed Graves' ophthalmopathy were included in the study. Allopurinol (300 mg daily) orally and nicotinamide (300 mg daily) orally were used for 3 months. A complete ophthalmologic examination was performed before and 1 and 3 months after initiation of treatment. The response to treatment was estimated separately for each component of the disease and overall by its effect on a total eye score. Eleven patients with mild or moderately severe, active, newly diagnosed Graves' ophthalmopathy who received placebo were also examined at the same time points. Patients in each group were recruited consecutively. Although nonsmoking was not an exclusion criterion, all patients were cigarette smokers.

RESULTS

Nine (82%) of 11 patients treated with oral antioxidants showed improvement of mild to moderately severe Graves' ophthalmopathy versus three (27%) of 11 patients in the control group (P <.05). Soft tissue inflammation was the component of the disease that responded more to treatment. No side effects of antioxidant treatment were recorded. Patients' satisfaction was high.

CONCLUSIONS

This pilot study presents encouraging results in the treatment of mild and moderately severe Graves' ophthalmopathy with antioxidant agents. To evaluate these preliminary results, randomized prospec-tive studies are needed.

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.

Immunodetection of manganese superoxide dismutase in cultured human retroocular fibroblasts using sera directed against the thyrotropin receptor

The identification of antigenic targets in the retroocular autoimmune response of Graves' ophthalmopathy is likely to increase our understanding of mechanisms underlying this disorder. While a number of putative autoantigens have been identified on the basis of molecular weight or cell of origin, a determination of the significance of these antigens is contingent upon an identification of the amino acid sequence. Our group has previously identified immunoreactive retroocular fibroblast (ROF) proteins recognized by thyrotropin receptor (hTSH-R) antisera (anti-p1), at molecular weights of 95, 71, 41, and 14-25 kDa. In the present study, proteins detected by anti-p1 and visualized by Ponceau staining were isolated and processed for microsequencing. Ponceau staining revealed dense bands at molecular weights of 14 and 23 kDa, and a weak band at 41 kDa. N-terminal sequencing was performed on the prominent band at approximately 23 kDa, showing it to be manganese superoxide dismutase (MnSOD), a mitochondrial enzyme responsible for protection against oxygen free radical-associated cellular damage. Sequence comparison of MnSOD to the hTSH-R peptide, p1, revealed a linear segment of amino acid homology. Preincubation of anti-p1 with p1 blocked immunodetection of the 23 kDa band corresponding to MnSOD, and immunoprecipitation of ROF protein using anti-pi yielded protein recognized by anti-MnSOD. Autoimmunity against human recombinant MnSOD was further assessed by ELISA. Patients with Graves' disease (n = 53) had significantly higher ELISA indices than normal control subjects (n = 29), while patients with Hashimoto's thyroiditis had intermediate values. These results document MnSOD autoantibodies in patients with Graves' disease and suggest that this may result from an immune cross-reactivity between MnSOD and the TSH-receptor.