Comprehending the Role of Endocrine Disruptors in Inducing Epigenetic Toxicity.

Endocrine disruptors are natural or man-made chemicals that interfere with the body's endocrine system leading to hormone synthesis and production defects. These chemicals are categorized as plasticizers and cosmetic chemicals, heavy metals, phytoestrogens, pesticides, detergents, surfactants, and flame retardants. Some of the most common endocrine disruptors are dioxins, bisphenol A, phthalates, perchlorate, perfluoroalkyl, and poly-fluoroalkyl substances (PFAs), phytoestrogens, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCB), triclosan, atrazine, lead, arsenic, mercury, organophosphate pesticides, and glycol ethers. Epigenetic alterations such as DNA methylation, histone modification, and miRNA regulation have been observed to play a major role in many diseases such as cancer, neurodegenerative diseases, PCOS, cardiovascular diseases, and various other disorders. In recent times, there has been a focus on endocrine-disrupting chemicals in epigenetic alterations. This review concentrates on estrogen and androgen disrupting effects, placental, and fetal effects, thyroid disrupting effects, and transgenerational effects of endocrine disruptors.

Exposure to prenatal PCBs shifts the timing of neurogenesis in the hypothalamus of developing rats.

The developing brain is highly sensitive to the hormonal milieu, with gonadal steroid hormones involved in neurogenesis, neural survival, and brain organization. Limited available evidence suggests that endocrine-disrupting chemicals (EDCs) may perturb these developmental processes. In this study, we tested the hypothesis that prenatal exposure to a mixture of polychlorinated biphenyls (PCBs), Aroclor 1221, would disrupt the normal timing of neurogenesis in two hypothalamic regions: the ventromedial nucleus (VMN) and the preoptic area (POA). These regions were selected because of their important roles in the control of sociosexual behaviors that are perturbed in adulthood by prenatal EDC exposure. Pregnant Sprague-Dawley rats were exposed to PCBs from Embryonic Day 8 (E8) to E18, encompassing the period of neurogenesis of all hypothalamic neurons. To determine the birth dates of neurons, bromo-2-deoxy-5-uridine (BrdU) was administered to dams on E12, E14, or E16. On the day after birth, male and female pups were perfused, brains immunolabeled for BrdU, and numbers of cells counted. In the VMN, exposure to PCBs significantly advanced the timing of neurogenesis compared to vehicle-treated pups, without changing the total number of BrdU+ cells. In the POA, PCBs did not change the timing of neurogenesis nor the total number of cells born. This is the first study to show that PCBs can shift the timing of neurogenesis in the hypothalamus, specifically in the VMN but not the POA. This result has implications for functions controlled by the VMN, especially sociosexual behaviors, as well as for sexual selection more generally.

Molecular characterization and expression of arginine vasotocin V1a2 receptor in Atlantic croaker brain: Potential mechanisms of its downregulation by PCB77.

The arginine vasotocin (AVT)-V1a receptor mediates critical reproductive behaviors of the nonapeptide vasotocin in the teleost brain. In this study, we report the molecular characterization of the AVT-V1a2 receptor and its messenger RNA (mRNA) and protein expressions in the Atlantic croaker brain after exposure to the planar polychlorinated biphenyl congener 3,3',4,4'-tetrachlorobiphenyl (PCB77). The full-length sequence of croaker AVT-V1a2 receptor complementary DNA (cDNA) is highly homologous to other teleost AVT-V1a2 receptor cDNAs. Double-labeled immunohistochemistry showed coexpression of AVT-V1a2 receptor and gonadotropin-releasing hormone-I (GnRH-I, a neuropeptide that regulates gonadotropin secretion) in hypothalamic neurons, thereby providing the anatomical basis for possible AVT modulation of croaker reproduction through alterations in GnRH-I secretion. AVT-V1a2 receptor mRNA and protein levels as well as GnRH-I mRNA levels were markedly decreased in hypothalamic tissues of croaker exposed to PCB77 (dose: 2 and 8 µg/g body weight for 4 weeks) compared with levels in untreated (control) fish. In contrast, hypothalamic cytochrome P450 1A (CYP1A, a monooxygenase enzyme) and interleukin-1ß (IL-1ß, a cytokine indicator of inflammation and response to neuronal damage) mRNA levels, and plasma protein carbonyl (PC, an indicator of reactive oxygen species) contents, important biomarkers of neural stress, were increased in PCB77-exposed fish compared with controls. Collectively, these results suggest that the downregulation of hypothalamic AVT-V1a2 receptor and GnRH-I transcripts due to PCB77 exposure is associated with induction of CYP1A, cellular inflammation and oxidative stress in Atlantic croaker, a marine teleost that inhabits estuaries along the US Atlantic coast and the Gulf of Mexico that are often contaminated with persistent organic pollutants such as PCBs.

Hepatic metabolomics reveals that liver injury increases PCB 126-induced oxidative stress and metabolic dysfunction.

The deleterious effects of PCB 126 are complex, and the role of the liver in modifying toxic insult is not well understood. We utilized metabolomics approaches to compare liver metabolites significantly affected by PCB 126 in control mice and a diet induced liver injury mouse model. In this 14-week study, mice were fed either an amino acid supplemented control diet (CD) or a methionine-choline deficient diet (MCD) which promoted nonalcoholic steatohepatitis (NASH) and were subsequently exposed to PCB 126. The liver metabolome was profiled by a global metabolomic analysis using LC-MS. There were clear differences between PCB 126 exposed and control mice in the hepatic metabolomic profiles (216 and 266 metabolites were altered in CD-fed and MCD-fed mice respectively after PCB 126 exposure). PCB 126 modulated glycerophospholipid metabolism, glutathione metabolism, and CoA biosynthesis pathways irrespective of diet; indicating that the disturbance in lipid metabolism and thiol metabolites are general markers of PCB 126 exposure irrespective of liver health. Additionally, metabolites associated with oxidative stress and mitochondrial dysfunction were greatly elevated in PCB 126 exposed mice with compromised livers (e.g., 4-hydroxy-nonenal glutathione, oxylipids, uric acid, and acylcarnitines). Moreover, PCB 126 exposure downregulated redox genes, and the effect was more pronounced in liver injury mice. In conclusion, this study demonstrates that PCB 126 could induce oxidative stress and metabolic dysfunction, and pre-existing liver injury can markedly modify PCB 126-induced metabolic changes. Using metabolic profiling, this study suggests mechanism of enhanced PCB 126 toxicity under liver injury settings.

[Apoptosis and Ca~(2+) balance disorder of BV-2 cells induced by polychlorinated biphenyl].

OBJECTIVE: To study the neurotoxicity and mechanism of polychlorinated biphenyl( PCB) in BV-2 cells. METHODS: The experiment was divided into control group and PCB118, 138, 153, 180 treated group, the dosages were 0. 000, 0. 015, 0. 030, 0. 050, 0. 100, 0. 150 µmol/L. Through the statistical analysis of the survival rate of the cells, the final dose was divided into low, middle and high dose levels. Among them, the high dose group except PCB118 was 0. 15 µmol/L, the PCB138, 153, 180 concentration was 0. 015, 0. 05 and 0. 1 µmol/L for the low, medium and high dose groups. In vitro culture of mouse microglia cells with different doses of PCB after exposure, CCK-8 method to detect cell growth and viabilities; FITC Annexin V/PI method to detect cell apoptosis rate; detection of lactate dehydrogenase( LDH) release by ELISA kit; fluorescence probe method( Fluo-4 AM) to detect the intracellular calcium content changes. RESULTS: CCK-8 and FITC Annexin V/PI double staining experiments showed that PCB118, 138, 153, 180 could inhibit cell activity, and with the increase in dose, cell survival rate decreased, apoptosis rate increased. PCB118 dose in 0. 15 µmol/L toxicity increased, cytoactive was reduced to( 66. 56 ± 0. 10) %, apoptosis rate increased to( 27. 39 ± 1. 80) %; PCB138, 153 in 0. 1 µmol/L cell survival rate reached( 66. 66 ± 0. 10) % and( 67. 17 ± 0. 12) %, apoptosis rate reached( 48. 77 ± 2. 43) % and( 56. 42 ± 3. 59) %; PCB180 dose of 0. 015µmol/L cell survival rate reached( 92. 07 ± 0. 38) %, cell apoptosis rate was( 6. 82 ±0. 51) %, significantly higher than that of the control group, the difference was statistically significant( P < 0. 05). LDH assay showed that the release amount of LDH was proportional to the dose of PCB. The lactate dehydrogenase amounts of PCB118, 138, 153 and 180 were( 523. 78 ± 13. 58) U/L, ( 430. 37 ± 22. 03) U/L, ( 540. 58 ± 13. 08)U/L, ( 411. 88 ± 21. 92) U/L, which were significantly higher than those in the control group, the difference was statistically significant( P < 0. 05). The result of Fluo-4 and AM showed that the average fluorescence intensity of intracellular calcium( Ca~(2+)) in PCB exposed group increased obviously. The average fluorescence intensity of Ca~(2+) in the PCB118, 138, 153 and 180 groups was( 10. 14 ± 2. 36), ( 32. 47 ± 1. 56), ( 16. 54 ± 0. 97)and( 40. 46 ± 2. 19) when the dose was 0. 015 µmol/L, significantly higher than that of the control group, the difference was statistically significant( P < 0. 05). CONCLUSION: PCB could cause neurotoxicity damage, increase LDH, destroy cell membrane integrity, induce the balance disorder of cell calcium and lead to the cell apoptosis.

Additive mixture effects of estrogenic chemicals in human cell-based assays can be influenced by inclusion of chemicals with differing effect profiles.

A growing body of experimental evidence indicates that the in vitro effects of mixtures of estrogenic chemicals can be well predicted from the estrogenicity of their components by the concentration addition (CA) concept. However, some studies have observed small deviations from CA. Factors affecting the presence or observation of deviations could include: the type of chemical tested; number of mixture components; mixture design; and assay choice. We designed mixture experiments that address these factors, using mixtures with high numbers of components, chemicals from diverse chemical groups, assays with different in vitro endpoints and different mixture designs and ratios. Firstly, the effects of mixtures composed of up to 17 estrogenic chemicals were examined using estrogenicity assays with reporter-gene (ERLUX) and cell proliferation (ESCREEN) endpoints. Two mixture designs were used: 1) a 'balanced' design with components present in proportion to a common effect concentration (e.g. an EC(10)) and 2) a 'non-balanced' design with components in proportion to potential human tissue concentrations. Secondly, the individual and simultaneous ability of 16 potential modulator chemicals (each with minimal estrogenicity) to influence the assay outcome produced by a reference mixture of estrogenic chemicals was examined. Test chemicals included plasticizers, phthalates, metals, PCBs, phytoestrogens, PAHs, heterocyclic amines, antioxidants, UV filters, musks, PBDEs and parabens. In all the scenarios tested, the CA concept provided a good prediction of mixture effects. Modulation studies revealed that chemicals possessing minimal estrogenicity themselves could reduce (negatively modulate) the effect of a mixture of estrogenic chemicals. Whether the type of modulation we observed occurs in practice most likely depends on the chemical concentrations involved, and better information is required on likely human tissue concentrations of estrogens and of potential modulators. Successful prediction of the effects of diverse chemical combinations might be more likely if chemical profiling included consideration of effect modulation.

[Impaired mitogen-induced lymphocyte transformation in patients with Yusho].

To investigate chronic immune effects of polychlorinated biphenyl (PCB) and polychlorinated dibenzofuran (PCDF), in vitro lymphocyte transformation in response to phytohemagglutinin (PHA) and concanavalin A (Con A) was studied in 139 patients with Yusho and 61 controls. PHA-induced lymphocyte transformation was significantly lower in patients with Yusho than in controls. PHA-induced lymphocyte transformation was inversely correlated with the concentrations of PCB and 2,3,4,7, 8-pentachlorodibenzofuran (PeCDF) in the blood. Con A-induced lymphocyte transformation showed similar inverse correlations with the concentrations of PCB and 2,3,4,7, 8-PeCDF. We conclude that impairment of mitogen-induced lymphocyte transformation in patients with Yusho may be associated with PCB and 2,3,4,7,8-PeCDF in the blood.

Effect of dietary selenium on the promotion of hepatocarcinogenesis by 3,3', 4,4'-tetrachlorobiphenyl and 2,2', 4,4', 5,5'-hexachlorobiphenyl.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants that have promoting activity in the liver. PCBs induce oxidative stress, which may influence carcinogenesis. Epidemiological studies strongly suggest an inverse relationship between dietary selenium (Se) and cancer. Despite evidence linking Se deficiency to hepatocellular carcinoma and liver necrosis, the underlying mechanisms for Se cancer protection in the liver remain to be determined. We examined the effect of dietary Se on the tumor promoting activities of two PCBs congeners, 3,3', 4,4'-tetrachlorobiphenyl (PCB-77) and 2,2', 4,4', 5,5'-hexachlorobiphenyl (PCB-153) using a 2-stage carcinogenesis model. An AIN-93 torula yeast-based purified diet containing 0.02 (deficient), 0.2 (adequate), or 2.0 mg (supplemental) selenium/kg diet was fed to Sprague-Dawley female rats starting ten days after administering a single dose of diethylnitrosamine (150 mg/kg). After being fed the selenium diets for 3 weeks, rats received four i.p. injections of either PCB-77 or PCB-153 (150 micromol/kg) administered every 14 days. The number of placental glutathione S-transferase (PGST)-positive foci per cm(3) and per liver among the PCB-77-treated rats was increased as the Se dietary level increased. Unlike PCB-77, rats receiving PCB-153 did not show the same Se dose-response effect; nevertheless, Se supplementation did not confer protection against foci development. However, the 2.0 ppm Se diet reduced the mean focal volume, indicating a possible protective effect by inhibiting progression of preneoplastic lesions into larger foci. Cell proliferation was not inhibited by Se in the liver of the PCB-treated groups. Se did not prevent the PCB-77-induced decrease of hepatic Se and associated reduction in glutathione peroxidase (GPx) activity. In contrast, thioredoxin reductase (TrxR) activity was not affected by the PCBs treatment or by Se supplementation. These findings indicate that Se does not inhibit the number of PGST-positive foci induced during promotion by PCBs, but that the size of the lesions may be inhibited. The effects of Se on altered hepatic foci do not correlate with its effects on GPx and TrxR.

Bioactive polychlorinated bibenzyls from the liverwort Riccardia polyclada.

GC-MS and (1)H NMR spectroscopic profiling of a CDCl 3 extract of the liverwort Riccardia polyclada (syn. R. umbrosa) revealed the presence of four main compounds bearing several chlorine atoms on a bibenzyl skeleton. Separation of a CH 2Cl 2 extract was achieved using preparative TLC, and structures 1- 4 were proposed on the basis of spectroscopic evidence. Compounds 1- 4 were active in a brine shrimp lethality bioassay ( Artemia salina). In addition, 2 and 4 displayed moderate antifeedant activity in disk-choice bioassays with Spodoptera littoralis larvae and inhibited the growth of Cladosporium herbarum cultures on TLC plates.

The influence of polychlorinated biphenyls (PCBs) and phytoestrogens in vitro on functioning of reproductive tract in cow.

Ovarian, endometrial and myometrial cells and strips of longitudinal myometrium from cows on defined days of estrous cycle were treated for 24-72 h with different doses (1-100 ng/ml) of PCBs mixture (Aroclor 1248) or with one of PCB congeners (126, 77, 153). The administered doses of PCBs neither affected the viability of cells nor influenced the ovarian steroidogenesis as measured by progesterone (P(4)), estradiol (E(2)) and testosterone secretion from luteal, granulosa and theca cells, respectively. In contrast, PCBs clearly inhibited a FSH and LH-stimulated effect on steroids secretion from granulosa and luteal cells. Moreover, PCBs significantly stimulated oxytocin (OT) secretion from the studied ovarian cells, and at least part of this effect is elicited through activation of glucocorticoid receptors. Further, PCBs were found to increase basal intracellular concentrations of Ca(2+) and both spontaneous and OT-stimulated contractions of myometrial strips. Concomitantly, PCBs increased endometrial secretion of PGF(2alpha), hence the ratio of PGF(2alpha):PGE(2) was also increased. Phytoestrogens (genistein, daidzein, coumestrol), with a different intensity, reduced the effect of PCBs on PGF(2alpha) secretion and myometrial contractions. Genistein inhibited PCBs' effect on OT secretion from granulosa cells, while PCB's effect on OT release from luteal cells was reduced mainly by genistein and daidzein. We conclude that PCBs can impair both ovarian functioning and uterine contractility, while phytoestrogens are able to reduce this effect.

Screening the oxidative potential of several mono- and di-halogenated biphenyls and biphenyl ethers in rat hepatocytes.

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 C(11)-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.

Polychlorinated biphenyls (PCB 153 and PCB 126) action on conversion of 20-hydroxylated cholesterol to progesterone, androstenedione to testosterone, and testosterone to estradiol 17beta.

To look for one of the possible mechanisms of action we investigated the effect of two congeners of polychlorinated biphenyls (PCB153 as one of the most prominent environmental contaminants and PCB 126 as one of the most toxic contaminants similar to dioxin) on the cellular conversion of steroid precursors as an indicator for enzyme activity (20-hydroxylated cholesterol to progesterone for P450 (scc,) androstendione to testosterone for 17-beta-HSD, and testosterone to estradiol for P450 (arom)). The net synthesis and secretion of particular steroids was used as the indicator of enzyme activity. Co-culture of pig granulosa and theca cells isolated from small (SF) and large (LF) follicles, was carried out in medium M199 supplemented with 100 ng/ml of PCB 153 or 100 pg/ml of PCB 126. The inhibitory action of both PCB 126 and PCB 153 on progesterone secretion by cells isolated from SF and LF follicles was reversed in the presence of 20-hydroxylated cholesterol. The addition of PCB 126 into the culture medium caused a decrease in testosterone secretion by cells isolated from both SF and LF and this effect was reversed in the presence of androstendione. The inhibitory action of PCB 153 on testosterone secretion was reversed by the addition of androstendione to the culture medium in SF, while it caused even additional stimulatory action on cells collected from LF. No effect of PCB 126 and statistically significant decrease in estradiol secretion by cells collected from SF under the influence of PCB153 was observed. The inhibitory effect of PCB 153 was reversed when the culture was supplemented with testosterone. The opposite effect of both tested congeners on estradiol secretion in both basal and testosterone supplemented culture was seen in LF. PCB 126 increased it while PCB 153 decreased both, the basal and testosterone-stimulated estradiol secretion. In conclusion, the presented results suggest that the effect of both PCBs on steroid secretion observed in an early stage of the follicular phase of the estrus cycle is due to the inhibition of cholesterol mobilisation and thus insufficient substrate availability for hormone synthesis. On the contrary, in large preovulatory follicles inhibition of testosterone secretion is due to their action on 17-beta-HSD while stimulatory or inhibitory action on estradiol secretion is the result of their action on P450 aromatase activity.

Differential effects of natural and environmental estrogens on endothelin synthesis in bovine oviduct cells.

Endothelin-1 (ET-1), a vasoconstrictor and mitogenic peptide that plays an important role within the endocrine/reproductive system, is synthesized by oviduct cells and regulates tubal contractility. Because 17beta-estradiol (estradiol) regulates oviduct function by influencing the synthesis of autocrine/paracrine factors, estradiol may also regulate ET-1 synthesis. Furthermore, environmental estrogens (EEs; phytoestrogens and xenoestrogens), which structurally resemble estradiol and possess estrogenic activity, may mimic the effects of estradiol on ET-1 synthesis and may influence the reproductive system. Using cultures of bovine oviduct cells (epithelial cells:fibroblasts, 1:1), we investigated and compared the modulatory effects of estradiol, phytoestrogens, and xenoestrogens on ET-1 synthesis and determined whether these effects were estrogen receptor (ER) mediated. A quantitative ELISA for ET-1 in the culture medium revealed that 17beta-estradiol inhibits ET-1 synthesis in a concentration-dependent manner (4-400 nmol/L). In contrast to estradiol, ET-1 synthesis was induced in cell cultures treated with xenoestrogens in the following order of potency (0.1 micromol/L): 4-hydroxy-trichlorobiphenyl > 4-hydroxy-dichlorobiphenyl > trichlorobiphenyl. The stimulatory effects of xenoestrogens on ET-1 production were mimicked by the phytoestrogens biochanin-A and genistein but not by formononetin, equol, and daidzein. The oviduct cells expressed both ERs (alpha and beta), but the modulatory effects of estradiol, but not EEs, on ET-1 synthesis were blocked by ICI-182 780 (1 microM), a pure ER antagonist. Our results provide evidence that estradiol inhibits ET-1 synthesis in oviduct cells via an ER-dependent mechanism, whereas, EEs induce ET-1 synthesis via an ER-independent mechanism. The contrasting effects of EEs on ET-1 synthesis suggests that EEs may act as endocrine modulators/disruptors and may have deleterious effects on the reproductive system by adversely influencing the biology and physiology of the oviduct.

Responsiveness of endometrial genes Connexin26, Connexin43, C3 and clusterin to primary estrogen, selective estrogen receptor modulators, phyto- and xenoestrogens.

Phytohormones and chemical compounds revealing estrogenic effects are of increasing interest for their possible influence on the physiology of the reproductive tract. The gap junction connexin (Cx) genes Cx26 and Cx43, the plasma glycoprotein clusterin gene and the complement C3 gene are highly regulated by estrogen in rat endometrium. To test the value of these genes as markers for estrogenic responsiveness we analyzed the effects of estradiol, diethylstilbestrol, the selective estrogen receptor modulators (SERMs) raloxifene and tamoxifen, the phytoestrogens genistein and daidzein, and the industrial compounds DDT (1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl) ethane) and polychlorinated biphenyl (PCB) on the transcription of these genes in rat endometrium in vivo. Enhancement of Cx26 and decrease of clusterin transcripts expression by estradiol was observed at 0.03 micro g/250 g body weight (BW), and induction of C3 expression was observed at 0.05 micro g/250 g BW. A comparable effect was obtained by a tenfold higher concentration of diethylstilbestrol. Tamoxifen had a regulatory effect on this set of genes at about a 300-fold higher concentration, while raloxifen revealed much weaker estrogenic activity. No effect on Cx43 transcripts was observed with any of the compounds at the concentrations used. An effect of genistein was observed only on Cx26 expression, while PCB decreased clusterin transcripts. These results show that Cx26, C3 and clusterin reveal a comparable sensitivity to estrogens and SERMs. With respect to the phytoestrogen genistein, however, Cx26 seems to be the most sensitive gene. The analysis of clusters of estrogen-sensitive endometrial genes could help to identify estrogenic substances, assess their potency, and elucidate their mechanism of action.

Effects of gender, diet, exogenous melatonin and subchronic PCB exposure on plasma immunoglobulin G in mink.

Effects of different fish-based diets (freshwater smelt, Baltic herring, marine herring/cod offal or their mixtures), gender, beta-glucan supplement, exogenous melatonin, and PCB exposure (Aroclor 1242((R)), 1 mg per animal per day in feed) on plasma immunoglobulin G (IgG) in the mink (Mustela vison) were studied. The aims of the study were to find out whether plasma IgG of the mink is affected by the subchronic PCB exposure, and whether biological, nutritional and hormonal effects are large enough to mask the possible IgG response. The concentration of IgG was determined using enzyme-linked immunosorbent assay (ELISA). Sexual dimorphism was detected, the males having higher levels of plasma IgG. In addition, melatonin tended to decrease IgG in females but not males. Diet also affected the humoral immune arm; the mixed-fish diets caused an unfavorable ratio of the oxidation products of lipids vs. vitamin E in liver, and resulted in low IgG concentration in plasma. In males fed Baltic herring, the beta-glucan supplement also lowered IgG levels. The PCBs failed to affect the plasma IgG of the smelt-fed female mink, and IgG concentration was not correlated with increased hepatic EROD activity or with the decreased total retinol in the liver of exposed mink. It is concluded that hormonal/seasonal and dietary factors affect the plasma IgG levels to such an extent that possible change in plasma IgG level due to PCBs in wild populations of mink is difficult to detect without a large amount of reference data.

Effects of selected polychlorinated biphenyl (PCB) congeners on hepatic glutathione, glutathione-related enzymes, and selenium status: implications for oxidative stress.

Polychlorinated biphenyls (PCBs) induce drug metabolism that may lead to the bioactivation of PCBs themselves or alternatively may lead to oxidative events within the cell. The goal of the present study was to determine the influence of congeneric PCBs, selected as substrates for or inducers of drug metabolism, upon hepatic glutathione, glutathione-related enzymes, and selenium status. Male and female Sprague-Dawley rats received two i.p. injections per week of PCB 3 (4-chlorobiphenyl), PCB 28 (2,4,4'-trichlorobiphenyl), PCB 38 (3,4,5-trichlorobiphenyl), PCB 77 (3,3',4,4'-tetrachlorobiphenyl), PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl), or both PCBs 77 and 153 (100 micromol/kg/injection) and were killed at the end of 1, 2, or 3 weeks. Whole liver homogenates, hepatic cytosol, and microsomes were prepared. Both glutathione reductase and glutathione transferase activities were increased significantly in both male and female rats receiving PCB 77, an aryl hydrocarbon receptor agonist, as well as in those receiving both PCBs 77 and 153. No significant trend was observed in the levels of hepatic total glutathione. PCB 77 treatment decreased hepatic selenium-dependent glutathione peroxidase (SeGPX) activity in both male and female rats significantly. This decrease in activity following PCB 77 treatment was accompanied by a decrease in the cytosolic selenium-dependent glutathione peroxidase gene (GSPx1) transcript, as well as a decrease in hepatic total selenium levels. These data support the concept that exposure to the coplanar PCB 77 suppresses, via gene regulatory mechanisms, the cellular antioxidant enzyme SeGPX and that this decrease involves selenium. Lower halogenated PCBs that may be bioactivated to reactive oxygen species (ROS)-producing metabolites, and higher halogenated PCBs that are not Ah receptor agonists, were inactive.

Dietary taurine alters ascorbic acid metabolism in rats fed diets containing polychlorinated biphenyls.

The effect of dietary taurine on ascorbic acid metabolism and hepatic drug-metabolizing enzymes was investigated in rats fed diets containing polychlorinated biphenyls (PCB) to determine whether taurine has an adaptive and protective function in xenobiotic-treated animals. Young male Wistar rats (60 g) were fed diets containing 0 or 0.2 g/kg diet PCB with or without 30 g/kg diet of taurine for 14 d. The rats fed the PCB-containing diets had greater liver weight, higher ascorbic acid concentrations in the liver and spleen and greater hepatic cytochrome P-450 contents than control rats that were not treated with PCB (P < 0.01). In PCB-fed rats, urinary ascorbic acid excretion was enhanced, and serum cholesterol concentration (especially HDL-cholesterol) was significantly elevated compared with those in control rats. Dietary taurine significantly potentiated the increases in the urinary excretion of ascorbic acid and the rise in the levels of cytochrome P-450 which were caused by PCB treatment. On the other hand, the supplementation of taurine to control diet did not alter these variables. Taurine may enhance the hepatic drug-metabolizing systems, leading to the stimulation of the ascorbic acid metabolism in rats fed diets containing PCB.

Short-run tests for determining harmful effects of PCB-containing engine oils on cells.

Our main objective was to set up reproducible methods for a rapid determination of harmful effects of PCB-containing engine oils on cells. We used a plate method and Scenedesmus quadricauda, Saccharomyces cerevisiae, Rhodotorula glutinis and Pseudomonas putida as test organisms.

Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor beta.

The rat, mouse and human estrogen receptor (ER) exists as two subtypes, ER alpha and ER beta, which differ in the C-terminal ligand-binding domain and in the N-terminal transactivation domain. In this study, we investigated the estrogenic activity of environmental chemicals and phytoestrogens in competition binding assays with ER alpha or ER beta protein, and in a transient gene expression assay using cells in which an acute estrogenic response is created by cotransfecting cultures with recombinant human ER alpha or ER beta complementary DNA (cDNA) in the presence of an estrogen-dependent reporter plasmid. Saturation ligand-binding analysis of human ER alpha and ER beta protein revealed a single binding component for [3H]-17beta-estradiol (E2) with high affinity [dissociation constant (Kd) = 0.05 - 0.1 nM]. All environmental estrogenic chemicals [polychlorinated hydroxybiphenyls, dichlorodiphenyltrichloroethane (DDT) and derivatives, alkylphenols, bisphenol A, methoxychlor and chlordecone] compete with E2 for binding to both ER subtypes with a similar preference and degree. In most instances the relative binding affinities (RBA) are at least 1000-fold lower than that of E2. Some phytoestrogens such as coumestrol, genistein, apigenin, naringenin, and kaempferol compete stronger with E2 for binding to ER beta than to ER alpha. Estrogenic chemicals, as for instance nonylphenol, bisphenol A, o, p'-DDT and 2',4',6'-trichloro-4-biphenylol stimulate the transcriptional activity of ER alpha and ER beta at concentrations of 100-1000 nM. Phytoestrogens, including genistein, coumestrol and zearalenone stimulate the transcriptional activity of both ER subtypes at concentrations of 1-10 nM. The ranking of the estrogenic potency of phytoestrogens for both ER subtypes in the transactivation assay is different; that is, E2 >> zearalenone = coumestrol > genistein > daidzein > apigenin = phloretin > biochanin A = kaempferol = naringenin > formononetin = ipriflavone = quercetin = chrysin for ER alpha and E2 >> genistein = coumestrol > zearalenone > daidzein > biochanin A = apigenin = kaempferol = naringenin > phloretin = quercetin = ipriflavone = formononetin = chrysin for ER beta. Antiestrogenic activity of the phytoestrogens could not be detected, except for zearalenone which is a full agonist for ER alpha and a mixed agonist-antagonist for ER beta. In summary, while the estrogenic potency of industrial-derived estrogenic chemicals is very limited, the estrogenic potency of phytoestrogens is significant, especially for ER beta, and they may trigger many of the biological responses that are evoked by the physiological estrogens.