We examined the therapeutic effect of nontoxic concentrations of curcumin, a plant polyphenol extracted from Curcuma longae, in primary cultures of orbital fibroblasts from Graves' orbitopathy (GO).The effect of curcumin on interleukin (IL)-1β induced-proinflammatory cytokine production was determined using quantitative real-time PCR, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis. Adipogenic differentiation was identified using Oil-Red O staining, and levels of peroxisome proliferator activator γ (PPARγ) and CCAAT-enhancer-binding proteins (C/EBP) α/β were determined by Western blot analyses. Antioxidant activity was measured using an oxidant-sensitive fluorescent probe to detect intracellular reactive oxygen species (ROS) generated in response to hydrogen peroxide (H2O2) and cigarette smoke extract (CSE).Treatment with curcumin resulted in a dose- and time-dependent decrease in IL-1β-induced synthesis of inflammatory cytokines, including IL-6, IL-8, MCP-1, and ICAM-1 at both mRNA and protein levels. Decrease in lipid droplets and expression of PPARγ and c/EBPα/β were noted in fibroblasts treated with curcumin during adipose differentiation. CSE- or H2O2-induced ROS synthesis was significantly lower in curcumin-treated fibroblasts in comparison with the control. Curcumin significantly suppressed IL-1β-induced phosphorylated extracellular signal-regulated kinase, Akt, c-Jun NH(2)-terminal kinase, and nuclear factor κ-light-chain-enhancer of activated B cells, p65 proteins and stimulated β-catenin translocation into nucleus during adipogenesis.Curcumin inhibits proinflammatory cytokine production, ROS synthesis, and adipogenesis in orbital fibroblasts of GO patients in vitro possibly related to multiple proinflammatory signaling molecules and β-catenin pathway. The results of the study support potential use of the curcumin in the treatment of GO.
