Inhibition of DNA synthesis in Caco-2 cells by oxidative stress: amelioration by epidermal growth factor.

The role of oxidative stress in the regulation of intestinal epithelial proliferation was examined by evaluating the effect of H2O2 and xanthine oxidase + xanthine (XO + X) on [3H]thymidine incorporation into DNA in Caco-2 cells. DNA synthesis was highest 4 and 5 days after seeding, while it declined rapidly between 5 and 12 days. Pretreatment for 0.5-24 h with H2O2 or XO + X reduced DNA synthesis on 4- to 6-day-old, but not on 7- to 20-day-old cells. The effect of XO + X on DNA synthesis was significantly reduced by catalase, superoxide dismutase, and ferric chloride, but pretreatment with deferoxamine potentiated XO + X-induced inhibition of DNA synthesis. Coadministration of epidermal growth factor (EGF) for 24 hr reduced the H2O2 and XO + X-induced inhibition of DNA synthesis; this effect of EGF was not observed up to 8 hr. Results show that O2- and H2O2 rapidly inhibit DNA synthesis in Caco-2 cells and that EGF restores DNA synthesis in oxidant-treated cells.