Bromination pattern of hydroxylated metabolites of BDE-47 affects their potency to release calcium from intracellular stores in PC12 cells.

Abstract

BACKGROUND:

Brominated flame retardants, including the widely used polybrominated diphenyl ethers (PBDEs), have been detected in humans, raising concern about possible neurotoxicity. Recent research demonstrated that the hydroxylated metabolite 6-OH-BDE-47 increases neurotransmitter release by releasing calcium ions (Ca2+) from intracellular stores at much lower concentrations than its environmentally relevant parent congener BDE-47. Recently, several other hydroxylated BDE-47 metabolites, besides 6-OH-BDE-47, have been detected in human serum and cord blood.

OBJECTIVE AND METHODS:

To investigate the neurotoxic potential of other environmentally relevant PBDEs and their metabolites, we examined and compared the acute effects of BDE-47, BDE-49, BDE-99, BDE-100, BDE-153, and several metabolites of BDE-47-6-OH-BDE-47 (and its methoxylated analog 6-MeO-BDE-47), 6 -OH-BDE-49, 5-OH-BDE-47, 3-OH-BDE-47, and 4 -OH-BDE-49--on intracellular Ca2+ concentration ([Ca2+]i), measured using the Ca2+-responsive dye Fura-2 in neuroendocrine pheochromocytoma (PC12) cells.

RESULTS:

In contrast to the parent PBDEs and 6-MeO-BDE-47, all hydroxylated metabolites induced Ca2+ release from intracellular stores, although with different lowest observed effect concentrations (LOECs). The major intracellular Ca2+ sources were either endoplasmic reticulum (ER; 5-OH-BDE-47 and 6 -OH-BDE-49) or both ER and mitochondria (6-OH-BDE-47, 3-OH-BDE-47, and 4 -OH-BDE-49). When investigating fluctuations in [Ca2+]i, which is a more subtle end point, we observed lower LOECs for 6-OH-BDE-47 and 4 -OH-BDE-49, as well as for BDE-47.

CONCLUSIONS:

The present findings demonstrate that hydroxylated metabolites of BDE-47 cause disturbance of the [Ca2+]i. Importantly, shielding of the OH group on both sides with bromine atoms and/or the ether bond to the other phenyl ring lowers the potency of hydroxylated PBDE metabolites.

• Authors: Milou M L Dingemans, Harm J Heusinkveld, Ake Bergman, Martin van den Berg, Remco H S Westerink
• Journal: Environmental health perspectives (Environ Health Perspect) Vol. 118 Issue 4 Pg. 519-25 (Apr 2010) ISSN: 1552-9924 [Electronic] United States
• PMID: 20368133 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Halogenated Diphenyl Ethers
• Polybrominated Biphenyls
• 2,2',4,4'-tetrabromodiphenyl ether
• Calcium

Topics

• Animals
• Calcium (metabolism)
• Cell Survival (drug effects)
• Halogenated Diphenyl Ethers
• Halogenation
• PC12 Cells (drug effects, metabolism)
• Polybrominated Biphenyls (chemistry, pharmacology)
• Rats
• Structure-Activity Relationship