Lack of DNA damage induced by fluoride on mouse lymphoma and human fibroblast cells by single cell gel (comet) assay

Fluoride subacute testicular toxicity in Wistar rats: Benchmark dose analysis for the redox parameters, essential elements and DNA damage

Excessive fluoride (F^-) levels in the environment could induce different pathological changes, including comorbidities in reproductive functions. Hence, the aim of the present in vivo study was to explore F^- subacute toxicity mechanisms via Benchmark dose (BMD) methodology on rat's testicles. The experiment was conducted on thirty male Wistar rats for 28 days, divided into six groups (n = 5): 1) Control (tap water); 2) 10 mg/L F^-; 3) 25 mg/L F^-; 4) 50 mg/L F^-; 5) 100 mg/L F^-; 6) 150 mg/L F^-. Testicles were dissected out and processed for the determination of F^- tissue concentrations, redox status parameters, essential elements level, and DNA damage. PROASTweb 70.1 software was used for determination of external and internal dose-response relationship. The results confirmed a significant increase in superoxide anion (O₂^.-), total oxidative status (TOS), copper (Cu), zinc (Zn), iron (Fe), DNA damage levels, and decrease in superoxide dismutase activity (SOD1) and total thiol (SH) groups. The dose-dependent changes were confirmed for SOD1 activity and DNA damage. The most sensitive parameters were SOD1 activity and DNA damage with the lowest BMDLs 0.1 μg F^-/kg b. w. Since human and animal populations are daily and frequently unconsciously exposed to F^-, this dose-response study is valuable for further research regarding the F^- health risk assessment.

The Effect of Lycopene on DNA Damage and Repair in Fluoride-Treated NRK-52E Cell Line

Exposure of fluorine at toxic concentrations causes serious damage by accumulating in especially bones, kidneys, and other soft tissues. Fluorine at cytotoxic concentrations may cause DNA damage. This study aims to determine the level of DNA damage due to sodium fluoride (NaF) at different hours (3rd, 12th, and 24th hours) and in IC₅₀ concentrations designated for each hour and reveal the protective effect of lycopene on possible damage. The best enhancer concentrations (1 μM) of microtitration (MTT) viability test and proliferation of lycopene and IC₅₀ values of NaF at the 3rd, 12th, and 24th hour were 9600, 5500, and 3200 μM, respectively. DNA damage significantly increased in all NaF-treated groups in comparison with the control group (p < 0.05). DNA damage due to NaF+LYC application significantly decreased in comparison with the control group (p < 0.05). Lycopene application significantly increased the expression levels of the Ku70 and Ku80 genes which have a part in DNA repair (p < 0.05). The statistical data showed that application of lycopene which is an important antioxidant molecule may be beneficial for decreasing NaF-induced DNA damage. In conclusion, applying lycopene for cytotoxicity due to fluorine in NRK-52E cell line had different effects based on the dosage and time; thus, it can be a potential option for preventing fluorosis-induced toxicity and developing new treatment approaches.

Genotoxicity of fluoride subacute exposure in rats and selenium intervention

The aims of this study were to: (i) examine the toxic effects of sodium fluoride (NaF) in blood, liver, spleen, and brain cells of Wistar rats after the subacute exposure; (ii) explore the potential protective properties of selenium (Se) against fluoride toxicity after the simultaneous administration. Twenty male Wistar rats, eight weeks old, weighing approximately 140-190 g, were divided into four experimental groups (n = 5) as follows: I control-tap water; II NaF 150 ppm; III NaF 150 ppm and Se 1.5 mg/L; IV Se 1.5 mg/L, and had available water with solutions ad libitum for 28 days. DNA damage detected by comet assay was confirmed in the liver, spleen, and brain cells, but not in blood. Selenium supplementation together with NaF decreased DNA damage in liver and spleen cells. According to the histological findings, no changes were observed in spleen and brain tissues after NaF administration. Unlike the observed Se protective effect on the DNA level, no significant reduction of liver tissue injury was observed after the NaF and Se treatment, resulting in mild inflammation. Data of this study suggest that DNA damage after NaF subacute exposure at moderately high concentration was reduced in liver and spleen cells due to Se supplementation, but a similar change was not seen in the brain.

Putative mechanisms of genotoxicity induced by fluoride: a comprehensive review

Genotoxicity is the ability of an agent to produce damage on the DNA molecule. Considering the strong evidence for a relationship between genetic damage and carcinogenesis, to elucidate the putative mechanisms of genotoxicity induced by fluoride are important to measure the degree of risk involved to human populations. The purpose of this article is to provide a comprehensive review on genotoxicity induced by fluoride on the basis of its mechanisms of action. In the last 10 years, all published data showed some evidence related to genotoxicity, which is due to mitochondrial disruption, oxidative stress, and cell cycle disturbances. However, this is an area that still requires a lot of investigation since the published data are not sufficient for clarifying the genotoxicity induced by fluoride. Certainly, the new information will be added to those already established for regulatory purposes as a safe way to promote oral healthcare and prevent oral carcinogenesis.

Cytotoxicity of the Diterpene 14-O-Methyl-ryanodanol from Erythroxylum passerinum in an Astrocytic Cells Model

Plant secondary metabolites, such as, specifically, alkaloids and terpenes, may present psychoactive properties that modify the function of the central nervous system (CNS) and induce neurotoxicity. Neurotoxicity involves the response of glial cells, mainly astrocytes, which play a fundamental role in the control of homeostasis of the CNS. Some Erythroxylum species are indigenous to the state of Bahia in Brazil. This study investigated the cytotoxic activity of the diterpene AEP-1, extracted from the fruit of E. passerinum in a GL-15 cell line, astrocytic, glial cells model. The effects on cell viability, analyzed by the MTT assay, demonstrated a dose-dependent cytotoxic effect, with maximum effect at 500 μg/mL of AEP-1, and with a reduction of about 40 and 47% on cellular viability after 24 h and 72 h treatment, respectively. Evidence for induction of apoptosis by AEP-1 was first obtained when GL-15 glial cells were incubated with 250 μg/mL AEP-1 causing reniform and/or pyknotic nuclei and apoptotic bodies revealed by chromatin staining with Hoechst 33258. Increase in DNA fragmentation was also observed by comet assays in cells incubated with 500 μg/mL of AEP-1. Moreover, cells exposed to a sub toxic dose of AEP-1 (250 μg/mL) showed significant changes in morphology – contraction of the cytoplasm and expansion of cellular projections – signifying the presence of astrocytic cytoskeletal protein and glial fibrillary acidic protein (GFAP). These findings indicated astrocytic cells as the target for terpene AEP-1 and suggest the involvement of glial cells with psychoactive symptoms observed in humans and animals after consumption of fruits of plants of the genus Erythroxylum.

Sodium fluoride promotes apoptosis by generation of reactive oxygen species in human lymphocytes

Fluoride generated the attention of toxicologists due to its deleterious effects at high concentrations in human populations suffering from fluorosis and with in vivo experimental models. Interest in its undesirable effects has resurfaced due to the awareness that this element interacts with cellular systems even at low doses. This study focused on examining the adverse effects of inorganic fluoride (NaF) on human lymphocyte cells in vitro. Mitochondrial function, oxidative stress, cell cycle progression, and mode of cell death were combined with genotoxic endpoints. Data demonstrated that NaF at lower concentrations, although not significantly cytotoxic and genotoxic, induced oxidative stress leading to apoptotic cell death. The results also suggested that at low concentrations (<1 μg/ml), NaF may affect cell cycle progression. Taken together, our findings confirm earlier reports on mechanisms involved in NaF-induced apoptosis.

Evaluation of in vitro anti-genotoxic potential of melatonin against arsenic and fluoride in human blood cultures

Melatonin has been known for its anti-oxidant potential but not much studied for the anti-genotoxic potential. The current study elucidate the role of melatonin against in vitro genotoxicity by arsenic (As) and fluoride (F). Human peripheral blood cultures were exposed to As (1.4 microM) and F (34 microM), alone and in combination, with and without melatonin (0.2 mM). Ethyl methane sulphonate (EMS; 1.9 mM) was selected as the positive control to analyze the genotoxic parameters like sister chromatid exchanges (SCEs), cell cycle proliferative index (CCPI) and primary DNA damage. The frequency of SCE/cell, SCE/chromosome and primary DNA damage reduced significantly (p<0.001) accompanied with a marked increase in CCPI upon addition of melatonin. Similarly marked recovery was attained by melatonin from As and F induced primary DNA damage as studied using comet assay. The results clearly indicate towards the protection of lymphocytes from toxic effects af As and F by melatonin in vitro.

The ability of the high-throughput comet assay to measure the sensitivity of five cell lines toward methyl methanesulfonate, hydrogen peroxide, and pentachlorophenol

A new, high-throughput version of the comet assay was developed using human fibroblasts (Stang and Witte, 2009). The present study examines the suitability of other adherent and non-adherent cell types in this high-throughput assay. We found that in addition to V79 human fibroblasts, HeLa cells, Hep-G2 cells, and lymphocytes can be used. The time intervals needed for attachment on the agarose-coated 96-well multi-chamber plate (MCP, specially developed for the high-throughput comet assay) differed for all adherent cell lines mentioned. V79 cells needed 6h for attachment, fibroblasts 2-4h, Hep-G2 required 18 h, and HeLa cells 16 h. After this period, chemical treatment could occur. Non-adherent lymphocytes could be treated with the chemicals directly after they had been pipetted into the wells of the MCP and centrifuged. We compared the sensitivities of these five cell types toward the directly DNA-damaging compounds methyl methanesulfonate (MMS), and hydrogen peroxide (H(2)O(2)), and toward the indirectly acting agent pentachlorophenol (PCP). Except for Hep-G2 cells, exposure to PCP was conducted in the presence of an S9 microsome fraction. DNA damage, measured as an increase in the percentage of DNA in the tail region of the comets, occurred in a concentration-dependent manner. Under the test conditions used in this study, human lymphocytes were the most sensitive cells toward the three chemicals tested, fibroblasts showed a similar sensitivity toward the directly acting MMS and H(2)O(2), but were less sensitive toward PCP. HeLa, V79, and Hep-G2 cells reacted with similar sensitivity.

Comparison of murine fibroblast cell response to fluor-hydroxyapatite composite, fluorapatite and hydroxyapatite by eluate assay

Fluorapatite (FA) is one of the inorganic constituents of bone or teeth used for hard tissue repairs and replacements. Fluor-hydroxyapatite (FHA) is a new synthetic composite that contains the same molecular concentration of OH(-) groups and F(-) ions. The aim of this experiment was to evaluate the cellular responses of murine fibroblast NIH-3T3 cells in vitro to solid solutions of FHA and FA and to compare them with the effect of hydroxyapatite (HA). We studied 24, 48 and 72 h effects of biomaterials on cell morphology, proliferation and cell cycle of NIH-3T3 cells by eluate assay. Furthermore, we examined the ability of FHA, FA and HA to induce cell death and DNA damage. Our cytotoxic/antiproliferative studies indicated that any of tested biomaterials did not cause the total inhibition of cell division. Biomaterials induced different antiproliferative effects increasing in the order HA < FHA < FA which were time- and concentration-dependent. None of the tested biomaterials induced necrotic/apoptotic death of NIH-3T3 cells. On the other hand, after 72 h we found that FHA and FA induced G0/G1 arrest of NIH-3T3 cells, while HA did not affect any cell cycle phases. Comet assay showed that while HA demonstrated weaker genotoxicity, DNA damage induced by FHA and FA caused G0/G1 arrest of NIH-3T3 cells. Fluoridation of hydroxyapatite and different FHA and FA structure caused different cell response of NIH-3T3 cells to biomaterials.