Thioredoxin Reductase Activity may be More Important than GSH Level in Protecting Human Lens Epithelial Cells against UVA Light

• Published in: Photochemistry and photobiology 2015-03, Vol.91 (2), p.387-396
• Main Authors: Padgaonkar, Vanita A., Leverenz, Victor R., Bhat, Aparna V., Pelliccia, Sara E., Giblin, Frank J.
• Format: Article
• Language: English
• Subjects: Antioxidants; Catalase - metabolism; Cell Count; Cell culture; Cell Line, Transformed; Cell Survival - drug effects; Cell Survival - radiation effects; Dinitrochlorobenzene - pharmacology; DNA damage; Epithelial Cells - cytology; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Epithelial Cells - radiation effects; Glutathione - antagonists & inhibitors; Glutathione - metabolism; Humans; Lens, Crystalline - cytology; Lens, Crystalline - drug effects; Lens, Crystalline - metabolism; Lens, Crystalline - radiation effects; Methionine Sulfoximine - analogs & derivatives; Methionine Sulfoximine - pharmacology; Morphology; Oxidative Stress; Oxygen - pharmacology; Photobiology; Thioredoxin Reductase 1 - metabolism; Thioredoxins - metabolism; Ultraviolet radiation; Ultraviolet Rays
• ISSN: 0031-8655; 1751-1097
• DOI: 10.1111/php.12404

This study compares the abilities of the glutathione (GSH) and thioredoxin (Trx) antioxidant systems in defending cultured human lens epithelial cells (LECs) against UVA light. Levels of GSH were depleted with either L‐buthionine‐(S,R)‐sulfoximine (BSO) or 1‐chloro‐2,4‐dinitrobenzene (CDNB). CDNB treatment also inhibited the activity of thioredoxin reductase (TrxR). Two levels of O2, 3% and 20%, were employed during a 1 h exposure of the cells to 25 J cm−2 of UVA radiation (338–400 nm wavelength, peak at 365 nm). Inhibition of TrxR activity by CDNB, combined with exposure to UVA light, produced a substantial loss of LECs and cell damage, with the effects being considerably more severe at 20% O2 compared to 3%. In contrast, depletion of GSH by BSO, combined with exposure to UVA light, produced only a slight cell loss, with no apparent morphological effects. Catalase was highly sensitive to UVA‐induced inactivation, but was not essential for protection. Although UVA light presented a challenge for the lens epithelium, it was well tolerated under normal conditions. The results demonstrate an important role for TrxR activity in defending the lens epithelium against UVA light, possibly related to the ability of the Trx system to assist DNA synthesis following UVA‐induced cell damage. Exposure of cultured human lens epithelial cells (LECs) to UVA light (25 J cm−2), or pretreatment of the cells with an inhibitor (1‐chloro‐2,4‐dinitrobenzene) of thioredoxin reductase (TrxR), produced no damaging cellular effects. However, a combination of the two challenges produced substantial loss of LECs and cell damage, including death (arrows) and threadlike structures (arrowheads). In contrast, depletion of reduced glutathione (GSH) by L‐buthionine‐(S,R)‐sulfoximine, combined with exposure to UVA light, produced only a slight cell loss, with no apparent morphological effects. The results demonstrate an important role for TrxR activity, possibly more so than GSH level, in defending the lens epithelium against UVA light.