The mammalian carboxylesterases: from molecules to functions

Functional proteomic analysis of corticosteroid pharmacodynamics in rat liver: Relationship to hepatic stress, signaling, energy regulation, and drug metabolism

Corticosteroids (CS) are anti-inflammatory agents that cause extensive pharmacogenomic and proteomic changes in multiple tissues. An understanding of the proteome-wide effects of CS in liver and its relationships to altered hepatic and systemic physiology remains incomplete. Here, we report the application of a functional pharmacoproteomic approach to gain integrated insight into the complex nature of CS responses in liver in vivo. An in-depth functional analysis was performed using rich pharmacodynamic (temporal-based) proteomic data measured over 66h in rat liver following a single dose of methylprednisolone (MPL). Data mining identified 451 differentially regulated proteins. These proteins were analyzed on the basis of temporal regulation, cellular localization, and literature-mined functional information. Of the 451 proteins, 378 were clustered into six functional groups based on major clinically-relevant effects of CS in liver. MPL-responsive proteins were highly localized in the mitochondria (20%) and cytosol (24%). Interestingly, several proteins were related to hepatic stress and signaling processes, which appear to be involved in secondary signaling cascades and in protecting the liver from CS-induced oxidative damage. Consistent with known adverse metabolic effects of CS, several rate-controlling enzymes involved in amino acid metabolism, gluconeogenesis, and fatty-acid metabolism were altered by MPL. In addition, proteins involved in the metabolism of endogenous compounds, xenobiotics, and therapeutic drugs including cytochrome P450 and Phase-II enzymes were differentially regulated. Proteins related to the inflammatory acute-phase response were up-regulated in response to MPL. Functionally-similar proteins showed large diversity in their temporal profiles, indicating complex mechanisms of regulation by CS.

SIGNIFICANCE

Clinical use of corticosteroid (CS) therapy is frequent and chronic. However, current knowledge on the proteome-level effects of CS in liver and other tissues is sparse. While transcriptomic regulation following methylprednisolone (MPL) dosing has been temporally examined in rat liver, proteomic assessments are needed to better characterize the tissue-specific functional aspects of MPL actions. This study describes a functional pharmacoproteomic analysis of dynamic changes in MPL-regulated proteins in liver and provides biological insight into how steroid-induced perturbations on a molecular level may relate to both adverse and therapeutic responses presented clinically.

Effect of diet on carboxylesterase activity of tadpoles (Rhinella arenarum) exposed to chlorpyrifos

An outdoor microcosm was performed with tadpoles (Rhinella arenarum) exposed to 125μgL^-1 chlorpyrifos and fed two types of food, i.e., lettuce (Lactuca sativa) and a formulated commercial pellet. Acetylcholinesterase (AChE) and carboxylesterase (CbE) activities were measured in liver and intestine after 10 days of pesticide exposure. Non-exposed tadpoles fed lettuce had an intestinal AChE activity almost two-fold higher than that of pellet-fed tadpoles. No significant differences were observed, however, in liver AChE activity between diets. Likewise, intestinal CbE activity - measured using two substrates, i.e. 1-naphthyl acetate (1-NA) and 4-nitrophenyl valerate (4-NPV) - was higher in tadpoles fed lettuce than in those fed pellets. However, the diet-dependent response of liver CbE activity was opposite to that in the intestine. Chlorpyrifos caused a significant inhibition of both esterase activities, which was tissue- and diet-specific. The highest inhibition degree was found in the intestinal AChE and CbE activities of lettuce-fed tadpoles (42-78% of controls) compared with pellet-fed tadpoles (<60%). Although chlorpyrifos significantly inhibited liver CbE activity of the group fed lettuce, this effect was not observed in the group fed pellets. In general, intestinal CbE activity was more sensitive to chlorpyrifos inhibition than AChE activity. This finding, together with the high levels of basal CbE activity found in the intestine, may be understood as a detoxification system able to reduce intestinal OP uptake. Moreover, the results of this study suggest that diet is a determinant factor in toxicity testing with tadpoles to assess OP toxicity, because it modulates levels of this potential detoxifying enzyme activity.

Comparative study of hydrolytic metabolism of dimethyl phthalate, dibutyl phthalate and di(2-ethylhexyl) phthalate by microsomes of various rat tissues

Phthalates are used in food packaging, and are transferred to foods as contaminants. In this study, we examined the hydrolytic metabolism of dimethyl phthalate (DMP), dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) by rat tissue microsomes. We found that carboxylesterase and lipase contribute differently to these activities. When DMP, DBP and DEHP were incubated with rat liver microsomes, DBP was most effectively hydrolyzed to the phthalate monoester, followed by DMP, and the activity toward DEHP was marginal. In contrast, small-intestinal microsomes exhibited relatively higher activity toward long-side-chain phthalates. Pancreatic microsomes showed high activity toward DEHP and DBP. Liver microsomal hydrolase activity toward DMP was markedly inhibited by bis(4-nitrophenyl)phosphate, and could be extracted with Triton X-100. The activity toward DBP and DEHP was partly inhibited by carboxylesterase inhibitor, and was partly solubilized with Triton X-100. Ces1e, Ces1d and Ces1f expressed in COS cells exhibited the highest hydrolase activity toward DBP, showing a similar pattern to that of liver microsomes. Ces1e showed activity towards DMP and DEHP. Pancreatic lipase also hydrolyzed DBP and DEHP. Thus, carboxylesterase and lipase contribute differently to phthalate hydrolysis: short-side-chain phthalates are mainly hydrolyzed by carboxylesterase and long-side-chain phthalates are mainly hydrolyzed by lipase.

Unveiling the functional diversity of the alpha/beta hydrolase superfamily in the plant kingdom

The alpha/beta hydrolase (ABH) superfamily is a widespread and functionally malleable protein fold recognized for its diverse biochemical activities across all three domains of life. ABH enzymes possess unexpected catalytic activity in the green plant lineage through selective alterations in active site architecture and chemistry. Furthermore, the ABH fold serves as the core structure for phytohormone and ligand receptors in the gibberellin, strigolactone, and karrikin signaling pathways in plants. Despite recent discoveries, the ABH family is sparsely characterized in plants, a sessile kingdom known to evolve complex and specialized chemical adaptations as survival responses to widely varying biotic and abiotic ecologies. This review calls attention to the ABH superfamily in the plant kingdom to highlight the functional adaptability of the ABH fold.

Structure and Protein-Protein Interactions of Human UDP-Glucuronosyltransferases

Mammalian UDP-glucuronosyltransferases (UGTs) catalyze the transfer of glucuronic acid from UDP-glucuronic acid to various xenobiotics and endobiotics. Since UGTs comprise rate-limiting enzymes for metabolism of various compounds, co-administration of UGT-inhibiting drugs and genetic deficiency of UGT genes can cause an increased blood concentration of these compounds. During the last few decades, extensive efforts have been made to advance the understanding of gene structure, function, substrate specificity, and inhibition/induction properties of UGTs. However, molecular mechanisms and physiological importance of the oligomerization and protein–protein interactions of UGTs are still largely unknown. While three-dimensional structures of human UGTs can be useful to reveal the details of oligomerization and protein–protein interactions of UGTs, little is known about the protein structures of human UGTs due to the difficulty in solving crystal structures of membrane-bound proteins. Meanwhile, soluble forms of plant and bacterial UGTs as well as a partial domain of human UGT2B7 have been crystallized and enabled us to predict three-dimensional structures of human UGTs using a homology-modeling technique. The homology-modeled structures of human UGTs do not only provide the detailed information about substrate binding or substrate specificity in human UGTs, but also contribute with unique knowledge on oligomerization and protein–protein interactions of UGTs. Furthermore, various in vitro approaches indicate that UGT-mediated glucuronidation is involved in cell death, apoptosis, and oxidative stress as well. In the present review article, recent understandings of UGT protein structures as well as physiological importance of the oligomerization and protein–protein interactions of human UGTs are discussed.

p38 Mitogen activated protein kinase (MAPK): a new therapeutic target for reducing the risk of adverse pregnancy outcomes

INTRODUCTION

Spontaneous preterm birth (PTB) and preterm premature rupture of the membranes (pPROM) remain as a major clinical and therapeutic problem for intervention and management. Current strategies, based on our knowledge of pathways of preterm labor, have only been effective, in part, due to major gaps in our existing knowledge of risks and risk specific pathways. Areas covered: Recent literature has identified physiologic aging of fetal tissues as a potential mechanistic feature of normal parturition. This process is affected by telomere dependent and p38 mitogen activated protein kinase (MAPK) induced senescence activation. Pregnancy associated risk factors can cause pathologic activation of this pathway that can cause oxidative stress induced p38 MAPK activation leading to senescence and premature aging of fetal tissues. Premature aging is associated with sterile inflammation capable of triggering preterm labor or preterm premature rupture of membranes. Preterm activation of p38MAPK can be considered as a key contributor to adverse pregnancies. Expert opinion: This review considers p38MAPK activation as a potential target for therapeutic interventions to prevent adverse pregnancy outcomes mediated by stress factors. In this review, we propose multiple strategies to prevent p38MAPK activation.

Development of bioresorbable bilayered systems for application as affordable wound dressings

The objective of this work was the preparation and evaluation of a bioresorbable bilayered system for application in the treatment of dermal lesions. The system was based on a polyesterurethane as the external layer and a gelatin membrane as the internal layer. The polyesterurethane was synthesized from poly(ε-caprolactone), polyethylene glycol of 1 or 10 kDa as a hydrophilic component or Pluronic F127 as an amphiphilic component and l-lysine ethyl ester diisocyanate as an urethane precursor. Gelatin membrane was obtained by crosslinking with the naturally occurring crosslinker genipin. Three important points were addressed in this study: the physicochemical characterization of the system, the in vitro behaviour and the in vivo performance on a full-thickness wound defect of rat. The polyesterurethane containing polyethylene glycol of 10 kDa presented the optimum properties for the designed application as to be tested in animal experiments. The in vivo results showed good healing of the lesion with the formation of epidermis similar to normal rat skin. These promising results suggest the potential of this system to be used as an affordable wound dressing in the treatment of different dermal lesions.

Extremely sensitive biomarker of acute organophosphorus insecticide exposure

Egasyn-βglucuronidase complex is located at the luminal site of liver microsomal endoplasmic reticulum. When organophosphorus insecticides (OP) are incorporated into the liver microsomes, they become tightly bound to egasyn, a carboxylesterase isozyme, and subsequently, β-glucuronidase (BG) is dissociated and released into blood. Consequently, the increase in plasma BG activity becomes a good biomarker of OP exposure. Thus, the single administration of EPN (O-ethyl O-p-nitrophenylphenylphosphonothioate), acephate and chlorpyrifos increased plasma BG activity in approximately 100-fold the control level in rats. The increase in plasma BG activity after OP exposure is a much more sensitive biomarker of acute OP exposure than acetylcholinesterase (AChE) inhibition.

A carboxylesterase-selective ratiometric fluorescent two-photon probe and its application to hepatocytes and liver tissues

Carboxylesterases (CEs) are widely distributed enzymes in the human body that catalyze hydrolysis of various endogenous and exogenous substrates. They are directly linked to hepatic drug metabolisms and steatosis, and their regulations are important issues in pharmacological and clinical applications. In this work, we have developed an emission ratiometric two-photon probe (SE1) for quantitatively detecting CE in situ. This probe is based on a translation of intramolecular charge transfer character upon reaction with CE. It shows a sensitive blue-to-yellow emission change in response to human CE activity, easy loading into cells, insensitivity to pH and other metabolites including ROS and RNS, high photostability, and low cytotoxicity. Using live hepatocytes and liver tissues, we found that ratiometric two-photon microscopic imaging with SE1 is an effective tool for monitoring CE activities at the subcellular level in live tissues. This probe will find useful applications in biomedical research, including studies of hepatic steatosis and drug developments.

Genome-culture coevolution promotes rapid divergence of killer whale ecotypes

Analysing population genomic data from killer whale ecotypes, which we estimate have globally radiated within less than 250,000 years, we show that genetic structuring including the segregation of potentially functional alleles is associated with socially inherited ecological niche. Reconstruction of ancestral demographic history revealed bottlenecks during founder events, likely promoting ecological divergence and genetic drift resulting in a wide range of genome-wide differentiation between pairs of allopatric and sympatric ecotypes. Functional enrichment analyses provided evidence for regional genomic divergence associated with habitat, dietary preferences and post-zygotic reproductive isolation. Our findings are consistent with expansion of small founder groups into novel niches by an initial plastic behavioural response, perpetuated by social learning imposing an altered natural selection regime. The study constitutes an important step towards an understanding of the complex interaction between demographic history, culture, ecological adaptation and evolution at the genomic level.

Killer whales have evolved into specialized ecotypes based on hunting strategies and ecological niches. Here, Andrew Foote and colleagues sequenced the whole genome of individual killer whales representing 5 different ecotypes from North Pacific and Antarctic, and show expansion of small founder groups to adapt to specific ecological niches.

Tunable self-assembly of Irinotecan-fatty acid prodrugs with increased cytotoxicity to cancer cells

The development of a clinical chemotherapeutic is not an easy task. One challenge is how to deliver the agent to cancer cells. Nano-formulation of prodrugs, which combines the strengths of nanotechnology and prodrugs, possesses many advantages for chemotherapeutic drug delivery, including high drug loading efficiency, improved drug availability and enhanced accumulation in cancer cells. Here, we have constructed a small library of Irinotecan-derived prodrugs, in which the 20-hydroxyl group was derived with fatty-acid moieties through esterification. This conjugation fine-tuned the polarity of the Irinotecan molecule, thus enhancing the lipophilicity of the prodrugs and inducing their self-assembly into nanoparticles with different morphologies. These nano-formulated prodrugs accumulated at higher levels in cancer cells and were much more cytotoxic than free drugs. The rational design of prodrug-based nano-formulations opens a new avenue for the engineering of more efficient drug-delivery systems.

Activity of MM-398, nanoliposomal irinotecan (nal-IRI), in Ewing's family tumor xenografts is associated with high exposure of tumor to drug and high SLFN11 expression

PURPOSE

To determine the pharmacokinetics and the antitumor activity in pediatric cancer models of MM-398, a nanoliposomal irinotecan (nal-IRI).

EXPERIMENTAL DESIGN

Mouse plasma and tissue pharmacokinetics of nal-IRI and the current clinical formulation of irinotecan were characterized. In vivo activity of irinotecan and nal-IRI was compared in xenograft models (3 each in nu/nu mice) of Ewing's sarcoma family of tumors (EFT), neuroblastoma (NB), and rhabdomyosarcoma (RMS). SLFN11 expression was assessed by Affymetrix HuEx arrays, Taqman RT-PCR, and immunoblotting.

RESULTS

Plasma and tumor concentrations of irinotecan and SN-38 (active metabolite) were approximately 10-fold higher for nal-IRI than for irinotecan. Two doses of NAL-IRI (10 mg/kg/dose) achieved complete responses maintained for >100 days in 24 of 27 EFT-xenografted mice. Event-free survival for mice with RMS and NB was significantly shorter than for EFT. High SLFN11 expression has been reported to correlate with sensitivity to DNA damaging agents; median SLFN11 mRNA expression was >100-fold greater in both EFT cell lines and primary tumors compared with NB or RMS cell lines or primary tumors. Cytotoxicity of SN-38 inversely correlated with SLFN11 mRNA expression in 20 EFT cell lines.

CONCLUSIONS

In pediatric solid tumor xenografts, nal-IRI demonstrated higher systemic and tumor exposures to SN-38 and improved antitumor activity compared with the current clinical formulation of irinotecan. Clinical studies of nal-IRI in pediatric solid tumors (especially EFT) and correlative studies to determine if SLFN11 expression can serve as a biomarker to predict nal-IRI clinical activity are warranted.

Investigating the impact of missense mutations in hCES1 by in silico structure-based approaches

Genetic variations in drug-metabolizing enzymes have been reported to influence pharmacokinetics, drug dosage, and other aspects that affect therapeutic outcomes. Most particularly, non-synonymous single-nucleotide polymorphisms (nsSNPs) resulting in amino acid changes disrupt potential functional sites responsible for protein activity, structure, or stability, which can account for individual susceptibility to disease and drug response. Investigating the impact of nsSNPs at a protein's structural level is a key step in understanding the relationship between genetic variants and the resulting phenotypic changes. For this purpose, in silico structure-based approaches have proven their relevance in providing an atomic-level description of the underlying mechanisms. The present review focuses on nsSNPs in human carboxylesterase 1 (hCES1), an enzyme involved in drug metabolism. We highlight how prioritization of functional nsSNPs through computational prediction techniques in combination with structure-based approaches, namely molecular docking and molecular dynamics simulations, is a powerful tool in providing insight into the underlying molecular mechanisms of nsSNPs phenotypic effects at microscopic level. Examples of in silico studies of carboxylesterases (CESs) are discussed, ranging from exploring the effect of mutations on enzyme activity to predicting the metabolism of new hCES1 substrates as well as to guiding rational design of CES-selective inhibitors.

Carboxylesterases: General detoxifying enzymes

Carboxylesterases (CE) are members of the esterase family of enzymes, and as their name suggests, they are responsible for the hydrolysis of carboxylesters into the corresponding alcohol and carboxylic acid. To date, no endogenous CE substrates have been identified and as such, these proteins are thought to act as a mechanism to detoxify ester-containing xenobiotics. As a consequence, they are expressed in tissues that might be exposed to such agents (lung and gut epithelia, liver, kidney, etc.). CEs demonstrate very broad substrate specificities and can hydrolyze compounds as diverse as cocaine, oseltamivir (Tamiflu), permethrin and irinotecan. In addition, these enzymes are irreversibly inhibited by organophosphates such as Sarin and Tabun. In this overview, we will compare and contrast the two human enzymes that have been characterized, and evaluate the biology of the interaction of these proteins with organophosphates (principally nerve agents).

In vitro metabolism of methiocarb and carbaryl in rats, and its effect on their estrogenic and antiandrogenic activities

In this work, we examined the metabolism of the carbamate insecticides methiocarb and carbaryl by rat liver microsomes and plasma, and its effect on their endocrine-disrupting activities. Methiocarb and carbaryl were not enzymatically hydrolyzed by rat liver microsomes, but were hydrolyzed by rat plasma, mainly to methylthio-3,5-xylenol (MX) and 1-naphthol, respectively. When methiocarb was incubated with rat liver microsomes in the presence of NADPH, methiocarb sulfoxide was formed. The hydrolysis product, MX, was also oxidized to the sulfoxide, 3,5-dimethyl-4-(methylsulfinyl)phenol (SP), by rat liver microsomes in the presence of NADPH. These oxidase activities were catalyzed by cytochrome P450 and flavin-containing monooxygenase. Methiocarb and carbaryl both exhibited estrogen receptor α (ERα) and ERβ agonistic activity. MX and 1-naphthol showed similar activities, but methiocarb sulfoxide and SP showed markedly decreased activities. On the other hand, methiocarb and carbaryl exhibited potent antiandrogenic activity in the concentration range of 1×10(-6)-3×10(-5) M. Their hydrolysis products, MX, and 1-naphthol also showed high activity, equivalent to that of flutamide. However, methiocarb sulfoxide and SP showed relatively low activity. Thus, hydrolysis of methiocarb and carbaryl and oxidation of methiocarb to the sulfoxide markedly modified the estrogenic and antiandrogenic activities of methiocarb and carbaryl.

Comparison of the Structure and Activity of Glycosylated and Aglycosylated Human Carboxylesterase 1

Human Carboxylesterase 1 (hCES1) is the key liver microsomal enzyme responsible for detoxification and metabolism of a variety of clinical drugs. To analyse the role of the single N-linked glycan on the structure and activity of the enzyme, authentically glycosylated and aglycosylated hCES1, generated by mutating asparagine 79 to glutamine, were produced in human embryonic kidney cells. Purified enzymes were shown to be predominantly trimeric in solution by analytical ultracentrifugation. The purified aglycosylated enzyme was found to be more active than glycosylated hCES1 and analysis of enzyme kinetics revealed that both enzymes exhibit positive cooperativity. Crystal structures of hCES1 a catalytically inactive mutant (S221A) and the aglycosylated enzyme were determined in the absence of any ligand or substrate to high resolutions (1.86 Å, 1.48 Å and 2.01 Å, respectively). Superposition of all three structures showed only minor conformational differences with a root mean square deviations of around 0.5 Å over all Cα positions. Comparison of the active sites of these un-liganded enzymes with the structures of hCES1-ligand complexes showed that side-chains of the catalytic triad were pre-disposed for substrate binding. Overall the results indicate that preventing N-glycosylation of hCES1 does not significantly affect the structure or activity of the enzyme.

An epididymis-specific carboxyl esterase CES5A is required for sperm capacitation and male fertility in the rat

Despite the fact that the phenomenon of capacitation was discovered over half century ago and much progress has been made in identifying sperm events involved in capacitation, few specific molecules of epididymal origin have been identified as being directly involved in this process in vivo. Previously, our group cloned and characterized a carboxyl esterase gene Ces5a in the rat epididymis. The CES5A protein is mainly expressed in the corpus and cauda epididymidis and secreted into the corresponding lumens. Here, we report the function of CES5A in sperm maturation. By local injection of Lentivirus-mediated siRNA in the CES5A-expressing region of the rat epididymis, Ces5a-knockdown animal models were created. These animals exhibited an inhibited sperm capacitation and a reduction in male fertility. These results suggest that CES5A plays an important role in sperm maturation and male fertility.

Tumor cell survival pathways activated by photodynamic therapy: a molecular basis for pharmacological inhibition strategies

Photodynamic therapy (PDT) has emerged as a promising alternative to conventional cancer therapies such as surgery, chemotherapy, and radiotherapy. PDT comprises the administration of a photosensitizer, its accumulation in tumor tissue, and subsequent irradiation of the photosensitizer-loaded tumor, leading to the localized photoproduction of reactive oxygen species (ROS). The resulting oxidative damage ultimately culminates in tumor cell death, vascular shutdown, induction of an antitumor immune response, and the consequent destruction of the tumor. However, the ROS produced by PDT also triggers a stress response that, as part of a cell survival mechanism, helps cancer cells to cope with the PDT-induced oxidative stress and cell damage. These survival pathways are mediated by the transcription factors activator protein 1 (AP-1), nuclear factor E2-related factor 2 (NRF2), hypoxia-inducible factor 1 (HIF-1), nuclear factor κB (NF-κB), and those that mediate the proteotoxic stress response. The survival pathways are believed to render some types of cancer recalcitrant to PDT and alter the tumor microenvironment in favor of tumor survival. In this review, the molecular mechanisms are elucidated that occur post-PDT to mediate cancer cell survival, on the basis of which pharmacological interventions are proposed. Specifically, pharmaceutical inhibitors of the molecular regulators of each survival pathway are addressed. The ultimate aim is to facilitate the development of adjuvant intervention strategies to improve PDT efficacy in recalcitrant solid tumors.

An in vitro screening with emerging contaminants reveals inhibition of carboxylesterase activity in aquatic organisms

Pharmaceuticals and personal care products (PPCPs) form part of the new generation of pollutants present in many freshwater and marine ecosystems. Although environmental concentrations of these bioactive substances are low, they cause sublethal effects (e.g., enzyme inhibition) in non-target organisms. However, little is known on metabolism of PPCPs by non-mammal species. Herein, an in vitro enzyme trial was performed to explore sensitivity of carboxylesterase (CE) activity of aquatic organisms to fourteen PPCPs. The esterase activity was determined in the liver of Mediterranean freshwater fish (Barbus meridionalis and Squalius laietanus), coastal marine fish (Dicentrarchus labrax and Solea solea), middle-slope fish (Trachyrhynchus scabrus), deep-sea fish (Alepocephalus rostratus and Cataetix laticeps), and in the digestive gland of a decapod crustacean (Aristeus antennatus). Results showed that 100μM of the lipid regulators simvastatin and fenofibrate significantly inhibited (30-80% of controls) the CE activity of all target species. Among the personal care products, nonylphenol and triclosan were strong esterase inhibitors in most species (36-68% of controls). Comparison with literature data suggests that fish CE activity is as sensitive to inhibition by some PPCPs as that of mammals, although their basal activity levels are lower than in mammals. Pending further studies on the interaction between PPCPs and CE activity, we postulate that this enzyme may act as a molecular sink for certain PPCPs in a comparable way than that described for the organophosphorus pesticides.

Human carboxylesterase 2: Studies on the role of glycosylation for enzymatic activity

Human carboxylesterase 2 (hCES2) is a glycoprotein involved in the metabolism of drugs and several environmental xenobiotics, whose crystallization has been proved to be a challenging task. This limitation could partly be due to glycosylation heterogeneity and has delayed the disclosure of the 3D structure of hCES2 which would be of upmost relevance for the development of new substrates and inhibitors. The present work evaluated the involvement of glycans in hCES2 activity and thermo stability in an attempt to find alternative active forms of the enzyme that might be adequate for structure elucidation. Partial or non-glycosylated forms of a secreted form of hCES2 have been obtained by three approaches: (i) enzymatic deglycosylation with peptide N-glycosidase F; (ii) incubation with the inhibitor tunicamycin; ii) site directed mutagenesis of each or both N-glycosylation sites. Deglycosylated protein did not show a detectable decrease in enzyme activity. On the other hand, tunicamycin led to decreased levels of secreted hCES2 but the enzyme was still active. In agreement, mutation of each and both N-glycosylation sites led to decreased levels of secreted active hCES2. However, the thermostability of the glycosylation mutants was decreased. The results indicated that glycans are involved, to some extent in protein folding in vivo, however, removal of glycans does not abrogate the activity of secreted hCES2.

Recovery study of cholinesterases and neurotoxic signs in the non-target freshwater invertebrate Chilina gibbosa after an acute exposure to an environmental concentration of azinphos-methyl

Azinphos-methyl belongs to the class of organophosphate insecticides which are recognized for their anticholinesterase action. It is one of the most frequently used insecticides in the Upper Valley of Río Negro and Río Neuquén in Argentina, where agriculture represents the second most important economic activity. It has been detected in water from this North Patagonian region throughout the year and the maximum concentration found was 22.48 μg L(-1) during the application period. Chilina gibbosa is a freshwater gastropod widely distributed in South America, particularly in Patagonia, Argentina and in Southern Chile. Toxicological studies performed with C. gibbosa in our laboratory have reported neurotoxicity signs and cholinesterase inhibition after exposure to azinphos-methyl for 48 h. Recovery studies together with characterization of the enzyme and sensitivity of the enzyme to pesticides can improve the toxicological evaluation. However, little is known about recovery patterns in organisms exposed to organophosphates. The aim of the present work was to evaluate the recovery capacity (during 21 days in pesticide-free water) of cholinesterase activity and neurotoxicity in C. gibbosa after 48 h of exposure to azinphos-methyl. Also, lethality and carboxylesterase activity were registered during the recovery period. Regarding enzyme activities, after a 48-h exposure to 20 μg L(-1) of azinphos-methyl, cholinesterases showed an inhibition of 85% with respect to control, while carboxylesterases were not affected. After 21 days in pesticide-free water, cholinesterases continued to be inhibited (70%). Severe neurotoxicity signs were observed after exposure: 82% of the snails presented lack of adherence to vessels, 11% showed weak adherence, and 96% exhibited an abnormal protrusion of the head-foot region from shell. After 21 days in pesticide-free water, only 15% of the snails presented severe signs of neurotoxicity. However, during the recovery period significant lethality (30%) was registered in treated snails. C. gibbosa is a very sensitive organism to azinphos-methyl. These snails play an important role in the structure and function of aquatic food webs in this region. Thus, a decline of this species' population would probably have an impact on aquatic and non-aquatic communities. Our results show that C. gibbosa is a relevant sentinel species for studying exposure and effects of azinphos-methyl using behavioral and biochemical biomarkers. Neurotoxic behavioral signs are very sensitive, non-destructive biomarkers, which can be easily detected for about one week after acute exposure. Cholinesterse activity is a very useful biomarker showing a high sensitivity and a slow recovery capacity increasing the possibility to indirectly detect organophosphates for long periods after a contaminant event.

Lipopolysaccharide suppresses carboxylesterase 2g activity and 2-arachidonoylglycerol hydrolysis: A possible mechanism to regulate inflammation

Inflammation is an important part of the innate immune response and is involved in the healing of many disease processes; however, chronic inflammation is a harmful component of many diseases. The regulatory mechanisms of inflammation are incompletely understood. One possible regulatory mechanism is the endocannabinoid system. Endocannabinoids such as 2-arachidonoylglycerol (2-AG) and anandamide (AEA) are generally anti-inflammatory via engagement of the cannabinoid receptor 2 (CB2) on innate cells; therefore, preventing the degradation of endocannabinoids by specific serine hydrolases such as fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), and carboxylesterases (CES) might decrease inflammation. We hypothesized that the activities of these catabolic enzymes would decrease with a subsequent increase in 2-AG and AEA in a model of inflammation. Mice were injected with lipopolysaccharide (LPS) for 6 or 24h, and inflammation was confirmed by an increase in interleukin-6 (il6) and il17 gene expression. Activity-based protein profiling (ABPP) of serine hydrolases showed no significant difference in various serine hydrolase activities in brain or liver, whereas a modest decrease in Ces activity in spleen after LPS administration was noted. 2-AG hydrolase activity in the spleen was also decreased at 6h post LPS, which was corroborated by LPS treatment of splenocytes ex vivo. ABPP-MudPIT proteomic analysis suggested that the decreased 2-AG hydrolysis in spleen was due to a reduction in Ces2g activity. These studies suggest that the endocannabinoid system could be activated via suppression of a 2-AG catabolic enzyme in response to inflammatory stimuli as one mechanism to limit inflammation.

Impact of wastewater on fish health: a case study at the Neckar River (Southern Germany) using biomarkers in caged brown trout as assessment tools

The present work describes a field survey aiming at assessing the impact of a sewage treatment plant (STP) effluent on fish health by means of biomarkers. Indigenous fish were absent downstream of the STP. To elucidate the reason behind this, brown trout (Salmo trutta f. fario) were exposed in floating steel cages up- and downstream of a STP located at the Neckar River near Tübingen (Southern Germany), for 10 and 30 days. A combination of biomarker methods (histopathological investigations, analysis of the stress protein Hsp70, micronucleus test, B-esterase assays) offered the possibility to investigate endocrine, geno-, proteo- and neurotoxic effects in fish organs. Biological results were complemented with chemical analyses on 20 accumulative substances in fish tissue. Even after short-term exposure, biomarkers revealed clear evidence of water contamination at both Neckar River sites; however, physiological responses of caged brown trout were more severe downstream of the STP. According to this, similar bioaccumulation levels (low μg/kg range) of DDE and 12 polycyclic aromatic hydrocarbons (PAHs) were detected at both sampling sites, while up to fourfold higher concentrations of four PAHs, methyl-triclosan and two synthetic musks occurred in the tissues of downstream-exposed fish. The results obtained in this study suggest a constitutive background pollution at both sites investigated at the Neckar River and provided evidence for the additional negative impact of the STP Tübingen on water quality and the health condition of fish.

Isoform-Specific Regulation of Mouse Carboxylesterase Expression and Activity by Prototypical Transcriptional Activators

Nuclear receptors and transcription factors regulate the mRNA expression of many drug metabolizing enzymes, including the carboxylesterases (Ces). However, there are few data regarding whether these changes in mRNA expression result in alteration of protein levels or activity. In the present study, we sought to determine the isoform-specific regulation of hepatic Ces mRNA expression and activity following the administration of pharmacological activators of the constitutive androstane receptor (CAR), pregnane X receptor (PXR), and nuclear factor E2-related protein (Nrf2) to mice. The CAR activator 1,4-bis-[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP) and PXR ligand pregnenolone-16a-carbonitrile (PCN) increased Ces mRNA expression of various Ces2 isoforms, whereas the Nrf2 activator butylated hydroxyanisole primarily reduced Ces3a mRNA expression and induced Ces1g mRNA. TCPOBOP and PCN increased Ces2 hydrolytic activity in an isoform-specific manner. Taken together, these data demonstrate that activation of CAR, PXR, and Nrf2 regulates not only Ces mRNA expression, but also isoform-specific activity.

DAG tales: the multiple faces of diacylglycerol--stereochemistry, metabolism, and signaling

The neutral lipids diacylglycerols (DAGs) are involved in a plethora of metabolic pathways. They function as components of cellular membranes, as building blocks for glycero(phospho)lipids, and as lipid second messengers. Considering their central role in multiple metabolic processes and signaling pathways, cellular DAG levels require a tight regulation to ensure a constant and controlled availability. Interestingly, DAG species are versatile in their chemical structure. Besides the different fatty acid species esterified to the glycerol backbone, DAGs can occur in three different stereo/regioisoforms, each with unique biological properties. Recent scientific advances have revealed that DAG metabolizing enzymes generate and distinguish different DAG isoforms, and that only one DAG isoform holds signaling properties. Herein, we review the current knowledge of DAG stereochemistry and their impact on cellular metabolism and signaling. Further, we describe intracellular DAG turnover and its stereochemistry in a 3-pool model to illustrate the spatial and stereochemical separation and hereby the diversity of cellular DAG metabolism.

Identification of carboxylesterase genes and their expression profiles in the Colorado potato beetle Leptinotarsa decemlineata treated with fipronil and cyhalothrin

Based on the Leptinotarsa decemlineata transcriptome dataset and the GenBank sequences, 70 novel carboxylesterases and 2 acetylcholinesterases were found. The 72 members belong to a multifunctional carboxylesterase/cholinesterase superfamily (CCE). A phylogenetic tree including the 72 LdCCEs and the CCEs from Tribolium castaneum, Drosophila melanogaster and Apis mellifera revealed that all CCEs fell into three main phylogenetic groups: dietary/detoxification, hormone/semiochemical processing, and neurodevelopmental classes. Numbers of L. decemlineata CCEs in the three classes were 52, 12 and 8, respectively. The dietary/detoxification class includes two clades: coleopteran xenobiotic metabolizing and α-esterase type CCEs. CCEs in the two clades have independently expanded in L. decemlineata. The hormone/semiochemical processing class has three clades: integument CCEs, β- and pheromone CCEs and juvenile hormone CCEs. Integument CCEs in L. decemlineata have also expanded. The neurodevelopmental CCEs are implicated the most ancient class, containing acetylcholinesterase, neuroligin, neurotactin, glutactin, gliotactin and others. Among the 70 novel CCE genes, KM220566, KM220530, KM220576, KM220527 and KM220541 were fipronil-inducible, and KM220578, KM220566, KM220542, KM220564, KM220561, KM220554, KM220527, KM220538 and KM220541 were cyhalothrin-inducible. They were the candidates involving in insecticide detoxification. Moreover, our results also provided a platform to understand the functions and evolution of L. decemlineata CCE genes.

Effect of carboxylesterase 1 c.428G > A single nucleotide variation on the pharmacokinetics of quinapril and enalapril

AIM

The aim of the present study was to investigate the effects of the carboxylesterase 1 (CES1) c.428G > A (p.G143E, rs71647871) single nucleotide variation (SNV) on the pharmacokinetics of quinapril and enalapril in a prospective genotype panel study in healthy volunteers.

METHODS

In a fixed-order crossover study, 10 healthy volunteers with the CES1 c.428G/A genotype and 12 with the c.428G/G genotype ingested a single 10 mg dose of quinapril and enalapril with a washout period of at least 1 week. Plasma concentrations of quinapril and quinaprilat were measured for up to 24 h and those of enalapril and enalaprilat for up to 48 h. Their excretion into the urine was measured from 0 h to 12 h.

RESULTS

The area under the plasma concentration-time curve from 0 h to infinity (AUC0-∞) of active enalaprilat was 20% lower in subjects with the CES1 c.428G/A genotype than in those with the c.428G/G genotype (95% confidence interval of geometric mean ratio 0.64, 1.00; P = 0.049). The amount of enalaprilat excreted into the urine was 35% smaller in subjects with the CES1 c.428G/A genotype than in those with the c.428G/G genotype (P = 0.044). The CES1 genotype had no significant effect on the enalaprilat to enalapril AUC0-∞ ratio or on any other pharmacokinetic or pharmacodynamic parameters of enalapril or enalaprilat. The CES1 genotype had no significant effect on the pharmacokinetic or pharmacodynamic parameters of quinapril.

CONCLUSIONS

The CES1 c.428G > A SNV decreased enalaprilat concentrations, probably by reducing the hydrolysis of enalapril, but had no observable effect on the pharmacokinetics of quinapril.

Carboxylesterase 2 as a Determinant of Response to Irinotecan and Neoadjuvant FOLFIRINOX Therapy in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Serine hydrolases (SHs) are among the largest classes of enzymes in humans and play crucial role in many pathophysiological processes of cancer. We have undertaken a comprehensive proteomic analysis to assess the differential expression and cellular localization of SHs, which uncovered distinctive expression of Carboxylesterase 2 (CES2), the most efficient carboxyl esterase in activating the prodrug irinotecan into SN-38, in pancreatic ductal adenocarcinoma (PDAC). We therefore assessed the extent of heterogeneity in CES2 expression in PDAC and its potential relevance to irinotecan based therapy.

METHODS

CES2 expression in PDAC and paired nontumor tissues was evaluated by immunohistochemistry. CES2 activity was assessed by monitoring the hydrolysis of the substrate p-NPA and correlated with irinotecan IC50 values by means of Pearson's correlation. Kaplan-Meier and Cox regression analyses were applied to assess the association between overall survival and CES2 expression in patients who underwent neoadjuvant FOLFIRINOX treatment. All statistical tests were two-sided.

RESULTS

Statistically significant overexpression of CES2, both at the mRNA and protein levels, was observed in PDAC compared with paired nontumor tissue (P < .001), with 48 of 118 (40.7%) tumors exhibiting high CES2 expression. CES2 activity in 11 PDAC cell lines was inversely correlated with irinotecan IC50 values (R = -0.68, P = .02). High CES2 expression in tumor tissue was associated with longer overall survival in resectable and borderline resectable patients who underwent neoadjuvant FOLFIRINOX treatment (hazard ratio = 0.14, 95% confidence interval = 0.04 to 0.51, P = .02).

CONCLUSION

Our findings suggest that CES2 expression and activity, by mediating the intratumoral activation of irinotecan, is a contributor to FOLFIRINOX sensitivity in pancreatic cancer and CES2 assessment may define a subset of patients likely to respond to irinotecan based therapy.

Esterase Activity and Intracellular Localization in Reconstructed Human Epidermal Cultured Skin Models

Background

Reconstructed human epidermal culture skin models have been developed for cosmetic and pharmaceutical research.

Objective

This study evaluated the total and carboxyl esterase activities (i.e., K_m and V_max, respectively) and localization in two reconstructed human epidermal culture skin models (LabCyte EPI-MODEL [Japan Tissue Engineering] and EpiDerm [MatTek/Kurabo]). The usefulness of the reconstruction cultured epidermis was also verified by comparison with human and rat epidermis.

Methods

Homogenized epidermal samples were fractioned by centrifugation. p-nitrophenyl acetate and 4-methylumbelliferyl acetate were used as substrates of total esterase and carboxyl esterase, respectively.

Results

Total and carboxyl esterase activities were present in the reconstructed human epidermal culture skin models and were localized in the cytosol. Moreover, the activities and localization were the same as those in human and rat epidermis.

Conclusion

LabCyte EPI-MODEL and EpiDerm are potentially useful for esterase activity prediction in human epidermis.

Pharmacokinetic characterization of BMS-936561, an anti-CD70 antibody-drug conjugate, in preclinical animal species and prediction of its pharmacokinetics in humans

CD70 is a tumor necrosis factor (TNF)-like type II integral membrane protein that is transiently expressed on activated T- and B-lymphocytes. Aberrant expression of CD70 was identified in both solid tumors and haematologic malignancies. BMS-936561 (αCD70_MED-A) is an antibody-drug conjugate composed of a fully human anti-CD70 monoclonal antibody (αCD70) conjugated with a duocarmycin derivative, MED-A, through a maleimide-containing citrulline-valine dipeptide linker. MED-A is a carbamate prodrug that is activated by carboxylesterase to its active form, MED-B, to exert its DNA alkylation activity. In vitro serum stability studies suggested the efficiencies of hydrolyzing the carbamate-protecting group in αCD70_MED-A followed a rank order of mouse>rat > >monkey>dog~human. Pharmacokinetics of αCD70_MED-A was evaluated in mice, monkeys, and dogs after single intravenous doses. In mice, αCD70_MED-A was cleared rapidly, with no detectable exposures after 15 min following dosing. In contrast, αCD70_MED-A was much more stable in monkeys and dogs. The clearance of αCD70_MED-A in monkeys was 58 mL/d/kg, ~2-fold faster than that in dogs (31 mL/d/kg). The human PK profiles of the total αCD70 and αCD70_MED-A were predicted using allometrically scaled monkeys PK parameters of αCD70 and the carbamate hydrolysis rate constant estimated in dogs. Comparing the predicted and observed human PK from the phase I study, the dose-normalized concentration-time profiles of αCD70_MED-A and the total αCD70 were largely within the 5(th)-95(th) percentile of the predicted profiles.

PEGylated graphene oxide for tumor-targeted delivery of paclitaxel

Aim: The graphene oxide (GO) sheet has been considered one of the most promising carbon derivatives in the field of material science for the past few years and has shown excellent tumor-targeting ability, biocompatibility and low toxicity. We have endeavored to conjugate paclitaxel (PTX) to GO molecule and investigate its anticancer efficacy. Materials & Methods: We conjugated the anticancer drug PTX to aminated PEG chains on GO sheets through covalent bonds to get GO-PEG-PTX complexes. The tissue distribution and anticancer efficacy of GO-PEG-PTX were then investigated using a B16 melanoma cancer-bearing C57 mice model. Results: The GO-PEG-PTX complexes exhibited excellent water solubility and biocompatibility. Compared with the traditional formulation of PTX (Taxol®), GO-PEG-PTX has shown prolonged blood circulation time as well as high tumor-targeting and -suppressing efficacy. Conclusion: PEGylated graphene oxide is an excellent nanocarrier for paclitaxel for cancer targeting.

The intrinsic disorder alphabet. III. Dual personality of serine

Proteins are natural polypeptides consisting of 20 major amino acid residues, content and order of which in a given amino acid sequence defines the ability of a related protein to fold into unique functional state or to stay intrinsically disordered. Amino acid sequences code for both foldable (ordered) proteins/domains and for intrinsically disordered proteins (IDPs) and IDP regions (IDPRs), but these sequence codes are dramatically different. This difference starts with a very general property of the corresponding amino acid sequences, namely, their compositions. IDPs/IDPRs are enriched in specific disorder-promoting residues, whereas amino acid sequences of ordered proteins/domains typically contain more order-promoting residues. Therefore, the relative abundances of various amino acids in ordered and disordered proteins can be used to scale amino acids according to their disorder promoting potentials. This review continues a series of publications on the roles of different amino acids in defining the phenomenon of protein intrinsic disorder and represents serine, which is the third most disorder-promoting residue. Similar to previous publications, this review represents some physico-chemical properties of serine and the roles of this residue in structures and functions of ordered proteins, describes major posttranslational modifications tailored to serine, and finally gives an overview of roles of serine in structure and functions of intrinsically disordered proteins.

In vivo and in vitro metabolites from the main diester and monoester diterpenoid alkaloids in a traditional chinese herb, the aconitum species

Diester diterpenoid alkaloids (DDAs), such as aconitine (AC), mesaconitine (MA), and hypaconitine (HA), are both pharmacologically active compounds and toxic ingredients in a traditional Chinese herb, the Aconitum species. Many DDA metabolism studies have been performed to explore mechanisms for reducing toxicity in these compounds and in Aconitum species extracts for safe clinical administration. In this review, we summarize recent progress on the metabolism of toxic AC, MA, and HA and corresponding monoester diterpenoid alkaloids (MDAs) in the gastrointestinal tract and liver in different animal species and humans in vivo and/or in vitro, where these alkaloids are primarily metabolized by cytochrome P450 enzymes, carboxylesterases, and intestinal bacteria, which produces phase I metabolites, ester hydrolysed products, and lipoalkaloids. Furthermore, we classify metabolites detected in the blood and urine, where the aforementioned metabolites are absorbed and excreted. Less toxic MDAs and nontoxic alcohol amines are the primary DDA metabolites detected in the blood. Most other DDAs metabolites produced in the intestine and liver detected in the urine have not been reported in the blood. We propose an explanation for this nonconformity. Finally, taking AC, for instance, we generalize a process of toxicity reduction in the body after oral AC administration for the first time.