Non-additivity of the functional properties of individual P450 species and its manifestation in the effects of alcohol consumption on the metabolism of ketamine and amitriptyline

To explore functional interconnections between multiple P450 enzymes and their manifestation in alcohol-induced changes in drug metabolism, we implemented a high-throughput study of correlations between the composition of the P450 pool and the substrate saturation profiles (SSP) of amitriptyline and ketamine demethylation in a series of 23 individual human liver microsomes preparations from donors with a known history of alcohol consumption. The SSPs were approximated with linear combinations of three Michaelis-Menten equations with globally optimized KM (substrate affinity) values. This analysis revealed a strong correlation between the rate of ketamine metabolism and alcohol exposure. For both substrates, alcohol consumption caused a significant increase in the role of the low-affinity enzymes. The amplitudes of the kinetic components and the total rate were further analyzed for correlations with the abundance of 11 major P450 enzymes assessed by global proteomics. The maximal rate of metabolism of both substrates correlated with the abundance of CYP3A4, their predicted principal metabolizer. However, except for CYP2D6 and CYP2E1, responsible for the low-affinity metabolism of ketamine and amitriptyline, respectively, none of the other potent metabolizers of the drugs revealed a positive correlation. Instead, in the case of ketamine, we observed negative correlations with the abundances of CYP1A2, CYP2C9, and CYP3A5. For amitriptyline, the data suggest inhibitory effects of CYP1A2 and CYP2A6. Our results demonstrate the importance of functional interactions between multiple P450 species and their decisive role in the effects of alcohol exposure on drug metabolism.

Bioconversion and P-gp-Mediated Transport of Depot Fluphenazine Prodrugs after Intramuscular Injection

Fluphenazine (FPZ) decanoate, an ester-type prodrug formulated as a long-acting injection (LAI), is used in the treatment of schizophrenia. FPZ enanthate was also developed as an LAI formulation, but is no longer in use clinically because of the short elimination half-life of FPZ, the parent drug, after intramuscular injection. In the present study, the hydrolysis of FPZ prodrugs was evaluated in human plasma and liver to clarify the reason for this difference in elimination half-lives. FPZ prodrugs were hydrolyzed in human plasma and liver microsomes. The rate of hydrolysis of FPZ enanthate in human plasma and liver microsomes was 15-fold and 6-fold, respectively, faster than that of FPZ decanoate. Butyrylcholinesterase (BChE) and human serum albumin (HSA) present in human plasma, and two carboxylesterase (CES) isozymes, hCE1 and hCE2, expressed in ubiquitous organs including liver, were mainly responsible for the hydrolysis of FPZ prodrugs. FPZ prodrugs may not be bioconverted in human skeletal muscle at the injection site because of lack of expression of BChE and CESs in muscle. Interestingly, although FPZ was a poor substrate for human P-glycoprotein, FPZ caproate was a good substrate. In conclusion, it is suggested that the shorter elimination half-life of FPZ following administration of FPZ enanthate compared with FPZ decanoate can be attributed to the more rapid hydrolysis of FPZ enanthate by BChE, HSA and CESs.

Tools for optimising pharmacotherapy in psychiatry (therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests): focus on antidepressants

Objectives: More than 40 drugs are available to treat affective disorders. Individual selection of the optimal drug and dose is required to attain the highest possible efficacy and acceptable tolerability for every patient.Methods: This review, which includes more than 500 articles selected by 30 experts, combines relevant knowledge on studies investigating the pharmacokinetics, pharmacodynamics and pharmacogenetics of 33 antidepressant drugs and of 4 drugs approved for augmentation in cases of insufficient response to antidepressant monotherapy. Such studies typically measure drug concentrations in blood (i.e. therapeutic drug monitoring) and genotype relevant genetic polymorphisms of enzymes, transporters or receptors involved in drug metabolism or mechanism of action. Imaging studies, primarily positron emission tomography that relates drug concentrations in blood and radioligand binding, are considered to quantify target structure occupancy by the antidepressant drugs in vivo. Results: Evidence is given that in vivo imaging, therapeutic drug monitoring and genotyping and/or phenotyping of drug metabolising enzymes should be an integral part in the development of any new antidepressant drug.Conclusions: To guide antidepressant drug therapy in everyday practice, there are multiple indications such as uncertain adherence, polypharmacy, nonresponse and/or adverse reactions under therapeutically recommended doses, where therapeutic drug monitoring and cytochrome P450 genotyping and/or phenotyping should be applied as valid tools of precision medicine.

Impact of single nucleotide polymorphisms (R132Q and W120R) on the binding affinity and metabolic activity of CYP2C19 toward some therapeutically important substrates

Although CYP2C19 is minor human liver enzyme, it is responsible for the metabolism of many clinically important drugs. In this work, CYP2C19 wild type and its SNP mutants (R132Q and W120R) were prepared using over-expression system in E. coli, purified by column chromatography and their biological activities were compared. The enzyme activity toward certain drugs (amitriptyline, imipramine, lansoprazole and omeprazole) was investigated. Resonance Raman and UV-VIS spectroscopies revealed a minimal effect of SNP mutations on the heme structure. However, the mutation greatly affected the drug metabolism activities of CYP2C19. The degree of these effects was dependent on both the mutation and the chemical structure of the substrate. Surprisingly, the affected amino acid residue is located remotely from the heme center. Therefore, the direct effect of the mutation on the metabolic center is excluded. Alternatively, the significant impairment in the drug metabolism of these mutants could be attributed to a decrease in the electron flow to the iron center. Accordingly, understanding the effect of SNPs of CYP2C19, and the extents in which they participate in the drug metabolism, are important pillars that can enhance the therapeutic drugs efficacy and improve the patient outcomes toward the development of patient's tailored medicine.

Drug vector representation: a tool for drug similarity analysis

DrugMatrix is a valuable toxicogenomic dataset, which provides in vivo transcriptome data corresponding to hundreds of chemical drugs. However, the relationships between drugs and how those drugs affect the biological process are still unknown. The high dimensionality of the microarray data hinders its application. The aims of this study are to (1) represent the transcriptome data by lower-dimensional vectors, (2) compare drug similarity, (3) represent drug combinations by adding vectors and (4) infer drug mechanism of action (MoA) and genotoxicity features. We borrowed the latent semantic analysis (LSA) technique from natural language processing to represent treatments (drugs with multiple concentrations and time points) by dense vectors, each dimension of which is an orthogonal biological feature. The gProfiler enrichment tool was used for the 100-dimensional vector feature annotation. The similarity between treatments vectors was calculated by the cosine function. Adding vectors may represent drug combinations, treatment times or treatment doses that are not presented in the original data. Drug-drug interaction pairs had a higher similarity than random drug pairs in the hepatocyte data. The vector features helped to reveal the MoA. Differential feature expression was also implicated for genotoxic and non-genotoxic carcinogens. An easy-to-use Web tool was developed by Shiny Web application framework for the exploration of treatment similarities and drug combinations (https://bioinformatics.fafu.edu.cn/drugmatrix/). We represented treatments by vectors and provided a tool that is useful for hypothesis generation in toxicogenomic, such as drug similarity, drug repurposing, combination therapy and MoA.

Effect of Drug Combination on Omeprazole Metabolism by Cytochrome P450 2C19 in Helicobacter pylori Eradication Therapy

Helicobacter pylori (H. pylori) infection is common and can result in gastric and duodenal ulcers, and in some cases, gastric lymphoma and cancer. Omeprazole (OMP)-in combination with clarithromycin (CLR), amoxicillin (AMX), tinidazole (TND), or metronidazole (MET)-is used in double or triple combination therapy for eradication of H. pylori. However, the roles of the drugs other than OMP are not clearly understood. Therefore, in the present study, we aimed to investigate any effects of these drugs on OMP metabolism by wild-type CYP2C19 using spectroscopy and enzyme kinetics. The dissociation constants (K_d) for CYP2C19 with OMP, CLR, AMX, TND, and MET were 8.6, 126, 156, 174, and 249 µM, respectively. The intrinsic clearance of OMP was determined to be 355 mL/min/µmol of CYP2C19. Metabolism of OMP was significantly inhibited by 69, 66, 28, and 40% in the presence of CLR, TND, AMX, and MET, respectively. Moreover, the combination of CLR and TND resulted in 76% inhibition of OMP metabolism, while the combination of AMX and MET resulted in 48% inhibition of OMP metabolism. Both combinations of drugs not only have antibacterial effects, but also enhance the effect of OMP by inhibiting its metabolism by CYP2C19. These results indicate that drug-drug interactions of co-administered drugs can cause complex effects, providing a basis for OMP dose adjustment when used in combination therapy for H. pylori eradication.

Investigation on drug-binding in heme pocket of CYP2C19 with UV-visible and resonance Raman spectroscopies

Cytochrome P450 (CYP) is a class of heme-containing enzymes which mainly catalyze a monooxygenation reaction of various chemicals, and hence CYP plays a key role in the drug metabolism. Although CYP2C19 isoform is a minor hepatic CYP, it metabolizes clinically important drugs such as omeprazole and S‑mephenytoin. In this work, the interaction of purified CYP2C19 WT (CYP2C19) with seven drugs (phenytoin, S‑mephenytoin, omeprazole, lansoprazole, cimetidine, propranolol, and warfarin) was investigated using spectroscopic methods. The binding of each drug and the induced structural change in the heme distal environment were evaluated. Ferric form of CYP2C19 was revealed to contain a six-coordinate low-spin heme with a water molecule as a sixth ligand in a distal site, and the addition of each drug caused varied minor fraction of five-coordinate heme. It was suggested that the ligated water molecule was partly moved away from the heme distal environment and that the degree of water removal was dependent on the type of drugs. The effect on the coordination was varied with the studied drugs with wide variation in the dissociation constants from 2.6 μM for lansoprazole to 5400 μM for warfarin. Phenytoin and S‑mephenytoin showed that binding to CYP2C19 occurred in a stepwise manner and that the coordination of a water molecule was facilitated in the second binding step. In the ferrous CO-bound state, ν(FeCO) stretching mode was clearly observed at 471 cm^-1 in the absence of drugs. The Raman line was greatly up-shifted by omeprazole (487 cm^-1) and lansoprazole (477 cm^-1) but was minimally affected by propranolol, phenytoin, and S‑mephenytoin. These results indicate that slight chemical modification of a drug greatly affects the heme distal environments upon binding.