Apoptosis is known to be induced either by direct oxidative damage from oxygen free radicals or hydrogen peroxide, or from their generation in cells by injurious agents. Peroxiredoxin plays an important role in eliminating peroxides generated during metabolism. The aim of this study is to elucidate the role of Prx (peroxiredoxin) enzymes during the cellular response to oxidative stress.

The presence of Prx isoforms was demonstrated by immunoblot analysis using Prx isoforms-specific antibodies, and RT-PCR using Prx isozyme coding sequences. Annexin V-FITO apoptosis detection method was used to measure the cell death following exposure to H₂O₂.

Treatment of MCF7 cell lines with H₂O₂ resulted in the dose-dependent expression of Prx I and II. Observed decreases in the mRNA expressions of Prx I and II, analyzed by RT-PCR, correlated well with the results of immunoblot analysis. The treatment of normal breast cell line, MCF10A, with H₂O₂ resulted in rapid cell death, while the breast cancer cell line, MCF7, was resistant. In addition, we confirmed that Prx I and II transfected MCF10A cells were more prone to cell death than MCF10A transfected with vector alone, after H₂O₂ treatment.

These findings suggest that Prx I and II have an important function as inhibitors of cell death during the cellular response to oxidative stress.