The effect of simvastatin and dexamethasone on the expression of endothelial nitric oxide synthase mRNA and the proliferation in osteoblast

Objective To study the effect of simvastatin and dexamethasone on the expression of endothelial nitric oxide synthase(eNOS)mRNA and the proliferation in osteoblast.Methods The osteoblast was collected from newborn SD rats,skull and cultured,and then randomly divided into 3 groups(8 samples for each group):in group A,the cells were treated with simvastatin of 1×10-7 mol/L,dexamethasone of 1×10-7 mol/L and DMSO of 1‰;in group B,the cells were treated with dexamethasone of 1×10-7 mol/L and DMSO of 1‰;in group C,the cells were treated with only DMSO of 1‰.The cells were collected and total RNA were obtained 96 h after culture.The expression of eNOS mRNA in the cells was analysed with Reverse Transcription-Polymerase Chain Reaction(RT-PCR).The amount of nitric oxide(NO)in culture medium was detected by the method of nitric acid reduction enzyme.The ratio of proliferation of osteoblast was measured using MTT reduction assay.Results The expression of eNOS mRNA in group A,B,C was 0.491±0.014,0.421±0.018,0.489±0.014.The level of NO in the culture medium in group A,B,C was(14.37±1.24)μmol/L,(12.94±0.69)μmol/L,(14.14±1.23)μmol/L.The ratio of osteoblast proliferation in group A,B,C was 0.3055±0.0178,0.2659±0.0105,0.3044±0.0213.There were significant differences of the expression of eNOS mRNA,level of NO and ratio of osteoblast proliferation between group A and group B,group B and group C(P 0.05),and no significant differences of that between group A and group C(P 0.05).Conclusion It demonstrates that the lower expression of eNOS in the osteoblasts induced by dexamethasone may be an important pathogenesis of glucocorticoid-induced osteoporosis.Simvastatin may inhibit the effect of dexamethasone and regulate the expression of eNOS mRNA in the cells and protect the proliferation of osteoblast.