Non-P450 Drug-Metabolizing Enzymes: Contribution to Drug Disposition, Toxicity, and Development

A hollow fiber membrane-based liver organoid-on-a-chip model for examining drug metabolism and transport

Liver-on-a-chip models predictive for both metabolism, and blood and canalicular transport of drug candidates in humans are lacking. Here, we established a bioengineered and 3Rs-complied (animal component-free) hepatocyte-like millifluidic system based on 3D hollow fiber membranes (HFMs), recombinant human laminin 332 coating and adult human stem cell-derived organoids. Organoid fragments formed polarized and tight monolayers on HFMs with improved hepatocyte-like maturation, as compared to standard 3D organoid cultures in Matrigel from matched donors. Gene expression profiling and immunofluorescence revealed that hepatocyte-like monolayers expressed a broad panel of phase I (e.g. CYP3A4, CYP2D6, CYP2C9) and II (e.g. UGTs, SULTs) drug-metabolizing enzymes and drug transporters (e.g. MDR1, MRP3, OATP1B3). Moreover, statically cultured monolayers displayed phase I and II metabolism of a cocktail of six relevant compounds, including midazolam and 7-hydroxycoumarin. We also demonstrated the disposition of midazolam in the basal/blood-like circulation and apical/canalicular-like compartment of the millifluidic chip. Finally, we studied the bioavailability of midazolam and coumarin on-a-chip in combination with a small intestine-like system. In conclusion, we generated a proof-of-concept liver organoid-on-a-chip model for examining metabolism and transport of drugs, which can be further developed to predict pharmacokinetics' (PK)/absorption, distribution, metabolism and excretion (ADME) profiles in humans.

Precision medication based on the evaluation of drug metabolizing enzyme and transporter functions

Pharmacogenomics, therapeutic drug monitoring, and the assessments of hepatic and renal function have made significant contributions to the advancement of individualized medicine. However, their lack of direct correlation with protein abundance/non-genetic factors, target drug concentration, and drug metabolism/excretion significantly limits their application in precision drug therapy. The primary task of precision medicine is to accurately determine drug dosage, which depends on a precise assessment of the ability to handle drugs in vivo, and drug metabolizing enzymes and transporters are critical determinants of drug disposition in the body. Therefore, accurately evaluating the functions of these enzymes and transporters is key to assessing the capacity to handle drugs and predicting drug concentrations in target organs. Recent advancements in the evaluation of enzyme and transporter functions using exogenous probes and endogenous biomarkers show promise in advancing personalized medicine. This article aims to provide a comprehensive overview of the latest research on markers used for the functional evaluation of drug-metabolizing enzymes and transporters. It also explores the application of marker omics in systematically assessing their functions, thereby laying a foundation for advancing precision pharmacotherapy.

Scaling factors to inform in vitro-in vivo extrapolation from preclinical and livestock animals: state of the field and recommendations for development of missing data

The use of in-vitro-in-vivo physiologically based pharmacokinetic (IVIVE-PBPK) modeling approaches assists for prediction of first-in animal or human trials. These approaches are underpinned by the scaling factors: microsomal protein per gram (MPPG) and cytosolic protein per gram (CPPG). In addition, IVIVE-PBPK has significant application in the reduction and refinement of live animal models in research. While human scaling factors are well-defined, many preclinical and livestock species remain poorly elucidated or uncharacterized. The MPPG parameter for liver (MPPGL) is the best characterized across all species and is well-defined for mouse, rat, and dog models. The MPPG parameters for Kidney (MPPGK) and intestine (MPPGI), are however; relatively indefinite for most species. Similarly, CPPG scaling factors for liver, kidney, and intestine (CPPGL/CPPGK/CPPGI) are generally sparse in all species. In addition to generation of mathematical values for scaling factors, methodological and animal-specific considerations, such as age, sex, and strain differences, have not yet been comprehensively described. Here, we review the current state-of-the-field for microsomal and cytosolic scaling factors, including highlighting areas that may need further description and development, with the intention of drawing attention to key knowledge gaps. The intention is to promote improved accuracy and precision in IVIVE-PBPK, concordance between laboratories, and stimulate work in underserved, but increasingly vital areas.

In vitro hydrolysis of areca nut xenobiotics in human liver

Areca nut (AN) is a substance of abuse consumed by millions worldwide, in spite of established oral and systemic toxicities associated with its use. Previous research demonstrates methyl ester alkaloids in the AN, such as arecoline and guvacoline, exhibit mood-altering and toxicological effects. Nonetheless, their metabolism has not been fully elucidated in humans. In the present study, an HPLC-UV bioanalytical method was developed to evaluate the hydrolytic kinetics and clearance rates of arecoline and guvacoline in human liver microsomes (HLM) and cytosol (HLC). The bioassay was capable of quantifying arecoline and guvacoline (and carboxylate metabolites arecaidine and guvacine, respectively) with good sensitivity, accuracy, and precision. Kinetics of arecoline and guvacoline hydrolysis best followed the Michaelis-Menten model. Apparent intrinsic clearance (Clint.in vivo) of arecoline was 57.8 ml/min/kg in HLM and 11.6 mL/min/kg in HLC, a 5-fold difference. Unexpectedly, guvacoline was dramatically less hydrolyzed than arecoline in both HLM and HLC, with Clint.in vivo estimates of 0.654 ml/min/kg and 0.466 ml/min/kg, respectively. These results demonstrate, for the first time, arecoline undergoes significant hydrolysis with high clearance rates in the liver. Furthermore, differential tissue metabolic rates and utilization of specific esterase inhibitors unequivocally demonstrated arecoline is a substrate for CES1 and not CES2.

A comprehensive pharmacokinetic strategy for systematic evaluation of whole interaction of different constituents in Astragali Radix -Fructus Corni to improve diabetic kidney disease

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali-Radix (the dried root of Astragalus mongholicus Bunge, AR) - Fructus Corni (the dried ripe fruit of Cornus officinalis Sieb. et Zucc., FC) has been used as a herb-pair remedy to treat diabetic kidney disease (DKD) for hundred years. Polysaccharides, saponins, and flavonoids in AR, and the iridoid glycosides in FC were deemed as the main bioactive constituents that can offer beneficial nephroprotective activities. A systematic evaluation of the nephroprotective effects of AR-FC herb pair, the main bioactive constituents extracted from the herb pair, and their combinations in different ratios was performed, CG6 (polysaccharides, flavonoids, saponins, and iridoid glycosides, in a ratio of 2:3:1:2) as the best compatibility proportion was screened out in our previous study.

AIM OF THE STUDY

This study aimed to investigate the pharmacokinetic characteristics of AR-FC herb-pair in DKD rats, and explore the interactions between constituents from AR-FC and the rational compatibility of different constituents.

MATERIALS AND METHODS

The protective effect of AR-FC and CG6 on renal injury caused by DKD was first verified by histopathological examination. Then, an analytical method based on UHPLC-Q-TOF-MS and UHPLC-QqQ-MS/MS for qualitative and quantitative metabolites without reference standards was established and applied to pharmacokinetic (PK) studies in following different aspects: between single groups (polysaccharides, flavonoids, saponins and iridoid glycosides) and compatibility groups (AR-FC, CG6), in normal and DKD rats, in single-dose administration and long-term administration.

RESULTS

Pathological observations confirmed that AR-FC could improve renal injury in DKD rats. PK profiles of nine prototypes and four metabolites in various groups were obtained, revealing the compatibility of multiple constitutes, pathological states, and long-term administration could alter PK characteristics of the main components from AR-FC, and promoting the absorption of them (Cmax, AUC0-t, and AUC0-t increased). Notably, co-administration of iridoid glycosides could significantly increase the absorption of flavonoids and saponins in vivo. The pharmacokinetics based on homologous compounds revealed that saponins first acted, then its initial metabolites affected flavonoids, and ultimately the metabolites of flavonoids influenced iridoid glycosides.

CONCLUSION

This study demonstrated the existence of interactions between constituents from AR-FC herb-pair and the importance of their rational compatibility. It provides experimental evidence for developing a therapeutic agent based on AR-FC (especially CG6) to treat DKD. It is also expected to provide a reference for the multi-component pharmacokinetic study of other herbal medicines.

Innovation in cancer pharmacotherapy through integrative consideration of germline and tumor genomes

Precision cancer medicine is widely established, and numerous molecularly targeted drugs for various tumor entities are approved or are in development. Personalized pharmacotherapy in oncology has so far been based primarily on tumor characteristics, for example, somatic mutations. However, the response to drug treatment also depends on pharmacological processes summarized under the term ADME (absorption, distribution, metabolism, and excretion). Variations in ADME genes have been the subject of intensive research for >5 decades, considering individual patients' genetic makeup, referred to as pharmacogenomics (PGx). The combined impact of a patient's tumor and germline genome is only partially understood and often not adequately considered in cancer therapy. This may be attributed, in part, to the lack of methods for combined analysis of both data layers. Optimized personalized cancer therapies should, therefore, aim to integrate molecular information, which derives from both the tumor and the germline genome, and taking into account existing PGx guidelines for drug therapy. Moreover, such strategies should provide the opportunity to consider genetic variants of previously unknown functional significance. Bioinformatic analysis methods and corresponding algorithms for data interpretation need to be developed to integrate PGx data in cancer therapy with a special meaning for interdisciplinary molecular tumor boards, in which cancer patients are discussed to provide evidence-based recommendations for clinical management based on individual tumor profiles. SIGNIFICANCE STATEMENT: The era of personalized oncology has seen the emergence of drugs tailored to genetic variants associated with cancer biology. However, the full potential of targeted therapy remains untapped owing to the predominant focus on acquired tumor-specific alterations. Optimized cancer care must integrate tumor and patient genomes, guided by pharmacogenomic principles. An essential prerequisite for realizing truly personalized drug treatment of cancer patients is the development of bioinformatic tools for comprehensive analysis of all data layers generated in modern precision oncology programs.

Characterization of human alcohol dehydrogenase 4 and aldehyde dehydrogenase 2 as enzymes involved in the formation of 5-carboxylpirfenidone, a major metabolite of pirfenidone

Pirfenidone (PIR) is used in the treatment of idiopathic pulmonary fibrosis. After oral administration, it is metabolized by cytochrome P450 1A2 to 5-hydroxylpirfenidone (5-OH PIR) and further oxidized to 5-carboxylpirfenidone (5-COOH PIR), a major metabolite excreted in the urine (90% of the dose). This study aimed to identify enzymes that catalyze the formation of 5-COOH PIR from 5-OH PIR in the human liver. 5-COOH PIR was formed from 5-OH PIR in the presence of NAD+ by human liver microsomes (HLMs) more than by human liver cytosol (HLC), with the concomitant formation of the aldehyde form (5-CHO PIR) as an intermediate metabolite. By purifying enzymes from HLMs, alcohol dehydrogenases (ADHs) were identified as candidate enzymes catalyzing 5-CHO PIR formation, although ADHs are localized in the cytoplasm. Among constructed recombinant ADH1-5 expressed in HEK293T cells, only ADH4 efficiently catalyzed 5-CHO PIR formation from 5-OH PIR with a Km value (29.0 ± 4.9 μM), which was close to that by HLMs (59.1 ± 4.6 μM). In contrast to commercially available HLC, HLC prepared in-house clearly showed substantial 5-CHO PIR formation, and ADH4 protein levels were significantly (rs = 0.772, P < .0001) correlated with 5-CHO PIR formation in 25 HLC samples prepared in-house. Some components of the commercially available HLC may inhibit ADH4 activity. Disulfiram, an inhibitor of aldehyde dehydrogenases (ALDH), decreased 5-COOH PIR formation and increased 5-CHO PIR formation from 5-OH PIR in HLMs. ALDH2 knockdown in HepG2 cells by siRNA decreased 5-COOH PIR formation by 61%. SIGNIFICANCE STATEMENT: This study clarified that 5-carboxylpirfenidone formation from 5-hydroxylpirfenidone proceeds via a 2-step oxidation reaction catalyzed by ADH4 and disulfiram-sensitive enzymes, including ALDH2. Interindividual differences in the expression levels or functions of these enzymes could cause variations in the pharmacokinetics of pirfenidone.

2-Arylhydrazinylidene-3-oxo-3-polyfluoroalkylpropanoic acids as selective and effective carboxylesterase inhibitors with powerful antioxidant potential

A series of 2-arylhydrazinylidene-3-oxo acids (AHOAs) was prepared by dealkylation of alkyl-2-arylhydrazinylidene-3-oxo-3-alkanoates with AlBr3. Using X-Ray, NMR spectroscopy, and quantum mechanical calculations (QM), the existence of AHOAs in a thermodynamically favorable Z-form stabilized by two intramolecular H-bonds was established. All AHOAs had acceptable ADME parameters. The esterase profile study showed that polyfluoroalkyl-AHOAs were effective and selective carboxylesterase (CES) inhibitors, while they were inactive against acetyl- and butyrylcholinesterase. In agreement with molecular docking, the most effective CES inhibitors (IC50 as low as 42 nM) were compounds bearing long polyfluoroalkyl substituents. The acids were also active against hCES1 and hCES2, and CF3-containing acids possessed selectivity against hCES2. Non-fluorinated acids did not inhibit CES, but they exhibited potent antioxidant capability. AHOAs having unsubstituted phenyl or electron-donating groups in the arylhydrazinylidene moiety displayed high primary antioxidant activity in the ABTS, FRAP, and ORAC tests, which did not depend on the substituent in the acyl fragment in the ABTS and ORAC assays. The radical-scavenging mechanism of AHOAs was investigated using QM calculations, showing a preference for cleavage of NH rather than OH bonds. For the lead antioxidants, 4-methoxysubstituted AHOAs, protective effects on erythrocyte membranes in AAPH-induced oxidative stress conditions were shown, including membrane stabilizing activity, inhibition of AAPH-induced lipid peroxidation of erythrocyte membranes, and Fe(II)-chelating ability. Thus, a new class of potent and selective CES inhibitors with powerful antioxidant potential has been developed as promising co-drugs capable of regulating the metabolism of esterified drugs and scavenging reactive radicals that form during Phase I biotransformation.

Arylacetamide deacetylase regulates hepatic iron homeostasis to protect against carbon tetrachloride-induced ferroptosis

Arylacetamide deacetylase (AADAC) catalyzes the hydrolysis of small molecules containing ester and amide bonds. Recently, it has been reported that AADAC can suppress reactive oxygen species production in cancer cells. This study aimed to elucidate the possibility that AADAC protects against drug-induced liver injury accompanied by oxidative stress and to explore its molecular mechanisms. Intraperitoneal administration of carbon tetrachloride induced significantly more severe liver injury in Aadac knockout (KO) mice (plasma alanine aminotransferase level: 19,381 ± 10,578 U/L) than in wild-type (WT) mice (7219 ± 4729 U/L). More severe liver injury in Aadac KO mice was accompanied by higher hepatic malondialdehyde and antioxidant gene mRNA levels than those in WT mice. The increase in plasma alanine aminotransferase levels in Aadac KO mice was substantially suppressed by pretreatment with the ferroptosis inhibitors deferoxamine or ferrostatin-1, suggesting that Aadac deficiency increases susceptibility to ferroptosis. Immunoprecipitation followed by proteomic analysis revealed that AADAC interacts with ceruloplasmin (CP), which oxidizes ferrous iron to ferric iron. Hepatic CP activity was significantly lower in Aadac KO mice than that in WT mice, resulting in elevated hepatic ferrous iron levels in Aadac KO mice. Overexpression of human AADAC in Huh-7 cells significantly attenuated carbon tetrachloride-induced cytotoxicity by suppressing ferrous iron accumulation, suggesting that AADAC interacts with CP to suppress hepatic ferrous iron accumulation. The hepatoprotective role of Aadac in ferroptosis was also observed in mice with acetaminophen-induced liver injury. This study demonstrates a novel function of AADAC in protecting against ferroptosis induced by hepatotoxicants, carbon tetrachloride and acetaminophen.

The association between trimethylamine N-oxide levels and coronary microvascular dysfunction and prognosis in patients with ST-elevation myocardial infarction

BACKGROUND AND AIMS

Coronary microvascular dysfunction (CMD) is common after ST-elevation myocardial infarction (STEMI), leading to adverse clinical outcomes. However, its diagnosis remains difficult, and mechanisms elusive. This study explores the role of Trimethylamine N-oxide (TMAO), a gut microbiota metabolite, as a potential biomarker for diagnosing CMD in STEMI patients.

METHODS

This prospective, observational study enrolled 210 STEMI patients with multivessel coronary artery disease who underwent primary percutaneous coronary intervention (PCI). TMAO levels were measured at baseline, 3 months, and 12 months post-PCI, whilst coronary physiology was assessed at 3 months. The primary endpoint was the incidence of CMD at 3 months, with the secondary endpoint being major adverse cardiovascular and cerebrovascular events (MACCE) at 12 months. An additional 59 consecutive patients were enrolled for validation.

RESULTS

TMAO levels varied from baseline to 3 months, then stabilised. The areas under the ROC curve for baseline TMAO and TMAO at 3-month were 0.55 (95 % CI 0.46-0.64; p = 0.426), and 0.80 (95 % CI 0.73-0.87; p < 0.001), respectively. The optimal cut-off for TMAO at 3-month to diagnose CMD was 3.91, with similar sensitivity and specificity in the derivation and validation cohort. The incidence of MACCE was higher in patients with TMAO≥3.91 (41.4 % vs 10.7 %; p < 0.001). The addition of 3-month TMAO improved the diagnostic performance of traditional risk factors.

CONCLUSION

TMAO is a robust biomarker for CMD and is significantly associated with the incidence of MACCE. TMAO has the potential in guiding clinical decision-making and suggests an interplay between gut microbiota and CMD.

Regulation of Human Hydrolases and Its Implications in Pharmacokinetics and Pharmacodynamics

Hydrolases represent an essential class of enzymes indispensable for the metabolism of various clinically essential medications. Individuals exhibit marked differences in the expression and activation of hydrolases, resulting in significant variability in the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs metabolized by these enzymes. The regulation of hydrolase expression and activity involves both genetic polymorphisms and nongenetic factors. This review examines the current understanding of genetic and nongenetic regulators of six clinically significant hydrolases, including carboxylesterase (CES)-1 CES2, arylacetamide deacetylase (AADAC), paraoxonase (PON)-1 PON3, and cathepsin A (CTSA). We explore genetic variants linked to the expression and activity of the hydrolases and their effects on the PK and PD of their substrate drugs. Regarding nongenetic regulators, we focus on the inhibitors and inducers of these enzymes. Additionally, we examine the developmental expression patterns and gender differences in the hydrolases when pertinent information was available. Many genetic and nongenetic regulators were found to be associated with the expression and activity of the hydrolases and PK and PD. However, hydrolases remain generally understudied compared with other drug-metabolizing enzymes, such as cytochrome P450s. The clinical significance of genetic and nongenetic regulators has not yet been firmly established for the majority of hydrolases. Comprehending the mechanisms that underpin the regulation of these enzymes holds the potential to refine therapeutic regimens, thereby enhancing the efficacy and safety of drugs metabolized by the hydrolases. SIGNIFICANCE STATEMENT: Hydrolases play a crucial role in the metabolism of numerous clinically important medications. Genetic polymorphisms and nongenetic regulators can affect hydrolases' expression and activity, consequently influencing the exposure and clinical outcomes of hydrolase substrate drugs. A comprehensive understanding of hydrolase regulation can refine therapeutic regimens, ultimately enhancing the efficacy and safety of drugs metabolized by the enzymes.

Insight into the mechanism and toxicology of nitrofurantoin: a metabolomics approach

Safety and effectiveness are the two ends of the balance in drug development that needs to be evaluated. The biotransformation of drugs within a living organism could potentiate biochemical insults in the tissue and compromise the safety of drugs. Nitrofurantoin (NFT) is a cheap clinical antibiotic with a wide array of activities against gram-positive and gram-negative organisms. The NFT scaffold has been utilized to develop other derivates or analogues in the quest to repurpose drugs against other infectious diseases. Several techniques were developed over the years to study the mechanism of NFT metabolism and toxicity, such as voltammetry, chromatographic analysis, protein precipitation, liquid-liquid extraction, etc. Due to limitations in these methods, the mechanism of NFT biotransformation in the cell is poorly understood. Metabolomics has been adopted in drug metabolism to understand the mechanism of drug toxicity and could provide a solution to overcome the limitations of current techniques to determine mechanisms of toxicity. Unfortunately, little or no information regarding the metabolomics approach in NFT metabolism and toxicity is available. Hence, this review highlights the metabolomic techniques that can be adopted in NFT metabolism and toxicological studies to encourage the research community to widely adopt and utilize metabolomics in understanding NFT's metabolism and toxicity.

Biotransformation research advances - 2023 year in review

This annual review marks the eighth in the series starting with Baillie et al. (2016) Our objective is to explore and share articles which we deem influential and significant in the field of biotransformation. Its format is to highlight important aspects captured in synopsis followed by a commentary with relevant figure and references.

Ocular drug-metabolizing enzymes: focus on esterases

This review describes current knowledge on the expression of ocular phase I and II drug-metabolizing enzymes in the main animal species used in ocular drug development and in humans, with a focus on ocular esterases and their prodrug substrates. The eye possesses a unique metabolic profile, exhibiting a lower and restricted expression of major cytochrome P450s (CYPs) and most transferases apart from glutathione S-transferases (GST) when compared to the liver. In contrast, hydrolytic enzymes are abundant in many ocular tissues. These enzymes have attracted interest because of their role in prodrug activation and drug elimination. A literature survey suggests profound variations in tissue expression levels and activities between different species but also points out significant gaps in knowledge. These uncertainties highlight a need for more detailed characterization of enzymes in individual ocular tissues and across species to aid future translational studies in ophthalmic drug research. Thus, an in-depth analysis of ocular drug metabolism and species differences is crucial for ocular drug development.

CYP3A Mediates an Unusual C(sp2)-C(sp3) Bond Cleavage via Ipso-Addition of Oxygen in Drug Metabolism

Mammalian cytochrome P450 drug-metabolizing enzymes rarely cleave carbon-carbon (C-C) bonds and the mechanisms of such cleavages are largely unknown. We identified two unusual cleavages of non-polar, unstrained C(sp2)-C(sp3) bonds in the FDA-approved tyrosine kinase inhibitor pexidartinib that are mediated by CYP3A4/5, the major human phase I drug metabolizing enzymes. Using a synthetic ketone, we rule out the Baeyer-Villiger oxidation mechanism that is commonly invoked to address P450-mediated C-C bond cleavages. Our studies in 18O2 and H2 18O enriched systems reveal two unusual distinct mechanisms of C-C bond cleavage: one bond is cleaved by CYP3A-mediated ipso-addition of oxygen to a C(sp2) site of N-protected pyridin-2-amines, and the other occurs by a pseudo-retro-aldol reaction after hydroxylation of a C(sp3) site. This is the first report of CYP3A-mediated C-C bond cleavage in drug metabolism via ipso-addition of oxygen mediated mechanism. CYP3A-mediated ipso-addition is also implicated in the regioselective C-C cleavages of several pexidartinib analogs. The regiospecificity of CYP3A-catalyzed oxygen ipso-addition under environmentally friendly conditions may be attractive and inspire biomimetic or P450-engineering methods to address the challenging task of C-C bond cleavages.

Impact of miR-222-3p-mediated downregulation of arylacetamide deacetylase on drug hydrolysis and lipid accumulation

Arylacetamide deacetylase (AADAC) is involved in drug hydrolysis and lipid metabolism. In 23 human liver samples, no significant correlation was observed between AADAC mRNA (19.7-fold variation) and protein levels (137.6-fold variation), suggesting a significant contribution of post-transcriptional regulation to AADAC expression. The present study investigated whether AADAC is regulated by microRNA in the human liver and elucidate its biological significance. Computational analysis predicted two potential miR-222-3p recognition elements in the 3'-untranslated region (UTR) of AADAC. Luciferase assay revealed that the miR-222-3p recognition element was functional in downregulating AADAC expression. In HEK293 cells transfected with an AADAC expression plasmid containing 3'-UTR, miR-222-3p overexpression decreased AADAC protein level and activity, whereas miR-222-3p inhibition increased them. Similar results were observed in human hepatoma-derived Huh-1 cells endogenously expressing AADAC and HepaSH cells that are hepatocytes from chimeric mice with humanized livers. In individual human liver samples, AADAC protein levels inversely correlated with miR-222-3p levels. Overexpression of miR-222-3p resulted in increased lipid accumulation in Huh-1 cells, which was reversed by AADAC overexpression. In contrast, miR-222-3p inhibition decreased lipid accumulation, which was reversed by AADAC knockdown. In conclusion, we found that hepatic AADAC was downregulated by miR-222-3p, resulting in decreased drug hydrolysis and increased lipid accumulation.

Harnessing the Power of Polyphenols: A New Frontier in Disease Prevention and Therapy

There are a wide variety of phytochemicals collectively known as polyphenols. Their structural diversity results in a broad range of characteristics and biological effects. Polyphenols can be found in a variety of foods and drinks, including fruits, cereals, tea, and coffee. Studies both in vitro and in vivo, as well as clinical trials, have shown that they possess potent antioxidant activities, numerous therapeutic effects, and health advantages. Dietary polyphenols have demonstrated the potential to prevent many health problems, including obesity, atherosclerosis, high blood sugar, diabetes, hypertension, cancer, and neurological diseases. In this paper, the protective effects of polyphenols and the mechanisms behind them are investigated in detail, citing the most recent available literature. This review aims to provide a comprehensive overview of the current knowledge on the role of polyphenols in preventing and managing chronic diseases. The cited publications are derived from in vitro, in vivo, and human-based studies and clinical trials. A more complete understanding of these naturally occurring metabolites will pave the way for the development of novel polyphenol-rich diet and drug development programs. This, in turn, provides further evidence of their health benefits.

Cyanide Trapping of Iminium Ion Reactive Metabolites: Implications for Clinical Hepatotoxicity

Reactive metabolite formation is a major mechanism of hepatotoxicity. Although reactive electrophiles can be soft or hard in nature, screening strategies have generally focused on the use of glutathione trapping assays to screen for soft electrophiles, with many data sets available to support their use. The use of a similar assay for hard electrophiles using cyanide as the trapping agent is far less common, and there is a lack of studies with sufficient supporting data. Using a set of 260 compounds with a defined hepatotoxicity status by the FDA, a comprehensive literature search yielded cyanide trapping data on an unbalanced set of 20 compounds that were all clinically hepatotoxic. Thus, a further set of 19 compounds was selected to generate cyanide trapping data, resulting in a more balanced data set of 39 compounds. Analysis of the data demonstrated that the cyanide trapping assay had high specificity (92%) and a positive predictive value (83%) such that hepatotoxic compounds would be confidently flagged. Structural analysis of the adducts formed revealed artifactual methylated cyanide adducts to also occur, highlighting the importance of full structural identification to confirm the nature of the adduct formed. The assay was demonstrated to add the most value for compounds containing typical structural alerts for hard electrophile formation: half of the severe hepatotoxins with these structural alerts formed cyanide adducts, while none of the severe hepatotoxins with no relevant structural alerts formed adducts. The assay conditions used included cytosolic enzymes (e.g., aldehyde oxidase) and an optimized cyanide concentration to minimize the inhibition of cytochrome P450 enzymes by cyanide. Based on the demonstrated added value of this assay, it is to be initiated for use at GSK as part of the integrated hepatotoxicity strategy, with its performance being reviewed periodically as more data is generated.

Diving into drug-screening: zebrafish embryos as an in vivo platform for antimicrobial drug discovery and assessment

The rise of multidrug-resistant bacteria underlines the need for innovative treatments, yet the introduction of new drugs has stagnated despite numerous antimicrobial discoveries. A major hurdle is a poor correlation between promising in vitro data and in vivo efficacy in animal models, which is essential for clinical development. Early in vivo testing is hindered by the expense and complexity of existing animal models. Therefore, there is a pressing need for cost-effective, rapid preclinical models with high translational value. To overcome these challenges, zebrafish embryos have emerged as an attractive model for infectious disease studies, offering advantages such as ethical alignment, rapid development, ease of maintenance, and genetic manipulability. The zebrafish embryo infection model, involving microinjection or immersion of pathogens and potential antibiotic hit compounds, provides a promising solution for early-stage drug screening. It offers a cost-effective and rapid means of assessing the efficacy, toxicity and mechanism of action of compounds in a whole-organism context. This review discusses the experimental design of this model, but also its benefits and challenges. Additionally, it highlights recently identified compounds in the zebrafish embryo infection model and discusses the relevance of the model in predicting the compound's clinical potential.

Role of carboxylesterase and arylacetamide deacetylase in drug metabolism, physiology, and pathology

Carboxylesterases (CES1 and CES2) and arylacetamide deacetylase (AADAC), which are expressed primarily in the liver and/or gastrointestinal tract, hydrolyze drugs containing ester and amide bonds in their chemical structure. These enzymes often catalyze the conversion of prodrugs, including the COVID-19 drugs remdesivir and molnupiravir, to their pharmacologically active forms. Information on the substrate specificity and inhibitory properties of these enzymes, which would be useful for drug development and toxicity avoidance, has accumulated. Recently,in vitroandin vivostudies have shown that these enzymes are involved not only in drug hydrolysis but also in lipid metabolism. CES1 and CES2 are capable of hydrolyzing triacylglycerol, and the deletion of their orthologous genes in mice has been associated with impaired lipid metabolism and hepatic steatosis. Adeno-associated virus-mediated human CES overexpression decreases hepatic triacylglycerol levels and increases fatty acid oxidation in mice. It has also been shown that overexpression of CES enzymes or AADAC in cultured cells suppresses the intracellular accumulation of triacylglycerol. Recent reports indicate that AADAC can be up- or downregulated in tumors of various organs, and its varied expression is associated with poor prognosis in patients with cancer. Thus, CES and AADAC not only determine drug efficacy and toxicity but are also involved in pathophysiology. This review summarizes recent findings on the roles of CES and AADAC in drug metabolism, physiology, and pathology.

Human Leucocyte Antigen Genetics in Idiosyncratic Drug-Induced Liver Injury with Evidence Based on the Roussel Uclaf Causality Assessment Method

The human leucocyte antigen (HLA) allele variability was studied in cohorts of patients with idiosyncratic drug-induced liver injury (iDILI). Some reports showed an association between HLA genetics and iDILI, proposing HLA alleles as a potential risk factor for the liver injury. However, the strength of such assumptions heavily depends on the quality of the iDILI diagnosis, calling for a thorough analysis. Using the PubMed database and Google Science, a total of 25 reports of case series or single cases were retrieved using the terms HLA genes and iDILI. It turned out that in 10/25 reports (40%), HLA genetics were determined in iDILI cases, for which no causality assessment method (CAM) was used or a non-validated tool was applied, meaning the findings were based on subjective opinion, providing disputable results and hence not scoring individual key elements. By contrast, in most iDILI reports (60%), the Roussel Uclaf Causality Assessment Method (RUCAM) was applied, which is the diagnostic algorithm preferred worldwide to assess causality in iDILI cases and represents a quantitative, objective tool that has been well validated by both internal and external DILI experts. The RUCAM provided evidence-based results concerning liver injury by 1 drug class (antituberculotics + antiretrovirals) and 19 different drugs, comprising 900 iDILI cases. Among the top-ranking drugs were amoxicillin-clavulanate (290 cases, HLA A*02:01 or HLA A*30:02), followed by flucloxacillin (255 cases, HLA B*57:01), trimethoprim-sulfamethoxazole (86 cases, HLA B*14:01 or HLA B*14:02), methimazole (40 cases, HLA C*03:02), carbamazepine (29 cases, HLA A*31:01), and nitrofurantoin (26 cases, HLA A*33:01). In conclusion, the HLA genetics in 900 idiosyncratic drug-induced liver injury cases with evidence based on the RUCAM are available for studying the mechanistic steps leading to the injury, including metabolic factors through cytochrome P450 isoforms and processes that activate the innate immune system to the adaptive immune system.

INTEDE 2.0: the metabolic roadmap of drugs

The metabolic roadmap of drugs (MRD) is a comprehensive atlas for understanding the stepwise and sequential metabolism of certain drug in living organisms. It plays a vital role in lead optimization, personalized medication, and ADMET research. The MRD consists of three main components: (i) the sequential catalyses of drug and its metabolites by different drug-metabolizing enzymes (DMEs), (ii) a comprehensive collection of metabolic reactions along the entire MRD and (iii) a systematic description on efficacy & toxicity for all metabolites of a studied drug. However, there is no database available for describing the comprehensive metabolic roadmaps of drugs. Therefore, in this study, a major update of INTEDE was conducted, which provided the stepwise & sequential metabolic roadmaps for a total of 4701 drugs, and a total of 22 165 metabolic reactions containing 1088 DMEs and 18 882 drug metabolites. Additionally, the INTEDE 2.0 labeled the pharmacological properties (pharmacological activity or toxicity) of metabolites and provided their structural information. Furthermore, 3717 drug metabolism relationships were supplemented (from 7338 to 11 055). All in all, INTEDE 2.0 is highly expected to attract broad interests from related research community and serve as an essential supplement to existing pharmaceutical/biological/chemical databases. INTEDE 2.0 can now be accessible freely without any login requirement at: http://idrblab.org/intede/.

Quantitative Analysis of mRNA and Protein Expression Levels of Aldo-Keto Reductase and Short-Chain Dehydrogenase/Reductase Isoforms in the Human Intestine

Enzymes catalyzing the reduction reaction of xenobiotics are mainly members of the aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase (SDR) superfamilies. The intestine, together with the liver, is responsible for first-pass effects and is an organ that determines the bioavailability of orally administered drugs. In this study, we evaluated the mRNA and protein expression levels of 12 AKR isoforms (AKR1A1, AKR1B1, AKR1B10, AKR1B15, AKR1C1, AKR1C2, AKR1C3, AKR1C4, AKR1D1, AKR1E2, AKR7A2, and AKR7A3) and 7 SDR isoforms (CBR1, CBR3, CBR4, DCXR, DHRS4, HSD11B1, and HSD17B12) in each region of the human intestine using next-generation sequencing and data-independent acquisition proteomics. At both the mRNA and protein levels, most AKR isoforms were highly expressed in the upper regions of the intestine, namely the duodenum and jejunum, and then declined toward the rectum. Among the members in the SDR superfamily, CBR1 and DHRS4 were highly expressed in the upper regions, whereas the expression levels of the other isoforms were almost uniform in all regions. Significant positive correlations between mRNA and protein levels were observed in AKR1A1, AKR1B1, AKR1B10, AKR1C3, AKR7A2, AKR7A3, CBR1, and CBR3. The mRNA level of AKR1B10 was highest, followed by AKR7A3 and CBR1, each accounting for more than 10% of the sum of all AKR and SDR levels in the small intestine. This expression profile in the human intestine was greatly different from that in the human liver, where AKR1C isoforms are predominantly expressed. SIGNIFICANCE STATEMENT: In this study comprehensively determined the mRNA and protein expression profiles of aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase isoforms involved in xenobiotic metabolism in the human intestine and found that most of them are highly expressed in the upper region, where AKR1B10, AKR7A3, and CBR1 are predominantly expressed. Since the intestine is significantly involved in the metabolism of orally administered drugs, the information provided here is valuable for pharmacokinetic studies in drug development.

Drug and pro-drug substrates and pseudo-substrates of human butyrylcholinesterase

Butyrylcholinesterase (BChE) is present in plasma and numerous cells and organs. Its physiological function(s) is(are) still unclear. However, this enzyme is of pharmacological and toxicological importance. It displays a broad specificity and is capable of hydrolyzing a wide range of substrates with turnovers differing by several orders of magnitude. Nowaday, these substrates include more than two dozen carboxyl-ester drugs, numerous acetylated prodrugs, and transition state analogues of acetylcholine. In addition, BChE displays a promiscuous hydrolytic activity toward amide bonds of arylacylamides, and slowly hydrolyzes carbamyl- and phosphoryl-esters. Certain pseudo-substrates like carbamates and organophosphates are major drugs of potential medical interest. The existence of a large genetic poly-allelism, affecting the catalytic properties of BChE is at the origin of clinical complications in the use of certain drugs catabolized by BChE. The number of drugs and prodrugs hydrolyzed by BChE is expected to increase in the future. However, very few quantitative data (Km, kcat) are available for most marketed drugs, and except for myorelaxants like succinylcholine and mivacurium, the impact of BChE genetic mutations on catalytic parameters has not been evaluated for most of these drugs.

Plant Polyphenols and Their Potential Benefits on Cardiovascular Health: A Review

Fruits, vegetables, and other food items contain phytochemicals or secondary metabolites which may be considered non-essential nutrients but have medicinal importance. These dietary phytochemicals exhibit chemopreventive and therapeutic effects against numerous diseases. Polyphenols are secondary metabolites found in vegetables, fruits, and grains. These compounds exhibit several health benefits such as immune modulators, vasodilators, and antioxidants. This review focuses on recent studies on using dietary polyphenols to treat cardiovascular disorders, atherosclerosis, and vascular endothelium deficits. We focus on exploring the safety of highly effective polyphenols to ensure their maximum impact on cardiac abnormalities and discuss recent epidemiological evidence and intervention trials related to these properties. Kaempferol, quercetin, and resveratrol prevent oxidative stress by regulating proteins that induce oxidation in heart tissues. In addition, polyphenols modulate the tone of the endothelium of vessels by releasing nitric oxide (NO) and reducing low-density lipoprotein (LDL) oxidation to prevent atherosclerosis. In cardiomyocytes, polyphenols suppress the expression of inflammatory markers and inhibit the production of inflammation markers to exert an anti-inflammatory response. Consequently, heart diseases such as strokes, hypertension, heart failure, and ischemic heart disease could be prevented by dietary polyphenols.

In Vitro Evaluation of the Reductase Activities of Human AKR1C3 Allelic Variants

Aldo-keto reductase 1C3 (AKR1C3) plays a role in the detoxification and activation of clinical drugs by catalyzing reduction reactions. There are approximately 400 single-nucleotide polymorphisms (SNPs) in the AKR1C3 gene, but their impact on the enzyme activity is still unclear. This study aimed to clarify the effects of SNPs of AKR1C3 with more than 0.5% global minor allele frequency on the reductase activities for its typical substrates. Recombinant AKR1C3 wild-type and R66Q, E77G, C145Y, P180S, or R258C variants were constructed using insect Sf21 cells, and reductase activities for acetohexamide, doxorubicin, and loxoprofen by recombinant AKR1C3s were measured by liquid chromatography-tandem mass spectrometry. Among the variants tested, the C145Y variant showed remarkably low (6%-14% of wild type) intrinsic clearances of reductase activities for all three drugs. Reductase activities of these three drugs were measured using 34 individual Japanese liver cytosols, revealing that heterozygotes of the SNP g.55101G>A tended to show lower reductase activities for three drugs than homozygotes of the wild type. Furthermore, genotyping of the SNP g.55101G>A causing C145Y in 96 Caucasians, 166 African Americans, 192 Koreans, and 183 Japanese individuals was performed by polymerase chain reaction-restriction fragment length polymorphism. This allelic variant was specifically detected in Asians, with allele frequencies of 6.8% and 3.6% in Koreans and Japanese, respectively. To conclude, an AKR1C3 allele with the SNP g.55101G>A causing C145Y would be one of the causal factors for interindividual variabilities in the efficacy and toxicity of drugs reduced by AKR1C3. SIGNIFICANCE STATEMENT: This is the first study to clarify that the AKR1C3 allele with the SNP g.55101G>A causing C145Y results in a decrease in reductase activity. Since the allele was specifically observed in Asians, the allele would be a factor causing an interindividual variability in sensitivity of drug efficacy or toxicity of drugs reduced by AKR1C3 in Asians.

Evaluation of Drug-Drug Interactions via Inhibition of Hydrolases by Orlistat, an Anti-Obesity Drug

Drug-drug interactions (DDI) have a significant impact on drug efficacy and safety. It has been reported that orlistat, an anti-obesity drug, inhibits the hydrolysis of p-nitrophenol acetate, a common substrate of the major drug-metabolizing hydrolases, carboxylesterase (CES) 1, CES2, and arylacetamide deacetylase (AADAC), in vitro. The aim of this study was to examine whether orlistat affects the pharmacokinetics of drug(s) metabolized by hydrolases in vivo after evaluating its inhibitory potencies against CES1, CES2, and AADAC in vitro. Orlistat potently inhibited the hydrolysis of acebutolol, a specific substrate of CES2, in a non-competitive manner (inhibition constant, K i = 2.95 ± 0.16 nM), whereas it slightly inhibited the hydrolysis of temocapril and eslicarbazepine acetate, specific substrates of CES1 and AADAC, respectively (IC50 >100 nM). The in vivo DDI potential was elucidated using mice, in which orlistat showed strong inhibition against acebutolol hydrolase activities in the liver and intestinal microsomes, similar to humans. The area under the curve (AUC) of acebutolol was increased by 43%, whereas the AUC of acetolol, a hydrolyzed metabolite of acebutolol, was decreased by 47% by co-administration of orlistat. The ratio of the K i value to the maximum unbound plasma concentration of orlistat (<0.012) is lower than the risk criteria for DDI in the liver defined by the US Food and Drug Administration guideline (>0.02), whereas the ratio of the K i value to the estimated intestinal luminal concentration (3.3 × 105) is considerably higher than the risk criteria in the intestine (>10). Therefore, this suggests that orlistat causes DDI by inhibiting hydrolases in the intestine. SIGNIFICANCE STATEMENT: This study demonstrated that orlistat, an anti-obesity drug, causes drug-drug interactions in vivo by potently inhibiting carboxylesterase 2 in the intestine. This is the first evidence that inhibition of hydrolases causes drug-drug interactions.

Butyric acid inhibits oxidative stress and inflammation injury in calcium oxalate nephrolithiasis by targeting CYP2C9

This study investigates the mechanism by which butyric acid can protect against calcium oxalate (CaOx) nephrolithiasis. To do so, a rat model was used with 0.75% ethylene glycol administration to induce CaOx crystal formation. Histological and von Kossa staining revealed calcium deposits and renal injury, while dihydroethidium fluorescence staining was used to detect reactive oxygen species (ROS) levels. Flow cytometry and TUNEL assays were used to assess apoptosis, respectively. Treatment with sodium butyrate (NaB) was found to partially reverse the oxidative stress, inflammation, and apoptosis associated with CaOx crystallization in the kidney. In addition, in HK-2 cells, NaB reversed the decreased cell viability, increased ROS levels and apoptosis damage caused by oxalate exposure. Network pharmacology was employed to predict the target genes of butyric acid, CYP2C9. Subsequently, NaB was found to significantly reduce CYP2C9 levels in vivo and in vitro, and inhibition of CYP2C9 by Sulfaphenazole (a specific CYP2C9 inhibitor), was able to reduce ROS levels, inflammation injury, and apoptosis in oxalate-induced HK-2 cells. Collectively, these findings suggest that butyric acid may inhibit oxidative stress and reduce inflammation injury in CaOx nephrolithiasis by suppressing CYP2C9.

Characterization of Enzymes Involved in Nintedanib Metabolism in Humans

Nintedanib, which is used to treat idiopathic pulmonary fibrosis and non-small cell lung cancer, is metabolized to a pharmacologically inactive carboxylate derivative, BIBF1202, via hydrolysis and subsequently by glucuronidation to BIBF1202 acyl-glucuronide (BIBF1202-G). Since BIBF1202-G contains an ester bond, it can be hydrolytically cleaved to BIBF1202. In this study, we sought to characterize these metabolic reactions in the human liver and intestine. Nintedanib hydrolysis was detected in human liver microsomes (HLMs) (Clearance [CL int]: 102.8 ± 18.9 µL/min per mg protein) but not in small intestinal preparations. CES1 was suggested to be responsible for nintedanib hydrolysis according to experiments using recombinant hydrolases and hydrolase inhibitors as well as proteomic correlation analysis using 25 individual HLM. BIBF1202 glucuronidation in HLM (3.6 ± 0.3 µL/min per mg protein) was higher than that in human intestinal microsomes (1.5 ± 0.06 µL/min per mg protein). UGT1A1 and gastrointestinal UGT1A7, UGT1A8, and UGT1A10 were able to mediate BIBF1202 glucuronidation. The impact of UGT1A1 on glucuronidation was supported by the finding that liver microsomes from subjects homozygous for the UGT1A1*28 allele showed significantly lower activity than those from subjects carrying the wild-type UGT1A1 allele. Interestingly, BIBF1202-G was converted to BIBF1202 in HLS9 at 70-fold higher rates than the rates of BIBF1202 glucuronidation. An inhibition study and proteomic correlation analysis suggested that β-glucuronidase is responsible for hepatic BIBF1202-G deglucuronidation. In conclusion, the major metabolic reactions of nintedanib in the human liver and intestine were quantitatively and thoroughly elucidated. This information could be helpful to understand the inter- and intraindividual variability in the efficacy of nintedanib. SIGNIFICANCE STATEMENT: To our knowledge, this is the first study to characterize the enzymes responsible for each step of nintedanib metabolism in the human body. This study found that β-glucuronidase may contribute to BIBF1202-G deglucuronidation.

In vitro deacetylation of N-acetylserotonin by arylacetamide deacetylase

Arylacetamide deacetylase (AADAC) is a deacetylation enzyme present in the mammalian liver, gastrointestinal tract, and brain. During our search for mammalian enzymes capable of metabolizing N-acetylserotonin (NAS), AADAC was identified as having the ability to convert NAS to serotonin. Both human and rodent recombinant AADAC proteins can deacetylate NAS in vitro, although the human AADAC shows markedly higher activity compared with rodent enzyme. The AADAC-mediated deacetylation reaction can be potently inhibited by eserine in vitro. In addition to NAS, recombinant hAADAC can deacetylate melatonin (to form 5-methoxytryptamine) and N-acetyltryptamine (NAT) (to form tryptamine). In addition to the in vitro deacetylation of NAS by the recombinant AADAC proteins, liver (mouse and human) and brain (human) extracts were able to deacetylate NAS; these activities were sensitive to eserine. Taken together, these results demonstrate a new role for AADAC and suggest a novel pathway for the AADAC-mediated metabolism of pineal indoles in mammals.

Opinion paper on the systematic application of integrated bioinformatic tools to actuate routine precision medicine in poly-treated patients

Precision Medicine is a reality in selected medical areas, as oncology, or in excellent healthcare structures, but it is still far to reach million patients who could benefit from this medical concept. Here, we sought to highlight how the time is ripe to achieve horizontal delivery to a significant larger audience of patients, represented by the poly-treated patients. Combination therapies are frequent (especially in the elderly, to treat comorbidities) and are related to decreased drug safety and efficacy, disease's exacerbation, additional treatments, hospitalization. But the recent development and validation of bioinformatic tools, aimed to automatic evaluation and optimization of poly-therapies, according to the unique individual characteristics (including genotype), is ready to change the daily approach to pharmacological prescription.

Possible Side Effects of Polyphenols and Their Interactions with Medicines

Polyphenols are an important component of plant-derived food with a wide spectrum of beneficial effects on human health. For many years, they have aroused great interest, especially due to their antioxidant properties, which are used in the prevention and treatment of many diseases. Unfortunately, as with any chemical substance, depending on the conditions, dose, and interactions with the environment, it is possible for polyphenols to also exert harmful effects. This review presents a comprehensive current state of the knowledge on the negative impact of polyphenols on human health, describing the possible side effects of polyphenol intake, especially in the form of supplements. The review begins with a brief overview of the physiological role of polyphenols and their potential use in disease prevention, followed by the harmful effects of polyphenols which are exerted in particular situations. The individual chapters discuss the consequences of polyphenols’ ability to block iron uptake, which in some subpopulations can be harmful, as well as the possible inhibition of digestive enzymes, inhibition of intestinal microbiota, interactions of polyphenolic compounds with drugs, and impact on hormonal balance. Finally, the prooxidative activity of polyphenols as well as their mutagenic, carcinogenic, and genotoxic effects are presented. According to the authors, there is a need to raise public awareness about the possible side effects of polyphenols supplementation, especially in the case of vulnerable subpopulations.

Identification of HSD17B12 as an enzyme catalyzing drug reduction reactions through investigation of nabumetone metabolism

Nabumetone, a nonsteroidal anti-inflammatory prodrug, is converted to a pharmacologically active metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA); however, it is 11-fold more efficiently converted to 4-(6-methoxy-2-naphthyl)butan-2-ol (MNBO) via a reduction reaction in human hepatocytes. The goal of this study was to identify the enzyme(s) responsible for MNBO formation from nabumetone in the human liver. MNBO formation by human liver microsomes (HLM) was 5.7-fold higher than in the liver cytosol. In a panel of 24 individual HLM samples with quantitative proteomics data, the 17β-hydroxysteroid dehydrogenase 12 (HSD17B12) protein level had the high correlation coefficient (r = 0.80, P < 0.001) among 4457 proteins quantified in microsomal fractions during MNBO formation. Recombinant HSD17B12 expressed in HEK293T cells exhibited prominent nabumetone reductase activity, and the contribution of HSD17B12 to the activity in the HLM was calculated as almost 100%. MNBO formation in HepG2 and Huh7 cells was significantly decreased by the knockdown of HSD17B12. We also examined the role of HSD17B12 in drug metabolism and found that recombinant HSD17B12 catalyzed the reduction reactions of pentoxifylline and S-warfarin, suggesting that HSD17B12 prefers compounds containing a methyl ketone group on the alkyl chain. In conclusion, our study demonstrated that HSD17B12 is responsible for the formation of MNBO from nabumetone. Together with the evidence for pentoxifylline and S-warfarin reduction, this is the first study to report that HSD17B12, which is known to metabolize endogenous compounds, such as estrone and 3-ketoacyl-CoA, plays a role as a drug-metabolizing enzyme.

Quantitative Evaluation of the Contribution of Each Aldo-Keto Reductase and Short-Chain Dehydrogenase/Reductase Isoform to Reduction Reactions of Compounds Containing a Ketone Group in the Human Liver

Enzymes of the aldo-keto reductase (AKR) and short-chain dehydrogenase/reductase superfamilies are involved in the reduction of compounds containing a ketone group. In most cases, multiple isoforms appear to be involved in the reduction of a compound, and the enzyme(s) that are responsible for the reaction in the human liver have not been elucidated. The purpose of this study was to quantitatively evaluate the contribution of each isoform to reduction reactions in the human liver. Recombinant cytosolic isoforms were constructed, i.e., AKR1C1, AKR1C2, AKR1C3, AKR1C4, and carbonyl reductase 1 (CBR1), and a microsomal isoform, 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), and their contributions to the reduction of 10 compounds were examined by extrapolating the relative expression of each reductase protein in human liver preparations to recombinant systems quantified by liquid chromatography-mass spectrometry. The reductase activities for acetohexamide, doxorubicin, haloperidol, loxoprofen, naloxone, oxcarbazepine, and pentoxifylline were predominantly catalyzed by cytosolic isoforms, and the sum of the contributions of individual cytosolic reductases was almost 100%. Interestingly, AKR1C3 showed the highest contribution to acetohexamide and loxoprofen reduction, although previous studies have revealed that CBR1 mainly metabolizes them. The reductase activities of bupropion, ketoprofen, and tolperisone were catalyzed by microsomal isoform(s), and the contributions of HSD11B1 were calculated to be 41%, 32%, and 104%, respectively. To our knowledge, this is the first study to quantitatively evaluate the contribution of each reductase to the reduction of drugs in the human liver. SIGNIFICANCE STATEMENT: To our knowledge, this is the first study to determine the contribution of aldo-keto reductase (AKR)-1C1, AKR1C2, AKR1C3, AKR1C4, carbonyl reductase 1, and 11β-hydroxysteroid dehydrogenase type 1 to drug reductions in the human liver by utilizing the relative expression factor approach. This study found that AKR1C3 contributes to the reduction of compounds at higher-than-expected rates.

Recent insights into oxidative metabolism of quercetin: catabolic profiles, degradation pathways, catalyzing metalloenzymes and molecular mechanisms

Quercetin is the most abundant polyphenolic flavonoid (flavonol subclass) in vegetal foods and medicinal plants. This dietary chemopreventive agent has drawn significant interest for its multiple beneficial health effects ("polypharmacology") largely associated with the well-documented antioxidant properties. However, controversies exist in the literature due to its dual anti-/pro-oxidant character, poor stability/bioavailability but multifaceted bioactivities, leaving much confusion as to its exact roles in vivo. Increasing evidence indicates that a prior oxidation of quercetin to generate an array of chemical diverse products with redox-active/electrophilic moieties is emerging as a new linkage to its versatile actions. The present review aims to provide a comprehensive overview of the oxidative conversion of quercetin by systematically analyzing the current quercetin-related knowledge, with a particular focus on the complete spectrum of metabolite products, the enzymes involved in the catabolism and the underlying molecular mechanisms. Herein we review and compare the oxidation pathways, protein structures and catalytic patterns of the related metalloenzymes (phenol oxidases, heme enzymes and specially quercetinases), aiming for a deeper mechanistic understanding of the unusual biotransformation behaviors of quercetin and its seemingly controversial biological functions.

Induction by Phenobarbital of Phase I and II Xenobiotic-Metabolizing Enzymes in Bovine Liver: An Overall Catalytic and Immunochemical Characterization

In cattle, phenobarbital (PB) upregulates target drug-metabolizing enzyme (DME) mRNA levels. However, few data about PB's post-transcriptional effects are actually available. This work provides the first, and an almost complete, characterization of PB-dependent changes in DME catalytic activities in bovine liver using common probe substrates and confirmatory immunoblotting investigations. As expected, PB increased the total cytochrome P450 (CYP) content and the extent of metyrapone binding; moreover, an augmentation of protein amounts and related enzyme activities was observed for known PB targets such as CYP2B, 2C, and 3A, but also CYP2E1. However, contradictory results were obtained for CYP1A, while a decreased catalytic activity was observed for flavin-containing monooxygenases 1 and 3. The barbiturate had no effect on the chosen hydrolytic and conjugative DMEs. For the first time, we also measured the 26S proteasome activity, and the increase observed in PB-treated cattle would suggest this post-translational event might contribute to cattle DME regulation. Overall, this study increased the knowledge of cattle hepatic drug metabolism, and further confirmed the presence of species differences in DME expression and activity between cattle, humans, and rodents. This reinforced the need for an extensive characterization and understanding of comparative molecular mechanisms involved in expression, regulation, and function of DMEs.