Abstract
Purpose: :
Thioredoxin (TRx) is a key redox regulator in the lens. This study is to investigate if hyperglycemic condition can affect TRx activity that may be associated with oxidative stress in the lenses of diabetes.
Methods: :
Fresh pig lenses were cultured in TC199 medium with 30 mM glucose for 12 hrs. Epithelial layer was removed and analyzed for GSH level and TRx activity. Human lens epithelial (HLE) B3 cells were grown in 20% FBS until confluent (2 x 106) and then exposed to 25 mM glucose for 0, 1, 2, 4, 6 and 8 hrs. The cells were lyzed and assayed for TRx activity. Lenses or cells cultured in normal glucose level were the controls.
Results: :
TRx activity in the epithelial layer was suppressed nearly 50% after the pig lens was exposed to high glucose for 12 hrs in comparison with the control. The activity loss was parallel to the depletion of GSH in the same tissue. These lenses also showed cortical haziness and hydration while the control lenses remained clear. HLE B3 cells exposed to high glucose during the 8 hrs showed no morphological change but the cellular TRx activity was progressively decreased to 80% at 2 hrs, 67% at 6 hrs and 40% at 8 hrs.
Conclusions: :
This is the first report of hyperglycemia-induced TRx inhibition in the lens epithelial cells/tissue. The results suggest that TRx activity loss in conjunction with GSH depletion under hyperglycemic condition can contribute to oxidative stress observed in diabetic conditions.
Keywords: stress response • enzymes/enzyme inhibitors • oxidation/oxidative or free radical damage