Antioxidation theory of non-steroidal anti-inflammatory drugs based upon the inhibition of luminol-enhanced chemiluminescence from the myeloperoxidase reaction

Anti-inflammatory and membrane stabilizing properties of methyl jasmonate in rats

The present investigation was carried out to evaluate anti-inflammatory and membrane stabilizing properties of methyl jasmonate (MJ) in experimental rat models of acute and chronic inflammation. The effects of MJ on acute inflammation were assessed using carrageenan-induced rat's paw edema model. The granuloma air pouch model was employed to evaluate the effects of MJ on chronic inflammation produced by carrageenan in rats. The number of white blood cells (WBC) in pouch exudates was estimated using light microscopy. The levels of biomarkers of oxidative stress, such as malondialdehyde (MDA), glutathione (GSH) and activity of antioxidant enzymes in the exudates, were determined using spectrophotometry. The membrane stabilizing property of MJ was assessed based on inhibition of hemolysis of rat red blood cells (RBC) exposed to hypotonic medium. Our results indicated that MJ (25-100 mg·kg^-1, i.p.) produced significant anti-inflammatory activity in carrageenan-induced paw edema in rats (P < 0.05). MJ reduced the volume of pouch exudates and the number of WBC in carrageenan-induced granulomatous inflammation. It also exhibited potent antioxidant and membrane stabilizing activities. In conclusion, these findings suggest the therapeutic potentials of methyl jasmonate in disease conditions associated with inflammation and its anti-inflammatory activity may be related to its antioxidant and membrane stabilizing activities.

Differential Effectiveness of Clinically-Relevant Analgesics in a Rat Model of Chemotherapy-Induced Mucositis

Chemotherapy-induced intestinal mucositis is characterized by pain and a pro-inflammatory tissue response. Rat models are frequently used in mucositis disease investigations yet little is known about the presence of pain in these animals, the ability of analgesics to ameliorate the condition, or the effect that analgesic administration may have on study outcomes. This study investigated different classes of analgesics with the aim of determining their analgesic effects and impact on research outcomes of interest in a rat model of mucositis. Female DA rats were allocated to 8 groups to include saline and chemotherapy controls (n = 8). Analgesics included opioid derivatives (buprenorphine; 0.05mg/kg and tramadol 12.5mg/kg) and NSAID (carprofen; 15mg/kg) in combination with either saline or 5-Fluorouracil (5-FU; 150mg/kg). Research outcome measures included daily clinical parameters, pain score and gut histology. Myeloperoxidase assay was performed to determine gut inflammation. At the dosages employed, all agents had an analgesic effect based on behavioural pain scores. Jejunal myeloperoxidase activity was significantly reduced by buprenorphine and tramadol in comparison to 5-FU control animals (53%, p = 0.0004 and 58%, p = 0.0001). Carprofen had no ameliorating effect on myeloperoxidase levels. None of the agents reduced the histological damage caused by 5-FU administration although tramadol tended to increase villus length even when administered to healthy animals. These data provide evidence that carprofen offers potential as an analgesic in this animal model due to its pain-relieving efficacy and minimal effect on measured parameters. This study also supports further investigation into the mechanism and utility of opioid agents in the treatment of chemotherapy-induced mucositis.

Synthesis, inhibition of NO production and antiproliferative activities of some indole derivatives

The synthesis and the biological evaluation of pyrano[3,2-e]indoles and their reaction intermediates are described. The compounds prepared were evaluated for their inhibition of NO production, antioxidant activity and also for their ability to inhibit in vitro the growth of four human tumor cell lines: large lung carcinoma (COR-L23), alveolar basal epithelial carcinoma (A549), amelanotic melanoma (C32) and melanoma (A375). The two reaction intermediates, 5a and 5b, showed the highest inhibition of NO production in murine monocytic macrophage (IC(50) = 1.1 microM and IC(50) = 2.3 microM respectively). Compound 5a was the most active against melanotic melanoma (IC(50) = 11.8 microM) while the other compounds exhibited weak cytotoxicity with IC(50) values >50 microM on all cell lines.

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.

The efficacy of herbal medicine (kampo) in reducing the adverse effects of IFN-beta in chronic hepatitis C

The purpose of this study was to determine if the adverse effects of interferon (IFN) in hepatitis C patients could be reduced by treatment with Japanese Oriental (Kampo) medicine. Twelve patients with chronic hepatitis C were treated with a combination of IFN-beta and either Mao-to or Dai-seiryu-to (groups A and B), and 16 patients were treated with IFN-beta alone (group C). Mao-to was administered to eight patients and Dai-seiryu-to was administered to four in groups A and B, respectively. Adverse effects were evaluated by clinical and laboratory examinations. The severity of symptoms was daily self-classified into four categories (1: none, 2: very slight, 3: moderate, and 4: serious), using a questionnaire consisting of 29 items. Scores of symptom such as discomfort and fever in group A, and discomfort, general malaise, paresthesia and arthralgia in group B were significantly lower than those in group C (p < 0.05). In all patients, HCV-RNA was negative at the end of the treatment, and serum alanine aminotransferase (ALT) levels had normalized transiently in all group A and B patients with genotype 1b by 2 weeks after cessation of IFN treatment. This study indicates that Kampo medicines are useful for reducing the adverse effects accompanying IFN treatment in patients with chronic hepatitis C without reducing the antiviral effects.

Discovery of molecular mechanisms of neuroprotection using cell-based bioassays and oligonucleotide arrays

Oxidative injury and the resulting death of neurons is a major pathological factor involved in numerous neurodegenerative diseases. However, the development of drugs that target this mechanism remains limited. The goal of this study was to test a compound library of approved Food and Drug Administration drugs against a hydrogen peroxide-induced oxidant injury model in neuroblastoma cells. We identified 26 neuroprotective compounds, of which megestrol, meclizine, verapamil, methazolamide, sulindac, and retinol were examined in greater detail. Using large-scale oligonucleotide microarray analysis, we identified genes modulated by these drugs that might underlie the cytoprotection. Five key genes were either uniformly upregulated or downregulated by all six drug treatments, namely, tissue inhibitor of matrix metalloproteinase (TIMP1), ret-proto-oncogene, clusterin, galanin, and growth associated protein (GAP43). Exogenous addition of the neuropeptide galanin alone conferred survival to oxidant-stressed cells, comparable to that seen with the drugs. Our approach, which we term "interventional profiling," represents a general and powerful strategy for identifying new bioactive agents for any biological process, as well as identifying key downstream genes and pathways that are involved.

Effects of non-steroidal anti-inflammatory drugs on the luminol and lucigenin amplified chemiluminescence of human neutrophils

A panel of non-steroidal anti-inflammatory drugs commonly used for therapeutic purposes was assessed for their effects on the respiratory burst of isolated human polymorphonuclear neutrophils. Cells were stimulated with opsonised yeast and the production of reactive oxygen species was measured by amplified chemiluminescence with luminol and lucigenin which are two luminogenic agents measuring different cellular events. A special attention was devoted to the establishment of dose-effect curves and calculation of ED50. Some of the drugs tested (acemetacine, diclofenac, flufenamic acid and niflumic acid) were able to decrease both luminol and lucigenin chemiluminescence in a dose-dependent manner reflecting an inhibitory effect on the respiratory burst. The most potent derivative was flufenamic acid (ED50 8 and 78 microM, respectively, with luminol and lucigenin), followed by diclofenac (21 and 98 microM), niflumic acid (97 and 227 microM) and acemetacine (585 and 427 microM). In contrast, several other drugs (flurbiprofen, ibuprofen, ketoprofen, piroxicam) stimulated both luminol and lucigenin chemiluminescence, suggesting a pro-oxidant activity. Acetylsalicylic acid (up to 1250 microM) was a modest inhibitor (maximum 25% inhibition) showing no dose-dependent effect and tolmetin (up to 125 microM) had no significant effect in both systems. The results were in agreement using both luminogenic agents, except for indomethacin, naproxen and tenoxicam which showed different kinds of effects. The unspecific and complex nature of the measurement systems used did not allow to give a complete mechanistic interpretation of the results, but the comparison with literature data gave some pertinent explanations for both anti- and pro-oxidant effects.

Ketamine attenuates endotoxin-induced leukocyte adherence in rat mesenteric venules

OBJECTIVES

To determine the influence of ketamine on endotoxin-induced leukocyte adherence and venular microhemodynamics.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Thirty male Wistar rats.

INTERVENTIONS

The rats were pretreated with ketamine (10 mg/kg iv) or 0.9% saline, and both groups were given endotoxin (Escherichia coli lipopolysaccharide; 5 mg/kg iv). The control group received two doses of 0.9% saline.

MEASUREMENTS AND MAIN RESULTS

The rates of leukocyte adherence and changes in microhemodynamics were monitored in rat mesenteric venules, using in vivo video microscopy. The number of adherent leukocytes was determined on-line in 10-min intervals from 60 mins before until 2 hrs after endotoxin administration. Venular diameters, red blood cell velocity, volumetric blood flow, and the venular wall shear rate were monitored before and at 10, 30, and 60 mins after endotoxin exposure. A 6.3-fold increase in the number of adherent leukocytes was observed 10 mins after administration of endotoxin when compared with control animals (5.87 +/- 0.69 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .001). This increase remained unchanged for 120 mins. In ketamine-pretreated rats, a 2.6-fold increase in leukocyte adherence occurred during the first 20 mins after endotoxin exposure (2.40 +/- 0.46 vs. 0.93 +/- 0.21 adherent cells/100 microns; p < .01). However, no difference in the number of adherent leukocytes between ketamine-pretreated and control animals was found after this 20-min period. In animals of the control group, no increase in leukocyte adherence occurred during the entire observation time. Diameters of mesenteric venules did not change after endotoxin exposure in any of the groups. Red blood cell velocity and venular blood flow in the endotoxin-treated groups decreased 10 mins after the injection of endotoxin when compared with controls, but these values did not show any difference when they were compared between ketamine and saline-pretreated animals. Similarly, venular wall shear rate in the endotoxin-treated groups decreased 10 and 30 mins after injection of endotoxin. However, no significant difference occurred between ketamine and saline-pretreated animals.

CONCLUSIONS

Pretreatment with ketamine attenuates endotoxin-induced leukocyte adherence by a shear rate-independent mechanism, suggesting reduced expression of adhesion molecules. These results indicate that ketamine exerts an anti-inflammatory effect, which might be beneficial in septic patients.

Effects of indole-3-acetic acid on croton oil- and arachidonic acid-induced mouse ear edema

The indole-3-acetic acid (IAA) is a plant growth hormone (auxin) being considered as a tryptophan metabolite in animals. The main purpose of this work was to verify IAA's topical anti-inflammatory action using croton oil- or arachidonic acid-induced mouse ear edema, in comparison to known anti-inflammatory agents. IAA antioxidant activity was also verified by measuring the inhibition of brain homogenate lipid peroxidation with the thiobarbituric acid reactive substances (TBARS) test. IAA inhibited the action of both croton oil-and arachidonic acid-induced edema in a dose-dependent manner (4.0 mumoles IAA inhibited 75.8% in croton oil and 82.5% in arachidonic acid induced ear edema). Both IAA (5.3 mM) and indomethacin (8.0 mM) inhibited TBARS formation. Data suggest that IAA exhibits antiinflammatory effect possibly by its anti-oxidant activity.

Limitation of myocardial infarct size in pigs with a dual lipoxygenase-cyclooxygenase blocking agent by inhibition of neutrophil activity without reduction of neutrophil migration

OBJECTIVES

The purpose of this study was to assess the effect of the dual cyclooxygenase-lipoxygenase blocking agent BW755C on the extent of myocardial infarction in the pig and to identify the mechanisms of any cardioprotective action of this drug.

BACKGROUND

Activated neutrophils contribute to reperfusion injury after myocardial infarction and inhibition of neutrophil function can limit infarct size.

METHODS

In 9 control and 10 study pigs pretreated with intravenous BW755C (10 mg/kg body weight) 30 min before coronary occlusion, ischemia was induced by a 50-min occlusion of the mid-left anterior descending coronary artery, followed by 3 h of reperfusion. Heart rate, arterial pressure, left ventricular end-diastolic pressure, the first derivative of left ventricular pressure (dP/dt) and regional myocardial blood flow were measured during control, occlusion and reperfusion periods. Infarct size was determined by histochemical staining; and myeloperoxidase activity, a marker for tissue neutrophil content, was assessed in normal and infarcted myocardium. The effect of BW755C on the function of isolated neutrophils stimulated with zymosan-activated serum was evaluated by measuring neutrophil degranulation, leukotriene B4 production, superoxide generation and chemotaxis.

RESULTS

Hemodynamic function and regional myocardial blood flow were similar in control and BW755C-treated animals. BW755C significantly reduced myocardial infarct size compared with that in control animals, as measured by infarct/risk areas by histochemical staining (39 +/- 5% vs. 63 +/- 7%, p < 0.05). Myocardial myeloperoxidase activity was similar in normal, salvaged and infarcted areas in the control and treated groups, indicating that neutrophil accumulation in injured myocardium was unaltered by BW755C. However, this agent attenuated function of isolated, stimulated (zymosan-activated serum) neutrophils. At a concentration of 0.03 mg/ml, BW755C inhibited degranulation (-46%), leukotriene B4 production (-48%) and superoxide generation (-74%), but there was minimal inhibition of chemotaxis in vitro.

CONCLUSIONS

These findings demonstrate that myocardial infarct size can be reduced by selective inhibition of neutrophil cytotoxic activity without affecting neutrophil migration into injured myocardium.

Role of oxygen radicals and arachidonic acid metabolites in the reverse passive Arthus reaction and carrageenin paw oedema in the rat

1. The role of arachidonic acid metabolites and oxygen radicals in carrageenin-induced rat paw oedema and dermal reverse passive Arthus reaction (RPA) have been investigated. 2. Indomethacin (10 mg kg-1, p.o.) inhibited carrageenin paw oedema when administered 30 min before, but not 2 h after carrageenin. BWB70C (10 mg kg-1, p.o.), a selective inhibitor of 5-lipoxygenase, had no effect whether administered before or after carrageenin. Administration of both indomethacin and BWB70C had no greater anti-inflammatory effect than indomethacin alone. 3. BW755C (20 mg kg-1, p.o.), which inhibits the cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism, or superoxide dismutase-polyethylene glycol conjugate (SOD-PEG, 3000 u, i.v.) inhibited carrageenin paw oedema whether administered either 30 min before, or 2 h after carrageenin. 4. Pretreatment with dexamethasone (0.1 mg kg-1) or colchicine (2 mg kg-1), likewise suppressed carrageenin paw oedema. 5. BW755C (25-100 mg kg-1, p.o.) dose-dependently reduced plasma leakage in the RPA, whereas indomethacin (5 mg kg-1, p.o.) or BWB70C either alone or in combination, did not. 6. SOD-PEG (300-3000 u, i.v.) dose-dependently inhibited plasma leakage in the RPA. In addition, the iron chelator and peroxyl radical scavenger, desferrioxamine (200 mg kg-1, s.c.) also inhibited plasma leakage. 7. Pretreatment with dexamethasone (0.1 mg kg-1) or colchicine (1 mg kg-1) reduced the plasma leakage in RPA, whereas MK-886 (10 mg kg-1) had no effect. 8. These results indicate an important role for oxygen radicals but not arachidonic acid metabolites in the maintenance of carrageenin paw oedema and the plasma leakage in RPA. Furthermore, the results suggest that the anti-inflammatory actions of BW755C can be dissociated from its effects on arachidonic acid metabolism and are attributed to its anti-oxidant activity.

Protection by antibiotics against myeloperoxidase-dependent cytotoxicity to lung epithelial cells in vitro

Myeloperoxidase, in the presence of noncytotoxic concentrations of H2O2, was used to induce cytotoxicity to the lung epithelial cell line, AKD. When the cationic aminoglycosides, tobramycin and gentamicin were added to the cells in the presence of myeloperoxidase and H2O2, cytotoxicity was completely inhibited. In addition, tobramycin prevented cytotoxicity induced by cystic fibrosis sputum and H2O2. Protection against myeloperoxidase and H2O2 was also observed with the thioether-containing antibiotics, ticarcillin and ceftazidime, but at higher concentrations than with the aminoglycosides. Analysis of spectral properties, dimethylsulfoxide-mediated reduction, and ethyl acetate/NaCl partitioning, demonstrated that aminoglycosides converted HOCl to hydrophilic noncytotoxic chloramines, but were unable to prevent the oxidation of sulfhydryls and methionine by HOCl. In contrast, ticarcillin and ceftazidime were highly effective inhibitors of HOCl-mediated sulfhydryl and methionine oxidation. These results suggest that aminoglycosides protect lung epithelial cells against myeloperoxidase-dependent oxidant injury by binding to anionic cell surfaces and converting HOCl to hydrophilic noncytotoxic chloramines, whereas penicillins and cephalosporins are potent HOCl scavengers capable of protecting critical extracellular molecules against oxidation.

Ibuprofen intervention in canine septic shock: reduction of pathophysiology without decreased cytokines

This study was undertaken to evaluate the effect of a cyclooxygenase inhibitor, ibuprofen, at various time intervals in a live Escherichia coli model of canine septic shock. Group I (control) animals (n = 5) received a LD100 dose of 10(9) live E. coli per kilogram were given no further treatment. Group II animals (n = 5) received a 10 mg/kg bolus of ibuprofen 10 min prior to bacterial infusion. Group III animals (n = 5) received ibuprofen 15 min after the bacterial infusion. Statistical analysis revealed the following: Group II animals had significantly higher MABP and significantly lower levels of serum fluorescent products (superoxide radical activity), plasma thromboxane B2, prostaglandin E2, and endotoxin levels compared to Group I animals (P less than 0.05). Plasma levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6) were significantly elevated (P less than 0.05) from baseline in all animals (Groups I, II, and III), but ibuprofen treatment failed to either increase or decrease these levels. This study demonstrates that ibuprofen treatment can significantly reverse the deleterious hemodynamic and metabolic effects commonly seen in live E. coli septic shock without depressing the endogenous production of TNF or IL-6. These data support the hypothesis that sepsis initiates a cascade of mediators with the cytokines TNF and IL-6 being proximal events which in turn stimulate the next level, with ibuprofen probably exerting its inhibitory effect distal to this point in the cascade.

Mechanism of inhibition of myeloperoxidase by anti-inflammatory drugs

Hypochlorous acid (HOCl) is the most powerful oxidant produced by human neutrophils, and should therefore be expected to contribute to the damage caused by these inflammatory cells. It is produced from H2O2 and Cl- by the heme enzyme myeloperoxidase (MPO). We used a H2O2-electrode to assess the ability of a variety of anti-inflammatory drugs to inhibit conversion of H2O2 to HOCl. Dapsone, mefenamic acid, sulfapyridine, quinacrine, primaquine and aminopyrine were potent inhibitors, giving 50% inhibition of the initial rate of H2O2 loss at concentrations of about 1 microM or less. Phenylbutazone, piroxicam, salicylate, olsalazine and sulfasalazine were also effective inhibitors. Spectral investigations showed that the inhibitors acted by promoting the formation of compound II, which is an inactive redox intermediate of MPO. Ascorbate reversed inhibition by reducing compound II back to the active enzyme. The characteristic properties that allowed the drugs to inhibit MPO reversibly were ascertained by determining the inhibitory capacity of related phenols and anilines. Inhibition increased as substituents on the aromatic ring became more electron withdrawing, until an optimum reduction potential was reached. Beyond this optimum, their inhibitory capacity declined. The best inhibitor was 4-bromoaniline which had an I50 of 45 nM. An optimum reduction potential enables inhibitors to reduce MPO to compound II, but prevents them from reducing compound II back to the active enzyme. Exploitation of this optimum reduction potential will help in targeting drugs against HOCl-dependent tissue damage.

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

The results presented herein demonstrate that the non-steroidal anti-inflammatory drug (NSAID) indomethacin is a strong inhibitor of the formation of HOCl by murine neutrophils (50% inhibition at 15 microM). Addition of 40 microM indomethacin to activated neutrophils caused 80% inhibition of HOCl formation throughout a 60-min time course while slightly increasing the levels of O2- and H2O2 produced. Comparable degrees of inhibition were achieved when the cells were stimulated with phorbol myristate acetate and with opsonized zymosan. Control experiments indicated that the drug did not act by scavenging HOCl. Direct inhibition of the chlorinating activity of myeloperoxidase (MPO) was confirmed using highly purified human enzyme in vitro. Kinetic analysis of the mechanism of inhibition showed that the drug was competitive with respect to Cl- and uncompetitive with respect to H2O2, showing a Ki of 37 microM. In contrast to its inhibition of the oxidation of Cl- by MPO, indomethacin had no effect on the peroxidative activity of the enzyme (oxidation of 4-aminoantipyrene), nor did it inhibit the activity of several other enzymes involved in H2O2 metabolism, including horseradish peroxidase, catalase, xanthine oxidase, and superoxide dismutase. Finally, it was found that inhibition of HOCl formation was a shared but non-uniform property of many NSAIDs; piroxicam, salicylate, sulindac, ibuprofen, and aspirin were all inhibitory but at widely different concentrations [Ki(app) values of 0.05, 0.18, 0.18, greater than 1, and 3 mM respectively] that correlated only partially with their therapeutic dose range. The results encourage further studies into the possibility that inhibition of HOCl formation may constitute an additional mechanism whereby NSAIDs reduce tissue destruction in chronically inflamed tissues.

Recent progress in testing the longevity determinant and dysdifferentiation hypotheses of aging

An overview of the longevity determinant and dysdifferentiation hypotheses is presented, highlighting some of the major postulates and predictions. Results of recent experiments testing these hypotheses are discussed, including the search for specific longevity determinant genes and evidence that cancer and aging may have common causative mechanisms of action and control. Regulation of oxidative stress is considered a potential longevity determinant mechanism and methods and results testing this prediction are reviewed. Possibility of enhancing protective mechanisms against oxidative stress is discussed by way of intervention of central regulatory mechanisms of antioxidants using the cyclase-arachidonic acidcyclooxygenase (GAC model).

Role of arachidonic acid metabolites in acid-pepsin injury to rabbit esophagus

The role of cyclooxygenase and lipoxygenase metabolites of arachidonic acid in experimental esophageal were lumenally perfused for 1 h with acidified saline (pH 2.0) with or without pepsin followed by a second hour with acidified saline. Separate groups of pepsin-perfused animals were pretreated with indomethacin, a cyclooxygenase inhibitor, or BW755C, a lipoxygenase-cyclooxygenase inhibitor. Esophageal injury was graded grossly. H+ and hemoglobin fluxes were determined. Acidified saline caused no significant damage. Pepsin induced moderate injury. Indomethacin decreased pepsin-induced H+ flux by 55% without affecting the other indices. BW755C, by all measurements, dramatically increased pepsin-induced injury. In separate experiments, cyclooxygenase activity was decreased by indomethacin and BW755C by 62% and 49%, respectively. Lipoxygenase activity was decreased 74% by BW755C and was not significantly affected by indomethacin. These results suggest that esophageal cytoprotection is mediated by endogenous lipoxygenase metabolites.

What do we measure by a luminol-dependent chemiluminescence of phagocytes?

The review presents a survey of published findings concerning the mechanism of luminol-dependent chemiluminescence in biological systems. The potential of various oxygen species (superoxide anion, hydrogen peroxide, hydroxyl radical) to react with luminol is discussed. The ability of commonly used enzymes (superoxide dismutase, catalase), inhibitors, and oxygen radical scavengers to discriminate between individual oxygen species is assessed together with the potential of a variety of substances encountered in biological systems to interfere in luminol-dependent chemiluminescence reactions. It is concluded that luminol-dependent chemiluminescence gives at present very little ability to discriminate between individual oxygen or radical species. Furthermore, luminol-dependent chemiluminescence used in biological systems is extremely prone to many interferences, which are very difficult to control.

Failure of the inhibition of rat gastric mucosal 5-lipoxygenase by novel acetohydroxamic acids to prevent ethanol-induced damage

1. The role of leukotriene B4 (LTB4) and LTC4 as mediators of gastric mucosal damage following ethanol challenge in vivo has been investigated using two selective 5-lipoxygenase inhibitors, BW A4C and BW A137C. 2. Oral administration of ethanol to rats in vivo, induced macroscopic damage to the gastric mucosa and markedly increased the formation of the 5-lipoxygenase products, LTB4 and LTC4, from the mucosa ex vivo. 3. Pretreatment with the acetohydroxamic acids BW A4C and BW A137C (5-50 mg kg-1 p.o.) dose-dependently reduced ethanol-stimulated LTB4 and LTC4 formation by the gastric mucosa, with an ID50 of approximately 5 mg kg-1 p.o. 4. A single oral dose of BW A4C (20 mg kg-1) induced near-maximal inhibition of mucosal LTB4 formation within 30 min, which was well maintained for 5 h, whereas BW A137C (20 mg kg-1 p.o.) induced maximal inhibition between 30 and 60 min after administration, which then diminished over the subsequent 5 h. 5. The mucosal formation of the cyclo-oxygenase product, 6-keto-prostaglandin F1 alpha, which was unaltered following ethanol challenge, was not inhibited by the acetohydroxamic acids. Likewise, the small increase in mucosal thromboxane B2 formation following challenge was not inhibited by BW A4C. 6. Neither BW A4C nor BW A137C, at doses that almost completely inhibited the mucosal synthesis of LTB4 or LTC4, reduced the macroscopic gastric mucosal damage induced by ethanol. 7. Pretreatment with the lipoxygenase inhibitor BW 755C (5-50 mg kg-1 p.o.) did reduce mucosal damage, but there was a dissociation between the degree of protection and the inhibition of leukotriene biosynthesis. 8. Oral administration of high doses of either BW A4C or BW A137C (300mgkg-1) did not induce macroscopic gastric damage over a 3 h period. 9. These findings suggest that the leukotrienes, LTB4 and LTC4 are not the primary mediators of ethanol-induced acute mucosal damage, but do not exclude their role in more chronic gastric damage and inflammation.

Deactivation of sulindac-sulphide by human renal microsomes

The renal metabolism of sulindac-sulphide was studied in subcellular fractions from human kidney. It was shown that renal microsomes, in the presence of NADPH, effectively catalyzed the sulphoxidation of sulindac-sulphide. Also the mitochondrial fraction catalyzed the reaction but at a ten-fold lower rate than the microsomes. Carbon monoxide, metyrapone and n-octylamine did not inhibit renal sulphoxidation of sulindac-sulphide and the reaction could occur in a monooxygenase containing fraction free from NADPH-cytochrome P-450 reductase. Hydroxylation of lauric acid was studied in microsomes and in the purified monooxygenase containing fraction under the same experimental condition as sulindac-sulphide sulphoxidation. Lauric acid is a substrate known to be metabolized by a renal cytochrome P-450 to 11 and 12-hydroxylated products. This reaction was sensitive to carbon monoxide and did not occur in the absence of NADPH cytochrome P-450 reductase. Based on these results we conclude that cytochrome P-450 plays at the most a limited role in human kidney metabolism of sulindac-sulphide. In contrast, sulphoxidation of sulindac-sulphide was substantially reduced in the presence of methimazole suggesting a role of the flavin-containing monooxygenase in the renal biotransformation of sulindac-sulphide in man.

The suppression of granulocyte functions by lipophilic antioxidants

The effects of several antioxidants on the three major functions of human neutrophils--oxidative burst, secretion and leukotriene formation--were investigated with special emphasis on the lipophilicity. The most striking differences were obtained when ascorbate and the lipophilic ester ascorbyl palmitate were compared. As expected, the luminol- and lucigenin-dependent chemiluminescence was inhibited by all antioxidants to a different degree. Ascorbyl palmitate was able to block the biphasic luminol-dependent response completely with IC50 values of 10 and 25 microM for the first and second phase, respectively. In contrast, ascorbate only blocked efficiently the first phase of the response. The secretion of elastase was inhibited by ascorbyl palmitate dose-dependently with an IC50 value of around 200 microM, whereas ascorbate was completely inactive. Electron microscopy supported the assumption that inhibition was due to a block in degranulation and not to enzyme inactivation. This was further supported by a parallel, although somewhat lower, inhibition of other secretory enzymes like myeloperoxidase, beta-glucuronidase or lysozyme. Cells treated with the Ca2+-ionophore A23187 responded by LTB4-synthesis which was also inhibited by ascorbyl palmitate. A very efficient inhibition was observed in cell homogenates with an IC50 value of 1.5 microM. No inhibition by ascorbate was detected in both systems. Concomitant with the inhibition of 5-lipoxygenase the activity of 15-lipoxygenase increased. We conclude that cellular reductants may control neutrophil functions and that the inhibition by ascorbyl palmitate of the three processes relevant for inflammatory responses could be of therapeutic importance.

Enhancement of human neutrophil function by platelets: effects of indomethacin

To characterize the influence of presence of platelets on human neutrophil function, neutrophil oxidative burst, chemotaxis, leukotriene B4 and prostacyclin generation were examined in the presence of physiologic concentration of platelets (40: 1). Presence of platelets significantly (P less than or equal to 0.05) increased all these neutrophil functions. To determine if cyclooxygenase products are involved in platelet-neutrophil interaction, neutrophils (+/- platelets) were incubated with indomethacin. Although high concentrations of indomethacin (10 microM) inhibited neutrophil (no platelets) chemotaxis and leukotriene B4 generation, these inhibitory effects of indomethacin were attenuated in the presence of platelets. Thus presence of platelets enhances neutrophil activity and overcomes the inhibitory effects of indomethacin on neutrophils.

Poly L-histidine. A potent stimulator of superoxide generation in human blood leukocytes

Poly-L-histidine (PHSTD) of molecular weight 26,000 induced the generation of large amounts of superoxide (O2-) and hydrogen peroxide (H2O2) in human neutrophils (PMNs). Despite its low solubility at neutral pH, PHSTD was bound very rapidly to the PMN surfaces. Maximal generation of O2- took place with 4-5 X 10(-6) M of PHSTD, starting after a lag of about 25 sec and proceeding for 15-17 min at a rate of 150 nmol/10(7) PMNs/min, suggesting that this polycation is one of the most potent stimulators of O2- generation known, PHSTD was found to be non-toxic for PMNs even at millimolar concentrations. Generation of O2- by PHSTD depended on extracellular calcium; it was inhibited by calcium channel blockers and by trifluoperazine, and it triggered a sharp rise in intracellular calcium as determined by the Quin 2 fluorescence technique. The generation of both O2- and H2O2 by PHSTD was partially inhibited by cytochalasin B or (CYB, CYE). On the other hand, CYB markedly enhanced the generation of both O2- and H2O2 following stimulation of PMNs either by PHSTD, polyarginine, histone, or by antibody-opsonized group A streptococci. Electron microscopic analysis and NBT reduction tests revealed that both PHSTD and PHSTD-opsonized streptococci were avidly phagocytosed by PMNs. Since CYB totally inhibited internalization of both PHSTD and the PHSTD-opsonized streptococci, it was suggested that these agents stimulated oxygen radical generation mainly on the leukocyte surfaces. Complexes (CX) formed between PHSTD and polyanethole sulfonate (a strong polyanion) or between histone and the polyanion mimicked immune CX in their ability to trigger the generation of large amounts of O2- which were inhibited by CYB. Generation of O2- and chemiluminescence either by PHSTD or by PHSTD-opsonized streptococci were markedly inhibited by poly-L-glutamate, suggesting that PHSTD acted as a cationic agent which interacted via electrostatic forces with some negatively charged sites in the leukocyte membrane. Generation of H2O2 by PHSTD was also markedly inhibited by deoxyglucose, KCN, DASA, as well as by the lipoxygenase inhibitors nordihydroguaiaretic acid, phenidone, and propylgallate. On the other hand, cyclooxygenase inhibitors such as aspirin, indomethacin, and piroxicam were inactive, suggesting that arachidonic acid metabolism via lipoxygenase pathway might have been involved in the activation by PHSTD of the NADPH oxidase in PMNs.(ABSTRACT TRUNCATED AT 400 WORDS)

The amplified chemiluminescence test to characterize antirheumatic drugs as oxygen radical scavengers

High levels of reactive oxygen species (ROS) are generated by phagocytes involved in host defence and inflammation. Thus, it appears highly desirable to learn more about the potential of antirheumatic drugs to scavenge ROS or to inhibit their enzymatic generation. Amplified chemiluminescence (CL) allows detection of O-2 using lucigenin (LgCL) or H2O2 using luminol (LuCL). A total of 43 compounds have been tested quantitatively in vitro (10(-6) to 10(-4) mol/l) with respect to three test parameters; varying cell-activity, and incubation-time employing two different phagocyte populations (neutrophils/macrophages). The most active compounds with LgCL were the known radical scavengers nordihydroguaiaretic acid (NDGA), N-propyl gallate, superoxide dismutase and chloroquine, the non-steroidal anti-inflammatory drugs (NSAID) benzydamine, timegadine, carprofen, enolicam, the known lipoxygenase inhibitors (e.g. CBS 1108/1114, BW 755C) and glucosaminoglucan polysulfate. Inactive in this system were corticosteroids (prednisolone, dexamethasone) most of the tested NSAID (N = 16/20), most disease modifying drugs (D-penicillamine, levamisole, gold-TM) and the anti-gout drugs (sulfinpyrazone, allopurinol, colchicine). Therefore amplified CL with lucigenin appears to be a rapid, kinetic, reproducible means of pharmacological profiling in vitro new anti-inflammatory drugs for radical scavenger activity.

Free radical production at the site of an acute inflammatory reaction as measured by chemiluminescence

A foot-pad oedema model was used to investigate the presence of free radicals using a chemiluminescence method. This model is an example of a cell mediated hypersensitivity reaction. Male rats were inoculated in the scruff with Freund's Complete Adjuvant (FCA) on Day 0 and then challenged 6 days later with FCA in one hind paw. An acute inflammatory reaction was initiated over the following 96 hours and within 4 hours of induction, reactive oxygen species were detected in the inflamed tissue. A peak of chemiluminescence activity was seen 8 hours after the induction of the inflammatory reaction, well before maximum oedema was observed. Using mannitol, catalase and DABCO to elucidate the nature of the reactive oxygen species it was found that hydroxyl radicals, hydrogen peroxide and singlet oxygen all contributed to this burst of oxidative activity and are therefore probably involved with the process of lipid peroxidation and the severity of an inflammatory reaction.

Variations of gastric transmucosal potential difference and lesion formation during hemorrhagic shock in the rat

We measured transmucosal potential difference (PD) of the stomach in anesthetized rats before, during, and after hemorrhagic shock, and investigated the effects of various drugs on the PD and gastric lesion during this period. After hemorrhagic shock, there was a decrease of PD and an increase of luminal pH in the saline-perfused stomach, the degree of these changes being dependent on a fall in the arterial blood pressure. The graded reduction of PD in response to hemorrhagic shock was similarly observed in the acid-perfused stomach as in the saline-perfused one. However, gastric lesions developed only in the former, and a significant correlation was found between the lesion index and the fall in blood pressure, the reduction in PD, or the concentration of HCl as the perfusate. Subcutaneously administered propantheline bromide (30 mg/kg) or cimetidine (100 mg/kg) had no effect on gastric lesion and PD reduction caused by hemorrhagic shock. These lesions were significantly inhibited by 16,16-dimethyl prostaglandin E2 (10 micrograms/kg) or sulindac (100 mg/kg), a scavenger of OH., and aggravated by indomethacin (1 mg/kg), with less effect on the PD reduction. Intravenous infusion of NaHCO3 (0.5 M) also significantly prevented the lesion with a concomitant suppression of the PD reduction in response to hemorrhagic shock, but these effects were significantly reversed by pretreatment of the animals with acetazolamide (50 mg/kg). These results indicate that during hemorrhagic shock the PD may largely reflect the impairment of mucosal blood flow and may be used as an indicator of mucosal vulnerability to acid, gastric lesions develop only in the presence of exogenous acid, and production of prostaglandins and superoxide radicals may be involved in the pathogenesis of gastric lesions.

The effects of cyclooxygenase inhibition on chemiluminescence and aggregation in sheep neutrophils

Antiinflammatory actions of cyclooxygenase inhibitors may be related to inhibition of the synthesis and release of prostaglandins and thromboxane or to nonspecific actions of particular drugs. The role of cyclooxygenase products of arachidonic acid was studied in two leukocyte functions, free radical release and aggregation, after complement activation. Dose response curves were constructed after treatment with meclofenamate or ibuprofen. To differentiate between effects on free radical release from complement activated neutrophils and scavenging free radicals, additional experiments were made with a cell free system to generate free radicals. Both drugs inhibited complement initiated neutrophil chemiluminescence in a dose dependent manner. Meclofenamate acted primarily as a scavenger while ibuprofen inhibited free radical release. Neither drug had any inhibitory effects on complement induced leukocyte aggregation.

Role of prostanoids in the protective actions of BW755C on the gastric mucosa

The ability of BW755C to reduce ethanol- or indomethacin-induced gastric damage and the role of prostanoids in the mechanism of this action were examined in the rat. BW755C (1-100 mg/kg) caused a dose-related reduction in the amount of damage produced by oral administration of 40% ethanol in 100 mM HCl. At the doses tested, BW755C had no significant effect on mucosal 6-keto-prostaglandin F1 alpha synthesis, but did cause a dose-dependent reduction in thromboxane B2 synthesis. The effect on thromboxane synthesis may be due to a selective inhibition of platelet cyclo-oxygenase by BW755C. The higher doses of BW755C (50 and 100 mg/kg) caused a significant increase in the volume of fluid present in the gastric lumen, which may contribute to the protective action of the drug against ethanol-induced damage. Oral administration of BW755C (50 mg/kg) significantly reduced the extent of gastric damage caused by subcutaneous injection of indomethacin (20 mg/kg) indicating that it is unlikely that the protective action of BW755C is mediated by endogenous prostanoids. The mechanism of the protective actions of BW755C may be related to its reported ability to inhibit lipoxygenase or to its actions as a free-radical scavenger.

Inhibition of plasmacytoma development in BALB/c mice by indomethacin

Indomethacin given continuously in the drinking water (20 micrograms/ml) to BALB/cAn pi mice during the latent period of pristane-induced plasmacytoma development dramatically reduced the plasmacytoma incidence from 34.9 to 2.2%. Additionally, indomethacin given from day 0 to 120 or begun as late as 60 d after a single injection of 1.0 ml pristane was also highly effective in reducing the development of plasmacytomas. Indomethacin treatment did not prevent the formation of a peritoneal inflammatory exudate or peritoneal oil granulomatous tissue, although it had a mild inhibitory effect on the intensity of the cellular inflammation, particularly after extensive treatment of greater than 100 d. Indomethacin treatment reduced the incidence of arthritis by 50%. A major effect of indomethacin treatment was a reduction in the appearance of microscopic plasmacytomas that appear in the oil granuloma before plasmacytomas can be detected by routine sampling of the peritoneal exudate. Between days 116 and 181, 16 of 20 mice given 0.5 ml pristane were found to have foci of plasmacytoma cells, while only 2 of 20 indomethacin-treated mice had foci-containing plasmacytoma cells. The number of mice with microscopic foci in the pristane-treated group greatly exceeded the expected incidence of plasmacytomas (22%) at this dose of pristane. The growth of primary plasmacytomas in transplant that is dependent on the pristane-conditioned peritoneal environment was not inhibited by indomethacin treatment. The role of indomethacin in inhibiting plasmacytoma development was not established; two possibilities are that it inhibits production of mutagenic and tissue destructive oxidants by inflammatory cells, and it inhibits prostaglandin synthesis and intracellular production of oxidant biproducts.

In vitro antioxidant properties of potential biotransformation products of salicylate, sulphasalazine and amidopyrine

2,3-and 2,5-dihydroxybenzoate (formed from salicylate by nonenzymatic or enzymatic hydroxylation), and 5-aminosalicylate (a prime metabolite of sulphasalazine) are highly efficient quenchers of the chemiluminescence (CL) produced by an oxy radical flux. Monohydric phenols (including salicylate) and meta-dihydric phenols are virtually inactive. These findings suggest that the para- or ortho-configuration of hydroxy/amino groups is important for this activity. These differences in activity between 2,3- and 2,5-dihydroxybenzoate, 5-aminosalicylate and monohydric phenols/2,4-, 2,6-dihydroxybenzoate were not seen in assays monitoring hydroxyl radicals. 4-aminophenazone (an oxidation product of both amidopyrine/aminopyrine and isopyrine), 4-hydroxyphenazone and some dietary catechols (and ascorbate), are also quenchers of oxy radical-associated CL.

The reactivity of neutrophils at the site of an acute inflammatory reaction as measured by chemiluminescence

In this study the technique of luminol-enhanced chemiluminescence (LECL), which was shown to be dependent on the generation of superoxide anion, has been employed to investigate the reactivity of polymorphonuclear leukocytes found at the site of inflammation. Cells derived from the pleural cavity of rats undergoing an acute inflammatory reaction initiated by an intrapleural injection of calcium pyrophosphate or normal serum demonstrated a significantly higher chemiluminescent response compared to cells derived from animals injected with plasma, saline or phosphate-buffered saline. In addition in vitro studies showed that calcium pyrophosphate crystals could stimulate the cells per se and could increase their reactivity.

Regulation of the human polymorphonuclear leukocyte inflammatory response by inhibitors of arachidonic acid metabolism

Perturbation of the neutrophil membrane by opsonized zymosan particles activates the cell's "respiratory burst." Associated with this activation process is the generation of highly reactive oxygen products, including superoxide, and the release of lysosomal enzymes. Membrane activation also stimulates arachidonic acid metabolism and the generation of a wide variety of products through both the lipoxygenase and cyclooxygenase pathways. In isolated human neutrophils, we have evaluated the effects inhibitors of cyclooxygenase and lipoxygenase upon opsonized zymosan stimulated chemiluminescence, superoxide generation, oxygen consumption, and beta-glucuronidase release. Nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase enzyme, suppressed chemiluminescence, superoxide generation, oxygen consumption, and beta-glucuronidase release. Both indomethacin, a cyclooxygenase inhibitor, and 5,8,11,14 - eicosatetraynoic acid (ETYA) an inhibitor of both cyclooxygenase and lipoxygenase, inhibited all tested neutrophil functions. However, when compared to NDGA, indomethacin and ETYA were considerably less potent. Our observations suggest that the lipooxygenase derived metabolites play a predominant regulatory role in these neutrophil inflammatory functions.

The effect of D-penicillamine on human myeloperoxidase, a mechanism for the efficacy of the drug in rheumatoid arthritis

We investigated the effect of D-penicillamine on the ability of myeloperoxidase, purified from human leukocytes, to catalyse the oxidation of chloride ions to hypochlorite (HOCl) in the presence of H2O2. It is shown that, due to the interaction of D-penicillamine with both myeloperoxidase itself and HOCl, the chlorinating activity of myeloperoxidase in the presence of H2O2 and chloride ions is prevented. A concentration of 100 microM D-penicillamine inhibits the chlorinating activity of myeloperoxidase completely, which Is due to the stabilization of Compound II, an inactive form of the enzyme. In addition, HOCl reacts directly with D-penicillamine. Analysis of the reaction products of D-penicillamine and HOCl showed that D-penicillamine was oxidized to penicillamine disulphide and penicillamine sulphinic acid, and eventually deaminated (indicated by the release of ammonia). Lower concentrations of D-penicillamine (10 microM) inhibited myeloperoxidase less, but still acted as effective scavengers of HOCl. In very low concentrations (1 microM), D-penicillamine did not scavenge HOCl effectively, but rather stimulated the chlorinating activity of myeloperoxidase. However, when instead of D-penicillamine a comparable amount of ascorbate was added, a similar but even larger stimulation was observed. Since the concentration of free D-penicillamine in serum from rheumatoid patients treated with this drug is about 20 microM (Saetre, R. and Rabenstein, D.L. (1978) Anal. Chem. 50, 276-280), the therapeutic effect of D-penicillamine may be due to the protection of tissues against the reactive HOCl released by activated granulocytes at inflammation sites.

Impairment of leukocyte myeloperoxidase bactericidal mechanisms with ketamine (Ketalar)

The ability of general anesthetics to depress immune function may lead to increased risk of infection in surgical patients. Recently, halothane, an inhalational anesthetic, was shown to inhibit neutrophil bactericidal mechanisms, the center of which is the reaction of myeloperoxidase with H2O2 and Cl. This study demonstrates the ability of ketamine, an injectable anesthetic, to interfere with the cytotoxic neutrophil myeloperoxidase-H2O2-Cl- reaction, as tested using a luminol-enhanced chemiluminescence assay. Ketamine, due to its phenolic structure, may scavenge the cytotoxic free radical intermediates of this reaction, as shown previously for non-steroidal anti-inflammatory drugs. This paper, then, identifies a potential mechanism whereby ketamine anesthesia could suppress neutrophil defense mechanisms, thus rendering the surgical patient more susceptible to infection.

Comparison of the effects of antioxidant non-steroidal anti-inflammatory drugs against myeloperoxidase and hypochlorous acid luminol-enhanced chemiluminescence

The interaction of myeloperoxidase (MPO) with H2O2 and Cl- provides a potent antimicrobial/cytotoxic system for polymorphonuclear leukocytes (PMNs). MPO-related cytotoxicity may be associated with the formation of toxic oxidant MPO intermediates, HOCl, or both. MPO itself is able to oxidize drugs and cellular components. Non-steroidal anti-inflammatory drugs (NSAIDs) able to act as antioxidant free radical scavengers have recently been shown to inhibit luminol-enhanced chemiluminescence (CL) which results from the MPO-H2O2-Cl- reaction. CL is a measure of the activity of this reaction. At that time it was not clear whether the source of CL which these NSAIDs affected was HOCl or components of the initial MPO-H2O2-Cl- reaction. A NSAID antioxidant mechanism could affect MPO oxidant intermediates and HOCl. This study compares the effects of antioxidant NSAIDs, methylprednisone and free radical scavengers against MPO-based and NaOCl-based luminol-enhanced CL. Most NSAIDs which affected both MPO and NaOCl-CL appeared to share similar mechanisms, suggesting that MPO oxidant intermediates and HOCl are susceptible to NSAID effects. However, most NSAIDs were more effective against MPO-CL. The effect of these NSAIDs against MPO-CL followed the profile of NSAIDs effective in previous studies against PMN-CL. One exception to this was methylprednisone, which has no effect on PMN or MPO-CL, yet inhibited NaOCl-CL. This and other data suggest that MPO and not HOCl-related reactions are a major source of PMN-CL. Less effective NSAIDs affected NaOCl-CL better than MPO-CL. While both HOCl and MPO oxidant intermediates may be affected by NSAIDs, it appears that MPO oxidant intermediates or MPO itself are the primary target for NSAID antioxidant free radical scavenging mechanisms. These antioxidant effects impair the major killing system of the PMN and may be NSAIDs' primary anti-inflammatory mechanism. Although our data suggests the production of superoxide anion and hydroxyl radical from the MPO-H2O2-Cl- reaction, the actual presence or involvement of these free radical species is not confirmed herein.