Gender and maturation affect glutathione status in human neonatal tissues

Influence of lung oxidant and antioxidant status on alveolarization: role of light-exposed total parenteral nutrition

Parenteral multivitamins (MVP) are linked to the generation of peroxides, which cause oxidant injury in lungs associated with alveolar remodelling linked to lung disease of prematurity. This study was to investigate the relationship between alveolar development and lung oxidant-antioxidant status as modulated by the mode of administration of multivitamins with total parenteral nutrition (TPN). Four groups of guinea pig pups received parenteral nutrition differing by 1) mode of MVP admixture: with amino acid solution (AA-MVP) or lipid emulsion (LIP-MVP); 2) light exposure: TPN exposed (LE) or shielded from light (LP). After 2 or 4 days of TPN, vitamins C and E, 8-isoprostaneF2alpha and alveolarization index were determined in lungs and GSSG/GSH in lungs and blood. Exposure to light and the mode of MVP admixture did not influence vitamin E and isoprostane levels. Blood glutathione redox potential was more oxidized in LE and LIP-MVP groups after 4-day infusions, whereas lung redox potential was more reduced in LE groups. LP and LIP-MVP had a beneficial effect, with higher number of alveoli. Globally, results indicate that in this model, alveolarization and modifications in lung redox potential are two independent events induced by light exposed TPN.

Mechanisms underlying developmental programming of elevated blood pressure and vascular dysfunction: evidence from human studies and experimental animal models

Cardiovascular-related diseases are the leading cause of death in the world in both men and women. In addition to the environmental and genetic factors, early life conditions are now also considered important contributing elements to these pathologies. The concept of 'fetal' or 'developmental' origins of adult diseases has received increased recognition over the last decade, yet the mechanism by which altered perinatal environment can lead to dysfunction mostly apparent in the adult are incompletely understood. This review will focus on the mechanisms and pathways that epidemiological studies and experimental models have revealed underlying the adult cardiovascular phenotype dictated by the perinatal experience, as well as the probable key causal or triggering elements. Programmed elevated blood pressure in the adult human or animal is characterized by vascular dysfunction and microvascular rarefaction. Developmental mechanisms that have been more extensively studied include glucocorticoid exposure, the role of the kidneys and the renin-angiotensin system. Other pathophysiological pathways have been explored, such as the role of the brain and the sympathetic nervous system, oxidative stress and epigenetic changes. As with many complex diseases, a unifying hypothesis linking the perinatal environment to elevated blood pressure and vascular dysfunction in later life cannot be presumed, and a better understanding of those mechanisms is critical before clinical trials of preventive or 'deprogramming' measures can be designed.

Variations in metabolic response to TPN are influenced more by sex than by light exposure

BACKGROUND

Failure to protect total parenteral nutrition (TPN) solutions from ambient light induces the generation of peroxides, which contributes to the oxidation of several amino acids. We hypothesized that photo-protection improves the metabolic response to TPN.

AIM

To study the effects of photo-protecting TPN on urinary nitrogen and vitamin C excretion and to evaluate in premature infants the influence of sex.

PATIENTS AND METHODS

Premature infants were randomized to receive from birth light-exposed (LE) or light-protected (LP) TPN. Upon reaching full TPN, parenteral nutrient intakes were correlated with normalized urinary nitrogen and vitamin C concentrations.

RESULTS

No differences were observed between LE and LP. However, sex-related differences were observed in nitrogen and vitamin C handling. In boys, 50% of the nitrogen loss was explained by parenteral amino acid intake, whereas in girls, no correlation was found. The inverse correlation observed between intake and urinary excretion only in girls suggests a state of greater vitamin C utilization in girls.

CONCLUSIONS

These results demonstrate that sex-related differences in nitrogen/protein metabolism reported during enteral nutrition are seen during TPN as well. Sex is an important variable that will need to be taken into account in future studies evaluating the potential clinical effects of photo-protecting TPN.

Shielding parenteral multivitamins from light increases vitamin A and E concentration in lung of newborn guinea pigs

BACKGROUND & AIMS

Exposure of parenteral multivitamin preparation (MVP) to light generates peroxides. Light-exposed MVP induces an oxidant stress in lung but not in liver. This discrepancy suggests differences in handling of infused antioxidant vitamins between the two organs.

HYPOTHESIS

antioxidant capacity of lung depends on the MVP concentration and light protection of infused solutions.

METHODS

Protocol 1: four groups of three-day old guinea pigs received the base solution (5% dextrose + 0.45% NaCl) enriched with 0%, 1%, 2% and 3% MVP. Protocol 2: three further groups received the base solution + 2% MVP either light-exposed or light-protected or light-protected + 300 microM H2O2. After 4 days, lung and liver were sampled for vitamin determinations. Data were analyzed by ANOVA.

RESULTS

In lung, vitamins A-C-E reached a plateau with 1% MVP. In liver, vitamin A and E increased according to their concentration in solutions. Light exposure and added-H2O2 were associated with lower vitamin E in lung and liver. Retinol was higher in lung and lower in liver of animals receiving light-protected compared to light-exposed solutions.

CONCLUSIONS

Light protection of 1% MVP is a better way to improve the pulmonary oxidant-antioxidant balance than to increase MVP (>1%) in parenteral nutrition.

V(D)J recombinase-mediated processing of coding junctions at cryptic recombination signal sequences in peripheral T cells during human development

V(D)J recombinase mediates rearrangements at immune loci and cryptic recombination signal sequences (cRSS), resulting in a variety of genomic rearrangements in normal lymphocytes and leukemic cells from children and adults. The frequency at which these rearrangements occur and their potential pathologic consequences are developmentally dependent. To gain insight into V(D)J recombinase-mediated events during human development, we investigated 265 coding junctions associated with cRSS sites at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus in peripheral T cells from 111 children during the late stages of fetal development through early adolescence. We observed a number of specific V(D)J recombinase processing features that were both age and gender dependent. In particular, TdT-mediated nucleotide insertions varied depending on age and gender, including percentage of coding junctions containing N-nucleotide inserts, predominance of GC nucleotides, and presence of inverted repeats (Pr-nucleotides) at processed coding ends. In addition, the extent of exonucleolytic processing of coding ends was inversely related to age. We also observed a coding-partner-dependent difference in exonucleolytic processing and an age-specific difference in the subtypes of V(D)J-mediated events. We investigated these age- and gender-specific differences with recombination signal information content analysis of the cRSS sites in the human HPRT locus to gain insight into the mechanisms mediating these developmentally specific V(D)J recombinase-mediated rearrangements in humans.

Influence of early postnatal nutritional management on oxidative stress and antioxidant defence in extreme prematurity

The increased survival of infants born at mid-gestation in the last decade is associated with significant oxygen free radical-mediated morbidities. Resuscitation with 100% oxygen, oxidant load from parenteral nutrition fluids, and oxidant stress inherent to the systemic inflammatory state subsequent to infection and tissue injury are all contributory.

CONCLUSION

Improving early postnatal protein nutrition and the formulation of parenteral nutrition fluids would potentially reduce the oxidative stress and enhance the antioxidant defence of extremely premature newborns.

Male sex and intraventricular hemorrhage

BACKGROUND

Neonatal mortality and morbidity are sex biased in low birth weight infants. The "Y chromosome effect" has been suggested to be responsible for these maturational differences.

OBJECTIVE

To examine the association of sex and neonatal outcomes.

DESIGN AND METHODS

A retrospective observational study. Data on all low birth weight infants who survived for >48 hrs were analyzed. Neonatal outcomes were compared between male and female infants. A regression model was used to detect the influence of sex on outcomes after controlling for confounders. Analysis was repeated after stratification of infants into three groups: group A (<1000 g), group B (1000-1499 g), and group C (1500-2499 g).

RESULTS

A total of 833 infants were included in this study; 419 female infants and 414 male infants. Male infants had an increased rate of overall intraventricular hemorrhage (IVH) (12.2% vs. 7.2%, p = .02) and IVH grades 3-4 (4.8% vs. 2.3%, p = .04). In addition, male infants had higher bilirubin levels (10.19 +/- 3.1 mg/dL vs. 9.32 +/- 2.94 mg/dL, p = .001). In a regression model, male sex continued to have significant influence on IVH, IVH grades 3-4, death, and bilirubin. In group A, male infants had a significantly increased prevalence of death (regression coefficient, 1.82 +/- 0.65; p = .005) that could not be explained by the increased prevalence of IVH (p = .18) in regression analysis. In group B, male sex was significantly associated with a higher bilirubin level (regression coefficient, 0.94 + 0.3; p = .002). In bivariate analyses, IVH and IVH grades 3-4 were significantly higher in male compared with female infants (19.8% vs. 3.9%, p < .0001) and (8.5% vs. 0.97%, p = .02), respectively, but these differences lost significance in multiple-regression analysis. In group C, male sex positively influenced the prevalence of IVH (regression coefficient, 1.7 +/- 0.57; p = .003). Bilirubin measured higher in male infants (11.38 +/- 2.87 mg/dL vs. 10.19 +/- 3.22 mg/dL, p = .0004), but the difference lost significance in regression analysis (regression coefficient, 0.21 +/- 0.31; p = .5).

CONCLUSIONS

Bilirubin, IVH, and death were significantly higher in male infants. In subgroup analysis, significance was retained in group A (<1000 g). Whether a single biological factor is responsible for these differences or perhaps a multi-causal process involving a complex interaction of physiologic, environmental, and pathologic responses needs to be further addressed in future research.

Thiol metabolism in preterm infants during the first week of life

BACKGROUND

Oxidative stress is implicated in the pathogenesis of several complications of prematurity. The glutathione cycle is one of the most important intracellular antioxidant systems. The synthesis of glutathione may not be adequate in preterm neonates because of the low levels of cysteine available. The aim of this study was to evaluate cysteine and glutathione metabolism during the first week of life in preterm infants.

METHODS

Plasma and erythrocyte thiol concentrations were measured in 78 preterm infants with a birthweight of 500-1500 g, and erythrocyte glutamate-cysteine ligase (GCL), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferases (GST) and glucose 6-phosphatedehydrogenase (G6PDH) in 26 infants with a birthweight of 1000-1500 g.

RESULTS

The mean (SD) plasma glutathione concentration increased from day 0 to day 1 (14.9 (7.1) vs. 27.7 (11.9) micromol/L, p < 0.001), and then decreased. The plasma cysteine concentration changed in the opposite direction (172 (59) vs. 129 (42) micromol/L, p < 0.01). In infants with respiratory distress syndrome (RDS) the mean plasma glutathione concentration, but not cysteine, was lower on day 0 compared with infants without RDS (11.7 (5.2) vs. 21.4 (5.6) micromol/L, p < 0.01). Erythrocyte glutathione concentration decreased during the first week of life, whereas erythrocyte cysteine concentration increased significantly from day 3 to day 7 (p < 0.01). Erythrocyte cysteine and glutathione concentrations had a positive correlation. The GCL and GR activities did not change, but GST and G6PDH activities decreased during the first week (p < 0.01). GPx activity decreased until day 3 (p < 0.01) and was higher on day 0 and day 1 in infants with RDS.

CONCLUSIONS

Very low birthweight infants have an initial increase in plasma glutathione and initial decrease in plasma cysteine level during the first week of life, and also a positive correlation between erythrocyte cysteine and glutathione levels.

Association study of human MTH1 gene polymorphisms with type 1 diabetes mellitus

Reactive oxygen species are considered to play a role in the development of diabetes mellitus and its complications. Human MTH1 (mutT homologue 1) has 8-oxo-7,8-dihydrodeoxyguanosine triphosphatase activity, which repairs oxidized forms of dGTP. This enzyme is known to have a thermolabile Met83 variant. We examined whether Val83Met polymorphism of human MTH1 gene is associated with type 1 diabetes mellitus. We recruited 156 type 1 diabetic patients (59 males and 97 females). The polymorphism was analyzed by restriction fragment length polymorphism analysis with Nsi I. The Met/Met genotype at codon 83 was very rare in both control and patient groups. Val/Met genotype tended to be more frequent in the whole type 1 diabetic patients than in controls. When subjects were divided into subgroups according to gender, there were no differences in the genotype and allele frequencies between patients and controls in males. On the other hand, in female type 1 diabetic patients, the Val/Met genotype was more frequent than in female controls (corrected P = 0.102). The Met allele was significantly more frequent in female type 1 diabetic patients than in female controls (corrected P = 0.022). Our results suggested that the Met allele at codon 83 of MTH1 gene might be involved in the development of type 1 diabetes mellitus in the Japanese female population.

Mutational spectral analysis at the HPRT locus in healthy children

There is growing evidence linking somatic mutational events during fetal development and childhood to an increasing number of multifactorial human diseases. Despite this, little is known about the relationship between endogenous and environmentally induced exogenous mutations during human development. Here we describe a comparative spectral analysis of somatic mutations at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) reporter gene locus in healthy children. We observed an age-specific decrease in the proportion of large alterations and a corresponding increase in the proportion of small alterations with increasing age following birth (P<0.001). The age specific decrease in the proportion of large alterations (67-30%) was mainly due to a decrease in the proportion of aberrant variable (V), diversity (D) and joining (J) (V(D)J) recombinase mediated HPRT deletions (P<0.001). The increase in the proportion of small alterations with age (28-64%) was associated with an increase in transversions from 8% in children at the late stages of fetal development to 31% in children 12-16 years old (P=0.003). Transitions decreased with age, especially at CpG dinucleotides (P=0.010), as transversions increased (P=0.009). These patterns of mutations provide insight into important spontaneous, genotoxic, and site-specific recombinational somatic mutational events associated with the age-specific development of human disease in children as well as adults.

Photoprotection prevents TPN-induced lung procollagen mRNA in newborn guinea pigs

BACKGROUND

Photo-exposed intravenous multivitamin solutions (MVP) carry a peroxide load. Peroxidation induces gene expression of procollagen. We hypothesized that photo exposure of the MVP solution might promote pulmonary fibrosis. The aim of the study was to assess the potential for MVP to increase procollagen mRNA.

METHODS

Three day old guinea pigs were assigned to the following intravenous regimens, either: Control (C): 5% dextrose + 0.45% NaCl; C + 200 or 500 microM H(2)O(2); C + 500 microM H(2)O(2) + 10 microM GSSG; [C + 1% MVP +/- [amino acids + lipids]] +/- photoprotected. After 4 d, levels of pulmonary alpha1(I) procollagen mRNA and glutathione were determined. Results were compared by ANOVA.

RESULTS

Photoprotection of MVP or TPN prevents light induction of procollagen mRNA. The effect of MVP + light was associated with a peroxide load coupled with a low glutathione level. This was also observed with the 500 microM H(2)O(2) group. The addition of GSSG prevented the increase of procollagen mRNA caused by H(2)O(2).

CONCLUSION

An oxidant stress caused by the infusion of peroxides in an organism with a weak antiperoxide capacity induces the transcription of the gene encoding for procollagen alpha1(I). The results confirm the antiperoxide activity of lung glutathione. Parenteral nutrition could be a clinical condition favoring the initiation of lung fibrosis, especially in premature newborn infants who have low glutathione levels.

Multivitamin solutions for enteral supplementation: a source of peroxides

OBJECTIVE

We investigated whether solutions of enteral vitamin supplementation are involved in the generation of peroxides and whether that contamination is biologically significant.

METHODS

Peroxide contents of oral multivitamin preparations were measured over 3 wk after the initial opening of the containers. In selected premature infants (younger than 35 wk gestation), urinary peroxides were measured after initiating oral multivitamin supplementation.

RESULTS

Peroxides in multivitamin solutions for enteral use are predominantly organic peroxides because they resist catalase. After the initial opening of the containers, there was a two-fold increase in total peroxides levels (P < 0.05) even in the preparation without riboflavin, a catalyst for the generation of peroxides. Initiation of oral vitamin supplementation was associated with increased (P < 0.05) urine peroxide levels. The high organic peroxide load did not correlate with its urinary excretion, mostly in the form of H(2)O(2). The excretion of H(2)O(2) corresponded to its oral intake from the multivitamin solution.

CONCLUSIONS

Compared with parenteral multivitamin solutions, the enteral preparations contained higher organic peroxide levels starting with the initial opening of the bottles. The increased urinary excretion of H(2)O(2) after enteral multivitamin supplementation suggested a systemic diffusion of peroxides or of components of the multivitamin preparation responsible for the generation of peroxides. This oxidant load was not quenched by the immature antioxidant defenses of premature infants.

Antioxidants as therapy in the newborn: some words of caution

Reactive oxygen and nitrogen species are considered to play a major role in the pathogenesis of a wide range of human disorders. This may be a particularly important pathogenetic mechanism in the newborn nursery. The phrase "oxygen radical disease of prematurity" has been coined to collectively describe a wide range of neonatal disorders based on the belief that premature newborns are deficient in antioxidant defenses at a time when they are subjected to acute and chronic oxidant stresses. This belief has led to a number of clinical trials of antioxidant therapies being undertaken in neonatal patients. The realization that reactive oxygen species play a critical role in neonatal illnesses has only recently been paralleled by an increased understanding of their physiologic roles. A major concern is that effective scavenging of reactive oxygen species, to attenuate their toxic effects, will also inhibit essential cellular functions such as growth in potential target organs such as lung, brain, intestine, and retina.

Gender difference in cytoprotection induced by estrogen on female and male bovine aortic endothelial cells

Before menopause, women have a lower risk of cardiovascular diseases than men. Studies attribute this gender difference to estrogenic protection in the female cardiovascular system. We have demonstrated that 17beta-estradiol (E2) protects female bovine aortic endothelial cells against oxidative injury, probably through the induction of antioxidant enzyme activities. In this study, we examined whether E2 confers a differential protection on male and female cells. Bovine aortic endothelial cells from both genders were preconditioned for 24 h with E2 (1 nM to 10 microM), and their resistance to paraquat (1 mM, 3 h), a superoxide generator, was measured using an MTT assay. In contrast to the protection observed in female bovine aortic endothelial cells, there was no protective effect by E2 on male bovine aortic endothelial cells at physiologic concentrations. However, E2 at 1-10 microM attenuated paraquat's toxicity in both male and female cells, probably through its direct antioxidant activity. E2 at 1 nM increased in female, but not in male, cells the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, which was associated with decreased levels of reactive oxygen species during subsequent paraquat exposure. This suggests that antioxidant enzyme induction plays some role in E2-augmented oxidative resistance in female endothelial cells.

Photoprotection of solutions of parenteral nutrition decreases the infused load as well as the urinary excretion of peroxides in premature infants

Light exposure and multivitamins are contributing factors to the generation of peroxides in solutions of parenteral nutrition. This article verifies if peroxides infused with parenteral nutrition are of biological significance in neonates. The mechanisms responsible for the generation of peroxides in total parenteral nutrition solutions are reviewed. The consequences of infused peroxides on an index of oxidant stress and on levels of a central antioxidant are evaluated in an animal model. The effect of photoprotection of parenteral nutrition on a biological marker of redox imbalance is evaluated in the urine of premature infants. Parenteral multivitamins produce a drop in glutathione and an oxidant stress similar to peroxides in the lungs of newborn guinea pigs. Infused peroxides elicited an increased urinary peroxide excretion in infants receiving parenteral nutrition exposed to light. Photoprotection reduced levels of infused and excreted peroxides. The results suggest that peroxides infused with total parenteral nutrition are not fully quenched by premature infants.

Parenteral multivitamin supplementation induces both oxidant and antioxidant responses in the liver of newborn guinea pigs

BACKGROUND

The multivitamin solution is a major component of photo-induced generation of peroxides in parenteral nutrition. The aim of this study was to determine whether the parenteral multivitamin preparation induces in the liver a peroxide-induced oxidant challenge or an antioxidant protection associated with the antiradical components of the solution.

METHODS

Newborn guinea pigs were infused with dextrose supplemented with peroxides (250 micromol/L H2O2 or 350 micromol/L tert-butylhydroperoxide) or with a multivitamin preparation (MVP, 1% vol/vol). After 4 days, total glutathione and a free radical-sensitive eicosanoid marker (prostaglandin I2 [PGI2]/total prostaglandins) were measured in livers.

RESULTS

There was a significant decrease in the PGI2/total prostaglandin ratio (mean +/- SEM) [dextrose: 0.068 +/- 0.007 vs. (dextrose + H2O2: 0.048 +/- 0.001, dextrose + TBH: 0.043 +/- 0.001)] and glutathione concentrations decreased [dextrose: 55 +/- 7 vs. (dextrose + H2O2: 37 +/- 7, dextrose + TBH: 18 +/- 7 nmol/mg protein)] after infusion of peroxides. Despite the peroxide load in the multivitamin solution, it did not alter the measured variables as prostanoid ratio remained at control concentrations (dextrose: 0.066 +/- 0.008 vs. dextrose + MVP: 0.065 +/- 0.006), as did glutathione levels (dextrose: 52 +/- 6 vs. dextrose + MVP: 45 +/- 7 nmol/mg prot).

CONCLUSION

In the liver of guinea pig pups, infused peroxides cause oxidation of membrane-derived prostanoids. The decrease in glutathione in response to administration of peroxides suggests consumption rather than a response to a free radical attack. Despite the oxidant load associated with peroxides generated in MVP, the multivitamin preparation protected membranes as the prostanoid ratio, and glutathione levels remained at control levels.

Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation

The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H(2)O(2) (0,250,500 microM) or multivitamins (0,1%), as well as parenteral nutrition supplemented with multivitamins (0,1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.

Thiol-based antioxidants

The thiol redox status of intracellular and extracellular compartments is critical in the determination of protein structure, regulation of enzyme activity, and control of transcription factor activity and binding. Thiol antioxidants act through a variety of mechanisms, including (1) as components of the general thiol/disulfide redox buffer, (2) as metal chelators, (3) as radical quenchers, (4) as substrates for specific redox reactions (GSH), and (5) as specific reductants of individual protein disulfate bonds (thioredoxin). The composition and redox status of the available thiols in a given compartment is highly variable and must play a part in determining the metabolic activity of each compartment. It is generally beneficial to increase the availability of specific antioxidants under conditions of oxidant stress. Cells have devised a number of mechanisms to promote increased intracellular levels of thiols such as GSH and thioredoxin in response to a wide variety of stresses. Exogenous thiols have been used successfully to increase cell and tissue thiol levels in cell cultures, in animal models, and in humans. Increased levels of GSH and other thiols have been associated with increased tolerance to oxidant stresses in all of these systems and in some cases, with disease prevention or treatment in humans. A wide variety of thiol-related compounds have been used for these purposes. These include thiols such as GSH and its derivatives, cysteine and NAC, dithiols such as lipoic acid, which is reduced to the thiol form intracellularly, and "prothiol" compounds such as OTC, which are enzymatically converted to free thiols within the cell. In choosing a thiol for a specific function (e.g., protection of lung from oxidant exposure or protection of organs from ischemia reperfusion injury), the global effects must also be considered. For example, large increases in free thiols in the circulation are associated with toxic effects. These effects may be the result of thiyl radical-mediated reactions but could also be due to destabilizing effects of increases in thiol/disulfide ratios in the plasma, which normally is in a more oxidized state than intracellular compartments. Changes in the thiol redox gradient across cells could also adversely affect any transport or cell signaling processes, which are dependent on formation and rupture of disulfide linkages in membrane proteins. Therapeutic thiol administration has been shown to have great potential, and its efficacy should be increased by selecting compounds and methods of delivery that will minimize perturbations in the thiol status of regions external to the targeted areas.

Expression of gamma-glutamylcysteine synthetase during development

Prematurity has been associated with low glutathione (GSH) concentrations in bronchoalveolar lavage fluid as well as in leukocytes from tracheal aspirates and peripheral blood. To elucidate whether this is caused by deficient GSH synthesis, the expression and activity of gamma-glutamylcysteine synthetase (glutamate-cysteine ligase, GCS, EC 6.3.2.2), the rate-limiting enzyme for GSH synthesis, were measured from fetal, neonatal, and adult human liver, lung, and kidney samples. The highest activity was measured in the liver, in which mRNA expression of the catalytic GCS heavy and the regulatory light subunits, as well as activity, were, on average, similar in the various stages of development. Although GCS light subunit mRNA concentrations in the lung were higher in neonates than in fetuses and adults, enzyme activities were similar. In the adult kidney, mean enzyme activity was somewhat higher than in fetal or neonatal kidney, but this may be accounted for by the variation in the small number of samples. In conclusion, GCS is expressed and active already in the second trimester and thus low GSH concentrations found in preterm neonates appear not to be explained by deficient GSH synthesis. Other factors, such as limited availability of the GSH precursor cysteine or increased GSH consumption, may account for the lower concentrations of GSH found in preterm infants.

Survival of guinea pig pups in hyperoxia is improved by enhanced nutritional substrate availability for glutathione production

The imbalance between high oxidant loads and immature antioxidant defenses is associated with long-term complications of prematurity. Glutathione is a central element among the antioxidants. Depletion of pulmonary glutathione accelerates the development of oxygen-induced lung injury in neonatal animal models. After the observation that newborn infants exposed to oxygen have low glutathione levels, a study was designed to test the hypothesis that in neonates from a species susceptible to oxygen toxicity, the lethal effect of hyperoxia is related to a low availability of substrates for glutathione production rather than an impairment in synthetic activity. One-day-old guinea pigs, randomly assigned to room air or oxygen (>95%), were fed by their mothers (n = 16) or i.v. by dextrose (n = 14) or by total parenteral nutrition (TPN, n = 20). After 3 d, glutathione and activities of enzymes involved in maintaining intracellular glutathione levels were determined in lungs and liver. The lethal effect of oxygen (p < 0.05) observed in animals without TPN was not related to glutathione depletion, as oxygen induced a 33% increase in lung glutathione, positively correlated (r2 = 0.35) with enhanced synthesis. With TPN, the animals were protected against the lethal effects of hyperoxia and lung glutathione increased by 67% in oxygen. The results suggest that the glutathione demand by the lungs in the presence of an oxidant stimulus was met by the increased (p < 0.001) hepatic production supported by TPN. Under hyperoxic conditions, early nutritional support is of vital importance.

Protecting solutions of parenteral nutrition from peroxidation

BACKGROUND

Light exposure induces the generation of peroxides in solutions of total parenteral nutrition (TPN). Peroxide toxicity has been documented in cell, in tissue, and in isolated organs. To decrease the infused peroxide load and to protect the quality of the parenteral nutrients, we tested the photoprotective properties of different infusion sets.

METHODS

Solutions of fat-free TPN and all-in-one total nutrient admixture (TNA) were run through sets of bags (clear and covered) and tubings (clear and colored: black, orange, and yellow) offering different levels of protection against light. Peroxide levels were determined by ferrous oxidation of xylenol orange, thiol functions by the 5,5,-dithiobis(2-nitrobenzoic acid) technique, and absorbance of tubings by spectroscopy.

RESULTS

Protection of only the bag had little effect on peroxide generation. In fat-free TPN solutions kept in covered bags, peroxide concentrations were 1.5 to 2 times higher when run through clear compared with colored tubings. When exposed to phototherapy or in the presence of lipids, peroxides were two to three times higher with the clear compared with the black tubing; meanwhile, orange and yellow tubings offered varying levels of protection related to their light-absorbing properties. Colored tubings offered a greater protection against the disappearance of thiol functions.

CONCLUSIONS

Covering bags and using orange and yellow tubings may be a practical solution to reduce infused peroxide loads from about 400 to 100 microM. This is especially relevant in patients with an immature or a compromised antioxidant capacity or when phototherapy or preparations of TNA are used.

Gender-specific frequency of background somatic mutations at the hypoxanthine phosphoribosyltransferase locus in cord blood T lymphocytes from preterm newborns

Limited information is available regarding the frequency, spectrum, and clinical relevance of somatic mutations in the developing fetus. The goal of this study was to determine somatic mutant frequencies (Mfs) at the hypoxanthine phosphoribosyltransferase (HPRT) reporter gene in cord blood T lymphocytes from preterm infants to gain insight into in utero mutational events. Mf determinations were made by using the HPRT T cell cloning assay on cord blood samples from 52 preterm infants. Natural logarithm Mfs (lnMfs) from preterm infants were compared with results from our database for full-term infants. Our analysis revealed higher lnMfs in cord blood T lymphocytes from preterm compared with full-term infants (P = 0.008). In addition, preterm females had significantly higher lnMfs compared with full-term females (P < 0.001), whereas preterm males were found to have significantly lower lnMfs than preterm females (P = 0.005). Regression analyses also demonstrate a significant relationship between lnMf and gestational age for preterm females that does not exist for preterm males. These results demonstrate the gender-specific association between Mf and age in humans.

Genomic imprinting of the X chromosome: a novel mechanism for the evolution of sexual dimorphism

Genomic imprinting is the differential marking of maternally and paternally inherited alleles of specific genes or chromosome regions during gametogenesis. The imprint silences the allele from 1 parent. A number of imprinted genes that are expressed in the brain have been identified in humans. They control the actions of other genes or regulate their products. Sexual dimorphism in the vertebrate brain is conventionally thought to be due to the epigenetic action of gonadal hormones. Sex differences could also reflect the actions of an imprinted X-linked locus. Until very recently no imprinted gene had been described on the X chromosome in humans. Here the implications of such a mechanism for the evolution of sexual dimorphism are discussed.

Paradoxical role of ascorbic acid and riboflavin in solutions of total parenteral nutrition: implication in photoinduced peroxide generation

In the presence of light, a multivitamin preparation is the main source of peroxides in solutions of total parenteral nutrition (TPN). This preparation contains two photosensitive products, 5'-phosphate flavin mononucleotide (FMN) and polysorbates (PS), as well as electron donors such as ascorbate (AH). We hypothesized that the admixture of FMN or PS with electron donors generates peroxides in TPN and alters the quality of nutrients. Using xylenol orange, peroxide concentrations were measured in solutions containing AH, FMN, and/or PS in water, a dextrose solution, an amino acid preparation, and a lipid emulsion. Thiol functions were evaluated by reduction of 5,5-dithiobis(2-nitrobenzoic acid) in the amino acid preparation. After 24-h light exposure, dextrose solutions with admixtures of AH + FMN or AH + FMN + PS generated peroxides at concentrations similar to those observed in a 1% multivitamin solution, and over three times higher than those observed with FMN, PS, or AH alone. However, in the presence of amino acids, FMN alone induced a generation of peroxides comparable to that observed with FMN + AH. In the lipid emulsion, peroxides increased over 3-fold in the presence of FMN or FMN + AH. The addition of catalase suggested that lipid peroxides and H2O2 were produced, and the loss of thiol function suggested that an oxidation of amino acids occurred. When exposed to light, FMN induces reactions with amino acids, polyunsaturated fatty acids, and even AH, altering the quality of nutrients. Paradoxically, AH without FMN has a protective effect on peroxide generation in TPN.