Elevated production of active oxygen in Bloom's syndrome cell lines.

Based on our previous evidence indicating that the elevated sister chromatid exchange that characterizes Bloom syndrome (BS) cells may arise in response to elevated production of active oxygen, we have quantitated the levels of active oxygen in two control, two BS and one BS revertant cell lines. Luminol-dependent chemiluminescence was used as a measure of active oxygen production following treatment of the cells with the calcium ionophore A23187 or the chemotactic tripeptide N-formylmethionylleucylphenylalanine. A peptide factor present in plasma was required for priming the cells to undergo the oxidative response. As determined with A23187, active oxygen production was elevated in BS cell lines by 48.6% above control. Using N-formylmethionylleucylphenylalanine, active oxygen production was found to be increased by 250-314%. Chemiluminescence was inhibited in a dose-dependent manner by diphenylene iodonium, which specifically binds to and inhibits membrane-associated NADPH oxidase activity. This compound inhibited oxygen radical production nearly 3 times more effectively in control cells than in BS cells. The capacity to produce elevated levels of oxygen radicals may contribute to the spontaneous chromosomal instability of BS cells and to the associated high incidence of neoplasia in individuals with BS.