Apoptosis and p53 induction in human lung fibroblasts exposed to chromium (VI): Effect of ascorbate and tocopherol

Some forms of hexavalent chromium [Cr(VI)] are known to cause damage to res piratory tract tissue, and are thought to be human lung carcinogens. Becaus e Cr(VI) is mutagenic and carcinogenic at doses that evoke cell toxicity, t he objective of these experiments was to examine the effect of Cr(VI) on th e growth, survival, and mode of cell death in normal human lung fibroblasts (HLF cells). DNA adduct formation was monitored as a marker for bioavailab ility of genotoxic chromium. We also examined the modulation of these endpo ints by vitamins C and E. Long-term Cr(VI) exposures were employed, which d ecreased clonogenic cell survival by 25% to 95% in a dose-dependent manner. The predominant cellular response to Cr(VI) was growth arrest. We found th at Cr(VI) caused up to 20% of HLF cells to undergo apoptosis, and documente d apoptotic morphology and the phagocytosis of apoptotic bodies by neighbor ing cells. P53 levels increased 4- to 6-fold in chromium-treated cells. In contrast with previous studies using CHO cells, the present study using HLF s found that pretreatment with either vitamin C or E did not exhibit a sign ificant effect on Cr-induced apoptosis or clonogenic survival. In addition, pretreatment with vitamin C did not affect the p53 induction observed afte r chromium treatment. Neither vitamin had any effect on Cr-DNA adduct forma tion. These data indicate that although pretreatment with vitamin C or E al ters the spectrum of cellular and/or genetic lesions induced by chromium(VI ), neither vitamin altered the initiation or progression of apoptosis in di ploid human lung cells.