Toxicity and carcinogenicity of potassium bromate--a new renal carcinogen

Changes in metabolic landscapes shape divergent but distinct mutational signatures and cytotoxic consequences of redox stress

Mutational signatures discerned in cancer genomes, in aging tissues and in cells exposed to toxic agents, reflect complex processes underlying transformation of cells from normal to dysfunctional. Due to its ubiquitous and chronic nature, redox stress contributions to cellular makeover remain equivocal. The deciphering of a new mutational signature of an environmentally-relevant oxidizing agent, potassium bromate, in yeast single strand DNA uncovered a surprising heterogeneity in the mutational signatures of oxidizing agents. NMR-based analysis of molecular outcomes of redox stress revealed profound dissimilarities in metabolic landscapes following exposure to hydrogen peroxide versus potassium bromate. The predominance of G to T substitutions in the mutational spectra distinguished potassium bromate from hydrogen peroxide and paraquat and mirrored the observed metabolic changes. We attributed these changes to the generation of uncommon oxidizing species in a reaction with thiol-containing antioxidants; a nearly total depletion of intracellular glutathione and a paradoxical augmentation of potassium bromate mutagenicity and toxicity by antioxidants. Our study provides the framework for understanding multidimensional processes triggered by agents collectively known as oxidants. Detection of increased mutational loads associated with potassium bromate-related mutational motifs in human tumors may be clinically relevant as a biomarker of this distinct type of redox stress.

Comparative study between effects of ginkgo biloba extract and extract loaded on gold nanoparticles on hepatotoxicity induced by potassium bromate

In human organs, potassium bromate (KBrO3) produces toxicity. The main causes of KBrO3 hepatotoxicity are the formation of reactive oxygen species (ROS) and DNA damage. The purpose of this study is to show how ginkgo biloba extract (GBE) and extract loaded with nanogold particles (GBE@AuNPs) affect hepatotoxicity caused by KBrO3. The rats were separated into eight groups: control (group I), GBE (group II), AuNPs (group III), GBE@AuNPs (group IV), KBrO3 (group V), KBrO3 and GBE (group VI), KBrO3 and AuNPS (group VII), and KBrO3 and GBE@AuNPs (group VIII). KBrO3 generated DNA damage spots in a comet assay, which were associated with increased inflammatory indicators (IL-6), decreased anti-apoptotic Bcl-2, and increased apoptotic markers (Bax and caspase-3). The inflammatory, apoptotic, and ultrastructural alterations in liver tissue produced by KBrO3 were reduced in treated groups VI, VII, or VIII. The hepatotoxic effects of KBrO3 were reduced when GBE, AuNPs, or GBE@AuNPs were used; the particular GBE@AuNPs were the most effective.

Iodine as a potential endocrine disruptor-a role of oxidative stress

PURPOSE

Iodine is an essential micronutrient required for thyroid hormone biosynthesis. However, overtreatment with iodine can unfavorably affect thyroid physiology. The aim of this review is to present the evidence that iodine-when in excess-can interfere with thyroid hormone synthesis and, therefore, can act as a potential endocrine-disrupting chemical (EDC), and that this action, as well as other abnormalities in the thyroid, occurs-at least partially-via oxidative stress.

METHODS

We reviewed published studies on iodine as a potential EDC, with particular emphasis on the phenomenon of oxidative stress.

RESULTS

This paper summarizes current knowledge on iodine excess in the context of its properties as an EDC and its effects on oxidative processes.

CONCLUSION

Iodine does fulfill the criteria of an EDC because it is an exogenous chemical that interferes-when in excess-with thyroid hormone synthesis. However, this statement cannot change general rules regarding iodine supply, which means that iodine deficiency should be still eliminated worldwide and, at the same time, iodine excess should be avoided. Universal awareness that iodine is a potential EDC would make consumers more careful regarding their diet and what they supplement in tablets, and-what is of great importance-it would make caregivers choose iodine-containing medications (or other chemicals) more prudently. It should be stressed that compared to iodine deficiency, iodine in excess (acting either as a potential EDC or via other mechanisms) is much less harmful in such a sense that it affects only a small percentage of sensitive individuals, whereas the former affects whole populations; therefore, it causes endemic consequences.

Effect of atmospheric nonthermal plasma on physicochemical, morphology and functional properties of sunn pest (Eurygaster integriceps)-damaged wheat flour

To improve the quality of sunn pests (Eurygaster integriceps)-damaged wheat flour, the effects of nonthermal plasma on physicochemical, rheological, functional, and microstructural properties were investigated. Gas type (air and oxygen), voltage (22 and 25 volts), and time (0, 2, 4, 6, 8, and 10 min) were the variables of the experiments conducted using a completely randomized design with three replications. The results show that with increasing voltage and time of plasma treatment, the pH decreased significantly (p ≥ .05), and brightness parameter, yellow-blue parameter, water-solubility, water absorption, oil absorption, and swelling power increased significantly (p ≥ .05). The duration of plasma treatment, voltage, and change in input gas from air to oxygen did not significantly change the gluten index, particle size, and negative electric charge of flour particles, and the amount of zeta potential of samples. Differential calorimetric analysis showed the first and second peaks of the thermogram in the range 55-99°C and also 114-99°C. Infrared spectroscopy (FT-IR) showed hydroxyl group, CH bonds, C=O bonds, as well as the presence of types I and II amide bonds in the structure. Microstructural results indicated that plasma treatment reduced the particle size and increased particle sorting. By Increasing voltage and the duration of plasma treatment, peak viscosity, final viscosity, breakdown viscosity, pasting time and temperature significantly increased and setback viscosity decreased (p ≥ .05), which reduced retrogradation which improved the dough stability during the cooling process.

Association of Ozone Exposures with the risk of thyroid nodules in Hunan Province: a population-based cohort study

BACKGROUND

Increasing evidence associates air pollution with thyroid dysfunction, whereas the potential relationship between exposure to ozone (O₃) and Thyroid Nodules (TNs) is unclear.

METHODS

This retrospective cohort study investigated the association between O₃ exposure and TNs in Hunan province, enrolling 191,357 Chinese adults who lived in Hunan province from January 2009 to December 2019 and received voluntary medical examinations. Individual exposure levels to O₃ from 2010 to 2019 were measured on account of participants' residential addresses at the district level. Associations of O₃ exposure with the risk of incidental TNs were assessed by restricted cubic splines and surveyed as odds ratios after adjusting for demographic factors.

RESULTS

In total, 81,900 adults were newly diagnosed with TNs during the study period. Age-standardized TNs detection rate in Hunan province increased from 25.9 to 46.3% between 2010 and 2019, with the greatest annual percent change being 8.1 [95% CI, 7.3-8.8]. A similar trend has been found in all tumor sizes, ages, and both sexes. O₃ exposure presented a statistically significant dose-dependent positive correlation (greater than 0.036 ppm) with TNs. Similarly, long-term exposure to high levels of O₃ (1-year average O₃ concentrations exceeding 0.0417 ppm) was found positively associated with increased TSH levels.

CONCLUSIONS

High-level O₃ exposure in the long term was associated with an increase in TSH. Consequently, increased TSH was related to the increased risk of TNs. Being exposed to high-level O₃ in the long term was related to the increased detection rates of TNs in Hunan province, which could be mediated by TSH.

New aspects in deriving health-based guidance values for bromate in swimming pool water

Bromate, classified as a EU CLP 1B carcinogen, is a typical by-product of the disinfection of drinking and swimming pool water. The aim of this study was (a) to provide data on the occurrence of bromate in pool water, (b) to re-evaluate the carcinogenic MOA of bromate in the light of existing data, (c) to assess the possible exposure to bromate via swimming pool water and (d) to inform the derivation of cancer risk-related bromate concentrations in swimming pool water. Measurements from monitoring analysis of 229 samples showed bromate concentrations in seawater pools up to 34 mg/L. A comprehensive non-systematic literature search was done and the quality of the studies on genotoxicity and carcinogenicity was assessed by Klimisch criteria (Klimisch et al., Regul Toxicol Pharmacol 25:1-5, 1997) and SciRAP tool (Beronius et al., J Appl Toxicol, 38:1460-1470, 2018) respectively. Benchmark dose (BMD) modeling was performed using the modeling average mode in BMDS 3.1 and PROAST 66.40, 67 and 69 (human cancer BMDL10; EFSA 2017). For exposure assessment, data from a wide range of sources were evaluated for their reliability. Different target groups (infants/toddlers, children and adults) and exposure scenarios (recreational, sport-active swimmers, top athletes) were considered for oral, inhalation and dermal exposure. Exposure was calculated according to the frequency of swimming events and duration in water. For illustration, cancer risk-related bromate concentrations in pool water were calculated for different target groups, taking into account their exposure using the hBMDL10 and a cancer risk of 1 in 100,000. Convincing evidence was obtained from a multitude of studies that bromate induces oxidative DNA damage and acts as a clastogen in vitro and in vivo. Since statistical modeling of the available genotoxicity data is compatible with both linear as well as non-linear dose-response relationships, bromate should be conservatively considered to be a non-threshold carcinogen. BMD modeling with model averaging for renal cancer studies (Kurokawa et al., J Natl. Cancer Inst, 1983 and 1986a; DeAngelo et al., Toxicol Pathol 26:587-594, 1998) resulted in a median hBMDL10 of 0.65 mg bromate/kg body weight (bw) per day. Evaluation of different age and activity groups revealed that top athletes had the highest exposure, followed by sport-active children, sport-active adults, infants and toddlers, children and adults. The predominant route of exposure was oral (73-98%) by swallowing water, followed by the dermal route (2-27%), while the inhalation route was insignificant (< 0.5%). Accepting the same risk level for all population groups resulted in different guidance values due to the large variation in exposure. For example, for an additional risk of 1 in 100,000, the bromate concentrations would range between 0.011 for top athletes, 0.015 for sport-active children and 2.1 mg/L for adults. In conclusion, the present study shows that health risks due to bromate exposure by swimming pool water cannot be excluded and that large differences in risk exist depending on the individual swimming habits and water concentrations.

Evaluation of a 4-day repeated-dose micronucleus test in rat glandular stomach and colon using aneugens and non-genotoxic non-carcinogens

Background

We previously developed a rodent gastrointestinal (GI) tract micronucleus (MN) test using the glandular stomach and/or colon, and evaluated this test method using several genotoxic carcinogens (clastogens) and genotoxic non-carcinogens; we demonstrated that this test method could detect genotoxic stomach and/or colon carcinogens with target organ specificity. In the present study, we further evaluated the sensitivity and specificity of the MN test for the rat glandular stomach and colon using three aneugens (colchicine, vinblastine sulfate, and docetaxel hydrate) and two non-genotoxic non-carcinogens (sodium chloride and sucrose).

Results

Male Crl:CD (SD) rats were administered test compounds through clinical administration route (orally or intravenously) for four consecutive days and then examined for the micronucleated cell frequencies in the glandular stomach and colon. We observed that all three aneugens significantly and dose-dependently increased the micronucleated cell frequencies in the stomach and colon. In contrast, neither of the two non-genotoxic non-carcinogens increased the micronucleated cell frequency in these tissues. Notably, an increase in cell proliferation was observed in the glandular stomach of rats administered a stomach toxicant, sodium chloride, but this increase did not affect the induction of micronuclei in the gastric cells.

Conclusions

In the present study, it was demonstrated that the glandular stomach and colon MN tests could detect aneugens as positive and could adequately evaluate non-genotoxic non-carcinogens as negative, including a chemical that enhances cell proliferation. These results provide important evidence supporting good performance of the rat glandular stomach and colon MN tests with a 4-day treatment regimen.

Clean Label in Bread

Bread is considered a staple food worldwide, and therefore there is much interest in research around the topic. The bread industry is usually looking for ways to improve its formulations. Therefore, other ingredients such as dough conditioners, crumb softeners, emulsifiers, and surfactants can be added to enhance bread quality. These ingredients perform functions such as helping standardize processes in the industry, reducing dough-mixing time, increasing water absorption, improving bread quality, and extending its shelf life. Consumers are concerned about the effect of these ingredients on their health, and this has increased the popularity of clean-label bread formulations. A clean label generally indicates that a product is free of chemical additives, has an ingredient list that is easy to understand, has undergone natural or limited processing, and/or is organic and free of additives or preservatives. However, there is no scientific definition of the term “clean label.” Researchers have focused on these clean-label initiatives to replace dough strengtheners and preservatives in bread formulations and give consumers what they perceive as a healthier product.

Analysis of the suspected cancer-causing potassium bromate additive in bread samples available on the market in and around Dhaka City in Bangladesh

Bread is one of the most popular foods consumed worldwide. It is a very popular foodstuff consumed in almost every house in Bangladesh as breakfast. Bread is prepared predominantly from flour to meet the daily carbohydrate demand and enhances its overall nutrition value using various ingredients. Potassium bromate (KBrO3) is an alluring additive to improve bread quality by bread makers. But due to the well-known toxic and carcinogenic effect, certain levels of KBrO3 residue are not suitable for bread, and it is therefore forbidden in many countries. The key objective of this study is to evaluate the safety status of bread in Dhaka City and its proximity to Bangladesh. Twenty-one randomly collected bread samples were tested in this study from different bakeries or shops in and around Dhaka City. The levels of KBrO3 were analyzed spectrophotometrically, and the maximum concentration found in the bread sample was 9.29 μg/g. A total of 67% of collected bread samples showed elevated levels of KBrO3 relative to the allowable amount prescribed by various Food and Drug Administration worldwide. KBrO3 is toxic to consumers and could endanger their health over continuous regular consumption and thus need to be monitored strictly.

Pro-Oxidative Effect of KIO3 and Protective Effect of Melatonin in the Thyroid-Comparison to Other Tissues

Not only iodine deficiency, but also its excess may contribute to thyroid cancer. Potassium iodate (KIO₃), which is broadly used in the salt iodization program, can increase oxidative damage to membrane lipids (lipid peroxidation, LPO) under experimental conditions, with the strongest damaging effect at KIO₃ concentration of ~10 mM (corresponding to physiological iodine concentration in the thyroid). Melatonin is an effective antioxidant, which protects against KIO₃-induced LPO in the thyroid. This study aimed to compare the protective effects of melatonin, used in the highest achievable in vitro concentration, against KIO₃-induced oxidative damage to membrane lipids in various porcine tissues (thyroid, ovary, liver, kidney, brain, spleen, and small intestine). Homogenates were incubated in the presence of KIO₃ (20; 15; 10; 7.5; 5.0; 0.0 mM) without/with melatonin (5 mM). The malondialdehyde + 4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. KIO₃ increased the LPO in all examined tissues; in the thyroid, the damaging effect of KIO₃ (10; and 7.5 mM) was lower than in other tissues and was not observed for the lowest concentration of 5 mM. Melatonin reduced LPO induced by KIO₃ (10, 7.5, and 5 mM) in all tissues, and in the thyroid it was also protective against as high a concentration of KIO₃ as 15 mM; the LPO level resulting from KIO₃ + melatonin treatment was lower in the thyroid than in other tissues. In conclusion, the thyroid is less sensitive tothe pro-oxidative effects of KIO₃ compared to other tissues. The strongest protective effect of melatonin was observed in the thyroid, but beneficial effects were significant also in other tissues. Melatonin should be considered to avoid the potential damaging effects of iodine compounds applied in iodine prophylaxis.

Potassium bromate (KBrO3) modulates oxidative stress and inflammatory biomarkers in sodium hydroxide (NaOH) - induced Crohn's colitis in Wistar rats

Potassium bromate (KBrO₃) present in consumed ozonised water was recently documented to exacerbate experimental gastric ulcer. Information, however, is vague as regards its effects in the colon where water reabsorption occurs. In this study, we observed the possible effects of KBrO₃ on oxidative stress and inflammatory biomarkers in sodium hydroxide (NaOH) - induced Crohn's colitis (CC). Wistar rats (180-200 g) were divided into six groups (n = 10): (i) control; (ii) untreated CC (induced by 1.4% NaOH; intra-rectal administration); and (iii-vi) CC treated with vitamin E, KBrO₃, vitamin E+KBrO₃, and sulphazalazine, respectively, for 7 days. Body weight and stool score were monitored daily. By day 3 and 7, excised colon was evaluated for ulcer scores and biochemical and histological analysis. Blood samples collected on days 3 and 7 were assayed for haematological indices using standard methods. Data were subjected to analysis of variance (ANOVA) and p ≤ 0.05 considered significant. Platelet/lymphocyte ratio, colonic ulcer score, malondialdehyde, and mast cells were significantly decreased while colonic sulfhydryl, and Ca²⁺- and Na⁺/K⁺-ATPase activities were increased following KBrO₃ treatment compared with untreated CC. These findings suggest that KBrO₃ may mitigate against NaOH-induced CC via inhibiting mast cell population and oxidative and inflammatory content but stimulating colonic sulfhydryl and Ca²⁺- and Na⁺/K⁺-ATPase activities.

Bottled water safety evaluations in IRAN: determination of bromide and oxyhalides (chlorite, chlorate, bromate) by ion chromatography

Bottled water is most well liked within the world and attention is drawn due to its health issues. Oxyhalides is one amongst the foremost important by-products in bottled water which is produced by disinfection process such as "ozonation". International standards have been set and justified to permissible levels for chlorate, chlorite and bromate as 700, 700 and 10 μg/l. Thereafter, 168 samples of bottled water (mineral and drinking water) from Iran market obtained with the optimal working conditions and analyzed by ion chromatography (IC) with conductivity detector. The results actuated that 23 and 17 out of 168 samples as mineral and drinking water revealed bromate content in charge of the national permissible level, found as the mean level of 37.04 and 33.58 μg/l, respectively. According to risk assessment results, the average of hazard quotient (HQ) and lifetime excess cancer (ELCR) were calculated 6.955 × 10^-3 and 0.25 × 10^-3, respectively. Thereupon, it is indispensable to control as well as make consumers aware of oxyholides hazard especially bromate following governmental authorities with an insight to health sectors monitoring guidelines due to its obvious harmful effects and aspects on health issues.

The effect of redox agents on conformation and structure characterization of gluten protein: An extensive review

Gluten protein as one of the plant resources is affected by redox agent. Chemical modifications by redox agent have myriad advantages mainly short reaction times, no requirement for specialized equipment, low cost, and highly clear modification impacts. The gluten network properties could be influenced through redox agents (oxidative and reducing agents) which are able to alter the strength of dough via different mechanisms for various purposes. The present review examined the impact of different redox compounds on gluten and its subunits based on their effects on their bonds and conformations and thus with their impacts on the physico-chemical, morphological, and rheological properties of gluten and their subunits. This allows for the use of gluten for different of purposes in the food and nonfood industry.

Go clean label: replacement of commercial dough strengtheners with hard red spring wheat flour in bread formulations

There is growing interest in the application of natural ingredients to replace chemical dough improvers in bread formulations in order to meet consumer demands of clean label products. The goal of this study was to evaluate the dough quality and baking quality of hard red spring (HRS) wheat flour blends to replace commercial dough improvers. Hard red winter (HRW) wheat flour is commonly used in bread and diner roll formulations. In this study, doughs were prepared by adding 10%, 20%, 30%, and 40% of HRS wheat flour to HRW wheat base-flour to compare the dough quality and baking quality relative to different levels of commercial improvers. Additional to commercial HRS flour, two commonly grown HRS wheat varieties (Glenn and Linkert) were included in the study. All of the HRS wheat flour blends had significantly (p < 0.05) higher farinograph stability and extensograph resistance at 135 min than doughs containing most of the commercial additives. Bread flour with 40% Glenn and 40% Linkert showed the highest loaf volumes of 920 cm3 and 950 cm3, respectively with the firmness of 1553.50 and 1525.50 mN, respectively. Baking quality of HRS wheat flour blends also showed significant (p < 0.05) correlation with dough rheology but commercial additives did not have the correlations. Therefore, HRS wheat flour may be used as a replacement for dough improvers, as it had better dough and bread properties compared to commercial additives and provides a great alternative for "clean-label" bread products.

The Alleviative Effect of Vitamin B2 on Potassium Bromate-Induced Hepatotoxicity in Male Rats

Potassium bromate (PB) is a food enhancer, water disinfection by-product, and a proven carcinogen. It elicits toxicities in the living organism due to exposure and in a dose-dependent manner. The present study discourses the ameliorative efficacy of riboflavin (RF) in PB-administered rodents. The animals were distributed into five treatment groups: control (group I), PB alone (group II, 150 mg/kg), RF alone (group III, 2 mg/kg), PB+RF1 (group IV, 150 mg/kg + 2 mg/kg), and PB+RF2 (group V, 150 mg/kg + 4 mg/kg). After the round of the treatment, the animals were sacrificed to collect their blood and liver samples for the detailed analysis. Group II depicted perturbed liver functions evidenced by altered serum and toxicity markers along with the disturbed redox balance. Also, these biochemical results were found harmonious with histopathological analysis and comet assay. However, group III showed no noticeable alteration in the same parameters, whereas the combination groups (IV and V) exhibited dose-dependent amelioration in the PB-induced toxicities. Interestingly, RF favored apoptosis concomitant with suppressing the necrosis in the PB-challenged groups, as shown by the activity of caspase-3 and lactate dehydrogenase. Histopathological analysis and comet assay further consolidate these results. Hence, RF has significant alleviative property against PB-induced hepatotoxicity in vivo that can be used in the consumer items containing the toxicant.

Interference on Iodine Uptake and Human Thyroid Function by Perchlorate-Contaminated Water and Food

BACKGROUND

Perchlorate-induced natrium-iodide symporter (NIS) interference is a well-recognized thyroid disrupting mechanism. It is unclear, however, whether a chronic low-dose exposure to perchlorate delivered by food and drinks may cause thyroid dysfunction in the long term. Thus, the aim of this review was to overview and summarize literature results in order to clarify this issue.

METHODS

Authors searched PubMed/MEDLINE, Scopus, Web of Science, institutional websites and Google until April 2020 for relevant information about the fundamental mechanism of the thyroid NIS interference induced by orally consumed perchlorate compounds and its clinical consequences.

RESULTS

Food and drinking water should be considered relevant sources of perchlorate. Despite some controversies, cross-sectional studies demonstrated that perchlorate exposure affects thyroid hormone synthesis in infants, adolescents and adults, particularly in the case of underlying thyroid diseases and iodine insufficiency. An exaggerated exposure to perchlorate during pregnancy leads to a worse neurocognitive and behavioral development outcome in infants, regardless of maternal thyroid hormone levels.

DISCUSSION AND CONCLUSION

The effects of a chronic low-dose perchlorate exposure on thyroid homeostasis remain still unclear, leading to concerns especially for highly sensitive patients. Specific studies are needed to clarify this issue, aiming to better define strategies of detection and prevention.

A novel zero valent metal bismuth for bromate removal: direct and ultraviolet enhanced reduction

Bromate (BrO₃⁻) is a carcinogenic and genotoxic by-product of the ozone disinfection process. In this study, a new zero-valent metal, bismuth, was used to reduce bromate. Bismuth samples were prepared by a solvothermal method and characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The morphology of the bismuth powder was microspheres assembled with dense nanosheets. The kinetics of the direct bromate reduction by bismuth accorded with the pseudo-first-order kinetics model. The rate coefficients of the initial bromate concentration of 1.00 mg L⁻¹, 2.50 mg L⁻¹, 5.00 mg L⁻¹ were identically close to 0.08 min⁻¹. For 0.20 mg L⁻¹, a reaction rate coefficient near 0.10 min⁻¹ was obtained. The reducing products of bromate included bromide ions (Br⁻) and bismuth oxybromides. The bromate removal efficiency was enhanced remarkably in the presence of ultraviolet (UV) light, and the corresponding kinetic coefficient was 4 times higher than that of direct reduction. The mechanism of ultraviolet enhancement was analyzed by diffuse reflectance spectroscopy (DRS), the density functional theory (DFT) calculation, open circuit potential (OCP) analysis, photocurrent measurement and linear sweep voltammetry (LSV). Besides, the influence of dissolved oxygen (DO) on bromate reduction efficiency and the sustainability of the as-prepared sample were investigated. DO inhibited the reduction rate obviously, but showed a slight effect on the formation of bromide ions. In the long-term periodic experiments, the kinetic coefficient decay occurred in both direct (without UV irradiation) and ultraviolet assisted bromate reduction. However, the kinetic coefficient of UV-assisted reduction (0.115 min⁻¹) was about 2 times higher than that of the direct reduction in the last cycle of periodic experiments. In conclusion, the novel bromate reduction strategy based on the zero-valent bismuth metal material has been proved efficient and sustainable, which contributes to the development of drinking water treatment technologies.

The inert metal bismuth is proved to be effective for the direct reduction of bromate while the reducing process is dramatically promoted under the presence of ultraviolet light, since bismuth is a typical semi-metal.

Cochlear Implantation after Bromate Intoxication-Induced Bilateral Deafness: A Case Report

Hearing loss is a common consequence of the strong acidosis induced by bromate poisoning. Partial hearing recovery has been achieved through medical or rehabilitative therapy but reports of surgical otology treatment for this condition are rare. We report the case of a 48-year-old female patient who underwent cochlear implantation after bromate intoxication had induced bilateral deafness. In cases with life-threatening renal damage, the diagnosis of hearing loss is sometimes delayed, but in our case, hearing impairment was unavoidable despite early detection of symptoms and early disruption of the use of diuretics that could cause hearing damage. Hearing loss 12 hours after bromate ingestion was successfully reversed through cochlear implantation (CI) six months after completing acute phase treatment, including dialysis for acute kidney injury. The benefit of CI for deafness by bromate intoxication is highlighted by this case.

Advances in Treatment of Brominated Hydrocarbons by Heterogeneous Catalytic Ozonation and Bromate Minimization

The formation of carcinogenic bromate ions is a constraint when ozone is used for the remediation of water containing brominated organic materials. With its strong oxidizing ability, ozone rapidly transforms bromide in aqueous media to bromate, through a series of reactions involving hydroxyl radicals. Several strategies, such as limiting the ozone concentration, maintaining pH < 6, or the use of ammonia or hydrogen peroxide were explored to minimize bromate generation. However, most of the above strategies had a negative effect on the ozonation efficiency. The advanced oxidation processes, using catalysts together with ozone, have proven to be a promising technology for the degradation of pollutants in wastewater, but very few studies have been conducted to find ways to minimize bromate formation during this approach. The proposed article, therefore, presents a comprehensive review on recent advances in bromate reduction in water by catalytic ozonation and proposes reaction mechanisms associated with the catalytic process. The main aim is to highlight any gaps in the reported studies, thus creating a platform for future research and a quest to find environment friendly and efficacious catalysts for minimizing bromate formation in aqueous media during ozonation of brominated organic compounds.

Identification of the Multifaceted Chemopreventive Activity of Curcumin Against the Carcinogenic Potential of the Food Additive, KBrO3

Background:

Potassium bromate (KBrO3), a food additive, has been used in many bakery products as an oxidizing agent. It has been shown to induce renal cancer in many in-vitro and in-vivo experimental models

Objectives:

This study evaluated the carcinogenic potential of potassium bromate (KBrO3) and the chemopreventive mechanisms of the anti-oxidant and anti-inflammatory phytochemical, curcumin against KBrO3-induced carcinogenicity.

Method:

Lactate dehydrogenase (LDH) cytotoxicity assay and morphological characteristics were used to assess curcumin's cytoprotective potential against KBrO3 toxicity. To assess the chemopreventive potential of curcumin against KBrO3-induced oxidative insult, intracellular H2O2 and the nuclear concen-tration of the DNA adduct 8-OHdG were measured. PCR array, qRT-PCR, and western blot analysis were used to identify dysregulated genes by KBrO3 exposure. Furthermore, immunofluorescence was used to evaluate the ciliary loss and the disturbance of cellular tight junction induced by KBrO3.

Results:

Oxidative stress assays showed that KBrO3 increased the levels of intracellular H2O2 and the DNA adduct 8-OHdG. Combination of curcumin with KBrO3 efficiently reduced the level of H2O2 and 8-OHdG while up-regulating the expression of catalase. PCR array, qRT-PCR, and western blot analysis revealed that KBrO3 dysregulated multiple genes involved in inflammation, proliferation, and apoptosis, namely CTGF, IL-1, and TRAF3. Moreover, qRT-PCR and immunofluorescence studies showed that KBrO3 negatively affected the tight junctional protein (ZO-1) and induced a degeneration of primary ciliary proteins. The negative impact of KBrO3 on cilia was markedly repressed by curcumin.

Conclusion:

Curcumin could potentially be used as a protective agent against carcinogenicity of KBrO3.

Overlooked Role of Sulfur-Centered Radicals During Bromate Reduction by Sulfite

In this work, the kinetics and mechanisms of the reductive removal of BrO₃^- by sulfite in air atmosphere were determined. BrO₃^- could be effectively reduced by sulfite at pH_ini 3.0-6.0, and the reduction rate of BrO₃^- increased with decreasing pH. The coexisting organic contaminants with electron-rich moieties could be degraded, accompanied with BrO₃^- reduction by sulfite. The reaction stoichiometries of -Δ[sulfite]/Δ[bromate] were determined to be 3.33 and 15.63 in the absence and presence of O₂, respectively. Many lines of evidence verified that the main reactions in the BrO₃^-/sulfite system in air atmosphere included the reduction of BrO₃^- to HOBr and its further reduction to Br^-, as well as the oxidation of H₂SO₃ by BrO₃^- to form SO₃^·- and its further transformation to SO₄^·-. Moreover, SO₄^·- rather than HOBr was determined to be the major active oxidant in the BrO₃^-/sulfite system. SO₃^·- played a key role in the over-stoichiometric sulfite consumption because of its rapid reaction with dissolved oxygen. However, the formed SO₃^·- was further oxidized by BrO₃^- in the N₂ atmosphere. BrO₃^- reduction by sulfite is an alternative for controlling BrO₃^- in water treatment because it was effective in real water at pH_ini ≤ 6.0.

Bromate-induced Changes in p21 DNA Methylation and Histone Acetylation in Renal Cells

Bromate (BrO3-) is a water disinfection byproduct (DBP) previously shown to induce nephrotoxicity in vitro and in vivo. We recently showed that inhibitors of DNA methyltransferase 5-aza-2'-deoxycytidine (5-Aza) and histone deacetylase trichostatin A (TSA) increased BrO3- nephrotoxicity whereas altering the expression of the cyclin-dependent kinase inhibitor p21. Human embryonic kidney cells (HEK293) and normal rat kidney (NRK) cells were sub-chronically exposed to BrO3- or epigenetic inhibitors for 18 days, followed by 9 days of withdrawal. DNA methylation was studied using a modification of bisulfite amplicon sequencing called targeted gene bisulfite sequencing. Basal promoter methylation in the human p21 promoter region was substantially lower than that of the rat DNA. Furthermore, 5-Aza decreased DNA methylation in HEK293 cells at the sis-inducible element at 3 distinct CpG sites located at 691, 855, and 895 bp upstream of transcription start site (TSS). 5-Aza also decreased methylation at the rat p21 promoter about 250 bp upstream of the p21 TSS. In contrast, sub-chronic BrO3- exposure failed to alter methylation in human or rat renal cells. BrO3- exposure altered histone acetylation in NRK cells at the p21 TSS, but not in HEK293 cells. Interestingly, changes in DNA methylation induced by 5-Aza persisted after its removal; however, TSA- and BrO3--induced histone hyperacetylation returned to basal levels after 3 days of withdrawal. These data demonstrate novel sites within the p21 gene that are epigenetically regulated and further show that significant differences exist in the epigenetic landscape between rat and human p21, especially with regards to toxicant-induced changes in histone acetylation.

Ameliorative effect of zinc oxide nanoparticles against potassium bromate-mediated toxicity in Swiss albino rats

Potassium bromate (PB) is a commonly used food additive, a prominent water disinfection by-product, and a class IIB carcinogen. It exerts a various degree of toxicity depending on its dose and exposure duration consumed with food and water in the living organisms. The present investigation aims to demonstrate the protective efficacy of zinc oxide nanoparticles (ZnO NPs) derived from Ochradenus arabicus (OA) leaf extract by green technology in PB-challenged Swiss albino rats. The rodents were randomly distributed, under the lab-standardized treatment strategy, into the following six treatment groups: control (group I), PB alone (group II), ZnO alone (group III), ZnO NP alone (group IV), PB + ZnO (group V), and PB + ZnO NPs (group VI). The rats were sacrificed after completion of the treatment, and their blood and liver samples were collected for further analysis. Group II showed extensive toxic effects with altered liver function markers (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lactate dehydrogenase, gamma-glutamyl transferase, glutathione-S-transferase, and thioredoxin reductase) and compromised redox status (SOD, CAT, GR, GPx, GSH, MDA, and total carbonyl content). The histopathological analysis and comet assay further supported the biochemical results of the same group. Besides, group III also showed moderate toxicity evidenced by an alteration in most of the studied parameters while group IV demonstrated mild toxicity after biochemical analysis indicating the excellent biocompatibility of the NPs. However, group VI exhibited attenuation of the PB-induced toxic insults to a significant level as compared to group II, whereas group V failed to show similar improvement in the studied parameters. All these findings entail that the ZnO NPs prepared by green synthesis have significant ameliorative property against PB-induced toxicity in vivo. Moreover, administration of the NPs improved the overall health of the treated animals profoundly. Hence, these NPs have significant therapeutic potential against the toxic effects of PB and similar compounds in vivo, and they are suitable to be used at the clinical and industrial levels.

Characterization and Exploration of Recombinant Wheat Catalase for Improvement of Wheat-Flour-Processing Quality

The wheat catalase gene ( wcat1) was cloned and overexpressed in Pichia pastoris. The purified wCat1 exhibits its highest activity at pH 7.5 and 35 °C with K_m and V_max of 22.95 mM and 0.24 μmol/min, respectively. wCat1 could markedly improve the farinographic properties of dough, with the stability time increasing and degree of softening decreasing, and enhance the rheological properties of dough. wCat1 could also elevate bread-making quality, with increased specific volume of the bread and decreased hardness, gumminess, and chewiness, which are attributable to increased amounts of SDS-insoluble protein in dough, resulting in extended glutenin networks and thus larger pores in the fermented dough and bread crumb. The decrease of hydrogen peroxide and increase of free thiol groups in wCat1-treated dough suggest that the decomposition of hydrogen peroxide by wCat1 likely promotes disulfide-bond formation and thus the cross-linking of dough proteins.

A Review of Iodine Status of Women of Reproductive Age in the USA

Iodine, an essential micronutrient, is required to produce thyroid hormones. Iodine deficiency disorders (IDD) comprise a range of adverse maternal and fetal outcomes, with the most significant irreversible effect resulting from neurodevelopmental deficits in fetal brain caused by deficient iodine status during early pregnancy. The objective of this scoping review was to summarize the studies that assessed iodine status of women of reproductive age in the USA. A systematic review of literature using the PRISMA Extension for Scoping Reviews (PRISMA-ScR) statement was conducted. PubMed, Medline, CINAHL, EMBASE, EBSCOHost, Cochrane, ERIC, Google Scholar, and Web of Science databases were searched, 1652 records were identified. One thousand six hundred forty-one records that did not satisfy the inclusion/exclusion criteria and quality review were excluded, and 11 peer-reviewed articles were determined to be eligible for this scoping review. Despite the USA being considered iodine sufficient for the general population, the US dietary iodine intakes have decreased drastically since the 1970s, with iodine deficiency reemerging in vulnerable groups such as women of reproductive age. Although data to conduct a scoping review of iodine status among women of reproductive age in the USA was scarce, majority of the articles reviewed demonstrate emergent iodine deficiency in this population of women of reproductive age, indicating alarm for a public health concern needing immediate attention.

Deleterious effects of perinatal exposure to potassium bromate on the development of offspring of Swiss mice

The present study aimed to investigate the impact of perinatal potassium bromate (KBrO₃) exposure on the development of sensorimotor reflexes and redox status, and on the histological architecture of the brain, liver, and kidney of newborn mice. Pregnant mice received 1-ml bottled drinking water daily by oral intubation and served as the control group. Another group of pregnant mice were supplemented orally with 200 mg/kg body weight KBrO₃ dissolved in drinking water from gestation day 5 to postnatal day 21. KBrO₃ induced a decrease in the postnatal body weight in the newborn mice. KBrO₃-exposed newborn mice showed poor performance and delayed development of the sensorimotor reflexes. Histological changes, increased lipid peroxidation, and altered antioxidants were reported in the cerebrum, cerebellum, medulla oblongata, liver, and kidney of the KBrO₃-exposed newborn mice. In conclusion, these findings demonstrated that perinatal exposure to bromate induced oxidative stress, histological and behavioral alterations, and was a potential teratogen in newborn mice.

Mechanisms of oxidative stress-induced in vivo mutagenicity by potassium bromate and nitrofurantoin

Oxidative stress is well known as a key factor of chemical carcinogenesis. However, the actual role of oxidative stress in carcinogenesis, such as oxidative stress-related in vivo mutagenicity, remains unclear. It has been reported that 8-hydroxydeoxyguanosine (8-OHdG), an oxidized DNA lesion, might contribute to chemical carcinogenesis. Potassium bromate (KBrO3) and nitrofurantoin (NFT) are known as renal carcinogens in rats. Our previous studies showed an increase in mutant frequencies accompanied by an increased level of 8-OHdG in the kidneys of rodents following KBrO3 or NFT exposure. Furthermore, KBrO3 and NFT induced different types of gene mutations. Thus, in the present study, we performed reporter gene mutation assays and 8-OHdG measurements following KBrO3 or NFT exposure using Nrf2-proficient and Nrf2-deficient mice to clarify the relationship between KBrO3- or NFT-induced oxidative stress and subsequent genotoxicity. Administration of 1,500 ppm of KBrO3 in drinking water resulted in an increase in deletion mutations accompanied by an increase in 8-OHdG level, and administration of 2,500 ppm of NFT in diet induced an increase in guanine base substitution mutations without elevation of the 8-OHdG level in Nrf2-deficient mice. These results demonstrated that the formation of 8-OHdG, which resulted from the oxidizing potential of KBrO3, was directly involved in the increase in deletion mutations, although factors related to oxidative stress other than 8-OHdG might be crucial for NFT-induced guanine base substitution mutations. The present study provides new insight into oxidative stress-related in vivo mutagenicity.

Potassium bromate as a food additive: a case study of Tunisian breads

This study is the first investigation of potassium bromate as a food additive in Tunisian breads. In this study, levels of residual bromate were determined in 91 commercial breads from 31 bakeries randomly selected in two Tunisian cities. In total, 13 different types of bread were analyzed using a spectrophotometric method of bromate analysis. Bromate concentrations ranged from 5.95 to 49.31 μg g^-1, with an overall mean concentration of 19.92 μg g^-1. Significant differences were noticed between bromate levels in breads from bakeries of the two cities (P < 0.01). Based on the types of breads, Muffin contained the highest mean concentration of bromate residue (29.92 μg g^-1) as opposed to bread without salt, which had the lowest mean bromate level (13.53 μg g^-1). Compared to data available from other countries, our results showed relatively high bromate levels, which could potentially lead to long term toxic and carcinogenic effects in the Tunisian population.

Effect of Launaea procumbens on thyroid glands lipid peroxidation and hormonal dysfunction: a randomized control trial

BACKGROUND

Launaea procumbens (Roxb.) Amin is traditionally used in Pakistan for the treatment of hormonal disorders and oxidative stress. The present study was aimed to evaluate the efficacy of Launaea procumbens methanol extract (LPME) against KBrO3-induced oxidative stress and hormonal dysfunction in thyroid.

METHODS

To examine the effects of LPME against the oxidative stress of KBrO3 in thyroid tissue, 36 male albino rats were used. Protective effects of LPME were observed on thyroid hormonal levels, activities of antioxidant enzymes, lipid peroxidation (TBARS) and DNA damage.

RESULTS

Treatment with KBrO3 significantly (P < 0.01) reduced the levels of T3 (55.13 ± 1.93) and T4 (14.7 ± 1.78) and increased TSH (55.13 ± 1.93) levels. KBrO3 exposure in rats reduced the activities of antioxidant enzymes viz.; CAT (1.16 ± 0.08); SOD (12.0 ± 0.08), GST (17.7 ± 1.1) and GSR (54.3 ± 2.1) but increased lipid peroxidation (20.3 ± 0.71) and DNA (30.4 ± 2.0) damage. Co-administration of LPME significantly (P < 0.01) improved these alterations with respect to hormonal levels, activities of antioxidant enzymes and lipid peroxidation close to those seen in control rats.

CONCLUSION

These results suggest that LPME can protect thyroid tissue against oxidative damage, possibly through the antioxidant effects of its bioactive compounds.

Deleterious effects of potassium bromate administration on renal and hepatic tissues of Swiss mice

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. The present study reports the side effects of KBrO₃ administration in Swiss mice. Animals were randomly divided into three groups: control, low dose KBrO₃ (100 mg/kg/day) and high dose KBrO₃ (200 mg/kg/day) groups. Administration of KBrO₃ led to decreased white blood corpuscles (WBCs), red blood corpuscles (RBCs) and platelets count in the animals of both the high and the low dose groups. Altered lipid profile represented as low density lipoprotein (LDL), high density lipoprotein (HDL) and cholesterol levels were observed in plasma samples of both KBrO₃ treated groups of mice. Also, an increased plasma level of LDH was detected in both KBrO₃ treated groups. Histological investigations showed impaired renal and hepatic histology that was concomitant with increased plasma Creatinine level in both of KBrO₃-treated groups. Nevertheless, decreased glutathione (GSH) level in both renal and hepatic tissue of mice after KBrO₃ intake was detected. These results show that KBrO₃ has serious damaging effects and therefore, its use should be avoided.

Oral administration of potassium bromate induces neurobehavioral changes, alters cerebral neurotransmitters level and impairs brain tissue of swiss mice

Background

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. The present study reports the side effects of KBrO₃ administration on the brain functions and behaviour of albino mice.

Methods

Animals were divided into three groups: control, low dose KBrO₃ (100 mg/kg/day) and high dose KBrO₃ (200 mg/kg/day) groups.

Results

Administration of KBrO₃ led to a significant change in the body weight in the animals of the high dose group in the first, second and the last weeks while water consumption was not significantly changed. Neurobehavioral changes and a reduced Neurotransmitters levels were observed in both KBrO₃ groups of mice. Also, the brain level of reduced glutathione (GSH) in KBrO₃ receiving animals was decreased. Histological studies favoured these biochemical results showing extensive damage in the histological sections of brain of KBrO₃-treated animals.

Conclusions

These results show that KBrO₃ has serious damaging effects on the central nervous system and therefore, its use should be avoided.

Effects of Nrf2 silencing on oxidative stress-associated intestinal carcinogenesis in mice

To assess the risk of colorectal cancer in humans with inactivation of NRF2, Nrf2‐proficient (Nrf2^+/+) and ‐deficient (Nrf2^−/−) mice were exposed to potassium bromate (KBrO₃) at concentrations of 750 or 1500 ppm for 52 weeks. Neoplastic proliferative lesions were observed in the small intestine and exhibited accumulations of β‐catenin and cyclin D1. The lesions had characteristics similar to those in experimental models of human hereditary colorectal cancer. An additional 13‐week study was performed to examine the role of Nrf2 in the effects of oxidative stress. Significant increase in combined incidences of preneoplastic and neoplastic lesions in Nrf2^−/− mice administered high‐dose KBrO₃. In the short‐term study, although 8‐hydroxydeoxyguanosine (8‐OHdG) levels in the epithelial DNA of Nrf2^−/− mice at the high dose were significantly lower than those of the corresponding Nrf2^+/+ mice, the difference was very small. mRNA levels of Nrf2‐regulated genes were increased in Nrf2^+/+ mice. Overexpression of cyclooxygenase 2 (COX2) and increased numbers of proliferating cell nuclear antigen (PCNA)‐positive cells in the jejunal crypts were observed in Nrf2^−/− mice administered high‐dose KBrO₃. Overall, these data suggested that individuals having single‐nucleotide polymorphisms in NRF2 may have a risk of colorectal cancer to some extent.

Biological properties of Alsidium corallinum and its potential protective effects against damage caused by potassium bromate in the mouse liver

In the course of searching for hepatoprotective agents from natural sources, the protective effect of chemical constituents of the marine red alga Alsidium corallinum (A. corallinum) against potassium bromate (KBrO3)-induced liver damage in adult mice was investigated. The in vitro antioxidant and antibacterial properties of A. corallinum were firstly investigated. Then, A. corallinum was tested in vivo for its potential protective effects against damage caused by KBrO3 in mice models divided into four groups: controls, KBrO3, KBrO3 + A. corallinum, and A. corallinum. Our results demonstrated the rich composition of A. corallinum in antioxidant compounds like phenolics, flavonoids, anthocyanins, polysaccharides, chlorophyll and carotenoids. Its antioxidant activity was also confirmed using β-carotene bleaching by linoleic acid assay, reducing sugar test and trolox equivalent antioxidant capacity. The ethanolic extract of A. corallinum also showed good inhibition of the tested bacteria. The coadministration of the red alga associated to the KBrO3 alleviated hepatotoxicity as monitored by the improvement of hepatic oxidative stress biomarkers and plasma biochemical parameters, when compared to the KBrO3-treated mice. These results were confirmed by the improvement of histological and molecular changes. Treatment with A. corallinum prevented liver damage induced by KBrO3, thus protecting the body against free radicals and reducing inflammation and hypercholesterolemia risks.

Mammalian models of chemically induced primary malignancies exploitable for imaging-based preclinical theragnostic research

Compared with transplanted tumor models or genetically engineered cancer models, chemically induced primary malignancies in experimental animals can mimic the clinical cancer progress from the early stage on. Cancer caused by chemical carcinogens generally develops through three phases namely initiation, promotion and progression. Based on different mechanisms, chemical carcinogens can be divided into genotoxic and non-genotoxic ones, or complete and incomplete ones, usually with an organ-specific property. Chemical carcinogens can be classified upon their origins such as environmental pollutants, cooked meat derived carcinogens, N-nitroso compounds, food additives, antineoplastic agents, naturally occurring substances and synthetic carcinogens, etc. Carcinogen-induced models of primary cancers can be used to evaluate the diagnostic/therapeutic effects of candidate drugs, investigate the biological influential factors, explore preventive measures for carcinogenicity, and better understand molecular mechanisms involved in tumor initiation, promotion and progression. Among commonly adopted cancer models, chemically induced primary malignancies in mammals have several advantages including the easy procedures, fruitful tumor generation and high analogy to clinical human primary cancers. However, in addition to the time-consuming process, the major drawback of chemical carcinogenesis for translational research is the difficulty in noninvasive tumor burden assessment in small animals. Like human cancers, tumors occur unpredictably also among animals in terms of timing, location and the number of lesions. Thanks to the availability of magnetic resonance imaging (MRI) with various advantages such as ionizing-free scanning, superb soft tissue contrast, multi-parametric information, and utility of diverse contrast agents, now a workable solution to this bottleneck problem is to apply MRI for noninvasive detection, diagnosis and therapeutic monitoring on those otherwise uncontrollable animal models with primary cancers. Moreover, it is foreseeable that the combined use of chemically induced primary cancer models and molecular imaging techniques may help to develop new anticancer diagnostics and therapeutics.

Low doses of ultraviolet radiation and oxidative damage induce dramatic accumulation of mitochondrial DNA replication intermediates, fork regression, and replication initiation shift

Oxidative damage is believed to cause pathological mitochondrial DNA (mtDNA) rearrangements. mtDNA damage induces specific changes in its maintenance, such as formation of x-junctions and changes in replication mode. The findings explain the significance of the different replication mechanisms that have been observed in mitochondria.

Mitochondrial DNA is prone to damage by various intrinsic as well as environmental stressors. DNA damage can in turn cause problems for replication, resulting in replication stalling and double-strand breaks, which are suspected to be the leading cause of pathological mtDNA rearrangements. In this study, we exposed cells to subtle levels of oxidative stress or UV radiation and followed their effects on mtDNA maintenance. Although the damage did not influence mtDNA copy number, we detected a massive accumulation of RNA:DNA hybrid–containing replication intermediates, followed by an increase in cruciform DNA molecules, as well as in bidirectional replication initiation outside of the main replication origin, O_H. Our results suggest that mitochondria maintain two different types of replication as an adaptation to different cellular environments; the RNA:DNA hybrid–involving replication mode maintains mtDNA integrity in tissues with low oxidative stress, and the potentially more error tolerant conventional strand-coupled replication operates when stress is high.

Kinetic Modeling Reveals the Roles of Reactive Oxygen Species Scavenging and DNA Repair Processes in Shaping the Dose-Response Curve of KBrO₃-Induced DNA Damage

We have developed a kinetic model to investigate how DNA repair processes and scavengers of reactive oxygen species (ROS) can affect the dose-response shape of prooxidant induced DNA damage. We used as an example chemical KBrO₃ which is activated by glutathione and forms reactive intermediates that directly interact with DNA to form 8-hydroxy-2-deoxyguanosine DNA adducts (8-OH-dG). The single strand breaks (SSB) that can result from failed base excision repair of these adducts were considered as an effect downstream from 8-OH-dG. We previously demonstrated that, in the presence of effective base excision repair, 8-OH-dG can exhibit threshold-like dose-response dependence, while the downstream SSB can still exhibit a linear dose-response. Here we demonstrate that this result holds for a variety of conditions, including low levels of GSH, the presence of additional SSB repair mechanisms, or a scavenger. It has been shown that melatonin, a terminal scavenger, inhibits KBrO₃-caused oxidative damage. Our modeling revealed that sustained exposure to KBrO₃ can lead to fast scavenger exhaustion, in which case the dose-response shapes for both endpoints are not substantially affected. The results are important to consider when forming conclusions on a chemical's toxicity dose dependence based on the dose-response of early genotoxic events.

Can vitamin C affect the KBrO3 induced oxidative stress on left ventricular myocardium of adult male albino rats? A histological and immunohistochemical study

Potassium bromate (KBrO₃) cardiotoxicity is not widely recognized, in spite of its well known oxidative cell and tissue damage. The wide exposure to KBrO₃ in food and water necessitates finding of a simple and available antidote for its hazards like vitamin C. There are growing evidences that the regulation of redox reactions in cells is intimately tied to the levels of antioxidants. As the heart is highly vulnerable for oxidative damage, left ventricle muscle was the spotlight of our study. For this purpose 20 adult male albino rats were categorized into four groups (five rats each). Group 1 served as control; group 2 received 30 mg/kg/day vitamin C for 4 weeks. Group 3 was injected intraperitoneally with KBrO₃ 20 mg/kg/dose twice weekly for 4 weeks, and group 4 received both vitamin C and KBrO₃ in the same scheme. Heart specimens were processed for various histological examinations. Sections from KBrO₃ treated animals showed focal disruption of cardiac myocytes, deeply stained nuclei and dilated congested blood vessels. Ultrastructurally, irregular indented nuclei, focal lysis of the myofibrils and swelling of mitochondria were also observed. In contrast, minimal changes were observed in rats treated concomitantly with both vitamin C and KBrO₃. Caspase 3 immunohistochemical reaction was nonsignificantly increased in group 3 cardiomyocytes. Semiquantitative morphological mitochondrial scoring and statistical analyses revealed significant changes between the studied groups. Finally, KBrO₃ induced structural changes in rat cardiac muscle could be ameliorated by concomitant treatment with vitamin C.

Epigenetic changes in p21 expression in renal cells after exposure to bromate

This study tested the hypothesis that bromate (KBrO3)-induced renal cell death is mediated by epigenetic mechanisms. Global DNA methylation, as assessed by 5-methylcytosine staining, was not changed in normal rat kidney cells treated with acute cytotoxic doses of KBrO3 (100 and 200 ppm), as compared with controls. However, KBrO3 treatment did increase p38, p53 and histone 2AX (H2AX) phosphorylation, and p21 expression. Treatment of cells with inhibitors of DNA methyltransferase (5-azacytidine or 5-Aza) and histone deacetylase (trichostatin A or TSA) in addition to KBrO3 increased cytotoxicity, as compared with cells exposed to KBrO3 alone. 5-Aza and TSA co-treatment did not alter p38 or p53 phosphorylation, but slightly decreased H2AX phosphorylation and significantly decreased p21 expression. We also assessed epigenetic changes in cells treated under sub-chronic conditions with environmentally relevant concentrations of KBrO3. Under these conditions (0-10ppm KBrO3 for up to 18 days), we detected no increases in cell death or DNA damage. In contrast, slight alterations were detected in the phosphorylation of H2AX, p38, and p53. Sub-chronic low-dose KBrO3 treatment also induced a biphasic response in p21 expression, with lower concentrations increasing expression, but higher concentrations decreasing expression. Methylation-specific PCR demonstrated that sub-chronic KBrO3 treatment altered the methylation of cytosine bases in the p21 gene, as compared with controls, correlating to alterations in p21 protein expression. Collectively, these data show the novel finding that KBrO3-induced renal cell death is altered by inhibitors of epigenetic modifying enzymes and that KBrO3 itself induces epigenetic changes in the p21 gene.

Bromate and trace metal levels in bread loaves from outlets within Ile-Ife Metropolis, Southwestern Nigeria

Bread loaves randomly sampled from nine outlets and bakeries within Ile-Ife were analysed to determine their safety levels for human consumption with respect to bromate and trace metal contents. Bromate determination was carried out via spectrophotometric method while trace metals in the digested bread samples were profiled using Flame Atomic Absorption Spectrophotometer. Bromate levels in the analyzed bread samples ranged from 2.051 ± 0.011 μg/g to 66.224 ± 0.014 μg/g while the trace metal levels were of the order: 0.03-0.10 μg/g Co = 0.03-0.10 μg/g Pb < 0.23-0.46 μg/g Cu < 2.23-6.63 μg/g Zn < 25.83-75.53 μg/g Mn. This study revealed that many bread bakers around Ile-Ife had not fully complied with the bromate-free rule stipulated by NAFDAC contrary to the "bromate free" inscribed on the labels of the bread. The bread samples contained both essential and toxic trace metals to levels that could threaten the health of consumers over prolonged regular consumption.

A new catalytic oxidation method for sensitive quantification of bromate in flours and bottled water using AgNPs

In this paper, a simple and sensitive spectrophotometric method for the determination of nanomolar level of bromate, based on the catalytic effect of silver nanoparticles on the oxidation of acid red 14 by potassium bromate, is described. The reaction rate was monitored spectrophotometrically by measuring the decrease in absorbance of acid red 14 at 516 nm. The detection limit of the method was 8 ng/mL, and the linear range was between 15 and 130 ng/mL. The effects of acidity, concentration of reactants and reaction time, and external ions were also discussed. The optimum reaction conditions were fixed, and some kinetic parameters determined. The relative standard deviation for the determination of bromate at the concentration of 50 ng/mL was calculated to be 0.996 % (n = 10). The method has been successfully applied to the determination of bromate in flours and bottled waters.

Mismatch repair deficient mice show susceptibility to oxidative stress-induced intestinal carcinogenesis

We have previously established an experimental system for oxidative DNA damage-induced tumorigenesis in the small intestine of mice. To elucidate the roles of mismatch repair genes in the tumor suppression, we performed oxidative DNA damage-induced tumorigenesis experiments using Msh2-deficient mice. Oral administration of 0.2% Potassium Bromate, KBrO₃, effectively induced epithelial tumors in the small intestines of Msh2-deficient mice. We observed a 22.5-fold increase in tumor formation in the small intestines of Msh2-deficient mice compared with the wild type mice. These results indicate that mismatch repair is involved in the suppression of oxidative stress-induced intestinal tumorigenesis in mice. A mutation analysis of the Ctnnb1 gene of the tumors revealed predominant occurrences of G:C to A:T transitions. The TUNEL analysis showed a decreased number of TUNEL-positive cells in the crypts of small intestines from the Msh2-deficient mice compared with the wild type mice after treatment of KBrO₃. These results suggest that the mismatch repair system may simultaneously function in both avoiding mutagenesis and inducing cell death to suppress the tumorigenesis induced by oxidative stress in the small intestine of mice.

Oxidative stress in the carcinogenicity of chemical carcinogens

This review highlights several in vivo studies utilizing non-genotoxic and genotoxic chemical carcinogens, and the mechanisms of their high and low dose carcinogenicities with respect to formation of oxidative stress. Here, we survey the examples and discuss possible mechanisms of hormetic effects with cytochrome P450 inducers, such as phenobarbital, a-benzene hexachloride and 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane. Epigenetic processes differentially can be affected by agents that impinge on oxidative DNA damage, repair, apoptosis, cell proliferation, intracellular communication and cell signaling. Non-genotoxic carcinogens may target nuclear receptors and induce post-translational modifications at the protein level, thereby impacting on the stability or activity of key regulatory proteins, including oncoproteins and tumor suppressor proteins. We further discuss role of oxidative stress focusing on the low dose carcinogenicities of several genotoxic carcinogens such as a hepatocarcinogen contained in seared fish and meat, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, arsenic and its metabolites, and the kidney carcinogen potassium bromate.

Oxidative damage to macromolecules in the thyroid - experimental evidence

Whereas oxidative reactions occur in all tissues and organs, the thyroid gland constitutes such an organ, in which oxidative processes are indispensable for thyroid hormone synthesis. It is estimated that huge amount of reactive oxygen species, especially of hydrogen peroxide (H₂O₂), are produced in the thyroid under physiological conditions, justifying the statement that the thyroid gland is an organ of “oxidative nature”. Apart from H₂O₂, also other free radicals or reactive species, formed from iodine or tyrosine residues, participate in thyroid hormone synthesis. Under physiological conditions, there is a balance between generation and detoxification of free radicals. Effective protective mechanisms, comprising antioxidative molecules and the process of compartmentalization of potentially toxic molecules, must have been developed in the thyroid to maintain this balance. However, with additional oxidative abuse caused by exogenous or endogenous prooxidants (ionizing radiation being the most spectacular), increased damage to macromolecules occurs, potentially leading to different thyroid diseases, cancer included.

Protective effects of rutin against potassium bromate induced nephrotoxicity in rats

BACKGROUND

Rutin, a polyphenolic flavonoid, was investigated for its protective effects against the KBrO(3) induced renal injuries in rat.

METHODS

Group I was control (untreated), group II was given saline 0.5 ml/kg bw (0.9% NaCl), group III was administered KBrO(3) (20 mg/kg bw) intragastric twice a week for four weeks. Rutin was administered to group VI (50 mg/kg bw) and Group V (70 mg/kg bw) along with KBrO(3) (20 mg/kg bw) while group VI was given rutin (70 mg/kg bw) alone twice a week for four weeks. Protective effects of rutin on KBrO(3)-induced nephrotoxicity in rats were determined for biochemical parameter of urine, and serum, various antioxidant enzymes, DNA and histopathological damages in kidneys.

RESULTS

The level of urinary red blood cells, leucocytes count, specific gravity, urea, creatinine and urobilinogen was increased (P<0.01) whereas creatinine clearance was reduced. Serum level of protein, albumin, globulin, nitrite, creatinine and blood urea nitrogen (BUN) was significantly increased (P<0.01) by KBrO(3). Marked histopathological lesions, elevated DNA fragmentation and AgNORs count in renal tissues was determined. Activity of antioxidant enzymes; catalase, superoxide dismutase, glutathione peroxidase, glutathione-S-transferase, glutathione reductase, and reduced glutathione contents were decreased (P<0.01) while thiobarbituric acid reactive substances were increased (P<0.01) with KBrO(3) treatment in kidneys. DNA ladder assay was intimately related with the DNA fragmentation assay. Telomerase activity was found positive in the KBrO(3) treated kidneys. Treatment with rutin effectively ameliorated the alterations in the studied parameters of rat. Rutin administration alone to rats did not exhibit any significant change in any of the parameters studied.

CONCLUSION

These results suggest that rutin works as an antioxidant in vivo by scavenging reactive oxygen species and this serves to prevent oxidative renal damage in rat treated with KBrO(3).

Acute kidney injury due to sodium bromate intoxication: a report of two cases

Sodium bromate is a strong oxidant used as a neutralizing solution in hair permanents, as well as an auxiliary agent in printing and dyeing. Accidental or deliberate ingestion of bromate solution has rarely been reported in Korea. The clinical manifestations of bromate intoxication are vomiting, diarrhea, central nervous system symptoms, oliguric or non-oliguric acute kidney injury, hemolytic anemia, and deafness; most of these manifestations are reversible, with the exception of renal failure and deafness. Here, we report on two patients who demonstrated distinct clinical progressions. In the first case, a 16-year-old woman was successfully treated with hemodialysis and recovered renal function without hearing loss. However, in the second case, delayed hemodialysis resulted in persistent renal failure and hearing loss in a 77-year-old woman. This suggests that emergency therapeutic measures, including hemodialysis, should be taken as soon as possible, as the rapid removal of bromate may be essential to preventing severe intoxication and its sequelae.

Kidney toxicogenomics of chronic potassium bromate exposure in f344 male rats

BACKGROUND

Potassium bromate (KBrO3), used in both the food and cosmetics industry, and a drinking water disinfection by-product, is a nephrotoxic compound and rodent carcinogen. To gain insight into the carcinogenic mechanism of action and provide possible biomarkers of KBrO3 exposure, the gene expression in kidneys from chronically exposed male F344 rats was investigated.

METHODS

Male F344 rats were exposed to KBrO3 in drinking water for 52 and 100 wk. Kidneys were removed, frozen, and stored at -80°C, then used for Affymetrix microarray analysis. Gene expression patterns were examined using a non-carcinogenic (20 ppm) and carcinogenic dose (400 ppm) at 52 wk, and compared to 100 wk high dose (400 ppm) and adenoma gene expression.

RESULTS

Statistical analysis revealed 144, 224, 43, and 994 genes out of 15866 from the 52 wk low, 52 wk high, 100 wk high, and adenomas respectively, were differentially expressed when compared to control kidneys. Gene ontology classification of the 52 wk high dose showed alterations of gene transcripts involved in oxidative stress, lipid metabolism, kidney function/ion transport, and cellular function. In a comparison of kidney development gene expression, alterations were seen in the adenomas but not in the 52 wk bromate-treated kidneys. However, the normal kidney from the high dose group resembled the adenoma expression pattern with early kidney development genes being up-regulated and adult phase genes being down-regulated. Moreover, eight genes were identified which could serve as biomarkers of carcinogenic exposure to bromate. The most promising of these was Pendrin, or Slc26a4, a solute carrier of chloride and iodide active in the kidney, thyroid, and inner ear. All these tissues are targets of KBrO3 toxicity. Expression array results were verified with quantitative real-time rtPCR.

CONCLUSIONS

These data demonstrate that the 400 ppm carcinogenic dose of KBrO3 showed marked gene expression differences from the 20 ppm non-carcinogenic dose. Comparison of kidney development gene expression showed that the adenoma patterns were more characteristic of embryonic than adult kidneys, and that the normal kidney from the high dose group resembled the adenoma-like gene expression pattern. Taken together, the analysis from this study identifies potential biomarkers of exposure and illuminates a possible carcinogenic mode of action for KBrO3.

Balancing the risks and benefits of drinking water disinfection: disability adjusted life-years on the scale

To evaluate the applicability of disability adjusted life-years (DALYs) as a measure to compare positive and negative health effects of drinking water disinfection, we conducted a case study involving a hypothetical drinking water supply from surface water. This drinking water supply is typical in The Netherlands. We compared the reduction of the risk of infection with Cryptosporidium parvum by ozonation of water to the concomitant increase in risk of renal cell cancer arising from the production of bromate. We applied clinical, epidemiologic, and toxicologic data on morbidity and mortality to calculate the net health benefit in DALYs. We estimated the median risk of infection with C. parvum as 10(-3)/person-year. Ozonation reduces the median risk in the baseline approximately 7-fold, but bromate is produced in a concentration above current guideline levels. However, the health benefits of preventing gastroenteritis in the general population and premature death in patients with acquired immunodeficiency syndrome outweigh health losses by premature death from renal cell cancer by a factor of > 10. The net benefit is approximately 1 DALY/million person-years. The application of DALYs in principle allows us to more explicitly compare the public health risks and benefits of different management options. In practice, the application of DALYs may be hampered by the substantial degree of uncertainty, as is typical for risk assessment.

The third United States-Japan meeting on the Toxicological Characterization of Environmental Chemicals

This report summarizes the discussion of the Third U.S.-Japan Meeting on the Toxicological Characterization of Environmental Chemicals held under the auspices of the U.S.-Japan cooperative in research and development in science and technology. Recent data on the interrelationships between toxicity, cell proliferation, and carcinogenicity are presented.