THE ROLE OF NONHEMOGLOBIN PROTEINS AND REDUCED GLUTATHIONE IN THE PROTECTION OF HEMOGLOBIN FROM OXIDATION IN VITRO

Quantitative proteomics and metabolomics analysis reveals the response mechanism of alfalfa (Medicago sativa L.) to o-coumaric acid stress

O-coumaric acid (OCA), as a significant phenolic allelochemical found in hairy vetch (Vicia villosa Roth.), that can hinder the growth of alfalfa (Medicago sativa L.), particularly the growth of alfalfa roots. Nonetheless, the mechanism by which OCA inhibits alfalfa root growth remains unclear. In this study, a liquid chromatography tandem mass spectrometry (LC-MS/MS)-based quantitative proteomics analysis was carried out to identify differentially accumulated proteins (DAPs) under OCA treatment. The findings indicated that 680 proteins were DAPs in comparison to the control group. Of those, 333 proteins were up-regulated while 347 proteins were down-regulated. The enrichment analysis unveiled the significance of these DAPs in multiple biological and molecular processes, particularly in ribosome, phenylpropanoid biosynthesis, glutathione metabolism, glycolysis/gluconeogenesis and flavonoid biosynthesis. The majority of DAPs reside in the cytoplasm (36.62%), nucleus (20.59%) and extracellular space (14.12%). In addition, phenylalanine deaminase was identified as a potential chemical-induced regulation target associated with plant lignin formation. DAPs were mainly enriched in flavonoid biosynthesis pathways, which were related to plant root size. Using the UPLC-ESI-MS/MS technique and database, a total of 87 flavonoid metabolites were discovered. The metabolites were predominantly enriched for biosynthesizing naringenin chalcone, which was linked to plant lignin formation, aligning with the enrichment outcomes of DAPs. Consequently, it was deduced that OCA impacted the structure of cell walls by mediating the synthesis of lignin in alfalfa roots, subsequently inducing wilt. Furthermore, a range of proteins have been identified as potential candidates for the breeding of alfalfa strains with enhanced stress tolerance.

The specific PKC-α inhibitor chelerythrine blunts costunolide-induced eryptosis

Costunolide, a natural sesquiterpene lactone, has multiple pharmacological activities such as neuroprotection or induction of apoptosis and eryptosis. However, the effects of costunolide on pro-survival factors and enzymes in human erythrocytes, e.g. glutathione and glucose-6-phosphate dehydrogenase (G6PDH) respectively, have not been studied yet. Our aim was to determine the mechanisms underlying costunolide-induced eryptosis and to reverse this process. Phosphatidylserine exposure was estimated from annexin-V-binding, cell volume from forward scatter in flow cytometry, and intracellular glutathione [GSH]_i from high performance liquid chromatography. The oxidized status of intracellular glutathione and enzyme activities were measured by spectrophotometry. Treatment of erythrocytes with costunolide dose-dependently enhanced the percentage of annexin-V-binding cells, decreased the cell volume, depleted [GSH]_i and completely inhibited G6PDH activity. The effects of costunolide on annexin-V-binding and cell volume were significantly reversed by pre-treatment of erythrocytes with the specific PKC-α inhibitor chelerythrine. The latter, however, had no effect on costunolide-induced GSH depletion. Costunolide induces eryptosis, depletes [GSH]_i and inactivates G6PDH activity. Furthermore, our study reveals an inhibitory effect of chelerythrine on costunolide-induced eryptosis, indicating a relationship between costunolide and PKC-α. In addition, chelerythrine acts independently of the GSH depletion. Understanding the mechanisms of G6PDH inhibition accompanied by GSH depletion should be useful for development of anti-malarial therapeutic strategies or for synthetic lethality-based approaches to escalate oxidative stress in cancer cells for their sensitization to chemotherapy and radiotherapy.

Effect of Exogenous Glutathione, Glutathione Reductase, Chlorine Dioxide, and Chlorite on Osmotic Fragility of Rat Blood In Vitro

Chlorine dioxide (CIO2), chlorite (CIO-2), and chlorate (CIO-3) in drinking water decreased blood glutathione and RBC osmotic fragility in vivo. The osmotic fragility and glutathione content were also studied in rat blood treated with CIO2, CIO-2, CIO-3 in vitro. RBC hemolysis was decreased in rat blood after 30, 60, and 120 minutes by all treatments. The glutathione content expressed as percentage of controls was decreased with incubation time. When CIO2 was added with reduced glutathione (GSH) to the blood, no effect on hemolysis was observed compared to control or to GSH alone at 2 hours, but decreased hemolysis was observed with CIO2 treatment alone. Addition of NADPH alone prevented CIO2 and CIO-2 and CIO-3 from exhibiting hemolysis resistance, while glutathione reductase (GR) and its cofactor (NADPH) increased hemolysis about 1.5–2 fold. Removing GR only resulted in increased resistance to hemolysis with CIO2 or CIO-2. The formation of disulfide bonds between sulfhydryl groups in erythrocytic membranes and hemoglobin, causing precipitation of hemoglobin (yielding apparent resistance to hemolysis) can account for the difference between the hemolysis before and after the addition of GR.

Toxicity of Chlorine Dioxide in Drinking Water

Chlorine dioxide (CIO2) is currently being considered as an alternate to chlorine as a disinfectant for public water supplies. Studies were conducted to determine the toxicity of CIO2 (0, 1, 10, 100, 1000 mg/L) and its metabolites, CIO-2 and CIO-3 (10, 100 mg/L) in drinking water in rats. After 9 months treatment the osmotic fragility of the red blood cells was decreased in all treatment groups, while a decreased blood glutathione was only observed in the metabolite groups. At 2, 4, and 6 months no significant hematologic changes were noted in treated rats compared to control. However, after 9 months RBC counts, hematocrit, and hemoglobin were decreased in all treatment groups. CIO2, CIO-2, and CIO-3 administered chronically in drinking water for 3 months inhibited the incorporation of 3H-thymidine into nuclei of rat testes. This inhibition was observed in the liver of CIO-2 groups and in the kidney of 100 mg/L CIO2 treatment. The incorporation in small intestinal nuclei was increased in both 10 and 100 mg/L CIO2 and in 10 mg/L CIO-2. The treatment with CI compounds decreased rat body weight in all groups after 10 and 11 months treatment.

The vasodilator effects of clevidipine on human internal mammary artery

Endothelial dysfunction and platelet activation with thromboxane release may contribute to spasm or alterations in internal mammary artery (IMA) graft flow during coronary artery surgery. Clevidipine, an ultrashort-acting dihydropyridine calcium channel blocker, is undergoing clinical development, but there are little data regarding its effects on human vasculature. We investigated the effects of clevidipine on human IMA obtained during surgery. After precontracting IMA segments with an analog of thromboxane (U46619, 10(-8) mol/L), acetylcholine and nitroglycerin were added cumulatively to examine endothelial function. Concentration-response curves to clevidipine were cumulatively obtained during submaximal contraction to the U46619 (10(-8) mol/L) in rings with and without endothelium. In the IMA samples with endothelium, acetylcholine did not completely reverse the U46619-mediated contraction, which implies impaired endothelial function (40% +/- 6% maximal response). Both clevidipine and nitroglycerin completely reversed U46619-induced contraction (clevidipine (50% effective concentration [EC50] = 3.88 +/- 0.84 x 10(-6) mol/L, nitroglycerin EC50 = 4.84 +/- 2.76 x 10(-8) mol/L). The responses to clevidipine were similar in preparations with or without intact endothelium. Clevidipine is an endothelium-independent arterial vasodilator that offers a potential therapeutic option in the treatment of perioperative arterial graft vasospasm and/or hypertension.

IMPLICATIONS

Clevidipine is a new ultrashort-acting dihydropyridine calcium antagonist. In human internal mammary arteries precontracted with a thromboxane A2 analog, clevidipine was an effective vasodilator on vessel segments in the presence and in the absence of endothelium.

Toxicology of selected nitric oxide-donating xenobiotics, with particular reference to azide

Nitric oxide (NO) has been discovered recently to be a ubiquitous, endogenous mediator, which is responsible for a variety of normal physiological functions. However, NO also has been implicated in several pathophysiological processes. For example, the pulmonary toxicity of various nitrogen oxides, including NO, found in photochemical smog has been studied for decades; endogenous NO also is associated with bleomycin-induced lung damage, as well as other adverse effects. Recently, a variety of xenobiotics have been shown to owe their biological activity in vivo to their biotransformation to NO. Thus, the therapeutic vasodilatation produced by drugs such as nitroglycerin and sodium nitroprusside is now believed to result from their release of NO, which then mimics the effects of endogenously synthesized NO. The toxic effects of NO prodrugs are, therefore, a matter of concern, especially the extent to which, if any, NO contributes to their toxicity. As reviewed here, NO does not appear to contribute importantly to the toxicity of the NO donors nitrite, hydroxylamine, or nitroprusside. However, it is by no means clear whether or not the NO generated in vivo from sodium azide contributes in a major way to its toxicity. Azide is almost as acutely toxic as cyanide, with which it shares a number of biological effects; yet, azide also has certain cardiovascular actions in common with nitrite. Unlike either cyanide or nitrite, some evidence suggests a tendency for azide to produce low-grade cumulative toxicity. In laboratory animals, azide frequently produces nonasphyxial convulsions, whereas most human deaths appear to be the result of cardiovascular collapse. Neither of these azide-induced syndromes appears to be due to the inhibition of cytochrome c oxidase. Azide is widely used as a preservative in aqueous laboratory reagents and as the propellant in automobile air bags and aircraft escape chutes. Both of these inflable systems are generally safe, and will prevent untold numbers of injuries and deaths. However, to protect workers who handle these devices and others who may come into contact with the sodium azide propellant in these systems, our rudimentary knowledge of azide toxicity needs to be expanded.

Toxicity of monochloramine in rat: an alternative drinking water disinfectant

Monochloramine (NH2Cl) is under consideration as an alternative to chlorine as a disinfectant in public water supplies, to avoid trihalomethanes formation. This study was conducted to investigate the toxicity of NH2Cl (0, 1, 10, 100 mg/l) in drinking water. Glutathione (GSH) content in rat blood was decreased significantly after 4 mo treatment, and the decreases were consistent throughout the treatment period. Treatment groups showed a slight increase in blood osmotic fragility. After acute administration (3 ml) of 20 and 40 mg NH2Cl/l, blood GSH levels were increased as early as 15 min and the increases were consistent up to 1 h. After 2 h exposure, however, the GSH content returned to the control value. At 3 mo, red-blood-cell count and hematocrit were decreased significantly, while after 10 mo treatment significant decreases in hemoglobin concentration and mean corpuscular hemoglobin were observed. Monochloramine administered in drinking water for 3 mo increased the incorporation of [3H]thymidine into nuclei of rat kidney and spleen in the 1- and 10-mg/l groups, while the incorporation in testes was increased only in the 100-mg/l group. The body weight of rats was decreased significantly in the highest treatment group after 3 mo treatment, and the decrease persisted throughout the period studied. An examination of blood chloroform content in all the groups after 4, 6, 9, and 12 mo showed no significant changes compared to the control.

Riboflavin deficiency in man: effects on haemoglobin and reduced glutathione in erythrocytes of different ages

1. Erythrocytes (RBC) from control and marginally riboflavin-deficient subjects were fractionated into nine fractions using a discrete density gradient. 2. Glutathione reductase (NAD(P)H: glutathione oxidoreductase; EC 1.6.4.2) activity and aspartate aminotransferase (EC 2.6.1.1) activity (with and without the appropriate co-enzymes) reduced glutathione, methaemoglobin, sulphaemoglobin and oxyhaemoglobin and susceptibility to peroxide were measured in RBC in the different fractions. 3. Glutathione reductase and aspartate aminotransferase activities and concentrations of reduced glutathione and oxyhaemoglobin all declined with age, while methaemogloblin, sulphaemoglobin and susceptibility to peroxide increased with age. 4. The only significant differences noted in the RBC from marginally-riboflavin-deficient subjects by comparison with controls, were lower glutathione reductase activities and higher concentrations of methaemoglobin. 5. The role of riboflavin in those systems controlling RBC integrity is discussed.

The possible role of hypertension in aggravating hemolytic episodes in G-6PD deficient persons

Approximately 13 percent of American Negro males carry a mutant [A-variant] glucose-6-phosphate dehydrogenase enzyme in their red blood cells that predisposes them to hemolytic episodes following exposure to oxidant drugs such as primaquine. Most hemolytic episodes to standard prophylactic treatment are mild and self-limited, but as many as 2 percent of Negro males develop severe hemolysis when similarly treated. The exaggerated response may be due in part to the combination of G-6-PD deficiency and hypertension since hypertension can cause red cell fragmentation, and the stressed cells of G-6-PD deficient person would be more sensitive to such fragmentation.

Red cell enzymes

As compared to other cells of the body, the mammalian red cell has one of the simplest structural organizations. As a result, this cell has been extensively used in studies involving the structure, function, and integrity of cell membranes as well as cytoplasmic events. Additionally, the metabolic activities of the red blood cell are also relatively simple. During the past quarter century or so, an ocean of knowledge has been gathered on various aspects of red cell metabolism and function. The fields of enzymes, hemoglobin, membrane, and metabolic products comprise the major portion of this knowledge. These advances have made valuable contributions to biochemistry and medicine. Despite these favorable aspects of this simple, anucleated cell, it must be conceded that our knowledge about the red cell is far from complete. We are still in the dark concerning the mechanism involved in several aspects of its membrane, hemoglobin, enzymes, and a large number of other constituents. For example, a large number of enzymes with known catalytic activity but with unknown function have eluded investigators despite active pursuit. This review will be a consolidation of our present knowledge of human red cell enzymes, with particular reference to their usefulness in the diagnosis and therapy of disease. Owing to the multitude of publications by prominent investigators on each of the approximately 50 enzymes discussed in this review, it was impossible to cite a majority of them.

Red cell glutathione in anaemia

Erythrocyte reduced glutathione (GSH) has been measured in 17 normal subjects and in 70 patients with anaemia of various causes; the red cells of most of the anaemic patients contained abnormally high levels of GSH. In the group of cases of untreated megaloblastic anaemia in which the haemoglobin concentration was less than 8.0 g. per 100 ml., there was an inverse relationship between the erythrocyte GSH level and the haemoglobin concentration. During initial therapy in megaloblastic anaemia, as the haemoglobin concentration increased, the GSH level decreased towards normal; the time taken for the GSH level to reach a value 2 standard deviations above the normal mean was inversely related to the initial haemoglobin concentration. In the red cells of patients with anaemia there was no correlation between the GSH level and the activity of glutathione peroxidase. The significance of these findings is discussed.

Erythrocyte catalase and detoxication of hydrogen peroxide

Erythrocytes from several animal species with widely differing catalase levels were exposed to H2O2and the susceptibility of Hb to oxidation measured. In the absence of glucose the rapidity of MHb formation was inversely related to the catalase activity and directly related to the concentration of H2O2attained. Added catalase or hemolysates of catalase-rich erythrocytes counteracted the effect of H2O2, while azide rendered Hb of even catalase-rich cells susceptible to rapid oxidation. Added glucose largely prevented the formation of MHb on exposure to H2O2; this protective effect was less marked in azide-treated cells than in control cells. These results suggest that catalase complements the protective action of glucose and thereby regulates MHb formation and accumulation in erythrocytes.