Interferon-gamma-inducible alpha-chemokine CXCL10 involvement in Graves' ophthalmopathy: modulation by peroxisome proliferator-activated receptor-gamma agonists.

CONTEXT: CXC alpha-chemokine CXCL10/inducing protein-10 play an important role in the initial phases of autoimmune thyroid disorders. Human thyrocytes in primary culture produce large amounts of CXCL10 when stimulated by interferon-gamma (IFNgamma) and TNFalpha.
OBJECTIVE: Serum CXCL10 levels (sCXCL10) were measured in patients with active or inactive Graves' ophthalmopathy (GO). The effects of IFNgamma and TNFalpha stimulation and peroxisome proliferator-activated receptor-gamma (PPARgamma) activation on CXCL10 secretion in primary cultures of thyrocytes, orbital fibroblasts, and preadipocytes were tested. PATIENTS: Sixty consecutive patients with Graves' disease, 60 age- and sex-matched patients with GO, and 60 controls were studied.
RESULTS: sCXCL10 was higher (P < 0.0001) in Graves' disease (120 +/- 83 pg/ml; n = 60) and GO (122 +/- 71; n = 60) patients than in age- and sex-matched euthyroid controls (72 +/- 32; n = 60). Among GO patients, sCXCL10 levels were significantly higher in those (n = 14) with active disease (171 +/- 197) than in those with inactive disease (114 +/- 45 pg/ml; P < 0.003). In primary cultures of thyrocytes, retrobulbar fibroblasts and retrobulbar preadipocytes from GO patients, CXCL10 production was absent under basal conditions; dose-dependent secretion of CXCL10 was not induced by TNFalpha alone, whereas stimulation with IFNgamma or TNFalpha plus IFNgamma induced CXCL10 release. Treatment of all cell types with the PPARgamma agonist, rosiglitazone, dose-dependently (0.1-10 microm) suppressed IFNgamma- plus TNFalpha-induced CXCL10 release.
CONCLUSIONS: We conclude that in GO, thyrocytes and retrobulbar cell types participate in the self-perpetuation of inflammation by releasing chemokines under the influence of cytokines. PPARgamma activation plays an inhibitory role in this process.