Alginate-coated activated charcoal enhances fecal excretion of 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice, with fewer side effects than uncoated one.

Activated charcoal (AC) is a potential candidate antidote against dioxins. However, it is difficult to take AC as a supplement on a daily basis, because its long-term ingestion causes side effects such as constipation and deficiency of fat-soluble essential nutrients and hypocholesterolemia. Alginate-coated AC, termed Health Carbon (HC), was developed to decrease the side effects of AC, but its pharmacological effects, including side effects, remains unclear. Here, we show that HC enhanced fecal excretion of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and decreased some side effects of unmodified AC, such as hypocholesterolemia, in male mice. Basal diet mixed with HC or unmodified AC at various concentrations was fed to mice for 16 days following a single intraperitoneal administration of [3H]TCDD. Both HC and unmodified AC at 3% or more significantly increased fecal excretion of [3H]TCDD in comparison with the control basal diet. Consistent with this, [3H]TCDD radioactivity in the liver-a major TCDD storage organ-was markedly decreased by HC at concentrations of 3% and 10%. In an examination of potential side effects, unmodified AC at 10% or more caused significant body weight reduction and at 20% caused significant hypocholesterolemia. In contrast, HC caused weight gain reduction only at a concentration of 20%, and there was no evidence of hypocholesterolemia at any dietary HC concentration. HC not only retains the ability of AC to enhance fecal excretion of TCDD but also reduces some of the side effects of AC.

Occurrence and Estimated Dietary Intake of PCBs and PCDD/Fs in Functional Foods Enriched with Omega-3 from Spain.

The polychlorinated biphenyl (PCB), polychlorinated dibenzo-p-dioxin, and dibenzofuran (PCDD/F) contents of six functional foods enriched with omega-3 were characterized. All the samples analyzed showed concentration levels below the maximal levels established by Regulation EC 1259/201120. PCB concentrations were higher than those of PCDD/Fs; oil supplements were the most contaminated samples [1.8 pg of WHO-TEQ/g of lipid weight (lw)] followed by chicken eggs (1.3 pg of WHO-TEQ/g of lw), cow's milk (0.23 pg of WHO-TEQ/g of lw), biscuits (0.15 pg of WHO-TEQ/g of lw), soy milks (0.11 pg of WHO-TEQ/g of lw), and soy lecithin (0.049 pg of WHO-TEQ/g of lw). The most abundant non-dl-PCBs were PCBs 52 and 101 in cow's milk, soy products, and biscuits, while in chicken eggs and oil supplements, they were PCBs 153 and 138. PCBs 118 and 105 were the most frequent dl-PCBs in all samples. Only oil supplements presented quantifiable concentrations for almost all PCDD/Fs, OCDD and OCDF being the most abundant. The estimated daily intake was 2.7 pg of WHO-TEQ/day for chicken eggs, 0.91 pg of WHO-TEQ/day for cow's milk, 0.45 pg of WHO-TEQ/day for soy milks, and 0.44 pg of WHO-TEQ/day for biscuits. For oil supplements, it was more variable, but always higher.

Lipidomic Evaluation of Aryl Hydrocarbon Receptor-Mediated Hepatic Steatosis in Male and Female Mice Elicited by 2,3,7,8-Tetrachlorodibenzo-p-dioxin.

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces hepatic steatosis mediated by the aryl hydrocarbon receptor. To further characterize TCDD-elicited hepatic lipid accumulation, mice were gavaged with TCDD every 4 days for 28 days. Liver samples were examined using untargeted lipidomics with structural confirmation of lipid species by targeted high-resolution MS/MS, and data were integrated with complementary RNA-Seq analyses. Approximately 936 unique spectral features were detected, of which 379 were confirmed as unique lipid species. Both male and female samples exhibited similar qualitative changes (lipid species) but differed in quantitative changes. A shift to higher mass lipid species was observed, indicative of increased free fatty acid (FFA) packaging. For example, of the 13 lipid classes examined, triglycerides increased from 46 to 48% of total lipids to 68-83% in TCDD treated animals. Hepatic cholesterol esters increased 11.3-fold in male mice with moieties consisting largely of dietary fatty acids (FAs) (i.e., linolenate, palmitate, and oleate). Phosphatidylserines, phosphatidylethanolamines, phosphatidic acids, and cardiolipins decreased 4.1-, 5.0-, 5.4- and 7.4-fold, respectively, while ceramides increased 6.6-fold. Accordingly, the integration of lipidomic data with differential gene expression associated with lipid metabolism suggests that in addition to the repression of de novo fatty acid synthesis and ß-oxidation, TCDD also increased hepatic uptake and packaging of lipids, while inhibiting VLDL secretion, consistent with hepatic fat accumulation and the progression to steatohepatitis with fibrosis.

2,3,7,8-TCDD-mediated toxicity in peripheral blood mononuclear cells is alleviated by the antioxidants present in Gelidiella acerosa: an in vitro study.

Seaweeds have been used as a source of traditional medicine worldwide for the treatment of various ailments, mainly due to their ability to quench the free radicals. The present study aims at evaluating the protective effect of methanolic extract of Gelidiella acerosa, an edible red seaweed against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity in peripheral blood mononuclear cells (PBMC). For evaluating the protective effect of G. acerosa, PBMC were divided into four groups: vehicle control, TCDD (10 nM), TCDD + G. acerosa (300 µg/ml), and G. acerosa alone treated. Scavenging of intracellular reactive oxygen species (ROS) induced by TCDD was assessed by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method. Alterations at macromolecular level were quantified through lipid peroxidation (LPO) level, protein carbonyl content (PCC) level, and comet assay. The cellular morphology upon TCDD toxicity and G. acerosa treatment was obtained by light microscopy and histopathological studies. The chemical composition present in the methanolic extract of G. acerosa was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The results reveal that 10 nM TCDD caused significant (P < 0.05) reduction in cell viability (94.10 ± 0.99), and treatment with 300 µg/ml extract increased the cell viability (99.24 ± 0.69). TCDD treatment resulted in a significant increase in the production of ROS, LPO (114 ± 0.09), and PCC (15.13 ± 1.53) compared to the control, whereas co-treatment with G. acerosa significantly (P < 0.05) mitigated the effects. Further, G. acerosa significantly (P < 0.05) prevented TCDD-induced genotoxicity and cell damage. GC-MS analysis showed the presence of n-hexadecanoic acid (retention time (RT) 13.15), cholesterol (RT 28.80), α-D-glucopyranose, 4-O-α-D-galactopyranosyl (RT 20.01), and azulene (RT 4.20). The findings suggest that G. acerosa has a strong protective ability against TCDD-induced cytotoxicity, oxidative stress, and DNA damage.

Enhanced anaerobic biodegradation of OCDD-contaminated soils by Pseudomonas mendocina NSYSU: microcosm, pilot-scale, and gene studies.

In this study, microcosm and pilot-scale experiments were performed to investigate the capability and effectiveness of Pseudomonas mendocina NSYSU (P. mendocina NSYSU) on the bioremediation of octachlorodibenzo-p-dioxin (OCDD)-contaminated soils. The objectives were to evaluate the (1) characteristics of P. mendocina NSYSU, (2) feasibility of enhancing OCDD biodegradation with the addition of P. mendocina NSYSU and lecithin, and (3) variation in microbial diversity and genes responsible for the dechlorination of OCDD. P. mendocina NSYSU was inhibited when salinity was higher than 7%, and it could biodegrade OCDD under reductive dechlorinating conditions. Lecithin could serve as the solubilization agent causing the enhanced solubilization and dechlorination of OCDD. Up to 71 and 62% of OCDD could be degraded after 65 days of incubation under anaerobic conditions with and without the addition of lecithin, respectively. Decreased OCDD concentrations caused significant increase in microbial diversity. Results from the pilot-scale study show that up to 75% of OCDD could be degraded after a 2.5-month operational period with lecithin addition. Results from the gene analyses show that two genes encoding the extradiol/intradiol ring-cleavage dioxygenase and five genes encoding the hydrolase in P. mendocina NSYSU were identified and played important roles in OCDD degradation.

Degradation of recalcitrant aliphatic and aromatic hydrocarbons by a dioxin-degrader Rhodococcus sp. strain p52.

This study investigates the ability of Rhodococcus sp. strain p52, a dioxin degrader, to biodegrade petroleum hydrocarbons. Strain p52 can use linear alkanes (tetradecane, tetracosane, and dotriacontane), branched alkane (pristane), and aromatic hydrocarbons (naphthalene and phenanthrene) as sole carbon and energy sources. Specifically, the strain removes 85.7 % of tetradecane within 48 h at a degradation rate of 3.8 mg h(-1) g(-1) dry cells, and 79.4 % of tetracosane, 66.4 % of dotriacontane, and 63.9 % of pristane within 9-11 days at degradation rates of 20.5, 14.7, and 20.3 mg day(-1) g(-1) dry cells, respectively. Moreover, strain p52 consumes 100 % naphthalene and 55.3 % phenanthrene within 9-11 days at respective degradation rates of 16 and 12.9 mg day(-1) g(-1) dry cells. Metabolites of the petroleum hydrocarbons by strain p52 were analyzed. Genes encoding alkane-hydroxylating enzymes, including cytochrome P450 (CYP450) enzyme (CYP185) and two alkane-1-monooxygenases, were amplified by polymerase chain reaction. The transcriptional activities of these genes in the presence of petroleum hydrocarbons were detected by reverse transcription-polymerase chain reaction. The results revealed potential of strain p52 to degrade petroleum hydrocarbons.

[Promotive excretion of causative agents of Yusho by fermented brown rice with Aspergillus oryze in Yusho patients].

Forty two years have passed since the outbreak of Kanemi rice oil poisoning, namely, Yusho in the western Japan. However, even now the Yusho patients have been still suffering from several objective and subjective symptoms. In order to improve or, if possible, to cure such symptoms, the most important therapeutic treatment is considered to actively excrete the causative agents, that is, polychlorinated dibenzofurans (PCDFs) from the bodies of the patients and to reduce their body burdens. In rats, chlorophyll and dietary fiber have been shown to promote the fecal excretion of PCDFs and polychlorinated dibenzo-p-dioxins (PCDDs) and to reduce their levels in rats. In this study, we have examined whether such kinds of effect are also observed by fermented brown rice with Aspergillus oryzae (FBRA) containing 5% spirulina, which is so-called spirulina HI * GENKI, the health food and relatively rich with chlorophyll and dietary fiber, in eighteen Yusho patients. They were divided into two groups, namely group A, ten patients (3 males and 7 females) with the mean age of 67.7 years old and group B, eight patients (4 males and 4 females) with the mean age of 64.1 years old. Among the patients of group A, three patients were especially highly contaminated with PCDFs and we classified them into group A (High). Respective mean concentrations of PCDFs in the blood just before initiating this study were as follows; group A : 145 pg/g lipid, group A (High) : 371 pg/g lipid and group B : 52.1 pg/g lipid. Contamination levels of PCDFs, PCDDs and dioxin-like polychlorinated biphenyls (PCBs) in group A (High) were 1.7 to 2.6 times higher than those in group A and 2.4 to 7.1 times higher than those in group B. Accordingly, concentrations of dioxins (PCDFs + PCDDs + dioxin-like PCBs) in the blood of groups A, A (High) and B were, respectively, 194, 458 and 85 pg-TEQ/g lipid. Concentrations of PCBs were also the highest in group A (High) : 1399 ng/g lipid, in group A : 748 ng/g lipid and the lowest in group B : 456 ng/g lipid. Groups A and A (High) took around 7.0 g of spirulina HI * GENKI after each meal and three times a day for the first one year and for the second one year, they did not take spirulina HI * GENKI anymore. Group B took spirulina HI * GENKI with the same manner as the group A only for the second one year. The concentrations of PCDFs, PCDDs, dioxin-like PCBs and PCBs in the blood were also measured at the end of the first and second year, respectively. Assuming the body fat is also contaminated with these compounds at their concentrations on lipid weight basis in the blood and the content of body fat is 20% of 60 kg body weight, we computed the average amounts in their net excretion from the body of the patients due to spirulina HI * GENKI in the three groups. As a result, in group A (High), 341 ng-TEQ/patient of dioxins was excreted from the body, which was 3.4 times greater than that in group A and 12 times higher than that in group B. Therefore, promotive excretions of causative agents of Yusho were the most effective in group A (High) and we consider spirulina HI * GENKI is more effective from the therapeutic point of view in more highly contaminated Yusho patients.

Screening level assessment of risks due to dioxin emissions from burning oil from the BP Deepwater Horizon Gulf of Mexico spill.

Between April 28 and July 19 of 2010, the U.S. Coast Guard conducted in situ oil burns as one approach used for the management of oil spilled after the explosion and subsequent sinking of the BP Deepwater Horizon platform in the Gulf of Mexico. The purpose of this paper is to describe a screening level assessment of the exposures and risks posed by the dioxin emissions from these fires. Using upper estimates for the oil burn emission factor, modeled air and fish concentrations, and conservative exposure assumptions, the potential cancer risk was estimated for three scenarios: inhalation exposure to workers, inhalation exposure to residents on the mainland, and fish ingestion exposures to residents. U.S. EPA's AERMOD model was used to estimate air concentrations in the immediate vicinity of the oil burns and NOAA's HYSPLIT model was used to estimate more distant air concentrations and deposition rates. The lifetime incremental cancer risks were estimated as 6 × 10(-8) for inhalation by workers, 6 × 10(-12) for inhalation by onshore residents, and 6 × 10(-8) for fish consumption by residents. For all scenarios, the risk estimates represent upper bounds and actual risks would be expected to be less.

Effects of selected food phytochemicals in reducing the toxic actions of TCDD and p,p'-DDT in U937 macrophages.

To assess the effectiveness of selected food phytochemicals in reducing the toxic effects of the environmental toxicants, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and p,p'-DDT (DDT), we tested the potencies of auraptene, nobiletin, zerumbone, and (±)-13-hydroxy-10-oxo-trans-11-octadecenoic acid (13-HOA) in reversing the inflammatory action of these toxicants in U937 human macrophages. Using quantitative RT-PCR as the initial screening assay, we identified antagonistic actions of zerumbone and auraptene against the action of TCDD and DDT in up-regulating the mRNA expressions of COX-2 and VEGF. The functional significance of the inhibitory action of zerumbone on COX-2 expression was confirmed by demonstrating its suppression of TCDD-induced activation of COX-2 gene expression in mouse MMDD1 cells. We tested auraptene on DDT-induced reactive oxygen species (ROS) formation in U937 macrophages and found that auraptene is a powerful agent antagonizing this action of DDT. To confirm the significance of these actions of zerumbone and auraptene at the cellular level, we assessed their influence on TCDD-induced apoptosis resistance in intact U937 macrophages and found that they are capable of reversing this action of TCDD. In conclusion, zerumbone and auraptene were identified to be the most effective agents in protecting U937 macrophages from developing these cell toxic effects of TCDD and DDT.

Peganum harmala L. is a candidate herbal plant for preventing dioxin mediated effects.

Dioxins are widespread environmental contaminants that have been linked with a variety of deleterious effects on human health including increased cancer rates. The detrimental effects of 2,3,7,8-tetrachlorodibenzo- P-dioxin (TCDD, one of the most common environmental dioxins) are mediated via the aryl hydrocarbon receptor (AhR). AhR is a transcription factor that regulates the expression of the carcinogen-activating enzyme, cytochrome P450 1a1 (Cyp1a1). In the present study, we examined the ability of the methanolic extract of Peganum harmala L. (Zygophyllaceae) fruiting tops to affect TCDD-activated AhR-mediated signal transduction in mouse hepatoma Hepa 1c1c7 cells. Our results showed that Peganum harmala extract significantly inhibited the TCDD-mediated induction of Cyp1a1 at mRNA, protein, and activity levels. A similar pattern of inhibition at the catalytic activity level was observed with the other AhR ligands tested. The ability of the extract to inhibit Cyp1a1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and electrophoretic mobility shift assays. Harmine and harmaline were found to be the dominant components of the plant extract with a relative abundance of 7 and 4.85 % (w/w), respectively. In addition, both of the active alkaloids showed an inhibitory effect on TCDD-induced Cyp1a1 activity level. We concluded that Peganum harmala L. can interfere with AhR ligands-mediated effects.

[Promotive excretion of causative agents of Yusho by intake of fermented brown rice with Aspergillus oryze in patients with Yusho --with regard to PCDFs and PCDDs].

Forty years have passed since the outbreak of Kanemi rice oil poisoning, namely, Yusho in the western Japan. However, even now the patients with Yusho have been still suffering from several objective and subjective symptoms. In order to improve or, if possible, to cure such symptoms, the most important therapeutic treatment is considered to actively excrete the causative agents, that is, polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) from the bodies of the patients and to reduce their body burdens. In rats, chlorophyll and dietary fiber have been shown to promote the fecal excretion of PCDFs and PCDDs and to reduce their levels in rats. In this study, we have examined whether such kinds of effect are also observed by fermented brown rice with Aspergillus oryzae (FBRA) containing 5% spirulina, which is so-called spirulina HI*GENKI, the health food and relatively rich with chlorophyll and dietary fiber, in eighteen patients with Yusho. They were divided into two groups, namely group A, ten patients (3 males and 7 females) with the mean age of 67.7 years old and group B, eight patients (4 males and 4 females) with the mean age of 64.1 years old. Respective mean concentrations of the three PCDF congeners, that is, 2,3,4,7,8-PenCDF, 1, 2,3,4,7,8-HxCDF and 1,2,3,6,7,8-HxCDF in the blood on lipid weight basis just before initiating this study were as follows; group A: 413, 152 and 45.7 pg/g lipid, and group B: 151, 42.7 and 17.3 pg/g lipid. Contamination levels of these PCDF congeners in group A were 2.6 to 3.6 times higher than those in group B. In respective mean concentrations of PCDFs, PCDDs and PCDFs/DDs in both groups were as follows; group A: 228, 30.9 and 258 pg-TEQ/g lipid, and group B: 82.4, 19.7 and 102 pg-TEQ/g lipid. Contamination levels of PCDFs and PCDDs were around 2 times higher in group A than in group B. Group A took around 7.0 g of spirulina HI*GENKI after each meal and tree times a day for the first one year and for the second one year, they did not take spirulina HI*GENKI any more. Group B took spirulina HI*GENKI with the same manner as the group A only for the second one year. The concentrations of PCDFs and PCDDs in the blood of groups A and B were also measured at the end of the first and second year, respectively. Assuming the body fat is also contaminated with PCDFs and PCDDs at their concentrations on lipid weight basis in the blood and the content of body fat is 20% of 60 kg body weight, we computed the average amounts in the net excretion of PCDFs and PCDFs/DDs from the body of the patients due to the intake of spirulina HI*GENKI in groups A and B. As a result, in group A, 85.0 and 99.6 ng-TEQ/patient, respectively were excreted from the body of the patients. In group B, only 38.1 nd 40.0 ng-TEQ/patient were excreted. Accordingly, promotive excretion of PCDFs and PCDDs from the patients with Yusho seemed much effective in group A, of which their concentrations in the blood were much higher than those of group B.

Influence of soil properties on the biodegradation of 1,3,6,8-tetrachlorodibenzo-p-dioxin and fungal treatment of contaminated paddy soil by white rot fungus Phlebia brevispora.

To examine the bioremediation potential of Phlebia brevispora in dioxin-contaminated soil, the fungus was inoculated into autoclaved soil that was contaminated with 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) or 1,3,6,8-tetrachlorodibenzo-p-dioxin (1,3,6,8-TCDD). Three types of soils, organic-rich soil (Andosol), organic-poor soil (Granitic Regosols), and paddy soil, were used for the construction of artificially contaminated soil to understand the influence of the soil property on fungal growth and dioxin degradation ability. Under a solid-state condition, although the growth of the fungus improved in organic-rich soil, the degradation of 2,7-DCDD was inhibited. Although the degradation of 1,3,6,8-TCDD under a solid-state condition was inhibited severely, 1,3,6,8-TCDD degradation was observed under a slurry-state condition in organic-poor soil. In the case of organic-rich soil, an increase in water content improved the 1,3,6,8-TCDD degradation efficiency. When the historically contaminated paddy soil was treated with P. brevispora under a slurry-state condition, 1,3,6,8-TCDD as the main contaminant degraded 50% after 90d incubation.

Promotive excretion of causative agents of Yusho by one year intake of FBRA in Japanese people.

Thirty-six years have passed since the outbreak of Kanemi rice oil poisoning, namely, Yusho in the western Japan. However, even now the patients with Yusho have been still suffering from several objective and subjective symptoms. In order to improve or, if possible, to cure the such symptoms, the most important therapeutic treatment is considered to actively excrete the causative agents, that is, polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) from the bodies of the patients and to reduce their body burdens. In rats, dietary fiber and chlorophyll have been shown to promote the fecal excretion of dioxins and to reduce their levels in rat liver. In this study, we examined whether such kinds of effect were also observed by FBRA, which was the health food and relatively rich with dietary fiber and chlorophyll, in nine married Japanese couples. As a result, concentrations of PCDFs and PCDDs on the lipid weight basis in the blood of the FBRA-intake group in which they took 7.0 to 10.5g of FBRA after each meal and three times a day for one year were more lowered than those in the blood of the non-intake group; Blood levels of PCDFs and PCDDs in the FBRA-intake group were decreased by 41.0 and 37.2%, respectively, and those decreases were 33.7 and 29.4% in the non-intake group. Their total body burdens just before and one year after the study were calculated on the assumptions that the body fat was also contaminated with these dioxins at their blood levels on the lipid weight basis and the content of body fat was 20% of the body weight. Then, we computed the average amounts in excretion of PCDFs and PCDDs from the body in both the FBRA-intake and non-intake groups. Consequently, the amounts of excretion of PCDFs and PCDDs in the FBRA-intake group were 1.81 and 1.74 times, respectively, greater than those in the non-intake group. Therefore, FBRA seemed to promote the fecal excretion of causative agents of Yusho, from the human body. We also expect FBRA to reduce their body burdens of patients with Yusho and to improve some objective and subjective symptoms of Yusho patients.

Photodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans in soil with vegetable oil.

GOAL, SCOPE AND BACKGROUND: This study was carried out to investigate the effect of olive oil on the photodegradation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in contaminated sawmill soil. Previous studies had shown that the solubility of PCDD/Fs in olive oil is high and a rapid photodegradation of PCDD/Fs takes place in olive oil when irradiated with ultraviolet (blacklight) lamps. The efficiency of this treatment method was evaluated under more practical conditions. These included the use of sunlight irradiation and a lower-grade olive oil, without a preliminary extraction of soil with olive oil. METHODS: A 1-cm layer of contaminated sawmill soil was blended with 20 weight-% of olive oil and exposed to sunlight for four weeks. In another experiment, a new dose of olive oil was added at the middle of the exposure period. The PCDD/F concentrations of the soils were monitored periodically. RESULTS AND DISCUSSION: A reduction in the concentration of 2,3,7,8-chlorinated PCDD/Fs by 59% and in WHO-TEQ in contaminated sawmill soil by 48% was attained after blending the soil with two doses (20 + 20%) of olive oil and exposing the mixture to sunlight for four weeks. Photodegradation with only one dose of olive oil was less efficient. This suggests that periodical additions of olive oil would be needed to maintain a proper degradation rate. After the oil additions, the WHO-TEQ content of the soil declined with first order reaction half-lives of 19.2 to 19.7 d. The overall half-life during the four-week treatment, however, was 30 d. CONCLUSION: A significant reduction in the PCDD/F concentration of aged sawmill soil can be achieved with a relatively simple olive oil-sunlight treatment. RECOMMENDATIONS AND OUTLOOK: Some theoretical and technological questions need to be solved before using the investigated soil decontamination method in larger-scale applications. The functions of vegetable oils in photodegradation processes should be studied in more detail. The amount of oil that is needed for a proper solubilisation and photodegradation of PCDD/Fs should be minimised. Moreover, special care should be taken to prevent mobilisation of PCDD/Fs to the surrounding environment and to avoid leaving bioavailable residuals of PCDD/Fs in soil.

Screening of the inhibitory effect of vegetable constituents on the aryl hydrocarbon receptor-mediated activity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The aryl hydrocarbon receptor (AhR) is a ligand-activated nuclear transcription factor that mediates responses to environmental contaminants such as dioxins, which have many adverse health effects. We performed a preliminary screening of the inhibitory effects of vegetable constituents on 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced activation of AhR using the AhR-based bioassay for dioxins, the Ah-Immunoassay. Ninety vegetable constituents including flavonoids, tannins, saponins, terpenes, etc., were assayed in vitro. Among them, flavones, flavonols, anthraquinones, piperine, coumestrol, brevifolincarboxylic acid, and resveratrol showed marked inhibitory effects on AhR-based bioassay activation by TCDD, and their effects were dose dependent. Curcumin, carnosol, and capsaicin also inhibited the activation of AhR in this assay, although to a lesser degree. These results suggest that several vegetable constituents might play a role in protection against dioxin toxicity.

Identification of potential aryl hydrocarbon receptor antagonists in green tea.

Previous investigations have implicated green tea to exert chemopreventive effects in animal models of chemical carcinogenesis, including polycyclic aryl hydrocarbon-induced cancers. In an effort to understand the compound(s) responsible for this protection, the effects of green tea extracts (GTE) and individual green tea catechins on aryl hydrocarbon receptor (AhR) gene induction were determined. Green tea (GT) was organically extracted and subsequently fractionated by column chromatography. The chemical composition of each fraction was determined by NMR. Several fractions inhibited tetrachlorodibenzo-p-dioxin-induced transcription of a dioxin responsive element-dependent luciferase reporter in stably transfected mouse hepatoma cells in a concentration-dependent manner. To determine the GT component(s) responsible for the observed effects, individual catechins were tested in the luciferase reporter system at concentrations found within the active fractions. Of the catechins tested, epigallocatechingallate (EGCG) and epigallocatechin (EGC) were the most potent antagonists, with IC(50) values of 60 and 100 microM, respectively. Re-creation of the active fractions using commercially available catechins further confirmed the identification of EGCG and EGC as the active AhR antagonists in green tea. These data suggest that EGCG and EGC are capable of altering AhR transcription and are responsible for most, if not all, of the AhR antagonist activity of GTE.

Active elimination of causative PCDFs/DDs congeners of Yusho by one year intake of FBRA in Japanese people.

Thirty-five years have been passing since the outbreak of Kanemi rice oil poisoning, namely, Yusho in the western Japan. However, even now the patients with Yusho have been still suffering from several objective and subjective symptoms. In order to improve or, if possible, to cure the such symptoms, the most important therapeutic treatment is considered to actively excrete the most toxic causative PCDFs/DDs congeners, that is, 2,3,4,7,8-pentachlorodibenzofuran (PenCDF) and 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (HxCDD) from the bodies of the patients and to reduce their body burdens. In rats, dietary fiber and chlorophyll have been shown to promote the fecal excretion of dioxins and to reduce their levels in rat liver. In this study, we examined whether such kinds of effect were also observed by FBRA, which was the health food and relatively rich with dietary fiber and chlorophyll in nine married Japanese couples. As a result, concentrations of PenCDF and HxCDD on the lipid weight basis in the blood of the FBRA-intake group in which they took 7.0 to 10.5 g of FBRA after each meal and three times a day for one year were more lowered than those in the blood of the non-intake group; Blood levels of PenCDF and HxCDD in the FBRA-intake group were decreased by 30.5 and 33.9%, respectively, and those decreases were 22.0 and 24.5% in the non-intake group. Their total body burdens just before and one year after the study were calculated on the assumptions that the body fat was also contaminated with these congeners at their blood levels on the lipid weight basis and the content of body fat was 20% of the body weight. Then, we computed the average amounts in excretion of PenCDF and HxCDD from the body in both the FBRA-intake and non-intake groups. Consequently, the amounts of excretion of PenCDF and HxCDD in the FBRA-intake group were 2.1 and 1.9 times, respectively, greater than those in the non-intake group. Therefore, FBRA seemed to promote the fecal excretion of PenCDF and HxCDD, the main causative PCDFs/DDs congeners of Yusho, from the human body. We also expect FBRA to reduce their body burdens of patients with Yusho and to improve some objective and subjective symptoms of Yusho patients.

Evaluation of TCDD biodegradability under different redox conditions.

Polychlorinated dibenzo-p-dioxins have been generated as unwanted by-products in many industrial processes. Although their widespread distribution in different environmental compartments has been recognized, little is known about their fate in the ultimate environment sinks. The highly stable dioxin isomer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been called the most toxic compound known to man. In this laboratory microcosm study, TCDD bioavailability was evaluated under five reduction/oxidation (redox) conditions including aerobic biodegradation, aerobic cometabolism, methanogenesis, iron reduction, and reductive dechlorination. Activated sludge and aquifer sediments from a TCDD and a pentachlorophenol (PCP) contaminated site were used as the inocula. Acetate, sludge cake, and cane molasses were used as the primary substrates (carbon sources) in cometabolism and reductive dechlorination microcosms. After a 90-day incubation period, microcosms constructed under reductive dechlorination conditions were the only treatment showing promising remediation results. The highest TCDD degradation rate [up to 86% of TCDD removal (with an initial concentration of 96 microg/kg of soil)] was observed in the microcosms with anaerobic activated sludge as the microbial inocula and sludge cakes as the primary substrates. Except for reductive dechlorination microcosms, no significant TCDD removal was observed in the microcosms prepared under other conditions. Thus, application of an effective primary substrate to enhance the reductive dechlorination process is a feasible method for TCDD bioremediation. Bioremediation expense can be significantly reduced by the supplement of some less expensive alternative substrates (e.g., sludge cakes, cane molasses). Results would be useful in designing a scale-up in situ or on-site bioremediation system such as bioslurry reactor for field application.

An investigation of the in vivo formation of octachlorodibenzo-p-dioxin.

The in vivo formation of dioxins from chemical precursors was investigated in rats. Sprague-Dawley rats were fed pentachlorophenol or a predioxin in peanut oil for 14 days. Mass balance calculations indicated that pentachlorophenol was not converted to dioxins; however, the predioxin, nonachloro-2-phenoxyphenol, was converted to OCDD. Conversion of the predioxin ranged from 0.5% to 153% and depended on the amount of predioxin and OCDD present in the diet. The analytical procedures used for sample preparation did not appear to cause conversion of the predioxin to OCDD. The mechanism for biological conversion may be enzymatic or spontaneous.

Suppression of cell cycle progression by flavonoids: dependence on the aryl hydrocarbon receptor.

Some flavonoids are ligands of the aryl hydrocarbon receptor (AHR) and cause cell cycle arrest. The dependency of the cytostatic effects of five flavonoids (flavone, alpha-naphthoflavone, apigenin, 3'-methoxy-4'-nitroflavone and 2'-amino-3'-methoxyflavone) on a functional AHR was examined in AHR-containing rat hepatoma 5L cells and an AHR-deficient cell line (BP8) derived from the 5L line. The potent AHR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was cytostatic to the 5L line due to the induction of a G(1) arrest and dramatically elevated steady-state levels of CYP1A1 mRNA. TCDD affected neither the proliferation nor CYP1A1 mRNA contents of BP8 cells. With the exception of apigenin, the flavonoids under study induced G(1) arrest in both 5L and BP8 cells when used at concentrations at which they functioned as AHR agonists, but not antagonists. Apigenin-treated 5L and BP8 cultures primarily arrested in G(2)/M. The AHR-containing murine hepatoma cell line 1c1c7 arrested following exposure to AHR agonist concentrations of flavone and alpha-naphthoflavone, but not TCDD. Unlike the G(1) arrest observed in 5L cultures, the latter two flavonoids caused principally G(2)/M arrest in 1c1c7 cells. These studies demonstrate that the cytostatic activities of flavonoids do not require the AHR and the site of checkpoint arrest with a specific flavonoid can vary with cell type.