Identification of a C-reactive protein binding site in two hepatic carboxylesterases capable of retaining C-reactive protein within the endoplasmic reticulum

Acoustofluidic separation of proteins from platelets in human blood plasma using aptamer-functionalized microparticles

Microfluidic liquid biopsy has emerged as a promising clinical assay for early diagnosis. Herein, we propose acoustofluidic separation of biomarker proteins from platelets in plasma using aptamer-functionalized microparticles. As model proteins, C-reactive protein and thrombin were spiked in human platelet-rich plasma. The target proteins were selectively conjugated with their corresponding aptamer-functionalized microparticles of different sizes, and the particle complexes served as a mobile carrier for the conjugated proteins. The proposed acoustofluidic device was composed of an interdigital transducer (IDT) patterned on a piezoelectric substrate and a disposable polydimethylsiloxane (PDMS) microfluidic chip. The PDMS chip was placed in a tilted arrangement with the IDT to utilize both vertical and horizontal components of surface acoustic wave-induced acoustic radiation force (ARF) for multiplexed assay at high-throughput. The two different-sized particles experienced the ARF at different magnitudes and were separated from platelets in plasma. The IDT on the piezoelectric substrate could be reusable, while the microfluidic chip can be replaceable for repeated assays. The sample processing throughput with the separation efficiency >95% has been improved such that the volumetric flow rate and flow velocity were 1.6 ml/h and 37 mm/s, respectively. For the prevention of platelet activation and protein adsorption to the microchannel, polyethylene oxide solution was introduced as sheath flows and coating on to the walls. We conducted scanning electron microscopy, x-ray photoemission spectroscopy , and sodium dodecyl sulfate- analysis before and after the separation to confirm the protein capture and separation. We expect that the proposed approach will provide new prospects for particle-based liquid biopsy using blood.

Therapeutic Lowering of C-Reactive Protein

In the blood of healthy individuals C-reactive protein (CRP) is typically quite scarce, whereas its blood concentration can rise robustly and rapidly in response to tissue damage and inflammation associated with trauma and infectious and non-infectious diseases. Consequently, CRP plasma or serum levels are routinely monitored in inpatients to gauge the severity of their initial illness and injury and their subsequent response to therapy and return to health. Its clinical utility as a faithful barometer of inflammation notwithstanding, it is often wrongly concluded that the biological actions of CRP (whatever they may be) are manifested only when blood CRP is elevated. In fact over the last decades, studies done in humans and animals (e.g. human CRP transgenic and CRP knockout mice) have shown that CRP is an important mediator of biological activities even in the absence of significant blood elevation, i.e. even at baseline levels. In this review we briefly recap the history of CRP, including a description of its discovery, early clinical use, and biosynthesis at baseline and during the acute phase response. Next we overview evidence that we and others have generated using animal models of arthritis, neointimal hyperplasia, and acute kidney injury that baseline CRP exerts important biological effects. In closing we discuss the possibility that therapeutic lowering of baseline CRP might be a useful way to treat certain diseases, including cancer.

Determination of the concentration range for 267 proteins from 21 lots of commercial human plasma using highly multiplexed multiple reaction monitoring mass spectrometry

Multiple reaction monitoring (MRM) is a key tool for biomarker validation and the translation of potential biomarkers into the clinic.

Human carboxylesterases: a comprehensive review

Mammalian carboxylesterases (CEs) are key enzymes from the serine hydrolase superfamily. In the human body, two predominant carboxylesterases (CES1 and CES2) have been identified and extensively studied over the past decade. These two enzymes play crucial roles in the metabolism of a wide variety of endogenous esters, ester-containing drugs and environmental toxicants. The key roles of CES in both human health and xenobiotic metabolism arouse great interest in the discovery of potent CES modulators to regulate endobiotic metabolism or to improve the efficacy of ester drugs. This review covers the structural and catalytic features of CES, tissue distributions, biological functions, genetic polymorphisms, substrate specificities and inhibitor properties of CES1 and CES2, as well as the significance and recent progress on the discovery of CES modulators. The information presented here will help pharmacologists explore the relevance of CES to human diseases or to assign the contribution of certain CES in xenobiotic metabolism. It will also facilitate medicinal chemistry efforts to design prodrugs activated by a given CES isoform, or to develop potent and selective modulators of CES for potential biomedical applications.

Extracellular esterase activity as an indicator of endoplasmic reticulum calcium depletion

CONTEXT

Endoplasmic reticulum (ER) calcium depletion is associated with diverse diseases, including cardiac, hepatic, and neurologic diseases.

OBJECTIVE

The aim of the present study was to identify and characterize an endogenous protein that could be used to monitor ER calcium depletion comparably to a previously described exogenous reporter protein.

MATERIALS AND METHODS

The use of a selective esterase-fluorescein diester pair allowed for carboxylesterase activity in extracellular fluid to be measured using a fluorescent readout. Cell culture media from three different cell lines, rat plasma, and human serum all possess quantifiable amounts of esterase activity.

RESULTS

Fluorescence produced by the interaction of carboxylesterases with a fluorescein diester substrate tracks with pharmacological and physiological inducers of ER calcium depletion. The fluorescence measured for in vitro and in vivo samples were consistent with ER calcium depletion being the trigger for increased esterase activity.

DISCUSSION

Decreased luminal ER calcium causes ER resident esterases to be released from the cell, and, when assessed concurrently with other disease biomarkers, these esterases may provide insight into the role of ER calcium homeostasis in human diseases.

CONCLUSION

Our results indicate that carboxylesterases are putative markers of ER calcium dysfunction.

Increased C-reactive protein and decreased Interleukin-2 content in serum from obese individuals with or without insulin resistance: Associations with leukocyte count and insulin and adiponectin content

AIMS

Chronic inflammation in obesity is associated with co-morbidities such as, hyperglycemia, hypertension and hyperlipidemia. Leukocytes play an important role in this inflammation and C-reactive protein (CRP) and Interleukin-2 (IL-2) can be important effectors during the immune response in obesity; however, the initial inflammatory events in obesity remain unclear. The aim of this study was to determine the circulating levels of CRP, IL-2, insulin and adiponectin, their association and the association with leukocyte count in obese individuals without co-morbidities and with or without insulin resistance (IR).

MATERIALS AND METHODS

Nineteen obese non-diabetic and 9 lean subjects were studied for serum levels of CRP, IL-2, insulin, adiponectin, lipids, glycated hemoglobin, glycemia, for homeostasis model assessment of insulin resistance (HOMA-IR), arterial pressure and anthropometric parameters, and for leukocyte counts. Neutrophil/lymphocyte ratio (N/L) was calculated using the loge of leukocyte counts. Associations were determined by Pearson's correlation.

RESULTS

None of the studied groups presented co-morbidities and two groups of obese individuals with normal or high levels of insulin (IR) were found. Increased CRP concentration and decreased IL-2 and adiponectin concentrations in obese were observed. Positive correlation between leukocyte type counts with CRP in obese with IR was found; however, no correlations with IL-2 in obese were observed. Insulin in obese were positively correlated with CRP and negatively correlated with IL-2 in IR obese individuals. Adiponectin in obese was negatively correlated with CRP.

CONCLUSION

CRP and IL-2 may represent two important effectors in the early inflammatory events in obese individuals without co-morbidities. Adiponectin and insulin may be involved in anti-inflammatory events.

Serum level of C-reactive protein is not a parameter to determine the difference between viral and atypical bacterial infections

C-reactive protein (CRP) is an acute-phase reactant that increases in the circulation in response to a variety of inflammatory stimuli. Elevated levels in serum during several infectious diseases have been reported. In this study, a highly sensitive CRP enzyme immunoassay was used to evaluate serum CRP values in patients with viral and atypical bacterial infections. Patients (n = 139) with different viral or atypical bacterial infections (systemic or respiratory) and healthy controls (n = 40) were tested for circulating CRP values. High levels of IgM antibodies against several viruses: Dengue virus (n = 36), Cytomegalovirus (n = 9), Epstein Barr virus (n = 17), Parvovirus B19 (n = 26), Herpes simplex 1 and 2 virus (n = 3) and Influenza A and B (n = 8) and against atypical bacteria: Legionella pneumophila (n = 15), Mycoplasma pneumoniae (n = 21) and Coxiella burnetii (n = 4) were found. High values of CRP in infected patients compared with controls (P < 0.001) were found; however, no significant differences between viral and atypical bacterial infections were found. Low levels of CRP in respiratory and Coxiella burnetii infections compared with exanthematic viral and other atypical bacterial infections were found. This study suggests that CRP values are useful to define viral and atypical bacterial infections compared with normal values, but, it is not useful to define type of infection.

Computational analysis of C-reactive protein for assessment of molecular dynamics and interaction properties

Serum C-reactive protein (CRP) is used as a marker of inflammation in several diseases including autoimmune disease and cardiovascular disease. CRP, a member of the pentraxin family, is comprised of five identical subunits. CRP has diverse ligand-binding properties which depend upon different structural states of CRP. However, little is known about the molecular dynamics and interaction properties of CRP. In this study, we used SAPS, SCRATCH protein predictor, PDBsum, ConSurf, ProtScale, Drawhca, ASAView, SCide and SRide server and performed comprehensive analyses of molecular dynamics, protein-protein and residue-residue interactions of CRP. We used 1GNH.pdb file for the crystal structure of human CRP which generated two pentamers (ABCDE and FGHIJ). The number of residues involved in residue-residue interactions between A-B, B-C, C-D, D-E, F-G, G-H, H-I, I-J, A-E and F-J subunits were 12, 11, 10, 11, 12, 11, 10, 11, 10 and 10, respectively. Fifteen antiparallel β sheets were involved in β-sheet topology, and five β hairpins were involved in forming the secondary structure. Analysis of hydrophobic segment distribution revealed deviations in surface hydrophobicity at different cavities present in CRP. Approximately 33 % of all residues were involved in the stabilization centers. We show that the bioinformatics tools can provide a rapid method to predict molecular dynamics and interaction properties of CRP. Our prediction of molecular dynamics and interaction properties of CRP combined with the modeling data based on the known 3D structure of CRP is helpful in designing stable forms of CRP mutants for structure-function studies of CRP and may facilitate in silico drug design for therapeutic targeting of CRP.

C-reactive protein concentrations in serum of dogs with naturally occurring renal disease

The current study was undertaken to investigate the relation between serum C-reactive protein (CRP) concentrations and parameters of renal function in dogs with naturally occurring renal disease. Dogs were assigned to groups according to plasma creatinine concentration, urinary protein-to-creatinine ratio (UP/UC), and exogenous plasma creatinine clearance (P-ClCr) rates. Group A (healthy control dogs; n = 8): non-azotemic (plasma creatinine <125 µmol/l) and nonproteinuric (UP/UC <0.2), with P-ClCr rates >90 ml/min/m2; group B (n = 11): non-azotemic, nonproteinuric dogs with reduced P-ClCr rates (50–89 ml/min/m2); group C (n = 7): azotemic, borderline proteinuric dogs (P-ClCr rates: 22–67 ml/min/m2); and group D (n = 6): uremic, proteinuric dogs (not tested for P-ClCr). The serum CRP concentrations were measured via commercial enzyme-linked immunosorbent assay. The CRP concentrations in the clinically healthy dogs (group A) ranged from 2.09 mg/l to 8.60 mg/l (median: 3.21 mg/l). In comparison with dogs of group A, median CRP concentrations were significantly ( P < 0.01) elevated in dogs of group B (17.6 mg/l, range: 17.0–19.2 mg/l), group C (24.8 mg/l, range: 18.0–32.5 mg/l), and group D (59.7 mg/l, range: 17.7–123 mg/l). Serum CRP was significantly related to P-ClCr ( r = –0.83; P < 0.001), plasma creatinine ( r = 0.81; P < 0.001), UP/UC ( r = 0.70; P < 0.001), and leukocytes ( r = 0.49; P < 0.01). The significant relations between serum CRP concentrations and biochemical parameters of kidney function in plasma and urine suggest that a stimulation of the acute phase response is implicated in the pathogenesis of canine renal disease.

Expression of C-reactive protein in human lung epithelial cells and upregulation by cytokines and carbon particles

C-reactive protein (CRP) is the prototypic human acute-phase protein and is found at increased levels in the blood during episodes of inflammation. CRP was generally thought to be produced only by hepatocytes; however, several studies have shown extrahepatic synthesis of CRP. A previous study showed that PM10 and ultrafine carbon black (ufCB) were able to induce CRP expression in A549 cells. This study aims to examine the factors that lead to the production of CRP in A549 cells. A549 human lung epithelial cells were treated with cytokines (interleukin 6, tumor necrosis factor alpha, interferon gamma, or interleukin 1beta) or carbon particles (CB and ufCB) for 18 h. It was found that CRP could be expressed within the cells and that CRP was secreted from the cells particularly with tumor necrosis factor alpha, CB and ufCB treatments. It was also found that this expression of CRP with CB and ufCB treatments was dependent on nuclear factor kappa B (NFkappaB). The expression of CRP in A549 cells may indicate an important role for CRP expression and secretion from lung epithelial cells in response to inflammatory stimuli.

Mammalian carboxylesterases: from drug targets to protein therapeutics

Our understanding of the detailed recognition and processing of clinically useful therapeutic agents has grown rapidly in recent years, and we are now able to begin to apply this knowledge to the rational treatment of disease. Mammalian carboxylesterases (CEs) are enzymes with broad substrate specificities that have key roles in the metabolism of a wide variety of clinical drugs, illicit narcotics and chemical nerve agents. Here, the functions, mechanism of action and structures of human CEs are reviewed, with the goal of understanding how these proteins are able to act in such a non-specific fashion, yet catalyze a remarkably specific chemical reaction. Current approaches to harness these enzymes as protein-based therapeutics for drug and chemical toxin clearance are described, as well as their uses for targeted chemotherapeutic prodrug activation. Also included is an outline of how selective CE inhibitors could be used as co-drugs to improve the efficacy of clinically approved agents.

Acidic residues emulate a phosphorylation switch to enhance the activity of rat hepatic neutral cytosolic cholesterol esterase

Site-directed mutagenesis of rat hepatic neutral cytosolic cholesteryl ester hydrolase (rhncCEH) was used to substitute acidic, basic or neutral amino acid residues for Ser506, required for activation by protein kinase A. The substitution of acidic Asp506 resulted in esterase activities with cholesteryl oleate, p-nitrophenylcaprylate (PNPC) and p-nitrophenylacetate (PNPA) equivalent to those of native rhncCEH with Ser506. The substitution of 2 acidic residues (Asp505/506), emulating the 2 negative charges of phosphoserine, resulted in a 10-fold greater cholesterol esterase activity than that of native rhncCEH, similar to the activity of rhncCEH treated with protein kinase A. In contrast to mutants with Ser506, protein kinase A did not increase the specific activities of mutants with Asp505/506. The substitution of basic (Lys506) or neutral (Asn506) residues abolished activity with cholesteryl oleate but not PNPC or PNPA. The substitution of neutral Gln for basic residues Lys496/Arg503 also abolished cholesterol esterase activity but not PNPC- and PNPA-esterase activities. These structure-activity relationships are modeled by homology with a recently reported crystal structure for the homologous human triacylglycerol hydrolase. The results suggest that the cholesterol esterase activity of carboxylesterases is enhanced by interactions between one or more basic residues on helix alpha16 (residues 485-503) and acidic groups at residues 505-506 in the adjacent surface loop.

C-reactive protein and end-stage renal disease

The significance of CRP and inflammation has increased over time, especially in the end-stage renal disease (ESRD) population. From a simple marker it now appears that CRP is an active participant in pro-atherosclerotic phenomenon including local pro-inflammatory and thrombotic events. Studies in the general population indicate the usefulness of CRP in prognostication and in monitoring response to therapy. The clinical usefulness of CRP monitoring in chronic kidney disease (CKD) and especially in ESRD deserves closer study. In the meantime, the utility of CRP measurements for monitoring and treatment is on a case-by-case basis. Management of traditional cardiovascular risk factors should be considered. In the interest of optimizing therapy it is prudent to use biocompatible membranes and ultrapure water. A careful search for infectious processes in dialysis patients is recommended, with special attention to vascular access sites, periodontitis, gastritis, and other potentially chronic or covert infections. ACE-inhibitor use should be maximized in all eligible CKD patients. The data on the use of statins in ESRD have been generally positive but await further validation. Individualized use for selected patients is probably beneficial.

Increased C reactive protein in response to acute stress in patients with rheumatoid arthritis

OBJECTIVE

To assess the effects of acute stress on inflammatory, haemostatic, rheological, and haemodynamic activity in patients with rheumatoid arthritis (RA) in comparison with patients with osteoarthritis (OA).

METHODS

21 patients with RA and 10 with OA underwent a brief mental stress task while standing. Inflammatory, haemostatic, rheological, and haemodynamic variables were measured at baseline, during the task, and at recovery.

RESULTS

At baseline, erythrocyte sedimentation rate and fibrinogen were higher in RA than OA. White blood cell count, fibrinogen, blood pressure, and pulse rate increased, whereas prothrombin time and plasma volume decreased during the task in both patient groups. The stress task increased C reactive protein (CRP) only in patients with RA, and more specifically in those patients with RA with high disease activity.

CONCLUSIONS

The increase in the inflammatory marker CRP, which was specific to patients with RA, combined with the haemostatic, rheological, and haemodynamic reactions to the stress task, over and above the already high baseline levels, could underlie the increased risk for myocardial infarction in this vulnerable patient group.

C-reactive protein and cardiovascular disease: new insights from an old molecule

The classical acute-phase protein, C-reactive protein (CRP), is an exquisitely sensitive systemic marker of disease with broad clinical utility for monitoring and differential diagnosis. Inflammation, the key regulator of CRP synthesis, plays a pivotal role in atherothrombotic cardiovascular disease. There is a powerful predictive association between raised serum CRP values and the outcome of acute coronary syndromes, and, remarkably, between even modestly increased CRP production and future atherothrombotic events in otherwise healthy individuals. Baseline CRP values also reflect metabolic states associated with atherothrombotic events. The presence of CRP within most atherosclerotic plaques and all acute myocardial infarction lesions, coupled with binding of CRP to lipoproteins and its capacity for pro-inflammatory complement activation, suggests that CRP may contribute to the pathogenesis and complications of cardiovascular disease. We review the biological properties of CRP, the association between CRP and cardiovascular disease, and the possibility that CRP may be a novel therapeutic target.

A plasminogen-like protein selectively degrades stearoyl-CoA desaturase in liver microsomes

Stearoyl-CoA desaturase (SCD) is an integral membrane protein of the endoplasmic reticulum that is rapidly and selectively degraded when isolated liver microsomes are incubated at 37 degrees C. We previously reported the purification of a 90-kDa microsomal protein with SCD protease activity and characterized the inhibitor sensitivity of the protease. Here we show that the 90-kDa protein is a microsomal form of plasminogen (Pg) and that the purified SCD protease contains a spectrum of plasmin-like derivatives. The 90-kDa protein was identified as Pg by mass spectrometry of its tryptic peptides. The purified SCD protease reacted with Pg antibody, and immunoblotting demonstrated enrichment of Pg by the purification procedure established for the SCD protease. Analysis of microsomes by zymography demonstrated a single band of proteolytic activity at 70-kDa corresponding to the mobility of Pg in nonreduced polyacrylamide gels. When microsomes were incubated at 37 degrees C prior to zymography, an intense band of proteolytic activity developed at 30-kDa. The purified SCD protease displayed a spectrum of proteolytic bands ranging from 70 to 30 kDa. Degradation of SCD by the purified protease and by microsomes was inhibited by bdellin, a plasmin inhibitor from the medicinal leech Hirudo medicinalis. To explore the role of Pg in the degradation of SCD in vivo, we examined SCD expression and degradation in microsomes isolated from Pg-deficient (Pg-/-) mice. Compared with microsomes from wild-type littermate control mice, liver microsomes from Pg-/- mice had significantly higher levels of SCD. Degradation of SCD in microsomes from Pg-/- mice was markedly diminished, whereas liver microsomes from control mice showed rapid SCD degradation similar to that observed in rat liver microsomes. These findings indicate that SCD is degraded by a protease related to Pg and suggest that plasmin moonlights as an intracellular protease.

Analytical performance of a highly sensitive C-reactive protein-based immunoassay and the effects of laboratory variables on levels of protein in blood

C-reactive protein (CRP) is an acute-phase reactant whose levels increase in response to a variety of inflammatory stimuli. Elevated levels in serum are observed after trauma, tissue necrosis, infection, surgery, and myocardial infarction and are associated with an increased risk of cardiovascular disease. CRP levels are also elevated in noninflammatory states, such as obesity, sleep disturbances, depression, chronic fatigue, aging, and physical inactivity. In this study, the performance of a highly sensitive CRP enzyme immunoassay was evaluated, along with common laboratory variables (specimen type, processing time, and storage conditions) that may influence measured blood concentrations of CRP. The measurement range of the assay was from 0.4 to 50 microg/liter. Total imprecision (coefficient of variation) ranged from 8.1 to 11.4%. CRP levels obtained with the enzyme immunoassay were highly correlated with those obtained with an automated immunonephelometric assay. Comparable results were obtained for plasma (heparin and EDTA treated) and serum samples, and levels were unaffected by delays in sample processing and storage temperature. CRP levels were also unaffected by up to seven freeze-thaw cycles. The median CRP concentration in healthy adults was determined to be 0.94 mg/liter, with a 95% working reference interval of 0 to 6.9 mg/liter. In view of these data, we recommend that serial serum or plasma samples for CRP should be stored at 4 degrees C for short periods of time or at -70 degrees C for longer periods and tested within the same run to minimize interassay variability.

Crystal structure of human carboxylesterase 1 complexed with the Alzheimer's drug tacrine: from binding promiscuity to selective inhibition

Human carboxylesterase 1 (hCE1) is a broad-spectrum bioscavenger that plays important roles in narcotic metabolism, clinical prodrug activation, and the processing of fatty acid and cholesterol derivatives. We determined the 2.4 A crystal structure of hCE1 in complex with tacrine, the first drug approved for treating Alzheimer's disease, and compare this structure to the Torpedo californica acetylcholinesterase (AcChE)-tacrine complex. Tacrine binds in multiple orientations within the catalytic gorge of hCE1, while it stacks in the smaller AcChE active site between aromatic side chains. Our results show that hCE1's promiscuous action on distinct substrates is enhanced by its ability to interact with ligands in multiple orientations at once. Further, we use our structure to identify tacrine derivatives that act as low-micromolar inhibitors of hCE1 and may provide new avenues for treating narcotic abuse and cholesterol-related diseases.

The cloning and expression of a murine triacylglycerol hydrolase cDNA and the structure of its corresponding gene

A novel murine cDNA for triacylglycerol hydrolase (TGH), an enzyme that is involved in mobilization of triacylglycerol from storage pools in hepatocytes, has been cloned and expressed. The cDNA consists of 1962 bp with an open reading frame of 1695 bp that encodes a protein of 565 amino acids. Murine TGH is a member of the CES1A class of carboxylesterases and shows a significant degree of identity to other carboxylesterases from rat, monkey and human. Expression of the cDNA in McArdle RH7777 hepatoma cells showed a 3-fold increase in the hydrolysis of p-nitrophenyl laurate compared to vector-transfected cells. The highest expression of TGH was observed in the livers of mice, with lower expression in kidney, heart, adipose and intestinal (duodenum/jejunum) tissues. The murine gene that encodes TGH was cloned and exon-intron boundaries were determined. The gene spans approx. 35 kb and contains 14 exons. The results will permit future studies on the function of this gene via gene-targeting experiments and analysis of transcriptional regulation of the TGH gene.

Cloning and sequencing of a novel murine liver carboxylesterase cDNA

Carboxylesterases (EC 3.1.1.1) comprise a group of serine hydrolases with at least 20 genetically distinct loci in mice. Here, we describe differential display PCR-based cloning of a cDNA, encoding a novel murine carboxylesterase termed ES-x, which was expressed predominantly in liver but also in kidney and lung. The cDNA of ES-x spanned a 2249-bp sequence with an open reading frame encoding 565 amino acids, including an N-terminal hydrophobic signal peptide which directs the synthesis into microsomal lumen and a C-terminal HVEL consensus sequence for retaining the protein in the lumen of the endoplasmic reticulum. The predicted amino acid sequence of ES-x exhibited 75% identity with rat liver pI 6.1 esterase. We further demonstrate that feeding mice with diets containing cholestyramine or sodium cholate increases mRNA-expression of ES-x in liver 2.5- to 3-fold.