Effects Of Fluoride On Proliferative Activity And Oxidative Stress Of Osteoblasts In Vitro

How to establish a rational relationship between oxidative stress and the activation of osteoblasts is one of the thorny issues which we need to face during studying the mechanism of skeletal fluorosis. Osteoblasts from mouse calvaria bone cells were cultured in vitro and exposed to fluoride. The concentrations of fluoride were a total of seven doses (0.5,1.0,2.0,4.0,8.0,12.0,20.0 mgF-/L), and the times of fluoride exposure were a total of four durations(24h,48h, 72h, 96h). The methods of morphology, biochemistry, Elisa,and RT-PCR were used to study the effects of different doses of fluoride on osteoblast proliferative activities and the levels of oxidative stress, and to investigate the role of oxidative stress on the proliferative mechanism of osteoblasts induced by fluoride. The main findings and conclusions of the present study are as follows:1. Low doses of fluoride (0.5-2.0 mgF-/L) significantly stimulated osteoblast proliferation. The stimulating effect was still significant until 8.0 mgF-/L. Large dose (20 mgF-/L) of fluoride inhibited cell proliferation.2. The levels of osteoblast's product OCN paralleled the activities of cell proliferation.The contents of OCN increased in the low-dose fluoride exposure, and decreases in the high-dose fluoride exposure.3. The levels of lipid peroxidation product MDA were partially higher, the activities of antioxidant enzyme GPX significantly increased, and the mRNA level of SOD was up-regulated in osteoblasts exposed to the low-dose fluoride,showing a lesser extent of oxidative stres.The level of MDA was still high, but the activities of SOD and GPX decreased in osteoblasts exposed to the high dose of fluoride, which reflected anexcessive state of oxidative stress in the osteoblasts.4.Osteoblast proliferation and oxidative stress simultaneously induced by low dose of fluoride suggesting that oxidative stress in a lesser extent may be involved in the signal transduction and regulation of cell proliferation,and activation rather than in the causation of cell damage. Further study is needed to confirm a causal link between oxidative stress and cell proliferation,activation,and differentiation.