ABSTRACT
Objective To analyze the changes of endoplasmic reticulum stress (ERS) in the spleen of water-improving fluorosis rat,to explore the mechanism of fluoride-induced immune system damage,and to provide a scientific basis for prevention and control of endemic fluorosis.Methods Forty-eight male Wistar rats of SPF grade were randomly divided into control group and low,medium and high fluoride dose groups according to body mass (120-140 g),12 rats in each group.The sodium fluoride (NaF) content was 0,50,100 and 150 mg/L,respectively.The animals were allowed free access to water and food.After 12 weeks of fluoride exposure,6 rats in each group were selected to isolate the spleen;the remaining rats in each group were changed to drink distilled water containing no NaF,and the spleen was separated after 12 weeks of feeding.The levels of mRNA of glucoseregulated protein (GRP78),spliced X-box binding protein 1 (XBP1-s),activating transcription factor 4 (ATF4),homologous protein (CHOP) and cysteine containing aspartate specific protease 12 (Caspase-12) in spleen were determined by quantitative real-time PCR (qRT-PCR).Results Before the water-improving,the expressions of GRP78 (1.00 ± 0.09,1.69 ± 0.35,1.39 ± 0.29,1.19 ± 0.19),XBP1-s (1.00 ± 0.12,1.40 ± 0.23,1.24 ± 0.26,1.38 ± 0.11),ATF4 (1.00 ± 0.17,1.86 ± 0.56,2.33 ± 0.55,1.95 ± 0.74),CHOP (1.00 ± 0.53,2.84 ± 0.68,3.06 ± 1.29,2.50 ± 0.35) and Caspase-12(1.00 ± 0.12,1.90 ± 0.29,1.56 ± 0.35,1.76 ± 0.23) mRNA in the control group and low,medium and high fluoride dose groups were statistically significant (F =8.45,5.38,6.38,8.21,11.31,P ＜ 0.05).Except for the GRP78 in high fluoride dose group,the above indicators in fluoride groups were higher than the control group (P ＜ 0.05).After the water-improving,the expressions of GRP78 (1.00 ± 0.36,0.75 ± 0.13,0.98 ± 0.41,0.47 ± 0.19),XBP1-s (1.00 ± 0.25,0.70 ± 0.06,0.74 ± 0.17,0.65 ± 0.21),ATF4 (1.00 ± 0.51,0.66 ± 0.09,0.91 ± 0.34,0.81 ± 0.29),CHOP (1.00 ± 0.36,0.92 ± 0.12,0.84 ± 0.16,0.67 ± 0.20) and Caspase-12 (1.00 ± 0.45,0.65 ± 0.11,0.65 ± 0.25,0.51 ± 0.27) mRNA in the control group and low,medium and high fluoride dose groups were not statistically significant (P ＞ 0.05).Before and after the water-improving,the expressions of XBP1-s,ATF4,CHOP and Caspase-12 mRNA were statistically significant in fluoride groups (P ＜ 0.05),and the GRP78 only had a statistically significant difference in the low fluoride dose group (P ＜ 0.05).Conclusions Fluoride exposure causes ERS response in rat spleen,up-regulation of ERS-related gene expression,which is decreased after water-improving,and the ERS response is weakened.The water-improving may contribute to the recovery of fluoride-induced immune function damage.
ABSTRACT
Objective To investigate the effect of fluoride on osteoclast in bone tissue of rats and its mechanism.Methods Twenty specific pathogen free male Wistar rats aged 3 weeks were randomly divided into two groups by weight (each group has 10).The rats of control group drink distilled water and treatment group drink distilled water containing 100 mg/L fluoride.The rats were fed for 3 month.The dental fluorosis in rats was observed.The ion selective electrode method was used to measure bone fluoride accumulation.The pathological changes of bone tissue in rats were observed under light microscope.The osteoclast was identified by tartrateresistant acid phosphatase (TRAP) staining.The calcineurin (CaN) activity of serum was measured by detection of free phosphate with malachite green.The bicinchoninic acid (BCA) method was used to detect total protein concentration of serum.The colorimetry method was used to detect calcium and malondialdehyde (MDA) levels in serum.The enzyme linked immunosorbent assay (ELISA) method was used to detect calmodulin (CaM) content.Results By the end of the experiment,none dental fluorosis was detected in control group,all rats in fluoride group had dental fluorosis.The bone fluoride content of rats in fluoride group [(4 460.671 ± 418.548) mg/kg] was about 7.6 times higher than that in control group [(582.534 ± 58.342) mg/kg,t =-29.020,P ＜ 0.01].Compared with the control group,the bone tissue of rats in fluoride group showed thicker bone trabecular,sclerotin fusion and incomplete mineralization.Positive signal intensity of TRAP staining of bone tissue in fluoride group was significantly higher than that in control group.The number of osteoclast formation in fluoride group [10 (5-12)] was significantly higher than that in control group [3 (2-4);U =92.5,P ＜ 0.01].CaN activity in serum of rats in fluoride group [(3.334 ± 0.654) nmol/mg prot] was significantly higher than that in control group [(1.289 ± 0.361) nmol/mg prot;t =-6.346,P ＜ 0.01].The Ca and CaM content of serum in rats were not significantly different between the two groups.However MDA content in fluoride group [(7.703 ± 2.954) μmol/L] was significantly higher than that in control group [(3.958 ± 1.965) μmol/L,t =-2.968,P ＜ 0.05].Conclusion Excessive fluoride may increase osteoclast formation in bone tissue of rats,and the mechanism might be fluoride stimulated CaN activity through oxidative stress pathway.