BDE-47-induced damage prevented by melatonin in grass carp hepatocytes (L8824)

Polybrominated diphenyl ethers (PBDEs) are toxic to organisms with melatonin (MT) providing protection for tissues and cells against these. This study investigates the mechanism of damage of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and the cellular protection of MT on grass carp hepatocytes. Grass carp hepatocytes were exposed to 25 μmol/L BDE-47 and/or 40 μmol/L MT for 24 h before testing. Acridine orange/ethidium bromide (AO/EB) double fluorescence staining results showed that BDE-47 could induce cell apoptosis. The expression levels of the endoplasmic reticulum (ER) stress-related genes ire1, atf4, grp78, perk, and chop were also significantly up-regulated (P < 0.01). The levels of the apoptosis-related genes caspase3, bax, and caspase9 were significantly up-regulated (P < 0.0001), while the level of bcl-2 was significantly down-regulated (P < 0.01). Compared with the BDE-47 group, the BDE-47 + MT group showed reduced levels of ER and apoptosis of hepatocytes, while the expression of the ER stress-related genes ire1, atf4, grp78, perk, and chop and the apoptosis-related genes caspase3, bax, and caspase9 were down-regulated (P < 0.05), and the level of bcl-2 was up-regulated (P < 0.01). In conclusion, BDE-47 can activate ER and apoptosis in grass carp hepatocytes, while MT can reduce these responses.

Derivatization strategy combined with parallel reaction monitoring for the characterization of short-chain fatty acids and their hydroxylated derivatives in mouse

Short-chain fatty acids (SCFAs) and hydroxylated short-chain fatty acids (OH-SCFAs) are crucial intermediates related to a variety of diseases, such as bowel disease, cardiovascular disease, renal disease and cancer. A global profiling method to screen SCFAs and OH-SCFAs was developed by tagging these analytes with d₀/d₆-N, N-dimethyl-6,7-dihydro-5H-pyrrolo [3,4-d] pyrimidine-2-amine (d₀/d₆-DHPP) and using ultra-high performance liquid chromatography coupled with high-resolution tandem mass spectrometry (UHPLC-MS/MS) in parallel reaction monitoring (PRM) mode. The derivatization procedure was simple and rapid. The targeted compounds could be derivatized within 3 min under mild condition and analyzed without the need of further purification. The derivatization significantly improved the chromatographic performance and mass spectrometry response. The d₆-DHPP tagged standards were used as internal standards, which remarkably reduced the matrix effects. The use of high resolution PRM mode made it possible to locate unknown SCFA and OH-SCFA species, and greatly reduced the false positive identification results. The developed method was successfully applied to the analysis of mouse fecal, serum, and liver tissue samples harvested from the breast cancer nude mice that had been exposed with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47). Results showed that 40 analytes (10 SCFAs and 30 OH-SCFAs) were characterized. Semi-quantitative analysis indicated that the exposure of BDE-47 to the mice altered the SCFA and OH-SCFA metabolism, especially in the high dose group. This study provides a high-throughput method to characterize SCFAs and OH-SCFAs in mouse samples.

Isoliquiritigenin as an antioxidant phytochemical ameliorates the developmental anomalies of zebrafish induced by 2,2',4,4'-tetrabromodiphenyl ether

2,2',4,4'-Tetrabromodiphenyl ether (BDE47) is the most abundant PBDE congeners in biological samples. It has strong tendencies to bioaccumulate and potentially endangers development of mammals through oxidative stress. Isoliquiritigenin (ISL), an emerging natural chalcone-type flavonoid, possesses various biological and pharmacological properties, including antioxidant, anti-allergic, anti-inflammatory, anti-tumor and estrogenic activities. The purpose of the study is to explore the antioxidant effect of ISL on the amelioration of developmental anomalies induced by BDE47. Zebrafish (Danio rerio) embryos were exposed to BDE47 (1 and 10 μM) and/or ISL (4 μM) for 4 to 120 hours post fertilization (hpf), and the morphology, development, behavior, oxidative stress status and related genes expression were assessed. The results showed that BDE47 contributed to dose-dependent growth retardation and deformities, including delayed hatching, spinal curvature, reduced body length, increased death rate, aberrant behaviors and impaired dark-adapted vision, which were significantly mitigated by ISL. Besides, ISL ameliorated excessive ROS accumulation, and exaggerated the expressions of apoptosis-related genes p53, Bcl-2, caspase 3 and caspase 9 induced by BDE47, suggesting that ISL protected zebrafish from the developmental toxicity of BDE47 by inactivation of programmed apoptosis and activation of antioxidant signaling pathways. Taken together, developing ISL as a dietary supplement might be a promising preventive strategy for the amelioration of developmental toxicity induced by environmental pollutants.

Reactive oxygen species (ROS) and the calcium-(Ca2+) mediated extrinsic and intrinsic pathways underlying BDE-47-induced apoptosis in rainbow trout (Oncorhynchus mykiss) gonadal cells

The brominated flame retardant, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), is well documented to exert potential negative impacts on different marine biota. However, the responsible mechanism remains unknown. The rainbow trout gonadal cell line RTG-2 was used as a model, and the mechanism and pathway underlying BDE-47 (6, 12.5 and 25 μM)-induced apoptosis and toxicity were examined in vitro. Apoptosis occurred in the RTG-2 cells exposed to BDE-47 in a clear concentration-dependent manner. The morphology of the mitochondrial alterations was observed using transmission electron microscopy. BDE-47 exposure decreased the cellular mitochondrial membrane potential, increased the cytochrome c released into the cytoplasm and elevated Fas protein expression. The mRNA expressions of Fas-associated death domain-containing protein (FADD), CHOP and GRP78 were also elevated, and similar increases were found in the activities of intracellular caspase-8, caspase-12, caspase-9 and caspase-3. These results indicated that the mitochondrial, endoplasmic reticulum and death-receptor pathways were involved in apoptosis in RTG-2 cells following BDE-47 exposure. ROS and Ca²⁺ were responsible for these changes because their overproduction was detected prior to apoptosis. However, the addition of the ROS scavenger N-acetyl-l-cysteine (NAC) and the intracellular calcium chelator (acetoxymethyl)-1,2-bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) did not significantly alleviate the apoptosis rate. The results of the present study show that BDE-47 exposure induced apoptosis in RTG-2 cells via ROS- and Ca²-mediated mitochondrial, endoplasmic reticulum and death-receptor apoptotic pathways.

Responses of antioxidant defenses in the clam Mactra veneriformis to 2,2',4,4'‑tetrabromodiphenyl ether exposure

Antioxidant enzymes play essential roles against oxidative stress caused by 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), which is ubiquitous in marine environment and organisms. However, research on antioxidant responses to BDE-47 in marine bivalves is scarce. In this study, we identified the full-length cDNA of catalase (CAT), and glutathione peroxidase (GPx) in the clam Mactra veneriformis. Subsequently, the responses of CAT, GPx, and copper, zinc-superoxide dismutase (Cu, Zn-SOD) were investigated in the clams exposed to 0.1, 1, and 10 μg/L BDE-47 for 7 days, and then depurated in natural seawater for 3 days. MvCAT and MvGPx contained conserved sequences. The deduced amino acid sequences shared high similarity with CATs and GPxs in other mollusks. M. veneriformis accumulated BDE-47 in a dose-dependent manner and eliminated BDE-47 poorly. BDE-47 induced a time- and dose-dependent increase of malondialdehyde content. Both the dose and the duration had significant effect on mRNA expressions and activities of the three antioxidants. Cu, Zn-SOD responded to BDE-47 earlier than CAT and GPx. The antioxidant responses could recover after depuration. These results suggested that M. veneriformis could accumulate BDE-47 efficiently. Antioxidant enzymes were triggered to counter the oxidative stress generated by BDE-47. Cu, Zn-SOD acted as the first defense against oxidative stress, while CAT and GPx intervened later. This study is therefore helpful in understanding the antioxidant responses to PBDEs in marine bivalves.

Perinatal exposure to low dose 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) alters sperm DNA methylation in adult rats

Polybrominated diphenyl ethers (PBDEs) are a group of ubiquitous reproductive toxins. Given that spermatogenesis requires extensive epigenetic changes, we hypothesize that PBDEs impact sperm DNA methylation. Pregnant Wistar rats were exposed perinatally to 0.2mg/kg 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) and caudal epididymal sperm were collected from offspring on postnatal days (PNDs) 65 and 120. Libraries were prepared from sperm DNA and sequenced with an average of 18.0 million unique reads per sample. Differential methylated regions (DMRs) were identified via MethPipe package. BDE-47 exposure increased DNA methylation of epididymal sperm on PND 65 in genes, promoters and intergenic regions; however, on PND120 methylation decreased in these genomic elements. We identified 21 and 9 exposure-related DMRs in sperm collected on PND65 and PND120, respectively. Two DMRs overlapped between the two time-points. This is the first study to demonstrate that environmentally-relevant perinatal exposure to PBDE results in long-lasting changes in sperm DNA methylation.

Identification of differentially expressed genes in the digestive gland of manila clam Ruditapes philippinarum exposed to BDE-47

Suppression subtractive hybridization (SSH) was used to identify alterations in gene transcription of the manila clam Ruditapes philippinarum after exposure to 5μg/L 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) for 15days. The ability to accumulate BDE-47 in digestive gland and gill was also evaluated in order to provide information for food safety. Analysis of tissue extracts indicated that digestive gland had the higher BDE-47 levels (12,463.1±1334.8 ng/g d.w.) compared to gill (6368.6±738.7ng/g d.w.) after a 15-day exposure period. Forward and reverse SSH libraries were made from pooled digestive glands of R. philippinarum, from which 75 high quality sequences were obtained by BLAST analysis. The expression of 39 genes with significant homology (E-value<10(-5)) out of the 75 sequences was investigated by quantitative RT-PCR. Among the 39 genes, 27 genes were found up-regulated while 12 genes were found down-regulated after the BDE-47 exposure. The 39 genes were involved in cellular cycle, cytoskeleton, substance and energy metabolism, stress response, innate immunity and cell signaling and transport which were extensively discussed. This study provides a preliminary basis for studying the response of marine bivalves upon exposure to PBDEs in terms of regulated gene expression.