The suitability of rat hepatoma cell line H4IIE for evaluating the potentials of compounds to induce CYP3A23 expression

Effect of Acrylamide Treatment on Cyp2e1 Expression and Redox Status in Rat Hepatocytes

Acrylamide (AA) toxicity is associated with oxidative stress. During detoxification, AA is either coupled to gluthatione or biotransformed to glycidamide by the enzyme cytochrome P450 2E1 (CYP2E1). The aim of our study was to examine the hepatotoxicity of AA in vivo and in vitro. Thirty male Wistar rats were treated with 25 or 50 mg/kg b.w. of AA for 3 weeks. Qualitative and quantitative immunohistochemical evaluation of inducible nitric oxide synthase (iNOS), CYP2E1, catalase (CAT), superoxide dismutase 1 (SOD1), and SOD2 expression in liver was carried out. Bearing in mind that the liver is consisted mainly of hepatocytes, in a parallel study, we used the rat hepatoma cell line H4IIE to investigate the effects of AA at IC20 and IC50 concentrations on the redox status and the activity of CAT, SOD, and glutathione-S-transferase (GST), their gene expression, and CYP2E1 and iNOS expression. Immunohistochemically stained liver sections showed that treatment with AA25mg induced a significant decrease of CYP2E1 protein expression (p < 0.05), while treatment with AA50mg led to a significant increase of iNOS protein expression (p < 0.05). AA treatment dose-dependently elevated SOD2 protein expression (p < 0.05), while SOD1 protein expression was significantly increased only at AA50mg (p < 0.05). CAT protein expression was not significantly affected by AA treatments (p > 0.05). In AA-treated H4IIE cells, a concentration-dependent significant increase in lipid peroxidation and nitrite levels was observed (p < 0.05), while GSH content and SOD activity significantly decreased in a concentration-dependent manner (p < 0.05). AA IC50 significantly enhanced GST activity (p < 0.05). The level of mRNA significantly increased in a concentration-dependent manner for iNOS, SOD2, and CAT in AA-treated H4IIE cells (p < 0.05). AA IC50 significantly increased the transcription of SOD1, GSTA2, and GSTP1 genes (p < 0.05), while AA IC20 significantly decreased mRNA for CYP2E1 in H4IIE cells (p < 0.05). Obtained results indicate that AA treatments, both in vivo and in vitro, change hepatocytes; drug-metabolizing potential and disturb its redox status.

Mechanisms of NADPH - cytochrome P450 oxidoreductase induction by dexamethasone in the H4IIE rat hepatoma cell line

Expression of NADPH - cytochrome P450 oxidoreductase (POR), electron donor for microsomal P450s, is induced in rat liver by dexamethasone (DEX), an activator of the glucocorticoid receptor (GR) and the pregnane X receptor (PXR). DEX induction of POR in rat liver is primarily PXR-mediated, although GR may contribute to mRNA effects. We examined the role of GR and PXR in the DEX induction of POR mRNA and protein in the H4IIE rat hepatoma cell line. The DEX EC₅₀ for a PXR target, CYP3A23, exceeded that for the GR targets tyrosine aminotransferase and PXR as well as POR itself. POR protein levels were induced 3- and 4-fold, respectively, by DEX concentrations activating GR selectively (100 nM) or both GR and PXR (10 μM). POR was induced by triamcinolone acetonide, a selective GR agonist, but not pregnenolone-16α-carbonitrile, a selective PXR agonist. POR induction was blocked by the GR antagonist RU486 but minimally influenced by the PXR antagonist FLB-12. The half-life for POR mRNA was prolonged by DEX at both 100 nM and 10 μM. GR is more important in DEX-induced POR expression in H4IIE cells compared to rat liver in vivo, calling into question the suitability of this cell model for mechanistic studies.

In vitro hepatotoxicity of Petasites hybridus extract (Ze 339) depends on the concentration, the cytochrome activity of the cell system, and the species used

Ze 339, a CO₂ extract prepared from the leaves of Petasites hybridus, possesses antispasmodic and anti‐inflammatory effects and is proven to be effective in the treatment of allergic rhinitis. To study possible hepatotoxic effects of Ze 339, its main constituents and metabolites, a series of in vitro investigations were performed. Furthermore, different reconstituted fractions of extract (petasins and fatty acid fraction) were examined in three in vitro test systems using hepatocytes: Two human cell lines, with lower and higher activity of cytochrome P450 enzymes (HepG2, HepaRG) as well as a rodent cell line with high cytochrome P450 activity (H‐4‐II‐E), were used. Metabolic activity, assessed by the WST‐1 assay, was chosen as indicator of cytotoxicity. To assess potential bioactivation of Ze 339 compounds, metabolic experiments using S9 fractions from rats, dogs, and humans and isolated cytochromes (human/rat) were performed, and the formation of reactive metabolites was assessed by measuring cellular concentrations of glutathione and glutathione disulphide.

Our data revealed that the cytotoxicity of Ze 339, its single constituents, and main metabolites depends on the concentration, the cytochrome activity of the cell system, and the species used.

In vitro toxicity and in silico docking analysis of two novel selective AH-receptor modulators

The mediator of dioxin toxicity, aryl hydrocarbon receptor (AHR), has also important physiological functions. Selective AHR modulators (SAHRMs) share some effects of dioxins, except for their marked toxicity. We recently characterised toxicologically two novel SAHRMs, prodrugs IMA-08401 and IMA-07101 in rats, demonstrating that they are far less deleterious than the most toxic AHR-agonist, TCDD. Here, we analysed the in vitro toxicity and in silico AHR binding of the respective active, deacetylated metabolites, IMA-06201 (N-ethyl-N-phenyl-5-chloro-1,2-dihydro-4-hydroxy-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-06504 (N-(4-trifluoromethylphenyl)-1,2-dihydro-4-hydroxy-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). In H4IIE rat hepatoma cells, IMA-06201 and IMA-06504 induced CYP1A1 with comparable potencies and efficacies to those of TCDD. They had little effect on cell viability as assessed by LDH leakage and MTT reduction assays, and were not mutagenic in the Ames test, but IMA-06504 elicited a maximally 2.7-fold increase in micronuclei. Molecular docking simulations showed that similar to TCDD, they occupy the central region of AHR ligand binding cavity. Hence, while showing low to negligible in vitro toxicity, these novel SAHRMs bind to the AHR qualitatively in a similar fashion to TCDD, and appear comparably powerful AHR agonists. Combined with our earlier results demonstrating that they seem considerably less toxic in vivo than TCDD, these compounds are thus highly interesting new SAHRMs.

Induction of xenobiotic-metabolizing enzymes in hepatocytes by beta-naphthoflavone: Time-dependent changes in activities, protein and mRNA levels

In the present study, time-dependency of the induction effect of a selective inducer on the activity, protein and mRNA levels of cytochromes P450 1A1/2 (CYP1A1/2), NAD(P)H:quinone oxidoreductase 1 (NQO1) and glutathione S-transferases (GSTA), in primary culture of rat hepatocytes was tested and evaluated. To show the differences in responses of tested enzymes, the common aryl hydrocarbon receptor (AhR) ligand agonist, beta-naphthoflavone (BNF), was used. Induction of CYP1A1/2 by BNF was detected at all time intervals and at all levels (i.e., mRNA, protein, enzyme activity). Different responses of NQO1 and GSTA upon BNF treatment were observed. Our results demonstrate that the responses of different xenobiotic-metabolizing enzymes to the inducer vary in time and depend on the measured parameter. For these reasons, an induction study featuring only one-time interval treatment and/ or one parameter testing could produce misleading information.

Multiscale cytometry and regulation of 3D cell cultures on a chip

Three-dimensional cell culture is emerging as a more relevant alternative to the traditional two-dimensional format. Yet the ability to perform cytometry at the single cell level on intact three-dimensional spheroids or together with temporal regulation of the cell microenvironment remains limited. Here we describe a microfluidic platform to perform high-density three-dimensional culture, controlled stimulation, and observation in a single chip. The method extends the capabilities of droplet microfluidics for performing long-term culture of adherent cells. Using arrays of 500 spheroids per chip, in situ immunocytochemistry and image analysis provide multiscale cytometry that we demonstrate at the population scale, on 10⁴ single spheroids, and over 10⁵ single cells, correlating functionality with cellular location within the spheroids. Also, an individual spheroid can be extracted for further analysis or culturing. This will enable a shift towards quantitative studies on three-dimensional cultures, under dynamic conditions, with implications for stem cells, organs-on-chips, or cancer research.3D cell culture is more relevant than the two-dimensional format, but methods for parallel analysis and temporal regulation of the microenvironment are limited. Here the authors develop a droplet microfluidics system to perform long-term culture of 3D spheroids, enabling multiscale cytometry of individual cells within the spheroid.

Drug target identification at the crossroad of neuronal apoptosis and survival

INTRODUCTION

Inappropriate activation of apoptosis may contribute to neurodegeneration, a multifaceted process that results in various chronic disorders, including Alzheimer's and Parkinson's diseases. Several in vitro and in vivo studies demonstrated that neuronal apoptosis is a multi-pathway cell-death program that requires RNA synthesis. Thus, transcriptionally activated genes whose products induce cell death can be triggered by different stimuli and antagonized by neurotrophic factors. Systems biology is now unveiling the series of intracellular signaling pathways and key drug targets at the intersection of neuronal apoptosis and survival. Areas covered: This review introduces a genomic approach that can be used to elucidate the systems biology of neuronal apoptosis and survival, and to rationally select drug targets, no longer oriented to emulate the action of growth factors at the membrane receptor level, but rather to modulate their downstream signals. Expert opinion: The advent of genomics is offering an unprecedented opportunity to explore how the delicate balance between apoptosis and survival-inducing signals triggers a transcriptional program. Characterization of this program can be useful to identify potential pharmacological targets for existing drugs. Such knowledge might pave the way towards an innovative pharmacology.

BDE47 induces rat CYP3A1 by targeting the transcriptional regulation of miR-23b

Cytochrome P450 3A (CYP3A) is the most abundant CYP450 enzyme in the liver and is involved in the metabolism of over 50% of xenobiotics. Our previous studies revealed that 2,2′,4,4′-tetrabromodiphenyl ether (BDE47) could induce rat CYP3A1 expression, but the molecular basis remains unclear. Using in silico analysis, we identified a potential miR-23b recognition element (MRE23b) in the 3′-UTR region of CYP3A1 mRNA, which was verified by the luciferase assay. The miR-23b mimic and inhibitor significantly down- and up-regulated the expression of CYP3A1, respectively. Additionally, BDE47 significantly down-regulated the expression of miR-23b in rats and in hepatic H4IIE cells. Induction or blockage of CYP3A1 by a miR-23b inhibitor or mimic could correspondingly alter BDE47-induced expression of CYP3A1 and cytotoxicity in H4IIE cells. Furthermore, LV-anti-miR-23b significantly decreased endogenous levels of miR-23b and increased the expression and activity of CYP3A1 in rat liver. LV-anti-miR-23b also significantly increased the hydroxylated metabolites of BDE47 (3-OH-BDE47, 4-OH-BDE42, and 4′-OH-BDE49) in rat serum. In conclusion, we first found that BDE47 induced rat CYP3A1 expression by targeting the transcriptional regulation of miR-23b. This study helps provide a better understanding of CYP3A regulation and offers novel clues for the role of miRNAs in the metabolism and distribution of environmental pollutants.

The NAE inhibitor pevonedistat (MLN4924) synergizes with TNF-α to activate apoptosis

Predicting and understanding the mechanism of drug-induced toxicity is one of the primary goals of drug development. It has been hypothesized that inflammation may have a synergistic role in this process. Cell-based models provide an easily manipulated system to investigate this type of drug toxicity. Several groups have attempted to reproduce in vivo toxicity with combination treatment of pharmacological agents and inflammatory cytokines. Through this approach, synergistic cytotoxicity between the investigational agent pevonedistat (MLN4924) and TNF-α was identified. Pevonedistat is an inhibitor of the NEDD8-activating enzyme (NAE). Inhibition of NAE prevents activation of cullin-RING ligases, which are critical for proteasome-mediated protein degradation. TNF-α is a cytokine that is involved in inflammatory responses and cell death, among other biological functions. Treatment of cultured cells with the combination of pevonedistat and TNF-α, but not as single agents, resulted in rapid cell death. This cell death was determined to be mediated by caspase-8. Interestingly, the combination treatment of pevonedistat and TNF-α also caused an accumulation of the p10 protease subunit of caspase-8 that was not observed with cytotoxic doses of TNF-α. Under conditions where apoptosis was blocked, the mechanism of death switched to necroptosis. Trimerized MLKL was verified as a biomarker of necroptotic cell death. The synergistic toxicity of pevonedistat and elevated TNF-α was also demonstrated by in vivo rat studies. Only the combination treatment resulted in elevated serum markers of liver damage and single-cell hepatocyte necrosis. Taken together, the results of this work have characterized a novel synergistic toxicity driven by pevonedistat and TNF-α.

Expression alterations of cytochromes P4501A1, 2E1, and 3A, and their receptors AhR and PXR caused by 1-octyl-3-methylimidazolium chloride in mouse mammary carcinoma cells

Cytochrome P450s (CYPs) play a key role in the metabolism of a wide range of environmental xenobiotics and endogenous compounds. The expression and activity levels of CYPs can be elevated by a process of induction involving the activation of nuclear receptors. The effects of the ionic liquid 1-octyl-3-methylimidazolium chloride ([C(8)mim][Cl]) on the expression of cytochrome P450 members, including CYP1A1, CYP2E1, and CYP3A, as well as on aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) in mouse mammary carcinoma cells (EMT6) were investigated by using quantitative real-time PCR in the present study. The results reveal that [C(8)mim][Cl]-exposure up-regulates the expressions of CYP1A1, CYP2E1, and CYP3A at mRNA level, suggesting that imidazolium-based ionic liquids can activate CYPs. Our results also suggest that [C(8)mim][Cl]-mediated CYP3A induction be PXR-dependent. This result may be beneficial to evaluating the environmental toxicity of imidazolium-based ionic liquids and investigating the metabolism of imidazolium-derivative drugs.