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

Arch Toxicol. 2021 Jan;95(1):207-228. doi: 10.1007/s00204-020-02903-2. Epub 2020 Oct 19.


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.

Keywords: 3D in vitro model; Developmental neurotoxicity; Flame retardants; Metabolomics; New approach methodologies; Transcriptomics.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain / drug effects*
  • Brain / embryology
  • Brain / metabolism
  • Cells, Cultured
  • Female
  • Flame Retardants / toxicity*
  • Gene Expression Profiling
  • Gestational Age
  • Halogenated Diphenyl Ethers / toxicity
  • Metabolome / drug effects
  • Metabolomics
  • Neurons / drug effects*
  • Neurons / metabolism
  • Neurons / pathology
  • Neurotoxicity Syndromes / etiology*
  • Neurotoxicity Syndromes / metabolism
  • Neurotoxicity Syndromes / pathology
  • Organophosphates / toxicity*
  • Pregnancy
  • Rats, Sprague-Dawley
  • Spheroids, Cellular
  • Transcriptome / drug effects
  • Tritolyl Phosphates / toxicity


  • Flame Retardants
  • Halogenated Diphenyl Ethers
  • Organophosphates
  • Tritolyl Phosphates
  • 2,2',4,4'-tetrabromodiphenyl ether
  • phenylphosphate
  • triphenyl phosphate