Cytoprotective effect of taurine against sodium chlorate-induced oxidative damage in human red blood cells: an ex vivo study.

Sodium chlorate (NaClO3) is a common non-selective herbicide that is also used in paper and pulp mills and is produced as a by-product during drinking water disinfection by chlorine dioxide. Here, we report the effect of dietary antioxidant taurine on NaClO3-induced cytotoxicity in human red blood cells (RBC). RBC were treated with 5 mM NaClO3, either alone or in presence of 1, 2.5 and 5.0 mM taurine. Incubation of RBC with NaClO3 alone caused hemolysis, increased oxidation of lipids and proteins, methemogobin level and decreased total sulfhydryl and glutathione content. It lowered the activities of antioxidant enzymes thioredoxin reductase, glutathione peroxidase, catalase and glutathione reductase, while Cu-Zn superoxide dismutase activity was increased. The antioxidant capacity of RBC was impaired. This strongly suggests that NaClO3 causes the induction of oxidative stress condition in RBC. The specific activities of lactate dehydrogenase, glucose 6-phosphate dehydrogenase and plasma membrane bound enzymes, were also greatly altered. However, prior treatment of RBC with taurine conferred significant protection against NaClO3-induced oxidative damage and also improved the antioxidant defence system of cells. These results were supported by electron microscopy images of RBC. Treatment with NaClO3 alone converted the normal biconcave discoidal RBC to acanthocytes and echinocytes but this transformation was greatly prevented in the presence of taurine. Thus, taurine mitigates the cytotoxicity of NaClO3 in human RBC and can function as an effective chemoprotectant.

Ameliorative effect of carnosine and N-acetylcysteine against sodium nitrite induced nephrotoxicity in rats.

The widespread use of sodium nitrite (NaNO2 ) for various industrial purposes has increased human exposure to alarmingly high levels of nitrate/nitrite. Because NaNO 2 is a strong oxidizing agent, induction of oxidative stress is one of the mechanisms by which it can exert toxicity in humans and animals. We have investigated the possible protection offered by carnosine (CAR) and N-acetylcysteine (NAC) against NaNO 2 -induced nephrotoxicity in rats. Animals orally received CAR at 100 mg/kg body weight/d for seven days or NAC at 100 mg/kg body weight/d for five days followed by a single oral dose of NaNO 2 at 60 mg/kg body weight. The rats were killed after 24 hours, and the kidneys were removed and processed for various analyses. NaNO 2 induced oxidative stress in kidneys, as shown by the decreased activities of antioxidant defense, brush border membrane, and metabolic enzymes. DNA-protein crosslinking and DNA fragmentation were also observed. CAR/NAC pretreatment significantly protected the kidney against these biochemical alterations. Histological studies supported these findings, showing kidney damage in NaNO 2 -treated animals and reduced tissue impairment in the combination groups. The protection offered by CAR and NAC against NaNO 2 -induced damage, and their nontoxic nature, makes them potential therapeutic agents against nitrite-induced nephrotoxicity.

Protective effect of carnosine and N-acetylcysteine against sodium nitrite-induced oxidative stress and DNA damage in rat intestine.

The widespread use of sodium nitrite (NaNO2) as food preservative, rampant use of nitrogenous fertilizers for agricultural practices, and improper disposal of nitrogenous wastes have drastically increased human exposure to high nitrite levels causing various health disorders and death. In the present study, the protective effect of carnosine and N-acetylcysteine (NAC) against NaNO2-induced intestinal toxicity in rats was investigated. Animals were given a single acute oral dose of NaNO2 at 60 mg/kg body weight with or without prior administration of either carnosine at 100 mg/kg body weight/day for 7 days or NAC at 100 mg/kg body weight/day for 5 days. Rats were killed after 24 h, and intestinal preparations were used for the evaluation of biochemical alterations and histological abrasions. Administration of NaNO2 alone decreased the activities of intestinal brush border membrane and metabolic enzymes and significantly weakened the anti-oxidant defense system. DNA damage was also evident as observed by increased DNA-protein crosslinking and fragmentation. However, prior administration of carnosine or NAC significantly ameliorated NaNO2-induced damage in intestinal cells. Histological studies support these biochemical results, showing intestinal damage in NaNO2-treated animals and reduced tissue injury in the combination groups. The intrinsic anti-oxidant properties of carnosine and NAC must have contributed to the observed mitigation of nitrite-induced metabolic alterations and oxidative damage. Based on further validation from clinical trials, carnosine and NAC can potentially be used as chemo-preventive agents against NaNO2 toxicity.

Acute oral dose of sodium nitrite causes redox imbalance and DNA damage in rat kidney.

Sodium nitrite (NaNO2 ) is widely used as a food additive and preservative in fish and meat products. We have evaluated the effect of a single acute oral dose of NaNO2 on oxidative stress parameters, antioxidant capacity, and DNA in rat kidney. Male Wistar rats were divided into four groups and given single oral dose of NaNO2 at 20, 40, 60, and 75 mg/kg body weight; untreated rats served as the control group. All animals in NaNO2 -treated groups showed marked alterations in various parameters of oxidative stress as compared to the control group. This included increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels, and decrease in reduced glutathione content and antioxidant capacity. Administration of NaNO2 also increased DNA damage as evident from release of free nucleotides and confirmed by comet assay. It also led to greater cross-linking of DNA to proteins. Histological analysis showed marked morphological changes in the kidney of NaNO2 -treated animals. These alterations could be due to increased free radical generation or direct chemical modification by reaction intermediates. Our results suggest that nitrite-induced nephrotoxicity is mediated through redox imbalance and results in DNA damage.

Carnosine and N-acetyl cysteine protect against sodium nitrite-induced oxidative stress in rat blood.

Sodium nitrite (NaNO2 ) is widely used in the food industry as a preservative and colorant in meat and fish products. Industrialization and improper agricultural practices have greatly increased human exposure to high nitrite levels, mainly through contaminated drinking water, causing various health disorders. We have investigated the protective effect of carnosine (CAR) and N-acetyl cysteine (NAC) on NaNO2 -induced toxicity in rat blood. CAR is a bioactive dipeptide found in mammalian muscle while NAC is a synthetic sulfhydryl amino acid and an important precursor of glutathione. Animals were given a single acute oral dose of NaNO2 at 60 mg/kg body weight with or without prior administration of either CAR or NAC. Rats were sacrificed after 24 h, blood was withdrawn and plasma and erythrocytes were isolated. Administration of NaNO2 alone increased methemoglobin levels and methemoglobin reductase activity, decreased the activities of antioxidant defense and metabolic enzymes and significantly weakened the total antioxidant capacity of rat erythrocytes. Similar effects were seen in plasma of NaNO2 -treated rats. In contrast, administration of CAR or NAC, prior to NaNO2 treatment, markedly attenuated the NaNO2 -elicited deleterious effects. Thus, CAR and NAC can mitigate nitrite-induced metabolic alterations and oxidative damage probably due to their intrinsic biochemical antioxidant properties. This study suggests that CAR and NAC can be potentially used as therapeutic/protective agents against NaNO2 toxicity.

Taurine mitigates nitrite-induced methemoglobin formation and oxidative damage in human erythrocytes.

Nitrite is present as a noxious contaminant in drinking water and causes oxidative damage in various tissues of humans and animals. It is a well-known methemoglobin-forming agent that has been shown to damage blood cells. The protective effect of taurine, a semi-essential sulfur-containing amino acid, was studied on sodium nitrite (NaNO2)-induced oxidative damage in human erythrocytes. Erythrocytes were incubated with NaNO2, in the presence and absence of taurine, and changes in oxidative stress parameters determined. Pretreatment with taurine significantly ameliorated NaNO2-induced oxidative damage to lipids, proteins, and plasma membrane. It also reduced the NaNO2-induced increase in methemoglobin levels and ROS production. Taurine improved the antioxidant capacity of cells, restored the alterations in the activities of various metabolic enzymes, and prevented morphological changes in erythrocytes. Thus, taurine can be potentially used as a protective agent against the damaging effects of nitrite.

Acute oral dose of sodium nitrite induces redox imbalance, DNA damage, metabolic and histological changes in rat intestine.

Industrialization and unchecked use of nitrate/nitrite salts for various purposes has increased human exposure to high levels of sodium nitrite (NaNO2) which can act as a pro-oxidant and pro-carcinogen. Oral exposure makes the gastrointestinal tract particularly susceptible to nitrite toxicity. In this work, the effect of administration of a single acute oral dose of NaNO2 on rat intestine was studied. Animals were randomly divided into four groups and given single doses of 20, 40, 60 and 75 mg NaNO2/kg body weight. Untreated animals served as the control group. An NaNO2 dose-dependent decline in the activities of brush border membrane enzymes, increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased thiol content was observed in all treated groups. The activities of various metabolic and antioxidant defense enzymes were also altered. NaNO2 induced a dose-dependent increase in DNA damage and DNA-protein crosslinking. Histopathological studies showed marked morphological damage in intestinal cells. The intestinal damage might be due to nitrite-induced oxidative stress, direct action of nitrite anion or chemical modification by reaction intermediates.

Sodium chlorate induces DNA damage and DNA-protein cross-linking in rat intestine: A dose dependent study.

Sodium chlorate (NaClO3) is widely used in paper and pulp industries and as a non-selective herbicide. It is also a major by-product generated upon disinfection of drinking water by chlorine dioxide. In this study, we have investigated the genotoxicity of NaClO3 on the small intestine of rats. Adult male rats were divided into 5 groups: one control and four NaClO3 treated groups. The NaClO3 treated groups were given a single acute oral dose of NaClO3 (100, 250, 500 and 750 mg/kg body weight) and sacrificed 24 h later. Administration of NaClO3 caused significant DNA damage in a dose dependent manner in the rat intestine. This was evident from the comet assay which showed DNA strand breaks and was further confirmed by agarose gel electrophoresis and release of free nucleotides. Increased DNA protein cross-linking in NaClO3 administered groups showed formation of a critical lesion which hampers activities of proteins/enzymes involved in DNA repair, transcription and replication. Thus, oral administration of NaClO3 induces DNA damage in the rat intestine, probably through chlorate induced production of reactive oxygen species.

Sodium chlorate, a major water disinfection byproduct, alters brush border membrane enzymes, carbohydrate metabolism and impairs antioxidant system of Wistar rat intestine.

Sodium chlorate (NaClO3 ) is a widely used nonselective herbicide. It is also generated as a by-product during disinfection of drinking water by chlorine dioxide. The purpose of this study was to evaluate the effect of NaClO3 on rat intestine. Adult male rats were randomly divided into five groups: control and remaining four groups were administered orally different doses of NaClO3 and sacrificed 24 h after the treatment. The administration of NaClO3 produced acute oxidative stress in the intestine, which manifested in the form of markedly enhanced malondialdehyde levels and carbonyl content and lowered total sulfhydryl groups and glutathione levels. The activities of several brush border membrane (BBM) enzymes were greatly reduced as compared to control. There were alterations in the activities of various enzymes of carbohydrate metabolism and those involved in maintaining the antioxidant defense system. Histological studies support the biochemical results showing NaClO3 dose-dependent increase in tissue damage. Thus, the present study shows that oral administration of NaClO3 decreases the activities of BBM enzymes, induces oxidative stress, alters metabolic pathways, and impairs the antioxidant system of rat intestine. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1607-1616, 2017.

Crocin protects human erythrocytes from nitrite-induced methemoglobin formation and oxidative damage.

Sodium nitrite (NaNO2 ) is a common contaminant of drinking water and food and feed chain. Nitrite induces oxidative damage in humans and animals. In this work, we studied the protective effect of crocin, the active constituent of Crocus sativus (saffron), on NaNO2 -induced oxidative damage in human erythrocytes. Changes in oxidative stress parameters following NaNO2 incubation of erythrocytes in presence and absence of crocin were determined. It was found that crocin pre-treatment significantly attenuated NaNO2 -induced oxidative damage of proteins, lipids, and plasma membrane. Crocin reduced the level of methemoglobin, the primary acute effect of nitrite intoxication. It also improved the antioxidant capacity of cells and NaNO2 -induced morphological changes in erythrocytes. Crocin is thus a potent protective agent against nitrite-induced cytotoxicity.

Sodium nitrite enhances generation of reactive oxygen species that decrease antioxidant power and inhibit plasma membrane redox system of human erythrocytes.

Nitrite/nitrate salts are used in fertilizers and as food preservatives. Human exposure to high levels of nitrite results in its uptake and subsequent entry into blood where it can interact with erythrocytes. We show that treatment of human erythrocytes with sodium nitrite (NaNO2 ) results in a dose-dependent increase in the production of reactive oxygen species. This was accompanied by a decrease in the antioxidant power which lowered the free radical quenching and metal-reducing ability. NaNO2 treatment also inhibited plasma membrane redox system (PMRS) of erythrocytes. These changes increase the susceptibility of erythrocytes to oxidative damage, decrease the antioxidant power of whole blood, and can be a major cause of nitrite-induced cellular toxicity.

Sodium Nitrate Induces Reactive Oxygen Species That Lower the Antioxidant Power, Damage the Membrane, and Alter Pathways of Glucose Metabolism in Human Erythrocytes.

Nitrate salts are widely used as food additives and nitrogenous fertilizers and are present as contaminants in drinking water supplies. The effect of different concentrations (1-15 mM) of sodium nitrate (NaNO3) on human erythrocytes was studied under in vitro conditions. Treatment of erythrocytes with NaNO3 resulted in increases in methemoglobin levels, lipid peroxidation, and protein oxidation and a decrease in glutathione content. There were changes in the activities of all major antioxidant defense enzymes, and the pathways of glucose metabolism were also affected. Increased generation of reactive oxygen species (ROS) took place while the antioxidant power was impaired. The osmotic fragility of cells was increased, and membrane-bound enzymes were greatly inhibited. All changes were statistically significant at a probability level of P < 0.05 at all concentrations of NaNO3 except the lowest (1 mM). Thus, NaNO3 generates ROS that cause significant damage to human erythrocytes and interfere in normal cellular pathways.

Sodium nitrite-induced oxidative stress causes membrane damage, protein oxidation, lipid peroxidation and alters major metabolic pathways in human erythrocytes.

Nitrite salts are present as contaminants in drinking water and in the food and feed chain. In this work, the effect of sodium nitrite (NaNO2) on human erythrocytes was studied under in vitro conditions. Incubation of erythrocytes with 0.1-10.0 mM NaNO2 at 37 °C for 30 min resulted in dose dependent decrease in the levels of reduced glutathione, total sulfhydryl and amino groups. It was accompanied by increase in hemoglobin oxidation and aggregation, lipid peroxidation, protein oxidation and hydrogen peroxide levels suggesting the induction of oxidative stress. Activities of all major erythrocyte antioxidant defense enzymes were decreased in NaNO2-treated erythrocytes. The activities of enzymes of glycolytic and pentose phosphate pathways were also compromised. However, there was a significant increase in acid phosphatase and also AMP deaminase, a marker of erythrocyte oxidative stress. Thus, the major metabolic pathways of cell were altered. Erythrocyte membrane damage was suggested by lowered activities of membrane bound enzymes and confirmed by electron microscopic images. These results show that NaNO2-induced oxidative stress causes hemoglobin denaturation and aggregation, weakens the cellular antioxidant defense mechanism, damages the cell membrane and also perturbs normal energy metabolism in erythrocytes. This nitrite-induced damage can reduce erythrocyte life span in the blood.