Damage to cultured lens epithelial cells of squirrels and rabbits by UV-A (99.9%) plus UV-B (0.1%) radiation and alpha tocopherol protection

The purpose of this research is to observe the near-UV radiation induced damage to cultured rabbit and squirrel lens epithelial cells as related to destruction and alterations of specific biochemical targets in the cells and to determine protective effects on the cells and targets that are provided by alpha-tocopherol. Confluent monolayers of cultured rabbit and squirrel lens epithelial cells were exposed to black light (BL) lamps, which emit predominantly UV-A radiation. These cells received a mixture 3 J/cm2 of UV-A and 4 mJ/cm2 of UV-B per h. This mixture is termed near UVA (i.e.: predominantly UV-A). Cells were exposed in Tyrode's or in MEM without or with alpha-tocopherol added at 2.5-10 micrograms/ml. Analyses of cell viability and survival, the physical state of cytoskeletal actin, and the activities of Na-K-ATPase and catalase were made. Exposure to near UVA damaged these cells as measured by vital staining and colony forming ability. Pretreatment with alpha-tocopherol decreased the magnitude of near UVA cytotoxicity. Near UVA exposure in MEM always produced more damage to the cells and biochemical targets than in Tyrode's. Cytoskeletal actin was degraded and the activities of Na-K-ATPase and catalase were markedly inhibited by UV-exposure. All of these targets were at least partially protected by alpha-tocopherol in the medium. Without alpha-tocopherol added to the media, the viability and survival of the cells did not recover even after 25 h of incubation. Cell viability was better protected from near UVA by alpha-tocopherol than was the ability to grow into colonies. This indicates that alpha-tocopherol protects actin, catalase, and Na-K-ATPase from near UVA damage.