Possible role of uric acid as an antioxidant in premature infants

Antioxidant status of neonates exposed in utero to tobacco smoke

To investigate the influence of maternal smoke exposure on neonatal and maternal antioxidant status, 39 mothers who were active smokers, 14 mothers exposed to environmental tobacco smoke (ETS), 17 controls, and their newborns were included in a prospective, controlled study. Plasma total antioxidant capacity, measured as total radical-trapping antioxidant parameter (TRAP) and ferric reducing antioxidant power (FRAP), and concentrations of specific antioxidants were measured in cord and in maternal blood. A similar, significant increase in ceruloplasmin concentration was observed in neonates born to actively smoking mothers and in those born to ETS exposed mothers. Uric acid and TRAP concentrations were significantly increased in ETS-exposed newborns and their mothers, compared to newborns and mothers from the active smoking and no-exposure groups with a trend towards increased uric acid, TRAP and FRAP concentrations being observed in the active smokers group. Neonatal and maternal antioxidant concentrations correlated significantly, except for ceruloplasmin. Cord blood vitamin A, E and C concentrations were unaffected by smoke exposure. These results show that maternal active smoking as well as ETS exposure significantly affect neonatal and maternal antioxidant status.

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.

No clinical correlation between bilirubin levels and severity of retinopathy of prematurity

PURPOSE

To evaluate the hypothesis that bilirubin has a protective effect against the development of severe retinopathy of prematurity (ROP).

METHODS

An assessment of 76 infants born at 24 and 25 weeks' gestation and admitted to the level III neonatal intensive care unit at Saitama Children's Medical Center was made. Indirect ophthalmoscopy fundus examinations were performed on all infants to identify the degree and progression to threshold ROP. We analyzed the daily bilirubin levels and grouped the patients according to the severity of ROP based on the infant's worst ROP examination. The first group was comprised of infants with less than stage 3 ROP and infants with stage 3 ROP. The second group was infants with less than prethreshold ROP or prethreshold ROP, and infants with threshold ROP. Next, we divided the infants into 3 groups: less than prethreshold ROP, prethreshold ROP, and threshold ROP. The daily changes in serum bilirubin concentrations during the first 14 days of life were determined for each infant. Three groups (less than prethreshold ROP, prethreshold ROP, and threshold ROP) were comparable as to their basic data, clinical characteristics, and treatments.

RESULTS

ROP was found in 76 infants. There were no statistical differences in the clinical characteristics and treatments, excluding the duration of phototherapy, among the 3 groups. During the first 14 days of age, there were no significant differences in the daily mean bilirubin concentrations according to the groups separated by severity of ROP.

CONCLUSION

These results indicate that there is no distinct protective effect of bilirubin on the development of severe ROP.

Oxidative stress in lavage fluid of preterm infants at risk of chronic lung disease

There is evidence that oxidative stress plays a role in the development of chronic lung disease (CLD), with immature lungs being particularly sensitive to the injurious effect of oxygen and mechanical ventilation. We analyzed total ascorbate, urate, and protein carbonyls in 102 bronchoalveolar lavage fluid samples from 38 babies (33 preterm, 24-36 wk gestation; 5 term, 37-39 wk gestation). Preterm babies had significantly decreasing concentrations of ascorbate, urate, and protein carbonyls during the first 9 days of life (days 1-3, 4-6, and 7-9, Kruskal-Wallis ANOVA: P = 0.016, P < 0.0001, and P = 0.010, respectively). Preterm babies had significantly higher protein carbonyl concentrations at days 1-3 and 4-6 (P = 0.005 and P = 0.044) compared with term babies. Very preterm babies (24-28 wk gestation) had increased concentrations of protein carbonyls at days 4-6 (P = 0.056) and significantly decreased ascorbate concentrations at days 4-6 (P = 0.004) compared with preterm babies (29-36 wk gestation). Urate concentrations were significantly elevated at days 1-3 (P = 0.023) in preterm babies who subsequently developed CLD. This study has shown the presence of oxidative stress in the lungs of preterm babies during ventilation, especially in those who subsequently developed CLD.

Detection of hepatic oxidative DNA damage in patients with hepatoblastoma and children with non-neoplastic disease

BACKGROUND

The authors have revealed a significant association between hepatoblastoma and low birth weight. This study was done to explore the evidence that liver cells were oxidatively damaged, based on the hypothesis that oxidative damage to DNA is involved in the development of hepatoblastoma in children of low birth weight.

PROCEDURE

Oxidative DNA damage in the liver was examined by immunohistochemically detecting the presence of a DNA repair product, 8-hydroxy-2'-deoxyguanosine (8-OHdG), in five patients with hepatoblastoma and 14 children with non-neoplastic disease.

RESULTS

Positive staining for 8-OHdG was observed in all five patients with hepatoblastoma. Distribution of 8-OHdG positivity was diffuse in the intralobular area in one patient and was restricted to the periportal area of the lobules in four patients. There was no apparent correlation between birth weight of the patients, histological findings in the liver, and the distribution of 8-OHdG positivity. In children with non-neoplastic disease, 8-OHdG was detected in nine of 14 patients, and 8-OHdG was positive in the intralobular area of the liver parenchyma except in one patient.

CONCLUSIONS

These results suggest that the cause of oxidative DNA damage in patients with hepatoblastoma may be different from the cause, extensive parenchymal damage to the liver, in children with non-neoplastic disease, but the 8-OHdG formation is not specific to hepatoblastoma patients of low birth weight. Further studies to elucidate the true reason for the high incidence of hepatoblastoma in children of low birth weight are necessary.

Oxidative stress and increased type-IV collagenase levels in bronchoalveolar lavage fluid from newborn babies

Oxidative stress may increase lung permeability by up-regulation of matrix-metalloproteinase-9 (MMP-9), a type-IV collagenase that can disrupt alveolar basement membranes. We have compared a marker of oxidative stress (protein carbonyl residues) with levels of MMP-9 and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), in bronchoalveolar lavage samples from newborn babies. Bronchoalveolar lavage samples (n = 87, two from each time point) were taken in the first 6 postnatal days from 41 ventilated babies: 18 of <29 wk gestation, 10 of 29-36 wk, 9 term with persistent fetal circulation, and 4 term without lung disease. Respiratory disease severity at the time of bronchoalveolar lavage was assessed using the arterial-alveolar oxygen tension ratio. One sample from each time point was used for the measurement of MMP-9 by zymography and TIMP-1 by ELISA. The second sample was used to measure carbonyl group concentrations, also using an ELISA. Correlations were calculated between protein carbonyls, arterial-alveolar oxygen tension ratio, and MMP-9 and TIMP-1 concentrations. Significant correlations were found between carbonyl concentrations and arterial-alveolar oxygen tension ratio (r = -0.325, p = 0.0031, n = 81), MMP-9 (r = 0.331, p < 0.0029, n = 79), and TIMP-1 (r = 0.436, p < 0.0001, n = 87). Worsening respiratory disease in newborn babies is associated with increased carbonyl concentrations in neonatal bronchoalveolar lavage fluid, and these correlated with MMP-9 and TIMP-1 levels. Increased oxidative stress may damage the lung by increasing type-IV collagenase activity, causing disruption of the extracellular matrix.

Case-control study of perinatal factors and hepatoblastoma in children with an extremely low birthweight

BACKGROUND

There is a significant association between hepatoblastoma and low birthweight. A case-control study was conducted to reveal risk factors for hepatoblastoma in children of extremely low birthweight (< 1,000 g).

METHODS

Prenatal and postnatal histories, including parental histories, of 12 hepatoblastoma cases and 75 birthweight-matched controls were compared.

RESULTS

The gestational age of the hepatoblastoma cases (23-32 weeks: median 25 weeks), tended to be lower than that of the controls (23-36 weeks; median, 27 weeks; P = 0.072). The time for an infant's bodyweight to return to the same level as the birthweight also tended to be longer in hepatoblastoma cases than in controls (P = 0.055). All hepatoblastoma cases received oxygen therapy for a period of 4-508 days (median 114 days), which was significantly longer than the 0-366 days (median 62 days) in the controls (P = 0.022). Furosemide was given to all hepatoblastoma cases and was used for a significantly longer period in these infants (6460 days; median 89 days) than in the controls (0-241 days; median 44 days P = 0.027). A univariate Cox regression demonstrated that the time taken to regain bodyweight at birth and the duration of both oxygen therapy and furosemide treatment were significantly associated with the development of hepatoblastoma (hazard ratio (HR)= 1.044, P= 0.013; HR = 1.006, P= 0.001; and HR = 1.007, P= 0.001, respectively). Although there were significant correlations between the factors, a multivariate Cox regression analysis identified the duration of oxygen therapy as a significant independent risk factor (HR = 1.006, P = 0.001).

CONCLUSIONS

Oxygen therapy and furosemide treatment, along with the rate of growth, are risk factors for the development of hepatoblastoma in children of extremely low birthweight, and the duration of oxygen therapy is the most important factor in predicting the development of hepatoblastoma. Further studies are necessary to determine the real reasons for the development of hepatoblastoma and to protect children of low birthweight from the development of cancer.