Increased response to oxidative stress challenge in Graves’ ophthalmopathy orbital fibroblasts

PURPOSE: To investigate whether orbital fibroblasts from patients with Graves’ ophthalmopathy (GO) are more responsive to oxidative stress. METHODS: Lipid peroxidation, oxidative DNA damage, reactive oxygen species (ROS) contents and activities of antioxidant enzymes were measured in cultured orbital fibroblasts from GO patients and age-matched normal controls in response to 200 μM hydrogen peroxide (H(2)O(2)). RESULTS: GO fibroblasts had increased basal levels of malondialdehyde (MDA), 8-hydroxy 2'-deoxyguanosine, superoxide anions, H(2)O(2), and manganese-dependent superoxide dismutase (Mn-SOD) activity, as well as decreased glutathione peroxidase (GPx) activity and the ratio between reduced (GSH) and oxidized glutathione (GSSG) compared with the orbital fibroblasts from normal subjects. After treatment of the cells with 200 μM H(2)O(2), the amplitude of increase in the intracellular levels of MDA (63% versus 26%), H(2)O(2) (24% versus 13%) and Mn-SOD activity (48% versus 23%) was exaggerated in GO fibroblasts compared with normal controls, respectively. In addition, treatment of GO fibroblasts with 200 μM H(2)O(2) led to a dramatic reduction of catalase activity (−59% versus −29%), GPx activity (−56% versus −13%), and GSH/GSSG ratio (−49% versus −21%), respectively. CONCLUSIONS: Elevated ROS and redox imbalance in GO orbital fibroblasts were exacerbated by H(2)O(2) as a result of exhaustion of GSH and compromise of antioxidant enzymes. Hypersensitivity to oxidative stress of GO orbital fibroblasts may play a role in the pathogenesis of GO.