Authors: Crystal Pace (1), Måns Ekelöf (2), Brian Horman (3), Heather Patisaul (3,4), David C. Muddiman (1,4,5)
Introduction: Flame retardants are chemicals added to furniture, electronics, and building materials to slow the ignition of fires. Brominated flame retardants are known to be endocrine disruptors, produce heightened anxiety in rats, and alter serotonin levels in the placenta and fetal brain. The placenta, a primary source of serotonin for fetal development, provides an excellent model for insight into biological implications from flame retardant exposure.
Objectives: The primary objective of this study was to determine if changes in abundance and spatial distribution of neurotransmitters in rat placenta could be correlated with exposure to flame retardants using IR-MALDESI mass spectrometry imaging.
Methods: Pregnant rats were dosed via oral consumption for 10 days of gestation. There were four exposure groups: control (vehicle), low (100 mg), mid (110 mg), and high (1000 mg). Placenta tissue was collected from each offspring sex at approximately day 18 of gestation and sectioned immediately before use. The tissue sections were thaw mounted onto glass slides and kept at -10℃ in a humidity-controlled enclosure for the entire experiment. A thin ice layer was formed by controlled exposure to ambient humidity prior to imaging. All samples were imaged using IR-MALDESI coupled to a Q Exactive Plus mass spectrometer and analyzed using MSiReader.
Results: Neurotransmitters were identified in rat placenta tissue using mass measurement accuracy and spectral accuracy. Most neurotransmitters had homogeneous spatial distributions across the whole placenta tissue, while a few neurotransmitters were more abundant in the maternal region. There were no observed changes in the spatial distributions of neurotransmitters with flame retardant exposure; however, there was a decrease in normalized abundance of neurotransmitters with increased exposure to flame retardants. The production and metabolism of decreasing neurotransmitters were further investigated by KEGG metabolic pathway analysis. The precursor molecules for downregulated neurotransmitters did not have a decreasing trend in abundance with exposure levels. Many of these downregulated neurotransmitters had the same enzyme responsible for metabolism, aromatic-L-amino-acid decarboxylase, providing more evidence for a change in enzyme activity as a result of flame retardant exposure.
Conclusion: IR-MALDESI mass spectrometry imaging was leveraged to distinguish between different features of the placenta such as the trophospongium which separates the maternal and fetal sides of the placenta. A few neurotransmitters were found to have a decrease in abundance with increasing exposure to flame retardants and were further investigated for changes in the metabolic pathway. The pathway analysis implied that the enzyme activity is likely disrupted by exposure to brominated flame retardants, resulting in less neurotransmitter production.
|Grants||yes||National Institute of Health|
|Planning to mention or discuss specific products or technology of the company(ies) listed above:||