In vitro toxicity screening of chemical mixtures using HepG2/C3A cells

Cancer Cell Culture: The Basics and Two-Dimensional Cultures

Despite significant advances in investigative and therapeutic methodologies for cancer, 2D cell culture remains an essential and evolving competency in this fast-paced industry. From basic monolayer cultures and functional assays to more recent and ever-advancing cell-based cancer interventions, 2D cell culture plays a crucial role in cancer diagnosis, prognosis, and treatment. Research and development in this field call for a great deal of optimization, while the heterogenous nature of cancer itself demands personalized precision for its intervention. In this way, 2D cell culture is ideal, providing a highly adaptive and responsive platform, where skills can be honed and techniques modified. Furthermore, it is arguably the most efficient, economical, and sustainable methodology available to researchers and clinicians alike.In this chapter, we discuss the history of cell culture and the varying types of cell and cell lines used today, the techniques used to characterize and authenticate them, the applications of 2D cell culture in cancer diagnosis and prognosis, and more recent developments in the area of cell-based cancer interventions and vaccines.

Cytotoxicity and Genotoxicity Evaluation of Some Stored Grain Insects and Their Infested Flour Using the BHK-21 Cell Line in an In Vitro Experimental Model

Globally, stored grain is vulnerable to pest infestation, resulting in significant economic losses for some crops. Wheat is one of the most important crops in the world. Many sucking, piercing insects infect wheat in the form of grains or flour and may produce toxic residues that are harmful to human health. The current study aimed to estimate the safe use of four stored grain insects by evaluating the potential genotoxic effects and cytotoxicity of crushed insects (T. granarium, S. oryzae, R. dominica, and T. castaneum) and their flour residues. MTT and comet assays were conducted to assess the effects of six concentrations of insect flour residues (0, 6.5, 12.5, 25, 50, and 100%) on the baby hamster kidney cell line (BHK-21). The lowest BHK-21 cell viability was noted against T. granarium (LC50% 36.42 μg/ml) followed by T. castaneum flour (LC50% 46.73 μg/ml) compared to the control (LC50% 808.2 μg/ml). Significantly high DNA comet (%) was observed in the treatments of T. castaneum flour (18.8%), S. oryzae wheat (15.6%), T. granarium (15.4%), T. castaneum (13.6%), and T. granarium wheat (13.1%). FTIR spectra of stored grain insects and their flour residues identified various functional metabolite groups, including alkynes and phenols, which could enhance cell apoptosis and genotoxicity. T. granarium, T. castaneum, and their flour residues had the highest cytotoxic and genotoxic effects on the BHK-21 cell line. The current study concludes that insect residues in flour may have cytotoxic and genotoxic effects on living cells, potentially affecting public health, particularly after consuming T. granarium and T. castaneum-infested flour. Therefore, good storage of stored grains and their products is recommended.

Chemical and biological assessments of environmental mixtures: A review of current trends, advances, and future perspectives

Considering the chemical complexity and toxicity data gaps of environmental mixtures, most studies evaluate the chemical risk individually. However, humans are usually exposed to a cocktail of chemicals in real life. Mixture health assessment remains to be a research area having significant knowledge gaps. Characterization of chemical composition and bioactivity/toxicity are the two critical aspects of mixture health assessments. This review seeks to introduce the recent progress and tools for the chemical and biological characterization of environmental mixtures. The state-of-the-art techniques include the sampling, extraction, rapid detection methods, and the in vitro, in vivo, and in silico approaches to generate the toxicity data of an environmental mixture. Application of these novel methods, or new approach methodologies (NAMs), has increased the throughput of generating chemical and toxicity data for mixtures and thus refined the mixture health assessment. Combined with computational methods, the chemical and biological information would shed light on identifying the bioactive/toxic components in an environmental mixture.

Three-dimensional (3D) liver cell models - a tool for bridging the gap between animal studies and clinical trials when screening liver accumulation and toxicity of nanobiomaterials

Despite the exciting properties and wide-reaching applications of nanobiomaterials (NBMs) in human health and medicine, their translation from bench to bedside is slow, with a predominant issue being liver accumulation and toxicity following systemic administration. In vitro 2D cell-based assays and in vivo testing are the most popular and widely used methods for assessing liver toxicity at pre-clinical stages; however, these fall short in predicting toxicity for NBMs. Focusing on in vitro and in vivo assessment, the accurate prediction of human-specific hepatotoxicity is still a significant challenge to researchers. This review describes the relationship between NBMs and the liver, and the methods for assessing toxicity, focusing on the limitations they bring in the assessment of NBM hepatotoxicity as one of the reasons defining the poor translation for NBMs. We will then present some of the most recent advances towards the development of more biologically relevant in vitro liver methods based on tissue-mimetic 3D cell models and how these could facilitate the translation of NBMs going forward. Finally, we also discuss the low public acceptance and limited uptake of tissue-mimetic 3D models in pre-clinical assessment, despite the demonstrated technical and ethical advantages associated with them.

Integrative description of changes occurring on zebrafish embryos exposed to water-soluble crude oil components and its mixture with a chemical surfactant

The effects of crude oil spills are an ongoing problem for wildlife and human health in both marine and freshwater aquatic environments. Bioassays of model organisms are a convenient way to assess the potential risks of the substances involved in oil spills. Zebrafish embryos (ZFE) are a useful to reach a fast and detailed description of the toxicity of the pollutants, including both the components of the crude oil itself and substances that are commonly used for crude oil spill mitigation (e.g. surfactants). Here, we evaluated the survival rate, as well as histological, morphological, and proteomic changes in ZFE exposed to Water Accumulated Fraction (WAF) of light crude oil and in mixture with dioctyl sulfosuccinate sodium (DOSS, e.g. CEWAF: Chemically Enhanced WAF), a surfactant that is frequently used in chemical dispersant formulations. Furthermore, we compared de hydrocarbon concentration of WAF and CEWAF of the sublethal dilution. In histological, morphological, and gene expression variables, the ZFE exposed to WAF showed less changes than those exposed to CEWAF. Proteomic changes were more dramatic in ZFE exposed to WAF, with important alterations in spliceosomal and ribosomal proteins, as well as proteins related to eye and retinal photoreceptor development and heart function. We also found that the concentration of high molecular weight hydrocarbons in water was slighly higher in presence of DOSS, but the low molecular weight hydrocarbons concentration was higher in WAF. These results provide an important starting point for identifying useful crude-oil exposure biomarkers in fish species.

HepG2 spheroids as a biosensor-like cell-based system for (geno)toxicity assessment

3D spheroids developed from HepG2 cells were used as a biosensor-like system for the detection of (geno)toxic effects induced by chemicals. Benzo(a)pyrene (B(a)P) and amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) with well-known mechanisms of action were used for system validation. HepG2 spheroids grown for 3 days were exposed to BaP and PhIP for 24 and 72 h. The growth and viability of spheroids were monitored by planimetry and Live/Dead staining of cells. Multi-parametric flow cytometric analysis was applied for simultaneous detection of specific end-effects including cell cycle analysis (Hoechst staining), cell proliferation (KI67 marker), and DNA double-strand breaks (ℽH2AX) induced by genotoxic compounds. Depending on the exposure concentration/time, BaP reduced spheroid growth, affected cell proliferation by arresting cells in S and G2 phase and induced DNA double-strand breaks (DSB). Simultaneous staining of ℽH2AX formation and cell cycle analysis revealed that after BaP (10 μM; 24 h) exposure 60% of cells in G0/G1 phase had DNA DSB, while after 72 h only 20% of cells contained DSB indicating efficient repair of DNA lesions. PhIP did not influence the spheroid size whereas accumulation of cells in the G2 phase occurred after both treatment times. The evaluation of DNA damage revealed that at 200 μM PhIP 50% of cells in G0/G1 phase had DNA DSB, which after 72-h exposure dropped to 40%, showing lower repair capacity of PhIP-induced DSB compared to BaP-induced. The developed approach using simultaneous detection of several parameters provides mechanistic data and thus contributes to more reliable genotoxicity assessment of chemicals as a high-content screening tool.

Testing the efficacy of broad-acting sorbents for environmental mixtures using isothermal analysis, mammalian cells, and H. vulgaris

The hazards associated with frequent exposure to polycyclic aromatic hydrocarbons (PAHs), pesticides, Aroclors, plasticizers, and mycotoxins are well established. Adsorption strategies have been proposed for the remediation of soil and water, although few have focused on the mitigation of mixtures. This study tested a hypothesis that broad-acting sorbents can be developed for diverse chemical mixtures. Adsorption of common and hazardous chemicals was characterized using isothermal analysis from Langmuir and Freundlich equations. The most effective sorbents included medical-grade activated carbon (AC), parent montmorillonite clay, acid-processed montmorillonite (APM), and nutrient-amended montmorillonite clays. Next, we tested the ability of broad-acting sorbents to prevent cytotoxicity of class-specific mixtures using 3 mammalian in vitro models (HLF, ESD3, and 3T3 cell lines) and the hydra assay. AC showed the highest efficacy for mitigating pesticides, plasticizers, PAHs, and mycotoxins. Clays, such as APM, were effective against pesticides, Aroclors, and mycotoxins, while amended clays were most effective against plasticizers. Finally, a sorbent mixture was shown to be broadly active. These results are supported by the high correlation coefficients for the Langmuir model with high capacity, affinity, and free energy, as well as the significant protection of cells and hydra (p < 0.05). The protection percentages in 3T3 cells and hydra showed the highest correlation as suggested by both Pearson and Spearman with r = 0.84 and rho = 0.73, respectively (p < 0.0001). Collectively, these studies showed that broad-acting sorbents may be effective in preventing toxic effects of chemical mixtures and provided information on the most effective sorbents based on adsorption isotherms, and in vitro and aquatic organism test methods.

Synthetic pyrethroids common metabolite 3-phenoxybenzoic acid induces caspase-3 and Bcl-2 mediated apoptosis in human hepatocyte cells

Synthetic pyrethroids are a group of insecticides frequently used in public health and agriculture, and 3-PBA is a common metabolite of them. Although the liver is the primary organ responsible for metabolizing many compounds including pesticides, to the authors' knowledge there have been no studies on the direct hepatotoxic effects of 3-PBA. Therefore, this study aimed to investigate the possible hepatotoxic effects of 3-PBA on a Human Hepatoma Cell Line (HepG2) and the underlying apoptotic mechanisms. Firstly, an LC₅₀ of 1041.242 µM was calculated for 3-PBA by using the WST-1 test with concentrations ranging between 1 µM and 10 mM. Following that, the HepG2 cells in the experimental group were exposed to 3 different concentrations of 3-PBA (1/5 LC₅₀, 1/10 LC₅₀ and 1/20 LC₅₀) for 24 hours. The apoptotic mechanism was evaluated by using flow cytometry, and immunofluorescence assays for Caspase 3 and Bcl-2. In the flow cytometry assay, the total number of apoptotic cells increased in a dose dependent manner (p < 0.05). In the immunofluorescence assay, the Caspase 3 protein showed strong immunoreactivity in the experimental groups, while the reaction to the Bcl-2 protein was minimal. These results demonstrated that 3-PBA has a significant hepatotoxic effect on HepG2 cells and induces apoptosis via the regulation of Caspase-3 and Bcl-2. Furthermore, our results could further the understanding of the fundamental molecular mechanisms of 3-PBA hepatotoxicity. More studies are needed to determine the effects of long-term exposure to 3-PBA and also the molecular mechanisms underlying hepatotoxicity.

Promotion of cadmium uptake and cadmium-induced toxicity by the copper transporter CTR1 in HepG2 and ZFL cells

Cadmium (Cd²⁺) is considered a human carcinogen as it causes oxidative stress and alters DNA repair responses. However, how Cd²⁺ is taken up by cells remains unclear. We hypothesized that Cd²⁺ could be transported into cells via a membrane copper (Cu) transporter, CTR1. CTR1 expression was not affected by Cd²⁺ exposure at the mRNA or protein level. Stable cell lines overexpressing either hCTR1, in the human liver cell line HepG2, or zCTR1, in the zebrafish liver cell line ZFL, were created to study their responses to Cd²⁺ insult. It was found that both HepG2 and ZFL cells overexpressing CTR1 had higher Cd²⁺ uptake and thus became sensitive to Cd²⁺. In contrast, hCTR1 knockdown in HepG2 cells led to a reduced uptake of Cd²⁺, making the cells relatively resistant to Cd²⁺. Localization studies revealed that hCTR1 had a clustered pattern after Cd²⁺ exposure, possibly in an attempt to reduce both Cd²⁺ uptake and Cd²⁺-induced toxicity. These in vitro results indicate that CTR1 can transport Cd²⁺ into the cell, resulting in Cd²⁺ toxicity.

Identification of novel αβ-tubulin modulators with antiproliferative activity directed to cancer therapy using ligand and structure-based virtual screening

Among several strategies related to cancer therapy targeting the modulation of αβ-tubulin has shown encouraging findings, more specifically when this is achieved by inhibitors located at the colchicine binding site. In this work, we aim to fish new αβ-tubulin modulators through a diverse and rational VS study, and thus, exhibiting the development of two VS pipelines. This allowed us to identify two compounds 5 and 9 that showed IC₅₀ values of 19.69 and 21.97 μM, respectively, towards possible modulation of αβ-tubulin, such as assessed by in vitro assays in C6 glioma and HEPG2 cell lines. We also evaluated possible mechanisms of action of obtained hits towards the colchicine binding site of αβ-tubulin by using docking approaches. In addition, assessment of the stability of the active (5 and 9) and inactive compounds (3 and 13) within the colchicine binding site was carried out by molecular dynamics (MD) simulations, highlighting the solvent effect and revealing the compound 5 as the most stable in the complex. At last, deep analysis of these results provided some valuable insights on the importance of using mixed ligand- and structure-based strategies in VS campaigns, in order to achieve higher chemical diversity and biological effect as well.

Activation of integrated stress response and disordered iron homeostasis upon combined exposure to cadmium and PCB77

Both cadmium and polychlorinated biphenyls (PCBs) can induce diverse detrimental effects on human health. Though these compounds co-exist in various environmental contexts and in the human body, studies on their joint toxicities are limited. Activation of the integrated stress response (ISR) and iron homeostasis are crucial for erythropoiesis. The impact of cadmium and PCBs on the ISR activation and iron homeostasis of erythroid progenitors is unknown. We investigated the adverse effects and mechanisms of CdCl₂ and PCB77 on HEL cells, a human cell model of erythroid progenitors. We found that at high concentrations of CdCl₂ and PCB77, cytotoxicity and apoptosis of HEL cells were mainly induced by CdCl₂. At low concentrations of CdCl₂ and PCB77, iron homeostasis inside HEL cells was disturbed by both of these two compounds. Both CdCl₂ and PCB77 activated ISR to combat stress, which at high concentration was mainly induced by ROS, leading to apoptosis, and at low concentration was partly induced by disordered iron homeostasis. The patterns of ISR activation and iron homeostasis disorder were different between CdCl₂ and PCB77. Their combined exposure exhibited synergetic effect on activating ISR but antagonistic effect on disturbing iron homeostasis. Our study demonstrates some previously unrecognized harmful characteristics and mechanisms of cadmium and PCB77.

In vitro toxicity testing in hemocytes of the marine mussel Mytilus galloprovincialis (L.) to uncover mechanisms of action of the water accommodated fraction (WAF) of a naphthenic North Sea crude oil without and with dispersant

Dispersants used in oil spills could result toxic to marine organisms and could influence the toxicity of oil compounds. The aim of this work was to uncover the mechanisms of action of the water accommodated fraction (WAF) of a naphthenic North Sea crude oil produced at 10, 15 and 20 °C without and with the dispersant Finasol OSR52 (WAF and WAFD, respectively) using hemocytes of the marine mussel Mytilus galloprovincialis. Primary cultures of hemocytes were exposed in glass-coated microplates to different WAF or WAFD dilutions (0.25, 2.5, 25, 50 and 100%) and to the dispersant alone at the same concentrations present in the WAFD dilutions (1.25, 12.5, 125, 250 and 500 mg/L). Of the two in vitro approaches tested, the second one was selected which involved exposure of hemocytes for 4 h to unfiltered WAF, WAFD and dispersant dilutions without cell culture media. WAF decreased hemocytes viability only at the highest dilution whereas WAFD and the dispersant alone were cytotoxic at the three highest concentrations. Temperature of production of WAF, WAFD and dispersant did not influence their cytotoxicity to hemocytes. WAF increased ROS production and MXR transport activity in hemocytes. Exposure to WAFD and dispersant increased ROS production, provoked plasma membrane and actin cytoskeleton disruption and decreased phagocytic activity. In conclusion, the dispersant tested was toxic to mussel hemocytes and it greatly increased the toxicity of WAFD. The present data could be useful for the environmental risk assessment of oil spills and their remediation strategies in the marine environment.

Comparative toxicity of Corexit® 9500, oil, and a Corexit®/oil mixture on the eastern oyster, Crassostrea virginica (Gmelin)

Given their particle feeding behavior, sessile nature, and abundance in coastal zones, bivalves are at significant risk for exposure to oil and oil dispersant following environmental disasters like the Deepwater Horizon oil spill. However, the effects of oil combined with oil dispersants on the health of oysters are not well studied. Therefore, eastern oysters (Crassostrea virginica) were exposed in vivo to Corexit^® 9500, crude oil (high-energy water accommodated fraction; HEWAF), and a Corexit^®/oil mixture (chemically-enhanced water accommodated fraction; CEWAF) to evaluate potential toxic effects on immunological (phagocytosis and respiratory burst), physiological (feeding rate), and histological endpoints. Phagocytosis was significantly increased following CEWAF exposure only. Respiratory burst was significantly decreased following Corexit^® exposure, but significantly increased following exposure to the highest concentration of CEWAF. Oyster feeding rates were significantly decreased following exposure to Corexit^®, HEWAF, and CEWAF, and were most sensitive to CEWAF exposure. These modulations of important immunological and physiological functions could result in serious health outcomes for oysters, such as increased parasitism and decreased growth. Our experiments showed that subtle, sub-lethal effects occurred following acute in vivo exposure to Corexit^®, HEWAF, and CEWAF, though oysters were not equally sensitive to the three components. Data from this study can be used for more accurate risk assessment concerning the impact of oil and Corexit^® on the health of oysters.

Evaluation of behavioral parameters, hematological markers, liver and kidney functions in rodents exposed to Deepwater Horizon crude oil and Corexit

The 2010 Deepwater Horizon (DWH) oil spill is the largest marine oil spill in US history. In the aftermath of the spill, the response efforts used a chemical dispersant, Corexit, to disperse the oil spill. The health impacts of crude oil and Corexit mixture to humans, mammals, fishes, and birds are mostly unknown. The purpose of this study is to investigate the in vivo effects of DWH oil, Corexit, and oil-Corexit mixture on the general behavior, hematological markers, and liver and kidney functions of rodents. C57 Bl6 mice were treated with DWH oil (80 mg/kg) and/or Corexit (95 mg/kg), and several hematological markers, lipid profile, liver and kidney functions were monitored. The results show that both DWH oil and Corexit altered the white blood cells and platelet counts. Moreover, they also impacted the lipid profile and induced toxic effects on the liver and kidney functions. The impacts were more pronounced when the mice were treated with a mixture of DWH-oil and Corexit. This study provides preliminary data to elucidate the potential toxicological effects of DWH oil, Corexit, and their mixtures on mammalian health. Residues from the DWH spill continue to remain trapped along various Gulf Coast beaches and therefore further studies are needed to fully understand their long-term impacts on coastal ecosystems.

In vitro study on the joint hepatoxicity upon combined exposure of cadmium and BDE-209

Joint toxicity is an important issue during the risk assessment of environmental pollutants. Contamination of heavy metals and persistent organic pollutants (POPs) under the environmental and biological settings poses substantial health risk to humans. Although previous studies demonstrated the co-occurrence of cadmium and decabrominated diphenyl ether (BDE-209) in environmental mediums, food chains and even human body, their potentially joint toxicities remain elusive thus far. Our investigation here with respect to the hepatotoxicity in vitro clearly demonstrated that combined exposure of cadmium and BDE-209 aggravated the injuries in hepatocytes, which was evidenced by the additive effects on the induction of remarkable morphological alternations, LDH release, cell apoptosis and necrosis, impairment of mitochondrial activity and transmembrane potential. Enhanced ROS production was one of the mechanisms for cell apoptosis and death upon joint treatment. Additionally, more cadmium-treated cells underwent apoptosis than BDE-209-treated cells while more ROS was generated with BDE-209 treatment, indicating that other mechanisms might be involved in cadmium-induced apoptosis. Our results would be helpful for evaluating the joint-hepatotoxicity upon combined exposure of cadmium and BDE-209 as well as investigating the underlying mechanisms.

Antioxidant responses and oxidative stress in sheepshead minnow larvae exposed to Corexit 9500® or its component surfactant, DOSS

Large-scale use of dispersants to remediate oil spills has raised concerns about their toxicity to marine organisms. Of particular concern is oxidative stress and resulting membrane damage due to exposure to surfactants in dispersant mixtures. We investigated the potential of the dispersant Corexit 9500^® and one of its major components, the anionic surfactant dioctyl sodium sulfosuccinate (DOSS), to induce oxidative stress in larval sheepshead minnows after 24 and 96h exposures, at two sublethal concentrations, the lesser being environmentally realistic for each compound. Corexit exposures elicited only minimal antioxidant responses for most antioxidant components tested, with increased glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities observed only after 96h and at the higher exposure concentration. In contrast, DOSS induced statistically significant increases in the levels of reactive oxygen species (ROS), GPx, and lipid peroxidation, as well as depleted reduced glutathione (GSH) levels at both time points and concentrations. These data indicate that short-term and environmentally realistic exposures to DOSS can impact antioxidant response capabilities, raising concern about its use in oil dispersants and other high volume use products where environmental releases are likely.

STAT3 Inhibition Suppresses Hepatic Stellate Cell Fibrogenesis: HJC0123, a Potential Therapeutic Agent for Liver Fibrosis

Hepatic Stellate Cells (HSCs) are the major source of the excessive extracellular matrix (ECM) production that replaces liver parenchyma with fibrous tissue during liver fibrosis. The signal transducer and activator of transcription 3 (STAT3) promotes HCSs survival, proliferation, and activation contributing to fibrogenesis. We have previously used a fragment-based drug design approach and have discovered a novel STAT3 inhibitor, HJC0123. Here, we explored the biological effects of HJC0123 on the fibrogenic properties of HSCs. HJC0123 treatment resulted in the inhibition of HSCs proliferation at submicromolar concentrations. HJC0123 reduced the phosphorylation, nuclear translocation, and transcriptional activity of STAT3. It decreased the expression of STAT3-regulated proteins, induced cell cycle arrest, promoted apoptosis and downregulated SOCS3. HJC0123 treatment inhibited HSCs activation and downregulated ECM protein fibronectin and type I collagen expression. In addition, HJC0123 increased IL-6 production and decreased TGF-β induced Smad2/3 phosphorylation. These results demonstrate that HJC0123 represents a novel STAT3 inhibitor that suppresses the fibrogenic properties of HSCs, suggesting its therapeutic potential in liver fibrosis.

Corexit-EC9527A Disrupts Retinol Signaling and Neuronal Differentiation in P19 Embryonal Pluripotent Cells

Corexit-EC9500A and Corexit-EC9527A are two chemical dispersants that have been used to remediate the impact of the 2010 Deepwater Horizon oil spill. Both dispersants are composed primarily of organic solvents and surfactants and act by emulsifying the crude oil to facilitate biodegradation. The potential adverse effect of the Corexit chemicals on mammalian embryonic development remains largely unknown. Retinol (vitamin A) signaling, mediated by all-trans retinoic acid (RA), is essential for neural tube formation and the development of many organs in the embryo. The physiological levels of RA in cells and tissues are maintained by the retinol signaling pathway (RSP), which controls the biosynthesis of RA from dietary retinol and the catabolism of RA to polar metabolites for removal. RA is a potent activating ligand for the RAR/RXR nuclear receptors. Through RA and the receptors, the RSP modulates the expression of many developmental genes; interference with the RSP is potentially teratogenic. In this study the mouse P19 embryonal pluripotent cell, which contains a functional RSP, was used to evaluate the effects of the Corexit dispersants on retinol signaling and associated neuronal differentiation. The results showed that Corexit-EC9500A was more cytotoxic than Corexit-EC9527A to P19 cells. At non-cytotoxic doses, Corexit-EC9527A inhibited retinol-induced expression of the Hoxa1 gene, which encodes a transcription factor for the regulation of body patterning in the embryo. Such inhibition was seen in the retinol- and retinal- induced, but not RA-induced, Hoxa1 up-regulation, indicating that the Corexit chemicals primarily inhibit RA biosynthesis from retinal. In addition, Corexit-EC9527A suppressed retinol-induced P19 cell differentiation into neuronal cells, indicating potential neurotoxic effect of the chemicals under the tested conditions. The surfactant ingredient, dioctyl sodium sulfosuccinate (DOSS), may be a major contributor to the observed effect of Corexit-EC9527A in the cell.

Combined cytotoxic effects of pesticide mixtures present in the Chinese diet on human hepatocarcinoma cell line

Consumers might be simultaneously exposed to several pesticide residues contained in their food. Based on the results of previous studies, 20 pesticides were selected due to their high exposure levels to which the Chinese population is likely exposed through the diet. The purpose of this study was to measure the cytotoxicity of these pesticides in HepG2 cells in vitro, as an alternative approach to assess the toxicity of chemicals. Then, the pesticides and some of the mixtures with comparatively high cell-proliferating inhibitory activities were selected to test the cellular ROS level and apoptosis-related protein Caspase-3/7 content in HepG2 cells. The combined effects of these pesticide mixtures with the prediction was based on a combination index (CI)-isobologram equation and the pesticide combinations exhibited various types of interactions (synergism, antagonism, and additivity). Two individuals, one binary combinations, and three uniform design (UD) mixtures of the pesticides were found to have significant cytotoxic effects, along with significant time- and dose-dependent induction of caspase-3/7 activity in vitro, indicating that cytotoxicity caused by these pesticides might be attributed to the pro-oxidative and apoptosis induced potential.

Human Hepatic HepaRG Cells Maintain an Organotypic Phenotype with High Intrinsic CYP450 Activity/Metabolism and Significantly Outperform Standard HepG2/C3A Cells for Pharmaceutical and Therapeutic Applications

Conventional in vitro human hepatic models for drug testing are based on the use of standard cell lines derived from hepatomas or primary human hepatocytes (PHHs). Limited availability, interdonor functional variability and early phenotypic alterations in PHHs restrict their use, whilst standard cell lines such as HepG2 lack a substantial and variable set of liver‐specific functions such as CYP450 activity. Alternatives include the HepG2‐derivative C3A cells selected as a more differentiated and metabolically active hepatic phenotype. Human HepaRG cells are an alternative organotypic co‐culture model of hepatocytes and cholangiocytes reported to maintain in vivo‐like liver‐specific functions, including intact Phase I–III drug metabolism. In this study, we compared C3A and human HepaRG cells using phenotypic profiling, CYP450 activity and drug metabolism parameters to assess their value as hepatic models for pre‐clinical drug testing or therapeutics. Compared with C3As, HepaRG co‐cultures exhibit a more organotypic phenotype, including evidence of hepatic polarity with the strong expression of CYP3A4, the major isoform involved in the metabolism of over 60% of marketed drugs. Significantly greater CYP450 activity and expression of CYP1A2, CYP2E1 and CYP3A4 genes in HepaRG cells (comparable with that of human liver tissue) was demonstrated. Moreover, HepaRG cells also preferentially expressed the hepatic integrin α₅β₁ – an important modulator of cell behaviour including growth and survival, differentiation and polarity. Drug metabolite profiling of phenacetin (CYP1A2) and testosterone (CYP3A4) using LC‐MS/MS and HPLC, respectively, revealed that HepaRGs had more intact (Phase I–II) metabolism profile. Thus, HepaRG cells significantly outperform C3A cells for the potential pharmaceutical and therapeutic applications.

Gene expression and metabolic responses of HepG2/C3A cells exposed to flame retardants and dust extracts at concentrations relevant to indoor environmental exposures

Humans are routinely exposed to mixtures of flame retardants (FRs) from multiple sources including indoor dust. As a model to explore the potential effects of FR exposure from indoor dust on human health, the molecular responses of human hepatoma cells (HepG2/C3A cells) to a defined mixture of FRs and to a dust extract were investigated using multiple non-targeted omics approaches. A solvent extract of an indoor dust standard reference material SRM2585 was used as the surrogate dust sample, while a mixture of four FRs (TCEP, TCIPP, TDCIPP and HBCD) was used to mimic the FR mixture in the indoor dust. Cytotoxicity tests indicated there were no significant changes to cell viability or cell integrity after a 24- or 72-h exposure of HepG2/C3A cells to the FR mixture or to the dust extract. However, transcriptomics revealed changes in gene expression associated with the metabolism of xenobiotics (e.g. CYP1A1, CYP1A2, CYP2B6) in the dust extract group but not in the FR mixture group after a 72-h exposure. Few metabolic or lipidomic changes were detected in response to either the FR mixture or to the dust extract group. Given that the dust extract contained components that elicited a biological response, in contrast to the lack of response induced by the FR mixture, our findings suggest that the most likely causes of the molecular responses to indoor dust exposure lie in components other than the four FRs investigated, e.g. caused by PAHs or PCBs.

Multiparametric luminescent cell viability assay in toxicology models: A critical evaluation

INTRODUCTION

In cellular viability assays the sole determination of a single parameter might not give precise information on the extent of toxicity. In our study we worked out a multiparametric microplate assay based on bioluminescent ATP quantification, esterase activity-related fluorescence, nucleic acid staining and total intracellular protein measurement from the same sample in MDCK and HepG2 tissue cultures.

METHODS

Dose-response analyses were done after ATP depletion by metabolic poisons (NaF, NaN3) and by ochratoxin A (OTA) mycotoxin treatments. A novel perchloric acid fixation/extraction technique was applied in order to obtain intracellular ATP levels, esterase activity, DNA content and protein data simultaneously. Esterase activity was assessed by a fluorogenic staining. Estimation of cell number was done by DAPI fluorescence. Our results were expressed as ATP/protein, calcein fluorescence/ATP, calcein fluorescence/protein and ATP/DAPI ratios. Apoptosis/necrosis rates were measured by Annexin V-propidium iodide and 7-aminoactinomycin D flow cytometric assays and effects of OTA on actin cytoskeleton were also studied by using labeled phalloidin for visualization of actin.

RESULTS

We could verify that the esterase assay was not an energy driven (true viability) process. ATP/protein, calcein fluorescence/ATP, calcein fluorescence/protein ratios, DAPI fluorescence and protein levels together with morphological and apoptosis/necrosis parameters deciphered subtle changes in cell viability with good between-run precision. Dose dependent loss in cell number and decreased protein levels were observed in all cases, while disorganization of actin microfilaments was seen in OTA treated cells. The two cell lines did not respond uniformly to the same treatments.

DISCUSSION

ATP/protein ratio proved to be a useful viability parameter however, the suppression and/or loss of intracellular protein could cause difficulty in interpreting ATP/protein data. We conclude that correct assessment of cellular viability should be done by measuring multiple parameters related to the specific mode of action of the tested toxic compound.

Predicting GHS toxicity using RTCA and discrete-time Fourier transform

In order to promote the acceptance of cell-based toxicity testings, the accuracy of cytotoxicity test must be determined when compared to in vivo results. Traditional methods of cytotoxicity analysis, such as LC[Formula: see text] (concentration where 50% of the cells are killed) can be problematic since they have been found to vary with time. Technological advances in cytotoxicity testing make it easy to record the dynamic data on changes in cell proliferation, morphology, and damage. To effectively and reasonably analyze the dynamic data, we present a new in vitro toxicity assessed method using the discrete-time Fourier transform (DTFT) which maps the measured cell index from the time domain to the frequency domain. The direct current (DC) component of the DTFT is extracted as a feature which reflects the intensity of cytotoxicity. The smaller the value, the higher the cytotoxicity. Then, a novel toxicity index, as expressed in terms of DC[Formula: see text], is calculated. Results generated with selected test chemicals are compared favorably with data obtained from The Interagency Coordinating Committee on the Validation of Alternative Method (ICCVAM) report concerning the prediction of acute systemic toxicity in rodents. The method can be applied with the standard and high throughput to estimate acute rodent oral toxicity which reduces the number of animals required in subsequent pharmacological/toxicological studies.

Evaluation of Pulmonary and Systemic Toxicity of Oil Dispersant (COREXIT EC9500A(®)) Following Acute Repeated Inhalation Exposure

INTRODUCTION

Oil spill cleanup workers come into contact with numerous potentially hazardous chemicals derived from the oil spills, as well as chemicals applied for mitigation of the spill, including oil dispersants. In response to the Deepwater Horizon Macondo well oil spill in the Gulf of Mexico in 2010, a record volume of the oil dispersant, COREXIT EC9500A, was delivered via aerial applications, raising concern regarding potential health effects that may result from pulmonary exposure to the dispersant.

METHODS

The current study examined the effects on pulmonary functions, cardiovascular functions, and systemic immune responses in rats to acute repeated inhalation exposure of COREXIT EC9500A at 25 mg/m(3), five hours per day, over nine work days, or filtered air (control). At one and seven days following the last exposure, a battery of parameters was measured to evaluate lung function, injury, and inflammation; cardiovascular function; peripheral vascular responses; and systemic immune responses.

RESULTS

No significant alterations in airway reactivity were observed at one or seven days after exposure either in baseline values or following methacholine (MCh) inhalation challenge. Although there was a trend for an increase in lung neutrophils and phagocyte oxidant production at one-day post exposure, there were no significant differences in parameters of lung inflammation. In addition, increased blood monocytes and neutrophils, and decreased lymphocyte numbers at one-day post exposure also did not differ significantly from air controls, and no alterations in splenocyte populations, or serum or spleen immunoglobulin M (IgM) to antigen were observed. There were no significant differences in peripheral vascular responsiveness to vasoconstrictor and vasodilator agonists or in blood pressure (BP) responses to these agents; however, the baseline heart rate (HR) and HR responses to isoproterenol (ISO) were significantly elevated at one-day post exposure, with resolution by day 7.

CONCLUSIONS

In summary, acute repeated exposure to COREXIT EC9500A did not alter pulmonary function, lung injury/inflammation, systemic immune responses, or vascular tone, but did cause transient chronotropic effects on cardiac function.

Toxic potentiality of bio-oils, from biomass pyrolysis, in cultured cells and Caenorhabditis elegans

Bio-oils, which are multicomponent mixtures, were produced from two different biomass (rice straw (rice oil) and sawdust of oak tree (oak oil)) by using the slow pyrolysis process, and chemical compositional screening with GC-MS detected several hazardous compounds in both bio-oil samples. The two bio-oils vary in their chemical compositional nature and concentrations. To know the actual hazard potentialities of these bio-oils, toxicological assessments were carried out in a comparative approach by using in vitro (Jurkat T and HepG2 cell) as well as in vivo (Caenorhabditis elegans) systems. A dose-dependent increase in cytotoxicity, cell death (apoptosis), and genotoxicity were observed in cultured cell systems. Similarly, the in vivo system, C. elegans also displayed a dose-dependent decrease in survival. It was found that in comparison with rice oil, oak oil displayed higher toxicity to all models systems, and the susceptibility order of the model systems were Jurkat T > HepG2 > C. elegans. Pursuing the study further toward the underlying mechanism by exploiting the C. elegans mutants screening assay, the bio-oils seem to mediate toxicity through oxidative stress and impairment of immunity. Taken together, bio-oils compositions mainly depend on the feedstock used and the pyrolysis conditions which in turn modulate their toxic potentiality.

Toxicological effect of single contaminants and contaminant mixtures associated with plant ingredients in novel salmon feeds

Increasing use of plant feed ingredients may introduce contaminants not previously associated with farming of salmonids, such as pesticides and PAHs from environmental sources or from thermal processing of oil seeds. To screen for interaction effects of contaminants newly introduced in salmon feeds, Atlantic salmon primary hepatocytes were used. The xCELLigence cytotoxicity system was used to select optimal dosages of the PAHs benzo(a)pyrene and phenanthrene, the pesticides chlorpyrifos and endosulfan, and combinations of these. NMR and MS metabolic profiling and microarray transcriptomic profiling was used to identify novel biomarkers. Lipidomic and transcriptomic profiling suggested perturbation of lipid metabolism, as well as endocrine disruption. The pesticides gave the strongest responses, despite having less effect on cell viability than the PAHs. Only weak molecular responses were detected in PAH-exposed hepatocytes. Chlorpyrifos suppressed the synthesis of unsaturated fatty acids. Endosulfan affected steroid hormone synthesis, while benzo(a)pyrene disturbed vitamin D3 metabolism. The primary mixture effect was additive, although at high concentrations the pesticides acted in a synergistic fashion to decrease cell viability and down-regulate CYP3A and FABP4 transcription. This work highlights the usefulness of 'omics techniques and multivariate data analysis to investigate interactions within mixtures of contaminants with different modes of action.

Cadmium and decabrominated diphenyl ether mixture: In vitro evaluation of cytotoxic, prooxidative and genotoxic effects

In order to look into the combined effects of Cd and BDE-209 in vitro, this study was aimed at examining cytotoxic and genotoxic effects using the human colon carcinoma cell line (SW 480) as a biological test system as well as to determine if ROS production was one of the possible mechanisms of their mixture action. This cell line was chosen since ingestion of contaminated food/water represents an important route of exposure to both Cd and BDE-209, which is why intestinal cells are a common target for the contaminants present in food and water. Cells were treated with single Cd in concentrations of 2.5, 7.5 or 15μg Cd/mL (corresponding to 22, 67 or 134μM), single BDE-209 in concentrations of 2.5, 5 or 10μg BDE209/mL (corresponding to 2.5, 5 or 10μM), and their mixtures (design 3×3). Mixture of Cd and BDE-209 has shown clear potential to reduce the viability of SW 480 cells, as evidenced by cytotoxicity associated with ROS generation. Factorial regression models used to identify type of interaction revealed synergism related to mixture citotoxicity and additive interaction for the effect on ROS production. The results from this introductory study could contribute to the issue of possible adverse effects associated with co-exposure and body burden with two persistent environmental pollutants, Cd and BDE-209.

Chemical dispersants used in the Gulf of Mexico oil crisis are cytotoxic and genotoxic to sperm whale skin cells

The 2010 Deepwater Horizon oil rig explosion in the Gulf of Mexico drew attention to the need for toxicological studies of chemical dispersants. We are still learning the effects these spills had on wildlife. Little is known about the toxicity of these substances in marine mammals. The objective of this study was to determine the toxicity of the two dispersants (Corexit 9500 and 9527). Corexit 9500 and 9527 were both cytotoxic to sperm whale skin fibroblasts. Corexit 9527 was less cytotoxic than 9500. S9 mediated metabolism did not alter cytotoxicity of either dispersant. Both dispersants were genotoxic to sperm whale skin fibroblasts; S9 mediated metabolism increased Corexit 9527 genotoxicity.

Evaluation of differential cytotoxic effects of the oil spill dispersant Corexit 9500

AIMS

The British Petroleum (BP) oil spill has raised several ecological and health concerns. As the first response, BP used a chemical dispersant, Corexit-9500, to disperse the crude oil in the Gulf of Mexico to limit shoreline contamination problems. Nevertheless, portions of this oil/Corexit mixture reached the shoreline and still remain in various Gulf shore environments. The use of Corexit itself has become a significant concern since its impacts on human health and environment is unclear.

MAIN METHODS

In this study, in vitro cytotoxic effects of Corexit were evaluated using different mammalian cells.

KEY FINDINGS

Under serum free conditions, the LC50 value for Corexit in BL16/BL6 cell was 16 ppm, in 1321N1 cell was 33 ppm, in H19-7 cell was 70 ppm, in HEK293 was 93 ppm, and in HK-2 cell was 95 ppm. With regard to the mechanisms of cytotoxicity, we hypothesize that Corexit can possibly induce cytotoxicity in mammalian cells by altering the intracellular oxidative balance and inhibiting mitochondrial functions. Corexit induced increased reactive oxygen species and lipid peroxide levels; also, it depleted glutathione content and altered catalase activity in H19-7 cells. In addition, there was mitochondrial complex-I inhibition and increase in the pro-apoptotic factors including caspase-3 and BAX expression.

SIGNIFICANCE

The experimental results show changes in intracellular oxidative radicals leading to mitochondrial dysfunctions and apoptosis in Corexit treatments, possibly contributing to cell death. Our findings raise concerns about using large volumes of Corexit, a potential environmental toxin, in sensitive ocean environments.

Effects of COREXIT dispersants on cytotoxicity parameters in a cultured human bronchial airway cells, BEAS-2B

The objective of this study was to assess the cytotoxicity of COREXIT dispersants EC9500A, EC9527A, and EC9580A on human airway BEAS-2B epithelial cells. Cells were exposed to dispersants for 2 or 24 h at concentrations ranging from 0 to 300 ppm. COREXIT EC9527 at 100 ppm produced 50% viability loss as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) at 24 h. COREXIT 9527 at 200 ppm produced 50% cell death at 2 h and 100% at 24 h. At 300 ppm COREXIT 9527 induced 100% cell death at 2 or 24 h. In the case of COREXIT 9500A 50% cell viability was noted with 200 ppm at 2 or 24 h, with a significant decrease in cell survival to 2% at 300 ppm. In contrast, no marked change in cell viability was observed in cells treated at any COREXIT 9580A concentration examined. Western blot analysis showed an increase in expression of LC3B, a marker of autophagy, in cells treated for 2 h with 300 ppm COREXIT EC9527A as well as 100 or 300 ppm Corexit EC9500A. No marked effect on LC3B expression was observed for any COREXIT 9580A concentration. Apoptosis markers as measured by cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) were detectable only in cells incubated with 300 ppm COREXIT EC9527A. Although all three dispersants induced enhanced generation of reactive oxygen species (ROS) after 2-h treatment at 300 ppm, Western blot analysis revealed that 2-h incubation was not sufficient to induce a significant change in the protein expression of superoxide dismutases SOD1, SOD2, and SOD3. Data thus indicate exposure to certain dispersants may be harmful to human airway epithelial cells in a concentration-dependent manner.