leukotriene-b4 and tepoxalin

Our aim was to determine the amounts of eicosanoids in blood and synovial tissue of patients with knee arthrosis and to examine the effects of 2 doses of tepoxalin (50 mg twice, 200 mg twice), administered p.o. for 3.5 days. Concentrations of leukotriene B4 (LTB4, LTC4, and thromboxane B2 (TXB2) were measured in blood before and after oral administration of tepoxalin and release of prostaglandin E2 (PGE2), 6-keto-PGF1alpha, and LTC4 was measured in incubation media of synovial tissue, taken at surgery from patients treated with tepoxalin. Radioimmunoassay (RIA) was used to determine the levels of the eicosanoids. LT and TXB2 release was reduced by tepoxalin in both doses used. Under these conditions, PGE2, 6-keto-PGF1alpha, and LTC4 release from synovial tissue was detectable only after stimulation with calcium ionophore A23187. Washed synovial tissue, in which tepoxalin concentrations should be reduced, released higher amounts of all eicosanoids measured than directly incubated synovial tissue did. Pain after tepoxalin administration was significantly reduced. Relevant drug concentrations were detected in plasma and synovial fluid. Tepoxalin was well tolerated and had no marked adverse effects. At 400 mg, tepoxalin is a dual inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5-LO) in blood and synovial tissue.

Topics: 6-Ketoprostaglandin F1 alpha; Administration, Oral; Aged; Anti-Inflammatory Agents, Non-Steroidal; Arthritis; Arthroplasty, Replacement, Knee; Dinoprostone; Double-Blind Method; Drug Administration Schedule; Female; Humans; Knee Joint; Leukotriene Antagonists; Leukotriene B4; Leukotriene C4; Male; Middle Aged; Pain; Pain Measurement; Premedication; Pyrazoles; Radioimmunoassay; Synovial Membrane; Thromboxane B2

Tepoxalin, a novel inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5-LO), was investigated for biochemical activity and pharmacokinetics in two studies. Study I was a 4-period, double-blind, randomized, single rising dose using 2 alternating panels (A, B) with interspersed placebo design (A: 25, 100, 400 mg, B: 50, 200, 800 mg p.o.). Study II was a 3-panel, randomized, placebo-controlled, double-blind, multiple dose study (A: 100 mg, B: 200 mg, C: 400 mg). In both studies, CO inhibition was assessed by generation of serum thromboxane (TxB2), 5-LO activity by LTB4 production ex vivo in Caionophore-stimulated blood. Plasma drug concentrations were assayed by HPLC for tepoxalin and its identified acid metabolite. It was found in both studies that at all dose levels the TxB2 generation was markedly suppressed (> 95% 2 h postdose). In study I, at 2 h postdose, % inhibition of LTB4 biosynthesis was marginal for the 3 lower doses but significant at 200 (14%), 400 (25%) and 800 mg (43%). In study II, the only significant inhibition occurred at the 400 mg dose at 6 h postdose on day 1 (17%) and on day 8 at 4, 6 and 8 h postdose (32, 42 and 32% respectively). In both studies and at all doses, plasma concentrations of tepoxalin varied widely between subjects. Linearity between plasma concentrations and dose could not be ascertained, and correlation between drug plasma levels and effect on LTB4 synthesis was poor. Single doses up to 800 mg and multiple doses up to 400 mg of tepoxalin were generally well tolerated.

Topics: Adult; Anti-Inflammatory Agents, Non-Steroidal; Area Under Curve; Cyclooxygenase Inhibitors; Double-Blind Method; Gastrointestinal Diseases; Humans; Leukotriene B4; Lipoxygenase Inhibitors; Liver Function Tests; Male; Metabolic Clearance Rate; Middle Aged; Platelet Aggregation Inhibitors; Pyrazoles; Thromboxane B2

Mast cells play an important role in both innate and acquired immunity as well as several pathological conditions including allergy, arthritis and neoplasia. They influence these processes by producing a variety of mediators including cytokines, chemokines and eicosanoids. Very little is currently known about the spectrum of inflammatory mediators, particularly eicosanoids (prostaglandins and leukotrienes), produced by canine mast cells. This is important since modulating mast cell derived eicosanoids may help in the treatment of autoimmune and inflammatory disorders. The purpose of this study was to investigate the spectrum of eicosanoids produced by normal canine mast cells and to evaluate the effects of cytokines and non-steroidal anti-inflammatory mediators (NSAIDS) on eicosanoid production and release. Canine bone marrow derived cultured mast cells (cBMCMCs) expressed COX-1, COX-2, and 5-LOX and synthesized and released PGD2, PGE2, LTB4, and LTC4 following activation by a variety of stimuli. The selective COX-2 NSAIDs carprofen (Rimadyl) and deracoxib (Deramaxx) inhibited PGD2 and PGE2 production but only slightly inhibited LTB4 and LTC4. The mixed COX-1/COX-2 inhibitor piroxicam blocked PGD2 and PGE2 production, but upregulated LTC4 following treatment while tepoxilan (Zubrin), a pan COX/LOX inhibitor, markedly reduced the production of all eicosanoids. The LOX inhibitor nordihydroguaiaretic acid (NDGA) prevented LTB4/LTC4 release and BMBMC degranulation. Pre-incubation of cBMCMCs with IL-4 and SCF sensitized these cells to degranulation in response to substance P. In conclusion, canine BMCMCs produce an array of eicosanoids similar to those produced by mast cells from other species. Tepoxilan appeared to be the most effective NSAID for blocking eicosanoid production and thus may be useful for modulating mast cell mediated responses in dogs.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonate 5-Lipoxygenase; Carbazoles; Cyclooxygenase 1; Cyclooxygenase 2; Dinoprostone; Dogs; Leukotriene Antagonists; Leukotriene B4; Leukotriene C4; Leukotrienes; Masoprocol; Mast Cells; Piroxicam; Prostaglandin Antagonists; Prostaglandin D2; Prostaglandins; Pyrazoles; Sulfonamides

To evaluate the effects of firocoxib, meloxicam, and tepoxalin administration in healthy cats by measuring the ability of stimulated tissues to synthesize eicosanoids ex vivo.. 8 healthy adult male cats.. In a blinded, randomized, crossover study design, cats were treated with firocoxib (1 mg/kg, PO, q 24 h), meloxicam (0.05 mg/kg, PO, q 24 h), tepoxalin (5.0 mg/kg, PO, q 12 h), or a placebo for 8 days. Blood samples and gastric and duodenal mucosal biopsy specimens were collected on days 0 (baseline; immediately before treatment), 3, and 8 of each treatment period. Thromboxane B2 (TXB2) concentrations were measured in serum, and prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) concentrations were measured in plasma. Prostaglandin E1 (PGE1) synthesis, PGE2 synthesis, and LTB4 concentrations were measured in mucosal biopsy specimens. A 21-day minimum washout period was observed between treatments. Repeated-measures analyses were performed.. Firocoxib and meloxicam administration resulted in a lower plasma PGE2 concentration than at baseline on days 3 and 8 of administration, whereas tepoxalin administration did not. Tepoxalin administration resulted in a lower serum TXB2 concentration and pyloric and duodenal PGE1 synthesis on both days, compared with baseline and placebo administration. Neither firocoxib nor meloxicam administration altered pyloric or duodenal PGE1 synthesis on either day, compared with placebo administration. Tepoxalin administration also resulted in lower pyloric mucosal LTB4 concentrations on both days, compared with baseline values.. Firocoxib and meloxicam administration had no effect on cyclooxygenase-1 activity, whereas tepoxalin administration resulted in inhibition of cyclooxygenase-1 and 5-lipoxygenase.

Topics: 4-Butyrolactone; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cats; Cross-Over Studies; Cyclooxygenase Inhibitors; Dinoprostone; Duodenum; Eicosanoids; Gastric Mucosa; Intestinal Mucosa; Kinetics; Leukotriene B4; Male; Meloxicam; Orchiectomy; Pyrazoles; Reference Values; Sulfones; Thiazines; Thiazoles

Inflammatory cells contribute to the acute and sub-acute sequelae of radiation therapy. Tepoxalin, an inhibitor of cyclooxygenase and 5-lipoxygenase that suppresses NF-kappaB activation, has potent anti-inflammatory activity.. To assess the effects of tepoxalin on radiation-induced inflammatory damage, and determine its mechanisms of action.. Leucocyte rolling, adhesion and emigration, and albumin leakage were determined by intra-vital microscopy in rat mesenteric venules. NF-kappaB activation was measured by electrophoretic mobility shift assays, and endothelial intercellular adhesion molecule-1 expression by the radiolabelled antibody technique. Groups of irradiated rats were treated with tepoxalin, N-acetyl-L-cysteine, zileuton (lipoxygenase inhibitor), or vehicle.. Irradiated animals had a marked increase in the number of rolling, adherent and emigrated leucocytes in mesenteric venules, and in microvascular permeability. Tepoxalin prevented leucocyte adhesion and the increase in permeability after radiation. Tepoxalin did not inhibit radiation-induced NF-kappaB activation or intercellular adhesion molecule-1 up-regulation, while N-acetyl-L-cysteine, which attenuated NF-kappaB activation, had no effect on leucocyte recruitment. In contrast, tepoxalin inhibited the increase in leukotriene B4 levels after radiation, and the anti-inflammatory effects of the drug were mimicked by zileuton.. Tepoxalin affords significant protection against radiation-induced inflammation and microvascular dysfunction in splanchnic organs through a mechanism dependent on leukotriene synthesis inhibition.

Topics: Abdomen; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cell Adhesion; Digestive System; Inflammation; Leukocytes; Leukotriene B4; Male; Permeability; Pyrazoles; Radiotherapy; Rats; Rats, Sprague-Dawley

Prostaglandins and thromboxanes are products of arachidonic acid metabolism via the cyclooxygenase (CO) enzyme and are responsible for the pain and swelling common to sites of inflammation. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the production of these substances and are used in the treatment of inflammatory diseases such as arthritis. However, one of the major side-effects of NSAID therapy is gastric ulceration. It is possible that inhibition of prostaglandin production and a related increase in the formation of leukotrienes via the 5-lipoxygenase (5-LO) enzymatic pathway are responsible for attracting inflammatory cells, causing local sites of inflammation and producing ulceration. To determine the effects of 5-LO inhibition on this hypothesis, studies were performed in rats to evaluate the effects of tepoxalin, a dual CO/LO inhibitor on leukotriene B4 levels in gastric mucosa and neutrophil adhesion in mesenteric venules. In rats, chronic oral administration of an NSAID, indomethacin (2 mg/kg daily over 4 days), resulted in 40% mortality, accompanied by intestinal adhesions and perforations when evaluated 24 h after the fourth dose of drug. Additionally, neutrophil adhesion was increased in the mesenteric venules and cell infiltration was evident in the mesenteric interstitium. These gastrointestinal side-effects were inhibited in a separate group of rats administered tepoxalin (20 mg/kg, p.o) 30 min prior to each daily indomethacin treatment. Further studies were performed to determine tepoxalin's effects on early events associated with NSAID-induced gastrointestinal inflammation, including neutrophil adhesion, lipid peroxide generation and LTB4 production. Indomethacin (100 mg/kg, p.o.) produced elevated levels of LTB4 in rat gastric mucosa 90 min after administration. Additionally, neutrophil adhesion in mesenteric venules was increased at this dose and with the administration of another NSAID, naproxen. No generation of lipid peroxides was evident in the gastric mucosa at this timepoint. Tepoxalin (up to 400 mg/kg, p.o.) did not have an effects on gastric mucosal LTB4 generation and lipid peroxide levels. A decrease in neutrophil adhesion was observed at the highest dose. In another study, pretreatment with tepoxalin (ED50=7.5 mg/kg, p.o.) or the selective 5-LO inhibitor zileuton (100 mg/kg, p.o.) prevented the increases in gastric mucosal LTB4 levels and neutrophil adhesion induced by indomethacin (100 mg/kg, p.o.). These data sugg

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Cell Adhesion; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Female; Gastric Mucosa; Gastroenteritis; Indomethacin; Leukotriene B4; Lipid Peroxides; Lipoxygenase Inhibitors; Mesenteric Veins; Neutrophils; Pyrazoles; Rats; Rats, Sprague-Dawley

Tepoxalin is a new dual cyclooxygenase/5-lipoxygenase anti-inflammatory compound currently under clinical investigation. It has been shown to possess anti-inflammatory activity in a variety of animal models and more recently to inhibit IL-2 induced signal transduction. The current study was conducted to evaluate the cytokine modulating activity of tepoxalin and the role of iron in these effects. In human peripheral blood mononuclear cells (PBMC) stimulated with OKT3/PMA, tepoxalin inhibited lymphocyte proliferation with an IC50 of 6 microM. Additionally, it inhibited the production of LTB4 (IC50 = 0.5 microM) and the cytokines IL-2, IL-6 and TNF alpha (IC50 = 10-12 microM). Cytotoxicity was not demonstrated at these concentrations. Add-back experiments with either cytokines (IL-2 or IL-6), LTB4 or conditioned media failed to restore the proliferative response in the presence of tepoxalin. However, the concurrent addition of iron (in the form of ferrous or ferric chloride and other iron salts) reversed the inhibition of proliferation caused by tepoxalin. Tepoxalin also inhibits the activation of NF kappa B, a transcription factor which acts on several cytokine genes. Tepoxalin's effect on NF kappa B is also reversed by the addition of iron salts. These data suggest that the action of tepoxalin to inhibit proliferation in PBMC may be at least in part due to its ability to reduce the amount of available iron resulting in decreased activation of NF kappa B and subsequent inhibition of cytokine production.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Antirheumatic Agents; Cell Division; Cells, Cultured; Cytokines; Ferrous Compounds; Humans; Immunosuppressive Agents; Leukocytes, Mononuclear; Leukotriene B4; NF-kappa B; Pyrazoles