Effect Of Moderate Exercise On Bone Remodeling In Fluorosis Mice

[Objective] Fluorosis is a kind of systemic toxic disease,which damages various tissues and organs of the body in different degrees,mainly skeleton damage,and clinically manifests as dental fluorosis and skeletal fluorosis.Exercise accelerates the metabolism of the body,which is beneficial to health,and it also affects bone development and promotes bone formation.Therefore,this experiment provides a new idea for the study of fluorosis by exploring the effect of exercise on bone remodeling of fluorosis mice.[Methods] According to the fluorine concentration of receiving water and exercise regime,120 male3-week-old ICR mice were randomly divided into 4 groups,which were control group(C,distilled water,no exercise),exercise group(E,distilled water,10 m/min,30 min/d),fluoride group(F,100 mg/L Na F,no exercise),fluoride plus exercise group(F+E,100 mg/L Na F,10 m/min,30 min/d).And the feeding period was 8 weeks.During the experiment,the daily condition,the changes of teeth,body weight,the drinking and feed situation of mice were recorded in detail.At the end of the feeding experimental,the mice were sacrificed and the serum and limb bones were collected for future study.The concentration of fluorine in the foreleg bone was measured by fluoride ion selective electrode method.The changes in the microstructural structure and morphology of femur tissue in mice were observed and analyzed by Micro CT scans and HE.And the activity of ALP and TRACP in serum,the content of Ca,P and related indexes of oxidative stress in bone homogenate were measured according to the instructions of the kits.The relative expression levels of m RNA and protein of osteoblasts and osteoclast-related genes in femur were detected by q RT-PCR,Western Blot and immunohistochemistry(IHC)methods.[Results] 1.The results of dental fluorosis suggested that compared to C group,the mice in F and F+E groups showed different degrees of dental fluorosis.The mild type usually exhibits some opaque white stripes on the surface of teeth.In serious cases,the enamel loses its glaze surface and shows matte chalk.Compared to C group,the proportion of level 1 and level 2 teeth in the F and F+E groups were obviously increased.Compared to F group,the proportion of level 1 teeth in F+E group was significantly increased,and the proportion of level 2 teeth was significantly decreased.2.In the results of the content of fluorine in bone,the fluorine concentration of F and F+E groups were significantly higher than that in C group;and compared to F group,the bone fluoride content of F+E group was significantly decreased.3.In the bone metabolism indexes,compared to C group,ALP and TRACP activities in serum of F and F+E groups were significantly increased.However,there was no obvious difference in F and F+E groups of these enzymes.The results of Ca and P in bone showed that there was no significant change in all groups except for the significant increase of Ca content in E group compared to C group.4.The results of HE and micro CT showed that exposure to 100 mg / L Na F for 8 weeks could make the trabeculae thicker and tighter,increase the number and area of the trabeculae of femur,and there was a tendency of osteosclerosis.Among the structural parameter indicators of trabeculae,the values of F and F+E groups increased(TMD,BMD,Tb.N,etc.)or decreased(Tb.Sp,Tb.Pf,etc.)in varying degrees,showing a trend of osteosclerosis,which was consistent with the results of HE.5.In the results of oxidative stress of bone tissue,compared to C group,fluoride exposure significantly increased the content of ROS and MDA,decreased the activities of CAT and GST.However,Compared to F group,the MDA content and the activities of SOD and GSH-Px in F+E group were successively reduced and enhanced,and the differences were significant.There was no significant difference in the content of T-AOC and GSH in all groups.6.The m RNA relative expression of osteoblasts and osteoclast-related genes were detected by q PT-PCR technology.The results showed that the m RNA expression levels of BMP-2,Smad-5,OPG and RANK in F group were significantly higher than those in C group,while these genes in F+E group was significantly decreased.In addition,in F group,the m RNA expression levels of Col IA1,Col IA2 and RANKL were significantly increased compared to C group;and they were decreased in F+E group,but there was no obvious difference compared to F group.The changes of Smad-1,Osterix and Runx2 m RNA relative expression and RANKL/OPG ratio in group C and other treatment groups were not significant.7.Western blot and IHC were used to test the expression of some proteins in OPG/RANKL/RANK signaling pathway.The results showed that the protein levels of OPG,RANKL and RANK in F group were significantly higher than those in C group,while the expression level of these three proteins in F+E group were suppressed by different degrees compared to F group.[Conclusion] 1.Fluoride exposure leads to oxidative stress in bone tissue,and moderate exercise alleviates the oxidative damage.2.Exposure to fluoride activates osteoblasts and osteoclasts in varying degrees,induces their corresponding enzyme activities to increase,up regulates the expression of related genes and proteins on BMP-2/Smads and OPG/RANKL/RANK signaling pathways,accelerates bone transformation,and thereby destroys the metabolic balance in the process of bone remolding,and makes the bone harden.Exercise can decrease the toxicity of fluoride by reducing the accumulation of fluorine in the body to relieve the bone damage caused by fluorosis.