Graves' ophthalmopathy (GO) is a disfiguring and sometimes blinding disease, which is characterized by
inflammation and swelling of orbital tissues, with
fibrosis and adipogenesis being predominant features. The aim of this study is to investigate whether the expression levels of
fibrosis-related genes, especially that of
connective tissue growth factor (CTGF), are altered in orbital fibroblasts of patients with GO. The role of oxidative stress in the regulation of CTGF expression in GO orbital fibroblasts is also examined. By a
SYBR Green-based real time quantitative PCR (RT-QPCR), we demonstrated that the
mRNA expression levels of
fibronectin,
apolipoprotein J, and CTGF in cultured orbital fibroblasts from patients with GO were significantly higher than those of age-matched normal controls (p = 0.007, 0.037, and 0.002, respectively). In addition, the
protein expression levels of
fibronectin,
apolipoprotein J, and CTGF analyzed by Western blot were also significantly higher in GO orbital fibroblasts (p = 0.046, 0.032, and 0.008, respectively) as compared with the control. Furthermore,
after treatment of orbital fibroblasts with a sub-lethal dose of
hydrogen peroxide (200 μM H2O2), we found that the H2O2-induced increase of CTGF expression was more pronounced in the GO orbital fibroblasts as compared with those in normal controls (20% vs. 7%, p = 0.007). Importantly, pre-incubation with
antioxidants including
N-acetylcysteine (NAC) and
vitamin C, respectively, resulted in significant attenuation of the induction of CTGF in GO orbital fibroblasts in response to H2O2 (p = 0.004 and 0.015, respectively). Taken together, we suggest that oxidative stress plays a role in the alteration of the expression of CTGF in GO orbital fibroblasts that may contribute to the pathogenesis and progression of GO.
Antioxidants may be used in combination with the therapeutic agents for effective treatment of GO.