Recycling of Glutathione during Oxidative Stress in Erythrocytes of the Newborn

Abstract

ABSTRAO. The ability of erythrocytes from newborn babies and adults to maintain reduced glutathione levels during oxidative stress was studied. In vitro incubation of erythrocytes with H202, with or without inactivation of catalase, caused a rapid depletion of reduced glutathione (CSH) and concomitant accumulation of oxidized glutathione followed by recovery of CSH and fall of oxidized glutathione to initial values in all subjects. In vitro and in vivo studies have shown that the erythrocytes of adult animals can protect other tissues, e.g. lung, against damage induced by reactive oxygen species (1). Erythrocytes can catabolize an H202 load produced by leukocytes (2) and have been shown to protect both cultured pulmonary endothelial cells (3) and the whole lung (4, 5) from oxidative damage. The action of catalase and the glutathione recycling system is believed to be the key factor in this protective mechanism (1).The preterm baby has poorly developed antioxidant enzyme systems in various organs, e.g. lung, and is susceptible to oxygeninduced tissue damage, e.g. bronchopulmonary dysplasia (6, 7). Thus, the ability of the erythrocyte to catabolize H202 may be of particular importance in these patients. The ability of the erythrocyte to handle oxidative stress induced by H202 can be assessed in vitro by serially measuring the initial fall of GSH and the concomitant rise of GSSG and the subsequent recovery of GSH and fall of GSSG to initial values. Glutathione recycling has already been used to assess the antioxidant capacity of erythrocytes of adults (8) and cell cultures (9, 10). We compared glutathione recycling during exposure to H202 in erythrocytes of newborn babies and adults. The erythrocyte activities of enzymes responsible for H202 catabolism, i.e. catalase, glutathione peroxidase, and glutathione reductase, were also measured. MATERIALS AND METHODSThis study was approved by the Scientific Committee of the Department of Pediatrics and the Ethical Committee of the University Hospital of Leiden.Patients. Umbilical cord blood samples were obtained from eight preterm and nine term infants (gestational age [mean (SD)] 32.9 (2.4) and 40.2 (1.5) wk, respectively) within 15 min after delivery of the placenta. The babies were of normal birth weight (10th-90th percentile) and showed no signs of birth asphyxia (Apgar score 1 min r 9, umbilical vein pH r 7.25), respiratory distress, or infection. Their mothers, healthy Caucasian nonsmokers (3), did not receive vitamin or iron supplements. Venous blood samples were taken from 10 healthy Caucasian volunteers (age [mean (SD)] 24.9 (2.4) y), who were nonsmokers.From an additional group of 10 healthy term infants (gestational age [mean (SD) 40.6 (1.4) wk, other characteristics as above) umbilical cord blood samples were obtained to study in vitro the influence of the hematocrit on glutathione recycling.Procedure. Blood was gently withdrawn ( 1.1 -mm diameter needle) into heparinized tubes and immediately centrifuged (750 x g, 10 min). Plasma and buffy coat were discarded ...

Glutathione Recycling and Antioxidant Enzyme Activities in Erythrocytes of Term and Preterm Newborns at Birth

“…Though obtained with a different experimental protocol (t-BOOH instead of H 2 O 2 ), the results of GSH recycling in newborns and adults were in good agreement with those obtained by other authors [14]. Using H 2 O 2 and RBC with inhibited CAT activity, Clahsen et al [14] found a shorter GSH recovery time in preterm than in term babies. Moreover, the GSH recovery time of preterm babies was correlated with the gestational age at birth.…”

“…CAT, GPX, and SOD activities did not differ between adults and newborns (table 3). A greater GR activity in neonates than in adults has also been found by other authors [14]. CAT and GPX activities were lower in erythrocytes of newborn babies than in RBC of adults, but not statistically significantly.…”

“…The RBC are equipped for oxidative stress [4,5,[14][15][16][17]26], and the present results (tables 2, 3; fig. 1) confirm the good reducing capacity of the GSH system at birth, both in term and preterm newborns, as we previously reported [27].…”

“…GSH is the main antioxidant factor of living organisms, and RBC are characterized by a good defensive repertoire [4,5,[14][15][16][17]. However, due to sudden contact of tissues with oxygen at birth, the concentration of GSH drops sharply during the first days of life.…”

Glutathione Synthesis Rates in Early Postnatal Life

“…Therefore, the increased total GSH concentration in the late group cannot be explained by different recycling rates between the groups. Moreover, recycling of oxidized GSSG back to GSH seems to be enhanced rather than decreased in preterm infants (23,24). Consequently, the increased GSH concentration is likely to be caused by decreased consumption of GSH after early AA administration in preterm infants.…”