Glutathione and neonatal lung disease

Concentrations of thioredoxin, a redox-regulating protein, in umbilical cord blood and breast milk

Growing evidence indicates that oxidative stress occurs during the fetal-to-neonatal transition. Such stress plays an important role in the pathogenesis of many neonatal diseases. Thioredoxin (TRX), a redox-regulating protein with antioxidant activity, is induced in various cells against oxidative stress and is secreted extracellularly. This study was undertaken to examine the clinical and biological importance of TRX in the perinatal setting. We measured concentrations of TRX in umbilical cord blood and breast milk using a sandwich ELISA. Our study demonstrated that concentrations of TRX in umbilical cord blood were six to seven times higher than those in blood of healthy adults. This study also showed that umbilical concentrations of TRX were correlated significantly with the extent of prematurity of the newborn, and that they were elevated significantly in newborns of mothers with preeclampsia compared to those of mothers without preeclampsia. In contrast, concentrations of coenzyme Q(10) and vitamin E in umbilical blood were lower than adult blood levels. Breast milk concentrations of TRX during the early postpartum period were seven to eight times higher than those in blood of lactating women. Those of the coenzyme Q(10) were lower than adult blood levels, while those of vitamin E were comparable to adult blood levels. Our findings suggest that the systemic release of TRX is enhanced at birth, and that early breast milk is a rich source of this protein. Consequent high levels of TRX in newborns may provide a unique protective mechanism that allows the maintenance of redox balance during the fetal-to-neonatal transition.

Is there a causal relationship between the receipt of blood transfusions and the development of chronic lung disease of prematurity?

The number and total volume of blood transfusions received by premature babies is, after gestational age and birth weight a good predictor of the likelihood of developing chronic lung disease of prematurity (CLD) and retinopathy of prematurity (ROP). Oxidative damage, inflammation and pulmonary infections are also strongly associated with the development of CLD. It is currently not clear whether there is a causal relationship between the receipt of blood transfusions and oxidative damage, infection, inflammation and CLD in these babies. Strong arguments may be made both for and against a causal relationship. The babies who receive blood transfusions are usually smaller than those who do not, and are ventilated, often with high oxygen levels, for a longer period of time. The longer the baby is on a ventilator the more likely it is to develop pulmonary infection and inflammation. All these factors will promote free radical production and oxidative damage irrespective of the receipt of blood transfusion. This would argue against a causal relationship. On the other hand, an argument may be presented which is based on iron promoted free radical generation, infection and fibrosis consequent to the breakdown of haeme released from transfused erythrocytes. Haeme is broken down by haeme oxygenase (HO) to iron, CO and bilirubin. Under normal circumstances the products of HO activity are beneficial to the organism, but when HO activity is excessive, the products are potentially damaging. Free iron, (in the Fe2+ form) if not sequestered with protein or urate, will generate highly toxic free radicals via the Fenton and Heber-Wiess reactions, predispose the tissue to infection and promote fibrosis. The iron chelating ability of the premature baby appears to be limited so that it would be difficult to deal with any increase in free iron production. Free iron will in turn induce HO activity leading to a potentially serious positive feedback process. The lung is particularly sensitive to iron induced HO activity. In addition, HO activity may be enhanced by other events occurring in the premature lung such as the production of proinflammatory cytokines and the reduced level of glutathione. Thus, the possibility of a causal relationship clearly exists and needs to be examined. This can be attempted by measuring the products of HO activity in relation to the receipt of blood transfusions.

Pulmonary antioxidant concentrations and oxidative damage in ventilated premature babies

OBJECTIVE

To determine the relation between lipid peroxidation and the antioxidants ascorbate, urate, and glutathione in epithelial lining fluid in ventilated premature babies, and to relate the biochemical findings to clinical outcome.

DESIGN

A cohort study conducted between January 1999 and June 2001.

SETTING

A NHS neonatal intensive care unit.

PATIENTS

An opportunity sample of 43 ventilated babies of less than 32 weeks gestation.

MAIN OUTCOME MEASURES

The duration of supplementary oxygen according to the definition of bronchopulmonary dysplasia (BPD; oxygen dependency at 36 weeks gestational age).

METHODS

Epithelial lining fluid was sampled by bronchoalveolar lavage. Ascorbate, urate, glutathione, and malondialdehyde (a marker of lipid peroxidation) were measured.

RESULTS

Babies who developed BPD had significantly lower initial glutathione concentrations (mean (SEM) 1.89 (0.62) v 10.76 (2.79) microM; p = 0.043) and higher malondialdehyde concentrations (mean (SEM) 1.3 (0.31) v 0.345 (0.09) microM; p < 0.05) in the epithelial lining fluid than those who were not oxygen dependent. These variables were poor predictors of the development of BPD. Gestational age, endotracheal infection, and septicaemia had good predictive power. The level of oxidative damage was associated with the presence of endotracheal infection/septicaemia rather than inspired oxygen concentration.

CONCLUSIONS

Endotracheal infection, septicaemia, and gestational age, rather than antioxidant concentrations, are the most powerful predictors of the development of BPD.

Oxidative stress in neonates: Evaluation using specific biomarkers

Increased oxidative stress has been implicated in pathogenesis of serious diseases in neonates. We measured urinary levels of 8-hydroxy-2'-deoxyguanosine (a marker of oxidative DNA damage), acrolein-lysine adduct (a marker of lipid peroxidation and oxidative protein damage), and nitrite/nitrate (a marker of endogenous nitric oxide formation) in one-month-old neonates to examine the status of oxidative stress and its relationship to the degree of prematurity and clinical condition in neonates. Study subjects comprised three groups: healthy term neonates, clinically stable preterm neonates requiring no supplemental oxygen, and clinically sick preterm neonates requiring supplemental oxygen and ventilator support. Urinary levels of 8-hydroxy-2'-deoxyguanosine and acrolein-lysine adduct were significantly higher in sick preterm neonates than those of stable preterm and healthy term neonates. In the sick preterm group, neonates developing active retinopathy showed significantly higher levels of acrolein-lysine adduct than the other neonates without retinopathy. There were no significant differences in both urinary markers of oxidative stress between stable preterm and healthy term neonates. The urinary nitrite/nitrate levels were not significantly different among the three groups, suggesting no difference in endogenous nitric oxide formation. Collectively, these results provide evidence of augmentation of oxidative damage to DNA, lipids and proteins, especially in clinically sick preterm neonates.

Role of glutathione redox dysfunction in diabetic wounds

We propose that diabetic foot ulcers and diabetic mouse wounds have insufficient glutathione to maintain correct cellular redox potential. Therefore, tissue samples from the wound edge of diabetic foot ulcers, diabetic mice wounds and nondiabetic mice wounds were obtained. Levels of glutathione, cysteine, and mixed protein disulfide were determined and topical application of esterified glutathione in carboxymethylcellulose or carboxymethylcellulose alone was applied to the mice wounds. Diabetic foot ulcer mean glutathione levels were 150.6 pmol/mg in the controls and 53.4 pmol/mg at the wound edge (p < 0.05), while mean cysteine levels were 22.3 pmol/mg in the control and 10.5 pmol/mg at the wound edge (p < 0.05). The mixed protein disulfide levels were elevated in the wounds (14.6 pmol/mg), but not in the control (6.9 pmol/mg) (p < 0.05). The glutathione levels were lower in the diabetic mouse wounds (155 pmol/mg) than the nondiabetic mouse wounds (205 pmol/mg) (p=0.04). The diabetic mouse treated with carboxymethylcellulose alone healed slower (19.5 +/- 2.2 days) than the nondiabetic mouse DM (11.5 +/- 0.5 days) (p < 0.001). The diabetic mouse that received topical glutathione healed significantly faster (12.5 +/- 0.8 days) than the carboxymethylcellulose-treated mice (19.5 +/- 2.2 days) (p < 0.001). Glutathione levels in the diabetic mouse (26.0 pmol/mg) were lower than in the nondiabetic mouse (311.7 pmol/mg) (p < 0.05) after glutathione treatment. In the glutathione-treated diabetic mouse, the oxidized glutathione was higher (26.7%) than in the nondiabetic mouse (9.9%) (p=0.05). These data suggest that cellular redox dysfunction and lower glutathione levels are present in diabetic foot ulcers and diabetic mouse wounds.

Glutathione and glutathione-related enzymes in reproduction. A review

Glutathione and glutathione-related enzymes are pivotal for the normal functioning of several important biological processes in humans. Glutathione and glutathione-related enzymes are involved in the metabolism and detoxification of cytotoxic and carcinogenic compounds as well as reactive oxygen species. The role of reactive oxygen species in reproduction was the subject of many investigations, and there is compelling evidence for the involvement of these species in the physiology and pathology of both male and female reproductive systems. The glutathione/glutathione-related enzyme system was extensively studied in gynaecological oncology, but to a lesser extent in other topics related to reproduction. In this paper a review is provided on the glutathione/glutathione-related enzyme system in reproduction. Attention is given to its role as a detoxicating system, and as an early marker for disease.