High Fluoride Group Research Articles

Association between drinking water fluoride and the serum alkaline phosphatase and phosphate levels in pregnant women and newborn infants.

Endemic fluorosis (skeletal and dental) is a serious public health problem in many parts of the world, especially in India. Age, sex, dietary calcium (Ca), the hormonal status, the dose and duration of the fluoride intake, and renal efficiency in handling fluoride all influence fluoride metabolism. The aim of the study was to evaluate the effect of the fluoride present in drinking water on the serum alkaline phosphatase (ALP) and phosphate levels in pregnant women and newborn infants. In the present cross-sectional study, the participants were categorized into 2 groups based on a fluoride concentration in their drinking water: the low/optimum-fluoride group (<1 ppm); and the high-fluoride group (≥1 ppm). Each group was comprised of 90 pregnant women who were recruited from the hospital at the time of admission for delivery. Fluoride was measured in their drinking water, urine, maternal serum, and cord blood. The ALP and phosphate levels were measured in serum using a fully automated analyzer. The drinking water consumed by the pregnant women contained fluoride, which was significantly positively correlated with the urine and blood serum fluoride levels. There were significant differences in the ALP levels between the 2 groups in both maternal serum and cord blood. The level of phosphate in maternal serum was significantly higher in the high-fluoride group. The results of both simple and multivariate regression analyses revealed that the fluoride content in drinking water was significantly associated with the ALP level in cord blood and the phosphate level in maternal serum. The ALP levels were negatively associated with drinking water fluoride concentrations in both maternal serum and cord blood. The phosphate levels in maternal serum were positively associated with drinking water fluoride concentrations.

Do methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 polymorphisms modify changes in intelligence of school-age children in areas of endemic fluorosis?

Background:Excessive exposure to fluoride can reduce intelligence. Methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 (MTHFD1) polymorphisms have important roles in neurodevelopment. However, the association of MTHFD1 polymorphisms with children's intelligence changes in endemic fluorosis areas has been rarely explored.Methods:A cross-sectional study was conducted in four randomly selected primary schools in Tongxu County, Henan Province, from April to May in 2017. A total of 694 children aged 8 to 12 years were included in the study with the recruitment by the cluster sampling method. Urinary fluoride (UF) and urinary creatinine were separately determined using the fluoride ion-selective electrode and creatinine assay kit. Children were classified as the high fluoride group and control group according to the median of urinary creatinine-adjusted urinary fluoride (UFCr) level. Four loci of MTHFD1 were genotyped, and the Combined Raven's Test was used to evaluate children's intelligence quotient (IQ). Generalized linear model and multinomial logistic regression model were performed to analyze the associations between children's UFCr level, MTHFD1 polymorphisms, and intelligence. The general linear model was used to explore the effects of gene-environment and gene-gene interaction on intelligence.Results:In the high fluoride group, children's IQ scores decreased by 2.502 when the UFCr level increased by 1.0 mg/L (β = −2.502, 95% confidence interval [CI]:−4.411, −0.593), and the possibility for having “excellent” intelligence decreased by 46.3% (odds ratio = 0.537, 95% CI: 0.290, 0.994). Children with the GG genotype showed increased IQ scores than those with the AA genotype of rs11627387 locus in the high fluoride group (P < 0.05). Interactions between fluoride exposure and MTHFD1 polymorphisms on intelligence were observed (Pinteraction < 0.05).Conclusion:Our findings suggest that excessive fluoride exposure may have adverse effects on children's intelligence, and changes in children's intelligence may be associated with the interaction between fluoride and MTHFD1 polymorphisms.

Comparison of surface roughness of root cementum and orthodontically induced root resorption craters from high- and low-fluoridation areas: a 3D confocal microscopy study

BackgroundFluoride has a major role in strengthening the structure of enamel against acids. Despite differences between caries and root resorption processes, both events inherently involve acidic dissolution of dental tissues. The aim of the present study was to investigate the effects of water fluoridation levels on the surface roughness of root cementum and resorption craters. The findings provided more insight into the influence of fluoride on the surfaces of intact cementum surface and resorption craters.MethodsTwenty-eight orthodontic patients were recruited from two cities in Turkey, with high (≥ 2 ppm) and low (≤ 0.05 ppm) water fluoridation. These patients needed bilateral maxillary first premolar extraction as part of their orthodontic treatment and were allocated into two study groups (n = 14 in each group) based on water fluoridation exposure level: the high-fluoride group (HF) and low-fluoride group (LF). 150 g of buccal tipping forces was applied to all maxillary first premolar teeth for 12 weeks with a beta-titanium spring which was reactivated every 4 weeks. All maxillary premolars were removed at the end of the experiment for surface roughness assessment using three-dimensional confocal microscopy and the associated software. The buccal root surface and the largest buccal resorption crater were investigated.ResultsResorption craters were significantly rougher in LF group compared to HF group (p = 0.002). Craters were rougher than the intact root surfaces (p = 0.000). Cervical and apical regions were significantly rougher than the middle region (p = 0.000 and p = 0.024, respectively).ConclusionsHigher water fluoridation level of ≥ 2 ppm resulted in significantly smoother root resorption craters than low water fluoridation level of ≤ 0.05 ppm when the teeth were subjected to 150 g of buccal tipping force. Fluoride seems to have a protective role at the interface of root resorption, and further mineral or histological studies may shed light on the exact protective process against root resorption.

Physical properties of root cementum: Part 28. Effects of high and low water fluoridation on orthodontic root resorption: A microcomputed tomography study

Transient inflammatory surface resorption, referred to as orthodontic induced inflammatory root resorption (OIIRR), is an iatrogenic consequence of orthodontic tooth movement. Systemic fluoride has been associated with a reduction of OIIRR. This study aimed to investigate the effects of water fluoridation levels on OIIRR in a clinically applicable human orthodontic model. Twenty-eight patients who required bilateral maxillary first premolar extraction as part of orthodontic treatment were selected from 2 cities with high and low water fluoridation of ≥2 ppm and≤0.05 ppm, respectively. Patients were separated into high fluoride (HF) and low fluoride (LF) groups on the basis of water fluoridation levels. Bilateral maxillary first premolar teeth were subjected to 150 g of buccal tipping forces for 12 weeks with reactivation every 4 weeks. Teeth were extracted at the end of 12 weeks. Root resorption crater volume was determined using microcomputed tomography and 3-dimensional reconstruction. HF group showed significantly less mean root resorption volume on the palatal root surface when compared with the LF group (P= 0.025). This difference was specifically displayed at palatal apical regions (P= 0.041). When root resorption volumes from the zones of orthodontic pressure (buccal cervical, palatal apical) were combined, the mean difference between HF and LF groups was statistically significant (P= 0.045). Findings of the present study indicated a positive correlation between water fluoridation and the reduction of OIIRR, especially at the zones of orthodontic pressure, using a clinically relevant human orthodontic model.

Microscopic observation of the enamel microstructures of SD rats with different degrees of fluorosis

Objective: To establish a dental fluorosis model of SD rats with various degrees, to observe the microstructures of enamel samples under scanning electron microscope and to clarify the changes of enamel microstructures with various degrees of dental fluorosis, so as to provide clinical reference for the treatment of patients with moderate and severe dental fluorosis. Methods: Thirty male SD rats (6 weeks of age) were randomly divided into 3 groups with 10 rats in each group. The control group was fed with deionized water without fluoride, the low fluoride group was fed with 50 mg/L NaF deionized water and the high fluoride group was fed with 100 mg/L NaF deionized water in order to establish the dental fluorosis model of rats. After feeding for 6 weeks, the rats were sacrificed and the mandibular incisor teeth were collected and recorded. The surface and sagittal plane of each tooth were observed by scanning electron microscopy and the enamel thickness was measured. Results: In the control group, the enamel color was brown yellow. Enamel color discoloration occurred both in low-fluoride group and high-fluoride group. The enamel color in low-fluoride group was mostly yellow and white striped while in high-fluoride group was mostly chalky white. Under electronic microscope, the enamel rods were alternately arranged and their structure was clear and plump in the control group. The enamel rods of moderate fluorosis were arranged in a straight orientation like tips of bamboo shoots. The enamel rods of severe fluorosis, however, became thinner and the tips of rods were broken. In the control group, sagittal images of enamel turned out to be a dense outer structure with clear boundaries among the inner. The structure of the middle layer was reticulated showing a clear boundary with middle and outer layers. The structure of enamel rods in the inner layers was arranged vertically and horizontally. In the moderate fluorosis group, the outer layer of the enamel became thinner and the middle layer disappeared although the boundary between the outer and middle layers was still clear. In the inner layer, the vertically arranged enamel rods seemed still clear, however the horizontal enamel rods disappeared. In the severe fluorosis group, the outer layer could not be traced. The middle layer was exposed to the air and the inner enamel rods contracted. The inner layers of the enamel had gradually become thinner with the development of the dental fluorosis. The thicknesses of inner layers in control, moderate and the severe groups were (180.71±7.01), (157.10±11.04) and (121.10±12.56) μm respectively. As for the thicknesses of the full layers in the above mentioned three groups, the same trend was observed. The thicknesses, in order of the severity of dental fluorosis, were (241.54±7.76), (207.42±14.36) and (143.79±14.60) μm. Conclusions: With the development of dental fluorosis, the outer enamel layers became thinner or disappeared and the inner enamel layers became thinner or lost its normal structure as well. It is highly recommended that the resin penetration could be used for the proper treatment of moderate and severe dental fluorosis and the strong bleaching and the micro-grinding should be used cautiously.

Altered miRNA expression profiling in enamel organ of fluoride affected rat embryos

Evidence has shown that miRNAs could play a role in dental fluorosis, but there is no study has investigated the global expression miRNA profiles of fluoride-exposed enamel organ. In this study, we analysed the differentially expressed (DE) miRNAs between fluoride-treated and control enamel organ for the first time and found several candidate miRNAs and signaling pathways worthy of further research. Thirty Wistar rats were randomly distributed into three groups and exposed to drinking water with different fluoride contents for 10 weeks and during the gestation. The three groups were a control group (distilled water), medium fluoride group (75 mg/L NaF), and high fluoride group (150 mg/L NaF). On the embryonic day 19.5, the mandible was dissected for histological analysis, and the enamel organ of the mandibular first molar tooth germ was collected for miRNA sequencing (miRNA-seq) and quantitative real-time PCR analysis (qRT-PCR). Typical dental fluorosis was observed in the incisors of the prepregnant rats. In addition to the disorganized structure of enamel organ cells, 39 DE miRNAs were identified in the fluoride groups compared with the control group, and good agreement between the miRNA-seq data and qRT-PCR data was found. The functional annotation of the target genes of 39 DE miRNAs showed significant enrichment in metabolic process, cell differentiation, calcium signaling pathway, and mitogen-activated protein kinase(MAPK) signaling pathway terms. This study provides a theoretical reference for an extensive understanding of the mechanism of fluorosis and potential valuable miRNAs as therapeutic targets in fluorosis.

Linear regression approach for predicting fluoride concentrations in maternal serum, urine and cord blood of pregnant women consuming fluoride containing drinking water

PurposeThe most common source of fluoride is from drinking water. Research comparing fluoride levels in maternal and cord blood have proved that fluoride crosses the placenta. But these results have not been correlated with the source of fluoride. ObjectiveFirstly, to assess and compare the fluoride concentrations in urine, serum and cord blood of pregnant women consuming low/optimum and high fluoride concentrations in drinking water. Secondly, application of the linear regression analysis model equation for the prediction of fluoride concentration in urine, maternal serum and cord blood of pregnant women. MethodsBased on the fluoride concentration in drinking water the subjects were divided into low/optimum and high fluoride groups. Each group consisted of 90 pregnant women. They were enrolled approximately one month prior to the due date. Fluoride was measured in their drinking water, urine, maternal serum, and cord blood. ResultsThe low/optimum fluoride concentration in drinking water as compared to urine, serum and cord blood correlated significantly (r = 0.458, 0.529, 0.473). The strength of the correlation was found to be high in high fluoride group when compared to low/optimum fluoride group (r = 0.868, 0.943, 0.695). The β values in urine, maternal serum and cord blood in low/optimum group was 0.247, 0.025, 0.017 respectively and in high fluoride group 0.773, 0.080, 0.060 respectively. ConclusionAs the fluoride concentration increases more than 1 ppm in drinking water the transfer of fluoride through urine, maternal serum and cord blood also increases. Linear regression analysis also displayed similar results.

The association of fluoride in drinking water with serum calcium, vitamin D and parathyroid hormone in pregnant women and newborn infants.

Chronic exposure to fluoride in drinking water causes an increase in plasma fluoride levels that is related to a reduction in calcium transport across the renal tubule endoplasmic reticulum and plasma membrane. In the present study, it was hypothesised that varying levels of fluoride present in drinking water are associated with serum levels of calcium and the related hormones vitamin D and parathyroid hormone in pregnant women and newborn infants. This cross-sectional study included two groups based on the fluoride concentration in drinking water. One group was considered low/optimum in which the fluoride concentration in drinking water was <1 ppm, and the other group was considered a high fluoride group with ≥1 ppm fluoride in drinking water. In each group, 90 pregnant women were recruited at the hospital during delivery. The participants were given a questionnaire regarding their medical history, sunshine exposure duration, and supplement use and a food frequency questionnaire (FFQ). Fluoride was measured in drinking water, urine, maternal serum and cord blood. Serum calcium, vitamin D, and parathyroid hormone were measured in a fully automated analyser. In pregnant women, drinking water that contained fluoride was significantly positively correlated with urine and blood serum. Low mean concentrations of vitamin D and deficient (<10 ng/ml) vitamin D were more prevalent among the high fluoride group irrespective of diet, sunshine exposure and supplementation. Serum calcium and parathyroid hormone (PTH) levels were significantly lower in the high fluoride group than in the low/optimum fluoride group in both pregnant mothers' blood and cord blood. Drinking water with high fluoride levels was significantly associated with calcium and the related hormones vitamin D and parathyroid hormone.

Effects and Molecular Mechanism of L-Type Calcium Channel on Fluoride-Induced Kidney Injury

This study aimed to investigate the role and molecular mechanism of L-type calcium channel (LTCC) on fluoride exposure-induced kidney injury. Subchronic and chronic fluoride exposures were included in the experiment. Each part contained 140 ICR male mice. They were randomly divided into 7 groups: control group, high-fluoride group (NaF 30 mg/L), low-fluoride group (NaF 5 mg/L), high/low-fluoride + agonist (FPL64176) group, high/low-fluoride + inhibitor (nifedipine) group. One week before the end of fluoride exposure, each mouse in the fluoride exposure group was injected intraperitoneally with LTCC agonist (FPL64176) or inhibitor (nifedipine) (5 mg/kg day). The apoptosis of kidney cell was observed by TUNEL, and the protein expression levels of Cav1.2 and CaM, CaMKII, Bcl-2, and Bax were detected by Western blot. Compared with the control group, the protein expression levels of Cav1.2, CaM, and Bax significantly increased, and those of CaMKII and Bcl-2 significantly decreased, the ratio of Bax/Bcl-2 also significantly increased, and the number of apoptotic kidney cells significantly increased in the high/low-fluoride group and in the high/low-fluoride + agonist group. The above indicators and fluoride exposure concentrationsshowed in time- and dose-dependent changes. Compared with the high/low-fluoride + agonist group, the protein expression level of the molecular in the kidney cellsabove mentioned was significantly opposite and the number of apoptotic kidney cells significantly decreased in the high/low-fluoride + inhibitor group. In conclusion, LTCC mediates the kidney injury induced by fluoride exposure in mice. Fluoride exposure induced abnormal expression of the Cav1.2 protein, Ca2+ signal transduction pathway, and apoptosis-regulated proteins, which is one of the molecular mechanisms. Nifedipine may be a new and effective anti-fluoride drug.

Regulation of osteoblast behaviors via cross-talk between Hippo/YAP and MAPK signaling pathway under fluoride exposure.

Titanium is widely used in implant materials, while excessive fluoride may have negative effects on the osseointegration between the titanium and osteoblasts. Although the underlying mechanisms are still not clear, the mitogen-activated protein kinase (MAPK) or Yes-associated protein (YAP) signaling pathways are thought to be involved. This study evaluated the role of Hippo/YAP and MAPK signaling pathway in osteoblast behaviors under excessive fluoride exposure in vitro and in vivo. Commercially pure Ti (cp-Ti) samples were exposed to fluoride (0, 0.1, and 1.0mM NaF) for 7days. Cell adhesion was observed using a laser scanning confocal microscope. Cell viability and apoptosis were evaluated by CCK-8 assay and flow cytometry, respectively. The expressions of osteoblast markers and key molecules in MAPK and YAP pathway were detected by Western blot. In vivo studies were evaluated by histology methods in C57/BL6 mice model. Our results showed that 1.0mM NaF destroyed the passivation film on cp-Ti surface, which further inhibited the osteoblast adhesion and spreading. Meanwhile, compared to other groups, 1.0mM NaF led to a remarkable reduction in cell viability (P < 0.05), as well as increased apoptosis (P < 0.05) and downregulation of osteogenesis protein expression (P < 0.05). MAPK and YAP signaling pathways were also activated under 1.0mM NaF exposure, and JNK seemed to regulate YAP phosphorylation in response to NaF impacts on osteoblasts. In vivo fluorosis mouse model further indicated that 100ppm NaF group (high fluoride group) increased bone resorption and inhibited the nuclear translocation of YAP. The osteoblast behaviors were negatively altered under excessive fluoride, and MAPK/JNK axis contributed to YAP signaling activation in regulating NaF-induced osteoblast behaviors. KEY MESSAGES: • Excessive fluoride inhibited osteoblast behaviors and bone formation. • YAP and MAPK signaling pathways were activated in osteoblasts under fluoride exposure. • Fluoride regulated osteoblast behaviors via the cross-talk between YAP and MAPK.

Comparative Transcriptomics Reveals the Role of the Toll-Like Receptor Signaling Pathway in Fluoride-Induced Cardiotoxicity.

Many studies have shown that fluorosis due to long-term fluoride intake has damaging effects on the heart. However, the mechanisms underlying cardiac fluorosis have not been illuminated in detail. We performed high-throughput transcriptome sequencing (RNA-Seq) on rat cardiac tissue to explore the molecular effects of NaF exposure. In total, 372 and 254 differentially expressed genes (DEGs) were identified between a group given 30 mg/L NaF and control and between a group given 90 mg/L NaF and control, respectively. The transcript levels of most of these genes were significantly down-regulated and many were distributed in the Toll-like receptor signaling pathway. Transcriptome analysis revealed that herpes simplex infection, ECM-receptor interaction, influenza A, cytokine-cytokine receptor interaction, apoptosis, and Toll-like receptor signaling pathway were significantly affected. IL-6 and IL-10 may play a crucial role in the cardiac damage caused by NaF as external stimuli according to protein-protein interaction (PPI) network analysis. The results of qRT-PCR and Western blotting showed a marked decreased mRNA and protein levels of IL-1, IL-6, and IL-10 in the low concentration fluoride (LF) and high concentration fluoride (HF) groups, which was in agreement with RNA-Seq results. This is the first study to investigate NaF-induced cardiotoxicity at a transcriptome level.

Matrix metalloproteinase-9 and p53 involved in chronic fluorosis induced blood-brain barrier damage and neurocyte changes.

IntroductionA large number of basic and clinical studies have confirmed that fluoride produces toxic effects on multiple organ systems in the body including the nervous system.Material and methodsOne hundred twenty Wistar rats were randomly divided into 4 groups with 30 in each group: a high fluoride group (drinking 200 mg/l fluoridated water, 24 weeks); a high fluoride control group (drinking distilled water, 24 weeks); a fluoride removal group (drinking fluoridated water, 12 W; then distilled water, 12 W) and a defluorination control group (drinking distilled water, 24 weeks).ResultsThe high fluoride and fluoride removal groups had spinal cord astrocyte edema. The apoptosis rate of spinal nerve cells in the high fluoride group and fluoride removal group were significantly higher (p < 0.01) than in the fluoride control and defluorination control group. The Evans blue (EB) content, matrix metalloproteinase-9 (MMP-9) and p53 expression in the high fluoride group and fluoride removal group were higher (p < 0.01) than in the fluoride control and defluorination control group.ConclusionsThe apoptosis of spinal cord nerve cells is obviously higher in rats with chronic fluoride exposure. Chronic fluoride exposure leads to high expression of MMP-9, and results in increased damage of the blood-spinal cord barrier. Increased p53 may be one of the factors causing damage. Short-term removal of fluoride has no obvious recovery in apoptosis of spinal cord nerve cells; highly expressed MMP-9 and p53 may be one of the reasons for unrecovered function.

Effects of drinking water fluorosis on L-type calcium channel of hippocampal neurons in mice

The study aimed to investigate the effects of drinking water fluorosis on L-type calcium channels (LTCCs) in mouse hippocampal neurons. A total of 60 newly weaned ICR male mice were randomly divided into control, low fluoride and high fluoride groups. After 3 and 6 months of exposure to fluoride, the patch clamp technique was used to detect the peak and relative values (I/Imax), steady-state activation curve ratio (G/Gmax), decay time constant, and tail current time constant of LTCCs currents in hippocampal CA1 region of mouse brain slices. Fluoride greatly reduced the serum and urinary calcium concentrations in mice, and the chronic fluorosis has a greater impact than subchronic fluorosis. The peak value of LTCCs current in pyramidal neurons of hippocampal CA1 area was significant and increased with the prolonged exposure time. The relative values of current and steady-state coefficients were changed greatly. The decay and tail current time increased significantly. High fluorine concentration indicates great peak value and open time of LTCCs opening. LTCCs are sensitive to fluoride exposure. The activation voltage of calcium channels induced by fluoride exposure is decreased, the opening time of calcium channels is prolonged, and the calcium influx per unit time increased, thereby overloading calcium concentration in neurons and this may be an explanation for intracellular calcium overload caused by fluoride. The imbalance of calcium metabolism caused by fluorosis may be a pathogenesis of brain injury induced by fluoride. Furthermore, the risk of brain damage from low-fluorine exposure cannot be ignored.

Effects of endoplasmic reticulum stress-induced apoptosis in thyroid injury caused by fluoride in rat

Objective: To explore the effects of endoplasmic reticulum stress-induced apoptosis in thyroid injury of rats caused by excessive fluoride intake. Methods: All 40 Wistar rats were randomly divided into four groups, control group, low fluoride group, medium fluoride group and high fluoride group. The rats in control group were fed with tap water (fluoride concentration=0.344 mg/L) and the experimental rats were fed with the water contaminated fluoride with the dose of 5, 10 and 20 mg/L. 10 rats (female: male=1∶1) in each group were sacrificed after 8 months of exposure through drinking water. The contents of urine fluoride were detected by fluorine ion selective electrode method. Morphology of thyroid was observed through light microscope and apoptosis in thyroid were detected by the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. The mRNA and protein expressions of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were analyzed by RT-PCR and immunohistochemistry respectively, and results were compared among groups. Results: The contents of urine fluoride in all fluoride treated groups were separately (4.74±1.88), (7.70±2.82) and (10.50±2.92) mg/L, which were gradually higher than that of control group (2.23±0.54) mg/L (P<0.05). Morphological changes were found in thyroid tissues of fluoride treated groups, thyroid follicular hyperplasia or even no cavity cell clusters were observed. Apoptosis in thyroid were notably increased in fluoride treated groups. The mRNA expression levels of GRP78 in all fluoride treated groups were separately 1.30±0.42, 1.39±0.29 and 1.50±0.27, which were significantly higher than that of control group (0.93±0.24) (P<0.05). And the mRNA expression levels of CHOP in medium and high fluoride groups were separately 1.17±0.29 and 1.30±0.26, which were significantly higher than that of control group (0.91±0.20) (P<0.05). The protein expression levels of GRP78 and CHOP in medium and high fluoride groups were respectively 29.68±4.04, 29.90±3.74 and 4.05±1.62, 4.44±1.81, which were significantly higher than those in the control group (separately 23.80±6.36, 2.27±0.89) (P<0.05). Conclusion: Excessive-fluoride intake can induce thyroid injury, and endoplasmic reticulum stress-induced apoptosis might be involved in the injury.

Fluoride-induced alterations of synapse-related proteins in the cerebral cortex of ICR offspring mouse brain

Fluoride (F) exposure causes cognitive dysfunction in humans and animals. However, the precise molecular mechanisms by which fluoride exerts its neurotoxic effects are poorly understood. In this study, an animal model of fluoride exposure was created by providing ICR mice were treated with vehicle F at a dose of 0 (control group), 50 (low-fluoride group) or 100 mg/L (high-fluoride group) in water for one month. After the mice mated, parents and offspring were treated and maintained under these conditions. The cognitive abilities of the mice were examined using a Morris water maze test. Results indicated that fluoride exposure significantly prolonged the escape latency period and decreased the number of crossings in a particular zone. Histopathologic analysis revealed the shrinkage and fragmentation of glial cells in the fluoride-treated groups. Pyramidal cells in the cerebral cortices of fluoride-treated groups were fewer than those of the control group. The expression of microtubule-associated protein 2 (MAP2) and synaptic proteins of the cerebral cortex in mouse offspring was assayed using RT-PCR and Western blot. Fluoride exposure possibly induced a significantly decreased expression of MAP2, synaptophysin (SYP) and developmentally regulated brain protein (Dbn) at protein and mRNA levels. Glutamate receptor (N-methyl-d-aspartate receptor, NMDAR) was also expressed, and this finding was consistent with the reduced MAP2, SYP and Dbn expression. Therefore, fluoride-mediated reduction in cognitive dysfunction is likely caused by the disruption of the expression of these synapse-associated proteins, resulting in attenuated neuronal functioning.

Fluoride-associated ultrastructural changes and apoptosis in human renal tubule: a pilot study.

The susceptibility of the kidneys to fluoride toxicity can largely be attributed to its anatomy and function. As the filtrate moves along the complex tubular structure of each nephron, it is concentrated in the proximal and distal tubules and collecting duct. It has been frequently observed that the children suffering from renal impairments also have some symptoms of dental and skeletal fluorosis. The findings suggest that fluoride somehow interferes with renal anatomy and physiology, which may lead to renal pathogenesis. The aim of this study was to evaluate the fluoride-associated nephrotoxicity. A total of 156 patients with childhood nephrotic syndrome were screened and it was observed that 32 of them had significantly high levels ( p ≤ 0.05) of fluoride in urine (4.01 ± 1.83 ppm) and serum (0.1 ± 0.013 ppm). On the basis of urinary fluoride concentration, patients were divided into two groups, namely group 1 (G-1) ( n = 32) containing normal urine fluoride (0.61 ± 0.17 ppm) and group 2 (G-2) ( n = 32) having high urine fluoride concentration (4.01 ± 1.83 ppm). Age-matched healthy subjects ( n = 33) having normal levels of urinary fluoride (0.56 ± 0.15 ppm) were included in the study as control (group 0 (G-0)). Kidney biopsies were taken from G-1 and G-2 only, who were subjected to ultrastructural (transmission electron microscopy) and apoptotic (terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling) analysis. Various subcellular ultrastructural changes including nuclear disintegration, chromosome condensation, cytoplasmic ground substance lysis, and endoplasmic reticulum blebbing were observed. Increased levels of apoptosis were observed in high fluoride group (G-2) compared to normal fluoride group (G-1). Various degrees of fluoride-associated damages to the architecture of tubular epithelia, such as cell swelling and lysis, cytoplasmic vacuolation, nuclear condensation, apoptosis, and necrosis, were observed.

A comparative study of dental fluorosis and non-skeletal manifestations of fluorosis in areas with different water fluoride concentrations in rural Kolar.

Background:Fluorosis is an endemic disease which results due to excess exposure to high fluoride from different sources. The climatic factors and dependency on ground water add to the risk of fluorosis in Kolar. In addition to it, the epidemiological studies conducted on fluorosis in Kolar are very few.Aims:(1) To estimate age-specific prevalence of dental fluorosis in the study population. (2) To determine the proportion of study subjects with non-skeletal manifestations of fluorosis (3) To assess and compare the influence of various socio-epidemiological factors in the occurrence of dental fluorosis among the study population in areas with high and normal fluoride.Methodology:A cross-sectional study was conducted among the residents of three randomly selected villages, Thimmasandra and Batwarahalli (high fluoride) and Maddinayakanahalli (normal fluoride) belonging to Bangarpet taluk, Kolar for 1 year. Dental fluorosis was assessed by the Dean's grading. Non-skeletal manifestations were elicited based on clinical features. Fluoride levels of drinking water sources were estimated by ion-electrode method. The Chi-square and Fisher's exact tests were used to see the difference in proportions and a P value of <0.05 was considered for statistical significance.Results:The prevalence of dental and non-skeletal fluorosis in the study groups with high and normal fluoride groups were 13.17%, 5.5%, 3.84%, 1.9%, respectively. The prevalence of dental fluorosis was significantly higher among the children and adolescents compared to adults (P < 0.05).Conclusion:Dental fluorosis is a public health problem mainly affecting children and adolescents in Bangarpet.

Effects of fluoride on synapse morphology and myelin damage in mouse hippocampus

To investigate the fluoride-induced neurotoxicity on mice hippocampus, healthy adult mice were exposed to 25, 50, and 100 mg NaF/L for 60 days. The results showed that medium and high fluoride administration induced ultrastructural alterations in the structure of neuron synapse, including indistinct and short synaptic cleft, and thickened postsynaptic density (PSD). The significant reduced mRNA expressions of proteolipid protein (PLP) in medium and high fluoride groups suggested that myelin damage occurred in hippocampus. The myelin damage in turn was determined by the increased myelin-associated glycoprotein (MAG) level, which is naturally released by injured myelin, in high fluoride group, compared to the medium fluoride group. In addition, high fluoride exposure also reduced the mRNA and protein levels of cAMP response element-binding protein (CREB), brain-derived neurotrophic factor (BDNF), and neural cell adhesion molecule (NCAM). These findings suggested that the alteration in synaptic structure and myelin damage may partly be due to adverse effects of fluoride on the neurotrophy and neuron adhesion in mice hippocampus.

Fluoride Depletes Acidogenic Taxa in Oral but Not Gut Microbial Communities in Mice.

Fluoridation of drinking water and dental products prevents dental caries primarily by inhibiting energy harvest in oral cariogenic bacteria (such as Streptococcus mutans and Streptococcus sanguinis), thus leading to their depletion. However, the extent to which oral and gut microbial communities are affected by host fluoride exposure has been underexplored. In this study, we modeled human fluoride exposures to municipal water and dental products by treating mice with low or high levels of fluoride over a 12-week period. We then used 16S rRNA gene amplicon and shotgun metagenomic sequencing to assess fluoride's effects on oral and gut microbiome composition and function. In both the low- and high-fluoride groups, several operational taxonomic units (OTUs) belonging to acidogenic bacterial genera (such as Parabacteroides, Bacteroides, and Bilophila) were depleted in the oral community. In addition, fluoride-associated changes in oral community composition resulted in depletion of gene families involved in central carbon metabolism and energy harvest (2-oxoglutarate ferredoxin oxidoreductase, succinate dehydrogenase, and the glyoxylate cycle). In contrast, fluoride treatment did not induce a significant shift in gut microbial community composition or function in our mouse model, possibly due to absorption in the upper gastrointestinal tract. Fluoride-associated perturbations thus appeared to have a selective effect on the composition of the oral but not gut microbial community in mice. Future studies will be necessary to understand possible implications of fluoride exposure for the human microbiome. IMPORTANCE Fluoride has been added to drinking water and dental products since the 1950s. The beneficial effects of fluoride on oral health are due to its ability to inhibit the growth of bacteria that cause dental caries. Despite widespread human consumption of fluoride, there have been only two studies of humans that considered the effect of fluoride on human-associated microbial communities, which are increasingly understood to play important roles in health and disease. Notably, neither of these studies included a true cross-sectional control lacking fluoride exposure, as study subjects continued baseline fluoride treatment in their daily dental hygiene routines. To our knowledge, this work (in mice) is the first controlled study to assess the independent effects of fluoride exposure on the oral and gut microbial communities. Investigating how fluoride interacts with host-associated microbial communities in this controlled setting represents an effort toward understanding how common environmental exposures may potentially influence health.

The Effect of Chronic Fluorosis on Calcium Ions and CaMKIIα, and c-fos Expression in the Rat Hippocampus.

This study investigated neurotoxicity of chronic fluorosis in the rat hippocampus. Newly weaning, male, Sprague-Dawley (SD) rats were administered 15, 30, and 60mg/L sodium fluoride (NaF) solution (fluorine ion concentration 8.25, 16.50, and 33.00mg/L, respectively), and tap water, for 18months. The neurotoxicological mechanism was examined with a focus on intracellular calcium overload. Results showed that as the fluoride concentration increased, calcium ion concentration [Ca2+], the expression of calcium/calmodulin-dependent protein kinase II α (CaMKIIα), and the expression of catus proto-oncogene protein c-fos (c-fos) all tend to increase. Compared to the control group, Ca2+, CaMKIIα, and c-fos significantly increased (P<0.05) in the moderate-fluoride and the high-fluoride groups. These results indicate that Ca2+/CaMKIIα/c-fos channel signal may be the molecular mechanism of central nervous system damage caused by chronic fluoride intoxication. Moreover, elevated Ca2+ concentration in the hippocampus may be the initiating factor of neuronal apoptosis induced by fluoride.