Chlorite and bromate alter the conjugative transfer of antibiotic resistance genes: Co-regulation of oxidative stress and energy supply.

The widespread use of disinfectants during the global response to the 2019 coronavirus pandemic has increased the co-occurrence of disinfection byproducts (DBPs) and antibiotic resistance genes (ARGs). Although DBPs pose major threats to public health globally, there is limited knowledge regarding their biological effects on ARGs. This study aimed to investigate the effects of two inorganic DBPs (chlorite and bromate) on the conjugative transfer of RP4 plasmid among Escherichia coli strains at environmentally relevant concentrations. Interestingly, the frequency of conjugative transfer was initially inhibited when the exposure time to chlorite or bromate was less than 24 h. However, this inhibition transformed into promotion when the exposure time was extended to 36 h. Short exposures to chlorite or bromate were shown to impede the electron transport chain, resulting in an ATP shortage and subsequently inhibiting conjugative transfer. Consequently, this stimulates the overproduction of reactive oxygen species (ROS) and activation of the SOS response. Upon prolonged exposure, the resurgent energy supply promoted conjugative transfer. These findings offer novel and valuable insights into the effects of environmentally relevant concentrations of inorganic DBPs on the conjugative transfer of ARGs, thereby providing a theoretical basis for the management of DBPs.

Adequate nutrient intake mitigate the toxic effects of bromate on the rotifer Brachionus calyciflorus.

Bromate is receiving increased attention as a typical disinfection by-product in aquatic environments, but bromate toxicity tests on invertebrate such as Brachionus calyciflorus rotifer are inadequate. In the present study, the long-term toxicity tests on B. calyciflorus were performed during 21 days under the exposure of different bromate concentrations and two algal density conditions. Furthermore, we evaluated the feeding behaviors of the rotifers under the impact of bromate. The maximum population density of rotifers was significantly reduced at 100 and 200 mg/L bromate exposure at the two algal density conditions. However, we observed that the maximum population density and population growth rate of rotifers were higher at 3.0 × 106 cells/mL algal density than those at 1.0 × 106 cells/mL under the same conditions of bromate exposure. These results suggest that higher food density may have alleviated the negative effects of bromate on rotifers. Meanwhile, the ingestion rate at an algal density of 3.0 × 106 cells/mL was higher than that at 1.0 × 106 cells/mL. The present study provides a basic reference to comprehensively evaluate the toxic effects of bromate on aquatic organisms.

Zinc Oxide Nanoparticles Blunt Potassium-Bromate-Induced Renal Toxicity by Reinforcing the Redox System.

Potassium bromate (PB) is a general food additive, a significant by-product during water disinfection, and a carcinogen (Class II B). The compound emits toxicity depending on the extent of its exposure and dose through consumable items. The current study targeted disclosing the ameliorative efficacy of zinc oxide nanoparticles (ZnO NPs) prepared by green technology in PB-exposed Swiss albino rats. The rats were separated into six treatment groups: control without any treatment (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 blood and kidney samples were retrieved from the animals after following the treatment plan and kept at -20 °C until further analysis. Contrary to the control (Group I), PB-treated rats (Group II) exhibited a prominent trend in alteration in the established kidney function markers and disturbed redox status. Further, the analysis of the tissue and nuclear DNA also reinforced the biochemical results of the same treatment group. Hitherto, Groups III and IV also showed moderate toxic insults. However, Group VI showed a significant improvement from the PB-induced toxic insults compared to Group II. Hence, the present study revealed the significant therapeutic potential of the NPs against PB-induced nephrotoxicity in vivo, pleading for their usage in medicines having nephrotoxicity as a side effect or in enhancing the safety of the industrial use of PB.

Overlooked Cytotoxicity and Genotoxicity to Mammalian Cells Caused by the Oxidant Peroxymonosulfate during Wastewater Treatment Compared with the Sulfate Radical-Based Ultraviolet/Peroxymonosulfate Process.

Byproduct formation (chlorate, bromate, organic halogen, etc.) during sulfate radical (SO4•-)-based processes like ultraviolet/peroxymonosulfate (UV/PMS) has aroused widespread concern. However, hypohalous acid (HOCl and HOBr) can form via two-electron transfer directly from PMS, thus leading to the formation of organic halogenated byproducts as well. This study found both PMS alone and UV/PMS can increase the toxicity to mammalian cells of wastewater, while the UV/H2O2 decreased the toxicity. Cytotoxicity of two wastewater samples increased from 5.6-8.3 to 15.7-29.9 mg-phenol/L, and genotoxicity increased from 2.8-3.1 to 5.8-12.8 µg 4-NQO/L after PMS treatment because of organic halogen formation. Organic halogen formation from bromide rather than chloride was found to dominate the toxicity increase. The SO4•--based process UV/PMS led to the formation of both organic halogen and inorganic bromate and chlorate. However, because of the very low concentration (<20 µg/L) and relatively low toxicity of bromate and chlorate, contributions of inorganic byproducts to toxicity increase were negligible. PMS would not form chlorate and bromate, but it generated a higher concentration of total organic halogen, thus leading to a more toxic treated wastewater than UV/PMS. UV/PMS formed less organic halogen and toxicity because of the destruction of byproducts by UV irradiation and the removal of byproduct precursors. Currently, many studies focused on the byproducts bromate and chlorate during SO4•--based oxidation processes. This work revealed that the oxidant PMS even needs more attention because it caused higher toxicity due to more organic halogen formation.

Low-dose Potassium bromate enhances ischemia-reperfusion-induced gastric ulcer healing in Thyroidectomised Rats.

Gastric ulcer healing is impaired in both hypothyroid and hyperthyroid conditions.  Thyroid hormones regulate growth, energy metabolism and mitochondrial oxidative metabolism. Xenobiotics have been documented to negatively impact the thyroid gland at high doses but the redox and cellular interactions at low doses during wound healing process remains unclear. Potassium bromate has been documented to be toxic at high doses but there is dearth of information on its activities at a low dose in varied thyroid states which was evaluated in this study. 60 male Wistar rats (g, n=10) were randomised into 2 conditions: Normal, ulcerated untreated, ulcerated treated with 12.5mg/kg p.o KBrO3 and thyroidectomised groups: thyroidectomised ulcerated, thyroidectomised ulcer treated with KBrO3 and thyroidectomised treated with thyroxine (100µg/kg) Total thyroidectomy was used to model hypothyroidism, and ischaemia-reperfusion-induced gastric ulcers were monitored for healing. Daily body weights, Levels of thyroxine, Gastric mucin content, redox and sodium pump activity were examined alongside other markers of hepatic and haematological toxicity by days 3 and 7 post ulceration. Data were analysed using descriptive statistics and ANOVA α 0.05. The bromate-exposed hypothyroid rats showed increased gastric ulcer healing potential with reduced gastric epithelial oedema and inflammation; hepatic steatosis, and periportal inflammation. Haematological variables and markers of hepatic functions were normal. There were reduced levels of gastric and hepatic malondialdehyde levels. Thyroxine and potassium bromate treatment resolved the redox and cellular toxicity possibly via increasing catalase and sulfhydryl levels and increased Na+ K+ pump activity. We conclude that potassium bromate enhanced gastric ulcer healing in hypothyroid state, similar to thyroxine treatment.

Toxicity assessment of potassium bromate and the remedial role of grape seed extract.

In this study, the multiple toxic effects of potassium bromate were investigated in Allium cepa L., an indicator test material. In addition, the toxicity-reducing effects of grape seed extract (GSE) were tested. The toxicity was investigated by some physiological (germination percentage, root length, weight gain, relative injury rate), cytogenetic [mitotic index (MI), micronucleus (MN), and chromosomal abnormalities (CAs)], biochemical [malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) levels] and anatomical parameters. A. cepa bulbs were divided into 6 groups as control and five treatment groups (Group II: 465 mg/L GSE, Group III: 930 mg/L GSE, Group IV: 100 mg/L potassium bromate, Group V: 100 mg/L potassium bromate + 465 mg/L GSE, Group VI: 100 mg /L potassium bromate + 930 mg/L GSE). The bulbs were germinated for 72 h and at the end of the period the bulbs were subjected to routine preparations and made ready for analysis and measurements. As a result, potassium bromate exposure caused statistically significant (p < 0.05) decreases in all physiological parameter values. Potassium bromate application decreased MI by 41.6%, and increased the MN and CAs frequencies. CAs such as fragment, sticky chromosome, and vagrant chromosome, unequal distribution of chromatin, reverse polarization, nuclear bud and disordered mitosis were induced in root meristem cells. The mechanism of potassium bromate genotoxicity has been associated with DNA-potassium bromate interaction supported by spectral shift. Potassium bromate caused a decrease in GSH levels and an increase in MDA, SOD and CAT levels, thereby disrupting the antioxidant/oxidant balance in root tip cells. GSE administration in two different doses together with potassium bromate reduced the toxic effects and caused improvements in all parameters examined. The most significant reduction in toxicity was in group VI, which received 930 mg/L GSE, and there was an improvement about 18% in MI levels and an improvement about 44% in GSH levels in this group. While GSE application increased physiological parameters and GSH levels, it decreased MDA, SOD, CAT levels, MN and CAs frequencies. As a result, it has been determined that potassium bromate causes multi-directional toxicity at high doses and A. cepa is a very reliable indicator in determining this toxicity. In addition, GSE extract has been found to have a strong role in reducing the toxicity induced by potassium bromate.

Potassium bromate-induced oxidative stress, genotoxicity and cytotoxicity in the blood and liver cells of mice.

Potassium bromate (KBrO3) is an oxidising agent that is extensively used as a food additive, it is also a product of cosmetic and pharmaceutical relevance. The objective of this study was to evaluate the oxidative stress, genotoxicity, and apoptosis induced by KBrO3 in an experimental animal model. To study the toxic effects and oxidative stress, different doses of KBrO3 below LD50 (The half maximal lethal dose, 50, 100 and 150 mg/kg body weight) were given intraperitoneally to the mice for multiple time periods (24, 48, and 72 h). The results showed that KBrO3 significantly induces oxidative damage by increasing the levels of reactive oxygen species (ROS) and lipid peroxidase and depleted the levels of catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) enzymes in the serum and liver. Moreover, a significant increase of chromosomal aberrations in bone marrow cells and an elevated incidence of micronuclei in the peripheral blood of mice were observed. KBrO3 induces 3 ´ -OH end double-strand DNA breaks, which was evident in liver sections of the treated mice, and increases the percentage of apoptotic cells, as observed in TUNEL assays and flow cytometry analysis. The present findings indicate that KBrO3 induces oxidative stress, genotoxicity, and cytotoxicity in a dose- and time-dependent manner in mice.

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.

Oral administration of a potassium bromate dosage: Determination and evaluation of accumulated bromate on the liver of male mice.

In this work, we developed a simple spectrophotometric strategy for BrO3- ions determination as a major water disinfection constituents in the mice's liver tissues by using pararosaniline (PRA). Mice were divided into seven main groups (6 doses): lowest dose KBrO3 (G1 0.01 mg L-1, G2 0.025 mg L-1 and G3 0.1 mg L-1), highest dose KBrO3 (G4 1 mg L-1, G5 10 mg·L-1 and G6 30 mg L-1) and control. All these groups maintained a dose-specific feeding for one month, just before the bromate assessment in mice's liver samples. The results revealed that groups of exposure to lower doses of drinking water did not detect the presence of BrO3- accumulated in the liver tissue during the study period (1-2 months). While, the BrO3- was detected in higher dosages for samples analyzed in first, second, third, fourth and fifth weeks (W1, W2, W3, W4, and W5). These results confirmed that the higher BrO3- dosages (1, 10, and 30 mg L-1) were fatal if introduced in drinking water and could accumulate in the liver tissues both for mice and for human. Detection the accuracy of the method for recovery of bromate ions in liver samples (N = 5) was found to be more than 95%. Relative standard deviations (RSDs) were found to be less than 2.0% confirming the reproducibility of the assay technique.

Protective effect of Urtica dioica in induced neurobehavioral changes, nephrotoxicity and hepatotoxicity after chronic exposure to potassium bromate in rats.

BACKGROUND AND PURPOSE: Chronic exposure to potassium bromate (KBrO3), a toxic halogen in the environment, has become a global problem of public health. The current study aims to elucidate for the first time the effect of Urtica dioica (UD) on behavioural changes, oxidative stress, and histopathological changes induced by KBrO3 in the cerebellum, kidney, liver and other organs of adult rats. STUDY DESIGN AND METHODS: The rats were divided into four groups: group 1 served as a control received physiological serum, Group 2 received KBrO3 (2 g/L of drinking water), group 3 received KBrO3 and Urtica dioica (100 mg/kg), and group 4 received KBrO3 and Urtica dioica (400 mg/kg). We then measured behavioural changes, oxidative stress, and biochemical and histological changes in the cerebellum, liver, kidney and others organs in these rats. After 30 days of treatment, the animals were sacrificed. RESULTS: We observed significant behavioural changes in KBrO3-exposed rats. When investigating redox homeostasis in the cerebellum, we found that mice treated with KBrO3 had increased lipid peroxidation and protein oxidation in the cerebellum. In addition, it inhibits hepatic and lipid peroxidation (malondialdehyde), advanced oxidation protein product (AOPP), attenuates KBrO3-mediated enzyme depletion, catalase, superoxide dismutase, glutathione peroxidase enzymatic and antioxidant activities in the liver and kidney. Rats that were co-managed with Urtica dioica at the high portion of 400 mg/kg indicated a higher effect than that treated with the low dose of 100 mg/kg practically in all the tests carried out. CONCLUSION: Our results demonstrate that Urtica dioica is a potential therapeutic agent for oxidative stress associated with neurodegenerative diseases.

Effects of bromate on life history parameters, swimming speed and antioxidant biomarkers in Brachionus calyciflorus.

The baking industries and disinfection of tap water released a considerable amount of bromate into surface water, which has been reported as a carcinogenic compound to mammals. Rotifers play an important role in freshwater ecosystems and are model organisms to assess environmental contamination. In the present study, the effects of different concentrations (0.001, 0.01, 0.1, 1, 10, 100 and 200 mg/L) of bromate on the life-table and population growth parameters were investigated in the rotifer Brachionus calyciflorus. The results showed that the 24-h LC50 of bromate to B. calyciflorus was 365.29 mg/L (95%Cl: 290.37-480.24). Treatments with 0.01, 10 and 200 mg/L bromate shorten the reproductive period. High levels of bromate (100 and 200 mg/L) significantly decreased net reproductive rate, intrinsic rate of population increase, life span, mictic rate of B. calyciflorus. To investigate the underlying mechanisms, swimming speed and antioxidative biomarkers were compared between bromate treatments and the control. The results showed that glutathione (GSH) and malondialdehyde (MDA) contents, total superoxide dismutase (T-SOD) and peroxidase (POD) activities decreased significantly in response to bromate exposure and the reasons required further investigation. Treatments with 0.001-200 mg/L bromate all significantly reduced swimming linear speed to rotifer larvae and treatments with 100-200 mg/L bromate significantly suppressed the swimming linear speed of adult rotifer. These changes would reduce filtration of algal food and could explain the decreased survival and reproduction. Overall, bromate may not show acute toxicity to rotifers, but still have potential adverse effects on rotifer behavior, which may then influence the community structure in aquatic ecosystems.

Potassium bromate-induced cell model of age-related macular degeneration in vitro.

Age­related macular degeneration (AMD) progression occurs due to oxidative stress in retinal pigment epithelium (RPE) cells. To develop a new model of AMD, the present study investigated the effects of potassium bromate (KBrO3) on ARPE­19 cells. Incubation with KBrO3 for 24 h significantly decreased ARPE­19 cell viability in a concentration­dependent manner compared with the control group. The MTT and lactate dehydrogenase assay results indicated that KBrO3 induced cell apoptosis. Compared with the control group, KBrO3 treatment significantly decreased the Bcl2/Bax ratio, as determined via western blotting, and caspase­3 mRNA expression levels. Fluorescence microscopy indicated the increased ROS levels in cells treated with KBrO3. Endogenous antioxidant enzyme activities, including superoxide dismutase and glutathione peroxidase, were significantly inhibited by KBrO3 compared with the control group. Moreover, the antioxidants tiron and phloroglucinol inhibited KBrO3­mediated effects on ARPE­19 cells in a dose­dependent manner. Additionally, GPR109A is the binding site of 4­hydroxynonenal (4­HNE). KBrO3 displayed cytotoxic effects in 293 cells, which naturally lack the GPR109A gene, but these effects were not observed in 4­HNE­treated 293 cells, suggesting that KBrO3 induced apoptosis without increasing endogenous 4­HNE levels in cells. Moreover, the results suggested that KBrO3­induced oxidative stress may activate STAT3 to increase VEGF expression in ARPE­19 cells. Collectively, the results of the present study supported the potential use of KBrO3 to induce an in vitro model of AMD in ARPE­19 cells.

Potassium bromate cytotoxicity in the Wister rat model of chronic gastric ulcers: Possible reversal by protocatechuic acid.

The interaction between ingested xenobiotics and the gastrointestinal epithelium influences the possibility of gut epithelial cytotoxicity and systemic toxicity. Potassium bromate (KBrO3 ) has been shown to perturb the central nervous system and it may be carcinogenic, albeit it is used as a food additive. This highlights the need to understand KBrO3 's effect on the stomach epithelium. Here, we report the cytotoxic potential of KBrO3 in an ulcerated stomach, as well as possible cytoprotection by the polyphenol - protocatechuic acid. Potassium bromate (12.5 mg/kg) and protocatechuic acid (120 mg/kg) were administered orally while omeprazole (20 mg/kg) was used as standard. Potassium bromate exacerbated gastric ulcers, increased malonaldehyde levels, catalase, and sodium pump activities, but reduced nitric oxide levels. Potassium bromate further increased mast cell count in the muscularis mucosa, while inducing chronic inflammation and moderate angiogenesis in the gastric mucosa. Our results delineate KBrO3 -induced gastric epithelial cytotoxicity that is ameliorated by protocatechuic acid. PRACTICAL APPLICATIONS: Potassium bromate is a known food additive in the baking, brewing, and cheese-making process. Conversely, protocatechuic acid (3,4-dihydroxybenzoic acid) is the polyphenolic content of plants like Hibiscus sabdariffa L that are commonly consumed as herbal drink, food, spices, and used in folk medicine. This study reports the cytoprotective effect of protocatechuic acid against gastric mucosa ulceration that has been aggravated by potassium bromate.

Dose-response analysis of potassium bromate-induced toxicity in Allium cepa L. meristematic cells.

In this study, the toxic effects of potassium bromate (KBrO3) were tested on Allium cepa L. meristematic cells. In order to determine the toxic effect and dose relationship, KBrO3 toxicity was investigated at doses of 25, 50, and 100 mg/L. The toxic effects were evaluated by using cytogenetic, biochemical, anatomical, and physiological parameters, and serious damages were observed depending on the dose. Significant reductions in germination percentage, weight gain, and radicle length were observed in all KBrO3-treated groups compared with the control. Mitotic activity decreased in meristematic cells after KBrO3 application. and mitotic index was decreased by 1.8 times in 100 mg/L KBrO3-treated group compared with the control group. The frequencies of micronucleus and chromosomal abnormalities tested as cytogenetic parameters were significantly higher in the group treated with 100 mg/L KBrO3 than those in the control group. Fragment and sticky chromosome were the most common types of chromosomal abnormalities. Lipid peroxidation measured in terms of MDA content increased with increasing doses of KBrO3. The activities of catalase and superoxide dismutase as antioxidant enzymes were importantly changed in KBrO3-treated groups. Anatomical changes such as cell deformation, substance accumulation, cell wall thickening, and flattened nucleus were determined after KBrO3 application, and it was observed that these changes reached a maximum level at 100 mg/L dose of KBrO3. As a result, KBrO3 treatments were been found to cause physiological, biochemical, cytogenetic, and anatomically toxic effects in meristematic cells of A. cepa, a eukaryotic model organism. The versatile toxicity induced by KBrO3 increased depending on the dose and reached a maximum level at 100 mg/L.

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.

Chemopreventive effect of riboflavin on the potassium bromate-induced renal toxicity in vivo.

Potassium bromate (PB) is a general food additive, flavor enhancer, a by-product of water disinfection, and a class 2 carcinogen. It exerts various toxic effects in a dose- and time-dependent manner in vivo. This study is to explore the chemopreventive efficacy of vitamin B2 (riboflavin, RF) in PB-administered Swiss albino rats. The rats were distributed into five groups: control (group 1), PB alone (group 2, 150 mg/kg), RF alone (group 3, 2 mg/kg), PB + RF1 (group 4, 150 and 2 mg/kg), and PB + RF2 (group 5, 150 and 4 mg/kg). All the rodents were sacrificed after the completion of the treatment cycle. Then, blood and kidney samples were subjected to biochemical analysis. Group 2 demonstrated vivid signs of renal toxicities evidenced by altered renal function markers (urea, creatinine, albumin, glutathione-S-transferase) and redox status parameters (superoxide dismutase, catalase, glutathione reductase, reduced glutathione, lipid, and protein oxidation products). However, group 3 exhibited a slight alteration in many of the parameters while groups 4 and 5 demonstrated dose-dependent chemopreventive efficiency of RF against PB-induced alterations. Besides, RF seemed to facilitate apoptosis as well as inhibition of the necrosis in the PB-pre-challenged groups, as demonstrated by the cleaved PARP and lactate dehydrogenase activity. Also, the histopathological analysis and comet assay validate the biochemical results of the treatment groups significantly. All these results plead that RF has a significant chemopreventive property against PB-induced toxicity in vivo. Therefore, RF is a suitable agent in preventing the PB-induced toxicities at the clinical and industrial levels.

Ammonia-Mediated Bromate Inhibition during Ozonation Promotes the Toxicity Due to Organic Byproduct Transformation.

Ammonia (NH4+) and hydrogen peroxide (H2O2) have been widely used to inhibit bromate formation during ozonation. However, organic byproducts can also pose a risk under these conditions. During bromate inhibition, the influence of NH4+ and H2O2 on organic byproducts and their toxicity should be elucidated. Our study found that NH4+ suppressed organic bromine, but might result in increased toxicity. Adding 0.5 mg/L of NH4+-N substantially increased both the formation of cytotoxicity and genotoxicity (DNA double-strand breaks) of organic byproducts from 0.6 to 1.6 mg-phenol/L, and from 0.3 to 0.8 µg-4-NQO/L (0.5 mg/L Br-, 5 mg/L O3). NH4+ decreased bromate, but increased the overall toxicity of the integrated byproducts (organic byproducts and bromate). Organic nitrogen measurements and 15N isotope analysis showed enhanced incorporation of nitrogen into organic matter when NH4+ and Br- coexisted during ozonation. NH4+ decreased the formation of brominated acetonitriles, but enhanced the formation of brominated nitromethanes and brominated acetamides. These brominated nitrogenous byproducts were partially responsible for this increase in toxicity. Different from ammonia, H2O2 could reduce both bromate and the toxicity of organic byproducts. In the presence of 0.5 mg/L Br- and 10 mg/L O3, adding H2O2 (0.5 mM) substantially suppressed bromate, cytotoxicity formation and genotoxicity formation by 88%, 63% and 67%. This study highlights that focusing on bromate control with NH4+ addition might result in higher toxicity. Efforts are needed to effectively control the toxicities of bromate and organic byproducts simultaneously.

Potassium bromate as positive assay control for the Fpg-modified comet assay.

The comet assay is a popular assay in biomonitoring studies. DNA strand breaks (or unspecific DNA lesions) are measured using the standard comet assay. Oxidative stress-generated DNA lesions can be measured by employing DNA repair enzymes to recognise oxidatively damaged DNA. Unfortunately, there has been a tendency to fail to report results from assay controls (or maybe even not to employ assay controls). We believe this might have been due to uncertainty as to what really constitutes a positive control. It should go without saying that a biomonitoring study cannot have a positive control group as it is unethical to expose healthy humans to DNA damaging (and thus potentially carcinogenic) agents. However, it is possible to include assay controls in the analysis (here meant as a cryopreserved sample of cells i.e. included in each experiment as a reference sample). In the present report we tested potassium bromate (KBrO3) as a positive comet assay control for the formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay. Ten laboratories used the same procedure for treatment of monocytic THP-1 cells with KBrO3 (0.5, 1.5 and 4.5 mM for 1 h at 37°C) and subsequent cryopreservation. Results from one laboratory were excluded in the statistical analysis because of technical issues in the Fpg-modified comet assay. All other laboratories found a concentration-response relationship in cryopreserved samples (regression coefficients from 0.80 to 0.98), although with different slopes ranging from 1.25 to 11.9 Fpg-sensitive sites (%DNA in tail) per 1 mM KBrO3. Our results demonstrate that KBrO3 is a suitable positive comet assay control.

Oxidative-stress-driven mutagenesis in the small intestine of the gpt delta mouse induced by oral administration of potassium bromate.

Tumorigenesis induced by oxidative stress is thought to be initiated by mutagenesis, but via an indirect mechanism. The dose-response curves for agents that act by this route usually show a threshold, for unknown reasons. To gain insight into these phenomena, we have analyzed the dose response for mutagenesis induced by the oral administration of potassium bromate, a typical oxidative-stress-generating agent, to gpt delta mice. The agent was given orally for 90 d to either Nrf2+ or Nrf2-knockout (KO) mice and mutants induced in the small intestine were analyzed. In Nrf2+mice, the mutant frequency was significantly greater than in the vehicle controls at a dose of 0.6 g/L but not at 0.2 g/L, indicating that a practical threshold for mutagenesis lies between these doses. At 0.6 g/L, the frequencies of G-to-T transversions (landmark mutations for oxidative stress) and G-to-A transitions were significantly elevated. In Nrf2-KO mice, too, the total mutant frequency was increased only at 0.6 g/L. G-to-T transversions are likely to have driven tumorigenesis in the small intestine. A site-specific G-to-T transversion at guanine (nucleotide 406) in a 5'-TGAA-3' sequence in gpt, and our primer extension reaction showed that formation of the oxidative DNA base modification 8-oxo-deoxyguanosine (8-oxo-dG) at nucleotide 406 was significantly increased at doses of 0.6 and 2 g/L in the gpt delta mice. In the Apc oncogene, guanine residues in the same or similar sequences (TGAA or AGAA) are highly substituted by thymine (G-to-T transversions) in potassium bromate-induced tumors. We propose that formation of 8-oxo-dG in the T(A)GAA sequence is an initiating event in tumor formation in the small intestine in response to oxidative stress.

Potassium bromate: Effects on bread components, health, environment and method of analysis: A review.

Potassium bromate, is an oxidizing agent and one of the best and cheapest dough improvers in the baking industry. Due to its positive effects it plays a major role in the bread-making industry. Potassium bromate has significant effect on food biomolecules, such as starch and protein, as it affects the extent of gelatinization, viscosity, swelling characteristics as well as gluten proteins; it removes the sulfhydryl group and leads to the formation of disulfide linkages and thus improves the bread properties. However, there are many reports elucidating its negative impact on human health. It is deemed as a potential human carcinogen by IARC and classified under class 2B. Due to this, countries across world have either partially or completely banned it. Numerous techniques have evolved to determine the concentration of potassium bromate in bread. This review explains in detail, the effects of potassium bromate on biomolecules, human health, environment and various methods of analysis.