Cytochrome P450 enzymes and drug metabolism--basic concepts and methods of assessment

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.

Hypercholesterolemia reduces the expression and function of hepatic drug metabolizing enzymes and transporters in rats

Hypercholesterolemia, one of the most common lipid metabolic diseases, may cause severe complications and even death. However, the effect of hypercholesterolemia on drug-metabolizing enzymes and transporters remains unclear. In this report, we established a rat model of diet-induced hypercholesterolemia. Quantitative real-time PCR and Western blot analysis were used to study the mRNA and protein expression of drug-metabolizing enzymes and transporters. The functions of these enzymes and transporters were evaluated by the cocktail assay. In hypercholesterolemic rats, the expression of phase I enzymes (CYP1A2, CYP2C11, CYP2E1, CYP3A1/2, CYP4A1 and FMO1/3) and phase II enzymes (UGT1A1/3, PROG, AZTG, SULT1A1, NAT1 and GSTT1) decreased. In addition, the mRNA levels of drug transporter Slco1a1/2, Slco1b2, Slc22a5, Abcc2, Abcb1a and Abcg2 decreased in rats with hypercholesterolemia, while Abcb1b and Abcc3 increased. The decreased expression of hepatic phase I and II enzymes and transporters may be caused by the changes of CAR, FXR, PXR, and Hnf4α levels. In conclusion, diet-induced hypercholesterolemia changes the expression and function of hepatic drug-metabolizing enzymes and transporters in rats, thereby possibly affecting drug metabolism and pharmacokinetics. In clinical hyperlipidemia, patients should strengthen drug monitoring to avoid possible drug exposure mediated risks.

In Silico Drug Discovery Strategies Identified ADMET Properties of Decoquinate RMB041 and Its Potential Drug Targets against Mycobacterium tuberculosis

The highly adaptive cellular response of Mycobacterium tuberculosis to various antibiotics and the high costs for clinical trials, hampers the development of novel antimicrobial agents with improved efficacy and safety. Subsequently, in silico drug screening methods are more commonly being used for the discovery and development of drugs, and have been proven useful for predicting the pharmacokinetics, toxicities, and targets, of prospective new antimicrobial agents. In this investigation we used a reversed target fishing approach to determine potential hit targets and their possible interactions between M. tuberculosis and decoquinate RMB041, a propitious new antituberculosis compound. Two of the 13 identified targets, Cyp130 and BlaI, were strongly proposed as optimal drug-targets for dormant M. tuberculosis, of which the first showed the highest comparative binding affinity to decoquinate RMB041. The metabolic pathways associated with the selected target proteins were compared to previously published molecular mechanisms of decoquinate RMB041 against M. tuberculosis, whereby we confirmed disrupted metabolism of proteins, cell wall components, and DNA. We also described the steps within these pathways that are inhibited and elaborated on decoquinate RMB041’s activity against dormant M. tuberculosis. This compound has previously showed promising in vitro safety and good oral bioavailability, which were both supported by this in silico study. The pharmacokinetic properties and toxicity of this compound were predicted and investigated using the online tools pkCSM and SwissADME, and Discovery Studio software, which furthermore supports previous safety and bioavailability characteristics of decoquinate RMB041 for use as an antimycobacterial medication.

IMPORTANCE This article elaborates on the mechanism of action of a novel antibiotic compound against both, active and dormant Mycobacterium tuberculosis and describes its pharmacokinetics (including oral bioavailability and toxicity). Information provided in this article serves useful during the search for drugs that shorten the treatment regimen for Tuberculosis and cause minimal adverse effects.

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.

An Evaluation of the Potential of Essential Oils against SARS-CoV-2 from In Silico Studies through the Systematic Review Using a Chemometric Approach

Essential oils (EOs) and their compounds have attracted particular attention for their reported beneficial properties, especially their antiviral potential. However, data regarding their anti-SARS-CoV-2 potential are scarce in the literature. Thus, this study aimed to identify the most promising EO compounds against SARS-CoV-2 based on their physicochemical, pharmacokinetic, and toxicity properties. A systematic literature search retrieved 1669 articles; 40 met the eligibility criteria, and 35 were eligible for analysis. These studies resulted in 465 EO compounds evaluated against 11 human and/or SARS-CoV-2 target proteins. Ninety-four EO compounds and seven reference drugs were clustered by the highest predicted binding affinity. Furthermore, 41 EO compounds showed suitable drug-likeness and bioactivity score indices (≥0.67). Among these EO compounds, 15 were considered the most promising against SARS-CoV-2 with the ADME/T index ranging from 0.86 to 0.81. Some plant species were identified as EO potential sources with anti-SARS-CoV-2 activity, such as Melissa officinalis Arcang, Zataria multiflora Boiss, Eugenia brasiliensis Cambess, Zingiber zerumbet Triboun & K.Larsen, Cedrus libani A.Rich, and Vetiveria zizanoides Nash. Our work can help fill the gap in the literature and guide further in vitro and in vivo studies, intending to optimize the finding of effective EOs against COVID-19.

Promising phytochemicals of traditional Himalayan medicinal plants against putative replication and transmission targets of SARS-CoV-2 by computational investigation

BACKGROUND

Identification and repurposing of therapeutic and preventive strategies against COVID-19 are rapidly undergoing. Several medicinal plants from the Himalayan region have been traditionally used to treat various human disorders. Thus, in our current study, we intended to explore the potential ability of Himalayan medicinal plant (HMP) bioactives against COVID-19 using computational investigations.

METHODS

Molecular docking was performed against six crucial targets involved in the replication and transmission of SARS-CoV-2. About forty-two HMP bioactives were analyzed against these targets for their binding energy, molecular interactions, inhibition constant, and biological pathway enrichment analysis. Pharmacological properties and potential biological functions of HMP bioactives were predicted using the ADMETlab and PASS webserver respectively.

RESULTS

Our current investigation has demonstrated that the bioactives of HMPs potentially act against COVID-19. Docking results showed that several HMP bioactives had a superior binding affinity with SARS-CoV-2 essential targets like 3CL^pro, PLpro, RdRp, helicase, spike protein, and human ACE2. Based on the binding energies, several bioactives were selected and analyzed for pathway enrichment studies. We have found that selected HMP bioactives may have a role in regulating immune and apoptotic pathways. Furthermore, these selected HMP bioactives have shown lower toxicity with pleiotropic biological activities, including anti-viral activities in predicting activity spectra for substances.

CONCLUSIONS

Current study results can explore the possibility of HMPs as therapeutic agents against COVID-19.

Deciphering the Interactions of Bioactive Compounds in Selected Traditional Medicinal Plants against Alzheimer's Diseases via Pharmacophore Modeling, Auto-QSAR, and Molecular Docking Approaches

Neurodegenerative diseases, for example Alzheimer’s, are perceived as driven by hereditary, cellular, and multifaceted biochemical actions. Numerous plant products, for example flavonoids, are documented in studies for having the ability to pass the blood-brain barrier and moderate the development of such illnesses. Computer-aided drug design (CADD) has achieved importance in the drug discovery world; innovative developments in the aspects of structure identification and characterization, bio-computational science, and molecular biology have added to the preparation of new medications towards these ailments. In this study we evaluated nine flavonoid compounds identified from three medicinal plants, namely T. diversifolia, B. sapida, and I. gabonensis for their inhibitory role on acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and monoamine oxidase (MAO) activity, using pharmacophore modeling, auto-QSAR prediction, and molecular studies, in comparison with standard drugs. The results indicated that the pharmacophore models produced from structures of AChE, BChE and MAO could identify the active compounds, with a recuperation rate of the actives found near 100% in the complete ranked decoy database. Moreso, the robustness of the virtual screening method was accessed by well-established methods including enrichment factor (EF), receiver operating characteristic curve (ROC), Boltzmann-enhanced discrimination of receiver operating characteristic (BEDROC), and area under accumulation curve (AUAC). Most notably, the compounds’ pIC₅₀ values were predicted by a machine learning-based model generated by the AutoQSAR algorithm. The generated model was validated to affirm its predictive model. The best models achieved for AChE, BChE and MAO were models kpls_radial_17 (R² = 0.86 and Q² = 0.73), pls_38 (R² = 0.77 and Q² = 0.72), kpls_desc_44 (R² = 0.81 and Q² = 0.81) and these externally validated models were utilized to predict the bioactivities of the lead compounds. The binding affinity results of the ligands against the three selected targets revealed that luteolin displayed the highest affinity score of −9.60 kcal/mol, closely followed by apigenin and ellagic acid with docking scores of −9.60 and −9.53 kcal/mol, respectively. The least binding affinity was attained by gallic acid (−6.30 kcal/mol). The docking scores of our standards were −10.40 and −7.93 kcal/mol for donepezil and galanthamine, respectively. The toxicity prediction revealed that none of the flavonoids presented toxicity and they all had good absorption parameters for the analyzed targets. Hence, these compounds can be considered as likely leads for drug improvement against the same.

Associations between CYP3A4, CYP3A5 and SCN1A polymorphisms and carbamazepine metabolism in epilepsy: A meta-analysis

BACKGROUND AND OBJECTIVE

CYP3A4 (rs2242480), CYP3A5 (rs776746) and SCN1A (rs3812718 and rs2298771) gene polymorphisms were previously indicated to be associated with carbamazepine (CBZ) metabolism and resistance in epilepsy. However, previous studies regarding the effects of these polymorphisms still remain controversial. Therefore, we performed a meta-analysis to evaluate whether the four polymorphisms are associated with CBZ metabolism and resistance.

METHODS

The PubMed, EMBASE, Cochrane library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database, China Biology Medicine disc and Wan Fang Database were searched up to January 2021 for appropriate studies regarding the association of rs2242480, rs776746, rs3812718 and rs2234922 polymorphisms with CBZ metabolism and resistance. The meta-analysis was conducted by Review Manager 5.3 software.

RESULTS

Eighteen studies involving 2546 related epilepsy patients were included. We found that the G allele of CYP3A4 rs2242480 markedly decreased the plasma CBZ concentration in epilepsy. For CYP3A5 rs776746 polymorphism, the GG genotype (homozygote codominant model: GG vs. AA) and GG + GA genotype (dominant model: GG + GA vs. AA and recessive model: GG vs. GA + AA) were respectively found to be significantly associated with increased CBZ plasma concentration. Additionally, it was also found that the SCN1A rs3812718 A allele was significantly associated with decreased CBZ plasma concentration and increased CBZ resistance. However, no association was observed between SCN1A rs2298771 polymorphism and CBZ metabolism and resistance.

CONCLUSION

The CYP3A4 rs2242480, CYP3A5 rs776746 and SCN1A rs3812718 polymorphisms may play important roles in CBZ metabolism and resistance, while SCN1A rs2298771 polymorphism is not associated with CBZ in epilepsy. These findings would improve the individualized therapy of epileptic patients in clinics.

Identification of the most potent acetylcholinesterase inhibitors from plants for possible treatment of Alzheimer’s disease: a computational approach

Background

Being one of the rapidly growing dementia type diseases in the world, Alzheimer’s disease (AD) has gained much attention from researchers in the recent decades. Many hypotheses have been developed that describe different reasons for the development of AD. Among them, the cholinergic hypothesis depicts that the degradation of an important neurotransmitter, acetylcholine by the enzyme acetylcholinesterase (AChE), is responsible for the development of AD. Although, many anti-AChE drugs are already available in the market, their performance sometimes yields unexpected results. For this reason, research works are going on to find out potential anti-AChE agents both from natural and synthetic sources. In this study, 50 potential anti-AChE phytochemicals were analyzed using numerous tools of bioinformatics and in silico biology to find out the best possible anti-AChE agents among the selected 50 ligands through molecular docking, determination of the druglikeness properties, conducting the ADMET test, PASS and P450 site of metabolism prediction, and DFT calculations.

Result

The predictions of this study suggested that among the selected 50 ligands, bellidifolin, naringenin, apigenin, and coptisine were the 4 best compounds with quite similar and sound performance in most of the experiments.

Conclusion

In this study, bellidifolin, naringenin, apigenin, and coptisine were found to be the most effective agents for treating the AD targeting AChE. However, more in vivo and in vitro analyses are required to finally confirm the outcomes of this research.

Traditional medicinal plants against replication, maturation and transmission targets of SARS-CoV-2: computational investigation

COVID-19 is an infectious pandemic caused by the SARS-CoV-2 virus. The critical components of SARS-CoV-2 are the spike protein (S-protein) and the main protease (M^pro). M^pro is required for the maturation of the various polyproteins involved in replication and transcription. S-protein helps the SARS-CoV-2 to enter the host cells through the angiotensin-converting enzyme 2 (ACE2). Since ACE2 is required for the binding of SARS-CoV-2 on the host cells, ACE2 inhibitors and blockers have got wider attention, in addition to S-protein and M^pro modulators as potential therapeutics for COVID-19. So far, no specific drugs have shown promising therapeutic potential against COVID-19. The current study was undertaken to evaluate the therapeutic potential of traditional medicinal plants against COVID-19. The bioactives from the medicinal plants, along with standard drugs, were screened for their binding against S-protein, M^pro and ACE2 targets using molecular docking followed by molecular dynamics. Based on the higher binding affinity compared with standard drugs, bioactives were selected and further analyzed for their pharmacological properties such as drug-likeness, ADME/T-test, biological activities using in silico tools. The binding energies of several bioactives analyzed with target proteins were relatively comparable and even better than the standard drugs. Based on Lipinski factors and lower binding energies, seven bioactives were further analyzed for their pharmacological and biological characteristics. The selected bioactives were found to have lower toxicity with a higher GI absorption rate and potent anti-inflammatory and anti-viral activities against targets of COVID-19. Therefore, the bioactives from these medicinal plants can be further developed as phytopharmaceuticals for the effective treatment of COVID-19.

Culinary spice bioactives as potential therapeutics against SARS-CoV-2: Computational investigation

Background

Coronavirus disease-2019 (COVID-19) is an infectious pandemic caused by SARS-CoV-2. SARS-CoV-2 main protease (M^pro) and spike protein are crucial for viral replication and transmission. Spike protein recognizes the human ACE2 receptor and transmits SARS-CoV-2 into the human body. Thus, M^pro, spike protein, and ACE2 receptor act as appropriate targets for the development of therapeutics against SARS-CoV-2. Spices are traditionally known to have anti-viral and immune-boosting activities. Therefore, we investigated the possible use of selected spice bioactives against the potential targets of SARS-CoV-2 using computational analysis.

Methods

Molecular docking analysis was performed to analyze the binding efficiency of spice bioactives against SARS-CoV-2 target proteins along with the standard drugs. Drug-likeness properties of selected spice bioactives were investigated using Lipinski's rule of five and the SWISSADME database. Pharmacological properties such as ADME/T, biological functions, and toxicity were analyzed using ADMETlab, PASS-prediction, and ProTox-II servers, respectively.

Results

Out of forty-six spice bioactives screened, six bioactives have shown relatively better binding energies than the standard drugs and have a higher binding affinity with at least more than two targets of SARS-CoV-2. The selected bioactives were analyzed for their binding similarities with the standard drug, remdesivir, towards the targets of SARS-CoV-2. Selected spice bioactives have shown potential drug-likeness properties, with higher GI absorption rate, lower toxicity with pleiotropic biological roles.

Conclusions

Spice bioactives have the potential to bind with the specific targets involved in SARS-CoV-2 infection and transmission. Therefore, spice-based nutraceuticals can be developed for the prevention and treatment of COVID-19.

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The SARS-CoV-2 M^pro, spike protein, and human ACE2 are critical targets for COVID-19.

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Spice bioactives from F. asafoetida and S. indicum potentially inhibit the SARS-CoV-2 targets.

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Selected bioactives have drug-likeness properties along with optimal pharmacological and biological activities.

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The development of spice-based nutraceuticals can be used for the prevention and treatment of COVID-19.

Analysis of plant-derived phytochemicals as anti-cancer agents targeting cyclin dependent kinase-2, human topoisomerase IIa and vascular endothelial growth factor receptor-2

Cancer is caused by a variety of pathways, involving numerous types of enzymes. Among them three enzymes i.e. Cyclin-dependent kinase-2 (CDK-2), Human topoisomerase IIα, and Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) are three of the most common enzymes that are involved in the cancer development. Although many chemical drugs are already available in the market for cancer treatment, plant sources are known to contain a wide variety of agents that are proved to possess potential anticancer activity. In this experiment, total thirty phytochemicals were analyzed against the mentioned three enzymes using different tools of bioinformatics and in silico biology like molecular docking study, drug likeness property experiment, ADME/T test, PASS prediction, and P450 site of metabolism prediction as well as DFT calculation to determine the three best ligands among them that have the capability to inhibit the mentioned enzymes. From the experiment, Epigallocatechin gallate was found to be the best ligand to inhibit CDK-2, Daidzein showed the best inhibitory activities towards the Human topoisomerase IIα, and Quercetin was predicted to be the best agent against VEGFR-2. They were also predicted to be quite safe and effective agents to treat cancer. However, more in vivo and in vitro analyses are required to finally confirm their safety and efficacy in this regard.

Using a high-resolution mass spectrometry-based metabolomics strategy for comprehensively screening and identifying biomarkers of phthalate exposure: Method development and application

Di-(2-propylheptyl) phthalate (DPHP) is an alternative plasticizer that can replace other phthalates currently being scrutinized, and its use and production volumes are increasing. This study aimed to develop a high-resolution mass spectrometry (HRMS)-based metabolomics strategy to comprehensively screen urinary biomarkers of DPHP exposure and filter out potentially useful DPHP exposure markers for human exposure assessments. This strategy included three stages: screening of biomarkers, verification of dose-response relationships in laboratory animals, and application in human subjects. The multivariate data analysis method known as orthogonal partial least-squares discriminant analysis (OPLS-DA) was used to screen and find meaningful signals in an MS dataset generated from urine samples collected from DPHP-administered rats. Thirty-six MS signals were verified as exposure marker candidates by assessing dose-response relationships in an animal feeding study. A biotransformation product of DPHP, mono-(2-propyl-7-dihydroxy-heptyl) phthalate, was suggested as a DPHP exposure marker for general human exposure assessments after the human application study and chemical structure identification. Three previously oxidized DPHP biotransformation products might be suitable for human exposure assessments in high-level exposure groups but not in the general population due to their low sensitivity.

Potential Drug-Drug Interactions with Antimicrobials in Hospitalized Patients: A Multicenter Point-Prevalence Study

Background

Improper use of antimicrobials can cause adverse drug events and high costs. The purpose of this study was to investigate the frequency and potential drug–drug interactions associated with antimicrobials among hospitalized patients.

Material/Methods

This study was conducted on the same day in 5 different hospitals in Turkey. We included patients aged ≥18 years who received at least 1 antimicrobial drug and at least 1 of any other drug. The Micromedex^® online drug reference system was used to control and describe the interactions. Drug interactions were classified as contraindicated, major, moderate, and minor.

Results

Potential drug–drug interactions with antimicrobials were 26.4% of all interactions. Five (42%) of 12 contraindicated interactions and 61 (38%) of 159 major interactions were with antimicrobials. Quinolones, triazoles, metronidazole, linezolid, and clarithromycin accounted for 173 (25.7%) of 673 prescribed antimicrobials, but were responsible for 141 (92.1%) of 153 interactions. In multivariate analysis, number of prescribed antimicrobials (odds ratio: 2.3001, 95% CI: 1.6237–3.2582), number of prescribed drugs (odds ratio: 1.2008, 95% CI: 1.0943–1.3177), and hospitalization in the university hospital (odds ratio: 1.7798, 95% CI: 1.0035–3.1564) were independent risk factors for developing drug interactions.

Conclusions

Due to risk of drug interactions, physicians should be more cautious when prescribing antimicrobials, particularly when prescribing quinolones, linezolid, azoles, metronidazole, and macrolides.

Comparison of metabolic pathways of different α-N-heterocyclic thiosemicarbazones

Clinical failure of novel drugs is often related to their rapid metabolism and excretion. This highlights the importance of elucidation of their pharmacokinetic profile already at the preclinical stage of drug development. Triapine, the most prominent representative of α-N-heterocyclic thiosemicarbazones, was investigated in more than 30 clinical phase I/II trials, but the results against solid tumors were disappointing. Recent investigations from our group suggested that this is, at least partially, based on the fast metabolism and excretion. In order to establish more detailed structure/activity/metabolism relationships, herein a panel of 10 different Triapine derivatives was investigated for their metabolic pathways. From the biological point of view, the panel consists of terminally dimethylated thiosemicarbazones with nanomolar IC₅₀ values, derivatives with micromolar cytotoxicities comparable to Triapine and a completely inactive representative. To study the oxidative metabolism, a purely instrumental approach based on electrochemistry/mass spectrometry was applied and the results were compared to the data obtained from microsomal incubations. Overall, the investigated thiosemicarbazones underwent the phase I metabolic reactions dehydrogenation, hydroxylation, oxidative desulfuration (to semicarbazone and amidrazone) and demethylation. Notably, dehydrogenation resulted in a ring-closure reaction with formation of thiadiazoles. Although strong differences between the metabolic pathways of the different thiosemicarbazones were observed, they could not be directly correlated to their cytotoxicities. Finally, the metabolic pathways for the most cytotoxic compound were elucidated also in tissues collected from drug-treated mice, confirming the data obtained by electrochemical oxidation and microsomes. In addition, the in vivo experiments revealed a very fast metabolism and excretion of the compound.

Graphical abstract

Mice Fed a High-Fat Diet Supplemented with Resistant Starch Display Marked Shifts in the Liver Metabolome Concurrent with Altered Gut Bacteria

BACKGROUND

High-amylose-maize resistant starch type 2 (HAMRS2) is a fermentable dietary fiber known to alter the gut milieu, including the gut microbiota, which may explain the reported effects of resistant starch to ameliorate obesity-associated metabolic dysfunction.

OBJECTIVE

Our working hypothesis was that HAMRS2-induced microbiome changes alter gut-derived signals (i.e., xenometabolites) reaching the liver via the portal circulation, in turn altering liver metabolism by regulating gene expression and other pathways.

METHODS

We used a multi-omics systems biology approach to characterize HAMRS2-driven shifts to the cecal microbiome, liver metabolome, and transcriptome, identifying correlates between microbial changes and liver metabolites under obesogenic conditions that, to our knowledge, have not previously been recognized. Five-week-old male C57BL/6J mice were fed an energy-dense 45% lard-based-fat diet for 10 wk supplemented with either 20% HAMRS2 by weight (n = 14) or rapidly digestible starch (control diet; n = 15).

RESULTS

Despite no differences in food intake, body weight, glucose tolerance, fasting plasma insulin, or liver triglycerides, the HAMRS2 mice showed a 15-58% reduction in all measured liver amino acids, except for Gln, compared with control mice. These metabolites were equivalent in the plasma of HAMRS2 mice compared with controls, and transcripts encoding key amino acid transporters were not different in the small intestine or liver, suggesting that HAMRS2 effects were not simply due to lower hepatocyte exposure to systemic amino acids. Instead, alterations in gut microbial metabolism could have affected host nitrogen and amino acid homeostasis: HAMRS2 mice showed a 62% increase (P < 0.0001) in 48-h fecal output and a 41% increase (P < 0.0001) in fecal nitrogen compared with control mice. Beyond amino acid metabolism, liver transcriptomics revealed pathways related to lipid and xenobiotic metabolism; and pathways related to cell proliferation, differentiation, and growth were affected by HAMRS2 feeding.

CONCLUSION

Together, these differences indicate that HAMRS2 dramatically alters hepatic metabolism and gene expression concurrent with shifts in specific gut bacteria in C57BL/6J mice.

Evaluation on activity of cytochrome p450 enzymes in turbot via a probe drug cocktail

Cytochrome P450s (CYPs) are the main catalytic enzymes for metabolism by a variety of endogenous and exogenous substrates in mammals, fish, insects, etc. We evaluated the application of a multidrug cocktail on changes in CYP1, CYP2, and CYP3 activity in Turbot Scophthalmus maximus. The probe drugs were a combination of caffeine (5 mg/kg body weight), dapsone (5 mg/kg), and chlorzoxazone (10 mg/kg). After a single intraperitoneal injection of the cocktail, the concentration of all three probe drugs in the plasma increased quickly to a peak and then decreased gradually over 24 h. Pharmacokinetic profiles of the three probe drugs were determined using a noncompartmental analysis, and the typical parameters were calculated. In the assay for CYP induction, pretreatment with rifampicin significantly reduced the typical pharmacokinetic metrics for caffeine and chlorzoxazone, but not dapsone, indicating that the activity of CYP1 and CYP2 in turbot were induced by rifampicin.

Simultaneous determination of cytochrome P450 1A, 2A and 3A activities in porcine liver microsomes

The aim of this study was to develop a robust method for the simultaneous determination of the activities of three porcine CYP450 enzymes in hepatic microsomes. A cocktail consisting of three selective CYP450 probe substrates, 7-ethoxyresorufin (CYP1A), coumarin (CYP2A) and 7-benzyloxy-4-trifluoromethylcoumarin (BFC; CYP3A), was incubated with porcine liver microsomes. The presence of 7-ethoxyresorufin appears to significantly influence the kinetics of coumarin hydroxylation and BFC O-debenzylation. These results indicate that the use of 7-ethoxyresorufin in substrate cocktails together with coumarin and BFC should be avoided.

Effect of ciprofloxacin and grapefruit juice on oral pharmacokinetics of riluzole in Wistar rats

Objectives

The objective of this study was to explore potential drug–drug/food interactions of ciprofloxacin and grapefruit juice, known hepatic cytochrome P450 (CYP) 1A2 inhibitors, on single-dose oral pharmacokinetics of riluzole, a substrate of CYP 1A2 enzymes.

Methods

Pharmacokinetic parameters of riluzole were determined in Wistar rats after single-dose co-administration with ciprofloxacin and grapefruit juice. In-vitro metabolic inhibition studies using rat and human liver microsomes and intestinal absorption studies of riluzole in a rat everted gut-sac model were conducted to elucidate the mechanism of interaction. A validated HPLC method was employed to quantify riluzole in the samples obtained in various studies.

Key findings

Co-administration of ciprofloxacin with riluzole caused significant increase in systemic exposure of riluzole (area under the curve, maximum plasma concentration and mean residence time were found to increase). Co-administration of grapefruit juice with riluzole did not cause any significant difference in the pharmacokinetic parameters of riluzole. In-vitro metabolism studies demonstrated significant inhibition of riluzole metabolism when it was co-incubated with ciprofloxacin or grapefruit juice. No significant change was observed in apparent permeability of riluzole.

Conclusions

Co-administration of ciprofloxacin with riluzole increases the systemic levels of riluzole and thereby the oral pharmacokinetic properties of riluzole while co-administration of grapefruit juice with riluzole has no significant effect.

In vitro drug metabolism using liver microsomes

Metabolic biotransformation of a drug can increase the rate of elimination from the body and have a significant effect on efficacy and safety. Drug candidates are screened early in the discovery process for metabolic stability using liver microsomes. Methods for microsome isolation and characterization and the determination of metabolic stability are presented.

Patient counseling about herbal-drug interactions

Many people have the mistaken notion that, being natural, all herbs and foods are safe; this is not so. Very often, herbs and food may interact with medications you normally take, result in serious reactions. During the latter part of this century the practice of herbalism has become mainstream throughout the world. This is due remove to the recognition of the value of traditional medical systems in the world. Herbal medicines are mixtures of more than one active ingredient. The multitude of pharmacologically active compounds obviously increases the likelihood of interactions taking place. Hence, the likelihood of herb-drug interactions is theoretically higher than drug-drug interactions because synthetic drugs usually contain single chemical entity. Case reports and clinical studies have highlighted the existence of a number of clinically important interactions, although cause-and-effect relationships have not always been established. Herbs and drugs may interact either pharmacokinetically or pharmacodynamically. The predominant mechanism for this interaction is the inhibition of cytochrome P-450 3A4 in the small intestine; result in a significant reduction of drug presystemic metabolism. An additional mechanism is the inhibition of Pglycoprotein, a transporter that carries drug from the enterocyte back to the gut lumen, result in a further increase in the fraction of drug absorbed. Some herbal products (e.g. St. John's wort) have been shown to lower the plasma concentration (and/or the pharmacological effect) of a number of conventional drugs including cyclosporine, indinavir, irinotecan, nevirapine, oral contraceptives and digoxin. The data available so far, concerning this interaction and its clinical implications are reviewed in this article. It is likely that more information regarding such interaction would crop up in the future, awareness of which is necessary for achieving optimal drug therapy.

Evaluation of CYP450 inhibitory effects and steady-state pharmacokinetics of genistein in combination with cholecalciferol and citrated zinc bisglycinate in postmenopausal women

Background

The combination of genistein 27 mg, cholecalciferol 200 IU, citrated zinc bisglycinate (4 mg elemental zinc) 20 mg per capsule in Fosteum^®, a prescription medical food regulated by the FDA and indicated for the dietary management of osteopenia and osteoporosis, was tested for drug interactions and to determine the pharmacokinetic profile for genistein, the principal bone-modulating ingredient in the product.

Methods

In vitro human liver microsome cytochrome P450 (CYP450) assays were used to test the product for potential drug interactions with the isoforms 1A2, 2C8, 2C9, 2C19, 2D6, and 3A4. Due to specific 2C8 and 2C9 inhibition, a steady-state pharmacokinetic study was performed to assess serum genistein concentrations by high-pressure liquid chromatography-coupled mass spectroscopy in healthy fasting (n = 10) and fed (n = 10) postmenopausal women.

Results

The product showed minimal inhibition of 1A2, 2C19, 2D6, and 3A4, exhibiting IC₅₀ > 10 μM, but 2C8 and 2C9 yielded IC₅₀ of 2.5 μM and 2.8 μM, respectively, concentrations which are theroretically achievable when dosing the product twice daily. After seven days of administration in a steady-state pharmacokinetic study, significant differences were found for unconjugated genistein (including free and protein-bound), regarding time to peak concentration (1.88 ± 1.36 hours), maximum concentration reached (0.052 ± 0.055 μM), elimination half-life (2.3 ± 1.6 hours), and area under the concentration-time curve (53.75 ± 17.59 ng · hour/mL) compared with results for total genistein (including glucuronidated and sulfonated conjugates) time to peak concentration (2.22 ± 1.09 hours), maximum concentration reached (2.95 ± 1.64 μM), elimination half-life (10.4 ± 4.1 hours), and area under the concentration-time curve (10424 ± 6290 ng · hour/mL) in fasting subjects. Coadministration of food tended to extend the time and extent of absorption as well as slow elimination of genistein, but not in a statistically significant manner.

Conclusion

Because the serum genistein concentrations achieved during pharmacokinetic testing at therapeutic doses were well below those required for enzyme inhibition in the in vitro liver microsome assays, these results indicate a low potential for drug interactions.

Diverse approaches for the enhancement of oral drug bioavailability

In conscious and co-operating patients, oral drug delivery remains the preferable route of drug administration. However, not all drugs possess the desirable physicochemical and pharmacokinetic properties which favor oral administration mainly due to poor bioavailability. This has in some cases led to the choice of other routes of administration, which may compromise the convenience and increase the risk of non-compliance. Poor bioavailability has necessitated the administration of higher than normally required oral doses which often leads to economic wastages, risk of toxicity, erratic and unpredictable responses. The challenge over the years has been to design techniques that will allow oral administration of most drugs, irrespective of their properties, to achieve a therapeutic systemic availability. This will be a worthy achievement since over 90% of therapeutic compounds are known to possess oral bioavailability limitations. In this review, an attempt has been made to explore various approaches that have been used in recent years to improve oral drug bioavailability, including physical and chemical means. This review strives to provide a comprehensive overview of advances made over the past 10 years (2000-2010) in the improvement of the oral bioavailability of drugs. Briefly, the design of prodrugs to bypass metabolism or to enhance solubility as well as modification of formulation techniques such as the use of additives, permeation enhancers, solubilizers, emulsifiers and non-aqueous vehicles have been discussed. Arising approaches, such as formulation modification techniques; novel drug delivery systems, which exploit the gastrointestinal regionality of drugs, and include the pharmaceutical application of nanotechnology as an emerging area in drug delivery; inhibition of efflux pumps; and inhibition of presystemic metabolism have been more extensively addressed. This critical review sought to assess each method aimed at enhancing the oral bioavailability of drugs in terms of the purpose, scientific basis, limitations, commercial application, as well as the areas in which current research efforts are being focused and should be focused in the future.

Cytotoxic drug residues in urine of dogs receiving anticancer chemotherapy

BACKGROUND

The presence of cytotoxic drug residues in urine of dogs may represent an exposure risk for pet owners and other people as well as a potential environmental contaminant. However, studies on cytotoxic drug residues in excretions of clinical patients are lacking in veterinary oncology.

HYPOTHESIS

Variable concentrations of cytotoxic residues are present in urine samples, depending on sampling time and substance.

ANIMALS

Client-owned dogs with lymphoma or mast cell tumors treated with standard chemotherapy protocols.

METHODS

Urine samples were collected before, directly after, and on days after administration of chemotherapy. Measurement of vincristine, vinblastine, cyclophosphamide, and doxorubicin residues in canine urine was performed by a quantitative liquid chromatography tandem mass spectrometry (LC/MS/MS) method.

RESULTS

Median cyclophosphamide residue concentration was 398.2 microg/L directly after treatment (d0) and was below the level of detection on days 1-3 (d1, d2, d3). Median vincristine residue concentration was 53.8 microg/L directly after treatment and was 20.2, 11.4, and 6.6 microg/L on days 1, 2, and 3. Median vinblastine residues were 144.9 (d0), 70.8 (d1), 35.6 (d2), and 18.7 microg/L (d3) with low concentrations detectable for 7 days after treatment. Median urine doxorubicin concentrations were 354.0 (d0), 165.6 (d1), 156.9 (d2), and 158.2 microg/L (d3). Low concentrations of doxorubicin were measurable up to 21 days after administration.

CONCLUSIONS AND CLINICAL IMPORTANCE

Variable concentrations of chemotherapeutics were measured in urine samples, depending on sampling time point and drug. Findings may inform current chemoprotection guidelines and help minimize exposure risks.

Human liver mitochondrial cytochrome P450 2D6--individual variations and implications in drug metabolism

Constitutively expressed human cytochrome P450 2D6 (CYP2D6; EC 1.14.14.1) is responsible for the metabolism of approximately 25% of drugs in common clinical use. It is widely accepted that CYP2D6 is localized in the endoplasmic reticulum of cells; however, we have identified this enzyme in the mitochondria of human liver samples and found that extensive inter-individual variability exists with respect to the level of the mitochondrial enzyme. Metabolic assays using 7-methoxy-4-aminomethylcoumarin as a substrate show that the human liver mitochondrial enzyme is capable of oxidizing this substrate and that the catalytic activity is supported by mitochondrial electron transfer proteins. In the present study, we show that CYP2D6 contains an N-terminal chimeric signal that mediates its bimodal targeting to the endoplasmic reticulum and mitochondria. In vitro mitochondrial import studies using both N-terminal deletions and point mutations suggest that the mitochondrial targeting signal is localized between residues 23-33 and that the positively-charged residues at positions 24, 25, 26, 28 and 32 are required for mitochondrial targeting. The importance of the positively-charged residues was confirmed by transient transfection of a CYP2D6 mitochondrial targeting signal mutant in COS-7 cells. Both the mitochondria and the microsomes from a CYP2D6 stable expression cell line contain the enzyme and both fractions exhibit bufuralol 1'-hydroxylation activity, which is completely inhibited by CYP2D6 inhibitory antibody. Overall, these results suggest that the targeting of CYP2D6 to mitochondria could be an important physiological process that has significance in xenobiotic metabolism.

Pharmacovigilance: effects of herbal components on human drugs interactions involving cytochrome P450

Cytochrome P450 (CYP P450) enzymes are a superfamily of mono-oxygenases that are found in all kingdoms of life. The CYP P450 enzymes constitute a large superfamily of haem-thiolate proteins involved in the metabolism of a wide variety of both exogenous and endogenous compounds. The CYP activities have been shown to be involved in numerous interactions especially between drugs and herbal constituents. The majority of serious cases of drug interactions are as a result of the interference of the metabolic clearance of one drug by yet another co-administered drug, food or natural product. Gaining mechanistic knowledge towards such interactions has been accepted as an approach to avoid adverse reactions. The inductions and inhibition of CYP enzymes by natural products in the presence of a prescribed drug has led to adverse effects. Herbal medicines such as St. John's wort (Hypericum perforatum), garlic (Allium sativa), piperine (from Piper sp.), ginseng (Ginseng sp.), gingko (Gingko biloba), soya beans (Glycine max), alfalfa (Medicago sativa) and grape fruit juice show clinical interactions when co-administered with medicines. This review documents the involvement of CYP enzymes in the metabolism of known available drugs and herbal products. We also document the interactions between herbal constituents & CYP enzymes showing potential drug-herb interactions. Data on CYP450 enzymes in activation (i.e. induction or inhibition) with natural constituents is also reviewed.

Development of a novel cytochrome p450 bioaffinity detection system coupled online to gradient reversed-phase high-performance liquid chromatography

A high-resolution screening platform, coupling online affinity detection for mammalian cytochrome P450s (Cyt P450s) to gradient reversed-phase high-performance liquid chromatography (HPLC), is described. To this end, the online Cyt P450 enzyme affinity detection (EAD) system was optimized for enzyme (beta-NF-induced rat liver microsomes), probe substrate (ethoxyresorufine), and organic modifier (methanol or acetonitrile). The optimized Cyt P450 EAD system has first been evaluated in a flow injection analysis (FIA) mode with 7 known ligands of Cyt P450 1A1/1A2 (alpha-naphthoflavone, beta-naphthoflavone, ellipticine, 9-hydroxy-ellipticine, fluvoxamine, caffein, and phenacetin). Subsequently, IC50 values were online in FIA-mode determined and compared with those obtained with standardmicrosomal assay conditions. The IC50 values obtained with the online Cyt P450 EAD system agreed well with the IC50 values obtained in the standard assays. For high affinity ligands of Cyt P450 1A1/1A2, detection limits of 1 to 3 pmol injected (n=3; signal to noise [S/N]=3) were obtained. The individual inhibitory properties of ligands in mixtures of the ligands were subsequently investigated using an optimized Cyt P450 EAD system online coupled to gradient HPLC. Using the integrated online gradient HPLC Cyt P450 EAD platform, detection limits of 10 to 25 pmol injected (n=1; S/N=3) were obtained for high-affinity ligands. It is concluded that this novel screening technology offers new perspectives for rapid and sensitive screening of individual compounds in mixtures exhibiting affinity for liver microsomal Cyt P450s.

Structure and redox properties of the haem centre in the C357M mutant of cytochrome P450cam

The effects of site-specific mutation of the axial cysteine (C357M) to a methionine residue in cytochrome P450cam on the enzyme's coordination geometry and redox potential have been investigated. The absorption spectra of the haem centre in the C357M mutant of the enzyme showed close similarity to those of cytochrome c both in the oxidised and reduced forms. A well-defined absorption peak at 695 nm, similar to that seen in the case of cytochrome c and characteristic of methionine ligation to the ferric haem, was observed. The results indicated that the haem of C357M cytochrome P450cam is possibly axially coordinated to a methionine and a histidine, analogously to cytochrome c. The circular dichroism spectra in the visible and the far-UV regions suggested that the tertiary structure of the haem cavity in the C357M mutant cytochrome P450cam was distinctly different from that in the wild-type enzyme or in cytochrome c, although the secondary structure of the mutant remained identical to that of the wild-type cytochrome P450cam. Comparison of the natures of the CD spectra in the 400 nm and 695 nm regions of the C357M mutant of cytochrome P450cam with those of horse cytochrome c suggested (R) chirality at the sulfur atom of the iron-bound methionine residue in the mutant. The redox potential of the haem centre, estimated by redox titration of the C357M mutant, was found to be +260 mV, which is much higher than that in the wild-type enzyme and similar to the redox potential of cytochrome c. This supported the concept that axial ligation of the haem plays the major role in tuning the redox potential of the haem centre in haem proteins.

Use of nonsteroidal antiinflammatory drugs and risk of colon cancer in a population-based, case-control study of African Americans and Whites

African Americans have the highest colon cancer incidence and mortality rates among all US ethnic groups. Epidemiologic studies suggest that use of nonsteroidal antiinflammatory drugs (NSAIDs) is associated with a reduced risk of colon cancer, but no study to date with adequate sample size has reported on the association among African Americans. The authors examined the association between NSAID use and risk of colon cancer in a population-based, case-control study in North Carolina that enrolled 731 African-American (294 cases, 437 controls) and 960 White (349 cases, 611 controls) participants between 1996 and 2000. Odds ratios were calculated using unconditional logistic regression for categories of NSAIDs and colon cancer risk. Inverse associations between regular NSAID use and colon cancer were similar for African Americans (odds ratio = 0.41, 95% confidence interval: 0.22, 0.77) and Whites (odds ratio = 0.48, 95% confidence interval: 0.28, 0.83) but stronger for women than men. Inverse associations were slightly weaker for occasional versus regular NSAID use, but they were similar for aspirin and nonaspirin NSAID use. These results add new knowledge suggesting that the protective effect of NSAIDs against colon cancer is similar among African Americans and Whites.

Cytochrome P4501A1 polymorphisms in the Amerindian and Mestizo populations of Mexico

Several polymorphisms in the CYP1A1 locus have been identified and their genotypes appear to exhibit population frequencies that depend on ethnicity. We studied two CYP1A1 polymorphic sites (position 4889 and 6235) in a group of 212 unrelated healthy individuals belonging to three different Mexican populations (106 Mexican Mestizos, 52 Teenek and 54 Mayos). Comparison among Mexican populations showed increased frequency of the *Ile allele (A on position 4889) in Mexican Mestizos when compared to Amerindians (p < 0.05). The analysis of position 6235 showed increased frequencies of *m2 (C in this position) allele in Teenek when compared to Mestizos and Mayos (p < 0.05) and of *m2/*m2 genotype when compared to Mestizos (p < 0.05). Amerindian populations (from Mexico and South America) presented the lowest frequencies of *Ile (position 4889) and *m1 (position 6235) alleles, however these frequencies vary according to the ethnic group studied. Mexican Amerindian groups together with other South Amerindian populations showed the highest frequencies for *Val at position 4889 and the *m2 allele at position 6235. The present study corroborates the high frequencies of*Val and *m2 alleles in the Amerindian populations and detects some differences between Mexican populations that correlate with linguistic differences. Our data could be helpful in understanding the distribution of these polymorphisms and in clarifying their roles as genetic and evolution markers in Amerindian populations.

Human Carbonyl Reduction Pathways and a Strategy for Their Study In Vitro

Carbonyl reduction plays a significant role in physiological processes throughout the body. Although much is known about endogenous carbonyl metabolism, much less is known about the roles of carbonyl-reducing enzymes in xenobiotic metabolism. Multiple pathways exist in humans for metabolizing carbonyl moieties of xenobiotics to their corresponding alcohols, readying these molecules for subsequent conjugation and/or excretion. When exploring carbonyl reduction clearance pathways for a drug development candidate, it is possible to assess the relative contributions of these enzymes due to their differences in subcellular locations, cofactor dependence, and inhibitor profiles. In addition, the contributions of these enzymes may be explored by varying incubation conditions, such as pH. Presently, individual isoforms of carbonyl-reducing enzymes are not widely available, either in recombinant or purified form. However, it is possible to study carbonyl reduction clearance pathways from simple experiments with commercially available reagents. This article provides an overview of carbonyl-reducing enzymes, including some kinetic data for substrates and inhibitors. In addition, an experimental strategy for the study of these enzymes in vitro is presented.

Anaesthetic implications of anticancer chemotherapy

In anaesthetic practice we deal with cancer patients who are scheduled for operations on tumours or other manifestations of malignant disease. Those patients are often debilitated and have significant weight loss accompanied with hypoproteinaemia, anaemia and coagulation disorders. Oncological patients usually present to the anaesthetist before tumour disease surgery, but they are also candidates for elective operations (e.g. hernia repair) and urgent/emergency surgery (e.g. trauma, fractures and ileus). Chemotherapeutic agents given to these patients are potentially noxious, can affect the conduct of anaesthesia and, furthermore, may aggravate the patient's condition. In this review the most commonly used cytostatic drug regimens and their common side-effects are listed. Some preclinical studies on anaesthetic and cytostatic drug metabolism and interactions are emphasized, as well as clinically relevant perioperative alterations that may affect anaesthetic management in cancer patients. An anaesthetist may have to modify a routine anaesthetic regimen in cancer patients especially if anticancer chemotherapeutics were given. Clinically silent toxic drug effects may become apparent during operation, trauma or in the early postoperative course in such patients. Altered reactions to commonly used anaesthetics in patients receiving chemotherapeutics and an impaired stress reaction may occur in such patients. Special attention must be drawn to protection against opportunistic infections.

Quantitative drug interactions prediction system (Q-DIPS): a dynamic computer-based method to assist in the choice of clinically relevant in vivo studies

Metabolic drug interactions are a major source of clinical problems, but their investigation during drug development is often incomplete and poorly specific. In vitro studies give very accurate data on the interactions of drugs with selective cytochrome P450 (CYP) isozymes, but their interpretation in the clinical context is difficult. On the other hand, the design of in vivo studies is sometimes poor (choice of prototype substrate, doses, schedule of administration, number of volunteers), with the risk of minimising the real potential for interaction. To link in vitro and in vivo studies, several authors have suggested using extrapolation techniques, based on the comparison of in vitro inhibition data with the active in vivo concentrations of the inhibitor. However, the lack of knowledge of one or several important parameters (role of metabolites, intrahepatocyte accumulation) often limits the possibility for safe and accurate predictions. In consequence, these methods are useful to complement in vitro studies and help design clinically relevant in vivo studies, but they will not totally replace in vivo investigation in the future. We have developed a computerised application, the quantitative drug interactions prediction system (Q-DIPS), to make both qualitative deductions and quantitative predictions on the basis of a database containing updated information on CYP substrates, inhibitors and inducers, as well as pharmacokinetic parameters. We also propose a global approach to drug interactions problems--'good interactions practice--to help design rational drug interaction investigations, sequentially associating in vitro studies, in vitrolin vivo extrapolation and finally well-designed in vivo clinical studies.