Carboxylesterase 1 and Precision Pharmacotherapy: Pharmacogenetics and Nongenetic Regulators

Species-specific in vivo exposure assessment and in vivo-in vitro correlation of the carboxylate esters prodrug HD56 targeting FK506 binding proteins: The pivotal role of humanized mice

HD561, which was designed to enhance nerve growth, was re-engineered into HD56, a carboxylic acid ester prodrug. The goal of this study was to compare the druggability, species differences, and the correlation between in vitro and in vivo transformation of HD56 to HD561 from a pharmacokinetic (PK) perspective, offering a scientific basis for HD56's clinical research. The bidirectional transmembrane transport of HD56 and HD561 was investigated using Caco-2 cells and LLC-PK1 cells overexpressing MDR1 monolayer cells. Recombinant enzymes and chemical inhibition methods were employed to identify the reaction phenotyping. The conversion of HD56 to HD561 was compared in hepatic and intestinal microsomes, as well as plasma, across different species, including humans, rats, monkeys, and mice with humanized liver. PK studies were conducted in rats, monkeys, and mice with different humanized liver proportions (Hu-URG, Hu-URG-Low, and Hu-URG-High). Finally, an in vivo-in vitro correlation was established between the conversion rate of HD56 to HD561. Results showed that HD56 had better permeability than HD561. HD56 could be hydrolyzed by carboxylesterase 1 to HD561 and be metabolized by cytochrome P450 isoenzymes, while HD561 underwent further metabolism via CYP2C9. Significant species differences existed, and a good in vivo-in vitro correlation was only achieved in humanized mice (r = 0.98). Both in vitro and in vivo PK characteristics of HD56 were remarkably superior to those of HD561, suggesting that HD56 held promise for development. Humanized liver mice serve as a powerful model to address the issue of species differences in ester prodrugs. SIGNIFICANCE STATEMENT: Prodrug HD56 showed superior pharmacokinetic properties compared with the active compound HD561, guiding similar prodrug research. The use of chimeric mice with human hepatocytes, for the first time, to study carboxylesterase (CES) prodrug HD56 provides a model that closely mimics human metabolism. Findings deepen understanding of HD56's behavior and offer a predictive tool for CES prodrugs' metabolic fate, streamlining drug development and improving preclinical accuracy.

Enzymatic hydrolysis of ∆8-THC-O, ∆9-THC-O, 11-α-HHC-O, and 11-β-HHC-O by pooled human liver microsomes to generate ∆8-THC, ∆9-THC, 11-α-HHC, and 11-β-HHC

PURPOSE

In recent years, analogues of ∆9-tetrahydrocannabinol (∆9-THC) have been widely distributed in Japan via the internet. Hexahydrocannabinol (HHC), synthesized by reducing THC, was controlled as a designated substance under the Pharmaceutical and Medical Device Act in Japan in 2022. However, other semi-synthetic cannabinoids, such as acetyl derivatives of THC and HHC, appeared soon. Herein, we examined whether the enzymatic hydrolysis of acetylated forms of ∆9-THC, ∆8-THC 11-α-HHC, and 11-β-HHC by human liver microsomes (HLM) occurs.

METHODS

The hydrolysis reaction was accomplished with HLM. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine products. Recombinant enzymes carboxylesterase 1C (CES1c), carboxylesterase 2 (CES2), and carboxylesterase inhibitor bis-(4-nitrophenyl) phosphate (BNPP) were used to clarify the principal hydrolysis enzymes for acetylated cannabinoids.

RESULTS

The acetylated form underwent hydrolysis with HLM time-dependently, with almost no acetylated product remaining after 60 min. Furthermore, results from LC-MS showed that only the deacetylated form was present after hydrolysis. Although hydrolysis did not occur when HLM was pre-incubated with the carboxylesterase inhibitor BNPP, it was observed when CES1c or CES2 was used for in vitro experiments.

CONCLUSION

This is the first time that it is elucidated that ∆9-THC-O, ∆8-THC-O, 11-α-HHC-O, and 11-β-HHC-O are enzymatically hydrolyzed with HLM to produce ∆9-THC, ∆8-THC, 11-α-HHC, and 11-β-HHC, respectively. Our results also support that CES1c and CES2 were the main enzymes involved in the hydrolysis of the acetylated cannabinoids. This study provides scientific support for the metabolism of newly regulated acetylated cannabinoids to cause the parent compound in vivo.

Impact of genetic polymorphisms and drug-drug interactions mediated by carboxylesterase 1 on remimazolam deactivation

Remimazolam (Byfavo, Acacia Pharma), a recent Food and Drug Administration-approved ester-linked benzodiazepine, offers advantages in sedation, such as rapid onset and predictable duration, making it suitable for broad anesthesia applications. Its favorable pharmacological profile is primarily attributed to rapid hydrolysis, the primary metabolism pathway for its deactivation. Thus, understanding remimazolam hydrolysis determinants is essential for optimizing its clinical use. This study aimed to identify the enzyme(s) and tissue(s) responsible for remimazolam hydrolysis and to evaluate the influence of genetic polymorphisms and drug-drug interactions on its hydrolysis in the human liver. An initial incubation study with remimazolam and PBS, human serum, and the S9 fractions of human liver and intestine demonstrated that remimazolam was exclusively hydrolyzed by human liver S9 fractions. Subsequent incubation studies utilizing a carboxylesterase inhibitor (bis(4-nitrophenyl) phosphate), recombinant human carboxylesterase 1 (CES1) and carboxylesterase 2 confirmed that remimazolam is specifically hydrolyzed by CES1 in human liver. Furthermore, in vitro studies with wild-type CES1 and CES1 variants transfected cells revealed that certain genetic polymorphisms significantly impair remimazolam deactivation. Notably, the impact of CES1 G143E was verified using individual human liver samples. Moreover, our evaluation of the drug-drug interactions between remimazolam and several other substrates/inhibitors of CES1-including simvastatin, enalapril, clopidogrel, and sacubitril-found that clopidogrel significantly inhibited remimazolam hydrolysis at clinically relevant concentrations, with CES1 genetic variants potentially influencing the interactions. In summary, CES1 genetic variants and its interacting drugs are crucial factors contributing to interindividual variability in remimazolam hepatic hydrolysis, holding the potential to serve as biomarkers for optimizing remimazolam use. SIGNIFICANCE STATEMENT: This investigation demonstrates that remimazolam is deactivated by carboxylesterase 1 (CES1) in the human liver, with CES1 genetic variants and drug-drug interactions significantly influencing its metabolism. These findings emphasize the need to consider CES1 genetic variability and potential drug-drug interactions in remimazolam use, especially in personalized pharmacotherapy to achieve optimal anesthetic outcomes.

Update on antithrombotic therapy and body mass: a clinical consensus statement of the European Society of Cardiology Working Group on Cardiovascular Pharmacotherapy and the European Society of Cardiology Working Group on Thrombosis

Obesity and underweight are a growing health problem worldwide and a challenge for clinicians concerning antithrombotic therapy, due to the associated risks of thrombosis and/or bleeding. This clinical consensus statement updates a previous one published in 2018, by reviewing the most recent evidence on antithrombotic drugs based on body size categories according to the World Health Organization classification. The document focuses mostly on individuals at the extremes of body weight, i.e. underweight and moderate-to-morbid obesity, who require antithrombotic drugs, according to current guidelines, for the treatment or prevention of cardiovascular diseases or venous thromboembolism. Managing antithrombotic therapy or thromboprophylaxis in these individuals is challenging, due to profound changes in body composition, metabolism and organ function, and altered drug pharmacokinetics and pharmacodynamics, as well as weak or no evidence from clinical trials. The document also includes artificial intelligence simulations derived from in silico pharmacokinetic/pharmacodynamic models, which can mimic the pharmacokinetic changes and help identify optimal regimens of antithrombotic drugs for severely underweight or severely obese individuals. Further, bariatric surgery in morbidly obese subjects is frequently performed worldwide. Bariatric surgery causes specific and additional changes in metabolism and gastrointestinal anatomy, depending on the type of the procedure, which can also impact the pharmacokinetics of antithrombotic drugs and their management. Based on existing literature, the document provides consensus statements on optimizing antithrombotic drug management for underweight and all classes of obese patients, while highlighting the current gaps in knowledge in these complex clinical settings, which require personalized medicine and precision pharmacology.

Carboxylesterase 1 directs the metabolic profile of dendritic cells to a reduced inflammatory phenotype

The metabolic profile of dendritic cells (DCs) shapes their phenotype and functions. The carboxylesterase 1 (CES1) enzyme is highly expressed in mononuclear myeloid cells; however, its exact role in DCs is elusive. We used a CES1 inhibitor (WWL113) and genetic overexpression to explore the role of CES1 in DC differentiation in inflammatory models. CES1 expression was analyzed during CD14+ monocytes differentiation to DCs (MoDCs) using quantitative polymerase chain reaction. A CES1 inhibitor (WWL113) was applied during MoDC differentiation. Surface markers, secreted cytokines, lactic acid production, and phagocytic and T cell polarization capacity were analyzed. The transcriptomic and metabolic profiles were assessed with RNA sequencing and mass spectrometry, respectively. Cellular respiration was assessed using seahorse respirometry. Transgenic mice were used to assess the effect of CES1 overexpression in DCs in inflammatory models. CES1 expression peaked early during MoDC differentiation. Pharmacological inhibition of CES1 led to higher expression of CD209, CD86 and MHCII. WWL113 treated MoDCs secreted higher quantities of interleukin (IL)-6, IL-8, tumor necrosis factor, and IL-10 and demonstrated stronger phagocytic ability and a higher capacity to polarize T helper 17 differentiation in an autologous DC-T cell coculture model. Transcriptomic profiling revealed enrichment of multiple inflammatory and metabolic pathways. Functional metabolic analysis showed impaired maximal mitochondrial respiration capacity, increased lactate production, and decreased intracellular amino acids and tricarboxylic acid cycle intermediates. Transgenic human CES1 overexpression in murine DCs generated a less inflammatory phenotype and increased resistance to T cell-mediated colitis. In conclusion, CES1 inhibition directs DC differentiation toward a more inflammatory phenotype that shows a stronger phagocytic capacity and supports T helper 17 skewing. This is associated with a disrupted mitochondrial respiration and amino acid depletion.

Randomized evaluation of the loss-of-function carboxylesterase 1 (CES1) G143E variant on clopidogrel and ticagrelor pharmacodynamics

Antiplatelet therapy with a P2Y12 receptor inhibitor, in combination with aspirin, is standard of care for medical management of patients with coronary artery disease, and flexibility in prescribing options among these medications offers great potential for individualizing patient care. Previously, we showed that a loss-of-function missense mutation (G143E) in carboxylesterase 1 (CES1), the primary enzyme responsible for clopidogrel degradation, significantly impacts on-clopidogrel platelet aggregation and recurrent cardiovascular event risk. In the current investigation, we conducted a prospective randomized crossover study of clopidogrel (75 mg/day for 7 days) and ticagrelor (180 mg/day for 7 days) in 50 individuals stratified by CES1 G143E genotype (N = 34 143GG and 16 143GE) to determine the effect of drug choice on inhibition of platelet aggregation (IPA). Consistent with prior reports, we observed strong association between G143E and adenosine diphosphate-stimulated platelet aggregation following clopidogrel administration (IPA = 71.6 vs. 48.0% in 143E-allele carriers vs. non-carriers, respectively, p = 3.8 × 10-5). Similar significant effects on platelet aggregation were also noted between 143E-allele carriers versus non-carriers in response to stimulation with arachidonic acid (45.8 vs. 25.8%, p = 0.04), epinephrine (44.4 vs. 18.8%, p = 0.03), and collagen (5 μg/mL, 25.8 vs. 11.4%, p = 3.7 × 10-3). In contrast, no relationship between CES1 G143E and IPA was observed following ticagrelor administration regardless of the platelet agonist used. Collectively, these data suggest that on-clopidogrel platelet aggregation is substantially modified by CES1 G143E genotype, that this variant does not modify ticagrelor pharmacodynamics, and that more consistent inhibition of platelet aggregation may be achieved by using ticagrelor in patients who carry clopidogrel response-modifying alleles in CES1.

Fluorogenic chemical tools to shed light on CES1-mediated adverse drug interactions

Studying factors that cause interindividual variability of carboxylesterase 1 (CES1) activity is currently difficult due to limited methods. Here, fluorogenic tools for measuring CES1 activity are developed and demonstrated to report on these factors in living cells. These tools enable experiments that will develop a deeper understanding of CES1 metabolism.

Brain Exposure to the Macrocyclic ALK Inhibitor Zotizalkib is Restricted by ABCB1, and Its Plasma Disposition is Affected by Mouse Carboxylesterase 1c

Zotizalkib (TPX-0131), a fourth-generation macrocyclic anaplastic lymphoma kinase (ALK) inhibitor, is designed to overcome resistance due to secondary ALK mutations in non-small cell lung cancer (NSCLC). We here evaluated the pharmacokinetic roles of the ABCB1 (P-gp/MDR1) and ABCG2 (BCRP) efflux transporters, OATP1 influx transporters and the metabolizing enzymes CES1 and CYP3A in plasma and tissue disposition of zotizalkib after oral administration in relevant mouse models. Zotizalkib was efficiently transported by hABCB1 in vitro. In vivo, a significant ∼9-fold higher brain-to-plasma ratio was observed in Abcb1a/b-/- and Abcb1a/b;Abcg2-/- compared to wild-type mice. No change in brain disposition was observed in Abcg2-/- mice, suggesting that mAbcb1a/b markedly restricts the brain accumulation of zotizalkib. ABCB1-mediated efflux of zotizalkib was completely inhibited by elacridar, a dual ABCB1/ABCG2 inhibitor, increasing brain exposure without any signs of acute CNS-related toxicities. In Oatp1a/b-/- mice, no marked changes in plasma exposure or tissue-to-plasma ratios were observed, indicating that zotizalkib is not a substantial in vivo substrate for mOatp1a/b. Zotizalkib may further be metabolized by CYP3A4 but only noticeably at low plasma concentrations. In Ces1-/- mice, a 2.5-fold lower plasma exposure was seen compared to wild-type, without alterations in tissue distribution. This suggests increased plasma retention of zotizalkib by binding to the abundant mouse plasma Ces1c. Notably, the hepatic expression of human CES1 did not affect zotizalkib plasma exposure or tissue distribution. The obtained pharmacokinetic insights may be useful for the further development and optimization of therapeutic efficacy and safety of zotizalkib and related compact macrocyclic ALK inhibitors.

Pharmacogenetic study of CES1 gene and enalapril efficacy

Enalapril is an orally administered angiotensin-converting enzyme inhibitor which is widely prescribed to treat hypertension, chronic kidney disease, and heart failure. It is an ester prodrug that needs to be activated by carboxylesterase 1 (CES1). CES1 is a hepatic hydrolase that in vivo biotransforms enalapril to its active form enalaprilat in order to produce its desired pharmacological impact. Several single nucleotide polymorphisms in CES1 gene are reported to alter the catalytic activity of CES1 enzyme and influence enalapril metabolism. G143E, L40T, G142E, G147C, Y170D, and R171C can completely block the enalapril metabolism. Some polymorphisms like Q169P, E220G, and D269fs do not completely block the CES1 function; however, they reduce the catalytic activity of CES1 enzyme. The prevalence of these polymorphisms is not the same among all populations which necessitate to consider the genetic panel of respective population before prescribing enalapril. These genetic variations are also responsible for interindividual variability of CES1 enzyme activity which ultimately affects the pharmacokinetics and pharmacodynamics of enalapril. The current review summarizes the CES1 polymorphisms which influence the enalapril metabolism and efficacy. The structure of CES1 catalytic domain and important amino acids impacting the catalytic activity of CES1 enzyme are also discussed. This review also highlights the importance of pharmacogenomics in personalized medicine.

Discovery of a novel homocysteine thiolactone hydrolase and the catalytic activity of its natural variants

Homocysteine thiolactone (HTL), a toxic metabolite of homocysteine (Hcy) in hyperhomocysteinemia (HHcy), is known to modify protein structure and function, leading to protein damage through formation of N-Hcy-protein. HTL has been highly linked to HHcy-associated cardiovascular and neurodegenerative diseases. The protective role of HTL hydrolases against HTL-associated vascular toxicity and neurotoxicity have been reported. Although several endogeneous enzymes capable of hydrolyzing HTL have been identified, the primary enzyme responsible for its metabolism remains unclear. In this study, three human carboxylesterases were screened to explore new HTL hydrolase and human carboxylesterase 1 (hCES1) demonstrates the highest catalytic activity against HTL. Given the abundance of hCES1 in the liver and the clinical significance of its single-nucleotide polymorphisms (SNPs), six common hCES1 nonsynonymous coding SNP (nsSNPs) variants were examined and characterized for their kinetic parameters. Variants E220G and G143E displayed 7.3-fold and 13.2-fold lower catalytic activities than its wild-type counterpart. In addition, the detailed catalytic mechanism of hCES1 for HTL hydrolysis was computational investigated and elucidated by Quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) method. The function of residues E220 and G143 in sustaining its hydrolytic activity of hCES1 was analyzed, and the calculated energy difference aligns well with experimental-derived results, supporting the validity of our computational insights. These findings provide insights into the potential protective role of hCES1 against HTL-associated toxicity, and warrant future studies on the possible association between specific genetic variants of hCES1 with impaired catalytic function and clinical susceptibility of HTL-associated cardiovascular and neurodegenerative diseases.

Strategies for the development of stimuli-responsive small molecule prodrugs for cancer treatment

Approved anticancer drugs typically face challenges due to their narrow therapeutic window, primarily because of high systemic toxicity and limited selectivity for tumors. Prodrugs are initially inactive drug molecules designed to undergo specific chemical modifications. These modifications render the drugs inactive until they encounter specific conditions or biomarkers in vivo, at which point they are converted into active drug molecules. This thoughtful design significantly improves the efficacy of anticancer drug delivery by enhancing tumor specificity and minimizing off-target effects. Recent advancements in prodrug design have focused on integrating these strategies with delivery systems like liposomes, micelles, and polymerosomes to further improve targeting and reduce side effects. This review outlines strategies for designing stimuli-responsive small molecule prodrugs focused on cancer treatment, emphasizing their chemical structures and the mechanisms controlling drug release. By providing a comprehensive overview, we aim to highlight the potential of these innovative approaches to revolutionize cancer therapy.

The antioxidant and antimicrobial activity of ethanolic extract in roots, stems, and leaves of three commercial Cymbopogon species

BACKGROUND

Cymbopogon is a member of the family Poaceae and has been explored for its phytochemicals and bioactivities. Although the antimicrobial activities of Cymbopogon spp. extracts have been extensively studied, comprehensive analyses are required to identify promising compounds for the treatment of antimicrobial resistance. Therefore, this study investigated the antioxidant and antimicrobial properties of Cymbopogon spp. ethanolic extracts in every single organ.

METHODS

Ethanolic extracts were obtained from three Indonesian commercial species of Cymbopogon spp., namely Cymbopogon citratus (L.) Rendle, Cymbopogon nardus (DC.) Spatf., and Cymbopogon winterianus Jowitt. The leaf, stem, and root extracts were evaluated via metabolite profiling using gas chromatography-mass spectrometry (GC-MS). In silico and in vitro analyses were used to evaluate the antioxidant and antimicrobial properties of the Cymbopogon spp. ethanolic extracts. In addition, bioactivity was measured using cytotoxicity assays. Antioxidant assays were performed using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis [3-ethylbenzothiazoline-6-sulfonic acid (ABTS) to determine toxicity to Huh7it-1 cells using a tetrazolium bromide (MTT) assay. Finally, the antimicrobial activity of these extracts was evaluated against Candida albicans, Bacillus subtilis, Staphylococcus aureus, and Escherichia coli using a well diffusion assay.

RESULTS

GC-MS analysis revealed 53 metabolites. Of these, 2,5-bis(1,1-dimethylethyl)- phenol (27.87%), alpha-cadinol (26.76%), and 1,2-dimethoxy-4-(1-propenyl)-benzene (20.56%) were the predominant compounds. C. winterianus and C. nardus leaves exhibited the highest antioxidant activity against DPPH and ABTS, respectively. Contrastingly, the MTT assay showed low cytotoxicity. C. nardus leaf extract exhibited the highest antimicrobial activity against E. coli and S. aureus, whereas C. winterianus stem extract showed the highest activity against B. substilis. Furthermore, computational pathway analysis predicted that antimicrobial activity mechanisms were related to antioxidant activity.

CONCLUSIONS

These findings demonstrate that the leaves had strong antioxidant activity, whereas both the leaves and stems showed great antimicrobial activity. Furthermore, all Cymbopogon spp. ethanolic extracts showed low toxicity. These findings provide a foundation for future studies that assess the clinical safety of Cymbopogon spp. as novel drug candidates.

ABCB1 attenuates brain exposure to the KRASG12C inhibitor opnurasib whereas binding to mouse carboxylesterase 1c influences its plasma exposure

Opnurasib (JDQ443) is a newly developed oral KRASG12C inhibitor, with a binding mechanism distinct from the registered KRASG12C inhibitors sotorasib and adagrasib. Phase I and II clinical trials for opnurasib in NSCLC are ongoing. We evaluated the pharmacokinetic roles of the ABCB1 (P-gp/MDR1) and ABCG2 (BCRP) efflux and OATP1 influx transporters, and of the metabolizing enzymes CYP3A and CES1 in plasma and tissue disposition of oral opnurasib, using genetically modified cell lines and mouse models. In vitro, opnurasib was potently transported by human (h)ABCB1 and slightly by mouse (m)Abcg2. In Abcb1a/b- and Abcb1a/b;Abcg2-deficient mice, a significant ∼100-fold increase in brain-to-plasma ratios was observed. Brain penetration was unchanged in Abcg2-/- mice. ABCB1 activity in the blood-brain barrier may therefore potentially limit the efficacy of opnurasib against brain metastases. The Abcb1a/b transporter activity could be almost completely reversed by co-administration of elacridar, a dual ABCB1/ABCG2 inhibitor, increasing the brain penetration without any behavioral or postural signs of acute CNS-related toxicity. No significant pharmacokinetic roles of the OATP1 transporters were observed. Transgenic human CYP3A4 did not substantially affect the plasma exposure of opnurasib, indicating that opnurasib is likely not a sensitive CYP3A4 substrate. Interestingly, Ces1-/- mice showed a 4-fold lower opnurasib plasma exposure compared to wild-type mice, whereas no strong effect was seen on the tissue distribution. Plasma Ces1c therefore likely binds opnurasib, increasing its retention in plasma. The obtained pharmacokinetic insights may be useful for further optimization of the clinical efficacy and safety of opnurasib, and might reveal potential drug-drug interaction risks.

Overview of Methamphetamine-Associated Pulmonary Arterial Hypertension

TOPIC IMPORTANCE

The global surge in methamphetamine use is a critical public health concern, particularly due to its robust correlation with methamphetamine-associated pulmonary arterial hypertension (MA-PAH). This association raises urgent alarms about the potential escalation of MA-PAH incidence, posing a significant and imminent challenge to global public health.

REVIEW FINDINGS

This comprehensive review meticulously explores MA-PAH, offering insights into its epidemiology, pathophysiology, clinical presentation, diagnostic intricacies, and management strategies. The pathogenesis, yet to be fully described, involves complex molecular interactions, including alterations in serotonin signaling, reduced activity of carboxylesterase 1, oxidative stress, and dysregulation of pulmonary vasoconstrictors and vasodilators. These processes culminate in the structural remodeling of the pulmonary vasculature, resulting in pulmonary arterial hypertension. MA-PAH exhibits a more severe clinical profile in functional class and hemodynamics compared with idiopathic pulmonary arterial hypertension. Management involves a multifaceted approach, integrating pulmonary vasodilators, cessation of methamphetamine use, and implementing social and rehabilitation programs. These measures aim to enhance patient outcomes and detect potential relapses for timely intervention.

SUMMARY

This review consolidates our understanding of MA-PAH, pinpointing knowledge gaps for future studies. Addressing these gaps is crucial for advancing diagnostic accuracy, unraveling mechanisms, and optimizing treatment for MA-PAH, thereby addressing the evolving landscape of this complex health concern.

Evaluation of the inhibitory effects of antigout drugs on human carboxylesterases in vitro

Gout is an immune-metabolic disease that frequently coexists with multiple comorbidities such as chronic kidney disease, cardiovascular disease and metabolic syndrome, therefore, it is often treated in combination with these complications. The present study aimed to evaluate the inhibitory effect of antigout drugs (allopurinol, febuxostat, topiroxostat, benzbromarone, lesinurad and probenecid) on the activity of the crucial phase I drug-metabolizing enzymes, carboxylesterases (CESs). 2-(2-benzoyl-3-methoxyphenyl) benzothiazole (BMBT) and fluorescein diacetate (FD) were utilized as the probe reactions to determine the activity of CES1 and CES2, respectively, through in vitro culturing with human liver microsomes. Benzbromarone and lesinurad exhibited strong inhibition towards CESs with Ki values of 2.16 and 5.15 μM for benzbromarone towards CES1 and CES2, respectively, and 2.94 μM for lesinurad towards CES2. In vitro-in vivo extrapolation (IVIVE) indicated that benzbromarone and lesinurad might disturb the metabolic hydrolysis of clinical drugs in vivo by inhibiting CESs. In silico docking showed that hydrogen bonds and hydrophobic interactions contributed to the intermolecular interactions of antigout drugs on CESs. Therefore, vigilant monitoring of potential drug-drug interactions (DDIs) is imperative when co-administering antigout drugs in clinical practice.

Regulation of carboxylesterases and its impact on pharmacokinetics and pharmacodynamics: an up-to-date review

INTRODUCTION

Carboxylesterase 1 (CES1) and carboxylesterase 2 (CES2) are among the most abundant hydrolases in humans, catalyzing the metabolism of numerous clinically important medications, such as methylphenidate and clopidogrel. The large interindividual variability in the expression and activity of CES1 and CES2 affects the pharmacokinetics (PK) and pharmacodynamics (PD) of substrate drugs.

AREAS COVERED

This review provides an up-to-date overview of CES expression and activity regulations and examines their impact on the PK and PD of CES substrate drugs. The literature search was conducted on PubMed from inception to January 2024.

EXPERT OPINION

Current research revealed modest associations of CES genetic polymorphisms with drug exposure and response. Beyond genomic polymorphisms, transcriptional and posttranslational regulations can also significantly affect CES expression and activity and consequently alter PK and PD. Recent advances in plasma biomarkers of drug-metabolizing enzymes encourage the research of plasma protein and metabolite biomarkers for CES1 and CES2, which could lead to the establishment of precision pharmacotherapy regimens for drugs metabolized by CESs. Moreover, our understanding of tissue-specific expression and substrate selectivity of CES1 and CES2 has shed light on improving the design of CES1- and CES2-activated prodrugs.

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.

Sex-Dependent Changes to the Intestinal and Hepatic Abundance of Drug Transporters and Metabolizing Enzymes in the SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized by death and dysfunction of motor neurons that result in a rapidly progressing loss of motor function. While there are some data on alterations at the blood-brain barrier (BBB) in ALS and their potential impact on CNS trafficking of drugs, little is reported on the impact of this disease on the expression of drug-handling proteins in the small intestine and liver. This may impact the dosing of the many medicines that individuals with ALS are prescribed. In the present study, a proteomic evaluation was performed on small intestine and liver samples from postnatal day 120 SOD1G93A mice (a model of familial ALS that harbors a human mutant form of superoxide dismutase 1) and wild-type (WT) littermates (n = 7/genotype/sex). Untargeted, quantitative proteomics was undertaken using either label-based [tandem mass tag (TMT)] or label-free [data-independent acquisition (DIA)] acquisition strategies on high-resolution mass spectrometric instrumentation. Copper chaperone for superoxide dismutase (CCS) was significantly higher in SOD1G93A samples compared to the WT samples for both sexes and tissues, therefore representing a potential biomarker for ALS in this mouse model. Relative to WT mice, male SOD1G93A mice had significantly different proteins (Padj < 0.05, |fold-change|>1.2) in the small intestine (male 22, female 1) and liver (male 140, female 3). This included an up-regulation of intestinal transporters for dietary glucose [solute carrier (SLC) SLC5A1] and cholesterol (Niemann-Pick c1-like 1), as well as for several drugs (e.g., SLC15A1), in the male SOD1G93A mice. There was both an up-regulation (e.g., SLCO2A1) and down-regulation (ammonium transporter rh type b) of transporters in the male SOD1G93A liver. In addition, there was both an up-regulation (e.g., phosphoenolpyruvate carboxykinase) and down-regulation (e.g., carboxylesterase 1) of metabolizing enzymes in the male SOD1G93A liver. This proteomic data set identified male-specific changes to key small intestinal and hepatic transporters and metabolizing enzymes that may have important implications for the bioavailability of nutrients and drugs in individuals with ALS.

Carboxylesterase-activated near-infrared fluorescence probe for highly sensitive imaging of liver tumors

Carboxylesterases (CESs) are critical for metabolizing ester-containing biomolecules and are specifically important in liver metabolic disorders. The modulation of CESs is also an important issue in pharmacology and clinical applications. Herein, we present a near-infrared (NIR) CES fluorescent probe (NCES) based on the protection-deprotection of the hydroxyl group for monitoring CES levels in living systems. The NCES probe has good selectivity and sensitivity for CESs with a limit of detection (LOD) of 5.24 mU mL-1, which allows for tracing the fluctuation of cellular CES after treatment with anticancer drugs and under inflammation and apoptosis states. Furthermore, NCES can be successfully applied for guiding liver cancer surgery with high-contrast in vivo imaging and detecting clinical serum samples from liver cancer patients. This work showed that the NCES probe has great potential in drug development, imaging applications for medical diagnosis, and early-stage detection for clinical liver diseases.

Simultaneously Predicting the Pharmacokinetics of CES1-Metabolized Drugs and Their Metabolites Using Physiologically Based Pharmacokinetic Model in Cirrhosis Subjects

Hepatic carboxylesterase 1 (CES1) metabolizes numerous prodrugs into active ingredients or direct-acting drugs into inactive metabolites. We aimed to develop a semi-physiologically based pharmacokinetic (semi-PBPK) model to simultaneously predict the pharmacokinetics of CES1 substrates and their active metabolites in liver cirrhosis (LC) patients. Six prodrugs (enalapril, benazepril, cilazapril, temocapril, perindopril and oseltamivir) and three direct-acting drugs (flumazenil, pethidine and remimazolam) were selected. Parameters such as organ blood flows, plasma-binding protein concentrations, functional liver volume, hepatic enzymatic activity, glomerular filtration rate (GFR) and gastrointestinal transit rate were integrated into the simulation. The pharmacokinetic profiles of these drugs and their active metabolites were simulated for 1000 virtual individuals. The developed semi-PBPK model, after validation in healthy individuals, was extrapolated to LC patients. Most of the observations fell within the 5th and 95th percentiles of simulations from 1000 virtual patients. The estimated AUC and Cmax were within 0.5-2-fold of the observed values. The sensitivity analysis showed that the decreased plasma exposure of active metabolites due to the decreased CES1 was partly attenuated by the decreased GFR. Conclusion: The developed PBPK model successfully predicted the pharmacokinetics of CES1 substrates and their metabolites in healthy individuals and LC patients, facilitating tailored dosing of CES1 substrates in LC patients.

High-Dose Methylphenidate and Carboxylesterase 1 Genetic Variability in Patients With Attention-Deficit/Hyperactivity Disorder: A Case Series

PURPOSE/BACKGROUND

Methylphenidate (MPH) is widely used to reduce symptoms of attention-deficit/hyperactivity disorder. Methylphenidate is metabolized by the carboxylesterase 1 (CES1) enzyme. Some patients need a very high dose of MPH to reach desired clinical effects, without having adverse effects. This may be due to differences in MPH pharmacokinetics (PK), potentially caused by DNA variants in CES1 , the gene encoding the enzyme that metabolizes MPH. Here we describe 3 patients requiring high-dose MPH and investigated the CES1 gene.

METHODS/PROCEDURES

The 3 patients were using short-acting MPH in a dose of 180 to 640 mg instead of the maximum advised dose of around 100 mg MPH in the Netherlands. Plasma concentrations of MPH were determined at scheduled time points (day-curve). Methylphenidate plasma concentrations were used for PK analysis using an earlier published 2-compartment PK population model of MPH. Individual data of the 3 patients were compared with simulated population data, when equivalent doses were used. In addition, CES1 was genotyped (number of gene copies and single nucleotide polymorphisms) using real-time polymerase chain reaction.

FINDINGS/RESULTS

Pharmacokinetic analysis in all 3 patients showed lower plasma concentrations of MPH in comparison with the population data. The mean absorption time and volume of distribution of the central compartment were equal, but the elimination clearance was higher. However, CES1 genotyping revealed no variations that could explain a higher metabolism of MPH.

IMPLICATIONS/CONCLUSIONS

In these 3 cases, we could not demonstrate a correlation between MPH clearance and known genetic variants of the CES1 gene.

Drug-Drug Interaction Potential of Remimazolam: CYP 450, Transporters, and Protein Binding

BACKGROUND

The ultra-short-acting benzodiazepine, remimazolam, is a new treatment modality for procedural sedation and general anesthesia. Its activity is terminated by carboxylesterase 1 (CES1).

OBJECTIVE

The objective of this study was to determine the drug-drug interaction (DDI) potential of remimazolam through mechanisms unrelated to its metabolizing enzyme, CES1.

METHODS

Conventional in vitro co-exposure experiments were conducted to study possible interactions of remimazolam and its primary metabolite, CNS7054, mediated by competitive binding to plasma protein or reactions with cytochrome P450 isoforms or drug transporters.

RESULTS

No relevant interactions of remimazolam or its metabolite with cytochrome P450 (CYP) isoforms at clinically relevant concentrations were identified. Likewise, standard experiments revealed no clinically relevant interactions with drug transporters and plasma proteins.

CONCLUSION

The present data and analyses suggest a very low potential of remimazolam for pharmacokinetic DDIs mediated by CYP isoforms, drug transporters, and protein binding.

Pharmacokinetics of asundexian with combined CYP3A and P-gp inhibitors and an inducer: Target in vitro and in vivo studies

AIMS

Asundexian is an oral, direct and reversible inhibitor of activated factor XI (FXIa) in development for the treatment of thromboembolic events. This article summarizes results from preclinical and clinical studies, including identification of enzymes involved in asundexian pharmacokinetics, and evaluation of potential target drug-drug interactions.

METHODS

In vitro studies investigated the substrate characteristics of asundexian towards several cytochrome P450 (CYP) isoforms, hydrolytic enzymes and drug transporters. Inhibition of the amide hydrolysis of asundexian was investigated in vitro for several relevant drugs. Phase 1 studies in healthy male participants investigated the pharmacokinetics (PK) of asundexian upon co-administration of combined inhibitors or an inducer of P-gp and CYP3A4 (itraconazole, verapamil or carbamazepine, respectively, or the moderate CYP3A4 inhibitor fluconazole). The pharmacodynamic (PD) markers are activated partial thromboplastin time and FXIa inhibition.

RESULTS

Asundexian was predominantly metabolized via carboxylesterase 1 and, to a lesser extent, via CYP3A4 and is a substrate of P-gp. The asundexian area under the plasma concentration-time curve (AUC) increased by 103% and 75.6% upon combined inhibition of P-gp and strong or moderate inhibition of CYP3A4, respectively, but was unaffected by moderate CYP3A4 inhibition. Combined P-gp and CYP3A4 induction by carbamazepine decreased asundexian AUC by 44.4%. PD is concentration-dependent, thus no differences in maximum responses and recovery commensurate with PK effect(s) were observed. Adverse events were mild and asundexian was well tolerated.

CONCLUSIONS

The presented studies confirmed that CYP3A4 and P-gp contribute to asundexian metabolism and excretion. Observed effects were in line with data from a previous mass balance study.

Identifying Sex-Specific Serum Patterns of Alzheimer's Mice through Deep TMT Profiling and a Concentration-Dependent Concatenation Strategy

Alzheimer's disease (AD) is the most prevalent form of dementia, disproportionately affecting women in disease prevalence and progression. Comprehensive analysis of the serum proteome in a common AD mouse model offers potential in identifying possible AD pathology- and gender-associated biomarkers. Here, we introduce a multiplexed, nondepleted mouse serum proteome profiling via tandem mass-tag (TMTpro) labeling. The labeled sample was separated into 475 fractions using basic reversed-phase liquid chromatography (RPLC), which were categorized into low-, medium-, and high-concentration fractions for concatenation. This concentration-dependent concatenation strategy resulted in 128 fractions for acidic RPLC-tandem mass spectrometry (MS/MS) analysis, collecting ∼5 million MS/MS scans and identifying 3972 unique proteins (3413 genes) that cover a dynamic range spanning at least 6 orders of magnitude. The differential expression analysis between wild type and the commonly used AD model (5xFAD) mice exhibited minimal significant protein alterations. However, we detected 60 statistically significant (FDR < 0.05), sex-specific proteins, including complement components, serpins, carboxylesterases, major urinary proteins, cysteine-rich secretory protein 1, pregnancy-associated murine protein 1, prolactin, amyloid P component, epidermal growth factor receptor, fibrinogen-like protein 1, and hepcidin. The results suggest that our platform possesses the sensitivity and reproducibility required to detect sex-specific differentially expressed proteins in mouse serum samples.

IL-33 Downregulates Hepatic Carboxylesterase 1 in Acute Liver Injury via Macrophage-derived Exosomal miR-27b-3p

Background and Aims

We previously reported that carboxylesterase 1 (CES1) expression was suppressed following liver injury. The study aimed to explore the role of interleukin (IL)-33 in liver injury and examine the mechanism by which IL-33 regulates CES1.

Methods

IL-33 and CES1 levels were determined in the livers of patients and lipopolysaccharide (LPS)-, acetaminophen (APAP)-treated mice. We constructed IL-33 and ST2 knockout (KO) mice. ST2-enriched immune cells in livers were screened to identify the responsible cells. Macrophage-derived exosome (MDE) activity was tested by adding exosome inhibitors. Micro-RNAs (miRs) were extracted from control and IL-33-stimulated MDEs (IL-33-MDEs) and subjected miR sequencing (miR-Seq). Candidate miR was tested in vitro and in vivo and its binding of a target gene was assessed by luciferase reporter assays. Lentivirus-vector cellular transfection and transcript silencing were used to examine pathways mediating IL-33 suppression of miR-27b-3p.

Results

Patient liver IL-33 and CES1 expression levels were inversely correlated. CES1 downregulation in liver injury was rescued in both IL-33-deficient and ST2 KO mice. Macrophages were shown to be responsible for IL-33 effects. IL-33-MDEs reduced CES1 levels in hepatocytes. Exosomal miR-Seq and qRT-PCR demonstrated increased miR-27b-3p levels in IL-33-MDEs; miR-27b-3p was implicated in Nrf2 targeting. IL-33 inhibition of miR-27b-3p was found to be GATA3-dependent.

Conclusions

IL-33-ST2-GATA3 pathway signaling increases miR-27b-3p content in MDEs, which upon being internalized by hepatocytes reduce CES1 expression by inhibiting Nrf2. The elucidation of this mechanism in this study contributes to a better understanding of CES1 dysregulation in liver injury.

PBPK Modelling for Drugs Cleared by Non-CYP Enzymes: State-of-the-Art and Future Perspectives

Physiologically-based pharmacokinetic (PBPK) modeling has become the established method for predicting human pharmacokinetics (PK) and drug-drug interactions (DDI). The number of drugs cleared by non-CYP enzyme metabolism has increased steadily and to date, there is no consolidated overview of PBPK modeling for drugs cleared by non-CYP enzymes. This review aims to describe the state-of-the-art for PBPK modeling for drugs cleared via non-CYP enzymes, to identify successful strategies, to describe gaps and to provide suggestion to overcome them. To this end, we conducted a detailed literature search and found 58 articles published before the 1st of January 2023 containing 95 examples of clinical PBPK models for 62 non-CYP enzyme substrates. Reviewed articles covered the drug clearance by uridine 5'-diphospho-glucuronosyltransferases (UGTs), aldehyde oxidase (AO), flavin-containing monooxygenases (FMOs), sulfotransferases (SULTs) and carboxylesterases (CES), with UGT2B7, UGT1A9, CES1, FMO3 and AO being the enzymes most frequently involved. In vitro-in vivo extrapolation (IVIVE) of intrinsic clearance and the bottom-up PBPK modeling involving non-CYP enzymes remains challenging. We observed that the middle-out modeling approach was applied in 80% of the cases, with metabolism parameters optimized in 73% of the models. Our review could not identify a standardized approach used for model optimization based on clinical data, with manual optimization employed most frequently. Successful development of models for UGT2B7, UGT1A9, CES1, and FMO3 substrates provides a foundation for other drugs metabolized by these enzymes and guides the way forward in creating PBPK models for other enzymes in these families. Significance Statement Our review charts the rise of PBPK modeling for drugs cleared by non-CYP enzymes. Analyzing 58 articles and 62 non-CYP enzyme substrates, we found that UGTs, AO, FMOs, SULTs, and CES were the main enzyme families involved and that UGT2B7, UGT1A9, CES1, FMO3 and AO are the individual enzymes with the strongest PBPK modeling precedents. Approaches established for these enzymes can now be extended to additional substrates and to drugs metabolized by enzymes that are similarly well characterized.

Enantioselective in vitro metabolism of the herbicide diclofop-methyl: Prediction of toxicokinetic parameters and reaction phenotyping

Human exposure to contaminants of emerging concern, like pesticides, has increased in the past decades. Diclofop-methyl (DFM) is a chiral herbicide that is employed as a racemic mixture (rac-DFM) in soybean and other crops against wild oats. Studies have shown that DFM has enantioselective action (higher for R-DFM), degradation (faster for S-DFM), and metabolism, producing diclofop (DF) which is also a pesticide. Although toxic effects have been reported for DFM, information regarding how DFM affects humans is lacking, especially when its chirality is concerned. In this study, the in vitro metabolism of rac-DFM and its isolated enantiomers was assessed by using a human model based on human liver microsomes. The kinetic model and parameters were obtained, and the hepatic clearance (CLH) and hepatic extraction ratio (EH) were estimated. Enzyme phenotyping was carried out by employing carboxylesterase isoforms (CES 1 and CES 2). DFM was metabolized through positive homotropic cooperativity with slight preference for (-)-DFM metabolism to (-)-DF. CLH and EH were above 19.60 mL min-1 kg-1 and 98 % for all the monitored reactions, respectively, and CES 1 was the main enzyme underlying the metabolism. These findings point out that liver contributes to DFM metabolism, which is fast, resulting in nearly complete conversion to DF after exposition to DFM.

Genome-wide DNA methylation sequencing identifies epigenetic perturbations in the upper airways under long-term exposure to moderate levels of ambient air pollution

While the link between exposure to high levels of ambient particulate matter (PM) and increased incidences of respiratory and cardiovascular diseases is widely recognized, recent epidemiological studies have shown that low PM concentrations are equally associated with adverse health effects. As DNA methylation is one of the main mechanisms by which cells regulate and stabilize gene expression, changes in the methylome could constitute early indicators of dysregulated signaling pathways. So far, little is known about PM-associated DNA methylation changes in the upper airways, the first point of contact between airborne pollutants and the human body. Here, we focused on cells of the upper respiratory tract and assessed their genome-wide DNA methylation pattern to explore exposure-associated early regulatory changes. Using a mobile epidemiological laboratory, nasal lavage samples were collected from a cohort of 60 adults that lived in districts with records of low (Simmerath) or moderate (Stuttgart) PM10 levels in Germany. PM10 concentrations were verified by particle measurements on the days of the sample collection and genome-wide DNA methylation was determined by enzymatic methyl sequencing at single-base resolution. We identified 231 differentially methylated regions (DMRs) between moderately and lowly PM10 exposed individuals. A high proportion of DMRs overlapped with regulatory elements, and DMR target genes were involved in pathways regulating cellular redox homeostasis and immune response. In addition, we found distinct changes in DNA methylation of the HOXA gene cluster whose methylation levels have previously been linked to air pollution exposure but also to carcinogenesis in several instances. The findings of this study suggest that regulatory changes in upper airway cells occur at PM10 levels below current European thresholds, some of which may be involved in the development of air pollution-related diseases.

Hormetic effects of EGC and EGCG on CES1 activity and its rescue from oxidative stress in rat liver S9

Carboxylesterase 1 (CES1) is a hydrolytic enzyme that plays an important role in the activation or deactivation of many therapeutic agents, thus affecting their pharmacokinetic and pharmacodynamic outcomes. Using rat liver S9 as an enzyme source and enalapril as a CES1 substrate, the present study examined effects of a number of flavonoids on the formation of enalaprilat (the active form of enalapril) produced by CES1-mediated hydrolysis. While a majority of flavonoids tested showed inhibition on CES1, an unexpected hormetic effect was observed for epigallocatechin (EGC) and epigallocatechin gallate (EGCG), i.e., stimulatory effect at low concentrations and enzyme inhibition at high concentrations. Further experiments revealed that oxidative stress caused by hydrogen peroxide, arachidonic acid plus iron, and oxidized low density lipoproteins (oxLOL) reduced CES1 activity in rat liver S9 and the loss of CES1 enzyme activity could be rescued largely by EGC or EGCG. In contrast, such effects were minimal in human liver S9, probably due to the presence of a higher ratio of reduced vs oxidized forms of glutathione. The above findings suggest that the polyphenolic nature of EGC or EGCG might be responsible for rescuing CES1 activity under oxidative stress. Because of the importance of CES1 in drug activation or deactivation and rat liver S9 as a versatile in vitro system used for drug metabolism studies and drug safety assessment, caution should be exercised to avoid potential biases for data interpretation and decision making when CES1 activity in rat liver S9 is evaluated with dependency on experimental conditions.

The development of blood protein profiles in extremely preterm infants follows a stereotypic evolution pattern

BACKGROUND

Preterm birth is the leading cause of neonatal mortality and morbidity. Early diagnosis and interventions are critical to improving the clinical outcomes of extremely premature infants. Blood protein profiling during the first months of life in preterm infants can shed light on the role of early extrauterine development and provide an increased understanding of maturation after extremely preterm birth and the underlying mechanisms of prematurity-related disorders.

METHODS

We have investigated the blood protein profiles during the first months of life in preterm infants on the role of early extrauterine development. The blood protein levels were analyzed using next generation blood profiling on 1335 serum samples, collected longitudinally at nine time points from birth to full-term from 182 extremely preterm infants.

RESULTS

The protein analysis reveals evident predestined serum evolution patterns common for all included infants. The majority of the variations in blood protein expression are associated with the postnatal age of the preterm infants rather than any other factors. There is a uniform protein pattern on postnatal day 1 and after 30 weeks postmenstrual age (PMA), independent of gestational age (GA). However, during the first month of life, GA had a significant impact on protein variability.

CONCLUSIONS

The unified pattern of protein development for all included infants suggests an age-dependent stereotypic development of blood proteins after birth. This knowledge should be considered in neonatal settings and might alter the clinical approach within neonatology, where PMA is today the most dominant age variable.

Natural deletion of mouse carboxylesterases Ces1c/d/e impacts drug metabolism and metabolic syndrome development

Mammalian carboxylesterase 1 enzymes can hydrolyze many xenobiotic chemicals and endogenous lipids. We here identified and characterized a mouse strain (FVB/NKI) in which three of the eight Ces1 genes were spontaneously deleted, removing Ces1c and Ces1e partly, and Ces1d entirely. We studied the impact of this Ces1c/d/e deficiency on drug and lipid metabolism and homeostasis. Ces1c/d/e-/- mice showed strongly impaired conversion of the anticancer prodrug irinotecan to its active metabolite SN-38 in plasma, spleen and lung. Plasma hydrolysis of the oral anticancer prodrug capecitabine to 5-DFCR was also profoundly reduced in Ces1c/d/e-/- mice. Our findings resolved previously unexplained FVB/NKI pharmacokinetic anomalies. On a medium-fat diet, Ces1c/d/e-/- female mice exhibited moderately higher body weight, mild inflammation in gonadal white adipose tissue (gWAT), and increased lipid load in brown adipose tissue (BAT). Ces1c/d/e-/- males showed more pronounced inflammation in gWAT and an increased lipid load in BAT. On a 5-week high-fat diet exposure, Ces1c/d/e deficiency predisposed to developing obesity, enlarged and fatty liver, glucose intolerance and insulin resistance, with severe inflammation in gWAT and increased lipid load in BAT. Hepatic proteomics analysis revealed that the acute phase response, involved in the dynamic cycle of immunometabolism, was activated in these Ces1c/d/e-/- mice. This may contribute to the obesity-related chronic inflammation and adverse metabolic disease in this strain. While Ces1c/d/e deficiency clearly exacerbated metabolic syndrome development, long-term (18-week) high-fat diet exposure overwhelmed many, albeit not all, observed phenotypic differences.

Characterization of Xenobiotic and Steroid Disposition Potential of Human Placental Tissue and Cell Lines (BeWo, JEG-3, JAR, and HTR-8/SVneo) by Quantitative Proteomics

The placenta is a fetal organ that performs critical functions to maintain pregnancy and support fetal development, including metabolism and transport of xenobiotics and steroids between the maternal-fetal unit. In vitro placenta models are used to study xenobiotic and steroid disposition, but how well these models recapitulate the human placenta is not well understood. We first characterized the abundance of proteins involved in xenobiotic and steroid disposition in human placental tissue. In pooled human placenta, the following xenobiotic and steroid disposition proteins were detected (highest to lowest), 1) enzymes: glutathione S-transferase P, carbonyl reductase 1, aldo-keto reductase 1B1, hydroxysteroid dehydrogenases (HSD3B1 and HSD11B1), aromatase, epoxide hydrolase 1 (EPHX1) and steryl-sulfatase, and 2) transporters: monocarboxylate transporters (MCT1 and 4), organic anion transporting polypeptide 2B1, organic anion transporter 4, and breast cancer resistance protein (BCRP). Then, the tissue proteomics data were compared with four placental cell lines (BeWo, JEG-3, JAR, and HTR-8/SVneo). The differential global proteomics analysis revealed that the tissue and cell lines shared 1420 cytosolic and 1186 membrane proteins. Although extravillous trophoblast and cytotrophoblast marker proteins were detected in all cell lines, only BeWo and JEG-3 cells expressed the syncytiotrophoblast marker, chorionic somatomammotropin hormone 1. BeWo and JEG-3 cells expressed most target proteins including aromatase, HSDs, EPHX1, MCT1, and BCRP. JEG-3 cells treated with commonly detected phthalates in human biofluids showed dysregulation of steroid pathways. The data presented here show that BeWo and JEG-3 cells are closer to the placental tissue for studying xenobiotic and steroid disposition. SIGNIFICANCE STATEMENT: This is the first study to compare proteomics data of human placental tissue and cell lines (BeWo, JAR, JEG-3, and HTR-8/SVneo). The placental cell line and tissue proteomes are vastly different, but BeWo and JEG-3 cells showed greater resemblance to the tissue in the expression of xenobiotic and steroid disposition proteins. These data will assist researchers to select an optimum cell model for mechanistic investigations on xenobiotic and steroid disposition in the placenta.

Frequency and characteristics of patients with bispectral index values of 60 or higher during the induction and maintenance of general anesthesia with remimazolam

In Korea, the approved anesthetic regimen of remimazolam starts with 6 mg/kg/h or 12 mg/kg/h until loss of consciousness, followed by maintenance at 1-2 mg/kg/h. Some patients receiving remimazolam for general anesthesia experience occasional difficulty maintaining bispectral index (BIS) value ˂ 60. This retrospective study aimed to analyze the data from patients undergoing elective surgery under remimazolam based-general anesthesia to determine the frequency and physical characteristics of patients with BIS values ˂ 60. The criterion was established for patients with a poorly maintained BIS value < 60. The frequency and physical characteristics of patients who satisfied this criterion were investigated through their medical records. The modified Brice interview was conducted within 24 h after surgery. Among the 1500 patients included in the analysis, 61 (4.1%) met the criteria for BIS ˂ 60. Based on the modified Brice interview, none of the patients with poorly maintained BIS ˂ 60 complained of intraoperative awareness based on the modified Brice interview or exhibit specific physical characteristics. These patients accounted for less than 5% of the total population studied. Notably, physical characteristics alone are insufficient to predict such patients before surgery.

Development of a next-generation endogenous OCT4 inducer and its anti-aging effect in vivo

The identification of small molecules capable of replacing transcription factors has been a longstanding challenge in the generation of human chemically induced pluripotent stem cells (iPSCs). Recent studies have shown that ectopic expression of OCT4, one of the master pluripotency regulators, compromised the developmental potential of resulting iPSCs, This highlights the importance of finding endogenous OCT4 inducers for the generation of clinical-grade human iPSCs. Through a cell-based high throughput screen, we have discovered several new OCT4-inducing compounds (O4Is). In this work, we prepared metabolically stable analogues, including O4I4, which activate endogenous OCT4 and associated signaling pathways in various cell lines. By combining these with a transcription factor cocktail consisting of SOX2, KLF4, MYC, and LIN28 (referred to as "CSKML") we achieved to reprogram human fibroblasts into a stable and authentic pluripotent state without the need for exogenous OCT4. In Caenorhabditis elegans and Drosophila, O4I4 extends lifespan, suggesting the potential application of OCT4-inducing compounds in regenerative medicine and rejuvenation therapy.

Association between the NEP rs701109 polymorphism and the clinical efficacy and safety of sacubitril/valsartan in Chinese patients with heart failure

OBJECTIVE

Sacubitril/valsartan is a commonly used medicine for treating heart failure (HF) patients, but the treatment effects significantly vary. Neprilysin (NEP) and carboxylesterase 1 (CES1) play an important role in the efficacy of sacubitril/valsartan. The purpose of this study was to explore the relationship between NEP and CES1 gene polymorphisms and the efficacy and safety of sacubitril/valsartan treatment in HF patients.

METHODS

Genotyping of 10 single nucleotide polymorphisms (SNPs) of the NEP and CES1 genes in 116 HF patients was performed by the Sequenom MassARRAY method, and logistic regression and haplotype analysis were used to evaluate the associations between SNPs and the clinical efficacy and safety of sacubitril/valsartan in HF patients.

RESULTS

A total of 116 Chinese patients with HF completed the whole trial, and T variations in rs701109 in NEP gene were an independent risk factor (P = 0.013, OR = 3.292, 95% CI:1.287-8.422) for the clinical efficacy of sacubitril/valsartan. Furthermore, haplotype analysis of 6 NEP SNPs (including rs701109) was performed and showed that the CGTACC and TGTACC haplotypes were significantly associated with clinical efficacy (OR = 0.095, 95%CI: 0.012-0.723, P = 0.003; OR = 5.586, 95% CI: 1.621-19.248, P = 0.005). Moreover, no association was found between SNPs of other selected genes in terms of efficacy in HF patients, and no association was observed between SNPs and symptomatic hypotension.

CONCLUSION

Our results suggest an association between rs701109 and sacubitril/valsartan response in HF patients. Symptomatic hypotension is not associated with the presence of NEP polymorphisms.

The design of small-molecule prodrugs and activatable phototherapeutics for cancer therapy

Cancer remains as one of the most significant health problems, with approximately 19 million people diagnosed worldwide each year. Chemotherapy is a routinely used method to treat cancer patients. However, current treatment options lack the appropriate selectivity for cancer cells, are prone to resistance mechanisms, and are plagued with dose-limiting toxicities. As such, researchers have devoted their attention to developing prodrug-based strategies that have the potential to overcome these limitations. This tutorial review highlights recently developed prodrug strategies for cancer therapy. Prodrug examples that provide an integrated diagnostic (fluorescent, photoacoustic, and magnetic resonance imaging) response, which are referred to as theranostics, are also discussed. Owing to the non-invasive nature of light (and X-rays), we have discussed external excitation prodrug strategies as well as examples of activatable photosensitizers that enhance the precision of photodynamic therapy/photothermal therapy. Activatable photosensitizers/photothermal agents can be seen as analogous to prodrugs, with their phototherapeutic properties at a specific wavelength activated in the presence of disease-related biomarkers. We discuss each design strategy and illustrate the importance of targeting biomarkers specific to the tumour microenvironment and biomarkers that are known to be overexpressed within cancer cells. Moreover, we discuss the advantages of each approach and highlight their inherent limitations. We hope in doing so, the reader will appreciate the current challenges and available opportunities in the field and inspire subsequent generations to pursue this crucial area of cancer research.

Carboxylesterase 1 family knockout alters drug disposition and lipid metabolism

The mammalian carboxylesterase 1 (Ces1/CES1) family comprises several enzymes that hydrolyze many xenobiotic chemicals and endogenous lipids. To investigate the pharmacological and physiological roles of Ces1/CES1, we generated Ces1 cluster knockout (Ces1 ^-/- ) mice, and a hepatic human CES1 transgenic model in the Ces1 ^-/- background (TgCES1). Ces1 ^-/- mice displayed profoundly decreased conversion of the anticancer prodrug irinotecan to SN-38 in plasma and tissues. TgCES1 mice exhibited enhanced metabolism of irinotecan to SN-38 in liver and kidney. Ces1 and hCES1 activity increased irinotecan toxicity, likely by enhancing the formation of pharmacodynamically active SN-38. Ces1 ^-/- mice also showed markedly increased capecitabine plasma exposure, which was moderately decreased in TgCES1 mice. Ces1 ^-/- mice were overweight with increased adipose tissue, white adipose tissue inflammation (in males), a higher lipid load in brown adipose tissue, and impaired blood glucose tolerance (in males). These phenotypes were mostly reversed in TgCES1 mice. TgCES1 mice displayed increased triglyceride secretion from liver to plasma, together with higher triglyceride levels in the male liver. These results indicate that the carboxylesterase 1 family plays essential roles in drug and lipid metabolism and detoxification. Ces1 ^-/- and TgCES1 mice will provide excellent tools for further study of the in vivo functions of Ces1/CES1 enzymes.

Rational design of a NIR fluorescent probe for carboxylesterase 1 detection during endoplasmic reticulum stress and drug-induced acute liver injury

An endoplasmic reticulum targeting NIR fluorescent probe (ERBM) was developed for real-time monitoring of carboxylesterase 1 (CES1) and exhibited excellent ER location in living cell imaging. In addition, ERBM was applied to illustrate the regulation characteristics of CES1 under ER stress and acute liver injury models at the cell and animal level.

Anesthesia Management of a Liver Transplant Recipient with Remimazolam

Background

Intraoperative anesthetic requirements might be altered due to the modulated metabolic function in living donor liver transplant recipients. Remimazolam may provide appropriate anesthesia in patients with cirrhosis. However, the efficacy and safety of remimazolam in liver transplant recipients have not been reported. We present the successful anesthesia management of a liver transplant recipient using remimazolam. Case Presentation. A 54-year-old woman who was diagnosed with Child-Pugh C cirrhosis of unknown etiology was scheduled for living donor liver transplantation. Remimazolam was used for anesthesia management under electroencephalogram monitoring, including bispectral index (BIS) and patient state index (PSI) values. Despite the prolonged surgical time (1,037 min) and massive blood loss (22,500 mL), BIS and PSI values were maintained within acceptable ranges intraoperatively. There was no intraoperative awareness/recall or adverse events associated with remimazolam administered perioperatively.

Conclusions

We safely managed general anesthesia for living donor liver transplantation with remimazolam using electroencephalogram monitoring.

Identification of regulatory variants of carboxylesterase 1 (CES1): A proof-of-concept study for the application of the Allele-Specific Protein Expression (ASPE) assay in identifying cis-acting regulatory genetic polymorphisms

It is challenging to study regulatory genetic variants as gene expression is affected by both genetic polymorphisms and non-genetic regulators. The mRNA allele-specific expression (ASE) assay has been increasingly used for the study of cis-acting regulatory variants because cis-acting variants affect gene expression in an allele-specific manner. However, poor correlations between mRNA and protein expressions were observed for many genes, highlighting the importance of studying gene expression regulation at the protein level. In the present study, we conducted a proof-of-concept study to utilize a recently developed allele-specific protein expression (ASPE) assay to identify the cis-acting regulatory variants of CES1 using a large set of human liver samples. The CES1 gene encodes for carboxylesterase 1 (CES1), the most abundant hepatic hydrolase in humans. Two cis-acting regulatory variants were found to be significantly associated with CES1 ASPE, CES1 protein expression, and its catalytic activity on enalapril hydrolysis in human livers. Compared to conventional gene expression-based approaches, ASPE demonstrated an improved statistical power to detect regulatory variants with small effect sizes since allelic protein expression ratios are less prone to the influence of non-genetic regulators (e.g., diseases and inducers). This study suggests that the ASPE approach is a powerful tool for identifying cis-regulatory variants.

Alcohol inhibits the metabolism of dimethyl fumarate to the active metabolite responsible for decreasing relapse frequency in the treatment of multiple sclerosis

Dimethyl fumarate (DMF) is a first-line prodrug for the treatment of relapsing-remitting multiple sclerosis (RRMS) that is completely metabolized to monomethyl fumarate (MMF), the active metabolite, before reaching the systemic circulation. Its metabolism has been proposed to be due to ubiquitous esterases in the intestines and other tissues, but the specific enzymes involved are unknown. We hypothesized based on its structure and extensive presystemic metabolism that DMF would be a carboxylesterase substrate subject to interaction with alcohol. We sought to determine the enzymes(s) responsible for the extensive presystemic metabolism of DMF to MMF and the effect of alcohol on its disposition by conducting metabolic incubation studies in human recombinant carboxylesterase-1 (CES1), carboxylesterase-2 (CES2) and human intestinal microsomes (HIM), and by performing a follow-up study in an in vivo mouse model. The in vitro incubation studies demonstrated that DMF was only metabolized to MMF by CES1. Consistent with the incubation studies, the mouse pharmacokinetic study demonstrated that alcohol decreased the maximum concentration and area-under-the-curve of MMF in the plasma and the brain after dosing with DMF. We conclude that alcohol may markedly decrease exposure to the active MMF metabolite in the plasma and brain potentially decreasing the effectiveness of DMF in the treatment of RRMS.

The Influence of Structural Variants of the CES1 Gene on the Pharmacokinetics of Enalapril, Presumably Due to Linkage Disequilibrium with the Intronic rs2244613

Variants in the CES1 gene encoding carboxylesterase 1 may affect the metabolism of enalapril to the active metabolite enalaprilat. It was shown that the A allele of rs71647871 and the C allele of rs2244613 led to a decrease in plasma enalaprilat concentrations. This study aimed to estimate the effect of structural haplotypes of CES1 containing the pseudogene CES1P1, or a hybrid of the gene and the pseudogene CES1A2, on the pharmacokinetics of enalapril. We included 286 Caucasian patients with arterial hypertension treated with enalapril. Genotyping was performed using real-time PCR and long-range PCR. Peak and trough plasma enalaprilat concentrations were lower in carriers of CES1A2. The studied haplotypes were in linkage disequilibrium with rs2244613: generally, the A allele was in the haplotype containing the CES1P1, and the C allele was in the haplotype with the CES1A2. Thus, carriers of CES1A2 have reduced CES1 activity against enalapril. Linkage disequilibrium of the haplotype containing the CES1P1 or CES1A2 with rs2244613 should be taken into account when genotyping the CES1 gene.

Going deeper into the toxicokinetics of synthetic cannabinoids: in vitro contribution of human carboxylesterases

Synthetic cannabinoids (SC) are new psychoactive substances known to cause intoxications and fatalities. One reason may be the limited data available concerning the toxicokinetics of SC, but toxicity mechanisms are insufficiently understood so far. Human carboxylesterases (hCES) are widely known to play a crucial role in the catalytic hydrolysis of drugs (of abuse). The aim of this study was to investigate the in vitro contribution of hCES to the metabolism of the 13 SC 3,5-AB-5F-FUPPYCA, AB-5F-P7AICA, A-CHMINACA, DMBA-CHMINACA, MBA-CHMINACA, MDMB-4F-BINACA, MDMB-4en-PINACA, MDMB-FUBICA, MDMB-5F-PICA, MMB-CHMICA, MMB-4en-PICA, MMB-FUBINACA, and MPhP-5F-PICA. The SC were incubated with recombinant hCES1b, hCES1c, or hCES2 and analyzed by liquid chromatography-ion trap mass spectrometry to assess amide or ester hydrolysis in an initial activity screening. Enzyme kinetic studies were performed if sufficient hydrolysis was observed. No hydrolysis of the amide linker was observed using those experimental conditions. Except for MDMB-5F-PICA, ester hydrolysis was always detected if an ester group was present in the head group. In general, SC with a terminal ester bearing a small alcohol part and a larger acyl part showed higher affinity to hCES1 isozymes. Due to the low hydrolysis rates, enzyme kinetics could not be modeled for the SC with a tert-leucine-derived moiety, but hydrolysis reactions of MPhP-5F-PICA and of those containing a valine-derived moiety followed classic Michaelis-Menten kinetics. In conclusion, drug-drug/drug-food interactions or hCES polymorphisms may prolong the half-life of SC and the current results help to estimate the risk of toxicity in the future after combining them with activity and clinical data.

Deciphering the species differences in CES1A-mediated hydrolytic metabolism by using a bioluminescence substrate

Carboxylesterases 1A (CES1A) is a key enzyme responsible for the hydrolytic metabolism of a great deal of endogenous and exogenous substrates bearing ester- or amide-bond(s). This study aimed to decipher the species difference in CES1A-mediated hydrolytic metabolism by using a newly developed bioluminescence CES1A sensor (termed NLMe) as the probe substrate, while the liver microsomes from six different mammalian species (human, cynomolgus monkey, dog, minipig, rat and mouse) were used as the enzyme sources. Metabolite profiling demonstrated that all tested liver microsomes from various species could catalyze NLMe hydrolysis, but significant difference in hydrolytic rate was observed. Kinetic plots of NLMe hydrolysis in liver microsomes from different species showed that the inherent clearance rates (C_lint) of NLMe in human liver microsomes (HLM), cynomolgus monkey liver microsomes (CyLM), and pig liver microsome (PLM) were comparable, while the C_lint values of NLMe in dog liver microsomes (DLM), mouse liver microsomes (MLM), and rat liver microsomes (RLM) were relatively small. Moreover, chemical inhibition assays showed that NLMe hydrolysis in all tested liver microsomes could be competently inhibited by BNPP (a potent broad-spectrum inhibitor of CES), but CUA (a selective inhibitor of human CES1A) only inhibited NLMe hydrolysis in human liver microsomes and dog liver microsomes. In summary, the species differences in CES1A-catalyzed NLMe hydrolysis were carefully investigated from the views of the similarities in metabolite profile, hydrolytic kinetics and inhibitor response. All these findings provide new insights into the species differences in CES1A-mediated hydrolytic metabolism and suggest that it is necessary for the pharmacologists to choose appropriate animal models to replace humans for evaluating the in vivo effects of CES1A inhibitors.

In vitro evaluation of the impact of Covid-19 therapeutic agents on the hydrolysis of the antiviral prodrug remdesivir

Remdesivir (RDV, Veklury®) is an FDA-approved prodrug for the treatment of hospitalized patients with COVID-19. Recent in vitro studies have indicated that human carboxylesterase 1 (CES1) is the major metabolic enzyme catalyzing RDV activation. COVID-19 treatment for hospitalized patients typically also involves a number of antibiotics and anti-inflammatory drugs. Further, individuals who are carriers of a CES1 variant (polymorphism in exon 4 codon 143 [G143E]) may experience impairment in their ability to metabolize therapeutic agents which are CES1 substrates. The present study assessed the potential influence of nine therapeutic agents (hydroxychloroquine, ivermectin, erythromycin, clarithromycin, roxithromycin, trimethoprim, ciprofloxacin, vancomycin, and dexamethasone) commonly used in treating COVID-19 and 5 known CES1 inhibitors on the metabolism of RDV. Additionally, we further analyzed the mechanism of inhibition of cannabidiol (CBD), as well as the impact of the G143E polymorphism on RDV metabolism. An in vitro S9 fraction incubation method and in vitro to in vivo pharmacokinetic scaling were utilized. None of the nine therapeutic agents evaluated produced significant inhibition of RDV hydrolysis; CBD was found to inhibit RDV hydrolysis by a mixed type of competitive and noncompetitive partial inhibition mechanism. In vitro to in vivo modeling suggested a possible reduction of RDV clearance and increase of AUC when coadministration with CBD. The same scaling method also suggested a potentially lower clearance and higher AUC in the presence of the G143E variant. In conclusion, a potential CES1-mediated DDI between RDV and the nine assessed medications appears unlikely. However, a potential CES1-mediated DDI between RDV and CBD may be possible with sufficient exposure to the cannabinoid. Patients carrying the CES1 G143E variant may exhibit a slower biotransformation and clearance of RDV. Further clinical studies would be required to evaluate and characterize the clinical significance of a CBD-RDV interaction.

Emerging role of carboxylesterases in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a global public health problem. Carboxylesterases (CESs), as potential influencing factors of NAFLD, are very important to improve clinical outcomes. This review aims to deeply understand the role of CESs in the progression of NAFLD and proposes that CESs can be used as potential targets for NAFLD treatment. We first introduced CESs and analyzed the relationship between CESs and hepatic lipid metabolism and inflammation. Then, we further reviewed the regulation of nuclear receptors on CESs, including PXR, CAR, PPARα, HNF4α and FXR, which may influence the progression of NAFLD. Finally, we evaluated the advantages and disadvantages of existing NAFLD animal models and summarized the application of CES-related animal models in NAFLD research. In general, this review provides an overview of the relationship between CESs and NAFLD and discusses the role and potential value of CESs in the treatment and prevention of NAFLD.

Recent Progress on NIR Fluorescent Probes for Enzymes

The majority of diseases' biomarkers are enzymes, and the regulation of enzymes is fundamental but crucial. Biological system disorders and diseases can result from abnormal enzymatic activity. Given the biological significance of enzymes, researchers have devised a plethora of tools to map the activity of particular enzymes in order to gain insight regarding their function and distribution. Near-infrared (NIR) fluorescence imaging studies on enzymes may help to better understand their roles in living systems due to their natural imaging advantages. We review the NIR fluorescent probe design strategies that have been attempted by researchers to develop NIR fluorescent sensors of enzymes, and these works have provided deep and intuitive insights into the study of enzymes in biological systems. The recent enzyme-activated NIR fluorescent probes and their applications in imaging are summarized, and the prospects and challenges of developing enzyme-activated NIR fluorescent probes are discussed.

Physiologically-Based Pharmacokinetic Modeling to Predict Methylphenidate Exposure Affected by Interplay Among Carboxylesterase 1 Pharmacogenetics, Drug-Drug Interactions, and Sex

BACKGROUND AND OBJECTIVE

The pharmacokinetics (PK) of methylphenidate (MPH) differ significantly among individuals. Carboxylesterase 1 (CES1) is the primary enzyme metabolizing MPH, and its function is affected by genetic variants, drug-drug interaction (DDI), and sex. The object of this study is to evaluate CES1 pharmacogenetics as related to MPH metabolism using human liver samples and develop a physiologically-based pharmacokinetic (PBPK) modeling approach to investigate the influence of CES1 genotypes and other factors on MPH PK.

METHODS

The effect of the CES1 variant G143E (rs71647871) on MPH metabolism was studied utilizing 102 individual human liver S9 (HLS9) fraction samples. PBPK models were developed using the population-based PBPK software PK-Sim® by incorporating the HLS9 incubation data. The established models were applied to simulate MPH PK profiles under various clinical scenarios, including different genotypes, drug-alcohol interactions, and the difference between males and females.

RESULTS

The HLS9 incubation study showed that subjects heterozygous for the CES1 variant G143E metabolized MPH at a rate of approximately 50% of that in non-carriers. The developed PBPK models successfully predicted the exposure alteration of MPH from the G143E genetic variant, ethanol-MPH DDI, and sex. Importantly, the study suggests that male G143E carriers who are alcohol consumers are at a higher risk of MPH overexposure.

CONCLUSION

PBPK modeling provides a means for better understanding the mechanisms underlying interindividual variability in MPH PK and PD and could be utilized to develop a safer and more effective MPH pharmacotherapy regimen.

Fluorine impairs carboxylesterase 1-mediated hydrolysis of T-2 toxin and increases its chondrocyte toxicity

Background

T-2 toxin is recognized as one of the high-risk environmental factors for etiology and pathogenesis of Kashin-Beck disease (KBD). Previous evidence indicates decreased serum fluorine level in KBD patients. However, whether fluoride could regulate carboxylesterase 1 (CES1)-mediated T-2 toxin hydrolysis and alter its chondrocyte toxicity remains largely unknown.

Methods

In this study, in vitro hydrolytic kinetics were explored using recombinant human CES1. HPLC-MS/MS was used to quantitative determination of hydrolytic metabolites of T-2 toxin. HepG2 cells were treated with different concentration of sodium fluoride (NaF). qRT-PCR and western blot analysis were used to compare the mRNA and protein expression levels of CES1. C28/I2 cells were treated with T-2 toxin, HT-2 toxin, and neosolaniol (NEO), and then cell viability was determined by MTT assay, cell apoptosis was determined by Annexin V-FITC/PI, Hoechst 33258 staining, and cleaved caspase-3, and cell cycle was monitored by flow cytometry assay, CKD4 and CDK6.

Results

We identified that recombinant human CES1 was involved in T-2 toxin hydrolysis to generate HT-2 toxin, but not NEO, and NaF repressed the formation of HT-2 toxin. Both mRNA and protein expression of CES1 were significantly down-regulated in a dose-dependent manner after NaF treatment in HepG2 cells. Moreover, we evaluated the chondrocyte toxicity of T-2 toxin and its hydrolytic metabolites. Results showed that T-2 toxin induced strongest cell apoptosis, followed by HT-2 toxin and NEO. The decreased the proportion of cells in G0/G1 phase was observed with the descending order of T-2 toxin, HT-2 toxin, and NEO.

Conclusions

This study reveals that CES1 is responsible for the hydrolysis of T-2 toxin, and that fluoride impairs CES1-mediated T-2 toxin detoxification to increase its chondrocyte toxicity. This study provides novel insight into understanding the relationship between fluoride and T-2 toxin in the etiology of KBD.