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ObjectiveTo investigate the expression of nuclear factor kappa B(NF-kB)-related mRNA and protein in bone tissue of rats with chronic fluorosis.MethodsThirty-six healthy SD rats,weighting 100 - 120 g,were randomly divided into three groups (twelve in each group ).Rats of control group were fed with tap water (NaF ＜ 1 mg/L) and the experimental rats were exposed to NaF(low-dose group5 mg/L,high-dose group50mg/L) through drinking water.All rats were killed at the eight month and metaphysic of femoral was collected.Bone tissues were stained with hematoxylin-eosin and observed under optical microscope.Bone fluorine was detected by ashing-fluorin ion selective electrode method.Serum content of tartrate-resistant acid phosphatase 5b(TRACP 5b)was detected by enzyme-linked immunosorbent assay(ELISA).The expressions of p50,p65 and IkBα's mRNA and protein in bone tissue was detected by real-time PCR and immunohistochemistry.ResultsBone sclerosis was observed under optical microscope.The contents of bone fluorine in both the low and high doses fluoride groups [(6.32 ± 1.23),( 10.89 ± 1.56) mg/kg] were significantly higher than that of the control [(3.06 ± 1.01 ) mg/kg,all P ＜ 0.05],and of that the high fluoride group was significantly higher than that of the low fluoride group(P ＜ 0.05).Serum content of TRACP 5b of the low fluoride group[(3.45 ± 1.85)U/L] was significantly higher than that of the control[(1.26 ± 0.23)U/L,P ＜ 0.05],but that of the high fluoride group[(2.74 ± 1.85)U/L] was lower than that of the low dose group(P ＜ 0.05).The mRNA expressions of p50 and IkBα in the low fluoride group(4.41 ± 0.44,1.15 ± 0.25) were significantly higher than that of the control(1.46 ± 0.10,0.26 ± 0.07,all P ＜ 0.05),but that of the high fluoride group(0.69 ± 0.09,0.14 ± 0.03) was lower than that of the low dose group(all P ＜ 0.05).The protein expressions of p50 and IkBα in the low fluoride group(152.96 ± 7.87,156.20 ± 9.75) were significantly higher than that of the control( 125.63 ± 9.85,118.97 ± 6.94,all P ＜ 0.05),but the high fluoride groups' ( 120.56 ±9.57,114.50 ± 7.61 ) was significantly lower than that of the low dose group(all P ＜ 0.05).ConclusionFluoride can lead to altered gene expression of NF-kB pathway,and the latter may be involved in fluoride induced bone damage.