Statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, have been used clinically as a cholesterol-lowering drug to treat hyperlipidemia. In recent years, accumulating evidence indicates the possible beneficial effect of statins on osteoporosis. However, the underlying molecular mechanism remains to be elucidated. In the present study, we investigated the therapeutic effects of simvastatin on cell viability, apoptosis, and alkaline phosphatase activity in murine osteoblastic MC3T3-E1 cells treated by hydrogen peroxide (H(2)O(2), 100 μM). It was shown that simvastatin suppressed H(2)O(2)-induced oxidative stress and attenuated H(2)O(2)-induced cell injury including increasing osteoblastic viability, inhibiting apoptosis, and promoting differentiation. Then, we examined the effects of simvastatin (10(-7) M) on Nox1, Nox2, and Nox4 expressions in osteoblastic cells treated by H(2)O(2) (100 μM). We found that in MC3T3-E1 cells, H(2)O(2)-induced upregulation of Nox4 expression was inhibited by simvastatin, which was restored by farnesyl pyrophosphate (5 μM) as well as geranylgeranyl pyrophosphate (5 μM). RNAi approach was used to reduce Nox4 protein levels in osteoblastic cells to explore its biological effects against H(2)O(2)-induced oxidative damage. When Nox4 expression was reduced in osteoblastic cells, H(2)O(2)-induced cell injury was attenuated markedly. We concluded that simvastatin protected osteoblast against H(2)O(2)-induced oxidative damage, at least in part, via inhibiting the upregulation of Nox4.