In utero exposure to lead and cord blood total IgE. Is there a connection?

BACKGROUND

Lead exposure and total immunoglobulin E (IgE) have been shown to be positively related in animals and humans even at lead levels below those recognized as toxic. In the last decades, exposure to lead has become more frequent in urban areas of industrialized as well as of developing countries where IgE-mediated allergy prevalence has also increased.

METHODS

We examined for the first time the relationship between in utero exposure to lead and cord blood total IgE in two samples of 137 and 237 mother-newborn pairs, respectively, recruited in Paris.

RESULTS

Cord blood IgE was positively related to hair lead level at birth, providing an integrated measure of long-term exposure in utero, in each cohort (Spearman's coefficient r = 0.32, P < 0.001 and r = 0.19, P < 0.01, respectively) and in the combined cohort (r = 0.21; P < 0.01). The relationship appeared to be more pronounced in newborns of nonallergic mothers (r = 0.24; P < 0.01) than in those of allergic mothers (r = 0.12). This could be due to the fact that familial history of allergy, the strongest determinant of IgE development, may overshadow the influence of lead on IgE in the offspring.

CONCLUSIONS

Our findings suggest a possible intervention of environmental exposure besides genetic factors in early life development of IgE production. Further studies are needed to confirm the finding.

[Biological materials collection within population of pregnant women at delivery]

Little is known about biochemical mechanisms associated with the normal psychomotor development of children. Many factors of the fetal environment likely interfere with these mechanisms. A prospective cohort study is essential to explain the implications of certain disturbances of biochemical nature during gestation on the later development of the nervous system. The study that we undertook with the maternity hospital Robert Debré had several objectives. The first was to examine, on an epidemiological scale, the possible role of the monoaminergic systems and the ATPases activity during the perinatal period on the later cognitive development of the child. The second was to study the influence of environmental in utero exposure on these mechanisms and consequently on the later psychomotor performances of the child. We examine here the advantages and the specific difficulties in such an approach within a population of women in childbirth.

Evolution of blood lead levels in urban French population (1979-1995)

BACKGROUND

The aim of the Council Directive of 29 March 1977 of the European Union was to measure non-occupational lead exposure levels in the general adult populations of European countries through biological monitoring. In France, such measurements were carried out during 1979 and 1982 in eight metropolitan areas (having more than 500 000 inhabitants), a period during which the lead content of petrol was decreased. The aim of this study conduct in 1995 was to evaluate the exposure trend to lead.

METHODS

In 1995 this measurement was repeated, only in the three largest urban areas (Paris, Marseilles and Lyons). The same sampling method used in the first two campaigns was retained to ensure that the results of 1995 could be compared with those from 1979 and 1982.

RESULTS

In these three metropolitan areas, the average blood lead levels decreased by the order of 60 microg/l between the beginning of the 1980's and 1995. This represents a fall of more than 50%.

CONCLUSIONS

Certainly car pollution is not the only vector of dissemination of lead in the centre of urban zones, but it is there that the most sustained efforts at eradication have been made. The improvement we have observed is probably due to the policy of eliminating lead from petrol. In conclusion, the blood lead levels in French urban populations seem to have greatly decreased from those of the early 1980s.

Cross sectional and longitudinal study on selenium, glutathione peroxidase, smoking, and occupational exposure in coal miners

OBJECTIVES

To understand the variations of selenium (Se) concentration relative to changes in occupational exposure to coal dust, taking into account age and changes in smoking habits in miners surveyed twice, in 1990 and 1994. To better understand the relation of Se concentration with glutathione peroxidase activities (GSH-Px) in these miners.

METHODS

In 1994, blood samples were obtained from active (n=131) and retired (n=40) miners without coal worker's pneumoconiosis, in whom Se concentration was available at both surveys and in whom International Labour Organisation (ILO) profusion grade had not been changed. Active miners were exposed to high dust concentrations (n=48) or low dust concentrations (n=83). Miners were classified into three subgroups according to their estimated cumulative exposure to dust, and into three subgroups according to their smoking habits.

RESULTS

Selenium concentration and GSH-Px activities were significantly lower in active than in retired miners (Se adjusted means: 62.6 v 72.2 ng/ml p=0.01). Moreover, Se concentration was lower in miners exposed to high compared with those exposed to low dust concentrations (adjusted means: 59.4 v 65.8). In miners exposed to high dust concentrations, Se concentration was significantly lower whereas erythrocyte GSH-Px activity was significantly higher in the subgroup with estimated cumulative exposure >68 mg/m(3).y. In all miners, plasma GSH-Px activity was correlated with Se concentration (r=0.22, p<0.005). The 4 year Se changes were negatively related to exposure to high dust concentrations and positively related to change in exposure from high to retirement and to change from smoker to ex-smoker (p=0.01).

CONCLUSION

The variations of Se concentration in relation to changes in occupational exposure to coal dust and in smoking habits, and the close correlation found between plasma Se concentration and GSH-Px activity suggest that both are required in antioxidant defence. These results agree well with the hypothesis that the decrease in Se concentration reflects its use against reactive oxygen species generated by exposure to coal mine dust and by smoking.

Negative relationships between erythrocyte Ca-pump activity and lead levels in mothers and newborns

Lead poisoning induces hematological, gastrointestinal and neurological dysfunctions. One of the potential mechanisms is the inhibition of calcium-pump (Ca-pump), a transport protein. We investigated the effects of an environmental low lead exposure on Ca-pump activity in 247 mothers and their newborns. Maternal and cord blood, and newborn and mother hair, were sampled at delivery. Geometric means for mother and cord blood lead (Pb-B), and for mother and newborn hair lead (Pb-H), were 6.3 and 4.8 microg/dl, and 1.7 and 1.1 microg/g. Means for mother and cord basal Ca-pump activities were 2,442 and 2,675 nM/mg/hr. Mother enzymatic activity was negatively related to her Pb-B and Pb-H and to the cord Pb-B and newborn Pb-H levels. Newborn enzymatic activity was negatively related to his Pb-H level only. Adjustment for gestational age, child's sex, mother's age at delivery, alcohol, coffee and tea consumption, and smoking habits during pregnancy did not modify these relationships. Our findings support the hypothesis that lead toxicity could be in part mediated by a reduction of Ca-pump activity. This effect could be observed at low environmental exposure, in mothers and newborns.

Neurodevelopmental evaluation of 9-month-old infants exposed to low levels of lead in utero: involvement of monoamine neurotransmitters

The objective of this work is to investigate the neurotoxicty of low-level lead exposure in utero on infants and the possible involvement of dopaminergic and serotonergic neurotransmitters. The correlation analysis for cord blood lead level, the concentrations of dopamine metabolite homovanillic acid (HVA) and serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in cord plasma and the neurodevelopmental scales of infants were conducted on 244 9-month-old children. Both score of sociability subscale and 5-HIAA concentration were correlated with cord blood lead level. The sociability score was negatively correlated with the concentration of HVA, whereas both the coordination score and the global score were negatively correlated with the concentration of 5-HIAA. With partial correlation analysis, after taking HVA into account, the significant negative correlation between the sociability score and the cord blood lead level that existed in the linear correlation analysis disappeared, and the score of global scale correlated negatively with lead level in cord blood. When taking 5-HIAA into account, the scores of all the neurodevelopmental subscales except the language subscale were significantly negatively correlated with lead level in cord blood. The results indicated that low-level lead exposure in utero could produce a neurotoxic effect on the developing serotonergic system in infants. The neurotoxicity of low-level lead exposure in utero may affect the sociability of infants. Serotonergic activity was shown to have a potential effect on neurodevelopmental assessment. It may interfere with the association between low-level lead exposure in utero and other neurodevelopmental performances of 9-month-old children.

Decrease in selenium status in relation to coal dust exposure

Selenium (Se) plasma levels were studied in 222 coal miners to assess whether selenium is decreased in relation to coal dust exposure, taking age, alcohol, and tobacco consumption into account. Selenium levels decreased significantly with age and current tobacco consumption, among miners aged 34-50. Long-term and current exposure to coal dust were studied. The lowest Se values were observed for those with both long-term and current exposure (60.2 ng/ml), the highest for those never or slightly exposed (64.1 ng/ml); those with long-term exposure not currently exposed fell in an intermediate position (61.3 ng/ml). No relation was observed with alcohol consumption. The association of coal dust with low selenium remained significant after adjustment for age and smoking.

Peripheral antioxidant enzyme activities and selenium in elderly subjects and in dementia of Alzheimer's type--place of the extracellular glutathione peroxidase

Defenses against free radical damage were determined in red blood cells and plasma from 40 patients with dementia of the Alzheimer-type (DAT) and 34 aged control subjects with normal cognitive function. No crude significant difference in erythrocyte copper-zinc superoxide dismutase (E-CuZnSOD), seleno-dependent glutathione peroxidase (E-GSH-Px), glutathione reductase (E-GSSG-RD) activities, and selenium (Se) concentration was found between DAT cases and control subjects. The peroxidation products evaluated in plasma by the thiobarbituric-reactive material (TBARS) were at the same level in the DAT group as compared to controls. In the DAT group, plasma GSH-Px (P-GSH-Px) activity and plasma Se (P-Se) were negatively correlated with age (r = -0.58; p < 0.001 and r = -0.63; p < 0.001 respectively). Moreover, erythrocyte GSH-Px activity and Se were also negatively correlated with age (r = -0.40; p < 0.01 and r = -0.46; p < 0.01, respectively). No significant correlation with age was observed in the controls. When controlling for age, a significant increase for P-GSH-Px activity and P-Se was observed in DAT patients as compared to controls. These significant differences mostly appeared in DAT subjects under 80 years. Some correlations were only observed in the DAT group such as P-GSH-Px and E-GSH-Px (r = +0.68; p < 0.001); P-GSH-Px and E-Se (r = +0.79; p < 0.001). Correlations between P-GSH-Px and P-Se, E-GSH-Px and P-Se, and P-Se with E-Se are greater in the DAT group (r = +0.84; p < 0.001; r = +0.76; p < 0.001 and r = 0.75; p < 0.001) than in the control group (r = 0.54, pI < 0.01; r = 0.43, p < 0.01 and r = +0.34, p < 0.05 respectively). The fact that first -- a significant increase in P-GSH-Px and P-Se, second -- some modifications in the relationships between antioxidant parameters, and third -- age-dependent decreases of glutathione-peroxidase activities and their cofactor, appeared only in the DAT group suggest that DAT is associated with an oxidative stress due to an imbalance between reactive oxygen species and the peripheral antioxidant opposing forces.

Inter-individual variation of selenium in maternal plasma, cord plasma and placenta

Selenium (Se) in high doses has been known to cause injury to the fetus and newborn. The major difficulty in assessing the effects of selenium on human reproduction stems from the need for a suitable means of estimating maternal and fetal exposure. The present investigation, therefore, examines the respective reliability of maternal plasma, cord plasma and placenta as epidemiological indicators as well as inter-individual variation of this trace element. An unselected population of 128 pregnancies was studied. Obstetrical characteristics were noted. Selenium concentrations were determined for maternal plasma, cord plasma, and placental tissue by fluorometric analysis. Maternal plasma selenium concentrations (Se-Bm) were significantly greater than fetal concentrations (Se-Bc). Placental selenium (Se-Pl) levels were four times that of fetal levels. Variability of Se-Bc is best explained by placental concentrations. Maternal weight and ethnic origin are significantly correlated with Se-Bc. Female newborn have higher selenium levels than male newborn. The present study demonstrates the significance of the placenta as an indicator of fetal selenium exposure.

In utero exposure to parental smoking, cotinine measurements, and cord blood IgE

The relationship between parental smoking and cord blood IgE has been studied in a survey conducted in 99 unselected newborn infants with a sensitive tests for IgE and cotinine as a biologic marker to validate smoking data. For both cord blood cotinine and maternal urine continine creatinine ratio (CCR), significantly higher levels were observed for smokers compared to nonsmokers. Furthermore, among nonsmokers, passive smokers had significantly higher cotinine levels than true nonsmokers, which demonstrates that cord blood may be used to assess active as well as passive maternal smoking. No association was observed in this study between cord blood IgE and maternal smoking assessed by questionnaire (geometric means of cord blood IgE levels were 0.11 IU/ml for newborn infants of smoking mothers and 0.12 IU/ml for newborn infants of nonsmoking mothers). The same observations were drawn from the analysis of cord blood IgE and cotinine levels, with correlation coefficients of -0.005 for cord blood CCR and 0.003 for maternal CCR. Additional studies are needed to determine whether maternal smoking is causally related to cord blood IgE and by which mechanisms.