Calcium preventing locomotor behavioral and dental toxicities of fluoride by decreasing serum fluoride level in rats

The fluorosis conundrum: bridging the gap between science and public health

Fluorosis, a chronic condition brought on by excessive fluoride ingestion which, has drawn much scientific attention and public health concern. It is a complex and multifaceted issue that affects millions of people worldwide. Despite decades of scientific research elucidating the causes, mechanisms, and prevention strategies for fluorosis, there remains a significant gap between scientific understanding and public health implementation. While the scientific community has made significant strides in understanding the etiology and prevention of fluorosis, effectively translating this knowledge into public health policies and practices remains challenging. This review explores the gap between scientific research on fluorosis and its practical implementation in public health initiatives. It suggests developing evidence-based guidelines for fluoride exposure and recommends comprehensive educational campaigns targeting the public and healthcare providers. Furthermore, it emphasizes the need for further research to fill the existing knowledge gaps and promote evidence-based decision-making. By fostering collaboration, communication, and evidence-based practices, policymakers, healthcare professionals, and the public can work together to implement preventive measures and mitigate the burden of fluorosis on affected communities. This review highlighted several vital strategies to bridge the gap between science and public health in the context of fluorosis. It emphasizes the importance of translating scientific evidence into actionable guidelines, raising public awareness about fluoride consumption, and promoting preventive measures at individual and community levels.

Fluoride Binding Potential of Selected Phytochemicals: A Pilot Study

Fluoride (F-) contamination in drinking water is a major global concern. According to several studies, India and China are the most affected by the presence of excess F-. Long-time exposure to F- concentrations above 1.5 ppm can lead to hard and soft tissue fluorosis (F- toxicity). There are no effective cure or treatment for fluorosis and the condition is almost irreversible. Considering water to be the prime media through which F- reaches humans, maintaining optimal F- levels in water remains the only possible remedy. F- endemic areas have adapted several conventional defluoridation techniques to resolve the issue. Among these, adsorption with plant compounds is widely used for F- removal. Studies have shown that plant metabolites can ameliorate the toxic effects of F-. Based on this, we attempt to elucidate the potential binding and electrochemical bio-sensing properties of selected phytochemicals towards F-. The focus of the present work is to evaluate the interactions of phytochemicals with F-; for which, the binding studies of phytochemicals with F- have been elaborated by UV-visible spectroscopy and emission techniques. Benesi-Hildebrand's (BH) plot was used to calculate the binding constant (CUR - 34.9 × 103 (M-1), QUER - 13 × 103 (M-1), ESC -6.3 × 103 (M-1), FIS - 5.36 × 103 (M-1) and PCA -1.5 × 103 (M-1), and detection limit (CUR - 1.54 × 10-7 M, QUER - 0.156 × 10-6 M, ESC - 0.221 × 10-6 M, FIS - 0.175 × 10-6 M, and PCA - 5.8 × 10-6 M) for the F-:phytochemical mixtures. Further, the binding characteristics were confirmed using 1H-NMR titration experiments. Our findings highlight the potential of phytochemicals as effective binding agents for F-, thereby reducing its bioavailability.

Fluoride Induced Neurobehavioral Impairments in Experimental Animals: a Brief Review

Fluoride is one of the major toxicants in the environment and is often found in drinking water at higher concentrations. Living organisms including humans exposed to high fluoride levels are found to develop mild-to-severe detrimental pathological conditions called fluorosis. Fluoride can cross the hematoencephalic barrier and settle in various brain regions. This accumulation affects the structure and function of both the central and peripheral nervous systems. The neural ultrastructure damages are reflected in metabolic and cognitive activities. Hindrances in synaptic plasticity and signal transmission, early neuronal apoptosis, functional alterations of the intercellular signaling pathway components, improper protein synthesis, dyshomeostasis of the transcriptional and neurotrophic factors, oxidative stress, and inflammatory responses are accounted for the fluoride neurotoxicity. Fluoride causes a decline in brain functions that directly influence the overall quality of life in both humans and animals. Animal studies are widely used to explore the etiology of fluoride-induced neurotoxicity. A good number of these studies support a positive correlation between fluoride intake and toxicity phenotypes closely associated with neurotoxicity. However, the experimental dosages highly surpass the normal environmental concentrations and are difficult to compare with human exposures. The treatment procedures are highly dependent on the dosage, duration of exposure, sex, and age of specimens among other factors which make it difficult to arrive at general conclusions. Our review aims to explore fluoride-induced neuronal damage along with associated histopathological, behavioral, and cognitive effects in experimental models. Furthermore, the correlation of various molecular mechanisms upon fluoride intoxication and associated neurobehavioral deficits has been discussed. Since there is no well-established mechanism to prevent fluorosis, phytochemical-based alleviation of its characteristic indications has been proposed as a possible remedial measure.

Effects of chronic fluorosis on the brain

This article reviews the effects of chronic fluorosis on the brain and possible mechanisms. We used PubMed, Medline and Cochraine databases to collect data on fluorosis, brain injury, and pathogenesis. A large number of in vivo and in vitro studies and epidemiological investigations have found that chronic fluorosis can cause brain damage, resulting in abnormal brain structure and brain function.Chronic fluorosis not only causes a decline in concentration, learning, and memory, but also has mental symptoms such as anxiety, tension, and depression. Several possible mechanisms that have been proposed: the oxidative stress and inflammation theory, neural cell apoptosis theory, neurotransmitter imbalance theory, as well as the doctrine of the interaction of fluorine with other elements. However, the specific mechanism of chronic fluorosis on brain damage is still unclear. Thus, a better understanding of the mechanisms via which chronic fluorosis causes brain damage is of great significance to protect the physical and mental health of people in developing countries, especially those living in the endemic areas of fluorosis. In brief, further investigation concerning the influence of fluoride on the brain should be conducted as the neural damage induced by it may bring about a huge problem in public health, especially considering growing environmental pollution.

A systematic review on fluoride-induced epigenetic toxicity in mammals

Fluoride, one of the global groundwater contaminants, is ubiquitous in our day-to-day life from various natural and anthropogenic sources. Numerous in vitro, in vivo, and epidemiological studies are conducted to understand the effect of fluoride on biological systems. A low concentration of fluoride is reported to increase oral health, whereas chronic exposure to higher concentrations causes fluoride toxicity (fluorosis). It includes dental fluorosis, skeletal fluorosis, and fluoride toxicity in soft tissues. The mechanism of fluoride toxicity has been reviewed extensively. However, epigenetic regulation in fluoride toxicity has not been reviewed. This systematic review summarizes the current knowledge regarding fluoride-induced epigenetic toxicity in the in vitro, in vivo, and epidemiological studies in mammalian systems. We examined four databases for the association between epigenetics and fluoride exposure. Out of 932 articles (as of 31 March 2022), 39 met our inclusion criteria. Most of the studies focused on different genes, and overall, preliminary evidence for epigenetic regulation of fluoride toxicity was identified. We further highlight the need for epigenome studies rather than candidate genes and provide recommendations for future research. Our results indicate a correlation between fluoride exposure and epigenetic processes. Further studies are warranted to elucidate and confirm the mechanism of epigenetic alterations mediated fluoride toxicity.

Probiotic Lactobacillus johnsonii BS15 Prevents Memory Dysfunction Induced by Chronic High-Fluorine Intake through Modulating Intestinal Environment and Improving Gut Development

In recent years, the influence of chronic fluorosis on the brain has been widely reported. Our study aimed to demonstrate the potential mechanism underlying the impairment of memory function by excessive fluorine intake. We also evaluated whether improvement of intestinal microflora could be a potential therapy to prevent the negative influences from the perspective of gut-brain axis. Male ICR mice were randomly divided into three groups and administered with either phosphate buffered saline (PBS) (Control and F groups) or Lactobacillus johnsonii BS15 (FP group; daily amounts of 1 × 10⁹ CFU/mL), a probiotic strain, by oral gavage throughout a 98-day experimental period. Sodium fluoride (100 mg/L) was added to the drinking water of the F and FP groups. Animals were sacrificed for sampling with or without water avoidance stress (WAS) at two phases of the experiment and behavioral tests including T-maze test and passive avoidance test were also performed. Based on the results of behavioral tests, probiotic reversed the fluorine-induced memory dysfunction. In addition, L. johnsonii BS15 also increased the antioxidant capacities (serum and hippocampal tissue) and hippocampal synaptic plasticity-related mRNA expression after excessive fluoride ingestion. Moreover, the increased colonization of L. johnsonii BS15 also protected the small intestines from the damages of growth performance, visceral indexes, intestinal development, digestive, and secretory functions by changing the structure of the microflora and then improving intestinal permeability and integrity. L. johnsonii BS15 also improved the ability of flourosis mice against psychological stress indicated by the changes in behavioral tasks, hippocampal antioxidant levels, and synaptic plasticity-related mRNA expressions. Lactobacillus johnsonii BS15 intake appears as a promising way to ameliorate fluorine-induced memory dysfunction, especially under psychological stress.

Protective Effect of Curcumin on Hippocampal and Behavior Changes in Rats Exposed to Fluoride During Pre- and Post-natal Period

Introduction:

Curcumin, a yellow-pigment, found in the popular Indian spice turmeric (Curcuma longa), poses pharmaceutical applications due to its anti-inflammatory, antioxidant, and chemoprotective properties. Excessive fluoride causes fluorosis leading to neurodegeneration and associated behavioral deficits, particularly in children. This study aimed at investigating the neuroprotective ability of curcumin on sodium fluoride (NaF)-related alterations of acetylcholine, catecholamines, histological changes in hippocampus and behavior of rats exposed to NaF during pre- and post-natal period.

Methods:

Pregnant albino Wistar rats were chosen and divided into four groups. The experimental period lasted 53 days (i.e. the gestational period of 23 days and post-gestational period of 30 days), at which the control group received normal tap water, the experimental group received NaF (20 ppm/kg bw) through drinking water, and the protective groups received curcumin (10 mg and 20mg/kg bw) by gavage and NaF (20 ppm/kg bw) through drinking water. Behavioral study (open field test) was done using postnatal pups aged 21 and 30 days. The brains of postnatal pups aged 1, 7, 14, 21, and 30 days were collected and used for biochemical analysis and those of pups aged 14, 21, and 30 days were used for histopathological analysis.

Results:

NaF-exposed rats showed a significant (P<0.05) decrease in body weight, brain weight, and behavioral activities, which were significantly reversed with curcumin treatment. The levels of epinephrine significantly (P<0.05) increased, whereas norepinephrine, dopamine and acetylcholine levels declined in NaF-treated group compared with the control group, which were significantly (P<0.05) reversed after treatment by curcumin (10 mg/kg bw and 20 mg/kg bw) along with NaF. The histological alterations, including shrinkage of neurons and nissal substances were observed in the hippocampus of NaF-treated pups that the control pups, whereas co-treatment with curcumin and NaF showed ameliorative effects and controlled the histological alterations.

Conclusion:

The results showed the neuroprotective effect of curcumin on behavior, neurotransmitter levels, and histological changes in the hippocampus against NaF-induced neurotoxicity in developing rat pups.

Subchronic Administration of High-Dose Sodium Fluoride Causes Deficits in Cerebellar Purkinje Cells But Not Motor Coordination of Rats

Fluoride is frequently added to drinking water supplies, various food products, toothpaste, and mouth rinses to prevent tooth damage. However, at high concentrations, fluoride can cause fluorosis and damage to the brain tissue due to its excitotoxicity and oxidative stress effects. The damage of the Purkinje cells of the cerebellum can lead to motor coordination disorders. The present study aimed at investigating the effects of sodium fluoride on the motor coordination and the number of Purkinje cells of the cerebellum of rats. Adult male Wistar rats were divided into four groups, namely a control group which received reverse osmosis distilled water and three treated groups which received sodium fluoride at doses of 5, 10, or 20 mg/kg bw. The treatment lasted for 30 days. The motor coordination of the rats was examined using a rotarod prior and subsequent to the treatments. The number of Purkinje cells was estimated using physical fractionator design. The numbers of Purkinje cells of the F10 and F20 groups were significantly lower than that of the control group. No significant differences in the results of the motor coordination test were found. The administration of sodium fluoride at doses of 10 and 20 mg/kg bw caused a decrease in the number of Purkinje cells of the cerebellum in rats.

Impact of Prenatal and Postnatal Treatment of Sodium Fluoride and Aluminum Chloride on Some Hormonal and Sensorimotor Aspects in Rats

In most communities, there is a constant exposure to environmental pollutants with probable negative impact on the development of the nervous system. Among these pollutants are the sodium fluoride (NaF) and aluminum chloride (AlCl₃) which may represent a real threat to the proper functioning of the brain. This study comprises two fundamentally different strategies; in the first one, pregnant rats were administered a daily dose of NaF (0.15 g /L) or AlCl₃ (500 mg/L) in the drinking water either separately or in combination with each other from day 6 of gestation until just after weaning. In the second approach, the male rats born to mothers exposed to the pollutants were divided into two groups. In the first, rats were continued to be treated with the same pollutants administered to them in the drinking water at the same dose level until the age of 70 days. The rats of the second group were supplied with drinking water without either one of the pollutants for a similar period of time. The rats exposed to NaF separately or in combination with AlCl₃ during the prenatal life and subsequently through the postnatal stages exhibited disturbance in the locomotor activities. This was concomitant with alterations in plasma, PTH, ACTH, and estradiol levels. Additionally, the serum levels of LH and testosterone were altered in the two groups treated with sodium fluoride during the prenatal and up to the weaning periods or in the group which continued to have the NaF until day 70 after birth.

Effects of perinatal fluoride exposure on the expressions of miR-124 and miR-132 in hippocampus of mouse pups

To investigate the effects of perinatal fluoride exposure on learning and memory ability of mouse offspring, ICR female mice were received different doses of sodium fluoride (0, 25, 50, 100 mg/L NaF) from pregnant day 7 to lactational day 21. Pups were exposed to fluoride through the cord blood and breast milk. Open field test showed that compared to the control group, perinatal fluoride exposure significantly decreased the number of entries into the center zone in 100 mg/L NaF group. In the eight-arm maze test, the number of working memory errors, reference memory errors, and the total arm entries were significantly increased in fluoride treatment groups, compared to the control group. Additionally, 100 mg/L NaF significantly elevated the expression levels of miR-124, miR-132, and DiGeorge syndrome chromosomal region 8 (DGCR8) in hippocampus of mouse pups at postnatal day (PND) 21. Contrarily, methyl CpG binding protein 2 (MeCP2) were dramatically reduced in 50 and 100 mg/L NaF groups, while cAMP-response element binding protein (CREB) mRNA level was significantly decreased in all fluoride groups. These findings suggested that the impairment of learning and memory in mouse offspring induced by perinatal fluoride exposure may partly result from the enhanced miR-124 and miR-132 and the alterations of their target genes.

An Evaluation of Neurotoxicity Following Fluoride Exposure from Gestational Through Adult Ages in Long-Evans Hooded Rats

At elevated levels, fluoride (F^-) exposure has been associated with adverse human health effects. In rodents, F^- exposure has been reported to induce deficits in motor performance and learning and memory. In this study, we examined Long-Evans hooded male rats maintained on a standard diet (20.5 ppm F^-) or a low F^- diet (3.24 ppm F^-) with drinking water exposure to 0, 10, or 20 ppm F^- from gestational day 6 through adulthood. At postnatal day 25, brain F^- levels were 0.048 or 0.081 μg/g and femur 235 or 379.8 μg/g for 10 and 20 ppm F^-, respectively. Levels increase with age and in adults, levels for plasma were 0.036 or 0.025 μg/ml; for the brain 0.266 or 0.850 μg/g; and for the femur, 681.2 or 993.4 μg/g. At these exposure levels, we observed no exposure-related differences in motor, sensory, or learning and memory performance on running wheel, open-field activity, light/dark place preference, elevated plus maze, pre-pulse startle inhibition, passive avoidance, hot-plate latency, Morris water maze acquisition, probe test, reversal learning, and Y-maze. Serum triiodothyronine (T3), thyroxine (T4), and thyroid stimulating hormone (TSH) levels were not altered as a function of 10 or 20 ppm F^- in the drinking water. No exposure-related pathology was observed in the heart, liver, kidney, testes, seminal vesicles, or epididymides. Mild inflammation in the prostate gland was observed at 20 ppm F^-. No evidence of neuronal death or glial activation was observed in the hippocampus at 20 ppm F^-.

Fluoride: A review of pre-clinical and clinical studies

Fluoride is ubiquitous in environment and profound in bones, teeth and calcified tissues of human body. Fluoride has been the topic of regular discussion and investigations. Besides its toxicity, fluoride has also been examined for its beneficial effects like prevention and treatment of tooth decay, microbial infection, inflammation, cancer, occurrence of renal stone and many more. Since last many decades, several efforts have been made at pre-clinical and clinical level to understand role of fluoride in biological system. The present review gives a brief account of prevalence, sources of fluoride toxicity and pre-clinical and clinical studies carried out on effects of fluoride in last six decades.

Sodium fluoride does not affect the working memory and number of pyramidal cells in rat medial prefrontal cortex

Fluoride is a chemical compound known to bring about fluorosis. It is thought to disrupt the central nervous system because of its ability to induce excitotoxicity and oxidative stress. Any damage of pyramidal cells in the prefrontal cortex would result in cognitive function and working memory regulation disorders. The present study aimed at investigating the effects of sodium fluoride (NaF) on the working memory and estimated total number of medial prefrontal cortex pyramidal cells of adult male rats. Thirty-two male Wistar rats were assigned into four groups, namely control and three treated groups receiving 5, 10 and 20 mg/kg BW, respectively, of oral NaF solution for 30 days. The working memory test was carried out using a Y-maze. The number of pyramidal cells in the medial prefrontal cortex was estimated using an unbiased stereological method. There was no significant difference among groups in the working memory and number of pyramidal neurons in the medial prefrontal cortex cells.

Medical Hydrogeology of Asian Deltas: Status of Groundwater Toxicants and Nutrients, and Implications for Human Health

Drinking water, a fluid primarily for human hydration, is also a source of mineral nutrients. Groundwater, a drinking water source for more than 70% of inhabitants living in Asian deltas, has received much attention because of its naturally occurring arsenic, but the linkage of arsenic toxicity with other water constituents has not been studied. In addition, although nutrients are generally provided by food, in under developed rural settings, where people subsist on low nutrient diets, drinking-water-nutrients may supply quantities critical to human health thereby preventing diseases. Here, we show, using augmented datasets from three Asian deltas (Bengal, Mekong, and Red River), that the chemical content of groundwater is so substantial that in some areas individuals obtain up to 50% or more of the recommended daily intake (RDI) of some nutrients (e.g., calcium, magnesium, iron) from just two litres of drinking water. We also show some indications of a spatial association of groundwater nutrients and health outcome using demographic health data from Bangladesh. We therefore suggest that an understanding of the association of non-communicable disease and poor nutrition cannot be developed, particularly in areas with high levels of dissolved solids in water sources, without considering the contribution of drinking water to nutrient and mineral supply.

Neurobehavioural effects of exposure to fluoride in the earliest stages of rat development

It is known that exposure to high concentrations of Fluoride (F) produces deleterious health effects in human population. However, in the last years it has been concluded that low concentrations of F may have adverse health effects as well. Transplacental passage of F and its incorporation into foetal tissues has been demonstrated. Therefore, the purpose of the present work was to study the effects of the exposure to low levels of F during pregnancy and lactation on the central nervous system functionality. Wistar rats were exposed to low F concentrations (5 and 10 mg/l) during pregnancy and lactation. Sensorimotor reflexes in the each pup were analysed and the postnatal day on which both eyes and auditory canals were opened was recorded. Locomotor activity and anxiety were subsequently analysed in 45- and 90-day-old offspring by an open field test and plus maze test, respectively. A significant delay in the development of eye opening was observed in all offspring whose mothers had been exposed to the two F concentrations tested. Exposure to 5 and 10 mg/l F was also found to significantly decrease locomotor activity only in 90-day-old male and female offspring. A low index of anxiety in the young females and in all adult offspring exposed to the two F concentrations tested was also detected. Taken together, findings from the present study show that exposure to low F concentrations during pregnancy and lactation produces dysfunction in the central nervous system mechanisms which regulate motor and sensitive development, locomotor activity and anxiety

Proteomic analysis of hippocampus in offspring male mice exposed to fluoride and lead

Fluoride and lead are two common pollutants in the environment. Previous investigations have found that high fluoride exposure can increase the lead burden. In this experiment, in order to study on the molecular mechanisms of central neural system injury induced by the above two elements, differently expressed protein spots in hippocampus of male mice treated with 150 mg sodium fluoride/L and/or 300 mg lead acetate/L in their drinking water were detected by two-dimensional electrophoresis (2-DE) and mass spectrometry (MS). The behavior tests showed that 56 days of fluoride and lead administration significantly reduced the vertical activity and lowered the memory ability of mice. In addition, results of 2-DE and MS revealed that nine spots demonstrated above a twofold change in the same trend in all treatment groups, which were mainly related with (1) energy metabolism, (2) cell stress response/chaperones, (3) cytoskeleton development, (4) protein metabolism, and (5) cell surface signal transduction. The findings could provide potential biomarkers for lesion in nervous system induced by fluoride and lead exposure.

Fluoride exposure during development affects both cognition and emotion in mice

Previous studies have suggested that sodium fluoride (NaF) may have adverse effects on neurodevelopment. In the present study, we evaluated developmental neurotoxicity by assessing in cognitive function and emotional behavior in BalB/C mice treated with NaF. Mice were weaned at 4weeks, and water or different NaF concentrations (2, 5, or 10mg/L in drinking water) were provided for 4weeks. We found that exploration preference in the novel object recognition test was significantly altered in mice treated with 5 and 10mg/L NaF compared with the water-treated control animals. Furthermore, mice treated with 5 and 10mg/L NaF showed significantly longer escape latencies, less time in the target quadrant, and fewer platform-crossing numbers in the Morris water maze compared to those in the control group. In addition, mice treated with 10mg/L NaF spent a lower percentage of time in the open arms in the elevated-plus maze, while no significant changes were noted in the open and close arm entries or the total arm entries. We also found that the cumulative immobility time in the tail suspension test was longer in mice treated with 5 and 10mg/L NaF compared to the control group. Only 10mg/L NaF-treated mice showed longer immobility time compared with the control group. Collectively, our data indicate that developmental exposure to NaF induces cognitive deficits and anxiety-depression-like behaviors in mice.

JNK and NADPH oxidase involved in fluoride-induced oxidative stress in BV-2 microglia cells

Excessive fluoride may cause central nervous system (CNS) dysfunction, and oxidative stress is a recognized mode of action of fluoride toxicity. In CNS, activated microglial cells can release more reactive oxygen species (ROS), and NADPH oxidase (NOX) is the major enzyme for the production of extracellular superoxide in microglia. ROS have been characterized as an important secondary messenger and modulator for various mammalian intracellular signaling pathways, including the MAPK pathways. In this study we examined ROS production and TNF-α, IL-1β inflammatory cytokines releasing, and the expression of MAPKs in BV-2 microglia cells treated with fluoride. We found that fluoride increased JNK phosphorylation level of BV-2 cells and pretreatment with JNK inhibitor SP600125 markedly reduced the levels of intracellular O₂^·− and NO. NOX inhibitor apocynin and iNOS inhibitor SMT dramatically decreased NaF-induced ROS and NO generations, respectively. Antioxidant melatonin (MEL) resulted in a reduction in JNK phosphorylation in fluoride-stimulated BV-2 microglia. The results confirmed that NOX and iNOS played an important role in fluoride inducing oxidative stress and NO production and JNK took part in the oxidative stress induced by fluoride and meanwhile also could be activated by ROS in fluoride-treated BV-2 cells.

Evaluation of standardized Bacopa monniera extract in sodium fluoride-induced behavioural, biochemical, and histopathological alterations in mice

Effect of standardized Bacopa monniera (BM; family: Scrophulariaceae) extract (100 and 300 mg/kg) against sodium fluoride (NaF; 100 and 200 ppm)-induced behavioural, biochemical, and neuropathological alterations in mice was evaluated. Akinesia, rotarod (motor coordination), forced swim test (depression), open field test (anxiety), transfer latency (memory), cholinesterase (ChE), and oxidative stress (superoxide dismutase, catalase, glutathione peroxidase, and lipid peroxidation) were determined in mice treated with NaF for 30 days alone and in combination with BM. NaF induced motor incoordination, depression, and memory impairment, and these were prevented by coadministration of BM in mice. However, NaF did not alter the weight gain, feed/water consumption, and anxiety profile. Suppression of ChE levels and increased oxidative stress were observed in mice treated with NaF. Coadministration of BM significantly improved the memory, ChE levels, and antioxidant enzymes but failed to alter the fluoride levels in NaF-treated mice. Histopathological studies revealed that BM protected the neuropathological alterations induced by NaF.

Assessment of fluoride-induced changes on physicochemical and structural properties of bone and the impact of calcium on its control in rabbits

Bone deformities caused by the chronic intake of large quantities of fluoride and the beneficial effect of calcium on its control have been studied for many years, but only limited data are available on the quantitative effect of fluoride intake and the beneficial impact of calcium on fluoride-induced changes in bone at the molecular level. It is necessary to determine the degree of fluoride-induced changes in bone at different levels of fluoride intake to evaluate the optimum safe intake level of fluoride for maintaining bone health and quality. The ameliorative effect of calcium at different dose levels on minimizing fluoride-induced changes in bone is important to quantify the amount of calcium intake necessary for reducing fluoride toxicity. Thirty rabbits, 2 months old, were divided into five groups. Group I animals received 1 mg/l fluoride and 0.11% calcium diet; groups II and III received 10 mg/l fluoride and diet with 0.11% or 2.11% calcium, respectively; and groups IV and V received 150 mg/l fluoride and diet with 2.11% or 0.11% calcium, respectively. Analysis of bone density, ash content, fluoride, calcium, phosphorus, and Ca:P molar ratio levels after 6 months of treatment indicated that animals that received high fluoride with low-calcium diet showed significant detrimental changes in physicochemical properties of bone. Animals that received fluoride with high calcium intake showed notable amelioration of the impact of calcium on fluoride-induced changes in bone. The degree of fluoride-induced characteristic changes in structural properties such as crystalline size, crystallinity, and crystallographic "c"-axis length of bone apatite cells was also assessed by X-ray diffraction and Fourier transform infrared studies. X-ray images showed bone deformity changes such as transverse stress growth lines, soft tissue ossification, and calcification in different parts of bones as a result of high fluoride accumulation and the beneficial role of calcium intake on its control.

Substance flow analysis: a case study of fluoride exposure through food and beverages in young children living in Ethiopia

CONTEXT

Dental and skeletal fluorosis is endemic in the Ethiopian Rift Valley. Children are especially vulnerable to excessive fluoride intake because their permanent teeth are still being formed. Strategies to reduce the total fluoride intake by children are thus warranted.

CASE PRESENTATION

By combining the results of field studies in Ethiopia, the relevant pathways for fluoride intake have been identified in 28 children 2-5 years of age living in two villages on the Wonji Shoa Sugar Estate in the Ethiopian Rift Valley. The focus of the present study was to simulate the fluoride intake of the children using the methods of material flow analysis (MFA) and substance flow analysis.

DISCUSSION

With a model based on MFA, we quantified the potential reduction in total fluoride intake given different scenarios-for example, by reducing the fluoride intake from drinking water and cooking water. The results show clearly that only by removing fluoride completely from both drinking and cooking water does the probability of remaining below the daily tolerable upper intake level exceed 50%. Both prepared food and food ingredients must be taken into consideration when assessing the total fluoride intake by children living in high-fluoride areas.

RELEVANCE

This knowledge will help health personnel, the government, and the food authorities to give scientifically based advice on strategies for reducing the total fluoride intake by children living in high-fluoride areas in the Ethiopian Rift Valley.

Fluoride causing abnormally elevated serum nitric oxide levels in chicks

Serum fluoride, nitric oxide (NO), malondialdehyde (MDA) contents and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) activities were determined in chicks treated with graded doses of sodium fluoride. Compared with chicks in the control group, in the groups treated with fluoride, serum NO and MDA levels largely increased, and the activities of SOD, GSH-Px, and CAT decreased, most of which changed significantly (P<0.05). Serum fluoride levels significantly and positively correlated with serum NO, MDA levels, respectively (P<0.05), and significantly and negatively with serum SOD, GSH-Px, CAT activities, respectively (P<0.05). The results indicated fluoride was associated with the elevated NO levels and the decreased activities of antioxidant enzymes and the deposit of lipid peroxides (LPO). We suggest the mechanism of fluoride injuring soft tissues as follows: fluoride causes excessive production of NO, LPO and oxygen free radicals, which can damage seriously the structure and function of soft tissues.