P. Van Antwerpen

The Reactions of Oxicam and Sulfoanilide Non Steroidal Anti-Inflammatory Drugs with Hypochlorous Acid: Determination of the Rate Constants with an Assay Based on the Competition with Para-aminobenzoic Acid Chlorination and Identification of Some Oxidation Products

Hypochlorous acid (HOCl) is an oxygen-derived species involved in physiological processes related to the defence of the organism that may cause adverse effects when its production is insufficiently controlled. In order to examine its reactivity with potential scavenging molecules from the non steroidal anti-inflammatory drugs (NSAIDs) family, a competition assay based on para-aminobenzoic acid (PABA) chlorination was developed. The original optimised in vitro fluorimetric procedure offered the possibility to determine rate constants (ks) for the reaction with HOCl in physiologically relevant conditions. The specificity of the system was improved by a liquid chromatography (LC) which allows the separation of the drugs and their oxidation products. After determination of the rate constant for PABA chlorination by HOCl (mean±SD in M-1 s-1: 4.3±0.3×103), the applied mathematical model for a chemical competition permits to obtain linear curves from competition studies between several NSAIDs and PABA. Their slopes provided the following rate constants for the different studied drugs: tenoxicam: 4.0±0.7×103, piroxicam: 3.6±0.7×103, lornoxicam: 4.3±0.7×103, meloxicam: 1.7±0.3×104, nimesulide: 2.3±0.6×102. Meloxicam therefore reacted significantly faster than the other oxicams and nimesulide, which is the weakest scavenger of the studied series. The identification of some of the oxidation products by NMR or MS permitted to explore the reaction mechanism and to examine some aspects of the structure/activity relationships for the molecules of the same chemical family.

Intriguing location of myeloperoxidase in the prostate: A preliminary immunohistochemical study

Myeloperoxidase (MPO) is a member of the peroxidase‐cyclooxygenase superfamily, which is secreted from stimulated leucocytes at inflammatory sites. It is well known that MPO catalyses oxidation reactions via the release of reactive halogenating and nitrating species and thus induces tissue damage. Several studies have already implicated MPO in the development of neoplasia. Chronic or recurrent prostatic inflammation has long been recognized as having the potential to initiate and promote the development of prostate cancer. The objective was to investigate whether MPO is present in the prostate.

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

Abstract 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.

Rational drug design applied to myeloperoxidase inhibition.

Abstract Rational drug design is a general approach using protein-structure technique in which the discovery of a ligand can be driven either by chance, screening, or rational theory. Myeloperoxidase (MPO) was rapidly identified as a therapeutical target because of its involvement in chronic inflammatory syndromes. In this context, the research of MPO inhibitors was intensified and development of new chemical entities was rationally driven by the research of ligands that enter into the MPO catalytic pocket. Actually, as soon as crystallography data of MPO have become available and its structure was virtually designed, the rational drug design has been applied to this peroxidase. Pharmaceutical industries and academic laboratories apply rational drug design on MPO by either optimizing known inhibitors or searching new molecules by high-throughput virtual screening. By these ways, they were able to find efficient MPO inhibitors and understand their interactions with the enzyme. During this quest of MPO inhibition, it appears that Glu268 is a crucial residue in order to optimize ligand–target interaction. This amino acid should be carefully considered by medicinal chemist when they design inhibitors interfering with MPO activity.AbstractRational drug design is a general approach using protein-structure technique in which the discovery of a ligand can be driven either by chance, screening, or rational theory. Myeloperoxidase (MPO) was rapidly identified as a therapeutical target because of its involvement in chronic inflammatory syndromes. In this context, the research of MPO inhibitors was intensified and development of new chemical entities was rationally driven by the research of ligands that enter into the MPO catalytic pocket. Actually, as soon as crystallography data of MPO have become available and its structure was virtually designed, the rational drug design has been applied to this peroxidase. Pharmaceutical industries and academic laboratories apply rational drug design on MPO by either optimizing known inhibitors or searching new molecules by high-throughput virtual screening. By these ways, they were able to find efficient MPO inhibitors and understand their interactions with the enzyme. During this quest of MPO inhib...

Myeloperoxidase and Prostate volume: A preliminary study

OBJECTIVES Oxidative stress is associated with the development of BPH and might be modulated by several factors. Myeloperoxidase (MPO) has recently been observed in prostate tissue. Our goal was to investigate the correlation between MPO and the prostate volume. MATERIAL AND METHODS Hundred and twenty-one patients (48-70 years) with a filled IPSS were prospectively included. Blood sampling (PSA, testosterone, Angiotensin II (AngII), MPO, Mox-LDL) and transrectal ultrasound of the prostate were performed with total volume (TV) and transitional zone volume (TZ) measurements. For correlation, univariate analyses were depicted by Pearsons coefficient. Multilinear regression analysis used a stepwise backward selection of the explicative variables. RESULTS In multivariate analysis, the TV was positively correlated to the combination of age and Ang II but negatively to MPO specific activity (Std Coef=-0.272, P=0.004). Significant correlations were confirmed between TZ, age and MPO specific activity but not with Ang II. A negative correlation between TZ and MPO specific activity was also observed (Std Coef=-0.21, P=0.016). No correlation was found with Mox-LDL. CONCLUSIONS Negative correlation between MPO and prostate volume was observed but careful interpretations may be endorsed and longitudinal study is necessary. It seems relevant to focus on the potential contribution of MPO in the development of prostatic diseases as this enzyme can also promote DNA oxidation. LEVEL OF EVIDENCE 4.

Special issue on “Peroxidase”

the authors compare ceruloplasmin interaction with both peroxidases. Thiocyanate is a pseudohalogenous anion, which is a substrate for peroxidases such as MPO, EPO, and LPO. Hypothiocyanous acid, which is the product of the reaction of thiocyanate and peroxidases, specifi cally oxidizes thiol (Cys) residues of proteins, resulting in the formation of reversible thiol oxidation products including sulfenic acids. These products can be reduced back to Cys by antioxidant enzyme systems. In the review entitled “ Biochemical mechanisms and therapeutic potential of thiocyanate in human health, ” Chandler and Day explore the oxidation of thiocyanate by Chordata peroxidases and underline the potential role of thiocyanate as therapeutical agent that could modulate peroxidase ’ s deleterious activity [5]. Interestingly, Morgan et al. demonstrate that the thiocyanate supplementation decreases the atherosclerotic plaque development in human MPO transgenic mice [6]. These authors emphasize the specifi c reversible oxidative modifi cations generated by hypothiocyanous acid compared with those of hypochlorous acid also produced by MPO, which produces irreversible oxidation products. Konradi et al. explore the role of reactive oxygen species (ROS) in vascular dysfunction [7]. This condition is generally admitted as an initial step in the development of heart failure and leukocyte peroxidases seem to be one of the promoting factors. The authors propose new therapeutical approaches that could include peroxidases as interesting drug targets. There is signifi cant evidence that peroxidases contribute to the production of ROS in vivo. In this context, the review of Carroll et al. entitled “ Reaction of low molecular mass organoselenium compounds (and their sulfur analogues) with infl ammation-associated oxidants ” provides a comprehensive overview of the role of selenium as an antioxidant [8]. Selenium has similar chemical properties to sulfur but in general, organoselenium compounds have a higher reactivity toward ROS. This exhaustive review explores the benefi ts of such compounds in the struggle against ROS, notably those produced by peroxidases. Special issue on “ Peroxidase ”