N-acetyl cysteine protects osteoblastic function from oxidative stress

We tested the protective potential of an antioxidant amino acid derivative, N-acetyl cysteine (NAC), in controlling oxidative stress against osteoblasts. Osteoblastic cells extracted from rat bone marrow were cultured. Oxidative stress was induced by adding 100 μM H₂O₂ into the culture media. Then, some H₂O₂-treated cultures were cotreated with 2.5 or 5 mM NAC. Addition of H₂O₂ decreased the number of cells to 50% of untreated cultures at days 2. Addition of 5 mM NAC into H₂O₂ cultures resulted in a dose-dependent increase in the number of cells, with the cell number being 50% greater than that in the 100 μM H₂O₂ culture. The gene expression levels of type I collagen, osteopontin, and osteocalcin were downregulated threefold by H₂O₂ on day 7. The H₂O₂-suppressed gene expression was fully recovered by NAC cotreatment. The mineralizing capability, assessed by Von Kossa staining on day 15, were approximately 1.8 times greater in the NAC + H₂O₂ cotreated group than in the culture with H₂O₂ alone. These NAC-mediated restorations were associated with an NAC dose-dependent increase of intracellular glutathione and a NAC dose-dependent decrease of intracellular reactive oxygen species. In conclusion, oxidative stress induced by H₂O₂ substantially impairs the proliferation, differentiation, and mineralization of osteoblasts. More importantly, the addition of NAC into the culture was found to restore these damages to a near normal level due to the improved redox balance, warranting further in vivo studies to test its therapeutic potential as a local antioxidative stress drug.