Aged ; Aged, 80 and over ; Alzheimer Disease ; metabolism ; pathology ; Brain ; metabolism ; Dentate Gyrus ; metabolism ; Dynamin I ; metabolism ; Hippocampus ; metabolism ; Humans ; Monomeric Clathrin Assembly Proteins ; metabolism ; Neuropil ; metabolism ; Synaptophysin ; metabolism

Objective To observe the learning and memory changes in coal-burning type of fluorosis rats, detect the expressions of neuronal nicotinic acetylcholine receptor(nAChR) at mRNA and protein levels in rat brains and to reveal the mechanism of changed learning and memory ability. Methods Twenty-four healthy SD rats, weighting 100 - 120 g, were randomly divided into three groups(8 in each). Control group was fed with normal diet, and low- and high-dose fluoride groups were fed with corn polluted with high fluoride (fluoride were 11.30,104.20 mg/kg, respectively) during drying processes with local burning-coal from the areas of endemic fluorosis to established rat model of chronic fluorosis. After exposed to fluoride for 6 months, behavioral changes were measured by Morris water maze. Animals were sacrificed, the brain was taken, after homogenizing the fluoride content of brain tissue was determined by fluoride ion selective electrode. The α3, α4 and α7 nAChR subunits at mRNA and protein levels were analyzed by real-time PCR and Western blotting, respectively. Results For rats in low- and high-fluoride groups, the escape latency time[(12.42 ± 8.03),(17.48 ± 8.05)s] was significantly longer than that in the control[(7.04 ± 3.29)s, all P< 0.05]. For rats in high-fluoride group, the numbers of crossing the platforms (1.62 ± 0.87) and the time of staying at the platforms[(16.70 ± 5.02)s] were significantly decreased as compared to that of control[3.53 ± 1.67, (23.33 ± 5.35)s, all P < 0.05]. The fluoride content in rat brain tissue in low- or high-fluoride groups [(1.14 ± 0.04), (1.79 ± 0.04)mg/kg] was significantly higher than that of control [ (0.52 ± 0.05) mg/kg, all P < 0.05]; in addition, the amount of fluoride in brain tissue of high-fluoride group was significantly higher than that of low-fluoride group(P < 0.05). In high-fluoride group, the mRNA expressions of α3, α4 and α7 nAChR subunits in rat brains(1.51 ± 0.20,1.45 ± 0.06,1.63 ± 0.08) were significantly lower as compared to controls (1.79 ± 0.11,1.66 ± 0.14,1.83 ± 0.06, all P< 0.05); whereas there were no significant changes in mRNA levels of these receptor subunits of the rat brains between low-fluoride group(1.65 ± 0.17,1.59 ± 0.09,1.71 ± 0.03) and controls (all P > 0.05). Furthermore, the protein levels of α3, α4 and α7 nAChR subunits in rat brains of highfluoride group(0.58 ± 0.13,0.16 ± 0.03,1.41 ± 0.38) and low-fluoride group(0.56 ± 0.23,0.08 ± 0.02,0.51 ± 0.16) were significantly lower than those of controls( 1.48 ± 0.42,0.57 ± 0.21,2.56 ± 0.26, P<0.05 or < 0.01). Conclusions Decreased ability of learning and memory in coal-burning type of fluorosis rats may be associated with declined expressions of nAChR at proteins and mRNA levels, which might be the main mechanism of the behavior change.

Objective To investigate the effect of fluoride on the expression of a subunit of calcium/calmodulin-dependent protein kinase- Ⅱ (α-CaMK Ⅱ ) at both mRNA and protein levels in human neuroblastoma cells were cultured in DMEM with final concentrations of NaF 0(control) ,0.05,0.50,2.00,5.00 mmol/L, respectively, for 48 hours. Then quantitative RT-PCR and Western blot were performed to detect the expression level of α-CaMK Ⅱ P1 (postnatal day 1) pups together with their mothers were randomly divided into three groups. Lactating rats were given drinking water containing NaF at concentrations 0(control) ,2,3 mmol/L. And pups were exposed to NaF through milk. In each group, 8 pups were sacrificed on day 14 after birth. In post-weaning period, another 8 pups in each group were given drinking water with the same dose of fluoride as their mother's 21 day after birth. After then, these pups were killed on day 28, and hippocampus was dissected immediately and Western blot was conducted mRNA and protein levels were decreased. When NaF concentrations were 0,0.05,0.50,2.00,5.00 mmol/L, the mRNA relative ratios of α-CaMKⅡ in SY5Y cells were 1.00 ± 0.00,0.77 ± 0.18,0.40 ± 0.11,0.22 ± 0.06 and 0.15 ± 0.03, and protein levels of α-CaMK Ⅱ were 100.00 ± 0.00,76.17 ± 2.08,59.16 ± 2.12,48.52 ± 2.71 and 43.51 ± 2.57, any mmol/L group, hippocampus α-CaMK Ⅱ protein levels on day 14 and 28(75.02 ± 2.88,73.83 ± 3.88 and 81.00 ± 2.54,45.70 ± 2.34) were significantly lower than that of control groups(100.00 ± 0.00,100.00 ± 0.00, all P < 0.01). In 3 mmol/L group, hippocampus α-CaMKⅡ protein level on day 28 was lower than that of 2 mmol/L group (P < 0.01). Conclusion Fluoride can decrease mRNA and protein levels of α-CaMK Ⅱ in nerve cells and hippocampus, which may be one of the mechanisms of learning and memory impairment by fluorosis.

Objective To investigate expression of glutathione S-transferase(GST) mRNA in peripheral blood of the population in coal-burning fluorosis area and to evaluate the effect of comprehensive control intervention. Methods Fifty samples of peripheral blood from patients in the coal-buring fluorosis area in Bijie county of Guizhou province were selected as fluorasis group and 50 samples of peripheral blood from patients in area with comprehensive management were selected as intervention group, respectively. Fifty samples from non-endemic fluorosis area were selected as the control group. Total RNA from blood was extracted and purified by the Trizol- Phenol-Chloroform one-step method. Expression of GST mRNA was detected by using SYBR Green I real-time fluorescence quantitative PCR. Results The data of GST mRNA in fluorosis group, intervention group and control group was 38.28±27.22,70.56±37.23 and 103.46 ± 46.62, respectively. There was a significant difference between the groups(F = 3.75, P < 0.05). Decreased expression of GST mRNA in fluorosis group and intervention group as compare to control was detected(all P < 0.05), and the expression of GST mRNA in intervention group was higher than that in fluorosis group(P < 0.05). Conclusion Coal-burning fluorosis possibly led to the decreased expression of GST mRNA in peripheral blood, and comprehensive control maybe prevent the decreased expression of GST in mRNA level.

Alzheimer Disease ; genetics ; metabolism ; therapy ; Humans ; tau Proteins ; genetics ; metabolism

Objective To investigate the expressions of receptor for advanced glycation endproducts (RAGE) and nuclear factor κB(NF-κB) in brain hippocampus of rat with chronic fluorosis,and to reveal the mechanism of brain damage resulted from chronic fluorosis.Methods Sixty clean grade SD rats were randomly divided to three groups(20 rats in each group,10 female and 10 male) fed with different contents of fluoride,control group with normal tap-water(＜ 0.5 mg/L fluoride),small dosage of fluoride exposure group(10 mg/L fluoride in tap-water) and large dosage of fluoride exposure group(50 mg/L fluoride) for six months.Then the rats were killed by femoral artery bleeding and hippocampus was removed.Protein and mRNA levels of RAGE and NF-κB in the hippocampus were determined by Western blotting and quantitative real time PCR,respectively.Results As compared to the control groups[(100.00 ± 2.60)％,(100.00 ± 7.80)％],the expressions of RAGE and NF-κB at protein level in the hippocampus were significantly increased in the small dosage of fluoride exposure groups [(205.00 ± 15.30)％,(156.00 ± 12.20)％] and the large dosage of fluoride exposure groups[(232.00 ± 10.90)％,(162.00 ± 9.80)％,all P ＜ 0.05]; for the mRNA level of RAGE and NF-κB,the expressions were higher in the small dosage of fluoride exposure groups(1.27 ± 0.09,0.83 ± 0.15) and the large dosage of fluoride exposure groups (2.60 ± 0.19,1.27 ± 0.19) than those of the control groups(0.66 ± 0.18,0.32 ± 0.08,all P＜ 0.05).Conclusions The increased expressions of RAGE and NF-κB in the hippocampus of rat brain are caused by chronic fluorosis,and these changes may be associated with the mechanism of nerve injury.

Objective Aim of the study is to investigate the expression of syndecan-4 and nuclear factor κB(NF-κB) in the kidney of rat with chronic fluorosis,and to reveal the mechanism of kidney damage resulted from the toxicity of excessive amount of fluoride.Methods According to body mass and sex,sixty SD rats were randomly divided to three groups according to body mass and fed with different contents of fluoride:control group with normal tap-water(＜ 0.5 mg/L fluoride),small dosage of fluoride exposure group (adding 10 mg/L fluoride in tap-water) and large dosage of fluoride exposure group (50 mg/L fluoride) for six months.The protein level of syndecan-4 and NF-κB in the kidney was detected by Western blotting and syndecan-4 mRNA level by quantitative real time PCR.Results As compared to the control group[(100.0 + 8.1)％],the expression of syndecan-4 at protein level in the kidney of rat was significantly increased in the small dosage of fluoride exposure group [(198.5 + 5.6)％,P ＜ 0.05] and large dosage of fluoride exposure group [(209.2 + 13.0)％,P ＜ 0.05]; the protein levels of NF-κB in the small dosage of fluoride exposure group[(284.4 + 11.1)％,P ＜ 0.05] and in the large dosage of fluoride exposure group[(343.2 + 2.9)％,P ＜ 0.05] were significantly increased than that of the control group[(100.0 ± 10.7)％].The mRNA levels of syndecan-4 in the kidney in the small dosage of fluoride exposure group and large dosage of fluoride exposure group(0.431 + 0.058 and 0.453 ± 0.065,both P ＜ 0.05,respectively) were significantly increased than that of the control(0.128 + 0.026).Conclusions The increased expression of NF-κB in the kidney is induced by increased expression of syndecan-4,which may be involved in kidney damage of chronic fluorosis.

Objective To investigate the expression of c-Jun-N-terminal kinase(JNK) in rat brains with chronic fluorosis and try to reveal the molecular mechanism for the neural impairment induced by the disease.Methods The rats were randomly divided into 3 groups, normal control group(drinking water containing less than 0.5 mg/L of sodium fluoride, NaF), lower fluoride exposed group(drinking water containing 5 mg/L NaF) and higher fluoride exposed group(drinking water containing 50 mg/L NaF), 24 in every group. The rats were examined at the sixth month after feeding. The concentration of fluorine in urine and blood was detected by F-ion selective electrode. The expression of JNK in brains was investigated by using Western blotting and immunohitochemistry staining, and analyze the correlation between activating of JNK and the concentration of fluorine in blood. Results The increased concentration of fluorine in urine(control: 0.92 ± 0.30, lower fluoride exposed group: 2.56 ± 0.91,higher fluoride exposed group: 5.73 ± 3.14, P ＜ 0.05) were observed when 6 months after the beginning of the experiment, and the amount of fluorine in blood was also higher in rats with fluorosis(control: 0.12 ± 0.07, lower fluoride exposed group: 0.36 ± 0.14, higher fluoride exposed group: 0.50 ± 0.18, P ＜ 0.05). The expression of phospho-JNK at protein levels were higher in the brains of rats with fluorosis than that of controls (control: 1.00 ± 0.37, lower fluoride exposed group: 1.20 ± 0.28, higher fluoride exposed group: 1.74 ± 0.69, P ＜ 0.05), whereas no change of total-JNK was found(F = 0.046, P ＞ 0.05). Furthermore, the expression of phospho-JNK in the parietal cortex(119.3 ± 14.1), occipital cortex(112.7 ± 5.4), hippocampus CA3(100.6 ± 8.9), dorsal thalamus (117.8 ± 10.4) and olivary nucleus( 112.6 ± 5.9) of rats in higher fluoride exposed group were higher than that in control( 104.1 ± 8.9,106.6 ± 9.6,106.6 ± 9.7,108.9 ± 6.4,100.3 ± 8.4, all P ＜ 0.05) and lower fluoride exposed group(96.7 ± 17.1,102.5 ± 8.3,106.4 ± 6.5,110.2 ± 9.3,102.4 ± 4.7,102.5 ± 9.8, all P＜ 0.05). The positive stained neurons of total-JNK also distributed in the same brain regions of rats, but no difference was detected between the rats with fluorosis and controls(all P ＞ 0.05). The increased level of phospho-JNK was positively correlated with the fluoride contents in blood of the rats with fluorosis (r = 0.677). Conclusions The expression of phospho-JNK in brains of rats with fluorosis was significantly increased with a correlation to fluoride content in blood, which might be connected to the mechanism of neural impairment induced by chronic fluorosis.

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.

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.