Grantee Research Project Results

The work conducted for Project 1 set the stage for future research by successfully developing the infrastructure upon which to build a larger prospective birth cohort and by demonstrating the feasibility of novel approaches to data collection including cognitive assessments of newborn infants in the hospital setting. Importantly, the results of this pilot work also support the hypothesized associations of prenatal exposures with the targeted contaminants. Specifically, both BPA and anti-androgenic phthalates were associated with altered anogenital distance in preliminary analyses conducted on a subset of the sample for whom exposure data were available. There were also suggestive associations of both BPA and anti-androgenic phthalates with decrements in attention in both newborns and older infants (7 months), and with declines in working memory in the latter age group. These findings are preliminary and will need to be confirmed in the full cohort prior to publication. Furthermore, although our sub- study of variability in urinary concentrations of BPA and phthalate metabolites in repeated samples across pregnancy) suggested that first morning urine collections may provide somewhat improved exposure assessment over random spot urines, the degree of variability within individuals was still considerable. This information was critical in our decision to collect and pool urine from multiple samples across pregnancy in the future, thus providing a measure of average exposure across pregnancy. We will be able to validate and build on the important preliminary findings from this pilot research with much greater statistical power in the full cohort (n = 600 infants) to be studied as part of our recently funded full Children's Center.

The work conducted for Project 2 provides preliminary support for the hypothesized association of adolescent BPA, but not antiandrogenic phthalate exposure, with poorer cognitive function in specific domains with likely sexual dimorphism in performance. Furthermore, the findings provide preliminary support for the secondary hypothesis of potential differential effects of exposure on boys vs. girls for cognitive measures. Both exposures (BPA, antiandrogenic phthalates) were associated with adverse behavior, especially ADHD-like behavior. However, because of small numbers in this pilot study (by design), analyses were adjusted for a limited number of potential confounders and, for many results, confidence limits were wide so it is not yet possible to make definitive conclusions. Most importantly, these formative center findings contributed to a research project proposal for a successful full Children's Environmental Health and Disease Prevention Research Center (P01). With analysis of the full study (n = 205 children) made possible via the full Center P01, we will be able to assess the reproducibility of these preliminary models, use more comprehensive models to account for confounding, and assess associations with functional measures (e.g., reaction time and errors on a continuous performance test, CPT) for which short-term exposure effects are possible.

Project 3 was designed to test the hypothesis that in utero exposure to BPA causes gonadal defects via estrogen receptor alpha (ERα). To test this hypothesis, we proposed the following specific aims: 1) determine whether loss of ERα renders developing gonads insensitive to deleterious effects of BPA, and 2) determine if overexpression of ERα increases the susceptibility of embryos to BPA. Collectively, the data indicate that maternal BPA exposure alters testis development in the offspring, and that the effects of BPA are likely non- monotonic because the low dose of BPA exerts a more dramatic effect than the high dose of BPA. Further, the data indicate that prenatal BPA exposure reduces healthy primordial follicle numbers in the ovary and that it inhibits antral follicle growth. The results also indicate that BPA inhibits progesterone, dehydroepiandrosterone, androstenedione, estrone, testosterone, and estradiol production by the mouse ovary. Finally, the data suggest that BPA may not exert toxicity in ovaries through ER pathways.

Project 4 was a pilot project designed to investigate whether bisphenol A (BPA) exposure during pre/perinatal development or during puberty alters cognitive areas of the brain or cognitive behavior in rats. The results indicate that BPA exposure increased maternal attention to pups at certain doses, which establishes that any effects of BPA are not due to insufficient maternal care. These data are preliminary at this time because of relatively low N. More animals will be added as part of the studies in the Center (P01) grant. Quantitative stereological analysis of the prefrontal cortex revealed that there were significant increases in the number of both neurons and glia in male rats exposed to 400 µg/kg/day of BPA perinatally compared to unexposed controls. In addition, the results indicate that there were no effects on body weight at weaning or in adulthood, or on levels of thyroid hormone or luteinizing hormone at weaning. Both sexes at doses of 4 and 40 µg/kg BPA had decreased follicle-stimulating hormone (FSH) levels, but there were no changes in the timing of puberty compared to controls. Exposure to BPA during adolescence resulted in opposite effects between the sexes in the number of glia in the prefrontal cortex as adults: females that had been exposed to BPA had more glia while males showed a general decrease following exposure. The implications of these changes in glia are being investigated further in the center grant.