Generation of stable ARE- driven reporter system for monitoring oxidative stress

The Combination of Gefitinib and Acetaminophen Exacerbates Hepatotoxicity via ROS-Mediated Apoptosis

Gefitinib is the well-tolerated first-line treatment of non-small cell lung cancer. As it need for analgesics during oncology treatment, particularly in the context ofthe coronavirus disease, where patients are more susceptible to contract high fever and sore throat. This has increased the likelihood of taking both gefitinib and antipyretic analgesic acetaminophen (APAP). Given that gefitinib and APAP overdose can predispose patients to liver injury or even acute liver failure, there is a risk of severe hepatotoxicity when these two drugs are used concomitantly. However, little is known regarding their safety at therapeutic doses. This study simulated the administration of gefitinib and APAP at clinically relevant doses in an animal model and confirmed that gefitinib in combination with APAP exhibited additional hepatotoxicity. We found that gefitinib plus APAP significantly exacerbated cell death, whereas each drug by itself had little or minor effect on hepatocyte survival. Mechanistically, combination of gefitinib and APAP induces hepatocyte death via the apoptotic pathway obviously. Reactive oxygen species (ROS) generation and DNA damage accumulation are involved in hepatocyte apoptosis. Gefitinib plus APAP also promotes the expression of Kelch-like ECH-associated protein 1 (Keap1) and downregulated the antioxidant factor, Nuclear factor erythroid 2-related factor 2 (Nrf2), by inhibiting p62 expression. Taken together, this study revealed the potential ROS-mediated apoptosis-dependent hepatotoxicity effect of the combination of gefitinib and APAP, in which the p62/Keap1/Nrf2 signaling pathway participates and plays an important regulatory role.

A Comprehensive Exploration of Bioluminescence Systems, Mechanisms, and Advanced Assays for Versatile Applications

Bioluminescence has been a fascinating natural phenomenon of light emission from living creatures. It happens when the enzyme luciferase facilitates the oxidation of luciferin, resulting in the creation of an excited-state species that emits light. Although there are many bioluminescent systems, few have been identified. D-luciferin-dependent systems, coelenterazine-dependent systems, Cypridina luciferin-based systems, tetrapyrrole-based luciferins, bacterial bioluminescent systems, and fungal bioluminescent systems are natural bioluminescent systems. Since different bioluminescence systems, such as various combinations of luciferin-luciferase pair reactions, have different light emission wavelengths, they benefit industrial applications such as drug discovery, protein-protein interactions, in vivo imaging in small animals, and controlling neurons. Due to the expression of luciferase and easy permeation of luciferin into most cells and tissues, bioluminescence assays are applied nowadays with modern technologies in most cell and tissue types. It is a versatile technique in a variety of biomedical research. Furthermore, there are some investigated blue-sky research projects, such as bioluminescent plants and lamps. This review article is mainly based on the theory of diverse bioluminescence systems and their past, present, and future applications.

Alpha-tocopherylquinone differentially modulates claudins to enhance intestinal epithelial tight junction barrier via AhR and Nrf2 pathways

Defects in intestinal epithelial tight junctions (TJs) allow paracellular permeation of noxious luminal antigens and are important pathogenic factors in inflammatory bowel disease (IBD). We show that alpha-tocopherylquinone (TQ), a quinone-structured oxidation product of vitamin E, consistently enhances the intestinal TJ barrier by increasing barrier-forming claudin-3 (CLDN3) and reducing channel-forming CLDN2 in Caco-2 cell monolayers (in vitro), mouse models (in vivo), and surgically resected human colons (ex vivo). TQ reduces colonic permeability and ameliorates colitis symptoms in multiple colitis models. TQ, bifunctionally, activates both aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways. Genetic deletion studies reveal that TQ-induced AhR activation transcriptionally increases CLDN3 via xenobiotic response element (XRE) in the CLDN3 promoter. Conversely, TQ suppresses CLDN2 expression via Nrf2-mediated STAT3 inhibition. TQ offers a naturally occurring, non-toxic intervention for enhancement of the intestinal TJ barrier and adjunct therapeutics to treat intestinal inflammation.

Application of ARE-reporter systems in drug discovery and safety assessment

The human body is continuously exposed to xenobiotics and internal or external oxidants. The health risk assessment of exogenous chemicals remains a complex and challenging issue. Alternative toxicological test methods have become an essential strategy for health risk assessment. As a core regulator of constitutive and inducible expression of antioxidant response element (ARE)-dependent genes, nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in maintaining cellular redox homeostasis. Consistent with the properties of Nrf2-mediated antioxidant response, Nrf2-ARE activity is a direct indicator of oxidative stress and thus has been used to identify and characterize oxidative stressors and redox modulators. To screen and distinguish chemicals or environmental insults that affect the cellular antioxidant activity and/or induce oxidative stress, various in vitro cell models expressing distinct ARE reporters with high-throughput and high-content properties have been developed. These ARE-reporter systems are currently widely applied in drug discovery and safety assessment. In the present review, we provide an overview of the basic structures and applications of various ARE-reporter systems employed for discovering Nrf2-ARE modulators and characterizing oxidative stressors.

Cell-Based Antioxidant Properties and Synergistic Effects of Natural Plant and Algal Extracts Pre and Post Intestinal Barrier Transport

In this work, both direct and indirect cell-based antioxidant profiles were established for 27 plant extracts and 1 algal extract. To evaluate the direct antioxidant effects, fluorescent AOP1 cell assay was utilized, which measures the ability of different samples to neutralize intracellular free radicals produced by a cell-based photo-induction process. As the intestinal barrier is the first cell line crossed by the product, dose response curves obtained from Caco-2 cells were used to establish EC50 values for 26 out of the 28 natural extracts. Among them, 11 extracts from Vitis, Hamamelis, Syzygium, Helichrysum, Ilex and Ribes genera showed remarkable EC50s in the range of 10 µg/mL. In addition to this, a synergistic effect was found when combinations of the most potent extracts (S. aromaticum, H. italicum, H. virginiana, V. vinifera) were utilized compared to extracts alone. Indirect antioxidant activities (i.e., the ability of cells to trigger antioxidant defenses) were studied using the ARE/Nrf2 luminescence reporter-gene assay in HepG2 cells, as liver is the first organ crossed by an edible ingredient once it enters in the bloodstream. Twelve extracts were subjected to an intestinal epithelial barrier passage in order to partially mimic intestinal absorption and show whether basolateral compartments could maintain direct or indirect antioxidant properties. Using postepithelial barrier samples and HepG2 cells as a target model, we demonstrate that indirect antioxidant activities are maintained for three extracts, S. aromaticum, H. virginiana and H. italicum. Our experimental work also confirms the synergistic effects of combinations of post-intestinal barrier compartments issued from apical treatment with these three extracts. By combining cell-based assays together with an intestinal absorption process, this study demonstrates the power of cell systems to address the issue of antioxidant effects in humans.

Live Cell Assays for the Assessment of Antioxidant Activities of Plant Extracts

Plant extracts and pharmacopoeias represent an exceptional breeding ground for the discovery of new antioxidants. Until recently, the antioxidant activity was only measured by chemical hydrogen atom transfer (HAT) and single-electron transfer (SET) cell-free assays that do not inform about the actual effect of antioxidants in living systems. By providing information about the mode of action of antioxidants at the subcellular level, recently developed live cell assays are now changing the game. The idea of this review is to present the different cell-based approaches allowing a quantitative measurement of antioxidant effects of plant extracts. Up to date, only four different approaches have reached a certain degree of standardization: (1) the catalase-like assay using H₂O₂ as a stressor, (2) the cell antioxidant assay (CAA) using AAPH as a stressor and DCFH-DA as a readout, (3) the AOP1 assay which uses photoinduction to monitor and control cell ROS production, and (4) the Nrf2/ARE gene reporter system. The molecular aspects of these assays are presented in detail along with their features, drawbacks, and benefits. The Nrf2/ARE gene reporter system dedicated to indirect antioxidant effect measurement currently represents the most standardized approach with high-throughput applications. AOP1, the first technology linking a fine-tuning of cell ROS production with a quantitative signal, appears to be the most promising tool for the assessment of direct cellular ROS-scavenging effects at an industrial scale.

Nanocurcumin as a novel stimulator of megakaryopoiesis that ameliorates chemotherapy-induced thrombocytopenia in mice

AIMS

Platelet production improvement can resolve concerns about the limitations of external platelet supply and platelet transfusion in thrombocytopenia patients. To this end, scientists encourage to induce the generation of megakaryocyte and platelet. Curcumin is a safe ingredient of turmeric that affects various cellular pathways. The effect of this component on platelet production has not been yet reported.

MAIN METHODS

Our in vitro experiments include the investigation of the effects of nanocurcumin on megakaryocytes production from K562 cells and hematopoietic stem cells via megakaryocyte markers expression, DNA content, ROS, and morphologic analysis, and CFC assay. The regulatory functions of MAPKs pathways were also determined. In the in vivo study tissue distribution of nanocurcumin was determined and two treatment schedules were used to evaluate the capability of nanocurcumin to prevent the occurrence of Busulfan-induced thrombocytopenia in the mouse model.

KEY FINDING

In vitro evidences demonstrated that nanocurcumin can induce MK production from K562 cells and hematopoietic stem cells. Inhibition of ERK1/2 and JNK pathways arrested this activity. In vivo experiments showed the uptake of nanocurcumin by tissues in mice. Administration of nanocurcumin could preserve bone marrow integrity and increase of the number of circulating platelets in the Busulfan-treated mice models.

SIGNIFICANCE

Our results have demonstrated that nanocurcumin administration can be useful for the improvement of megakaryocytes and platelet generation in vitro. This component may be exerting these beneficial effects on megakaryopoiesis by modulating ERK1/2 and JNK pathways. As well as nanocurcumin has the potential to prevent thrombocytopenia in chemotherapy threated mice.

Design and Application of A Bioluminescent Biosensor for Detection Of Toxicity Using Huh7-CMV-Luc Cell Line

Cell-based biosensors (CBBs) are becoming important tools for biosecurity a lications and rapid diagnostics in food microbiology for their unique capability of detecting hazardous materials. Pollutants, such as heavy metals and chemicals, are now considered as a global threat and are associated with detrimental health outcomes. Fast and accurate detection of pollutants is essential to reduce these threats. In this study, the enhancer sequence of human cytomegalovirus (hCMV) IE genes cloned upstream of luc gene in PGL4.26 plasmid, in order to increase basal luciferase activity. This recombinant vector was transfected into Huh7 cell line and after 21 days of treatment with Hygromycin B selectable marker, stable cell line was generated. After several passages, cells containing this vector showed high luciferase activity in normal conditions without any induction following to overexpression of luc gene. Huh7-CMV-luc cell line was able to detect the slightest changes in ATP level, due to the effect of different toxins on the cell which disrupt cellular respiration and ATP production processes. In order to investigate the sensitivity of the cell line, the cells were incubated with 0.1-10 μM of chemical toxins affecting ATP production. These toxins affect luciferase activity in a dose dependent manner, with maximal sensitivity approximately about 0.2 μM to toxin concentrations. Additionally, this biosensor provided a rapid detection as early as 4 h in response to the toxicants. Whole cell biosensors like huh7-CMV-luc cell line can be considered as a powerful tool for the sensitive and efficient monitoring of general toxins, drugs, and environmental pollutants.

Effects of Maerua subcordata (Gilg) DeWolf on electrophile-responsive element (EpRE)-mediated gene expression in vitro

Plant extracts and phytochemicals may prevent chronic diseases via activation of adaptive cellular stress response pathways including induction of antioxidant and phase II detoxifying enzymes. The regulatory regions of these inducible genes encode the electrophile-response element (EpRE). This study tested the EpRE induction ability of Maerua subcordata (fruit, leaf, root, seed) methanol extracts and selected candidate constituents thereof, identified by liquid chromatography coupled with multistage mass spectroscopy, employing an EpRE luciferase reporter gene assay using hepa-1c1c7 mouse hepatoma cells. A parallel Cytotox CALUX assay using human osteosarcoma U2OS cells was used to monitor any non-specific changes in luciferase activity or cytotoxicity. Results showed that fruit, root, and seed extracts were non-cytotoxic up to a concentration of 30 gram dry weight per litre but the leaf extract exhibited some cytotoxicity and that the leaf (despite some cytotoxicity), fruit, and seed extracts showed strong induction of EpRE mediated gene expression while induction by the root extract was minimal. Selected candidates included glucosinolates, isothiocyanates, and some biogenic amines. Subsequent studies showed that methyl-, ethyl-, isopropyl-, isobutyl- isothiocyanates, and sec-butyl thiocyanate as well as glucobrassicin induced concentration (1–100 μM) dependent EpRE-mediated gene expression while the biogenic amines stachydrine and trigonelline acted as inhibitors of EpRE-mediated gene expression at 100 μM. The identification of glucolepidiin, glucobrassicin, glucocapparin, stachydrine, and trigonelline in all extracts was confirmed using standards and based on multiple reaction monitoring; yet, glucobrassicin level in the root extract was negligible. In conclusion, this study provided a first report on EpRE mediated gene expression effects of M. subcordata; and despite detection of different glucosinolates in all extracts, those containing glucobrassicin particularly displayed high EpRE induction. Because EpRE inducers are cytoprotective and potential chemopreventive agents while inhibitors are suggested adjuvants of chemotherapy, results of this study imply that process manipulation of this plant may result in herbal preparations that may be used as chemopreventive agents or adjuvants of chemotherapies.

Antioxidant response elements: Discovery, classes, regulation and potential applications

Exposure to antioxidants and xenobiotics triggers the expression of a myriad of genes encoding antioxidant proteins, detoxifying enzymes, and xenobiotic transporters to offer protection against oxidative stress. This articulated universal mechanism is regulated through the cis-acting elements in an array of Nrf2 target genes called antioxidant response elements (AREs), which play a critical role in redox homeostasis. Though the Keap1/Nrf2/ARE system involves many players, AREs hold the key in transcriptional regulation of cytoprotective genes. ARE-mediated reporter constructs have been widely used, including xenobiotics profiling and Nrf2 activator screening. The complexity of AREs is brought by the presence of other regulatory elements within the AREs. The diversity in the ARE sequences not only bring regulatory selectivity of diverse transcription factors, but also confer functional complexity in the Keap1/Nrf2/ARE pathway. The different transcription factors either homodimerize or heterodimerize to bind the AREs. Depending on the nature of partners, they may activate or suppress the transcription. Attention is required for deeper mechanistic understanding of ARE-mediated gene regulation. The computational methods of identification and analysis of AREs are still in their infancy. Investigations are required to know whether epigenetics mechanism plays a role in the regulation of genes mediated through AREs. The polymorphisms in the AREs leading to oxidative stress related diseases are warranted. A thorough understanding of AREs will pave the way for the development of therapeutic agents against cancer, neurodegenerative, cardiovascular, metabolic and other diseases with oxidative stress.

Nanocurcumin-Mediated Down-Regulation of Telomerase Via Stimulating TGFβ1 Signaling Pathway in Hepatocellular Carcinoma Cells

Background

Curcumin, extracted from turmeric, represents enormous potential to serve as an anticancer agent. Telomerase is viewed as a prominent molecular target of curcumin, and Transforming growth factor-β1 (TGFβ1) has proven to be a major inhibitory signaling pathway for telomerase activity. In the current study, we aimed to explore suppressive effects of nanocurcumin on telomerase expression through TGFβ1 pathway in a hepatocellular carcinoma cell line (Huh7).

Methods

MTT assay was used to determine the effect of nonocurcumin on viability of Huh7 cells. RT-PCR was used to analyze the gene expression patterns.

Results

MTT assay revealed that nanocurcumin acts in a dose- and time-dependent manner to diminish the cell viability. RT-PCR analysis indicated that nanocurcumin results in augmentation of TGFβ1 72 hours post treatment and leads to the reduction of telomerase expression 48 and 72 hours post exposure. Also, up-regulation of Smad3 and E2F1 and down-regulation of Smad7 confirmed the effect of nanocurcumin on intermediate components of TGFβ1 pathway. Furthermore, transfection of the proximal promoter of telomerase triggered a significant reduction in luciferase activity.

Conclusion

The data from the present study lead us to develop a deeper understanding of the mechanisms underlying nanocurcumin-mediated regulation of telomerase expression, thereby presenting a new perspective to the landscape of using nanocurcumin as a cancer-oriented therapeutic agent.

Covalent binding of quinones activates the Ah receptor in Hepa1c1c7 cells

Highly reactive quinone species produced by photooxidation and/or metabolic activation of mono- or bi-aromatic hydrocarbons modulate cellular homeostasis and electrophilic signal transduction pathways through the covalent modification of proteins. Polycyclic aromatic hydrocarbons, but not mono- or bi-aromatic hydrocarbons, are well recognized as ligands for the aryl hydrocarbon receptor (AhR). However, quinone species produced from mono- and bi-aromatic hydrocarbons could potentially cause AhR activation. To clarify the AhR response to mono- and bi-aromatic hydrocarbon quinones, we studied Cyp1a1 (cytochrome P450 1A1) induction and AhR activation by these quinones. We detected Cyp1a1 induction during treatment with quinones in Hepa1c1c7 cells, but not their parent compounds. Nine of the twelve quinones with covalent binding capability for proteins induced Cyp1a1. Cyp1a1 induction mediated by 1,2-naphthoquinone (1,2-NQ), 1,4-NQ, 1,4-benzoquinone (1,4-BQ) and tert-butyl-1,4-BQ was suppressed by a specific AhR inhibitor and was not observed in c35 cells, which do not have a functional AhR. These quinones stimulated AhR nuclear translocation and interaction with the AhR nuclear translocator. Interestingly, 1,2-NQ covalently modified AhR, which was detected by an immunoprecipitation assay using a specific antibody against 1,2-NQ, resulting in enhancement of xenobiotic responsive element (XRE)-derived luciferase activity and binding of AhR to the Cyp1a1 promoter region. While mono- and bi-aromatic hydrocarbons are generally believed to be poor ligands for AhR and hence unable to induce Cyp1a1, our study suggests that the quinones of these molecules are able to modify AhR and activate the AhR/XRE pathway, thereby inducing Cyp1a1. Since we previously reported that 1,2-NQ and tert-butyl-1,4-BQ also activate NF-E2-related factor 2, it seems likely that some of quinones are bi-functional inducers for phase-I and phase-II reaction of xenobiotics.

Effects of multi-component mixtures of polyaromatic hydrocarbons and heavy metal/loid(s) on Nrf2-antioxidant response element (ARE) pathway in ARE reporter-HepG2 cells

Exposure to polyaromatic hydrocarbons (PAHs) and heavy metal/loid(s) has been demonstrated to induce an oxidative stress response in mammalian cells. The combined effect of PAHs and heavy metal/loid(s) on the oxidative stress response has not been reported extensively. The Nrf2 antioxidant response pathway plays an important role in cellular antioxidant defense against oxidative stress-induced cell damage. In this study, we have determined the combined effect of four PAHs (benzo[a]pyrene (B[a]P), naphthalene (Nap), phenanthrene (Phe) and pyrene (Pyr)) and three heavy metal/loid(s) (arsenic (As), cadmium (Cd) and lead (Pb)) on the Nrf2 antioxidant pathway using the ARE reporter-HepG2 cell line. The mixture study was carried out for binary, ternary, quaternary and seven-component combinations of PAHs and heavy metal/loid(s). Initially, individual dose responses for the PAHs (B[a]P, Nap, Phe and Pyr) and heavy metal/loid(s) (As, Cd and Pb), as well as their respective concentrations that induced an induction ratio of 1.5 (ECIR1.5), were determined. The luciferase assay system was used to quantify the induction of the Nrf2 antioxidant pathway. The individual dose response study showed that both PAHs and heavy metal/loid(s) activated the Nrf2 antioxidant pathway in ARE reporter-HepG2 cells. Among these chemicals, Cd was the most potent inducer, followed by B[a]P and As. Based on the individual dose response findings, PAHs and heavy metal/loid(s) were mixed at equipotent ratios using a fixed concentration ratio, and the effects of the mixtures of PAHs and heavy metal/loid(s) (binary to seven-component) on the Nrf2 antioxidant pathway were determined. The mixture effects were predicted by using the concentration addition (CA) model. Overall, the results showed that the multi-component mixtures of PAHs and heavy metal/loid(s) induced an oxidative stress response in ARE reporter-HepG2 cells, and that the CA model is an appropriate model to predict the interaction effect of these selected mixtures. A human cell line-based reporter gene assay system was successfully used to determine the mixture effects of two groups of common contaminants on oxidative stress response pathway.