High-affinity leukotriene receptor antagonists. Synthesis and pharmacological characterization of 2-hydroxy-3-[(2-carboxyethyl)thio]-3-[2-(8-phenyloctyl)phenyl] propanoic acid

Facile preparation of fluorine-containing 2,3-epoxypropanoates and their epoxy ring-opening reactions with various nucleophiles

We describe herein a facile method to access 2,3-epoxyesters with fluorine-containing substituents at their 3-position starting from the corresponding enoates by utilization of the low-costed and easy-to-handle reagent, NaOCl·5H2O. Because very little has been disclosed about the reactivity of such 2,3-epoxyesters, their epoxy ring opening by a variety of nucleophiles was carried out and we succeeded in clarifying these chemo- as well as regioselective processes proceeding via the SN2 mechanism to mainly afford 2-substituted 3-hydroxyesters usually in a highly anti selective manner.

Classification models and SAR analysis on CysLT1 receptor antagonists using machine learning algorithms

Cysteinyl leukotrienes 1 (CysLT1) receptor is a promising drug target for rhinitis or other allergic diseases. In our study, we built classification models to predict bioactivities of CysLT1 receptor antagonists. We built a dataset with 503 CysLT1 receptor antagonists which were divided into two groups: highly active molecules (IC₅₀ < 1000 nM) and weakly active molecules (IC₅₀ ≥ 1000 nM). The molecules were characterized by several descriptors including CORINA descriptors, MACCS fingerprints, Morgan fingerprint and molecular SMILES. For CORINA descriptors and two types of fingerprints, we used the random forests (RF) and deep neural networks (DNN) to build models. For molecular SMILES, we used recurrent neural networks (RNN) with the self-attention to build models. The accuracies of test sets for all models reached 85%, and the accuracy of the best model (Model 2C) was 93%. In addition, we made structure-activity relationship (SAR) analyses on CysLT1 receptor antagonists, which were based on the output from the random forest models and RNN model. It was found that highly active antagonists usually contained the common substructures such as tetrazoles, indoles and quinolines. These substructures may improve the bioactivity of the CysLT1 receptor antagonists.

Nitrile biotransformations for highly efficient and enantioselective syntheses of electrophilic oxiranecarboxamides

Catalyzed by a nitrile hydratase/amidase-containing microbial Rhodococcus sp. AJ270 whole-cell catalyst, a number of racemic trans-2,3-epoxy-3-arylpropanenitriles 1 underwent rapid and efficient hydrolysis under very mild conditions to afford 2R,3S-2-arylglycidamides 2 in excellent yield with enantiomeric excess higher than 99.5%. The overall enantioselectivity of the biotransformations originated from the combined effects of a dominantly high 2S-enantioselective amidase and low 2S-enantioselective nitrile hydratase involved in the cell. The influence of the substrates on both reaction efficiency and enantioselectivity was also discussed in terms of steric and electronic effects.

Galphimia glauca organic fraction antagonizes LTD(4)-induced contraction in guinea pig airways

Galphimia glauca is used for the treatment of asthma and allergies in Latin American traditional medicine. The ethylacetate fraction from its aerial parts was assayed for bronchoconstriction induced by antigen and several agonists in guinea pig tracheae. The organic fraction significantly inhibited the contractile response to ovalbumin in tracheae from sensitized guinea pigs, and significantly and selectively inhibited the bronchoconstriction induced by leukotriene D(4) (LTD(4)). The relative potency of the ethylacetate fraction of G. glauca to produce a concentration-dependent rightward shift of LTD(4) concentration-response curve was similar to that reported for SK&F 104353, a well-known competitive LTD(4)-antagonist.

Synthesis and structure-activity relationships of carboxyflavones as structurally rigid CysLT1 (LTD4) receptor antagonists

The synthesis and CysLT1 receptor affinities of a new series of highly rigid 3'- and 4'-(2-quinolinylmethoxy)- or 3'- and 4'-[2-(2-quinolinyl)ethenyl]-substituted, 6-, 7-, or 8-carboxylated flavones are described. CysLT1 receptor affinities of the flavones (down to 11 nM) were determined by their ability to displace [3H]LTD4 from its receptor in guinea pig lung membranes. Structure-affinity relationship studies showed that the relative positions of the carboxylic acid and the quinoline moiety were critical for CysLT1 affinities. While the carboxyl is optimal in the 8 position but tolerated in the 6 position, only the 6- and not the 8-tetrazole has significant activity. The quinoline moiety may be connected to the flavone skeleton by an ethenyl or a methoxy linker, but the substitution position is important for high affinity, especially in the 6-carboxylated flavones. 4'-Substituted 6-carboxyflavones are essentially inactive, whereas the 3'-substituted analogues have submicromolar CysLT1 affinity. Replacement of the quinoline by other heteroaromates generally leads to decreased affinities, with the phenyl and naphthyl analogues displaying only little or no affinity, while the 7-chloroquinoline analogue is comparable in activity to the quinoline. Flavones having CysLT1 receptor affinities of 10-30 nM were selected for determination of their inhibitory effects on the LTD4-induced contraction of guinea pig ileum in vitro. The IC50 values ranged between 15 and 100 nM. Compound 5d (8-carboxy-6-chloro-3'-(2-quinolinylmethoxy)flavone, VUF 5087) was selected for further research because of its high potency in the functional assay. This series contains the most rigid CysLT1 receptor antagonists known to date, and they are useful in the development of a CysLT1 antagonist model, which is discussed in the companion paper.

Synthesis and structure-activity relationships of carboxylated chalcones: a novel series of CysLT1 (LTD4) receptor antagonists

The synthesis and CysLT1 antagonistic activities of a new series of 2-, 3-, and 4-(2-quinolinylmethoxy)- and 3- and 4-[2-(2-quinolinyl)ethenyl]-substituted, 2'-, 3'-, 4'-, or 5'-carboxylated chalcones are described. Structure-activity relationship studies indicate a preference for the presence of a negatively charged (acidic) moiety, although in some cases nitrile or ester analogues also exhibit moderate activity. The quinoline moiety may be substituted at either the 3- or the 4-position. Replacement of this heterocycle by other aromatic groups results in compounds with comparable affinities [2-(7-chloroquinoline), 1-(1-methyl-2-benzimidazole), or 1-(2-benzothiazole)] or substantially lower activities [1-(1-ethoxyethyl)-2-benzimidazole, 2-naphthyl, or phenyl]. The quinoline and chalcone moieties may be connected by either an ethenyl or a methoxy spacer. The acidic moiety at the chalcone B ring may be attached to the 2'-, 3'-, 4'-, or 5'-position, for both the 3- and 4-substituted chalcones. There are no general patterns to specify which substitution positions gave the most potent compounds. The series contains several potent CysLT1 receptor antagonists, with K(D) values approaching the nanomolar range, as measured by the displacement of [3H]LTD4 from guinea pig lung membranes. Antagonism of LTD4-induced contraction of guinea pig ileum, the inhibition of antigen-induced contraction of guinea pig trachea in vitro, and the inhibition of LTD4-induced increase of vascular permeability in vivo are determined for chalcones with high CysLT1 receptor affinities (K(D) values below 0.1 microM). 2'-Hydroxy-4-(2-quinolinylmethoxy)-5'-(5-tetrazolyl)chalcone (14, VUF 4819) showed good activity in both in vitro and in vivo assays and has been selected for further evaluation.

SK&F 104353, a selective leukotriene receptor antagonist, inhibits leukotriene D4- and antigen-induced bronchoconstriction in cynomolgus monkeys

The ability of SK&F 104353 to prevent and reverse leukotriene (LT) D4- and antigen (Ag)-induced bronchoconstriction was examined in anesthetized, spontaneously breathing cynomolgus monkeys. Aerosol administration of LTD4 (10 micrograms/ml; 20 breaths) produced a sustained increase in pulmonary resistance and decrease in dynamic lung compliance. Aerosolized SK&F 104353 (150 breaths, 0.3 or 4.4 mg/ml) administered 15 min prior to LTD4 challenge antagonized these changes in a dose-dependent manner. When given intravenously 6 min after LTD4, SK&F 104353 (5 mg/kg) rapidly and completely reversed the ongoing bronchoconstriction. In mepyramine-pretreated (2 mg/kg i.v.) monkeys sensitive to aerosolized Ascaris suum Ag, intravenously administered SK&F 104353 (5 mg/kg) substantially reversed, but did not abolish, Ag-induced bronchoconstriction when administered 12 min after the Ag challenge. In contrast, SK&F 104353 (5 mg/kg i.v.) did not reverse Ag-induced bronchoconstriction in animals that had not been pretreated with mepyramine. Similar results were obtained when SK&F 104353 (20 mg/kg i.v.) was administered (as a pretreatment) 5 min prior to Ag under these conditions. Thus, SK&F 104353 reduced Ag-induced bronchoconstriction in mepyramine-pretreated monkeys, but had little effect in the absence of mepyramine. The data suggest that LTs, in addition to histamine, play a role in allergic bronchoconstriction in cynomolgus monkeys.

Characterization of the leukotriene D4 receptor in hyperreactive rat lung

A [3H]leukotriene D4 radioreceptor binding assay has been established in rat lung and has been used to fully characterize the leukotriene D4 receptor in lung membranes from an inbred strain of rats displaying non-specific bronchial hyperreactivity. [3H]leukotriene D4 specific binding in this tissue is of high affinity (KD 0.12 nM), saturable (Bmax 42 fmol/mg protein), inhibited by both guanine nucleotide analogues and sodium ions and increased by divalent cations. In addition, Ki values show that agonists, but not antagonists, compete for [3H]leukotriene D4 binding in rat lung with the same potency as they compete for [3H]leukotriene D4 binding in guinea-pig lung, the classical tissue for leukotriene D4 receptor studies. Finally, [3H]leukotriene D4 binding in hyperreactive rat lung has been compared with [3H]leukotriene D4 binding in lung tissue from Fischer rats, which are a less responsive strain.

Pharmacologic and pharmacokinetic profile of SK&F S-106203, a potent, orally active peptidoleukotriene receptor antagonist, in guinea-pig

In this report the pharmacologic and pharmacokinetic profile of the leukotriene receptor antagonist 3(S)-[(2-carboxyethyl)thio]-3-[2-(8-phenyloctyl)phenyl] propanoic acid (SK&F S-106203) in guinea-pigs is described. In isolated guinea-pig tracheae SK&F S-106203 was a potent, competitive antagonist of leukotriene (LT) D4-induced contractions (pA2 = 7.6). SK&F S-106203 was also a potent antagonist of LTE4-induced contractions (pKB = 7.3), but had little effect on those elicited by LTC4 (pKB = 5.5). SK&F S-106203 (10 microM) had no effect on contractions produced by histamine, carbachol, KCl, U-44069, PGF2 alpha or PGD2. In addition, SK&F S-106203 (10 microM) did not inhibit cyclic nucleotide phosphodiesterase (PDE) activity of several PDE isozymes. In guinea-pig lung membrane preparations, SK&F S-106203 was a potent antagonist of 3H-LTD4 binding with a Ki = 19.4 +/- 2.1 nM (n = 5). The pharmacokinetic profile of SK&F S-106203 was determined in unanesthetized guinea-pigs. Following an i.v. (bolus) dose (25 mg/kg), SK&F S-106203 disappeared from plasma in a biphasic fashion with half-lives of 0.1 h (50% of the area under the plasma concentration-time curve, AUC) and 11 h. The AUC obtained for SK&F S-106203 following i.v. administration was 87.3 +/- 7.5 micrograms-h/ml. Following an oral dose of SK&F S-106203 (100 mg/kg), the maximal plasma concentration (Cmax) and the time Cmax was achieved (Tmax) were 21.62 +/- 2.26 micrograms/ml and 4 +/- 1 h, respectively; the AUC was 279.9 +/- 41.8 micrograms-h/ml. Studies examining the effects of i.v. infusion of SK&F S-106203 revealed that marked inhibition of LTD4-induced bronchospasm was produced with steady-state plasma levels of SK&F S-106203 less than 1 microgram/ml (less than 2 microM). Oral (p.o.) pretreatment with 100 mumol/kg SK&F S-106203 for up to 24 h essentially abolished LTD4-induced bronchospasm; this correlated with sustained plasma concentrations of greater than 2 micrograms/ml. The results indicate that in guinea-pig airways, SK&F S-106203 is a potent and selective LT receptor antagonist that is active via aerosol, oral and i.v. routes of administration. When given orally, SK&F S-106203 is highly bioavailable and has a very long duration of action which correlates with the pharmacokinetic profile of the compound. SK&F S-106203 may be useful therapy in asthma and other disorders in which the LTs are thought to play a prominent pathophysiological role.

Enhanced renal leukotriene production in murine lupus: role of lipoxygenase metabolites

To investigate the potential role of leukotrienes in murine lupus, we measured renal hemodynamics and renal leukotriene production in MRL-lpr/lpr mice at 12 and 20 weeks of age. Over this age range, these animals develop overt manifestations of autoimmune disease with nephritis similar to human SLE. In the current study, we demonstrated that glomerular filtration rate (GFR) and PAH clearance (CPAH) deteriorated with age in MRL-lpr/lpr mice, but not in MRL(-)+/+ controls. Impaired renal hemodynamic function in MRL-lpr/lpr mice was associated with enhanced ionophore-stimulated production of both leukotriene B4 (LTB4) and leukotriene C4 (LTC4) by preparations of renal cortex. There was a significant inverse correlation between GFR and in vitro production of both LTC4 and LTB4 in kidneys from MRL-lpr/lpr mice, but not in control animals. In addition, in vitro LTC4 production was correlated with the severity of renal histomorphologic abnormalities. Administration of the specific peptidoleukotriene receptor antagonist SKF104353 to 20 week old MRL-lpr/lpr mice significantly improved both GFR and CPAH, whereas this agent had no effect of renal hemodynamics in MRL(-)+/+ controls. These results suggest that renal production of LTC4 and LTB4 is increased in MRL-lpr/lpr mice with nephritis, and that enhanced production of peptidoleukotrienes causes reversible renal dysfunction. Increased leukotriene production within the kidney may therefore be important in the pathogenesis of lupus nephritis.

Transient activation of topoisomerase I in leukotriene D4 signal transduction in human cells

U937 human monoblast cells incubated with leukotriene D4 (LTD4) rapidly released arachidonic acid metabolites into the culture medium. Release was suppressed by the high-affinity LTD4 receptor antagonist SK&F 104353. Arachidonic acid release induced by LTD4 has been linked to a rapid induction of gene expression, and the propagation of the receptor binding signal is probably associated with enzymes that regulate gene expression. We have studied the participation of DNA topoisomerase I in LTD4 signal transduction. LTD4-specific release of arachidonic acid metabolites was inhibited (60-80%) by the topoisomerase I inhibitor camptothecin. LTD4 increased protein-linked DNA strand breakage induced by camptothecin in U937 cells; this enhancement was prevented by coincubation of the cells with LTD4 plus the receptor antagonist SK&F 104353. In addition, LTD4 produced a rapid transient increase in extractable topoisomerase I activity, which was maximum within the first 10 min after addition of LTD4 to the culture medium. Incubation of cultures for greater than 10 min with LTD4 before the addition of camptothecin resulted in no enhancement of camptothecin-induced DNA strand breakage, consistent with a reversal of topoisomerase I activation. Staurosporine, an inhibitor of protein kinase C, blocked LTD4-induced arachidonic acid release and attenuated the effect of LTD4 on camptothecin-induced DNA strand breakage. These results are consistent with the view that the regulation of topoisomerase I activity is involved in the propagation of LTD4-mediated signals in U937 cells.

Characterization of LTC4 effects on rabbit ileal mucosa in vitro

The effects of peptidoleukotriene C4 (LTC4) on electrical properties and Na+ and Cl- fluxes in the presence or absence of the LTD4/LTE4 antagonist, 2(S)-hydroxy-3-(R)-carboxyethylthio)-3-[2-(8-phenyloctyl)phe nyl] propanoic acid (SK&F 104353) were investigated in stripped ileal mucosa from rabbits placed in Ussing chambers. Results from this study demonstrate that serosal addition of LTC4 produced a dose-dependent increase in short-circuit current (Isc) which is not affected by pretreatment of the tissue with SK&F 104353 (0.1 microM). The concentration of LTC4 which produced an increase in Isc of 4 mu Eq/h.cm2 was 181 nM in the absence of SK&F 104353 and this value did not differ significantly from the value of 212 nM in the presence of SK&F 104353 (0.1 microM). SK&F 104353 (0.1 microM) reduced the increase in Isc elicited by LTD4 and LTE4 by greater than 95%. Mucosal addition of LTC4 failed to alter Isc. The time course of the increase in Isc in response to LTC4 is qualitatively similar to that seen with both LTD4 and LTE4. Increases in Isc produced by LTC4 are not inhibited by removal of Ca2+ from the serosal bathing solution but are inhibited by pretreatment of the tissue with indomethacin (1 microM). The histamine receptor antagonist, mepyramine, reduced the change in Isc resulting from stimulation with LTC4 by 20% while the cholinergic antagonist, atropine, and the excitable tissue Na+ channel blocker, tetrodotoxin, were without effect. Measurement of unidirectional and net Na+ and Cl- fluxes revealed that LTC4 reduces Na+ and Cl- absorption and that subsequent addition of PGE1 produced no further decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Interactive effects of peptidoleukotrienes and histamine on microvascular permeability and their involvement in experimental cutaneous and conjunctival immediate hypersensitivity

The involvement of peptidoleukotrienes (LTs) in mediating the increase in microvascular permeability associated with experimental cutaneous immediate hypersensitivity was studied by examining the effect of SK&F 104353, a potent and selective LT-antagonist, on the response evoked by graded, intradermal injections of antigen. SK&F 104353, employed at doses that profoundly blocked LTC4, LTD4 and LTE4 responses, significantly reduced the response produced by experimental cutaneous immediate hypersensitivity. The response to the lowest antigen dose (0.1 microgram) was, however, entirely insusceptible to SK&F 104353. The effect of SK&F 104353 was also examined in combination with a pyrilamine-cimetidine dosing regimen sufficient to remove the histaminergic component of cutaneous immediate hypersensitivity. The non-histaminergic component associated with higher antigen doses (10 and 100 micrograms) was significantly reduced but not abolished by SK&F 104353; the non-histaminergic component associated with low antigen doses (0.1 and 1 microgram) was not susceptible to SK&F 104353. Thus, the increase in cutaneous microvascular permeability evoked by immediate hypersensitivity appears to comprise three components: (1) A histaminergic response apparent for all antigen doses; (2) a LT-mediated component which is manifest in response to high antigen doses; (3) a third, unidentified component that is present for the entire antigen dose-range but contributes less to the overall response when high antigen doses are used. A distinct non-histaminergic, non-leukotriene mediated component was not a feature of conjunctival immediate hypersensitivity. SK&F 104353 administered in combinatio with pyrilamine-cimetidine virtually abolished the response with a small residual remaining only for the highest antigen dose. In further contrast to cutaneous immediate hypersensitivity, SK&F 104353 alone was comparatively ineffective in type 1 allergic conjunctivitis. This difference in susceptibility to SK&F 104353 appears to reflect the type of histamine-LTD4 interactive effect on microvascular permeability. Histamine and LTD4 were additive in terms of cutaneous microvascular permeability. In the conjunctiva, histamine and LTD4 appeared mutually exclusive in that the level of response produced by the combination tended not to exceed that of the single component which caused the greater effect.

Lipoxin A4 antagonizes cellular and in vivo actions of leukotriene D4 in rat glomerular mesangial cells: evidence for competition at a common receptor

Lipoxin A4 (LXA4) was competitive with [3H]leukotriene D4 (LTD4) for specific binding to cultured rat glomerular mesangial cells. Half-maximal inhibition was obtained with 100 nM LXA4, compared with 10 nM for unlabeled LTD4. At 10 and 50 nM LXA4 induced low, but significant, increases in mesangial-cell inositol trisphosphate generation: 48% and 44% increases as compared to vehicle controls, respectively (compared with 146% and 106% increments obtained for equimolar LTD4), which were abolished in the presence of 100-fold concentrations of the LTD4 receptor antagonist, SKF 104353. In addition, exposure to 100 nM LXA4 prevented mesangial cell inositol trisphosphate generation induced by 10 nM LTD4. To test the in vivo relevance of these results, we established a dose-response curve for the reducing effects of intrarenal arterial LTD4 on glomerular filtration rate and renal plasma flow in anesthetized rats (LTD4 doses were 0.5, 7.0, 14.0, and 20.0 micrograms/kg per min) without or with LXA4 at 1 microgram/kg per min. Mean percent decreases in glomerular filtration rate/renal plasma flow during LTD4 administration were 27*/24, 25*/40*, 70*/65*, and 73*/70* at the above doses, respectively (*P less than 0.05 versus baseline). With LXA4, these values were as follows: 9/20*, 11/37*, 42*/51*, and 50*/68*, the latter value representing a shift in the LTD4/glomerular filtration rate dose-response curve. Thus, LXA4 competes for [3H]LTD4 binding to mesangial cells, its presence prevents LTD4-induced inositol trisphosphate generation, and its own stimulation of mesangial-cell inositol trisphosphate is blocked by an LTD4 receptor antagonist. In vivo, LXA4 antagonizes LTD4-induced falls in glomerular filtration rate but not renal plasma flow, implying prevention of LTD4-mediated reductions in the glomerular ultrafiltration coefficient, a consequence of mesangial-cell contraction. These results suggest that LTD4 and LXA4 interact at a common site on rat mesangial cells at which LXA4 provokes partial agonist responses and competitively antagonizes both the cellular and physiological actions of LTD4. Moreover, these results provide evidence for a potential counterregulatory interaction between leukotrienes and lipoxins that may be relevant during glomerular inflammation.

Preservation of the glomerular capillary ultrafiltration coefficient during rat nephrotoxic serum nephritis by a specific leukotriene D4 receptor antagonist

Leukotriene D4, a potent biologically active lipoxygenase derivative of arachidonic acid in activated leukocytes, depresses the glomerular capillary ultrafiltration coefficient (Kf) and contracts mesangial cells in culture. We therefore investigated its potential role in mediating the reduction in nephron filtration rate seen after induction of experimental nephrotoxic serum (NTS)-induced glomerulonephritis in the rat. Micropuncture measurements were performed in euvolemic Munich-Wistar rats 2 h after i.v. administration of 0.8 ml of rabbit serum (group 1, n = 6), 0.8 ml of rabbit anti-rat glomerular basement membrane antibody in the absence (group 2, n = 8), or presence (group 3, n = 7) of the new highly specific LTD4 receptor antagonist SK&F 104353. Quantitation of antibody binding and neutrophil infiltration revealed no differences between groups 2 and 3. Antagonism of endogenous LTD4 actions, however, was associated with prevention of the NTS-induced fall in SNGFR because of the abrogation of the fall in Kf which characterizes this form of experimental glomerulonephritis. Antagonism of endogenous LTD4 had no effect on the NTS-induced increases in pre- and postglomerular arteriolar resistances, and did not affect nephron plasma flow rate or net transcapillary hydraulic pressure difference. The observed highly localized protective action of the LTD4 antagonist on the glomerular capillary points to a possibly major functional role for intraglomerularly released LTD4, likely originating from infiltrating leukocytes, in the pathophysiology of this form of glomerulonephritis.