Prevention & control of fluorosis & linked disorders: Developments in the 21st Century - Reaching out to patients in the community & hospital settings for recovery

Comparative evaluation of cranberry extract and sodium fluoride as mouth rinses on S. mutans counts in children: a double-blind randomized controlled trial

BACKGROUND

Recently, research in the field of caries prevention is emphasizing upon identification of edible non-toxic compounds that can interfere with the formation of cariogenic biofilm.

AIM

This trial aimed to assess the effectiveness of non-dialyzable material (NDM) containing cranberry mouth rinse (C-MR) on the Streptococcus mutans (S. mutans) counts and compare with that of a sodium fluoride (F-MR) mouth rinse.

METHODS

280 children (8-12 years old) were enrolled in this double-blind single center, parallel, one-month, IRB/IEC approved non-inferiority trial. The participants fulfilling the inclusion criteria were randomly allocated into one of the two groups: C-MR and F-MR. All participants were given verbal and written instructions about at-home mouth-rinsing regimen under parental supervision for a month. Dental plaque samples were collected before and after a month of mouth-rinsing and subjected to culture techniques. S. mutans counts were assessed and compared in both groups. Primary outcome was the difference in the S. mutans counts between two interventions. Both intention-to-treat (ITT) and per-protocol analysis were carried out using two-sample t test with equal variance.

RESULTS

The mean S. mutans counts (after log transformation) in C-MR group were: 14.66 (90% CI 14.4,14.9) at baseline and 12.85 (90% CI 12.5, 13.2) colony-forming units/ml (CFU/ml) at one-month post intervention (p = 0.001); while these counts were 14.69 (90% CI 14.5, 14.9) at baseline and 12.71 (90% CI 12.3, 13.1) at one-month intervention in F-MR groups (p = 0.001). ITT analysis showed an inter- group difference of 0.14 CFU/ml (90% CI - 0.32,0.59) in post-SM counts between groups (p = 0.629).

CONCLUSION

The study demonstrated that the cranberry mouth rinse was non-inferior to the fluoride mouth rinse in terms of S. mutans levels change. Cranberry-based mouth rinse can be used effectively to reduce the S. mutans counts in children.

TRIAL REGISTRATION

Registration number in case of Clinical Trials-CTRI/2019/05/019395.

Study of anaemia in pregnancy and low birth weight in fluoride endemic area of Western Rajasthan: a cohort study

Background

Fluoride is a noxious element known to destroy gastrointestinal mucosa, leading to erythrocytes' destruction and causing anaemia. The birth weight of newborn babies is a significant indicator of a child's vulnerability to the risk of childhood diseases and chances of existence.

Methods

This prospective cohort study was planned to find linkages between fluorosis and the low-birth weight of newborn babies with anaemic mothers. Antenatal mothers until the 20th week of gestation were followed up till delivery in the Antenatal Clinic of a District Hospital in one of the known fluoride-endemic districts (Nagaur) and the other not-so-endemic district (Jodhpur) of Western Rajasthan.

Results

Around 19% of the newborn in Jodhpur and around 22% in Nagaur had low birth weight. Mean fluoride values in water samples were measured to be 0.57 (range from 0.0 to 2.7 PPM) in Jodhpur and 0.7 (range from 0.0 to 3.4 PPM) in Nagaur.

Conclusions

Thus, in fluoride endemic areas, other factors should be included besides iron and folic acid supplementation for improving anaemia in pregnant women. This calls for assessing the effectiveness of de-fluoridation activities along with the area's most common indigenous food practices.

Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis

INTRODUCTION

Fluoride exposure may have various adverse health effects, including affecting thyroid function and disease risk, but the pattern of such relation is still uncertain.

METHODS

We systematically searched human studies assessing the relation between fluoride exposure and thyroid function and disease. We compared the highest versus the lowest fluoride category across these studies, and we performed a one-stage dose-response meta-analysis for aggregated data to explore the shape of the association.

RESULTS

Most retrieved studies (27 of which with a cross-sectional design) were conducted in Asia and in children, assessing fluoride exposure through its concentrations in drinking water, urine, serum, or dietary intake. Twenty-four studies reported data on thyroid function by measuring thyroid-related hormones in blood (mainly thyroid-stimulating-hormone - TSH), 9 reported data on thyroid disease, and 4 on thyroid volume. By comparing the highest versus the lowest fluoride categories, overall mean TSH difference was 1.05 μIU/mL. Dose-response curve showed no change in TSH concentrations in the lowest water fluoride exposure range, while the hormone levels started to linearly increase around 2.5 mg/L, also dependending on the risk of bias of the included studies. The association between biomarkers of fluoride exposure and TSH was also positive, with little evidence of a threshold. Evidence for an association between fluoride exposure and blood concentrations of thyroid hormones was less evident, though there was an indication of inverse association with triiodothyronine. For thyroid disease, the few available studies suggested a positive association with goiter and with hypothyroidism in both children and adults.

CONCLUSIONS

Overall, exposure to high-fluoride drinking water appears to non-linearly affect thyroid function and increase TSH release in children, starting above a threshold of exposure, and to increase the risk of some thyroid diseases.

Combined Effects of Fluoride and Arsenic on Mitochondrial Function in the Liver of Rat

Biochemical and/or molecular mechanisms of arsenic or fluoride toxicity in experimental animals have been widely investigated in the recent past. However, their combined effects on target cells/organelle are poorly understood. The present study was executed to delineate their combined effects on mitochondrial function in the liver of rat. Female Wistar rats (140 ± 20 g) were force fed individually or in combination with sodium arsenate (4 mg/kg body weight) and sodium fluoride (4 mg/kg body weight) for 90 days. Thereafter, established markers of mitochondrial function viz. mitochondrial lipid peroxidation, oxidative phosphorylation, ATPase, succinic dehydrogenase, and caspase-3 activity were determined. Cytochrome C release and oxidative DNA damage were also estimated in the liver of respective groups of rats. The study showed significant differences in these results amongst the three groups. Observations on parameters viz. LPO, cytochrome-C, caspase-3, and 8-OHdG suggested an antagonistic relationship between these two elements. Results on ATPase, SDH, and ADP:O ratio indicated synergism. It is concluded that AsIII + F in combination may express differential effects on signalling pathways and proapoptotic/antiapoptotic proteins/genes that contribute to liver cell death. Interaction of As and F with mitochondria.

Screening of differentially methylated genes in skeletal fluorosis of rats with different types and involvement of aberrant methylation of Cthrc1

Fluoride is a widespread pollutant in the environment. There is a high risk of developing skeletal fluorosis from excessive fluoride exposure. Skeletal fluorosis has different phenotypes (including osteosclerotic, osteoporotic and osteomalacic) under the same fluoride exposure and depends on dietary nutrition. However, the existing mechanistic hypothesis of skeletal fluorosis cannot well explain the condition's different pathological manifestations and their logical relation with nutritional factors. Recent studies have shown that DNA methylation is involved in the occurrence and development of skeletal fluorosis. DNA methylation is dynamic throughout life and may be affected by nutrition and environmental factors. We speculated that fluoride exposure leads to the abnormal methylation of genes related to bone homeostasis under different nutritional statuses, resulting in different skeletal fluorosis phenotypes. The mRNA-Seq and target bisulfite sequencing (TBS) result showed differentially methylated genes in rats with different skeletal fluorosis types. The role of the differentially methylated gene Cthrc1 in the formation of different skeletal fluorosis types was explored in vivo and in vitro. Under normal nutritional conditions, fluoride exposure led to hypomethylation and high expression of Cthrc1 in osteoblasts through TET2 demethylase, which promoted osteoblast differentiation by activating Wnt3a/β-catenin signalling pathway, and participated in the occurrence of osteosclerotic skeletal fluorosis. Meanwhile, the high CTHRC1 protein expression also inhibited osteoclast differentiation. Under poor dietary conditions, fluoride exposure led to hypermethylation and low expression of Cthrc1 in osteoblasts through DNMT1 methyltransferase, and increased the RANKL/OPG ratio, which promoted the osteoclast differentiation and participated in the occurrence of osteoporotic/osteomalacic skeletal fluorosis. Our study expands the understanding of the role of DNA methylation in regulating the formation of different skeletal fluorosis types and provides insights into new prevention and treatment strategies for patients with skeletal fluorosis.

TFE3-mediated impairment of lysosomal biogenesis and defective autophagy contribute to fluoride-induced hepatotoxicity

Excessive fluoride exposure can cause liver injury, but the specific mechanisms need further investigation. We aimed to explore the role of impaired lysosomal biogenesis and defective autophagy in fluoride-induced hepatotoxicity and its potential mechanisms, focusing on the role of transcription factor E3 (TFE3) in regulating hepatocyte lysosomal biogenesis. To this end, we established a Sprague-Dawley (SD) rat model exposed to sodium fluoride (NaF) and a rat liver cell line (BRL3A) model exposed to NaF. The results showed that NaF exposure diminished liver function and led to apoptosis as well as autophagosome accumulation and impaired autophagic degradation. In addition, NaF exposure caused compromised lysosome biogenesis and decreased lysosomal degradation, and inhibited TFE3 nuclear translocation. Notably, the mTOR inhibitors rapamycin (RAPA) and Ad-TFE3 promoted lysosomal biogenesis and enhanced lysosomal degradation function. Furthermore, RAPA and Ad-TFE3 reduced NaF-induced apoptosis by alleviating impaired autophagic degradation. In conclusion, NaF impairs lysosomal biogenesis by inhibiting TFE3 nuclear translocation, decreasing lysosomal degradation function, resulting in impaired autophagic degradation, and ultimately inducing apoptosis. Therefore, TFE3 may be a promising therapeutic target for fluoride-induced hepatotoxicity.

Fluoride regulates the differentiation and atrophy through FGF21/ERK signaling pathway in C2C12 cells

Excess intake of fluoride leads to a serious health issue called fluorosis. Fluorosis patients exhibit the symptom of muscle damage, but the specific mechanism remains unclear. Fibroblast growth factor 21 (FGF21) is a novel myokine that is involved in the regulation of myogenic differentiation, but whether fluoride induces skeletal muscle damage via FGF21 signaling has not been reported yet. In the current study, C2C12 cells were used to investigate the impact of fluoride on myogenic development and the involved regulatory role of FGF21/ERK signaling pathway. The expressions of the markers of myoblasts development and FGF21/ERK signaling pathway-related molecules were detected after fluoride treatment. The results indicated that fluoride notably inhibited the expressions of myogenic regulatory genes MyoD, MyoG and MyHC in C2C12 cells. In addition, fluoride increased the expressions of muscle atrophy-related markers MuRF1 and MAFbx. We proved that fluoride significantly inhibited the expression of FGF21 based on the RNA-seq results, and detected the expressions of downstream molecules FGFR1, KLB, Raf, MEK and ERK. Moreover, FGF21 pretreatment reversed the adverse effect of fluoride on the C2C12 cells and alleviated the atrophy of myotubes. Taken together, these findings indicated that fluoride suppressed differentiation and aggravated atrophy via FGF21/ERK signaling pathway in C2C12 cells. Our study has provided new evidence for the role of FGF21/ERK in fluoride-induced skeletal muscle damage and FGF21 may be one of the potential targets for prevention and treatment of fluorosis.

In Silico Analysis of Ferroptosis-Related Genes and Its Implication in Drug Prediction against Fluorosis

Fluorosis is a serious global public health problem. Interestingly, so far, there is no specific drug treatment for the treatment of fluorosis. In this paper, the potential mechanisms of 35 ferroptosis-related genes in U87 glial cells exposed to fluoride were explored by bioinformatics methods. Significantly, these genes are involved in oxidative stress, ferroptosis, and decanoate CoA ligase activity. Ten pivotal genes were found by the Maximal Clique Centrality (MCC) algorithm. Furthermore, according to the Connectivity Map (CMap) and the Comparative Toxicogenomics Database (CTD), 10 possible drugs for fluorosis were predicted and screened, and a drug target ferroptosis-related gene network was constructed. Molecular docking was used to study the interaction between small molecule compounds and target proteins. Molecular dynamics (MD) simulation results show that the structure of the Celestrol-HMOX1 composite is stable and the docking effect is the best. In general, Celastrol and LDN-193189 may target ferroptosis-related genes to alleviate the symptoms of fluorosis, which may be effective candidate drugs for the treatment of fluorosis.

A Review on Experimentally Proven Medicinal Plants and Their Constituents against Fluoride Toxicity

Fluoride toxicity, principally by polluted groundwater, is regarded as a momentous global public health risk, as there is no particular and proven treatment for chronic fluoride toxicity i.e., fluorosis which leads to several serious health complications. Scientific literature reveals several medicinal plants and natural products alleviate experimentally induced fluoride toxicity. The present review attempts to collate those experimental studies on medicinal plants and plant derived natural products with fluoride toxicity ameliorative effects. Literature scrutiny was performed by using online bibliographic databases and the studies for the last 15 years were considered. Minerals and semi-synthetic or synthetic analogs of natural products were excluded. Literature study revealed that 25 medicinal plants and 17 natural products exhibited significant protection from fluoride toxicity in experimental animal models i.e., preclinical studies. Two clinical studies on medicinal plants were also found in literature showing beneficial yet poorly correlated outcome. Relevant research in this field could lead to development of a potentially useful agent in therapeutic management of fluoride toxicity in humans.

Antioxidant Phytochemicals for the Prevention of Fluoride-Induced Oxidative Stress and Apoptosis: a Review

Fluorosis is a major public health problem globally. The non-availability of specific treatment and the irreversible nature of dental and skeletal lesions poses a challenge in the management of fluorosis. Oxidative stress is known to be one of the most important mechanisms of fluoride toxicity. Fluoride promotes the accumulation of reactive oxygen species by inhibiting the activity of antioxidant enzymes, resulting in the excessive production of reactive oxygen species at the cellular level which further leads to activation of cell death processes such as apoptosis. Phytochemicals that act as antioxidants have the potential to protect cells from oxidative stress. Evidence confirms that clinical symptoms of fluorosis can be mitigated to some extent or prevented by long-term intake of antioxidants and plant products. The primary purpose of this review is to examine recent findings that focus on the amelioration of fluoride-induced oxidative stress and apoptosis by natural and synthetic phytochemicals and their molecular mechanisms of action.

Effect of Moringa oleifera leaves on hematological profile of fluorosis affected rats

Fluorosis is a metabolic disease that is endemic in nearly 25 countries with India being one of the most affected. It primarily affects the bone and the teeth. Moringa oleifera (MO) leaves are known to reduce the effect of fluorosis on various tissues. Therefore, it is of interest to document the effect of Moringa oleifera leaves on the hematological profile of fluorosis affected rats. Twenty four Sprague Dawley rats were housed two per cage in a room with 12 hours light and 12 hours dark cycle. The rats were allowed to adjust to the laboratory environment for about one to two weeks before the beginning of the study. This study reveals that MO leaves is effective in reducing the plasma fluoride content. It also helps in improving the Hb % and RBC count in fluorosis affected rats. Data shows that Moringa olifera leaves powder is effective in reducing the plasma fluoride content. It also helps in improving the Hemoglobin percentage & Red Blood Cell count in fluorosis affected rats.

Geospatial Assessment of Ground Water Quality and Associated Health Problems in the Western Region of India

Groundwater constitutes a significant component of freshwater resources in India being vital for its economy and domestic water security. The quantity, quality and accessibility of water resources forms the basis of balanced socio-economic development and its optimum utilization cannot be sustained unless its quality is assessed. The current study tries to access the quality and suitability of groundwater for drinking purposes in western drier parts of India in the state of Rajasthan. Based on collected data, selected hydro-geochemical parameters, the quality of water has been determined and Water Quality Index (WQI) have been prepared using GIS applications. Applying the Inverse Distance Weighting method, WQI values for 89 villages in the area have been computed, which ranged between 71.23 and 447.39. While 68% of the region had “poor water quality”, only 32% is sustained as ‘good water’ for consumption. The fluoride content ranging between 1.66 and 8.60 mg/L and TDS > 1000 mg/L with average pH levels > 7 (8–9 pH) were found to be very high amongst all the 12 water quality parameters taken for the study. The northeastern region with a WQI value of >250 had the worst water quality. Furthermore, the existing water quality is also examined for influencing two water borne diseases, i.e., gastroenteritis and fluorosis in the region. The study thus establishes that the majority of groundwater in the region is beyond the permissible safer consumption limits, and a large population of the region, which is directly dependent on groundwater sources, is prone to water borne health hazards. A significantly high correlation was observed between Specific Water Quality Parameters in the region and prevalence of gastroenteritis (and fluorosis diseases with R2 = 0.530 and R2 = 0.813, respectively).

Diagnosis of Dental Fluorosis Using Micro-Raman Spectroscopy Applying a Principal Component-Linear Discriminant Analysis

Dental fluorosis is an irreversible condition caused by excessive fluoride consumption during tooth formation and is considered a public health problem in several world regions. The objective of this study was to evaluate the capability of micro-Raman spectroscopy to classify teeth of different fluorosis severities, applying principal component analysis and linear discriminant analysis (PCA-LDA), and estimate the model cross-validation accuracy. Forty teeth of different fluorosis severities and a control group were analyzed. Ten spectra were captured from each tooth and a total of 400 micro-Raman spectra were acquired in the wavenumber range of 250 to 1200 cm⁻¹, including the bands corresponding to stretching and bending internal vibrational modes ν₁, ν₂, ν₃, and ν₄ (PO₄³⁻). From the analysis of the micro-Raman spectra an increase in B-type carbonate ion substitution into the phosphate site of the hydroxyapatite as fluorosis severity increases was identified. The PCA-LDA model showed a sensitivity and specificity higher than 94% and 93% for the different fluorosis severity groups, respectively. The cross-validation accuracy was higher than 90%. Micro-Raman spectroscopy combined with PCA-LDA provides an adequate tool for the diagnosis of fluorosis severity. This is a non-invasive and non-destructive technique with promising applications in clinical and epidemiological fields.

Effect of Endemic Fluorosis on Cognitive Function of School Children in Alappuzha District, Kerala: A Cross Sectional Study

Background:

Exposure to high fluoride levels in drinking water can lead to a number of adverse effects in children, including cognitive dysfunction. Despite being endemic for fluorosis, studies on its effect on the cognitive function of children are lacking in Kerala.

Aims:

The aim of this study was to compare the cognitive function of school children with fluorosis with that of normal children and to correlate between the severity of dental fluorosis and cognitive function.

Settings and Design:

Cross-sectional study, conducted in collaboration with the National Fluorosis Control Programme, among school children in Alappuzha district, Kerala.

Methods:

Children aged 8–10 years, studying in 2 lower primary schools in Alappuzha district with confirmed fluorosis were selected, and compared with healthy age- and sex-matched children from the same school. Raven's Standard Progressive Matrices and MISIC digit span subtest were used to assess the cognitive function.

Statistical Analysis:

Continuous variables were assessed by independent samples t test and categorical variables by Chi-square test. The relationship between severity of dental fluorosis and grade of cognitive impairment was assessed using Spearman's correlation.

Results:

There were 60 children each in fluorosis and control groups. The mean age of the children was 8.95 ± 0.50. Only 15% of the children with fluorosis scored Grade I and II Raven's SPM grades (Intellectually superior/above the average) versus 30% in the control group. None of the children without fluorosis scored Grade V (intellectually impaired) category versus 20% in the fluorosis group. The mean digit span was significantly higher in the control group. A strong positive correlation between severity of dental fluorosis and Raven's SPM grades was found (Spearman's correlation coefficient = 0.740).

Conclusions:

Fluorosis is associated with impaired cognition in children. There is a positive correlation between severity of dental fluorosis and the grade of cognitive impairment.

Chemical Aspects of Human and Environmental Overload with Fluorine

Over the last 100-120 years, due to the ever-increasing importance of fluorine-containing compounds in modern technology and daily life, the explosive development of the fluorochemical industry led to an enormous increase of emission of fluoride ions into the biosphere. This made it more and more important to understand the biological activities, metabolism, degradation, and possible environmental hazards of such substances. This comprehensive and critical review focuses on the effects of fluoride ions and organofluorine compounds (mainly pharmaceuticals and agrochemicals) on human health and the environment. To give a better overview, various connected topics are also discussed: reasons and trends of the advance of fluorine-containing pharmaceuticals and agrochemicals, metabolism of fluorinated drugs, withdrawn fluorinated drugs, natural sources of organic and inorganic fluorine compounds in the environment (including the biosphere), sources of fluoride intake, and finally biomarkers of fluoride exposure.

Fluoride enhances generation of reactive oxygen and nitrogen species, oxidizes hemoglobin, lowers antioxidant power and inhibits transmembrane electron transport in isolated human red blood cells

Fluoride is a widespread environmental pollutant that at high levels exerts numerous deleterious effects on human health. The toxic effects of fluoride are a matter of serious concern since many countries have regions of endemic fluorosis. The main source of fluoride exposure for humans is intake of contaminated groundwater. Fluoride is absorbed from the gastrointestinal tract and enters the circulating blood, where the abundant red blood cells (RBC) are an early and major target of fluoride toxicity. Chronic fluoride exposure generates free radicals, reactive species which leads to redox imbalance, cytotoxicity and hematological damage. This study aimed to determine the effect of sodium fluoride (NaF) on human RBC under in vitro conditions. Isolated RBC were incubated with different concentrations of NaF (10-500 µM) for 8 h at 37 °C. Several biochemical parameters were determined in hemolysates or whole cells. Treatment of RBC with NaF enhanced the generation of reactive oxygen and nitrogen species. This increased the oxidation of hemoglobin to yield methemoglobin and oxoferrylhemoglobin, which are inactive in oxygen transport. NaF treatment increased the degradation of heme causing release of free iron from its porphyrin ring. Cellular antioxidant power was significantly decreased in NaF-treated RBC, lowering the metal reducing and free radical quenching ability of cells. The two pathways of glucose metabolism in RBC i.e. glycolysis and hexose monophosphate shunt, were inhibited. NaF also inhibited the plasma membrane redox system, and its associated ascorbate free radical reductase, to disrupt transmembrane electron transport. These results suggest that fluoride generates reactive species that cause extensive oxidative modifications in human RBC.

Assessment of fluoride levels during pregnancy and its association with early adverse pregnancy outcomes

Background and Aim:

There is sparse data available on human subjects regarding the affect of excessive fluoride exposures on pregnancy. The aim of this study was to examine the association between elevated urinary fluoride levels during early pregnancy and maternal anemia and adverse fetal outcome.

Patients and Methods:

We enrolled 600 pregnant patients with gestational age less than 20 weeks and with a high urinary fluoride levels(>1 mg/L).We also documented the fluoride levels in the tap water and ground water samples collected from the areas where these women resided during pregnancy. These patients were also evaluated for hemoglobin levels and detailed fetal examination by ultrasound. Data was assessed by SSPS version 16.0 software and P < 0.05 was considered to be significant.

Results:

Urinary fluoride averaged 2.65 mg/L and ranged from 1.0 to 4.3 mg/L while all the water samples revealed fluoride levels greater than WHO prescribed the limit of 1.5 mg/L. A total of 402 patients (67%) were found to be anemic with hemoglobin levels ranging from 6.2 to 11.9 g/dl (9.28 ± 1.29). Eighty one patients (13.5%) had adverse fetal outcomes that comprised abortions, congenital abnormalities, and intrauterine deaths (IUDs). There was a negative correlation between urinary fluoride and hemoglobin levels (P = 0.031, r= -0.59) and females with elevated urinary fluoride levels were found to have a strong association with the pregnancy complications, i.e., anemia, miscarriage, abortion, and still birth (χ² = 9.23, P < 0.05).

Conclusions:

Excess fluoride exposures can have deleterious effects on the expecting mother and fetus and is associated with adverse pregnancy outcomes.