Role of calpain in hydrogen peroxide induced cataract

The purpose of these experiments was to examine the relationship between oxidation cataract and proteolysis in cultured rat lens. Hydrogen peroxide cataract showed insolubilization of protein, loss of 31 kDa βB1-crystallin polypeptide, decreases in soluble calpain, and increases in insoluble calpain. This suggested that calpain may be activated in hydrogen peroxide treated lenses, since βBl is a known calpain substrate, and calpain undergoes autolysis and degradation when activated. Furthermore, the cysteine protease inhibitor E64 was partially effective in preventing development of H₂O₂-cataract. E64 also prevented the loss of the 31 kDa βBl-crystallin polypeptide and decreased the loss of calpain in the lens. These results suggested that development of hydrogen peroxide induced cataract in rat lenses was associated with activation of calpain.