The development of a pregnancy PBPK Model for Bisphenol A and its evaluation with the available biomonitoring data

Recent studies suggest universal fetal exposure to Bisphenol A (BPA) and its association with the adverse birth outcomes. Estimation of the fetal plasma BPA concentration from the maternal plasma BPA would be highly useful to predict its associated risk to this specific population. The objective of current work is to develop a pregnancy-physiologically based pharmacokinetic (P-PBPK) model to predict the toxicokinetic profile of BPA in the fetus during gestational growth, and to evaluate the developed model using biomonitoring data obtained from different pregnancy cohort studies. To achieve this objective, first, the adult PBPK model was developed and validated with the human BPA toxicokinetic data. This validated human PBPK model was extended to develop a P-PBPK model, which included the physiological changes during pregnancy and the fetus sub-model. The developed model would be able to predict the BPA pharmacokinetics (PKs) in both mother and fetus. Transplacental BPA kinetics parameters for this study were taken from the previous pregnant mice study. Both oral and dermal exposure routes were included into the model to simulate total BPA internal exposure. The impact of conjugation and deconjugation of the BPA and its metabolites on fetal PKs was investigated. The developed P-PBPK model was evaluated against the observed BPA concentrations in cord blood, fetus liver and amniotic fluid considering maternal blood concentration as an exposure source. A range of maternal exposure dose for the oral and dermal routes was estimated, so that simulation concentration matched the observed highest and lowest mother plasma concentration in different cohorts' studies. The developed model could be used to address the concerns regarding possible adverse health effects in the fetus being exposed to BPA and might be useful in identifying critical windows of exposure during pregnancy.

Bisphenol A alteration of type 1 diabetes in non-obese diabetic (NOD) female mice is dependent on window of exposure

Type 1 diabetes (T1D) is an autoimmune disease in which pancreatic β-cell destruction can be mediated by dysbiosis, infiltration of pro-inflammatory immune cells, and cytokines/chemokines. Exposure to bisphenol A (BPA), an endocrine disruptor (ED), can lead to aberrant immunity and gut microbiota. We determined whether BPA had age-dependent effects on T1D by modulating immune homeostasis following various windows of exposure in non-obese diabetic (NOD) mice. Juvenile NOD females were orally exposed to 0 or 30 µg BPA/kg BW from postnatal day (PND) 28 to PND56. Adult NOD females were exposed to 0 or 300 µg BPA/kg BW. Female and male NOD offspring were exposed to 0 or 300 µg BPA/kg BW perinatally from gestation day 5 to PND28 by dosing the dams. It was found that BPA increased T1D risk in juvenile females with gut microbiota shifted towards pro-inflammation (e.g. increased Jeotgalicoccus). In agreement with our previous study, adult females had a trend of increased T1D and a general increase in immune responses. However, female offspring had a reduced T1D development. Consistently, female offspring had a shift towards anti-inflammation (e.g. decreased pro-inflammatory F4/80⁺Gr1⁺ cells). In contrast, BPA had minimal effects on immunity and T1D in male offspring. Thus, it was concluded that BPA had age- and sex-dependent effects on T1D with the alteration of gut microbiota and inflammation being the primary mechanisms for T1D exacerbation in juvenile exposure and decreases of inflammation being responsible for attenuated T1D in perinatally exposed females.

Exposure to pesticides and childhood leukemia risk: A systematic review and meta-analysis

Despite the abundance of epidemiological evidence concerning the association between pesticide exposure and adverse health outcomes including acute childhood leukemia (AL), evidence remains inconclusive, and is inherently limited by heterogeneous exposure assessment and multiple statistical testing. We performed a literature search of peer-reviewed studies, published until January 2021, without language restrictions. Summary odds ratios (OR) and 95% confidence intervals (CI) were derived from stratified random-effects meta-analyses by type of exposure and outcome, exposed populations and window of exposure to address the large heterogeneity of existing literature. Heterogeneity and small-study effects were also assessed. We identified 55 eligible studies (n = 48 case-control and n = 7 cohorts) from over 30 countries assessing >200 different exposures of pesticides (n = 160,924 participants). The summary OR for maternal environmental exposure to pesticides (broad term) during pregnancy and AL was 1.88 (95%CI: 1.15-3.08), reaching 2.51 for acute lymphoblastic leukemia (ALL; 95%CI: 1.39-4.55). Analysis by pesticide subtype yielded an increased risk for maternal herbicide (OR: 1.41, 95%CI: 1.00-1.99) and insecticide (OR: 1.60, 95%CI: 1.11-2.29) exposure during pregnancy and AL without heterogeneity (p = 0.12-0.34). Meta-analyses of infant leukemia were only feasible for maternal exposure to pesticides during pregnancy. Higher magnitude risks were observed for maternal pesticide exposure and infant ALL (OR: 2.18, 95%CI: 1.44-3.29), and the highest for infant acute myeloid leukemia (OR: 3.42, 95%CI: 1.98-5.91). Overall, the associations were stronger for maternal exposure during pregnancy compared to childhood exposure. For occupational or mixed exposures, parental, and specifically paternal, pesticide exposure was significantly associated with increased risk of AL (ORparental: 1.75, 95%CI: 1.08-2.85; ORpaternal: 1.20, 95%CI: 1.07-1.35). The epidemiological evidence, supported by mechanistic studies, suggests that pesticide exposure, mainly during pregnancy, increases the risk of childhood leukemia, particularly among infants. Sufficiently powered studies using repeated biomarker analyses are needed to confirm whether there is public health merit in reducing prenatal pesticide exposure.