Screening the Oxidative Potential of Several Mono- and Di-Halogenated Biphenyls and Biphenyl Ethers in Rat Hepatocytes

Hande      Gurer-Orhan; Hilme      Orhan; Nico   P.   Vermeulen; John   H.   Meerman

doi:10.2174/138620706777698517

Abstract

The present study was designed to investigate the potential of reactive oxygen species (ROS) generating and subsequent ROS-mediated lipid peroxidation (LPO) inducing effect of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes in vitro. For this aim, 4-chloro- and 4-bromo biphenyl (4-CB and 4-BB), 4-OH, 4-BB, 4-bromo diphenylether (4-BDE), 4,4-dichlorobiphenyl (4,4-DCB), 4,4-dibromobiphenyl (4,4-DBB), and 3,4- dichlorobiphenyl (3,4-DCB) were incubated with freshly isolated rat hepatocytes. Their oxidative potential was evaluated by detecting the intracellular ROS formation by oxidant-sensing fluorescent probes (2,7-dichlorofluorescein diacetate and C11-BODIPY 581/591 ) using a multiplate reader and determining the levels of eight LPO products (formaldehyde, malondialdehyde, propanal, butanal, pentanal, hexanal, octanal, and nonanal) by a gas chromatography-electron capture detection. 4-BDE was found to be active both in cytoplasm and in the cell membrane in terms of inducing the formation of ROS. Another important finding was the increase in ROS-inducing potential of 4-BB when the same concentration of the hydroxylated derivative, 4-OH,4-BB, was incubated with hepatocytes. 4-BDE was also found to be the most effective among all tested compounds in inducing LPO where 4-OH, 4-BB was again more potent than its unmetabolized form, 4- BB. Lactate dehydrogenase leakage analyses indicated that all tested compounds are cytotoxic; 4-BDE caused the highest LDH leakage compared to other mono-halogenated biphenyls tested. Our results suggest that ROS formation by chlorinated biphenyls and mono-hydroxylated bromobiphenyls, and concomitant induction of LPO might be involved in the cytotoxic effects of these industrial pollutants. Similar effects of mono-BDE are also reported, which is a novel observation.

Keywords: lactate dehydrogenase, thiobarbi-turic acid (TBA) assay, lipid peroxidation, Reactive oxygen species (ROS), Polybrominated diphenyl ethers

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