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Objective To investigate the expression and distribution of the downstream substrate of extracellular regulated protein kinase(ERK1/2) pathway, ternary complex factor phospho-Elk-1, in rat brains with chronic fluorosis, and reveal the mechanism of the impaired learning and memory ability caused by chronic fluorosis. Methods Seventy-two SD rats, weighing 100 - 120 g, were randomly divided into 3 groups, 24 in each group (half male and half female). The rats in control group were fed with tap water (fluoride < 0.5 mg/L); low- and high-dose fluoride groups were fed with tap water with different concentrations of NaF(5.0,50.0 mg/L F-, respectively). After 6 months, body weight was weighed, dental fluorosis was determined by observation and urinary fluoride and bone fluoride were detected by fluorine ion-selective electrode; the learning ability of rats was measured by navigation test of Morris water maze, and memory ability by spatial probe test in Morris water maze; the expression and distribution of phospho-Elk-1 in different brain regions were detected by immunohistochemistry method. Results In low- and high-fluoride groups, the body weight of rat[(449.2 ± 77.1), (312.8 ± 89.7)g] was significantly decreased than that of control [(635.5 ± 76.2 )g, all P< 0.05], the varying degrees of dental fluorosis were observed(x2 = 7.83, P<0.05), urinary fluoride[(2.56 ±0.91),(5.73 ±3.14)mg/L] and bone fluoride[(709.2 ± 37.4) ,(1306.3 ± 102.4) mg/kg] were significantly higher than those in controls[(0.92 ± 0.30)mg/L,(348.5 ± 89.2)mg/kg, all P< 0.05]. The escape latency of low- and high-fluoride groups[ (7.4 ± 4.1), (12.2 ± 5.7)s] was longer than that of control [(4.8 ± 2.7 )s, all P < 0.05] and the escape latency in high-fluoride group was significantly longer than that in other groups (all P < 0.05); in spatial probe test, the time of first crossing platform was longer in rats with fluorosis [(4.18 ± 1.10),(5.89 ± 0.56)s] as compared to control[(1.17 ± 0.75)s, all P< 0.05]. Expressions of phospho-Elk-1 in the hippocampus CA1(167.4 ± 8.3,163.2 ± 9.4), CA2(175.7 ± 5.0,183.3 ± 4.2), CA3(165.2 ± 11.6,162.9 ± 4.4), CA4(168.7± 6.9,169.5 ±5.3), fascia dentate (185.2 ±4.0,193.1 ±6.1) and caudate putamen( 181.4 ± 3.8, 179.8 ± 5.5) in low- and high-fluoride groups were higher than those of controls(142.4 ± 8.1,144.9 ± 8.4,143.6 ± 5.8, 116.8 ± 9.1,140.2 ± 7.8,163.1 ± 13.1, all P< 0.05). Conclusion Chronic fluorosis can cause increased expression of phospho-Elk-1 in the hippocampus and caudate putamen region of rat brains, which might be related to the mechanisms of decreased learning and memory ability of rats overexposed to fluoride.
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Objective To observe the influence of coal burning fluorosis on learning and memory ability in rats and reveal its possible mechanisms. Methods Healthy 48 SD rats were divided into control, low-fluoride and high-fluoride group. All rats in fluoride exposed groups were fed with the eom polluted by drying processes with burning coal containing high level of fluoride obtained from the endemic fluorosis area to produce the animal model of fluorosis. The experiment period were 3,6 mouths, respectively. The ability of leaning and memory was measured by Morris test and cholinesterase activity detected by photometric method at 3 or 6 month after experiment, respectively. Results Fluoride contents signifieantlly influenced the escape latency, the numbers of crossing the platforms and the time of staying the platforms(the value of F was 29.29,6.47,6.50, respectively, P<0.01).In addition, the numbers of crossing the platforms and the time of staying the platforms were influenced by the exposed time(the value of F was 16.11,45.59, P<0.01). Furthermore, the fluoride contents and the exposed time had an interaction between the numbers of crossing the platforms and the time of staying the platforms (the value of F was 4.67,5.68, P<0.05 or<0.01). Three months after the experiment, the mean values of escape latency [(14.71± 4.85)s] of rats in highly fluoride exposed group were significantly prolonged as compared with controls [(9.28±4.22)s]; 6 month after the experiment, the mean values of escape latency[(12.42±8.03)s, (17.48± 8.05)s] of rats in both groups exposed to fluoride were significantly prolonged as compared to controls [(7.04± 3.29)s, P<0.05]. The decreased numbers of crossing the platforms[(1.62±0.87)number] and the declined time of staying the platforms[(16.70±5.02)s] were found in the rats exposed to high fluoride as compared to controls [(3.53±1.67 )number, (23.33±5.35)s, P<0.05]. The fluoride contents obviously influenced the activities of acetylcholinesterase and butylcolinesterase (the value of F was 12.83,13.27, P<0.01). On the other hand, the times of breeding also influnced the activities of butylcolinesterase (the value of F was 16.26, P<0.01). In 3 months of the experiment, the activities of butylcolinesterase [(0.55±0.12)kU/g] in low fluoride exposed group were significantly decreased in comparison with controls[(0.73±0.10)kU/g, P<0.05]. The activities of acetylcholinesterase[(0.62±0.42)kU/g] and butylcolioesterase[(0.58±0.10)kU/g] in high fluoride group were significantly decreased as compared to eontrois[(1.41±0.52), (0.73±0.10)kU/g, P<0.05]. The correlation analysis showed that there was a negative correlation between the cholinesterase and the escape latency(r=-0.68, P< 0.01), and a positive correlation between the cholinesterase and the time of staying the platforms(r=0.57, P< 0.01). Conclusions The ability of learning and memory in rats with coal buring fluorosis was decreased, which might be connected to the decreased activity of cholinesterase in a dose-effect correlation.
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Objective To investigate the expression of extraeellular signal-regulated protein kinase (ERK1/2)pathway in rat brains with fluorosis and the effects of fluoride on learning and memory of the rats,and to reveal the mechanisms of damaged nervous system resulted from the toxicity of the ion.Methods Seventy-two SD rats were divided into 3 groups and 24 rats were in each group.Three groups were fed respectively with different concentrations of fluoride(NaF)for 6 months to establish rat models with fluorosis.Controls were fed with tap water (NaF＜0.5 mg/L):lower and higher concentration group were fed with water containing NaF(5,50 ms/L).Animals are sacrificed after 6 months of treatment with fluoride and the dissected brains were kept for analysis.The protein levels of ERK1/2 in rat brains were detected by Western-blotting and the mRNA level by RT-PCR. The spatial learning and memorizing ability was measured by Morris water maze test. Results The ERK1/2 protein in control group,lower and higher concentration group was 0.944±0.10,1.253±0.02,1.953±0.07,the differece being statistieally sighificant between any two groups (P ＜ 0.05). The phospho-ERKl/2 protein in control group,lower and higher concentration group was 0.73±0.08,0.77±0.07,1.28±0.11,the differece being statistieally sighificant between any two groups(P ＜ 0.05);the activation rate of phospho-ERK1/2 in lower and higher concentration group [(68.4± 3.8)%,(64.1±3.2)%] was decreased compared to control group[ (82.3±10.7)%],the differece being significant(P ＜ 0.05). In the navigation trial,longer escape latencies of lower concentration group on the second, the third,the fifth and the sixth day were observed[ (46.0±8.0),(24.0±2.7),(8.9±5.3),(7.4±4.1 )s] compared to the control[ (39.3±6.9),(19.1±9.1 ),(8.3±3.4),(4.8±2.7)s],the differece being significant (P ＜ 0.05 or ＜ 0.01 );the similar results were also observed in the higher concentration group[ (36.9±16.8),(37.7±12.9), (19.7±7.6),(12.2±5.7 )s],and the escape latencies of the higher concentration group on the third,the fifth and the sixth day were longer than that in lower concentration group. In the probe test,the rats took more time to reach the first cross in lower and higher concentration group[(1.17±0.75),(4.18±1.10)s] than control group[ (5.89± 0.56 ) s ],the differece being significant (P ＜ 0.05 or ＜ 0.01 ) ;stayed shorter [ ( 17.05±4.25 ),(18.20±4.57 ) s ] than control [(25.37±5.65 )s ] in platform area (P ＜ 0.01 );the activation rates of ERK1/2 were directly correlated with the time taken to reach the first cross platform located in the probe test(r = 0.364,P ＜ 0.05) and the activation rates were also directly correlated with the escape latencies on the sixth day(r = 0.497,P ＜ 0.05). Conclusion Long-term exposure of excessive fluoride induces the change of expression and activating rate of the ERK1/2 in rat brains,leading to the decreased capacity of learning and memory.
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Objective To investigate the changes of oxidative stress level in brain tissues and serum, and learning and memory in rats with oxidative stress level in nerve damage in chronic fluorosis. Methods The rats were randomly divided into 3 groups according to the body weight, eight rats in each group, i.e., control group, drinking water containing less than 0.5 mg/L of fluoride; lower fluoride exposure group, drinking water containing 5 mg/L of fluoride; higher fluoride exposure group, drinking water containing 50 mg/L of fluoride. The animals were examined six months after initiating the experiment. The total antioxidant capacity (T-AOC) and malondialdehyde (MDA), as well as learning and memory, were measured. Results Escape latency in higher fluoride exposed group[ (14.37±3.48)s] was significantly higher than that of controls[ (5.84±1.87)s] and exposed te lower fluoride [ (7.18±1.42)s], the difference being statistically signifieant(P<0.05). As compared with controls[ (2.17±0.11)× 103 U/L , (0.79±0.11)×103 U/g Pr] ,the rats exposed to higher fluoride and lower fluoride exhibited lower levels of T-AOC [(1.37±0.27)×103 U/L,(0.24±0.06)×103 U/g Prand (1.20±0.14) x 103 U/L,(0.41 ~ 0.10)×103 U/g Pr], the difference being statistically signifieant(P<0.05). As compared with controls[ (2.34±0.16) mmoL/L, (2.97±0.11)mmol/g Pr] and low fluoride exposed group[ (2.68±0.33)mmoL/L, (3.38±0.21)mmol/g Pr], higher level of MDA were observed in higher fluoride exposed group[ (3.72±0.59)retool/L, (4.01±0.21)mmol/g Pr], the difference being statistically significant(P<0.05). Conclusion The results indicated that higher amount of fluoride induced an increased level of oxidation, which might result in the decreased capacity of intelligence of rats with fluorosis.
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<p><b>OBJECTIVE</b>To investigate the influence of fluorosis on nicotinic acetylcholine receptors (nAChRs) in protein and gene levels in SH-SY5Y cells and the mechanism of the receptor modification.</p><p><b>METHODS</b>SH-SY5Y cells, a human neuroblastoma cell line, were incubated with different concentrations of fluoride or with antioxidant for 48 hours. The functions of cells were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) method, and protein oxidation detected by carbonyl content; the alpha3 and alpha7 nAChR subunits in protein level were measured by Western blotting and in mRNA level by RT-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>In high-dose group as compared to the control, the decreased MTT (49%), increased protein oxidation (72%), and lower expression of alpha3 (51%) and alpha7 (47%) nAChR subunit proteins were obviously observed in SH-SY5Y cells. There were no changes in expression of nAChR subunit mRNAs between the cells treated with fluoride and those un-treated in controls. Prior treatment with antioxidant resulted in preventing the decrease of nAChR protein in cells exposed to the high doses of fluoride.</p><p><b>CONCLUSION</b>Fluorosis should result in damage of cells and the declined expression of nAChRs in protein levels, but no influences on gene expression of the receptors in human neuroblastoma neurons. The decreased nAChR proteins might be involved in the mechanism of oxidative stress induced by fluorosis.</p>