Amentoflavone Induces Cell-cycle Arrest, Apoptosis, and Invasion Inhibition in Non-small Cell Lung Cancer Cells.

BACKGROUND/AIM: Amentoflavone, an effective compound derived from medicinal plants, has been shown to boost therapeutic efficacy of chemotherapy in non-small cell lung cancer (NSCLC). However, anti-NSCLC effect of amentoflavone is ambiguous. The major purpose of the present study was to verify the inhibitory effects of amentoflavone in NSCLC cells. MATERIALS AND METHODS: The effects of amentoflavone on growth and invasion of NSCLC CL-1-5-F4 cells were evaluated by cell viability assay, flow cytometry, colony formation assay, nuclear factor-kappa B (NF-κB) reporter gene assay, immunofluorescence staining, transwell invasion, and western blot assay. RESULTS: Amentoflavone effectively induced cell growth inhibition, G1 cell-cycle arrest, apoptosis, and suppression of invasion. Furthermore, amentoflavone not only triggered expression of p27, cleaved caspase-3, -8 also reduced NF-κB signaling, protein levels of matrix metalloproteinase (MMP)-2, -9, Cyclin-D1, and vascular endothelial growth factor (VEGF). CONCLUSION: Cell-cycle arrest, apoptosis induction, NF-κB signaling inhibition are associated with amentoflavone-inhibited growth and invasion of NSCLC cells.

Modulation of CYP3A4 and CYP2C9 activity by Bulbine natalensis and its constituents: An assessment of HDI risk of B. natalensis containing supplements.

BACKGROUND: Bulbine natalensis is an African-folk medicinal plant used as a dietary supplement for enhancing sexual function and muscle strength in males by presumably boosting testosterone levels, but no scientific information is available about the possible herb-drug interaction (HDI) risk when bulbine-containing supplements are concomitantly taken with prescription drugs. PURPOSE: This study was aimed to investigate the HDI potential of B. natalensis in terms of the pregnane X receptor (PXR)-mediated induction of major drug-metabolizing cytochrome P450 enzyme isoforms (i.e., CYP3A4 and CYP2C9) as well as inhibition of their catalytic activity. RESULTS: We found that a methanolic extract of B. natalensis activated PXR (EC50 6.2 ± 0.6 µg/ml) in HepG2 cells resulting in increased mRNA expression of CYP3A4 (2.40 ± 0.01 fold) and CYP2C9 (3.37 ± 0.3 fold) at 30 µg/ml which was reflected in increased activites of the two enzymes. Among the constituents of B. natalensis, knipholone was the most potent PXR activator (EC50 0.3 ± 0.1 µM) followed by bulbine-knipholone (EC50 2.0 ± 0.5 µM), and 6'-methylknipholone (EC50 4.0 ± 0.5 µM). Knipholone was also the most effective in increasing the expression of CYP3A4 (8.47 ± 2.5 fold) and CYP2C9 (2.64 ± 0.3 fold) at 10 µM. Docking studies further confirmed the unique structural features associated with knipholones for their superior inductive potentials in the activation of PXR compared to other anthraquinones. In a CYP inhibition assay, the methanolic extract as well as the anthraquinones strongly inhibited the catalytic activity of CYP2C9 while, inhibition of CYP3A4 was weak. CONCLUSIONS: These results suggest that consumption of B. natalensis may pose a potential risk for HDI if taken with conventional medications that are substrates of CYP3A4 and CYP2C9 and may contribute to unanticipated adverse reactions or therapeutic failures. Further studies are warranted to validate these findings and establish their clinical relevancy.

Inhibition of CYP2C9 by natural products: insight into the potential risk of herb-drug interactions.

Due to the rapidly increasing global interest in the use of herbs, phytomedicines and other natural products as medical or complementary remedies, concerns about the clinical medication safety have drawn much attention worldwide. Particularly, many natural ingredients exhibit inhibitory effects on cytochrome P450 (CYP) enzymes, which are the most important Phase I metabolism enzymes in liver. CYP2C9 is one of the most abundant CYP enzymes and responsible for the metabolism of over 15% clinical drugs, including oral sulfonylurea hypoglycemics, nonsteroidal anti-inflammatory agents, selective cyclooxygenase-2 inhibitors, antiepileptics, angiotensin II receptor inhibitors and anticoagulants. Diclofenac (4'-hydroxylase) and tolbutamide (methylhydroxylation) are widely used as probe substrates for CYP2C9. To date, numerous natural products have been reported to have the capabilities of inhibiting the catalytic activity of CYP2C9 and further influencing the pharmacokinetic and pharmacodynamic behaviors of drugs that are mainly metabolized by CYP2C9, leading to potential herb-drug interactions. Moreover, some fatal adverse interactions may occur for drugs with a narrow therapeutic window when they are coadministered with a CYP2C9 inhibitor, especially irreversible inactivators. For the purpose of better understanding the interactions of natural products with CYP2C9, we comprehensively reviewed the characteristics of CYP2C9, the natural ingredients that inhibit CYP2C9, the related research approaches and strategies, the types of inhibition and the underlying mechanisms.

Effect of 95% Ethanol Khat Extract and Cathinone on in vitro Human Recombinant Cytochrome P450 (CYP) 2C9, CYP2D6, and CYP3A4 Activity.

BACKGROUND AND OBJECTIVE: A significant number of people worldwide consume khat on daily basis. Long term of khat chewing has shown negative impact on several organ systems. It is likely that these people are co-administered khat preparations and conventional medication, which may lead to khat-drug interactions. This study aimed to reveal the inhibitory potencies of khat ethanol extract (KEE) and its major active ingredient (cathinone) on human cytochrome P450 (CYP) 2C9, CYP2D6, and CYP3A4 enzymes activities, which are collectively responsible for metabolizing 70-80% clinically used drugs. METHODS: In vitro fluorescence-based enzyme assays were developed and the CYP enzyme activities were quantified in the presence and absence of KEE and cathinone employing Vivid® CYP450 Screening Kits. RESULTS: KEE inhibited human CYP2C9, CYP2D6, and CYP3A4 enzyme activities with IC50 of 42, 62, and 18 µg/ml. On the other hand, cathinone showed negligible inhibitory effect on these CYPs. Further experiments with KEE revealed that KEE inhibited CYP2C9 via non-competitive or mixed mode with Ki of 14.7 µg/ml, CYP2D6 through competitive or mixed mode with Ki of 17.6 µg/ml, CYP3A4 by mixed inhibition mode with Ki of 12.1 µg/ml. CONCLUSION: Khat-drug interactions are possible due to administration of clinical drugs metabolized by CYP2C9/CYP2D6/CYP3A4 together with khat chewing. Further in vivo studies are required to confirm our findings and identify the causative constituents of these inhibitory effects.

Identification of Selective Dual ROCK1 and ROCK2 Inhibitors Using Structure-Based Drug Design.

A HTS campaign identified compound 1, an excellent hit-like molecule to initiate medicinal chemistry efforts to optimize a dual ROCK1 and ROCK2 inhibitor. Substitution (2-Cl, 2-NH2, 2-F, 3-F) of the pyridine hinge binding motif or replacement with pyrimidine afforded compounds with a clean CYP inhibition profile. Cocrystal structures of an early lead compound were obtained in PKA, ROCK1, and ROCK2. This provided critical structural information for medicinal chemistry to drive compound design. The structural data indicated the preferred configuration at the central benzylic carbon would be ( R), and application of this information to compound design resulted in compound 16. This compound was shown to be a potent and selective dual ROCK inhibitor in both enzyme and cell assays and efficacious in the retinal nerve fiber layer model after oral dosing. This tool compound has been made available through the AbbVie Compound Toolbox. Finally, the cocrystal structures also identified that aspartic acid residues 176 and 218 in ROCK2, which are glutamic acids in PKA, could be targeted as residues to drive both potency and kinome selectivity. Introduction of a piperidin-3-ylmethanamine group to the compound series resulted in compound 58, a potent and selective dual ROCK inhibitor with excellent predicted drug-like properties.

Interactions of casticin, ipriflavone, and resveratrol with serum albumin and their inhibitory effects on CYP2C9 and CYP3A4 enzymes.

Polyphenols are abundant molecules in the plant kingdom. They interact with several proteins in the body resulting in their complex biological effects. Previous studies demonstrated that polyphenols can interfere significantly with the pharmacokinetics of drugs by acting on their biotransformation, albumin-binding, and/or carrier-mediated transport. Casticin (CAS), ipriflavone (IPR), and resveratrol (RES) are well-known polyphenols often added to dietary supplements in high doses. In this study, we investigated the albumin-binding of these polyphenols by fluorescence spectroscopy, and their ability to displace the Sudlow's Site I ligand warfarin and the Site II ligand naproxen by ultrafiltration. Furthermore, the effects of CAS, IPR, and RES on CYP2C9 and CYP3A4 enzymes were examined, employing diclofenac and testosterone as substrates, respectively. Our main observations are the following: (1) Polyphenols formed stable complexes with albumin (K = 104-105 L/mol); (2) CAS and RES slightly displaced naproxen from human albumin, while albumin-binding of warfarin was not affected; (3) CAS and RES significantly inhibited CYP2C9, with CAS being as potent as the positive control warfarin; (4) each polyphenol significantly inhibited CYP3A4, with RES being stronger and CAS slightly weaker than the known inhibitor naringenin. Our results suggest that high intake of CAS and RES may interfere with the albumin-binding of Site II ligands as well as the metabolism of drugs by CYP2C9 and/or CYP3A4 enzymes, while large doses of IPR may affect the CYP3A4-catalyzed biotransformation of some drugs.

Pharmacokinetic interaction of diosmetin and silibinin with other drugs: Inhibition of CYP2C9-mediated biotransformation and displacement from serum albumin.

Diosmin and silibinin (SIL) are polyphenolic compounds which are the active components of several drugs and dietary supplements. After the oral administration of diosmin (flavonoid glycoside), only its aglycone diosmetin (DIO) reaches the systemic circulation. Both DIO and SIL form complexes with serum albumin and are able to inhibit several cytochrome P450 enzymes. Therefore, it is reasonable to hypothesize that these polyphenols may displace some drugs from serum albumin and inhibit their biotransformation, potentially leading to the disruption of drug therapy. In this study, the inhibitory action of DIO and SIL on CYP2C9-catalyzed metabolism of diclofenac to 4'-hydroxydiclofenac was examined, using warfarin as a positive control. Furthermore, interaction of DIO and SIL with human and bovine serum albumins as well as the displacement of warfarin from albumin by DIO and SIL were tested, employing steady-state fluorescence spectroscopy, fluorescence anisotropy, ultrafiltration, and molecular modeling. It is demonstrated that DIO and SIL are potent inhibitors of CYP2C9 enzyme and are able to displace the Site I ligand warfarin from human serum albumin. Because DIO and SIL may interfere with the pharmacokinetics of several drugs through both ways, we need to consider the potentially hazardous consequences of the consumption of diosmin or SIL together with other drugs.

Cytochrome P450 2C9-natural antiarthritic interactions: Evaluation of inhibition magnitude and prediction from in vitro data.

Many dietary supplements are promoted to patients with osteoarthritis (OA) including the three naturally derived compounds, glucosamine, chondroitin and diacerein. Despite their wide spread use, research on interaction of these antiarthritic compounds with human hepatic cytochrome P450 (CYP) enzymes is limited. This study aimed to examine the modulatory effects of these compounds on CYP2C9, a major CYP isoform, using in vitro biochemical assay and in silico models. Utilizing valsartan hydroxylase assay as probe, all forms of glucosamine and chondroitin exhibited IC50 values beyond 1000 µM, indicating very weak potential in inhibiting CYP2C9. In silico docking postulated no interaction with CYP2C9 for chondroitin and weak bonding for glucosamine. On the other hand, diacerein exhibited mixed-type inhibition with IC50 value of 32.23 µM and Ki value of 30.80 µM, indicating moderately weak inhibition. Diacerein's main metabolite, rhein, demonstrated the same mode of inhibition as diacerein but stronger potency, with IC50 of 6.08 µM and Ki of 1.16 µM. The docking of both compounds acquired lower CDOCKER interaction energy values, with interactions dominated by hydrogen and hydrophobic bondings. The ranking with respect to inhibition potency for the investigated compounds was generally the same in both in vitro enzyme assay and in silico modeling with order of potency being diacerein/rhein > various glucosamine/chondroitin forms. In vitro-in vivo extrapolation of inhibition kinetics (using 1 + [I]/Ki ratio) demonstrated negligible potential of diacerein to cause interaction in vivo, whereas rhein was predicted to cause in vivo interaction, suggesting potential interaction risk with the CYP2C9 drug substrates.

Effects of Ojeok-san on the Pharmacokinetics of Celecoxib at Steady-state in Healthy Volunteers.

Ojeok-san is a frequently used herbal medication for the management of osteoarthritic pain. We evaluated the effect of Ojeok-san on the pharmacokinetics of celecoxib at steady-state in healthy individuals. An open-label, fixed-sequence, two-period, two-treatment cross-over study was conducted. In period I, the individuals received celecoxib capsule 200 mg once daily for 4 days. In period II, only Ojeok-san (14.47 g/pack, three times daily) was administered for 4 days, followed by co-administration with celecoxib for 4 days. On the fourth (final) day of administration, Ojeok-san was administered as a single dose. The blood samples for pharmacokinetic evaluation were collected for up to 48 hr after the administration of celecoxib in each study period. Of the 22 enrolled individuals, 20 individuals completed the study. In the presence of Ojeok-san, the systemic exposure of celecoxib was decreased. The geometric mean ratios ([celecoxib + Ojeok-san]/celecoxib) and the 90% confidence intervals for the maximum plasma concentration (Cmax ) and the area under the plasma concentration-time curve during dosing interval (AUCτ ) of celecoxib at steady-state were 0.725 (0.620-0.848) and 0.885 (0.814-0.962), respectively. The changes in the mean of the Cmax and AUCτ of celecoxib were greater in intermediate metabolizers of cytochrome 2C9 (CYP2C9) than in normal metabolizers. Our results suggested that the Cmax and AUCτ of celecoxib were reduced by Ojeok-san co-administration. This finding may be beneficial to determine the required adjustment of celecoxib dosage when co-administered with Ojeok-san.

Screening of Drug Metabolizing Enzymes for the Ginsenoside Compound K In Vitro: An Efficient Anti-Cancer Substance Originating from Panax Ginseng.

Ginsenoside compound K (CK), a rare ginsenoside originating from Panax Ginseng, has been found to possess unique pharmacological activities specifically as anti-cancers. However, the role of cytochrome P450s (CYPs) in the metabolism of CK is unclear. In this study, we screened the CYPs for the metabolism of CK in vitro using human liver microsomes (HLMs) or human recombinant CYPs. The results showed that CK inhibited the enzyme activities of CYP2C9 and CYP3A4 in the HLMs. The Km and Vmax values of CK were 84.20±21.92 µM and 0.28±0.04 nmol/mg protein/min, respectively, for the HLMs; 34.63±10.48 µM and 0.45±0.05 nmol/nmol P450/min, respectively, for CYP2C9; and 27.03±5.04 µM and 0.68±0.04 nmol/nmol P450/min, respectively, for CYP3A4. The IC50 values were 16.00 µM and 9.83 µM, and Ki values were 14.92 µM and 11.42µM for CYP2C9 and CYP3A4, respectively. Other human CYP isoforms, including CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP2C19, showed minimal or no effect on CK metabolism. The results suggested that CK was a substrate and also inhibitors for both CYP2C9 and CYP3A4. Patients using CK in combination with therapeutic drugs that are substrates of CYP2C9 and CYP3A4 for different reasons should be careful, although the inhibiting potency of CK is much poorer than that of enzyme-specific inhibitors.

Inhibition of cytochrome P450 2C9 expression and activity in vitro by allyl isothiocyanate.

The growing interest in the use of natural herbal products and dietary supplements to treat and prevent diseases raises the question of medicinal drug safety. Allyl isothiocyanate, a hydrolysis product of a glucosinolate, sinigrin, has multiple beneficial properties, and based on this fact, allyl isothiocyanate-containing dietary supplements have been developed. To date, no studies of the effects of this compound on the cytochrome P450 2C9 have been reported. In this study, we found that allyl isothiocyanate reduced catalytic activity, messenger ribonucleic acid, and protein expression of cytochrome P450 2C9 in HepaRG cells. An investigation of the transcriptional activity of the pregnane X receptor and the constitutive androstane receptor revealed that allyl isothiocyanate disrupted the transcriptional coregulation effects of the pregnane X receptor/constitutive androstane receptor with several important coregulators and interfered with the assembly of transcriptional complexes of the cytochrome P450 2C9 pregnane X receptor/constitutive androstane receptor-response element. The decrease of cytochrome P450 2C9 expression and activity mediated by allyl isothiocyanate suggested that this agent could alter the metabolism of drugs metabolized by cytochrome P450 2C9. This may cause food/dietary supplement-drug interactions or alter the therapeutic effects, and even the toxicity of drugs coadministered with allyl isothiocyanate. Since the consumption of allyl isothiocyanate-containing food/dietary supplements continues to increase, it is important to predict and ultimately avoid interactions with concomitant drugs. It is required that these possible pharmacokinetic interactions be characterized and the recommendations available to patients and healthcare professionals be improved.

Potent inhibitory effect of alpha-viniferin on human cytochrome P450.

α-Viniferin isolated from Caragana chamlagu is a trimer of resveratrol, and has several biological activities, which include anti-inflammatory, anti-oxidant, anti-arthritis, and anti-tumor activities. Herb-drug interactions are the source of the most harmful complications in patients coadministered herbal and modern medicines, and are caused by modulation of the activities of drug metabolizing enzymes. Here, the authors investigated the inhibitory effects of α-viniferin on the activities of 9 human cytochrome P450 (CYP) isoforms using a cocktail of probe substrates and LC-MS/MS in pooled human liver microsomes (HLMs). α-Viniferin strongly inhibited 7 of the 9 CYP isoforms (except CYP2A6 and CYP2E1). Furthermore, α-viniferin strongly inhibited CYP2C19-mediated omeprazole 5-hydroxylation and CYP3A4-catalyzed midazolam 1-hydroxylation with IC50 values of 0.93 and 1.2 µM, respectively. α-Viniferin strongly inhibited the activities of these two CYPs dose dependently, but not time-dependently. Lineweaver-Burk plots and secondary plots indicated a typical pattern of mix-mode inhibition for CYP2C19 and 3A4. This is the first investigation conducted on the inhibitory effect of α-viniferin on CYP2C19 and 3A4 in HLMs to predict a potential herb-drug interaction.