The metabolic activation of and platelet response to vicagrel vary with P-glycoprotein deficiency, rather than P-glycoprotein inhibition, in mice.

This study aimed to determine changes in the hydrolysis of vicagrel, a substrate drug of arylacetamide deacetylase (Aadac) and carboxylesterase 2 (Ces2), in P-glycoprotein (P-gp)-deficient or P-gp-inhibited mice and to elucidate the mechanisms involved.Male wild-type (WT) and P-gp knock-out (KO) mice were used to investigate the systemic exposure of vicagrel thiol active metabolite H4 and platelet response to vicagrel, and the mRNA and protein expression levels of intestinal Aadac and Ces2. Moreover, WT mice were administered vicagrel alone or in combination with elacridar (a potent P-gp inhibitor) to determine drug-drug interactions.Compared with WT mice, P-gp KO mice exhibited significant increases in the systemic exposure of H4, the protein expression levels of intestinal Aadac and Ces2, and inhibition of ADP-induced platelet aggregation by vicagrel. Further, the H4 exposure was positively correlated with intestinal Aadac protein expression levels but did not vary with short-term inhibition of P-gp efflux activity by elacridar.P-gp-deficient mice, rather than elacridar-treated mice, exhibited significant upregulation of intestinal Aadac and Ces2 and thus, enhanced metabolic activation of and platelet response to vicagrel, suggesting that the metabolic activation of vicagrel may vary with P-gp deficiency, not P-gp inhibition, in mice.

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.

The Crystal Structure of Mouse Ces2c, a Potential Ortholog of Human CES2, Shows Structural Similarities in Substrate Regulation and Product Release to Human CES1.

Members of the carboxylesterase 2 (Ces2/CES2) family have been studied intensively with respect to their hydrolytic function on (pro)drugs, whereas their physiological role in lipid and energy metabolism has been realized only within the last few years. Humans have one CES2 gene which is highly expressed in liver, intestine, and kidney. Interestingly, eight homologous Ces2 (Ces2a to Ces2h) genes exist in mice and the individual roles of the corresponding proteins are incompletely understood. Mouse Ces2c (mCes2c) is suggested as potential ortholog of human CES2. Therefore, we aimed at its structural and biophysical characterization. Here, we present the first crystal structure of mCes2c to 2.12 Å resolution. The overall structure of mCes2c resembles that of the human CES1 (hCES1). The core domain adopts an α/ß hydrolase-fold with S230, E347, and H459 forming a catalytic triad. Access to the active site is restricted by the cap, the flexible lid, and the regulatory domain. The conserved gate (M417) and switch (F418) residues might have a function in product release similar as suggested for hCES1. Biophysical characterization confirms that mCes2c is a monomer in solution. Thus, this study broadens our understanding of the mammalian carboxylesterase family and assists in delineating the similarities and differences of the different family members.

Carboxylesterase 2 proteins are efficient diglyceride and monoglyceride lipases possibly implicated in metabolic disease.

Carboxylesterase 2 (CES2/Ces2) proteins exert established roles in (pro)drug metabolism. Recently, human and murine CES2/Ces2c have been discovered as triglyceride (TG) hydrolases implicated in the development of obesity and fatty liver disease. The murine Ces2 family consists of seven homologous genes as opposed to a single CES2 gene in humans. However, the mechanistic role of Ces2 protein family members is not completely understood. In this study, we examined activities of all Ces2 members toward TGs, diglycerides (DGs), and monoglycerides (MGs) as the substrate. Besides CES2/Ces2c, we measured significant TG hydrolytic activities for Ces2a, Ces2b, and Ces2e. Notably, these Ces2 members and CES2 efficiently hydrolyzed DGs and MGs, and their activities even surpassed those measured for TG hydrolysis. The localization of CES2/Ces2c proteins at the ER may implicate a role of these lipases in lipid signaling pathways. We found divergent expression of Ces2 genes in the liver and intestine of mice on a high-fat diet, which could relate to changes in lipid signaling. Finally, we demonstrate reduced CES2 expression in the colon of patients with inflammatory bowel disease and a similar decline in Ces2 expression in the colon of a murine colitis model. Together, these results demonstrate that CES2/Ces2 members are highly efficient DG and MG hydrolases that may play an important role in liver and gut lipid signaling.

Discovery of pyrazolones as novel carboxylesterase 2 inhibitors that potently inhibit the adipogenesis in cells.

Carboxylesterase 2 (CES2) is one of the most important Phase I drug metabolizing enzymes in the carboxylesterase family. It plays crucial roles in the bioavailability of oral ester prodrugs and the therapeutic effect of some anticancer drugs such as irinotecan (CPT11) and capecitabine. In addition to the well-known roles of CES2 in xenobiotic metabolism, the enzyme also participates in endogenous metabolism and the production of lipids. In this study, we synthesized a series of pyrazolones and assayed their inhibitory effects against CES2 in vitro. Structure-activity relationship analysis of these pyrazolones reveals that the introduction of 4-methylphenyl unit (R1), 4-methylbenzyl (R2) and cyclohexyl (R3) moieties are beneficial for CES2 inhibition. Guided by these SARs results, 1-cyclohexyl-4-(4-methylbenzyl)-3-p-tolyl-1H- pyrazol-5(4H)-one (27) was designed and synthesized. Further investigations demonstrated that the compound 27 exhibited stronger CES2 inhibition activity with a lower IC50 value (0.13 µM). The inhibition kinetic study demonstrated that compound 27 inhibited the hydrolysis of CES2-fluorescein diacetate (FD) through non-competitive inhibition. In addition, the molecular docking showed that the core of pyrazolone, the cyclohexane moiety, 4-methylbenzyl and 4-methylphenyl groups in compound 27 all played important roles with the amino acid residues of CSE2. Also, compound 27 could inhibit adipocyte adipogenesis induced by mouse preadipocytes. In brief, we designed and synthesized a novel pyrazolone compound with a strong inhibitory ability on CES2 and could inhibit the adipogenesis induced by mouse preadipocytes, which can be served as a promising lead compound for the development of more potent pyrazolone-type CES2 inhibitors, and also used as a potential tool for exploring the biological functions of CES2 in human being.

Overexpressed CES2 has prognostic value in CRC and knockdown CES2 reverses L-OHP-resistance in CRC cells by inhibition of the PI3K signaling pathway.

CES-2 (carboxylesterase-2) belongs to the carboxylesterase gene family, which plays crucial roles in lipid mobilization and chemosensitivity to irinotecan. However, its role in chemosensitivity to oxaliplatin (L-OHP) remains unclear. Herein, L-OHP-resistant cells (HCT-116L and RKOL) were established by increasing the concentration of L-OHP. The results showed that CES2 expression was upregulated in L-OHP-resistant tissues and cells lines (both P < 0.01). Low expression of CES2 correlated with a better survival, and the results were further confirmed in the R2 platform: a biologist friendly web-based genomics analysis and visualization application. Downregulation of CES2 suppressed cell proliferation, induced apoptosis and reversed L-OHP resistance by medicating the PI3K signaling pathway in L-OHP-resistant cells. However, both PI3K inhibitor (LY294002) and activator (IGF-1) could not medicate CES2 expression. These findings indicated that CES2 may be utilized as a novel biomarker and therapeutic target for L-OHP resistance in CRC treatment.

Discovery of Thai mangrove tetranortriterpenoids as agonists of human pregnane-X-receptor and inhibitors against human carboxylesterase 2.

Human pregnane-X-receptor (hPXR) is considered to be the key target for the treatment of cholestasis and liver injury. Agonists of hPXR are potential drug leads. Potent and selective inhibitors of human carboxylesterase 2 (hCES2) could be utilized to alleviate the toxicity induced by ester drugs. In this work, fifteen new tetranortriterpenoids with structure diversity, named thaigranatins F-T (1-15), including four limonoids containing a C1-O-C29 bridge (1-4), four mexicanolides (5-8), three phragmalins (9-11), two limonoids belonging to the small group of trichiliton A (12-13), and two apotirucallanes (14-15), were isolated from seeds of the Thai mangrove, Xylocarpus granatum. The structures of these compounds were established by high resolution-electrospray ionization mass spectroscopy, extensive NMR spectroscopic investigations, single-crystal X-ray diffraction analyses, and the comparison of experimental electronic circular dichroism spectra. Most notably, thaigranatins L (7) and P (11) exhibited agonistic effects on hPXR at the concentration of 10.0 µM and 10.0 nM, respectively, whereas thaigranatins J (5), M (8), and T (15) showed inhibitory activities against hCES2 with IC50 values of 6.63, 11.35, and 5.05 µM, respectively. The 8α,30α-epoxy moiety of mexicanolide and the Δ8,14 double bond of phragmalin are pivotal for agonistic effects of these limonoids on hPXR, whereas the 6-OAc group of mexicanolide is crucial for its inhibitory activity against hCES2. Additionally, the flexible C-17-side-chain with appropriate hydroxy groups is considered to be important for the inhibitory activity of apotirucallane against hCES2.

[Construction and application of pharmacophore model of human carboxylesterase 2 inhibitors].

According to human carboxylesterase 2(hCE2) inhibitors reported in the literature, the pharmacophore model of hCE2 inhibitors was developed using HipHop module in Discovery Studio 2016. The optimized pharmacophore model, which was validated by test set, contained two hydrophobic, one hydrogen bond acceptor, and one aromatic ring features. Using the pharmacophore model established, 5 potential hCE2 inhibitors(CS-1,CS-2,CS-3,CS-6 and CS-8) were screened from 20 compounds isolated from the roots of Paeonia lactiflora, which were further confirmed in vitro, with the IC_(50) values of 5.04, 5.21, 5.95, 6.64 and 7.94 µmol·L~(-1), respectively. The results demonstrated that the pharmacophore model exerted excellent forecasting ability with high precision, which could be applied to screen novel hCE2 inhibitors from Chinese medicinal materials.

Construction and application of a high-content analysis for identifying human carboxylesterase 2 inhibitors in living cell system.

Human carboxylesterase 2 (hCE2), one of the most principal drug-metabolizing enzymes, catalyzes the hydrolysis of a variety of endogenous esters, anticancer agents, and environmental toxicants. The significant roles of hCE2 in both endobiotic and xenobiotic metabolism sparked great interest in the discovery and development of efficacious and selective inhibitors. However, the safe and effective inhibitors of hCE2 are scarce, due to the lack of efficient screening and evaluation systems for complex biological systems. To offer a solution to this problem, a high-content analysis (HCA)-based cell imaging and multiparametric assay method was constructed for evaluating the inhibitory effect and safety of hCE2 inhibitors in living cell system. In this study, we first established a cell imaging-based method for identifying hCE2 inhibitors at the living cell level with hCE2 fluorescent probe NCEN. Meanwhile, two nuclear probes, Hoechst 33342 and PI, were integrated to evaluate the potential cytotoxicity of compounds simultaneously. Then, the accuracy of the HCA-based method was verified by the LC-FD-based method with a positive inhibitor BNPP, and the results showed that the HCA-based method exhibited excellent precision, robustness, and reliability. Finally, the newly established HCA-based multiparametric assay panel was successfully applied to re-evaluate a series of reported hCE2 inhibitors in living cells. In summary, the HCA-based multiparametric method could serve as an efficient tool for the accuracy measurement inhibitory effect and cytotoxicity of compounds against hCE2 in living cell system. Graphical abstract.

Discovery of natural alkaloids as potent and selective inhibitors against human carboxylesterase 2.

Human Carboxylesterase 2A (hCES2A), one of the most important serine hydrolases, plays crucial roles in the hydrolysis and the metabolic activation of a wide range of esters and amides. Increasing evidence has indicated that potent inhibition on intestinal hCES2A may reduce the excessive accumulation of SN-38 (the hydrolytic metabolite of irinotecan with potent cytotoxicity) in the intestinal tract and thereby alleviate the intestinal toxicity triggered by irinotecan. In this study, more than sixty natural alkaloids have been collected and their inhibitory effects against hCES2A are assayed using a fluorescence-based biochemical assay. Following preliminary screening, seventeen alkaloids are found with strong to moderate hCES2A inhibition activity. Primary structure-activity relationships (SAR) analysis of natural isoquinoline alkaloids reveal that the benzo-1,3-dioxole group and the aromatic pyridine structure are beneficial for hCES2A inhibition. Further investigations demonstrate that a steroidal alkaloid reserpine exhibits strong hCES2A inhibition activity (IC50 = 0.94 µM) and high selectivity over other human serine hydrolases including hCES1A, dipeptidyl peptidase IV (DPP-IV), butyrylcholinesterase (BChE) and thrombin. Inhibition kinetic analyses demonstrated that reserpine acts as a non-competitive inhibitor against hCES2A-mediated FD hydrolysis. Molecular docking simulations demonstrated that the potent inhibition of hCES2A by reserpine could partially be attributed to its strong σ-π and S-π interactions between reserpine and hCES2A. Collectively, our findings suggest that reserpine is a potent and highly selective inhibitor of hCES2A, which can be served as a promising lead compound for the development of more efficacious and selective alkaloids-type hCES2A inhibitors for biomedical applications.

A novel 15-spiro diterpenoid dimer from Andrographis paniculata with inhibitory potential against human carboxylesterase 2.

The phytochemical investigation of Andrographis paniculata resulted in the isolation of a novel 15-spiro diterpenoid dimer bisandrographolide G (1). Its structure was determined by 1D and 2D NMR, HRESIMS, electronic circular dichroism (ECD), and TD DFT calculations of ECD spectra. It showed potent inhibitory activity against human carboxylesterase 2 (CES 2) with an IC50 value of 4.61 ± 0.23 µM, and it was defined as a mixed-competitive type inhibitor with a Ki value of 8.88 µM based on the inhibition kinetics result. This finding gave us a hit to develop new generation of human CES 2 inhibitors.

Twenty-five limonoids from the Hainan mangrove, Xylocarpus granatum.

Twenty-four new limonoids (1-24), named hainanxylogranins A-X, were isolated from leaves and barks of the Hainan mangrove, Xylocarpus granatum, together with a known compound, tabulvelutin B (25). The structures of these compounds were established by high resolution electrospray ionization mass spectroscopy (HRESIMS), extensive NMR spectroscopic investigations, single-crystal X-ray diffraction analyses, and the comparison of experimental electronic circular dichroism (ECD) spectra. Most notably, the absolute configurations of seven compounds, viz., 1, 2, 6, 16, 17, 22, and 25, were unambiguously determined by single-crystal X-ray diffraction analyses, conducted with Cu Kα radiation. Compounds 1-4 belong to a unique group of mexicanolides containing a C3-O-C8 bridge and a C-17 substituted γ(21)-hydroxybutenolide moiety, whereas 5-9 are mexicanolides comprising a C1-O-C8 bridge. Compounds 10-16 are typical mexicanolides, among which 14 and 15 contain a C-17 substituted γ(23)-hydroxybutenolide moiety. Compounds 17 and 18 are phragmalin 8,9,30-orthoesters, whereas 19 and 20 are phragmalin 1,8,9-orthoesters. Compound 21 consists of a C1-O-C29 bridge, while 22-24 are derivatives of azadirone. The inhibitory activities of 1, 5-8, 11, 17, 19, 21-23, and 25 against human carboxylesterase 2 (CES2) were assayed. All the tested compounds exhibited inhibition rates of 30-64% at the concentration of 100.0 µM.

Near-infrared emission tracks inter-individual variability of carboxylesterase-2 via a novel molecular substrate.

A low-molecular-weight molecule (4-(2-(3-(dicyanomethyl)-5,5-dimethylcyclohex-1-en-1-yl)vinyl)phenyl-benzoate, DDPB) has been developed. The organic framework possesses very weak fluorescence . The feasibility of the signal transduction has been performed via fluorometric titrations in solution. DDPB gives rise to responses to carboxylesterase 2 (CES2) based on "off-on" responses. The red emission at 670 nm has been derived from the enzyme-induced hydrolysis of ester linkages, thus suppressing the intramolecular charge transfer (ICT) effect and thereby generating the fluorescent segment. The optical excitation window for this probe is extended to the visible light range (λex = 516 nm), and it will induce less harmful influence on biological substances. The detection limit for the measurement of CES2 concentration is as low as 2.33 mU/mL. The conventional studies concerning the activation process are generally performed within only a single liveing cell system. In this study, it is the first time that expression of carboxylesterase 2 in five kinds of cell lines (HeLa > C1498 > active T cell > Jurkat > unactive T cell) has been clarified by flow cytometry, Western blotting, and confocal microscopy analysis. The elucidation of CES2 and its variability in a variety of cells will open new ways for drug metabolism and disease prevention. Graphical abstract We reported a new "substrate-mediated light-on" strategy based on an ester bond cleavage reaction. Most of prepared nanomaterials and organic fluorophores possessed short wavelength emissions in the blue or green region which will not be difficult for cellular imaging. In this study, a novel functional molecule (DDPB) was considered as the substrate for CES2 and the optical "off-on" response was realized. DDPB was cell permeable and possessed very low cytotoxicity. Moreover, the identification of CES2 and their subtle changes in five different cells afforded the sequence for carboxylesterase-2 as Hela > C1498 > Active T cell > Jurkat > Unactive T cell. Inhibition studies showed that the hydrolysis of DDPB was effectively suppressed by bis-p-nitrophenyl phosphate and the cellular tracking results firmly supported this point. To our knowledge, the inter-individual variability for the CES2 expressions in five different cell lines has never been reported via the substrate induced optical changes.

Characterization and structure-activity relationship studies of flavonoids as inhibitors against human carboxylesterase 2.

Human carboxylesterases (hCEs) are key enzymes from the serine hydrolase superfamily. Among all identified hCEs, human carboxylesterase 2 (hCE2) plays crucial roles in the metabolic activation of ester drugs including irinotecan and flutamide. Selective and potent hCE2 inhibitors could be used to alleviate the toxicity induced by hCE2-substrate drugs. In this study, more than fifty flavonoids were collected to assay their inhibitory effects against hCE2 using a fluorescence-based method. The results demonstrated that C3 and C6 hydroxy groups were essential for hCE2 inhibition, while O-glycosylation or C-glycosylation would lead to the loss of hCE2 inhibition. Among all tested flavonoids, 5,6-dihydroxyflavone displayed the most potent inhibitory effect against hCE2 with the IC50 value of 3.50 µM. The inhibition mechanism of 5,6-dihydroxyflavone was further investigated by both experimental and docking simulations. All these findings are very helpful for the medicinal chemists to design and develop more potent and highly selective flavonoid-type hCE2 inhibitors.

Development of amide-based fluorescent probes for selective measurement of carboxylesterase 1 activity in tissue extracts.

Carboxylesterases are well known for their role in the metabolism of xenobiotics. However, recent studies have also implicated carboxylesterases in regulating a number of physiological processes including metabolic homeostasis and macrophage development, underlying the need to quantify them individually. Unfortunately, current methods for selectively measuring the catalytic activity of individual carboxylesterases are not sufficiently sensitive to support many biological studies. In order to develop a more sensitive and selective method to measure the activity of human carboxylesterase 1 (hCE1), we generated and tested novel substrates with a fluorescent aminopyridine leaving group. hCE1 showed at least a 10-fold higher preference for the optimized substrate 4-MOMMP than the 13 other esterases tested. Because of the high stability of 4-MOMMP and its hydrolysis product, this substrate can be used to measure esterase activity over extended incubation periods yielding a low picogram (femtomol) limit of detection. This sensitivity is comparable to current ELISA methods; however, the new assay quantifies only the catalytically active enzyme facilitating direct correlation to biological processes. The method described herein may allow hCE1 activity to be used as a biomarker for predicting drug pharmacokinetics, early detection of hepatocellular carcinoma, and other disease states where the activity of hCE1 is altered.

Comparison of in vitro methods for carboxylesterase activity determination in immortalized cells representative of the intestine, liver and kidney.

Herein we compare the fluorimetric determination of total and specific carboxylesterase activity in immortalized human derived living cells and in cell lysates. The cell lines chosen are representative of metabolism occurring in the intestine (Caco-2 and HT-29), kidney (HEK-293T) and liver (Hep G2). Caco-2 and HT-29, as cells prone to differentiation, were tested along the differentiation time. For evaluation of both methods when distinguishing activity of different carboxylesterases, HEK-293T transfected with the human carboxylestarase-2 (hCES2) were also tested. Application to Caco-2 or HT-29 cells demonstrated higher activity detected in cell lysates than in cell monolayers. The difference is most striking when comparing the methods at different stages of Caco-2 and HT-29 cell maturation, highlighting substrate accessibility as a limiting step in the in vivo hydrolysis rates (possibly limited by plasma and Endoplasmic Reticulum membrane permeability) with increasing relevance as the cells differentiate. Application to Hep G2 or to hCES2 transfected and non-transfected HEK-293T cells, demonstrated a tendency for higher sensitivity in living cell suspensions than that obtained with the cell lysates which indicates the importance of cell environment in the maintenance of enzyme activity. However, quantification of hCES2 activity relative to total esterase, or to total carboxylesterase activity, was not significantly different in any case. The results herein presented help to clarify which method is best suited for evaluation of carboxylesterase activity in vitro depending on the final goal of the study.

Ganodermanontriol Suppresses the Progression of Lung Adenocarcinoma by Activating CES2 to Enhance the Metabolism of Mycophenolate Mofetil.

New anti-lung cancer therapies are urgently required to improve clinical outcomes. Since ganodermanontriol (GDNT) has been identified as a potential antineoplastic agent, its role in lung adenocarcinoma (LUAD) is investigated in this study. Concretely, lung cancer cells were treated with GDNT and/or mycophenolate mofetil (MMF), after which MTT assay, flow cytometry and Western blot were conducted. Following bioinformatics analysis, carboxylesterase 2 (CES2) was knocked down and rescue assays were carried out in vitro. Xenograft experiment was performed on mice, followed by drug administration, measurement of tumor growth and determination of CES2, IMPDH1 and IMPDH2 expressions. As a result, the viability of lung cancer cells was reduced by GDNT or MMF. GDNT enhanced the effects of MMF on suppressing viability, promoting apoptosis and inducing cell cycle arrest in lung cancer cells. GDNT up-regulated CES2 level, and strengthened the effects of MMF on down-regulating IMPDH1 and IMPDH2 levels in the cells. IMPDH1 and IMPDH2 were highly expressed in LUAD samples. CES2 was a potential target for GDNT. CES2 knockdown reversed the synergistic effect of GDNT and MMF against lung cancer in vitro. GDNT potentiated the role of MMF in inhibiting tumor growth and expressions of CES2 and IMPDH1/2 in lung cancer in vivo. Collectively, GDNT suppresses the progression of LUAD by activating CES2 to enhance the metabolism of MMF.

Relationship between CES2 genetic variations and rifampicin metabolism.

OBJECTIVES: Rifampicin is known to be deacetylated in vivo, resulting in its metabolite 25-desacetyl rifampicin, but the enzyme metabolizing rifampicin and the association of this process with any genetic variation have not yet been elucidated. In this study, genetic variations of a surrogate enzyme, carboxylesterase 2 (CES2), and their association with the metabolism of this drug, were investigated. METHODS: Plasma concentrations of rifampicin and 25-desacetyl rifampicin were measured in 35 patients with tuberculosis receiving a first-line antituberculosis treatment. Direct PCR-based sequencing of the CES2 gene, covering all 12 exons, the 5'-untranslated region (UTR), the 3'-UTR and intronic and promoter regions, was performed. A dual luciferase reporter assay was carried out to assess whether variations in the promoter region affected the transcription of this gene. RESULTS: Ten variations were detected, of which two were in the candidate promoter region, five in introns and three in the 3'-UTR. One of the variations in the 3'-UTR was a novel variation. Genotypes at three closely linked variations (c.-2263A > G, c.269-965A > G and c.1612 + 136G > A) and c.1872*302_304delGAA were associated with significantly different plasma rifampicin concentrations. The mean plasma rifampicin concentration significantly increased with the number of risk alleles at the three closely linked variations, while the plasma concentration decreased along with an increase in the number of risk alleles at c.1872*302_304delGAA. When HepG2 cells were transfected with a luciferase reporter construct bearing the c.-2263G allele, luciferase activities were consistently decreased (by 5%-10%) compared with those harbouring the c.-2263A sequence. CONCLUSIONS: Variations in CES2, especially c.-2263A > G in the promoter region, may alter rifampicin metabolism by affecting expression of the gene.

Discovery of novel carboxylesterase 2 inhibitors for the treatment of delayed diarrhea and ulcerative colitis.

Human carboxylesterase 2 (hCES2) is an enzyme that metabolizes irinotecan to SN-38, a toxic metabolite considered a significant source of side effects (lethal delayed diarrhea). The hCES2 inhibitors could block the hydrolysis of irinotecan in the intestine and thus reduce the exposure of intestinal SN-38, which may alleviate irinotecan-associated diarrhea. However, existing hCES2 inhibitors (except loperamide) are not used in clinical applications due to lack of validity or acceptable safety. Therefore, developing more effective and safer drugs for treating delayed diarrhea is urgently needed. This study identified a lead compound 1 with a novel scaffold by high-throughput screening in our in-house library. After a comprehensive structure-activity relationship study, the optimal compound 24 was discovered as an efficient and highly selective hCES2 inhibitor (hCES2: IC50 = 6.72 µM; hCES1: IC50 > 100 µM). Further enzyme kinetics study indicated that compound 24 is a reversible inhibitor of hCES2 with competitive inhibition mode (Ki = 6.28 µM). The cell experiments showed that compound 24 could reduce the level of hCES2 in living cells (IC50 = 6.54 µM). The modeling study suggested that compound 24 fitted very well with the binding pocket of hCES2 by forming multiple interactions. Notably, compound 24 can effectively treat irinotecan-induced delayed diarrhea and DSS-induced ulcerative colitis, and its safety has also been verified in subtoxic studies. Based on the overall pharmacological and preliminary safety profiles, compound 24 is worthy of further evaluation as a novel agent for irinotecan-induced delayed diarrhea.

Prognostic and Immunological Roles of CES2 in Breast Cancer and Potential Application of CES2-Targeted Fluorescent Probe DDAB in Breast Surgery.

Purpose: The expression and function of CES2 in breast cancer (BRCA) has not been fully elucidated. The purpose of this study was to investigate its clinical significance in BRCA. Patients and Methods: Bioinformatics analysis tools and databases, including The Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO) databases, SURVIVAL packages, STRING database, Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, Gene set variation analysis (GSVA), and Tumor Immunity Estimation Resource (TIMER), were utilized to measure the expression level and clarify the clinical significance of CES2 in BRCA. In addition, we verified the expression level of CES2 in BRCA at the cellular and tissue levels by Western blot, immunohistochemistry (IHC) and real-time fluorescence quantitative PCR assays. Furthermore, DDAB is the first reported near-infrared fluorescent probe that can be used to monitor CES2 in vivo. We applied the CES2-targeted fluorescent probe DDAB in BRCA for the first time and verified its physicochemical properties and labeling sorting ability by CCK-8, cytofluorimetric imaging, flow cytometry fluorescence detection, and isolated human tumor tissue imaging assays. Results: The expression of CES2 was higher in normal tissues than that in BRCA tissues. Patients with lower CES2 expression in the BRCA T4 stage had a poorer prognosis. Finally, we applied the CES2-targeted fluorescent probe DDAB in BRCA for the first time, which was demonstrated to have good cellular imaging performance with low biological toxicity in BRCA cells and ex vivo human breast tumor tissue models. Conclusion: CES2 can be considered a potential biomarker to predict the prognosis of breast cancer at stage T4 and might contribute to the development of immunological treatment strategies. Meanwhile, CES2 is able to distinguish between breast normal and tumor tissues, the CES2-targeting NIR fluorescent probe DDAB may have potential for surgical applications in BRCA.