Relationship of nuclear factor kappa B-related gene expression and osteoclast apoptosis induced by fluoride in bone tissue / 中国地方病学杂志

ABSTRACT

Objective To investigate the relationship between change of relevant gene of nuclear factor kappa B(NF-κB) and osteoclast apoptosis in bone injury of rats with chronic fluorosis,and to reveal the mechanism of skeletal fluorosis.Methods Thirty-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 group50 mg/L) through drinking water to established chronic fluorosis model.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.Serum content of tartrateresistant acid phosphatase 5b (TRACP 5b) was detected by enzyme-linked immunosorbent assay (ELISA).Osteoclast was identified and counted by tartrate-resistant acid phosphatase staining(TRAP).The expression of p50,IκBα,Bcl-2 and Bax's mRNA and protein of bone tissue was detected by Real-time PCR and immunohistochemistry.Results Bone sclerosis was observed under optical microscope.The content of TRACP 5b in serum and the number of osteoclast in the low fluoride group[(3.45 ± 1.85)U/L,(6.75 ± 1.29)/slice]were significantly higher than that of the control[(1.26 ± 0.23)U/L,(3.92 ± 1.38)/slice,all P ＜ 0.05],but that of the high fluoride group [(2.74 ± 1.85)U/L,(3.33 ± 1.07)/slice]were lower than that of the low dose group(all P ＜ 0.05).The mRNA expressions of p50,IκBα,Bcl-2 and Bax in low fluoride group(4.41 ± 0.44,1.15 ± 0.25,2.02 ± 0.11,1.25 ± 0.22) were significantly higher than that of the control(1.46 ± 0.10,0.26 ± 0.07,1.00 ± 0.06,0.74 ± 0.09,all P ＜ 0.05),but the high fluoride groups' (0.69 ± 0.09,0.14 ± 0.03,0.95 ± 0.08,0.62 ± 0.08) were lower than that of the low dose group(all P ＜ 0.05).The protein expressions of p50 and IκBα 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 group(120.56 ± 9.57,114.50 ± 7.61) were lower than the low dose group(all P ＜ 0.05).The protein expressions of Bcl-2 and Bax(170.61 ± 6.60,160.77 ± 7.66) and the ratio of Bcl-2/Bax (1.07 ± 0.08) were higher than the control(l10.73 ± 5.27,114.64 ± 5.83,0.96 ± 0.04,all P＜ 0.05),but the high fluoride group(81.70 ± 8.00,99.93 ± 3.83,0.81 ± 0.08) were lower than that of the control and the low dose group (all P ＜ 0.05).There was a significant positive correlation between protein expression of p50,IκBα and Bcl-2/Bax (r =0.587,0.676,all P ＜ 0.05).Conclusions Chronic fluorosis can cause change of the relevant gene of NF-κB in rat bone tissues and osteoclast apoptosis.The mechanism of skeletal fluorosis might be related to the abnormal of osteclast apoptosis caused by changes of NF-κB p50 and IκBα.