PCB 50 stimulates release of arachidonic acid and prostaglandins from late gestation rat amnion fibroblast cells

Human-Based New Approach Methodologies in Developmental Toxicity Testing: A Step Ahead from the State of the Art with a Feto-Placental Organ-on-Chip Platform

Developmental toxicity testing urgently requires the implementation of human-relevant new approach methodologies (NAMs) that better recapitulate the peculiar nature of human physiology during pregnancy, especially the placenta and the maternal/fetal interface, which represent a key stage for human lifelong health. Fit-for-purpose NAMs for the placental-fetal interface are desirable to improve the biological knowledge of environmental exposure at the molecular level and to reduce the high cost, time and ethical impact of animal studies. This article reviews the state of the art on the available in vitro (placental, fetal and amniotic cell-based systems) and in silico NAMs of human relevance for developmental toxicity testing purposes; in addition, we considered available Adverse Outcome Pathways related to developmental toxicity. The OECD TG 414 for the identification and assessment of deleterious effects of prenatal exposure to chemicals on developing organisms will be discussed to delineate the regulatory context and to better debate what is missing and needed in the context of the Developmental Origins of Health and Disease hypothesis to significantly improve this sector. Starting from this analysis, the development of a novel human feto-placental organ-on-chip platform will be introduced as an innovative future alternative tool for developmental toxicity testing, considering possible implementation and validation strategies to overcome the limitation of the current animal studies and NAMs available in regulatory toxicology and in the biomedical field.

Metabolomics and lipidomics to identify biomarkers of effect related to exposure to non-dioxin-like polychlorinated biphenyls in pigs

Recent epidemiological studies show that current levels of exposure to polychlorinated biphenyls (PCBs) remain of great concern, as there is still a link between such exposures and the development of chronic environmental diseases. In this sense, most studies have focused on the health effects caused by exposure to dioxin-like PCBs (DL-PCBs), although chemical exposure to non-dioxin-like PCB (NDL-PCB) congeners is more significant. In addition, adverse effects of PCBs have been documented in humans after accidental and massive exposure, but little is known about the effect of chronic exposure to low-dose PCB mixtures. In this work, exposure to Aroclor 1260 (i.e. a commercially available mixture of PCBs consisting primarily of NDL-PCB congeners) in pigs is investigated as new evidence in the risk assessment of NDL-PCBs. This animal model has been selected due to the similarities with human metabolism and to support previous toxicological studies carried out with more frequently used animal models. Dietary exposure doses in the order of few ng/kg body weight (b.w.) per day were applied. As expected, exposure to Aroclor 1260 led to the bioaccumulation of NDL-PCBs in perirenal fat of pigs. Metabolomics and lipidomics have been applied to reveal biomarkers of effect related to Aroclor 1260 exposure, and by extension to NDL-PCB exposure, for 21 days. In the metabolomics analysis, 33 metabolites have been identified (level 1 and 2) as significantly altered by the Aroclor 1260 administration, while in the lipidomics analysis, 39 metabolites were putatively annotated (level 3) and associated with NDL-PCB exposure. These biomarkers are mainly related to the alteration of fatty acid metabolism, glycerophospholipid metabolism and tryptophan-kynurenine pathway.

Exposure to organochlorines and mercury through fish and marine mammal consumption: associations with growth and duration of gestation among Inuit newborns

BACKGROUND

Several studies have reported negative associations of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB) and mercury (Hg) with duration of gestation and fetal growth in fish eating populations. Docosahexaenoic acid (DHA) from fish, seafood and marine mammal intake has been reported to be positively related with pregnancy duration and fetal growth. So far, it remains unclear, however, if the associations of environmental contaminants (ECs) with growth are direct or mediated through their relation with the duration of gestation and the degree to which DHA intake during pregnancy attenuates the negative association of ECs with fetal growth.

OBJECTIVES

To investigate direct and indirect associations of in utero exposure to ECs with fetal growth and pregnancy duration while taking into account the possible positive effects of DHA.

METHODS

Pregnant Inuit women (N=248) from Arctic Quebec were recruited and cord blood samples were analyzed for PCBs, HCB, Hg and DHA. Anthropometric measurements were assessed at birth. Path models were used to evaluate direct and indirect associations.

RESULTS

Cord concentrations of PCB 153, HCB and Hg were significantly associated with shorter duration of pregnancy (β varying from -0.17 to -0.20, p<0.05). Path models indicated that the associations of PCBs, HCB and Hg with reduced fetal growth (β varying from -0.09 to -0.13, p<0.05) were mediated through their relations with shorter gestation duration. Cord DHA was indirectly related to greater growth parameters (β varying from 0.17 to 0.20, p<0.05) through its positive association with gestation duration.

CONCLUSION

Prenatal exposure to ECs was associated with reduced gestation duration, which is a recognized determinant of fetal growth. DHA intake during pregnancy appeared to have independent positive association with fetal growth by prolonging gestation. Whether these associations are causal remains to be elucidated.

Isoprostanes 8-iPF2alpha-III: risk markers of premature rupture of fetal membranes?

AIMS

Isoprostanes may serve as sensitive and specific markers of in vivo oxidative stress intensity. We wanted to determine, whether or not isoprostane concentration may be considered as a risk marker of premature rupture of fetal membranes (PROM).

METHODS

On the basis of the presence of PROM and gestational maturity, a total of 128 patients were divided into: (1) preterm PROM (pPROM) group; (2) PROM at term group; (3) control preterm (C1) group and (4) control at term (C2) group. The concentrations of 8-iPF(2alpha)-III were determined using the enzyme-linked immunosorbent assay method.

RESULTS

The mean free isoprostane concentrations, examined in amniotic fluid and maternal plasma in the PROM at term patients were significantly higher than in C2 individuals (p < 0.01). The mean concentrations of free 8-iPF(2alpha)-III measured in blood plasma from women in the C1 group were significantly lower than in patients from the pPROM, PROM at term and C2 groups (p < 0.001, p < 0.00001 and p < 0.00001, respectively).

CONCLUSION

The measurement of free isoprostane concentration in maternal plasma and amniotic fluid may be considered as a laboratory marker of a PROM-risk pregnancy.

Non-dioxin-like polychlorinated biphenyls induce a release of arachidonic acid in liver epithelial cells: a partial role of cytosolic phospholipase A(2) and extracellular signal-regulated kinases 1/2 signalling

Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) have been shown to act as tumor promoters in liver; however, the exact mechanisms of their action are still only partially understood. One of the interesting effects of NDL-PCBs is the acute inhibition of gap junctional intercellular communication (GJIC), an effect, which has been often found to be associated with tumor promotion. As previous studies have suggested that NDL-PCB-induced disruption of lipid signalling pathways might correspond with GJIC inhibition, we investigated effects of PCBs on the release of arachidonic acid (AA) in the rat liver epithelial WB-F344 cell line, a well-established model of liver progenitor cells. We found that both 2,2',4,4'-tetrachlorobiphenyl (PCB 47) and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), but not the dioxin-like, non-ortho-substituted, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), induce a massive release of AA. The AA release, induced by PCB 153, was partially inhibited by extracellular signal-regulated kinases 1/2 (ERK1/2) signalling inhibitor, U0126, and by cytosolic phospholipase A(2) (cPLA(2)) inhibitor, AACOCF(3). Although PCB 153 induced both ERK1/2 and p38 activation, the specific p38 kinase inhibitor, SB203580, had no effect on AA release. Inhibitors of other phospholipases, including phosphatidylcholine-specific phospholipase C or phosphatidylinositol-specific phospholipase C, were also without effect. Taken together, our findings suggest that the AA release, induced by non-dioxin-like PCBs in liver progenitor cell line, is partially mediated by cytosolic PLA(2) and regulated by ERK1/2 kinases. Our results suggest that more attention should be paid to cell signalling pathways regulated by AA or eicosanoids after PCB exposure, which might be involved in their toxic effects.

Changing ratios of omega-6 to omega-3 fatty acids can differentially modulate polychlorinated biphenyl toxicity in endothelial cells

Exposure to persistent organic pollutants, such as polychlorinated biphenyls (PCBs) can cause endothelial cell (EC) activation by inducing pro-inflammatory signaling pathways. Our previous studies indicated that linoleic acid (LA, 18:2), a major omega-6 unsaturated fatty acid in the American diet, can potentiate PCB77-mediated inflammatory responses in EC. In addition, omega-3 fatty acids (such as alpha-linolenic acid, ALA and 18:3) are known for their anti-inflammatory properties. We tested the hypothesis that mechanisms of PCB-induced endothelial cell activation and inflammation can be modified by different ratios of omega-6 to omega-3 fatty acids. EC were pretreated with LA, ALA, or different ratios of these fatty acids, followed by exposure to PCB77. PCB77-induced oxidative stress and activation of the oxidative stress sensitive transcription factor nuclear factor kappaB (NF-kappaB) were markedly increased in the presence of LA and diminished by increasing the relative amount of ALA to LA. Similar protective effects by increasing ALA were observed by measuring NF-kappaB-responsive genes, such as vascular cell adhesion molecule-1 (VCAM-1) and cyclooxygenase-2 (COX-2). COX-2 catalyzes the rate limiting step of the biosynthesis of prostaglandin E(2) (PGE(2)). PCB77 exposure also increased PGE(2) levels, which were down-regulated with relative increasing amounts of ALA to LA. The present studies suggest that NF-kappaB is a critical player in the regulation of PCB-induced inflammatory markers as modulated by omega-6 and omega-3 fatty acids.