| Fluoride is an essential trace elements in living organisms, but the body’s long-term intake of excessive fluoride can lead to the accumulation of a systemic chronic poisoning, namely the endemic fluorosis. Fluorosis can lead to skeletal fluorosis, dental fluorosis, organs such as the damage, also can damage the fragments organs such as blood and nervous system. Fluoride accumulation in tissues and organs is the material basic of damage effect, and kidney is main organ of fluoride accumulation, elimination and toxic effects, so excess fluoride intake will damage kidney in a certain degree. Selenium as a trace element with antioxidant effects received extensive attention. It could antagonize high concentrations of fluoride in rats, promote urinary fluoride excretion, scavenge free radical, improve the antioxidant capacity of the fluorosis body. So far, although researchs of kidney damage by fluoride exposure have been repored, But the relationship between fluoride induced kidney’s oxidative damage and the mitochondrial apoptosis pathway related protein/gene is very rare, at that the reports on the fluorosis mainly in different concentrations of fluoride on the same infected time are compared, and the lack of the longitudinal comparison between different period of feed fluoride, the research of selenium on the influence of fluoride is also that. Therefore, on the basis of previous studies, this study made improvement on experimental method and the indexes selection, and to explore the molecular mechanism of drinking water fluorosis cause kidney damage and the influence of selenium. To provide a theoretical foundation and scientific basis for the prevention and treatment of endemic fluorosis.In this study, we chose 160 healthy early weanling male SD rats. Rats were randomly divided into 4 groups.1. Control group, sodium fluoride-treated group (NaF,100mg/L), selenium-treated groups (sodium selenite,1.5mg/L), NaF+ selenium-treated groups (NaF, 100mg/L+sodium selenite,1.5mg/L), all the above solution used tap water as the solvent. The male rats were decapitated respectively after three and six months. Each experimental group took rat kidney viscera coefficient, kidney damage related blood indexes, the microstructure of renal tissue, biochemical index of renal tissue,apoptosis of renal cells, and the mRNA and protein expression levels of CytC, Caspase 9,Caspase 3 as indicators of observation.The results are shown as follows:(1) The results of weight and organ coefficients of rats:Compared with the control group, weight of 3 months and 6 months rats in Se group were significantly decreased (p<0.05), the other groups weight had no significant difference (p>0.05), but there were a certain decrease trend. Compared with the F group, weight of 3 months and 6 months rats in Se group were significantly decreased (p<0.05), the F+Se group weight had no significant difference (p> 0.05). The organ coefficient of kidney of rats in each group Change were not obvious, and had no statistical difference. Compared with 3 months rats, the organ coefficient of kidney had no significant difference (p>0.05), but there were a certain decrease trend.(2)The determination results of kidney damage-related blood indicators of rats: Compared with the control group, the BUN, UA content of 3 months rats and the Cr, BUN, UA content of 6 months rats in F group increased significantly (p<0.05), the Cr content of 3 months rats had a rising trend, but no statistical difference. Compared with the F group, the BUN, UA content of 3 months rats and the Cr, BUN, UA content of 6 months rats in F+Se group decreased significantly (p<0.05), the Cr content of 3 months rats had a decrease trend, but no statistical difference(p>0.05).(3)The observation of the microstructure in renal tissue:The microstructure of control group weren’t abnormal structural changes. Fluoride group increase of bowman’s capsule, edema of renal tubular epithelial cells, granular degeneration, some vacuoles degeneration, at the junction of cortex and medulla renal tubule obvious dilatation; the kidney microstructure of F+Se group improved significantly. And compared with 3 months, the kidney damage of F group significantly increased, the kidney damage of F+Se group obviously improved.(4) The results of enzyme activity in renal tissue:Compared with the control group, the GSH-Px activity of 3 months rats and the SOD and GSH-Px activity of 6 months rats in F group highly decreased significantly (p<0.01), and the content of MDA highly increased significantly (p<0.01), the SOD activity of 3 months rats in F group had a decrease trend, but no statistical difference (p>0.05). Compared with the F group, the GSH-Px activity of 3 months rats and the SOD and GSH-Px activity of 6 months rats in F+Se group highly increased significantly (p<0.01), and the content of MDA highly decreased significantly (p<0.01), the SOD activity of 3 months rats in F+Se group had a increase trend, but no statistical difference (p>0.05). Compared with 3 months rats, the activity of SOD decreased significantly (p<0.05) and the content of MDA increased significantly (p<0.01) in F group, the activity of SOD the Se and F+Se group decreased significantly (p<0.05).(5) The results of renal cell apoptosis in rats:Under optical microscope, there were brown yellow or brown particles in the nucleus of apoptosis cells. The apoptotic cells were rarely seen in control group, compared with the control group, the amount of apoptotic cells increased obviously in F group and Se group, compared with the F group, apoptotic cells of the F+Se group obviously decreased. Compared with 3 months rats, apoptotic cells of in F group had a certain decrease trend, and apoptotic cells of the F+Se group had a certain decrease trend.(6) The results of RT-PCR:Compared with the control group, the mRNA expression levels of Cyt C, Caspase 9, Caspase 3 highly increased significantly (p<0.01) in F group. Compared with the F group, the mRNA expression levels of Cyt C, Caspase 9, Caspase 3 highly decreased significantly (p<0.01) in F+Se group. Compared with 3 months rats, the mRNA expression levels of Cyt C, Caspase 9, Caspase 3 increased significantly (p<0.05) in F group,the mRNA expression levels of Cyt C, Caspase 9, Caspase 3 decreased significantly (p<0.05) in F+Se group.(7) The results of Western blot:Compared with the control group, the protein expression levels of Cyt C, cleaved Caspase 9 highly increased significantly (p<0.01) in F group, Se group and F+Se group, and except the protein expression levels of Cyt C increased significantly (p<0.05) in F+Se group of 6 months rats, the protein expression levels of cleaved Caspase 3 highly increased significantly (p<0.01) in F and Se group, the protein expression levels of cleaved Caspase 3 increased significantly (p<0.05) in F+Se group. Compared with the F group, the protein expression levels of Cyt C,cleaved Caspase 9,cleaved Caspase 3 highly decreased significantly (p<0.01) in F+Se group. Compared with 3 months rats, the protein expression levels of Cyt C, cleaved Caspase 9,cleaved Caspase 3 increased significantly (p<0.05) in F group,the protein expression levels of Cyt C, Caspase 9, Caspase 3 decreased significantly (p<0.05) in F+Se group.In conclusion, drinking water fluorosis could cause renal tissue oxidative stress damage and renal cell apoptosis increases, and then affected the renal function. It suggests the mitochondrial CytC-Caspase 9-Caspase 3 apoptosis pathway in the kindney was one of the mechanisms leading to fluorosis-induced kindney damage.In addition, the same concentration of selenium have different biological effects under different exposure mode, it exhibited toxic effects on the body when exposed alone, while a moderate amount of selenium could antagonism fluorosis-induced kidney damage when it used together with fluoride, and this intervention might become more significant as time increasing. |
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