Involvement of reactive oxygen species in brominated diphenyl ether-47-induced inflammatory cytokine release from human extravillous trophoblasts in vitro

Abstract

Polybrominated diphenyl ethers (PBDEs) are widely used flame retardant compounds. Brominated diphenyl ether (BDE)-47 is one of the most prevalent PBDE congeners found in human breast milk, serum and placenta. Despite the presence of PBDEs in human placenta, effects of PBDEs on placental cell function are poorly understood. The present study investigated BDE-47-induced reactive oxygen species (ROS) formation and its role in BDE-47-stimulated proinflammatory cytokine release in a first trimester human extravillous trophoblast cell line, HTR-8/SVneo. Exposure of HTR-8/SVneo cells for 4 h to 20 μM BDE-47 increased ROS generation 1.7 fold as measured by the dichlorofluorescein (DCF) assay. Likewise, superoxide anion production increased approximately 5 fold at 10 and 15 μM and 9 fold at 20 μM BDE-47 with a 1-h exposure, as measured by cytochrome c reduction. BDE-47 (10, 15 and 20 μM) decreased the mitochondrial membrane potential by 47–64.5% at 4, 8 and 24 h as assessed with the fluorescent probe Rh123. Treatment with 15 and 20 μM BDE-47 stimulated cellular release and mRNA expression of IL-6 and IL-8 after 12 and 24 h exposures: the greatest increases were a 35-fold increased mRNA expression at 12 h and a 12-fold increased protein concentration at 24 h for IL-6. Antioxidant treatments (deferoxamine mesylate, (±)α-tocopherol, or tempol) suppressed BDE-47-stimulated IL-6 release by 54.1%, 56.3% and 37.7%, respectively, implicating a role for ROS in regulation of inflammatory pathways in HTR-8/SVneo cells. Solvent (DMSO) controls exhibited statistically significantly decreased responses compared with non-treated controls for IL-6 release and IL-8 mRNA expression, but these responses were not consistent across experiments and times. Nonetheless, it is possible that DMSO (used to dissolve BDE-47) may have attenuated the stimulatory actions of BDE-47 on cytokine responses. Because abnormal activation of proinflammatory responses can disrupt trophoblast functions necessary for placental development and successful pregnancy, further investigation is warranted of the impact of ROS and BDE-47 on trophoblast cytokine responses.

Propofol alleviates acute lung injury following orthotopic autologous liver transplantation in rats via inhibition of the NADPH oxidase pathway

“…Oxidative stress and the inflammatory reaction interact in a complex way to act in the pathogenesis of lung damage. Studies have demonstrated that ROS are fundamental to oxidative stress and the inflammatory reaction (38,39). The current study demonstrated that NAC and AP application inhibited NAPDH oxidase in the earlier phase and reduced or eliminated ROS production.…”

Effect of omega-3 fatty acid oxidation products on the cellular and mitochondrial toxicity of BDE 47

“…We also wanted to minimize the potential for artifacts from co-administration, specifically with regards to the presence of serum in the treatment media, which can decrease the bioavailability of lipophilic toxicants including BDE 47 in vitro [65, 66]. Supplementation of the pretreatment exposure media with 5-10% FBS was required for administration of oxEPA/oxDHA to HepG2 cells [37], whereas BDE 47 exposure media utilized in similar in vitro studies are supplemented with very low concentrations of serum (1%) [32, 42], or is serum-free [25, 67]. Thus, co-treatment of cells with oxEPA/oxDHA and BDE 47 should be addressed in future experiments, but was somewhat out of the scope of the current manuscript due to reasons including the aforementioned differences in experimental exposure methods that are required for administering these compounds to cells.…”

“…In human [32, 42], fish [29, 30], and rodent cells [26] exposed to BDE 47, oxidative injury is not typically observed below concentrations in the 20-50 μM range. Hence, it is plausible that the antioxidant effects of oxEPA/oxDHA may provide greater protection against, or ameliorate, the toxicity of lower doses of BDE 47 representative of environmental exposures.…”

“…The mechanisms of BDE 47 toxicity are poorly understood, but substantial evidence indicates the induction of cellular oxidative stress, via generation of reactive oxygen species (ROS), may play a major role [25-29]. Importantly, BDE 47-induced oxidative stress is associated with a loss of cellular viability and proliferation, and a loss of mitochondrial membrane potential [28, 30-32]. …”

“…This hypothesis is supported by studies showing that induction of intracellular GSH by the antioxidant N -acetylcysteine (NAC), a GSH precursor, protects human fetal hematopoietic stem cells [31], human hepatocytes [27], and T lymphocyte cell lines [28] against BDE 47 toxicity. Others have demonstrated that oxidative stress-mediated inflammation resulting from in vitro exposure to BDE 47 [32, 42] and similar persistent organic contaminants [39] can be reduced by treatment with dietary antioxidant compounds, including via activation of Nrf2 by free radical-oxidized EPA and DHA.…”