Effect of exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated biphenyls (PCBs) on mitochondrial DNA (mtDNA) copy number in rats.

Mitochondria are intracellular organelles responsible for biological oxidation and energy production. These organelles are susceptible to damage from oxidative stress and compensate for damage by increasing the number of copies of their own genome, mitochondrial DNA (mtDNA). Cancer and environmental exposure to some pollutants have also been associated with altered mtDNA copy number. Since exposures to polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been shown to increase oxidative stress, we hypothesize that mtDNA copy number will be altered with exposure to these compounds. mtDNA copy number was measured in DNA from archived frozen liver and lung specimens from the National Toxicology Program (NTP) study of female Harlan Sprague Dawley rats exposed to TCDD (3, 10, or 100 ng/kg/day), dioxin-like (DL) PCB 126 (10, 100, or 1000 ng/kg/day), non-DL PCB 153 (10, 100, or 1000 µg/kg/day), and PCB 126 + PCB 153 (10 ng/kg/day + 10 µg/kg/day, 100 ng/kg/day + 100 µg/kg/day, or 1000 ng/kg/day + 1000 µg/kg/day, respectively) for 13 and 52 weeks. An increase in mtDNA copy number was observed in the liver and lung of rats exposed to TCDD and the lung of rats exposed to the mixture of PCB 126 and PCB 153. A statistically significant positive dose-dependent trend was also observed in the lung of rats exposed to PCB 126 and a mixture of PCB 153 and PCB 126, although in neither case was the control copy number significantly exceeded at any dose level. These exposures produced a range of pathological responses in these organs in the two-year NTP studies. Conversely, there was a significant decrease or no change in mtDNA copy number in the liver and lung of rats exposed to non-DL PCB 153. This is consistent with a general lack of PCB 153 mediated liver or lung injury in the NTP study, with the exception of liver hypertrophy. Together, the results suggest that an increase in mtDNA copy number may serve as a sensitive, early biomarker of mitochondrial injury and oxidative stress that contributes to the development of the toxicity of dioxin-like compounds.

Disposition of PCB 11 in Mice Following Acute Oral Exposure.

PCB 11 (3,3'-dichloro-biphenyl) is an emerging environmental contaminant that represents a public health concern. Here, we investigated the distribution of PCB 11 and its metabolites in mice exposed orally to PCB 11. PCB 11 tissue levels followed the rank order adipose > lung ∼ muscle > liver > brain > blood 4 h after PCB 11 exposure, which varied from the rank order predicted with a composition-based model. We detected hydroxylated and sulfate metabolites in the liver and sulfate and glucuronide metabolites in serum. These findings lay the groundwork for future toxicity studies with PCB 11.

Cardiovascular and cancer mortality in relation to dietary polychlorinated biphenyls and marine polyunsaturated fatty acids: a nutritional-toxicological aspect of fish consumption.

BACKGROUND: Co-exposure to environmental contaminants present in fish could mitigate the beneficial effects of fish consumption and possibly explain the lack of association observed for mortality in some geographical regions. OBJECTIVE: To assess the independent associations of dietary exposure to polychlorinated biphenyls (PCBs) and long-chain omega-3 fish fatty acids intake with cardiovascular and cancer mortality. METHODS: We used the prospective population-based Swedish Mammography Cohort and the Cohort of Swedish Men comprising 32 952 women and 36 545 men, free from cancer, cardiovascular disease and diabetes at baseline in 1998. Validated estimates of dietary PCBs and long-chain omega-3 fish fatty acids [i.e. eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] intake were obtained via a food frequency questionnaire at baseline. Information on death was ascertained through register linkage. RESULTS: During a mean follow-up of 15.5 years, we ascertained 16 776 deaths. We observed for cardiovascular mortality, comparing extreme quintiles in multivariable models mutually adjusted for PCBs and EPA-DHA, dose-dependent associations for dietary PCB exposure, hazard ratio (HR) 1.31 (CI 95%: 1.08 to 1.57; P-trend 0.005) and for dietary EPA-DHA intake, HR 0.79 (CI 95%: 0.66 to 0.95; P-trend 0.041). For cancer mortality, no clear associations were discerned. CONCLUSION: The beneficial effect of fish consumption on the cardiovascular system seems compromised by co-exposure to PCBs - one likely explanation for the inconsistent associations observed between fish consumption and mortality.

Concentration dependence of human and mouse aryl hydrocarbon receptor responsiveness to polychlorinated biphenyl exposures: Implications for aroclor mixtures.

1. Aryl hydrocarbon receptor (AhR) ligands, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated biphenyls (PCBs), are endocrine disrupting chemicals associated with nonalcoholic fatty liver disease. This study documents the species-specific differences between mouse (high affinity mAhR) and human AhR (hAhR) activation by PCB congeners and Aroclor mixtures. 2. AhR activation by TCDD or PCBs 77, 81, 114, 114, 126, and 169 was measured using luciferase reporter constructs transfected into either Hepa1c1c7 mouse or HepG2 human liver cell lines. The EC50 values were lower in Hepa1c1c7 cells than HepG2 cells for all compounds tested except PCB 81. The results for TCDD and PCB 126 were validated in primary human and mouse hepatocytes by measuring CYP1A1 gene transcript levels. 3. Because humans are exposed to PCB mixtures, several mixtures (Aroclors 1254; 1260; and 1260 + 0.1% PCB126 each at 10 µg/ml) were then tested. Neither Aroclor 1254 nor Aroclor 1260 increased luciferase activity by the transfected AhR reporter construct. The Aroclor 1260 + 0.1% PCB 126 mixture induced mAhR-mediated transactivation, but not hAhR activation in cell lines. 4. In summary, significant concentration-dependent differences exist between human and mouse AhR activation by PCBs. Relative effect potencies differed, in some cases, from published toxic equivalency factors.

Estimation of daily intake of polychlorinated biphenyls not similar to dioxins (NDL-PCB) from fish consumption in Spain in different population groups.

OBJECTIVE: To assess the daily intake of polychlorinated biphenyls not similar to dioxins (NDL-PCB) derived from fish consumption in Spain and compare it with tolerance limits in order to establish a safe threshold so that the nutritional benefits derived from fish consumption may be optimized. DESIGN: Analysis of NDL-PCB in fish samples and ecological study of the estimated intake of NDL-PCB from fish consumption in different Spanish population groups. SUBJECTS: National representative sample of the Spanish population. RESULTS: The intake of NDL-PCB was estimated in two different scenarios: upper bound (UB) and lower bound (LB). Estimating intake using the average concentration of NDL-PCB found in the fish samples, the intake for 'other children' is estimated as: 1·80 (UB) and 5·33 (LB) ng/kg per d at the 50th percentile (P50); 7·39 (UB) and 21·94 (LB) ng/kg per d at the 95th percentile (P95) of fish consumption. Estimated NDL-PCB intake shoots up in the toddler group, reaching values of 30·43 (UB) and 90·37 (LB) ng/kg per d at P95. Estimated intake values are lower than those previously estimated in Europe, something expected since in previous studies intake was estimated through total diet. In adults, our estimated values are 1·59 (UB) and 4·72 (LB) ng/kg per d at P50; 4·95 (UB) and 14·72 (LB) ng/kg per d at P95. CONCLUSIONS: NDL-PCB concentration in fish is under the tolerance limits in most samples. However, daily intake in consumers of large quantities of fish should be monitored and special attention should be given to the youngest age groups due to their special vulnerability and higher exposure.

Uptake of radiolabeled 3,3',4,4'-tetrachlorobiphenyl into Japanese quail egg compartments and embryo following air cell and albumen injection.

The avian embryo is an excellent model for testing adverse developmental effects of environmental chemicals as well as uptake and movement of xenobiotics within the egg compartments. Before incubation at embryonic day 0, 14 C 3,3',4,4'-tetrachlorobiphenyl (14 C PCB 77) was injected into Japanese quail eggs either onto the air cell or into the albumen. All egg components were collected on embryonic day 1, 5, or 10, and concentrations of 14 C PCB 77 were measured in various egg components (shell, membrane, yolk, albumen, and embryo). The results showed measurable 14 C PCB 77 in all egg components, with changing concentrations in each egg component over the course of embryonic development. Specifically, concentrations in the shell content decreased between embryonic days 1 and 10, increased in albumen from embryonic days 1 to 5 and then decreased at embryonic day 10, and increased in both yolk and embryo from embryonic days 1 to 10. Vehicle and injection site both influenced 14 C PCB 77 allantoic fluid concentrations, with little effect on other egg components except for the inner shell membrane. The fatty acid vehicle injected into the albumen yielded the highest 14 C PCB 77 recovery. These findings demonstrate dynamic movement of toxicants throughout the egg components during avian embryonic development and a steady increase of relatively low levels of 14 C PCB 77 in the embryo compared with the yolk, albumen, and shell, suggesting that embryonic uptake (i.e., exposure) mirrors utilization of egg components for nutrition and growth during development. Environ Toxicol Chem 2018;37:126-135. © 2017 SETAC.

Impact of Lactational Exposure to Polychlorinated Biphenyl Causes Epigenetic Modification and Impairs Sertoli Cells Functional Regulators in F1 Progeny.

Polychlorinated biphenyl (PCB) is an endocrine-disrupting chemical. Sertoli cells (SCs) provide physical and nutritional support for developing germ cells. Dysfunction in SCs has adverse effects on spermatogenesis. Previously, we found that the lactational exposure of PCBs (1, 2, and 5 mg/kg birth weight/day, orally from postnatal days 1 to 20) decreased the follicle-stimulating hormone receptor (FSHR) and androgen receptor (AR) expression in SCs of F1 progeny. Transcription factors initiate and regulate the transcription of genes. DNA methylation plays an important role in epigenetic gene regulation. Hence, this study was aimed to identify the level of transcription factors regulating FSHR, AR gene expression, and DNA methylation in the promoter of these genes in SCs of both F1 prepuberal and puberal offspring. DNA methylation in the promoter of FSHR and AR genes was examined by sodium bisulfite conversion technique. The protein levels of transcription factors (steroidogenic factor 1 [SF1], upstream stimulatory factors 1 and 2, c-fos, c-jun, and CREB-binding protein) and enzymes DNA methyltransferases (Dnmt1, Dnmt3ab, Dnmt3l, and histone deacetylase 1 [HDAC1]) were analyzed by Western blotting. The transcription factors that regulate the FSHR and AR gene in SCs were decreased in both the PCB-exposed F1 progeny. Methylation was observed in the promoter of FSHR, AR, and SF1. The protein levels of Dnmt1, Dnmt3ab, Dnmt3l, and HDAC1 were increased in the PCBs-treated groups. Subsequently, it leads to transcriptional repression of the genes in SCs. Our finding suggests that PCBs caused epigenetic change in SCs, thereby it impaired SCs function in F1 progeny.

Cocaine self-administration in male and female rats perinatally exposed to PCBs: Evaluating drug use in an animal model of environmental contaminant exposure.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental toxicants known to adversely impact human health. Ortho-substituted PCBs affect the nervous system, including the brain dopaminergic system. The reinforcing effects of psychostimulants are typically modulated via the dopaminergic system, so this study used a preclinical (i.e., rodent) model to evaluate whether developmental contaminant exposure altered intravenous self-administration (IV SA) for the psychostimulant cocaine. Long-Evans rats were perinatally exposed to 6 or 3 mg/kg/day of PCBs throughout gestation and lactation and compared with nonexposed controls. Rats were trained to lever press for a food reinforcer in an operant chamber under a fixed-ratio 5 (FR5) schedule and later underwent jugular catheterization. Food reinforcers were switched for infusions of 250 µg of cocaine, but the response requirement to earn the reinforcer remained. Active lever presses and infusions were higher in males during response acquisition and maintenance. The same sex effect was observed during later sessions which evaluated responding for cocaine doses ranging from 31.25-500 µg. PCB-exposed males (not females) exhibited an increase in cocaine infusions (with a similar trend in active lever presses) during acquisition, but no PCB-related differences were observed during maintenance, examination of the cocaine dose-response relationship, or progressive ratio (PR) sessions. Overall, these results indicated perinatal PCB exposure enhanced early cocaine drug-seeking in this preclinical model of developmental contaminant exposure (particularly the males), but no differences were seen during later cocaine SA sessions. As such, additional questions regarding substance abuse proclivity may be warranted in epidemiological studies evaluating environmental contaminant exposures. (PsycINFO Database Record

Anxiety-like behaviors in adulthood are altered in male but not female rats exposed to low dosages of polychlorinated biphenyls in utero.

Exposure to polychlorinated biphenyls (PCBs), a class of endocrine-disrupting chemicals, can result in altered reproductive behavior in adulthood, especially when exposure occurs during critical periods of brain sexual differentiation in the fetus. Whether PCBs alter other sexually dimorphic behaviors such as those involved in anxiety is poorly understood. To address this, pregnant rat dams were injected twice, on gestational days 16 and 18, with the weakly estrogenic PCB mixture Aroclor 1221 (A1221) at one of two low dosages (0.5mg/kg or 1.0mg/kg, hereafter 1.0 and 0.5), estradiol benzoate (EB; 50µg/kg) as a positive estrogenic control, or the vehicle (3% DMSO in sesame oil). We also conducted a comprehensive assessment of developmental milestones of the F1 male and female offspring. There were no effects of treatment on sex ratio at birth and age at eye opening. Puberty, assessed by vaginal opening in females and preputial separation in males, was not affected in females but was advanced in males treated with A1221 (1.0). Males and females treated with A1221 (both dosages) were heavier in early adulthood relative to controls. The earliest manifestation of this effect developed in males prior to puberty and in females slightly later, during puberty. Anxiety-like behaviors were tested using the light:dark box and elevated plus maze tests in adulthood. In females, anxiety behaviors were unaffected by treatment. Males treated with A1221 (1.0) showed reduced indices of anxiety and increased activity in the light:dark box but not the elevated plus maze. EB failed to replicate the phenotype produced by A1221 for any of the developmental and behavioral endpoints. Collectively, these results indicate that PCBs increase body weight in both sexes, but their effects on anxiety-like behaviors are specific to males. Furthermore, differences between the results of A1221 and EB suggest that the PCBs are likely acting through mechanisms distinct from their estrogenic activity.

Dioxin-like rather than non-dioxin-like PCBs promote the development of endometriosis through stimulation of endocrine-inflammation interactions.

Polychlorinated biphenyls (PCBs) contain 209 congeners with various structure-activities. Exposure to PCBs was related to disorders of female reproduction. Endometriosis (EM) is an estrogen- and inflammation-dependent disease with high prevalence and severe health outcomes. Epidemiological studies have shown the effects of PCBs exposure on EM in regard to various structures of PCBs. However, little evidence is available from the toxicology considering the structure of PCBs. In the study, environmentally relevant concentrations of PCBs were used to treat primary cultured endometrial cells and an EM mouse model. Dioxin-like CB126, but not non-dioxin-like CB153, significantly enhanced 17ß-estradiol (E2) biosynthesis in a dose-dependent manner. Among the genes related to estrogen metabolism, the level of 17ß-hydroxysteroid dehydrogenase 7 (HSD17B7) showed significant increase following CB126 exposure. We further found that CB126 exposure decreased the methylation of the HSD17B7 promoter. Elevated expression of HSD17B7 was observed in the eutopic endometrium of EM patients. CB126 rather than CB153 triggered the inflammatory response by directly stimulating the secretion of inflammatory factors and indirectly reducing the level of lipoxin A4 (LXA4). Furthermore, the inflammation enhanced the expression of HSD17B7. Antagonism of the aryl hydrocarbon receptor (AhR) diminished the effects induced by CB126. In vivo, the PCB-treated EM mouse model confirmed that CB126 rather than CB153 increased the levels of both E2 and inflammatory factors in peritoneal fluid and promoted the development of endometriotic lesions. In all, CB126, but not CB153, triggered EM development by stimulating estrogen biosynthesis, inflammation and their interactions and that these effects were mediated by the AhR receptor.

Dietary polychlorinated biphenyls, long-chain n-3 polyunsaturated fatty acids and incidence of malignant melanoma.

BACKGROUND: For malignant melanoma, other risk factors aside from sun exposure have been hardly explored. Polychlorinated biphenyls (PCBs)-mainly from fatty fish- may affect melanogenesis and promote melanoma progression, while long-chain n-3 polyunsaturated fatty acids seem to exert antineoplastic actions in melanoma cells. OBJECTIVES: We aimed to assess the association of validated estimates of dietary PCB exposure as well as the intake of eicosapentaenoic acid and docosahexaenoic acid (EPA-DHA), accounting for sun habits and skin type, with the risk of malignant melanoma in middle-aged and elderly women. METHODS: We included 20,785 women at baseline in 2009 from the prospective population-based Swedish Mammography Cohort. Validated estimates of dietary PCB exposure and EPA-DHA intake were obtained via a food frequency questionnaire. Incident melanoma cases were ascertained through register-linkage. RESULTS: During 4.5 years of follow-up, we ascertained 67 incident cases of melanoma. After multivariable adjustments, exposure to dietary PCBs was associated with four-fold increased risk of malignant melanoma (hazard ratio [HR], 4.0 [95% confidence interval {CI}, 1.2-13; P for trend = 0.02]), while EPA-DHA intake was associated with 80% lower risk (HR, 0.2 [95% CI, 0.1-0.8; P for trend = 0.03]), comparing the highest exposure tertiles with the lowest. CONCLUSION: While we found a direct association between dietary PCB exposure and risk of melanoma, EPA-DHA intake showed to have a substantial protective association. Question of benefits and risk from fish consumption is very relevant and further prospective studies in the general population verifying these findings are warranted.

Exposure to polychlorinated biphenyl-153 decreases incidence of autoimmune Type 1 diabetes in non-obese diabetic mice.

Type 1 diabetes (T1D) incidence has been steadily rising across the globe. Exposure to persistent organic pollutants (POP) has been implied as one potential cause of increased T1D occurrence. Since data regarding the role of POP polychlorinated biphenyl-153 (PCB-153) in autoimmune T1D development in experimental animal models are lacking, this study sought to evaluate the effect of PCB-153 exposure on T1D development in a non-obese diabetic (NOD) mouse model. As T1D is an autoimmune, T-cell-dependent disease, PCB-153 effects on T-cells were studied as well. Pre-diabetic 8-9-week-old NOD mice were exposed to intraperitoneal injections of PCB-153 in a 10-day short- (subacute exposure; 0.5 or 50 mg/kg) or 16-week long-term (subchronic exposure; 0.125 or 12.5 mg/kg) fashion. A significant decrease in incidence of T1D was observed in both low- and high-dose subchronically exposed mice. Analysis of various immune parameters, including T-cell types and subtypes, T-cell proliferative responses - as well as their cytokine secretions, revealed that both short- and long-term exposure to PCB-153 caused significant immunosuppression. PCB-153-induced immunosuppression was reflected in reductions in levels of T helper (TH)-type cells and their functions after subacute treatment with low- and high-dose PCB-153. In agreement, decreased levels of TH cells, reduced proliferation and IL-2 secretion seemed to be a mechanism of PCB-153 action in the development of T1D in subchronically exposed mice. In conclusion, this study for the first time revealed the effects of PCB-153 on development of T1D, bridging the existing experimental knowledge gap regarding the association of non-dioxin-like PCBs and T1D.

Analysis of the Enantioselective Effects of PCB95 in Zebrafish (Danio rerio) Embryos through Targeted Metabolomics by UPLC-MS/MS.

As persistent organic pollutants, polychlorinated biphenyls (PCBs) accumulate in the bodies of animals and humans, resulting in toxic effects on the reproductive, immune, nervous, and endocrine systems. The biological and toxicological characteristics of enantiomers of chiral PCBs may differ, but these enantioselective effects of PCBs have not been fully characterized. In this study, we performed metabolomics analysis, using ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) to investigate the enantioselective toxic effects of PCB95 in zebrafish (Danio rerio) embryos after exposure to three dose levels of 0.1, 1, and 10 µg/L for 72 h. Multivariate analysis directly reflected the metabolic perturbations caused by PCB95. The effects of (-)-PCB95 and (+)-PCB95 were more prominent than those of the racemate in zebrafish embryos. A total of 26 endogenous metabolites were selected as potential marker metabolites with variable importance at projection values larger than 1 and significant differences (p<0.05). These metabolites included amino acids, organic acids, nucleosides, betaine, and choline. The changes in these biomarkers were dependent on the enantiomer-specific structures of PCB95. Fifteen metabolic pathways were significantly affected, and several nervous and immune system-related metabolites were significantly validated after exposure. These metabolic changes indicated that the toxic effects of PCB95 may be associated with the interaction of PCB95 with the nervous and immune systems, thus resulting in disruption of energy metabolism and liver function.

[Study on the dietary intake level for indicator polychlorinated biphenyls in China].

OBJECTIVE: To obtain representative data on levels of indicator polychlorinated biphenyls (PCBs) in foods consumed by the general population and to estimate the dietary intake of indicator PCBs in China. METHODS: The food samples were collected during the fifth China Total Diet Study (2009-2013). Based on the geographical location and dietary habits, China was divided into the south area and the north area, and 10 province regions from each area were chosen. In each province region, one urban site and two rural sites were selected to collect food samples. Considering the food consumption level and the PCBs contaminate rule, a total of 160 samples including meat, eggs, fish, milk, cereals, beans, potatoes and vegetables were selected. The concentration of 7 indicator PCBs in food were determined by stable isotope dilution gas chromatography-mass, and combined with food consumption to calculate the dietary intake of indicator PCBs. RESULTS: The concentration of indicator PCBs in 8 categories of food were in the range of 0.8-1 300.1 pg/g. The levels of indicator PCBs were significantly higher in the aquatic products, averaging (307.8±302.4) pg/g, followed by eggs at (76.6±92.1) pg/g and meat at (63.0±54.9) pg/g. The daily dietary intake of indicator PCBs varied from province to province, ranging from 0.13 ng·kg(-1)·d(-1) to 3.58 ng·kg(-1)·d(-1), averaging (0.67±0.77) ng·kg(-1)·d(-1). Fujian had the highest level (3.58 ng·kg(-1)·d(-1)) , followed by Shanghai (1.48 ng·kg(-1)·d(-1)) and Zhejiang (1.09 ng·kg(-1)·d(-1)) . Compared with the minimum risk level (MRL) value (20 ng·kg(-1)·d(-1)) proposed by US Agency for Toxic Substances and Disease Registry, the highest dietary intake level was only 17.9% MRL, the average dietary intake level was 3.4%MRL. Aquatic products was still the major contributor to the dietary intake of indicator PCBs in China, 48% of average dietary intake level (0.32 ng·kg(-1)·d(-1)/0.67 ng·kg(-1)·d(-1)) . CONCLUSION: The dietary intake of indicator PCBs in China was at a low level, and showing a declining trend.

Dioxin-like pollutants increase hepatic flavin containing monooxygenase (FMO3) expression to promote synthesis of the pro-atherogenic nutrient biomarker trimethylamine N-oxide from dietary precursors.

The etiology of cardiovascular disease (CVD) is impacted by multiple modifiable and non-modifiable risk factors including dietary choices, genetic predisposition, and environmental exposures. However, mechanisms linking diet, exposure to pollutants, and CVD risk are largely unclear. Recent studies identified a strong link between plasma levels of nutrient-derived Trimethylamine N-oxide (TMAO) and coronary artery disease. Dietary precursors of TMAO include carnitine and phosphatidylcholine, which are abundant in animal-derived foods. Dioxin-like pollutants can upregulate a critical enzyme responsible for TMAO formation, hepatic flavin containing monooxygenase 3 (FMO3), but a link between dioxin-like PCBs, upregulation of FMO3, and increased TMAO has not been reported. Here, we show that mice exposed acutely to dioxin-like PCBs exhibit increased hepatic FMO3 mRNA, protein, as well as an increase in circulating levels of TMAO following oral administration of its metabolic precursors. C57BL/6 mice were exposed to 5µmol PCB 126/kg mouse weight (1.63mg/kg). At 48h post-PCB exposure, mice were subsequently given a single gavage of phosphatidylcholine dissolved in corn oil. Exposure to 5 µmole/kg PCB 126 resulted in greater than 100-fold increase in FMO3 mRNA expression, robust induction of FMO3 protein, and a 5-fold increase in TMAO levels compared with vehicle treated mice. We made similar observations in mice exposed to PCB 77 (49.6mg/kg twice); stable isotope tracer studies revealed increased formation of plasma TMAO from an orally administered precursor trimethylamine (TMA). Taken together, these observations suggest a novel diet-toxicant interaction that results in increased production of a circulating biomarker of cardiovascular disease risk.

Two-hit exposure to polychlorinated biphenyls at gestational and juvenile life stages: 1. Sexually dimorphic effects on social and anxiety-like behaviors.

Endocrine disrupting chemicals (EDCs) are widespread environmental contaminants that affect many neuroendocrine functions. The brain is particularly vulnerable to EDCs during critical periods of gestational development when gonadal hormones exert organizational effects on sexually dimorphic behaviors later in life. Peripubertal development is also a time of continued neural sensitivity to organizing effects of hormones, yet little is known about EDC actions at these times. We sought to determine effects of prenatal or juvenile exposures to a class of EDCs, polychlorinated biphenyls (PCBs) at human-relevant dosages on development, physiology, and social and anxiety-related behaviors later in life, and the consequences of a second juvenile "hit" following prenatal treatment. We exposed male and female Sprague-Dawley rats to PCBs (Aroclor 1221, 1mg/kg/day, ip injection) and/or vehicle during prenatal development (embryonic days 16, 18, 20), juvenile development (postnatal days 24, 26, 28), or both. These exposures had differential effects on behaviors in sex and age-dependent ways; while prenatal exposure had more effects than juvenile, juvenile exposure often modified or unmasked the effects of the first hit. Additionally, females exhibited altered social and anxiety behavior in adolescence, while males displayed small but significant changes in sociosexual preferences in adulthood. Thus, the brain continues to be sensitive to organizing effects of EDCs through juvenile development. As humans are exposed to EDCs throughout multiple periods in their life, these findings have implications for our understanding of EDC effects on physiology and behavior.

Chronic Exposure to Low-Level Cadmium in Diabetes: Role of Oxidative Stress and Comparison with Polychlorinated Biphenyls.

Among the most important physiological functions, maintenance of the oxidation reduction equilibrium in cells stands out as a major homeostatic event. Many environmental contaminants efficiently trap cellular reducing compounds, but the actual importance of this mode of toxicity is far from being precisely known. This statement applies to cases of slowly developing chronic diseases, such as neurodegenerations, diabetes, and many others. The involvement of oxidative challenge in diabetes is considered in connection with chronic dietary exposure to low-level concentrations of cadmium. Comparison is made with polychlorobiphenyl molecules (PCB): they are structurally unrelated to cadmium, they preferentially distribute into different organs than cadmium, and they follow different metabolic pathways. Yet, they have also pro-oxidative properties, and they are associated with diabetes. Since neither cadmium nor PCB is a direct oxidant, they both follow indirect pathways to shift the redox equilibrium. Thus, a difference must be made between the adaptable response of the organism, i.e. the anti-oxidant response, and the irreversible damage generated by oxidizing species, i.e. oxidative damage, when exposure occurs at low concentrations. The approximate border between high and low levels of exposure is estimated in this review from the available relevant data, and the strengths and weaknesses of experimental models are delineated. Eventually, chronic low level exposure to these contaminants sparks cellular responses setting ground for dysfunction and disease, such as diabetes: oxidative damage is an accompanying phenomenon and not necessarily an early mechanism of toxicity.

Absorption of PCB126 by upper airways impairs G protein-coupled receptor-mediated immune response.

PCB126 is a dioxin-like polychlorinated biphenyl (PCB) environmental pollutant with a significant impact on human health, as it bioaccumulates and causes severe toxicity. PCB126-induced immune toxicity has been described, although the mechanisms have not been fully elucidated. In this study, an in vivo protocol of PCB126 intoxication into male Wistar rats by intranasal route was used, which has not yet been described. The intoxication was characterised by PCB126 accumulation in the lungs and liver, and enhanced aryl hydrocarbon receptor expression in the liver, lungs, kidneys, and adipose tissues. Moreover, an innate immune deficiency was characterised by impairment of adhesion receptors on blood leukocytes and by reduced blood neutrophil locomotion and oxidative burst activation elicited by ex vivo G protein-coupled receptor (GPCR) activation. Specificity of PCB126 actions on the GPCR pathway was shown by normal burst oxidative activation evoked by Toll-like receptor 4 and protein kinase C direct activation. Moreover, in vivo PCB180 intoxication did not alter adhesion receptors on blood leukocytes either blood neutrophil locomotion, and only partially reduced the GPCR-induced burst oxidative activation on neutrophils. Therefore, a novel mechanism of in vivo PCB126 toxicity is described which impairs a pivotal inflammatory pathway to the host defence against infections.

Sexually dimorphic effects of gestational endocrine-disrupting chemicals on microRNA expression in the developing rat hypothalamus.

This study examined developmental changes and sexual dimorphisms in hypothalamic microRNAs, and whether gestational exposures to environmental endocrine-disrupting chemicals (EDCs) altered their expression patterns. Pregnant rat dams were treated on gestational days 16 and 18 with vehicle, estradiol benzoate, or a mixture of polychlorinated biphenyls. Male and female offspring were euthanized on postnatal days (P) 15, 30, 45, or 90, and microRNA and mRNA targets were quantified in the medial preoptic nucleus (MPN) and ventromedial nucleus (VMN) of the hypothalamus. MicroRNAs showed robust developmental changes in both regions, and were sexually dimorphic in the MPN, but not VMN. Importantly, microRNAs in females were up-regulated by EDCs at P30, and down-regulated in males at P90. Few changes in mRNAs were found. Thus, hypothalamic microRNAs are sensitive to prenatal EDC treatment in a sex-, developmental age-, and brain region-specific manner.

Dietary exposure to polychlorinated biphenyls and risk of myocardial infarction - a population-based prospective cohort study.

BACKGROUND: Fish consumption may promote cardiovascular health. The role of major food contaminants, such as polychlorinated biphenyls (PCBs) common in fatty fish, is unclear. We assessed the association between dietary PCB exposure and risk of myocardial infarction taking into account the intake of long-chain omega-3 fish fatty acids. METHODS: In the prospective population-based Swedish Mammography Cohort, 33,446 middle-aged and elderly women, free from cardiovascular disease, cancer and diabetes at baseline (1997) were followed-up for 12 years. Validated estimates of dietary PCB exposure and intake of fish fatty acids (eicosapentaenoic acid and docosahexaenoic acid; EPA-DHA) were obtained via a food frequency questionnaire at baseline. RESULTS: During follow-up 1386 incident cases of myocardial infarction were ascertained through register-linkage. Women in the highest quartile of dietary PCB exposure (median 286 ng/day) had a multivariable-adjusted RR of myocardial infarction of 1.21 (95% confidence interval [CI], 1.01-1.45) compared to the lowest quartile (median 101 ng/day) before, and 1.58 (95% CI, 1.10-2.25) after adjusting for EPA-DHA. Stratification by low and high EPA-DHA intake, resulted in RRs 2.20 (95% CI, 1.18-4.12) and 1.73 (95% CI, 0.81-3.69), respectively comparing highest PCB tertile with lowest. The intake of dietary EPA-DHA was inversely associated with risk of myocardial infarction after but not before adjusting for dietary PCB. CONCLUSION: Exposure to PCBs was associated with increased risk of myocardial infarction, while some beneficial effect was associated with increasing EPA and DHA intake. To increase the net benefits of fish consumption, PCB contamination should be reduced to a minimum.