Establishment of a stable aryl hydrocarbon receptor-responsive HepG2 cell line

Fraglide-1 from traditional Chinese aromatic vinegar: A natural AhR antagonist for atopic dermatitis

Traditional Chinese Zhenjiang aromatic vinegar (Kozu) contains Fraglide-1 (FG1), a bioactive lactone with demonstrated peroxisome proliferator-activated receptor gamma (PPARγ) agonist and antioxidant activities. This study explored FG1's novel ability to antagonize the aryl hydrocarbon receptor (AhR) signaling pathway, which regulates artemin expression and contributes to itching and inflammation in atopic dermatitis. Through molecular docking simulations and cell-based assays in human keratinocytes, we demonstrated FG1's potent antagonistic activity against AhR signaling. FG1 effectively suppressed FICZ-induced inflammatory responses, including artemin expression, with potency (half maximal inhibitory concentration, IC50 = 5.1 μM) comparable to the synthetic antagonist StemRegenin 1 (SR1) while demonstrating a superior safety profile (median lethal concentration, LC50 > 100 μM vs. 27.5 μM for SR1). These findings expand our understanding of bioactive compounds from traditional fermented foods and their regulatory effects on AhR signaling, providing a foundation for future studies on FG1's role in modulating skin inflammation.

In Vitro, In Vivo, and In Silico Analysis of Pyraclostrobin and Cyprodinil and Their Mixture Reveal New Targets and Signaling Mechanisms

Pyraclostrobin and cyprodinil are broad-spectrum fungicides that are used in crops to control diseases. However, they are excessively used and, as a result, end up in the environment and threaten human health and ecosystems. Hence, knowledge of their mechanisms of action is critical to revealing their environmental fate and negative effects and regulating their use. In the present study, we conducted a comprehensive study to show the adverse effects of pyraclostrobin, cyprodinil, and their mixture using zebrafish larvae and different cell lines. Several end points were investigated, including mortality, development, gene expression, reporter assays, and molecular docking simulations. We found that both compounds and their mixture caused developmental delays and mortality in zebrafish, with a higher effect displayed by pyraclostrobin. Both compounds altered the expression of genes involved in several signaling pathways, including oxidative stress and mitochondrial function, lipid and drug metabolisms, the cell cycle, DNA damage, apoptosis, and inflammation. A noteworthy result of this study is that cyprodinil and the mixture group acted as NFκB activators, while pyraclostrobin demonstrated antagonist activity. The AHR activity was also upregulated by cyprodinil and the mixture group; however, pyraclostrobin did not show any effect. For the first time, we also demonstrated that pyraclostrobin had androgen receptor antagonist activity.

Promotion of ABCG2 gene expression by neolignans from Piper longum L

We focused on Piper longum L., a herbal drug produced in Myanmar, which has a renoprotective effect. Thus, we attempted to isolate and identify compounds that enhance the expression of the ABCG2 gene from the aerial parts of the plant except for the fruit. Among the various P. longum extracts, we isolated and identified the components. Using Caco-2 cells, the hABCG2 mRNA expression-enhancing effects of the isolated compounds were compared with the positive reference compound (3-methylcholanthrene [3MC]) using real-time polymerase chain reaction. Six compounds were isolated and identified from the methanol extract of P. longum. Among the isolated compounds, licarin A and neopomatene had lower toxicity and higher hABCG2 mRNA expression-enhancing effects in Caco-2 cells. Suppression of hAhR expression by siRNA reduced the activity of licarin A and neopomatene, as well as the hAhR agonist 3MC, suggesting that these 2 compounds may act as hAhR agonists to promote hABCG2 expression.

Physiological effects of food ingredients on intestinal epithelial cell function

Understanding the physiological effects of food ingredients on bodily functions is crucial for the development of foods for specified health use (FoSHU) and functional foods. To investigate this, intestinal epithelial cells (IECs) have been widely studied as they are most frequently exposed to the highest concentrations of food ingredients. Among the various functions of IECs, in this review, we have discussed glucose transporters and their involvement in preventing metabolic syndromes such as diabetes. Phytochemicals are also discussed, as they significantly inhibit glucose and fructose absorption via sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 5 (GLUT5), respectively. Additionally, we have focused on the barrier functions of IECs against xenobiotics. Phytochemicals induce detoxification of metabolizing enzymes via pregnane X receptor or aryl hydrocarbon receptor activation, which suggests that food ingredients can enhance barrier function. This review will provide insights into the role of food ingredients and glucose transporters, as well as detoxification metabolizing enzymes in IECs, and help guide future research on these aspects.

Novel fluorescent and secreted transcriptional reporters for quantifying activity of the xenobiotic sensor aryl hydrocarbon receptor (AHR)

Aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor that plays a critical role in diverse biological processes, including xenobiotic metabolism, carcinogenesis, and physiological functions such as regulation of the immune system and cell differentiation. To improve studies of AHR activity, we constructed two new reporter genes: a fluorescent GFP-tagged histone 2B (XRE-H2B-eGFP) and a secreted nanoluciferase (XRE-pNL1.3[secNluc]). Here, we demonstrate how these reporters can be used to monitor AHR activity in different types of cells, including human primary trophoblasts and cell lines, following incubation with a strong AHR ligand, benzo[a]pyrene (B[a]P), or an AHR inhibitor (CH223191). Compared to vehicle control cells, a significant increase in AHR activity was observed in cells treated with 0.5 and/or 2 µM B[a]P and a significant decrease was detected in response to treatment with 3 µM CH223191. These new plasmids have great potential for use in a variety of applications, such as screening for endogenous or exogenous ligands of AHR.

Identification of Modulators of the C. elegans Aryl Hydrocarbon Receptor and Characterization of Transcriptomic and Metabolic AhR-1 Profiles

The Aryl hydrocarbon Receptor (AhR) is a xenobiotic sensor in vertebrates, regulating the metabolism of its own ligands. However, no ligand has been identified to date for any AhR in invertebrates. In C. elegans, the AhR ortholog, AHR-1, displays physiological functions. Therefore, we compared the transcriptomic and metabolic profiles of worms expressing AHR-1 or not and investigated the putative panel of chemical AHR-1 modulators. The metabolomic profiling indicated a role for AHR-1 in amino acids, carbohydrates, and fatty acids metabolism. The transcriptional profiling in neurons expressing AHR-1, identified 95 down-regulated genes and 76 up-regulated genes associated with neuronal and metabolic functions in the nervous system. A gene reporter system allowed us to identify several AHR-1 modulators including bacterial, dietary, or environmental compounds. These results shed new light on the biological functions of AHR-1 in C. elegans and perspectives on the evolution of the AhR functions across species.

Effect of Compounds from Moringa oleifera Lam. on in Vitro Non-Alcoholic Fatty Liver Disease (NAFLD) Model System

Non-alcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease in the world, with a prevalence of 25 % in many countries. To date, no drug has been approved to treat NAFLD, therefore, the use of phytochemicals to prevent this disease is meaningful. In this study, we focused on the effects of Moringa oleifera Lam. on diabetes, attempted to isolate compounds that regulate NAFLD. Compounds 1 and 2 were isolated from the ethyl acetate fraction of M. oleifera. Spectral data revealed that they were 1-hydroxy-3-phenylpropan-2-yl benzoate (1) and benzyl benzylcarbamate (2), respectively. The three-dimensional structure of compound 1 was determined by single crystal X-ray structural analysis. Neither compound was toxic to HepG2 cells, and compound 1 was found to have a concentration-dependent inhibitory effect on intracellular lipid accumulation induced by stimulation of linoleic acid (LA). As a result of measuring the effects of compound 1 on the intracellular lipid production-related protein, it was found that compound 1 enhanced protein expression that promotes lipolysis. On the other hand, since the action of compound 1 was similar to that of PPARα agonists, it is deduced that compound 1 enhanced the activity of PPARα and further enhanced the expression of lipolytic proteins, which is related to the suppression of intracellular lipid accumulation. Furthermore, as the result of docking simulation, compound 1 had a higher binding affinity to the ligand binding site of PPARα than fenofibrate, which is a PPARα agonist, and thus compound 1 was considered to be promising as an agonist of PPARα.

Characterization of Glyceollins as Novel Aryl Hydrocarbon Receptor Ligands and Their Role in Cell Migration

Recent studies strongly support the use of the aryl hydrocarbon receptor (AhR) as a therapeutic target in breast cancer. Glyceollins, a group of soybean phytoalexins, are known to exert therapeutic effects in chronic human diseases and also in cancer. To investigate the interaction between glyceollin I (GI), glyceollin II (GII) and AhR, a computational docking analysis, luciferase assays, immunofluorescence and transcriptome analyses were performed with different cancer cell lines. The docking experiments predicted that GI and GII can enter into the AhR binding pocket, but their interactions with the amino acids of the binding site differ, in part, from those interacting with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Both GI and GII were able to weakly and partially activate AhR, with GII being more potent. The results from the transcriptome assays showed that approximately 10% of the genes regulated by TCDD were also modified by both GI and GII, which could have either antagonistic or synergistic effects upon TCDD activation. In addition, we report here, on the basis of phenotype, that GI and GII inhibit the migration of triple-negative (ER-, PgR-, HER2NEU-) MDA-MB-231 breast cancer cells, and that they inhibit the expression of genes which code for important regulators of cell migration and invasion in cancer tissues. In conclusion, GI and GII are AhR ligands that should be further investigated to determine their usefulness in cancer treatments.

Lycii fructus extract ameliorates hydrogen peroxide-induced cytotoxicity through indirect antioxidant action

Lycii Fructus is the dried ripe fruits of Lycium chinense and L. barbarum, which has long been used as a traditional food material in East Asia. The purpose of this study was to investigate the role of the indirect antioxidative action in the Lycii fructus extract (LFE)-induced cytoprotective effect in vitro. LFE significantly enhanced the expression of the drug-metabolizing enzyme genes and intracellular glutathione level in mouse hepatoma Hepa1c1c7 cells. LFE stimulated the nuclear translocation of aryl hydrocarbon receptor as well as nuclear factor (erythroid-derived 2)-like 2. The pretreatment of LFE for 24 h, but not for 30 min, completely inhibited the cytotoxic effect of hydrogen peroxide. Furthermore, chlorogenic acid, one of the main constituents of LFE, showed cytoprotection against hydrogen peroxide with the enhanced phase 2 enzyme gene expression. These results suggested that LFE exhibits a cytoprotective effect, possibly through the enhancement of the antioxidant gene expression.

abbreviations: LFE: Lycii Fructus extract; GSH: glutathione; NQO1: NAD(P)H:quinone oxidoreductase 1; HO-1: heme oxygenase-1; GCLC: glutamate-cysteine ligase, catalytic subunit; xCT: a component of cysteine/glutamate antiporter (cystine/glutamate exchanger); CYP1A1: cytochrome P450 1A1; GSH: glutathione; AhR: aryl hydrocarbon receptor; Nrf2: nuclear factor (erythroid-derived 2)-like 2; CGA: chlorogenic acid; RT-PCR: reverse transcription-polymerase chain reaction; DTT: dithiothreitol; PMSF: phenylmethylsulfonyl fluoride; ARE: antioxidant response element; XRE: xenobiotic responsive element.

Mechanisms of xenobiotic receptor activation: Direct vs. indirect

The so-called xenobiotic receptors (XRs) have functionally evolved into cellular sensors for both endogenous and exogenous stimuli by regulating the transcription of genes encoding drug-metabolizing enzymes and transporters, as well as those involving energy homeostasis, cell proliferation, and/or immune responses. Unlike prototypical steroid hormone receptors, XRs are activated through both direct ligand-binding and ligand-independent (indirect) mechanisms by a plethora of structurally unrelated chemicals. This review covers research literature that discusses direct vs. indirect activation of XRs. A particular focus is centered on the signaling control of the constitutive androstane receptor (CAR), the pregnane X receptor (PXR), and the aryl hydrocarbon receptor (AhR). We expect that this review will shed light on both the common and distinct mechanisms associated with activation of these three XRs. This article is part of a Special Issue entitled: Xenobiotic nuclear receptors: New Tricks for An Old Dog, edited by Dr. Wen Xie.