UVA Light-mediated Ascorbate Oxidation in Human Lenses.

Whether ascorbate oxidation is promoted by UVA light in human lenses and whether this process is influenced by age and GSH levels are not known. In this study, we used paired lenses from human donors. One lens of each pair was exposed to UVA light, whereas the other lens was kept in the dark for the same period of time as the control. Using LC-MS/MS analyses, we found that older lenses (41-73 years) were more susceptible to UVA-induced ascorbate oxidation than younger lenses (18-40 years). Approximately 36% of the ascorbate (relative to control) was oxidized in older lenses compared to ~16% in younger lenses. Furthermore, lenses with higher levels of GSH were less susceptible to UVA-induced ascorbate oxidation compared to those with lower levels, and this effect was not dependent on age. The oxidation of ascorbate led to elevated levels of reactive α-dicarbonyl compounds. In summary, our study showed that UVA light exposure leads to ascorbate oxidation in human lenses and that such oxidation is more pronounced in aged lenses and is inversely related to GSH levels. Our findings suggest that UVA light exposure could lead to protein aggregation through ascorbate oxidation in human lenses.