The cholinergic system, intelligence, and dental fluorosis in school-aged children with low-to-moderate fluoride exposure.

Disruption of cholinergic neurotransmission can affect cognition, but little is known about whether low-to-moderate fluoride exposure affects cholinergic system and its effect on the prevalence of dental fluorosis (DF) and intelligence quotient (IQ). A cross-sectional study was conducted to explore the associations of moderate fluoride exposure and cholinergic system in relation to children's DF and IQ. We recruited 709 resident children in Tianjin, China. Ion selective electrode method was used to detect fluoride concentrations in water and urine. Cholinergic system was assessed by the detection of choline acetyltransferase (ChAT), acetylcholinesterase (AChE) and acetylcholine (ACh) levels in serum. Compared with children in the first quartile, those in fourth quartile the risk of either developing DF or IQ < 120 increased by 19% and 20% for water and urinary fluoride. The risk of having both increased by 58% and 62% in third and fourth quartile for water fluoride, 52% and 65% for urinary fluoride. Water fluoride concentrations were positively associated with AChE and negatively associated with ChAT and ACh, trends were same for urinary fluoride except for ACh. The risk of either developing DF or having non-high intelligence rose by 22% (95%CI: 1.07%, 1.38%) for the fourth quartile than those in the first quartile of AChE, for having the both, the risk was 1.27 (95%CI: 1.07, 1.50), 1.37 (95%CI: 1.17, 1.62) and 1.44 (95%CI: 1.23, 1.68) in second, third and fourth quartiles. The mediation proportion by AChE between water fluoride and either developing DF or IQ < 120 was 15.7%. For both to exist, the proportion was 6.7% and 7.2% for water and urinary fluoride. Our findings suggest low-to-moderate fluoride exposure was associated with dysfunction of cholinergic system for children. AChE may partly mediate the prevalence of DF and lower probability of having superior and above intelligence.

Spirally deformable soft actuators and their designable helical actuations based on a highly oriented carbon nanotube film.

Spiral configurations and helical curlings of plant tendrils and seed pods are very common in nature. Many researchers have tried to develop spirally deformable actuators to mimic these natural spirals through several approaches, such as preforming helical shapes, processing diagonal stripes and employing anisotropic organic layers. However, these methods are usually complex and time-consuming. Here, we used an efficient method to produce a highly oriented carbon nanotube (CNT) film and develop a series of spirally deformable soft actuators which perform various controllable helical actuations. The actuator consists of a CNT layer with strong anisotropy and a silicone layer. By simply adjusting the orientations of the aligned CNTs, the prepared actuators can accomplish left- or right-handed spiral deformations with different helical forms when driven by electricity. Finite element analyses and simulations were conducted to investigate the mechanism. It is confirmed that it is the anisotropic moduli of the CNT film that regulate the internal stress distributions of the actuators and lead to helical actuations. Moreover, complex actuator designs and functional applications were also carried out. A V-shaped actuator can simultaneously achieve left- and right-handed curling with large angles (630°), which vividly imitates the spiral winding of a tendril. A Y-shaped actuator performed three-dimensional movements, which can manipulate lightweight objects deftly. By virtue of easy preparation and flexible function design, the spirally deformable actuators based on the oriented CNT film will be very promising in artificial muscles and bionic soft robots.

Roles of mitochondrial fission inhibition in developmental fluoride neurotoxicity: mechanisms of action in vitro and associations with cognition in rats and children.

Fluoride neurotoxicity is associated with mitochondrial disruption. Mitochondrial fission/fusion dynamics is crucial to maintain functional mitochondria, yet little is known about how fluoride perturbs this dynamics and whether such perturbation contributes to impaired neurodevelopment. Here in human neuroblastoma SH-SY5Y cells treated with sodium fluoride (NaF, 20, 40 and 60 mg/L), mitochondrial fission suppression exerted a central role in NaF-induced mitochondrial abnormalities and the resulting autophagy deficiency, apoptosis augmentation, and compromised neuronal survival. Mechanically, pharmacological inhibition of mitochondrial fission exacerbated NaF-induced mitochondrial defects and cell death through promoting apoptosis despite partial autophagy restoration. Conversely, genetic enhancement of mitochondrial fission alleviated NaF-produced detrimental mitochondrial and cellular outcomes by elevating autophagy and inhibiting apoptosis. Further suppressing autophagy was harmful, while blocking apoptosis was beneficial for cellular survival in this context. Consistently, using Sprague-Dawley rats developmentally exposed to NaF (10, 50, and 100 mg/L) from pre-pregnancy until 2 months of delivery to mimic human exposure, we showed that perinatal exposure to environmentally relevant levels of fluoride caused learning and memory impairments, accompanied by hippocampal mitochondrial morphological alterations manifested as fission suppression and fusion acceleration, along with defective autophagy, excessive apoptosis and neuronal loss. Intriguingly, the disturbed circulating levels of identified mitochondrial fission/fusion molecules were closely associated with intellectual loss in children under long-term environmental drinking water fluoride exposure. Collectively, our results suggest that mitochondrial fission inhibition induces mitochondrial abnormalities, triggering abnormal autophagy and apoptosis, thus contributing to neuronal death, and that the mitochondrial dynamics molecules may act as promising indicators for developmental fluoride neurotoxicity.

Low-to-moderate fluoride exposure in relation to overweight and obesity among school-age children in China.

High fluoride exposure has been related to harmful health effects, but the impacts of low-to-moderate fluoride on child growth and obesity-related outcomes remain unclear. We performed a large-scale cross-sectional study to examine the association between low-to-moderate fluoride in drinking water and anthropometric measures among Chinese school-age children. We recruited 2430 resident children 7-13 years of age, randomly from low-to-moderate fluorosis areas of Baodi District in Tianjin, China. We analyzed the fluoride contents in drinking water and urine samples using the national standardized ion selective electrode method. Multivariable linear and logistic analyses were used to assess the relationships between fluoride exposure and age- and sex-standardized height, weight and body mass index (BMI) z-scores, and childhood overweight/obesity (BMI z-score > 1). In adjusted models, each log unit (roughly 10-fold) increase in urinary fluoride concentration was associated with a 0.136 unit increase in weight z-score (95% CI: 0.039, 0.233), a 0.186 unit increase in BMI z-score (95% CI: 0.058, 0.314), and a 1.304-fold increased odds of overweight/obesity (95% CI: 1.062, 1.602). These associations were stronger in girls than in boys (Pinteraction = 0.016), and children of fathers with lower education levels were more vulnerable to fluoride (Pinteraction = 0.056). Each log unit (roughly 10-fold) increase in water fluoride concentration was associated with a 0.129 unit increase in height z-score (95% CI: 0.005, 0.254), but not with other anthropometric measures. Our results suggest low-to-moderate fluoride exposure is associated with overweight and obesity in children. Gender and paternal education level may modify the relationship.

Association between dental fluorosis prevalence and inflammation levels in school-aged children with low-to-moderate fluoride exposure.

Inflammation mediates the neurological deficits caused by fluoride. Thus, whether inflammation is the underlying mechanism of dental fluorosis (DF) in school-aged children is worth exploring. A cross-sectional study was conducted to investigate the association between inflammation and the prevalence and severity of DF with low-to-moderate fluoride exposure. Fasting morning urine and venous blood samples were collected from 593 children aged 7-14 years. The fluoride content in the water and urine samples was measured using a fluoride ion-selective electrode assay. The levels of interleukin-1ß (IL-1ß) and C-reactive protein (CRP) were detected using an enzyme-linked immunosorbent assay. The Dean's index was used when performing dental examinations. Regression, stratified, and mediation analyses were performed to analyze the association between fluoride exposure, inflammation, and DF prevalence. In the adjusted regression models, the prevalence of mild DF was 1.723-fold (95% confidence interval [CI]:1.612, 1.841) and 1.594-fold (1.479, 1.717) greater than that of normal DF for each 1 mg/L increase in water and urinary fluoride content, respectively. The prevalence of mild DF increased by 3.3% for each 1 pg/mL increase in the IL-1ß level and by 26.0% for each 1 mg/L increase in the CRP level. Stratified analysis indicated a weaker association between fluoride concentration and DF prevalence in boys than in girls, and susceptibility in the boys was reflected by the association of IL-1ß with very mild and moderate DF prevalence. For every 1 mg/L increase in water and urinary fluoride levels, the proportion of IL-1ß-mediated effects on the prevalence of mild DF was 10.0% (6.1%, 15.8%) and 8.7% (4.8%, 15.2%), respectively, and the proportion of CRP-mediated effects was 9.2% (5.5%, 14.9%) and 6.1% (3.3%, 11.0%), respectively. This study indicates that the DF prevalence may be sex-specific. Inflammatory factors may partially mediate the increased prevalence of mild DF in school-aged children with low-to-moderate fluoride exposure.

Low-to-moderate fluoride exposure, relative mitochondrial DNA levels, and dental fluorosis in Chinese children.

BACKGROUND: The alteration of mitochondrial DNA (mtDNA) content contributes to many diseases, however, little is known about its effect on the prevalence of dental fluorosis (DF). OBJECTIVES: We conducted a cross-sectional study to investigate the association of low-to-moderate fluoride exposure with relative mtDNA levels in relation to DF in children. METHODS: We recruited 616 resident children, aged 7-13 years, randomly from low-to-moderate fluoride areas in Tianjin, China. We measured the fluoride concentrations in drinking water and urine using the national standardized ion selective electrode method, and determined the relative levels of mtDNA using a quantitative real-time polymerase chain reaction assay. The association among fluoride exposure, relative mtDNA levels, and the prevalence of DF were examined using multivariable linear and logistic regression models. We also performed stratified and mediation analyses. RESULTS: The relative mtDNA levels of participants in the DF group were significantly lower than in the non-DF group (0.95 ±â€¯0.44 vs. 1.12 ±â€¯0.45, P < 0.001). In the adjusted models, we found that a 1 mg/L increment in water fluoride concentration was associated with a 0.10-unit decrease in circulating relative mtDNA levels (95% CI: -0.14, -0.06) and a 2.85-fold increase (95% CI: 2.01, 3.92) in moderate DF prevalence. A 1 mg/L increment in urinary fluoride level was associated with a 0.12-unit decrease in circulating relative mtDNA levels (95% CI: -0.14, -0.09) and a 1.85-fold increase (95% CI: 1.39, 2.39) in moderate DF prevalence. Stratified analysis indicated a weaker positive association of DF prevalence with fluoride exposure, while a stronger inverse relationship with relative mtDNA levels in boys than in girls. Assuming causality, we estimated that circulating mtDNA levels mediated 13.0% (95% CI: 5.2, 28.7%) and 9.6% (95% CI: 4.7, 18.5%) of the estimated effect of a 1 mg/L increment in water fluoride and urinary fluoride on prevalence of moderate DF, respectively. CONCLUSIONS: Gender potentially modifies the associations of DF prevalence with relative mtDNA levels and low-to-moderate fluoride exposure. The reduced circulating mtDNA levels may partly mediate the elevated prevalence of moderate DF in children under such exposure.

ERK1/2-mediated disruption of BDNF-TrkB signaling causes synaptic impairment contributing to fluoride-induced developmental neurotoxicity.

Excessive exposure to fluoride has adverse effects on neurodevelopment, but the mechanisms remain unclear. This study aimed to investigate the effects of fluoride exposure on synaptogenesis, and focused on the role of brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling in these effects. Using Sprague-Dawley rats developmentally exposed to sodium fluoride (NaF) from pregnancy until 6 months of delivery as in vivo model, we showed that fluoride impaired the cognitive abilities of offspring rats, decreased the density of dendritic spines and the expression of synapse proteins synaptophysin (SYN) and postsynaptic density protein-95 (PSD-95) in hippocampus, suggesting fluoride-induced cognitive deficit associates with synaptic impairment. Consistently, NaF treatment reduced dendritic outgrowth and expression of SYN and PSD-95 in human neuroblastoma SH-SY5Y cells. Further studies demonstrated that the BDNF-TrkB axis was disrupted in vivo and in vitro, as manifested by BDNF accumulation and TrkB reduction. Importantly, fluoride treatment increased phospho-extracellular signal-regulated kinases 1 and 2 (p-ERK1/2) expression, while inhibition of p-ERK1/2 significantly attenuated the effects of NaF, indicating a regulating role of p-ERK1/2 in BDNF-TrkB signaling disruption. Collectively, these data suggest that the developmental neurotoxicity of fluoride is associated with the impairment of synaptogenesis, which is caused by ERK1/2-mediated BDNF-TrkB signaling disruption.

Excessive ER stress and the resulting autophagic flux dysfunction contribute to fluoride-induced neurotoxicity.

Fluoride is capable of inducing neurotoxicity, but its mechanisms remain elusive. This study aimed to explore the roles of endoplasmic reticulum (ER) stress and autophagy in sodium fluoride (NaF)-induced neurotoxicity, focusing on the regulating role of ER stress in autophagy. The in vivo results demonstrated that NaF exposure impaired the learning and memory capabilities of rats, and resulted in histological and ultrastructural abnormalities in rat hippocampus. Moreover, NaF exposure induced excessive ER stress and associated apoptosis, as manifested by elevated IRE1α, GRP78, cleaved caspase-12 and cleaved-caspase-3, as well as defective autophagy, as shown by increased Beclin1, LC3-II and p62 expression in hippocampus. Consistently, the in vitro results further verified the findings of in vivo study that NaF induced excessive ER stress and defective autophagy in SH-SY5Y cells. Notably, inhibition of autophagy in NaF-treated SH-SY5Y cells with Wortmannin or Chloroquine decreased, while induction of autophagy by Rapamycin increased the cell viability. These results were correlated well with the immunofluorescence observations, thus confirming the pivotal role of autophagic flux dysfunction in NaF-induced cell death. Importantly, mitigation of ER stress by 4-phenylbutyrate in NaF-treated SH-SY5Y cells inhibited the expressions of autophagy markers, and decreased cell apoptosis. Taken together, these data suggest that neuronal death resulted from excessive ER stress and autophagic flux dysfunction contributes to fluoride-elicited neurotoxicity. Moreover, the autophagic flux dysfunction was mediated by excessive ER stress, which provided novel insight into a better understanding of fluoride-induced neurotoxicity.

Threshold effects of moderately excessive fluoride exposure on children's health: A potential association between dental fluorosis and loss of excellent intelligence.

BACKGROUND: Excessive fluoride exposure is associated with adverse health outcomes, but little is known of the effects of moderately chronic fluoride exposure on children's health. OBJECTIVES: We conducted a cross-sectional study to explore the health impact of moderately excessive fluoride in drinking water. METHODS: We recruited 2886 resident children, aged 7 to 13 years, randomly from endemic and non-endemic fluorosis areas in Tianjin, China. The fluoride levels in drinking water and urine were measured using the national standardized ion selective electrode method. We examined the dose-response effects of low-to-moderate fluoride exposure on dental fluorosis (DF) and intelligence quotient (IQ), and evaluated the potential relationships between DF grades and intelligence levels using piecewise linear regression and multiple logistic regression, respectively. RESULTS: The adjusted odds ratios (ORs) of DF were 2.24 (95% confidence interval [CI]: 2.02 to 2.48) for every 0.1 mg/L increment in the water fluoride concentration in the range of 0.80 to 1.50 mg/L, and 2.61 (95% CI: 2.32 to 2.93) for every 0.5 mg/L increment in the urinary fluoride level up to 1.80 mg/L. Every 0.5 mg/L increment in the water fluoride level was associated with a reduction of 4.29 in the IQ score (95% CI: -8.09 to -0.48) in the range of 3.40 to 3.90 mg/L, and a decreased probability of developing excellent intelligence (IQ ≥ 130, OR = 0.60, 95% CI: 0.47 to 0.77) in the range of 0.20-1.40 mg/L, respectively. Every 0.5 mg/L increment in the urinary fluoride level was related to a decrease of 2.67 in the IQ scores (95% CI: -4.67 to -0.68) between 1.60 mg/L to 2.50 mg/L. Excellent intelligence decreased by 51% in children with higher urinary fluoride, and by 30% with each degree increment of DF. CONCLUSIONS: Our study suggests threshold and saturation effects of moderately excessive fluoride exposure on DF and intelligence loss in children, and a potential association between DF and the loss of excellent intelligence.