Structure and catalytic properties of carboxylesterase isozymes involved in metabolic activation of prodrugs

In vitro pharmacokinetic behavior in lung of harringtonine, an antagonist of SARS-CoV-2 associated proteins: New insights of inhalation therapy for COVID-19

BACKGROUND

Recent studies have shown that harringtonine (HT) could specifically bind with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein and host cell transmembrane serine protease 2 (TMPRSS2) to block membrane fusion, which is an effective antagonist for SARS-CoV-2.

PURPOSE

Our study focused on in-depth exploration of in vitro pharmacokinetic characteristics of HT in lung.

METHODS

HPLC-fluorescence detection method was used to detect changes of HT content. Incubation systems of lung microsomes for phase I metabolism and UGT incubation systems for phase II metabolism were performed to elucidate metabolites and metabolic mechanisms of HT, and then the metabolic enzyme phenotypes for HT were clarified by chemical inhibition method and recombinant enzyme method. Through metabolomics, we comprehensively evaluated the physiological dynamic changes in SD rat and human lung microsomes, and revealed the relationship between metabolomics and pharmacological activity of HT.

RESULTS

HPLC-fluorescence detection method showed strong specificity, high accuracy, and good stability for rapid quantification of HT. We confirmed that HT mainly underwent phase I metabolism, and the metabolites of HT in different species were all identified as 4'-demethyl HT, with metabolic pathway being hydrolysis reaction. CYP1A2 and CYP2E1 participated in HT metabolism, but as HT metabolism was not NADPH dependent, the esterase HCES1 in lung also played a role. The main KEGG pathways in SD rat and human lung microsomes were cortisol synthesis and secretion, steroid hormone biosynthesis and linoleic acid metabolism, respectively. The downregulated key biomarkers of 11-deoxycortisol, 21-deoxycortisol and 9(10)-EpOME suggested that HT could prevent immunosuppression and interfere with infection and replication of SARS-CoV-2.

CONCLUSION

HT was mainly metabolized into 4'-demethyl HT through phase I reactions, which was mediated by CYP1A2, CYP2E1, and HCES1. The downregulation of 11-deoxycortisol, 21-deoxycortisol and 9(10)-EpOME were key ways of HT against SARS-CoV-2. Our study was of great significance for development and clinical application of HT in the treatment of COVID-19.

Pharmacokinetic/Pharmacodynamic Assessment of the Structural Refinement of Clopidogrel Focusing on the Balance between Bioactivation and Deactivation

The delicate balance between ischemic and bleeding risks is a critical factor in antiplatelet therapy administration. Clopidogrel and prasugrel, belonging to the thienopyridine class of antiplatelet drugs, are known for their variability in individual responsiveness and high incidence of bleeding events, respectively. The present study is centered on the development and assessment of a range of deuterated thienopyridine derivatives, leveraging insights from structure-pharmacokinetic relationships of clopidogrel and prasugrel. Our approaches were grounded in the molecular framework of clopidogrel and incorporated the C2-pharmacophore design from prasugrel. The selection of ester or carbamate substituents at the C2-position facilitated the generation of the 2-oxointermediate through hydrolysis, akin to prasugrel, thereby bypassing the issue of CYP2C19 dependency. The bulky C2-pharmacophore in our approach distinguishes itself from prasugrel's acetyloxy substituent by exhibiting a moderated hydrolysis rate, resulting in a more gradual formation of the active metabolite. Excessive and rapid release of the active metabolite, believed to be linked with an elevated risk of bleeding, is thus mitigated. Our proposed structural modification retains the hydrolysis-sensitive methyl ester of clopidogrel but substitutes it with a deuterated methyl group, shown to effectively reduce metabolic deactivation. Three promising compounds demonstrated a pharmacokinetic profile similar to that of clopidogrel at four times the dose, while also augmenting its antiplatelet activity. SIGNIFICANCE STATEMENT: Inspired by the structure-pharmacokinetic relationship of clopidogrel and prasugrel, a range of clopidogrel derivatives were designed, synthesized, and assessed. Among them, three promising compounds have been identified, striking a delicate balance between efficacy and safety for antiplatelet therapy. Additionally, the ozagrel prodrug conjugate was discovered to exert a synergistic therapeutic effect alongside clopidogrel.

Absorption, distribution, metabolism and excretion of linaprazan glurate in rats

Linaprazan (AZD0865, TX07) is one of potassium-competitive acid blockers. However, linaprazan is rapidly excreted from the body, shortening its acid inhibition property. Linaprazan glurate (X842) is a prodrug of linaprazan with a prolonged inhibitory effect on gastric acid secretion. Linaprazan glurate has entered clinical trials, but few studies have reported its metabolism in non-clinical and clinical settings. In this study, we studied the pharmacokinetics, tissue distribution, mass balance, and metabolism of linaprazan glurate in rats after a single oral dose of 2.4 mg/kg (100 µCi/kg) [14C]linaprazan glurate. The results demonstrated that linaprazan glurate was mainly excreted via feces in rats with 70.48% of the dose over 168 h. The plasma AUC0-∞ of linaprazan glurate in female rats was 2 times higher than that in male rats. Drug-related substances were mainly concentrated in the stomach, eyes, liver, small intestine, and large intestine after administration. In blood, drug-related substances were mostly distributed into plasma instead of hemocytes. In total, 13 metabolites were detected in rat plasma, urine, feces, and bile. M150 (2,6-dimethylbenzoic acid) was the predominant metabolite in plasma, accounting for 80.65% and 67.65% of AUC0-24h in male and female rats, respectively. Based on the structures, linaprazan glurate was mainly hydrolyzed into linaprazan, followed by a series of oxidation, dehydrogenation, and glucuronidation in rats. Besides, CES2 is the main metabolic enzyme involved in the hydrolysis of linaprazan glurate to linaprazan.

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.

Association between organophosphate flame retardant exposure and lipid metabolism: data from the 2013-2014 National Health and Nutrition Examination Survey

Organophosphate flame retardants (OPFRs) are emerging environmental pollutants that can be detected in water, dust, and biological organisms. Certain OPFRs can disrupt lipid metabolism in animal models and cell lines. However, the effects of OPFRs on human lipid metabolism remain unclear. We included 1,580 participants (≥20 years) from the 2013-2014 National Health and Nutrition Examination Survey (NHANES) to explore the relationship between OPFR exposure and lipid metabolism biomarkers. After adjusting for confounding factors, results showed that one-unit increases in the log levels of diphenyl phosphate (DPhP) (regression coefficient = -5.755; S.E. = 2.289; p = 0.023) and log bis-(1-chloro-2-propyl) phosphate (BCPP) (regression coefficient = -4.637; S.E. = 2.019; p = 0.036) were negatively associated with the levels of total cholesterol (TC) in all participants. One-unit increases in the levels of DPhP (regression coefficient = -2.292; S.E. = 0.802; p = 0.012), log bis (1,3-dichloro-2-propyl) phosphate (BDCPP) (regression coefficient = -2.046; S.E. = 0.825; p = 0.026), and log bis-2-chloroethyl phosphate (BCEP) (regression coefficient = -2.604; S.E. = 0.704; p = 0.002) were negatively associated with the levels of high-density lipoprotein cholesterol (HDL-C). With increasing quartiles of urine BDCPP levels, the mean TC levels significantly decreased in all participants (p value for trend = 0.028), and quartile increases in the levels of DPhP (p value for trend = 0.01), BDCPP (p value for trend = 0.001), and BCEP (p value for trend<0.001) were negatively corelated with HDL-C, with approximately 5.9, 9.9, and 12.5% differences between the upper and lower quartiles. In conclusion, DPhP, BDCPP, and BCEP were negatively related to HDL-C concentration, whereas DPhP and BCPP levels were negatively associated with TC level. Thus, exposure to OPFRs may interfere with lipid metabolism.

New Near-Infrared Fluorescence Imaging Platform with Large Stokes Shift for Carboxylesterase 2 Detection in Thyroid Cancer and Inflammatory Diseases Diagnosis

Development of new near-infrared fluorophores is one of the eternal themes in the field of biosensing and biological imaging. In this work, we constructed a novel fluorophore platform MOR by replacing methylindole of hemicyanine fluorophore (CyR) with benzoxazole to acquire better fluorescence characteristics. Based on the platform, a near infrared (NIR) fluorescent probe MOR-CES2 was synthesized for the specific "off-on" response to carboxylesterase 2 (CES2). The probe exhibited excellent properties including near-infrared emission (735 nm), large Stokes shift (105 nm), high sensitivity (LOD, 0.3 ng/mL), and rapid response (15 min). The successful application of MOR-CES2 in biological imaging of CES2 in mice with thyroid cancer and inflammatory bowel disease demonstrated that the probe could identify cancer cells and tissues and sensitively respond to inflammation. The results proved the potency of MOR-CES2 as an efficient imaging tool to assist in the surgical resection of CES2-related tumors.

Simultaneous determination of HD56, a novel prodrug, and its active metabolite in cynomolgus monkey plasma using LC-MS/MS for elucidating its pharmacokinetic profile

An LC-MS/MS method was developed and validated for the simultaneous determination of the carboxylic acid ester precursor HD56 and the active product HD561 in cynomolgus monkey plasma. Then, the pharmacokinetic characteristics of both compounds following single and multiple i.g. administrations in cynomolgus monkeys were elucidated. In the method, chromatographic separation was achieved with a C18 reversed-phase column and the target quantification was carried out by an electrospray ionization (ESI) source coupled with triple quadrupole mess detector in positive ionization mode with multiple reaction monitoring (MRM) approach. Using the quantification method, the in vitro stability of HD56 in plasma and HD56 pharmacokinetic behavior after i.g. administration in cynomolgus monkey were investigated. It was approved that HD56 did convert into HD561 post-administration. The overall systemic exposure of HD561 post-conversion from HD56 accounted for only about 17% of HD56. After repeated administration at the same dose, there was no significant difference in exposure levels of both HD56 and HD561. However, after multiple dosing, the exposure of HD56 tended to decrease while that of HD561 tended to increase, resulting in a 30% in the exposure ratio. Remarkably, with a carboxylesterase (CES) activity profile akin to humans, the observed in vivo pharmacokinetic profile in cynomolgus monkeys holds promise for predicting HD56/HD561 PK profiles in humans.

Discovery of potent thiazolidin-4-one sulfone derivatives for inhibition of proliferation of osteosarcoma in vitro and in vivo

Chemotherapy combining with surgical treatment has been the main strategy for osteosarcoma treatment in clinical. Due to unclear pathogenesis and unidentified drug targets, significant progress has not been made in the development of targeted drugs for osteosarcoma during the past 50 years. Our previous discovery reported compound R-8i with a high potency for the treatment of osteosarcoma by phenotypic screening. However, both the metabolic stability and bioavailability of R-8i are poor (T1/2 = 5.36 min, mouse liver microsome; and bioavailability in vivo F = 52.1 %, intraperitoneal administration) which limits it use for further drug development. Here, we described an extensive structure-activity relationship study of thiazolidine-4-one sulfone inhibitors from R-8i, which led to the discovery of compound 68. Compound 68 had a potent cellular activity with an IC50 value of 0.217 μM, much higher half-life (T1/2 = 73.8 min, mouse liver microsome) and an excellent pharmacokinetic profile (in vivo bioavailability F = 115 %, intraperitoneal administration). Compound 68 also showed good antitumor effects and low toxicity in a xenograft model (44.6 % inhibition osteosarcoma growth in BALB/c mice). These results suggest that compound 68 is a potential drug candidate for the treatment of osteosarcoma.

Tight-Binding Small-Molecule Carboxylesterase 2 Inhibitors Reduce Intracellular Irinotecan Activation

As the primary enzyme responsible for the activatable conversion of Irinotecan (CPT-11) to SN-38, carboxylesterase 2 (CES2) is a significant predictive biomarker toward CPT-11-based treatments for pancreatic ductal adenocarcinoma (PDAC). High SN-38 levels from high CES2 activity lead to harmful effects, including life-threatening diarrhea. While alternate strategies have been explored, CES2 inhibition presents an effective strategy to directly alter the pharmacokinetics of CPT-11 conversion, ultimately controlling the amount of SN-38 produced. To address this, we conducted a high-throughput screening to discover 18 small-molecule CES2 inhibitors. The inhibitors are validated by dose-response and counter-screening and 16 of these inhibitors demonstrate selectivity for CES2. These 16 inhibitors inhibit CES2 in cells, indicating cell permeability, and they show inhibition of CPT-11 conversion with the purified enzyme. The top five inhibitors prohibited cell death mediated by CPT-11 when preincubated in PDAC cells. Three of these inhibitors displayed a tight-binding mechanism of action with a strong binding affinity.

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.

Functional roles and localization of hydrolases in the Japanese mitten crab Eriocheir japonica

The Japanese mitten crab Eriocheir japonica inhabits rivers throughout Japan and is being cultivated for food. To conduct aquaculture efficiently, it is crucial to comprehend the physiological functions of the target organisms. However, there is a lack of fundamental information on Japanese mitten crabs. In this study, hydrolases were extracted from the midgut glands of Japanese mitten crabs and their metabolic activities were analyzed. An enzyme with hydrolytic activity was discovered within the cytosol of the midgut gland. Western blot analysis also revealed that the Japanese mitten crab contains a hydrolase with cross-reactivity to human carboxylesterase 1 (hCES1) antibodies. The substrate specificity of the S9 fraction of the midgut gland was investigated and, interestingly, it was revealed that it reacts well with indomethacin phenyl ester and fluorescein diacetate, which are substrates of hCES2, not substrates of hCES1. Furthermore, this enzyme was observed to metabolize the ester derivative of astaxanthin, which is a red pigment inherent to the Japanese mitten crab. These findings underscore the significance the midgut gland in the Japanese mitten crab as an important organ for metabolizing both endogenous and exogenous ester-type compounds.

In Silico Study of Camptothecin-Based Pro-Drugs Binding to Human Carboxylesterase 2

Pro-drugs, which ideally release their active compound only at the site of action, i.e., in a cancer cell, are a promising approach towards an increased specificity and hence reduced side effects in chemotherapy. A popular form of pro-drugs is esters, which are activated upon their hydrolysis. Since carboxylesterases that catalyse such a hydrolysis reaction are also abundant in normal tissue, it is of great interest whether a putative pro-drug is a probable substrate of such an enzyme and hence bears the danger of being activated not just in the target environment, i.e., in cancer cells. In this work, we study the binding mode of carboxylesters of the drug molecule camptothecin, which is an inhibitor of topoisomerase I, of varying size to human carboxylesterase 2 (HCE2) by molecular docking and molecular dynamics simulations. A comparison to irinotecan, known to be a substrate of HCE2, shows that all three pro-drugs analysed in this work can bind to the HCE2 protein, but not in a pose that is well suited for subsequent hydrolysis. Our data suggest, moreover, that for the irinotecan substrate, a reactant-competent pose is stabilised once the initial proton transfer from the putative nucleophile Ser202 to the His431 of the catalytic triad has already occurred. Our simulation work also shows that it is important to go beyond the static models obtained from molecular docking and include the flexibility of enzyme-ligand complexes in solvents and at a finite temperature. Under such conditions, the pro-drugs studied in this work are unlikely to be hydrolysed by the HCE2 enzyme, indicating a low risk of undesired drug release in normal tissue.

Developing an adult stem cell derived microphysiological intestinal system for predicting oral prodrug bioconversion and permeability in humans

Microphysiological systems (MPS) incorporating human intestinal organoids have shown the potential to faithfully model intestinal biology with the promise to accelerate development of oral prodrugs. We hypothesized that an MPS model incorporating flow, shear stress, and vasculature could provide more reliable measures of prodrug bioconversion and permeability. Following construction of jejunal and duodenal organoid MPS derived from 3 donors, we determined the area under the concentration-time (AUC) curve for the active drug in the vascular channel and characterized the enzymology of prodrug bioconversion. Fosamprenavir underwent phosphatase mediated hydrolysis to amprenavir while dabigatran etexilate (DABE) exhibited proper CES2- and, as anticipated, not CES1-mediated de-esterification, followed by permeation of amprenavir to the vascular channel. When experiments were conducted in the presence of bio-converting enzyme inhibitors (orthovanadate for alkaline phosphatase; bis(p-nitrophenyl)phosphate for carboxylesterase), the AUC of the active drug decreased accordingly in the vascular channel. In addition to functional analysis, the MPS was characterized through imaging and proteomic analysis. Imaging revealed proper expression and localization of epithelial, endothelial, tight junction and catalytic enzyme markers. Global proteomic analysis was used to analyze the MPS model and 3 comparator sources: an organoid-based transwell model (which was also evaluated for function), Matrigel embedded organoids and finally jejunal and duodenal cadaver tissues collected from 3 donors. Hierarchical clustering analysis (HCA) and principal component analysis (PCA) of global proteomic data demonstrated that all organoid-based models exhibited strong similarity and were distinct from tissues. Intestinal organoids in the MPS model exhibited strong similarity to human tissue for key epithelial markers via HCA. Quantitative proteomic analysis showed higher expression of key prodrug converting and drug metabolizing enzymes in MPS-derived organoids compared to tissues, organoids in Matrigel, and organoids on transwells. When comparing organoids from MPS and transwells, expression of intestinal alkaline phosphatase (ALPI), carboxylesterase (CES)2, cytochrome P450 3A4 (CYP3A4) and sucrase isomaltase (SI) was 2.97-, 1.2-, 11.3-, and 27.7-fold higher for duodenum and 7.7-, 4.6-, 18.1-, and 112.2-fold higher for jejunum organoids in MPS, respectively. The MPS approach can provide a more physiological system than enzymes, organoids, and organoids on transwells for pharmacokinetic analysis of prodrugs that account for 10% of all commercial medicines.

Identification of the first selective bioluminescent probe for real-time monitoring of carboxylesterase 2 in vitro and in vivo

Carboxylesterase (CES), a main hydrolysis enzyme family in the human body, plays a crucial role in drug metabolism. Among them, CES1 and CES2 are the primary subtypes, and each exhibits distinct distribution and functions. However, convenient and non-invasive methods for distinguishing them and the real-time monitoring of CES2 are relatively rare, hindering the further understanding of physiological functions and underlying mechanisms. In this study, we have designed, synthesized, and evaluated the first selective bioluminescent probe (CBP 1) for CES2 with high sensitivity, high specificity and rapid reactivity. This probe offers a promising approach for the real-time detection of CES2 and its dynamic fluctuations both in vitro and in vivo.

Diketopyrrolopyrrole-based fluorescent probe for visualizing over-expressed carboxylesterase in fever via ratiometric imaging

Fever is the result of inflammation and the innate self-defense response of organisms, can cause abnormal changes in the activity of many enzymes in organisms, including the important carboxylesterase (CE). Monitoring the activity changes of CE in vivo during a fever will help to understand heat-related pathological mechanisms. In this paper, we designed diketopyrrolopyrrole-based ratiometric fluorescent probes DPP-FBC-P and DPP-FBO-P containing alkyl chain and diethylene glycol monomethyl ether chain respective for detection of CE. Both probes could realized fast response to CE and displayed good selectivity and high sensitivity. Compared with DPP-FBO-P, DPP-FBC-P had better biocompatibility, larger signal to noise ratio (225-fold vs 125-fold) and lower detection limit (1.6 × 10-5 U/mL vs 4.2 × 10-5 U/mL). Moreover, the probe DPP-FBC-P had been successfully applied to image the endogenous CE in HepG2 cells and solid tumors, and also visualized the over expressed CE in fever cells. Most importantly, the changes of CE level in the liver of fever mice model induced by LPS were monitored with the assistance of DPP-FBC-Pvia dual channel ratio imaging for the first time. In addition, fluorescence color signal in solution was captured by smart phone, and the linear relationship between RGB ratio (G/R) and CE concentration was established. This work will provide a potential approach for investigating the physiological and pathological processes of heat related diseases.

Synthesis and evaluation of indomethacin prodrugs with a diester structure that are metabolically activated by human carboxylesterases

1. Carboxylesterase (CES) has been studied extensively, mostly with substrates in the monoester structures. We investigated the relationship between indomethacin diester prodrugs and metabolic activation by microsomes and recombinant human CES.2. Eight indomethacin diester prodrugs were synthesised in two steps. They were used as substrates and hydrolysis rates were calculated.3. As a result, the major hydrolysis enzyme was CES. The hydrolysis rate of recombinant CES2A1 was comparable to that of recombinant CES1A1.4. In this study, by changing the structure of the prodrug to a diester structure, it was found that CES2 activity was equivalent to CES1 activity.5. It should be noted that the use of diester prodrugs in prodrug discovery, where organ-specific hydrolysis reactions are expected, may not yield the expected results.

Hydroxyl Group Acetylation of Quercetin Enhances Intracellular Absorption and Persistence to Upregulate Anticancer Activity in HepG2 Cells

Quercetin, a flavonoid compound widely distributed in many plants, is known to have potent antitumor effects on several cancer cells. Our previous study revealed that the acetylation of quercetin enhanced its antitumor effect. However, the mechanisms remain unknown. This study aimed to elucidate the bioavailability of acylated quercetin in the HepG2 cell model based on its antitumor effect. The positions of quercetin 3,7,3',4'-OH were acetylated as 3,7,3',4'-O-tetraacetylquercetin (4Ac-Q). The inhibitory effect of 4Ac-Q on HepG2 cell proliferation was assessed by measuring cell viability. The apoptosis was characterized by apoptotic proteins and mitochondrial membrane potential shifts, as well as mitochondrial reactive oxygen species (ROS) levels. The bioavailability of 4Ac-Q was analyzed by measuring the uptake and metabolites in HepG2 cells with high performance liquid chromatography (HPLC)-photodiode array detector (PDA) and-ultraviolet/visible detector (UV/Vis). The results revealed that 4Ac-Q enhanced the inhibitory effect on HepG2 cell proliferation and induced its apoptosis significantly higher than quercetin. Protein array analysis of apoptosis-related protein indicated that 4Ac-Q increased the activation or expression of pro-apoptotic proteins, including caspase-3, -9, as well as second mitochondria-derived activator of caspases (SMAC), and suppressed the expression of apoptosis inhibiting proteins such as cellular inhibitor of apoptosis (cIAP)-1, -2, Livin, Survivin, and X-linked inhibitor of apoptosis (XIAP). Furthermore, 4Ac-Q stimulated mitochondrial cytochrome c release into the cytosol by enhancing ROS level and depolarizing the mitochondrial membrane. Finally, the analysis of uptake and metabolites of 4Ac-Q in HpG2 cells with HPLC-PDA and -UV/Vis revealed that 4Ac-Q was metabolized to quercetin and several different acetylated quercetins which caused 2.5-fold higher quercetin present in HepG2 cells than parent quercetin. These data demonstrated that acetylation of the quercetin hydroxyl group significantly increased its intracellular absorption. Taken together, our findings provide the first evidence that acetyl modification of quercetin not only substantially augments the intracellular absorption of quercetin but also bolsters its metabolic stability to elongate its intracellular persistence. Therefore, acetylation could serve as a strategic approach to enhance the ability of quercetin and analogous flavonoids to suppress cancer cell proliferation.

Quisinostat is a brain-penetrant radiosensitizer in glioblastoma

Histone deacetylase (HDAC) inhibitors have garnered considerable interest for the treatment of adult and pediatric malignant brain tumors. However, owing to their broad-spectrum nature and inability to effectively penetrate the blood-brain barrier, HDAC inhibitors have failed to provide substantial clinical benefit to patients with glioblastoma (GBM) to date. Moreover, global inhibition of HDACs results in widespread toxicity, highlighting the need for selective isoform targeting. Although no isoform-specific HDAC inhibitors are currently available, the second-generation hydroxamic acid-based HDAC inhibitor quisinostat possesses subnanomolar specificity for class I HDAC isoforms, particularly HDAC1 and HDAC2. It has been shown that HDAC1 is the essential HDAC in GBM. This study analyzed the neuropharmacokinetic, pharmacodynamic, and radiation-sensitizing properties of quisinostat in preclinical models of GBM. It was found that quisinostat is a well-tolerated and brain-penetrant molecule that extended survival when administered in combination with radiation in vivo. The pharmacokinetic-pharmacodynamic-efficacy relationship was established by correlating free drug concentrations and evidence of target modulation in the brain with survival benefit. Together, these data provide a strong rationale for clinical development of quisinostat as a radiosensitizer for the treatment of GBM.

Rationally Engineered hCES2A Near-Infrared Fluorogenic Substrate for Functional Imaging and High-Throughput Inhibitor Screening

Human carboxylesterase 2A (hCES2A) is an important endoplasmic reticulum (ER)-resident enzyme that is responsible for the hydrolytic metabolism or activation of numerous ester-bearing drugs and environmental toxins. The previously reported hCES2A fluorogenic substrates suffer from limited emission wavelength, low specificity, and poor localization accuracy, thereby greatly limiting the in situ functional imaging of hCES2A and drug discovery. Herein, a rational ligand design strategy was adopted to construct a highly specific near-infrared (NIR) substrate for hCES2A. Following scaffold screening and recognition group optimization, HTCF was identified as a desirable NIR fluorophore with excellent photophysical properties and high ER accumulation ability, while several HTCF esters held a high potential to be good hCES2A substrates. Further investigations revealed that TP-HTCF (the tert-pentyl ester of HTCF) was an ideal substrate with ultrahigh sensitivity, excellent specificity, and a substantial signal-to-noise ratio. Upon the addition of hCES2A, TP-HTCF could be rapidly hydrolyzed to release HTCF, a chemically stable product that emitted bright fluorescent signals at around 670 nm. A TP-HTCF-based biochemical assay was then established for the high-throughput screening of potent and cell-active hCES2A inhibitors from an in-house compound library. Furthermore, TP-HTCF displayed high imaging resolution for imaging hCES2A in living cells as well as mouse liver slices and tumor-xenograft mice. Collectively, this study demonstrates a rational strategy for developing highly specific fluorogenic substrates for an ER-resident target enzyme, while TP-HTCF can act as a practical tool for sensing hCES2A in living systems.

Biotransformation and brain distribution of the anti-COVID-19 drug molnupiravir and herb-drug pharmacokinetic interactions between the herbal extract Scutellaria formula-NRICM101

The aim of this study was to explore the effects of herbal drug pharmacokinetic interactions on the biotransformation of molnupiravir and its metabolite β-D-N4-hydroxycytidine (NHC) in the blood and brain. To investigate the biotransformation mechanism, a carboxylesterase inhibitor, bis(4-nitrophenyl)phosphate (BNPP), was administered. Not only molnupiravir but also the herbal medicine Scutellaria formula-NRICM101 is potentially affected by coadministration with molnupiravir. However, the herb-drug interaction between molnupiravir and the Scutellaria formula-NRICM101 has not yet been investigated. We hypothesized that the complex bioactive herbal ingredients in the extract of the Scutellaria formula-NRICM101, the biotransformation and penetration of the bloodbrain barrier of molnupiravir are altered by inhibition of carboxylesterase. To monitor the analytes, ultrahigh-performance liquid chromatography tandem mass spectrometry (UHPLCMS/MS) coupled with the microdialysis method was developed. Based on the dose transfer from humans to rats, a dose of molnupiravir (100 mg/kg, i.v.), molnupiravir (100 mg/kg, i.v.) + BNPP (50 mg/kg, i.v.), and molnupiravir (100 mg/kg, i.v.) + the Scutellaria formula-NRICM101 extract (1.27 g/kg, per day, for 5 consecutive days) were administered. The results showed that molnupiravir was rapidly metabolized to NHC and penetrated into the brain striatum. However, when concomitant with BNPP, NHC was suppressed, and molnupiravir was enhanced. The blood-to-brain penetration ratios were 2% and 6%, respectively. In summary, the extract of the Scutellaria formula-NRICM101 provides a pharmacological effect similar to that of the carboxylesterase inhibitor to suppress NHC in the blood, and the brain penetration ratio was increased, but the concentration is also higher than the effective concentration in the blood and brain.

Design of prodrug for stereoisomers of omapatrilat to cross the blood-brain barrier using docking, homology modeling, MD, and QM/MM methods

In this study, we designed a suitable ester prodrug for omapatrilat to penetrate the blood-brain barrier and treat CNS diseases. Based on the ADMET properties, the methyl carboxylate ester of omapatrilat was chosen from among several prodrug structures. Sixteen methyl carboxylate esters were constructed for omapatrilat. The structure of brain carboxylesterase was derived via homology modeling, and molecular docking was used to determine the most potent stereoisomers against brain carboxylesterase. The top three stereoisomer complexes, and the apo form of the protein, were then considered using molecular dynamics simulation and MM/GBSA analysis. Following the simulation, structural analysis was performed using RMSD, RMSF, Rg, and hydrogen bond analysis tools. Our data demonstrated that the prodrug of RSSR is a suitable structure for crossing the blood-brain barrier and binding to brain carboxylesterase. In addition, we found via QM/MM calculation that the catalytic reaction of the prodrug of RSSR against brain carboxylesterase occurs via two steps, including acylation and diacylation steps. Based on our findings, we propose a clinical trial of a methyl carboxylate ester prodrug of omapatrilat's RSSR for the treatment of brain diseases.Communicated by Ramaswamy H. Sarma.

Design, synthesis, and biological evaluation studies of novel carboxylesterase 2 inhibitors for the treatment of irinotecan-induced delayed diarrhea

Human carboxylesterase 2 (hCES2A), one of the most important serine hydrolases distributed in the small intestine and colon, plays a crucial role in the hydrolysis of various prodrugs and esters. Accumulating evidence has demonstrated that the inhibition of hCES2A effectively alleviate the side effects induced by some hCES2A-substrate drugs, including delayed diarrhea caused by the anticancer drug irinotecan. Nonetheless, there is a scarcity of selective and effective inhibitors that are suitable for irinotecan-induced delayed diarrhea. Following screening of the in-house library, the lead compound 01 was identified with potent inhibition on hCES2A, which was further optimized to obtain LK-44 with potent inhibitory activity (IC50 = 5.02 ± 0.67 μM) and high selectivity on hCES2A. Molecular docking and molecular dynamics simulations indicated that LK-44 can formed stable hydrogen bonds with amino acids surrounding the active cavity of hCES2A. The results of inhibition kinetics studies unveiled that LK-44 inhibited hCES2A-mediated FD hydrolysis in a mixed inhibition manner, with a Ki value of 5.28 μM. Notably, LK-44 exhibited low toxicity towards HepG2 cells according to the MTT assay. Importantly, in vivo studies showed that LK-44 significantly reduced the side effects of irinotecan-induced diarrhea. These findings suggested that LK-44 is a potent inhibitor of hCES2A with high selectivity against hCES1A, which has potential as a lead compound for the development of more effective hCES2A inhibitors to mitigate irinotecan-induced delayed diarrhea.

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

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

CES1-Triggered Liver-Specific Cargo Release of CRISPR/Cas9 Elements by Cationic Triadic Copolymeric Nanoparticles Targeting Gene Editing of PCSK9 for Hyperlipidemia Amelioration

The broad application of clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 genome editing tools is hindered by challenges in the efficient delivery of its two components into specific cells and intracytoplasmic release. Herein, a novel copolymer for delivery of Cas9-mRNA/ single-guide RNA (Cas9-mRNA/sgRNA) in vitro and vivo, using carboxylesterase-responsive cationic triadic copolymeric nanoparticles targeted proprotein convertase subtilisin/kexin type 9 (PCSK9) for hyperlipidemia amelioration is reported. A dimethyl biguanide derivative is designed and synthesized to form cationic block, and copolymerization onto prepolymer with propyl methacrylate, to fabricate a triadic copolymer mPEG-b-P(Met/n-PMA). The copolymer can self-assemble with Cas9-mRNA/sgRNA, indicating the excellent potential of nanoparticles to form a delivery carrier. This vehicle can efficiently release RNA in response to the hepatocytes carboxylesterase for genome editing. It was demonstrated that the mPEG-b-P(Met/n-PMA)/Cas9 mRNA/sgRNA nanoparticles effectively accumulated in hepatocytes, lead to the inhibition of PCSK9, and lowered the levels of Low-density lipoprotein cholesterol and total cholesterol in mouse serum down 20% of nontreatment. Interestingly, the nanoparticles even enable multiple functions in the regulation of blood glucose and weight. This study establishes a novel method to achieve complex CRISPR components stable loading, safe delivery, and fixed-point release, which expand the application of CRISPR delivery systems.

Discovery of seven-membered ring berberine analogues as highly potent and specific hCES2A inhibitors

Human carboxylesterase 2A (hCES2A) is a key serine hydrolase responsible for the metabolic clearance of large number of compounds bearing the ester- or amide-bond(s). Inhibition of hCES2A can relieve the chemotherapy-induced toxicity and alter the pharmacokinetic bahaviors of some orally administrate esters-containing agents. However, most of the hCES2A inhibitors show poor cell-membrane permeability and poor specificity. Herein, guided by the structure activity relationships (SAR) of fifteen natural alkaloids against hCES2A, fifteen new seven-membered ring berberine analogues were designed and synthesized, and their anti-hCES2A activities were evaluated. Among all tested compounds, compound 28 showed potent anti-hCES2A effect (IC₅₀ = 1.66 μM) and excellent selectivity over hCES1A (IC₅₀ > 100 μM). The SAR analysis revealed that the seven-membered ring of these berberine analogues was a crucial moiety for hCES2A inhibition, while the secondary amine group of the ring-C is important for improving their specificity over other serine hydrolases. Inhibition kinetic analyses and molecular dynamic simulation demonstrated that 28 strongly inhibited hCES2A in a mixed-inhibition manner, with an estimated K_i value of 1.035 μM. Moreover, 28 could inhibit intracellular hCES2A in living HepG2 cells and exhibited suitable metabolic stability. Collectively, the SAR of seven-membered ring berberine analogues as hCES2A inhibitors were studied, while compound 28 acted as a promising candidate for developing highly selective hCES2A inhibitors.

Determination of Intracellular Esterase Activity Using Ratiometric Raman Sensing and Spectral Phasor Analysis

Carboxylesterases (CEs) are a class of enzymes that catalyze the hydrolysis of esters in a variety of endogenous and exogenous molecules. CEs play an important role in drug metabolism, in the onset and progression of disease, and can be harnessed for prodrug activation strategies. As such, the regulation of CEs is an important clinical and pharmaceutical consideration. Here, we report the first ratiometric sensor for CE activity using Raman spectroscopy based on a bisarylbutadiyne scaffold. The sensor was shown to be highly sensitive and specific for CE detection and had low cellular cytotoxicity. In hepatocyte cells, the ratiometric detection of esterase activity was possible, and the result was validated by multimodal imaging with standard viability stains used for fluorescence microscopy within the same cell population. In addition, we show that the detection of localized ultraviolet damage in a mixed cell population was possible using stimulated Raman scattering microscopy coupled with spectral phasor analysis. This sensor demonstrates the practical advantages of low molecular weight sensors that are detected using ratiometric Raman imaging and will have applications in drug discovery and biomedical research.

Hydrolysis of dibutyl phthalate and di(2-ethylhexyl) phthalate in human liver, small intestine, kidney, and lung: An in vitro analysis using organ subcellular fractions and recombinant carboxylesterases

Phthalates are widely used plasticizers that are primarily and rapidly metabolized to monoester phthalates in mammals. In the present study, the hydrolysis of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in the human liver, small intestine, kidney, and lung was examined by the catalytic, kinetic, and inhibition analyses using organ microsomal and cytosolic fractions and recombinant carboxylesterases (CESs). The V_max (y-intercept) values based on the Eadie-Hofstee plots of DBP hydrolysis were liver > small intestine > kidney > lung in microsomes, and liver > small intestine > lung > kidney in cytosol, respectively. The CL_int values (x-intercept) were small intestine > liver > kidney > lung in both microsomes and cytosol. The V_max and CL_int or CL_max values of DEHP hydrolysis were small intestine > liver > kidney > lung in both microsomes and cytosol. Bis(4-nitrophenyl) phosphate (BNPP) effectively inhibited the activities of DBP and DEHP hydrolysis in the microsomes and cytosol of liver, small intestine, kidney, and lung. Although physostigmine also potently inhibited DBP and DEHP hydrolysis activities in both the microsomes and cytosol of the small intestine and kidney, the inhibitory effects in the liver and lung were weak. In recombinant CESs, the V_max values of DBP hydrolysis were CES1 (CES1b, CES1c) > CES2, whereas the CL_max values were CES2 > CES1 (CES1b, CES1c). On the other hand, the V_max and CL_max values of DEHP hydrolysis were CES2 > CES1 (CES1b, CES1c). These results suggest an extensive organ-dependence of DBP and DEHP hydrolysis due to CES expression, and that CESs are responsible for the metabolic activation of phthalates.

Experimental and computational models to investigate intestinal drug permeability and metabolism

Oral administration is the preferred route for drug administration that leads to better therapy compliance. The intestine plays a key role in the absorption and metabolism of oral drugs, therefore, new intestinal models are being continuously proposed, which contribute to the study of intestinal physiology, drug screening, drug side effects, and drug-drug interactions.Advances in pharmaceutical processes have produced more drug formulations, causing challenges for intestinal models. To adapt to the rapid evolution of pharmaceuticals, more intestinal models have been created. However, because of the complexity of the intestine, few models can take all aspects of the intestine into account, and some functions must be sacrificed to investigate other areas. Therefore, investigators need to choose appropriate models according to the experimental stage and other requirements to obtain the desired results.To help researchers achieve this goal, this review summarised the advantages and disadvantages of current commonly used intestinal models and discusses possible future directions, providing a better understanding of intestinal models.

Rational design of a turn-on near-infrared fluorescence probe for the highly sensitive and selective monitoring of carboxylesterase 2 in living systems

In vivo selective fluorescence imaging of carboxylesterase 2 (CES2) remains a great challenge because existing fluorescence probes can potentially suffer from interference by other hydrolases. In addition, some fluorescent probes that have been separately reported for measuring CES2 activity in vitro are affected by autofluorescence and absorption of the biological matrix due to their limited emission wavelength or short Stokes shift. Herein, based on the substrate preference and catalytic performance of CES2, a novel and NIR fluorescent probe was developed, in which a hemi-cyanine dye ester derivative was used as the basic fluorescent group. In the presence of CES2, the probe was hydrolyzed to expose the fluorophore CZX-OH (λ_abs ∼ 675 nm, λ_em ∼ 850 nm), which led to a notable red-shift in the fluorescence (∼175 nm) spectrum. Confocal imaging of cells and live mice demonstrated that the fluorescent signal of this probe was related to the real activities of CES2 in cancer cells. All these results will powerfully promote the screening of CES2 regulators and the analysis of CES2-related physiological and pathological processes.

Generation of Caco-2 cells with predictable metabolism by CYP3A4, UGT1A1 and CES using the PITCh system

Caco-2 cells are widely used as an in vitro intestinal model. However, the expression levels of the drug-metabolizing enzymes CYP3A4 and UGT1A1 are lower in these cells than in intestinal cells. Furthermore, the majority of prodrugs in use today are ester-containing, and carboxylesterase (CES) 1 and CES2 are among the enzymes that process the prodrugs into drugs. In the human small intestine, CES1 is hardly expressed while CES2 is highly expressed, but the CES expression pattern in Caco-2 cells is the opposite. In this study, we generated CYP3A4-POR-UGT1A1-CES2 knock-in (KI) and CES1 knock-out (KO) Caco-2 (genome-edited Caco-2) cells using a PITCh system. Genome-edited Caco-2 cells were shown to express functional CYP3A4, POR, UGT1A1 and CES2 while the expression of the CES1 protein was completely knocked out. We performed transport assays using temocapril. The Papp value of temocapril in genome-edited Caco-2 cells was higher than that in WT Caco-2 cells. Interestingly, the amount of temocaprilat on the apical side in genome-edited Caco-2 cells was lower than that in WT Caco-2 cells. These results suggest that genome-edited Caco-2 cells are more suitable than WT Caco-2 cells as a model for predicting intestinal drug absorption and metabolism.

Structural insights into catalytical capability for CPT11 hydrolysis and substrate specificity of a novel marine microbial carboxylesterase, E93

Introduction

CPT11 (Irinotecan; 7-ethyl-10-[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin) is an important camptothecin-based broad-spectrum anticancer prodrug. The activation of its warhead, SN38 (7-ethyl-10-hydroxycamptothecin), requires hydrolysis by carboxylesterases. NPC (7-ethyl-10-[4-(1-piperidino)-1-amino] carbonyloxycamptothecin) is a metabolic derivative of CPT11 and is difficult to be hydrolyzed by human carboxylesterase. Microbial carboxylesterase with capability on both CPT11 and NPC hydrolysis is rarely reported. A marine microbial carboxylesterase, E93, was identified to hydrolyze both substrates in this study. This enzyme was an appropriate subject for uncovering the catalytic mechanism of carboxylesterases to CPT11 and NPC hydrolysis.

Methods

X-ray diffraction method was applied to obtain high-resolution structure of E93. Molecular docking was adopted to analyze the interaction of E93 with p-NP (p-nitrophenyl), CPT11, and NPC substrates. Mutagenesis and enzymatic assay were adopted to verify the binding pattern of substrates.

Results

Three core regions (Region A, B, and C) of the catalytic pocket were identified and their functions on substrates specificity were validated via mutagenesis assays. The Region A was involved in the binding with the alcohol group of all tested substrates. The size and hydrophobicity of the region determined the binding affinity. The Region B accommodated the acyl group of p-NP and CPT11 substrates. The polarity of this region determined the catalytic preference to both substrates. The Region C specifically accommodated the acyl group of NPC. The interaction from the acidic residue, E428, contributed to the binding of E93 with NPC.

Discussion

The study analyzed both unique and conserved structures of the pocket in E93, for the first time demonstrating the discrepancy of substrate-enzyme interaction between CPT11 and NPC. It also expanded the knowledge about the substrate specificity and potential application of microbial Family VII carboxylesterases.

Treatment of respiratory viral infections through inhalation therapeutics: Challenges and opportunities

Respiratory viral infections are the leading cause of death worldwide. The current pandemic of coronavirus infection (COVID-19) challenged human beings for the treatment and prevention of this respiratory viral infection since its outbreak in 2019. Despite advancements in the medical field, scientists were helpless to give timely treatment and protection against this viral infection. Several drugs, whether antiviral or not, were given to the patients to reduce mortality and morbidity rate. Vaccines from various pharmaceutical manufacturers are now available to give immunization against covid-19. Still, coronavirus is continuously affecting people in the form of variants after mutation. Each new variant increases the infection risk and forces scientists to develop some innovative and effective treatments for this infection. The virus uses the host's cell machinery to grow and multiply in numbers. Therefore, scientists are facing challenges to develop antivirals that stop the virus without damaging the host cells too. The production of suitable antivirals or vaccines for the new virus would take several months, allowing the strain to cause severe damage to life. Inhalable formulation facilitates the delivery of medicinal products directly to the respiratory system without causing unwanted side effects associated with systemic absorption. Scientists are focusing on developing an inhaled version of the existing antivirals for the treatment of respiratory infections. This review focused on the inhalable formulations of antiviral agents in various respiratory viral infections including the ongoing covid-19 pandemic and important findings of the clinical studies. We also reviewed repurposed drugs that have been given through inhalation in covid-19 infection.

A fast fluorescent probe for tracing endoplasmic reticulum-located carboxylesterase in living cells

Carboxylesterase (CEs), mainly localized in endoplasmic reticulum (ER), are responsible for hydrolyzing compounds containing various ester bonds. They have been closely associated with drug metabolism and cellular homeostasis. Although some CE fluorescent probes have been developed, there are still a lack of probes that could target to the ER. Here, we developed a novel fluorescent probe CR with a specific ER anchor for monitoring CEs. In CR, p-toluenesulfonamide was chosen for precise ER targeting. A simple acetyl moiety was used as the CE response site and fluorescence modulation unit. During the spectral tests, CR displayed a fast response speed (within 10 s) towards CEs. In addition, it showed high sensitivity [limit of detection (LOD) = 5.1 × 10^-3 U/ml] and high selectivity with CEs. In biological imaging, probe CR could especially locate in the ER in HepG2 cells. After cells were treated with orilistat, CR succeeded in monitoring the changes in the CEs. Importantly, CR also had the ability to trace the changes in CEs in a tunicamycin-induced ER stress model. Therefore, probe CR could be a powerful molecular tool for further investigating the functions of CEs in the ER.

Unveiling chlorpyrifos mineralizing and tomato plant-growth activities of Enterobacter sp. strain HSTU-ASh6 using biochemical tests, field experiments, genomics, and in silico analyses

The chlorpyrifos-mineralizing rice root endophyte Enterobacter sp. HSTU-ASh6 strain was identified, which enormously enhanced the growth of tomato plant under epiphytic conditions. The strain solubilizes phosphate and grew in nitrogen-free Jensen's medium. It secreted indole acetic acid (IAA; 4.8 mg/mL) and ACC deaminase (0.0076 μg/mL/h) and hydrolyzed chlorpyrifos phosphodiester bonds into 3,5,6-trichloro-2-pyridinol and diethyl methyl-monophosphate, which was confirmed by Gas Chromatography - Tandem Mass Spectrometry (GC-MS/MS) analysis. In vitro and in silico (ANI, DDH, housekeeping genes and whole genome phylogenetic tree, and genome comparison) analyses confirmed that the strain belonged to a new species of Enterobacter. The annotated genome of strain HSTU-ASh6 revealed a sets of nitrogen-fixing, siderophore, acdS, and IAA producing, stress tolerance, phosphate metabolizing, and pesticide-degrading genes. The 3D structure of 28 potential model proteins that can degrade pesticides was validated, and virtual screening using 105 different pesticides revealed that the proteins exhibit strong catalytic interaction with organophosphorus pesticides. Selected docked complexes such as α/β hydrolase-crotoxyphos, carboxylesterase-coumaphos, α/β hydrolase-cypermethrin, α/β hydrolase-diazinon, and amidohydrolase-chlorpyrifos meet their catalytic triads in visualization, which showed stability in molecular dynamics simulation up to 100 ns. The foliar application of Enterobacter sp. strain HSTU-ASh6 on tomato plants significantly improved their growth and development at vegetative and reproductive stages in fields, resulting in fresh weight and dry weight was 1.8-2.0-fold and 1.3-1.6-fold higher in where urea application was cut by 70%, respectively. Therefore, the newly discovered chlorpyrifos-degrading species Enterobacter sp. HSTU-ASh6 could be used as a smart biofertilizer component for sustainable tomato cultivation.

A hemicyanine-based fluorescent probe for simultaneous imaging of Carboxylesterases and Histone deacetylases in hepatocellular carcinoma

Carboxylesterases (CESs) and Histone deacetylases (HDACs) are regarded as important signaling enzymes highly associated with the development and progression of multiple cancers, including hepatocellular carcinoma (HCC). In this work, a near-infrared (NIR) fluorescent probe named Lys-HXPI was designed and synthesized, which linked a hemicyanine dye and 6-acetamidohexanoic acid via an ester bond. Lys-HXPI displayed a remarkable increase with a NIR emission at 720 nm, a low detection limit (<10 nM) for HDAC1, HDAC 6, CES1 and CES2, as well as a high selectivity for the target enzymes over other relevant analytes. Furthermore, Lys-HXPI was used to image endogenous target enzymes in living cells, tumor-bearing nude mice and tissue slices. The ability of Lys-HXPI to simultaneous image CESs and HDACs was demonstrated with RT-qPCR and the confocal imaging in Hep G2 and MDA-MB-231. Taking advantage of NIR emission, the probe was also successfully applied to imaging Hep G2 tumor mice and tissue slices. Lys-HXPI is expected to be useful for the effective detecting of CESs and HDACs in complex biosystems.

A Single Nucleotide Polymorphism Translates into a Radical Amino Acid Substitution at the Ligand-Binding Site in Fasciola hepatica Carboxylesterase B

Fasciola hepatica anthelmintic resistance may be associated with the catalytic activity of xenobiotic metabolizing enzymes. The gene expression of one of these enzymes, identified as carboxylesterase B (CestB), was previously described as inducible in adult parasites under anthelmintic treatment and exhibited a single nucleotide polymorphism at position 643 that translates into a radical amino acid substitution at position 215 from Glutamic acid to Lysine. Alphafold 3D models of both allelic sequences exhibited a significant affinity pocket rearrangement and different ligand-docking modeling results. Further bioinformatics analysis confirmed that the radical amino acid substitution is located at the ligand affinity site of the enzyme, affecting its affinity to serine hydrolase inhibitors and preferences for ester ligands. A field genotyping survey from parasite samples obtained from two developmental stages isolated from different host species from Argentina and Mexico exhibited a 37% allele distribution for 215E and a 29% allele distribution for 215K as well as a 34% E/K heterozygous distribution. No linkage to host species or geographic origin was found in any of the allele variants.

Esterases Involved in the Rapid Bioconversion of Esmolol after Intravenous Injection in Humans

Esmolol is indicated for the acute and temporary control of ventricular rate due to its rapid onset of action and elimination at a rate greater than cardiac output. This rapid elimination is achieved by the hydrolysis of esmolol to esmolol acid. It has previously been reported that esmolol is hydrolyzed in the cytosol of red blood cells (RBCs). In order to elucidate the metabolic tissues and enzymes involved in the rapid elimination of esmolol, a hydrolysis study was performed using different fractions of human blood and liver. Esmolol was slightly hydrolyzed by washed RBCs and plasma proteins while it was extensively hydrolyzed in plasma containing white blood cells and platelets. The negligible hydrolysis of esmolol in RBCs is supported by its poor hydrolysis by esterase D, the sole cytosolic esterase in RBCs. In human liver microsomes, esmolol was rapidly hydrolyzed according to Michaelis-Menten kinetics, and its hepatic clearance, calculated by the well-stirred model, was limited by hepatic blood flow. An inhibition study and a hydrolysis study using individual recombinant esterases showed that human carboxylesterase 1 isozyme (hCE1) is the main metabolic enzyme of esmolol in both white blood cells and human liver. These studies also showed that acyl protein thioesterase 1 (APT1) is involved in the cytosolic hydrolysis of esmolol in the liver. The hydrolysis of esmolol by hCE1 and APT1 also results in its pulmonary metabolism, which might be a reason for its high total clearance (170-285 mL/min/kg bodyweight), 3.5-fold greater than cardiac output (80.0 mL/min/kg bodyweight).

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.

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.

Major implications of single nucleotide polymorphisms in human carboxylesterase 1 on substrate bioavailability

The number of studies and reviews conducted for the Carboxylesterase gene is limited in comparison with other enzymes. Carboxylesterase (CES) gene or human carboxylesterases (hCES) is a multigene protein belonging to the α/β-hydrolase family. Over the last decade, two major carboxylesterases (CES1 and CES2), located at 16q13-q22.1 on human chromosome 16 have been extensively studied as important mediators in the metabolism of a wide range of substrates. hCES1 is the most widely expressed enzyme in humans, and it is found in the liver. In this review, details regarding CES1 substrates include both inducers (e.g. Rifampicin) and inhibitors (e.g. Enalapril, Diltiazem, Simvastatin) and different types of hCES1 polymorphisms (nsSNPs) such as rs2244613 and rs71647871. along with their effects on various CES1 substrates were documented. Few instances where the presence of nsSNPs exerted a positive influence on certain substrates which are hydrolyzed via hCES1, such as anti-platelets like Clopidogrel when co-administered with other medications such as angiotensin-converting enzyme (ACE) inhibitors were also recorded. Remdesivir, an ester prodrug is widely used for the treatment of COVID-19, being a CES substrate, it is a potent inhibitor of CES2 and is hydrolyzed via CES1. The details provided in this review could give a clear-cut idea or information that could be used for further studies regarding the safety and efficacy of CES1 substrate.

Assessment of metabolic activation of felbamate in chimeric mice with humanized liver in combination with in vitro metabolic assays

Felbamate (FBM) is an antiepileptic drug that has minimal toxicity in preclinical toxicological species but has a serious idiosyncratic drug toxicity (IDT) in humans. The formation of reactive metabolites is common among most drugs associated with IDT, and 2-phenylpropenal (2-PP) is believed to be the cause of IDT by FBM. It is important to consider the species difference in susceptibility to IDT between experimental animals and humans. In the present study, we used an in vitro and in vivo model system to reveal species difference in IDT of FBM. Human cytochrome P450 (CYP) and carboxylesterase (CES) expressing microsomes were used to clarify the isozymes involved in the metabolism of FBM. The remaining amount of FBM was significantly reduced in incubation with microsomes expressing human CYP2C8, 2C9, 2E1, and CES1c isozymes. Chimeric mice with humanized liver are expected to predict IDT in humans. Therefore, metabolite profiles in chimeric mice with humanized liver were investigated after administration of FBM. Metabolites after glutathione (GSH) conjugation of 2-phenylpropenal (2-PP), which is the reactive metabolite responsible for FBM-induced IDT, were detected in chimeric mice plasma and liver homogenate. Mass spectrometry imaging (MSI) visualizes distribution of FBM and endogenous GSH, and GSH levels in human hepatocyte were decreased after administration of FBM. In this study, we identified CYP and CES isozymes involved in the metabolism of FBM and confirmed reactive metabolite formation and subsequent decrease in GSH using humanized animal model. These results would provide useful information for the susceptibility to IDT between experimental animals and humans.

B-esterases characterisation in the digestive tract of the common octopus and the European cuttlefish and their in vitro responses to contaminants of environmental concern

Cephalopods are a group of marine invertebrates that have received little attention as sentinel species in comparison to other molluscs, such as bivalves. Consequently, their physiological and biochemical xenobiotic metabolism responses are poorly understood. Here we undertake a comparative analysis of the enzymatic activities involved in detoxification reactions and neural transmission in the digestive tract of two commercial cephalopods: the Common octopus, Octopus vulgaris, and the European cuttlefish, Sepia officinalis. For methodological purposes, several common B-esterases (five carboxylesterase (CE) substrates and three cholinesterase (ChE) determinations) were assayed as a proxy of metabolic and neuronal activities, respectively. Four components of the digestive tract in each species were considered: salivary glands, the stomach, the digestive gland and the caecum. The in vitro responses of digestive gland homogenates to model chemicals and contaminants of environmental concern were contrasted between both cephalopod species. The baseline biochemical activities in the four digestive tract components were also determined. Moreover, in order to validate the protocol, purified proteins, recombinant human CE (CE1 and CE2) and purified eel acetylcholinesterase (AChE) were included in the analysis. Overall, carboxylesterase activities were higher in octopus than in cuttlefish, with the activity quantified in the digestive tract components in the following order: digestive gland ≈ caecum > stomach ≈ salivary glands, with higher hydrolysis rates reached with naphthyl-derived substrates. In contrast, cuttlefish hydrolysis rates with ChE substrates were higher than in octopus. This trend was also reflected in a higher sensitivity to CE inhibitors in octopus and to AChE inhibitors in cuttlefish. Given the detoxification character of CEs and its protective role preventing AChE inhibition, octopus could be regarded as more efficiently protected than cuttlefish from neurotoxic exposures. A full characterisation of B-esterases in the digestive tract of the two common cephalopods is also provided.

Inhibition of Radix Scutellariae flavones on carboxylesterase mediated activations of prodrugs

AIMS

Carboxylesterase (CES) plays an essential role in the hydrolysis of ester prodrugs. Our study explored the inhibitions of Radix Scutellariae flavones, including baicalein (B), baicalin (BG), wogonin (W), wogonoside (WG), oroxylin A (OXA) and oroxylin A-7-O-glucuronide (OAG), on CES-mediated hydrolysis of seven prodrugs (capecitabine, clopidogrel, mycophenolate mofetil, dabigatran etexilate, acetylsalicylic acid, prasugrel and irinotecan).

MAIN METHODS

In vitro screenings were developed by incubating the flavones with prodrugs in rat plasma, intestine S9 and liver S9. Docking simulations were conducted using AMDock v1.5.2. In vivo evaluations were performed in rats co-administered with the selected flavone and prodrug via oral gavage/intravenous administration for five consecutive days.

KEY FINDINGS

The in vitro investigation showed that B and OXA demonstrated strongest inhibitions on the hydrolysis of irinotecan followed by dabigatran in rat plasma, intestine S9 and liver S9. Consistent results showed in the molecular docking analyses. Additionally, in rats receiving irinotecan, B/OXA intravenous and oral pre-treatments both led to reduction trends on the active metabolite SN-38 formation in plasma. Besides, significant decreases of SN-38/irinotecan plasma concentration ratios were found in the B/OXA oral pre-treatment group with quicker and stronger inhibition potential in OXA pre-treatment than that from B pre-treatment. OXA oral pre-treatment was also found to be able to significantly inhibit intestinal CES2 activities at 0.5 h and 5 h after irinotecan administration.

SIGNIFICANCE

Our current findings for the first time alert on potential CES-mediated HDIs between RS flavones and prodrugs, which provide a constructive information referring to rational drug combinations in clinical practice.

Folic acid intervention during pregnancy alters DNA methylation, affecting neural target genes through two distinct mechanisms

Background

We previously showed that continued folic acid (FA) supplementation beyond the first trimester of pregnancy appears to have beneficial effects on neurocognitive performance in children followed for up to 11 years, but the biological mechanism for this effect has remained unclear. Using samples from our randomized controlled trial of folic acid supplementation in second and third trimester (FASSTT), where significant improvements in cognitive and psychosocial performance were demonstrated in children from mothers supplemented in pregnancy with 400 µg/day FA compared with placebo, we examined methylation patterns from cord blood (CB) using the EPIC array which covers approximately 850,000 cytosine–guanine (CG) sites across the genome. Genes showing significant differences were verified using pyrosequencing and mechanistic approaches used in vitro to determine effects on transcription.

Results

FA supplementation resulted in significant differences in methylation, particularly at brain-related genes. Further analysis showed these genes split into two groups. In one group, which included the CES1 gene, methylation changes at the promoters were important for regulating transcription. We also identified a second group which had a characteristic bimodal profile, with low promoter and high gene body (GB) methylation. In the latter, loss of methylation in the GB is linked to decreases in transcription: this group included the PRKAR1B/HEATR2 genes and the dopamine receptor regulator PDE4C. Overall, methylation in CB also showed good correlation with methylation profiles seen in a published data set of late gestation foetal brain samples.

Conclusion

We show here clear alterations in DNA methylation at specific classes of neurodevelopmental genes in the same cohort of children, born to FA-supplemented mothers, who previously showed improved cognitive and psychosocial performance. Our results show measurable differences at neural genes which are important for transcriptional regulation and add to the supporting evidence for continued FA supplementation throughout later gestation. This trial was registered on 15 May 2013 at www.isrctn.com as ISRCTN19917787.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-022-01282-y.

Molecular and functional characterization of three novel carboxylesterases in the detoxification of permethrin in the mosquito, Culex quinquefasciatus

Carboxylesterases (CarEs) belong to a super family of multifunctional enzymes associated with the degradation of endogenous and exogenous compounds. Many insect CarEs are known to play important roles in catalyzing the hydrolysis of organophosphates (OPs), carbamates, and synthetic pyrethroids (SPs). The elevation of esterase activity through gene amplification and overexpression of estα2 and estβ2 genes contributes to the development of resistance to OP insecticides in the mosquito Culex quinquefasciatus. Three additional CarE genes are upregulated in permethrin-resistant Cx. quinquefasciatus according to an RNA-seq analysis, but their function remains unknown. In this study, we, for the first time, characterized the function of these three novel genes using in vitro protein expression, an insecticide metabolism study and molecular docking analysis. All three CarE genes were significantly overexpressed in resistant mosquito larvae, but not adults, compared to susceptible strain. No gene copy differences in these three genes were found in the mosquitoes tested. In vitro high-performance liquid chromatography (HPLC) revealed that CPIJ018231, CPIJ018232, and CPIJ018233 metabolized 30.4% ± 2.9%, 34.7% ± 6.8%, and 23.2% ± 2.2% of the permethrin, respectively. No mutations in resistant strains might significantly affect their CarE hydrolysis ability. A docking analysis further confirmed that these three CarEs from resistant strain all potentially metabolize permethrin. Taken together, these three carboxylesterase genes could play important roles in the development of permethrin resistance in Cx. quinquefasciatus larvae through transcriptional overexpression, metabolism, and detoxification.

Structural and mechanistic insights into enantioselectivity toward near-symmetric esters of a novel carboxylesterase RoCE

A novel carboxylesterase RoCE was identified with relatively high enantioselectivity toward “hard-to-be-discriminated” oxyheterocyclic esters. Molecular basis of enantioselectivity was elucidated and applied in increasing enantioselectivity of RoCE.

Drug-oxidizing and conjugating non-cytochrome P450 (non-P450) enzymes in cynomolgus monkeys and common marmosets as preclinical models for humans

Many drug oxidations and conjugations are mediated by a variety of cytochromes P450 (P450) and non-P450 enzymes in humans and non-human primates. These non-P450 enzymes include aldehyde oxidases (AOX), carboxylesterases (CES), flavin-containing monooxygenases (FMO), glutathione S-transferases (GST), arylamine N-acetyltransferases (NAT),sulfotransferases (SULT), and uridine 5'-diphospho-glucuronosyltransferases (UGT) and their substrates include both endobiotics and xenobiotics. Cynomolgus macaques (Macaca fascicularis, an Old-World monkey) are widely used in preclinical studies because of their genetic and physiological similarities to humans. However, many reports have indicated the usefulness of common marmosets (Callithrix jacchus, a New World monkey) as an alternative non-human primate model. Although knowledge of the drug-metabolizing properties of non-P450 enzymes in non-human primates is relatively limited, new research has started to provide an insight into the molecular characteristics of these enzymes in cynomolgus macaques and common marmosets. This mini-review provides collective information on the isoforms of non-P450 enzymes AOX, CES, FMO, GST, NAT, SULT, and UGT and their enzymatic profiles in cynomolgus macaques and common marmosets. In general, these non-P450 cynomolgus macaque and marmoset enzymes have high sequence identities and similar substrate recognitions to their human counterparts. However, these enzymes also exhibit some limited differences in function between species, just as P450 enzymes do, possibly due to small structural differences in amino acid residues. The findings summarized here provide a foundation for understanding the molecular mechanisms of polymorphic non-P450 enzymes and should contribute to the successful application of non-human primates as model animals for humans.

Human carboxylesterase 1A plays a predominant role in the hydrolytic activation of remdesivir in humans

Remdesivir, an intravenous nucleotide prodrug, has been approved for treating COVID-19 in hospitalized adults and pediatric patients. Upon administration, remdesivir can be readily hydrolyzed to form its active form GS-441524, while the cleavage of the carboxylic ester into GS-704277 is the first step for remdesivir activation. This study aims to assign the key enzymes responsible for remdesivir hydrolysis in humans, as well as to investigate the kinetics of remdesivir hydrolysis in various enzyme sources. The results showed that remdesivir could be hydrolyzed to form GS-704277 in human plasma and the microsomes from human liver (HLMs), lung (HLuMs) and kidney (HKMs), while the hydrolytic rate of remdesivir in HLMs was the fastest. Chemical inhibition and reaction phenotyping assays suggested that human carboxylesterase 1 (hCES1A) played a predominant role in remdesivir hydrolysis, while cathepsin A (CTSA), acetylcholinesterase (AchE) and butyrylcholinesterase (BchE) contributed to a lesser extent. Enzymatic kinetic analyses demonstrated that remdesivir hydrolysis in hCES1A (SHUTCM) and HLMs showed similar kinetic plots and much closed K_m values to each other. Meanwhile, GS-704277 formation rates were strongly correlated with the CES1A activities in HLM samples from different individual donors. Further investigation revealed that simvastatin (a therapeutic agent for adjuvant treating COVID-19) strongly inhibited remdesivir hydrolysis in both recombinant hCES1A and HLMs. Collectively, our findings reveal that hCES1A plays a predominant role in remdesivir hydrolysis in humans, which are very helpful for predicting inter-individual variability in response to remdesivir and for guiding the rational use of this anti-COVID-19 agent in clinical settings.