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.
Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
Afrooz
A
Anbaraki
Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
Kazem
K
Khoshaman
Department of Pharmaceutical Biotechnology and Pharmaceutical Sciences Research Center, Faculty of Pharmacy, Shiraz University of Medical Sciences, Shiraz 71345, Iran.
Younes
Y
Ghasemi
Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran. Electronic address: ryousefi@shirazu.ac.ir.
Reza
R
Yousefi
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003459:Crystallins / Q000187:drug effects* / Q000528:radiation effects*; D000067493:Dynamic Light Scattering; D004591:Electrophoresis, Polyacrylamide Gel; D005453:Fluorescence; D007908:Lens, Crystalline / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D055503:Protein Multimerization / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D012256:Riboflavin / Q000737:chemistry / Q000633:toxicity*; D013056:Spectrophotometry, Ultraviolet; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013472:Sunlight
D000975:Antioxidants; D003432:Cross-Linking Reagents; D003459:Crystallins; D013438:Sulfhydryl Compounds; D002918:Chymotrypsin; D012256:Riboflavin
Lens antioxidant system; Lens crystallins; Oligomerization; Photosensitizer; Riboflavin; Sunlight