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Objective: To explore the potential mechanism of lysionotin in treating glioma. Methods: First, target prediction based on Bernoulli Naïve Bayes profiling and pathway enrichment was used to predict the biological activity of lysionotin. The binding between 5-lipoxygenase (5-LO) and lysionotin was detected by surface plasmon resonance (SPR) and molecular docking, and the inhibitory effects of lysionotin on 5-LO and proliferation of glioma were determined using enzyme inhibition assay in vitro and cell viability analysis, respectively. Furthermore, the pharmaceutical effect of lysionotin was explored by cell survival rate analysis and liquid chromatography with tandem mass spectrometry (LC-MS/MS). The protein expression, intracellular calcium ion concentration and cytoskeleton detection were revealed by Western blot, flow cytometry and fluorescence labeling, respectively. Results: Target prediction and pathway enrichment revealed that lysionotin inhibited 5-LO, a key enzyme involved in the arachidonic acid metabolism pathway, to inhibit the proliferation of glioma. Molecular docking results demonstrated that 5-LO can be binding to lysionotin through hydrogen bonds, forming bonds with His600, Gln557, Asn554, and His372. SPR analysis further confirmed the interaction between 5-LO and lysionotin. Furthermore, enzyme inhibition assay in vitro and cell survival rate analysis revealed that 50% inhibition concentration of lysionotin and the median effective concentration of lysionotin were 90 and 16.58 µmol/L, respectively, and the results of LC-MS/MS showed that lysionotin inhibited the production of 5S-hydroperoxy-eicosatetraenoic acid (P<0.05), and moreover, the LC-MS/MS results indicated that lysionotin can enter glioma cells well (P<0.01) and inhibit their proliferation. Western blot analysis demonstrated that lysionotin can inhibit the expression of 5-LO (P<0.05) and downstream leukotriene B4 receptor (P<0.01). In addition, the results showed that lysionotin affected intracellular calcium ion concentration by inhibiting 5-LO to affect the cytoskeleton, as determined by flow cytometry and fluorescence labeling. Conclusion: Lysionotin binds to 5-LO could suppress glioma by inhibiting arachiodonic acid metabolism pathway. [ABSTRACT FROM AUTHOR]

5‐Lipoxygenase (5‐LO) is one of the significant drug targets for the development of various anti‐inflammatory drugs. Herein, we designed, optimized, and synthesized a novel N‐((6‐(substituted‐amino)‐2‐methyl‐2H‐chromen‐2‐yl)methyl)‐N‐methylbenzenesulfonamide derivatives as potential 5‐LO inhibitors. Among the synthesized compounds, 10a, 10b, and 10g exhibited inhibitory activity toward 5‐LO according to the in vitro studies including enzyme activity assay (≥78% inhibition rate at 1 μM) and cell‐based assay (≥72% inhibition rate at 1 μM). 10b was selected for further in vivo efficiency using an ear edema mouse model, which was induced by arachidonic acid. Oral administration of 10b successfully suppressed ear edema and myeloperoxidase activity (MPO activity). Molecular docking studies showed alkyl and pi‐alkyl interactions of compound 10b with Ile126 and Val110 of 5‐LO as well as a hydrogen bonding with Arg138 as key protein‐ligand interactions. [ABSTRACT FROM AUTHOR]

The arachidonic acid metabolism through 5-lipoxygenase (5-LO) pathways is involved in modulating both tumorigenesis and angiogenesis. Although anti-carcinogenic activities of certain 5-LO inhibitors have been reported, the role of zileuton, a well known 5-LO inhibitor, on the endothelial cell proliferation and angiogenesis has not been fully elucidated. Here, we report that zileuton has an anti-angiogenic effect, and the underlying mechanisms involved activation of the large-conductance Ca2+-activated K+ (BK) channel. Our results show that zileuton significantly prevented vascular endothelial growth factor (VEGF)-induced proliferation of human umbilical vein endothelial cells (HUVECs) in vitro, as well as in vivo. However, such anti-angiogenic effect of zileuton was abolished by iberiotoxin (IBTX), a BK channel blocker, suggesting zileuton-induced activation of BK channel was critical for the observed anti-angiogenic effect of zileuton. Furthermore, the anti-angiogenic effect of zileuton was, at least, due to the activation of pro-apoptotic signaling cascades which was also abolished by IBTX. Additionally, zileuton suppressed the expression of VCAM-1, ICAM-1, ETS related gene (Erg) and the production of nitric oxide (NO). Taken together, our results show that zileuton prevents angiogenesis by activating the BK channel dependent-apoptotic pathway, thus highlighting its therapeutic capacity in angiogenesis-related diseases, such as cancer.

Leukotrienes ( LTs) are a class of lipid mediators implicated in numerous inflammatory disorders. Caffeic acid phenethyl ester ( CAPE) possesses potent anti- LTs activity through the inhibition of 5-lipoxygenase (5- LO), the key enzyme in the biosynthesis of LTs. In this study, we describe the design and synthesis of CAPE analogs as radical scavengers and 5- LO inhibitors. Caffeic esters bearing propargyl and allyl linkers between the caffeoyl and aryl moieties ( 4a-i and 5a-i, respectively) were synthesized by Sonogashira and Heck cross-coupling reactions to probe the effects of flexibility and aryl substitution on 5- LO inhibition. Caffeoyl alcohol and ethers ( 6, 7a-b) as well as caffeoyl aldehyde and ketones ( 8a-e) were synthesized to elucidate the importance of the ester linkage for inhibitory activity. All tested compounds proved to be good radical scavengers ( IC50 of 10-30 μ m). After preliminary anti- LTs activity screening in HEK293 cell models, 5- LO inhibition potential of selected compounds was determined in human polymorphonuclear leukocytes ( PMNL). Most screened compounds outperformed CAPE 3 in concentration-dependent assays on PMNL, with ester dimers 4i and 5i along with caffeoyl ethers 7a-b being roughly eight-, seven-, and 16-fold more potent than Zileuton, with IC50 values of 0.36, 0.43, and 0.18 μ m, respectively. [ABSTRACT FROM AUTHOR]

In this work the synthesis, structure–activity relationship (SAR) and biological evaluation of a novel series of triazole-containing 5-lipoxygenase (5-LO) inhibitors are described. The use of structure-guided drug design techniques provided compounds that demonstrated excellent 5-LO inhibition with IC 50 of 0.2 and 3.2 μ m in cell-based and cell-free assays, respectively. Optimization of binding and functional potencies resulted in the identification of compound 13d , which showed an enhanced activity compared to the parent bioactive compound caffeic acid 5 and the clinically approved zileuton 3 . Compounds 15 and 16 were identified as lead compounds in inhibiting 5-LO products formation in neutrophils. Their interference with other targets on the arachidonic acid pathway was also assessed. Cytotoxicity tests were performed to exclude a relationship between cytotoxicity and the increased activity observed after structure optimization. [ABSTRACT FROM AUTHOR]

Some studies suggest that 5-lipoxygenase (5- LOX) inhibition or leukotriene receptor antagonism may effectively attenuate different kinds of pain. In the present study, we investigated whether esculetin (which, among other actions, potently inhibits 5- LOX) possesses analgesic activity in acute non-inflammatory pain and acute inflammatory pain models in rats. We also examined the effects of zileuton, a selective 5- LOX inhibitor, on esculetin activity. Plasma concentrations of leukotriene B4 ( LTB4) after administration of esculetin were also determined. Esculetin (1.25-20 mg/kg, i.p.) dose-dependently alleviated hyperalgesia and exhibited antinociceptive effects in both experimental models. The greatest effect of esculetin was observed with a dose of 20 mg/kg. In carrageenan-induced inflammatory pain in rats, 20 mg/kg esculetin reversed or mitigated hyperalgesia, increasing the threshold to mechanical stimuli from a control value of −23.8 ± 1.8% to 15.2 ± 2.2% ( P < 0.01) and that to thermal stimuli from −52.5 ± 6.1% to −9.5 ± 3.9% ( P < 0.01). In non-inflammatory pain, after esculetin (20 mg/kg) administration the threshold values to mechanical and thermal stimuli increased to 75.9 ± 4.2% and 59.2 ± 4.3%, respectively ( P < 0.01 for both). Zileuton (30 mg/kg, p.o.) alone slightly but significantly increased the pain threshold in the non-inflammatory and inflammatory acute pain models. Pretreatment with 30 mg/kg, p.o., zileuton significantly enhanced the analgesic activity of 5 mg/kg, i.p., esculetin in both pain models. Moreover, esculetin (10 mg/kg, i.p.) decreased LTB4 concentrations in the blood from 244 ± 29 pg/mL in the control group to 185 ± 11 pg/mL ( P < 0.005). The results of the present study suggest the involvement of the 5- LOX pathway in esculetin analgesia. [ABSTRACT FROM AUTHOR]

• PH-251 is a pharmacologically active oxazolidinone hydroxamic acid derivative. • PH-251 is a novel dual inhibitor of 5-Lipoxygenase and mast cell degranulation. • PH-251 has anti-allergic, anti-asthmatic and anti-inflammatory effects. We have recently reported the discovery of a series of oxazolidinone hydroxamic acid derivatives that are potent inhibitors of 5-lipoxygenase (5-LO) [arachidonate 5-lipoxygenase; EC 1.13.11.34]. We now report that one of the most active members of this series, compound PH-251, [(R)- N -((3-(3-fluoro-4-morpholinophenyl)-2-oxooxazolidin-5-yl) methyl)-N-hydroxyoctanamide], also possesses a unique and strong ability to concurrently inhibit mast cell degranulation. PH-251 inhibited the biosynthesis of leukotriene C4 (LTC 4), as well as degranulation of IgE/allergen-activated bone marrow-derived mouse mast cells (BMMC) in vitro. In contrast, zileuton (the prototype 5-LO inhibitor) inhibited leukotriene generation, but not degranulation. Consistent with its dual activity, compound PH-251 also significantly inhibited both the early and the late anaphylactic contractions of guinea pig lung parenchymal strip, whereas zileuton inhibited only the late (leukotriene-dependent) contractions. Comparative structure–activity analysis of PH-251 and its structural analogues showed that the anti-degranulation effect appeared to be dependent on the length of the straight-chain hydrocarbon substitution on the hydroxamic acid moiety. In the in vivo studies, PH-251 (3–30 mg/kg s.c.) strongly inhibited various components of zymosan-induced peritonitis - a typical non-allergic LT-dependent animal model of inflammation. In the mouse allergic asthma model, the compound significantly inhibited allergen-induced bronchial eosinophilic inflammation and airway hyper-responsiveness to inhaled methacholine. These results show that PH-251 is a unique dual inhibitor of 5-LO and mast cell degranulation, with in vivo activity in animal models of disease and may therefore offer potential advantages over single-target drugs in the treatment of asthma and other allergic and inflammatory diseases. [ABSTRACT FROM AUTHOR]

Highlights: [•] First reported development and validation of a clinical LC–MS/MS assay for zileuton. [•] The quantification range (3.05–20,000ng/mL) spans clinically relevant blood levels. [•] The assay reliably quantified zileuton in pediatric pharmacokinetic trials. [ABSTRACT FROM AUTHOR]

The interstitial cells of Cajal (ICCs) are pacemakers in the gastrointestinal tract and transient receptor potential melastatin type 7 (TRPM7) is a candidate for pacemaker channels. The effect of the 5-lipoxygenase (5-LOX) inhibitors NDGA, AA861, MK886 and zileuton on pacemaking activity of ICCs was examined using the whole cell patch clamp technique. NDGA and AA861 decreased the amplitude of pacemaker potentials in ICC clusters, but the resting membrane potentials displayed little change, respectively. Also, perfusing NDGA and AA861 into the bath reduced both inward current and outward current in TRPM7-like current in single ICC, respectively. But, they had no effects on Ca activated Cl currents. The 5-LOX inhibitors MK886 and zileuton were, however, ineffective in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC, respectively. A specific TRPC3 inhibitor, pyrazole compound (Pyr3), and a specific TRPM4 inhibitor, 9-phenanthrol, had no effects in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC. These results suggest that, among the tested 5-LOX inhibitors, NDGA and AA861 modulate the pacemaker activities of the ICCs, and that the TRPM7 channel can affect intestinal motility. [ABSTRACT FROM AUTHOR]

5-Lipoxygenase inhibitor 3- O-acetyl-9,11-dehydro-β-boswellic acid was detected in the extract of Boswellia serrata gum resulting from unstable 11-hydroxy precursor. It was reported more potent than other Boswellic acids in its inhibition of 5-Lipoxygenase. Here, we report the method of conversion of 3-acetoxy-β-boswellic acid to 3- O-acetyl-9,11-dehydro-β-boswellic acid, and the crystal structure of later. This compound crystallizes in orthorhombic space group P222 with cell parameters of a = 12.726(1) Å, b = 16.597(1) Å, c = 27.332(2) Å, α = β = γ = 90°, V = 5772.7(5) Å, D = 1.143 Mg/m, and Z = 8. The X-ray structure investigation indicates that the rings A, B, D and E are exhibit chair and the ring C adopts a distorted half chair conformation. The conformational difference of the two structures in the arrangement is due to crystal packing of 3- O-acetyl-9,11-dehydro-β-boswellic acid. The molecular packing is stabilized by C-H···O and O-H···O types of hydrogen bonding interactions. Graphical Abstract: Synthesis and crystal structure analysis of 5-Lipoxygenase Inhibitor 3- O-acetyl-9,11-dehydro-β-boswellic acid are reported. Rings A, B, D and E of the inhibitor adopt chair conformation and the C-ring exhibit a distorted half chair conformation. The molecular packing is stabilized by C-H···O and O-H···O types of hydrogen bonding interactions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Background/Aim: To discover new 5-lipoxygenase (5-LO) inhibitors applicable to inflammation-related skin disease, we identified and examined antiinflammatory properties of a novel 5-LO inhibitor, KR-33749, in vitro and in vivo. Methods: 5-LO enzyme activity was assayed using insect cell lysates overexpressing rat 5-LO. The leukotriene B4 (LTB4) level was assayed in rat basophilic leukemia (RBL-1) cell line. Mouse ear edema was induced by topical application of arachidonic acid. Atopic dermatitis-like skin lesion was induced by topical application of 1-chloro-2,4-dinitrobenzene (DNCB) to NC/Nga mice. Results: KR-33749 inhibited 5-LO activity with an IC50 value of 70.5 ± 6.0 nmol/l in parallel with LTB4 inhibition in RBL-1 cells. The compound exhibited a >1,000-fold selectivity against 12-LO and 15-LO. KR-33749 showed in vivo protective effects against arachidonic acid-induced ear edema and DNCB-induced atopic dermatitis-like symptoms in NC/Nga mice. Conclusion: Our results show that KR-33749, a new 5-LO inhibitor exhibits potent antiinflammatory activities in vitro as well as in vivo. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Zileuton has been demonstrated to act as an anti-inflammatory agent by virtue of its well-known ability to inhibit 5-lipoxygenase (5-LO). However, the effects of zileuton on cardiovascular disease and cardiomyocyte apoptosis are unclear. Here, we investigated the effects of zileuton on apoptosis of cardiac myogenic H9c2 cells and neonatal rat cardiomyocytes (NRCMs), and examined the possible role of PKCδ-mediated induction of COX-2 in these effects. Treatment of H9c2 cells with zileuton efficiently induced COX-2 expression and PGE2 biosynthesis in a time- and dose-dependent manner. Zileuton also exerted a profound protective effect against H2O2-induced oxidative stress, a mimic of reperfusion damage in vitro, and this protective effect was abolished by COX-2-selective inhibitor. When we investigated the signalling pathways involved in zileuton-induced COX-2 expression, we found that zileuton acts as a PKCδ activator, causing it to translocate from the cytosol to nucleus. Inhibition of PKCδ activation with rottlerlin, a PKCδ-specific inhibitor, abolished the zileuton-induced protection against H2O2-induced cell death and inhibited zileuton-induced COX-2 expression and PGE2 production. The protective effect of zileuton was dramatically diminished by treatment with LY294002 or PD98059. Furthermore, zileuton-stimulated ERK1/2 and Akt phosphorylation was attenuated by rottlerin, indicating that PKCδ might act upstream of ERK1/2 and Akt. Moreover, inhibition of either ERK1/2 or Akt activation abolished zileuton-induced COX-2 expression. Knockdown of PKCδ with siRNA also reversed the protective effect of zileuton and blocked the induction of COX-2. These results suggest that zileuton-induced COX-2 expression is sequentially mediated through PKCδ-dependent activation of ERK1/2 and Akt. Based on these findings, we propose that zileuton might provide a new therapeutic strategy for ischemia/reperfusion injury of the heart. [Copyright &y& Elsevier]

Background: Aspirin desensitization followed by daily aspirin therapy is effective add-on treatment for patients with aspirin-exacerbated respiratory disease. Prior studies used 650 mg of aspirin twice daily, but studies at lower dosages were inconclusive. Objective: We sought to determine the optimal daily dosage of aspirin treatment. Methods: We studied 137 patients who had undergone successful aspirin desensitization and randomized them into 2 groups, 650 mg twice daily versus 325 mg twice daily. After 1 month, patients either increased or decreased their dosage based on their symptom control and continued that dosage for the remainder of the year. Results: Patients taking either 650 mg twice daily or 325 mg twice daily showed significant improvements in number of sinus infections, sinus operations, and hospitalizations for asthma (all P < .0001). Anosmia, nasal/sinus symptoms, and asthma symptoms also improved in both groups (all P < .03). Systemic corticosteroid dosages decreased by 3- and 4-fold in the 325 mg twice daily and 650 mg twice daily groups, respectively. Of the 137 patients, 32 had adverse effects from or discontinued aspirin therapy: 14 (44%) of 32 from the group randomized to taking 650 mg twice daily and 18 (56%) of 32 from the group randomized to 325 mg twice daily. The most common adverse effect was dyspepsia. Conclusion: Both dosages were efficacious, and side effects occurred in both groups at similar frequencies. Some patients initially taking 325 mg twice daily required an increase to 650 mg twice daily for optimal symptom control. Clinical implications: We recommend that patients begin daily aspirin therapy with 650 mg twice daily and subsequently decrease to the lowest effective dosage (usually 325 mg twice daily). [Copyright &y& Elsevier]

Summary: Background: Inhalation of swine house dust induces acute airway inflammation and increased bronchial responsiveness in healthy subjects. Objective: The aim of the study was to investigate whether 5-lipoxygenase products such as leukotrienes may have a role in this reaction. Methods: Twenty-three healthy subjects were randomised into two groups receiving treatment with either zileuton (600mg) or placebo four times a day. After 5 days of treatment, all subjects were exposed for 3h in a swine barn. Bronchial responsiveness, exhaled nitric oxide (NO), and mediators in nasal lavage (NAL), blood and urine were measured before and after the exposure. Results: The exposure induced an increased bronchial responsiveness to methacholine in both groups with 2–3 doubling concentration steps, no significant difference between treatments. Leukotriene E4 in urine increased significantly following exposure in the placebo group from 37.3 (29.1–45.6) (mean (95% confidence interval)) ng/mmol creatinine to 47.7 (36.3–59.0) ng/mmol creatinine (), but not in the zileuton group. The post-exposure increase of LTB4 levels in NAL fluid was totally abolished in the zileuton group ( vs. the placebo). The levels of exhaled NO increased significantly (), two-fold in both groups. The PGD2 metabolite 9α, 11β-PGF2 increased in placebo-treated subjects (; vs. zileuton), strengthening mast cell participation. Neutrophil counts and levels of IL-6 in peripheral blood increased in both groups, with a significantly larger increase in zileuton treated subjects ( and , respectively compared to placebo). Conclusions: Pre-treatment with clinically recommended doses of the 5-lipoxygenase inhibitor zileuton did not affect the increase of bronchial reactivity induced by swine dust exposure. The intervention totally abolished the LTB4 release in NAL fluid, but only partially inhibited the formation of leukotrienes as monitored by urinary levels. The enhanced increase of neutrophils and IL-6 in peripheral blood in the zileuton group, suggests that inhibition of 5-lipoxygenase may have pro-inflammatory effects. [Copyright &y& Elsevier]

Summary Histologically, granuloma annulare (GA) is a common non-infectious necrobiotic granulomatous reaction pattern that correlates with a number of different, but relatively specific clinical presentations. The cause or causes of GA are unknown: when localized, it is usually self-limiting, but it may be persistent when disseminated. We present three women who had had disseminated GA for more than 1 year. One patient had previously been treated with isotretinoin with no response. All three patients were treated with vitamin E 400 IU daily and zileuton 2400 mg daily. All responded within 3 months with complete clinical clearing. The anti-inflammatory and immune regulatory effects of vitamin E and zileuton may be an effective treatment in some patients with prolonged disseminated/generalized GA. [ABSTRACT FROM AUTHOR]

ABT-761 is a 5-lipoxygenase inhibitor developed for the treatment of asthma. The present study was undertaken to evaluate different crystal forms of ABT-761 and their impact on in vitro and in vivo performance in capsule formulations. Two crystal forms of ABT-761, hemihydrate and non-solvate from different sources, were characterized by thermal analysis, x-ray powder diffraction, moisture sorption, and intrinsic dissolution studies. An in vitro test was performed to assess the effect of formulation and drug from different sources on drug release. Crossover design was also used to evaluate oral bioavailability of ABT-761 hemihydrate formulations in beagle dogs. Plasma concentrations of ABT-761 were analyzed using a reverse-phase high-performance liquid chromatography (HPLC) assay. It was found that in vivo oral absorption as well as in vitro dissolution of ABT-761 were influenced by different formulations. Capsule formulations of ABT-761 hemihydrate are bioequivalent to the solution formulation in terms of extent of absorption, but formulation and the method of granulation preparation can have a major impact on the absorption rate. In conclusion, a single crystal form of ABT-761, i.e., hemihydrate, is preferred for subsequent product development. However, exposure of the drug to conditions that may facilitate phase transformation should be avoided. [ABSTRACT FROM AUTHOR]

Abstract Nine dogs meeting the diagnostic criteria for canine atopic dermatitis were enrolled in a double-blind, placebo-controlled, cross-over clinical trial. In this pilot study, zileuton (a 5-lipoxygenase inhibitor) given orally at 2 mg kg-1 three times daily for 4 weeks significantly decreased erythema in dogs with atopic dermatitis but had no effect on pruritus. Zileuton was well tolerated and no adverse clinical signs were noted. However, one dog developed mild alanine aminotransaminase elevation, which resolved within 1 week of discontinuation of therapy. Monitoring of alanine aminotransaminase may be necessary in dogs receiving zileuton. Further studies with larger number of dogs are needed to evaluate the efficacy of zileuton as treatment for canine atopic dermatitis. [ABSTRACT FROM AUTHOR]

Background TMK688 is being developed as an anti-allergic drug having both 5-lipoxygenasc inhibitory activity and anti-histaminc activity. Method We compared the inhibition of the late asthmatic responses by TMK688 with that by other anti-allergic agents in actively sensitized guinea pigs, and examined the relationship between 5-lipoxygetiase inhibition and the late asthmatic responses. Results At 1-3.2 mg/kg, TMK688 inhibited the increases in respiratory resistance, leukotriene (LT) B4 and C4 production in the lungs and eosinophil infiltration into the alveoli during the late asthmatic response, whereas the effects tended to lessen at the dose of 10 mg/kg. These effects are thought to be caused by the 5-lipoxygenase inhibitory activity of TMK688 because Azelastine. an anti-allergic drug having potent antihistamine activity, exhibited no effect. ONO-1078. a peptide LT antagonist. inhibited the late-phase bronchoconstriction at a dose of 100mg/kg p.o.. but not the increase in the infiltration of inflammatory cells into the alveoli, suggesting that the latephase bronchoconstriction is induced, in part, by peptide LTs. i.e. LT C4 D4 and E4 and that the inflammatory cell infiltration may be caused by LTB4. TMK6SK inhibited the immediate bronchoconstriction dose-dependently, and the effect was significant at a dose of 10 mg/kg orally. Since Azelastine. Ketotifen and Oxatomide suppressed the bronchoconstriction at far lower doses than did TMK688, the inhibitory effect was mainly caused by its antihistamine activity. Conclusions TMK688 appears to be a novel anti-allergic drug having inhibitory effects on both the bronchoconstriction and the infiltration of inflammatory cells during late asthmatic responses. [ABSTRACT FROM AUTHOR]

Purpose. A variety of methods exist which determine the rate and extent of intestinal absorption. The method described here employs an internal absorption reference probe and portal blood sampling in unanesthetized rat. Methods. Theophylline and tritiated water were selected as absorption reference probes since they are quantitatively absorbed in conscious rat. The fraction of an intestinal dose which reaches portal blood was determined from the resulting portal-systemic blood concentration gradients of the drug relative to the absorption probe. The absorption probes provide a means to calculate the drug mass reaching portal blood without the need of measuring the portal blood flow rate. The technique was evaluated with verapamil and a well-absorbed 5-lipoxygenase inhibitor, A-79035. Results. The fraction of an intrajejunal dose of A-79035 reaching the portal vein (F) was 0.86 using theophylline as the absorption probe. Verapamil, which is susceptible to extensive hepatic first-pass elimination, was completely absorbed (F = 0.98) within 1 hour, but was only 21.4% bioavailable. Absorption rate constants, estimated from initial appearance rates in portal blood, were used to monitor factors that affect drug absorption. For example, with a dose solution containing 30% PEG-400, the absorption rate constants of theophylline and A-79035 were significantly reduced. Anesthesia reduced the absorption rate constant for theophylline in rats by 40% compared to conscious animals. Conclusions. The technique detailed here allows reliable, direct measurement of intestinal absorption which may assist in characterizing oral dosing for novel therapeutic agents. [ABSTRACT FROM AUTHOR]

Zileuton ( N-(1-benzo[ b]thien-2-ylethyl) N-hydroxyurea) is a powerful 5-lipoxygenase inhibitor. The chemical degradation of Zileuton and related hydroxyurea derivatives was studied in aqueous solutions as a function of pH and temperature. The pH profile for the degradation of Zileuton shows an acid-catalyzed region at pH values below 2, water hydrolysis of the protonated form at pH values from 3 to 8, and water hydrolysis of the unprotonated form at pH values greater than 9. Hydrolysis of the hydroxyurea moiety to give the hydroxylamine derivative represents the main degradation pathway for Zileuton. This product, however, is not stable and is present at low concentrations at pH values below 6 and not observed at pH values greater than 7. Further decomposition of the hydroxylamine derivative leads to the observed degradation products. Air oxidation to the isomeric oximes accounts for the observed products at pH values greater than 7. Hydrolysis of the oximes to the ketone derivative accounts for the observed products at pH values 2 to 6. Parallel decomposition pathways to the alcohol derivative were noted under strongly acidic conditions, pH 0 to 2. [ABSTRACT FROM AUTHOR]

The o-naphthoquinone derivative, CGS 8515 ( I), is a potent inhibitor (IC, 0.1 µ M) of 5-lipoxygenase, but its therapeutic potential is compromised by a short plasma half-life (22 min) and extremely poor oral bioavailability (<2%). Poor biopharmaceutical properties of CGS 8515 were attributed to poor aqueous solubility and rapid in vivo hydrolysis of its methyl ester function to an inactive metabolite (IC, 100 µ M). An active amide analogue ( II) was synthesized to prevent rapid hydrolysis. While analogue II appeared to be stable in vivo, its plasma half-life was also short (10 min), possibly because of rapid tissue distribution rather than metabolic elimination. Therefore, three potent analogues with increased aqueous solubilities were synthesized and compared with respect to their pharmacokinetic properties. The analogue with the highest aqueous solubility ( V) demonstrated a plasma concentration vs time profile with the largest area under the curve (AUC) and the smallest distribution (α) phase of all the analogues studied. The percentage AUC of the terminal phase (β) for three analogs paralleled their aqueous solubilities. The oral bioavailability of V was improved to 27%, compared to 2% for the parent compound, CGS 8515. [ABSTRACT FROM AUTHOR]

The main left coronary artery of rats was ligated near its origin under light ether anaesthesia and the infarction observed for 48 h. The ischaemic area was determined after an intravenous injection of pontamine sky blue dye 1 h before induction of cardiac arrest with potassium chloride. The unstained area (true ischaemic area) decreased with time to 27.1% of the left ventricle at 48 h, whereas the intensely stained area between the normal and the true ischaemic areas increased with time, suggesting that blood was flowing to the border from the normal surrounding tissue. The infarcted area, identified by its lack of triphenyltetrazolium chloride staining, became evident after 3 h and stabilised at 12 h (42% of left ventricle). The polymorphonuclear leucocyte counts in the hearts, differentiated by staining of their chloroacetate esterase, increased gradually up to 5500 cells per section at 24 h. The leukotriene B4 concentration, determined by radioimmunoassay after freezing of the beating heart in liquid nitrogen, increased to eight times that of the sham operated hearts and peaked at 8 h (9.4(0.6) ng per heart, mean(SEM) n=5) before the leucocyte counts reached their maximum. A single oral dose of a selective 5-lipoxygenase inhibitor (AA-861, 80 mg·kg−1, 1 h before ligation) lowered the leukotriene B4 concentration to that of the sham operated hearts and decreased the leucocyte count by 49.4% and 41.2% at 12 and 24 h respectively. The inhibitor also reduced the infarct size at 48 h by 34.4%. It was concluded that leukotriene B4, generated in ischaemic cardiac tissue, may increase infarct size through migration of polymorphonuclear leucocytes. [ABSTRACT FROM PUBLISHER]

The pharmacokinetics of zileuton, a novel selective 5-lipoxygenase inhibitor, were studied in 37 patients with rheumatoid arthritis after administration of 200 mg, 400 mg, and 600 mg zileuton for 4 weeks. Patients had 6-h pharmacokinetic evaluation of zileuton on day 14. Plasma zileuton concentrations were quantitated using HPLC. Zileuton pharmacokinetic parameters were estimated using standard noncompartmental methods. A population analysis of zileuton pharmacokinetics was also performed with the NONMEM computer program. The pharmacokinetics of zileuton in patients with rheumatoid arthritis were similar to those previously estimated in normal healthy humans. The peak concentrations and the areas under the curves during the dosing interval were dose proportional. The noncompartmental means of the CL/ f, terminal-phase half-life, and V/f of zileuton were approximately 545 ml min, 1.4 h, and 64.3 1, respectively. The estimate of population typical values of the CL/ f for a 70-kg person (540 ml min) and V/f for a 70-kg person (64.8 1) from the NONMEM analysis were in agreement with the noncompartmental estimates. Differences in body weight, but not age or gender, helped explain some of the variability in the pharmacokinetics of zileuton in patients. Therefore, there is no pharmacokinetic basis for alteration of the zileuton dose size or the dosing schedule in patients with rheumatoid arthritis. [ABSTRACT FROM AUTHOR]

The inhibitory effects of the semi-quinone U-66,858 and its metabolite U-68,244 on the ionophore-induced formation of leukotriene B (LTB) were examined in human whole blood (WB). Preincubation of U-66,858 and U-68,244 for 1 min prior to challenge of blood with calcium ionophore A23187 resulted in IC values of 1080±644 and 820±442 nmol/L, respectively (NS). After 60 min preincubation, values were 250±85 and 270±79 nmol/L (NS). The activity of the lipoxygenase inhibitor AA-861 in this system was similar to that of U-66,858, while vitamin K and the sulphate conjugate of U-66,858 showed significant inhibition of LTB release only at micromolar concentrations. U-66,858 exhibited significant inhibition of thromboxane A release ( p<0.02) in a comparative study with the known cyclooxygenase (CO) inhibitor flurbiprofen. The metabolism of U-66,858 in contact with WB at 37°C was monitored for 70 min using [C]-labelled drug and reverse-phase HPLC, the majority of recovered radioactivity no longer in the form of U-66,858 being accounted for by U-68,244 and polar conjugates of U-66,858. Thus, U-66,858 is a potent inhibitor of LTB production in human whole blood and undergoes deacetylation to an initial metabolite with similar pharmacological potency. However, other metabolites of U-66,858 such as the sulphate conjugate, are relatively weak inhibitors of 5-lipoxygenase (5-LO) under similar conditions. [ABSTRACT FROM AUTHOR]

Background: Zileuton, a 5-lipoxygenase inhibitor, reduces the number of inflammatory lesions in moderate acne and inhibits the synthesis of sebaceous lipids.Objective: To detect whether zileuton directly reduces sebum synthesis.Methods: A 40-year-old female with mild disseminated sebaceous gland hyperplasia and seborrhea was treated with zileuton 4 x 600 mg/day over 2 weeks, was followed-up for 6 weeks after discontinuation of zileuton and was re-treated with low-dose isotretinoin 10 mg/2nd day over 5 weeks. Casual skin surface lipids and sebum synthesis were determined.Results: Under treatment with zileuton increased casual skin surface lipids were normalized and synthesis of facial sebum was decreased. Six weeks after discontinuation of treatment casual skin surface lipids were increased again and synthesis of sebum returned to baseline. Subsequent low-dose isotretinoin treatment led to similar changes of casual skin surface lipids and sebum synthesis with zileuton already after 2 weeks.Conclusion: Zileuton directly inhibits sebum synthesis in a transient manner with a potency similar to low-dose isotretinoin at least in our patient. [ABSTRACT FROM AUTHOR]

The arachidonic acid metabolism through 5-lipoxygenase (5-LO) pathways is involved in modulating both tumorigenesis and angiogenesis. Although anti-carcinogenic activities of certain 5-LO inhibitors have been reported, the role of zileuton, a well known 5-LO inhibitor, on the endothelial cell proliferation and angiogenesis has not been fully elucidated. Here, we report that zileuton has an anti-angiogenic effect, and the underlying mechanisms involved activation of the large-conductance Ca2+-activated K+ (BK) channel. Our results show that zileuton significantly prevented vascular endothelial growth factor (VEGF)-induced proliferation of human umbilical vein endothelial cells (HUVECs) in vitro, as well as in vivo. However, such anti-angiogenic effect of zileuton was abolished by iberiotoxin (IBTX), a BK channel blocker, suggesting zileuton-induced activation of BK channel was critical for the observed anti-angiogenic effect of zileuton. Furthermore, the anti-angiogenic effect of zileuton was, at least, due to the activation of pro-apoptotic signaling cascades which was also abolished by IBTX. Additionally, zileuton suppressed the expression of VCAM-1, ICAM-1, ETS related gene (Erg) and the production of nitric oxide (NO). Taken together, our results show that zileuton prevents angiogenesis by activating the BK channel dependent-apoptotic pathway, thus highlighting its therapeutic capacity in angiogenesis-related diseases, such as cancer. [ABSTRACT FROM AUTHOR]