A highly toxic PCB produces unusual changes in the fatty acid composition of rat liver

Disposition and metabolomic effects of 2,2',5,5'-tetrachlorobiphenyl in female rats following intraperitoneal exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Disposition and Metabolomic Effects of 2,2',5,5'-Tetrachlorobiphenyl in Female Rats Following Intraperitoneal Exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Highlights

PCB 52 was present in adipose, brain, liver, and serum 3 weeks after PCB exposureLiver and serum contained hydroxylated, sulfated, and methylated PCB 52 metabolitesMetabolomics analysis revealed minor changes in endogenous serum metabolitesLevels of dopamine and its metabolites in the brain were not affected by PCB 52.

Risk of cardiovascular diseases following residential exposure to airborne polychlorinated biphenyls: A register-based cohort study

BACKGROUND

Indoor air in buildings constructed with materials containing polychlorinated biphenyls (PCBs) may be contaminated with especially lower-chlorinated PCBs. So far, the cardiovascular consequences of living with such contamination are unknown.

OBJECTIVES

To determine the risk of cardiovascular disease (CVD) following residential exposure to predominantly lower-chlorinated PCBs in indoor air.

METHODS

The Health Effects of PCBs in Indoor Air (HESPAIR) cohort is register-based with 51 921 residents of two residential areas near Copenhagen: Farum Midtpunkt and Brøndby Strand Parkerne. Here, indoor air was contaminated with PCB in one third of the apartments due to construction with materials containing PCB. Individual PCB exposure was estimated based on register-based information on relocation dates and indoor air PCB measurements in subsets of the apartments. Information on CVD was retrieved from the Danish National Patient Register for the follow-up period of 1977-2018. We estimated adjusted hazard ratios using Cox regression with time-varying exposure.

RESULTS

Cumulative residential exposure to airborne PCB was not associated with a higher overall risk for CVD (HR for highly exposed (≥3300 ng/m³ PCB × year): 1.02, 95% CI 0.94-1.10). This was also the case for most of the specific cardiovascular diseases, apart from acute myocardial infarction where a higher risk was observed for residents exposed to ≥3300 ng/m³ PCB × year compared to the reference group (HR 1.17, 95% CI 1.00-1.35). However, no exposure-response relationship was apparent and additional adjustment for education attenuated the risk estimate.

DISCUSSION

In this, to our knowledge, first study ever to examine the risk of CVD following residential exposure to PCBs in indoor air, we observed limited support for cardiovascular effects of living in PCB-contaminated indoor air. Considering the prevalence of exposure to airborne PCBs and lack of literature on their potential health effects, these findings need to be corroborated in other studies.

Metabolic Disrupting Effects of Polychlorinated Biphenyls Revealed by Long-Term Temporal Variations of Lipids in Detritivorous Fish from the Rio de la Plata Basin

The long-term covariation (2002-2017) of lipids, polychlorinated biphenyls (PCBs), and sewage tracers was studied in the detritivorous fish (Prochilodus lineatus) and settling detritus from the Rio de la Plata. Fatty fish from polluted Buenos Aires area (BA) exhibited a significant decrease of muscle lipids (71 ± 12 to 29 ± 8.6% dry weight; p < 0.0001), triglycerides (94 to 85%, p < 0.001), and 18 carbon fatty acids (18C-FA: 59 ± 4.8 to 48 ± 1.4%; p < 0.01), reflecting a reduction of lipid accumulation, largely triglycerides enriched in 18C-FA, with a concomitant ∼20-times decline of PCBs (∼20 to >1 μg g^-1 dw). The 2017 individuals of the BA series converged with leaner and more pristine northern fish (N), which showed no significant temporal variation (20 ± 10% lipids, 67 ± 8.7% triglycerides, 41 ± 8.1% 18C-FA, and 0.22 ± 0.42 μg g^-1 dw PCB). In contrast, the fecal sterol tracer coprostanol remained abnormally higher in BA fish muscle with no significant temporal trend (120 ± 102 vs 6.6 ± 10 μg g^-1 dw or 4.4 ± 2.8 vs 0.63 ± 1.2% sterols at N). The same pattern was observed in BA settling detritus, i.e., a temporal decrease of PCBs with high, stable coprostanol concentrations denoting sustained sewage inputs, while northern detritus was enriched in plant sterols. This long-term covariation of lipids and PCBs in fish muscle from polluted BA converging with more pristine and homogeneous northern specimens while maintaining a sewage-derived diet provides rare field evidence of the declining effect of PCBs controlling the temporal variation of muscular lipids in fish.

Relationship Between the Content of Chlorinated Hydrocarbons and Fatty Acid Composition of Milk Fat

Introduction

Reports that the presence of persistent organic pollutants in fat may affect fatty acid metabolism prompted this research aiming to study the relationship between the contents of γ-HCH and DDT, DDE, DDD, and ΣDDT, and fatty acid composition of milk fat.

Material and Methods

The material consisted of 50 samples of cow and mare milk, collected in 2015. Ludwicki’s and the Röse-Gottlieb and IDF Standard methods were used to prepare the samples. Statistical analyses were conducted using Statistica 12.0.

Results

There was a negative correlation between the content of γ-HCH and C16:1, C17:1, C18:1c9, C18:1c9c12, and ΣMUFA in cow milk fat and C13:0, C14:0, and C10:1 in mare milk fat. A positive correlation was observed between γ-HCH and C6:0 to C12:0, C14:0, C18:1t16, and ΣSFA in cow milk fat, and between this compound and C14:0iso, C16:1, C17:1, C18:1c9,11, and ΣMUFA in mare milk fat. A negative correlation between the contents of ΣDDT and C16:1, C17:1, C18:1c9,11,13 and ΣMUFA in cow milk fat and C16:0iso, C17:0, and C18:3 in mare milk fat was noted. A positive correlation was found between the contents of ΣDDT and saturated and polyunsaturated fatty acids and ΣSFA and ΣPUFA in cow milk fat, and C18:2c9c12 in mare milk fat.

Conclusion

The correlation between the content of selected organochlorine compounds and the composition of fatty acids in cow and mare milk fat indicates the strong influence of these environmental pollutants on the nutritional value of milk fat.

Relationship between the content of chlorinated hydrocarbons and fatty acid composition of milk fat

Introduction

Reports that the presence of persistent organic pollutants in fat may affect fatty acid metabolism prompted this research aiming to study the relationship between the contents of γ-HCH and DDT, DDE, DDD, and ΣDDT, and fatty acid composition of milk fat.

Material and Methods

The material consisted of 50 samples of cow and mare milk, collected in 2015. Ludwicki’s and the Röse-Gottlieb and IDF Standard methods were used to prepare the samples. Statistical analyses were conducted using Statistica 12.0.

Results

There was a negative correlation between the content of γ-HCH and C16:1, C17:1, C18:1c9, C18:1c9c12, and ΣMUFA in cow milk fat and C13:0, C14:0, and C10:1 in mare milk fat. A positive correlation was observed between γ-HCH and C6:0 to C12:0, C14:0, C18:1t16, and ΣSFA in cow milk fat, and between this compound and C14:0iso, C16:1, C17:1, C18:1c9,11, and ΣMUFA in mare milk fat. A negative correlation between the contents of ΣDDT and C16:1, C17:1, C18:1c9,11,13 and ΣMUFA in cow milk fat and C16:0iso, C17:0, and C18:3 in mare milk fat was noted. A positive correlation was found between the contents of ΣDDT and saturated and polyunsaturated fatty acids and ΣSFA and ΣPUFA in cow milk fat, and C18:2c9c12 in mare milk fat.

Conclusion

The correlation between the content of selected organochlorine compounds and the composition of fatty acids in cow and mare milk fat indicates the strong influence of these environmental pollutants on the nutritional value of milk fat.

Identification of lipidomic markers of chronic 3,3',4,4',5-pentachlorobiphenyl (PCB 126) exposure in the male rat liver

Exposure to PCB 126, an environmentally relevant aryl hydrocarbon receptor agonist, is an environmental factor causing hepatic steatosis in rodent models; however, the lipidome of PCB 126-exposed rats has not been investigated in-depth. The objective of the present study was therefore to characterize dose-dependent changes in the lipid profile in the liver of male Sprague-Dawley rats exposed to PCB 126. Rats were exposed for three month to intraperitoneal injections of 0.01, 0.05 and 0.2μmol/kg bw PCB 126 in corn oil. Control animals were exposed in parallel and received corn oil alone. Lipids were extracted from whole liver homogenate and levels of polar lipids and fatty acids incorporated into triglycerides (FATAGs) were determined with tandem mass spectrometry using electrospray ionization. PCB 126 exposure increased the hepatic content of polar lipids and FATAGs. Protein adjusted levels of several polar lipid classes, in particular phosphatidylserine levels, decreased, whereas FATAGs levels typically increased with increasing PCB 126 dose. Sensitive, dose-dependent endpoints of PCB 126 exposure included an increase in levels of adrenic acid incorporated into triglycerides and changes in levels of certain ether-linked phospholipid and 1-alkyl/1-alkenyldiacylglycerol species, as determined using partial least square discriminant analysis (PLS-DA) and ANOVA. These changes in the composition of polar lipids and fatty acid in the liver of PCB 126 exposed rats identified several novel markers of PCB 126-mediated fatty liver disease that need to be validated in further studies.

Optimized Multiresidue Analysis of Organic Contaminants of Priority Concern in a Daily Consumed Fish (Grass Carp)

The organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), are of priority concern because of their persistence, toxicity, and long-distance transportation in global environment. Their residues in a daily consumed fish (grass carp) pose potential threat to human health and aquatic ecosystems. The present study optimized an analytical protocol of microwave-assisted extraction (MAE), lip-removal by gel permeation chromatography (GPC), cleanup by solid phase cartridge (SC) or adsorption chromatography column (CC), and gas chromatography-mass spectrometry (GC/MS). Besides traditional statistical parameters, some indicators were calculated to judge the performances of extraction by various methods. The optimization experiment showed that n-hexane/acetone was the best MEA extraction solvent; an optimal fraction time of 10-39 min could simultaneously elute all the target chemicals in a single GPC run. Both CC and SC showed good recoveries. However, CC performed better than SC (p < 0.05) for OCPs, and SC performed better than CC for PBDEs (p < 0.05). We also emphasized the limitations and advantages of SC and CC and finally proposed SC as the promising cleanup method because of its low-cost materials, time-saving steps, being free of manual filling, and operation by automated SPE system.

Fatty acid alterations in the detritivorous Prochilodus lineatus promoted by opportunistic feeding on sewage discharges in the Río de la Plata estuary

Muscle fatty acid profiles and PCB contents of the detritivorous species Prochilodus lineatus and its diet (stomach contents, settling particles and sediments) were analysed from reference and polluted areas of the Paraná-Rio de la Plata basin, to evaluate the alterations produced by opportunistic feeding on sewage discharges. Overall muscle fatty acid composition was dominated by saturated and monounsaturated 16 and 18 carbon (18 C-FA) components with reduced long-chain polyunsaturated fatty acids (LC-PUFA). Compared to sediments, settling particles and stomach contents were enriched in lipids and had a similar fatty acid composition. Opportunistic feeding on sewage detritus at Buenos Aires resulted in enhanced PCB and triglyceride accumulation, with higher proportions of 18 C-FA and lower proportions of 16:1 and LC-PUFA compared to fish from northern pristine reaches of the basin. Mid-Paraná showed intermediate values reflecting mixing of the North stock with migrating Buenos Aires P. lineatus identified by their lipid and contaminant profile. According to multivariate analyses, this geographical variation of fatty acid composition was strongly influenced by PCB concentration. Prochilodus lineatus assimilates the energy subsidy of sewage inputs through enhanced lipogenesis with dominant 18 C-FA and significant amounts of valuable LC-PUFA. This lipid alteration facilitates the bioaccumulation of PCBs which in turn may reinforce the adipogenic effect of sewage feeding.

Dioxin-Produced Alteration in the Profiles of Fecal and Urinary Metabolomes: A Change in Bile Acids and Its Relevance to Toxicity

This study investigated dioxin-induced changes in metabolomes in pubertal rat excrement. The administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or restricting dietary intake (pair-fed group) markedly altered the metabolomic profile including lipids, hormones, and vitamins in the urine and feces. TCDD caused an increase in the fecal chenodeoxycholic acid and taurocholic acid content and in urinary adrenaline and 17β-estradiol, while the urinary melatonin level was reduced by TCDD. These changes were not observed in the pair-fed group. In accordance with the elevated level of fecal bile acids, TCDD reduced the intestinal expression of the apical sodium-dependent bile salt transporter, which plays a role in resorbing bile acids from the bile duct. In addition, CYP7A1, a rate-limiting enzyme for bile acid biosynthesis, was attenuated by TCDD treatment, although TCDD induced hepatic CYP8B1, an enzyme essential for cholic acid synthesis. Supplying cholic acid or chenodeoxycholic acid to TCDD-exposed rats tended to restore the TCDD-produced reduction in serum triglycerides, whereas no similar trend was observed in wasting syndrome and lipid accumulation in the liver. These results suggest that: 1) TCDD alters the circulating levels of bile acids and hormones via a mechanism distinct from an attenuation in dietary intake, although the majority of TCDD-induced changes in nutrient contents in the excrement is due to a reduction in food intake; and 2) TCDD facilitates the excretion of bile acids and disrupts their biosynthesis, resulting in the disturbance of lipid homeostasis.

Effect of seafood mediated PCB exposure on desaturase activity and PUFA profile in Faroese septuagenarians

Polychlorinated biphenyl (PCB) exposure may affect serum concentrations of polyunsaturated fatty acids (PUFAs) by inhibiting desaturases ∆5 and ∆6 that drive their synthesis from precursor fatty acids. Such changes in the composition of fatty acids may affect cardiovascular disease risk, which is thought to increase at elevated PCB exposures. This population-based cross-sectional study examined 712 Faroese men and women aged 70-74 years. The serum phospholipid fraction of fasting blood samples was used to determine the PUFA profile, including linoleic acid, dihomo-γ-linolenic acid, arachidonic acid, eicosatrienoic acid, and other relevant fatty acids. Ratios between precursor and metabolite fatty acids were used as proxies for ∆5 and ∆6 desaturase activity. Tertiles of serum-PCB concentrations were used in multiple regression analyses to determine the association between the exposure and desaturase activity. In multiple regression models, PCB exposure was inversely related to the estimated Δ6 desaturase activity resulting in accumulation of precursor fatty acids and decrease in the corresponding product PUFAs. A positive association between PCB and Δ5 desaturation was also found. A relative increase in EA was also observed, though only in the third tertile of PCB exposure. Non-linear relationships between the exposure and the desaturase activity were not found. Consuming fish and seafood may not be translated into beneficial fatty acid profiles if the diet simultaneously causes exposure to PCBs. Although the desaturase estimates were likely influenced by dietary intakes of product PUFAs, the association between PCB exposure and ∆6 desaturase activity is plausible and may affect cardiovascular disease risk.

Changes in morphometry and association between whole-body fatty acids and steroid hormone profiles in relation to bioaccumulation patterns in salmon larvae exposed to perfluorooctane sulfonic or perfluorooctane carboxylic acids

In the present study, we have used salmon embryos whose continuous exposure to waterborne PFOA or PFOS at 100 μg/L started as freshly fertilized eggs, and lasted for a total of 52 days. PFOS and PFOA were dissolved in methanol (carrier vehicle) whose concentration never exceeded 0.01% of total tank volume. Samples were collected at day 21, 28, 35, 52, 49 and 56 after the start of the exposure. Note that days 49 and 56 represent end of exposure and 1 week after a recovery period, respectively. Tissue bioaccumulations were determined by HPLC/MS/MS, steroid hormones, fatty acids (FAs) and lipids were determined by GC-MS, while mRNA expression levels of genes were determined by qPCR in whole body homogenate. We observed that PFOS and PFOA showed a steady increase in whole body burden during the exposure period, with a slight decrease after the recovery period. Calculated somatic indexes showed that PFOA produced increases in heart-, thymus-, liver- and kidney somatic indexes (HSI, TSI, LSI and KSI). PFOA and PFOS exposure produced significant decreases in whole body dehydroepiandrosterone (DHEA), estrone and testosterone at sampling day 21 and a strong increase of cortisol and cholesterol at the end of recovery period (day 56). PFOA and PFOS effects differed with DHEA and estrone. While PFOS decreased DHEA levels, PFOA produced an increase at day 49, and while PFOS decreased estrone, PFOA produced a slight increase at day 56. We observed changes in FA composition that predominantly involved increases in FA methyl esters (FAMEs), mono- and poly-unsaturated FA (MUFA and PUFA) and a decrease in n-3/n-6 PUFA ratio by both PFOA and PFOS. Particularly, an increase in - pentadecenoic MUFA (15:1), two n-3 PUFAs α-linolenic acid [ALA: 18:3 n3] and eicosapentaenoic acid [EPA: 20:5 n-3] and n-6 PUFA: arachidonic acid [ARA: 20:4 n6], docosapentaenoic acid (DPA) by PFOA and PFOS were observed. These effects were associated with changes in mRNA expression of FA elongase (FAE), Δ5-desaturase (FAD5) and Δ6-desaturase (FAD6) genes. In summary, the changes in hormonal and FA profiles may represent cellular and/or physiological adaptation to continuous PFOS and PFOA exposure by increasing membrane fluidity, and/or overt developmental effects. The present findings provide some potential insights and basis for a better understanding on the possible mechanisms of PFCs toxicity in fish.

N-acetylcysteine (NAC) diminishes the severity of PCB 126-induced fatty liver in male rodents

Potent aryl hydrocarbon receptor agonists like PCB 126 (3,3',4,4',5-pentachlorobiphenyl) cause oxidative stress and liver pathology, including fatty liver. Our question was whether dietary supplementation with N-acetylcysteine (NAC), an antioxidant, can prevent these adverse changes. Male Sprague-Dawley rats were fed a standard AIN-93G diet (sufficient in cysteine) or a modified diet supplemented with 1.0% NAC. After one week, rats on each diet were exposed to 0, 1, or 5μmol/kg body weight PCB 126 by i.p. injection (6 rats per group) and euthanized two weeks later. PCB-treatment caused a dose-dependent reduction in growth, feed consumption, relative thymus weight, total glutathione and glutathione disulfide (GSSG), while relative liver weight, glutathione transferase activity and hepatic lipid content were dose-dependently increased with PCB dose. Histologic examination of liver tissue showed PCB 126-induced hepatocellular steatosis with dose dependent increase in lipid deposition and distribution. Dietary NAC resulted in a reduction in hepatocellular lipid in both PCB groups. This effect was confirmed by gravimetric analysis of extracted lipids. Expression of CD36, a scavenger receptor involved in regulating hepatic fatty acid uptake, was reduced with high dose PCB treatment but unaltered in PCB-treated rats on NAC-supplemented diet. These results demonstrate that NAC has a protective effect against hepatic lipid accumulation in rats exposed to PCB 126. The mechanism of this protective effect appears to be independent of NAC as a source of cysteine/precursor of glutathione.

Migratory behaviour of a dominant detritivorous fish Prochilodus lineatus evaluated by multivariate biochemical and pollutant data

This paper studies the migration pathways and ranges of a dominant detritivorous fish Prochilodus lineatus along pollution gradients in the Río de la Plata basin using multivariate analysis of biochemical and pollutant data. Biochemical composition (water, ash, lipids, proteins, carbohydrates, neutral lipids classes and fatty acids), aliphatic hydrocarbons (ALI), polychlorinated biphenyls (PCB), linear alkylbenzenes (LAB) and organochlorine pesticides (OClP) were determined in muscle samples of P. lineatus collected in Metropolitan Buenos Aires, the lower Paraná River (Paraná: 200-1000 km from Buenos Aires) and the middle Paraná and Paraguay Rivers (North: 1000-1400 km north). Biochemical variables and pollutants exhibited large variability [Lipids 1.1-89.5% wet mass; ALI 1.4-413; LABs not detectable (n.d.)-115.2; PCBs n.d.-27.9; OClPs n.d.-11.8 µg g(-1) dry mass], due to the contrast of Buenos Aires with North fish. Fish from Buenos Aires were fatty (lipids 24.7 ± 12.3% wet mass), enriched in 18 carbon fatty acids and severely contaminated (ALI 152.4 ± 72.3; LABs 65.1 ± 26.4; PCBs 15.2 ± 6.8; OClPs 1.8 ± 1.9 µg g(-1) dry mass mean ±S.D.). In contrast, fish from North were lean (4.1 ± 3.1% wet mass), enriched in long chain (>20 carbons) polyunsaturated fatty acids, with average one to two orders of magnitude lower pollutant levels (ALI 41.2 ± 51.9; PCBs 2.2 ± 3.5; LABs 8.8 ± 21.1; OClPs 0.67 ± 0.75 µg g(-1) dry mass mean ±S.D.). Paraná showed intermediate values in all variables, denoting the mixing of different fish stocks. Based on principal component analysis, 14 outliers from 60 North and Paraná samples (representing 26 from 108 individual fish) were identified as pertaining to the Buenos Aires group with very similar lipid and pollutant levels. Data suggest that P. lineatus migrates a highly variable distance, exceeding 800-1000 km in multiple spatial and temporal overlapping ranges. Chemometric analysis of biochemical and pollutant data effectively discriminates fish according to the chemical signature acquired by detritus feeding in pristine and contaminated urban or industrial areas.

The metabonomics of combined dietary exposure to phthalates and polychlorinated biphenyls in mice

Humans undergo simultaneous daily exposure to a multitude of endocrine-disrupting compounds (EDCs). In present study, after combined exposure to endocrine disruptors DEHP and Aroclor 1254 for 12 days, a liquid chromatography/time-of-flight mass spectrometer method combining both reversed-phase (RP) and hydrophilic interaction chromatography (HILIC) separations was carried out to investigate the metabolic responses in mice. The metabolic profiles of endogenous metabolites could differentiate the dose and control groups in both RPLC and HILIC modes. Moreover, the male mice and female mice in different groups could be obviously clustered in their own regions with combined model. Fourteen lysoPCs, PC(18:4/18:1), lysoPE(18:2/0:0), phenylalanine and tryptophan were identified as potential biomarkers for the combined toxicity of DEHP and Aroclor 1254. Different change trends could be observed for the identified lysoPCs, due to their different levels of uptake and metabolism in mice. Moreover, gender-specific differences in several lysoPCs (e.g. lysoPC(18:0), lysoPC(22:6), lysoPC(20:3), and PC(18:4/18:1)) were observed for treated mice. The metabonomic results indicated the combined exposure led to a disturbance of lipid metabolism. The mRNA expressions of PLA2, ACOX1, CPT1, FAS and SCD1 involved in lipid metabolism were investigated. Among them, significant increases of FAS and SCD1 expressions in the liver induced by the exposure could be observed for both male and female mice, contributing to the hepatic lipid accumulation in mice. Besides lipid metabolism, tryptophan metabolism and phenylalanine metabolism may also be involved with the toxic responses to these EDCs. The present study not only improves the understanding of the combined toxicity of phthalates and PCBs but also shows that the metabonomic approach may prove to be a promising technique for the toxicity research of EDCs.

Placental docosahexaenoic and arachidonic acids correlate weakly with placental polychlorinated dibenzofurans (PCDF) and are uncorrelated with polychlorinated dibenzo-p-dioxins (PCDD) or polychlorinated biphenyls (PCB) at delivery: a pilot study

Long chain polyunsaturated fatty acids (LC-PUFA), ARA (arachidonic acid, 20:4n-6) and DHA (docosahexaenoic acid, 22:6n-3) have positive effects and environment pollutants, polychlorinated dibenzo-p-dioxins/dibenzofurans(PCDD/F) and polychlorinated biphenyls (PCB) have negative effects on neural development during early life. Placental dioxin/PCB serves as markers for cumulative exposure to fetus. Fatty acid composition of placenta depends on nutrient supply during pregnancy, serving as indicators for fetal ARA and DHA accretion. This study investigated correlation between placental PCDD/F and PCB toxic equivalent (TEQ) and LC-PUFA in 34 pregnant women from Taiwan. Placental PCDF TEQ were inversely correlated with placental ARA (p=0.020), C20:3n-6 (p=0.01), C22:4n-6 (p=0.04), C22:5n-6 (p<0.01) and with DHA (p=0.03), but ARA and DHA did not vary with PCDD, dioxin-like and indicator PCB. After adjustment for age and body mass index, a one-unit PCDF TEQ increase was associated with 1.021%w/w and 0.312%w/w decreases in ARA (β=-1.021, p=0.03) and DHA (β=-0.312, p=0.03). Since ARA and DHA were unrelated to three classes of toxins, and a weak negative association was found with PCDF, these data provide no basis for discouraging marine fish consumption during pregnancy for Taiwan women on the basis of these organics. Pregnant women should consume fish for its unique package of nutrients while avoiding few species with high organic pollutant or mercury contamination.

Geospatial patterns of hospitalization rates for stroke with comorbid hypertension in relation to environmental sources of persistent organic pollutants: results from a 12-year population-based study

PURPOSE

Recent evidence indicates that exposure to persistent organic pollutants (POPs) is emerging as an important risk factor for atherosclerosis-related diseases, including stroke. Hypertension (HTN) is a major risk factor for stroke, and some studies suggest that exposure to POPs is also a risk factor for HTN. We hypothesized that POPs increase the environmental burden of stroke with comorbid HTN.

METHODS

A population-based study of hospitalization rates for stroke with comorbid HTN in populations presumably exposed to POPs, based on the zip code of residence, was conducted. Data on hospitalizations for stroke with comorbid HTN were obtained from the New York Statewide Planning and Research Cooperative System for 1993-2004. Relative risks, with 95% confidence intervals (RR, 95% CI), of hospitalization were estimated by multiple Poisson regression analysis.

RESULTS

RR of hospitalization for stroke with comorbid HTN was 13.4% higher in populations residing in zip codes containing or abutting environmental sources of POPs (RR = 1.134; 95% CI, 1.036-1.241; p = 0.006). Also, hospitalization rates were significantly higher in males than in females (RR = 1.397; 95% CI, 1.357-1.437; p < 0.001), in African Americans than in Caucasians (RR = 3.902; 95% CI, 3.617-4.208; p < 0.001), and in older age groups (p for trend < 0.001). These statistically significant findings of the effect of demographic factors are highly consistent with the current knowledge of stroke and serve as indirect quality indicators for our model.

CONCLUSIONS

Results of our study support the hypothesis that exposure to POPs increases the environmental burden of both stroke and HTN.

Increased hospitalizations for ischemic stroke with comorbid diabetes and residential proximity to sources of organic pollutants: a 12-year population-based study

BACKGROUND

Evidence is emerging that exposure to persistent organic pollutants (POP) is a risk factor for atherosclerosis-related diseases and for diabetes mellitus (DM). We hypothesized that residential proximity to sources of POP will be associated with an increase in hospitalization rates for ischemic stroke (IS) with comorbid DM (IS-DM).

METHODS

We examined IS-DM hospitalization rates in the New York State (exclusive of New York City) during a 12-year period. POP exposure status was assessed based on residency in a zip code containing or abutting environmental sources of POP. Adjusted relative risks (RR) of IS-DM hospitalization were estimated by multivariate Poisson regression.

RESULTS

A statistically significant 10% increase in IS-DM hospitalization rates was observed in populations environmentally exposed to POP (adjusted RR 1.10, 95% confidence interval, CI, 1.01-1.20; p = 0.031). IS-DM hospitalization rates were also higher in males (adjusted RR 1.34, 95% CI 1.30-1.39; p < 0.001), in blacks (adjusted RR 4.54, 95% CI 4.16-4.94; p < 0.001) and in older age groups (p for trend <0.001).

CONCLUSIONS

Residential proximity to sources of POP is associated with an increase in RR of IS-DM hospitalization. Our findings support the hypothesis of POP being a risk factor for IS. Further studies are warranted.

Residential proximity to environmental sources of persistent organic pollutants and first-time hospitalizations for myocardial infarction with comorbid diabetes mellitus: a 12-year population-based study

OBJECTIVES

Environmental exposure to persistent organic pollutants (POPs) has been associated with an increased risk of both acute myocardial infarction (AMI) and diabetes mellitus (DM). A study of first-time hospitalizations for AMI with DM as a comorbidity in populations presumed to be exposed or not exposed on the basis of residence near POPs sites was conducted to investigate whether exposure to POPs increases the environmental burden of disease.

MATERIALS AND METHODS

We examined the association between residential proximity to environmental sources of POPs and hospitalization rates for first-time AMI with comorbid DM in 31,428 patients aged 25-74 years, using the New York Statewide Planning and Research Cooperative System data for a 12-year period (1993-2004). Environmental exposure status was assessed based on the zip code of residence. Adjusted relative risks (RR) of AMI hospitalization were estimated by multivariate Poisson regression.

RESULTS

Hospitalization rates for first-time AMI with comorbid DM were significantly greater in populations living near POPs sites (adjusted RR = 1.169, 95% CI: 1.014-1.347, p < 0.05). These rates were also significantly higher in African Americans than in Caucasians (adjusted RR = 1.902, 95% CI: 1.659-2.180, p < 0.001), in males (adjusted RR = 1.767, 95% CI: 1.695-1.843, p < 0.001), and for older ages (p for trend < 0.001). These findings, consistent with established non-modifiable risk factors, support the plausibility of our model.

CONCLUSIONS

Residential proximity to environmental sources of POPs is associated with a significant increase in hospitalization rates for first-time AMI with comorbid DM, compared to respective rates in populations not exposed to POPs.

Exposure to Persistent Organic Pollutants Increases Hospitalization Rates for Myocardial Infarction with Comorbid Hypertension

Studies suggest that environmental exposure to persistent organic pollutants (POPs) may be an emerging risk factor for ischemic heart disease, including acute myocardial infarction (AMI). However, some studies indicate that exposure to POPs may also be a risk factor for hypertension, a well-established risk factor for AMI. To investigate effect of POPs on the environmental burden of cardiovascular disease, a study of AMI with comorbid hypertension in populations environmentally exposed to persistent organic pollutants, based on the zip code of residence, was conducted. Data on hospital discharges for AMI with comorbid hypertension were obtained from the New York Statewide Planning and Research Cooperative System for 1993-2004. Patients residing in zip codes containing or abutting POPs contaminated sites were considered environmentally exposed. Relative risks (RR) - with corresponding 95% confidence intervals (95% CI) - of hospitalization for AMI with comorbid hypertension were estimated by Poisson regression, adjusting for known confounders. Adjusted hospitalization rates for AMI with comorbid hypertension were 12.4% higher in populations residing in proximity to a POPs site (adjusted RR = 1.124, 95% CI 1.025-1.233, p < 0.05), compared to not in proximity to a POPs site. Also, hospitalization rates for AMI with comorbid hypertension were higher in males than in females (adjusted RR = 2.157, 95% CI 2.100-2.215, p < 0.05), in African Americans than in Caucasians (adjusted RR = 1.631, 95% CI 1.483-1.794, p < 0.05), and in older age groups (p for trend <0.05). These findings are consistent with the established effects of non-modifiable risk factors and serve as indirect quality indicators for our model. In conclusion, our results support the hypothesis that environmental exposure to POPs increases the burden of cardiovascular disease in exposed populations.

Fatty acid alterations in liver and milk of cadmium exposed rats and in brain of their suckling offspring

Fatty acid composition was studied in milk at day 14 and in liver at day 24 after parturition of lactating rats exposed to 0 ppm, 5 ppm or 25 ppm cadmium (Cd) via drinking water for 17 days during lactation, and in the brain of their offspring at day 19 after birth. In the liver phospholipid fraction, 22:5(n-3) was significantly higher, while in the triacylglycerol fraction 22:6(n-3)/20:5(n-3) ratio was significantly lower in the 25 ppm group compared to the controls. Significantly higher proportions of 16:0 and lower proportions of medium-chain fatty acids, 8:0-14:0, were observed in milk of dams in the 25 ppm group, indicating decreased enzymatic activity of thiotransferase II in the mammary gland. Slightly increased levels of 20:3(n-6) were observed in brains of pups in the 25 ppm group compared to control. The results indicate that Cd exposure influences fatty acid metabolism in lactating rats.

Response of the Pacific oyster Crassostrea gigas to hydrocarbon contamination under experimental conditions

Hydrocarbon contamination perturbs the metabolism of the marine bivalve Crassostrea gigas. To understand the response of this organism to hydrocarbon exposure, a suppression subtractive hybridisation method was employed to characterise up- and down-regulated genes during hydrocarbon exposure. The number of differentially expressed gene sequences obtained via this method was 258. The expression of genes involved in hydrocarbon detoxification (cytochrome p4501A1-like protein, cytochrome b(5), flavin-containing monooxygenase 2 and glutathione S-transferase omega class), protection against oxidative stress (copper/zinc superoxide dismutase) and cell protection (heat shock protein 70 family) was analysed by RT-PCR. An increase in the mRNA level of all genes studied was observed. A quantification of HSP70 by Enzyme Linked Immunosorbent Assay (ELISA) showed a significant increase of this protein during exposure. This study provides a basis for studying hydrocarbon detoxification processes in marine bivalves, especially C. gigas.

Fatty acid metabolism in neonatal chickens (Gallus domesticus) treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 3,3',4,4',5-pentachlorobiphenyl (PCB-126) in ovo

Treatment of chickens as pre-incubation embryos with TCDD or PCB-126 altered fatty acid concentrations in their plasma 21 days later, compared with their oil vehicles (sunflower and corn oils, respectively). TCDD increased the concentrations of total fatty acids, lipid classes (phospholipids and cholesterol ester), fatty acid families (saturated, n-7 and n-6), and many specific fatty acids. The only fatty acid concentrations decreased by TCDD treatment were those of cholesterol ester fatty acids 20:3n3 and 24:6n3 and overall plasma 24:6n3. In contrast, PCB-126 treatment decreased total phospholipid, saturated and plasmogen fatty acid concentrations with generally decreasing trends in specific fatty acid concentrations. However, both TCDD and PCB-126 treatments increased total 22:1n9 and decreased 24:6n3 concentrations compared with their respective vehicles. The potential relationship between those fatty acid concentrations altered by toxicant treatment and alterations in brain symmetry was then examined using correlation analysis. Several fatty acid concentrations were significantly correlated with differences in brain morphology between the right and left hemispheres and these potential associations were different between toxicant and vehicle.

Arachidonic acid status during pregnancy is associated with polychlorinated biphenyl exposure

BACKGROUND

Seafood is an important source of long-chain polyunsaturated fatty acids (LCPs), which are essential for normal growth and development. However, the nutritional benefits could be limited by polychlorinated biphenyl (PCB) contamination. In particular, inhibition of desaturase activities by PCBs may affect the maintenance of arachidonic acid (AA) status during development.

OBJECTIVE

The aim was to evaluate AA status in a birth cohort from a fishing community with a high seafood intake and a wide range of PCB exposures.

DESIGN

We measured LCP concentrations in paired mother and umbilical cord serum samples obtained from 182 consecutive births in the Faroe Islands, where PCB-contaminated whale blubber forms part of the diet. PCB exposure was determined from maternal concentrations.

RESULTS

Serum phospholipid AA concentrations averaged 9.14% and 16.5% (by wt) in maternal and cord serum, respectively. After adjustment for gestational age and concentrations of linoleic, alpha-linolenic, and eicosapentaenoic acids, a decrease in AA concentrations of 0.17% (by wt) (95% CI: 0.03%, 0.31%) and 0.31% (by wt) (95% CI: 0.10%, 0.52%) was seen in maternal and cord serum, respectively, for each doubling of PCB exposure.

CONCLUSIONS

Increased PCB exposure was associated with a modest decrease in serum AA concentrations, which is in accordance with the experimental evidence of desaturase inhibition by PCBs. Such interference with LCP utilization could attenuate the beneficial effects of the essential lipids contained in seafood. Because AA is of key importance for growth and development, these results suggest that this possible mechanism for PCB toxicity deserves to be explored.

Fatty acids, lipids, and cytochrome p-450 monooxygenase in hepatic microsomes of minks fed fish-based diets and exposed to Aroclor 1242

Minks were fed different fish-based diets and exposed to 1 mg/d of the commercial polychlorinated biphenyl (PCB) mixture Aroclor 1242 for 4 wk (November-December 1995) or 21 wk (July-December 1998). In all the dietary groups, the PCBs increased hepatic phospholipid (PL) content. No significant increase was detected in hepatic triacylglycerols (TGs). In the minks fed the different fish diets, the PCBs caused qualitatively and quantitatively different changes in the microsomal fatty acids. In the minks that were fed a diet rich in fat and low in polyunsaturated fatty acids (PUFAs), the PCBs increased the percentage of oleic acid (18:1n-9, characteristic of the storage TGs) at the expense of n-3 PUFAs. This seemed to be due to inclusions of TGs in the membrane fragments and partly due to incorporation of TG-derived fatty acids into the membrane PLs. In addition, significant decrease of PUFAs was detected also in the hepatic TGs. The concomitant decrease in the concentrations of hepatic vitamin E suggested that lipid oxidation may also contribute to the decrease of the PUFAs. In the liver of the minks fed a low-fat but PUFA- and vitamin E-rich diet, the fatty acid changes due to the PCBs (the 21-wk exposure) remained small but the cytochrome P-450 system was significantly activated. In the minks fed Baltic herring (rich in organochlorines via the foodweb), the cytosolic glutathione S-transferase (GST) activity, levels of microsomal thiobarbituric acid-reactive substances (TBARS), and hepatic PLs were significantly elevated. In conclusion, in the mink the microsomal fatty acid changes were not directly connected with the ethoxyresorufin O-deethylase (EROD) activity or P-450 expression. Apparently, the PCBs produced definite fatty acid changes only in certain lipid matrices of tissue. In addition, a rich dietary supply of PUFAs and vitamin E may prevent these changes, even in a long-term subchronic exposure.

Linoleic acid amplifies polychlorinated biphenyl-mediated dysfunction of endothelial cells

Selected dietary lipids may increase the atherogenicity of environmental chemicals, such as polychlorinated biphenyls (PCBs), by cross-amplifying mechanisms leading to dysfunction of the vascular endothelium. To investigate this hypothesis, cultured endothelial cells were treated with 90 microM linoleic acid (18:2n-6), followed by either one of two PCBs, 3,3',4,4'-tetrachlorobiphenyl (PCB 77) or 2,2'4,4',5,5'-hexachlorobiphenyl (PCB 153). These PCBs were selected for their varying binding activities with the aryl hydrocarbon (Ah) receptor and differences in their induction of cytochrome P450. PCB 77 disrupted endothelial barrier function by allowing an increase in albumin transfer across endothelial monolayers. Prior cellular enrichment with 18:2 before PCB treatment further diminished endothelial barrier function, as compared to cells treated only with the PCB. This phenomenon appears to be mediated by increased oxidative stress, which is supported by enhanced 2,7-dichlorofluorescein fluorescence, activation data of the oxidative stress-sensitive nuclear transcription factor-kappaB (NF-kappaB), as well as an observed decrease in vitamin E content in the culture media. Similar to the endothelial permeability data, pre-enrichment of cells with 18:2 further increased the PCB-mediated induction of cytochrome P450 1A. In contrast to PCB 77, PCB 153 (or 18:2 plus PCB 153) had little or no effect on endothelial barrier function. Our results suggest that certain unsaturated fatty acids can potentiate PCB-mediated endothelial cell dysfunction and that oxidative stress and activation of the cytochrome P450 1A subfamily may be, in part, responsible for these metabolic events. These findings have implications for understanding the involvement of certain environmental contaminants in diseases that involve dysfunction of the vascular endothelium.

Selective fatty acid release from intracellular phospholipids caused by PCBs in rat renal tubular cell cultures

The purpose of this study was to explore the influence of different polychlorinated biphenyls (PCBs) upon the release of oleic and palmitic acid from the intracellular lipids, which were previously labeled with [3H]oleic or [3H]palmitic acid, respectively. Studies have been realized with Aroclor 1248 (a commercial PCB mixture with 48% chlorine by weight), and two pure PCB congeners: 3,3',4, 4'-tetrachlorobiphenyl (a non-ortho-substituted planar congener) and 2,2',4,4',5,5'-hexachlorobiphenyl (a di-ortho-substituted nonplanar congener). The treatment of cells with Aroclor 1248 increased [3H]oleic acid release in a concentration-dependent manner. Our results showed that only the di-ortho-substituted congener which prefers a nonplanar configuration stimulated the release of [3H]oleic acid from the intracellular phospholipids to the culture medium, while the exposure of cell cultures to the chosen non-ortho-substituted coplanar congener did not alter the release of [3H]oleic acid to the culture medium. Finally, none of the PCBs studied could increase the release of [3H]palmitic acid from the intracellular stores significantly. The possibility that these differential alterations in the fatty acid release affect cell function during PCB exposure should therefore be postulated.

A highly toxic coplanar polychlorinated biphenyl compound suppresses Delta5 and Delta6 desaturase activities which play key roles in arachidonic acid synthesis in rat liver

The effect of 3,3',4,4',5-pentachlorobiphenyl (PenCB) on the synthesis of unsaturated fatty acids was studied in male Wistar rats. The arachidonic acid (20:4) content in the total lipids of liver homogenates was significantly reduced on day 5 of PenCB administration, while those of linoleic acid (18:2) and bishomo-gamma-linolenic acid (20:3) were increased. These changes in the total lipids of liver homogenates were observed following doses of PenCB ranging from 0.5 to 25 mg/kg of body weight. The same changes in these fatty acids were seen with four subtypes of microsomal glycerophospholipids in the liver. The marked reduction in the molar ratio of 20:4 to 18:2 in the lipids suggests alteration of the activity of the enzymes responsible for the synthesis of unsaturated fatty acids. The activity of Delta5 and Delta6 desaturases (arachidonic acid synthetase) in the liver microsomes was 17 and 13% of that of pair-fed control animals, whereas the activity of 1-acylglycerophosphorylcholine or 1-acylglycerophosphate acyltransferase, which transfers 20:4 or 18:2 to phospholipids, was not affected by the treatment. Thus, the reduction in the level of 20:4 that was observed can be explained by a reduction in desaturase activity. These results are evidence that the coplanar PenCB has a significant effect on the reduced synthesis of physiologically essential long-chain unsaturated fatty acids.