Interferon-γ up-regulates expressions of indoleamine 2,3-dioxygenase and tryptophanyl-tRNA-synthetase in human thyrocytes

Abstract

Objective To investigate the effect of interferon-γ(IFN-γ) on the expression of indoleamine 2,3-dioxygenase(IDO),and tryptophanyl-tRNA-synthetase (TTS) in thyrocytes; and to study the relevant immunopathological significance in Graves' disease.Methods The expressions of IDO and TTS genes in IFN-γ stimulated Nthy-ori3-1 cell line and human thyrocytes,as well as in human thyroid tissues were determined by realtime quantitative PCR.Results IDO and TTS genes were expressed slightly in both Nthy-ori3-1 cell line and human thyrocytes,and were significantly up-regulated after IFN-γ stimulation(P＜0.01).Compared to healthy controls,TTS mRNA level was higher in thyroid tissues of patients with Graves' disease (P =0.018 2),while IDO mRNA level showed no difference,but was notably correlated with IFN-γ mRNA level (R2 =0.716,P =0.002).Conclusion In the early stage of Graves' disease,thyrocytes may decompose local tryptophan by enhancing the expression of IDO and TTS under IFN-γstimulation,thus inhibit auto-reactive function of lymphocytes and balance excessive autoimmune reaction. Key words: Interferon-γ; Graves' disease; Thyrocytes; Indoleamine 2, 3-dioxygenase; Tryptophanyl-tRNA-synthetase