PROTECTION AGAINST CIGARETTE SMOKE-INDUCED DAMAGE TO INTACT TRANSFORMED RABBIT CORNEAL CELLS BY N-ACETYL-L-CYSTEINE

In order to assess cigarette smoke-induced oxidative damage to intact cells, an assay was developed to measure cell detachment and protectio n. Due to the complex nature of cigarette smoke, which contains molecu les that can interfere with conventional spectrophotometric and fluoro metric biochemical assays, transformed rabbit corneal cells were radio labeled with tritiated thymidine and then subjected to direct stream s moke. As a result, cell damage in response to the smoke from only two cigarettes could be measured in a time-dependent manner. When cells we re prelabeled with N-acetyl-L-cysteine (NAC), a substrate for glutathi one synthesis, a significant reduction in damage was measured. Additio nally, when buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, was incubated with cells, a reduction in the effectiveness of NAC was observed, although NAC still retained some activity. Furthe rmore, vitamin E conferred no protection to cells in this system nor w as NAC active in a separate assay that appears to favor peroxyl radica l generation. From these results we conclude that cigarette smoke dama ge can easily be determined at the cellular level with this technique and that NAC acted to prevent this damage in two ways: first, as gluta thione precursor and, secondly, as an antioxidant capable of scavengin g non-peroxyl radicals.