Constitutive androstane receptor weakens the induction of panaxytriol on CYP3A4 by repressing the activation of pregnane X receptor

Effects of polyphenols extracted from Keemun black tea on CYP450s activity and molecular mechanisms

Keemun black tea (KBT) is a luxurious traditional tea in China that has been commonly consumed because of its superior aroma and special taste. However, the risks remain unknown when KBT is used concomitantly with other drugs or food products. Therefore, we aimed to explore the effect of the tea polyphenols from KBT on the protein and mRNA levels of CYP450 and related mechanisms. The extraction of tea polyphenols from KBT and the content and component analysis of polyphenols were performed. A total of 24 female C57BL/6J mice were given tea polyphenols (0, 75, 150, 300 mg/kg) for 7 days, respectively. Liver tissues were collected 2 h after the last administration. The expression of Cyp3a11, Cyp1a2, Cyp2e1, Cyp2c37, and PXR mRNA was detected by real-time PCR, and the expression of Cyp3a11, Cyp1a2, Cyp2e1, Cyp2c37, and PXR protein was detected by Western blotting. A transient co-transfection reporter gene assay on HepG2 cells was also used to verify the role of PXR in regulating CYP3A4 expression. Our results showed that tea polyphenols from KBT significantly induced the expression of CYP 3A11 and PXR in general, inhibited the expression of Cyp1a2 and Cyp2e1 in general, and significantly inhibited the mRNA expression of Cyp2c37 but induced its protein expression. The reporter gene-transfected cells demonstrated that tea polyphenols could enhance the PXR-mediated transactivation of the CYP3A4 promoter via rifampicin-induction. Meanwhile, tea polyphenols could significantly accelerate CYP3A11/3A4 expression by activating the PXR-CYP3A4 pathway. In conclusion, KBT polyphenols could significantly affect the expression of various subtypes of the Cyp450 enzyme in mice livers via the PXR-CYP450 pathway, suggesting that metabolism-based interactions can occur when they are used in combination with medicines.

Panaxytriol upregulates CYP3A4 expression through the interaction between nuclear regulators and DNA response elements

ETHNOPHARMACOLOGICAL RELEVANCE

Cytochrome P3A4 (CYP3A4) is a crucial drug-metabolizing enzyme, and its expression is regulated by the pregnane X receptor (PXR), constitutive androstane receptor (CAR), steroid receptor coactivator 1 (SRC-1), and acetyltransferase P300. Panaxytriol is a naturally derived active substance extracted from the roots of Panax ginseng C. A. Mey. which is widely used clinically. Our previous studies have shown that panaxytriol induces CYP3A4 expression through PXR activation, which is antagonized by high CAR expression. However, the underlying mechanism remains unclear.

AIM OF THE STUDY

This study aimed to investigate the mechanism of panaxytriol in inducing CYP3A4 expression via interactions between nuclear regulators and DNA response elements.

MATERIALS AND METHODS

Immunoprecipitation technique was used to assess the binding levels of PXR and CAR with the coactivators SRC-1 and P300 in HepG2 and Huh-7 cells. Furthermore, chromatin immunoprecipitation assay was used to investigate the PXR and CAR interaction with the CYP3A4 promoter response element ER-6/DR-3.

RESULTS

The binding of PXR to SRC-1, P300, and the response elements ER-6 and DR-3 was improved with an increase in panaxytriol concentration (10-80 μM), and the binding affinity was further enhanced upon CAR silencing. The binding of CAR to SRC-1 and the response elements ER-6 and DR-3 was significantly higher at 80 μM panaxytriol, whereas no significant binding was observed between CAR and P300.

CONCLUSION

Panaxytriol promoted the recruitment of PXR to SRC-1 and P300, binding to ER-6 and DR-3, and upregulating CYP3A4 expression. Furthermore, an interactive dialogue regulatory mechanism between PXR and CAR was observed.

Transcription Factors and ncRNAs Associated with CYP3A Expression in Human Liver and Small Intestine Assessed with Weighted Gene Co-Expression Network Analysis

CYP3A4, CYP3A5, and CYP3A7, which are located in a multigene locus (CYP3A), play crucial roles in drug metabolism. To understand the highly variable hepatic expression of CYP3As, regulatory network analyses have focused on transcription factors (TFs). Since long non-coding RNAs (lncRNAs) likely contribute to such networks, we assessed the regulatory effects of both TFs and lncRNAs on CYP3A expression in the human liver and small intestine, main organs of CYP3A expression. Using weighted gene co-expression network analysis (WGCNA) of GTEx v8 RNA expression data and multiple stepwise regression analysis, we constructed TF-lncRNA-CYP3A co-expression networks. Multiple lncRNAs and TFs displayed robust associations with CYP3A expression that differed between liver and small intestines (LINC02499, HNF4A-AS1, AC027682.6, LOC102724153, and RP11-503C24.6), indicating that lncRNAs contribute to variance in CYP3A expression in both organs. Of these, HNF4A-AS1 had been experimentally demonstrated to affect CYP3A expression. Incorporating ncRNAs into CYP3A expression regulatory network revealed additional candidate TFs associated with CYP3A expression. These results serve as a guide for experimental studies on lncRNA-TF regulation of CYP3A expression in the liver and small intestines.

Research progress of ginseng in the treatment of gastrointestinal cancers

Cancer has become one of the major causes of human death. Several anticancer drugs are available; howeve their use and efficacy are limited by the toxic side effects and drug resistance caused by their continuous application. Many natural products have antitumor effects with low toxicity and fewer adverse effects. Moreover, they play an important role in enhancing the cytotoxicity of chemotherapeutic agents, reducing toxic side effects, and reversing chemoresistance. Consequently, natural drugs are being applied as potential therapeutic options in the field of antitumor treatment. As natural medicinal plants, some components of ginseng have been shown to have excellent efficacy and a good safety profile for cancer treatment. The pharmacological activities and possible mechanisms of action of ginseng have been identified. Its broad range of pharmacological activities includes antitumor, antibacterial, anti-inflammatory, antioxidant, anti-stress, anti-fibrotic, central nervous system modulating, cardioprotective, and immune-enhancing effects. Numerous studies have also shown that throuth multiple pathways, ginseng and its active ingredients exert antitumor effects on gastrointestinal (GI) tract tumors, such as esophageal, gastric, colorectal, liver, and pancreatic cancers. Herein, we introduced the main components of ginseng, including ginsenosides, polysaccharides, and sterols, etc., and reviewed the mechanism of action and research progress of ginseng in the treatment of various GI tumors. Futhermore, the pathways of action of the main components of ginseng are discussed in depth to promote the clinical development and application of ginseng in the field of anti-GI tumors.

Polyacetylenes in herbal medicine: A comprehensive review of its occurrence, pharmacology, toxicology, and pharmacokinetics (2014-2021)

Polyacetylenes are a kind of small active compounds with carbon-carbon triple bond with vast occurrence in plants. Polyacetylenes have attracted considerable attention owing to their diverse biofunctions like tumor suppression, immunity regulation, depression resistance and neural protection. The present review intends to reconstruct data concerning the occurrence, pharmacology, toxicology and pharmacokinetics of polyacetylenes from herbal medicine in a systematic and integrated way, with a view to backing up their curative potential and healthcare properties (2014-2021). The natural polyacetylene-related data were all acquired from the scientific search engines and databases that are globally recognized, such as PubMed, Web of Science, Elsevier, Google Scholar, ResearchGate, SciFinderⁿ and CNKI. A total of 183 polyacetylenes were summarized in this paper. Modern pharmacological studies indicated that polyacetylenes possess multiple biological activities including antitumor, immunomodulatory, neuroprotective, anti-depression, anti-obesity, hypoglycemic, antiviral, antibacterial, antifungal, hepatoprotective and renoprotective activities. As important bioactive components of herbal medicine, the pharmacological curative potential of polyacetylenes has been described against carcinomas, inflammatory responses, central nervous system, endocrine disorders and microbial infection in this review. While, further in-depth studies on the aspects of polyacetylenes for toxicity, pharmacokinetics, and molecular mechanisms are still limited, thereby intensive research and assessments should be performed.

Panaxytriol upregulates CYP3A4 expression based on the interaction of PXR, CAR, HSP90α, and RXRα

BACKGROUND

Cytochrome P450 3A4 (CYP3A4) is one of the most important drug-metabolizing enzymes in the human body, mainly existing in the liver, small intestine, and kidney. Panaxytriol is one of the key active components in red ginseng and Shenmai injection. Our previous study demonstrated that panaxytriol regulates CYP3A4 expression mainly by activating pregnancy X receptor (PXR). At a high concentration of panaxytriol (80 μM), the constitutive androstane receptor (CAR) is also involved in the upregulation of CYP3A4.

PURPOSE

This study investigated how the cofactors heat shock protein 90 alpha (HSP90α) and retinoid X receptor alpha (RXRα) interact with PXR and CAR to participate in the regulation of CYP3A4 by panaxytriol from the perspective of the PXR and CAR interaction.

METHODS

The mRNA and protein expressions of PXR, CAR, CYP3A4, RXRα, and HSP90α in HepG2 cells and Huh-7 cells were detected by quantitative PCR and western blot analysis, respectively. The binding levels of PXR and CAR to RXRα and HSP90α were determined by co-immunoprecipitation analysis. The nuclear translocation of PXR and RXRα into HepG2 cells and human (hCAR)-silenced HepG2 cells were measured by immunofluorescence.

RESULTS

In HepG2 cells and Huh-7 cells, panaxytriol (10-80 μM) upregulated CYP3A4 expression in a concentration-dependent manner by decreasing PXR binding to HSP90α and increasing PXR binding to RXRα. When hCAR was silenced, panaxytriol further enhanced CYP3A4 expression by strengthening PXR binding to RXRα, but it had no significant effect on the binding level of PXR and HSP90α. Additionally, at the high concentration of 80 μM panaxytriol, CAR binding to HSP90α was weakened while binding to RXRα was enhanced.

CONCLUSION

Panaxytriol can upregulate CYP3A4 expression by promoting PXR dissociation from HSP90α and enhancing PXR binding to RXRα in HepG2 cells and Huh-7 cells. At high concentrations of panaxytriol, CAR also participates in the induction of CYP3A4 through a similar mechanism. However, in general, CAR antagonizes PXR binding to RXRα, thereby attenuating the upregulation of CYP3A4 by panaxytriol.