Biomedical subjects

R S Bahn

Publications and source records attributed to R S Bahn.

At least 19 recordsLinked to original sources

PubMed2004

TSH receptor expression in orbital tissue and its role in the pathogenesis of Graves' ophthalmopathy.

The TSH receptor (TSHr) is the autoantigen responsible for the hyperthyroidism of Graves' disease. Recent studies suggest that this receptor may also be an autoimmune target in Graves' ophthalmopathy (GO) and pretibial dermopathy (PTD). Its involvement in the pathogenesis of these conditions would help to explain the close clinical associations between hyperthyroidism, GO and PTD. TSHr has been shown to be present in normal orbital and dermal tissues and evidence supports the conviction that expression may be increased in tissues involved in GO and PTD. In the setting of Graves' disease, the expression of this antigen in connective tissues throughout the body may lead to systemic, subclinical connective tissue inflammation. Given this background, local or environmental factors such as circulating or local cytokines, gravitational dependency, anatomic constraint of the bony orbit, or trauma, may augment clinical disease involvement within the orbit and pretibial skin. Alternately, locally enhanced expression of this protein at the sites of clinical disease may not be directly involved in pathogenesis, but could be secondary to the ongoing process, and nonetheless important in disease progression.

Adipocytes↗

PubMed2001

A prospective, randomized, double-blind, placebo-controlled study of orbital radiotherapy for Graves' ophthalmopathy.

CONTEXT: Although widely used for more than 85 years, the efficacy of radiotherapy for Graves' ophthalmopathy (GO) has not been established convincingly. OBJECTIVE: To evaluate the efficacy of radiotherapy for GO. DESIGN: Prospective, randomized, internally controlled, double-blind clinical trial in a tertiary care academic medical center. PARTICIPANTS: The patients were ethnically diverse males and females over age 30 seen in a referral practice. The patients had moderate, symptomatic Graves' ophthalmopathy (mean clinical activity score, 6.2) but no optic neuropathy, diabetes, recent steroid treatment, previous decompression, or muscle surgery. Forty-two of 53 consecutive patients were enrolled after giving informed consent and fulfilling study entry criteria. Eleven eligible patients declined to participate because of inconvenience, desire for alternative therapy, or concern about radiation. INTERVENTION: One randomly selected orbit was treated with 20 Gy of external beam therapy; sham therapy was given to the other side. Six months later, the therapies were reversed. MAIN OUTCOME MEASURES: Every 3 months for 1 year, we measured the volume of extraocular muscle and fat, proptosis, range of extraocular muscle motion, area of diplopia fields, and lid fissure width. Effective treatment for GO will modify one or more of these parameters. RESULTS: No clinically or statistically significant difference between the treated and untreated orbit was observed in any of the main outcome measures at 6 months. At 12 months, muscle volume and proptosis improved slightly more in the orbit that was treated first. CONCLUSIONS: In this group of patients, representative of those for whom radiotherapy is frequently recommended, we were unable to demonstrate any beneficial therapeutic effect. The slight improvement noted in both orbits at 12 months may be the result of natural remission or of radiotherapy, but the changes are of marginal clinical significance.

Adult↗

PubMed2001

Induction of leptin expression in orbital preadipocyte fibroblasts.

Graves' ophthalmopathy (GO) is an autoimmune disease characterized by an increase in the volume of the orbital fatty/connective tissues and extraocular muscles. This volume change is due to expansion of the adipose tissues and to accumulation of glycosaminoglycans and edema within the connective tissues of the orbit. We have shown previously that a subpopulation of confluent human orbital preadipocyte fibroblasts can be induced in vitro to differentiate into cells with morphological features of adipocytes and that these cultures express functional thyrotropin receptor (TSHR). In order to identify and study these cells further, we examined the expression of leptin protein and TSHR and leptin mRNA in these cultures. Using immunocytochemistry with objective measurement of immunofluorescent staining intensity on digitized microscopic images, we determined leptin protein expression to be 6 to 37 times greater in differentiated cultures than in control cultures. In addition, we showed that the expression of both genes is enhanced in differentiated cultures. We suggest that an unknown humoral stimulus, present in Graves' disease, might act to induce the differentiation of normal orbital fibroblasts into TSHR-bearing adipocytes. This process would be expected to result in expansion of the orbital adipose tissues and increased TSHR expression within the orbit.

Adipocytes↗

PubMed2001

Interleukin-6 stimulates thyrotropin receptor expression in human orbital preadipocyte fibroblasts from patients with Graves' ophthalmopathy.

The thyrotropin receptor (TSHR) is the thyroid autoantigen against which stimulating autoantibodies are directed in Graves' hyperthyroidism. Recent evidence suggests that TSHR may also serve as an orbital autoantigen in Graves' ophthalmopathy (GO) and that expression of this protein is increased in the fatty connective tissues of the orbit in this condition. It has been shown that orbital fibroblasts from patients with GO increase thyrotropin (TSH)-dependent cyclic adenosine monophosphate (cAMP) production and TSHR gene expression when cultured under conditions known to stimulate adipocyte differentiation. In the current study, we wanted to determine whether treatment of these cells with particular cytokines (each 1 ng/mL) during differentiation might further augment TSHR expression. We found that exposure to interleukin (IL)-6 increased TSHR expression above control levels in cells from patients with GO. In contrast, this cytokine did not affect TSHR expression in normal orbital cells. Neither IL-4 nor IL-1alpha had a significant stimulatory effect in either normal or Graves' cultures. These findings suggest that IL-6 may play a role in the pathogenesis of GO by increasing expression of the putative autoantigen within the adipose/connective tissues of the orbit.

Adipocytes↗

PubMed2001

Effect of tumor necrosis factor-alpha, interferon-gamma, and transforming growth factor-beta on adipogenesis and expression of thyrotropin receptor in human orbital preadipocyte fibroblasts.

Graves' ophthalmopathy (GO) is an orbital autoimmune disease that is closely associated with Graves' hyperthyroidism. Examination of retroorbital tissues in GO reveals an accumulation of glycosaminoglycans, increased fat volume, lymphocytic infiltration, and the presence of several inflammatory cytokines. A subpopulation of human orbital fibroblasts can be differentiated in vitro into cells with the morphologic features of adipocytes. We demonstrated recently that these differentiated cultures show increased expression of functional TSH receptor (TSHr). To determine whether the presence of inflammatory cytokines might impact adipogenesis or TSHr expression in these cultures, we treated orbital fibroblasts from normal individuals or GO patients with tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), or transforming growth factor-beta. We found that each of these cytokines inhibits TSH-dependent cAMP production and TSHr gene expression, and that TNF-alpha and IFN-gamma also inhibit morphological adipocyte differentiation. When cytokines were added after differentiation, the inhibition was less pronounced. Our results suggest that TNF-alpha, IFN-gamma, and transforming growth factor-beta may act within the orbit in GO to modulate expression of the putative orbital autoantigen, TSHr. In addition, the former two cytokines may play a role in determining the extent to which the volume of the orbital adipose tissue increases in this condition.

Adipocytes↗

PubMed2000

Understanding the immunology of Graves' ophthalmopathy. Is it an autoimmune disease?

The notion that Graves' ophthalmopathy is an autoimmune disease has been based primarily on the clinical associations between it and Graves' hyperthyroidism, and on the frequently beneficial response of the disease to immunosuppressive therapy. Recent advances in molecular biology have led to new insights into the pathogenesis that support an autoimmune basis for this condition. In particular, there is now compelling--although not definitive--evidence that, if verified, would represent disease transfer by thyroid-secreting hormone receptor-sensitized T cells. Future studies using animal models and in vitro systems will allow definitive identification of the immune cell types, autoantigens, and autoantibodies involved in the pathogenesis of Graves' ophthalmopathy.

Animals↗

PubMed2000

Relationship between disease duration and predominant orbital T cell subset in Graves' ophthalmopathy.

We sought to determine whether the predominant orbital T helper (T(H)) cell subset in orbital T cell clones established from patients with Graves' ophthalmopathy (GO) might be related to disease duration. A total of 117 clones were established from orbital adipose/connective tissues of 6 GO patients, and cytokine production was measured in 57 CD3+CD4+ clones. T(H)1-type clones were predominant in cultures from patients with recent onset (<2 yr) Graves' hyperthyroidism (n = 44; TH1/TH0/TH2 = 57/29/14%) or GO (n = 53 clones; TH1/TH0/TH2 = 47/30/23%). In contrast, TH2-type clones predominated in cultures from patients with more remote onset (>2 yr) hyperthyroidism (n = 13; TH1/TH0/TH2 = 0/31/69%; P < 0.005) or GO (n = 4; TH1/TH0/TH2 = 0/25/75%; P = 0.05). In addition, we established T cell clones from 1 TH1-dominant patient with recent-onset thyroid and eye disease using either IL-2 (12.5 ng/mL) alone or IL-2 plus IL-4 (5 ng/mL) and found no shift toward recovery of TH2-type clones in the latter. In conclusion, although the CD3+CD4+ clones characterized were not necessarily tissue antigen specific, our findings suggest that cell-mediated (TH1-type) immune reactions may predominate in the orbit in early GO, whereas humoral immunity (TH2-type) might play the greater role in later stages of the disease.

Adipose Tissue↗

PubMed1999

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.

Catalase↗

PubMed1999

Differentiation of human orbital preadipocyte fibroblasts induces expression of functional thyrotropin receptor.

Although the autoantigen involved in Graves' hyperthyroidism is known to be the TSH receptor (TSHr), whether this antigen plays a primary role in the pathogenesis of Graves' ophthalmopathy (GO) is unclear. We sought to determine whether fibroblasts derived from orbital adipose/connective tissue are capable of differentiating into adipocytes that bear immunoreactive and functional TSHr. In addition, we assessed relative levels of TSHr gene expression in normal and GO orbital adipose/connective tissue specimens. GO and normal orbital preadipocyte fibroblasts, cultured under conditions known to stimulate adipocyte differentiation, showed evidence of adipogenesis and positive immunostaining for TSHr protein. In addition, significantly more cAMP was produced in response to TSH stimulation in the differentiated cultures than in undifferentiated cultures derived from the same individuals' cells. Other studies demonstrated relatively greater TSHr gene expression in GO than in normal orbital tissue specimens. These results indicate that orbital preadipocyte fibroblasts increase their TSHr expression with differentiation and suggest that these cells play an important role in the pathogenesis of GO. Furthermore, our studies support the concept that TSHr may be an important target antigen in this condition. Factors that stimulate adipocyte differentiation and TSHr expression in the orbit in GO have yet to be defined.

Adipocytes↗

PubMed1998

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.

Amino Acid Sequence↗

PubMed1998

Thyrotropin receptor expression in cultured Graves' orbital preadipocyte fibroblasts is stimulated by thyrotropin.

Our laboratory has shown recently that the thyrotropin receptor (TSHr) is expressed in orbital adipose/connective tissues from patients with Graves' ophthalmopathy (GO), and that this receptor is not demonstrable in orbital tissues from normal individuals. In order to study the regulation of TSHr expression in the orbit in GO, we treated cultures of Graves' orbital preadipocyte fibroblasts with the TSHr ligand thyrotropin (TSH; 100 mU/L). We found increased expression of both intact (2.4 kb) and variant (1.3 kb) TSHr mRNA and of TSHr protein in orbital fibroblasts following 72 hr treatment with TSH. These studies suggest that the expression of this receptor in the orbit in vivo may be stimulated by TSH or other TSHr ligands, and that this stimulation may be important in the development of GO.

Adipocytes↗

PubMed1998

Cytokines in thyroid eye disease: potential for anticytokine therapy.

Interactions between between orbital fibroblasts and immunocompetent cells that infiltrate or reside within the orbit are thought to be important in the pathogenesis of thyroid eye disease (TED). These interactions are mediated primarily by cytokines; interferon-gamma, tumor necrosis factor-alpha, interleukin-1alpha and leukoregulin are of particular interest in this regard. These mediators induce or enhance the in vitro expression of immunomodulatory proteins in orbital fibroblasts, and stimulate proliferative and metabolic activities of these cells. The stimulation by particular cytokines of glycosaminoglycan synthesis in orbital fibroblasts is an important factor in the development of the clinical disease. A similarly important pathophysiological role for cytokines has been defined in rheumatoid arthritis. In this disease, the chronic erosive changes in the cartilage and bone of the joints result from cytokine-stimulated production of collegenases and other neutral proteases by synovial cells and articular chondrocytes. Advances in the understanding of the pathogenesis of rheumatologic joint disease has led to treatment trials aimed at immune-modulation, including trials of anticytokine therapy. Lessons learned in early clinical trials using these biological therapies in the treatment of rheumatoid arthritis can be applied to studies of similar agents in the treatment of TED.

Arthritis, Rheumatoid↗

PubMed1998

Thyrotropin receptor expression in Graves' orbital adipose/connective tissues: potential autoantigen in Graves' ophthalmopathy.

It is acknowledged that the TSH receptor (TSHr) on thyroid follicular cells is the autoantigen involved in the hyperthyroidism of Graves' disease. However, whether this receptor is expressed in extrathyroidal tissues, and whether it participates directly in the pathogenesis of Graves' ophthalmopathy (GO) are unclear. We sought to detect the expression of TSHr messenger ribonucleic acid (mRNA) and protein in orbital adipose/connective tissue specimens and in human orbital preadipocyte fibroblast cultures using liquid hybridization analysis and immunohistochemical methods. We demonstrated intact and variant TSHr mRNA transcripts and TSHr-like immunoreactivity in orbital adipose/connective tissue specimens from patients with GO. In addition, TSHr-like immunoreactivity was detected in early passage GO preadipocyte fibroblast cultures that were shown to include some adipose cells. In contrast, neither TSHr mRNA nor protein was detected in normal orbital adipose/connective tissue specimens or in late passage GO orbital fibroblast cultures containing no lipid-laden adipose cells. In conclusion, we showed that TSHr is expressed in the adipose/connective tissue of the diseased orbit in GO. In addition, TSHr is demonstrable in early passage GO preadipocyte orbital fibroblast cultures that contain a subpopulation of adipocytes. Subsequent passaging of these cells results in the loss of both TSHr expression and adipocyte-specific staining. These results suggest that both the expression of this receptor and the accumulation of adipose tissue in the orbit in GO may be induced in vivo by a humoral factor(s) not present in the cell culture environment.

Adipocytes↗

PubMed1997

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.

Allopurinol↗

PubMed1997

Thyrotropin receptor expression in adrenal, kidney, and thymus.

Because the thyrotropin receptor (TSHR) has long been considered a thyroid-specific protein, its presence in extrathyroidal tissues has been controversial. In this study, we sought to detect and quantify this potentially low abundance mRNA in various extrathyroidal tissues using liquid hybridization analysis (LHA) and to detect protein with immunohistochemical studies. Strongly positive protected bands, indicating the presence of both intact (2.4 kb) and variant (1.3 kb) TSHr mRNA, were apparent in LHA gel lanes corresponding to normal thyroid, Graves' thyroid, and thymus. Less abundant protected bands of the same sizes were present in lanes corresponding to normal adrenal, and samples from normal kidney were faintly positive. The full-length transcript:variant transcript ratio was approximately 1:1 in all positive tissues. Immunohistochemical analysis of TSHR-like reactivity in paraffin-embedded thymus, adrenal, and kidney revealed specific staining in each of these tissues. No TSHR mRNA or TSHR-like immunoreactivity was detected in samples from several other normal human tissues. We conclude that measurable TSHR mRNA and protein expression is not restricted to the thyroid gland. Further study is warranted to determine whether these extrathyroidal receptors play a role in normal physiology or in disease.

Adrenal Glands↗

PubMed1997

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.

Edema↗

PubMed1996

Management of thyroid nodules in pregnancy.

BACKGROUND: Disorders of the thyroid are common in pregnancy. In particular, a thyroid nodule is frequently discovered before or during pregnancy. OBJECTIVE: To develop guidelines for the management of thyroid nodules during pregnancy. METHODS: We reviewed the cases of 40 pregnant patients with thyroid nodules evaluated during a 10-year period Cytological findings were compared with available histological findings, and concordance rates were determined. The rank sum test was used for statistical analysis. RESULTS: Fine-needle aspirations of thyroid nodules in 62% of patients were benign cytologically (25 patients). Of 8 patients with negative cytological results who had thyroidectomy, all had benign disease histologically (100% concordance rate). Cytological findings of papillary cancer (3 patients) strongly correlated with final histological diagnosis (100% concordance rate), whereas papillary cancer was confirmed histologically in only 2 of 4 patients with cytological findings suspicious for this disease (50% concordance rate). All 3 nodules with cytological findings suspicious for follicular neoplasm were benign adenomas histologically. Of 2 nodules suspicious for Hürthle cell neoplasm, l was Hürthle cell adenoma and the other was Hürthle cell carcinoma (100% concordance rate). Thyroidectomy during the second trimester of pregnancy or the early postpartum period was successful. CONCLUSIONS: The approach to thyroid nodules in pregnancy should be similar to that for nonpregnant patients. Thyroidectomy should be performed (1) during the second trimester for malignant lesions and cytological findings suspicious for papillary cancer and (2) in the postpartum period for cytological findings suspicious for follicular neoplasm.

Adult↗

PubMed1996

Molecular analysis of antigen receptor variable region repertoires in T lymphocytes infiltrating the intrathyroidal and extrathyroidal manifestations in patients with Graves' disease.

To determine whether T cells infiltrating thyroid, orbital and pretibial tissue of patients with Graves' ophthalmopathy (GO) and pretibial dermopathy (PTD) represent a primary immune response that is directed against certain antigenic determinants shared between these involved tissues, we characterized these T cells at the molecular level. T cell antigen receptor (TcR) variable (V) region gene usage in thyroid, orbital, pretibial tissue and peripheral blood mononuclear cells of patients with GD, GO and PTD was assessed using RT-PCR and 22 V alpha and 23 V beta gene-specific oligonucleotide primers, followed by Southern hybridization analysis using TcR C-region-specific, digoxigenin-labelled oligonucleotide probes. In some instances, CDR3- and junctional regions of TcR V beta genes were sequenced. Marked restriction and similarities of V alpha and V beta gene usage were detected in samples derived from patients with active GO and PTD of recent onset. Moreover, sequence analysis of junctional domains of V beta families revealed oligoclonality of some intrathyroidal, orbital and pretibial T cell populations as well as the presence of conserved junctional motifs shared by T cells derived the thyroid gland and the extrathyroidal sites. These data suggest that similar antigenic determinants may be responsible for the recruitment and oligoclonal expansion of T cells both within the thyroid gland and at the involved extrathyroidal sites in Graves' disease.

Eye Diseases↗