Drug Metabolism of Hepatocyte-like Organoids and Their Applicability in In Vitro Toxicity Testing.

Emerging advances in the field of in vitro toxicity testing attempt to meet the need for reliable human-based safety assessment in drug development. Intrahepatic cholangiocyte organoids (ICOs) are described as a donor-derived in vitro model for disease modelling and regenerative medicine. Here, we explored the potential of hepatocyte-like ICOs (HL-ICOs) in in vitro toxicity testing by exploring the expression and activity of genes involved in drug metabolism, a key determinant in drug-induced toxicity, and the exposure of HL-ICOs to well-known hepatotoxicants. The current state of drug metabolism in HL-ICOs showed levels comparable to those of PHHs and HepaRGs for CYP3A4; however, other enzymes, such as CYP2B6 and CYP2D6, were expressed at lower levels. Additionally, EC50 values were determined in HL-ICOs for acetaminophen (24.0−26.8 mM), diclofenac (475.5−>500 µM), perhexiline (9.7−>31.5 µM), troglitazone (23.1−90.8 µM), and valproic acid (>10 mM). Exposure to the hepatotoxicants showed EC50s in HL-ICOs comparable to those in PHHs and HepaRGs; however, for acetaminophen exposure, HL-ICOs were less sensitive. Further elucidation of enzyme and transporter activity in drug metabolism in HL-ICOs and exposure to a more extensive compound set are needed to accurately define the potential of HL-ICOs in in vitro toxicity testing.

Uptake, Transport, and Toxicity of Pristine and Weathered Micro- and Nanoplastics in Human Placenta Cells.

BACKGROUND: The first evidence of micro- and nanoplastic (MNP) exposure in the human placenta is emerging. However, the toxicokinetics and toxicity of MNPs in the placenta, specifically environmentally relevant particles, remain unclear. OBJECTIVES: We examined the transport, uptake, and toxicity of pristine and experimentally weathered MNPs in nonsyncytialized and syncytialized BeWo b30 choriocarcinoma cells. METHODS: We performed untargeted chemical characterization of pristine and weathered MNPs using liquid chromatography high-resolution mass spectrometry to evaluate compositional differences following particle weathering. We investigated cellular internalization of pristine and weathered polystyrene (PS; 0.05-10µm) and high-density polyethylene (HDPE; 0-80µm) particles using high-resolution confocal imaging and three-dimensional rendering. We investigated the influence of particle coating with human plasma on the cellular transport of PS particles using a transwell setup and examined the influence of acute MNP exposure on cell viability, damage to the plasma membrane, and expression of genes involved in steroidogenesis. RESULTS: Chemical characterization of MNPs showed a significantly higher number of unique features in pristine particles in comparison with weathered particles. Size-dependent placental uptake of pristine and weathered MNPs was observed in both placental cell types after 24 h exposure. Cellular transport was limited and size-dependent and was not influenced by particle coating with human plasma. None of the MNPs affected cell viability. Damage to the plasma membrane was observed only for 0.05µm PS particles in the nonsyncytialized cells at the highest concentration tested (100µg/mL). Modest down-regulation of hsd17b1 was observed in syncytialized cells exposed to pristine MNPs. DISCUSSION: Our results suggest that pristine and weathered MNPs are internalized and translocated in placental cells in vitro. Effects on gene expression observed upon pristine PS and HDPE particle exposure warrant further examination. More in-depth investigations are needed to better understand the potential health risks of MNP and chemicals associated with them under environmentally relevant exposure scenarios. https://doi.org/10.1289/EHP10873.

Short-term associations between barbecue fumes and respiratory health in young adults.

BACKGROUND: Epidemiological studies have associated biomass combustion with (respiratory) morbidity and mortality, primarily in indoor settings. Barbecuing results in high outdoor air pollution exposures, but the health effects are unknown. OBJECTIVE: The objective was to investigate short-term changes in respiratory health in healthy adults, associated with exposure to barbecue fumes. METHODS: 16 healthy, adult volunteers were exposed to barbecue smoke in outdoor air in rest during 1.5 h, using a repeated-measures design. Major air pollutants were monitored on-site, including particulate matter <2.5 µm (PM2.5), particle number concentrations (PNC) and black- and brown carbon. At the same place and time-of-day, subjects participated in a control session, during which they were not exposed to barbecue smoke. Before and immediately after all sessions lung function was measured. Before, immediately after, 4- and 18 h post-sessions nasal expression levels of interleukin (IL)-8, IL6 and Tumor Necrosis Factor alpha (TNFα) were determined in nasal swabs, using quantitative polymerase chain reaction. Associations between major air pollutants, lung function and inflammatory markers were assessed using mixed linear regression models. RESULTS: High PM2.5 levels and PNCs were observed during barbecue sessions, with averages ranging from 553 to 1062 µg/m3 and 109,000-463,000 pt/cm3, respectively. Average black- and brown carbon levels ranged between 4.1-13.0 and 5.0-16.2 µg/m3. A 1000 µg/m3 increase in PM2.5 was associated with 2.37 (0.97, 4.67) and 2.21 (0.98, 5.00) times higher expression of IL8, immediately- and 18 h after exposure. No associations were found between air pollutants and lung function, or the expression of IL6 or TNFα. DISCUSSION: Short-term exposure to air pollutants emitted from barbecuing was associated with a mild respiratory response in healthy young adults, including prolonged increase in nasal IL8 without a change in lung function and other measured inflammatory markers. The results might indicate prolonged respiratory inflammation, due to short-term exposure to barbecue fumes.

Acetylcholinesterase inhibition in electric eel and human donor blood: an in vitro approach to investigate interspecies differences and human variability in toxicodynamics.

In chemical risk assessment, default uncertainty factors are used to account for interspecies and interindividual differences, and differences in toxicokinetics and toxicodynamics herein. However, these default factors come with little scientific support. Therefore, our aim was to develop an in vitro method, using acetylcholinesterase (AChE) inhibition as a proof of principle, to assess both interspecies and interindividual differences in toxicodynamics. Electric eel enzyme and human blood of 20 different donors (12 men/8 women) were exposed to eight different compounds (chlorpyrifos, chlorpyrifos-oxon, phosmet, phosmet-oxon, diazinon, diazinon-oxon, pirimicarb, rivastigmine) and inhibition of AChE was measured using the Ellman method. The organophosphate parent compounds, chlorpyrifos, phosmet and diazinon, did not show inhibition of AChE. All other compounds showed concentration-dependent inhibition of AChE, with IC50s in human blood ranging from 0.2-29 µM and IC20s ranging from 0.1-18 µM, indicating that AChE is inhibited at concentrations relevant to the in vivo human situation. The oxon analogues were more potent inhibitors of electric eel AChE compared to human AChE. The opposite was true for carbamates, pointing towards interspecies differences for AChE inhibition. Human interindividual variability was low and ranged from 5-25%, depending on the concentration. This study provides a reliable in vitro method for assessing human variability in AChE toxicodynamics. The data suggest that the default uncertainty factor of ~ 3.16 may overestimate human variability for this toxicity endpoint, implying that specific toxicodynamic-related adjustment factors can support quantitative in vitro to in vivo extrapolations that link kinetic and dynamic data to improve chemical risk assessment.

Anti-tumor properties of methoxylated analogues of resveratrol in malignant MCF-7 but not in non-tumorigenic MCF-10A mammary epithelial cell lines.

Resveratrol is a plant-derived polyphenol that is known for its anti-inflammatory and anti-tumorigenic properties in in vitro and in vivo models. Recent studies show that some resveratrol analogues might be more potent anti-tumor agents, which may partly be attributed to their ability to activate the aryl hydrocarbon receptor (AHR). Here, the anti-tumorigenic properties of resveratrol and structural analogues oxyresveratrol, pinostilbene, pterostilbene and tetramethoxystilbene (TMS) were studied in vitro, using in the malignant human MCF-7 breast cancer cell line and non-tumorigenic breast epithelial cell line MCF-10A. Cell viability and migration assays showed that methoxylated analogues of resveratrol are more potent anti-tumorigenic compounds than resveratrol and its hydroxylated analogue oxyresveratrol, with 2,3',4,5'-tetramethoxy-trans-stilbene (TMS) being the most potent compound. TMS decreased MCF-7 tumor cell viability with 50% at 3.6 µM and inhibited migration with 37.5 ± 14.8% at 3 µM. In addition, TMS activated the AHR more potently (EC50 in a reporter gene assay 2.0 µM) and induced AHR-mediated induction of cytochrome P450 1A1 (CYP1A1) activity (EC50 value of 0.7 µM) more than resveratrol and the other analogues tested. Cell cycle analysis showed that TMS induced a shift in cell cycle status from the G1 to the G2/M phase causing a cell cycle arrest in the MCF-7 cells, while no effect of TMS was observed in the non-tumorigenic MCF-10A mammary epithelial cell line. Gene expression analysis showed that 3 µM TMS increased gene expression of CYP1A1 (289-fold), CYP1B1 (5-fold) and Nqo1 (2-fold), and decreased gene expression of IL-8 (3-fold) in MCF-7 cells. In MCF-10A cells, 10 µM TMS also increased gene expression of CYP1A1 (5-fold) and CYP1B1 (2-fold), but decreased gene expression of Nqo1 (1.4-fold) in contrast to MCF-7 cells. TMS displays more potent anti-tumorigenic properties and activates the AHR more effectively than resveratrol. In addition, this is the first study to show that TMS, but not resveratrol, selectively inhibits the cell cycle of breast tumor cells and not the non-tumorigenic cells. Our study provides more insight in the anti-tumor properties of the methoxylated analogues of resveratrol in breast cells in vitro.

Excessive levels of diverse phytoestrogens can modulate steroidogenesis and cell migration of KGN human granulosa-derived tumor cells.

Phytoestrogens are plant-derived estrogen-like compounds that are increasingly used for their suggested health promoting properties, even by healthy, young women. However, scientific concerns exist regarding potential adverse effects on female reproduction. In this study, naringenin (NAR), 8-prenylnaringenin (8-PN), genistein (GEN), coumestrol (COU), quercetin (QUE) and resveratrol (RSV) up-regulated steroidogenic acute regulatory protein (StaR) mRNA levels in KGN human granulosa-like tumor cells. Most of the phytoestrogens tested also increased CYP19A1 (aromatase) mRNA levels via activation of ovary-specific I.3 and II promoters. Yet, only NAR (3 and 10 µM), COU (10 and 30 µM) and QUE (10 µM) also statistically significantly induced aromatase activity in KGN cells after 24 h. 8-PN, aromatase inhibitor letrozole and estrogen receptor antagonist ICI 182,780 concentration-dependently inhibited aromatase activity with IC50 values of 8 nM, 10 nM and 72 nM, respectively. Co-exposure with ICI 182,780 (0.1 µM) statistically significantly attenuated the induction of aromatase activity by QUE and COU, but not NAR. Cell cycle status and proliferation of KGN cells were not affected by any of the phytoestrogens tested. Nonetheless, the migration of KGN cells was significantly reduced with approximately 30% by COU, RSV and QUE and 46% by GEN at 10 µM, but not NAR and 8-PN. Our results indicate that phytoestrogens can affect various pathways in granulosa-like cells in vitro at concentrations that can be found in plasma upon supplement intake. This implies that phytoestrogens may interfere with ovarian function and caution is in place regarding the use of supplements with high contents of phytoestrogens.

Phytoestrogens in menopausal supplements induce ER-dependent cell proliferation and overcome breast cancer treatment in an in vitro breast cancer model.

Breast cancer treatment by the aromatase inhibitor Letrozole (LET) or Selective Estrogen Receptor Modulator Tamoxifen (TAM) can result in the onset of menopausal symptoms. Women often try to relieve these symptoms by taking menopausal supplements containing high levels of phytoestrogens. However, little is known about the potential interaction between these supplements and breast cancer treatment, especially aromatase inhibitors. In this study, interaction of phytoestrogens with the estrogen receptor alpha and TAM action was determined in an ER-reporter gene assay (BG1Luc4E2 cells) and human breast epithelial tumor cells (MCF-7). Potential interactions with aromatase activity and LET were determined in human adrenocorticocarcinoma H295R cells. We also used the previously described H295R/MCF-7 co-culture model to study interactions with steroidogenesis and tumor cell proliferation. In this model, genistein (GEN), 8-prenylnaringenin (8PN) and four commercially available menopausal supplements all induced ER-dependent tumor cell proliferation, which could not be prevented by physiologically relevant LET and 4OH-TAM concentrations. Differences in relative effect potencies between the H295R/MCF-7 co-culture model and ER-activation in BG1Luc4E2 cells, were due to the effects of the phytoestrogens on steroidogenesis. All tested supplements and GEN induced aromatase activity, while 8PN was a strong aromatase inhibitor. Steroidogenic profiles upon GEN and 8PN exposure indicated a strong inhibitory effect on steroidogenesis in H295R cells and H295R/MCF-7 co-cultures. Based on our in vitro data we suggest that menopausal supplement intake during breast cancer treatment should better be avoided, at least until more certainty regarding the safety of supplemental use in breast cancer patients can be provided.

Induction of glutathione synthesis and conjugation by 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-dihydroxymethamphetamine (HHMA) in human and rat liver cells, including the protective role of some antioxidants.

MDMA (3,4-methylenedioxymethamphetamine) metabolism is a major cause of MDMA-mediated hepatotoxicity. In this study the effects of MDMA and its metabolites on the glutathione system were evaluated. Glutathione (GSH/GSSG) levels and gene expression of glutamate cysteine ligase catalytic subunit (GCLC), glutathione-S-transferase (GST) and pregnane X receptor (PXR) were compared in the immortalized human liver epithelial cell line THLE-Neo lacking phase I metabolism and primary rat hepatocytes expressing both phase I and II metabolism. Furthermore, we evaluated the potential protective effects of two antioxidants, N-acetyl-cysteine (NAC) and sulforaphane (SFN) in these cell systems. In THLE-Neo cells, the MDMA metabolite 3,4-dihydroxymetamphetamine (HHMA) significantly decreased cell viability and depleted GSH levels, resulting in an increased expression of GCLC and GST up to 3.4- and 2.2-fold, respectively. In primary rat hepatocytes, cell viability or GSH levels were not significantly affected upon MDMA exposure. GCLC expression levels where not significantly altered either, although GST expression was increased 2.3-fold. NAC counteracted MDMA-induced cytotoxicity and restored GSH levels. Phase II enzyme expression was also reverted. Conversely, SFN increased MDMA-induced cytotoxicity and GSH depletion, while GCLC and GST expression were significantly induced. In addition, PXR expression decreased after HHMA and MDMA exposure, while co-exposure to SFN induced it up to 3.6- and 3.9-fold compared to vehicle-control in the THLE-Neo cells and rat hepatocytes, respectively. Taken together, these data indicate that HHMA is a major factor in the MDMA-mediated hepatotoxicity through interaction with the glutathione system. The results of our study show that for MDMA intoxication the treatment with an antioxidant such as NAC may counteract the potentially hepatotoxicity. However, SFN supplementation should be considered with care because of the indications of possible drug-drug interactions.

3,4-methylenedioxymethamphetamine (MDMA) interacts with therapeutic drugs on CYP3A by inhibition of pregnane X receptor (PXR) activation and catalytic enzyme inhibition.

Metabolism of MDMA (3,4-methylenedioxymethamphetamine, Ecstasy) by the major hepatic drug-metabolizing enzyme cytochrome P450 3A (CYP3A), plays an important role in MDMA-induced liver toxicity. In the present study, we investigated interactions between MDMA and several therapeutic and recreational drugs on CYP3A and its regulator pregnane X receptor (PXR), using a human PXR-mediated CYP3A4-reporter gene assay, rat primary hepatocytes and microsomes. MDMA significantly inhibited hPXR-mediated CYP3A4-reporter gene expression induced by the human PXR activator rifampicin (IC50 1.26 ± 0.36 mM) or the therapeutic drugs paroxetine, fluoxetine, clozapine, diazepam and risperidone. All these drugs concentration-dependently inhibited CYP3A activity in rat liver microsomes, but in combination with MDMA this inhibition became more efficient for clozapine and risperidone. In rat primary hepatocytes that were pretreated with or without the rodent PXR activator pregnenolone 16alpha-carbonitrile (PCN), MDMA inhibited CYP3A catalytic activity with IC50 values of 0.06 ± 0.12 and 0.09 ± 0.13 mM MDMA, respectively. This decrease appeared to be due to decreased activation of PXR and subsequent decreased CYP3A gene expression, and catalytic inhibition of CYP3A activity. These data suggest that in situations of repeated MDMA use in combination with other (therapeutic) drugs, adverse drug-drug interactions through interactions with PXR and/or CYP3A cannot be excluded.

Differential roles of phase I and phase II enzymes in 3,4-methylendioxymethamphetamine-induced cytotoxicity.

Metabolism plays an important role in the toxic effects caused by 3,4-methylenedioxymethamphetamine (MDMA). Most research has focused on the involvement of CYP2D6 enzyme in MDMA bioactivation, and less is known about the contribution of other cytochrome P450 (P450) and phase II metabolism. In this study, we researched the differential roles of phase I P450 enzymes CYP1A2, CYP3A4, and CYP2D6 and phase II enzymes glutathione S-transferase (GST) and catechol-O-methyltransferase (COMT) on the toxic potential of MDMA. MDMA acts as inhibitor of its own metabolism with a relative potency of inhibition of CYP2D>CYP3A>> CYP1A in rat liver microsomes and in human liver [immortalized human liver epithelial cells (THLE)] cells transfected with individual CYP1A2, CYP3A4, or CYP2D6. Cytotoxicity measurements [by 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] in THLE cells showed that the inhibition of phase I enzymes CYP1A2 by alpha-naphthoflavone and CYP3A4 by troleandomycin does not affect MDMA-induced cytotoxicity. MDMA metabolism by CYP2D6 significantly increased cytotoxicity, which was counteracted by CYP2D6 inhibition by quinidine. Inhibition of COMT by 2'-fluoro-3,4-dihydroxy-5-nitrobenzophenone (Ro-41-0960) and GST by buthionine sulfoximine showed that COMT is mainly involved in detoxification of CYP2D6-formed MDMA metabolites, whereas glutathione (GSH) is mainly involved in detoxification of CYP3A4-formed MDMA metabolites. Liquid chromatography/tandem mass spectrometry analyses of MDMA-metabolites in the THLE cell culture media confirmed formation of the specific MDMA metabolites and corroborated the observed cytotoxicity. Our data suggest that CYP2D6 as well as CYP3A4 play an important role in MDMA bioactivation. In addition, further studies are needed to address the differential roles of CYP3A4 and GSH/GST in MDMA bioactivation and detoxification.

Chemopreventive actions by enterolactone and 13 VIOXX-related lactone derivatives in H295R human adrenocortical carcinoma cells.

Cytochrome P450c17 (CYP17) has been linked to various hormone-related diseases, including breast cancer, thus being a potential target for cancer chemoprevention. We studied the naturally occurring phytochemical enterolactone (ENL) and 13 VIOXX-related lactone derivatives (CRI-1 to CRI-13) for their effects on CYP17 activity and expression and on cell cycle status in the human H295R adrenocorticocarcinoma cell line. Of the tested compounds, only CRI-3, -7, -10 and -12 showed to be inhibitors of CYP17 activity in H295R cells. This inhibition was not due to decreased mRNA expression, but was apparently caused by post-translational modification of the CYP17 enzyme. The MAPK kinase (MEK) inhibitor PD98059 induced CYP17 activity by 24%, while co-incubation of the CRI-s with PD98059, reduced CYP17 activity even further than the reduction caused by the CRI-s alone. In addition, CRI-3, -7, -10 and -12 arrested the cell cycle in the G(2)/M phase. The structure-activity similarities of the CRI-s with known micro-tubule binding agents strongly suggest that cell cycle arrest is a result of interaction with tubulin. We conclude that the proposed cancer chemopreventive actions of ENL are not mediated through interaction with CYP17 or cell cycle status. Of the VIOXX-related lactone derivatives, CRI-7 could prove useful in the prevention of hormone-dependent cancers, such as breast cancer, since in vitro it shows low cytotoxicity, it is a potent inhibitor of CYP17 activity and strong inducer of cell cycle arrest.