Preterm newborns show slower repair of oxidative damage and paternal smoking associated DNA damage.

Newborns have to cope with hypoxia during delivery and a sudden increase in oxygen at birth. Oxygen will partly be released as reactive oxygen species having the potential to cause damage to DNA and proteins. In utero, increase of most (non)-enzymatic antioxidants occurs during last weeks of gestation, making preterm neonates probably more sensitive to oxidative stress. Moreover, it has been hypothesized that oxidative stress might be the common etiological factor for certain neonatal diseases in preterm infants. The aim of this study was to assess background DNA damage; in vitro H(2)O(2) induced oxidative DNA damage and repair capacity (residual DNA damage) in peripheral blood mononucleated cells from 25 preterm newborns and their mothers. In addition, demographic data were taken into account and repair capacity of preterm was compared with full-term newborns. Multivariate linear regression analysis revealed that preterm infants from smoking fathers have higher background DNA damage levels than those from non-smoking fathers, emphasizing the risk of paternal smoking behaviour for the progeny. Significantly higher residual DNA damage found after 15-min repair in preterm children compared to their mothers and higher residual DNA damage after 2 h compared to full-term newborns suggest a slower DNA repair capacity in preterm children. In comparison with preterm infants born by caesarean delivery, preterm infants born by vaginal delivery do repair more slowly the in vitro induced oxidative DNA damage. Final impact of passive smoking and of the slower DNA repair activity of preterm infants need to be confirmed in a larger study population combining transgenerational genetic and/or epigenetic effects, antioxidant levels, genotypes, repair enzyme efficiency/levels and infant morbidity.

An aphidicolin-block nucleotide excision repair assay measuring DNA incision and repair capacity.

The objective of the present study was to develop a cellular phenotype assay for nucleotide excision repair (NER), using benzo[a]pyrene diol epoxide (BPDE) as model mutagen. Since in vitro exposure to BPDE may lead to DNA strand breaks resulting from both direct interaction with DNA and incisions introduced by the repair enzymes, we aimed to discriminate between both types of breaks using the comet assay and quantified the DNA strand breaks after in vitro challenge of peripheral blood mononucleated cells (PBMCs) with BPDE in the presence or absence of the DNA polymerase inhibitor aphidicolin (APC). The assay was performed with a low (0.5 microM) and a high (2.5 microM) BPDE concentration. The individual NER capacity was defined as the amount of DNA damage induced by BPDE in presence of APC, diminished with the damage induced by BPDE and APC alone. First, the assay was applied to a NER-deficient human fibroblast cell line (XPA-/-) to validate the methodology. Lower repair capacity and a higher amount of BPDE-induced DNA adducts were observed for the XPA-/- fibroblasts as compared to the wild-type fibroblasts. Repeated experiments on PBMCs from four donors showed low intra-individual, intra-experimental and inter-assay variation for both concentrations, indicating the reliability of the method. To assess the inter-individual variation, the assay was applied to PBMCs from 22 donors, comparing the repair capacity after exposure to 0.5 microM (N = 10) and 2.5 microM (N = 12) BPDE. The repair capacity showed a higher inter-individual variation as compared to the intra-individual variation. Moreover, this difference was more pronounced using the low concentration. All these results indicate the adequacy of the method using this low concentration. Further improvement, however, should be recommended by applying the study with low BPDE concentration in a larger population and taking into account the relevant genotypes for NER.

Vertical transmission of HIV in Belgium: a 1986-2002 retrospective analysis.

Prophylactic interventions have lead to the reduction of the mother-to-child transmission (MTCT) of human immunodeficiency virus type 1 (HIV-1) to less than 2% in industrialized countries. The aim of this study was to evaluate the changes over time in vertical transmission according to the standard care of prophylaxis in the practice of a single large reference center and to identify the risk factors for failure. The rate of MTCT decreased progressively from 10% in 1986-1993 to 4.7% in 1999-2002, reflecting the progressive implementation of newly available means of prevention. During the last period evaluated (1999-2002), where highly active antiretroviral therapy (HAART) prophylaxis was the standard of care, 17% of women had a viral load between 400 and 20,000 copies/ml around delivery and 5% had a viral load above 20,000 copies/ml. High viral load and low CD4 lymphocyte count were strongly associated with vertical transmission. The rate of MTCT in women who received HAART for more than one month during pregnancy was 1.7%, compared to 13.3% in women treated with HAART for less than one month. The risk of vertical transmission in the absence of therapy was four times higher than before the era of antiretroviral therapy (ART; p=0.05). In conclusion, since the prevention of MTCT of HIV with HAART is the standard of care, a short duration or absence of ART during pregnancy linked to late or absent prenatal care is associated with a high risk of transmission. The early detection of HIV-1 infection in pregnant women, and close follow up and support during pregnancy are crucial to the success of the prevention of transmission.

Genetic susceptibility of newborn daughters to oxidative stress.

A central question in risk assessment is whether newborns' susceptibility to mutagens is different from that of adults. Therefore we investigated whether genotype and/or the DNA strand break repair phenotype in combination with the MN assay would allow estimation of the relative sensitivity of a newborn as compared to his mother for oxidative DNA damage. We compared the in vitro genetic susceptibility for H2O2 in PBMC of 17 mother-newborn daughter pairs taking into account genotypes for relevant DNA repair (hOGG1, XRCC1, XRCC3, XPD) and folate metabolism (MTHFR) polymorphisms. After in vitro challenge with H2O2 the repair capacity was assessed by the Comet assay and chromosome/genome mutations by the cytokinesis-block MN assay. No statistically significant differences were found between mothers and their newborn daughters either for initial DNA damage or for residual DNA damage. Mothers showed higher background frequencies of MN as compared to their newborn daughters, due to the age factor. This was confirmed by significantly higher frequencies of MN observed in mothers versus newborn daughters for several genotypes. No genotype with a significant effect on DNA repair capacity in newborns was identified. Concerning MN frequencies, however, newborns carrying the variant XRCC3(241) genotype might be at higher risk for the induction of MN by oxidative stress. Multivariate analysis revealed a significant protective effect of maternal antioxidant supplementation during pregnancy against oxidative DNA damage in newborns in terms of MN frequencies. However, these conclusions might not be extrapolable to other types of DNA damage and need confirmation in a study on a larger population.

Lower nucleotide excision repair capacity in newborns compared to their mothers: a pilot study.

Recognition of the potential vulnerability of children and newborns and protection of their health is essential, especially regarding to genotoxic compounds. Benzo(a)pyrene B(a)P a commonly found carcinogen, and its metabolite BPDE, are known to cross the placenta. To investigate how well newborns are able to cope with BPDE-induced DNA damage, a recent developed nucleotide excision repair cell phenotype assay was applied in a pilot study of 25 newborn daughters and their mothers, using the Alkaline Comet Assay and taking demographic data into account. Newborns seemed to be less able to repair BPDE-induced DNA damage since lower repair capacity levels were calculated compared to their mothers although statistical significance was not reached. Assessment of repair capacity in combination with genotypes will provide important information to support preventive strategies in neonatal care and to define science based exposure limits for pregnant women and children.

The nutritional iodine supply of Belgian neonates is still insufficient.

UNLABELLED: Belgium used to be affected by mild iodine deficiency. Improvement in iodine nutrition has been recently documented in schoolchildren in Belgium in spite of the absence of any systematic programme of iodine supplementation. The question arises as to whether this 'silent iodine prophylaxis' affected also the neonates. A total of 185 random urine samples were collected from 90 full term and 65 preterm neonates in Brussels on day 5 and repeated on day 30 in 30 preterms who were bottle-fed with iodine-enriched formula-milk. The iodine content was also determined in 58 samples of breast-milk on day 5. The median urinary iodine on day 5 in full term neonates was 86 micro g/l, which is markedly higher than the figure of 48 micro g/L reported 15 years previously in neonates in the same area but still much lower than normal for this age group (150-200 micro g/l). The mean iodine content of breast-milk was 78 micro g/l, which is unchanged as compared to 15 years ago and is about 66% of normal. Finally, the median urinary iodine increased from 60 micro g/l on day 5 to 150 micro g/l on day 30 in preterms bottle-fed with iodine-enriched formula-milk. CONCLUSION: the status of iodine nutrition has also improved spontaneously in Belgian neonates but has not yet normalised. Lactating and probably pregnant women remain clearly iodine deficient. The iodine-enriched formula-milk for preterms is efficient in correcting their iodine deficiency. National measures are urgently required for correction of iodine deficiency in Belgium.