Hypersensitive Response to Oxidative stress Challenge in Graves' Ophthalmopathy Orbital Fibroblasts

1. Chieh-Chih Tsai 1
2. Hui-Chuan Kau 2
3. Shu-Ching Kao 1
4. Shui-Mei Lee 1
5. Yau-Huei Wei 3

1. Department of Ophthalmology, Taipei Veterans General Hospital and National Yang-Ming University, Taipei 112, Taiwan
2. Department of Ophthalmology, Koo Foundation Sun Yat-Sen Cancer Center, Taipei 112, Taiwan
3. Department of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan

Purpose: To investigate whether orbital fibroblasts from Graves' Ophthalmopathy (GO) patients have exaggerated hypersensitivity to oxidative stress.

Methods: Lipid peroxidation, oxidative DNA damage, reactive oxygen species (ROS) contents and activities of antioxidant enzymes were evaluated in cultured orbital fibroblasts from GO patients and normal controls in response to 200 μM hydrogen peroxide (H2O2).

Results: GO fibroblasts had increased basal levels of malondialdehyde (MDA), 8-hydroxy 2'-deoxyguanosin, superoxide anions, H2O2, and manganese 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 normal subjects. After treatment with 200 μM H2O2, the amplitude of increase in the intracellular levels of MDA (63% vs. 26%), H2O2 (24% vs. 13%) and Mn-SOD activity (48% vs. 23%) was exaggerated in GO fibroblasts compared with normal controls. In addition, H2O2 treatment led to an aggravated reduction of catalase activity (-59% vs. -29%), GPx activity (-56% vs. -13%), and GSH/GSSG ratio (-49% vs. -21%) in GO fibroblasts.

Conclusions: Elevated ROS and redox imbalance in GO orbital fibroblasts were exacerbated by H2O2 as a result of exhaustion of GSH and antioxidant enzymes. GO orbital fibroblasts hypersensitivity may play a role in the pathogenesis of GO.