Mechanism of the hydrogen peroxide hemolysis test and its reversal with phenols

Glutathione synthetase deficiency: a novel mutation with femur agenesis

Introduction: Glutathione synthetase (GSS) deficiency is an autosomal recessive disorder (frequency < 1/1,000,000) with different varyingly severe clinical manifestations that include metabolic acidosis, hemolytic anemia, hyperbilirubinemia, neurological disorders and sepsis. Case report: This infant was small for gestational age, had hemolytic anemia, metabolic acidosis, bilateral subependymal pseudocysts and increased echogenicity of the basal ganglia. GSS deficiency was confirmed by genetic analysis. The patient also had unilateral right femur agenesis. Conclusion: By using next generation sequencing analysis, we identified a novel homozygous variant c.800G > A, p.Arg267Gln in the GSS gene of this patient. Femur agenesis had not previously been associated with GSS.

In Vitro Studies on Degradation of Gamma-L-Glutamyl-L-Cysteine and Gamma-L-Glutamyl-D-Cysteine in Blood: Implications for Treatment of Stroke

Treatment for ischemic stroke involves a thrombolytic agent to re-establish blood flow in the brain. However, delayed reperfusion may cause injury to brain capillaries. Previous studies indicate that the antioxidant gamma-L-glutamyl-L-cysteine (γ-Glu-Cys) contributes to reducing reperfusion injury to the cerebral vasculature in rats, when administered intravascularly. To determine the stability of γ-Glu-Cys in blood, the peptide was incubated in rat serum in vitro, and its degradation was quantified by high-pressure liquid chromatography. The half-time (t1/2) for degradation of γ-Glu-Cys was 11 ± 1 minute (mean ± SD, n = 3). A similar pattern of degradation was observed when γ-Glu-Cys was incubated in the presence of human plasma (t1/2 = 17 ± 8 minutes, n = 3). In a second series of experiments, degradation of an analog (γ-Glu-D-Cys) was tested in rat serum and found to be more stable than the native molecule. The initial velocity for degradation of γ-Glu-D-Cys (0.12 ± 0.02 mM/min; mean ± SD, n = 3) was significantly (P = 0.006) less than that of γ-Glu-Cys (0.22 ± 0.03 mM/min; mean ± SD, n = 3). Furthermore, an in vitro assay indicated that the analog has as an oxidative capacity that equals that of the original peptide in the presence of rat serum and human plasma. Finally, both peptides were found to be similarly effective in preventing lysis of intact cells using in vitro assays. These studies show that γ-Glu-Cys remains intact in blood for several minutes, and the analog γ-Glu-D-Cys may be a more stable, but similarly effective antioxidant.

Probe-assisted flow cytometric analysis of erythrocyte membrane response to site-specific oxidant stress

BACKGROUND

Probe-assisted flow cytometry was used to monitor the response of membranes of living cells to oxidant stress in the presence and absence of antioxidants. Test conditions (fluorophore loading, oxidant concentration) were investigated and storage-related changes in erythrocyte response to oxidant stress explored.

METHODS

Erythrocytes were incubated with a lipophilic fluorescent probe and exposed to site-specific oxidant challenge, induced by cumene hydroperoxide, in the presence and absence of urate, ascorbate, or alpha tocopherol in physiological amounts. Fluorescence of labeled and treated erythrocytes was measured for 120 min using a Coulter EPICS Elite ESP flow cytometer.

RESULTS

Probe loading was dose and time dependent. Cumene hydroperoxide exhibited a potent and dose-dependent oxidant effect on erythrocyte membranes. Alpha tocopherol slowed, but did not prevent, membrane oxidation. Ascorbate appeared to have no effect on peroxidation initially, but then slowed and stopped propagation of membrane oxidation. The effect of urate was slight.

CONCLUSIONS

This technique can provide insight into oxidative processes at the cellular level. Results indicated that lipophilic alpha tocopherol was the most effective antioxidant in slowing membrane peroxidation, but ascorbate appears to stop chain propagation. This effect may be owing to vitamin C/E interaction. Further study is needed.

Clinical, biochemical, and molecular characterization of patients with glutathione synthetase deficiency

Pyroglutamic aciduria (5-oxoprolinuria) is a rare autosomal recessive disorder caused by either glutathione synthetase deficiency (GSSD) or 5-oxoprolinase deficiency. GSSD results in low glutathione levels in erythrocytes and may present with hemolytic anemia alone or together with pyroglutamic aciduria, metabolic acidosis, and CNS damage. Five patients with pyroglutamic aciduria were studied. All presented with hemolytic anemia and metabolic acidosis. Two (brothers) also had Fanconi nephropathy, which is not seen in pyroglutamic aciduria. Molecular analyses of the GSS gene was performed in 3 patients. RT-PCR and heteroduplex analysis identified a homozygous deletion in 1 patient and a homozygous mutation in 2 others (brothers with Fanconi nephropathy). Sequencing of glutathione synthetase (GSS) cDNA from the first patient showed a 141-bp deletion corresponding to the entire exon 4, whilst the corresponding genomic DNA showed a G491 --> A homozygous splice site mutation. Sequencing of GSS cDNA from the Fanconi nephropathy patients showed a C847 --> T [ARG283 --> CYS] mutation in exon 9.

Micronutrient deficiencies in the preterm neonate

The nutrition of the premature infant poses a critically important challenge to clinicians. Premature infants are a heterogeneous group; maternal status, gestational age, drug intake, respiratory distress, phototherapy, and infection all conspire to make it extremely unlikely that a recommendation for daily intakes will satisfactorily encompass all babies. Clinical and subclinical deficiencies evidently do occur, and the impact of nutrient imbalance may have serious implications for outcome. If advances in clinical practice mean enhanced survival rates of babies of very small gestational age, then it is of vital importance that we work to establish the most appropriate regimens for vitamin and mineral intakes in this group.

The early anaemia of the premature infant: is there a place for vitamin E supplementation?

1. The efficacy of oral vitamin E supplementation in preventing the early anaemia of the premature infant was assessed in a 10-week double-blind trial. Forty-two babies received either a placebo or 5 or 15 mg supplementary vitamin E/d with oral feeding. No infant received less than the recommended vitamin E:polyunsaturated fatty acid (E:PUFA) value of 0.6. No iron supplement was given. 2. Weekly full blood counts were taken, and plasma vitamin E assay and in vitro haemolysis tests performed on blood sampled on day 1, and also at 6 and 10 weeks of age. All blood withdrawn and transfused and all feeds were documented. 3. Thirty-six (86%) of the babies had a plasma vitamin E level at birth below the accepted adult norm, i.e. less than 5200 micrograms/l. At 6 weeks of age thirty-three (79%) and at 10 weeks thirty-five (83%) of the babies had levels within the normal adult range. No baby showed either clinical or haematological evidence of a vitamin E deficiency state during the trial. 4. It is concluded that in the absence of Fe supplementation and observing the minimum recommended E:PUFA value, contemporary feeding practices allow for the absorption of sufficient vitamin E by the premature baby to prevent the development of an early haemolytic anaemia. 5. No significant relation was found between plasma vitamin E levels and the degree of peroxide haemolysis.

Inhibitors of hydrogen peroxide-induced haemolysis of bovine erythrocytes

The optimal conditions for the haemolysis of bovine erythrocytes by H2O2 have been established. The parameters were concentration of erythrocytes, H2O2 concentration, time, and influence of the solvent in which the substances tested were dissolved. Some inhibitors of this oxidative haemolysis have been employed to serve as model substances for further antihaemolytic investigations with natural products.

Human biochemical response to ozone and vitamin E

To determine whether vitamin E (dl-alpha-tocopherol) supplementation of the diet provides protection from inhaled oxidants such as ozone (O3) in community air pollution, its effects were studied in healthy adult volunteers, Experimental groups received 800 or 1600 IU of vitamin E for 9 wk or more; control groups received placebos. Double-blind conditions were maintained throughout the study. Biochemical parameters studied included red blood cell fragility; hematocrit and hemoglobin values; red cell glutathione concentration; and the enzymes acetylcholinesterase, glucose-6-phosphate dehydrogenase, and lactic acid dehydrogenase. No significant differences between the responses of the supplemented and placebo groups to a controlled O3 exposure (0.5 ppm for 2 h) were found for any of these parameters. The results indicate that vitamin E supplementation in humans, at the levels employed in this experiment, gives no added protection against blood biochemical effects of O3 in intermittently exercising subjects under exposure conditoins simulating summer ambient air pollution episodes.

An examination of the role of vitamin E in glucose-6-phosphate dehydrogenase deficiency

The effect of vitamin E on erythrocyte glutathione stability was studied both in vitro and in vivo on subjects with glucose-6-phosphate dehydrogenase deficiency. The results suggest that lipid membrane peroxidation in glucose-6-phosphate dehydrogenase deficient erythrocytes, which has been postulated to occur under conditions of oxidative stress, does not result in significant depletion of erythrocyte reduced glutathione pools. Vitamin E supplementation in these individuals was shown to have little or no effect on the response of their erythrocytes to oxidative stress.

Nitrogen dioxide inhalation and human blood biochemistry

Blood from ten young adult male humans, exposed to 1 ppm or 2 ppm nitrogen dioxide (NO2) for 2.5--3.0 hr, was examined for evidence of biochemical changes. The experiments lasted three days. The subjects entered an environmental chamber, performed mild exercise, and completed a series of measurements of pulmonary physiology while breathing filtered air. Blood samples were then taken and analyzed. This regimen was repeated on the second and third day, except that the chamber atmosphere now contained 1 ppm or 2 ppm NO2. Paired group analyses were performed on the data. A statistically significant decrease was observed in the activity of the erythrocyte membrane enzyme acetylcholinesterase at both NO2 levels. Levels of peroxidized red blood cell lipids showed statistically significant elevations after inhalation of 2 ppm NO2 but not 1 ppm. Glucose-6-phosphate dehydrogenase was significantly elevated only after the second 2-ppm NO2 exposure. Small but statistically significant decreases were observed in both hemoglobin and hematocrit values after exposure to both NO2 levels. The experiment was repeated with NO2, (i.e., three days of filtered air) to detect possible effects of the experimental procedure. Decreases were again seen in hemoglobin and hematocrit, and acetyecholinesterase, although of smaller magnitude than when NO2 was inhaled. Other data showed random variations that were not additive over the three-day sham exposure period. It was concluded that significant blood biochemical changes resulted from NO2 inhalation, although the three-day experimental regimen independently produced changes that account for some of the apparent response.

Biochemical response of squirrel monkeys to ozone

Biochemical studies were performed on blood and lung tissue of squirrel monkeys (Saimiri sciureus) following acute exposure to 0.75 ppm ozone (O3) for 4 h/d for 4 consecutive days. One group of animals was sacrificed at the end of the last exposure day and another group was sacrificed 4 d later after the last exposure. Evidence was sought for oxidation-induced changes known to occur in rodents when high levels of O3 are inhaled. A significant increase in red blood cell membrane fragility was observed, as well as significant decreases in red blood cell glutathione and erythrocyte acetylcholinesterase; however, the red blood cell enzymes, lactic acid dehydrogenase (LDH), and glucose-6-phosphate dehydrogenase (G6PDH) were not changed significantly. Lung tissue analysis showed that lipid peroxidation was markedly increased and tissue vitamin E levels were significantly decreased. The tissue enzymes G6PDH, glutathione reductase, and LDH significantly increased in activity. No significant changes were seen in either superoxide dismutase or malic acid dehydrogenase. The results of this experiment indicate that O3, or reaction products resulting from O3-tissue interaction in the lung, pass the air-blood barrier and are capable of producing biochemical changes in blood as well as in lung tissue.

5-oxoprolinuria: biochemical observations and case report

We have studied a patient with 5-oxoprolinuria who presented with hemolysis and metabolic acidosis as a neonate; he has had normal growth and development to one year of age. Compensated hemolytic anemia persists, and he requires alkalinizing agents for correction of acidosis. Biochemical studies have confirmed that a deficiency of glutathione synthetase is responsible for the 5-oxoprolinuria. Genetic heterogeneity was apparent on comparative study of glutathione synthetase kinetics in cells from two patients with this disorder. The consequences of the deficiency of glutathione synthetase, decreased intracellular glutathione, and overproduction of 5-oxoproline are discussed with reference to the possible cellular roles of these compounds.

Cytotoxicity of ascorbate and other reducing agents towards cultured fibroblasts as a result of hydrogen peroxide formation

Several types of cultured fibroblasts, including chick embryo, human and mouse, were killed by the addition of sodium ascorbate at final concentrations of 0.05-0.25 mM to cultures at the time of inoculation or to attached cells. Ascorbate did not affect the attachment of cells to the substratum. The effect on chick embryo fibroblasts was visible by four hours and by six hours almost all cells had swelled and were becoming detached. By 24 hours detached cells had either lysed or become crenated in appearance. Other end-diol reducing agents and also glutathione and cysteine were effective while gulonolactone, a non-reducing analogue of ascorbate, was ineffective. Preincubation of medium containing ascorbate but no cells, conditions which result in degradation of the vitamin, led to loss of toxicity, indicating that a degradation product was not the lethal agent and that a component of the medium was not converted to a lethal substance. The lethal effect of both ascorbate and glutathione was prevented by the addition of catalase to the medium suggesting that H2O2 formed by intracellular reactions and then excreted into the medium was the cytotoxic agent. This conclusion was supported by the findings that 0.05 mM H2O2 added to chick embryo fibroblasts was lethal and that the effect of this compound on cellular morphology was almost identical to that of ascorbate.

Role of dietary iron and fat on vitamin E deficiency anemia of infancy

Thirty-five infants weighing less than 1500 g at birth were fed four commercial formulas (A-D) varying in polyunsaturated fatty acid composition (32 per cent linoleic acid in A and B and 12 per cent linoleic acid in C and D) and in iron content (smaller than 1.0 in A and B; 12 to 12 mg per liter in B and D). Infants receiving formula B showed significantly lower hemoglobins (p smaller than 0.01) and higher reticulocyte counts (p smaller than 0.005) than infants fed the other three formulas. Infants receiving the two formulas with higher concentrations of unsaturated fatty acids (A and B) showed significantly greater hydrogen-peroxide-induced hemolysis (p smaller than 0.001) than those given diets containing lower amounts. Infants in groups A and B also had lower serum tocopherol concentrations. Infant red-cell membranes are altered by the increased amounts of polyunsaturated fatty acids and iron in the diet. It appears that the development of vitamin E deficiency anemia occurs in infants receiving iron supplementation.

Ozone and human blood

Statistically significant changes (P less than .05) were observed in erythrocytes (RBC) and sera of young adult human males following a single short-term exposure to 0.50 ppm ozone (O3) for 2 3/4 hours. The RBC membrane fragility, glucose-6-phosphate dehydrogenase (G-6-PDH) and lactate dehydrogenase (LDH) enzyme activities were increased, while RBC acetylcholinesterase (AcChase) activity and reduced glutathione (GSH) levels were decreased. The RBC glutathione reductase (GSSRase) activities were not significantly altered. Serum GSSRase activity, however, was significantly decreased while serum vitamin E, and lipid peroxidation levels were significantly increased. These alterations tend to disappear gradually, but were still detectable two weeks following exposure.

Changes in fatty acid metabolism after erythrocyte peroxidation: stimulation of a membrane repair process

To study certain membrane repair processes in human erythrocytes, vitamin E-deficient cells were incubated with hydrogen peroxide. The incorporation of exogenous fatty acid and the transfer of fatty acid from phosphatidylcholine and neutral lipid into phosphatidylethanolamine were examined using radioactive fatty acids. Hydrogen peroxide stimulated the incorporation of fatty acid into all membrane phospholipids. The specific activity of phosphatidylethanolamine was increased disproportionately. The lipids of the membranes of erythrocytes were labeled with saturated and unsaturated fatty acid. When these erythrocytes were subsequently incubated with hydrogen peroxide, both types of fatty acid were transferred from superficial erythrocyte neutral lipids into phosphatidylethanolamine. However, the unsaturated fatty acids of phosphatidylethanolamine were subsequently altered by hydrogen peroxide, whereas the saturated fatty acids were not. The cumulative effect of these processes was a relative decrease in unsaturated fatty acid and an increase in saturated fatty acid in the phosphatidylethanolamine of the erythrocyte membrane. The net effect of these events represents the operation of repair processes which distort the usual fatty acid composition of erythrocyte membranes in the presence of H(2)O(2). This distortion may contribute to membrane permeability changes which occur during peroxide exposure and which precede the eventual hemolysis of these cells.