Comparison of PBDE congeners as inducers of oxidative stress in zebrafish.

A proposed primary pathway through which polybrominated diphenyl ethers (PBDEs) disrupt normal biological functions is oxidative stress. In the present study, 4 PBDE congeners were evaluated for their potential to initiate oxidative stress in zebrafish during development: BDE 28, BDE 47, BDE 99, and BDE 100. N-acetylcysteine (NAC) was used to increase intracellular glutathione concentrations and only decreased the effects of BDE 28 at 10 ppm and 20 ppm and BDE 47 at 20 ppm. N-acetylcysteine coexposure did not alter the rates of mortality or curved body axis compared with PBDE exposure alone. The activity of glutathione-S-transferase (GST) was not altered at 24 h postfertilization (hpf), but increased following 10 ppm BDE 28 exposure at 120 hpf. Transcription of several genes associated with stress was also evaluated. At 24 hpf, cytochrome c oxidase subunit 6a (COX6a) transcription was up-regulated in embryos exposed to BDE 99, and BDE 28 exposure up-regulated the transcription of Glutathione-S-transferase-pi (GSTpi). At 24 hpf, glutamate-cysteine ligase (GCLC) was slightly down-regulated by all congeners evaluated. At 120 hpf, TNF receptor-associated protein 1 (TRAP1) and COX6A were up-regulated by all congeners, however GSTpi was down-regulated by all congeners. The results of quantitative real-time transcription polymerase chain reaction are mixed and do not strongly support a transcriptional response to oxidative stress. According to the authors' data, PBDEs do not induce oxidative stress. Oxidative stress may occur at high exposure concentrations; however, this does not appear to be a primary mechanism of action for the PBDE congeners tested.