Specific Immunological Extraction Followed By Enzymatic Detection Research Articles

Effects of Juglone on Neutrophil Degranulation and Myeloperoxidase Activity Related to Equine Laminitis.

Experimental laminitis, characterized by a failure of the dermal–epidermal interface of the foot, can be induced in horses by the oral administration of a black walnut extract (BWE). In the early phase of this severe and painful disease, an activation of neutrophil occurs, with the release of myeloperoxidase (MPO), a pro-oxidant enzyme of neutrophils, in plasma, skin, and laminar tissue. Juglone, a naphthoquinone derivative endowed with redox properties, is found in walnuts and has been incriminated in this neutrophil activation. We report for the first time the inhibitory activity of juglone on the degranulation of neutrophils induced by cytochalasin B and formyl-methionyl-leucyl-phenylalanine as monitored by the MPO release (>90% inhibition for 25 and 50 μM). Moreover, it also acts on the peroxidase activity of MPO by interacting with the intermediate “π cation radical,” as evidenced by the classical and specific immunological extraction followed by enzymatic detection (SIEFED) assays. These results are confirmed by a docking study showing the perfect positioning of juglone in the MPO enzyme active site and its interaction with one of the amino acids (Arg-239) of MPO apoprotein. By chemiluminescence and electron paramagnetic resonance techniques, we demonstrated that juglone inhibited reactive oxygen species (ROS) and superoxide anion free radical produced from phorbol myristate acetate (PMA)-activated polymorphonuclear neutrophils (PMNs). These results indicate that juglone is not the trigger for equine laminitis, at least if we focus on the modulation of neutrophil activation.

Sevoflurane modulates the release of reactive oxygen species, myeloperoxidase, and elastase in human whole blood: Effects of different stimuli on neutrophil response to volatile anesthetic in vitro.

Volatile anesthetics have been shown to modulate polymorphonuclear neutrophil (PMN) functions. The aim of this study was to examine the impact of clinically relevant concentrations of sevoflurane (SEVO), a volatile anesthetic, on the release of reactive oxygen species (ROS), myeloperoxidase (MPO), and elastase (EL) from human activated PMNs. For this purpose, samples of whole blood were collected from healthy volunteers and exposed in vitro to 2.3% or 4.6% SEVO in air. To assess for a stimulus-dependent effect of the volatile anesthetic, PMNs were activated using different validated protocols. Artificial stimulation of neutrophils involved either a combination of cytochalasin B (CB) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) or phorbol 12-myristate 13-acetate (PMA). In addition, a combination of lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNF-α) was also tested as a natural activation mean of PMNs. The production of ROS by PMNs was assessed by L-012 chemiluminescence. Total MPO and EL released in supernatant were measured by enzyme-linked immunosorbent assay (ELISA). Furthermore, degranulation of the active fraction of MPO was also measured by specific immunological extraction followed by enzymatic detection (SIEFED). Overall, SEVO enhanced the release of ROS, MPO, and EL following artificial stimulation of PMNs but the volatile anesthetic inhibited the degranulation of active MPO and EL after neutrophil exposure to LPS and TNF-α. This study highlighted that the effect of SEVO on activated PMNs is dependent on the conditions of cell stimulation. These properties should be taken into consideration in future studies investigating immunomodulatory effects of volatile anesthetics.

Effect of honey on purified equine myeloperoxidase activity and superoxide radical production in activated Polymorphonuclear neutrophils

Three Algerian honey samples (nectar honey, mixed honey and honeydew honey) were analysed for their total phenolic content (TPC) using the Folin–Ciocalteu reagent and total flavonoid content (TFC) by the aluminium chloride method. The antioxidant activity was tested both against reactive oxygen species (ROS) produced by phorbol 12-myristate 13-acetate (PMA)-stimulated equine polymorphonuclear neutrophils (PMNs) and on purified equine myeloperoxidase (MPO) enzyme activity. The ROS production by stimulated PMNs was measured by lucigenin-enhanced chemiluminescence. Specific immunological extraction followed by enzymatic detection (SIEFED) was used to measure specifically the activity of equine MPO. Nectar honey, mixed honey and honeydew honey had TPCs of 59.52 ± 1.31, 68.36 ± 1.20 and 122.76 ± 4.20 mg gallic acid equivalents (GAE)/100 g honey, respectively (mean ± SD). As for the TPC, the highest TFC was observed for honeydew honey [20.55 ± 0.72 mg catechine equivalents (CE)/100 mg honey], followed by mixed honey (7.47 ± 0.07 CE/100 mg honey) and nectar honey (4.80 ± 0.08 CE/100 mg honey). All the tested honeys displayed a dose-dependent inhibitory effect on the oxidant activities of PMNs. By the SIEFED technique, it was shown that most of the honeys interact directly with MPO: the light honeys (nectar honey and mixed honey) were inhibitors of MPO activity, while the dark honey had less inhibiting effect and even behaved as an enhancer of MPO activity at high concentrations.

An immunological method to combine the measurement of active and total myeloperoxidase on the same biological fluid, and its application in finding inhibitors which interact directly with the enzyme

Myeloperoxidase (MPO) is a pro-oxidant enzyme involved in inflammation, and the measurement of its activity in biological samples has emerged essential for laboratory and clinical investigations. We will describe a new method which combines the SIEFED (specific immunological extraction followed by enzymatic detection) and ELISA (ELISAcb) techniques to measure the active and total amounts of MPO on the same human sample and with the same calibration curve, as well as to define an accurate ratio between both the active and total forms of the enzyme.The SIEFED/ELISAcb method consists of the MPO extraction from aqueous or biological samples by immobilized anti-MPO antibodies coated onto microplate wells. After a washing step to eliminate unbound material, the activity of MPO is measured in situ by adding a reaction solution (SIEFED). Following aspiration of the reaction solution, a secondary anti-MPO antibody is added into the wells and the ELISAcb test is carried out in order to measure the total MPO content.To validate the combined method, a comparison was made with SIEFED and ELISA experiments performed separately on plasma samples isolated from human whole blood, after a neutrophil stimulation.The SIEFED/ELISAcb provides a suitable tool for the measurement of specific MPO activity in biological fluids and for the estimation of the inhibitory potential of a fluid. The method can also be used as a pharmacological tool to make the distinction between a catalytic inhibitor, which binds to MPO and inhibits its activity, and a steric inhibitor, which hinders the enzyme and prevents its immunodetection.

Effects of isoflurane and sevoflurane on the neutrophil myeloperoxidase system of horses

Volatile anaesthestics have shown to modulate the oxidative response of polymorphonuclear neutrophils (PMNs). We investigated the effects of isoflurane and sevoflurane on the degranulation of total and active myeloperoxidase (MPO) from horse PMNs and their direct interaction with MPO activity. Whole blood from horse was incubated in 1 and 2 minimal alveolar concentrations (MAC) of isoflurane or sevoflurane for 1h and PMNs were stimulated with cytochalasin B (CB) plus N-formyl-méthionyl-leucyl-phenylalanine (fMLP). After stimulation, the plasma was collected to measure total and active MPO by enzyme-linked immunosorbent assay (ELISA) and specific immunological extraction followed by enzymatic detection (SIEFED) respectively. The effects of 1 and 2 MAC of isoflurane and sevoflurane on the peroxidase and chlorination activity of pure MPO were assessed by fluorescence using Amplex red and 3′-(p-aminophenyl) fluorescein (APF) respectively and in parallel with a SIEFED assay to estimate the potential interaction of the anaesthetics with the enzyme. Although isoflurane and sevoflurane had inconsistent effects on total MPO release, both volatile agents reduced active MPO release and showed a direct inhibition on the peroxidase and the chlorination activity of the enzyme. A persistent interaction between MPO and anaesthetics was evidenced with isoflurane but not with sevoflurane.

Sevoflurane inhibits equine myeloperoxidase release and activity in vitro

ObjectiveTo investigate the effects of the volatile anaesthetic sevoflurane on the release of total and active myeloperoxidase (MPO) by non-stimulated and stimulated polymorphonuclear neutrophils (PMNs) in whole blood from healthy horses. Study designIn vitro experimental study. AnimalsAdult healthy horses. MethodsSamples of whole venous blood were collected and incubated in air or in air plus 2.3% or 4.6% sevoflurane for 1 hour. PMNs were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP), with a combination of cytochalasin B (CB) and fMLP or with phorbol myristate acetate (PMA). Total and active MPO contents released by PMNs in blood were measured by enzyme-linked immunosorbent assay (ELISA) and specific immunological extraction followed by enzymatic detection (SIEFED) respectively. Additional experiments were performed to assess the effect of sevoflurane on the peroxidase and chlorination cycles of purified equine MPO using Amplex Red and 3’-(p-aminophenyl) fluorescein as fluorogenic substrates respectively. ResultsAs compared with air alone, 1 hour exposure of whole blood to 4.6% sevoflurane in air significantly inhibited the release of total and active MPO by unstimulated and both fMLP- and CB + fMLP-stimulated PMNs but not by PMA-stimulated PMNs. Although 2.3% sevoflurane had no effect on total MPO release by unstimulated and stimulated PMNs, it significantly reduced the release of active MPO by unstimulated and fMLP-stimulated PMNs. Additionally, sevoflurane reversibly inhibited the activity of MPO, especially the peroxidase cycle of the enzyme. Conclusions and clinical relevanceAlthough our experimental study was not designed to assess the effects of sevoflurane in vivo, this inhibition of MPO release and activity may have relevance for anaesthetized horses and deserves further studies to examine the clinical importance of these findings.

Equine myeloperoxidase: A novel biomarker in synovial fluid for the diagnosis of infection

Equine joint infection is a life-threatening disorder, and confirmation of the diagnosis can be difficult. Synovial fluid biomarkers may assist the discrimination between infectious and noninfectious joint disease. This study investigates whether the immunological detection of total and enzymatically active myeloperoxidase (MPO) assists the diagnosis of joint infection in horses. The following 4 sample groups were included: healthy; osteochondritis dissecans (OCD); traumatic synovitis; and culture-confirmed infected joints. Synovial fluid was analysed for total MPO by a horse-specific sandwich enzyme-linked immunosorbent assay (ELISA) and for active MPO using the specific immunological extraction followed by enzymatic detection (SIEFED) technique. Western blot analysis was performed to confirm the antibody specificity. Synovial fluid from infected joints contained significantly more total and active MPO than samples from healthy joints, joints affected by OCD and joints with traumatic synovitis. Cut-off values were set at 5000 and 350 ng/ml for total and active MPO, respectively, with fair sensitivity, specificity, positive and negative predictive values and likelihood ratios for infection. Correlation coefficients were reported between the total as well as the active MPO levels and the routine synovial fluid parameters, i.e. the white blood cell count, the neutrophil count and the total protein level. No correlation was observed between MPO and either the age of the horse or the joint affected. Western blotting confirmed the antibody specificity for equine MPO. Synovial fluid MPO was identified as a very promising biomarker to augment the discrimination of infectious vs. noninfectious joint disease in horses. Both ELISA and SIEFED techniques can be used for its specific and rapid detection. The analysis of synovial fluid MPO can be used as a complementary test to aid in the discrimination between infectious and noninfectious joint disease, especially when the white blood cell counts and the total protein level are inconclusive.

Polyphenol content and modulatory activities of some tropical dietary plant extracts on the oxidant activities of neutrophils and myeloperoxidase.

Young leaves of Manihot esculenta Crantz (Euphorbiaceae), Abelmoschus esculentus (Malvaceae), Hibiscus acetosella (Malvaceae) and Pteridium aquilinum (Dennstaedtiaceae) are currently consumed as green vegetables by peoples in sub-Saharan Africa, Latin America, Asia and their migrants living in Western Europe. Sub-Saharan peoples use Manihot, Abelmoschus and Hibiscus also in the folk medicine to alleviate fever and pain, in the treatment of conjunctivitis, rheumatism, hemorrhoid, abscesses, ... The present study investigates the effects of aqueous extracts of those plants on the production of reactive oxygen species (ROS) and the release of myeloperoxidase (MPO) by equine neutrophils activated with phorbol 12-myristate 13-acetate (PMA). The ROS production was measured by lucigenin-enhanced chemiluminescence (CL), and the release of total MPO by an ELISA method. The study also investigates the effect of the extracts on the activity of MPO by studying its nitration activity on tyrosine and by using a new technique called SIEFED (Specific Immunological Extraction Followed by Enzymatic Detection) that allows studying the direct interaction of compounds with the enzyme. In all experiments, the aqueous extracts of the plants developed concentration-dependent inhibitory effects. A moderate heat treatment did not significantly modify the inhibitory capacity of the extracts in comparison to not heated ones. Total polyphenol and flavonoid contents were determined with an HPLC-UV/DAD analysis and a spectroscopic method using Folin-Ciocalteu reagent. Some polyphenols with well-known antioxidant activities (caffeic acid, chlorogenic acid, hyperoside, rosmarinic acid and rutin) were found in the extracts and may partly explain the inhibitory activities observed. The role of those dietary and medicinal plants in the treatment of ROS-dependent inflammatory diseases could have new considerations for health.

Clinical significance of active myeloperoxidase in carotid atherosclerotic plaques

Assessment of vulnerable carotid artery plaques is a majorunresolved issue. Patients presenting unstable angina have evidenceof unstable carotid artery plaque [1] suggesting systemic vascularvulnerability [2].Neutrophil myeloperoxidase (MPO) is a powerful producer ofoxidant molecule [3]. MPO level is higher in patients with coronaryartery disease and in patients undergoing percutaneous coronaryintervention for unstable coronary syndrome compared to stablepatients [4,5], carrying predictive value of adverse outcome [6].MPO levels measured by immunological methods (ELISA or RIA)quantify the total concentration of the enzyme without providing itsenzymatic activity [7]. MPO activity is currently measured byspectrophotometry or fluorimetry [8,9]. However, these methodsare not applicable to complex biological samples such as humantissue. We recently developed a new technique, the SIEFED (SpecificImmunological Extraction Followed by Enzymatic Detection) tomeasure the activity of the enzyme in biological fluids and developedit for equine MPO and thereafter for human use [10,11]. The aims ofthis study were to assess the presence of the active form of MPO inhuman carotid atherosclerotic lesions, to compare active MPO withtotal MPO, and to assess the potential significance of total and/oractive MPO by comparing their levels in symptomatic and asymp-tomtic patients.We prospectively collected 90 carotid artery plaque specimensobtained by surgical thrombo-endarteriectomy according to theNASCET criteria [12].Carotid atherosclerotic plaques were surgically collected andrinsed with 0.9% NaCl solution before freezing at −20 °C. Methodol-ogy and validation of SIEFED technique as well as ELISA method havebeen previously described [7,10,11]. The activity of the total MPOexpressed in ng/mL was reported to the total protein concentration(mg/mL) measured in the supernatant of carotid extracts using the

Modulatory activities of Agelanthus dodoneifolius (Loranthaceae) extracts on stimulated equine neutrophils and myeloperoxidase activity

Agelanthus dodoneifolius DC Danser (Loranthaceae) is used for the treatment of various diseases including asthma. The aqueous and hydroalcoholic extracts have been reported to have anti-inflammatory, spasmolytic and bronchorelaxant activities. The present study investigates the effects of the aqueous decoction and the diethyl ether, ethyl acetate and butanolic fractions of Agelanthus dodoneifolius DC Danser (Loranthaceae) on reactive oxygen species (ROS) production and myeloperoxidase (MPO) release by phorbol 12-myristate 13-acetate (PMA)-stimulated equine neutrophils and on purified equine MPO activity. ROS production and MPO release by the PMA-stimulated neutrophils were measured by the lucigenin-enhanced chemiluminescence and ELISA assays, respectively. Specific immunological extraction followed by enzymatic detection (SIEFED) was used to specifically measure the equine MPO activity. Identification and quantification of the individual and total phenolic and flavonoid compounds were performed using UPLC-MS/MS equipment and colorimetric methods involving Folin-Ciocalteu and AlCl₃, respectively. All the tested extracts displayed dose-dependent inhibitory effects on the oxidant activities of neutrophils; a stronger effect was observed with the organic fractions than the aqueous decoction. These findings could be correlated with a high content of phenolic and flavonoid compounds. The results confirm the previously shown anti-inflammatory effect of Agelanthus dodoneifolius and its potential use for the treatment of neutrophil-dependent inflammatory diseases.

A new easy method for specific measurement of active myeloperoxidase in human biological fluids and tissue extracts

The SIEFED (“Specific Immunological Extraction Followed by Enzymatic Detection”) method already developed for the specific detection of the activity of equine myeloperoxidase (MPO) was adapted for the specific measurement of active human MPO in biological fluids or tissue extracts. The method consists of the extraction of MPO from aqueous solutions by immobilized anti-MPO antibodies followed by a washing (to eliminate the extraction medium and the biological fluid with their possible interfering molecules) and the measurement of the activity of MPO with a detection system containing a fluorogenic substrate, H 2O 2 and nitrite ions as reaction enhancer. The SIEFED was applied to study active MPO in human biological fluids (plasma, bronchoalveolar lavage fluid and supernatant from carotids extracts). The SIEFED for human MPO has a sensitivity limit of 0.080 mU/mL and showed good precision with intra- and inter-assay coefficients of variation below 10 and 20% respectively within a broad range of MPO activities establish from 0.156 to 473 mU/mL. The SIEFED for human MPO will be useful for the specific detection of active MPO in complex fluids and can be complementary to an ELISA to determine an active/total MPO ratio in healthy volunteers and patients especially in case of chronic or acute inflammatory diseases.

Resveratrol Inhibits the Activity of Equine Neutrophil Myeloperoxidase by a Direct Interaction with the Enzyme

Resveratrol is a polyphenolic antioxidant present in beverage and food known for its multiple protective effects. We report the inhibitory effects of resveratrol on equine myeloperoxidase (MPO), a hemic peroxidase present in the granules of the neutrophils involved in the inflammatory response. Resveratrol inhibited the production of reactive oxygen species (ROS) by stimulated equine neutrophils by acting as a direct scavenger of the ROS released by the cells but did not modify the degranulation of the stimulated neutrophils as the amounts of released MPO were unchanged. Resveratrol strongly inhibited the chlorination, oxidation, and nitration activities of MPO in a dose-dependent manner. By an original technique of specific immunological extraction followed by enzymatic detection (SIEFED), we demonstrated that resveratrol inhibited the peroxidasic activity of the MPO measured by a direct interaction such as the fixation of resveratrol on the enzyme. The observation of a decrease of the accumulation of compound II suggested that resveratrol acts as an electron donor for MPO reduction.

A Specific Method for Measurement of Equine Active Myeloperoxidase in Biological Samples and in in Vitro Tests

An original method called SIEFED (specific immunological extraction followed by enzymatic detection) was developed for the specific detection of the activity of equine myeloperoxidase (MPO). The method consists of the extraction of MPO from aqueous solutions by immobilized anti-MPO antibodies followed by washing (to eliminate proteins and interfering molecules) and measurement of MPO activity using a detection system containing a fluorogenic substrate, hydrogen peroxide, and nitrite as reaction enhancer. The SIEFED technique was applied to study active MPO in horse biological fluids and the effects of 2 polyphenolic molecules, curcumin and resveratrol, on MPO activity. The detection limit of the SIEFED was 0.23 mU/ml. The SIEFED exhibited good precision with intra-assay and interassay coefficients of variation below 10% and 20%, respectively, for MPO activities ranging from 0.25 to 6.4 mU/ml. The activity of MPO was generally higher than 1 mU/ml in the fluids collected from horses with inflammatory diseases. Curcumin and resveratrol exerted a dose-dependent inhibition on MPO activity and, as they were removed before the enzymatic detection of MPO, the results suggest a direct drug-nzyme interaction or an enzyme structure modification by the drug. The SIEFED is a new tool that would be useful for specific detection of active MPO in complex media and for selection of MPO activity modulators.