The research team, led by the North Carolina State University, has found a connection between exposure to a common flame retardant chemical mix and normal placental functions in rats, affecting the production of serotonin, a neurotransmitter.
The flame retardant mix FireMaster 550 (FM550) was first identified by researchers at Duke University and developed to replace PBDEs, a type of fire retardants being phased out due to safety concerns. Heather Patisaul, professor of biology at the North Carolina State University, and her team, found that "FM550 exposure can impact multiple placental pathways critical for early brain development". This is of concern, as the chemical mix is commonly found in foam-based baby products and furniture. Also of concern for Patisaul, is that some evidence shows the alteration of placental serotonin production. "This is important because in early development the placenta is the sole source of serotonin for the developing forebrain", explained the professor.
Recent research demonstrated that the FM 550 is an endocrine disruptor, with developmental exposure affecting anxiety- and hyperactivity-related behaviors in rats in sex-specific ways. It was also determined that three of its components accumulate in placenta depending on dosage, with levels higher in male-associated placentas. Furthermore, endocrine, inflammatory and neurotransmitter signaling pathway disruption was also identified in the placentas. For the first time, data has shown that flame retardants can have sex-specific effects on placental functions that are critical for brain development.
Patisaul and graduate student, Kylie Rock tested if FM550 could sex-specifically impact the developing brain by altering placental function. They exposed pregnant female rats to 0, 300, or 1,000 micrograms of FM550 per day during a 10-days gestation period. The team used metabolomics and high throughput RNA sequencing, amongst other tools, to examine the placentas and the developing brains of the offspring to identify possible pathways impacted by the chemical mixture. All the dose levels tested were below the 50 milligrams per day currently considered safe.
In rat offspring exposed to 300 or 1,000 micrograms of FM550, the researchers found dose-dependent upregulation of multiple genes linked to inflammatory and endocrine processes, some of which were sex-specific. For example, levels of estrogen and androgen receptors were upregulated in female-associated placentas while inflammatory markers associated with increased risk of behavioral disorders were upregulated in placentas from both sexes. Additionally, the ratio of the serotonin metabolite 5-HIAA to serotonin was reduced in female placentas and fetal forebrains compared to the control group, demonstrating disruption of neurotransmitter production in the placenta and the developing brain.
Rock, Patisaul, et al. EDC IMPACT: Molecular effects of developmental FM 550 exposure in Wistar rat placenta and fetal forebrain. Endocr Connect EC-17-0373; published ahead of print January 19, 2018, doi:10.1530/EC-17-0373