Inhibition of CYP3A4 enhances aloe-emodin induced hepatocyte injury.

Aloe-emodin (AE) is a natural hydroxyanthraquinone derivative that was found in many medicinal plants and ethnic medicines. AE showed a wide array of pharmacological activities including anticancer, antifungal, laxative, antiviral, and antibacterial effects. However, increasing number of published studies have shown that AE may have some hepatotoxicity effects but the mechanism is not fully understood. Studies have shown that the liver injury induced by some free hydroxyanthraquinone compounds is associated with the inhibition of some metabolic enzymes. In this study, the CYP3A4 and CYP3A1 were found to be the main metabolic enzymes of AE in human and rat liver microsomes respectively. And AE was metabolized by liver microsomes to produce hydroxyl metabolites and rhein. When CYP3A4 was knocked down in L02 and HepaRG cells, the cytotoxicity of AE was increased significantly. Furthermore, AE increased the rates of apoptosis of L02 and HepaRG cells, accompanied by Ca2+ elevation, mitochondrial membrane potential (MMP) loss and reactive oxygen species (ROS) overproduction. The mRNA expression of heme oxygenase-1 in L02 and HepaRG cells increased significantly in the high-dose of AE (40 µmol/L) group, and the mRNA expression of quinone oxidoreductase-1 was activated by AE in all concentrations. Taken together, the inhibition of CYP3A4 enhances the hepatocyte injury of AE. AE can induce mitochondrial injury and the imbalance of oxidative stress of hepatocytes, which results in hepatocyte apoptosis.

The pharmacokinetic study on the interaction between nobiletin and anemarsaponin BII in vivo and in vitro.

CONTEXT: The interaction between nobiletin and anemarsaponin BII could affect the pharmacological activity of these two drugs during their combination. OBJECTIVE: The co-administration of nobiletin and anemarsaponin BII was investigated to explore the interaction and the potential mechanism. MATERIALS AND METHODS: Male Sprague-Dawley rats were only orally administrated with 50 mg/kg nobiletin as the control and another six rats were pre-treated with 100 mg/kg anemarsaponin BII for 7 d followed by the administration of nobiletin. The transport and metabolic stability of nobiletin were evaluated in vitro, and the effect of anemarsaponin BII on the activity of CYP3A4 was also assessed to explore the potential mechanism underlying the interaction. RESULTS: The increasing Cmax (2309.67 ± 68.06 µg/L vs. 1767.67 ± 68.86 µg/L), AUC (28.84 ± 1.34 mg/L × h vs. 19.57 ± 2.76 mg/L × h), prolonged t1/2 (9.80 ± 2.33 h vs. 6.24 ± 1.53 h), and decreased clearance rate (1.46 ± 0.26 vs. 2.42 ± 0.40) of nobilein was observed in rats. Anemarsaponin BII significantly enhanced the metabolic stability of nobiletin in rat liver microsomes (half-life increased from 31.56 min to 39.44 min) and suppressed the transport of nobiletin in Caco-2 cells (efflux rate decreased from 1.57 ± 0.04 to 1.30 ± 0.03). The inhibitory effect of anemarsaponin BII on CYP3A4 was also found with an IC50 value of 10.23 µM. DISCUSSION AND CONCLUSIONS: The interaction between anemarsaponin BII and nobiletin was induced by the inhibition of CYP3A4, which should draw special attention in their clinical co-administration.

Effect of Vitamin K-Mediated PXR Activation on Drug-Metabolizing Gene Expression in Human Intestinal Carcinoma LS180 Cell Line.

The pregnane X receptor (PXR) is the key regulator of our defense mechanism against foreign substances such as drugs, dietary nutrients, or environmental pollutants. Because of increased health consciousness, the use of dietary supplements has gradually increased, and most of them can activate PXR. Therefore, an analysis of the interaction between drugs and nutrients is important because altered levels of drug-metabolizing enzymes or transporters can remarkably affect the efficiency of a co-administered drug. In the present study, we analyzed the effect of vitamin K-mediated PXR activation on drug metabolism-related gene expression in intestine-derived LS180 cells via gene expression studies and western blotting analyses. We demonstrated that menaquinone 4 (MK-4), along with other vitamin Ks, including vitamin K1, has the potential to induce MDR1 and CYP3A4 gene expression. We showed that PXR knockdown reversed MK-4-mediated stimulation of these genes, indicating the involvement of PXR in this effect. In addition, we showed that the expression of MDR1 and CYP3A4 genes increased synergistically after 24 h of rifampicin and MK-4 co-treatment. Our study thus elucidates the importance of drug-nutrient interaction mediated via PXR.

Saikosaponins and the deglycosylated metabolites exert liver meridian guiding effect through PXR/CYP3A4 inhibition.

ETHNOPHARMACOLOGICAL RELEVANCE: Radix Bupleuri (RB), traditionally used to treat inflammatory disorders and infectious diseases, represents one of the most successful and widely used herbal drugs in Asia over the past 2000 years. Being realized the role in regulating metabolism and controlling Yin/Yang, RB is not only chosen specifically for treating liver meridian and the corresponding organs, but also believed to have liver meridian guiding property and help potentiate the therapeutic effects of liver. However, the ingredients in RB with liver meridian guiding property and the underly mechanism have not been comprehensively investigated. AIM OF STUDY: Considering the important role of CYP3A4 in first-pass metabolism and the liver exposure of drugs, the present study aimed to determine whether saikosaponins (SSs) and the corresponding saikogenins (SGs) have a role in inhibiting the catalytic activity of CYP3A4 in human liver microsomes and HepG2 hepatoma cells and whether they could suppress CYP3A4 expression by PXR-mediated pathways in HepG2 hepatoma cells. MATERIALS AND METHODS: The effect of SSs and SGs on CYP3A4-mediated midazolam1'-hydroxylation activities in pooled human liver microsomes (HLMs) was first studied. Dose-dependent experiments were performed to obtain the half inhibit concentration (IC50) values. HepG2 cells were used to assay catalytic activity of CYP3A4, reporter function, mRNA levels, and protein expression. The inhibitory effects of SSa and SSd on CYP3A4 activity are negligible, while the corresponding SGs (SGF and SGG) have obvious inhibitory effects on CYP3A4 activity, with IC50 values of 0.45 and 1.30 µM. The similar results were obtained from testing CYP3A4 catalytic activity in HepG2 cells, which correlated well with the suppression of the mRNA and protein levels of CYP3A4. Time-dependent testing of CYP3A4 mRNA and protein levels, as well as co-transfection experiments using the CYP3A4 promoter luciferase plasmid, further confirmed that SSs and SGs could inhibit the expression of CYP3A4 at the transcription level. Furthermore, PXR protein expression decreased in a concentration- and time-dependent manner after cells were exposed to SSs and SGs. PXR overexpression and RNA interference experiments further showed that SSs and SGs down-regulate the catalytic activity and expression of CYP3A4 in HepG2 may be mainly through PXR-dependent manner. CONCLUSION: SSs and SGs inhibit the catalytic activity and expression of CYP3A4 in a PXR-dependent manner, which may be highly related to the liver meridian guiding property of RB.

Exploration of components and mechanisms of Polygoni Multiflori Radix-induced hepatotoxicity using siRNA -mediated CYP3A4 or UGT1A1 knockdown liver cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Polygoni Multiflori Radix, the dried root of Polygonum multiflorum Thunb., and its processed products have been used as restoratives for centuries in China. However, the reports of Polygoni Multiflori Radix-induced liver injury (PMR-ILI) have received wide attention in recent years, and the components and mechanism of PMR-ILI are not completely clear yet. Our previous studies found that the PMR-ILI was related to the down-regulation of some drug metabolism enzymes (DME). AIM OF THE STUDY: To explore the effect of the inhibition of CYP3A4 or UGT1A1 on PMR-ILI, screen the relevant hepatotoxic components and unveil its mechanism. METHODS: RT-qPCR was used to detect the effects of water extract of Polygoni Multiflori Radix (PMR) and its main components on the mRNA expression of CYP3A4 and UGT1A1 in human hepatic parenchyma cell line L02. High-performance liquid chromatography (HPLC) was employed to detect the content of major components in the PMR. And then, the stable CYP3A4 or UGT1A1 knockdown cells were generated using short hairpin RNAs (shRNA) in L02 and HepaRG cells. Hepatotoxic components were identified by cell viability assay when PMR and its four representative components, 2,3,5,4'-tetrahydroxy stilbene glycoside (TSG), emodin (EM), emodin-8-O-ß-D-glucoside (EG), and gallic acid (GA), acted on CYP3A4 or UGT1A1 knockdown cell lines. The PMR-ILI mechanism of oxidative stress injury and apoptosis in L02 and HepaRG cells were detected by flow cytometry. Finally, the network toxicology prediction analysis was employed to excavate the targets of its possible toxic components and the influence on the metabolic pathway. RESULTS: PMR and EM significantly inhibited the mRNA expression of CYP3A4 and UGT1A1 in L02 cells, while TSG and GA activated the mRNA expression of CYP3A4 and UGT1A1, and EG activated CYP3A4 expression while inhibited UGT1A1 expression. The contents of TSG, EG, EM and GA were 34.93 mg/g, 1.39 mg/g, 0.43 mg/g and 0.44 mg/g, respectively. The CYP3A4 or UGT1A1 knockdown cells were successfully constructed in both L02 and HepaRG cells. Low expression of CYP3A4 or UGT1A1 increased PMR cytotoxicity remarkably. Same as PMR, the toxicity of EM and GA increased in shCYP3A4 and shUGT1A1 cells, which suggested EM and GA may be the main components of hepatotoxicity in PMR. Besides, EM not only inhibited the expression of metabolic enzymes but also reduced the cytotoxicity threshold. EM and GA affected the level of ROS, mitochondrial membrane potential, Ca2+ concentration, and dose-dependent induced hepatocyte apoptosis in L02 and HepaRG cells. The network toxicology analysis showed that PMR-ILI was related to drug metabolism-cytochrome P450, glutathione metabolism, and steroid hormone biosynthesis. CONCLUSION: The inhibition of mRNA expression of CYP3A4 or UGT1A1 enhanced hepatotoxicity of PMR. EM and GA, especially EM, may be the main hepatotoxic components in PMR. The mechanism of PMR, EM and GA induced hepatotoxicity was proved to be related to elevated levels of ROS, mitochondrial membrane potential, Ca2+ concentration, and induction of apoptosis in liver cells.

Effect of CYP3A4 on liver injury induced by triptolide.

Triptolide (TP), one of the main bioactive diterpenes of the herbal medicine Tripterygium wilfordii Hook F, is used for the treatment of autoimmune diseases in the clinic and is accompanied by severe hepatotoxicity. CYP3A4 has been reported to be responsible for TP metabolism, but the mechanism remains unclear. The present study applied a UPLC-QTOF-MS-based metabolomics analysis to characterize the effect of CYP3A4 on TP-induced hepatotoxicity. The metabolites carnitines, lysophosphatidylcholines (LPCs) and a serious of amino acids were found to be closely related to liver damage indexes in TP-treated female mice. Metabolomics analysis further revealed that the CYP3A4 inducer dexamethasone improved the level of LPCs and amino acids, and defended against oxidative stress. On the contrary, pretreatment with the CYP3A4 inhibitor ketoconazole increased liver damage with most metabolites being markedly altered, especially carnitines. Among these metabolites, except for LPC18:2, LPC20:1 and arginine, dexamethasone and ketoconazole both affected oxidative stress induced by TP. The current study provides new mechanistic insights into the metabolic alterations, leading to understanding of the role of CYP3A4 in hepatotoxicity induced by TP.

Isolation, synthesis, and drug interaction potential of secondary metabolites derived from the leaves of miracle tree (Moringa oleifera) against CYP3A4 and CYP2D6 isozymes.

BACKGROUND: Moringa oleifera Lam. is known as a drumstick tree that is widely cultivated in various subtropical and tropical provinces. Previous studies indicated that both aqueous and methanolic extracts of M. oleifera leaves have potent inhibitory effects on two major drug metabolizing Cytochrome P450 enzymes, namely, CYP3A4 and CYP2D6. PURPOSE: The current study was aimed to isolate the secondary metabolites from M. oleifera and investigate their cytotoxicity and inhibitory effects on CYP3A4 and CYP2D6 to assess their herb-drug interaction (HDI) potential. METHODS: Chemical structure elucidation was achieved by interpreting the spectroscopic data (UV, IR, 1D, and 2D NMR experiments), confirming by HR-ESI-MS, and comparing with the previously reported data in the literature. All the isolates were evaluated for their cytotoxicity against a panel of cell lines (SK-MEL, KB, BT-549, SK-OV-3, VERO, LLC-PK1, and HepG2) and inhibition of two principal CYP isozymes (CYP3A4 and CYP2D6). RESULTS: Phytochemical investigation of M. oleifera leaves resulted in the isolation and characterization of one new compound, namely omoringone (1), along with twelve known secondary metabolites (2-13) belonging to several chemical classes including flavonoids, terpenoids, lignans, and phenylalkanoids. A plausible biosynthetic pathway for compound 1 was provided. Because of the low isolation yield and limited supply, omoringone (1) and niazirin (12) were successively synthesized. No cytotoxicity was observed on any of the tested cell lines up to 50 µM. The extract exhibited an inhibitory effect on CYP3A4 isoform (IC50 = 52.5 ±â€¯2.5 µg/ml). Among the isolates, 1-4 and 7-9 inhibited CYP3A4 with the IC50 values ranging from 41.5 to 100 µM with no remarkable effect on CYP2D6 isozyme. CONCLUSION: This work aided in ascertaining components of M. oleifera contributing to CYP3A4 inhibition exhibited by the extract using an in vitro assay. Nonetheless, further studies are warranted to determine the bioavailability of the phytochemicals and extrapolate these findings in more physiologically relevant conditions to further establish the clinical relevance of in vitro observations.

Tenacigenin B ester derivatives from Marsdenia tenacissima actively inhibited CYP3A4 and enhanced in vivo antitumor activity of paclitaxel.

ETHNOPHARMACOLOGICAL RELEVANCE: Marsdenia tenacissima (Roxb.) Wight et Arn is a vine distributed in southwest area of China and used in folk medicine for treatment of tumors. Recent decades of studies on this plant reveal its synergistic effects with certain anticancer drugs in cancer therapy. In our previous study, an extract ETA which contains total aglycones made from M. tenacissima significantly enhanced antitumor activity of paclitaxel in tumor-bearing mice. However, the effective constituents in ETA and the underlying mechanisms remain unclear. AIM OF THE STUDY: Reveal the active components in ETA as well as the molecular mechanism in enhancing antitumor efficacy of paclitaxel. MATERIAL AND METHODS: Main constituents in ETA were purified by chemical methods. Effects of the purified constituents on metabolic activity of CYP450 enzymes were evaluated in human liver microsomes. Ability of the constituents to enhance antitumor activity of paclitaxel were investigated in nude mice bearing HeLa tumors. Pharmacokinetic study was performed in SD rats. Molecular docking was carried out for investigation of drug-protein interactions. RESULTS: Three main C21 steroidal aglycones, 11α-O-tigloyl-12ß-O-acetyl-tenacigenin B (MT1), 11α-O-2-methylbutanoyl-12ß-O-tigloyl-tenacigenin B (MT2) and 11α-O-2-methylbutanoyl-12ß-O-acetyl-tenacigenin B (MT3), together with tenacigenin B (MT4) was prepared from ETA. Among them, MT1, MT2 and MT3 strongly inhibit the metabolic activity of CYP3A4. MT2 also showed inhibitory effects on CYP2C8, CYP2B6 and CYP2C19. In HeLa tumor xenografts, MT1, MT2 and MT3 (30 mg/kg) did not affect tumor growth themselves, but significantly enhanced paclitaxel-induced growth inhibition. In addition, coadministration of MT2 with paclitaxel resulted in significant reduction of liver CYP2C8. In pharmacokinetic study, MT2 significantly increased the blood concentration of paclitaxel with increased AUC value by 2.2-5.3 folds. Molecular docking analysis suggested hydrophobic interaction modes of tenacigenin B derivatives with CYP3A4, and also the essential roles of the C-11 and C-12 ester groups for effective interaction with CYP3A4. CONCLUSION: Our study proves that, 11α-O-tigloyl-12ß-O-acetyl-tenacigenin B, 11α-O-2-methylbutanoyl-12ß-O-tigloyl-tenacigenin B and 11α-O-2-methylbutanoyl-12ß-O-acetyl-tenacigenin B, which are the main constituents of ETA, are active inhibitors of CYP3A4 with potential to increase therapeutic efficacy of anticancer drugs that are substrates of CYP3A4. Tenacigenin B derivatives with C-11 and C-12 ester group substitutions, or at least a large part of them, are active components in ETA and M. tenacissima to enhance in vivo antitumor efficacies of paclitaxel.

Effect of panaxytriol on cytochrome P450 3A4 via the pregnane X receptor regulatory pathway.

Panaxytriol (PXT) is one of the major effective components of red ginseng and Shenmai injection. The present study aimed to explore the effect of PXT on cytochrome P450 3A4 (CYP3A4) based on the pregnane X receptor (PXR)-CYP3A4 regulatory pathway in HepG2 cells and hPXR-overexpressing HepG2 cells treated with PXT for different time periods using quantitative polymerase chain reaction, Western blot, and dual-luciferase reporter gene assays. PXT could upregulate the levels of PXR and CYP3A4 mRNA in HepG2 cells treated with PXT for 1 hr, with no impact on the expression of their protein levels. The expression levels of both PXR and CYP3A4 mRNA and protein in HepG2 cells treated with PXT for 24 hr increased in a concentration-dependent manner. The effects of PXT on the expression of PXR and CYP3A4 mRNA and protein in hPXR-overexpressing HepG2 cells were similar to those in HepG2 cells. Moreover, the influence trend of PXT on CYP3A4 was consistent with that of PXR in HepG2 cells and hPXR-overexpressing HepG2 cells. The dual-luciferase reporter gene assay in HepG2 cells further demonstrated that PXT treatment for specific time periods could significantly induce the expression of CYP3A4 mediated by the PXR regulatory pathway.

Effectiveness and Safety of Clopidogrel Co-administered With Statins and Proton Pump Inhibitors: A Korean National Health Insurance Database Study.

Simultaneous competition for cytochrome P450 (CYP) 2C19 and CYP3A4 might diminish clopidogrel's antiplatelet effect by impacting its metabolic activation. This pharmacoepidemiologic study investigated whether proton pump inhibitors (PPIs) and CYP3A4-metabolized statins individually and jointly increase thrombotic events by attenuating clopidogrel's effectiveness. From Korean nationwide claims data (2007-2015), we selected 59,233 patients who initiated clopidogrel and statins after coronary stenting and compared thrombotic risks by PPI or CYP3A4-metabolized statin use or both. PPIs were associated with increased thrombotic risks (hazard ratio (HR) 1.27, 95% confidence interval (CI) 1.12-1.45), unlike CYP3A4-metabolized statins (HR 1.03, 95% CI 0.98-1.07). PPIs with high CYP2C19-inhibitory potential were more relevant than those with low potential (HR 1.28, 95% CI 1.02-1.61). Joint effects of PPIs and CYP3A4-metabolized statins were nonsignificant (relative excess risk due to interaction -0.14, 95% CI -0.34 to 0.07). Concurrent PPIs were associated with increased thrombotic risks in patients receiving clopidogrel and statins; CYP3A4-metabolized statins did not exacerbate PPI-associated risks.

Adverse event reporting patterns of concomitant botanical dietary supplements with CYP3A4 interactive & CYP3A4 non-interactive anticancer drugs in the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS).

BACKGROUND: To examine the adverse event (AE) reporting patterns for concomitant Botanical Dietary Supplements (BDS) and anticancer drugs. RESEARCH DESIGN AND METHODS: Using the 2004-2015 U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) database, AEs involving commonly used BDS and anticancer drugs (categorized into CYP3A4 interactive and CYP3A4 non-interactive) were examined. Disproportionality analyses using reporting odds ratios (RORs) assessed the relative reporting rates of 1) serious AEs (i.e., mortality and morbidity) with concomitant use of BDS (overall and by type) and anticancer drugs compared to anticancer drugs only; and 2) AEs by specific System Organ Classes (SOCs). RESULTS: A total of 3,264 AEs were reported involving concomitant BDS and CYP3A4 interactives, and 3,885 involving concomitant BDS and non-interactive anticancer drugs. ROR of serious AEs with concomitant all BDS and anticancer drugs compared to anticancer drugs alone showed a potential protective signal (ROR = 0.65, 95% CI = 0.62,0.68), but ROR for açaí and non-interactive anticancer drugs indicated potential risk (ROR = 1.70, 95% CI = 1.01,2.86). Heterogeneity of reporting patterns of AEs related to certain SOCs was observed for use of BDS along with anticancer drugs. CONCLUSION: This study identified potential protective and risk signals for AEs with concomitant use of BDS and anticancer drugs.

Development of (6 R)-2-Nitro-6-[4-(trifluoromethoxy)phenoxy]-6,7-dihydro-5 H-imidazo[2,1- b][1,3]oxazine (DNDI-8219): A New Lead for Visceral Leishmaniasis.

Discovery of the potent antileishmanial effects of antitubercular 6-nitro-2,3-dihydroimidazo[2,1- b][1,3]oxazoles and 7-substituted 2-nitro-5,6-dihydroimidazo[2,1- b][1,3]oxazines stimulated the examination of further scaffolds (e.g., 2-nitro-5,6,7,8-tetrahydroimidazo[2,1- b][1,3]oxazepines), but the results for these seemed less attractive. Following the screening of a 900-compound pretomanid analogue library, several hits with more suitable potency, solubility, and microsomal stability were identified, and the superior efficacy of newly synthesized 6 R enantiomers with phenylpyridine-based side chains was established through head-to-head assessments in a Leishmania donovani mouse model. Two such leads ( R-84 and R-89) displayed promising activity in the more stringent Leishmania infantum hamster model but were unexpectedly found to be potent inhibitors of hERG. An extensive structure-activity relationship investigation pinpointed two compounds ( R-6 and pyridine R-136) with better solubility and pharmacokinetic properties that also provided excellent oral efficacy in the same hamster model (>97% parasite clearance at 25 mg/kg, twice daily) and exhibited minimal hERG inhibition. Additional profiling earmarked R-6 as the favored backup development candidate.

In Vitro and in Vivo Inhibitory Effects of Glycyrrhetinic Acid in Mice and Human Cytochrome P450 3A4.

Glycyrrhetinic acid (GA) has been used clinically in the treatment of patients with chronic hepatitis. This study evaluated the effect of GA on the activity of five P450(CYP450) cytochrome enzymes: CYP2A6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4, in human liver microsomes (HLMs) and recombinant cDNA-expressed enzyme systems using a HPLC-MS/MS CYP-specific probe substrate assay. With midazolam as the probe substrate, GA greatly decreased CYP3A4 activity with IC50 values of 8.195 µM in HLMs and 7.498 µM in the recombinant cDNA-expressed CYP3A4 enzyme system, respectively. It significantly decreased CYP3A4 activity in a dose- but not time-dependent manner. Results from Lineweaver-Burk plots showed that GA could inhibit CYP3A4 activity competitively, with a Ki value of 1.57 µM in HLMs. Moreover, CYP2C9 and CYP2C19 could also be inhibited significantly by GA with IC50 of 42.89 and 40.26 µM in HLMs, respectively. Other CYP450 isoforms were not markedly affected by GA. The inhibition was also confirmed by an in vivo study of mice. In addition, it was observed that mRNA expressions of the Cyps2c and 3a family decreased significantly in the livers of mice treated with GA. In conclusion, this study indicates that GA may exert herb-drug interactions by competitively inhibiting CYP3A4.

Interaction potential of Trigonella foenum graceum through cytochrome P450 mediated inhibition.

OBJECTIVE: The seeds of Trigonella foenum-graecum (TFG) (family: Leguminosae) are widely consumed both as a spice in food and Traditional Medicine in India. The present study was undertaken to evaluate the inhibitory effect of standardized extract of TFG and its major constituent trigonelline (TG) on rat liver microsome (RLM) and cytochrome P450 (CYP450) drug metabolizing isozymes (CYP3A4 and CYP2D6), which may indicate the possibility of a probable unwanted interaction. MATERIALS AND METHODS: Reverse phase-high performance liquid chromatography method was developed to standardize the hydroalcoholic seed extract with standard TG. The inhibitory potential of the extract and TG was evaluated on RLM and CYP isozymes using CYP450-carbon monoxide (CYP450-CO) complex assay and fluorescence assay, respectively. RESULTS: The content of TG in TFG was found to be 3.38% (w/w). The CYP-CO complex assay showed 23.32% inhibition on RLM. Fluorescence study revealed that the extract and the biomarker had some inhibition on CYP450 isozymes e.g. CYP3A4 and CYP2D6 (IC50 values of the extract: 102.65 ± 2.63-142.23 ± 2.61 µg/ml and TG: 168.73 ± 4.03-180.90 ± 2.49 µg/ml) which was very less compared to positive controls ketoconazole and quinidine. Inhibition potential of TFG was little higher than TG but very less compared to positive controls. CONCLUSIONS: From the present study, we may conclude that the TFG or TG has very less potential to inhibit the CYP isozymes (CYP3A4, CYP2D6), so administration of this plant extract or its biomarker TG may be safe.

The significant inhibition on CYP3A caused by radix Aconiti single herb is not observed in the Wutou decoction: The necessity of combination therapy of radix Aconiti.

ETHNOPHARMACOLOGICAL RELEVANCE: Wutou (WT, Radix Aconiti), the mother root of Aconitum carmichaelii Debx., is a famous Chinese herb against rheumatoid arthritis. In Chinese clinics, PWT is often prepared as a decoction in combination with other herbs, such as Wutou decoction (WTD). The present study aimed to compare the effects of PWT single herb and WTD on CYP3A activity ex vivo and in vivo. MATERIALS AND METHODS: In the ex vivo study, CYP3A activity was determined by using testosterone (Tes) as a specific probe. Levels of Tes and its metabolite 6ß-hydroxytestosterone (6ß-OH-Tes) were measured using a validated ultra-performance liquid chromatography (UPLC) method. CYP3A protein and mRNA levels were measured by using Western blot and real-time PCR, respectively. In the in vivo study, CYP3A activity was determined by using buspirone (BP) as a specific probe. The plasma concentrations of BP and its primary metabolites, namely, 1-(2-pyrimidinyl) piperazine (1-PP) and 6'-hydroxybuspirone (6'-OH-BP), were determined using a validated UPLC-tandem mass spectrometry (UPLC/MS/MS) method. RESULTS: Compared with the control group, the formation rates of 6ß-OH-Tes from Tes ex vivo significantly decreased in groups treated with PWT at the tested doses, and this decrease was accompanied by a striking decrease in CYP3A protein and mRNA levels. However, a significant increase was observed in the ratios in the WTD groups compared with PWT single herb groups. In vivo, both formation ratios of 6'-OH-BP and 1-PP from BP showed no significant change in the WTD group. CONCLUSIONS: PWT can significantly inhibit CYP3A activity ex vivo at the tested doses because of the down-regulation of CYP3A protein and mRNA expression levels. WTD can significantly reverse the inhibition caused by PWT. WTD also had no significant effect on CYP3A activity in vivo. Results implied that the use of PWT as a part of the WTD prescription rather than PWT single herb is more appropriate in clinics.

Purple rice bran extract attenuates the aflatoxin B1-induced initiation stage of hepatocarcinogenesis by alteration of xenobiotic metabolizing enzymes.

Pigmented rice bran has been suggested to be a valuable source of beneficial phytochemicals. We investigated genotoxic and anti-genotoxic effects of purple rice bran extract (PRBE) in rats using a liver micronucleus assay. Purple rice bran was extracted with methanol, obtaining large amounts of phenolic compounds, including anthocyanins and small amounts of gamma-oryzanol. The experimental protocols were divided into two sets. Male rats were divided into three groups. Group 1 was a negative control, while Groups 2 and 3 were fed with 100 and 500 mg/kg bw of PRBE, respectively, for 28 days. PRBE had no effect on micronucleus formation or xenobiotic metabolizing enzymes in rat liver. Experiments concerning the effect of PRBE on AFB1 showed that PRBE significantly lessened the amount of micronucleated hepatocytes in AFB1 treated rats. Furthermore, it modulated metabolic activation of AFB1 metabolism in the liver by suppressing activity and protein expression of CYP1A2, CYP3A and CYP 450 reductase, and enhancing phase II enzymes including GST and UGT. Overall, purple rice bran extract was not genotoxic in rats. It exhibited anti-genotoxicity by modulation some xenobiotic enzymes active in AFB1 metabolism.

Pinelliae rhizoma, a toxic chinese herb, can significantly inhibit CYP3A activity in rats.

Raw Pinelliae Rhizoma (RPR) is a representative toxic herb that is widely used for eliminating phlegm or treating cough and vomiting. Given its irritant toxicity, its processed products, including Pinelliae Rhizoma Praeparatum (PRP) and Pinelliae Rhizoma Praeparatum cum Zingibere et Alumine (PRPZA), are more commonly applied and administered concomitantly with other chemical drugs, such as cough medications. This study aimed to investigate the effects of RPR, PRP, and PRPZA on CYP3A activity. Testosterone (Tes) and buspirone (BP) were used as specific probe substrates ex vivo and in vivo, respectively. CYP3A activity was determined by the metabolite formation ratios from the substrates. Ex vivo results show that the metabolite formation ratios from Tes significantly decreased, indicating that RPR, PRP, and PRPZA could inhibit CYP3A activity in rats. CYP3A protein and mRNA levels were determined to explore the underlying mechanism. These levels showed marked and consistent down-regulation with CYP3A activity. A significant decrease in metabolite formation ratios from BP was also found in PRPZA group in vivo, implying that PRPZA could inhibit CYP3A activity. Conclusively, co-administration of PR with other CYP3A-metabolizing drugs may cause drug-drug interactions. Clinical use of PR-related formulae should be monitored carefully to avoid adverse interactions.

The effect of Cree traditional medicinal teas on the activity of human cytochrome P450-mediated metabolism.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhododendron groenlandicum (Bog Labrador tea), Rhododendron tomentosum (Marsh Labrador tea) and Juniperus communis (Juniper) are used in medicinal teas by Canadian aboriginal cultures alone and in combination with conventional drug products. The safety of this combination had not been previously examined and this study was initiated to examine the potential of medicinal teas to inhibit the major human drug metabolizing enzyme, cytochrome P450 3A4 (CYP3A4). MATERIALS AND METHODS: The decoctions of Rhododendron groenlandicum and Rhododendron tomentosum leaves and Juniperus communis berries were examined in a microtiter fluorometric assay to examine their potential to inhibit CYP-mediated metabolism. RESULTS: The decoctions showed progressive inhibition towards CYP3A4 the longer the leaves or berries were brewed. R. Rhododendron groenlandicum and Juniperus communis may have the potential to inhibit CYP3A4-mediated metabolism. CONCLUSIONS: The findings of this study with these traditional medicines are significant in that they provide mechanistic support that these products have the potential to affect the safety and efficacy of other health and medicinal products. As this study only examined CYP3A4, it is possible that these medicinals contain substances that could also affect other metabolic enzymes.

In vitro and in vivo evaluation of the effect of puerarin on hepatic cytochrome p450-mediated drug metabolism.

Puerarin (8-ß-D-glucopyranosyl-7-hydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) is a major pharmacological component of Puerariae Radix, the root of Pueraria lobata. We investigated the effect of puerarin on hepatic cytochrome P450-mediated drug metabolism in rats and humans. The in vitro cytochrome P450 inhibitory effect of puerarin in human and rat liver microsomes was evaluated using the following model cytochrome P450 substrates: phenacetin for CYP1A, diclofenac for CYP2C, dextromethorphan for CYP2D, and testosterone for CYP3A. The in vivo pharmacokinetics of intravenous and oral buspirone, a probe substrate for CYP3A, was studied with single simultaneous intravenous coadministration of puerarin in rats. In the in vitro cytochrome P450 inhibition study, the rate of disappearance of testosterone was significantly reduced in the presence of 10 µM PU, while that of other cytochrome P450 substrates was not significantly affected in both human and rat liver microsomes, suggesting that puerarin inhibits the in vitro hepatic CYP3A-mediated metabolism in the human and rat systems (IC50 = 15.5 ± 3.9 µM). After intravenous administration of buspirone with single simultaneous coadministration of intravenous puerarin at a dose of 10 mg/kg in rats, the total area under the plasma concentration-time curve from time zero to time infinity was increased while time-averaged total body clearance decreased. When buspirone was orally administered in rats with the 10 mg/kg intravenous puerarin coadministration, both total area under the plasma concentration-time curve from time zero to time infinity and the extent of absolute oral bioavailability were significantly increased. Therefore, results of the in vitro microsomal and in vivo pharmacokinetic studies suggest the possible inhibition of hepatic CYP3A-mediated drug metabolism by puerarin administration, potentially leading to metabolism-mediated herb-drug interactions with clinical significance.