Anti-inflammatory effects of luteolin on experimental autoimmune thyroiditis in mice

Hashimoto's thyroiditis (HT) is the most common organ-specific autoimmune disease and is believed to be a predominately T cell-mediated autoimmunity. Signal transducer and activator of transcription (STAT)3 is a crucial transcription factor of T cell-mediated immunity, with key roles in the proliferation and migration of T helper (Th) cells, differentiation of Th cells into Th17 cells, and the balance between Treg cells and Th17 cells. Flavonoid luteolin has been shown to markedly inhibit Tyr705 activation/phosphorylation of STAT3 and exert anti-inflammatory effects in multiple sclerosis. In the present study, the effect of luteolin on experimental autoimmune thyroiditis (EAT) was analyzed in C57BL/6 mice. Hematoxylin and eosin examination showed that luteolin attenuated lymphocytic infiltration and follicle destruction in thyroid glands. Immunohistochemistry results demonstrated that luteolin significantly reduced the phosphorylation of STAT3 within the thyroid. An in vitro study was carried out in a RAW264.7 macrophage cell line. Western blot findings demonstrated that luteolin significantly inhibited interferon-γ-induced increases in cyclooxygenase 2, phosphorylated STAT1 and phosphorylated STAT3 expression levels and the secretion of the proinflammatory cytokine tumor necrosis factor-α in supernatants. The present findings indicated that luteolin may exert potent anti-inflammatory effects on murine EAT, which may provide a novel therapeutic medication strategy for the early intervention of HT.