Maternal exposure to low dose BDE209 and Pb mixture induced neurobehavioral anomalies in C57BL/6 male offspring

Polybrominated diphenyl ethers (PBDEs) and lead (Pb) are common pollutants that co-exist in the environment. These chemicals may be associated with autism spectrum disorder (ASD), yet direct evidence is lacking. More importantly, how co-exposure of these chemicals might affect ASD has never been explored. For assessing the relationship between PBDE/Pb exposure and ASD, pregnant C57BL/6 J female mice were exposed to BDE209 (0.12 ng/day), Pb (1.2 ng/day), or a BDE209/Pb mixture from gestational day (GD) 9.5 to postnatal day (PND) 21 using ALZET osmotic pumps. Polyinosinic-polycytidylic acid (poly I:C) was included as a positive control, as its single dose injection (20 mg/kg.bw; i.p.) at mid-pregnancy (GD 12.5) produces ASD-like behaviors in mouse offspring. These ASD-like phenotypes include decreased preference for social novelty, increased marble burying behavior, and learning impairment. Similar to the poly I:C control, perinatal exposure to Pb or BDE209/Pb mixture elicited increased marble burying and learning impairment, but it had no effect on sociability. Consistent with these behavioral anomalies, Pb and BDE209/Pb co-exposure as well as poly I:C exposure increased the production of pro-inflammation cytokines interleukin 4 (IL-4), interleukin 6 (IL-6), interleukin 10 (IL-10), tumor necrosis factor α (TNFα), interferon γ (IFNγ), and interleukin 17 A (IL-17 A) in the serum, and decreased neuronal cells in the CA1 and CA3 subregions of the hippocampus. The majority of these changes in the BDE209/Pb mixture group were due to the effect of Pb rather than BDE209. However, BDE209/Pb co-exposure elicited a synergistic increase in the production of IL-4, IL-6, TNFα, IFNγ, and IL-17A in the serum. BDE209 exposure alone also significantly affected spatial learning and increased the production of IL-10, TNFα, and IL-17 A in the serum of male offspring. Our work demonstrates that perinatal exposure to a low dose of Pb or the BDE209/Pb mixture, although it did not induce typical ASD-like symptoms, elicited restricted, repetitive patterns of behavior and affected learning in male offspring. In addition, the synergistic increase in the systemic inflammatory response in the BDE209/Pb co-exposure group underscores the importance of evaluating chemical mixtures in disease onset.