The oxidative stress response is region specific in organogenesis stage mouse embryos exposed to 5-bromo-2'-deoxyuridine

The exposure of mouse embryos to 5-bromo-2'-deoxyuridine (BrdU), a model teratogen, generates oxidative stress, induces c-Fos dependent activator protein-1 (AP-1) DNA binding activity, and causes skeletal malformations (Sahambi and Hales, 2006). The goal of this study was to test the hypothesis that the ability of BrdU to induce oxidative stress, rather than its incorporation into DNA per se, is responsible for triggering the ensuing malformations. To test this hypothesis, we examined the regional localization of BrdU incorporation, 8-oxoguanine (8-oxoG), a marker of oxidative stress, and c-Fos immunoreactivity in organogenesis stage mouse embryos exposed to a teratogenic dose of BrdU.

Timed pregnant CD1 mice received vehicle (saline) or BrdU (600 or 1000 mg/kg body weight) on gestation day 9. N-acetyl-L-cysteine, a glutathione precursor, was administered to GD 9 mice 2 hours before treatment with vehicle or BrdU to determine the impact of inhibiting the oxidative stress response. Embryos were excised 3 hours after BrdU treatment and processed for staining for BrdU incorporated into DNA, 8-oxoG, and c-Fos.

BrdU incorporation, 8-oxoG adduct formation and c-Fos immunoreactivity were highest in the rostral and caudal developing tissues of BrdU-exposed embryos. Although preadministration of N-acetyl-L-cysteine at a dose that decreased BrdU teratogenicity dampened the oxidative stress response, it did not affect the incorporation of BrdU into DNA.

These data show that rostral and caudal neuroepithelial cells are particularly susceptible to oxidative stress in the organogenesis-stage embryo.