Preventive role of lens antioxidant defense mechanism against riboflavin-mediated sunlight damaging of lens crystallins.
The main components of sunlight reaching the eye lens are UVA and visible light exerting their photo-damaging effects indirectly by the aid of endogenous photosensitizer molecules such as riboflavin (RF). In this study, lens proteins solutions were incubated with RF and exposed to the sunlight. Then, gel mobility shift analysis and different spectroscopic assessments were applied to examine the structural damaging effects of solar radiation on these proteins. Exposure of lens proteins to direct sunlight, in the presence of RF, leads to marked structural crosslinking, oligomerization and proteolytic instability. These structural damages were also accompanied with reduction in the emission fluorescence of Trp and Tyr and appearance of a new absorption peak between 300 and 400nm which can be related to formation of new chromophores. Also, photo-oxidation of lens crystallins increases their oligomeric size distribution as examined by dynamic light scattering analysis. The above mentioned structural insults, as potential sources of sunlight-induced senile cataract and blindness, were significantly attenuated in the presence of ascorbic acid and glutathione which are two important components of lens antioxidant defense system. Therefore, the powerful antioxidant defense mechanism of eye lens is an important barrier against molecular photo-damaging effects of solar radiations during the life span.
['Anbaraki|Afrooz|A|', 'Khoshaman|Kazem|K|', 'Ghasemi|Younes|Y|', 'Yousefi|Reza|R|']
D000818:Animals D000975:Antioxidants D002417:Cattle D002918:Chymotrypsin D003432:Cross-Linking Reagents D003459:Crystallins D000067493:Dynamic Light Scattering D004591:Electrophoresis, Polyacrylamide Gel D005453:Fluorescence D007908:Lens, Crystalline D010084:Oxidation-Reduction D055503:Protein Multimerization D059748:Proteolysis D012256:Riboflavin D013056:Spectrophotometry, Ultraviolet D013438:Sulfhydryl Compounds D013472:Sunlight
Sunlight Lens crystallins Photosensitizer Riboflavin Oligomerization Lens antioxidant system