thromboxane-b2 and zileuton

We have recently reported that the 5-lipoxygenase (5-LO) inhibitor, zileuton, alters lung inflammation produced by segmental antigen challenge in ragweed-allergic human subjects. Specifically, zileuton inhibited the urinary excretion of leukotriene E4 produced by antigen challenge, and the significant increase in bronchoalveolar lavage (BAL) eosinophils observed in subjects on placebo was not seen in subjects on zileuton. In this manuscript, we report additional data obtained during that study which provide information about mechanisms important during IgE-mediated inflammatory reactions in the lung. Three different areas are addressed: 1) the time to recovery of the lung from an IgE-mediated inflammatory response; 2) mechanisms related to the generation of cyclooxygenase products in the lung after antigen challenge and the effect of 5-LO inhibition on the production of cyclooxygenase metabolites; and 3) mechanisms responsible for the production of peptide leukotrienes in the lung and lung injury (as shown by albumin influx into the alveolar air space) 24 h after antigen challenge. We observed the following: 1) a significant BAL eosinophilia and basophilia remained 31 days (range 21-48) after segmental antigen challenge and bronchoalveolar lavage; 2) a decreased quantity of BAL cyclooxygenase products, as well as lipoxygenase products, in the presence of 5-LO inhibition; and 3) correlative analyses which suggest that while eosinophils appear most important for the production of peptide leukotrienes and lung injury 24 h after antigen challenge in subjects taking placebo, other effector mechanisms, perhaps those involving basophils and the initial mast cell triggering event, appear to gain in importance when the IgE-mediated inflammatory reaction is blunted by 5-LO inhibition.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Arachidonate 5-Lipoxygenase; Bronchial Provocation Tests; Bronchoalveolar Lavage Fluid; Bronchoscopy; Cross-Over Studies; Dinoprost; Dinoprostone; Double-Blind Method; Eosinophils; Humans; Hydroxyurea; Leukotriene B4; Leukotriene E4; Leukotrienes; Lipoxygenase Inhibitors; Lung; Lung Injury; Placebos; Prostaglandin D2; Prostaglandin-Endoperoxide Synthases; Proteins; Regression Analysis; Respiratory Hypersensitivity; Thromboxane B2

The potential pharmacokinetic and pharmacodynamic interactions between zileuton, a 5-lipoxygenase inhibitor, and naproxen, a nonsteroidal anti-inflammatory drug that acts as a cyclo-oxygenase inhibitor, have been investigated in 24 healthy volunteers. Coadministration of these 2 drugs had no effect upon the plasma concentration-time curves of either zileuton (800mg) or naproxen (500mg) when compared with each drug administered alone. Both naproxen plasma concentrations during the elimination phase and area under the plasma concentration-time curve values were statistically significantly raised upon coadministration with zileuton, when compared with naproxen alone. However, these differences in these 2 values were sufficiently small to be of no clinical significance. There is no evidence that the combination of zileuton and naproxen had an effect on leukotriene B4 levels that was different from the inhibitory effect of zileuton alone, or had an effect on serum thromboxane B2 levels that was different from the effect of naproxen alone. Moreover, inhibition of the 5-lipoxygenase pathway by zileuton did not appear to aggravate the gastrointestinal adverse events commonly associated with naproxen administration. It is concluded that zileuton and naproxen may be coadministered with minimal risk of a clinically significant interaction.

Topics: Administration, Oral; Adolescent; Adult; Anti-Inflammatory Agents, Non-Steroidal; Cyclooxygenase Inhibitors; Digestive System; Dose-Response Relationship, Drug; Double-Blind Method; Drug Interactions; Endoscopy; Humans; Hydroxyurea; Intestinal Mucosa; Leukotriene B4; Lipoxygenase Inhibitors; Male; Naproxen; Thromboxane B2

Cyclooxygenase (COX) and 5-lipoxygenase (5-LOX) play an important role in inflammatory bowel diseases (IBDs). We investigated the effects of flavocoxid, a dual COX/LOX inhibitor, in experimental colitis induced with either dinitrobenzenesulfonic acid (DNBS) or dextrane sulphate sodium (DSS) In the first model, colitis was induced in rats by a single intra-colonic instillation (25mg in 0.8ml 50% ethanol) of DNBS; after 24h animals were randomized to receive orally twice a day, flavocoxid (10mg/kg), zileuton (50mg/kg), or celecoxib (5mg/kg). Sham animals received 0.8ml of saline by a single intra-colonic instillation. Rats were killed 4 days after induction and samples were collected for analysis. In the second model, colitis was induced in rats by the administration of 8% DSS dissolved in drinking water; after 24h animals were randomized to the same above reported treatments. Sham animals received standard drinking water. Rats were killed 5 days after induction and samples were collected for analysis. Flavocoxid, zileuton and celecoxib improved weight loss, reduced colonic myeloperoxydase activity, macroscopic and microscopic damage, and TNF-α serum levels. Flavocoxid and celecoxib also reduced malondialdheyde, 6-keto PGF1α and PGE-2 levels while flavocoxid and zileuton decreased LTB-4 levels. In addition, flavocoxid treatment improved histological features and apoptosis as compared to zileuton and celecoxib; moreover only flavocoxid reduced TXB2, thus avoiding an imbalance in eicosanoids production. Our results show that flavocoxid has protective effect in IBDs and may represents a future safe treatment for inflammatory bowel diseases.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Apoptosis; Arachidonate 5-Lipoxygenase; Body Weight; Catechin; CD3 Complex; Celecoxib; Colitis; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Dinoprostone; Drug Combinations; Eating; Gene Expression Regulation; Hydroxyurea; Leukotriene B4; Lipid Peroxidation; Lipoxygenase Inhibitors; Male; Neutrophil Infiltration; Rats; Rats, Sprague-Dawley; Thromboxane B2; Tumor Necrosis Factor-alpha

Leukotrienes, generated from arachidonic acid via the lipoxygenase pathway, play an important role in the pathophysiology of asthma. Therefore, leukotriene inhibitors, such as Zileuton, are used in the treatment of asthma. However, thromboxanes, generated from arachidonic acid via the cyclooxygenase pathway, play an important role in platelet aggregation and thrombosis. Therefore, we studied whether Zileuton, by shifting arachidonic acid to the cyclooxygenase pathway, enhances thromboxane production and, hence, platelet aggregation. Blood samples were collected from 10 asthmatic patients before and 2 weeks after standard Zileuton treatment. Spontaneous platelet aggregation was measured in platelet-rich plasma. Platelet-rich plasma was also used to determine thromboxane B(2), a stable metabolite of thromboxane A(2), as the indirect measure of thromboxane A(2) because thromboxane A(2) is too unstable for assay. Baseline thromboxane B(2) and platelet aggregation values in the 10 asthmatic patients were normal. Treatment with Zileuton for 2 weeks significantly increased thromboxane B(2) levels from baseline levels of 267 +/- 54 microg/l to 389 +/- 62 microg/l after 2 weeks of treatment (P < 0.0002). Spontaneous platelet aggregation also increased significantly from baseline values of 4.2 +/- 2.4% to 6.8 +/- 2.8% after 2 weeks of treatment (P < 0.0001). These results establish that Zileuton, an effective drug for asthma, adversely affects in vitro platelet function. The findings suggest that this drug, and perhaps related agents also, may pose a thrombotic risk; clinical attention will be needed to address this possibility.

Topics: Adult; Aged; Asthma; Female; Humans; Hydroxyurea; Lipoxygenase Inhibitors; Male; Middle Aged; Platelet Aggregation; Thromboxane A2; Thromboxane B2

In vitro pharmacological profiles of E3040, 6-hydroxy-5, 7-dimethyl-2-(methylamino)-4-(3-pyridylmethyl) benzothiazole were investigated. Against the 5-lipoxygenase activity of rat basophilic leukemia cells, E3040 and zileuton (a 5-lipoxygenase inhibitor) had an IC(50) of 0.23 and 0.93 microM, respectively. Against the thromboxane A(2) synthetase activity of human platelets, E3040 had an IC(50) of 0.01 microM, which was comparable to that of OKY-1581 (sodium (E)-3-[4-(3-pyridylmethyl) phenyl]-2-methylacrylate, a thromboxane A(2) synthetase inhibitor). Against cyclooxygenase activity of sheep seminal vesicles, E3040 showed no inhibition (IC(50), >300 microM). Sulfasalazine and 5-aminosalicylic acid, therapeutic drugs for inflammatory bowel disease, inhibited 5-lipoxygenase activity with an IC(50) of 293 and 970 microM, respectively. Sulfasalazine inhibited thromboxane A(2) synthetase activity with an IC(50) of 20 microM. In rat peritoneal leukocytes, E3040 inhibited leukotriene B(4) and thromboxane B(2) production with an IC(50) of 0.17 and 0.24 microM, respectively. E3040 inhibited leukotriene B(4) production in human neutrophils and thromboxane B(2) production in human platelets (IC(50) of 0.21 and 0.09 microM, respectively). These results indicated that E3040 potently inhibited 5-lipoxygenase and thromboxane A(2) synthetase and blocked leukotriene B(4) and thromboxane B(2) production in rat peritoneal and human blood cells.

Topics: Animals; Arachidonate 5-Lipoxygenase; Benzothiazoles; Dinoprostone; Dose-Response Relationship, Drug; Eicosanoids; Humans; Hydroxyurea; Indomethacin; Leukocytes; Leukotriene B4; Lipoxygenase Inhibitors; Male; Mesalamine; Methacrylates; Neutrophils; Peritoneal Cavity; Prostaglandin-Endoperoxide Synthases; Pyridines; Rats; Rats, Inbred F344; Sheep; Sulfasalazine; Thiazoles; Thromboxane B2; Thromboxane-A Synthase

As part of our research for the development of novel antiinflammatory drug candidates, we have designed and synthesized a series of (E)-3-(1,4-benzoquinonyl)-2-[(3-pyridyl)alkyl]-2-propenoic acid derivatives as dual inhibitors of 5-lipoxygenase (5-LO) and thromboxane (TX) A2 synthetase. In order to increase the absorption after oral administration, we introduced a carboxylic acid moiety into the 1,4-benzoquinone skeleton, which has 5-LO-inhibitory character. Introduction of a 3-pyridylalkyl group at the double bond of the 1,4-benzoquinonyl propenoic acid moiety afforded good to moderate inhibitory activities against the production of leukotriene (LT) B4 and TXA2 while not significantly inhibiting that of prostaglandin E2 by glycogen-induced peritoneal cells of rat (in vitro). The length of the methylene chain of the 3-pyridylalkyl group influenced the inhibition of LTB4 and TXB2 production. An increase of lipophilicity by introducing a more lipophilic alkoxy group did not markedly increase the inhibitory activity on LTB4 production. The position of alkoxy group on the 1,4-benzoquinone skeleton played an important role in TXA2 synthetase inhibition. Compounds such as 20c (E6700) with an appropriate alkoxy group and proper length of methylene side chain, together with a polar substituent (carboxylic acid), showed good inhibition of both 5-LO and TXA2 synthetase and possess a variety of pharmacologically beneficial effects.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzoquinones; Blood Platelets; Cells, Cultured; Humans; Hydroxyurea; Leukotriene B4; Lipoxygenase Inhibitors; Magnetic Resonance Spectroscopy; Methacrylates; Molecular Structure; Neutrophils; Pyridines; Rats; Structure-Activity Relationship; Thromboxane B2; Thromboxane-A Synthase

1. This paper describes the pre-clinical pharmacology of ICI D2138, a potent orally-active non-redox inhibitor of 5-lipoxygenase which is undergoing clinical evaluation. 2. ICI D2138 potently inhibited leukotriene synthesis in murine peritoneal macrophages (IC50 = 3 nM) and human blood (IC50 = 20 nM). In human and dog blood, ICI D2138 did not inhibit thromboxane B2 synthesis at a concentration of 500 microM, thus the selectivity ratio (cyclo-oxygenase: 5-lipoxygenase) was greater than 20,000. In contrast, zileuton (a 5-lipoxygenase inhibitor also undergoing clinical evaluation) exhibited a selectivity ratio of 15-100. 3. ICI D2138 potently and dose-dependently inhibited ex vivo leukotriene B4 (LTB4) synthesis by rat blood with ED50 values of 0.9, 4.0 and 80.0 mg kg-1 p.o. at 3, 10 and 20 h respectively after dosing. Similar activity was observed for inhibition of LTB4 production in a zymosan-inflamed rat air pouch model. Zileuton produced ED50 values of 5 and 20 mg kg-1 at 3 and 10 h respectively. 4. Oral administration of 1, 3 or 10 mg kg-1 ICI D2138 to dogs produced maximal inhibition of ex vivo LTB4 synthesis by blood for 5, 9 and 31 h respectively. A dose of 5 mg kg-1 p.o. of zileuton caused maximal inhibition of LTB4 for 24 h. 5. Oral administration of 10 mg kg-1 ICI D2138 caused total inhibition of LTB4 production in zymosan-inflamed rabbit knee joint. 6. Topical administration of ICI D2138 to rabbit skin caused a dose-related inhibition of arachidonic acid-induced plasma extravasation with an ID30 of 1.08 nmol per site. Zileuton was approximately 40 times less potent.7. Oral anti-inflammatory activity was assessed in an arachidonic acid-induced mouse ear oedema model in animals treated with indomethacin to block pro-inflammatory prostanoids. ICI D2138, given orally, caused dose-dependent inhibition of oedema with an approximate ID50 of 1.8 mg kg'. Zileuton was approximately 10 times less potent.8. ICI D2138 caused a dose-dependent inhibition of antigen-induced broncho-constriction in guineapigs with an approximate ID50 of 0.1 mg kg-', i.v. Zileuton was approximately 10 times less potent.9. In view of the pharmacological profile described here, ICI D2138 has the potential to provide improved clinical efficacy compared to existing lipoxygenase inhibitors such as zileuton.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Bronchoconstriction; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Guinea Pigs; Hydroxyurea; Inflammation; Knee Joint; Leukotriene B4; Lipoxygenase Inhibitors; Macrophages; Male; Mice; Oxidation-Reduction; Pyrans; Quinolones; Rabbits; Rats; Thromboxane B2