Oxidative damage to mitochondria is a preliminary step to caspase-3 activation in fluoride-induced apoptosis in HL-60 cells

A correlation between oxidative stress and diabetic retinopathy: An updated review

Oxidative stress (OS) is a cytopathic outcome of excessively generated reactive oxygen species (ROS), down regulated antioxidant defense signaling pathways, and the imbalance between the produced radicals and their clearance. It plays a role in the genesis of several illnesses, especially hyperglycemia and its effects. Diabetic retinal illness, a micro vascular side effect of the condition, is the prime reason of diabetic related blindness. The OS (directly or indirectly) is associated with diabetic retinopathy (DR) and related consequences. The OS is responsible to induce and interfere the metabolic signaling pathways to enhance influx of the polyol cascades and hexosamine pathways, stimulate Protein Kinase-C (PKC) variants, and accumulate advanced glycation end products (AGEs). Additionally, the inequity between the scavenging and generation of ROS is caused by the epigenetic alteration caused by hyperglycemia that suppresses the antioxidant defense system. Induced by an excessive buildup of ROS, retinal changes in structure and function include mitochondrial damage, cellular death, inflammation, and lipid peroxidation. Therefore, it is crucial to comprehend and clarify the mechanisms connected to oxidative stress that underlie the development of DR.

Fluoride-induced apoptosis in non-skeletal tissues of experimental animals: A systematic review and meta-analysis

Different studies have suggested that fluoride can induce apoptosis in non-skeletal tissues, however, evidence from these experimental studies is still controversial. This meta-analysis aims to clarify the mechanism of fluoride-induced apoptosis in non-skeletal tissues of experimental animals. Primary studies which measured apoptosis were identified through exhaustive database searching in PubMed, Embase, Web of Science Core Collection, Scopus, and references of included studies. A random effects model with standardized mean difference (SMD) was used for meta-analyses. The heterogeneity of the studies was evaluated using Higgin's I2 statistics. The risk of bias and publication bias were assessed using the SYRCLE's risk of bias tool and Egger's test, respectively. There was an increase in total apoptotic cells, and the expression of Bax, Bax/Bcl-2 ratio, caspase-3, caspase-8, caspase-9, Cyt c, and p53, and a decrease in the expression of Bcl-2 in the fluoride-treated groups as compared to the control groups. However, there was no evidence of a difference in the expression of APAF-1 in the two groups. The subgroup analysis highlighted the role of the intervention period in modification of the apoptotic effect of fluoride and that the susceptibility and tolerance of different animal species and tissues vary. Meta-regression analysis indicated that the studies' effect size for total apoptotic cells was influenced by animal species and that of Bax by the sample source. The results of this meta-analysis revealed that fluoride causes apoptosis by up-regulating caspase-3, -8, and -9, Cyt c, p53, Bax, and down-regulating Bcl-2 with a concomitant up-regulation of the Bax/Bcl-2 ratio.

Ameliorative effects of nano Moringa on fluoride-induced testicular damage via down regulation of the StAR gene and altered steroid hormones

Fluoride is a common environmental contaminant that has harmful effects on human health when it is present in high concentrations. Fluoride enters the bloodstream after being absorbed by the gastrointestinal system when fluoride-contaminated groundwater is consumed by people. The aim of the present study was to determine whether polyphenol-rich nano Moringa oleifera (NMO) could protect rat testicles from sodium fluoride (NaF) damage by evaluating sperm quality, sex hormones, testicular oxidative status, histopathology, and StAR gene expression. Twenty-eight adult Wistar rats were divided equally and randomly into four groups: group one received distilled water; group two received NMO at a dosage of 250 mg/kg/body weight; group three received NaF at a dosage of 10 mg/kg/body weight; and group four received NaF and NMO. The rats were orally administrated daily for a duration of eight weeks. The study's findings demonstrated that, in comparison to rats exposed to NaF alone, co-administration of NMO and NaF enhanced sperm motility and viability, decreased sperm morphological changes, restored the balance between oxidant and antioxidant status, improved testosterone and dehydroepiandrosterone, improved testicular histology, raised the Johnson score, and upregulated the StAR gene in testicular tissue. These findings show that NMO is promise as a prophylactic medication against sodium fluoride-induced testicular damage because administration of NMO had no adverse effects and enhanced reproductive health.

Histo-anatomical mutilations of developing chick brain induced by in-ovo fluoride and bifenthrin exposure

Comparative developing brain histo-anatomical pathologies of Fluoride ions and Bifenthrin in-ovo exposures were explored in the golden black variety of domestic chick. Three exposure groups were -the Vehicle control group (Vg); Fluoride (F) group and the Bifenthrin (Bn) group each with forty fertilized eggs and received their respective group treatment at zero day of incubation. Embryos were extracted, dissected from head region and the embryonic whole brains were recovered after 14 days of incubation. The embryonic brains were preserved in bouin fixative for 24 h for further studies. The morphological results show the atrophied and hypertrophied embryonic brain in F and Bn groups respectively as compared to Vg group. The toxicological signs of encephalic anatomy and histology of F and Bn exposure were the enlarged third ventricles, optocoeles and arachnoid mater, encephalic spongiosis and decreased neuroglial density. The morphometric data showed significant decrease (p ≤ 0.05) in mean weight and density of whole brain in F and Bn groups compared Vg. The mean length and width of whole brain in F were significantly lower than that of the Bn and Vg. whereas, the mean breadth of third ventricle in Bn remained significantly lower than F and Vg groups. On the other hand, the mean breadth of optocoele and fourth ventricle in F and Bn groups remained significantly higher than Vg. Conversely the mean optic lobe wall thickness in F remained significantly lower than Bn and Vg. Additionally, the mean neuronal density in diencephalon, optic lobe and cerebellum in F group and Bn group remained significantly (p ≤ 0.05) lower than Vg. Results show that low dose in-ovo fluoride or bifenthrin exposure may cause neuro-developmental abnormalities in the developing chick embryos indicating that the Fluoride-ions and Bifenthrin harbor strong developmental neurotoxic capacity.

Aloe vera protects against fluoride-induced teratogenic effects during pre- and postnatal development in mice

Pregnancy and feto-gestational toxicities on exposure to fluoride and its possible amelioration on co-administration with aloe vera were studied in pregnant Swiss albino mice. Once the confirmed pregnancy was tested, animals were equally divided into four groups as follows: group I was given no treatment and served as control, and groups II and III were administered with 100 and 300 ppm sodium fluoride, respectively, while group IV was co- administered aloe vera (300 mg/kg bw) along with sodium fluoride (300 ppm) daily for 14 days prior to gestation and continued till the 18th day of gestation. Animals were sacrificed on the 19th day of gestation for prenatal observations. Maternal body weight, the gravid uterine weight, number of corpora lutea in both the ovaries, number of implantations and resorptions, number of live (mature and immature) fetuses, and number of dead fetuses were examined in each dam. The treatment continued in another set of animals till the completion of the weaning period to observe postnatal changes due to test substances on the mother and pups. Sodium fluoride-treated animals showed morphometric and skeletal changes which were more pronounced in the high-dose group showing significantly decreased body weight gain in pregnant mothers and dead/immature fetuses. Morphometric changes included open eyelids, limb defects, wrinkles on the whole body, anophthalmia, pulmonary edema, enlarged esophagus, and decreased body weight of fetuses and pups. Alizarin-prepared skeletal structures of fetuses of such female mice showed delayed ossification or bending in the number of bones of skull, thoracic, and limb regions. However, concomitant exposure to sodium fluoride and aloe vera in treated animals led to a marked improvement in all the prenatal and postnatal variables. The study suggests that sodium fluoride at high concentrations may be teratogenic while co-administration of aloe vera during fluoride exposure might be beneficial in reducing these toxic effects. The use of aloe vera as a preventive agent or as a complimentary agent is thus recommended following fluoride exposure through the oral route.

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.

Biphasic Functions of Sodium Fluoride (NaF) in Soft and in Hard Periodontal Tissues

Sodium fluoride (NaF) is widely used in clinical dentistry. However, the administration of high or low concentrations of NaF has various functions in different tissues. Understanding the mechanisms of the different effects of NaF will help to optimize its use in clinical applications. Studies of NaF and epithelial cells, osteoblasts, osteoclasts, and periodontal cells have suggested the significant roles of fluoride treatment. In this review, we summarize recent studies on the biphasic functions of NaF that are related to both soft and hard periodontal tissues, multiple diseases, and clinical dentistry.

Edaravone prevents high glucose-induced injury in retinal Müller cells through thioredoxin1 and the PGC-1α/NRF1/TFAM pathway

CONTEXT

Oxidative injury in a high-glucose (HG) environment may be a mechanism of diabetic retinopathy (DR) and edaravone can protect retinal ganglion cells by scavenging ROS.

OBJECTIVE

To explore the effect of edaravone on HG-induced injury.

MATERIALS AND METHODS

First, Müller cells were cultured by different concentrations of glucose for different durations to obtain a suitable culture concentrations and duration. Müller cells were then divided into Control, HG + Vehicle, HG + Eda-5 μM, HG + Eda-10 μM, HG + Eda-20 μM, and HG + Eda-40 μM groups. Cells were cultured by 20 mM glucose and different concentrations of edaravone for 72 h.

RESULTS

The IC₅₀ of glucose at 12-72 h is 489.3, 103.5, 27.92 and 20.71 mM, respectively. When Müller cells were cultured in 20 mM glucose for 72 h, the cell viability was 52.3%. Edaravone significantly increased cell viability compared to Vehicle (68.4% vs 53.3%; 78.6% vs 53.3%). The EC₅₀ of edaravone is 34.38 μM. HG induced high apoptosis rate (25.5%), while edaravone (20 and 40 μM) reduced it to 12.5% and 6.89%. HG increased the DCF fluorescence signal (189% of Control) and decreased the mitochondrial membrane potential by 57%. Edaravone significantly decreased the DCF fluorescence signal (144% and 132% of Control) and recovered the mitochondrial membrane potential to 68% and 89% of Control. Furthermore, HG decreased the expression of TRX1, PGC-1α, NRF1 and TFAM, which were restored by edaravone.

DISCUSSION AND CONCLUSION

These findings provide a new potential approach for the treatment of DR and indicated new molecular targets in the prevention of DR.

Thyroid stimulating hormone aggravates diabetic retinopathy through the mitochondrial apoptotic pathway

Diabetic retinopathy (DR) is a common complication of diabetes mellitus. High glucose-induced mitochondrial apoptosis is involved in the loss of retinal pericytes (PCs), which is considered to be a predominant pathologic change of diabetic retinopathy (DR). A high thyroid stimulating hormone (TSH) serum level is associated with an increased prevalence of DR in diabetic patients. Here, we investigated whether TSH regulated glucose-induced PCs loss through TSH-receptor (TSHR)-dependent mitochondrial apoptosis. First, the serum TSH level was found to be an independent risk factor for DR in Type 2 diabetic study participants (odds ratio = 2.294; 95% confidence interval: 1.925-2.733; p ≤ 0.001). Second, human PCs were treated with different concentrations of glucose, with or without bovine TSH (b-TSH). Glucose induced mitochondrial apoptosis through various mechanisms, including through regulating the expression of apoptosis-related proteins and inducing mitochondrial dysfunction, which could be deteriorated by costimulation of glucose and b-TSH. Additionally, we detected functional TSHR in PCs; blocking TSHR significantly restricted TSH-induced apoptosis. Thus, the presence of functional TSHR in human retinal PCs may facilitate the effect of high TSH on high glucose-induced PCs loss through TSHR-dependent mitochondrial apoptosis.

Comparison of the toxicity of pure compounds and commercial formulations of imidacloprid and acetamiprid on HT-29 cells: Single and mixture exposure

Neonicotinoids, which are widely used worldwide, including in Turkey, are an insecticide group that are synthetic derivatives of nicotine. Recently, they have attracted attention due to their toxic effects on non-target organisms, especially bees. Numerous studies have shown that neonicotinoids have been found in detectable levels in the environment and cause various undesirable effects on living organisms, including humans and other mammals. In this study, the possible toxic effects of imidacloprid and acetamiprid, commonly used neonicotinoids, are investigated by their pure forms and commercial formulations on HT-29 cells with individual and combined exposures. According to our results, imidacloprid and acetamiprid induced cytotoxicity by caspase-mediated apoptosis, mitochondrial membrane depolarization, DNA damage, and oxidative stress under these experimental conditions. It is worth mentioning low doses of DNA damage, mixture exposure causes toxic effects at lower concentrations than individual exposure, and formulation groups are at the forefront of toxicity formation, though this varies depending on the parameters.

Fluoride effects on cell viability and ENaC expression in kidney epithelial cells

Fluoride (F) at micromolar (µM) concentrations induces apoptosis in several cell lines. Moreover, proteomic studies have shown major changes in the profile of proteins involved in signal transduction. These effects may negatively affect ion transport in the kidneys. The activity of epithelial sodium channels (ENaCs) is a limiting factor for sodium and water resorption in the kidneys, which is essential for the maintenance of the electrolyte balance and homeostasis of the body. Here we investigated the effects of F, at different concentrations (10, 40, 100, 200, and 400 μM), on the viability of renal epithelial cells (M-1), and ENaC expression. We showed that sodium fluoride (NaF) reduces cell viability in a concentration-dependent manner (p < 0.05) up to a 96-h time-point when compared to control. Sodium fluoride at moderate concentrations (100 and 200 μM), upregulated the ENaC subunit genes Scnn1a and Scnn1g, but not Scnn1b. Sodium fluoride downregulated all three ENaC subunit genes at a higher concentration of 400 μM (p < 0.05). Immunofluorescence analysis showed that Scnn1a and Scnn1g expression was decreased within 24 h of NaF treatment. After 48 h, NaF (400 μM) increased the expression of Scnn1a but not Scnn1g. However, NaF decreased the expression of Scnn1g at all studied concentrations. We conclude that F, at µM concentrations, modulates the expression of ENaC subunit genes, which is likely to significantly affect molecular signaling in kidney epithelial cells.

Hesperidin protects liver and kidney against sodium fluoride-induced toxicity through anti-apoptotic and anti-autophagic mechanisms

AIM

High dose of fluoride intake is associated with toxic effects on liver and kidney tissues. One approach to tackle these toxicities is using natural antioxidants as supplements. This study evaluated the ameliorative effects of hesperidin (HSP) against sodium fluoride (NaF)-induced hepatotoxicity and nephrotoxicity in wistar albino rats.

MATERIALS AND METHODS

In the present study, the rats were randomly allocated into five groups of seven male rats each group: control, NaF (600 ppm), HSP-200, NaF + HSP-100 and NaF + HSP 200.

KEY FINDINGS

Hepatic and renal injuries induced by NaF were confirmed by the alteration in kidney function parameters in the serum (urea and creatinine), levels of liver enzymes (ALT, ALP and AST), activities of the antioxidant enzymes (SOD, CAT and GPx) and levels of inflammatory markers (NF-κB, IL-1β and TNF-α). NaF also inhibited PI3K/Akt/mTOR pathway, increased levels of autophagic markers (Beclin-1, LC3A and LC3B) and expression levels of apoptotic and anti-apoptotic proteins (Bax, Bcl-2, cytochrome c, p53 and procaspase-3) in the liver and kidney tissues. Administration of HSP concurrently with NaF significantly ameliorated the deviation in the above-studied parameters.

SIGNIFICANCE

The results of the current study revealed that HSP could be used as a beneficial adjuvant that confers protection against NaF-induced liver and kidney damage through antioxidant, anti-inflammatory, anti-apoptotic and anti-autophagic mechanisms.

Human cultured IMR-32 neuronal-like and U87 glial-like cells have different patterns of toxicity under fluoride exposure

BACKGROUND

Fluoride (F) is a naturally exists in nature but several studies have indicated it as an environmental toxicant to all leaving beings. Human F exposure has increased over the years since this ion has been used by industry on foods, beverages, toothpastes and on water supply. Although F is safe at optimal concentrations in water supply, human exposure to high levels could trigger neurofunctional deficits.

MATERIALS AND METHODS

In this study, human glial-like (U87) and neuronal-like (IMR-32) cells lineages were used to access F toxicity and CNS cell sensibility on both cell facing the same protocol. Cells were exposed to F over 3, 5 and 10 days on two different F concentrations. Fluoride exposed cells were evaluated by standard toxicity assays to cell viability, apoptosis, necrosis and general cell metabolism. Oxidative stress parameters were evaluated by ATP and ROS levels, lipid peroxidation, GSH/GSSG ratio and comet assay.

RESULTS

No changes were observed in IMR-32 at any given time while after 10 days of exposure to 0.22μg/mL, U87 glial-like cells showed signs of toxicity such as decreased cell viability by necrosis while general cell metabolism was increased. Oxidative stress parameters were next evaluated only on U87 glial-like cells after 10 days of exposure. F induced a decrease on ATP levels while no changes were observed on reactive oxygen species and lipid peroxidation. GSH/GSSG ratio was decreased followed by DNA damage both on 0.22μg/mL F.

CONCLUSIONS

Our results suggest an important differential behavior of the distinct types of cells exposed to the different fluoride concentrations, pointing that the U87 glial-like cells as more susceptible to damage triggered by this ion.

Upregulation of miR-200c-3p induced by NaF promotes endothelial apoptosis by activating Fas pathway

Fluoride has been considered as a risk factor of cardiovascular disease due to its endothelial toxicology. However, the mechanism underlying the endothelial toxicity of fluoride has not been clearly illustrated. MiR-200c-3p was strongly linked with endothelial function and its level is increased in serum of fluorosis patients, but it is unclear the role of miR-200c-3p in the fluoride induced endothelial dysfunction. In this study, we confirmed that fluoride exposure induced the apoptosis of endothelial cells both in established rats model and cultured human umbilical vein endothelial cells (HUVECs). And miR-200c-3p was found to be upregulated in NaF treated HUVECs. Fluoride stimulation increased caspase-dependent apoptosis through miR-200c-3p upregulation, with repressing expression of its target gene Fas-associated phosphatase 1 (Fap-1), which functioned as Fas inhibitor. This resulted in activation of Fas-associated extrinsic apoptosis via interaction with increased Fas, Fadd, Cleaved Caspase-8 and Cleaved Caspase-3. The activation of Fas-associated extrinsic apoptosis was abrogated by miR-200c-3p inhibitor. Furthermore, the antiapoptotic effect of downregulated miR-200c-3p was restored by Fap-1 siRNA. These results suggested a determinant role of the miR-200c-3p/Fap-1 axis in fluoride induced endothelial apoptosis.

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.

The Influence of fluoride on chronic kidney disease of uncertain aetiology (CKDu) in Sri Lanka

Fluoride is an element that is widely distributed in the environment. The involvement of fluoride in pathogenesis of Chronic Kidney Disease of uncertain aetiology (CKDu) in Sri Lanka is a much-debated topic. This study aimed to investigate the fluoride concentration in drinking water in CKDu affected areas in Sri Lanka and to evaluate the possible effect of renal impairment on serum fluoride levels in CKDu patients. Drinking water (n = 60) from the common water sources from two CKDu prevalent areas and serum samples of CKDu patients (n = 311) and healthy controls (n = 276) were collected. Both environmental and biological samples were analysed for the concentration of fluoride. The fluoride concentration in over 95% of drinking water samples was below the WHO guideline of 1.5 mg/L. Serum fluoride concentrations in majority of the unaffected and early-stage CKDu patients (stages 1 and 2, eGFR >60 ml/min/1.73m2) were below the normal upper concentration of 50 μg/l and significantly higher levels were observed in patients in late stages of CKDu compared to the healthy controls. The available guidelines for drinking water are solely based on healthy populations with normal renal function. But, it is evident that once the kidney function is impaired, patients enter a vicious cycle as fluoride gradually accumulates in the body, further damaging the kidney tissue. Thus, close monitoring of serum fluoride levels in CKDu patients and establishing health-based target guidelines for fluoride in drinking water for the CKDu patients are recommended to impede the progression to end stage renal disease.

Toxicity of fluoride: critical evaluation of evidence for human developmental neurotoxicity in epidemiological studies, animal experiments and in vitro analyses

Recently, epidemiological studies have suggested that fluoride is a human developmental neurotoxicant that reduces measures of intelligence in children, placing it into the same category as toxic metals (lead, methylmercury, arsenic) and polychlorinated biphenyls. If true, this assessment would be highly relevant considering the widespread fluoridation of drinking water and the worldwide use of fluoride in oral hygiene products such as toothpaste. To gain a deeper understanding of these assertions, we reviewed the levels of human exposure, as well as results from animal experiments, particularly focusing on developmental toxicity, and the molecular mechanisms by which fluoride can cause adverse effects. Moreover, in vitro studies investigating fluoride in neuronal cells and precursor/stem cells were analyzed, and 23 epidemiological studies published since 2012 were considered. The results show that the margin of exposure (MoE) between no observed adverse effect levels (NOAELs) in animal studies and the current adequate intake (AI) of fluoride (50 µg/kg b.w./day) in humans ranges between 50 and 210, depending on the specific animal experiment used as reference. Even for unusually high fluoride exposure levels, an MoE of at least ten was obtained. Furthermore, concentrations of fluoride in human plasma are much lower than fluoride concentrations, causing effects in cell cultures. In contrast, 21 of 23 recent epidemiological studies report an association between high fluoride exposure and reduced intelligence. The discrepancy between experimental and epidemiological evidence may be reconciled with deficiencies inherent in most of these epidemiological studies on a putative association between fluoride and intelligence, especially with respect to adequate consideration of potential confounding factors, e.g., socioeconomic status, residence, breast feeding, low birth weight, maternal intelligence, and exposure to other neurotoxic chemicals. In conclusion, based on the totality of currently available scientific evidence, the present review does not support the presumption that fluoride should be assessed as a human developmental neurotoxicant at the current exposure levels in Europe.

Sesamin promotes angiogenesis and accelerates wound healing in rats via alleviates TBHP-induced apoptosis in human umbilical vein endothelial cells

Acute stress induces tissue damage through excessive cellular apoptosis. In our study, the effects of sesamin on apoptosis and wound healing were investigated. The angiogenesis effect of sesamin was evaluated by the abilities of adherence, migration and tube formation in human umbilical vein endothelial cells (HUVECs). Our data demonstrated that treatment with sesamin dose-dependently promoted the proliferation, adherence, migration and enhanced their angiogenic ability in vitro. Moreover, the increased apoptosis in HUVECs, which stimulated by tert-butyl hydroperoxide (TBHP) was significantly attenuated by the sesamin treatment. Furthermore, we revealed that neogenesis of granulation tissue and deposition and remodeling of the collagen matrix were accelerated by the administration of sesamin in our in vivo study. These results confirm that sesamin accelerates wound healing at least partly through its antiapoptotic effects on endothelial cells at the injury site. Thus, sesamin represents a potential therapeutic medicine for vessel injury-related wounds.

Principles of fluoride toxicity and the cellular response: a review

Fluoride is ubiquitously present throughout the world. It is released from minerals, magmatic gas, and industrial processing, and travels in the atmosphere and water. Exposure to low concentrations of fluoride increases overall oral health. Consequently, many countries add fluoride to their public water supply at 0.7-1.5 ppm. Exposure to high concentrations of fluoride, such as in a laboratory setting often exceeding 100 ppm, results in a wide array of toxicity phenotypes. This includes oxidative stress, organelle damage, and apoptosis in single cells, and skeletal and soft tissue damage in multicellular organisms. The mechanism of fluoride toxicity can be broadly attributed to four mechanisms: inhibition of proteins, organelle disruption, altered pH, and electrolyte imbalance. Recently, there has been renewed concern in the public sector as to whether fluoride is safe at the current exposure levels. In this review, we will focus on the impact of fluoride at the chemical, cellular, and multisystem level, as well as how organisms defend against fluoride. We also address public concerns about fluoride toxicity, including whether fluoride has a significant effect on neurodegeneration, diabetes, and the endocrine system.

Fluoride Affects Dopamine Metabolism and Causes Changes in the Expression of Dopamine Receptors (D1R and D2R) in Chosen Brain Structures of Morphine-Dependent Rats

Disturbances caused by excess or shortages of certain elements can affect the cerebral reward system and may therefore modulate the processes associated with the development of dependence as was confirmed by behavioural studies on animals addicted to morphine. Earlier publications demonstrated and proved the neurodegenerative properties of both low and high doses of fluoride ions in animal experiments and in epidemiological and clinical studies. The aim of the experiments conducted in the course of the present study was to analyse the effect of pre- and postnatal exposure to 50 ppm F⁻ on the initiation/development of morphine dependence. For this purpose, the following were conducted: behavioural studies, the analysis of concentrations of dopamine and its metabolites, and the analyses of mRNA expression and dopamine receptor proteins D1 and D2 in the prefrontal cortex, striatum, hippocampus, and cerebellum of rats. In this study, it was observed for the first time that pre- and postnatal exposure to fluoride ions influenced the phenomenon of morphine dependence in a model expressing withdrawal symptoms. Behavioural, molecular, and neurochemical studies demonstrated that the degenerative changes caused by toxic activity of fluoride ions during the developmental period of the nervous system may impair the functioning of the dopaminergic pathway due to changes in dopamine concentration and in dopamine receptors. Moreover, the dopaminergic disturbances within the striatum and the cerebellum played a predominant role as both alterations of dopamine metabolism and profound alterations in striatal D1 and D2 receptors were discovered in these structures. The present study provides a new insight into a global problem showing direct associations between environmental factors and addictive disorders.

Gas Chromatography-Mass Spectrometry Based Midgut Metabolomics Reveals the Metabolic Perturbations under NaF Stress in Bombyx mori

Fluoride tolerance is an important economic trait in sericulture, especially in some industrial development regions. Analyses of physiological changes involving structural damage to the insect body and molecular analyses of some related genes have focused on this area; however, the changes that occur at the metabolic level of silkworms after eating fluoride-contaminated mulberry leaves remain unclear. Here, metabonomic analysis was conducted using gas chromatography-mass spectrometry (GC-MS) to analyze the changes in midgut tissue after NaF stress using silkworm strains 733xin (susceptible stain) and T6 (strain resistant to fluoride), which were previously reported by our laboratory. Differential metabolomics analysis showed that both T6 and 733xin strains displayed complex responses after exposure to 200 mg/kg NaF. The purine metabolism and arginine and proline metabolic pathways of fluoride-tolerant strains reached significant levels, among which 3′-adenylic acid and hypoxanthine were significantly upregulated, whereas guanine, allantoic acid, xanthine, N-acetyl-L-glutamic acid, and pyruvate were significantly downregulated. These metabolic pathways may be related to the fluoride tolerance mechanism of NaF poisoning and tolerant strains.

The Potential Protective Effects of Diosmin on Streptozotocin-Induced Diabetic Cardiomyopathy in Rats

BACKGROUND

Diabetic cardiomyopathy (DCM) is a nonischemic myocardial disorder characterized by metabolic disturbances and oxidative stress in diabetic patients. The present paper aims to determine the protective effect of the phlebotrophic drug, diosmin, on DCM in a model of high-fat diet-fed and streptozotocin-induced type 2 diabetes in the rat.

MATERIALS AND METHODS

The animals were divided into 4 groups (8 rats/group) as follows: vehicle-treated nondiabetic control group, vehicle-treated diabetic group, diosmin (50 mg/kg)-treated diabetic group and diosmin (100 mg/kg)-treated diabetic group. Treatment was given once daily orally by gavage for 6 weeks. Oxidant and antioxidant stress markers, inflammatory markers and proapoptotic and antiapoptotic gene expression using quantified real-time polymerase chain reaction were investigated.

RESULTS

Diosmin treatment in diabetic rats lowered elevated blood glucose levels, homeostatic model assessment for insulin resistance, cardiac creatine kinase and lactate dehydrogenase enzymes, cardiac malondialdehyde and nitric oxide. Moreover, diosmin increased plasma insulin and c-peptide levels, cardiac glutathione content, superoxide dismutase, catalase and glutathione S-transferase activities. Also, diosmin treatment significantly (P < 0.05) lowered the levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), down-regulated cardiac Bcl-2-associated X protein and caspase 3 and 9 and up-regulated B-cell lymphoma 2 mRNA expression levels.

CONCLUSIONS

Diosmin may have a sizeable therapeutic potential in the treatment of DCM due to antidiabetic, antioxidative stress, anti-inflammatory and antiapoptotic effects. Detailed studies are needed to disclose the precise mechanisms motivating the protective effect of diosmin‏.

Nitrate and Phosphate Transporters Rescue Fluoride Toxicity in Yeast

Organisms are exposed to fluoride in the air, water, and soil. Yeast and other microbes utilize fluoride channels as a method to prevent intracellular fluoride accumulation and mediate fluoride toxicity. Consequently, deletion of fluoride exporter genes (FEX) in S. cerevisiae resulted in over 1000-fold increased fluoride sensitivity. We used this FEX knockout strain to identify genes, that when overexpressed, are able to partially relieve the toxicity of fluoride exposure. Overexpression of five genes, SSU1, YHB1, IPP1, PHO87, and PHO90, increase fluoride tolerance by 2- to 10-fold. Overexpression of these genes did not provide improved fluoride resistance in wild-type yeast, suggesting that the mechanism is specific to low fluoride toxicity in yeast. Ssu1p and Yhb1p both function in nitrosative stress response, which is induced upon fluoride exposure along with metal influx. Ipp1p, Pho87p, and Pho90p increase intracellular orthophosphate. Consistent with this observation, fluoride toxicity is also partially mitigated by the addition of high levels of phosphate to the growth media. Fluoride inhibits phosphate import upon stress induction and causes nutrient starvation and organelle disruption, as supported by gene induction monitored through RNA-Seq. The combination of observations suggests that transmembrane nutrient transporters are among the most sensitized proteins during fluoride-instigated stress.

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.

Possible protective effect of curcumin on the thyroid gland changes induced by sodium fluoride in albino rats: light and electron microscopic study

OBJECTIVES

Thyroid gland regulates the body's metabolic rate and plays an exquisitely important role in the human health. Fluoride exposure can affect thyroid function. Curcumin is a potent antioxidant that works through several mechanisms. The aim of the present study was to demonstrate the hormonal, histological, and ultrastructural changes occurred in the thyroid gland induced by exposure to sodium fluoride (NaF) and study the possible protective effect of curcumin on the NaF-induced effects.

METHODS

Thirty male albino rats were randomly divided into 3 equal groups (10 rats each): the control group, NaF group, and NaF+Curcumin (NaF+Cur) group. Thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) levels were assayed and thyroid tissues processed for light and transmission electron microscopic study.

RESULTS

In NaF group, serum T3 and T4 levels were significantly decreased whereas TSH level was significantly increased compared to the control group. Thyroid tissues showed flattening of the epithelial lining with several follicular cell degenerations, hyperplasia, decreased colloid, disrupted basement membrane, cytoplasmic vacuolations, degenerated mitochondria, widening of rough endoplasmic reticulum cisternae, and vascular congestion compared to the control group. In the NaF+Cur group, serum TSH levels were significantly decreased in comparison with NaF group and no significant difference in comparison with the control group. Thyroid sections appeared apparently normal compared to the control group and NaF group.

CONCLUSIONS

Sodium fluoride affected both the function and structure of the thyroid gland while curcumin was protective against these toxic effects.

Ferulic acid ameliorates pentylenetetrazol-induced seizures by reducing neuron cell death

To investigate the neuroprotective effect of ferulic acid (FA) in a pentylenetetrazol (PTZ)-induced seizures model in rat, the motor response, spatial learning ability and memory capability of the rats were assessed. Both the antioxidation and anti-apoptosis pathways were also investigated. In this study, male Wistar rats were randomly divided into 3 groups (n = 12 in each group). For 28 days, the rats were administered saline alone (i.p. normal saline, NS group), PTZ (40 mg/kg, i.p., PTZ group) once daily to induce seizures, or FA (i.p. 60 mg/kg) 20 min before being given PTZ (40 mg/kg, i.p., FA + PTZ group) to assess the neuroprotective effect of FA. The motor response of the rats was analysed with the Racine scale. The spatial learning and memory capacity of the rats were assessed by the Morris water maze test. The superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured, and both in situ staining with the DNA-binding bisbenzimide Hoechst 33258 and TUNEL assays were used to assess apoptosis. Western blotting was used to further analyse the expression of Apaf-1, caspase-9, caspase-3, Bcl-2, Bid, Bax, cleaved caspase-3 and cytochrome c. The results showed that compared to the those of the PTZ group, FA pre-treatment significantly (p <  0.01) reduced the Racine scores starting at day 4, prolonged the latency of the onset of seizure at day 28, reduced the escape latency period starting at day 2, increased the frequency of crossing the platform location, increased the SOD activity, reduced the MDA content and apoptosis percentage, and upregulated the Bcl-2 levels whilst downregulating the Bax, cytochrome c, Apaf-1, caspase-9, caspase-3, cleaved caspase-3 and Bid expression levels. This study demonstrated that pre-treatment with FA exerts strong neuroprotective effects by reducing the motor response and by improving spatial learning ability and memory capacity. The neuroprotective effect may be a result of a reduction in neuron cell death that occurs via the antioxidative and anti-apoptotic pathways.

Evaluation of citrinin-induced toxic effects on mouse Sertoli cells

Penicillium citrinum-derived mycotoxin citrinin (CTN) is known to be a toxic agent for humans and animals. Previous studies have shown that CTN leads to toxicity in many biological systems; however, a limited number of studies have been performed to demonstrate the harmful effects of CTN on the male reproductive system. In the present study, the effects of CTN on cytotoxicity and apoptosis were examined in Sertoli cells as a model. Sertoli cells were treated with eight different CTN concentrations (from 0 up to 200 µM, for 6-72 h). Toxic potential of CTN was estimated by measuring metabolic activity (MTT test), DNA synthesis (BrdU test), and cell membrane damage (LDH test) as well as apoptosis and necrosis (via staining with propidium iodide and Hoechst 33342). The results showed that CTN significantly decreased the cell viability and cell proliferation, increased cytotoxicity, apoptosis, and necrosis in a concentration-dependent manner. Furthermore, CTN showed cytotoxicity in Sertoli cells with an IC50 value of 116.5 µM for 24 h. In conclusion, these findings clearly showed that, CTN affects Sertoli cells even at low concentrations. Thus, as a result of the damage of CTN shown in Sertoli cells, it can be deduced that CTN may also have detrimental effects on the testes.

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.

Comparative transcriptome analysis of Eogammarus possjeticus at different hydrostatic pressure and temperature exposures

Hydrostatic pressure is an important environmental factor affecting the vertical distribution of marine organisms. Laboratory-based studies have shown that many extant shallow-water marine benthic invertebrates can tolerate hydrostatic pressure outside their known natural distributions. However, only a few studies have focused on the molecular mechanisms of pressure acclimatisation. In the present work, we examined the pressure tolerance of the shallow-water amphipod Eogammarus possjeticus at various temperatures (5, 10, 15, and 20 °C) and hydrostatic pressures (0.1–30 MPa) for 16 h. Six of these experimental groups were used for transcriptome analysis. We found that 100% of E. possjeticus survived under 20 MPa at all temperature conditions for 16 h. Sequence assembly resulted in 138, 304 unigenes. Results of differential expression analysis revealed that 94 well-annotated genes were up-regulated under high pressure. All these findings indicated that the pressure tolerance of E. possjeticus was related to temperature. Several biological processes including energy metabolism, antioxidation, immunity, lipid metabolism, membrane-related process, genetic information processing, and DNA repair are probably involved in the acclimatisation in deep-sea environments.

Liver Proteome of Mice with Distinct Genetic Susceptibilities to Fluorosis Treated with Different Concentrations of F in the Drinking Water

Appropriate doses of fluoride (F) have therapeutic action against dental caries, but higher levels can cause disturbances in soft and mineralized tissues. Interestingly, the susceptibility to the toxic effects of F is genetically determined. This study evaluated the effects of F on the liver proteome of mice susceptible (A/J) or resistant (129P3/J) to the effects of F. Weanling male A/J (n = 12) and 129P3/J (n = 12) mice were housed in pairs and assigned to two groups given low-F food and drinking water containing 15 or 50 ppm F for 6 weeks. Liver proteome profiles were examined using nano-LC-ESI-MS/MS. Difference in expression among the groups was determined using the PLGS software. Treatment with the lower F concentration provoked more pronounced alterations in fold change in liver proteins in comparison to the treatment with the higher F concentration. Interestingly, most of the proteins with fold change upon treatment with 15 ppm F were increased in the A/J mice compared with their 129P3/J counterparts, suggesting an attempt of the former to fight the deleterious effects of F. However, upon treatment with 50 ppm F, most proteins with fold change were decreased in the A/J mice compared with their 129P3/J counterparts, especially proteins related to oxidative stress and protein folding, which might be related to the higher susceptibility of the A/J animals to the deleterious effects of F. Our findings add light into the mechanisms underlying genetic susceptibility to fluorosis.

A mini review of fluoride-induced apoptotic pathways

Fluorine or fluoride can have toxic effects on bone tissue and soft tissue at high concentrations. These negative effects include but not limited to cytotoxicity, immunotoxicity, blood toxicity, and oxidative damage. Apoptosis plays an important role in fluoride-induced toxicity of kidney, liver, spleen, thymus, bursa of Fabricius, cecal tonsil, and cultured cells. Here, apoptosis activated by high level of fluoride has been systematically reviewed, focusing on three pathways: mitochondrion-mediated, endoplasmic reticulum (ER) stress-mediated, and death receptor-mediated pathways. However, very limited reports are focused on the death receptor-mediated apoptosis pathways in the fluoride-induced apoptosis. Therefore, understanding and discovery of more pathways and molecular mechanisms of fluoride-induced apoptosis may contribute to designing measures for preventing fluoride toxicity.

Sab concentrations indicate chemotherapeutic susceptibility in ovarian cancer cell lines

The occurrence of chemotherapy-resistant tumors makes ovarian cancer (OC) the most lethal gynecological malignancy. While many factors may contribute to chemoresistance, the mechanisms responsible for regulating tumor vulnerability are under investigation. Our analysis of gene expression data revealed that Sab, a mitochondrial outer membrane (MOM) scaffold protein, was down-regulated in OC patients. Sab-mediated signaling induces cell death, suggesting that this apoptotic pathway is diminished in OC. We examined Sab expression in a panel of OC cell lines and found that the magnitude of Sab expression correlated to chemo-responsiveness; wherein, OC cells with low Sab levels were chemoresistant. The Sab levels were reflected by a corresponding amount of stress-induced c-Jun N-terminal kinase (JNK) on the MOM. BH3 profiling and examination of Bcl-2 and BH3-only protein concentrations revealed that cells with high Sab concentrations were primed for apoptosis, as determined by the decrease in pro-survival Bcl-2 proteins and an increase in pro-apoptotic BH3-only proteins on mitochondria. Furthermore, overexpression of Sab in chemoresistant cells enhanced apoptotic priming and restored cellular vulnerability to a combination treatment of cisplatin and paclitaxel. Contrariwise, inhibiting Sab-mediated signaling or silencing Sab expression in a chemosensitive cell line resulted in decreased apoptotic priming and increased resistance. The effects of silencing on Sab on the resistance to chemotherapeutic agents were emulated by the silencing or inhibition of JNK, which could be attributed to changes in Bcl-2 protein concentrations induced by sub-chronic JNK inhibition. We propose that Sab may be a prognostic biomarker to discern personalized treatments for OC patients.

Mitochondria-Mediated Pathway Regulates C2C12 Cell Apoptosis Induced by Fluoride

This study was designed to investigate the mechanisms of excessive fluoride-induced apoptosis via mitochondria-mediated pathway in skeletal muscle cells (C2C12 cells). C2C12 cells were cultured with the fluoride concentrations (0, 1, and 2.5 mmol/L) for 48 h. The morphology and ultrastructural changes of C2C12 cells were observed using a light microscope and transmission electron microscope (TEM). The protein expression levels of apoptosis factors, including Bax, Bcl-2, cytochrome c (Cyt c), caspase-3, and caspase-9, were measured using real-time polymerase chain reaction (real-time PCR) and immunocytofluorescence. The morphology and ultrastructure of C2C12 cells were seriously damaged by fluoride at 1 and 2.5 mmol/L doses, including swollen mitochondria, vacuolization, ridge breakage, and disappearance of the nuclear membrane. Simultaneously, compared with the control group, the expression levels of Bax, Bcl-2, Cyt c, caspase-3, and caspase-9 were up-regulated after fluoride treatment. Excessive fluoride damages the ultrastructure in mitochondria, leading to the release of Cyt c from the mitochondria to cytoplasm in C2C12 cells; thereby, activated caspases cascade apoptosis process through a mitochondria-mediated pathway.

The mitochondrial pathway is involved in sodium fluoride (NaF)-induced renal apoptosis in mice

The objective of the present study was to explore the molecular mechanism of apoptosis induced by sodium fluoride (NaF) in the mouse kidney by using the methods of flow cytometry, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting, and experimental pathology. 240 four-week-old ICR mice were randomly divided into 4 groups and exposed to different concentrations of NaF (0 mg kg-1, 12 mg kg-1, 24 mg kg-1 and 48 mg kg-1) for a period of 42 days. The results demonstrated that NaF increased cell apoptosis and the depolarization of the mitochondrial membrane potential (MMP), and that the mitochondrial pathway was involved in NaF-induced apoptosis. Alteration of the mitochondrial pathway was characterized by significantly increasing mRNA and protein expression levels of cytosolic cytochrome c (Cyt c), the second mitochondrial activator of caspases/direct inhibitors of the apoptosis binding protein with low pI (Smac/Diablo), the serine protease high-temperature-requirement protein A2/Omi (HtrA2/Omi), the apoptosis inducing factor (AIF), endonuclease G (Endo G), cleaved-cysteine aspartate specific protease-9 (cleaved-caspase-9), cleaved-cysteine aspartate specific protease-3 (cleaved-caspase-3), Bcl-2 antagonist killer (Bak), Bcl-2 associated X protein (Bax), Bcl-2 interacting mediator of cell death (Bim), cleaved-poly-ADP-ribose polymerase (cleaved-PARP), p-p53, and decreasing mRNA and protein expression levels of B-cell lymphoma-2 (Bcl-2), Bcl-extra large (Bcl-xL), and X chromosome-linked inhibitors of apoptosis proteins (XIAPs). To our knowledge, the mitochondrial pathway is reported for the first time in NaF-induced apoptosis of the human or animal kidney. Also, this study provides novel insights for further studying fluoride-induced nephrotoxicity.

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.

The toxic effect of sodium fluoride on Spodoptera frugiperda 9 cells and differential protein analysis following NaF treatment of cells

Accumulation of excess fluoride has a destructive effect on the environment, endangering human health, affecting organism growth and development, and leading to damage to the biological chain, thereby affecting ecological environment balance. In recent years, numerous studies focused on the molecular mechanisms associated with fluoride toxicity; however, fluoride-toxicity mechanisms in insect cells remain unclear. This study explored the toxic impact of sodium fluoride (NaF) on Spodoptera frugiperda 9 (Sf9) insect cells. High concentrations of NaF (10^-4 M, 10^-3 M and 10^-2 M) resulted in cell enlargement, cell membrane blurring and breakage, and release of cellular contents. Dose-response curves indicated that NaF-specific inhibition rates on Sf9-cell activity increased along with increases in NaF concentration, with a half-inhibitory concentration (IC₅₀) for NaF of 5.919 × 10^-3 M at 72 h. Compared with controls, the percentages of early and late apoptotic and necrotic cells clearly increased based on observed increases in NaF concentrations. Two-dimensional gel electrophoresis combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to detect differentially expressed proteins in Sf9 cells treated with IC₅₀ NaF, identifying 17 proteins, seven of which were upregulated and 10 downregulated. These results demonstrated that Sf9 cells showed signs of NaF-mediated toxicity through alterations in cell morphology, apoptosis rates, and protein expression.

SIRT1-mediated FoxOs pathways protect against apoptosis by promoting autophagy in osteoblast-like MC3T3-E1 cells exposed to sodium fluoride

Fluorine may result in damage to teeth, bones and other body tissues, and is a serious public health problem. SIRT1 deacetylates FOXOs, which brings about apoptosis and autophagy promotion or suppression. Fluorine may induce cell apoptosis, however, the role of autophagy in apoptosis induced by fluorine is still poorly understood, and the interaction between SIRT1 and FOXOs should be further illustrated. Therefore, this study investigated the mechanisms underlying the NaF- induced apoptosis and autophagy in osteoblast-like MC3T3-E1 cells in vitro through activating or inhibiting SIRT1. Via RT-PCR, western blot, flow cytometry assays, fluorescence and laser confocal microscopy, it was found that NaF induced both cell apoptosis and autophagy. Results also showed that NaF up-regulated SIRT1 expression in a dose-dependent manner. The autophagy of MC3T3-E1 was also up- regulated indirectly whilst apoptosis was significantly attenuated when incubated with the SIRT1 activator SRT1720. When SIRT1 inhibitor Ex-527 was used, the latter effects were reversed. Furthermore, SIRT1 increased deacetylation of FoxO1 and promoted the up-regulation of its target substrate Rab7, as well as increase of Bnip3 which was substrate of FoxO3, and we hypothesize that these pathways may cause an increase in autophagic flux and a reduction in apoptosis. In conclusion, SIRT1-induced autophagy enhancement protects against fluoride-induced apoptosis through autophagy induction in MC3T3-E1 cells, which may be associated with a SIRT1-FoxO1-Rab7 axis and a SIRT1-FoxO3-Binp3 axis. The role of SIRT1 in selecting between cell survival and death provides a potential therapeutic strategy in fluorosis.

Mycotoxins and oxidative stress: where are we?

Mycotoxins are the most common contaminants of food and feed worldwide and are considered an important risk factor for human and animal health. Oxidative stress occurs in cells when the concentration of reactive oxygen species exceeds the cell’s antioxidant capacity. Oxidative stress causes DNA damage, enhances lipid peroxidation, protein damage and cell death. This review addresses the toxicity of the major mycotoxins, especially aflatoxin B1, deoxynivalenol, nivalenol, T-2 toxin, fumonisin B1, ochratoxin, patulin and zearalenone, in relation to oxidative stress. It summarises the data associated with oxidative stress as a plausible mechanism for mycotoxin-induced toxicity. Given the contamination caused by mycotoxins worldwide, the protective effects of a variety of natural compounds due to their antioxidant capacities have been evaluated. We review data on the ability of vitamins, flavonoids, crocin, curcumin, green tea, lycopene, phytic acid, L-carnitine, melatonin, minerals and mixtures of anti-oxidants to mitigate the toxic effect of mycotoxins associated with oxidative stress.

The Benefits of the Citrus Flavonoid Diosmin on Human Retinal Pigment Epithelial Cells under High-Glucose Conditions

We investigate diosmin for its effect on the ARPE-19 human retinal pigment epithelial cells exposed to high glucose, a model of diabetic retinopathy (DR). After incubation for 4 days with a normal (5 mmol/L) concentration of D-glucose, ARPE-19 cells were exposed separately to normal or high concentrations of D-glucose (30 mmol/L) with or without diosmin at different concentrations (0.1, 1, 10 μg/mL) for another 48 h. Next, we assessed cell viability, reactive oxygen species (ROS) generation and antioxidant enzyme activities. In order to examine the underlying molecular mechanisms, we meanwhile analyzed the expressions of Bax, Bcl-2, total and phosphorylated JNK and p38 mitogen-activated protein kinase (MAPK). Diosmin dose dependently enhanced cell viability following high glucose treatment in ARPE-19 cells. The activities of superoxide dismutase and glutathione peroxidase, as well as the levels of reduced glutathione were decreased, while it was observed that levels of ROS in high glucose cultured ARPE-19 cells increased. High glucose also disturbed Bax and Bcl-2 expression, interrupted Bcl-2/Bax balance, and triggered subsequent cytochrome c release into the cytosol and activation of caspase-3. These detrimental effects were ameliorated dose dependently by diosmin. Furthermore, diosmin could abrogate high glucose-induced apoptosis as well as JNK and P38 MAPK phosphorylation in ARPE-19 cells. Our results suggest that treatment ARPE-19 cells with diosmin halts hyperglycemia-mediated oxidative damage and thus this compound may be a candidate for preventing the visual impairment caused by DR.

Impairment of gill structural integrity by manganese deficiency or excess related to induction of oxidative damage, apoptosis and dysfunction of the physical barrier as regulated by NF-κB, caspase and Nrf2 signaling in fish

This study is for the first time to explore the possible effects of dietary manganese (Mn) on structural integrity and the related signaling in the gills of fish. Grass carp (Ctenopharyngodon idella) were fed with six diets containing graded levels of Mn [3.65-27.86 mg Mn/kg diet] for 8 weeks. The results firstly demonstrated that Mn deficiency aggravated inflammation indicated by up-regulation of pro-inflammatory cytokines (tumour necrosis factor α, interleukin 8, and interleukin 1β mRNA levels) and down-regulation of anti-inflammatory cytokines (interleukin 10, transforming growth factor-β1) mRNA levels, which might be partially related to the up-regulation of nuclear factor kappa B (NF-κB p65) and down-regulation of nuclear inhibitor factor κBα (iκBα) mRNA levels in the gills of fish. Meanwhile, Mn deficiency caused DNA fragmentation, which might be partially associated with the up-regulation of the apoptosis signaling (caspase-3, caspase-8 and caspase-9) in the gills of fish. Furthermore, Mn deficiency-caused apoptosis might be partly related to the increases of oxidative damage that indicated by increases of lipid peroxidation and protein oxidation, and decreases of antioxidant enzyme activities [included Mn superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST)]. However, Mn deficiency only down-regulated MnSOD and GST mRNA levels, which might be partially related to the up-regulation of NF-E2-related factor-2 (Nrf2) inhibitor (Keap1), and only down-regulated the gene expression of claudin-b and claudin-15 to disrupt the TJ in the gills of fish. Excessive Mn led to negative effects on partial parameters studied in the gills of fish. The optimal levels of Mn based on protecting against ROS, MDA and PC in the gills of grass carp were 17.04, 16.86 and 21.20 mg/kg diet, respectively. Collectively, Mn deficiency or excess could cause inflammation, apoptosis, antioxidant system disruption and change tight junction protein (claudin-b and claudin-15) transcription abundances, which might be partially related to the NF-κB p65, caspase-(3,8,9) and Nrf2 signaling, in the gills of fish.

Pro-apoptotic effects of lipid oxidation products: HNE at the crossroads of NF-κB pathway and anti-apoptotic Bcl-2

The axis between lipid oxidation products and cell death is explicitly linked. 4-Hydroxynonenal (HNE), as well as other lipid oxidation products was also established to induce apoptosis in various experimental settings. Yet, the decision leading to apoptotic execution not only includes upregulation of pro-apoptotic signals but also involves a downregulation of anti-apoptotic signals. Within the frames of this paradigm, HNE acts significantly different from other lipid oxidation products in the regulation of two widely known anti-apoptotic elements, Nuclear Factor-κB (NF-κB) transcription factors and its target anti-apoptotic B-Cell Lymphoma-2 (Bcl-2) protein. Even so, a review inclusively linking these anti-apoptotic factors and their crosstalk upon HNE exposure is still at demand. In order to elucidate presence of such crosstalk, reports on the link between HNE and NF-κB pathway, on the link between HNE and anti-apoptotic Bcl-2 and on the crossroad of these links during HNE exposure were summarized and discussed. IKK, the upstream kinase of NF-κB, has been shown to regulate HNE mediated phosphorylation and inactivation of Bcl-2 by our group. Based on this observation and other studies reporting on HNE-NF-κB pathway interaction, IKK was proposed to mediate the crosstalk of NF-κB pathway and anti-apoptotic Bcl-2 protein, when HNE is present. These reports further suggested that HNE based inhibition of NF-κB pathway is highly likely. Besides, evidence on the HNE-anti-apoptotic Bcl-2 axis supported the deduction of HNE mediated NF-κB pathway inhibition and IKK mediated Bcl-2 inactivation. In conclusion, through combining all evidences, three possible scenarios intervening the HNE mediated crosstalk between NF-κB pathway and anti-apoptotic Bcl-2 protein, was extrapolated.

The effect of fluoride on the structure, function, and proteome of a renal epithelial cell monolayer

High concentrations of fluoride in the body may cause toxic effects. Here, we investigated the effects of fluoride on the structure, function, and proteome of a cortical collecting duct epithelium in vitro. Kidney tubule cells (M-1) were chosen because the concentration of fluoride in the kidney is 4-5-fold higher than that in plasma. Mouse M-1 cell monolayers were incubated in fluoride-containing media, and the amiloride-sensitive short-circuit current and transepithelial resistance were measured. The Young's modulus of the epithelium was determined using atomic force microscopy, and the effect of fluoride on epithelial structure was assessed using scanning and transmission electron microscopy, and immunofluorescence. Differences in the expression of membrane proteins were evaluated using proteomics and bioinformatics. Fluoride exposure reduced both transepithelial Na⁺ transport and resistance. The IC₅₀ for fluoride was ∼300 µM for both effects, and the half-times for the decays of ion transport and resistance were 8.4 h and 3.6 days, respectively. Fluoride treatment did not affect the sensitivity of Na⁺ transport to amiloride. The Young's modulus of the epithelium was also unaffected by fluoride; however, the functional effects of fluoride were accompanied by marked structural effects. Proteomic analysis revealed changes in expression of a number of proteins, and particularly mitochondrial proteins. Treatment with fluoride had profound effects on the structure, function and proteome of a model cortical collecting duct epithelium. Significantly, however, these effects were produced only at concentrations considerably higher than those likely to be encountered in vivo. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1455-1467, 2017.

Effects of fluoride on insulin signaling and bone metabolism in ovariectomized rats

Fluoride is an essential trace element for the maintenance of bone health owing to its capacity to stimulate proliferation and osteoblastic activity that can lead to increased bone formation. However, excessive sodium fluoride (NaF) intake can impair carbohydrate metabolism thereby promoting hyperglycemia, insulin resistance, and changes in insulin signaling. Thus, this study aimed to evaluate the effect of chronic treatment with NaF in bone metabolism, insulin signaling, and plasma concentrations of glucose, insulin, tumor necrosis factor-α (TNF-α), osteocalcin (OCN), and fluoride in ovariectomized rats. Thirty-two ovariectomized Wistar rats were randomly distributed into two groups: Control (OVX-C) and those undergoing treatment with NaF (50mg F/L) in drinking water for 42days (OVX-F). Glucose and insulin levels were assessed, followed by homeostasis model assessment of insulin resistance (HOMA-IR). Akt serine phosphorylation was evaluated by western blotting. Plasma concentrations of TNF-α and OCN were evaluated by ELISA. The left and right tibia was collected for immunohistochemical and histomorphometric analysis, respectively. Chronic treatment with NaF promoted insulin resistance, decreased insulin signal, increased plasma concentration of insulin, fluoride, OCN and TNF-α, decreased trabecular bone area of the tibia, and caused changes in bone metabolism markers in ovariectomized rats. These results suggest the need for caution in the use of NaF for the treatment of osteoporosis, especially in postmenopausal woman.

Fluoride impairs oocyte maturation and subsequent embryonic development in mice

The damage caused by fluorosis is permanent, and has been recognized as a public health problem in a number of regions of the world. Although multiple studies provided evidence that sodium fluoride (NaF) elicits adverse effects on reproductive function, the effect of fluoride on female germ cell development is not well understood. Therefore, the present study aimed at evaluating the effect of fluoride treatments on in vivo maturation and developmental potential of mouse oocytes, in which female ICR mice were treated with a range of doses (0, 30, 60, and 150 mg/L) of NaF. After treatment, mice were superovulated to collect ovulated oocytes. The effects of NaF on oocyte quality, fertilization potential and early embryonic development were evaluated, as well as the underlying mechanisms were primarily investigated. The findings of this study showed that NaF treatment resulted in abnormal spindle configuration, actin cap formation, and cortical granule-free domain formation. Additionally, overexposure of mice to NaF notably reduced ATP production and mitochondrial membrane potential, further influencing in vitro fertilization and subsequent embryonic development. These results indicated that NaF treatment impairs the subsequent embryonic developmental potential of the oocytes. In conclusion, overexposure to fluoride in vivo was associated with a significant disruption of cytoskeletal dynamics and decreased oocyte quality, affecting the oocyte's subsequent fertilization and embryonic development. Results of this study provide a rationale for treating reproductive diseases such as infertility or miscarriage caused by environmental contaminants. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1486-1495, 2016.