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Comparative proteomic analysis following treatment with acetaminophen (APAP) was performed on two different models of APAP-mediated hepatocellular injury in order to both identify common targets for adduct formation and track drug-induced changes in protein expression. Male C57BL/6 mice were used as a model for APAP-mediated liver injury in vivo, and TAMH cells were used as a model for APAP-mediated cytotoxicity in vitro. SEQUEST was unable to identify the precise location of sites of adduction following treatment with APAP in either system. However, semiquantitative analysis of the proteomic data sets using spectral counting revealed a downregulation of P450 isoforms associated with APAP bioactivation and an upregulation of proteins related to the electron transport chain by APAP compared to the control. Both mechanisms are likely compensatory in nature as decreased P450 expression is likely to attenuate toxicity associated with N-acetyl-p-quinoneimine (NAPQI) formation, whereas APAP-induced electron transport chain component upregulation may be an attempt to promote cellular bioenergetics. [ABSTRACT FROM AUTHOR]

The polybrominated diphenyl ethers (PBDEs) are a group of flame retardants whose residues have markedly increased in the environment and in human tissues during the last decade. Of the various congeners, BDE 47 (2,2′,4,4′-tetrabromodiphenyl ether) is typically the predominant congener observed in fish and wildlife samples, as well as in human tissues. Several studies indicate in utero transfer of PBDEs during pregnancy with residues accumulating in fetal tissues, and thus the potential for BDE 47–mediated injury in utero is of concern. In this study, we examined the mechanisms of BDE 47–mediated injury to primary human fetal liver hematopoietic stem cells (HSCs), which comprise a large proportion of fetal hepatic cells and play a key role in hematopoiesis during fetal development. Incubation of fetal liver HSCs with BDE 47 led to a loss of mitochondrial membrane potential and the onset of apoptosis. These effects were observed in the low micromolar range of BDE 47 exposures. At higher concentrations, BDE 47 elicited a loss of viability, which was accompanied by the generation of reactive oxygen species and peroxidation of HSC lipids. Preincubation of fetal liver HSCs with N-acetylcysteine, a glutathione (GSH) precursor, caused an increase in cellular GSH concentrations, restored mitochondrial redox status, and ameliorated the toxicity of BDE 47. BDE 47–mediated cytotoxicity or oxidative injury was not evident at the lower concentrations (< 1μM). Collectively, these data support a role for oxidative stress in the cytotoxicity of BDE 47 and indicate that oxidative stress–associated biomarkers may be useful in assessing the sublethal effects of BDE 47 toxicity in other models. However, the fact that BDE 47 undergoes a concentration-dependent accumulation in other primary cells in media that can underestimate cellular concentrations (W. R. Mundy et al., 2004, Toxicol. Sci. 82, 164–169) suggests that the HSC cell injury observed in our study may be of less relevance to human in utero PBDE exposures. [ABSTRACT FROM AUTHOR]