Tamarind seed coat ameliorates fluoride induced cytotoxicity, oxidative stress, mitochondrial dysfunction and apoptosis in A549 cells

Fermented Rooibos tea (Aspalathus linearis) Ameliorates Sodium Fluoride-Induced Cardiorenal Toxicity, Oxidative Stress, and Inflammation via Modulation of NF-κB/IκB/IκKB Signaling Pathway in Wistar Rats

High dose of fluoride intake is associated with toxic effects on kidney and cardiac tissues. This study evaluated the potential protective effect of fermented rooibos tea (RTE) on sodium fluoride (NaF)-induced cardiorenal toxicity in rats. Male Wistar rats (n = 56) were randomly allocated into one of seven equal groups: control, NaF (100 mg/kg orally), NaF + RTE (2%, w/v), NaF + RTE (4%, w/v), NaF + lisinopril (10 mg/kg orally), 2% RTE, and 4% RTE. The experiment lasted for 14 days and RTE was administered to the rats as their sole source of drinking fluid. NaF induced cardiorenal toxicity indicated by elevated level of urea, creatinine, LDH, creatinine kinase-MB, and cardiac troponin I in the serum, accompanied by altered histopathology of the kidney and heart. Furthermore, levels of H2O2, malondialdehyde, and NO were elevated, while GSH level was depleted in the kidney and heart due to NaF intoxication. Protein levels of c-reactive protein, TNFα, IL-1B, and NF-κB were increased by NaF in the serum, kidney, and heart. RTE at 2% and 4% (w/v) reversed cardiorenal toxicity, resolved histopathological impairment, attenuated oxidative stress and inhibited formation of pro-inflammatory markers. RTE at both concentrations down-regulates the mRNA expression of NF-κB, and upregulates the mRNA expression of both IκB and IκKB, thus blocking the activation of NF-κB signaling pathway. Taken together, these results clearly suggest that the protective potential of rooibos tea against NaF-induced cardiorenal toxicity, oxidative stress, and inflammation may be associated with the modulation of the NF-κB signaling pathway.

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.

Role of oxidative stress-mediated cell death and signaling pathways in experimental fluorosis

Free radicals and other oxidants have enticed the interest of researchers in the fields of biology and medicine, owing to their role in several pathophysiological conditions, including fluorosis (Fluoride toxicity). Radical species affect cellular biomolecules such as nucleic acids, proteins, and lipids, resulting in oxidative stress. Reactive oxygen species-mediated oxidative stress is a common denominator in fluoride toxicity. Fluorosis is a global health concern caused by excessive fluoride consumption over time. Fluoride alters the cellular redox homeostasis, and its toxicity leads to the activation of cell death mechanisms like apoptosis, autophagy, and necroptosis. Even though a surfeit of signaling pathways is involved in fluorosis, their toxicity mechanisms are not fully understood. Thus, this review aims to understand the role of reactive species in fluoride toxicity with an outlook on the effects of fluoride in vitro and in vivo models. Also, we emphasized the signal transduction pathways and the mechanism of cell death implicated in fluoride-induced oxidative stress.

Effects of fluoride exposure on mitochondrial function: Energy metabolism, dynamics, biogenesis and mitophagy

Fluoride is ubiquitous in the environment. Furthermore, drinking water represents the main source of exposure to fluoride for humans. Interestingly, low fluoride concentrations have beneficial effects on bone and teeth development; however, chronic fluoride exposure has harmful effects on human health. Besides, preclinical studies associate fluoride toxicity with oxidative stress, inflammation, and apoptosis. On the other hand, it is well-known that mitochondria play a key role in reactive oxygen species production. By contrast, fluoride's effect on processes such as mitochondrial dynamics, biogenesis and mitophagy are little known. These processes modulate the size, content, and distribution of mitochondria and their depuration help to counter the reactive oxygen species production and cytochrome c release, thereby allowing cell survival. However, a maladaptive response could enhance fluoride-induced toxicity. The present review gives a brief account of fluoride-induced mitochondrial alterations on soft and hard tissues, including liver, reproductive organs, heart, brain, lung, kidney, bone, and tooth.

The Effects of Sodium Fluoride (NaF) Treatment on the PI3K/Akt Signal Pathway in NRK-52E Cells

The effects of the element fluorine on the phosphoinositide-3-kinase-protein kinase B/Akt (PI3K/Akt) pathway has a significant role in regulation of intracellular molecular mechanisms. NRK-52E rat kidney epithelial cell line was selected as the material of the study. NaF was used as the fluorine source in the study. The NaF dose was determined with the MTT assay. The NaF concentrations were determined as the proliferation concentration of 10 μM and IC₂₅ (2250 μM) and IC₅₀ (4250 μM) for 24 h. In the study, the erb-b2 receptor tyrosine kinase 2 (ERBB2), phosphoinositide-3-kinase (PI3K), Protein kinase B (PKB,Akt), Mammalian target of rapamycin (mTOR), and the Tumor protein 53 (TP53) genes were considered as the target genes. NaF concentration was administered on the cells. Total mRNA was isolated. mRNAs were turned into cDNA. The expression levels of the target genes were determined by RT-qPCR method. According to the results obtained in the study, the low NaF concentration increased the expression levels of the ERBB2, PI3K, and Akt genes, while the higher concentrations did not significantly affect these levels. The expression of mTOR decreased at all given concentrations. The expression of the TP53 gene did not change at the low concentration, while it increased at the high concentrations. Based on the results, it may be stated that fluorine may inhibit the kinase enzymes in the PI3K/Akt pathway. In summary, in the pathogenesis of the cell damage caused by fluorine in the NRK-52E cell line, the PI3K/Akt/mTOR pathway is an important signal pathway.

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.

Sirt3-mediated mitochondrial dysfunction is involved in fluoride-induced cognitive deficits

Excessive fluoride is capable of inducing cognitive deficits, but the mechanisms remain elusive. This study aimed to investigate the effects and underlying mechanisms of fluoride on mitochondrial dysfunction and neurobiological alterations, as well as cognitive impairment. C57BL/6 mice were orally administered 25, 50, and 100 mg/L NaF for 90 days. Cultured human neuroblastoma SH-SY5Y cells were exposed to NaF (110 mg/L) for 24 h in the presence or absence of Sirt3 overexpression. The results demonstrated that chronic exposure to high fluoride induced cognitive deficits and neural/synaptic injury in mice. Fluoride reduced mitochondrial antioxidant enzyme activities and elevated SOD2 acetylation by downregulating Sirt3 expression in the brains of mice and NaF-treated SH-SY5Y cells. Moreover, fluoride lowered mtDNA transcription and induced mitochondrial dysfunction along with increased FoxO3A acetylation in the brains of mice and NaF-treated SH-SY5Y cells. Subsequent experiments revealed that overexpression of Sirt3 significantly attenuated the adverse effects of fluoride on radical scavenging capabilities and mtDNA transcription, as well as mitochondrial function in SH-SY5Y cells. These results suggest that chronic long-term fluoride exposure evokes neural/synaptic injury and cognitive impairment through mitochondrial dysfunction and its associated oxidative stress, which is, at least partly, mediated by Sirt3 inhibition in the mouse brain.

Sodium fluoride activates the extrinsic apoptosis via regulating NOX4/ROS-mediated p53/DR5 signaling pathway in lung cells both in vitro and in vivo

An extensive body of research has demonstrated that pulmonary toxicity induced by fluoride is related to cell apoptosis. Although induction of death receptor-initiated extrinsic apoptosis by sodium fluoride (NaF) has been reported, its mechanism of action is still not clearly defined. Herein, we found that NaF treatment induced activation of caspase-8 in BEAS-2B cells, resulting in apoptosis, which was markedly reduced by blocking caspase-8 using small interfering RNA (siRNA). In this study, we report that death receptor 5 (DR5), a major component of the extrinsic apoptotic pathway, is markedly induced upon NaF stimulation. Enhanced DR5 induction was necessary for the apoptotic effects of NaF, inasmuch as transfected BEAS-2B cells with DR5 siRNA attenuated NaF-induced caspase-8 activation in lung cells. Mechanism investigation indicated that the induction of DR5, following NaF exposure, was mediated by tumor protein 53 (p53)-dependent transcriptional activation. Notably, we demonstrated that NaF could induce a significant increase in intracellular reactive oxygen species (ROS) level derived from nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). Specifically, NOX4 knockdown inhibited NaF-induced the activation of p53/DR5 axis by reducing NOX4-derived ROS production. Further in vivo investigation demonstrated that NOX4 deficiency markedly attenuates NaF-induced lung injury, apoptosis, and ROS levels in the lung. Moreover, the expressions of p53 and DR5 were significantly reduced after NaF treatment in NOX4 knockout mice compared with the wild type mice. Taken together, our findings provide a novel insight into for the pulmonary apoptosis in response to NaF exposure.

Relationship of fluoride in drinking water with blood pressure and essential hypertension prevalence: a systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

Previous studies showed controversial results of the relationship between fluoride exposure through drinking water and elevated blood pressure. We conducted a systematic review and meta-analysis to assess the direct relationship of drinking water fluoride exposure with blood pressure and essential hypertension prevalence in general populations.

METHODS

We conducted a systematic search in databases including Web of Knowledge, PubMed, Scopus, and Embase by MeSH and non-MeSH terms for relevant studies with any design published until August 2019, with no limitation in time and language. The pooled effect measure was calculated within a 95% confidence interval (CI).

RESULTS

Our search retrieved 630 journal articles, six of which were eligible for data extraction. The random-effects model found significantly higher systolic blood pressure (mean difference = 6.49 mmHg; 95% CI 3.73-9.25; p value < 0.01) and diastolic blood pressure (mean difference = 4.33 mmHg; 95% CI 1.39-7.26; p value < 0.01) in groups exposed to high-fluoride drinking water than in groups exposed to normal/low-fluoride drinking water. A significant relationship was also found between high-fluoride drinking water and essential hypertension (odds ratio = 2.14; 95% CI 1.02-4.49; p value = 0.045).

CONCLUSION

The risk of elevated blood pressure increases in the general population of fluoride endemic areas. However, more research is needed to make a firm conclusion about the adverse effects of excess fluoride intake on the cardiovascular system at the individual level.

The effect of vitamin E and selenium combination in repairing fluoride-induced DNA damage to NRK-52E cells

Prolonged and excessive fluoride exposure can lead to fluorosis. The kidney is one of the organs that are injured mostly due to fluoride-induced damage. Fluoride can induce DNA damage at cytotoxic concentrations. This study aims to determine the extent of NaF-induced DNA damage and to investigate the effect of vitamin E and selenium combination (ES) in preventing and repairing this damage. For this purpose, we administered different combinations of NaF and ES to NRK-52E cells and determined the effective concentrations of ES and the NaF IC₅₀ values associated with different incubation times (3, 12, and 24 h) by using the MTT assay. The determined quantities of NaF IC₅₀ in association with time and the NaF IC₅₀ + ES combination were administered to the cells. The extent of DNA damage was determined with the comet assay and the expression levels of the Ku70/80 and PARP-1 genes were determined with the RT-qPCR method. DNA damage significantly increased in all experimental groups compared to the control group (p < 0.05). It was found out that the NaF and ES combination statistically reduced the DNA damage compared to the damage observed in the NaF-treated groups (p < 0.05). Treatment of the ES combination significantly increased the expressions of Ku70 and Ku80 genes involved in DNA repair (p < 0.05). We concluded that vitamin E and selenium can potentially be effective in the repair of fluoride-induced DNA damage based on the results of this in vitro study. Our results may shed light on the prevention of DNA damage associated with fluorosis.

Antioxidant, anti-inflammatory and healing potential of ethyl acetate fraction of Bauhinia ungulata L. (Fabaceae) on in vitro and in vivo wound model

The present work aimed to investigate the antioxidant, anti-inflammatory and wound healing potential of ethyl acetate fraction from Bauhinia ungulata L. (FABU) on in vitro and in vivo models. Wound healing assay using human lung adenocarcinoma A549 cell line was employed to evaluate the ability of FABU in modulating cell migration. In addition, a surgical wound model in C57BL/6 mice was used to study the healing potential of FABU incorporated into gel carbomer 940 (Carbopol®). Evaluation of lipid peroxidation, inflammatory and anti-inflammatory mediator gene expression, rate of wound closure, and histological analysis were done. FABU significantly reduced the gap area in in vitro wound healing assay, 24 h after treatment. In the animal model, FABU at 0.5% topically applied once-daily for 5 days to the surgical wounds significantly reduced the lesion area. Moreover, it significantly decreased the levels of lipid peroxidation in the lesions and decreased the relative gene expression levels of IL-1β and TNF-α in the injured region. In conclusion, our study suggests that Bauhinia ungulata can effectively promote the wound healing, probably by regulating the inflammatory environment during the early stages of the process.

Fluoride-induced renal dysfunction via respiratory chain complex abnormal expression and fusion elevation in mice

A fluoride exposure mouse model is established to evaluate the relationship between mitochondrial respiratory chain complexes and renal dysfunction. Morphological changes in kidney tissues were observed. Renal function and cell proliferation in the kidneys were evaluated. The expression of mitochondrial fusion protein including mitofusin-1 (Mfn1) and optic atrophy 1 (OPA1), and mitochondrial respiratory chain complex subunits, including NDUFV2, SDHA, CYC1 and COX Ⅳ, were detected via real-time polymerase chain reaction, immunohistochemistry staining and Western blot, respectively. Results showed that the structures of renal tubule, renal glomerulus and renal papilla were seriously damaged. Renal function was impaired, and cell proliferation was remarkably inhibited by excessive fluoride in kidney. The mRNA and protein expression levels of Mfn1, OPA1, NDUFV2, CYC1 and COX Ⅳ were significantly increased after excessive fluoride exposure. However, the mRNA and protein expression of SDHA significantly decreased. Overall, our findings revealed that excessive fluoride can damage kidney structure, inhibit renal cell proliferation, interfere with the expression of mitochondrial respiratory chain complexes and elevate mitochondrial fusion. Consequently, renal function disorder occurred.

Protective role of resveratrol, a natural polyphenol, in sodium fluoride-induced toxicity in Drosophila melanogaster

Sodium fluoride (NaF) is used in water fluoridation and dental products such as mouth rinses and toothpastes. Resveratrol is a natural polyphenol with antioxidant and anti-inflammatory properties. The present study was carried out to evaluate the toxicity of NaF and the protective role of resveratrol in Drosophila melanogaster. For longevity assay, Harwich strain of D. melanogaster was treated with NaF (0, 10, 30, 50, 70 and 90 mg/kg diet) throughout the lifespan and daily mortality recorded. Then, flies were again treated with similar doses of NaF for seven days to evaluate survival rate and oxidative stress markers. Thereafter, 60 mg resveratrol/kg diet was selected to determine its ameliorative role in NaF (70 mg/kg)-induced toxicity in flies: Group A (control), Group B (60 mg resveratrol/kg diet), Group C (70 mg NaF/kg diet), and Group D (resveratrol, 60 mg/kg diet) + NaF, 70 mg/kg diet). Thereafter, Glutathione-S-transferase (GST), catalase and acetylcholinesterase (AchE) activities, as well as total thiol (T-SH), nitrites/nitrates and hydrogen peroxide (H2O2) levels were determined. The results showed that resveratrol prevented NaF-induced elevation of H2O2and nitrites/nitrates levels, as well as catalase activity. In addition, resveratrol restored NaF-induced inhibition of GST and AChE activities and depletion of T-SH content ( P < 0.05). Conclusively, resveratrol offered protective benefit against NaF-mediated toxicity in flies due to its antioxidant and anti-inflammatory properties.

Impact statement

D. melanogaster was used to understand the impact of NaF on lifespan and emergence rate as well as the rescue role of resveratrol. These parameters are difficult to carry out in previously used models such as rodents. This further enforces in part, the suitability of D. melanogaster in studying NaF-induced toxicity and the therapeutic effects of drugs. Additionally, we found that resveratrol rescued D. melanogaster from oxidative stress-induced by sodium fluoride (NaF) administration. This study is of public health significance as it indicated that the consumption of fruits rich in resveratrol such as grapes may offer protective role against inadvertent exposure to NaF and related chemicals.

Tamarind: A diet-based strategy against lifestyle maladies

The modern-day review article is an exquisite attempt to demonstrate the extreme therapeutic potential of tamarind fruit (Tamarindus indica), particularly its pulp, seed, and leaf extract, against lifestyle-related chronic disorders. The rapid transition in the diet patterns and also the varying lifestyle of the people has made its way forth, a momentous upsurge in a number of chronic as well as degenerative diseases. An excess of foods having functional and nutraceutical significance has come into view recently. These foods have emerged as effective therapeutical remedies against these disorders owing to their natural phytochemical constituents present in them, in abundance. Tamarindus indica serves as a proverbial herbal medicine in each and every part of the world that is known to mankind. Also, the tamarind kernel powder (TKP) is of immense commercial significance in some of the major, leading industries of the World. The derivation of an important gel-forming substance (polysaccharide), named as "jellose," from the decorticated seed kernels of tamarind fruit has led to the manufacture of pectin. It is used in industrial scale in the preparation of various products like jams, jellies, and most important in the preparation of cheese. It plays an evident role as a stabilizer of commercial significance, and it has also been greatly recommend by the scientists to be used as a potent ingredient in a range of pharmaceutical products. The leaves of tamarind plant are also used as part of the daily diet in several countries where they are readily consumed in fresh form and especially during drought season.

Calcium Alleviates Fluoride-Induced Bone Damage by Inhibiting Endoplasmic Reticulum Stress and Mitochondrial Dysfunction

Excessive fluoride mainly causes skeletal lesions. Recently, it has been reported that an appropriate level of calcium can alleviate fluorosis. However, the appropriate concentration and mechanism of calcium addition is unclear. Hence, we evaluated the histopathology and ultrastructure, DNA fragmentation, hormonal imbalances, biomechanical levels, and expression of apoptosis-related genes after treating the rats with 150 mg/L NaF and different concentrations of CaCO₃. Our results suggested that NaF induced the histopathological and ultrastructural injury, with a concomitant increase in the DNA fragmentation (P < 0.05) and serum OC (17.5 ± 0.89 pmoL/L) at 120 days. In addition, the qRT-PCR and western blotting results indicated that NaF exposure upregulated the mRNA and protein expression of Bax, Calpain, Caspase 12, Caspase 9, Caspase 7, Caspase 3, CAD, PARP, and AIF while downregulated Bcl-2 (P < 0.01) and decreased the bone ultimate load by 27.1%, the ultimate stress by 10.1%, and the ultimate deformity by 23.3% at 120 days. However, 1% CaCO₃ supplementation decreased the serum OC (14.7 ± 0.65 pmoL/L), bone F content (P < 0.01), and fracture and breakage of collagen fibers and changed the expression of endoplasmic reticulum pathway-related genes and proteins at 120 days. Further, 1% CaCO₃ supplementation increased the bone ultimate load by 20.9%, the ultimate stress by 4.89%, and the ultimate deformity by 21.6%. In summary, we conclude that 1% CaCO₃ supplementation alleviated fluoride-induced bone damage by inhibiting endoplasmic reticulum stress and mitochondrial dysfunction.

Vitamin C Attenuates Sodium Fluoride-Induced Mitochondrial Oxidative Stress and Apoptosis via Sirt1-SOD2 Pathway in F9 Cells

Increasing evidence has suggested an important role played by reactive oxygen species (ROS) in the pathogenesis of fluorosis. Accumulating evidence demonstrates that vitamin C administration ameliorate sodium fluoride (NaF)-induced oxidative stress. However, the potentially beneficial effects of vitamin C against NaF-induced cytotoxicity and the underlying molecular mechanisms of this protection are not fully understood. Here, we found that NaF stimulated cytotoxicity, increased mitochondrial reactive oxygen species (mROS) production, and induced apoptosis in F9 embryonic carcinoma cells. Consistent with this finding, NaF exposure was associated with decreased Sirtuin 1 (Sirt1) protein expression, thus promoted the acetylation of manganese superoxide dismutase (SOD2), a key enzyme involved in regulating mROS production. However, all NaF-induced mitochondrial oxidative injuries were efficiently ameliorated by overexpression of Sirt1 or incubation with Mito-TEMPO (a SOD2 mimetic). Moreover, pretreatment with vitamin C enhanced the expression of Sirt1 and decreased NaF-induced mitochondrial oxidative stress and apoptosis. Knockdown of Sirt1 blocked the vitamin C-mediated reduction in mROS and apoptosis via inhibiting Sirt1-SOD2 signaling. Importantly, sodium-dependent vitamin C transporter 2 (SVCT-2) siRNA was found to partially block the ability of vitamin C to promote Sirt1/SOD2 signaling. In summary, our data indicate that Sirt1 plays a pivotal role in the ability of vitamin C to stimulate SOD2 activity and attenuate mitochondrial oxidative stress, which partially through vitamin C receptor in NaF-induced F9 cells injury.

Selenium attenuates apoptosis and p-AMPK expressions in fluoride-induced NRK-52E cells

Fluoride is widely distributed in the environment, and excessive fluoride intake can induce cytotoxicity, DNA damage, and cell cycle changes in many tissues and organs, including the kidney. Accumulating evidence demonstrates that selenium (Se) administration ameliorates sodium fluoride (NaF)-induced kidney damage. However, the potentially beneficial effects of Se against NaF-induced cytotoxicity of the kidney and the underlying molecular mechanisms of this protection are not fully understood. At present, in this study, the normal rat kidney cell (NRK-52E) was used to investigate the potentially protective mechanism of Se against NaF-induced apoptosis, by using the methods of pathology, colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, flow cytometry, and Western blot. The experiment was designed with a control group, two NaF-treated groups (NaF, 5, 20 mg/L), two sodium selenite-treated groups (Na₂SeO₃, 17.1, 34.2 μg/L), and four Se + NaF-treated groups (Na₂SeO₃, 17.1, 34.2 μg/L; NaF, 5, 20 mg/L). The results indicate that selenium can attenuate apoptosis and AMPK phosphorylation in the NRK-52E cell induced with fluoride. These results imply that selenium is capable to modulate fluoride-induced NRK-52E cell apoptosis via regulating the expression levels of the proteins involved in mitochondrial pathway and changes in p-AMPK expressions may also be a key process in preventing fluorosis.

SIRT1 suppresses p53-dependent apoptosis by modulation of p21 in osteoblast-like MC3T3-E1 cells exposed to fluoride

Fluoride is very crucial for development of teeth and bones. Excessive fluoride, however, causes damage to teeth and bones resulting in serious public health problem. SIRT1 regulates physiological and pathological processes such as apoptosis and cell cycle. Although SIRT1 inhibits p53-mediated transactivation, how SIRT1 regulates p53 in fluorosis remains unclear. This study aims to investigate the involvement of SIRT1 in fluoride-induced cell cycle arrest and apoptosis in MC3T3-E1 cells and the underlying mechanism. Cell apoptosis was determined using Annexin V-FITC/PI dual staining, cell cycle detected with PI staining, intracellular ROS levels measured with DCFH-DA probe, and apoptosis-related protein expressions determined using Western blotting. Results showed that there was a promotion in apoptosis rate, intracellular ROS levels, the ratio of Bax/Bcl-2, protein expression (Cyt c, Caspase-3, p53, Ac-p53 and p21) and blockage of S phase after cells were exposed to NaF. Afterwards, the influence of SIRT1 on apoptosis was explored after SRT1720 (SIRT1 activator) and Ex-527 (SIRT1 inhibitor) was introduced. Results indicated that SRT1720 in combination with fluoride significantly decreased the intracellular ROS levels, the protein expression of Caspase-3, Ac-p53 and p21 and alleviated apoptosis, while it was reversed by Ex-527. Collectively, SIRT1 plays an essential role in protection against fluoride-induced oxidative stress and mitochondria-dependent apoptosis in MC3T3-E1 cells. The SIRT1/p53/p21 pathway may be a potential therapeutic target for fluorosis.

JNK/STAT signalling pathway is involved in fluoride-induced follicular developmental dysplasia in female mice

Excessive fluoride (F) intake decreases the development of potential oocytes by inducing oxidative stress and apoptosis in female mice in our previous study. This study aims to investigate the underlying mechanisms of F-induced follicular developmental dysplasia. Pathomorphological changes in the ovary tissues were observed under light and transmission electron microscopes. DNA damage and proliferation in granulosa cells were analysed by TUNEL staining and BrdU measurement. The protein expression of cell proliferation related regulatory factors including JNK, STAT3, STAT5, CDK2, CDK4, PCNA and Ki67 in the ovary tissues was measured by immunohistochemistry and Western blot analyses. Results indicated that the structure of granulosa cells in the ovary was seriously damaged by excessive F, evident by the swollen endoplasmic reticulum, mitochondria with vacuoles and nucleus shrinkage. F treatment also considerably enhanced the apoptosis and inhibited the proliferation of granulosa cells. The number of granulosa cells around the oocyte decreased after F treatment. The expression levels of STAT3, CDK2, CDK4 and Ki67 in the ovary tissues were up-regulated, and STAT5 and PCNA did not change significantly after F treatment, whereas JNK expression was down-regulated with increasing F dose. In summary, changes in the expression levels of JNK, STAT3, STAT5, CDK2, CDK4, PCNA and Ki67 in the JNK/STAT signalling pathway are involved in F-induced follicular dysplasia in the ovary.

Tamarind seed coat extract restores fluoride-induced hematological and biochemical alterations in rats

Fluoride (F^-) is becoming an ineluctable environmental pollutant causing deleterious effects in humans. In the present study, we examined whether tamarind seed coat extract (TSCE) is beneficial against the F^--induced systemic toxicity and hematological changes. Wistar rats were randomly grouped as follows: group I served as control; group II intoxicated with sodium fluoride (NaF, 300 ppm) in drinking water; group III was administered through oral intubation with TSCE (100 mg/kg bw); group IV was treated with NaF (300 ppm) in association with TSCE (100 mg/kg bw) for 30 days. The results indicated that F^- exposure induced oxidative stress as evidenced by elevated levels of reactive oxygen species and lipid peroxidation in the brain, liver, and kidney. F^- administration modulates hematological indices-WBC, RBC, and mean corpuscular volume. Moreover, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, acetylcholinesterase, and monoamine oxidase significantly increased on F^- exposure. Conversely, δ-aminolevulinic acid dehydratase and glutathione/reduced glutathione ratio were decreased. Activity of antioxidants-superoxide dismutase, catalase, glutathione peroxidase, and vitamin C-was also significantly decreased due to F^- administration. Treatment with TSCE effectively mitigated the alterations through its antioxidant potential. The data suggested that the TSCE had beneficial effects in alleviating the F^--induced toxicity and hence can serve as a promising neutraceutical agent.

Chronic Exposure to Sodium Fluoride Triggers Oxidative Biochemistry Misbalance in Mice: Effects on Peripheral Blood Circulation

The excessive fluoride (F) exposure is associated with damage to cellular processes of different tissue types, due to changes in enzymatic metabolism and breakdown of redox balance. However, few studies evaluate doses of F compatible with human consumption. Thus, this study evaluated the effects of chronic exposure to sodium fluoride (NaF) on peripheral blood of mice from the evaluation of biochemical parameters. The animals were divided into three groups (n = 10) and received three concentrations of NaF in the drinking water for 60 days: 0 mg/L F, 10 mg/L F, and 50 mg/L F. The blood was then collected for trolox equivalent antioxidant capacity (TEAC), thiobarbituric acid reactive substances (TBARS), concentrations of nitric oxide (NO), superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH). The results showed that doses of 10 mg/L F and 50 mg/L F were able to increase TBARS concentration and decrease NO levels and CAT activity in the blood, but there was no statistical difference for SOD levels. The 50 mg/L F group showed an increase in TEAC levels and a decrease in the GSH content when compared to the control group. In this way, oxidative changes in blood from chronic exposure to F, especially at the highest dose, indicate that F may be a toxic agent and, therefore, the long-term exposure to excessive doses should be avoided.

Effects of Fluoride on SOD and CAT in Testis and Epididymis of Mice

Oxidative damage has been implicated to be one of main mechanisms by which fluoride (F) induces toxic effects. Previous studies reported that F destroyed the epididymal structure of mouse and rabbit. Epididymis is the important place for sperm maturation. However, little is known about the effect of F on the oxidative stress status of epididymis. Therefore, the aim of the present study was to explore the changes in the activities and transcriptional levels of CuZn superoxide dismutase (CuZn-SOD, SOD1) and catalase (CAT), as well as the ultrastructure, in testis and epididymis of mice administrated with F. Sixty health Kunming mice were randomly divided into four groups. With one group untreated as controls, the others were treated with 25, 50, and 100 mg NaF/L in drinking water. After 10 weeks administration, mitochondrial ultrastructural changes in testis and epididymis were observed, including the incomplete membrane and the dissolved or disappeared cristae. Compared to the control group, the activities of both SOD1 and CAT in testis and epididymis were significantly reduced by 50 or 100 mg NaF exposure. In addition, the mRNA expressions of testicular SOD1 and CAT were also decreased significantly in 100 mg NaF/L group, while the SOD1 and CAT mRNA expressions in epididymides were significantly reduced in all F treatment groups. The above results suggest that in the presence of F, similar to testis, epididymis also loses the balance between oxidative stress and antioxidative defense, and perhaps more sensitive to F.

Crosstalk between p38 MAPK and caspase-9 regulates mitochondria-mediated apoptosis induced by tetra-α-(4-carboxyphenoxy) phthalocyanine zinc photodynamic therapy in LoVo cells

Photodynamic therapy (PDT) is considered to be an advancing antitumor technology. PDT using hydrophilic/lipophilic tetra-α-(4-carboxyphenoxy) phthalocyanine zinc (TαPcZn-PDT) has exhibited antitumor activity in Bel-7402 hepatocellular cancer cells. However, the manner in which p38 MAPK and caspase-9 are involved in the regulation of mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo human colon carcinoma cells remains unclear. Therefore, in the present study, a siRNA targeting p38 MAPK (siRNA-p38 MAPK) and the caspase-9 specific inhibitor z-LEHD-fmk were used to examine the crosstalk between p38 MAPK and caspase-9 during mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells. The findings revealed that the TαPcZn-PDT treatment of LoVo cells resulted in the induction of apoptosis, the formation of p38 MAPK/caspase-9 complexes, the activation of p38 MAPK, caspase-9, caspase-3 and Bid, the downregulation of Bcl-2, the reduction of mitochondrial membrane potential (ΔΨm), the upregulation of Bax and the release of apoptosis-inducing factor (AIF) and cytochrome c (Cyto c). By contrast, siRNA-p38 MAPK or z-LEHD-fmk both attenuated the effects of TαPcZn-PDT in the LoVo cells. Furthermore, the results revealed that siRNA-p38 MAPK had more significant inhibitory effects on apoptosis and mitochondria compared with the effects of z-LEHD-fmk in TαPcZn-PDT-treated LoVo cells. These findings indicated that p38 MAPK plays the major regulatory role in the crosstalk between p38 MAPK and caspase-9 and that direct interaction between p38 MAPK and caspase-9 may regulate mitochondria-mediated apoptosis in the TαPcZn-PDT-treated LoVo cells.

Melatonin-mediated upregulation of Sirt3 attenuates sodium fluoride-induced hepatotoxicity by activating the MT1-PI3K/AKT-PGC-1α signaling pathway

Mitochondrial reactive oxygen species (ROS) production has been implicated in the pathogenesis of fluoride toxicity in liver. Melatonin, an indolamine synthesized in the pineal gland, was previously shown to protect against sodium fluoride (NaF)-induced hepatotoxicity. This study investigated the protective effects of melatonin pretreatment on NaF-induced hepatotoxicity and elucidates the potential mechanism of melatonin-mediated protection. Reducing mitochondrial ROS by melatonin substantially attenuated NaF-induced NADPH oxidase 4 (Nox4) upregulation and cytotoxicity in L-02 cells. Melatonin exerted its hepatoprotective effects by upregulating Sirtuin 3 (Sirt3) expression level and its activity. Melatonin increased the activity of manganese superoxide dismutase (SOD2) by promoting Sirt3-mediated deacetylation and promoted SOD2 expression through Sirt3-regulated DNA-binding activity of forkhead box O3 (FoxO3a), thus inhibiting the production of mitochondrial ROS induced by NaF. Notably, increased peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α) by melatonin activated the Sirt3 expression, which was regulated by an estrogen-related receptor (ERR) binding element (ERRE) mapped to Sirt3 promoter region. Analysis of the cell signaling pathway profiling systems and specific pathway inhibition indicated that melatonin enhances PGC-1α expression by activating the PI3K/AKT signaling pathway. Importantly, inhibition of melatonin receptor (MT)-1 blocked the melatonin-activated PI3K/AKT-PGC-1α-Sirt3 signaling. Mechanistic study revealed that the protective effects of melatonin were associated with down-regulation of JNK1/2 phosphorylation. Our findings provided a theoretical basis that melatonin mitigated NaF-induced hepatotoxicity, which, in part, was mediated through the activation of the Sirt3 pathway.

Pulmonary fluorosis: a review

The increased industrialization and improvised human lifestyle lead to a surge in environmental pollution nowadays. Even the chemicals which are known as prophylactic agents were currently liable to be toxic. One among them is inorganic fluoride whose wider application in numerous processes makes it as an inevitable environmental contaminant and industrial pollutant. Although the systemic toxicity of fluoride has been extensively studied, still there is lacuna in the field of pulmonary fluoride toxicity. Hence, we have focused on the molecular mechanism of action of fluoride compounds on pulmonary system. A study of literatures that focused on the potential physiological and toxicological consequences of fluoride on pulmonary system was carried out. The goal of this review is to present an overview of the research carried out till date on the molecular aspects of fluoride exposure with emphasis on pulmonary system and their possible mechanisms.

Differential expression of myocardial heat shock proteins in rats acutely exposed to fluoride

Acute fluoride (F-) toxicity is known to cause severe cardiac complications and leads to sudden heart failure. Previously, we reported that increased myocardial oxidative damage, apoptosis, altered cytoskeleton and AMPK signaling proteins associated with energy deprivation in acute F- induced cardiac dysfunction. The present study was aimed to decipher the status of myocardial heat shock proteins (Hsps-Hsp27, Hsp32, Hsp40, Hsp60, Hsp70, Hsp90) and heat shock transcription factor 1 (Hsf1) in acute F--intoxicated rats. In order to study the expression of myocardial Hsps, male Wistar rats were treated with single oral doses of 45 and 90 mg/kg F- for 24 h. The expression levels of myocardial Hsps were determined using RT-PCR, western blotting, and immunohistochemical studies. Acute F--intoxicated rats showed elevated levels of both the transcripts and protein expression of Hsf1, Hsp27, Hsp32, Hsp60, and Hsp70 when compared to control. In addition, the expression levels of Hsp40 and Hsp90 were significantly declined in a dose-dependent fashion in F--treated animals. Our result suggests that differential expression of Hsps in the rat myocardium could serve as a balance between pro-survival and death signal during acute F--induced heart failure.

The Effect of Sodium Fluoride on Cell Apoptosis and the Mechanism of Human Lung BEAS-2B Cells In Vitro

Sodium fluoride (NaF) is a source of fluoride ions used in many applications. Previous studies found that NaF suppressed the proliferation of osteoblast MC3T3 E1 cells and induced the apoptosis of chondrocytes. However, little is known about the effects of NaF on human lung BEAS-2B cells. Therefore, we investigated the mode of cell death induced by NaF and its underlying molecular mechanisms. BEAS-2B cells were treated with NaF at concentrations of 0, 0.25, 0.5, 1.0, 2.0, and 4.0 mmol/L. Cell viability decreased and apoptotic cells significantly increased as concentrations of NaF increased over specific periods of time. The IC₅₀ of NaF was 1.9 and 0.9 mM after 24 and 48 h, respectively. The rates of apoptosis increased from 4.8 to 37.7% after NaF exposure. HE staining, electron microscopy, and single cell gel electrophoresis revealed that morphological changes of apoptosis increased with exposure concentrations. RT-PCR and Western blotting were used to detect the apoptotic pathways. The expressions of bax, caspase-3, caspase-9, p53, and the cytoplasmic CytC of the NaF groups increased, while bcl-2 and mitochondrial CytC decreased compared with that of the control group (P < 0.05). Further, the fluorescence intensities of ROS in the NaF groups were higher than those in the control group, and the membrane potential of mitochondria in the NaF group was significantly lower than that of the control group (P < 0.05). These findings suggested that NaF induced apoptosis in the BEAS-2B cells through mitochondria-mediated signal pathways. Our study provides the theoretical foundation and experimental basis for exploring the mechanisms of human lung epithelial cell damage and cytotoxicity induced by fluorine.

Intracellular calcium promotes radioresistance of non-small cell lung cancer A549 cells through activating Akt signaling

Radiotherapy is a major therapeutic approach in non-small cell lung cancer but is restricted by radioresistance. Although Akt signaling promotes radioresistance in non-small cell lung cancer, it is not well understood how Akt signaling is activated. Since intracellular calcium (Ca²⁺) could activate Akt in A549 cells, we investigated the relationship between intracellular calcium (Ca²⁺) and Akt signaling in radioresistant A549 cells by establishing radioresistant non-small cell lung cancer A549 cells. The radioresistant cell line A549 was generated by dose-gradient irradiation of the parental A549 cells. The cell viability, proliferation, and apoptosis were, respectively, assessed using the cell counting kit-8, EdU labeling, and flow cytometry analysis. The phosphorylation of Akt was evaluated by Western blotting, and the intracellular Ca²⁺ concentration was assessed by Fluo 4-AM. The radioresistant A549 cells displayed mesenchymal morphology. After additional irradiation, the radioresistant A549 cells showed decreased cell viability and proliferation but increased apoptosis. Moreover, the intracellular Ca²⁺ concentration and the phosphorylation level on the Akt473 site in radioresistant A549 cells were higher than those in original cells, whereas the percentage of apoptosis in radioresistant A549 cells was less. All these results could be reversed by verapamil. In conclusion, our study found that intracellular Ca²⁺ could promote radioresistance of non-small cell lung cancer cells through phosphorylating of Akt on the 473 site, which contributes to a better understanding on the non-small cell lung cancer radioresistance, and may provide a new target for radioresistance management.

Sodium fluoride induces nephrotoxicity via oxidative stress-regulated mitochondrial SIRT3 signaling pathway

Accumulation of mitochondrial reactive oxygen species (mROS) has been implicated in the pathogenesis of fluorosis. As the main mitochondrial deacetylase, SIRT3 is closely associated with oxidative stress. To investigate the role of SIRT3 in response to sodium fluoride (NaF)-induced nephrotoxicity. Our results showed that NaF treatment impaired mitochondrial ultrastructure, decreased cell viability and increased apoptosis in TCMK-1 cells. Oxidative stress, detected by mROS and 8-Hydroxy-2’-deoxyguanosine (8-OHdG) were higher in NaF-treated cells, accompanied by decreased level of reduced glutathione (GSH). NaF reduces manganese superoxide dismutase (SOD2) expression through SIRT3-mediated DNA-binding activity of FoxO3a and decrease SOD2 activity by inhibiting SIRT3-mediated deacetylation. These effects were ameliorated by overexpression of SIRT3. Peroxisome proliferator-activated receptor-coactivator 1a (PGC-1α) interacted with nuclear factor erythroid 2 (NF-E2)-related factor 2 (NRF2) that bound to SIRT3 promoter to regulate SIRT3 expression. The study provides new insights into a critical NRF2/PGC-1α-SIRT3 pathway in response to NaF-induced nephritic oxidative injury. In vivo treatment of SIRT3-expressing adenovirus protects against NaF-induced nephritic injury in mice. Moreover, mechanistic study revealed that ERK1/2 activation was associated with increased apoptosis induced by NaF. In conclusion, these data shedding light on new approaches for treatment of NaF-induced nephrotoxicity.

Sodium fluoride induces hypertension and cardiac complications through generation of reactive oxygen species and activation of nuclear factor kappa beta

Human exposure to sodium fluoride through its daily usage is almost inevitable. Cardiovascular and renal dysfunction has been associated with fluoride toxicity. Therefore, this study investigated the mechanism of action of sodium fluoride (NaF) induced hypertension and cardiovascular complications Forty male albino rats of an average of 10 rats per group were used. Group A received clean tap water. Toxicity was induced in Group B to D by administering graded doses of NaF through drinking water ad libitum for 10 days at 150 ppm, 300 ppm, and 600 ppm concentration respectively. Following administration of NaF, there was significant increase in systolic pressure, diastolic pressure and mean arterial pressure. Markers of oxidative stress; malondialdehyde, hydrogen peroxide, advance oxidation protein products, and protein carbonyl were significantly increased in dose-dependent pattern in the cardiac and renal tissues of rats together with significant decrease in the GST activity in NaF-treated rats compared to the control. Also serum markers of inflammation, cardiac, and renal damage including myeloperoxidase, xanthine oxidase, blood urea nitrogen, creatinine, Lactate dehydrogenase (LDH), and Creatinine kinase myocardial band (CK-MB) significantly increased indicating induction of oxidative stress, renal, and cardiac damage after exposure. Histopathology of the kidney and heart revealed aberrations in the histological architecture in NaF-treated rats. Also, immunohistochemistry showed higher expression of nuclear factor kappa beta (NF-kB) in the cardiac and renal tissues of rats administered NaF. Combining all, these results indicate NaF-induced hypertension through generation of reactive oxygen species and activation of renal and cardiac NF-kB expressions. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1089-1101, 2017.