Inhibitory effects of cytochrome P450 enzymes CYP1A2, CYP2A6, CYP2E1 and CYP3A4 by extracts and alkaloids of Gelsemium elegans roots

Systematic Review of Naturally Derived Substances That Act as Inhibitors of the Nicotine Metabolizing Enzyme Cytochrome P450 2A6

Tobacco smoking has been highlighted as a major health challenge in modern societies. Despite not causing death directly, smoking has been associated with several health issues, such as cardiovascular diseases, respiratory disorders, and several cancer types. Moreover, exposure to nicotine during pregnancy has been associated with adverse neurological disorders in babies. Nicotine Replacement Therapy (NRT) is the most common strategy employed for smoking cessation, but despite its widespread use, NRT presents with low success and adherence rates. This is attributed partially to the rate of nicotine metabolism by cytochrome P450 2A6 (CYP2A6) in each individual. Nicotine addiction is correlated with the high rate of its metabolism, and thus, novel strategies need to be implemented in NRT protocols. Naturally derived products are a cost-efficient and rich source for potential inhibitors, with the main advantages being their abundance and ease of isolation. This systematic review aims to summarize the natural products that have been identified as CYP2A6 inhibitors, validated through in vitro and/or in vivo assays, and could be implemented as nicotine metabolism inhibitors. The scope is to present the different compounds and highlight their possible implementation in NRT strategies. Additionally, this information would provide valuable insight regarding CYP2A6 inhibitors, that can be utilized in drug development via the use of in silico methodologies and machine-learning models to identify new potential lead compounds for optimization and implementation in NRT regimes.

In Vitro Investigations into the Potential Drug Interactions of Pseudoginsenoside DQ Mediated by Cytochrome P450 and Human Drug Transporters

Pseudoginsenoside DQ (PDQ), an ocotillol-type ginsenoside, is synthesized with protopanaxadiol through oxidative cyclization. PDQ exhibits good anti-arrhythmia activity. However, the inhibitory effect of PDQ on the cytochrome 450 (CYP450) enzymes and major drug transporters is still unclear. Inhibition of CYP450 and drug transporters may affect the efficacy of the drugs being used together with PDQ. These potential drug-drug interactions (DDIs) are essential for the clinical usage of drugs. In this study, we investigated the inhibitory effect of PDQ on seven CYP450 enzymes and seven drug transporters with in vitro models. PDQ has a significant inhibitory effect on CYP2C19 and P-glycoprotein (P-gp) with a half-inhibitory concentration (IC50) of 0.698 and 0.41 μM, respectively. The inhibition of CYP3A4 and breast cancer-resistant protein (BCRP) is less potent, with IC50 equal to 2.02-6.79 and 1.08 μM, respectively.

Comparative study of the interaction mechanism of astilbin, isoastilbin, and neoastilbin with CYP3A4

The interactions of human CYP3A4 with three selected isomer flavonoids, such as astilbin, isoastilbin and neoastilbin, were clarified using spectral analysis, molecular docking, and molecular dynamics simulation. During binding with the three flavonoids, the intrinsic fluorescence of CYP3A4 was statically quenched in static mode with nonradiative energy conversion. The fluorescence and ultraviolet/visible (UV/vis) data revealed that the three flavonoids had a moderate and stronger binding affinity with CYP3A4 due to the order of the Ka1 and Ka2 values ranging from 104 to 105  L·mol-1 . In addition, astilbin had the highest affinity with CYP3A4, then isoastilbin and neoastilbin, at the three experimental temperatures. Multispectral analysis confirmed that binding of the three flavonoids resulted in clear changes in the secondary structure of CYP3A4. It was found from fluorescence, UV/vis and molecular docking analyses that these three flavonoids strongly bound to CYP3A4 by means of hydrogen bonds and van der Waals forces. The key amino acids around the binding site were also elucidated. Furthermore, the stabilities of the three CYP3A4 complexes were evaluated using molecular dynamics simulation.

Twenty-four hours of Thiamethoxam: In vivo and molecular dynamics simulation study on the toxicokinetic and underlying mechanisms in quails (Coturnix japonica)

Neonicotinoids is the most widely used insecticide, its contamination has led to sustained bird population declines. However, the toxicokinetic and underlying mechanisms of neonicotinoid toxicity in birds are largely unknown. Thiamethoxam (TMX), as a representative neonicotinoid insecticide, is now widely detected in most environmental medium and animal bodies. In this study, 5 mg/kg body weight TMX (potential environmental intake level) were orally administrated to male Japanese quails (Coturnix japonica). We found a rapid absorption, distribution, metabolism and elimination of TMX in quails in a period of 24 h, with the main metabolite, clothianidin (CLO), being extensively distributed and rapidly eliminated from tissues as well. The maximum plasm concentration of CLO was consistent with wild birds. Metabolomics analysis and followed determination of liver enzymes mRNA expression indicated the rapid metabolism was mediated mainly by CYPs and GSTs that involved riboflavin metabolism and glutathione metabolism pathways upon TMX exposure. Molecular dynamic simulation showed the strongest binding interaction in quail CYP2H1-TMX and CYP3A12-CLO complexes among a set of CYPs-substrate. The present study elucidated toxicokinetic and underlying metabolic mechanisms of TMX in quails at environmentally-relevant concentration, the findings would facilitate the understanding of potential risks of TMX and its metabolites to birds.

Potential Effects of Ibuprofen, Remdesivir and Omeprazole on Dexamethasone Metabolism in Control Sprague Dawley Male Rat Liver Microsomes (Drugs Often Used Together Alongside COVID-19 Treatment)

The role of individual cytochrome P450 (CYPs) responsible for the drug metabolism can be determined through their chemical inhibition. During the pandemic, dexamethasone and remdesivir with omeprazole were used for the treatment of COVID-19, while Ibuprofen was taken to treat the symptoms of fever and headache. This study aimed to examine the potency of ibuprofen remdesivir, and omeprazole as inhibitors of cytochrome P450s using rat liver microsomes in vitro. Dexamethasone a corticosteroid, sometimes used to reduce the body’s immune response in the treatment of COVID-19, was used as a probe substrate and the three inhibitors were added to the incubation system at different concentrations and analysed by a validated High Performance Liquid Chromatography (HPLC) method. The CYP3A2 isoenzyme is responsible for dexamethasone metabolism in vitro. The results showed that ibuprofen acts as a non-competitive inhibitor for CYP3A2 activity with K_i = 224.981 ± 1.854 µM and IC₅₀ = 230.552 ± 2.020 µM, although remdesivir showed a mixed inhibition pattern with a K_i = 22.504 ± 0.008 µM and IC₅₀ = 45.007 ± 0.016 µM. Additionally, omeprazole uncompetitively inhibits dexamethasone metabolism by the CYP3A2 enzyme activity with a K_i = 39.175 ± 0.230 µM and IC₅₀ = 78.351 ± 0.460 µM. These results suggest that the tested inhibitors would not exert a significant effect on the CYP3A2 isoenzyme responsible for the co-administered dexamethasone drug’s metabolism in vivo.

Sempervirine Inhibits Proliferation and Promotes Apoptosis by Regulating Wnt/β-Catenin Pathway in Human Hepatocellular Carcinoma

Gelsemium elegans (G. elegans) Benth., recognized as a toxic plant, has been used as traditional Chinese medicine for the treatment of neuropathic pain and cancer for many years. In the present study, we aim to obtain the anti-tumor effects of alkaloids of G. elegans and their active components in hepatocellular carcinoma (HCC) and the potential mechanism was also further investigated. We demonstrated that sempervirine induced HCC cells apoptosis and the apoptosis was associated with cell cycle arrest during the G₁ phase, up-regulation of p53 and down-regulation of cyclin D1, cyclin B1 and CDK2. Furthermore, sempervirine inhibited HCC tumor growth and enhances the anti-tumor effect of sorafenib in vivo. In addition, inactivation of Wnt/β-catenin pathway was found to be involved in sempervirine-induced HCC proliferation. The present study demonstrated that alkaloids of G. elegans were a valuable source of active compounds with anti-tumor activity. Our findings justified that the active compound sempervirine inhibited proliferation and induced apoptosis in HCC by regulating Wnt/β-catenin pathway.

Hepatotoxicity of decabromodiphenyl ethane (DBDPE) and decabromodiphenyl ether (BDE-209) in 28-day exposed Sprague-Dawley rats

Decabromodiphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are heavily used in various industrial products as flame retardant. They have been found to be persistent in the environment and have adverse health effects in humans. Although some former studies have reported toxic effects of BDE-209, the study of DBDPE's toxic effects is still in its infancy, and the effects of DBDPE on hepatotoxicity are also unclear. This study aimed to evaluate and compare the hepatotoxicity induced by BDE-209 and DBDPE using a rat model. Sprague-Dawley rats were administered DBDPE or BDE-209 (5, 50, 500 mg/kg bodyweight) intragastrically once a day for 28 days. Twenty-four hours after the end of treatment, the rats were sacrificed, and body liver weight, blood biochemical parameters, liver pathology, oxidative stress, inflammation, pregnane X receptor (PXR), constitutive androstane receptor (CAR), and changes in cytochrome P450 (CYP3A) enzymes were measured. Our results showed that both BDE-209 and DBDPE could cause liver morphological changes, induce oxidative stress, increase γ-glutamyl transferase and glucose levels in serum, and down-regulate PXR, CAR, and CYP3A expression. In addition, BDE-209 was found to increase liver weight and the ratio of liver/body weight, lead to elevated total bilirubin and indirect bilirubin levels in serum, and induce inflammation. The present study indicated that BDE-209 and DBDPE may interfere with normal metabolism in rats through oxidative stress and inflammation, which inhibit PXR and CAR to induce the expression of CYP3A enzymes, and finally produce hepatotoxic effects and cause liver damage in rats. Comparatively, our results show that the damage caused by BDE-209 was more serious than that caused by DBDPE.

Validation of an HPLC Method for the Simultaneous Quantification of Metabolic Reaction Products Catalysed by CYP2E1 Enzyme Activity: Inhibitory Effect of Cytochrome P450 Enzyme CYP2E1 by Salicylic Acid in Rat Liver Microsomes

Inhibition of cytochrome P450 (CYP) alters the pharmacokinetic parameters of the drug and causes drug–drug interactions. Salicylic acid been used for the treatment of colorectal cancer (CRC) and chemoprevention in recent decades. Thus, the aim of this study was to examine the in vitro inhibitory effect of salicylic acid on CYP2E1 activity in rat liver microsomes (RLMs) using high-performance liquid chromatography (HPLC). High-performance liquid chromatography analysis of a CYP2E1 assay was developed on a reversed phase C₁₈ column (SUPELCO 25 cm × 4.6 mm × 5 µm) at 282 nm using 60% H₂O, 25% acetonitrile, and 15% methanol as mobile phase. The CYP2E1 assay showed a good linearity (R² > 0.999), good reproducibility, intra- and inter-day precision (<15%), acceptable recovery and accuracy (80–120%), and low detection (4.972 µM and 1.997 µM) and quantitation limit values (15.068 µM and 6.052 µM), for chlorzoxazone and 6-hydroxychlorzoxazone, respectively. Salicylic acid acts as a mixed inhibitor (competitive and non-competitive inhibition), with K_i (inhibition constant) = 83.56 ± 2.730 µM and concentration of inhibitor causing 50% inhibition of original enzyme activity (IC₅₀) exceeding 100 µM (IC₅₀ = 167.12 ± 5.460 µM) for CYP2E1 enzyme activity. Salicylic acid in rats would have both low and high potential to cause toxicity and drug interactions with other drugs that are substrates for CYP2E1.

Construction and Analysis of circRNA-miRNA-mRNA Molecular Regulatory Networks During Herba Gelsemium elegans Intoxication

Gelsemium elegans (Gardner & Champ.) Benth. (GE) has therapeutic effects for pain and malignant tumors but also has high toxicity. Its mechanism of toxicity has not yet been fully clarified, thus limiting its application. Meanwhile, evidence has shown that circRNAs are closely related to the progression of disease. However, very little is known about their expression profiles during intoxication. In this paper, circRNA/mRNA microarrays were respectively performed to detect their expression profiles in mice with acute GE intoxication versus normal controls. CircRNAs were verified by qRT-PCR in subsequent experiments. A regulation pattern of circRNA→miRNA→mRNA was deduced based on intersection analysis of circRNA/mRNA microarrays. The results revealed circRNAs (143) and mRNAs (1,921) were significantly expressed during intoxication. Most of the circRNAs were exonic, and most distributions in chromosomes were transcribed from chr1, chr2, chr7, and chr11. Furthermore, dysregulated expression of mmu-circRNA-013703 and mmu-circRNA-010022 was verified. Then a circRNA-targeted miRNA-mRNA co-expression network was constructed. The network map contained 2 circRNAs, 52 miRNAs, and 752 mRNAs. GO & KEGG analysis further predicted that mmu-circRNA-013703 and mmu-circRNA-010022 may participate in cellular survival/demise-related, neuron/synapse-related, and channel-related pathways. Based on functional modules analysis, a new network was formed, in which mmu-circRNA-013703 VS mmu-miR-361-3p linked to most mRNAs. Most of these mRNAs were known to be involved in the aforementioned functional module. This indicated that mmu-circRNA-013703 functioned as a sponge of miRNAs to regulate the more comprehensive circRNA-miRNA-mRNA co-expression network. Our approach revealed a landscape of dysregulated circRNA-miRNA-mRNA and may be valuable for the identification of new biomarkers during intoxication.

CYP3A4/5 mediates the metabolic detoxification of humantenmine, a highly toxic alkaloid from Gelsemium elegans Benth

Gelsemium elegans Benth., a well-known toxic herbal plant, is widely used to treat rheumatic arthritis, inflammation and other diseases. Gelsemium contains humantenmine (HMT), which is an important bioactive and toxic alkaloid. Cytochrome P450 enzymes (CYPs) play important roles in the elimination and detoxification of exogenous substances. This study aimed to investigate the roles of CYPs in the metabolism and detoxification of HMT. First, metabolic studies were performed in vitro by using human liver microsomes, selective chemical inhibitors and recombinant human CYPs. Results indicated that four metabolites, including hydroxylation and oxidation metabolites, were found in human liver microsomes and identified based on their high-resolution mass spectrum. The isoform responsible for HMT metabolism was mainly CYP3A4/5. Second, the toxicity of HMT on L02 cells in the presence of the nicotinamide adenine dinucleotide phosphate system (NADPH) was significantly less than that without NADPH system. A CYP3A4/5 activity inhibition model was established by intraperitoneally injecting ketoconazole in mice and used to evaluate the role of CYP3A4/5 in HMT detoxification. In this model, the 14-day survival rate of the mice decreased to 17% after they were intragastrically treated with HMT, along with hepatic injury and increasing alanine aminotransferase (ALT) /aspartate aminotransferase (AST) levels. Overall, CYP3A4/5 mediated the metabolism and detoxification of HMT.

Gene Discovery in Gelsemium Highlights Conserved Gene Clusters in Monoterpene Indole Alkaloid Biosynthesis

Genome mining is a routine technique in microbes for discovering biosynthetic pathways. In plants, however, genomic information is not commonly used to identify novel biosynthesis genes. Here, we present the genome of the medicinal plant and oxindole monoterpene indole alkaloid (MIA) producer Gelsemium sempervirens (Gelsemiaceae). A gene cluster from Catharanthus roseus, which is utilized at least six enzymatic steps downstream from the last common intermediate shared between the two plant alkaloid types, is found in G. sempervirens, although the corresponding enzymes act on entirely different substrates. This study provides insights into the common genomic context of MIA pathways and is an important milestone in the further elucidation of the Gelsemium oxindole alkaloid pathway.

Potential Metabolic Drug-Drug Interaction of Citrus aurantium L. (Rutaceae) Evaluating by Its Effect on 3 CYP450

Aim:Fructus aurantii (FA) is widely used in clinic as an expectorant and digestant herb in traditional Chinese medicine and proven to have a variety of pharmacological functions. FA is close to grapefruit either by botanical taxonomy or by their same components (flavonoids, etc.) and grapefruit has been proven to cause drug-drug interaction when co-administrated with CYP3A4 substrates. Besides, FA contains many compounds, such as flavonoids, which have been reported to impact the expressions of CYP450. However, the effect of FA on CYP450, whose change may affect drug safety and clinical efficacy attributed to drug-drug interaction, still remains unknown. Methods: The protein, mRNA expression and enzyme activity of CYP1A2, CYP3A4, and CYP2E1 in rat were determined by Western Blotting, RT-PCR method, the cocktail method, respectively, after orally administration of FA in succession for 7 days. CYP1A2, CYP3A4, and CYP2E1 mRNA expression were investigated in HepG2 cells following FA-medicated serum incubation for 24 h. Results: In rat, compared to the control group, CYP1A2, CYP3A4 protein, and mRNA expression were significantly induced consistent with the corresponding CYP activities; the protein expression of CYP2E1 was significantly upregulated, while the corresponding mRNA expression and enzyme activity showed no significant change. In HepG2 cells, compared to the control group, the mRNA expression of CYP1A2 and CYP3A4 was up-regulated statistically while CYP2E1 mRNA expression was not significantly induced or inhibited. Conclusion: FA may be a potential slight inducer of CYP1A2 and CYP3A4 and is unlikely to impact CYP2E1 until clinical researches are conducted.

In Vitro Antidiabetic Activity and Mechanism of Action of Brachylaena elliptica (Thunb.) DC

In South Africa, the number of people suffering from diabetes is believed to be rising steadily and the current antidiabetic therapies are frequently reported to have adverse side effects. Ethnomedicinal plant use has shown promise for the development of cheaper, cost-effective antidiabetic agents with fewer side effects. The aim of this study was to investigate the antidiabetic activity and mechanism of action of aqueous leaf extract prepared from Brachylaena elliptica. The potential of the extract for cytotoxicity was evaluated using MTT assay in HepG2 cells. The effects of the plant extract on glucose utilization in HepG2 cells and L6 myotubes, triglyceride accumulation in 3T3-L1, INS-1 proliferation, glucose metabolism in INS-1 cells, and NO production in RAW macrophages were also investigated using cell culture procedures. The inhibitory effects of the extract on the activities of different enzymes including alpha-amylase, alpha-glucosidase, pancreatic lipase, dipeptidyl peptidase IV (DPP-IV), collagenase, and CYP3A4 enzymes were evaluated. The extract also tested against protein glycation using standard published procedure. The plant extract displayed low level of toxicity, where both concentrations tested did not induce 50% cell death. The extract caused a significant increase in glucose uptake in HepG2 liver cells, with efficacy significantly higher than the positive control, berberine. The crude extract also displayed no significant effect on muscle glucose uptake, triglyceride accumulation in 3T3-L1, glucose metabolism in INS-1 cells, alpha-amylase, alpha-glucosidase, DPP-IV, lipase, protein glycation, and collagenase compared to the respective positive controls. The extract displayed a proliferative effect on INS-1 cells at 25 μg/ml when compared to the negative control. The plant also produced a concentration-dependent reduction in NO production in RAW macrophages and also demonstrated weak significant inhibition on CYP3A4 activity. The findings provide evidence that B. elliptica possess antidiabetic activity and appear to exact its hypoglycemic effect independent of insulin.

Herba Gelsemii elegantis is detoxified by ramulus et folium Mussaendae pubescentis extract by modulating hepatic cytochrome P450 and glutathione S-transferase enzymes in rats

Herba Gelsemii elegantis (GE) has been frequently used as a Chinese folk medicine but has high acute toxicity. In Traditional Chinese Medicine, it may be detoxified by Ramulus et Folium Mussaendae pubescentis (MP), but the detoxification mechanism has remained elusive. The present study aimed to evaluate the detoxification mechanisms by which MP modulates the effect of GE in rats, including the inhibition of hepatic cytochrome P (CYP)450 and glutathione S-transferase (GST) enzymes. Male Sprague Dawley rats were orally administered GE at three doses (0.36, 0.43 or 0.54 g/kg) alone and, at the highest dose, in combination with MP (21.6 g/kg) every day for 7 consecutive days. The control group of animals received the same volume of saline. The mRNA and protein expression of hepatic CYPs representative of two subfamilies (CYP2E1 and CYP1A2) were separately assessed by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), western blot and immunohistochemistry assays. The mRNA and protein expression as well as enzyme activity of hepatic GST were assessed by RT-qPCR, western blot and colorimetric assays, respectively. The results indicated that GE significantly inhibited CYP2E1 mRNA and protein expression in a dose-dependent manner. Co-administration of MP increased CYP2E1 mRNA and protein expression as compared with the high GE dose alone. Cells expressing CYP2E1, located around the hepatic vascular plexus under a clear background, were identified by immunohistochemical staining. The results for CYP1A2 were similar to those for CYP2E1. At all concentrations used, GE significantly inhibited GST mu 1 (GSTm1) mRNA and protein expression in a dose-dependent manner, as compared with the control. Combination of GE and MP increased the mRNA and protein expression of GSTm1 as compared with the high dose of GE. However, the differences in GST-pi mRNA and protein expression between the GE and GE + MP groups were not significant. Of note, rats co-treated with MP were significantly protected from the decrease in GST activity produced by GE. The present study indicated that co-administration of GE and MP upregulated the activities of CYP450 and GST enzymes when compared with GE alone. This modulation may explain for the effect of MP in reducing the acute toxicity of GE.

Effect of Gelsemium elegans and Mussaenda pubescens, the Components of a Detoxification Herbal Formula, on Disturbance of the Intestinal Absorptions of Indole Alkaloids in Caco-2 Cells

Gelsemium elegans (GE) is a kind of well-known toxic plant. It can be detoxified by Mussaenda pubescens (MP), but the detoxification mechanism is still unclear. Thus, a detoxification herbal formula (GM) comprising GE and MP was derived. The Caco-2 cells monolayer model was used to evaluate GM effects on transporting six kinds of indole alkaloids of GE. The bidirectional transport studies demonstrated that absorbance percentage of indole alkaloids in GE increased linearly over time. But in GM, Papp (AP→BL) values of the most toxic members, gelsenicine, humantenidine, and gelsevirine, were lower than that of Papp (BL→AP) (P < 0.05). The prominent analgesic effect members, gelsemine and koumine, were approximately 1.00 in γ values. Nowhere was this increasing efflux more pronounced than in the case of indole alkaloids with N-O structure. In the presence of verapamil, the γ values of humantenidine, gelsenicine, gelsevirine, and humantenine were decreased by 43.69, 41.42, 36.00, and 8.90 percent, respectively. The γ values in presence of ciclosporin were homologous with a decrease of 42.32, 40.59, 34.00, and 15.07 percent. It suggested that the efflux transport was affected by transporters. Taken together, due to the efflux transporters participation, the increasing efflux of indole alkaloids from GM was found in Caco-2 cells.

The potential of Epimedium koreanum Nakai for herb–drug interaction

Objectives

This study aims to investigate potential herb–drug interactions (HDI) of Epimedium koreanum Nakai.

Methods

Human liver microsomes (HLMs) were used to determine the enzyme kinetics of the major human cytochrome P450s (CYPs). Inducible potential of E. koreanum on CYP1A2, 2B6, 2C19 and 3A4 activities of human primary hepatocytes was also examined.

Key findings

Ethanol extract of E. koreanum showed direct inhibitory potency for CYP1A2 (IC50 = 121.8 μg/ml, Ki = 110.7 ± 36.8 μg/ml) and CYP2B6 (IC50 = 59.5 μg/ml, Ki = 18.1 ± 2.9 μg/ml). For CYP2C9, 2C19, 2D6, 2E1 and 3A4, only negligible effect was observed. Time-dependent (irreversible) inhibition by E. koreanum was observed for CYP1A2 (KI = 32.9 ± 18.4 μg/ml, kinact = 0.031 ± 0.006 min−1). However, ethanol extract of E. koreanum (1.5–150 μg/ml) did not change the activity or mRNA expressions for CYP3A4, 1A2, 2C19 and 2B6.

Conclusions

The ethanol extract of E. koreanum is not likely to cause HDI via inducing the major human CYPs. But the potential for interactions between E. koreanum extract and substrates of CYP1A2 or 2B6 cannot be overlooked.

Development of an IgY Antibody-Based Immunoassay for the Screening of the CYP2E1 Inhibitor/Enhancer from Herbal Medicines

Cytochrome P450 (CYP) 2E1 is an important enzyme involved in the metabolism of many endogenous and exogenous compounds. It is essential to evaluate the expression of CYP2E1 in the studies of drug–drug interactions and the screening of drugs, natural products, and foodstuffs. The present work is a feasibility study on the development of immunoassays using a specific and sensitive chicken-sourced anti-CYP2E1 IgY antibody. Cloning, expression, and purification of a recombinant CYP2E1 (mice origin) protein were carried out. Anti-CYP2E1 IgY antibodies were generated by immunizing white Leghorn chickens with purified recombinant CYP2E1 protein and were purified by immune affinity chromatography. The IgY titer attained a peak level (≥1:128,000) after the fifth booster injection. For evaluation of the expression of CYP2E1 in different herbal treatment samples, the mice were treated by oral gavage for 3 days with alcohol (50% 15 mL/kg), acetaminophen (APAP, 300 mg/kg), Cornus officinalis extract (100 mg/kg), Alhagi-honey extract (100 mg/kg), Apocynum venetum extract (100 mg/kg), hyperoside (50 mg/kg), isoquercetin (50 mg/kg), 4-hydroxyphenylacetic acid (50 mg/kg), 3-hydroxyphenylacetic acid (50 mg/kg), and 3,4-hydroxyphenylacetic acid (50 mg/kg). The expression of CYP2E1 was determined by Western blot analysis, immunohistochemistry, ELISA, and immunomagnetic beads (IMBs) using anti-CYP2E1 IgY in liver tissue. The results showed that C. officinalis extract, Alhagi-honey extract, A. venetum extract, hyperoside, isoquercetin, and their xenobiotics 4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and 3,4-hydroxyphenylacetic acid significantly decreased CYP2E1 levels. Alcohol and APAP treatments significantly increased CYP2E1 levels as analyzed with Western blot analysis, immunohistochemistry, and ELISA. The IMB method is suitable for large-scale screening, and it is a rapid screening (20 min) that uses a portable magnet and has no professional requirements for the operator, which makes it useful for on-the-spot analysis. Considering these results, the anti-CYP2E1 IgY could be applied as a novel research tool in screening for the CYP2E1 inhibitor/enhancer.

Development of GC-MS based cytochrome P450 assay for the investigation of multi-herb interaction

As drug interactions with cytochrome P450 enzymes become increasingly important in the field of drug discovery, a high-throughput screening method for analysing the effects of a drug is needed. We have developed a simple and rapid simultaneous analytical method using a cocktail approach for measuring the activities of seven cytochrome P450 enzymes (CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4). Human liver microsomes were used as a source for the seven cytochrome P450 enzymes, and a gas chromatography-mass spectrometry (GC-MS) was used for analysing their activities. Kinetic studies and inhibition assays of CYP enzymes were performed using known substrates and inhibitors for validating and comparing the reaction rates and time-dependent activities between methods using each substrate versus a method using a cocktail solution. The optimized cocktail method was successfully applied to evaluate the effects of the decoction of Socheongryong-tang (SCRT) on cytochrome P450 enzymes. Our cocktail method provides a simultaneous high-throughput activity assay using GC-MS for the first time. This method is applicable for analysing the drug interactions of various plant-derived mixtures.

A Potential Mechanism for the Anti-Apoptotic Property of Koumine Involving Mitochondrial Pathway in LPS-Mediated RAW 264.7 Macrophages

Koumine is a kind of alkaloid extracted from Gelsemium elegans (G. elegans). Benth, which has shown promise as an anti-tumor, anxiolytic, and analgesic agent. In our present study, the effect of koumine on lipopolysaccharide (LPS)-mediated RAW 264.7 cell apoptosis was evaluated. MTT assays showed that koumine obviously increased cell viability in LPS-mediated RAW 264.7 macrophages. Preincubation with koumine ameliorated LPS-medicated apoptosis by decreasing reactive oxygen species (ROS) production, which resulted in a significant decrease in the levels of nitric oxide (NO) and inducible nitric oxide synthase (iNOS). In addition, koumine-pretreated RAW 264.7 macrophages exhibited reduction of LPS-induced levels of TNF-α, IL-1β, and IL-6 mRNA. Furthermore, pretreatment with koumine suppressed LPS-mediated p53 activation, loss of mitochondrial membrane potential, caspase-3 activation, decrease of Bcl-2 expression, and elevation of Bax and caspase-3 expressions, suggesting that koumine might act directly on RAW 264.7 cells to inhibit LPS-induced apoptosis. It seems as though the mechanism that koumine possesses is the anti-apoptotic effect mediated by suppressing production of ROS, activation of p53, and mitochondrial apoptotic pathways in RAW 264 cells. Koumine could potentially serve as a protective effect against LPS-induced apoptosis.

Flavokawain A inhibits Cytochrome P450 in in vitro metabolic and inhibitory investigations

ETHNOPHARMACOLOGICAL RELEVANCE

Flavokawain A, the major chalcone in kava extracts, was served as beverages for informal social occasions and traditional ceremonials in most South Pacific islands. It exhibited strong antiproliferative and apoptotic effects against human prostate and urinary bladder cancer cells.

AIM OF THE STUDY

The current study was purposed to investigate the interaction between Flavokawain A and Cytochrome P450, including the inhibitory effects of Flavokawain A on predominant CYP450 isotypes and further clarified the inhibitory mechanism of FKA on CYP450 enzymes. Besides, study about identifying the key CYP450 isotypes responsible for the metabolism of FKA was also performed.

MATERIALS AND METHODS

In this study, probe-based assays with rat liver microsome system were used to characterize the inhibitory effects of FKA. Molecular docking study was performed to further explore the binding site of FKA on CYP450 isoforms. In addition, chemical inhibition experiments using specific inhibitors (a-naphthoflavone, quinidine, sulfamethoxazde, ketoconazole, omeprazole) were performed to clarify the individual CYP450 isoform that are responsible for the metabolism of FKA.

RESULTS

FKA showed significant inhibition on CYP1A2, CYP2D1, CYP2C6 and CYP3A2 activities with IC50 values of 102.23, 20.39, 69.95, 60.22μmol/L, respectively. The inhibition model was competitive, mixed-inhibition, uncompetitive, and noncompetitive for CYP1A2, CYP2D1, CYP2C6 and CYP3A2 enzymes. Molecular docking study indicated the ligand-binding conformation of FKA in the active site of CYP450 isoforms. The chemical inhibition experiments showed that the metabolic clearance rate of Flavokawain A decreased to 19.84%, 50.38%, and 67.02% of the control in the presence of ketoconazole, sulfamethoxazde and a-naphthoflavone.

CONCLUSION

The study showed that Flavokawain A has varying inhibitory effect on CYP450 enzymes and CYP3A2 was the principal CYP isoform contributing to the metabolism of Flavokawain A. Besides, CYP2C6 and CYP1A2 isoforms also play important roles in the metabolism of FKA. Our results provided a basis for better understanding the biotransformation of FKA and prediction of drug-drug interaction of FKA.

Aconitum carmichaelii protects against acetaminophen-induced hepatotoxicity via B-cell lymphoma-2 protein-mediated inhibition of mitochondrial dysfunction

We previously reported the clinical profile of processed Aconitum carmichaelii (AC, Aconibal(®)), which included inhibition of cytochrome P450 (CYP) 2E1 activity in healthy male adults. CYP2E1 is recognized as the enzyme that initiates the cascade of events leading to acetaminophen (APAP)-induced toxicity. However, no studies have characterized its role in APAP-induced hepatic injury. Here, we investigated the protective effects of AC on APAP-induced hepatotoxicity via mitochondrial dysfunction. AC (5-500 μg/mL) significantly inhibited APAP-induced reduction of glutathione. In addition, AC decreased mitochondrial membrane potential (Δψm) and B-cell lymphoma 2 (Bcl-2)-associated X protein levels (% change 46.63) in mitochondria. Moreover, it increased Bcl-2 (% change 55.39) and cytochrome C levels (% change 38.33) in mitochondria, measured using immunofluorescence or a commercial kit. Furthermore, cell membrane integrity was preserved and nuclear fragmentation inhibited by AC. These results demonstrate that AC protects hepatocytes against APAP-induced toxicity by inhibiting mitochondrial dysfunction.

Effect of an ethanol extract of Descurainia sophia seeds on Phase I and II drug metabolizing enzymes and P-glycoprotein activity in vitro

Background

Descurainia sophia seeds have a variety of pharmacological functions and been widely used in traditional folk medicine. However, their effects on human drug metabolizing enzyme (DME) activities have not been elucidated. The present study investigated the inhibitory effects of an ethanol extract of D. sophia seeds (EEDS) on human Phase I/II (DMEs) and P-glycoprotein (p-gp) in vitro.

Methods

The enzyme activities of human Phase I (cytochrome P450s, CYPs), Phase II (uridine diphosphate glucuronosyltransferases, UGTs) DMEs, and the drug transporter P-gp were determined in the presence of various concentrations of EEDS using commercially available luminogenic assay systems. The mode of enzyme inhibition and the inhibitory constant (K_i) value of EEDS were graphically determined with Lineweaver-Burk double reciprocal plots and secondary plots, respectively.

Results

The enzyme activity assays showed that EEDS moderately inhibited the CYP1A2, CYP2C9, and CYP2C19 isoforms with half maximal inhibitory concentrations (IC₅₀) of 47.3, 25.8, and 38.7 μg/mL, respectively. Graphical analyses with Lineweaver-Burk double reciprocal plots and secondary plots indicated that EEDS competitively inhibited CYP2C9 with a K_i value of 19.8 μg/mL; however, it inhibited CYP2C9 and CYP2C19 in a mixed mode with K_i values of 5.2, and 11.9 μg/mL, respectively. Other Phase I (CYP2C8, CYP2D6, and CYP3A4) and Phase II (UGT1A1 and UGT2B7) enzymes as well as P-gp were weakly or negligibly affected by EEDS with concentrations up to 500 μg/mL.

Conclusions

EEDS is a selective inhibitor of CYP1A2, CYP2C9, and CYP2C19 with moderate enzymatic inhibition. Clinically, full consideration should be given to a potential toxic adverse effect from a herb-drug interaction when drugs that are particularly susceptible to CYP1A2, CYP2C9, or CYP2C19-mediated metabolism are taken together with EEDS. Characterization of metabolic profiles of specific herbal drugs could help consumers and medical specialists to use them safely as a complementary and alternative medicine.