Abstract
Purpose: :
Solar UVB radiation is a known risk factor for human cataract development. The purpose of this study was to investigate the ability of a UV-absorbing soft contact lens on UVB damage in cultured human lens epithelial cells.
Methods: :
A human lens epithelial cell line HLE B-3 was irradiated using monochromatic UVB radiation at 302 nm (6.7 W/m2) at a distance of 12 cm. The bandwidth was 5 nm. A cut off filter Corning CS 0-53 was used to further filter radiation below 300 nm. Cells exposed in the presence of either a Senofilcon A contact lens (Class I UV Blocking Lens), a non UV-absorbing contact lens or no contact lens at all were irradiated for 2 minutes to produce a total fluence of 800 J/m2 (Andley et al., IOVS, 1994) equivalent to 18 hr of maximum exposure of human lens epithelial cells to UVB radiation from sunlight. Effects on cells were evaluated after 4 hr by proteomic analysis using 2D gel electrophoresis and mass spectrometric analysis (performed by the Washington University Proteomics Core Lab). MS/MS samples were analyzed by Mascot. Scaffold proteomic software was used to validate MS/MS based peptide and protein identifications. Effects on lens epithelial cell cytoskeleton were evaluated after 4 hr by fluorescence phalloidin staining of F-actin and immunolabeling of beta-tubulin and confocal microscopy.
Results: :
Several protein spots were found to increase by UVB exposure of HLE B-3 cells. The Senofilcon A lens completely protected their increased abundance, but not the non UV-absorbing contact lens. The protein identifications were beta-actin (2.09 fold), G3PDH (1.95 fold), Annexin A2 (1.75 fold), Triose phosphate isomerase (2.08 fold), and ubiquitin B precursor (2.08 fold). Examples of proteins that decreased with UVB were caldesmon 1 isoform (-2.01 fold), DEAD-Box polypeptide 3 (-1.7 fold) and eukaryotic translational initiation factor (-1.85 fold). The Senofilcon A lens protected completely against their decreased abundance by UVB, however, the non UV-absorbing contact lens showed no protection. Confocal microscopy analysis showed substantial reduction in the intensity of fluorescein phalloidin fluorescence in UVB irradiated cells, which was completely protected by Senofilcon A contact lens, but not by the non UV-absorbing contact lens. Beta-tubulin immunostaining revealed a clumping of microtubule cytoskeleton in UVB irradiated cells. This damage was protected completely by Senofilcon A lenses, whereas the non UV-absorbing contact lens offered no protection.
Conclusions: :
The Senofilcon A contact lens is highly protective of lens epithelial cells against UVB-induced damage in culture, including protein expression and cytoskeletal changes.
Keywords: radiation damage: light/UV • cataract • contact lens