Organophosphorus flame retardants are developmental neurotoxicants in a rat primary brainsphere in vitro model

• Published in: Archives of toxicology Vol. 95; no. 1; pp. 207 - 228
• Main Authors: Hogberg, Helena T., de Cássia da Silveira E Sá, Rita, Kleensang, Andre, Bouhifd, Mounir, Cemiloglu Ulker, Ozge, Smirnova, Lena, Behl, Mamta, Maertens, Alexandra, Zhao, Liang, Hartung, Thomas
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.01.2021; Springer Nature B.V
• Subjects: Animals; Biomedical and Life Sciences; Biomedicine; Brain - drug effects; Brain - embryology; Brain - metabolism; Cell cycle; Cells, Cultured; Congeners; Cytokines; Cytotoxicity; Diagnostic systems; Diphenyl ether; Dopamine; Dopamine transporter; Environmental Health; Female; Flame retardants; Flame Retardants - toxicity; Gene Expression Profiling; Gestational Age; Gliosis; Halogenated Diphenyl Ethers - toxicity; Immune response; Inflammation; Inflammatory response; Lipid metabolism; Lipids; Mass spectroscopy; Metabolome - drug effects; Metabolomics; Myelination; N-Acetylaspartate; Neurons - drug effects; Neurons - metabolism; Neurons - pathology; Neurotoxicity; Neurotoxicity Syndromes - etiology; Neurotoxicity Syndromes - metabolism; Neurotoxicity Syndromes - pathology; Neurotransmitters; Occupational Medicine/Industrial Medicine; Organ Toxicity and Mechanisms; Organophosphates - toxicity; Pharmacology/Toxicology; Polybrominated diphenyl ethers; Pregnancy; Rats; Rats, Sprague-Dawley; Receptors; Retardants; Signaling; Spheroids, Cellular; Synaptic transmission; Three dimensional models; Toxicity; Transcriptome - drug effects; Tricresyl phosphate; Tritolyl Phosphates - toxicity; γ-Aminobutyric acid; Flame retardants; Metabolomics; 3D in vitro model; Developmental neurotoxicity; Transcriptomics; New approach methodologies
• ISSN: 0340-5761; 1432-0738
• DOI: 10.1007/s00204-020-02903-2

Due to regulatory bans and voluntary substitutions, halogenated polybrominated diphenyl ether (PBDE) flame retardants (FR) are increasingly substituted by mainly organophosphorus FR (OPFR). Leveraging a 3D rat primary neural organotypic in vitro model (rat brainsphere), we compare developmental neurotoxic effects of BDE-47—the most abundant PBDE congener—with four OPFR (isopropylated phenyl phosphate—IPP, triphenyl phosphate—TPHP, isodecyl diphenyl phosphate—IDDP, and tricresyl phosphate (also known as trimethyl phenyl phosphate)—TMPP). Employing mass spectroscopy-based metabolomics and transcriptomics, we observe at similar human-relevant non-cytotoxic concentrations (0.1–5 µM) stronger developmental neurotoxic effects by OPFR. This includes toxicity to neurons in the low µM range; all FR decrease the neurotransmitters glutamate and GABA (except BDE-47 and TPHP). Furthermore, n -acetyl aspartate (NAA), considered a neurologic diagnostic molecule, was decreased by all OPFR. At similar concentrations, the FR currently in use decreased plasma membrane dopamine active transporter expression, while BDE-47 did not. Several findings suggest astrogliosis induced by the OPFR, but not BDE-47. At the 5 µM concentrations, the OPFR more than BDE-47 interfered with myelination. An increase of cytokine gene and receptor expressions suggests that exposure to OPFR may induce an inflammatory response. Pathway/category overrepresentation shows disruption in 1) transmission of action potentials, cell–cell signaling, synaptic transmission, receptor signaling, (2) immune response, inflammation, defense response, (3) cell cycle and (4) lipids metabolism and transportation. Taken together, this appears to be a case of regretful substitution with substances not less developmentally neurotoxic in a primary rat 3D model.