Evaluation of the inhibition potential of plumbagin against cytochrome P450 using LC-MS/MS and cocktail approach

Investigation of cytochrome P450 inhibitory properties of deoxyshikonin, a bioactive compound from Lithospermum erythrorhizon Sieb. et Zucc

Deoxyshikonin, a natural naphthoquinone compound extracted from Lithospermum erythrorhizon Sieb. et Zucc (Boraginaceae), has a wide range of pharmacological activities, including anti-tumor, anti-bacterial and wound healing effects. However, the inhibitory effect of deoxyshikonin on cytochrome P450 (CYP) remains unclear. This study investigated the potential inhibitory effects of deoxyshikonin on CYP1A2, 2B1/6, 2C9/11, 2D1/6, 2E1 and 3A2/4 enzymes in human and rat liver microsomes (HLMs and RLMs) by the cocktail approach in vitro. The single-point inactivation experiment showed that deoxyshikonin presented no time-dependent inhibition on CYP activities in HLMs and RLMs. Enzyme inhibition kinetics indicated that in HLMs, deoxyshikonin was not only a competitive inhibitor of CYP1A2 and 2E1, but also a mixed inhibitor of CYP2B6, 2C9, 2D6 and 3A4, with Ki of 2.21, 1.78, 1.68, 0.20, 4.08 and 0.44 μM, respectively. In RLMs, deoxyshikonin not only competitively inhibited CYP2B1 and 2E1, but also exhibited mixed inhibition on CYP1A2, 2C11, 2D1 and 3A2, with Ki values of no more than 18.66 μM. In conclusion, due to the low Ki values of deoxythiokonin on CYP enzymes in HLMs, this may lead to drug-drug interactions (DDI) and potential toxicity.

Pharmacokinetics of Herb-Drug Interactions of Plumbagin and Tazemetostat in Rats by UPLC-MS/MS

Objective

A sensitive and rapid UPLC-MS/MS method for determination of tazemetostat in rat plasma was developed, and the pharmacokinetics of herb-drug interactions (HDIs) of plumbagin (PLB) and tazemetostat was investigated.

Methods

After the rat plasma samples were precipitated by acetonitrile, tazemetostat and verubecestat (ISTD) were detected. Gradient elution was performed with 0.1% formic acid and acetonitrile as mobile phases. The multi-reaction monitoring was used with ESI+ source, and the ion pairs for tazemetostat and ISTD were m/z 573.12→135.99 and m/z 410.10→124.00, respectively. 12 SD rats were randomly divided into the control group and the experimental group, 6 rats in each group. The rats in the experimental group were given PLB 100 mg/kg by gavage once a day for 7 consecutive days. The rats in the control group were given the same amount of 0.1% sodium carboxymethyl cellulose solution by gavage once a day for 7 consecutive days. At the seventh day, tazemetostat (80 mg/kg) was given and the blood was collected at different time points. The main parameters of pharmacokinetics were calculated and the herb-drug interactions (HDIs) were evaluated.

Results

In the calibrated range of 1–1000 ng/mL, tazemetostat had a good linearity. The extraction recovery was more than 84%, and the RSD of intra-batch and inter-batch precision were both less than 15%. The C_max of tazemetostat in the experimental group was 32.48% higher than that in the control group, and the AUC_(0-t) and AUC_(0−∞) of tazemetostat in the experimental group were 46.24% and 46.67% higher than that in the control group, respectively, and the t_1/2 was prolonged from 10.56 h to 11.73 h.

Conclusion

A simple, rapid and sensitive UPLC-MS/MS method for the determination of tazemetostat in rat plasma was established. PLB can inhibit the metabolism of tazemetostat and increase the plasma exposure of tazemetostat in rats.

Evaluation of Herb–Drug Interaction Between Danshen and Rivaroxaban in Rat and Human Liver Microsomes

The combination of Salvia miltiorrhiza (Danshen) and rivaroxaban is a promising treatment option in clinical practice in China, but the herb–drug interaction between Danshen and rivaroxaban remains unclear. Therefore, this study aims to reveal the interaction between Danshen and rivaroxaban. We not only investigated the inhibitory properties of Danshen tablet on rivaroxaban metabolism in rat and human liver microsomes but also evaluated the inhibitory effects of Danshen tablet and its eight active components (dihydrotanshinone I, tanshinone I, tanshinone IIA, cryptotanshinone, danshensu, salvianolic acid A, salvianolic acid B, and salvianolic acid C) on cytochrome P450 (CYP) enzymes. The results showed that Danshen tablet potently inhibited the metabolism of rivaroxaban in rat and human liver microsomes. In the CYP inhibition study, we found that dihydrotanshinone I, the active component of Danshen tablet, potently inhibited the activities of rat CYP3A and CYP2J, with IC₅₀ values at 13.85 and 6.39 μM, respectively. In further inhibition kinetic study, we found that Danshen tablet is a mixed inhibitor in rivaroxaban metabolism in rat and human liver microsomes, with the K_i value at 0.72 and 0.25 mg/ml, respectively. In conclusion, there is a potential interaction between Danshen tablet and rivaroxaban. Danshen tablet inhibits the metabolism of rivaroxaban, which may be because its lipid-soluble components such as dihydrotanshinone I strongly inhibit the activities of CYP enzymes, especially CYP3A and CYP2J. Therefore, when Danshen tablet and rivaroxaban are used simultaneously in the clinic, it is necessary to strengthen the drug monitoring of rivaroxaban and adjust the dosage.

Brain pharmacokinetics and metabolism of the AMP-activated protein kinase selective inhibitor SBI-0206965, an investigational agent for the treatment of glioblastoma

PURPOSE

Emerging evidence suggests that 5' Adenosine Monophosphate-Activated Protein Kinase (AMPK), a key regulator of cellular bioenergetics, is a novel target for the treatment of glioblastoma (GBM), a lethal brain tumor. SBI-0206965, an aminopyrimidine derivative, is a potent AMPK inhibitor being investigated for the treatment of GBM. Here we characterized the systemic and brain pharmacokinetics (PK) and hepatic metabolism of SBI-0206965.

METHODS

We performed intracerebral microdialysis to determine brain partitioning of SBI-0206965 in jugular vein cannulated rats. We assessed systemic PK of SBI-0206965 in rats and C57BL/6 mice following oral administration. Employing human, mouse, and rat liver microsomes we characterized the metabolism of SBI-0206965.

RESULTS

SBI-0206965 is quickly absorbed, achieving plasma and brain extracellular fluid (ECF) peak levels within 0.25 - 0.65 h. Based on the ratio of C_max and AUC in brain ECF to plasma (corrected for protein binding), brain partitioning is ~ 0.6-0.9 in rats. However, the compound has a short elimination half-life (1-2 h) and low relative oral bioavailability (~ 0.15). The estimated in-vitro hepatic intrinsic clearance of SBI-0206965 in mouse, rat and human was 325, 76 and 68 mL/min/kg, respectively. SBI-0206965 metabolites included desmethylated products, and the metabolism was strongly inhibited by ketoconazole, a CYP3A inhibitor.

CONCLUSION

SBI-0206965 has adequate brain permeability but low relative oral bioavailability which may be due to rapid hepatic metabolism, likely catalyzed by CYP3A enzymes. Our observations will facilitate further development of SBI-0206965, and/or other structurally related molecules, for the treatment of GBM and other brain tumors.

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.

ZY12201, A Potent TGR5 Agonist: Identification of a Novel Pan CYP450 Inhibitor Tool Compound for In-Vitro Assessment

BACKGROUND

Identification of clinical drug-drug interaction (DDI) risk is an important aspect of drug discovery and development owing to poly-pharmacy in present-day clinical therapy. Drug metabolizing enzymes (DME) plays important role in the efficacy and safety of drug candidates. Hence evaluation of a New Chemical Entity (NCE) as a victim or perpetrator is very crucial for DDI risk mitigation. ZY12201 (2-((2-(4-(1H-imidazol-1-yl) phenoxy) ethyl) thio)-5-(2-(3, 4- dimethoxy phenyl) propane-2-yl)-1-(4-fluorophenyl)-1H-imidazole) is a novel and potent Takeda-G-protein-receptor-5 (TGR-5) agonist. ZY12201 was evaluated in-vitro to investigate the DDI liabilities.

OBJECTIVE

The key objective was to evaluate the CYP inhibition potential of ZY12201 for an opportunity to use it as a tool compound for pan CYP inhibition activities.

METHOD

In-vitro drug metabolizing enzymes (DME) inhibition potential of ZY12201 was evaluated against major CYP isoforms (1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4/5), aldehyde oxidase (AO), monoamine oxidase (MAO), and flavin-containing monooxygenase (FMO in human liver cytosol/mitochondrial preparation/ microsomes using probe substrates and Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) method.

RESULTS

The study conducted on ZY12201 at 100 µM ZY12201 was found to reduce the metabolism of vanillin (AO probe substrate), tryptamine (MAO probe substrate), and benzydamine (FMO probe substrate) by 49.2%, 14.7%, and 34.9%, respectively. ZY12201 Ki values were 0.38, 0.25, 0.07, 0.01, 0.06, 0.02, 7.13, 0.03 and 0.003 μM for CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4/5 (substrate: testosterone) and CYP3A4/5 (substrate: midazolam), respectively. Time-dependant CYP inhibition potential of ZY12201 was assessed against CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4/5 and no apparent IC50 shift was observed.

CONCLUSIONS

ZY12201, at 100 µM concentration showed low inhibition potential of AO, MAO, and FMO. ZY12201 was found as a potent inhibitor of CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, and 3A4/5 while moderately inhibits to CYP2E1. Inhibition of CYP1A2, CYP2B6, CYP2C19, and CYP2E1 by ZY12201 was competitive, while inhibition of CYP2C8, CYP2C9, CYP2D6, and CYP3A4/5 was of mixed-mode. ZY12201 is a non-time-dependent inhibitor of CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4/5. In summary, the reported Ki values unequivocally support that ZY12201 has a high potential to inhibit all major CYP isoforms. ZY12201 can be effectively used as a tool compound for in-vitro evaluation of CYP-based metabolic contribution to total drug clearance in the lead optimization stage of Drug Discovery Research.

Design, synthesis, and evaluation of potent RIPK1 inhibitors with in vivo anti-inflammatory activity

RIPK1 plays a key role in the necroptosis pathway that regulates inflammatory signaling and cell death in various diseases, including inflammatory and neurodegenerative diseases. Herein, we report a series of potent RIPK1 inhibitors, represented by compound 70. Compound 70 efficiently blocks necroptosis induced by TNFα in both human and mouse cells (EC₅₀ = 17-30 nM). Biophysical assay demonstrates that compound 70 potently binds to RIPK1 (K_d = 9.2 nM), but not RIPK3 (K_d > 10,000 nM). Importantly, compound 70 exhibits greatly improved metabolic stability in human and rat liver microsomes compared to compound 6 (PK68), a RIPK1 inhibitor reported in our previous work. In addition, compound 70 displays high permeability in Caco-2 cells and excellent in vitro safety profiles in hERG and CYP assays. Moreover, pre-treatment of 70 significantly ameliorates hypothermia and lethal shock in SIRS mice model. Lastly, compound 70 possesses favorable pharmacokinetic parameters with moderate clearance and good oral bioavailability in SD rat. Taken together, our work supports 70 as a potent RIPK1 inhibitor and highlights its potential as a prototypical lead for further development in necroptosis-associated inflammatory disorders.

Risk assessment of the inhibition of hydroxygenkwanin on human and rat cytochrome P450 by cocktail method

Hydroxygenkwanin (HGK), a natural flavonoid extracted from the buds of Daphne genkwa Sieb.et Zucc. (Thymelaeaceae), possesses a wide range of pharmacological activities, including anti-inflammatory, antibacterial and anticancer. However, the inhibitory effect of HGK on cytochrome P450 (CYP) remains unclear. This study investigated the potential inhibitory effects of HGK on CYP1A2, 2B1/6, 2C9/11, 2D1/6, 2E1 and 3A2/4 enzymes in human and rat liver microsomes (HLMs and RLMs) by the cocktail approach. HGK exhibited no time-dependent inhibition of CYP activities in HLMs and RLMs. Enzyme inhibition kinetics indicated that HGK was not only a competitive inhibitor of human CYP1A2 and 2C9, but also competitively inhibited rat CYP1A2 and 2C11 activities, with K_i value at 0.84 ± 0.03, 8.09 ± 0.44, 2.68 ± 0.32 and 8.35 ± 0.31 μM, respectively. Further studies showed that the inhibitory effect of HGK on CYP enzymes was weaker than that of diosmetin, which may be related to the substitution of hydroxyl and methoxy in the A and B rings of the flavone skeleton. Therefore, the low K_i values of HGK for CYP1A2 and 2C may lead to potential drug-drug interactions and toxicity.

Synthesis and comparison of in vitro dual anti-infective activities of novel naphthoquinone hybrids and atovaquone

A principal factor that contributes towards the failure to eradicate leishmaniasis and tuberculosis infections is the reduced efficacy of existing chemotherapies, owing to a continuous increase in multidrug-resistant strains of the causative pathogens. This accentuates the dire need to develop new and effective drugs against both plights. A series of naphthoquinone-triazole hybrids was synthesized and evaluated in vitro against Leishmania (L.) and Mycobacterium tuberculosis (Mtb) strains. Their cytotoxicities were also evaluated, using the human embryonic kidney cell line (HEK-293). The hybrids were found to be non-toxic towards human cells and had demonstrated micromolar cellular antileishmanial and antimycobacterial potencies. Hybrid 13, i.e. 2-{[1-(4-methylbenzyl)-1H-1,2,3-triazol-4-yl]methoxy}naphthalene-1,4-dione was the most active of all. It was found with MIC₉₀ 0.5 µM potency against Mtb in a protein free medium, and with half-maxima inhibitory concentrations (IC₅₀) of 0.81 µM and 1.48 µM against the infective promastigote parasites of L. donavani and L. major, respectively, with good selectivity towards these pathogens (SI 22 - 65). Comparatively, the clinical naphthoquinone, atovaquone, although less cytotoxic, was found to be two-fold less antimycobacterial potent, and six- to twelve-fold less active against leishmania. Hybrid 13 may therefore stand as a potential anti-infective hit for further development in the search for new antitubercular and antileishmanial drugs. Elucidation of its exact mechanism of action and molecular targets will constitute future endeavour.

Inhibition and Induction by Poziotinib of Different Rat Cytochrome P450 Enzymes In Vivo and in an In Vitro Cocktail Method

Poziotinib is an orally active, irreversible, pan-HER tyrosine kinase inhibitor used to treat non-small cell lung cancer, breast cancer, and gastric cancer. Poziotinib is currently under clinical investigation, and understanding its drug-drug interactions is extremely important for its future development and clinical application. The cocktail method is most suitable for evaluating the activity of cytochrome P450 enzymes (CYPs). As poziotinib is partially metabolized by CYPs, cocktail probes are used to study the interaction between drugs metabolized by each CYP subtype. Midazolam, bupropion, dextromethorphan, tolbutamide, chlorzoxazone, phenacetin, and their metabolites were used to examine the effects of poziotinib on the activity of cyp1a2, 2b1, 2d1, 2c11, 2e1, and 3a1/2, respectively. The in vitro experiment was carried out by using rat liver microsomes (RLMs), whereas the in vivo experiment involved the comparison of the pharmacokinetic parameters of the probes after co-administration with poziotinib to rats to those of control rats treated with only probes. UPLC-MS/MS was used to detect the probes and their metabolites in rat plasma and rat liver microsomes. The in vitro results revealed that the half-maximal inhibitory concentration values of bupropion and tolbutamide in RLMs were 8.79 and 20.17 μM, respectively, indicating that poziotinib showed varying degrees of inhibition toward cyp2b1 and cyp2c11. Poziotinib was a competitive inhibitor of cyp2b1 and cyp2c11, with Ki values of 16.18 and 17.66 μM, respectively. No time- or concentration-dependence of inhibition by poziotinib was observed toward cyp2b1 and cyp2c11 in RLMs. Additionally, no obvious inhibitory effects were observed on the activity of cyp1a2, cyp2d1, cyp2e1, and cyp3a1/2. In vivo analysis revealed that bupropion, tolbutamide, phenacetin, and chlorzoxazone showed significantly different pharmacokinetic parameters after administration (p < 0.05); there was no significant difference in the pharmacokinetic parameters of dextromethorphan and midazolam. These results show that poziotinib inhibited cyp2b1 and cyp2c11, but induced cyp1a2 and cyp2e1 in rats. Thus, poziotinib inhibited cyp2b1 and cyp2c11 activity in rats, suggesting the possibility of interactions between poziotinib and these CYP substrates and the need for caution when combining them in clinical settings.

Assessment of the inhibition risk of paris saponins, bioactive compounds from Paris polyphylla, on CYP and UGT enzymes via cocktail inhibition assays

Paris saponins, also known as polyphyllins, are natural compounds extracted from Paris polyphylla, which have many pharmacological activities, such as anti-inflammation and anti-cancer. In particular, paris saponin I, II, VII and polyphyllin VI are the components of the quality standard for Paris polyphylla. However, the inhibition risk of polyphyllins on cytochrome P450 (CYP) and UDP-glucuronosyltransferases (UGT) remains unclear. Therefore, this report investigated the potential inhibitory effects of paris saponin I, II, VII and polyphyllin VI on the activities of CYP (CYP1A2, CYP2B1, CYP2C11, CYP2D1, CYP2E1 and CYP3A2) and UGT (UGT1A1, UGT1A3, UGT1A6, PROG and AZTG) through cocktail inhibition assays in vitro. In the study of CYP, polyphyllin VI exhibited weak inhibition on CYP2D1 activity in rat liver microsomes with IC₅₀ value at 45.2 μM, while paris saponin VII weakly inhibited CYP2C11 and CYP2E1 activities with IC₅₀ value at 42.0 and 67.7 μM, respectively. In the study of UGT, none of the four steroidal saponins showed significant inhibition risk. In conclusion, paris saponin I, II, VII and polyphyllin VI have very low potential to cause the possible toxicity and drug interactions involving CYP and UGT enzymes, indicating that they are safe enough to take with drugs.

Approaching treatment for immunological rejection of living-donor liver transplantation in rats

Background

The anti-immunological rejection therapy for small-for-size syndrome (SFSS) after live donor liver transplantation (LDLT) play a central role in keeping graft survival. The hepatocyte number and grafts function has undergone real-time changes with the proliferation and apoptosis of the grafts after reperfusion. Lacking an accurate and effective treatment regiments or indicators to guide the use of immunosuppressive drugs in SFS liver transplantation has made immunotherapy after SFS liver transplantation an urgent problem to be solved. Herein, we established small-for-size (SFS) and normal size liver transplantation model in rats to explore the effective indicators in guiding immunotherapy, to find an effective way for overcoming SFSS.

Methods

Lewis rats (donors) and BN rats (recipients) were used to mimic allograft liver transplantation and treated with tacrolimus. Local graft immune response was analyzed through haematoxylin and eosin and immunohistochemistry. Flow cytometry was used to assess the overall immune status of recipient. The pharmacokinetics mechanism of immunosuppressive drugs was explored through detecting CYP3A2 expression at mRNA level and protein levels.

Results

The results showed the local immune reaction of SFS grafts and systemic immune responses of recipient were significantly increased compared with those in normal size grafts and their recipient at four days after liver transplantation. Regression equation was used to regulate the tacrolimus dose which not only controlled tacrolimus serum concentration effectively but alleviated liver damage and improved survival rate.

Conclusions

This study showed that AST level and tacrolimus serum concentrations are effective indicators in guiding immunotherapy. Regression equation (T_D = − 0.494T_C-0.0035AST + 260.487) based on AST and tacrolimus serum concentration can be used as a reference for adjustment of immunotherapy after SFS liver transplantation, which is applicable in clinical practice.

Evaluation of the inhibition risk of shikonin on human and rat UDP-glucuronosyltransferases (UGT) through the cocktail approach

Shikonin, a natural red colorant, is widely used for food garnishment and cosmetic ingredient in the world. Shikonin also possesses a variety of pharmacological actions, including anti-inflammation and anti-cancer activities. However, little is known about its effects on the UDP-glucuronosyltransferases (UGT) activity. Therefore, the aim of this study was to evaluate the effect of shikonin on the UGT1A1, UGT1A3, UGT1A6, UGT1A9 and UGT2B7 activities via the human and rat liver microsomal assay and cocktail approach. The results showed shikonin inhibited human and rat liver microsomal UGT activity only in a dose-dependent manner. The further enzyme kinetic studies demonstrated that shikonin was not only a competitive inhibitor of human UGT1A1, UGT1A9, and UGT2B7, but also presented competitive inhibition on rat UGT1A1 and AZTG reactions. In conclusion, shikonin as a reversible inhibitor of UGT enzyme has a high-risk potential to cause the possible toxicity, especially drug-drug or food-drug interactions.

Diet-induced obese alters the expression and function of hepatic drug-metabolizing enzymes and transporters in rats

Obesity increases the incidences of metabolic syndrome, including type 2 diabete, fatty liver, dyslipidemia, hyperglycemia, heart disease, hypertension and cancer. In particular, pharmacokinetics and pharmacodynamics of many drugs have changed in obese patients. However, little is known about the hepatic drug-metabolizing enzymes and transporters that are influenced by diet-induced obese. In this report, we established obesity and fatty liver models in male rats by high-fat diet. The expression profiles of drug-metabolizing enzymes and transporters were studied by quantitative real-timePCR and Western blotting analysis. The function of these enzymes and transporters were assessed by their substrates and cocktail methods. The expression and activity of phase I enzymes (CYP1A2, CYP2B1, CYP2C11, CYP3A1, CYP4A1 and FMO1) and phase II enzymes (UGT1A1, UGT1A3, UGT1A6, UGT1A9, UGT2B7, NAT1 and GSTT1) were decreased in the liver of obese rats. In addition, the mRNA levels of hepatic transporter Slco1a2, Slco1b2, Slc22a5, Abcc2, Abcc3, Abcb1a and Abcg2 decreased significantly in obese animals, while Abcb1b increased significantly. Furthermore, the decreased expression of hepatic phase I and II enzymes and transporter may be due to changes of Hnf4α, LXRα and FXR. In conclusion, the diet-induced obese altered the expression and function of hepatic drug-metabolizing enzymes and transporters in male rats, thereby impacting drug metabolism and pharmacokinetics.

Effects of dibutyl phthalate and di(2-ethylhexyl) phthalate with their metabolites on CYP2C9*1 and CYP2C19*1 activities in vitro

The aim of this article is to assess the effect of phthalates on the activities of CYP2C9 and CYP2C19 in vitro. In this study, recombinant CYP2C9*1 and CYP2C19*1 microsomes were used to investigate the effects of phthalates and their metabolites on corresponding enzyme activities in vitro. 2-100 μM substrate of enzyme was incubated with series concentration of phthalates for 30 min at 37 °C. The metabolic products were detected using ultra-high performance liquid chromatography (UHPLC) and ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) methods. The results showed dibutyl phthalate (DBP) significantly inhibited CYP2C9*1 with an activity inhibition rate of 67.3% and half-maximal inhibitory concentration (IC50) of 29.63 μmol L^-1, but its metabolite monobutyl phthalate (MBP) had no significant effect. On the other hand, di(2-ethylhexyl)phthalate (DEHP) had no effect on CYP2C9*1, but its metabolite monoethylhexyl phthalate (MEHP) significantly inhibited the enzyme activity with an activity inhibition rate of 90.6% and IC50 of 6.37 μmol L^-1. With regards to CYP2C19*1, DBP completely inhibited the enzyme activity with an activity inhibition rate of 100% and IC50 of 2.63 μmol L^-1, but its metabolite MBP had no effect on it. DEHP and MEHP also inhibited the activity of CYP2C19*1. Further investigation showed MEHP was a competitive inhibitor of CYP2C9*1 (Ki = 7.063 μmol L^-1), and DBP was a competitive inhibitor of CYP2C19*1 (Ki = 7.013 μmol L^-1) against their substrates, both phthalates were non-competitive inhibitors of the cofactor NADPH. Our results suggested that DBP, DEHP, and their metabolites exhibited significant inhibitory effects toward either CYP2C9*1 or CYP2C19*1. These findings provided valuable information for a potentially toxic mechanism of DEHP and DBP on endocrine disruption and a useful guidance for safe and effective usage of drugs in patients with long-term DEHP and DBP exposure.

Design and optimization of the cocktail assay for rapid assessment of the activity of UGT enzymes in human and rat liver microsomes

Along with the prevalence of drug combination therapies, an increasing number of cases about drug-drug interactions (DDI) have been reported, which has drawn a lot of attention due to the potential toxicity and/or therapeutic failure. Pharmacokinetic interactions based on drug metabolic enzymes should be responsible for a great many of DDI. UDP-glucuronosyltransferases (UGT) as the main phase II metabolic enzymes are involved in the metabolism of many endogenous and exogenous substrates. Herein, we designed and optimized a validated cocktail method for the simultaneous evaluation of drug-mediated inhibition of the main five UGT isoforms using respective specific probe substrates (estradiol for UGT1A1, chenodeoxycholic acid for UGT1A3, serotonin for UGT1A6, propofol for UGT1A9/PROG and zidovudine for UGT2B7/AZTG) in human and rat liver microsomes by liquid chromatography-tandem mass spectrometry (LCMS/MS). Moreover, we investigated the risk of interactions among UGT probe substrates, and validated the cocktail method by known positive inhibitors of UGT isoforms. To minimize the substrates interaction, we developed two cocktail subgroups which were further optimized via exploring the experimental conditions. In particular, the cocktail inhibition assay for rapid assessment of in vitro rat UGTs was firstly reported and the values of K_m in the liver microsomes from humans and rats were close to each other in the specific UGT subtype. In conclusion, this study has successfully established the cocktail approach to explore UGT activity, especially for UGT inhibition in a fast and efficient way.

Enzyme Kinetics and Molecular Docking Studies on Cytochrome 2B6, 2C19, 2E1, and 3A4 Activities by Sauchinone

Sauchinone, an active lignan isolated from the aerial parts of Saururus chinensis (Saururaceae), exhibits anti-inflammatory, anti-obesity, anti-hyperglycemic, and anti-hepatic steatosis effects. As herb–drug interaction (HDI) through cytochrome P450s (CYPs)-mediated metabolism limits clinical application of herbs and drugs in combination, this study sought to explore the enzyme kinetics of sauchinone towards CYP inhibition in in vitro human liver microsomes (HLMs) and in vivo mice studies and computational molecular docking analysis. In in vitro HLMs, sauchinone reversibly inhibited CYP2B6, 2C19, 2E1, and 3A4 activities in non-competitive modes, showing inhibition constant (K_i) values of 14.3, 16.8, 41.7, and 6.84 μM, respectively. Also, sauchinone time-dependently inhibited CYP2B6, 2E1 and 3A4 activities in vitro HLMs. Molecular docking study showed that sauchinone could be bound to a few key amino acid residues in the active site of CYP2B6, 2C19, 2E1, and 3A4. When sibutramine, clopidogrel, or chlorzoxazone was co-administered with sauchinone to mice, the systemic exposure of each drug was increased compared to that without sauchinone, because sauchinone reduced the metabolic clearance of each drug. In conclusion, when sauchinone was co-treated with drugs metabolized via CYP2B6, 2C19, 2E1, or 3A4, sauchinone–drug interactions occurred because sauchinone inhibited the CYP-mediated metabolic activities.

Plant natural product plumbagin presents potent inhibitory effect on human cytochrome P450 2J2 enzyme

BACKGROUND

Cytochrome P450 2J2 (CYP2J2) is not only highly expressed in many kinds of human tumors, but also promotes tumor cell growth via regulating the metabolism of arachidonic acids. CYP2J2 inhibitors can significantly reduce proliferation, migration and promote apoptosis of tumor cells by inhibiting epoxyeicosatrienoic acids (EETs) biosynthesis. Therefore screening CYP2J2 inhibitors is a significant way for the development of anti-cancer drug.

PURPOSE

The aim of this study was to identify a new CYP2J2 inhibitor from fifty natural compounds obtained from plants.

STUDY DESIGN

CYP2J2 inhibitor was screened from a natural compounds library and further the inhibitory manner and mechanism were evaluated. Its cytotoxicity against HepG2 and SMMC-7721 cell lines was also estimated.

METHODS

The inhibitory effect was evaluated in rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant CYP2J2 (rCYP2J2), using astemizole as a probe substrate and inhibitory mechanism was illustrated through molecular docking. The cytotoxicity was detected using SRB.

RESULTS

In all candidates, plumbagin showed the strongest inhibitory effect on the CYP2J2-mediated astemizole O-demethylation activity. Further study revealed that plumbagin potently inhibited CYP2J2 activity with IC₅₀ value at 3.82 µM, 3.37 µM and 1.17 µM in RLMs, HLMs and rCYP2J2, respectively. Enzyme kinetic studies showed that plumbagin was a mixed-type inhibitor of CYP2J2 in HLMs and rCYP2J2 with K_i value of 1.88 µM and 0.92 µM, respectively. Docking data presented that plumbagin interacted with CYP2J2 mainly through GLU 222 and ALA 223. Moreover, plumbagin showed strongly cytotoxic effects on hepatoma cell lines, such as HepG2 and SMMC-7721, with lower toxicity on rat primary hepatocytes. Plumbagin had no effect on the protein expression of CYP2J2 in HepG2 and SMMC-7721, while down-regulated the mRNA level of anti-apoptosis protein Bcl-2.

CONCLUSION

This study found out a new CYP2J2 inhibitor plumbagin from fifty natural compounds. Plumbagin presented a potential of anti-cancer pharmacological activity.

Effect of codeine on CYP450 isoform activity of rats

CONTEXT

Codeine, also known as 3-methylmorphine, is an opiate used to treat pain, as a cough medicine and for diarrhoea. No study on the effects of codeine on the metabolic capacity of CYP enzyme is reported.

OBJECTIVE

In order to investigate the effects of codeine on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B1, CYP2D1, CYP1A2, CYP3A2 and CYP2C11.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into codeine group (low, medium, high) and control group. The codeine group rats were given 4, 8, 16 mg/kg (low, medium, high) codeine by continuous intragastric administration for 14 days. Five probe drugs bupropion, metroprolol, phenacetin, midazolam and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS.

RESULTS AND CONCLUSION

The pharmacokinetic parameters of bupropion and metroprolol experienced obvious change with AUC_(0-t), C_max increased and CL decreased for bupropion in medium dosage group and midazolam low dosage group. This result indicates that the 14 day-intragastric administration of codeine may inhibit the metabolism of bupropion (CYP2B1) and midazolam (CYP3A2) in rat. Additional, there are no statistical differences for albumin (ALB), alkaline phosphatase (ALP), creatinine (Cr) after 14 intragastric administration of codeine, while alanine aminotransferase (ALT), aspartate aminotransferase (AST), uric acid (UA) increased compared to control group. The biomedical test results show continuous 14 day-intragastric administration of codeine would cause liver damage.

Cytochrome P450 3A selectively affects the pharmacokinetic interaction between erlotinib and docetaxel in rats

Erlotinib as a first-line drug is used in non-small cell lung cancer (NSCLC) patients with sensitive EGFR mutations, while resistance to this drug will occur after several years of treatment. Therefore, the microtubule disturber docetaxel is introduced as combined regimen in clinical trials. This report investigated the potentials and mechanisms of drug-drug interaction (DDI) between erlotinib and docetaxel using wild type (WT) and Cyp3a1/2 knockout (KO) rats. The erlotinib O-demethylation and docetaxel hydroxylation reactions in the absence or the presence of another drug were analyzed in vitro via the assay of rat liver microsomes. In whole animal studies, erlotinib and docetaxel were given to WT and KO rats individually or jointly, and the pharmacokinetic profiles of these two drugs were analyzed and compared among different groups. The results showed that docetaxel not only inhibited the CYP3A-mediated biotransformation of erlotinib in vitro, but also significantly increased the maximum concentration and systemic exposure of erlotinib in vivo in WT rats. In contrast, the DDI was significantly attenuated in KO rats. On the other hand, erlotinib did not influence docetaxel either in vitro biotransformation or in vivo pharmacokinetic behaviors. These results exhibited the potentials of erlotinib-docetaxel interaction and indicated that the CYP3A played the perpetrating role of docetaxel on erlotinib in rats. A better understanding of this DDI with CYP3A may help the regulation of the use of these two drugs, avoid potential problems, and adjust dose carefully and early in clinic.

CRISPR knockout rat cytochrome P450 3A1/2 model for advancing drug metabolism and pharmacokinetics research

Cytochrome P450 (CYP) 3A accounts for nearly 30% of the total CYP enzymes in the human liver and participates in the metabolism of over 50% of clinical drugs. Moreover, CYP3A plays an important role in chemical metabolism, toxicity, and carcinogenicity. New animal models are needed to investigate CYP3A functions, especially for drug metabolism. In this report, Cyp3a1/2 double knockout (KO) rats were generated by CRISPR-Cas9 technology, and then were characterized for viability and physiological status. The Cyp3a1/2 double KO rats were viable and fertile, and had no obvious physiological abnormities. Compared with the wild-type (WT) rat, Cyp3a1/2 expression was completely absent in the liver of the KO rat. In vitro and in vivo metabolic studies of the CYP3A1/2 substrates indicated that CYP3A1/2 was functionally inactive in double KO rats. The Cyp3a1/2 double KO rat model was successfully generated and characterized. The Cyp3a1/2 KO rats are a novel rodent animal model that will be a powerful tool for the study of the physiological and pharmacological roles of CYP3A, especially in drug and chemical metabolism in vivo.

Biosynthesis and molecular actions of specialized 1,4-naphthoquinone natural products produced by horticultural plants

The 1,4-naphthoquinones (1,4-NQs) are a diverse group of natural products found in every kingdom of life. Plants, including many horticultural species, collectively synthesize hundreds of specialized 1,4-NQs with ecological roles in plant-plant (allelopathy), plant-insect and plant-microbe interactions. Numerous horticultural plants producing 1,4-NQs have also served as sources of traditional medicines for hundreds of years. As a result, horticultural species have been at the forefront of many basic studies conducted to understand the metabolism and function of specialized plant 1,4-NQs. Several 1,4-NQ natural products derived from horticultural plants have also emerged as promising scaffolds for developing new drugs. In this review, the current understanding of the core metabolic pathways leading to plant 1,4-NQs is provided with additional emphasis on downstream natural products originating from horticultural species. An overview on the biochemical mechanisms of action, both from an ecological and pharmacological perspective, of 1,4-NQs derived from horticultural plants is also provided. In addition, future directions for improving basic knowledge about plant 1,4-NQ metabolism are discussed.