Activities of metabolizing enzymes in human placenta.

In addition to the transfer across the placenta, placenta displays hormonal and xenobiotic metabolism, as well as enzymatic defense against oxidative stress. We analyzed aromatase (CYP19A1), uridine 5'-diphospho-glucuronyltransferase (UGT), glutathione-S-transferase (GST) and catalase (CAT) activities in over 70 placentas from nonsmokers stored at -80 °C from former perfusion studies. A wide interindividual variation in all activities was found. Longterm storage at -80 °C did not affect the activities. Ethoxyresorufin-O-deethylase (EROD, CYP1A1) was not detected in any of the studied placentas perfused with chemicals. Several compounds in placental perfusion changed statistically significantly the enzyme activities in placental tissue. Melamine and nicotine increased CYP19A1, melamine increased UGT and GST, PhIP with ethanol decreased CYP19A1 and increased GST, and PhIP with buprenorphine decreased CAT. Antipyrine in 100 µg/ml also changed the studied enzyme activities, but not statistically significantly. Because antipyrine is a reference compound in placental perfusions, its potential effects must be taken into account in human placental perfusion. Enzyme activities deserve further studies as biomarkers of placental toxicity. Finally, enzyme activities deserve further studies as biomarkers of placental toxicity.

Maternal-Fetal Cancer Risk Assessment of Ochratoxin A during Pregnancy.

Increasing evidence has demonstrated that in utero exposure to environmental chemicals may interfere with fetal development and increase the risk of disease and cancer development later in life. Ochratoxin A (OTA) has been proven to induce diverse toxic effects including teratogenicity, carcinogenicity, immunotoxicity and potential endocrine disruption. Due to the continuous and widespread occurrence of OTA as a potential contaminant of staple foods, there is increasing concern of in utero exposure of fetus to this mycotoxin. In this study, maternal-fetal risk assessment of OTA during pregnancy was conducted using the benchmark dose approach for genotoxic carcinogens. The daily intake of OTA for Egyptian pregnant women was estimated based on their serum OTA level using the refined Klaassen equation for pregnancy. Fetal exposure level was also estimated based on the maternal data. Comparison between the estimated daily exposure and the negligible cancer risk intake (NCRI), and the calculation of margin of exposure (MOE) implicated that OTA exposure from dietary intake would be of low health concern for this general subpopulation of Egyptian women. This subpopulation of pregnant women was generally estimated not to be in high-risk for toxicity induced by OTA.

Individual and combined effects of Fusarium toxins on the mRNA expression of pro-inflammatory cytokines in swine jejunal epithelial cells.

Fusarium toxins have been arousing public interest in recent years because of their potential health hazards for humans and agricultural livestock. It was hypothesized that selected pro-inflammatory cytokines might serve as sensitive biomarkers of the predicted adverse effects of Fusarium toxins on the basis of their potential ability to induce immune and intestinal alterations comparable to those in human chronic inflammatory infection. Consequently, the aim of this study was to elucidate individual and combined effects of four common Fusarium toxins, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA) and fumonisin B1 (FB1) on the mRNA expression of pro-inflammatory cytokines (IL1α, IL1ß, IL6, IL8, TNFα and MCP-1) using a porcine jejunal epithelial cell line, IPEC-J2. Based on a dose-response relationship between individual mycotoxins and cell viability (MTT assay) that was previously established, cytotoxic and non-cytotoxic concentrations were selected to investigate combinations of two, three and all four of the mycotoxins. In general, up-regulation of pro-inflammatory cytokine mRNA expression occurred for both individual and mixtures of Fusarium toxins at cytotoxic concentrations, whereas significant up-regulation of pro-inflammatory cytokine mRNA mostly obtained when the toxins existed in mixtures at non-cytotoxic concentrations and these mixtures were found to cause cytotoxicity from MTT assay determined previously. Therefore, it may be concluded that some of the changes in the mRNA expression of IL1α, IL1ß, IL6, IL8, TNFα and MCP-1 could be cytotoxicity-related. It was also noted that additive effects were not always observed for the mixtures. These data suggest that individual or mixtures of Fusarium toxins could cause or exacerbate intestinal inflammation. These also provide a better understanding of the possible effects of Fusarium toxins, alone or in combinations on the immunological defense mechanisms of IECs, which would contribute to the risk assessment of these toxins.

Potential endocrine disrupting effect of ochratoxin A on human placental 3ß-hydroxysteroid dehydrogenase/isomerase in JEG-3 cells at levels relevant to human exposure.

Ochratoxin A (OTA) is a common foodborne mycotoxin. Besides its classical toxicities, it is also associated with the impairment of steroidogenesis in rats. It is hypothesized that OTA may act as an endocrine disruptor by intervening 3ß-hydroxysteroid dehydrogenase/isomerase (3ß-HSD). To address this hypothesis, human placental cells JEG-3 were used in vitro to examine the effects of short- and long-term OTA exposures on expression levels of 3ß-HSD1 and progesterone secretion at 24-96h. Results showed that both cytotoxic and non-cytotoxic levels of OTA induced 3ß-HSD1 mRNA expression by 281-378% at 72 and 96h. A significant induction (43-316%) of 3ß-HSD1 protein expression was observed at 48, 72 and 96h, and the progesterone production with the involvement of 3ß-HSD1 was significantly increased by 22-89% after 48-96h. This is the first study to demonstrate OTA up-regulates 3ß-HSD1 expression in human placental cells, indicating the potential endocrine-disrupting property of OTA.

Modulation of porcine ß-defensins 1 and 2 upon individual and combined Fusarium toxin exposure in a swine jejunal epithelial cell line.

Defensins are small antimicrobial peptides (AMPs) that play an important role in the innate immune system of mammals. Since the effect of mycotoxin contamination of food and feed on the secretion of intestinal AMPs is poorly understood, the aim of this study was to elucidate the individual and combined effects of four common Fusarium toxins, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA), and fumonisin B1 (FB1), on the mRNA expression, protein secretion, and corresponding antimicrobial effects of porcine ß-defensins 1 and 2 (pBD-1 and pBD-2) using a porcine jejunal epithelial cell line, IPEC-J2. In general, upregulation of pBD-1 and pBD-2 mRNA expression occurred following exposure to Fusarium toxins, individually and in mixtures (P < 0.05). However, no significant increase in secreted pBD-1 and pBD-2 protein levels was observed, as measured by enzyme-linked immunosorbent assay (ELISA). Supernatants from IPEC-J2 cells exposed to toxins, singly or in combination, however, possessed significantly less antimicrobial activity against Escherichia coli than untreated supernatants. When single toxins and two-toxin combinations were assessed, toxicity effects were shown to be nonadditive (including synergism, potentiation, and antagonism), suggesting interactive toxin effects when cells are exposed to mycotoxin combinations. The results show that Fusarium toxins, individually and in mixtures, activate distinct antimicrobial defense mechanisms possessing the potential to alter the intestinal microbiota through diminished antimicrobial effects. Moreover, by evaluating toxin mixtures, this improved understanding of toxin effects will enable more effective risk assessments for common mycotoxin combinations observed in contaminated food and feed.

Fate of the teratogenic and carcinogenic ochratoxin A in human perfused placenta.

Ochratoxin A (OTA) is one of the most frequent mycotoxins detected in human blood worldwide. Apart from its well known nephrotoxicity, OTA-induced teratogenicity and carcinogenicity proven in animals are potential effects also in humans. Pregnant women have been exposed to this food contaminant via dietary exposure in a continuous and widespread manner. Although the transplacental transfer of OTA has been demonstrated in laboratory animals and the presence of OTA in human fetal samples has been reported, little is known about the role of human placenta in OTA toxicokinetics. In this study, human perfused placenta was used to reveal the actual placental toxicokinetics of OTA using concentrations found in serum of pregnant women. Moreover, the effect of protein concentration and biological significance of placental transporters on the OTA transfer in human placenta were also determined. Our study is the first to pursue the transfer of OTA through perfused human placenta. The transfer of OTA through term human placenta was barely detectable in all perfusions. Inhibitors of neither ABCG2 nor ABCC2 increased the transport of OTA to fetal circulation in placental perfusion, and thus these transporters apparently do not have biological significance in inhibiting transplacental transfer of OTA. Human albumin has inhibited OTA transfer through a tight monolayer of BeWo b30 cells. Finding from this study clearly contradict the existing epidemiological studies reporting higher OTA levels in fetal than in maternal circulation in vivo.