Inhibition of the myeloperoxidase-H2O2-Cl- system of neutrophils by indomethacin and other non-steroidal anti-inflammatory drugs

Marrubiin Inhibits Peritoneal Inflammatory Response Induced by Carrageenan Application in C57 Mice

Marrubiin is a diterpene with a long history of a wide range of biological activities. In this study, the anti-inflammatory effects of marrubiin were investigated using several in vitro and in vivo assays. Marrubiin inhibited carrageenan-induced peritoneal inflammation by preventing inflammatory cell infiltration and peritoneal mast cell degranulation. The anti-inflammatory activity was further demonstrated by monitoring a set of biochemical parameters, showing that the peritoneal fluid of animals treated with marrubiin had lower levels of proteins and lower myeloperoxidase activity compared with the fluid of animals that were not treated. Marrubiin exerted the most pronounced cytotoxic activity towards peripheral mononuclear cells, being the main contributors to peritoneal inflammation. Additionally, a moderate lipoxygenase inhibition activity of marrubiin was observed.

The healing bitterness of Gentiana lutea L., phytochemistry and biological activities: A systematic review

Over many years, natural products have been a source of healing agents and have exhibited beneficial uses for treating human diseases. The Gentiana genus is the biggest genus in the Gentianaceae, with over 400 species distributed mainly in alpine zones of temperate countries around the world. Plants in the Gentiana genus have historically been used to treat a wide range of diseases. Still, only in the last years has particular attention been paid to the biological activities of Gentiana lutea Linn., also known as yellow Gentian or bitterwort. Several in vitro/vivo investigations and human interventional trials have demonstrated the promising activity of G. lutea extracts against oxidative stress, microbial infections, inflammation, obesity, atherosclerosis, etc.. A systematic approach was performed using Pubmed and Scopus databases to update G. lutea chemistry and activity. Specifically, this systematic review synthesized the major specialized bitter metabolites and the biological activity data obtained from different cell lines, animal models, and human interventional trials. This review aims to the exaltation of G. lutea as a source of bioactive compounds that can prevent and treat several human illnesses.

Myeloperoxidase Inhibitory and Antioxidant Activities of (E)-2-Hydroxy-α-aminocinnamic Acids Obtained through Microwave-Assisted Synthesis

Myeloperoxidase (MPO) is an enzyme present in human neutrophils, whose main role is to provide defenses against invading pathogens. However, highly reactive oxygen species (ROS), such as HOCl, are generated from MPO activity, leading to chronic diseases. Herein, we report the microwave-assisted synthesis of a new series of stable (E)-(2-hydroxy)-α-aminocinnamic acids, in good yields, which are structurally analogous to the natural products (Z)-2-hydroxycinnamic acids. The radical scavenging activity (RSA), MPO inhibitory activity and cytotoxicity of the reported compounds were evaluated. The hydroxy derivatives showed the most potent RSA, reducing the presence of DPPH and ABTS radicals by 77% at 0.32 mM and 100% at 0.04 mM, respectively. Their mechanism of action was modeled with BDE_OH, IP and ΔE_H-L theoretical calculations at the B3LYP/6 − 31 + G(d,p) level. Compounds showed in vitro inhibitory activity of MPO with IC₅₀ values comparable to indomethacin and 5-ASA, but cytotoxicities below 15% at 100–200 µM. Docking calculations revealed that they reach the amino acid residues present in the distal cavity of the MPO active site, where both the amino and carboxylic acid groups of the α-aminopropenoic acid arm are structural requirements for anchoring. (E)-2-hydroxy-α-aminocinnamic acids have been synthesized for the first time with a reliable method and their antioxidant properties demonstrated.

The effect of indomethacin, myeloperoxidase, and certain steroid hormones on bactericidal activity: an ex vivo and in vivo experimental study

BACKGROUND

The role of myeloperoxidase (MPO) is essential in the killing of phagocytosed bacteria. Certain steroid hormones increase MPO plasma concentration. Our aim was to test the effect of MPO, its inhibitor indomethacin, and certain steroid hormones on bactericidal activity.

METHODS

Human polymorphonuclear leukocytes (PMN) were incubated with opsonised Escherichia coli and either MPO, indomethacin, estradiol, or hydrocortisone. Intracellular killing capacity was evaluated with UV microscopy after treatment with fluorescent dye. Next, an in vivo experiment was performed with nine groups of rats: in the first phase of the study indomethacin treatment and Pasteurella multocida infection (Ii), indomethacin treatment without infection (I0), untreated control with infection (Mi) and untreated control without infection (M0); in the second phase of the study rats with infection and testosterone treatment (NT), castration, infection and testosterone treatment (CT), castration, infection and estradiol treatment (CE), non-castrated infected control (N0), and castrated infected control (C0). After treatment bacteria were reisolated from the liver and heart blood on agar plates, and laboratory parameters were analyzed. For the comparison of laboratory results ANOVA or Kruskal-Wallis test and LSD post hoc test was used.

RESULTS

Indomethacin did not have a remarkable effect on the bacterial killing of PMNs, while the other compounds increased bacterial killing to various degrees. In the animal model indomethacin and infection caused a poor clinical state, a great number of reisolated bacteria, elevated white blood cell (WBC) count, decreased C-reactive protein (CRP) and serum albumin levels. Testosterone treatment resulted in less bacterial colony numbers in group NT, but not in group CT compared to respective controls (N0, C0). Estradiol treatment (CE) decreased colony numbers compared to control (C0). Hormone administration resulted in lower WBC counts, and in group CE, a decreased CRP.

CONCLUSIONS

MPO, estradiol, and hydrocortisone improve bacterial killing activity of PMNs. Indomethacin treatment and castration weaken immune responses and clinical state of infected rats, while testosterone and estradiol have a beneficial effect.

Influence of organophosphorus pesticides on peroxidase and chlorination activity of human myeloperoxidase

Inhibitory effects of five organophosphorus pesticides (diazinon, malathion, chlorpyrifos, azinphos-methyl and phorate) and their oxo-analogs on human myeloperoxidase (MPO) activity were investigated. While inspecting separately peroxidase and chlorination activity, it was observed that investigated OPs affect peroxidase activity, but not chlorination activity. Among investigated pesticides, malathion and malaoxon have showed the highest power to inhibit MPO peroxidase activity with IC50 values of the order of 3×10(-7) and 5×10(-9) M, respectively. It was proposed that inhibition trend is rendered by molecular structure which invokes steric hindrance for OPs interaction with MPO active center responsible for peroxidase activity. In addition, it was concluded that physiological function of MPO is not affected by any of the investigated OPs.

α-Lipoic acid has anti-inflammatory and anti-oxidative properties: an experimental study in rats with carrageenan-induced acute and cotton pellet-induced chronic inflammations

α-Lipoic acid (ALA) has been termed the 'ideal' antioxidant, a readily absorbed and bioavailable compound capable of scavenging a number of free radicals, and it has been used for treating diseases in which oxidative stress plays a major role. The present study was designed to gain a better understanding for the positive effects of ALA on the models of acute and chronic inflammation in rats, and also determine its anti-oxidative potency. In an acute model, three doses of ALA (50, 100 and 200 mg/kg) and one dose of indomethacin (25 mg/kg) or diclofenac (25 mg/kg) were administered to rats by oral administration. The paw volumes of the animals were calculated plethysmometrically, and 0·1 ml of 1 % carrageenan (CAR) was injected into the hind paw of each animal 1 h after oral drug administration. The change in paw volume was detected as five replicates every 60 min by plethysmometry. In particular, we investigated the activities of catalase, superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), inducible NO synthase (iNOS) and myeloperoxidase (MPx), and the amounts of lipid peroxidation (LPO) or total GSH in the paw tissues of CAR-injected rats. We showed that ALA exhibited anti-inflammatory effects on both acute and chronic inflammations, and a strongly anti-oxidative potency on linoleic acid oxidation. Moreover, the administration of CAR induced oedema in the paws. ALA significantly inhibited the ability of CAR to induce: (1) the degree of acute inflammation, (2) the rise in MPx activity, (3) the increases of GST and iNOS activities and the amount of LPO and (4) the decreases of GPx, GR and SOD activities and the amount of GSH. In conclusion, these results suggest that the anti-inflammatory properties of ALA, which has a strong anti-oxidative potency, could be related to its positive effects on the antioxidant system in a variety of tissues in rats.

Evaluation of anti-inflammatory and antioxidant activities of Peltigera rufescens lichen species in acute and chronic inflammation models

The anti-inflammatory effects of the methanol extract of the lichen species Peltigera rufescens (Weis.) Humb (MEPR) (Peltigeraceae) on acute (carrageenan-induced) and chronic (cotton pellet granule) phases of inflammation were investigated. The MEPR was capable of reducing carrageenan-induced inflammation and showed a potent antiproliferative effect (63.5%) in the chronic inflammation model. Inflammation is related to neutrophil infiltration and the production of neutrophil-derived mediators and free radicals. The MEPR reduced the myeloperoxidase and inducible nitric oxide synthase (NOS) activities, which were increased by carrageenan injection. Carrageenan injection also increased the lipid peroxidation (LPO) as compared with untreated paw tissues. The administration of MEPR, diclofenac, and indomethacin reduced the LPO in paw tissues through amelioration of the antioxidant defense systems. Neutrophil infiltration and neutrophil-derived free radicals in tissues therefore appeared to play an important role in the inflammation process induced by carrageenan. The anti-inflammatory effect of MEPR could be attributed to its reducing effect on the neutrophil-derived free radicals and its ameliorating effect on the antioxidant defense systems.

Lactoperoxidase catalyzes in vitro activation of acrylonitrile to cyanide

Acrylonitrile (ACN) is a widely used industrial chemical. Although it is a well reported animal carcinogen, its current designation to humans is "possibly carcinogenic". The present study aimed at investigating the ability of LPO enzyme system to oxidize ACN to cyanide (CN(-)) in vitro. Detection of CN(-) served as a marker for the possible generation of free radical intermediates implicated in ACN induced toxicity in the activation process. Optimum conditions for the oxidation of ACN to CN(-) were characterized with respect to pH, temperature and time of incubation as well as ACN, LPO and H(2)O(2) concentrations in incubation mixtures. Maximum reaction velocity (V(max)) and Michaelis-Menten constant (K(m)) were assessed. Addition of nitrite (NO(2)(-)) salts to the reaction mixtures significantly enhanced the rate of the reaction. Free radical scavengers (quercetin and trolox C), LPO enzyme inhibitor (resorcinol) and competitors for LPO binding (sodium azide and indomethacin) were found to reduce the rate of CN(-) production. Inclusion of the sulfhydryl compounds glutathione (GSH), NAC (N-acetylcysteine), D-penicillamine or L-cysteine enhanced the rate of ACN oxidation. The present results demonstrate the ability of LPO enzyme system to oxidize ACN to CN(-) and provide insight for the elucidation of ACN chronic toxicity.

Oxidation of Quercetin by Myeloperoxidase

Study of effect of myeloperoxidase on quercetin at pH 6.0 indicated quercetin oxidation via the formation of the oxidation product. The stability of quercetin and oxidation product was investigated as a function of time by using spectrophotometric and HPLC techniques. The apparent pseudo first-order rate constants were calculated and discussed.

Flavonoids as substrates and inhibitors of myeloperoxidase: molecular actions of aglycone and metabolites

Myeloperoxidase (MPO), secreted by activated neutrophils and macrophages at the site of inflammation, may be implicated in the oxidation of protein/lipoprotein during the development of cardiovascular diseases. Flavonoids have been suggested to act as antioxidative and anti-inflammatory agents in vivo; however, their molecular actions have not yet been fully understood. In this study, we examined the molecular basis of the inhibitory effects of dietary flavonoids, such as quercetin, and their metabolites on the catalytic reaction of MPO using a combination of biological assays and theoretical calculation studies. Immunohistochemical staining showed that a quercetin metabolite was colocalized with macrophages, MPO, and dityrosine, an MPO-derived oxidation product of tyrosine, in human atherosclerotic aorta. Quercetin and the plasma metabolites inhibited the formation of dityrosine catalyzed by the MPO enzyme and HL-60 cells in a dose-dependent manner. Spectrometric analysis indicated that quercetin might act as a cosubstrate of MPO resulting in the formation of the oxidized quercetin. Quantitative structure-activity relationship studies showed that the inhibitory actions of flavonoids strongly depended not only on radical scavenging activity but also on hydrophobicity (log P). The requirement of a set of hydroxyl groups at the 3, 5, and 4'-positions and C2-C3 double bond was suggested for the inhibitory effect. The binding of quercetin and the metabolites to a hydrophobic region at the entrance to the distal heme pocket of MPO was also proposed by a computer docking simulation. The current study provides the structure-activity relationships for flavonoids as the anti-inflammatory dietary constituents targeting the MPO-derived oxidative reactions in vivo.

Beneficial effects of vegetable oils (corn, olive and sunflower oils) and alpha-tocopherol on anti-inflammatory and gastrointestinal profiles of indomethacin in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin are widely used in the treatment of inflammation, fever and pain. However, NSAIDs cause gastric damage as a major adverse reaction. In this study, the effects of vegetable oils (corn, olive and sunflower oils) and alpha-tocopherol on anti-inflammatory and gastrointestinal profiles of indomethacin were evaluated in rats. Results showed that indomethacin given with sunflower, corn and olive oils reduced paw edema induced by carrageenan by 79.5%, 74.0% and 60.5%, whereas individual indomethacin and diclofenac reduced paw edema by 56.2% and 50.7%, respectively. Furthermore, it has been found that the vegetable oils possess significant anti-inflammatory effect against paw edema when given alone. These results showed that the vegetable oils have beneficial effects on reduction paw edema induced by carrageenan. Besides, the administration of indomethacin together with the vegetable oils and alpha-tocopherol did not cause a statistically significant gastric damage in rats (P>0.05). However, indomethacin caused statistically significant gastric lesions as compared with untreated rats (P<0.05). Moreover, it was also found that the effects of the vegetable oils and alpha-tocopherol improved the levels of antioxidant defense systems in rat stomach tissues against oxidative damage. These results suggest that indomethacin as well as other NSAIDs do not have any adverse effect on the gastrointestinal tract when they are used together with vegetable oils and vitamin E or as the preparations of the oils.

Gastroprotective and antioxidant effects of amiodarone on indomethacin-induced gastric ulcers in rats

Reactive oxygen species (ROS) have been implicated in the etiology of indomethacin-induced gastric mucosal damage. This study investigated amiodarone's protective effects against oxidative gastric mucosal damage induced by indomethacin. Amiodarone is a widely used antiarrhythmic agent. We have investigated alterations in the glutathione level, and the activities of antioxidative enzymes [superoxide dismutase, catalase, glutathione s-transferase glutathione reductase and myeloperoxidase], as markers for ulceration process following oral administration of amiodarone and ranitidine in rats with indomethacin-induced ulcers. In the present study we found that 1) amiodarone, lansoprazole and ranitidine reduced the development of indomethacin-induced gastric damages, at a greater magnitude for amiodarone and lansoprazole than for ranitidine; 2) amiodarone and ranitidine alleviated increases in the activities of catalase and glutathione s-transferase enzymes resulting from ulcers; 3) amiodarone and ranitidine ameliorated depressions in the glutathione level and the activities of superoxide dismutase and glutathione reductase enzymes caused by indomethacin administration; and 4) all doses of amiodarone amplified the myeloperoxidase activity resulting from indomethacin-induced gastric ulcers. The results indicate that the gastroprotective activity of amiodarone, which may be linked to its intrinsic antioxidant properties, cannot be attributed to its effect on myeloperoxidase activity.

Gastroprotective and anti-oxidative properties of ascorbic acid on indomethacin-induced gastric injuries in rats

Reactive oxygen species (ROS) have been implicated in the etiology of indomethacin-induced gastric mucosal damage. This study investigated ascorbic acid (vitamin C)'s protective effects against oxidative gastric mucosal damage induced by indomethacin. Ascorbic acid is a powerful antioxidant because it can donate a hydrogen atom and form a relatively stable ascorbyl free radical. We have investigated alterations in the levels of myeloperoxidase, antioxidant system enzymes (glutathione S-transferase, superoxide dismutase, glutathione reductase, catalase, glutathione peroxidase), lipid peroxidation and glutathione, as markers for ulceration process following oral administration of ascorbic acid, famotidine, lansoprazole, and ranitidine in rats with indomethacin-induced ulcers. In the present study, we found that (1) ascorbic acid, famotidine, lansoprazole and ranitidine reduced the development of indomethacin-induced gastric damages; (2) the administration of indomethacin caused a significant decrease in the levels of superoxide dismutase, glutathione peroxidase, glutathione S-transferase and glutathione, and an increase in the lipid peroxidation level; (3) the administration of ascorbic acid reversed the trend, inducing a significant increase of these enzymes' levels and a reduction in lipid peroxidation level in tissues; and (4) catalase, glutathione reductase and myeloperoxidase activities, increased by indomethacin, were found to be lower in the ascorbic acid, famotidine, lansoprazole and ranitidine-treated groups. The results indicate that the gastroprotective properties of ascorbic acid could be related to its positive effects on the antioxidant system and myeloperoxidase activity in indomethacin-induced gastric ulcers in rats.

Myeloperoxidase: a target for new drug development?

Myeloperoxidase (MPO), a member of the haem peroxidase-cyclooxygenase superfamily, is abundantly expressed in neutrophils and to a lesser extent in monocytes and certain type of macrophages. MPO participates in innate immune defence mechanism through formation of microbicidal reactive oxidants and diffusible radical species. A unique activity of MPO is its ability to use chloride as a cosubstrate with hydrogen peroxide to generate chlorinating oxidants such as hypochlorous acid, a potent antimicrobial agent. However, evidence has emerged that MPO-derived oxidants contribute to tissue damage and the initiation and propagation of acute and chronic vascular inflammatory disease. The fact that circulating levels of MPO have been shown to predict risks for major adverse cardiac events and that levels of MPO-derived chlorinated compounds are specific biomarkers for disease progression, has attracted considerable interest in the development of therapeutically useful MPO inhibitors. Today, detailed information on the structure of ferric MPO and its complexes with low- and high-spin ligands is available. This, together with a thorough understanding of reaction mechanisms including redox properties of intermediates, enables a rationale attempt in developing specific MPO inhibitors that still maintain MPO activity during host defence and bacterial killing but interfere with pathophysiologically persistent activation of MPO. The various approaches to inhibit enzyme activity of MPO and to ameliorate adverse effects of MPO-derived oxidants will be discussed. Emphasis will be put on mechanism-based inhibitors and high-throughput screening of compounds as well as the discussion of physiologically useful HOCl scavengers.

Leptin protects vital organ functions after sepsis through recovering tissue myeloperoxidase activity: an anti-inflammatory role resonating with indomethacin

In this research, the role of leptin on sepsis-induced organ dysfunction was evaluated. Making use of a mice sepsis model, changes of alanine transaminase and uric acid in serum, myeloperoxidase activity, leptin levels and histological alterations in heart, lung, liver and kidney were determined. Results showed that sepsis induced significantly higher levels of serum alanine transaminase and uric acid, decreased tissue myeloperoxidase activity and leptin levels, and triggered distinct histological alterations. However, leptin and indomethacin injections reversed those impairments at 6h and/or 12h after injury. These data reveal a protective role of both leptin and indomethacin on vital organ functions after sepsis by recovering tissue myeloperoxidase activity.

Amiodarone has anti-inflammatory and anti-oxidative properties: An experimental study in rats with carrageenan-induced paw edema

Amiodarone is a widely used anti-arrhythmic agent. We have investigated alterations in the glutathione (GSH) level and the activities of anti-oxidative enzymes (superoxide dismutase, catalase, glutathione s-transferase and glutathione reductase) and myeloperoxidase, as marker of acute inflammation, following oral administration of amiodarone and diclofenac in rats with carrageenan-induced paw edema. In the present study, we found that 1) Amiodarone reduced the development of carrageenan-induced paw edema, to a greater degree than diclofenac; 2) Amiodarone and diclofenac alleviated increases in the activities of catalase and glutathione s-transferase enzymes resulting from edema; 3) Amiodarone and diclofenac ameliorated depressions in the GSH level and the activities of superoxide dismutase and glutathione reductase enzymes caused by carrageenan injection; and 4) All doses of amiodarone and diclofenac caused an amplification in myeloperoxidase activity resulting from induced paw edema. These results suggest that the anti-inflammatory effect of amiodarone on carrageenan-induced acute inflammation can be attributed to its ameliorating effect on the oxidative damage.

Inhibitory and enhancing effects of piroxicam on whole blood chemiluminescence

The effects of piroxicam on the production of reactive oxygen species by stimulated phagocytes was studied in whole blood by a chemiluminescence (CL) technique in relation to maximum activity, localization and kinetics of radical generation. We found that piroxicam dose-dependently inhibited total (intra- and extracellular) zymosan-stimulated luminol CL (LCL) at a high stimulant concentration (p = 0.0001). Piroxicam additionally decreased cytochalasin B-reduced LCL, which shows that the effect of the drug should be sought in the extracellular component of the response. Piroxicam inhibited the first phase of extracellular LCL in a dose-dependent manner (p = 0.0001) and revealed itself as an enhancing agent of CL in later time intervals after the start of respiratory burst, in a model system containing horseradish peroxidase (HRP) and sodium azide. It enhanced LCL of a cell-free system, i.e. influenced the CL due to HRP-catalysed decomposition of hydrogen peroxide. It also dose-dependently inhibited the early extracellular superoxide production, evaluated by lucigenin CL (p = 0.022). Piroxicam inhibited the total fMLP-stimulated LCL by 70% approximately and, only by about 30%, the first phase of fMLP-stimulated extracellular LCL, which presupposes an effect on myeloperoxidase-catalysed formation of hypochloric acid. Piroxicam slightly increased the intracellular LCL by phagocytes (p = 0.02), an effect that is probably connected with its ability to induce the release of secondary messengers in signal transduction. In conclusion, the anti-inflammatory effect of piroxicam is probably related to the inhibition of the extracellular generation of superoxide and hypochloric acid in the early stages of phagocyte activation.

Exploitation of the unusual thermodynamic properties of human myeloperoxidase in inhibitor design

Myeloperoxidase plays a fundamental role in oxidant production by neutrophils. It uses hydrogen peroxide and chloride to catalyze the production of hypochlorous acid (HOCl), which contributes to both bacterial killing and oxidative injury of host tissue. Thus, MPO is an interesting target for anti-inflammatory therapy. Here, based on the extraordinary and MPO-specific redox properties of its intermediates compound I and compound II, we present a rational approach in selection and design of reversible inhibitors of HOCl production mediated by MPO. In detail, indole and tryptamine derivatives were investigated for their ability to reduce compounds I and II and to affect the chlorinating activity of MPO. It is shown that these aromatic one-electron donors bound to the hydrophobic pocket at the distal heme cavity and were oxidized efficiently by compound I (k3), which has a one-electron reduction potential of 1.35 V. By contrast, compound II (E degrees ' of the compound II/ferric couple is 0.97 V) reduction (k4) was extremely slow. As a consequence compound II, which does not participate in the halogenation cycle, accumulated. The extent of chlorinating activity inhibition (IC50) was related to the k3/k4 ratio. The most efficient inhibitors were 5-fluorotryptamine and 5-chlorotryptamine with IC50 of 0.79 microM and 0.73 microM and k3/k4 ratios of 386,000 and 224,000, respectively. The reversible mechanism of inhibition is discussed with respect to the enzymology of MPO and the development of drugs against HOCl-dependent tissue damage.

Effect of therapeutic plasma concentrations of non-steroidal anti-inflammatory drugs on the production of reactive oxygen species by activated rat neutrophils

The release of reactive oxygen specie (ROS) by activated neutrophil is involved in both the antimicrobial and deleterious effects in chronic inflammation. The objective of the present investigation was to determine the effect of therapeutic plasma concentrations of non-steroidal anti-inflammatory drugs (NSAIDs) on the production of ROS by stimulated rat neutrophils. Diclofenac (3.6 microM), indomethacin (12 microM), naproxen (160 microM), piroxicam (13 microM), and tenoxicam (30 microM) were incubated at 37 masculineC in PBS (10 mM), pH 7.4, for 30 min with rat neutrophils (1 x 10(6) cells/ml) stimulated by phorbol-12-myristate-13-acetate (100 nM). The ROS production was measured by luminol and lucigenin-dependent chemiluminescence. Except for naproxen, NSAIDs reduced ROS production: 58 +/- 2% diclofenac, 90 +/- 2% indomethacin, 33 +/- 3% piroxicam, and 45 +/- 6% tenoxicam (N = 6). For the lucigenin assay, naproxen, piroxicam and tenoxicam were ineffective. For indomethacin the inhibition was 52 +/- 5% and diclofenac showed amplification in the light emission of 181 +/- 60% (N = 6). Using the myeloperoxidase (MPO)/H2O2/luminol system, the effects of NSAIDs on MPO activity were also screened. We found that NSAIDs inhibited both the peroxidation and chlorinating activity of MPO as follows: diclofenac (36 +/- 10, 45 +/- 3%), indomethacin (97 +/- 2, 100 +/- 1%), naproxen (56 +/- 8, 76 +/- 3%), piroxicam (77 +/- 5, 99 +/- 1%), and tenoxicam (90 +/- 2, 100 +/- 1%), respectively (N = 3). These results show that therapeutic levels of NSAIDs are able to suppress the oxygen-dependent antimicrobial or oxidative functions of neutrophils by inhibiting the generation of hypochlorous acid.

The metabolism of sulindac enhances its scavenging activity against reactive oxygen and nitrogen species

Sulindac is a sulfoxide prodrug that, in vivo, is converted to the metabolites sulindac sulfide and sulindac sulfone. It is therapeutically used as an anti-inflammatory and analgesic in the symptomatic treatment of acute and chronic rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis. In addition to its anti-inflammatory properties, sulindac and its metabolites have been shown to have an important role in the prevention of colonic carcinogenesis. Although the inhibition of prostaglandin synthesis constitutes the primary mechanism of action of sulindac, it is well known that reactive oxygen species (ROS) and reactive nitrogen species (RNS) are implicated in the pathophysiology of inflammation and cancer. Thus, the aim of this study was to evaluate the scavenging activity of sulindac and its sulfone and sulfide metabolites for an array of ROS (HO*, O2(*-), and HOCl) and RNS (*NO and ONOO-) using in vitro systems. The results we obtained demonstrate that the metabolism of sulindac increases its scavenging activity for all RNS and ROS studied, notably with regard to the scavenging of HOCl. These effects may strongly contribute to the anti-inflammatory and anticarcinogenic efficacy that has been shown for sulindac.

The in vitro effects of Hypericum species on human leukocyte myeloperoxidase activity

Myeloperoxidase (MPO) is a major component of the antimicrobial system of polymorphonuclear neutrophils. The heme enzyme MPO catalyzes the conversion of hydrogen peroxide and chloride to hypochlorous acid. Hypochlorous acid is the major strong oxidant produced by neutrophils and may contribute to inflammatory tissue damage. It was reported that certain antiinflammatory drugs are capable of inhibiting MPO activity and this inhibition may account for their antiinflammatory effect. Hypericum L. is a genus of about 400 species, widespread throughout the world. Some species of genus exhibit a significant antiinflammatory activity beside their several pharmacological properties such as antidepressant, diuretic, antihelmintic, and antibacterial. In this study, we investigated the in vitro effects of three Hypericum species, which exhibit antiinflammatory activity, on human polymorphonuclear leukocyte MPO activity. We found that each extract of Hypericum species reduced the peroxidative and chlorinating activity of human leukocyte MPO in concentration-dependent manner. The antiinflammatory activity of these species may be related with inhibition of MPO activity.

The effect of oxidation on the enzyme-catalyzed hydrolytic biodegradation of poly(urethane)s

Although the biodegradation of polyurethanes (PU) by oxidative and hydrolytic agents has been studied extensively, few investigations have reported on the combination of their effects. Since neutrophils (PMN) arrive at an implanted device first and release HOCl, followed by monocyte-derived macrophages (MDM) which have potent esterase activities and oxidants of their own, the combined effect of oxidative and hydrolytic degradation on radiolabeled polycarbonate-polyurethanes (PCNU)s was investigated and compared to that of a polyester-PU (PESU) and a polyether-PU (PEU). The PCNUs were synthesized with PCN (MW = 1,000), and butanediol (14C-BD) and one of two diisocyanates, hexane-1,6-diisocyanate (14C-HDI) or methylene bis-p-phenyl diisocyanate (MDI). The PESU and PEU were synthesized using toluene-diisocyanate (14C-TDI), with polycaprolactone and polytetramethylene oxide as soft segments respectively, and ethylene diamine as the chain extender. The effect of pre-treatment with 0.1 mM HOC1 for 1 week on the HDI-based PCNUs and both TDI-based PUs resulted in a significant inhibition of radiolabel release (RR) elicited by cholesterol esterase (CE), when compared to buffer alone, whereas the MDI-based PCNU showed a small but significant increase. When PMN were activated on the HDI-based PCNU surface with phorbol myristate acetate (PMA), HOCl was released for 3 h, and was almost completely abolished by sodium azide (AZ). Simultaneously, the PMN-elicited RR, shown previously to be due to the esterolytic cleavage by serine proteases, was inhibited approximately 75% by PMA-activation of the cells, but significantly increased relative to the latter when AZ was added. Both in vitro oxidation by HOCl and the release of HOCI by PMN were associated with the inhibition of RR and suggest perturbations between oxidative and hydrolytic mechanisms of biodegradation.

Ambroxol inhibits peroxynitrite-induced damage of alpha1-antiproteinase and free radical production in activated phagocytic cells

The present study examined the effect of ambroxol on toxic action of peroxynitrite and the respiratory burst in activated phagocytic cells. Ambroxol decreased the inactivation or destruction of alpha1-antiproteinase induced by peroxynitrite (ONOO-) or hypochlorous acid (HOCl), which was similar to penicillamine and glutathione and was greater than diclofenac sodium and naproxen sodium. Ambroxol significantly decreased ONOO--mediated tyrosine nitration and iron plus EDTA-mediated degradation of 2-deoxy-D-ribose. Ambroxol significantly attenuated the production of superoxide, hydrogen peroxide, HOCl, and nitric oxide in fMLP- or IL-1-activated phagocytic cells, while the inhibitory effects of antiinflammatory and thiol compounds were only observed in HOCl production. Ambroxol and antiinflammatory drugs did not show a cytotoxic effect on macrophages. The results suggest that ambroxol protects tissue components against oxidative damage by an action different from antiinflammatory drugs. Ambroxol may interfere with oxidative damage of alpha1-antiproteinase through a scavenging action on ONOO- and HOCl and inhibition of the respiratory burst of phagocytic cells.

Inhibition of the myeloperoxidase chlorinating activity by non-steroidal anti-inflammatory drugs investigated with a human recombinant enzyme

Non-steroidal anti-inflammatory drugs (NSAIDs) were investigated for their ability to affect the chlorinating activity of human myeloperoxidase and to scavenge HOCl, the main myeloperoxidase system product. Fourteen drugs representative of various NSAIDs families were tested with the chlorination of taurine used as a detection system. All were unable to inhibit taurine chlorination in a system without myeloperoxidase. In contrast, most of them induced a dose-dependent inhibition of the taurine chlorination mediated by a myeloperoxidase/H2O2/Cl- system. This took place at variable drug concentrations and IC50 were calculated. The inhibitory effect was therefore due to a direct interaction with the enzyme rather than to HOCl scavenging. A spectroscopic method used to measure the myeloperoxidase compound II lifetime in presence of the different drugs showed that all the drugs, which inhibited chlorination activity were able to induce accumulation of compound II. The extent of chlorinating activity inhibition (IC50) was inversely related to the duration of the block of enzyme in compound II form. This further demonstrates that myeloperoxidase is an interesting target for anti-inflammatory therapy. The recombinant myeloperoxidase used for the first time in this kind of study was as convenient for pharmacological purposes as the purified one.

Influence of cyclooxygenase and lipoxygenase inhibitors on oxidative stress-induced lung injury

OBJECTIVE

Hypochlorous acid (HOCl) is the main oxidant of activated neutrophil granulocytes. It is generated by their myeloperoxidase during respiratory burst. This study investigates the effects of HOCl on vascular permeability and pulmonary artery pressure (PAP) and characterizes the influence of the cyclooxygenase inhibitor acetylsalicylic acid (ASA) and the 5-lipoxygenase inhibitor caffeic acid (CaA) on the observed alterations.

DESIGN

Prospective experimental study using isolated perfused rabbit lungs.

SETTING

Experimental laboratory in a university teaching hospital.

INTERVENTIONS

HOCl was infused into the perfusate containing either no inhibitors, ASA (500 micromol/L), or CaA (1 micromol/L).

MEASUREMENTS AND MAIN RESULTS

PAP, pulmonary venous pressure, and ventilation pressure as well as lung weight gain were continuously recorded. Capillary filtration coefficient [Kf,c (10(-4) cm3 x sec(-1) x cm H2O(-1) x g(-1)]) was calculated before and 30, 60, and 90 mins after start of HOCl application. Continuous HOCl application (500, 1000, and 2000 nmol/min) resulted in a time- and dose-dependent increase in Kf,c and PAP with a threshold dose at 500 nmol/min. The onset of these changes was inversely related to the HOCl dose used. Both inhibitors, CaA and ASA, exhibited protective effects on the HOCl-induced alterations in pulmonary microcirculation. ASA predominantly reduced the HOCl-induced pressure response and had a minor but also significant inhibitory effect on edema formation as measured by Kf,c and fluid retention. CaA reduced significantly the rise in Kf,c and subsequent edema formation without effects on pulmonary pressure response.

CONCLUSIONS

Cyclooxygenase and 5-lipoxygenase are involved in oxidative stress induced acute lung injury, suggesting a link between neutrophil-derived oxidative stress and endothelial eicosanoid metabolism.

The neutrophil: function and regulation in innate and humoral immunity

The neutrophil is a critical effector cell in humoral and innate immunity and plays vital roles in phagocytosis and bacterial killing. Discussed here are the neutrophil components necessary for these processes and the diseases in which these components are either lacking or dysfunctional, illustrating that normal neutrophil function is vital for health.

Inactivation of creatine kinase during the interaction of indomethacin with horseradish peroxidase and hydrogen peroxide: involvement of indomethacin radicals

Creatine kinase (CK) was used as a marker molecule to examine the side effect of damage to tissues by indomethacin (IM), an effective drug to treat rheumatoid arthritis and gout, with horseradish peroxidase and hydrogen peroxide (HRP-H2O2). IM inactivated CK during its interaction with HRP-H2O2. Under aerobic conditions, inactivation of CK significantly decreased. CK in rat heart homogenate was also inactivated by IM with HRP-H2O2. When IM was incubated with HRP-H2O2, the maximum absorption of IM at 280 nm rapidly decreased and a new peak at 410 nm occurred with isosbestic points at 260 and 312 nm. In contrast, under anaerobic conditions, the spectral change of IM was almost absent, indicating IM was oxidized to the yellow substance by HRP-H2O2. Adding catalase strongly inhibited the production of yellow substance. Sodium azide also blocked the formation of yellow substance and the inactivation of CK. Electron spin resonance signals of IM carbon-centered radical were detected using 2-methyl-2-nitrosopropane during the interaction of IM with HRP-H2O2 under anaerobic conditions. Oxygen was consumed during the interaction of IM with HRP-H2O2. These results suggest that IM carbon-centered radicals may rapidly react with O2 to generate the peroxyl radicals. Sulfhydryl groups and tryptophane residues of CK decreased during the interaction of IM with HRP-H2O2. Other sulfhydryl enzymes, including alcohol dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase, were also readily inactivated during the interaction with HRP-H2O2. Sulfhydryl enzymes seem to be very sensitive to IM activated by HRP-H2O2.

Osteoprotegerin is produced when prostaglandin synthesis is inhibited causing osteoclasts to detach from the surface of mouse parietal bone and attach to the endocranial membrane

Osteoclast differentiation and activation is controlled, at least in part, by the counterbalancing influences of osteoprotegerin ligand (OPGL) and osteoprotegerin (OPG). Nonsteroidal anti-inflammatory drugs have been shown to inhibit bone loss in vivo and bone resorption in vitro, and this is associated with a loss of osteoclasts from the bone surface. We test the hypothesis that OPG mediates the inhibition of osteoclast activity that occurs with indomethacin in the mouse calvaria. Recombinant human OPG, like indomethacin, was found to cause osteoclasts to detach from the bone surface and attach to the adjacent endocranial membrane (periosteum). Recombinant human OPG also inhibited the stimulatory effect of prostaglandin E2 (PGE2), parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D3 (1,25D3) on osteoclast adhesion to bone after an incubation with indomethacin. A function-blocking antibody to OPG and soluble human OPGL both inhibited the effect of indomethacin, leaving active osteoclasts on the bone. OPG activity was detected in the culture medium from indomethacin-treated bones and PTH, PGE2, 1,25D3, and dexamethasone all inhibited the production of OPG activity. We conclude that, in the absence of specific stimulators of bone resorption, OPG is produced by the mouse calvaria in vitro, which inhibits bone resorption by causing osteoclasts to detach from the bone surface.

Neutrophil-mediated biodegradation of medical implant materials

During the acute inflammatory response to implanted medical devices, human neutrophils (PMN) release oxidative and hydrolytic activities which may ultimately contribute to the degradation of the biomaterial. In this study, the biological activities secreted by live PMNs which may contribute to biodegradation were investigated using a 14C label in the monomer unit of a poly(ester-urea-urethane) (PEUU) substrate. By using specific inhibitors, it was possible to propose a mechanism for PMN-mediated biodegradation. PMN, labeled with 3H-arachidonic acid, released significantly more 3H when adherent to PEUU than when adherent to tissue culture grade polystyrene (P<0.05). The phospholipase A2 (PLA2) inhibitors, aristolochic acid (ARIST) and quinacrine (QUIN), decreased the release of 3H and inhibited PEUU biodegradation (>50%, P<0.05). ARIST had no effect on cell viability, whereas QUIN significantly decreased it. The serine protease inhibitor, phenylmethylsulfonylfluoride inhibited biodegradation, but did not decrease cell survival. There is evidence to suggest that activation via the PLA2 pathway caused the release of hydrolytic activities which were able to elicit 14C release from PEUU. The role of oxidative compounds which were released via activation by phorbol myristate acetate (PMA), was not apparent, since PMA inhibited biodegradation and cell survival (>40%, P<0.05). This study has shown that it is possible to find out the differences in PMN activation through the PLA2 pathway when exposed to different material surfaces, making this a model system worthy of further investigation.

The inhibitory effect of ambroxol on hypochlorous acid-induced tissue damage and respiratory burst of phagocytic cells

Ambroxol (100 microM and 1 mM) and the thiols (all 1 mM), glutathione, tiopronin and cysteine, significantly attenuated the myeloperoxidase, H(2)O(2) and Cl(-) system-caused destruction of alpha(1)-antiproteinase and the HOCl-induced destruction of collagen, whereas they did not affect the elastase-induced destruction of collagen. Glutathione, tiopronin and cysteine almost completely decomposed both HOCl and H(2)O(2), while ambroxol up to 1 mM did not show a scavenging action on H(2)O(2). Ambroxol (1 to 100 microM) and 1 mM thiol compounds markedly inhibited the HOCl-induced alteration of elastase activity. Thiol compounds significantly attenuated the HOCl production caused by degraded immunoglobulin G-activated neutrophils. Ambroxol depressed superoxide and H(2)O(2) production induced by degraded immunoglobulin G-activated neutrophils and by lipopolysaccharide-activated alveolar macrophages in a dose-dependent manner. The results show that ambroxol may interfere with oxidative tissue damage and decrease proteolytic tissue destruction by attenuation of oxidative stress-induced inactivation of alpha(1)-antiproteinase through both decomposition of HOCl and inhibition of the respiratory burst in phagocytic cells.

The inhibition of myeloperoxidase by ceruloplasmin can be reversed by anti-myeloperoxidase antibodies

BACKGROUND

The purpose of this study was to characterize the recently reported inhibition of myeloperoxidase (MPO) by ceruloplasmin and to determine whether this may be disturbed in the presence of anti-MPO antibodies.

METHODS

Specificity of the binding between ceruloplasmin and MPO was confirmed by Western blotting and enzyme-linked immunosorbent assay (ELISA), and the enzymatic activity of MPO was measured in the presence of ceruloplasmin, affinity-purified anti-MPO antibodies, or both. The affinity of the binding between MPO and ceruloplasmin and MPO and the anti-MPO antibodies was measured using a biosensor, with the results confirmed by chaotrope ELISA.

RESULTS

Affinity-purified anti-MPO antibodies from patients with microscopic polyangiitis and florid renal vasculitis inhibited the binding between ceruloplasmin and MPO to a maximum of 72.9 +/- 12.8%, whereas those from patients with Wegener's granulomatosis and only minimal renal involvement inhibited the binding to a maximum of only 36.8 +/- 10.9% (P < 0. 001), with comparable reversal of the ceruloplasmin-mediated inhibition of MPO activity. Measurement of the affinity of the interactions demonstrated that binding between MPO and the anti-MPO antibodies is stronger than that between MPO and ceruloplasmin (1.61 x 107 to 1.33 x 108 vs. 7.46 x 106 m-1), indicating that binding to the autoantibody would be favored in vivo.

CONCLUSIONS

This study confirms a role for ceruloplasmin as a physiological inhibitor of MPO, and demonstrates how the inhibition may be disrupted in the presence of anti-MPO antibodies. Because a majority (16 of 21) of the antibodies did not themselves inhibit MPO activity, their interference with the inhibition mediated by ceruloplasmin may be brought about by steric hindrance consequent upon the binding of the antibody to a dominant epitope at or near the active site.

Effects of anti-inflammatory drugs upon nitrate and myeloperoxidase levels in the mouse pleurisy induced by carrageenan

The effects of several drugs (terfenadine, bradykinin B2 receptor antagonists: HOE 140, NPC 17731, diacerein, indomethacin, meloxicam, nabumetone, and dexamethasone) upon myeloperoxidase and nitrate levels were analyzed in an inflammation model characterized by biphasic peaks (4 and 48 h) of cell migration and of fluid leakage. Myeloperoxidase levels were significantly higher only in the first phase (4 h; median and range; 537.5; 323.6-683.7 mU/ml; P < 0.01), whereas increased mean nitrate levels were detected in both phases (4 h: 19.0; 6.2-32 microM and 48 h: 13.7; 8.9-17.8 microM; P < 0.01). Enhancement of both cell migration and myeloperoxidase levels, 4 h after pleurisy induction, was effectively inhibited by all studied drugs. All of them, except diacerein also inhibited exudation. At this time, nabumetone and diacerein also significantly reduced nitrate levels (P < 0.01). Regarding the second phase (48 h), although dexamethasone, diacerein, and terfenadine decreased either cell migration or exudation, no drugs caused any change in the levels of nitrate. These results indicate that the degree of inhibition of the tested drugs upon the parameters studied do not match, suggesting that differences in these effects may certainly interfere with their efficacy.

Inhibition of PMN- and HOC1-induced vascular injury in isolated rabbit lungs by acetylsalicylic acid: a possible link between neutrophil-derived oxidative stress and eicosanoid metabolism?

Neutrophils are involved in the pathogenesis of acute lung injury. The neutrophil-derived enzyme myeloperoxidase (MPO) catalyzes the formation of the oxidant hypochlorous acid (HOCl). This study characterizes the effects of (A) continuous HOCl infusion, and (B) stimulated neutrophils on pulmonary circulation in an isolated rabbit lung model. Furthermore, the effect of cyclooxygenase inhibition by acetylsalicylic acid (ASA, 0.5 mM) on these effects was investigated. (A) Infusion of HOCl (in nmol min-1, groups: 0, 0+ASA, 1000, 1000+ASA, 2000, and 2000+ASA) into the isolated organ was started after a 45-min steady-state period (t=0). (B) Neutrophils (PMN group: 1480+/-323 and ASA group 1294+/-320 microliter-1) were added into the perfusate between (t=-45 min) and stimulated with FMLP (1 microM) after two 45-min steady-state periods (t=0). Perfusate MPO activity was measured at t=-90, -45, 0, 1, 2, 3, 5, 10, 15, 30, 60, and 90 min. For both groups, pulmonary artery pressure (PAP) and lung weight were continuously recorded and the capillary filtration coefficient (Kf,c in 10(-4) cm(3) s(-1) cm H2O(-1) g(-1) was calculated from the slope of weight gain after a hydrostatic challenge at t=-45, -15, 30, 60 and 90 min. (A) Continuous HOCl infusion (1000/2000 nmol min-1) evoked a significant increase in DeltaPAP and an up to 10-fold increase in Kf,c reaching the maximum extent of the observed effects significant earlier in the 2000 nmol min-1 group. ASA reduced DeltaPAPmax significantly to about 50% in corresponding groups and the increase in PAP and Kf,c occurred later in the ASA groups. (B) Neutrophil stimulation (PMN group/ASA group) evoked a rapid increase in DeltaPAP and MPO activity, while the changes in vascular permeability were rather moderate, but still significant. The release of MPO activity was similar in both groups. ASA significantly reduced the increase in DeltaPAP without affecting the release of MPO activity. Compared to baseline values, the preventive effects on vascular permeability increase reached level of significance as well. In summary, the described changes in pulmonary circulation caused by HOCl infusion or by neutrophil stimulation are significantly reduced by ASA. An involvement of cyclooxygenase products in the mediation of neutrophil-derived oxidative stress could be concluded.

Mechanism of inactivation of myeloperoxidase by 4-aminobenzoic acid hydrazide

Hypochlorous acid is the most powerful oxidant generated by neutrophils and is likely to contribute to the damage mediated by these inflammatory cells. The haem enzyme myeloperoxidase catalyses its production from hydrogen peroxide and chloride. 4-Aminobenzoic acid hydrazide (ABAH) is a potent inhibitor of hypochlorous acid production. In this investigation we show that, in the presence of hydrogen peroxide, ABAH irreversibly inactivates myeloperoxidase. ABAH was oxidized by myeloperoxidase, and kinetic analysis of the inactivation conformed to that for a mechanism-based inhibitor. Inactivation was exacerbated by concentrations of hydrogen peroxide greater than 50 microM and by the absence of oxygen. Hydrogen peroxide alone caused minimal inactivation. Reduced glutathione inhibited the oxidation of ABAH as well as the irreversible inhibition of myeloperoxidase. In the presence of oxygen, ABAH and hydrogen peroxide initially converted myeloperoxidase into compound III, which subsequently lost haem absorbance. In the absence of oxygen, the enzyme was converted into ferrous myeloperoxidase and its haem groups were rapidly destroyed. We propose that myeloperoxidase oxidizes ABAH to a radical that reduces the enzyme to its ferrous intermediate. Ferrous myeloperoxidase reacts either with oxygen to allow enzyme turnover, or with hydrogen peroxide to give irreversible inactivation.

Lactoperoxidase-catalysed oxidation of indomethacin, a nonsteroidal antiinflammatory drug, through the formation of a free radical

Lactoperoxidase (LPO, EC 1.11.1.7; donor-H2O2 oxidoreductase) catalyses the oxidation of indomethacin, a nonsteroidal antiinflammatory drug by H2O2 as measured by time-dependent decay of indo-methacin extinction at 280 nm and concurrent appearance of stable oxidation product(s) at 412 nm. From a plot of log Vmax against varying pH of indomethacin oxidation, involvement of an ionizable group of the enzyme having pka = 5.7 could be ascertained for controlling the oxidation process. Spectral studies revealed that LPO-compound II oxidises indomethacin through one-electron transfer and is reduced to the native ferric state as shown by its spectral shift from 430 nm to 412 nm through an isosbestic point at 421 nm. The one-electron oxidation product is a nitrogen-centered free radical detected as a 5,5-dimethyl-l-pyrroline N-oxide (DMPO) adduct (alpha N = 15 G, alpha H beta = 16 G) in electron spin resonance spectroscopy. The free radical is scavenged by reaction with O2 as shown by O2 consumption sensitive to the free-radical trap, DMPO. Binding studies by optical difference spectroscopy indicate that indomethacin binds to LPO with an apparent KD value of 24.5 microM. The free energy change, delta G', for the binding is -26.3 KJ mol-1, suggesting that the interaction is favourable for oxidation. Indomethacin binding remains unaltered by a change of pH from 5.25 to 7.5, presumably because of hydrophobic interaction. The binding is competitive with resorcinol, an aromatic electron donor, showing the KD value to be as high as 100 microM. We suggest that indomethacin interacts at the aromatic donor binding site and is oxidised by one-electron transfer by LPO catalytic intermediates to stable oxidation product(s) through the formation of a free radical.

Plasmacytoma-refractory BALB/cAnPt mice have naive T cell and highly specific B cell responses to antigen

Recently, a reduction in the incidence of pristane-induced plasmacytomas in BALB/cAnPt (BALB/c) mice that were kept in viral specific pathogen-free (SPF) conditions has been reported. Environmentally, these SPF-BALB/c mice differed from conventionally-housed (CON) mice only in viral exposure and diet (i.e. sterilization of mouse chow), since microbial colonization of the intestinal tract was seen to be equivalent. This report assessed the ability of SPF- and CON-BALB/c mice to respond to immunologic challenge with soluble antigen, i.e. hen egg white lyzosyme (HEL), as a means of evaluating differences in T and B cell function and, indirectly, evaluating the possible effects these differences might have on plasmacytoma development. When cultured in vitro for 5 days with HEL, HEL-primed lymph node cells (LNC) from SPF-BALB/c mice proliferated to a significantly lesser extent than HEL-primed CON-BALB/c LNC. Moreover, HEL-induced production of IFN-gamma and IL-5 was significantly lower in SPF LNC. Serum IgG1 levels were 10-fold lower in SPF-BALB/c mice with, or without prior immunization with HEL and were not reconstituted by repeated injections of HEL in adjuvant. Serum IgM levels of SPF- and CON-BALB/c mice were equivalent. This reduction in immune responses could not be attributed to a lack of colonization of secondary lymphoid organs, since flow cytometric analysis of LNC revealed no difference in the number of recoverable cells and the proportion of lymphocyte subsets (CD4+, CD8+ and CD45+ cells) obtained from SPF- and CON-BALB/c mice. However, only CON LNC were induced to increase surface expression of CD44 after antigenic or mitogenic stimulation in vitro. Antibody responsiveness to HEL, as evidenced by serum anti-HEL binding or splenic hybridoma studies, demonstrated higher levels of IgG1 antibodies in CON BALB/c mice than in SPF mice. However, a greater proportion of the SPF IgG1 antibodies present were specifically directed against HEL, so that specific activity was greater in SPF-BALB/c mice. Therefore, while SPF BALB/c mice have a more restricted response to HEL than CON-BALB/c mice, those antibodies that are produced are more specifically directed against HEL with very little apparent bystander/polyclonal activation of multireactive cells. Resistance to plasmacytomas in SPF-BALB/c mice, therefore, may stem from a reduced number of circulating memory T and B cells, which are capable of reacting and/or crossreacting with a chronic inflammatory stimulus.

Inhibition of prostaglandin synthesis leads to a change in adherence of mouse osteoclasts from bone to periosteum

When mouse parietal bones were incubated for 1 day in medium containing indomethacin (Ind), the number of tartrate-resistant acid phosphatase-positive osteoclasts (TRAP+OC) counted on the bone surface was drastically reduced. This reduction did not occur with calcitonin or if the endocranial membrane (periosteum) was removed prior to incubation with Ind. The aim of this work was to determine the mechanism involved. TRAP+OC were found to be increased on the endocranial membrane adjacent to the resorbing surface after Ind treatment, compared with cultures supplemented with parathyroid hormone (PTH) or prostaglandin E2 (PGE2). However, this increase accounted for only half of those lost from the bone surface. TRAP negative osteoclasts were also seen on the membrane and, to a lesser extent, on the bone. Increased TRAP specific activity could be extracted from the endocranial membranes of bones incubated with Ind compared with PGE2 controls. When bones that had been exposed to Ind were then cultured for 1 day in PGE2, an increase in TRAP+OC occurred. This increase was blocked by the removal of the endocranial membrane prior to incubation with PGE2. We conclude that when prostaglandin production ceases, TRAP+OC become less adherent to bone and more adherent to the endocranial membrane. Stimulators of bone resorption appear to reverse this process.

Elevated interleukin 6 is induced by prostaglandin E2 in a murine model of inflammation: possible role of cyclooxygenase-2

Injection of mineral oils such as pristane into the peritoneal cavities of BALB/c mice results in a chronic peritonitis associated with high tissue levels of interleukin 6 (IL-6). Here we show that increased prostaglandin E2 (PGE2) synthesis causes induction of IL-6 and that expression of an inducible cyclooxygenase, Cox-2, may mediate this process. Levels of both PGE2 and IL-6 are elevated in inflammatory exudates from pristane-treated mice compared with lavage samples from untreated mice. The Cox-2 gene is induced in the peritoneal macrophage fraction isolated from the mice. A cause and effect relationship between increased macrophage PGE2 and IL-6 production is shown in vitro. When peritoneal macrophages are activated with an inflammatory stimulus (polymerized albumin), the Cox-2 gene is induced and secretion of PGE2 and IL-6 increases, with elevated PGE2 appearing before IL-6. Cotreatment with 1 microM indomethacin inhibits PGE2 production by the cells and reduces the induction of IL-6 mRNA but has no effect on Cox-2 mRNA, consistent with the fact that the drug inhibits catalytic activity of the cyclooxygenase but does not affect expression of the gene. Addition of exogenous PGE2 to macrophages induces IL-6 protein and mRNA synthesis, indicating that the eicosanoid stimulates IL-6 production at the level of gene expression. PGE2-stimulated IL-6 production is unaffected by addition of indomethacin. Taken together with the earlier finding that indomethacin diminishes the elevation of IL-6 in pristane-treated mice, the results show that PGE2 can induce IL-6 production in vivo and implicate expression of the Cox-2 gene in the regulation of this cytokine.

Inhibition of myeloperoxidase by benzoic acid hydrazides

Myeloperoxidase is the most abundant protein in neutrophils and catalyses the conversion of H2O2 and chloride into HOCl. To help clarify the role of this enzyme in bacterial killing and inflammation, a specific and potent inhibitor needs to be identified. We have studied a series of benzoic acid hydrazides and found that in general they inhibit the peroxidation activity of myeloperoxidase with an IC50 value of less than 10 microM. The IC50 values of derivatives with substituents containing oxygen or nitrogen were related to their Hammett substituent constants. This indicates that myeloperoxidase oxidizes the hydrazide group of these compounds, and the degree to which they inhibit the enzyme is dependent on the ease of their oxidation. Unsubstituted benzoic acid hydrazide and its 4-chloro derivative were poor inhibitors of peroxidation. Thus it is likely that hydrogen-bonding of the enzyme to substituents containing oxygen or nitrogen increases the binding affinity of the hydrazides and enhances their oxidation by myeloperoxidase. 4-Aminobenzoic acid hydrazide (ABAH) was the most potent inhibitor of peroxidation. It irreversibly inhibited HOCl production by the purified enzyme, having an IC50 value of 0.3 microM. With neutrophils stimulated with opsonized zymosan or phorbol myristate acetate, ABAH inhibited HOCl production by up to 90% and the IC50 values were 16 microM and 2.2 microM respectively. In the presence of superoxide dismutase, these values decreased to 6.4 microM and 0.6 microM respectively. ABAH had no effect on superoxide radical (O2-.) production and degranulation by neutrophils, nor did it inhibit catalase or glutathione peroxidase. Thus ABAH is an effective and selective inhibitor that should be useful for determining the contribution of myeloperoxidase to oxidant-mediated reactions of neutrophils.

Modulation of polymorphonuclear leukocyte responsiveness by copper (II)2 (niflumate)4

Antiinflammatory activities and modulations of PMNL responses produced by treatment with tetrakis-mu-2-[3-(trifluoromethyl)-phenyl]aminonicotinatodicopper (II) [Cu(II)2(niflumate)4] and niflumic acid were studied in isologous serum-induced rat pleurisy. Doses of 10 or 30 mg/kg (35 or 106 mumol/kg) of niflumic acid or Cu(II)2(niflumate)4 (8 or 23 mumol/kg) caused significant (p < 0.01) reductions in pleural exudate and number of polymorphonuclear leukocytes (PMNLs) in the exudate. While both doses of Cu(II)2(niflumate)4 produced significant dose-related reductions in both parameters, only the higher dose of niflumic acid produced a significant dose-related reduction in both parameters. Boyden chamber measurements of N-formyl-methionyl-leucyl-phenylalanine (f-MLP) chemotaxis by PMNLs incubated with 10 or 30 micrograms/ml niflumic acid (35 or 106 nmol/ml) or Cu(II)2(niflumate)4 (8 or 23 nmol/ml) were significantly (p < 0.01 to p < 0.001) decreased in dose-related fashions. Chemotaxis of PMNLs from pleuritic rats treated orally with 10 or 30 mg/kg niflumic acid or Cu(II)2(niflumate)4 was significantly (p < 0.001) inhibited by the larger dose of niflumic acid and both doses of Cu(II)2(niflumate)4. Opsonized zymosan (OZ)-stimulated chemiluminescence (CL) of PMNLs from pleuritic rats treated orally with these same doses of niflumic acid or Cu(II)2(niflumate)4 was only significantly (p < 0.05 or p < 0.01 respectively) decreased by the larger doses. Superoxide (O2-) production by these cells was significantly decreased by the larger dose of niflumic acid (p < 0.05) while both doses of Cu(II)2(niflumate)4 produced significant (p < 0.05 to p < 0.01) decreases.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of anti-inflammatory drugs on myeloperoxidase-dependent hydroxyl radical generation by human neutrophils

Neutrophils comprise a group of leukocytes that play a pivotal role in inflammation and vascular diseases like ischemia/reperfusion. These activated phagocytic cells are drawn to the site of injury, secreting superoxide and other oxidants derived from the formation of this free radical. This series of events frequently results in localized tissue damage. Surprisingly, free radical scavengers frequently offer only minimal relief. Why this is so may be due, in part, to our limited understanding of mechanisms that govern generation of free radicals in these settings. Although the metal ion-catalyzed Haber-Weiss reaction is considered the classical pathway for neutrophil-derived hydroxyl radical, an alternative mechanism, such as the myeloperoxidase-dependent pathway, may undoubtedly contribute to the formation of this free radical by stimulated neutrophils. In this study, we explored this possibility by investigating the role of different classes of anti-inflammatory drugs to ameliorate hydroxyl radical generation via the myeloperoxidase-dependent pathway. In this paper, we report that meclofenamic acid inhibited myeloperoxidase-dependent hydroxyl radical generation through scavenging of hypochlorous acid and not by direct inhibition of myeloperoxidase. The importance of these results with regard to the clinical efficacy of this anti-inflammatory compound remains to be determined as studies into the significance of myeloperoxidase-dependent hydroxyl radical formation in inflammatory tissue injury continue.

The number of tartrate-resistant acid phosphatase-positive osteoclasts on neonatal mouse parietal bones is decreased when prostaglandin synthesis is inhibited and increased in response to prostaglandin E2, parathyroid hormone, and 1,25 dihydroxyvitamin D3

The culture of parietal bones from 4-day old mice in indomethacin (Ind) for 1 day caused a large reduction in the number of tartrate-resistant acid phosphatase positive osteoclasts (TRAP + OC) relative to both control bones and to freshly isolated bones. This reduction did not occur if prostaglandin E2 (PGE2) was present. When 5-bromo-2'-deoxyuridine (BDU) was injected into 4-day old mice, newly formed TRAP + OC nuclei became labeled 1 day later; these bones were then cultured with Ind for 1 day. TRAP + OC and newly labeled TRAP+OC nuclei were commensurately decreased in number. This suggests an active down-regulation rather than merely the inhibition of new TRAP+OC formation. Incubation of bones with Ind and either PGE2, parathyroid hormone, or 1,25 dihydroxyvitamin D3 for 6 hours following a 1-day preincubation in Ind, resulted in an increase in TRAP + OC compared with Ind alone. Using BDU labeling in vitro and in vivo, we show that this increase in number of TRAP+OC is not the result of cell proliferation, but rather differentiation of postmitotic precursors.

Effect of indomethacin on thrombin-induced pulmonary edema in the rat

The preventive effect of indomethacin on thrombin-induced pulmonary edema was studied in rats. Administration of thrombin caused a significant increase in lung weight, wet weight to dry weight ratio (WW/DW), and relative lung water content. During infusion of thrombin, mean pulmonary artery pressure rose and mean systemic artery pressure fell, PaO2 decreased progressively and there was a continuous rise in pH and PaCO2. An inhibitor of cyclooxygenase, indomethacin, at a dose of 1 mg/kg body weight, induced a significant further increase in lung weight (p < 0.05), and a tendency towards an increase in WW/DW and water content compared with animals given thrombin alone. Treatment with indomethacin, however, counteracted the elevated pulmonary artery pressure occurring in the early phase after thrombin infusion, but not that in the late phase. Systemic artery pressure was not affected by indomethacin. The increases in pH and PaCO2 after thrombin infusion were attenuated and remained stable almost at baseline level after indomethacin administration. Indomethacin did not prevent the hypoxemia induced by thrombin infusion. In conclusion, although indomethacin prevented the early increase in pulmonary artery pressure due to thrombin and the decrease in pH and the increase in PaCO2, it caused lung vascular permeability to protein to increase more than with thrombin alone.

Influence of anti-inflammatory drugs on adhesion of neutrophils to endothelial cells cultured on microcarriers: a novel in vitro system as an alternative to animal experimentation

Pharmacological control of inflammation by steroidal (SAIDs) and nonsteroidal (NSAIDs) antiinflammatory drugs is of substantial clinical importance. To reduce the number of animals used in pharmacological and toxicological evaluation of these drugs we developed a novel assay to determine adhesion of bovine neutrophils (PMN) to bovine aortic endothelial cells (BAEC) cultured on microcarriers in a flow-through system. Pretreatment of BAEC with thrombin (10(-7)-10(-4) M) led to a dose-dependent increase of PMN-adhesion (10(-6)-10(-4) M:P < 0.05); platelet-activating factor (10(-9) M) and 1:200 diluted zymosan-activated serum (ZAS) had similar effects (P < 0.001). Pretreatment of PMN with SAIDs (50.9 and 509 microM dexamethasone, 12.2 and 24.4 microM flumethasone) did inhibit adhesion to ZAS-treated BAEC dose-dependently. Pretreatment of PMN with NSAIDs had a less consistent influence on adhesion to ZAS-stimulated BAEC. While phenylbutazone (0.33 and 3.3 mM), diclofenac (0.392 and 0.574 mM), indomethacine (0.436 and 0.872 mM), and acetylsalicylic acid (3.47 and 16.94 mM) induced dose-dependent inhibition of PMN-adhesion to ZAS-treated BAEC, piroxicam (0.377 and 0.754 mM) inhibited PMN-adhesion strongly (P < 0.001) but not dose-dependently, and ketoprofene (0.614 and 1.228 mM) had no effect on PMN-adhesion. The method presented here is efficient for evaluating the pharmacological modulation of PMN interaction with endothelial cells, and useful for studying further aspects of endothelial cell biology.