Ascorbic acid dehydroascorbate induces cell cycle arrest at G(2)/M DNA damage checkpoint during oxidative stress

Reactive oxygen species induce cellular damage and have been implicated as mediators for cellular signaling pathways. However, a linkage between the c ellular redox status and cell cycle progression has not been demonstrated. We previously demonstrated, using the Chinese hamster ovary cell line AS52, that the cytotoxic and mutagenic effects of oxidative stress is prevented by ascorbic acid (AA), but only when cells ore treated with AA prior to tre atment with the stressor. To elucidate the mechanism(s) responsible for thi s effect, we determined the effect of AA on cell cycle progression during o xidative stress. Flow cytometric analyses demonstrated that treatment of AS 52 cells with AA (50 mu M), prior to treatment with a radical generating sy stem (RGS), enhanced cell cycle arrest at the G(2)/M DNA damage checkpoint when compared to cells treated with RGS. AA had no effect on cell cycle pro gression in the absence of oxidative stress. Furthermore, under conditions that pre vent the reduction of dehydroascorbate (DHA), the oxidized form of AA, cell cycle arrest was also induced at the G(2)/M DNA damage checkpoint . These observations demonstrate that during periods of oxidative stress, A A functions as an antioxidant and DHA enhances transient arrest at the G(2) /M checkpoint by delaying the activation of cyclin B-cdc2. These results su ggest the presence of a unique redox mechanism for the regulation of cell c ycle progression and also demonstrate a novel mechanism by which AA protect s cells from damage due to oxidative stress. (C) 1999 Wiley-Liss, Inc.