Effects of singlet oxygen on human lens crystallins in vitro.

We have recently demonstrated that singlet oxygen-mediated photooxidation can cause an increase in blue fluorescence and covalent cross-linking in bovine lens crystallins in vitro. Because these changes closely parallel modifications known to occur in human crystallins during aging and cataractogenesis, it was suggested that singlet oxygen may play an important role in these processes in vivo. to confirm these results, obtained with photosensitizers free in solution, we now report results from experiments with a polymer-bound photosensitizer and with photophysically generated singlet oxygen. Singlet oxygen photodynamically generated by polymer-immobilized rose bengal produced the following modifications to human lens crystallins in vitro: covalent cross-linking, increased blue fluorescence, yellow pigmentation, and formation of heavy-molecular-weight aggregates. Singlet oxygen generated photophysically was shown to cause an increase in blue fluorescence and covalent cross-linking in human crystallins. These findings substantiate the hypothesis that singlet oxygen may play an important role in the changes seen in human lens proteins during aging and cataractogenesis.