Identification of early target genes of aflatoxin B1 in human hepatocytes, inter-individual variability and comparison with other genotoxic compounds

Deciphering Aflatoxin B1 affected critical molecular pathways governing cancer: A bioinformatics study using CTD and PANTHER databases

Aflatoxin B1 (AFB1) is a fungal toxin consistently found as a contaminant in food products such as cereals, nuts, spices, and oilseeds. AFB1 exposure can lead to hepatotoxicity, cancer, immune suppression, reproductive deficiency, nutritional dysfunction, and growth impairment. AFB1 has also been listed as one of the most potent human carcinogens by the International Agency for Research on Cancer. Although the correlation between AFB1 exposure and cancer initiation and progression is already reported in the literature, very little information is available about what molecular pathways are affected during cancer development. Considering this, we first selected AFB1-responsive genes involved in five deadliest cancer types including lung, colorectal, liver, stomach, and breast cancers from the Comparative Toxicogenomics Database (CTD). Then, using the PANTHER database, a statistical overrepresentation test was performed to identify the significantly affected pathways in each cancer type. The gonadotropin-releasing hormone receptor (GnRHR) pathway, the CCKR signaling pathway, and angiogenesis were found to be the most affected pathways in lung, breast, liver, and stomach cancers. In addition, AFB1 toxicity majorly impacted apoptosis and Wnt signaling pathways in liver and stomach cancers, respectively. Moreover, the most affected pathways in colorectal cancer were the Wnt, CCKR, and GnRHR pathways. Furthermore, gene analysis was also performed for the most affected pathways associated with each cancer and identified thirteen key genes (e.g., FOS, AKT1) that may serve as biological markers for a particular type of AFB1-induced cancer as well as for in vitro AFB1 toxicological studies using specific cancer cell lines.

Cytotoxic Effects of Major and Emerging Mycotoxins on HepaRG Cells and Transcriptomic Response after Exposure of Spheroids to Enniatins B and B1

Mycotoxins, produced by fungi, frequently occur at different stages in the food supply chain between pre- and postharvest. Globally produced cereal crops are known to be highly susceptible to contamination, thus constituting a major public health concern. Among the encountered mycotoxigenic fungi in cereals, Fusarium spp. are the most frequent and produce both regulated (i.e., T-2 toxin, deoxynivalenol -DON-, zearalenone -ZEA-) and emerging (i.e., enniatins -ENNs-, beauvericin -BEA-) mycotoxins. In this study, we investigated the in vitro cytotoxic effects of regulated and emerging fusariotoxins on HepaRG cells in 2D and 3D models using undifferentiated and differentiated cells. We also studied the impact of ENN B1 and ENN B exposure on gene expression of HepaRG spheroids. Gene expression profiling pinpointed the differentially expressed genes (DEGs) and overall similar pathways were involved in responses to mycotoxin exposure. Complement cascades, metabolism, steroid hormones, bile secretion, and cholesterol pathways were all negatively impacted by both ENNs. For cholesterol biosynthesis, 23/27 genes were significantly down-regulated and could be correlated to a 30% reduction in cholesterol levels. Our results show the impact of ENNs on the cholesterol biosynthesis pathway for the first time. This finding suggests a potential negative effect on human health due to the essential role this pathway plays.

Role of RNA modifications in carcinogenesis and carcinogen damage response

The field of epitranscriptomics encompasses the study of post-transcriptional RNA modifications and their regulatory enzymes. Among the numerous RNA modifications, N6 -methyladenosine (m6 A) has been identified as the most common internal modification of messenger RNA (mRNA). Although m6 A modifications were first discovered in the 1970s, advances in technology have revived interest in this field, driving an abundance of research into the role of RNA modifications in various biological processes, including cancer. As analogs to epigenetic modifications, RNA modifications also play an important role in carcinogenesis by regulating gene expression post-transcriptionally. A growing body of evidence suggests that carcinogens can modulate RNA modifications to alter the expression of oncogenes or tumor suppressors during cellular transformation. Additionally, the expression and activity of the enzymes that regulate RNA modifications can be dysregulated and contribute to carcinogenesis, making these enzymes promising targets of drug discovery. Here we summarize the roles of RNA modifications during carcinogenesis induced by exposure to various environmental carcinogens, with a main focus on the roles of the most widely studied m6 A mRNA methylation.

Deepening the Whole Transcriptomics of Bovine Liver Cells Exposed to AFB1: A Spotlight on Toll-like Receptor 2

Aflatoxin B1 (AFB1) is a food contaminant metabolized mostly in the liver and leading to hepatic damage. Livestock species are differently susceptible to AFB1, but the underlying mechanisms of toxicity have not yet been fully investigated, especially in ruminants. Thus, the aim of the present study was to better characterize the molecular mechanism by which AFB1 exerts hepatotoxicity in cattle. The bovine fetal hepatocyte cell line (BFH12) was exposed for 48 h to three different AFB1 concentrations (0.9 µM, 1.8 µM and 3.6 µM). Whole-transcriptomic changes were measured by RNA-seq analysis, showing significant differences in the expression of genes mainly involved in inflammatory response, oxidative stress, drug metabolism, apoptosis and cancer. As a confirmatory step, post-translational investigations on genes of interest were implemented. Cell death associated with necrosis rather than apoptosis events was noted. As far as the toxicity mechanism is concerned, a molecular pathway linking inflammatory response and oxidative stress was postulated. Toll-Like Receptor 2 (TLR2) activation, consequent to AFB1 exposure, triggers an intracellular signaling cascade involving a kinase (p38β MAPK), which in turn allows the nuclear translocation of the activator protein-1 (AP-1) and NF-κB, finally leading to the release of pro-inflammatory cytokines. Furthermore, a p38β MAPK negative role in cytoprotective genes regulation was postulated. Overall, our investigations improved the actual knowledge on the molecular effects of this worldwide relevant natural toxin in cattle.

Model-based translation of DNA damage signaling dynamics across cell types

Interindividual variability in DNA damage response (DDR) dynamics may evoke differences in susceptibility to cancer. However, pathway dynamics are often studied in cell lines as alternative to primary cells, disregarding variability. To compare DDR dynamics in the cell line HepG2 with primary human hepatocytes (PHHs), we developed a HepG2-based computational model that describes the dynamics of DDR regulator p53 and targets MDM2, p21 and BTG2. We used this model to generate simulations of virtual PHHs and compared the results to those for PHH donor samples. Correlations between baseline p53 and p21 or BTG2 mRNA expression in the absence and presence of DNA damage for HepG2-derived virtual samples matched the moderately positive correlations observed for 50 PHH donor samples, but not the negative correlations between p53 and its inhibitor MDM2. Model parameter manipulation that affected p53 or MDM2 dynamics was not sufficient to accurately explain the negative correlation between these genes. Thus, extrapolation from HepG2 to PHH can be done for some DDR elements, yet our analysis also reveals a knowledge gap within p53 pathway regulation, which makes such extrapolation inaccurate for the regulator MDM2. This illustrates the relevance of studying pathway dynamics in addition to gene expression comparisons to allow reliable translation of cellular responses from cell lines to primary cells. Overall, with our approach we show that dynamical modeling can be used to improve our understanding of the sources of interindividual variability of pathway dynamics.

Susceptibility to develop cancer varies among people, partially due to differences in genetic background. Ideally, healthy human-derived cells are used to investigate intracellular signaling pathways and their interindividual variability contributing to cancer susceptibility. Because cells from healthy human tissue are difficult to obtain and culture for periods longer than a few days, cell lines are often used as substitute. However, it is unclear to what extent signaling dynamics in cell lines represent dynamics in healthy human tissue. We asked whether we could reproduce interindividual variability in DNA damage response gene expression in a set of 50 human liver cell donors. Therefore, we built a mathematical model that simulates temporal expression dynamics of the DNA damage response in the HepG2 liver cell line upon chemical activation and used the simulations to create virtual donors. Our virtual donors displayed similar relations between genes as the samples from human donors, provided that we adjusted the strength of specific molecular interactions. Thus, our approach can be used to examine the applicability of widely used cell systems to healthy human tissue in terms of their dynamic responses.

Comparative Analysis of Transcriptional Responses to Genotoxic and Non-Genotoxic Agents in the Blood Cell Model TK6 and the Liver Model HepaRG

Transcript signatures are a promising approach to identify and classify genotoxic and non-genotoxic compounds and are of interest as biomarkers or for future regulatory application. Not much data, however, is yet available about the concordance of transcriptional responses in different cell types or tissues. Here, we analyzed transcriptomic responses to selected genotoxic food contaminants in the human p53-competent lymphoblastoid cell line TK6 using RNA sequencing. Responses to treatment with five genotoxins, as well as with four non-genotoxic liver toxicants, were compared with previously published gene expression data from the human liver cell model HepaRG. A significant overlap of the transcriptomic changes upon genotoxic stress was detectable in TK6 cells, whereas the comparison with the HepaRG model revealed considerable differences, which was confirmed by bioinformatic data mining for cellular upstream regulators or pathways. Taken together, the study presents a transcriptomic signature for genotoxin exposure in the human TK6 blood cell model. The data demonstrate that responses in different cell models have considerable variations. Detection of a transcriptomic genotoxin signature in blood cells indicates that gene expression analyses of blood samples might be a valuable approach to also estimate responses to toxic exposure in target organs such as the liver.

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.

RNA A-to-I editing, environmental exposure, and human diseases

Epigenetic modifications have gained attention since they can be potentially changed with environmental stimuli and can be associated with adverse health outcomes. Epitranscriptome field has begun to attract attention with several aspects since RNA modifications have been linked with critical biological processes and implicated in diseases. Several RNA modifications have been identified as reversible indicating the dynamic features of modification which can be altered by environmental cues. Currently, we know more than 150 RNA modifications in different organisms and on different bases which are modified by various chemical groups. RNA editing, which is one of the RNA modifications, occurs after transcription, which results in RNA sequence different from its corresponding DNA sequence. Emerging evidence reveals the functions of RNA editing as well as the association between RNA editing and diseases. However, the RNA editing field is beginning to grow up and needs more empirical evidence in regard to disease and toxicology. Thus, this review aims to provide the current evidence-based studies on RNA editing modifying genes for genotoxicity and cancer. The review presented the association between environmental xenobiotics exposure and RNA editing modifying genes and focused on the association between the expression of RNA editing modifying genes and cancer. Furthermore, we discussed the future directions of scientific studies in the area of RNA modifications, especially in the RNA editing field, and provided a knowledge-based framework for further studies.

Transcriptomic alterations induced by aflatoxin B1 and ochratoxin A in LMH cell line

Aflatoxin B1 (AFB1) and ochratoxin A (OTA), which are toxic metabolites of ubiquitously occurring molds, show diverse toxicological effects such as hepatotoxicity, genotoxicity, and immunotoxicity in human and animals. Despite poultry show sensitivity to AFB1 and OTA, the mechanism of these mycotoxins in chickens has not been fully investigated. Here, we aimed to elucidate the molecular mechanism induced by AFB1 and/or OTA in chicken hepatic cells using transcriptomic analysis. Aflatoxin B1 and OTA induced cytotoxic effects in a dose-dependent manner at 48 h after exposure. Furthermore, correlation effect indicated an antagonism between the 2 toxins. The mRNA sequencing of AFB1-treated or OTA-treated chicken hepatocarcinoma and functional analysis revealed the pathways that were commonly regulated by both mycotoxins, especially PPAR signaling, focal adhesion, and MAPK signaling. Based on these findings, a possible hypothesis is that AFB1 and OTA have similar toxic mechanisms and compete for some steps in the chicken liver, and it is expected that the mycotoxins would have antagonistic effects. In addition, genes identified through transcriptome analysis provide candidates for further study of AFB1 and OTA toxicity and targets for efforts to improve the health of chickens exposed to mycotoxins.

Environmental epitranscriptomics

Chemical modifications of RNA molecules have gained increasing attention since evidence emerged for their substantive roles in a range of biological processes, such as the stability and translation of mRNA transcripts. More than 150 modifications have been identified in different organisms to date, collectively known as the 'epitranscriptome', with 6-methyladenosine (m⁶A), 5-methylcytidine (m⁵C), pseudouridine and N1-methyladenosine (m¹A) the most extensively investigated. Although we are just beginning to elucidate the roles of these modifications in cellular functions, there is already evidence for their dysregulation in diseases such as cancer and neurodevelopmental disorders. There is currently more limited knowledge regarding how environmental exposures affect the epitranscriptome and how this may mediate disease risk, but evidence is beginning to emerge. Here, we review the current evidence for the impact of environmental exposures such as benzo[a]pyrene, bisphenol A, pesticides, metals and nanoparticles upon RNA modifications and the expression of their 'writers' (methyl transferases), 'erasers' (demethylases) and 'readers'. We discuss future directions of the field and identify areas of particular promise and consider the technical challenges that are faced.

Black tea and curcumin synergistically mitigate the hepatotoxicity and nephropathic changes induced by chronic exposure to aflatoxin-B1 in Sprague-Dawley rats

The study aimed to clarify the characteristics of black tea (BTE) and/or curcumin (CMN) against aflatoxin-B1 (AFB1). Forty eight adult male Sprague-Dawley rats were divided into eight groups. G1 was non-treated control. G2, G3, and G4 were olive oil, BTE, and CMN, respectively. G5 was olive oil-dissolved AFB1 (25 µg/kg b.w). G6, G7, and G8 were AFB1 along with BTE (2%), CMN (200 mg/kg b.w.), and BTE plus CMN, respectively. All treatments were orally given for consecutive 90 days. After treatment period, rats were sacrificed. Serobiochemical analysis and histopathology showed hepatorenal dysfunction in response to AFB1. Glutathione-antioxidants were significantly decreased versus increased lipid peroxides (p < .05-.001). AFB1 significantly increased the expression of the antitumor p53, but decreased that of antiapoptotic Bcl2 in liver or kidney tissue, either (p < .05). BTE or CMN ameliorated those changes induced by AFB1 in both liver and kidney with highly pronounced improvement when combined BTE/CMN was used. PRACTICAL APPLICATIONS: Black tea (BTE) and curcumin (CMN) were known for their antioxidant effects, and several studies reported their independent effects against different toxicities including aflatoxicosis. The current study clarifies the ameliorative characteristics of both agents; BTE and/or CMN, against the toxicity resulted from the chronic exposure to aflatoxin-B1 (AFB1) (25 µg/kg b.w. for consecutive 90 days). The dose of either agents, BTE or CMN, was 200 mg/kg b.w. along with AFB1. The pathologic changes, serobiochemical parameters, oxidative stress, histological changes, and the molecular disruption, induced by AFB1 in both liver and kidney were obviously and significantly ameliorated after BTE and/or CMN treatments in variable potencies where both agents showed the most effective antitoxic capacities.

Hemoadsorption Improves Survival of Rats Exposed to an Acutely Lethal Dose of Aflatoxin B1

Mycotoxins, such as aflatoxin B1 (AFB1), pose a serious threat as biological weapons due to their high toxicity, environmental stability, easy accessibility and lack of effective therapeutics. This study investigated if blood purification therapy with CytoSorb (CS) porous polymer beads could improve survival after a lethal aflatoxin dose (LD90). The effective treatment window and potential therapeutic mechanisms were also investigated. Sprague Dawley rats received a lethal dose of AFB1 (0.5-1.0 mg/kg) intravenously and hemoperfusion with a CS or Control device was initiated immediately, or after 30, 90, or 240-minute delays and conducted for 4 hours. The CS device removes AFB1 from circulation and significantly improves survival when initiated within 90 minutes of toxin administration. Treated subjects exhibited improved liver morphology and health scores. Changes in the levels of cytokines, leukocytes and platelets indicate a moderately-severe inflammatory response to acute toxin exposure. Quantitative proteomic analysis showed significant changes in the level of a broad spectrum of plasma proteins including serine protease/endopeptidase inhibitors, coagulation factors, complement proteins, carbonic anhydrases, and redox enzymes that ostensibly contribute to the therapeutic effect. Together, these results suggest that hemoadsorption with CS could be a viable countermeasure against acute mycotoxin exposure.

Transcriptomic effect marker patterns of genotoxins - a comparative study with literature data

Microarray approaches are frequently used experimental tools which have proven their value for example in the characterization of the molecular mode of action of toxicologically relevant compounds. In a regulatory context, omics techniques are still not routinely used, amongst others due to lacking standardization in experimental setup and data processing, and also due to issues with the definition of adversity. In order to exemplarily determine whether consensus transcript biomarker signatures for a certain toxicological endpoint can be derived from published microarray datasets, we here compared transcriptome data from human HepaRG hepatocarcinoma cells treated with different genotoxins, based on re-analyzed datasets extracted from the literature. Comparison of the resulting data show that even with similarly-acting compounds in the same cell line, considerable variation was observed with respect to the numbers and identities of differentially expressed genes. Greater concordance was observed when considering the whole data sets and biological functions associated with the genes affected. The present results highlight difficulties and possibilities in inter-experiment comparisons of omics data and underpin the need for future efforts towards improved standardization to facilitate the use of omics data in risk assessment. Existing omics datasets may nonetheless prove valuable in establishing biological context information essential for the development of adverse outcome pathways.

Lactobacillus plantarum C88 protects against aflatoxin B1-induced liver injury in mice via inhibition of NF-κB-mediated inflammatory responses and excessive apoptosis

Background

Probiotics play an important role in the human and animal defense against liver damage. However, the protective mechanism of Lactobacillus plantarum C88 on chronic liver injury induced by mycotoxin remains unclear.

Results

In this study, the addition of L. plantarum C88 obviously ameliorated the increased contents of alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total cholesterol and triglyceride, the diminish contents of total protein and albumin in serum of mice challenged with AFB₁. Simultaneously, L. plantarum C88 attenuated the inflammatory response via significantly reducing the levels of pro-inflammatory factors, including interleukin-1β (IL-1β), IL-6, IL-8, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) in serum. Furthermore, L. plantarum C88 remarkably down-regulated the nuclear factor kappa B (NF-κB) signaling pathways by weakening the expression of toll-like receptor 2 (TLR2) and TLR4, and inhibited NF-κB nuclear translocation through enhancing the expression of NF-κB inhibitor (IκB). Neutralization experiments confirmed that L. plantarum C88 decreased the levels of some pro-inflammatory factors due to the suppression of the NF-κB signaling pathways. Besides, L. plantarum C88 decreased the levels of Bax and Caspase-3, elevated the level of Bcl-2, and reduced mRNA expressions of Fatty acid synthetase receptor (Fas), FAS-associated death domain (FADD), TNF receptor associated death domain (TRADD) and Caspase-8 in the liver.

Conclusions

Probiotic L. plantarum C88 prevented AFB₁-induced secretion of pro-inflammatory cytokines by modulating TLR2/NF-κB and TLR4/NF-κB pathways. The molecular mechanisms of L. plantarum C88 in ameliorating AFB₁-induced excessive apoptosis included regulating the mitochondrial pathway and cell death receptor pathways.

Electronic supplementary material

The online version of this article (10.1186/s12866-019-1525-4) contains supplementary material, which is available to authorized users.

The importance of inter-individual Kupffer cell variability in the governance of hepatic toxicity in a 3D primary human liver microtissue model

The potential for nanomaterial (NM) translocation to secondary organs is a realistic prospect, with the liver one of the most important target organs. Traditional in vitro or ex vivo hepatic toxicology models are often limiting and/or troublesome (i.e. short life-span reduced metabolic activity, lacking important cell populations, high inter-individual variability, etc.). Building on previous work, this study utilises a 3D human liver microtissue (MT) model (MT composed of mono-culture of hepatocytes or two different co-culture MT systems with non-parenchymal cell (NPC) fraction sourced from different donors) to investigate the importance of inter-donor variability of the non-parenchymal cell population in the overall governance of toxicological response following exposure to a panel of NMs. To the best of our knowledge, this is the first study of its kind to investigate inter-donor variability in hepatic NPC population. The data showed that the Kupffer cells were crucial in dictating the overall hepatic toxicity following exposure to the materials. Furthermore, a statistically significant difference was noted between the two co-culture MT models. However, the trend for particle-induced biological responses was similar between the co-cultures (cytotoxicity, cytokine production and caspase activity). Therefore, despite the recognition of some discrepancies in the absolute values between the co-culture models, the fact that the trends and patterns of biological responses were comparable between the multi-cellular models we propose the 3D liver MT to be a valuable tool in particle toxicology.

Current Status and Future Opportunities of Omics Tools in Mycotoxin Research

Mycotoxins are toxic secondary metabolites of low molecular weight produced by filamentous fungi, such as Aspergillus, Fusarium, and Penicillium spp. Mycotoxins are natural contaminants of agricultural commodities and their prevalence may increase due to global warming. Dangerous mycotoxins cause a variety of health problems not only for humans, but also for animals. For instance, they possess carcinogenic, immunosuppressive, hepatotoxic, nephrotoxic, and neurotoxic effects. Hence, various approaches have been used to assess and control mycotoxin contamination. Significant challenges still exist because of the complex heterogeneous nature of food composition. The potential of combined omics approaches such as metabolomics, genomics, transcriptomics, and proteomics would contribute to our understanding about pathogen fungal crosstalk as well as strengthen our ability to identify, isolate, and characterise mycotoxins pre and post-harvest. Multi-omics approaches along with advanced analytical tools and chemometrics provide a complete annotation of such metabolites produced before/during the contamination of crops. We have assessed the merits of these individual and combined omics approaches and their promising applications to mitigate the issue of mycotoxin contamination. The data included in this review focus on aflatoxin, ochratoxin, and patulin and would be useful as benchmark information for future research.

Aflatoxin B1 invokes apoptosis via death receptor pathway in hepatocytes

The fungal metabolites produced by Aspergillus flavus and Aspergillus parasiticus cause detrimental health effects on humans and animals. Particularly aflatoxin B1 (AFB1) is the most studied and a well-known global carcinogen, producing hepatotoxic, genotoxic and immunotoxic effects in multiple species. AFB1 is shown to provoke liver dysfunctioning by causing hepatocytes apoptosis and disturbing cellular enzymatic activities. In liver, AFB1 causes apoptosis via extrinsic mechanism because of high expression of death receptor pathway. The detailed mechanism of AFB1 induced hepatocytes apoptosis, via death receptor pathway still remains elusive. So the present study was conducted to explore apoptotic mechanism initiated by death receptors and associated genes in aflatoxin B1 induced liver apoptosis in chickens fed with AFB1 for 3 weeks. Results from the present study displayed histopathological and ultrastructural changes in liver such as hydropic degeneration, fatty vacuolar degeneration and proliferation of bile duct in hepatocytes in AFB1 group, along with imbalance between reactive oxygen species (ROS) and antioxidant defense system upon AFB1 ingestion. Moreover, AFB1 intoxicated chickens showed upregulation of death receptors FAS, TNFR1 and associated genes and downregulation of inhibitory apoptotic proteins XIAP and BCL-2. The results obtained from this novel and comprehensive study including histopathological, ultrastructural, flow cytometrical and death receptor pathway gene expression profiles, will facilitate better understanding of mechanisms and involvement of death receptor pathway in hepatocytes apoptosis induced by AFB1 and ultimately may be helpful in bringing down the toxigenic potential of AFB1.

The mitochondrial and death receptor pathways involved in the thymocytes apoptosis induced by aflatoxin B1

Aflatoxin B₁ (AFB₁) is a potent immunosuppressive agent in endotherms, which can be related to the up-regulated apoptosis of immune organs. In this study, we investigated the roles of the mitochondrial, death receptor, and endoplasmic reticulum pathways in Aflatoxin B₁ induced thymocytes apoptosis. Chickens were fed an aflatoxin B₁ containing diet (0.6 mg/kg AFB₁) for 3 weeks. Our results showed that (1) AFB₁ diet induced the decrease of T-cell subsets, morphological changes, and excessive apoptosis of thymus. (2) The excessive apoptosis involved the mitochondrial pathway (up-regulation of Bax, Bak, cytC and down-regulation of Bcl-2 and Bcl-xL) and death receptor pathway (up-regulation of FasL, Fas and FADD). (3) Oxidative stress, an apoptosis inducer, was confirmed in the thymus. In conclusion, this is the first study to demonstrate that mitochondrial and death receptor pathways involved in AFB₁ induced thymocytes apoptosis in broilers.

Stem cell proliferation patterns as an alternative for in vivo prediction and discrimination of carcinogenic compounds

One of the major challenges in the development of alternative carcinogenicity assays is the prediction of non-genotoxic carcinogens. The variety of non-genotoxic cancer pathways complicates the search for reliable parameters expressing their carcinogenicity. As non-genotoxic and genotoxic carcinogens have different cancer risks, the objective of this study was to develop a concept for an in vivo test, based on flatworm stem cell dynamics, to detect and classify carcinogenic compounds. Our methodology entails an exposure to carcinogenic compounds during the animal's regeneration process, which revealed differences in proliferative responses between non-genotoxic and genotoxic carcinogens during the initial stages of the regeneration process. A proof of concept was obtained after an extensive study of proliferation dynamics of a genotoxic and a non-genotoxic compound. A pilot validation with a limited set of compounds showed that the proposed concept not only enabled a simple prediction of genotoxic and non-genotoxic carcinogens, but also had the power to discriminate between both. We further optimized this discrimination by combining stem cell proliferation responses with a phenotypic screening and by using specific knockdowns. In the future, more compounds will be tested to further validate and prove this concept.

Evaluation of the bioactive extract of actinomyces isolated from the Egyptian environment against aflatoxin B1-induce cytotoxicity, genotoxicity and oxidative stress in the liver of rats

This study aimed to determine the bioactive compounds of actinomyces (ACT) isolated from the Egyptian environment (D-EGY) and to evaluate their protective activity against AFB₁ in female Sprague-Dawley rats. Six groups of animals were treated orally for 3 weeks included: C, the control group, T1, AFB₁-treated group (80 μg/kg b.w), T2 and T3, the groups received ACT extract at low (25 mg/kg b.w) or high (50 mg/kg b.w) doses, T4 and T5, the groups received AFB₁ plus the low or high dose of ACT extract. Blood, bone marrow and tissue samples were collected for different analyses and histological examination. The results revealed the identification of 40 components, representing 99.98%. Treatment with AFB₁ disturbs liver function parameters, oxidative stress markers, antioxidant gene expressions, DNA fragmentation and induced severe histological changes. ACT extract at the low or high doses did not induce significant changes in all the tested parameters or histological picture of the liver. Moreover, ACT extract succeeded to induce a significant protection against the toxicity of AFB₁. It could be concluded that the bioactive compounds in ACT are promise candidate for the development of food additive or drugs for the protection and treatment of liver disorders in the endemic area.

Transcriptional, Functional, and Mechanistic Comparisons of Stem Cell-Derived Hepatocytes, HepaRG Cells, and Three-Dimensional Human Hepatocyte Spheroids as Predictive In Vitro Systems for Drug-Induced Liver Injury

Reliable and versatile hepatic in vitro systems for the prediction of drug pharmacokinetics and toxicity are essential constituents of preclinical safety assessment pipelines for new medicines. Here, we compared three emerging cell systems—hepatocytes derived from induced pluripotent stem cells, HepaRG cells, and three-dimensional primary human hepatocyte (PHH) spheroids—at transcriptional and functional levels in a multicenter study to evaluate their potential as predictive models for drug-induced hepatotoxicity. Transcriptomic analyses revealed widespread gene expression differences between the three cell models, with 8148 of 17,462 analyzed genes (47%) being differentially expressed. Expression levels of genes involved in the metabolism of endogenous as well as xenobiotic compounds were significantly elevated in PHH spheroids, whereas genes involved in cell division and endocytosis were significantly upregulated in HepaRG cells and hepatocytes derived from induced pluripotent stem cells, respectively. Consequently, PHH spheroids were more sensitive to a panel of drugs with distinctly different toxicity mechanisms, an effect that was amplified by long-term exposure using repeated treatments. Importantly, toxicogenomic analyses revealed that transcriptomic changes in PHH spheroids were in compliance with cholestatic, carcinogenic, or steatogenic in vivo toxicity mechanisms at clinically relevant drug concentrations. Combined, the data reveal important phenotypic differences between the three cell systems and suggest that PHH spheroids can be used for functional investigations of drug-induced liver injury in vivo in humans.

Therapeutical potential of deregulated lysine methyltransferase SMYD3 as a safe target for novel anticancer agents

INTRODUCTION

SET and MYND domain containing-3 (SMYD3) is a member of the lysine methyltransferase family of proteins, and plays an important role in the methylation of various histone and non-histone targets. Proper functioning of SMYD3 is very important for the target molecules to determine their different roles in chromatin remodeling, signal transduction and cell cycle control. Due to the abnormal expression of SMYD3 in tumors, it is projected as a prognostic marker in various solid cancers. Areas covered: Here we elaborate on the general information, structure and the pathological role of SMYD3 protein. We summarize the role of SMYD3-mediated protein interactions in oncology pathways, mutational effects and regulation of SMYD3 in specific types of cancer. The efficacy and mechanisms of action of currently available SMYD3 small molecule inhibitors are also addressed. Expert opinion: The findings analyzed herein demonstrate that aberrant levels of SMYD3 protein exert tumorigenic effects by altering the epigenetic regulation of target genes. The partial involvement of SMYD3 in some distinct pathways provides a vital opportunity in targeting cancer effectively with fewer side effects. Further, identification and co-targeting of synergistic oncogenic pathways is suggested, which could provide much more beneficial effects for the treatment of solid cancers.

Lophirones B and C prevent aflatoxin B1-induced oxidative stress and DNA fragmentation in rat hepatocytes

Context Despite the reported anticarcinogenic activity of lophirones B and C, no scientific information exists for its activity in rat hepatocytes. Objective Effect of lophirones B and C on aflatoxin B1 (AFB1)-induced oxidative stress, and DNA fragmentation in rat hepatocytes was investigated. Materials and methods Wistar rat hepatocytes were incubated with lophirones B and C (1 mg/mL) or sylimarin (1 mg/mL) in the presence or absence of AFB1. For an in vivo study, rats were orally administered with lophirones B and C, and/or AFB1 (20 μg/d) for 9 weeks. Results Lophirones B and C lowered AFB1-mediated increase in nitric oxide, superoxide anion radicals, caspase-3 and fragmented DNA. Lophirones B and C attenuated AFB1-mediated decrease in superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and reduced glutathione. Also, lophirones B and C attenuated AFB1-mediated increase in conjugated dienes, lipid hydroperoxides and malondialdehyde in rat hepatocytes. Furthermore, AFB1-mediated alterations in alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, albumin, total bilirubin and globulin in rat serum were significantly annulled in lophirones B and C-treated rats. Conclusion This study revealed that lophirones B and C prevented AFB1-induced oxidative damage in rat hepatocytes.

Hepatic Transcriptome Responses of Domesticated and Wild Turkey Embryos to Aflatoxin B₁

The mycotoxin, aflatoxin B₁ (AFB₁) is a hepatotoxic, immunotoxic, and mutagenic contaminant of food and animal feeds. In poultry, AFB₁ can be maternally transferred to embryonated eggs, affecting development, viability and performance after hatch. Domesticated turkeys (Meleagris gallopavo) are especially sensitive to aflatoxicosis, while Eastern wild turkeys (M. g. silvestris) are likely more resistant. In ovo exposure provided a controlled AFB₁ challenge and comparison of domesticated and wild turkeys. Gene expression responses to AFB₁ in the embryonic hepatic transcriptome were examined using RNA-sequencing (RNA-seq). Eggs were injected with AFB₁ (1 μg) or sham control and dissected for liver tissue after 1 day or 5 days of exposure. Libraries from domesticated turkey (n = 24) and wild turkey (n = 15) produced 89.2 Gb of sequence. Approximately 670 M reads were mapped to a turkey gene set. Differential expression analysis identified 1535 significant genes with |log₂ fold change| ≥ 1.0 in at least one pair-wise comparison. AFB₁ effects were dependent on exposure time and turkey type, occurred more rapidly in domesticated turkeys, and led to notable up-regulation in cell cycle regulators, NRF2-mediated response genes and coagulation factors. Further investigation of NRF2-response genes may identify targets to improve poultry resistance.

Chitosan nanoparticles and quercetin modulate gene expression and prevent the genotoxicity of aflatoxin B1 in rat liver

The aims of the current study were to prepare chitosan nanoparticles (CNPs) and to evaluate its protective role alone or in combination with quercetin (Q) against AFB₁-induce cytotoxicity in rats. Male Sprague-Dawley rats were divided into 12 groups and treated orally for 4 weeks as follow: the control group, the group treated with AFB₁ (80 μg/kg b.w.) in corn oil, the groups treated with low (140 mg/kg b.w.) or high (280 mg/kg b.w.) dose of CNPs, the group treated with Q (50 mg/kg b.w.), the groups treated with Q plus the low or the high dose of CNPs and the groups treated with AFB₁ plus Q and/or CNPs at the two tested doses. The results also revealed that administration of AFB₁ resulted in a significant increase in serum cytokines, Procollagen III, Nitric Oxide, lipid peroxidation and DNA fragmentation accompanied with a significant decrease in GPx I and Cu–Zn SOD-mRNA gene expression. Q and/or CNPs at the two tested doses overcome these effects especially in the group treated with the high dose of CNPs plus Q. It could be concluded that CNPs is a promise candidate as drug delivery enhances the protective effect of Q against the cytogenetic effects of AFB₁ in high endemic areas.

Aflatoxin exposure is inversely associated with IGF1 and IGFBP3 levels in vitro and in Kenyan schoolchildren

SCOPE

This study explores the relationship between aflatoxin and the insulin-like growth factor (IGF) axis and its potential effect on child growth.

METHODS AND RESULTS

One hundred and ninety-nine Kenyan schoolchildren were studied for aflatoxin-albumin adduct (AF-alb), IGF1 and IGF-binding protein-3 (IGFBP3) levels using ELISA. AF-alb was inversely associated with IGF1 and IGFBP3 (p < 0.05). Both IGF1 and IGFBP3 were significantly associated with child height and weight (p < 0.01). Children in the highest tertile of AF-alb exposure (>198.5 pg/mg) were shorter than children in the lowest tertile (<74.5 pg/mg), after adjusting for confounders (p = 0.043). Path analysis suggested that IGF1 levels explained ∼16% of the impact of aflatoxin exposure on child height (p = 0.052). To further investigate this putative mechanistic pathway, HHL-16 liver cells (where HHL-16 is human hepatocyte line 16 cells) were treated with aflatoxin B1 (0.5, 5 and 20 μg/mL for 24-48 h). IGF1 and IGFBP3 gene expression measured by quantitative PCR and protein in culture media showed a significant down-regulation of IGF genes and reduced IGF protein levels.

CONCLUSION

Aflatoxin treatment resulted in a significant decrease in IGF gene and protein expression in vitro. IGF protein levels were also lower in children with the highest levels of AFB-alb adducts. The data suggest that aflatoxin-induced changes in IGF protein levels could contribute to growth impairment where aflatoxin exposure is high.

Structure and function of SET and MYND domain-containing proteins

SET (Suppressor of variegation, Enhancer of Zeste, Trithorax) and MYND (Myeloid-Nervy-DEAF1) domain-containing proteins (SMYD) have been found to methylate a variety of histone and non-histone targets which contribute to their various roles in cell regulation including chromatin remodeling, transcription, signal transduction, and cell cycle control. During early development, SMYD proteins are believed to act as an epigenetic regulator for myogenesis and cardiomyocyte differentiation as they are abundantly expressed in cardiac and skeletal muscle. SMYD proteins are also of therapeutic interest due to the growing list of carcinomas and cardiovascular diseases linked to SMYD overexpression or dysfunction making them a putative target for drug intervention. This review will examine the biological relevance and gather all of the current structural data of SMYD proteins.

The glucosinolate metabolite 1-methoxy-3-indolylmethyl alcohol induces a gene expression profile in mouse liver similar to the expression signature caused by known genotoxic hepatocarcinogens

SCOPE

Breakdown products of certain glucosinolates induce detoxifying enzymes and demonstrate preventive activities against chemically induced tumourigenesis in animal models. However, other breakdown products are genotoxic. 1-Methoxy-3-indolylmethyl alcohol (1-MIM-OH) is mutagenic in bacterial and mammalian cells upon activation by sulphotransferases and forms DNA adducts in mouse tissues. This effect is enhanced in mice transgenic for human sulphotransferases 1A1/2 (FVB/N-hSULT1A1/2). Therefore, we explored gene expression changes induced by 1-MIM-OH in mouse liver.

METHODS AND RESULTS

FVB/N-hSULT1A1/2 mice were orally treated with 1-MIM-OH for 21 or 90 days, leading to high levels of hepatic 1-MIM-DNA adducts. Genome-wide expression analyses demonstrated no influence on detoxifying enzymes, but up-regulation of many mediators of the tumour suppressor p53 and down-regulation of Fhit and other long genes. While this p53 response might indicate protection, it was unable to prevent the accumulation of DNA adducts. However, various epidemiological studies reported inverse associations between the intake of cruciferous vegetables and cancer. This association may be due to the presence of other glucosinolates with tumour-preventing influences possibly outweighing adverse effects of some metabolites.

CONCLUSION

1-MIM-OH is a genotoxic substance inducing a gene expression profile similar to the expression signature caused by known genotoxic hepatocarcinogens.

Transcriptomic alterations induced by Monuron in rat and human renal proximal tubule cells in vitro and comparison to rat renal-cortex in vivo

Monuron (1,1-dimethyl-3-(4-chlorophenyl)urea) is a widely used herbicide in developing countries although concerns have been raised about its toxicity and carcinogenicity.

Noncoding RNA response to xenobiotic exposure: an indicator of toxicity and carcinogenicity

INTRODUCTION

Human exposure to certain environmental and occupational chemicals is one of the major risk factors for noncommunicable diseases, including cancer. Therefore, it is desirable to take advantage of subtle exposure-related adverse cellular events for early disease detection and to identify potential dangers caused by new and currently under-evaluated drugs and chemicals. Nongenotoxic events due to carcinogen/toxicant exposure are a general hallmark of sustained cellular stress leading to tumorigenesis. These processes are globally regulated via noncoding RNAs (ncRNAs). Tumorigenesis-associated genotoxic and nongenotoxic events lead to the altered expression of ncRNAs and may provide a mechanistic link between chemical exposure and tumorigenesis. Current advances in toxicogenomics are beginning to provide valuable insight into gene-chemical interactions at the transcriptome level.

AREAS COVERED

In this review, we summarize recent information about the impact of xenobiotics on ncRNAs. Evidence highlighted in this review suggests a critical role of ncRNAs in response to carcinogen/toxicant exposure.

EXPERT OPINION

Benefits for the use of ncRNAs in carcinogenicity assessment include remarkable tissue specificity, early appearance, low baseline variability, and their presence and stability in biological fluids, which suggests that the incorporation of ncRNAs in the evaluation of cancer risk assessment may enhance substantially the efficiency of toxicity and carcinogenicity testing.

Ameliorative effects of thyme and calendula extracts alone or in combination against aflatoxins-induced oxidative stress and genotoxicity in rat liver

The aims of the current work were to evaluate the hepatoprotective effect of calendula flowers and/or thyme leave extracts on aflatoxins (AFs)-induced oxidative stress, genotoxicity and alteration of p53 bax and bcl2 gene expressions. Eighty male Sprague-Dawley rats were divided into eight equal groups including: the control group, the group fed AFs-contaminated diet (2.5 mg/kg diet) for 5 weeks, the groups treated orally with thyme and/or calendula extract (0.5 g/kg b.w) for 6 weeks and the groups pretreated orally with thyme and/or calendula extract 1 week before and during AFs treatment for further 5 weeks. Blood, liver and bone marrow samples were collected for biochemical analysis, gene expression, DNA fragmentation and micronucleus assay. The results showed that AFs induced significant alterations in oxidative stress markers, increased serum AFP and inflammatory cytokine, percentage of DNA fragmentation, the expression of pro-apoptotic gene p53 and bax accompanied with a decrease in the expression of bcl2. Animals treated with the extracts 1 week before AFs treatment showed a significant decrease in oxidative damage markers, micronucleated cells, DNA fragmentation and modulation of the expression of pro-apoptotic genes. These results suggested that both calendula and thyme extracts had anti-genotoxic effects due to their higher content of total phenolic compounds.

Evaluation of STAT5A Gene Expression in Aflatoxin B1 Treated Bovine Mammary Epithelial Cells

PURPOSE

Aflatoxin B1 (AFB1) is a potent mycotoxin which has been produced by fungi such as Aspergillus flavus and Aspergillus parasiticus as secondary metabolites due to their growth on food stuffs and induces hepatocellular carcinoma in many animal species, including humans. In the present study, the effect of AFB1 on STAT5A gene expression was investigated in bovine mammary epithelial cells using real time RT-PCR.

METHODS

Bovine mammary epithelial cells were seeded in a 24-well culture plate for three-dimensional (3D) culture in Matrigel matrix. After 21 days of 3D culture and reaching the required number of cells, cells were treated with AFB1 and incubated for 8 h. For real time PCR reaction, total RNA from the cultured and treated cells was extracted and used for complementary DNA synthesis.

RESULTS

The expression of STAT5A gene was significantly down regulated by AFB1 in dose- dependent manner and led to the reduction of proliferation and differentiation of epithelial cells, which has direct effect in milk protein quantity and quality.

CONCLUSION

According to the results, it seems that down regulation of STAT5A gene in AFB1-treated cells maybe due to DNA damage induced by AFB1 in bovine mammary epithelial cells.

Cytochrome P450 isoforms are differently up-regulated in aflatoxin B₁-exposed human lymphocytes and monocytes

CONTEXT

Aflatoxins (AFs) are highly hazardous mycotoxins with potent carcinogenic, mutagenic and immune disregulatory properties. Cytochrome P450 (CYP) isoforms are central for enhanced AFB₁ toxicity in situ. It remains to be seen whether and how these AFB₁ activators work in human leukocytes.

OBJECTIVE

To investigate the involvement of CYP isoforms in AFB₁ toxicity of circulating mononuclear cells, we examined the impact of environmentally relevant levels of AFB1 on lymphocytes and monocytes.

MATERIALS AND METHODS

Very low and moderate doses of AFB₁ with/without CYP inducers on transcription of key CYP isoforms and toll-like receptor 4 (TLR4) were examined in human lymphocytes, monocytes and HepG2 cells; cell cycle distribution and viability were also analyzed in AFB₁-exposed lymphocytes and monocytes.

RESULTS

Only CYP1A1, CYP1B1, CYP3A4, CYP3A5 and CYP3A7 expressed in lymphocytes and monocytes. TLR4 much more expressed in monocytes than in lymphocytes, but HepG2 showed little TLR4 transcription. While CYP1A1, CYP1B1 and CYP3A4 were highly induced by AFB₁ in monocytes, in lymphocytes only CYP1A1 was induced. Among CYP1A1, CYP1B1 and CYP3A4 only CYP1A1 responded to low and moderate levels of AFB₁. Enhanced transcripts of CYPs by AFB₁ yielded little synergies on TLR4 transcription in lymphocytes and monocytes. Cell cycle arrest and necrosis were also detected in AFB₁-exposed lymphocytes and monocytes.

CONCLUSIONS

Our novel findings indicate that AFB₁ more intensively stimulates CYP genes expression in monocytes than in lymphocytes. Mechanistically, this could explain a more pronounced immunotoxicity of AFB₁ in myeloid than in lymphoid lineage cells in vitro/situ/vivo.

RNA-Seq profiling reveals novel hepatic gene expression pattern in aflatoxin B1 treated rats

Deep sequencing was used to investigate the subchronic effects of 1 ppm aflatoxin B1 (AFB1), a potent hepatocarcinogen, on the male rat liver transcriptome prior to onset of histopathological lesions or tumors. We hypothesized RNA-Seq would reveal more differentially expressed genes (DEG) than microarray analysis, including low copy and novel transcripts related to AFB1’s carcinogenic activity compared to feed controls (CTRL). Paired-end reads were mapped to the rat genome (Rn4) with TopHat and further analyzed by DESeq and Cufflinks-Cuffdiff pipelines to identify differentially expressed transcripts, new exons and unannotated transcripts. PCA and cluster analysis of DEGs showed clear separation between AFB1 and CTRL treatments and concordance among group replicates. qPCR of eight high and medium DEGs and three low DEGs showed good comparability among RNA-Seq and microarray transcripts. DESeq analysis identified 1,026 differentially expressed transcripts at greater than two-fold change (p<0.005) compared to 626 transcripts by microarray due to base pair resolution of transcripts by RNA-Seq, probe placement within transcripts or an absence of probes to detect novel transcripts, splice variants and exons. Pathway analysis among DEGs revealed signaling of Ahr, Nrf2, GSH, xenobiotic, cell cycle, extracellular matrix, and cell differentiation networks consistent with pathways leading to AFB1 carcinogenesis, including almost 200 upregulated transcripts controlled by E2f1-related pathways related to kinetochore structure, mitotic spindle assembly and tissue remodeling. We report 49 novel, differentially-expressed transcripts including confirmation by PCR-cloning of two unique, unannotated, hepatic AFB1-responsive transcripts (HAfT’s) on chromosomes 1.q55 and 15.q11, overexpressed by 10 to 25-fold. Several potentially novel exons were found and exon refinements were made including AFB1 exon-specific induction of homologous family members, Ugt1a6 and Ugt1a7c. We find the rat transcriptome contains many previously unidentified, AFB1-responsive exons and transcripts supporting RNA-Seq’s capabilities to provide new insights into AFB1-mediated gene expression leading to hepatocellular carcinoma.

Effect of Aflatoxin B1 on Growth of Bovine Mammary Epithelial Cells in 3D and Monolayer Culture System

PURPOSE

Many studies have been showed transfer of aflatoxins, toxins produced by Aspergillus flvaus and Aspergillus parasiticus fungi, into milk. These toxins are transferred into the milk through digestive system by eating contaminated food. Due to the toxicity of these materials, it seems that it has side effects on the growth of mammary cells. Therefore, the present work aimed to investigate possible toxic effects of aflatoxin B1 (AFB1) on bovine mammary epithelial cells in monolayer and three-dimensional cultures.

METHODS

Specimens of the mammary tissue of bovine were sized out in size 2×2 cm in slaughterhouse. After disinfection and washing in sterile PBS, primary cell culture was performed by enzymatic digestion of tissue with collagenase. When proper numbers of cells were achieved in monolayer culture, cells were seeded in a 24-well culture plate for three-dimensional (3D) culture in Matrigel matrix. After 21 days of 3D culture and reaching the required number of cells, the concentrations of 15, 25 and 35 µL of AFB1 were added to the culture in quadruplicate and incubated for 8 hours. Cellular cytotoxicity was examined using standard colorimetric assay and finally, any change in the morphology of the cells was studied by microscopic technique.

RESULTS

Microscopic investigations showed necrosis of the AFB1-exposed cells compared to the control cells. Also, bovine mammary epithelial cells were significantly affected by AFB1 in dose and time dependent manner in cell viability assays.

CONCLUSION

According to the results, it seems that AFB1 can induce cytotoxicity and necrosis in bovine mammary epithelial cells.

Optimization of the HepaRG cell model for drug metabolism and toxicity studies

The HepaRG cell line is the first human cell line able to differentiate in vitro into mature hepatocyte-like cells. Our main objective within the framework of the EEC-LIINTOP project was to optimize the use of this cell line for drug metabolism and toxicity studies, especially after repeat treatments. The main results showed that differentiated HepaRG cells: (i) retained their drug metabolism capacity (major CYPs, phase 2 enzymes, transporters and nuclear receptors) and responsiveness to prototypical inducers at relatively stable levels for several weeks at confluence. The levels of several functions, including some CYPs such as CYP3A4, were dependent on the addition of dimethyl sulfoxide in the culture medium; (ii) sustained the different types of chemical-induced hepatotoxicity, including steatosis, phospholipidosis and cholestasis, after acute and/or repeat treatment with reference drugs. In particular, drug-induced vesicular steatosis was demonstrated in vitro for the first time. In conclusion, our results from the LIINTOP project, together with other studies reported concomitantly or more recently in the literature, support the conclusion that the metabolically competent human HepaRG cells represent a surrogate to primary human hepatocytes for investigating drug metabolism parameters and both acute and chronic effects of xenobiotics in human liver.

The HepaRG cell line: a unique in vitro tool for understanding drug metabolism and toxicology in human

INTRODUCTION

HepaRG is a unique cell line showing a great plasticity, which differentiates to both canaliculae-like and hepatocyte-like cells. The long-term stability of key cell functions, for example, the drug-metabolizing cytochrome P450 (CYP) enzyme activities, in culture is especially useful in drug metabolism, disposition and toxicity studies.

AREAS COVERED

This review describes features of the HepaRG cells focusing on drug-metabolizing enzymes and drug transporters, their functionality and regulation. Several applications in drug discovery studies are discussed and the use of HepaRG, as a human relevant predictive in vitro CYP induction model, is described. In addition, promising studies using HepaRG cells for understanding liver toxicity mechanisms by drug compounds are also discussed.

EXPERT OPINION

HepaRG cells exhibit features which make them useful as an in vitro model for drug metabolism, disposition and toxicity studies, and could, for many studies, replace the requirement for primary human hepatocytes. Care should be taken since HepaRG cells are of a specific genotype which is reflected in the expression of drug processing proteins. The finding that HepaRG cells form tight junctions provides the basis for formation of functional canalicular structures and this should be investigated further to aid development of human relevant hepatic in vitro 2D and 3D models.