Graves’ Ophthalmopathy: A Comprehensive Role For Platelet-Derived Growth Factors

Autoimmune thyroid disorders include Graves’ disease (GD), which leads to hyperthyroidism, and Hashimoto’s thyroiditis, which leads to hypothyroidism. The incidence of autoimmune hypothyroidism is around five times higher than the incidence of autoimmune hyperthyroidism, but together these autoimmune thyroid disorders are the most common autoimmune conditions in the Western population and affect around 2-5% of the population. Estimates for the incidence of autoimmune hyperthyroidism vary considerably, but a recent review estimates an incidence of 80/100.000/year for women and 8/100.000/year for men in Caucasian populations. Graves’ disease (GD) is the most common cause of hyperthyroidism in Western and other iodine-sufficient populations, and accounts for ~80% of cases of hyperthyroidism

Whole orbital tissue culture identifies imatinib mesylate and adalimumab as potential therapeutics for Graves' ophthalmopathy

Background and aims Biologicals and small inhibitory molecules are used to treat inflammatory diseases, but their efficacy varies upon clinical application. Using a whole orbital tissue culture system, we tested the potential efficacy of imatinib mesylate (a tyrosine kinase inhibitor that blocks platelet-derived growth factor (PDGF)-receptor, c-Abl and c-Kit activity) and adalimumab (an anti-TNF-alpha antibody) for the treatment of Graves' ophthalmopathy (GO). Methods Orbital fat tissue from GO patients (n=10) was cultured with or without imatinib mesylate or adalimumab. PDGF-B and tumour necrosis factor (TNF)-alpha mRNA expression levels were determined in the primary orbital tissue, and interleukin (IL)-6 and hyaluronan were measured in tissue-culture supernatants. Results Imatinib mesylate significantly (p=0.005) reduced IL-6 and hyaluronan production. The inhibition of hyaluronan production correlated positively and significantly (p<0.05) with the PDGF-B mRNA level in the primary tissue. Adalimumab also significantly (p=0.005) reduced IL-6 production. The amount of IL-6 inhibition correlated positively with the TNF-alpha mRNA level in the primary tissue, but this was not significant. Conclusions Imatinib mesylate can be expected to reduce inflammation and tissue remodelling in GO, while adalimumab can be mainly expected to reduce inflammation. This in vitro tissue-culture model may, in future, prove valuable to test novel therapeutics for their presumed effect in GO as well as in other inflammatory diseases

PDGF Enhances Orbital Fibroblast Responses to TSHR Stimulating Autoantibodies in Graves' Ophthalmopathy Patients

Purpose: Thyroid-stimulating hormone receptor (TSHR) stimulating autoantibodies are associated with Graves' ophthalmopathy (GO), the orbital manifestation of Graves' disease (GD). TSHR autoantibody levels and orbital TSHR expression levels correlate positively with GO disease activity. Platelet-derived growth factors (PDGF) are increased in GO and potently activate orbital fibroblast effector functions. We investigated the possible relationship between PDGF and TSHR expression on orbital fibroblasts and how that influences the immunopathological effects of TSHR autoantibodies on orbital fibroblast activity. Methods: Orbital fibroblasts were stimulated with PDGF-AA, PDGF-AB, and PDGF-BB, and TSHR expression was determined by flow cytometry. Stimulatory effects of bovine TSH and GD immunoglobulins on orbital fibroblasts (with or without PDGF-BB preincubation) were determined by IL-6, IL-8, chemokine (C-C motif) ligand (CCL)-2, CCL5, CCL7, and hyaluronan ELISA. The TSHR blocking antibody K1-70 and the cAMP inhibitor H89 were used to determine involvement of TSHR signaling. Results: PDGF-AB and PDGF-BB stimulation increased TSHR expression on orbital fibroblasts, whereas PDGF-AA did not. Furthermore, stimulation with bovine TSH and immunoglobulins from GD patients induced IL-6, IL-8, CCL2, and hyaluronan production by orbital fibroblasts, and PDGF-BB preincubation enhanced this response of orbital fibroblasts. Blocking studies with a TSHR blocking antibody and a cAMP inhibitor inhibited these effects, indicating the involvement of TSHR signaling and thus of TSHR st Conclusions: These findings indicate that PDGF-B containing PDGF isoforms amplify the immunopathological effects of TSHR-stimulating autoantibodies in GO patients by stimulating TSHR expression on orbital fibroblasts. (J Clin Endocrinol Metab 97: E944-E953, 2012

Platelet-Derived Growth Factor-BB: A Stimulus for Cytokine Production by Orbital Fibroblasts in Graves' Ophthalmopathy

PURPOSE. Graves' ophthalmopathy (GO) is characterized by the infiltration of immune cells into the orbit, a process in which cytokines play a central role. Orbital fibroblasts are potent producers of cytokines on different stimuli. Recently, the authors showed increased expression of the PDGF-B chain in GO orbital tissue. The dimeric PDGF-BB molecule has been described to activate the NF-kappa B pathway, which is well recognized for its role in regulating cytokine production. This study was conducted to determine the role of PDGF-BB in the production of proinflammatory cytokines by orbital fibroblasts in GO. METHODS. Orbital, lung, and skin fibroblasts were stimulated with PDGF-BB, and cytokine (IL-1 beta, IL-6, IL-8, IL-16, CCL2, CCL5, CCL7, TNF-alpha) production was measured by ELISA. Involvement of NF-kappa B activation through PDGF signaling was investigated by electrophoretic mobility shift assay, specific NF-kappa B inhibitors, and the PDGF-receptor kinase inhibitor imatinib mesylate. RESULTS. IL-6, IL-8, CCL2, CCL5, and CCL7 production by orbital fibroblasts was increased by PDGF-BB stimulation, whereas IL-16, IL-1 beta, and TNF-alpha production was not affected. PDGF-BB induced NF-kappa B activity in orbital fibroblasts, and both NF-kappa B inhibitors and imatinib mesylate reduced PDGF-BB-induced cytokine production. Similar, but less vigorous, effects of PDGF-BB on cytokine production were observed in lung and skin fibroblasts. CONCLUSIONS. PDGF-BB is a potent inducer of proinflammatory cytokines via the NF-kappa B pathway in orbital fibroblasts, whereas cytokine production by fibroblasts from other anatomic locations showed a moderate response. These data suggest a possible role for PDGF-BB in regulating orbital inflammation in GO and identify the PDGF signaling cascade as a therapeutic target in GO. (Invest Ophthalmol Vis Sci. 2010;51:1002-1007) DOI:10.1167/iovs.09-433

Imatinib Mesylate and AMN107 Inhibit PDGF-Signaling in Orbital Fibroblasts: A Potential Treatment for Graves' Ophthalmopathy

PURPOSE. Excessive orbital fibroblast proliferation and hyaluronan production are characteristic of Graves' ophthalmopathy (GO) and are driven by local mediators. Imatinib mesylate and AMN107 are tyrosine kinase inhibitors that inhibit fibroblast proliferation and collagen production in lungs and skin. This study was conducted to determine whether imatinib mesylate and AMN107 inhibit orbital fibroblast proliferation and hyaluronan production induced by PDGF-BB and TGF-beta(1) and whether expression of the genes PDGF-BB and TGF-beta(1) (growth factors suggested to play a role in GO) are increased in GO orbital tissues. METHODS. PDGF-B and TGF-B-1 mRNA levels were determined in orbital tissues of 13 patients with GO and 5 control patients. Orbital fibroblasts were cultured from eight patients with GO and three control patients and the effect of imatinib mesylate and AMN107 on PDGF-BB and TGF-beta(1)-induced orbital fibroblast proliferation, signaling cascades, hyaluronan synthase (HAS) gene expression and hyaluronan production were determined. RESULTS. PDGF-B and TGF-B-1 mRNA levels were significantly increased in GO orbital tissues. Imatinib mesylate and AMN107 inhibited PDGF-BB-induced orbital fibroblast proliferation, HAS induction and hyaluronan production by blocking PDGF-receptor phosphorylation. TGF-beta(1) induced HAS expression and hyaluronan production. This induction was not inhibited by imatinib mesylate or AMN107, due to the inability of TGF-beta(1) to activate c-Abl kinase activity in orbital fibroblasts. CONCLUSIONS. Imatinib mesylate and AMN107 inhibit orbital fibroblast proliferation and hyaluronan production induced by PDGF-BB; a factor highly expressed in orbital tissue from patients with GO. The drugs, however, had no effect on TGF-beta(1)-induced HAS expression and hyaluronan production. Nevertheless, imatinib mesylate and AMN107 should be considered as treatment candidates for GO. (Invest Ophthalmol Vis Sci. 2009;50:3091-3098) DOI:10.1167/iovs.08-244

PDGF enhances orbital fibroblast responses to TSHR stimulating autoantibodies in Graves' ophthalmopathy patients

Purpose: Thyroid-stimulating hormone receptor (TSHR) stimulating autoantibodies are associated with Graves' ophthalmopathy (GO), the orbital manifestation of Graves' disease (GD). TSHR autoantibody levels and orbital TSHR expression levels correlate positively with GO disease activity. Platelet-derived growth factors (PDGF) are increased in GO and potently activate orbital fibroblast effector functions. We investigated the possible relationship between PDGF and TSHR expression on orbital fibroblasts and how that influences the immunopathological effects of TSHR autoantibodies on orbital fibroblast activity. Methods: Orbital fibroblasts were stimulated with PDGF-AA, PDGF-AB, and PDGF-BB, and TSHR expression was determined by flow cytometry. Stimulatory effects of bovine TSH and GD immunoglobulins on orbital fibroblasts (with or without PDGF-BB preincubation) were determined by IL-6, IL-8, chemokine (C-C motif) ligand (CCL)-2, CCL5, CCL7, and hyaluronan ELISA. The TSHR blocking antibody K1-70 and the cAMP inhibitor H89 were used to determine involvement of TSHR signaling. Results: PDGF-AB and PDGF-BB stimulation increased TSHR expression on orbital fibroblasts, whereas PDGF-AA did not. Furthermore, stimulation with bovine TSH and immunoglobulins from GD patients induced IL-6, IL-8, CCL2, and hyaluronan production by orbital fibroblasts, and PDGF-BB preincubation enhanced this response of orbital fibroblasts. Blocking studies with a TSHR blocking antibody and a cAMP inhibitor inhibited these effects, indicating the involvement of TSHR signaling and thus of TSHR stimulating autoantibodies herein. Conclusions: These findings indicate that PDGF-B containing PDGF isoforms amplify the immunopathological effects of TSHR-stimulating autoantibodies in GO patients by stimulating TSHR expression on orbital fibroblasts. Copyrigh

Orbit-infiltrating mast cells, monocytes, and macrophages produce PDGF isoforms that orchestrate orbital fibroblast activation in graves' ophthalmopathy

Purpose: Platelet-derived growth factors (PDGF) are regulators of fibroblast activity that may be involved in the pathophysiology of Graves' ophthalmopathy (GO). We unraveled the expression and origin of PDGF family members in GO orbital tissue and investigated the effect of PDGF isoforms on IL-6 and hyaluronan production and proliferation by orbital fibroblasts. Methods: PDGF-A, PDGF-B, PDGF-C, PDGF-D, PDGF-Rα, and PDGF-Rβ expression was determined by real-time quantitative PCR and PDGF-A and PDGF-B protein expression was determined by Western blot in orbital tissues. Orbital tissues were immunohistochemically stained for PDGF-A and PDGF-B expression, together with stainings for T cells, monocytes, B cells, macrophages, and mast cells. Effects of PDGF-AA, PDGF-AB, and PDGF-BB on orbital fibroblast proliferation and IL-6 and hyaluronan production were examined. Finally, effects of PDGF-BB- and PDGF-AA-neutralizing antibodies on IL-6 and hyaluronan production in GO whole orbital tissue cultures were tested. Results: GO orbital tissue showed increased PDGF-A and PDGF-B mRNA and protein levels. Increased numbers of PDGF-A- and PDGF-B-positive monocytes, macrophages, and mast cells were present in GO orbital tissue. PDGF-BB stimulated proliferation and hyaluronan and IL-6 production by orbital fibroblasts the most, followed by PDGF-AB and PDGF-AA. Finally, in particular imatinib mesylate and PDGF-BB-neutralizing antibodies reduced IL-6 and hyaluronan production by whole orbital tis

Platelet-derived growth factor-BB: A stimulus for cytokine production by orbital fibroblasts in graves' ophthalmopathy

Purpose. Graves' ophthalmopathy (GO) is characterized by the infiltration of immune cells into the orbit, a process in which cytokines play a central role. Orbital fibroblasts are potent producers of cytokines on different stimuli. Recently, the authors showed increased expression of the PDGF-B chain in GO orbital tissue. The dimeric PDGF-BB molecule has been described to activate the NF-κB pathway, which is well recognized for its role in regulating cytokine production. This study was conducted to determine the role of PDGF-BB in the production of proinflammatory cytokines by orbital fibroblasts in GO. Methods. Orbital, lung, and skin fibroblasts were stimulated with PDGF-BB, and cytokine (IL-1β, IL-6, IL-8, IL-16, CCL2, CCL5, CCL7, TNF-α) production was measured by ELISA. Involvement of NF-κB activation through PDGF signaling was investigated by electrophoretic mobility shift assay, specific NF-κB inhibitors, and the PDGF-receptor kinase inhibitor imatinib mesylate. Results. IL-6, IL-8, CCL2, CCL5, and CCL7 production by orbital fibroblasts was increased by PDGF-BB stimulation, whereas IL-16, IL-1β, and TNF-α production was not affected. PDGF-BB induced NF-κB activity in orbital fibroblasts, and both NF-κB inhibitors and imatinib mesylate reduced PDGF-BB-induced cytokine production. Similar, but less vigorous, effects of PDGF-BB on cytokine production were observed in lung and skin fibroblasts. Conclusions. PDGF-BB is a potent inducer of proinflammatory cytokines via the NF-κB pathway in orbital fibroblasts, whereas cytokine production by fibroblasts from other anatomic locations showed a moderate response. These data suggest a possible role for PDGF-BB in regulating orbital inflammation in GO and identify the PDGF signaling cascade as a therapeutic target in GO