Involvement of nitric oxide in the inhibition of cell proliferation by scavenging hydrogen peroxide

POLICASTRO L; ROJAS PA; SCHÖPFER F; MOLINARI B; PODEROSO JJ; DURÁN H

Mar del Plata

Congreso; II Congress II Congress South American Group for Free Radical Research. .; 2001

South American Group for Free Radical Research. .

Some experimental evidence suggests a role of H2O2 in the induction of cell proliferation. In this sense, we have previously demonstrated the inhibition of cell growth by treatments with exogenous catalase in several cell types. The aim of  the present work was to study the mechanisms by which scavenging of H2O2 inhibits cell proliferation, evaluating the possible role of nitric oxide in this process. We used normal and tumor epithelial cell lines derived from mouse skin (PB and CH72-T4 cells) and from human mammary epithelium (HBL100 and MCF-7). The inhibition of cell proliferation after treatments with catalase was evaluated by BrdU incorporation and by direct cell count. The induction of apoptosis was evaluated by Hoechst and DNA laddering techniques. To study the role of nitric oxide (NO), we evaluated the production of nitrites and the levels of nitric oxide synthase (NOS) by western blot in cells treated with catalase and L-NAME, an inhibitor of NOS. We demonstrated a significant inhibition of 40-70% of BrdU incorporation after 6 and 24 h of treatment with 1000 U/ml catalase for all the cell lines. Treatments with catalase did not induce apoptosis. Regarding NO, we demonstrated higher levels of production of nitrites and eNOS expression in normal than in malignant cells and a significant 1.6-2 fold increase in the production of nitrites in cells treated with 1000 U/ml catalase. In PB cells, an increase in the levels of enOS was demonstrated after treatments with catalase, and other isoforms of NOS (nNOS and iNOS) were not detected. Treatments of cells with L-NAME and catalase resulted in a partial reversion of the inhibition of proliferation. These results suggest that cell growth inhibition by scavenging H2O2 is due to an arrest of the cell cycle and could be mediated by an increase in NO production.