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

Fischer's oligopeptide ratio in ischemic hypoxia: prophylactic amendment of sophoretin and melatonin supplementation

Aim: The fundamental pathophysiology of ischemic-hypoxia is oxygen depletion. Fischer's ratio is essential for monitoring hypoxia intensity. Methods: the current study highlighted the prophylactic role of sophoretin (QRC) and/or melatonin (MLN) versus sodium nitrite (SN) brain hypoxia. Results: Prophylactic treatment with sophoretin and MLN, was preceded with hypoxia-induction via sodium nitrite (60 mg/kg, S.C.). SN decreased hemoglobin (Hb), elevated HIF-α, HSP-70, IL-6 and TNF-α. Sophoretin and/or MLN restored the ameliorated inflammatory biomarkers, modulated norepinephrine, dopamine, serotonin and gamma-aminobutyric acid (GABA). Similarly, single-cell gel electrophoresis (SCGE or COMET) DNA damage assay confirmed this finding. Conclusion: Treatment via sophoretin and MLN was the most effective therapy for improving sodium nitrite-induced brain injury.

Nitrite decreases sickle hemoglobin polymerization in vitro independently of methemoglobin formation

The root cause of sickle cell disease (SCD) is the polymerization of sickle hemoglobin (HbS) leading to sickling of red blood cells (RBC). Earlier studies showed that in patients with SCD, high-dose nitrite inhibited sickling, an effect originally attributed to HbS oxidation to methemoglobin-S even though the anti-sickling effect did not correlate with methemoglobin-S levels. Here, we examined the effects of nitrite on HbS polymerization and on methemoglobin formation in a SCD mouse model. In vitro, at concentrations higher than physiologic (>1 μM), nitrite increased the delay time for polymerization of deoxygenated HbS independently of methemoglobin-S formation, which only occurred at much higher concentrations (>300 μM). In vitro, higher nitrite concentrations oxidized 100% of normal hemoglobin A (HbA), but only 70% of HbS. Dimethyl adipimidate, an anti-polymerization agent, increased the fraction of HbS oxidized by nitrite to 82%, suggesting that polymerized HbS partially contributed to the oxidation-resistant fraction of HbS. At low concentrations (10 μM-1 mM), nitrite did not increase the formation of reactive oxygen species but at high concentrations (10 mM) it decreased sickle RBC viability. In SCD mice, 4-week administration of nitrite yielded no significant changes in methemoglobin or nitrite levels in plasma and RBC, however, it further increased leukocytosis. Overall, these data suggest that nitrite at supra-physiologic concentrations has anti-polymerization properties in vitro and that leukocytosis is a potential nitrite toxicity in vivo. Therefore, to determine whether the anti-polymerization effect of nitrite observed in vitro underlies the decreases in sickling observed in patients with SCD, administration of higher nitrite doses is required.

Enhancement of dissimilatory nitrate/nitrite reduction to ammonium of Escherichia coli sp. SZQ1 by ascorbic acid: Mechanism and performance

Dissimilatory nitrate reduction to ammonium (DNRA) can be used for nitrogen recovery. However, due to the low conversion efficiency of the DNRA process of microorganisms, the process cannot be industrially applied. Ascorbic acid (ASA) can improve DNRA efficiency of Escherichia coli sp. SZQ1 (E. coli). Experimental studies suggest that 10 g L^-1 ASA promoted DNRA process of E. coli at high concentrations of nitrite (10-20 mM). In the 5 g L^-1 ASA system, 9.2 mM nitrite was reduced to 8.21 mM ammonium by E. coli in 120 h. Mechanistic studies reveal that ASA reduced the oxidation-reduction potential (ORP) of the system and scavenged reactive oxygen species (ROS) in the cell of E. coli. Meanwhile, ASA was utilized by E. coli as the sole carbon source and provided electrons to DNRA process through ASA metabolic pathways. This study proposes a new strategy for increasing the efficiency of DNRA.

Borate Ameliorates Sodium Nitrite-Induced Oxidative Stress Through Regulation of Oxidant/Antioxidant Status: Involvement of the Nrf2/HO-1 and NF-κB Pathways

The widespread industrial use of nitrite in preservatives, colorants, and manufacturing rubber products and dyes increases the possibilities of organ toxicity. Lithium borate (LB) is known as an antioxidant and an oxidative stress reliever. Therefore, this study is aimed at examining the effect of LB on nitrite-induced hepatorenal dysfunction. Twenty-eight male Swiss mice were divided into four equal groups. Group 1, the control group, received saline. Group 2 received LB orally for 5 consecutive days at a dose of 15 mg/kg bw. Group 3, the nitrite group, received sodium nitrite (NaNO₂) on Day 5 (60 mg/kg bw intraperitoneally). Group 4, the protective group (LB + NaNO₂ group), received LB for 5 days and then a single dose of NaNO₂ intraperitoneally on Day 5, the same as in Groups 2 and 3, respectively. Samples of blood and kidney were taken for serum analysis of hepatorenal biomarkers, levels of antioxidants and cytokines, and the expression of genes associated with oxidative stress and inflammation. NaNO₂ intoxication increased markers of liver and kidney functions yet decreased reduced glutathione (GSH), superoxide dismutase (SOD), and catalase activities in blood. NaNO₂ also increased the expression of tumor necrosis factor (TNF-α), interleukin-1β and interleukin-6 (IL-1β and IL-6). Pre-administration of LB protected mice from oxidative stress, lipid peroxidation, and the decrease in antioxidant enzyme activity. Moreover, LB protected mice from cytokine changes, which remained within normal levels. LB ameliorated the changes induced by NaNO₂ on the mRNA of nuclear factor erythroid 2-related factor 2 (Nfr2), heme oxygenase-1 (HO-1), nuclear factor-kappa B (NF-κB), transforming growth factor-beta 2 (TGF-β2), and glutathione-S-transferase (GST) as determined using quantitative real-time PCR (qRT-PCR). These results collectively demonstrate that LB ameliorated NaNO₂-induced oxidative stress by controlling the oxidative stress biomarkers and the oxidant/antioxidant state through the involvement of the Nrf2/HO-1 and NF-κB signaling pathways.

Toward Intracellular Bioconjugation Using Transition-Metal-Free Techniques

Bioconjugation is the chemical strategy of covalent modification of biomolecules, using either an external reagent or other biomolecules. Since its inception in the twentieth century, the technique has grown by leaps and bounds, and has a variety of applications in chemical biology. However, it is yet to reach its full potential in the study of biochemical processes in live cells, mainly because the bioconjugation strategies conflict with cellular processes. This has mostly been overcome by using transition metal catalysts, but the presence of metal centers limit them to in vitro use, or to the cell surface. These hurdles can potentially be circumvented by using metal-free strategies. However, the very modifications that are necessary to make such metal-free reactions proceed effectively may impact their biocompatibility. This is because biological processes are easily perturbed and greatly depend on the prevailing inter- and intracellular environment. With this taken into consideration, this review analyzes the applicability of the transition-metal-free strategies reported in this decade to the study of biochemical processes in vivo.

Protective Effect of Red Okra (Abelmoschus esculentus (L.) Moench) Pods against Sodium Nitrite-Induced Liver Injury in Mice

Vegetables, drinking water, and preserved meats may contain sodium nitrite (NaNO₂), which causes liver disease by inducing oxidative stress. Phytochemicals are highly recommended as an alternative to synthetic drugs and affordable medicines to treat liver disease because they have fewer or no side effects. Therefore, this study aims to determine the antioxidant and hepatoprotective potential of red okra fruit ethanol extract against NaNO₂-induced liver damage. Thirty-six male mice were separated into six groups. The normal control group (WA) was given distilled water only, and the NaNO₂ (SN) group was given only 50 mg/kg BW NaNO₂. The other four groups (P1, P2, P3, and P4) were given NaNO₂ and red okra ethanol extract at doses of 25, 50, 75, and 100 mg/kg BW, respectively. Gavage was administered orally for 21 consecutive days. Commercial kits define all biochemical parameters according to the manufacturer's instructions. Liver tissue staining followed standard protocols using hematoxylin and eosin. The study revealed that NaNO₂ induction causes oxidative stress and damages the liver. The activity of antioxidant enzymes (superoxide dismutase and catalase) significantly increased in the groups treated (P2-P4) with ethanol extract of red okra (p < 0.05). Besides, the oxidants (malondialdehyde, F2-isoprostanes, and nitric oxide) in the liver homogenate significantly decreased in the P4 group, which were given red okra ethanol extract (p < 0.05). Likewise, red okra pods decreased significantly for the serum biochemical parameters of liver damage (aspartate aminotransferase, alkaline phosphatase, and alanine aminotransferase) in the P3 and P4 groups (p < 0.05). Then, it led to a restoration of the histological structure compared to exposed mice (SN), as the pathological scores decreased significantly in the P3 and P4 groups (p < 0.05), as well as the number of the necrotic and swollen liver cells was reduced. Hepatocytes returned to normal. The results showed that the ethanol extract of red okra fruit could be helpful as an affordable medicine. It is an antioxidant and hepatoprotective agent to protect the liver from damage caused by NaNO₂.

Impact of Thymus vulgaris extract on sodium nitrite-induced alteration of renal redox and oxidative stress: Biochemical, molecular, and immunohistochemical study

Thyme (Thymus vulgaris) is an herbal plant with pleiotropic medicinal properties. In this study, we examined the possible protective effect of an ethanolic extract of thyme leaves against the renal oxidative stress induced by sodium nitrite (NaNO₂ ). Male Swiss mice received either saline or thyme extract for 15 days (0.5 g/kg body weight, orally). NaNO₂ (60 mg/kg) was injected intraperitoneally at Day 14. The protective group received the thyme extract for 15 days and NaNO₂ on Day 14. Blood and kidney samples were taken from all groups to measure serum urea, blood urea nitrogen (BUN), creatinine, serum, tissue antioxidant activity, and the inflammatory cytokines IL-1β and IL-6. Quantitative real-time PCR (qRT-PCR) was used to examine the expression of kidney injury marker-1 (Kim-1), TNF-α, nuclear factor erythroid-2 related factor 2 (Nrf2), and hemoxygenase-1 (HO-1), all of which are associated with kidney redox and oxidative stress. Pretreatment with thyme extract reduced the effects of NaNO₂ on urea, BUN, and creatinine, and reversed its effect on tissue and serum antioxidants. NaNO₂ -induced nephritis as demonstrated by the upregulation in mRNA expression of Kim-1 and TNF-α, which was, however, recovered and protected by pretreatment with thyme extract. Expression of Nrf2 and HO-1 was upregulated by treatment with thyme extract and downregulated by NaNO₂ intoxication. NaNO₂ -induced congestion in glomeruli and dilatation of the renal tubules, conditions that were restored in the group pretreated with thyme extract. NaNO₂ upregulated Bax immunoreactivity and caused apoptosis in renal structures. Thus, thyme extract is effective in managing the renal toxicity associated with oxidative stress and renal redox. PRACTICAL APPLICATIONS: The results from this study have shown that use of thyme extract may promote better health due to its high antioxidant activity. For instance, it could be ingested to alleviate the symptoms of renal inflammation and oxidative stress associated with nitrite toxicity. Thyme extract regulated renal redox, oxidative stress, antioxidant levels, and inflammation-associated genes at the molecular, biochemical, and cellular immunohistochemical levels.

Hepatoprotective effect of Thymus vulgaris extract on sodium nitrite-induced changes in oxidative stress, antioxidant and inflammatory marker expression

The herb thyme (Thymus vulgaris) has multiple therapeutic uses. In this study, we explored how T. vulgaris leaf extract protects liver cells against sodium nitrite-(NaNO₂) induced oxidative stress. Mice were divided into four groups; each group received one of the following treatments orally: saline; T. vulgaris extract alone; NaNO₂ alone; or T. vulgaris extract + NaNO₂. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), reduced glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), IL-1β, IL-6, TNF-α, and total proteins were measured in serum using standard methods. TNF-α, hemooxygenase-1 (HO-1), thioredoxin, SOD, and GSH synthase, all of which are linked to oxidative stress, were measured using quantitative real-time PCR (qRT-PCR). In mice treated with T. vulgaris extract, the effect of NaNO₂ on ALT and AST levels and total proteins was reduced, and its effect on antioxidant levels was reversed. Normally, NaNO₂ causes hepatocyte congestion and severe hepatic central vein congestion. Tissues in the mice treated with T. vulgaris were restored to normal conditions. Our results demonstrate that NaNO₂-induced hepatic injury is significantly reduced by pretreatment with T. vulgaris extract, which protects against hepatic oxidative stress and its associated genes at the biochemical, molecular, and cellular levels.

Mechanism underlying nephroprotective property of curcumin against sodium nitrite-induced nephrotoxicity in male Wistar rat

The current work examined the outcome of curcumin (20 mg/kg body weight/day) administration on arginase and adenosine deaminase (ADA) activities and other kidney markers, as well as markers of oxidative stress, in Wistar rats exposed to sodium nitrite (NaNO₂ ) (60 mg/kg of body weight, single dose) for 28 days. The results revealed that the NaNO₂ exposed rats had significantly altered the ADA activities, arginase activities alongside other biomarkers of kidney function, and oxidative stress. However, pretreatment with curcumin significantly mitigated the altered activities ADA and arginase as well as other parameters. This was supported by the histopathological examination of the kidney tissues. Our findings suggest that the alteration in the activities of ADA and arginase could be involved in the mechanism of action employed by NaNO₂ and curcumin in the respective induction and prevention of nephrotoxicity. PRACTICAL APPLICATIONS: These results suggest that moderate exposure to the acceptable daily dose of curcumin can improve food-related kidney damage through regulations of ADA and arginase activities, enhancement in the antioxidant system, and suppression of lipid peroxidation.

Human Erythrocytes Exposed to Phthalates and Their Metabolites Alter Antioxidant Enzyme Activity and Hemoglobin Oxidation

Phthalates used as plasticizers have become a part of human life because of their important role in various industries. Human exposure to these compounds is unavoidable, and therefore their mechanisms of toxicity should be investigated. Due to their structure and function, human erythrocytes are increasingly used as a cell model for testing the in vitro toxicity of various xenobiotics. Therefore, the purpose of our study was to assess the effect of selected phthalates on methemoglobin (metHb), reactive oxygen species (ROS) including hydroxyl radical levels, as well as the activity of antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), in human erythrocytes. Erythrocytes were incubated with di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP), and their metabolites, i.e., mono-n-butyl phthalate (MBP) and monobenzyl phthalate (MBzP), at concentrations ranging from 0.5 to 100 µg/mL for 6 or 24 h. This study shows that the analyzed phthalates disturbed the redox balance in human erythrocytes. DBP and BBP, at much lower concentrations than their metabolites, caused a statistically significant increase of metHb and ROS, including hydroxyl radical levels, and changed the activity of antioxidant enzymes. The studied phthalates disturbed the redox balance in human erythrocytes, which may contribute to the accelerated removal of these cells from the circulation.

Acetaldehyde-induced oxidative modifications and morphological changes in isolated human erythrocytes: an in vitro study

Acetaldehyde is a toxic, mutagenic and carcinogenic metabolite of alcohol which can bind to proteins, DNA and several other cellular macromolecules. Chronic alcohol consumption increases intracellular acetaldehyde levels which enhances the generation of reactive oxygen and nitrogen species (ROS and RNS). In this study, we have examined the effect of acetaldehyde on human erythrocytes under in vitro conditions. Treatment of human erythrocytes with different concentrations of acetaldehyde (0.05-2 mM) for 24 h at 37 °C increased intracellular generation of ROS and RNS. It also increased oxidation of proteins and lipids but decreased glutathione, total sulphhydryl and free amino group content. Methemoglobin level was increased accompanied by a decrease in methemoglobin reductase activity. Acetaldehyde impaired the antioxidant defence system and lowered the total antioxidant capacity of the cell. It decreased the activity of metabolic and membrane-bound enzymes and altered erythrocyte morphology. Our results show that acetaldehyde enhances the generation of ROS and RNS that results in oxidative modification of cellular components. This will lower the oxygen transporting ability of blood and shorten erythrocyte lifespan (red cell senescence).

Effect of acute sodium nitrite intoxication on some essential biometals in mouse spleen

BACKGROUND AND AIM

Sodium nitrite (NaNO₂) is an inorganic salt with numerous applications in a variety of industries, as well as in medicine. Nevertheless, exposure to high levels of NaNO₂ is toxic for animals and humans. Sodium nitrite intoxication is shown to decrease the activity of major antioxidant defence enzymes which is dependent on the maintenance of specific ion equilibrium. The aim of the present study was to investigate the effect of acute NaNO₂ intoxication on the content of the essential metals iron (Fe), calcium (Ca) and zinc (Zn) in mouse spleen.

METHODS

Mature male ICR mice were divided into four groups and subjected to acute NaNO₂ exposure by a single intraperitoneal injection of 120 mg/kg body weight. Animals in each group were sacrificed at certain time interval after treatment (1 h, 5 h, 1 day and 2 days). Spleens were excised and processed for atomic absorption spectrometry analysis of Fe, Ca and Zn content.

RESULTS

At the first hour after treatment, a decrease in Fe and Ca levels was observed. One day following NaNO₂ administration, Zn concentration reached its lowest value and Ca levels remained lower, compared to the untreated controls. In contrast, Fe concentration increased on the first and second day after treatment.

CONCLUSION

The results of the present study demonstrate that acute NaNO₂ intoxication provokes changes in the endogenous levels of Fe, Ca and Zn in mouse spleen. These findings suggest disruption of the ionic balance and impact on the activity of antioxidant defence enzymes.

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.

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.