Activities of xenobiotic metabolizing enzymes in rat placenta and liver in vitro

Aflatoxin B1 targeted gene expression profiles in human placental primary trophoblast cells

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Gene expression profiles were studied in human primary trophoblast cells.

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170 genes were significantly dysregulated in aflatoxin B1-exposed trophoblasts.

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AhR-mediated estrogen receptor signalling was dysregulated in response to AFB1.

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Transcripts involved in endocrine signalling and energy homeostasis were disrupted.

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Cellular growth and development, cell cycle and DNA repair processes were affected.

Aflatoxin B1 (AFB1) is a mycotoxin produced by Aspergillus flavus and A. parasiticus. A high exposure (40 nM and 1 µM AFB1 for 72 h) was used to study mechanistic effects of AFB1 on gene expression patterns in human primary trophoblast cells, isolated from full term placentae after delivery. Gene expression profiling was conducted, and Ingenuity pathway analysis (IPA) software was used to identify AFB1-regulated gene networks and regulatory pathways.

In response to 40 nM AFB1, only 7 genes were differentially expressed whereas 1 µM AFB1 significantly dysregulated 170 genes (124 down- and 46 upregulated, ±1.5-fold, p < 0.05) in AFB1-exposed trophoblasts when compared to controls. The top downregulated genes were involved in endocrine signalling and biosynthesis of hormones, and lipid and carbohydrate metabolism. The top upregulated genes were involved in protein synthesis and regulation of cell cycle. The main canonical pathways identified by IPA were associated with endocrine signalling including growth hormone signalling, and corticotropin releasing hormone signalling. Furthermore, genes involved in aryl hydrocarbon receptor (AhR)-mediated estrogen receptor signalling were dysregulated in response to AFB1.

Our findings indicate that a high concentration 72 h AFB1 exposure caused relatively moderate number of changes on transcript level to human placental primary trophoblast cells. However, these preliminary results need to be confirmed with human-relevant concentrations of AFB1.

The effects of β-naphthoflavone on rat placental development

The morphological effects of β-naphthoflavone (β-NF) on placental development in pregnant rats were examined. β-NF, administered to pregnant rats intraperitoneally at 15 mg/kg bw from gestation day (GD) 9 to GD 14, had no effect on maternal body weight gain, mortality, or clinical sign. In the β-NF-exposed rats, intrauterine growth retardation (IUGR) rates increased on GDs 17 and 21, although there was no effect on fetal mortality rate, fetal or placental weight, or external fetal abnormality. Histopathologically, β-NF induced apoptosis and inhibition of cell proliferation of the trophoblastic septa in the labyrinth zone, resulting in its poor development. In the basal zone, β-NF induced spongiotrophoblast apoptosis and delayed glycogen islet regression, resulting in their cystic degeneration. β-NF-induced CYP1A1 expression was detected in the endothelial cells of the fetal capillaries in the labyrinth zone and in the endothelial cells of the spiral arteries in the metrial gland, but not in any trophoblasts. This indicates that CYP1A1 is inducible in the endothelial cells of the fetal capillaries in the labyrinth zone, and that these cells have an important role in metabolizing CYP1A1 inducers crossing the placental barrier.

Chemoprevention of elite tea variety CFT-1 rich in EGCG against chemically induced liver cancer in rats

Camellia sinensis (L.) O. Kuntze cv. CFT-1 is an elite tea variety bred by sexual hybridization with a high content of epigallocatechin-3-gallate (EGCG) as 134.2 mg/g (which is 2.54-fold that of the common variety). This study was to evaluate the chemopreventive effects of CFT-1 green tea infusion (CFT-1) against N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis in rats and its mechanisms. The results showed that CFT-1 had a superior inhibitory effect in NDEA-initiated hepatocarcinogenesis compared to that of common tea. CFT-1 significantly reduced the hepatic nodules incidence, size, and number and prevented the hepatic adenoma or hepatocellular carcinoma (HCC) formation. In particular, CFT-1-treated animals had the least incidence of HCC (8.33%) followed by common tea treatment (40.00%) and model control rats (87.50%). CFT-1 treatment significantly ameliorated abnormal liver function enzymes, reduced serum AFP, CEA, TSGF, and TNF-α levels, inhibited the dickkopf-related protein-1 expression, enhanced antioxidant capacity, suppressed the production of livers 8-hydroxy-2'-deoxyguanosine, and regulated hepatic phase I and II xenobiotic-metabolizing enzymes. Transcriptomic analysis of liver tissue suggested that compared to common tea, administration of CFT-1 regulated larger gene sets, which were located in several important pathways of antioxidants, inflammatory network, xenobiotic-metabolizing enzymes, apoptosis, cell proliferation, and metabolism associated with liver tumorigenesis. We identified some genes as potential molecular targets involved in the prevention of CFT-1 and found that CFT-1 inhibited inflammation response, proliferation, and accelerated apoptosis by inhibiting NF-κB and PI3K/Akt pathway. Thus, EGCG-rich CFT-1 green tea might be a potential choice for liver cancer prevention/treatment in the future.

Unhealthy Levels of Phthalates and Bisphenol A in Mexican Pregnant Women with Gestational Diabetes and Its Association to Altered Expression of miRNAs Involved with Metabolic Disease

Several studies indicate that bisphenol A (BPA) and phthalates may have a role in the development of metabolic diseases using different molecular pathways, including epigenetic regulatory mechanisms. However, it is unclear whether exposure to these chemicals modifies serum levels of miRNAs associated with gestational diabetes mellitus (GDM) risk. In the present study, we evaluated the serum levels of miRNAs associated with GDM (miR-9-5p, miR-16-5p, miR-29a-3p and miR-330-3p) and urinary levels of phthalate metabolites (mono-n-butyl phthalate (MBP), mono-isobutyl phthalate (MiBP), mono-benzyl phthalate (MBzP) and mono(2-ethyl hexyl) phthalate (MEHP)) and bisphenol A in GDM patients and women without GDM during the second trimester of gestation. We observed higher levels of miR-9-5p, miR-29a-3p and miR-330-3p in sera of patients with GDM compared to non-diabetic subjects. Phthalates were detected in 97–100% of urine samples, while BPA only in 40%. Urinary MEHP and BPA concentrations were remarkably higher in both study groups compared to previously reported data. Unadjusted MEHP levels and adjusted BPA levels were higher in non-diabetics than in GDM patients (p = 0.03, p = 0.02). We found positive correlations between adjusted urinary MBzP levels and miR-16-5p expression levels (p < 0.05), adjusted MEHP concentrations and miR-29a-3p expression levels (p < 0.05). We also found negative correlations between unadjusted and adjusted MBP concentrations and miR-29a-3p expression levels (p < 0.0001, p < 0.05), unadjusted MiBP concentrations and miR-29a-3p expression levels (p < 0.01). Urinary MEHP levels reflect a striking exposure to di(2-ethylhexyl) phthalate (DEHP) in pregnant Mexican women. This study highlights the need for a regulatory strategy in the manufacture of several items containing endocrine disruptors in order to avoid involuntary ingestion of these compounds in the Mexican population.

Preventive effects of combinative natural foods produced by elite crop varieties rich in anticancer effects on N-nitrosodiethylamine-induced hepatocellular carcinoma in rats

The World Cancer Research Fund International has released 32 anticancer effects (ACEs) that targeted every stage of cancer processes. Thus, we designed two formulas of natural food combination Diet I and Diet II, mainly produced by elite crop varieties rich in ACEs with different mixture ratios, and evaluated their cancer preventive effects on N-nitrosodiethylamine (NDEA)-induced hepatocarcinogenesis. After 20 weeks of dietary intervention, Diet I and Diet II reduced incidence, size, and number of hepatic nodules (p < 0.01) and prevented hepatic tumor formation in NDEA-induced hepatocarcinogenesis rats. Low-grade hepatic dysplasia incidence was 20% for Diet II and 40% for Diet I, and apparent hepatocellular carcinomas (HCC) rates were both 0, while 90% HCC in control diet treatment group (p < 0.01). Diet I and Diet II ameliorated abnormal liver function enzymes, reduced serum alpha fetal protein, tumor-specific growth factor, dickkopf-related protein 1, tumor necrosis factor-alpha and interleukin-6 levels, regulated hepatic phase I and II xenobiotic-metabolizing enzymes, enhanced antioxidant capacity, suppressed NDEA-initiated oxidative DNA damage, and induced apoptosis coupled to down-regulation of proinflammatory, invasion, and angiogenesis markers. Daily intake of combination diet produced from ACEs-rich elite crop varieties can effectively prevent or delay occurrence and development of NDEA-induced hepatocarcinogenesis in rats.

Can the inhibition of cytochrome P450 in aquatic invertebrates due to azole fungicides be estimated with in silico and in vitro models and extrapolated between species?

Azole fungicides, designed to halt fungal growth by specific inhibition of fungal cytochrome P450 (CYP51), inhibit cytochrome P450s involved in the metabolism of xenobiotics in several non-target organisms thus raising environmental concern. The present study investigates the degree by which inhibition strengths of azoles toward cytochrome P450 in rat liver, the insect Chironomus riparius larvae and the snail Lymnaea stagnalis can be extrapolated from estimated in silico affinities. Azoles' affinities toward human cytochrome P450 isoforms involved in xenobiotic metabolism (CYP3A4, CYP2C9 and CYP2D6) as well as fungal CYP51 were estimated with a ligand-protein docking model based on the ChemScore scoring function. Estimated affinities toward the selected enzymatic structures correlated strongly with measured inhibition strengths in rat liver (ChemScore vs. logIC₅₀ among cytochrome P450 isoforms: -0.662 < r < -0.891, n = 17 azoles), while weaker correlations were found for C. riparius larvae (-0.167 < r < -0.733, n = 9) and L. stagnalis (-0.084 < r < -0.648, n = 8). Inhibition strengths toward C. riparius and rat liver activities were found to be highly correlated to each other (r: 0.857) while no significant relationship was found between either of the species and L. stagnalis. The inhibition of cytochrome P450 due to azole fungicides could be estimated in vitro and to a lesser extent in silico for C. riparius but not for L. stagnalis, possibly due to different enzymatic susceptibility toward azole inhibition among the species.

Maternal-Fetal Disposition and Metabolism of Retrorsine in Pregnant Rats

Pyrrolizidine alkaloids (PAs) are extensively synthesized by plants, are commonly present in herbs and foodstuffs, and exhibit hepatotoxicity requiring metabolic activation by cytochrome P450 3A to form the electrophilic metabolites-pyrrolic esters. PAs also cause embryo toxicity, but the metabolic profiles of PAs in fetus and placenta have been far from clear. In this study, we determined the basal metabolic activation of retrorsine (RTS) in rat maternal liver, placenta, and fetal liver in vitro and examined the fetal toxicity and bioactivation of RTS in vivo. Detection of microsomal RTS metabolites in vitro showed that the basal metabolic activity of fetal liver and placenta to RTS was much weaker than that of maternal liver. In addition, a higher rate of pyrrolic ester formation was found in normal male fetal liver compared with that of female pups. In vivo exposure to RTS caused fetal growth retardation, as well as placental and fetal liver injury. Little difference in serum RTS was observed in dams and fetuses, but the content of pyrrole-protein adduction in the fetal liver was much lower than that in maternal liver, which was consistent with basal metabolic activity. Unexpectedly, compared with basal metabolism in fetal liver, exposure to RTS during middle and late pregnancy caused an opposite gender difference in RTS metabolism and CYP3A expression in the fetal liver. For the first time, our study showed that RTS can permeate the placenta barrier and entering fetal circulation, whereas the intrauterine pyrrolic metabolite was generated mainly by fetal liver but not transported from the maternal circulation. Induction of CYP3A by RTS was gender-dependent in the fetal liver, which was probably responsible for RTS-induced fetal hepatic injury, especially for female pups.