Oxidative properties of hydroxylated polybrominated diphenyl ether metabolites

Polybrominated diphenyl ethers (PBDEs) are organobromine compounds used as flame retardants in consumer products made out of petroleum-based polymers. Instead of being chemically bonded, PBDEs are added or blended into these polymeric materials. Lacking the chemical bonds, PBDEs can easily leach from the product during use or disposal. These organic pollutants have been detected in the air, water, soil, sediment, and sewage around the world. Bioaccumulation of PBDEs have also been detected in fish, birds, animals, as well as human blood serum and milk. A few in vitro studies have showed PBDEs can disturb the thyroid hormone hemeostasis. However, in vitro studies suggest that the hydroxylated metabolites of the CYP-mediated PBDE metabolism may be responsible for the observed disruption of the thyroid hormone homeostasis. Hydroxylated metabolites of PBDEs (OH-PBDEs) have been detected in blood samples of rats, fish, birds, and mammals after exposure to PBDE mixtures. Additionally, OH-PBDEs may also induce oxidative stress, but this has not been widely studied. The limited research of OH-PBDEs on oxidative stress showed changes in enzymatic activity, antioxidant stores, and concentration of reactive oxygen species. In this study, the in vitro oxidative effect of three PBDE metabolites (2,4-dibromophenol, 2,4,4’-tribromo-2’-hydroxy diphenyl ether (OH-BDE-28), and 4,4’-dibromo-2’-hydroxy diphenyl ether (OH-BDE-15)) on DNA and lipid models was investigated. In the oxidation of 2-deoxyribose, OH-BDE-28 had a much greater pro-oxidant effect than OH-BDE-15 while 2,4-dibromophenol did not have any significant activity. In the oxidation of lipids, all PBDE metabolites had antioxidant activity. OH-BDE-28 had the least antioxidant effect while OH-BDE-15 had the greatest antioxidant effect. None of the PBDE metabolites had any significant effect on the oxidation of 2’-deoxyguanosine. Moreover, none of these PBDE metabolites exhibited any ability in scavenging free radicals.