Inhibition of antigen-induced bronchoconstriction and eosinophil infiltration in the guinea pig by the cyclic AMP-specific phosphodiesterase inhibitor, rolipram.

Selective inhibition of the low Km cyclic AMP-specific phosphodiesterase has been shown to inhibit inflammatory cell function and relax airway smooth muscle. These studies were conducted to characterize the bronchodilator and anti-inflammatory activity of rolipram, an archetypical cyclic AMP-specific phosphodiesterase inhibitor, in in vitro and in vivo guinea pig airway models. In isolated tracheal rings from ovalbumin (OA)-sensitive guinea pigs, both R- and S-enantiomers of rolipram (1 microM) significantly antagonized OA-induced contractions. In contrast, neither enantiomer at concentrations up to 1 microM significantly inhibited histamine- or LTD4-induced contractions. In superfusion and mediator release experiments, both enantiomers of rolipram significantly reduced antigen-induced prostaglandin D2 release, but had minimal effect on histamine release. In anesthetized, ventilated OA-sensitive guinea pigs, racemic rolipram or enantiomers reduced OA-induced bronchoconstriction with ID50 values of approximately 0.25 mg/kg i.v. Histamine- and leukotriene D4-induced bronchoconstriction were not affected by doses of rolipram which abolished the response to OA. Higher doses (3-10 mg/kg) reduced histamine-, but not the leukotriene D4-induced bronchoconstriction. In conscious OA-sensitive guinea pigs, intragastric pretreatment with rolipram dose-dependently reduced both the OA-induced decreases in specific conductance as well as the corresponding pulmonary eosinophil influx as assessed by both bronchoalveolar lavage and histological evaluation. Therefore, rolipram produces significant inhibition of antigen-induced bronchoconstrictor and inflammatory responses, thus providing strong evidence that this pharmacological approach may be of significant therapeutic value in allergic asthma.(ABSTRACT TRUNCATED AT 250 WORDS)

Lack of late-phase airway responses in conscious guinea pigs after a variety of antigen challenges.

Guinea pigs were actively sensitized by parenteral injections of ovalbumin (OA), house dust extract (HD) or Ascaris suum extract (As) in a variety of multidose regimens. At least 3 weeks after the initial sensitization injection, aerosols of the appropriate antigen were administered to conscious guinea pigs in a double-chamber body plethysmograph. OA elicited the most consistent and intense bronchoconstriction (BC) as measured by decreases in specific airway conductance (sGAW). The airway responses to As were clearly separable into responders and nonresponders. HD produced essentially no BC. However, intense lacrimation and rhinorrhea occurred in all HD-sensitized, but not unsensitized, animals. No late-phase changes in sGAW or increased reactivity to other spasmogens were seen up to 8 h after any antigen challenge. Eosinophil influx of magnitude similar to that measured by 24 h post-antigen bronchoalveolar lavage (BAL) occurred with all the three antigens. Animals which did not bronchoconstrict to As experienced an equal or greater pulmonary eosinophilia as airway responders. The present data with HD and As suggest that acute BC in response to antigen provocation is not a prerequisite for the eventual pulmonary eosinophilia. The lack of late-phase airway reactions in these models raises a doubt in the direct extrapolation to airway responses in allergic human asthma. The acute lacrimation and rhinorrhea to HD may suggest utility as a model of allergic rhinitis.

Arabidopsis Acetohydroxyacid Synthase Expressed in Escherichia coli Is Insensitive to the Feedback Inhibitors.

Acetohydroxyacid synthase (AHAS), the first enzyme unique to the biosynthesis of isoleucine, leucine, and valine, is the target enzyme for several classes of herbicides. The AHAS gene from Arabidopsis thaliana, including the chloroplast transit peptide, was cloned into the bacterial expression plasmid pKK233-2. The resulting plasmid was used to transform an AHAS-deficient Escherichia coli strain MF2000. The growth of the MF2000 strain of E. coli was complemented by the functional expression of the Arabidopsis AHAS. The AHAS protein was processed to a molecular mass of 65 kilodaltons that was similar to the mature protein isolated from Arabidopsis seedlings. The AHAS activity extracted from the transformed E. coli cells was inhibited by imidazolinone and sulfonylurea herbicides. AHAS activity extracted from Arabidopsis is inhibited by valine and leucine; however, this activity was insensitive to these feedback inhibitors when extracted from the transformed E. coli.

Overexpression of Acetohydroxyacid Synthase from Arabidopsis as an Inducible Fusion Protein in Escherichia coli: Production of Polyclonal Antibodies, and Immunological Characterization of the Enzyme.

Acetohydroxyacid synthase (AHAS, EC 4.1.3.18) is the first enzyme unique to the biosynthesis of valine, leucine, and isoleucine. This enzyme is the target site of several classes of structurally unrelated herbicides. The conventional method of antibody production using purified protein has not been successful with this enzyme. Two separate fragments of a gene encoding a portion of the mature region of AHAS from Arabidopsis were fused with the trpE gene from Escherichia coli using the pATH1 vector. E. coli cells transformed with each respective plasmid expressed a fusion protein at levels greater than 10% of the total cell protein. The fusion protein was purified and used to immunize rabbits. Antisera obtained from the immunized rabbits immunoprecipitated AHAS activity from Arabidopsis cell free extracts. The anti-AHAS antisera reacted with a 65 kilodalton protein band in electrophoretically resolved extracts of Arabidopsis. In cross-reactivity tests, this antibody was able to immunoprecipitate AHAS activity from various plant species. Furthermore, a protein band with a molecular mass of 65 kilodaltons was detected in the crude extracts of all plant species tested on a Western blot. These results indicate that the 65 kilodalton protein represents AHAS in various plant species. The wide spectrum of cross-reactivity for the antisera supports the view that the AHAS enzyme is highly conserved across all plant species.

N-[(arylmethoxy)phenyl] carboxylic acids, hydroxamic acids, tetrazoles, and sulfonyl carboxamides. Potent orally active leukotriene D4 antagonists of novel structure.

Four series of N-[(arylmethoxy)phenyl] compounds were prepared as leukotriene D4 (LTD4) antagonists. In the hydroxamic acid series, methyl 3-(2-quinolinylmethoxy)benzeneacetohydroxamate (Wy-48,422, 20) was the most potent inhibitor of LTD4-induced bronchoconstriction with an oral ED50 of 7.9 mg/kg. Compound 20 also orally inhibited ovalbumin-induced bronchoconstriction in the guinea pig with an ED50 of 3.6 mg/kg. In vitro, against LTD4-induced contraction of isolated guinea pig trachea pretreated with indomethacin and 1-cysteine, 20 produced a pKB value of 6.08. In the sulfonyl carboxamide series, N-[(4-methylphenyl)sulfonyl]-3-(2-quinolinylmethoxy)-benzamide (Wy-49,353, 30) was the most potent antagonist. Compound 30 orally inhibited both LTD4- and ovalbumin-induced bronchoconstriction with ED50s of 0.4 and 20.2 mg/kg, respectively. In vitro, against LTD4-induced contraction of isolated guinea pig trachea, 30 produced a pKB value of 7.78. In the carboxylic acid series, which served as intermediates for the above two series, 3-(2-quinolinylmethoxy)benzeneacetic acid (Wy-46,016, 5) was the most potent inhibitor of LTD4-induced bronchoconstriction (99% at 25 mg/kg, intraduodenally); however, the pKB for this compound was disappointing (5.79). In the tetrazole series, the most potent inhibitor was 2-[[3-(1H-tetrazol-5-ylmethyl)phenoxy]methyl]quinoline (Wy-49,451, 41). The respective inhibitory ED50s were 3.0 mg/kg versus LTD4 and 17.5 mg/kg versus ovalbumin. In the isolated guinea pig trachea, 41 produced a pKB value of 6.70.

The transit peptide of a chloroplast thylakoid membrane protein is functionally equivalent to a stromal-targeting sequence.

The role of transit peptides in intraorganellar targeting has been studied for a chlorophyll a/b binding (CAB) polypeptide of photosystem II (PSII) and the small subunit of ribulose-1,5-bisphosphate carboxylase (RBCS) from Pisum sativum (pea). These studies have involved in vitro import of fusion proteins into isolated pea chloroplasts. Fusion of the CAB transit peptide to RBCS mediates import to the stroma, as evidenced by assembly of RBCS with chloroplast-synthesized large subunit (RBCL) to form holoenzyme. Similarly, fusion of the RBCS transit peptide to the mature CAB polypeptide mediates import and results in integration of the processed CAB protein into the thylakoid membrane. Correct integration was indicated by association with PSII and assembly with chlorophyll to form the light-harvesting chlorophyll a/b protein complex (LHCII). We interpret these results as evidence that the CAB transit peptide is functionally equivalent to a stromal-targeting sequence and that intraorganellar sorting of the CAB protein must be determined by sequences residing within the mature protein. Our results and those of others suggest that import and integration of CAB polypeptides into the thylakoid proceeds via the stroma.

Isolation of a cDNA encoding mitochondrial citrate synthase from Arabidopsis thaliana.

We isolated a cDNA clone from Arabidopsis thaliana encoding the TCA cycle enzyme, citrate synthase. The plant enzyme displays 48% and 44% amino acid residue similarity with the pig, and yeast polypeptides, respectively. Many proteins, including citrate synthase, which are destined to reside in organelles such as mitochondria and chloroplasts, are the products of the nucleocytoplasmic protein synthesizing machinery and are imported post-translationally to the site of function. We present preliminary investigations toward the establishment of an in vitro plant mitochondrial import system allowing for future studies to dissect this process in plants where the cell must differentiate between mitochondria and chloroplast and direct their polypeptides appropriately.

Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]methane sulfonamide) an orally active leukotriene D4 antagonist: pharmacological characterization in vitro and in vivo in the guinea pig.

The following communicates the pharmacology of Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]methanesulfonamide) a chemically novel and orally potent leukotriene (LT) D4 receptor antagonist. In the isolated guinea-pig trachea pretreated with indomethacin (5 microM) and L-cysteine (10 mM), Wy-48,252 antagonized TD4-induced contraction with a pKB = 7.6. Against LTC4 on tissues pretreated with IND and glutathione (10 mM), Wy-48,252 had a pKB greater than 5. Wy-48,252 (10 microM) did not antagonize pilocarpine-, histamine- or PGF2 alpha-induced tracheal contraction. Further, in the presence of indomethacin and chlorpheniramine (1 microM), Wy-48,252 dose-dependently inhibited the antigen-induced contraction of guinea-pig trachea in a manner consistent with antagonism at the LTD4 receptor and inhibition of LT synthesis. In the Konzett-Rossler model of i.v. LTD4-induced bronchoconstriction in indomethacin treated guinea pigs, intragastric Wy-48,252 (2 hr) had an ID50 of 100 micrograms/kg and a functional half-life of 5 hr. Against i.v. antigen-induced bronchoconstriction in guinea pigs treated with indomethacin and chlorpheniramine, intragastric Wy-48,252 (2 hr) had an ID50 of 0.6 mg/kg and a 5 hr half life. Intragastric Wy-48,252 also selectively blocked the cutaneous wheal reaction to intradermal LTD4 but not histamine. We conclude that Wy-48,252 is distinguished from other selective LTD4 receptor antagonists by its oral potency and should be useful in ascertaining the role of LTD4 mediated processes in asthma, allergy and animal models.

N-[(arylmethoxy)phenyl] and N-[(arylmethoxy)naphthyl] sulfonamides: potent orally active leukotriene D4 antagonists of novel structure.

Two series of compounds, N-[(arylmethoxy)phenyl] sulfonamides and N-[(arylmethoxy)naphthyl] sulfonamides, were prepared as leukotriene D4 (LTD4) antagonists. In the phenyl series, N-[3-(2-quinolinylmethoxy)phenyl]-trifluoromethanesulfonamide (Wy-48,252, 16) was the most potent inhibitor of LTD4-induced bronchoconstriction in the guinea pig. With an intragastric ID50 of 0.1 mg/kg (2-h pretreatment), 16 was 300 times more potent than LY-171,883. Compound 16 also intragastrically inhibited ovalbumin-induced bronchoconstriction in the guinea pig with an ID50 of 0.6 mg/kg. In vitro against LTD4-induced contraction of isolated guinea pig trachea pretreated with indomethacin and L-cysteine, 16 produced a pKB value of 7.7. In the rat PMN assay 16 inhibited both 5-lipoxygenase and cyclooxygenase (IC50's = 4.6 and 3.3 microM). In the naphthyl series, N-[7-(2-quinolinylmethoxy)-2-naphthyl]trifluoromethanesulfonamide (Wy-48,090, 47) in addition to potent LTD4 antagonist activity (on isolated guinea pig trachea 47 had a pKB value of 7.04) also had antiinflammatory activity (63% inhibition at 50 mg/kg in the rat carrageenan paw edema assay and 34% inhibition of TPA-induced inflammation at 1 mg/ear in the mouse ear edema model). Perhaps the antiinflammatory activity of 47 was due to its additional activity of inhibiting both 5-lipoxygenase and cyclooxygenase enzymes (IC50's = 0.23 and 11.9 microM, respectively, in rat PMN).

Pharmacological characterization using selected antagonists of the leukotriene receptors mediating contraction of guinea-pig trachea.

The effects of six leukotriene (LT) antagonists on LTC4-, D4- and E4-induced contraction of isolated guinea-pig tracheal spirals were examined. Concentration-response effects of the leukotrienes were determined by cumulative addition in the presence of indomethacin (5 microM) alone for LTE4, or with 10 mM of either glutathione or L-cysteine to inhibit metabolism of LTC4 or LTD4, respectively. Concentration-response curves to the LTs were obtained in the absence and presence of Wy-45,911, Wy-44,329, FPL-55,712, Ly-171,883, Wy-48,252 and ICI-198,615 representing three structurally different chemical groups of LT antagonists. At 30 microM, the antagonists produced little or no antagonism of LTC4-induced contractions. Analysis of the Schild plots for antagonism of LTD4 and E4 suggested two receptors for the agonist effects of LTD4 and a single receptor for the agonist effects of LTE4. Comparison of pA2 values for Wy-45,911, FPL-55,712, LY-171,883 and Wy-48,252 provided evidence that LTE4 is acting at the antagonist high affinity LTD4 receptor to produce contractile effects. From the data, we conclude that there are three LT receptors (one for LTC4 and two LTD4 subtypes) through which exogenously applied LTs evoke contraction of the isolated guinea-pig trachea.

Prevention and reversal of aerosol LTD4-induced changes in guinea pig pulmonary mechanics by Wy-48252, an orally active LTD4/E4 receptor antagonist.

Anesthetized male albino guinea pigs were prepared for recording changes in the pulmonary mechanics parameters, dynamic compliance (Cdyn) and airway conductance (Gaw). Two aerosol leukotriene D4 (LTD4) challenges (0.125 microgram/ml, 3-7 breaths, 1 h apart) were administered via an ultrasonic nebulizer to each animal and, produced reductions in Cdyn that were approximately 60% of those of Gaw. Intraduodenal administration of the LTD4/E4 receptor antagonists Wy-48252 (30 min), Wy-45911 and Ly-171883 (15 min) produced dose-related inhibition of the second LTD4 challenge. From the data, ID50 values were calculated and, Wy-48252 was 8- to 17-fold more potent (mg/kg) than Wy-45911 or Ly-171883. Responses to histamine were not altered by the antagonists. In separate experiments, Wy-48252 (0.3 and 1 mg/kg i.v.) rapidly reversed aerosol LTD4-induced decreases of Cdyn and Gaw, but did not reverse pulmonary mechanics decreases produced by prostaglandin F2 alpha. The results indicate that systemically administered LTD4 receptor antagonists can both prevent and reverse bronchoconstriction produced by aerosol LTD4 in the guinea pig.

Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]membrane sulfonamide), an orally active leukotriene antagonist: effects on arachidonic acid metabolism in various inflammatory cells.

The LTD4 antagonist, Wy-48,252 (1,1,1-trifluoro-N-[3-(2-quinolinylmethoxy)phenyl]methanesulfonamide), was assessed for its ability to modulate arachidonic acid metabolism in several inflammatory cells. In A23187-stimulated rat neutrophils, Wy-48,252 effectively inhibited the conversion of exogenous [14C]arachidonic acid to radiolabeled 5-hydroxyeicosatetraenoic acid (5-HETE) and thromboxane B2 (TxB2) (IC50 = 2 and 9.1 microM, respectively). Synthesis of immunoreactive leukotriene B4 (LTB4) (IC50 = 4.6 microM) and TxB2 (IC50 = 3.3 microM) from endogenous substrate by these cells in the absence of [14C]arachidonic acid was similarly reduced. Wy-48,252 also reduced leukotriene C4 (LTC4) and PGE2 synthesis by zymosan-activated mouse peritoneal macrophages (IC50 = 4.4 and 4.3 microM, respectively). 5-Lipoxygenase (5-LO) catalyzed reactions in human neutrophils, lung mast cells and basophils activated by various stimuli were dose dependently inhibited by Wy-48,252 while PGD2 synthesis by lung mast cells was inhibited at 100 microM. By contrast, 12-LO, 15-LO, phosphodiesterase activity and histamine release from mast cells and basophils were unaffected by Wy-48,252. These data suggested that the LTD4 antagonist, Wy-48,252, also inhibited the synthesis of eicosanoids, a feature that may contribute to its pharmacological actions in vivo.

Bronchoprotective and bronchodilator activity of anaritide (human atrial natriuretic factor [102-126]) infusion in the anesthetized guinea pig.

The present study examined the bronchoprotective and bronchodilator efficacy of infused human atrial natriuretic factor [102-126] (Anaritide) in the guinea pig. Anesthetized and paralyzed male guinea pigs, ventilated via a tracheal cannula, were placed in a plethysmograph for measurement of agonist-induced changes in pulmonary mechanics. Reductions in dynamic compliance of the lung and airway conductance were produced either by 3 to 7 tidal volume breaths of leukotriene D4 (0.125 micrograms/ml) delivered through an ultrasonic nebulizer or by intravenous histamine (2.8 +/- 0.2 micrograms/kg). Infusion of Anaritide (1 microgram/kg/min), before evoking bronchoconstriction with either LTD4 or histamine, produced a significant protection against bronchoconstriction produced by aerosol LTD4, but not against histamine-induced bronchoconstriction of similar magnitude. In other experiments, Anaritide infusion (0.5-2 micrograms/kg/min) also rapidly reversed a stable LTD4-induced decrease in airway conductance, but did not produce a similar reversal of the decrease in dynamic compliance. The data provide evidence that intravenous Anaritide exerts both bronchoprotective and bronchodilator effects against LTD4-induced bronchospasm.

Effect of a novel leukotriene D4 antagonist with 5-lipoxygenase and cyclooxygenase inhibitory activity, Wy-45,911, on leukotriene-D4-and antigen-induced bronchoconstriction in the guinea pig.

Wy-45,911 (4-[hydroxy-[3-(2-quinolinylmethoxy)phenyl] amino]-4-oxabutanoic acid, methyl ester) was found to inhibit competitively leukotriene D4 (LTD4)-induced contractions of the isolated guinea pig trachea but not those of leukotriene C4 (LTC4), even in the presence of a gamma-glutamyltranspeptidase inhibitor, reduced glutathione (GSH). Tracheal contractions induced by histamine or pilocarpine were also not significantly altered by Wy-45,911. The drug inhibited the tracheal contractions induced by antigen, even in the presence of GSH. This latter effect resulted from inhibition of 5-lipoxygenase (5-LO), as the synthesis of 5-LO products by rat polymorphonuclear leukocytes and by mouse macrophages was markedly reduced by Wy-45,911. The drug inhibited both LTD4-induced and antigen-induced bronchoconstriction when injected intraduodenally or intragastrically into intact guinea pigs though it was more potent against LTD4-induced bronchoconstriction. We conclude that Wy-45,911 is a novel, orally active LTD4 antagonist in the guinea pig, with some 5-LO inhibitory activity.

Phenylephrine derivatives as leukotriene D4 antagonists.

Two series of phenylephrine derivatives were prepared and tested as inhibitors of leukotriene D4 (LTD4) induced and ovalbumin-induced bronchospasm in the guinea pig. The most potent compound of the urea series, (R)-N,N-diethyl-N-[2-hydroxy-2-[3-(2-quinolinylmethoxy)phenyl]ethyl]-N- methylurea (3, Wy-47,120), was orally active with ED50's of 56 mg/kg vs. LTD4 and 55 mg/kg vs. ovalbumin. When tested as an antagonist of LTD4-induced contraction of isolated guinea pig tracheal strips, 3 was a competitive inhibitor with a p kappa B value of 5.22. In the second series, (R)-3-methyl-5-[3-(2-quinolinylmethoxy)phenyl]-2-oxazolidinone (26, Wy-47,674) had oral ED50's of 36 mg/kg against LTD4 and 95 mg/kg against ovalbumin. Compound 26 selectively antagonized contractile responses of guinea pig trachea evoked by LTD4 (p kappa B = 6.09). In the cat coronary artery, 3 dilated the preparation and blocked the coronary constrictor effect of LTD4. Compound 3 (0.13 mg/kg, iv) also preserved myocardial integrity in rats 48 h after coronary artery ligation. When tested in the rat alcohol-induced gastric lesion model, 3 and 26 manifested a dose-dependent mucosal protection against ethanol.

Pharmacological comparison of L-serine borate and glutathione as inhibitors of metabolism of LTC4 to LTD4 by the isolated guinea pig trachea.

Cumulative dose-response curves to leukotriene C4 (LTC4) and leukotriene D4 (LTD)4 were obtained on indomethacin (5 microM) treated isolated guinea pig tracheal spiral strips. LTC4 curves, in the presence of either glutathione (GSH; 10 mM) or L-serine borate (SB; 45 mM), were not antagonized by FPL-55712 (3 microM), a selective LTD4 receptor antagonist. LTC4 curves on trachea treated with a lower concentration of GSH (1 mM), and LTD4 curves were competitively antagonized by FPL-55712. LTC4 curves on GSH (10 mM) treated trachea were 2 fold to the left of those on SB treated tissues. This effect of GSH was blocked by pretreatment with nordihydroguiaretic acid (30 microM), an inhibitor of 5-lipoxygenase. GSH (10 mM) and SB (45 mM) are effective inhibitors of conversion of LTC4 into functionally important levels of LTD4 by the guinea pig trachea. In addition, GSH appears to enhance LTC4 responsiveness by increasing synthesis of a contractile 5-lipoxygenase product(s), possibly LTC4. From the data it is suggested that for inhibition of LTC4 metabolism, SB may be more useful when examining responses to exogenously applied LTC4, while GSH (10 mM) may be more useful when examining responses to endogenously generated LTC4.

Leukotriene D4 antagonists and 5-lipoxygenase inhibitors. Synthesis of benzoheterocyclic [(methoxyphenyl)amino]oxoalkanoic acid esters.

A series of novel benzoheterocyclic [(methoxyphenyl)amino]oxoalkanoic acid esters has been prepared. These compounds were tested as inhibitors of rat polymorphonuclear leukocyte 5-lipoxgenase (LO) in vitro and as inhibitors of leukotriene D4 (LTD4) and ovalbumin (OA) induced bronchospasm in the guinea pig (GP) in vivo. In general, inhibitory activity against 5-LO, LTD4, and OA was broadest for benzthiazole-containing analogues (benzthiazole greater than benzimidazole much greater than benzoxazole, benzofuran). The most potent 5-LO inhibitor, 4-[[3-(2-benzthiazolylmethoxy)-phenyl]hydroxyamino]-4-oxobutanoic acid methyl ester (7), had an IC50 of 0.36 microM. Compound 7, however, was inactive vs. OA. The most potent compound in vivo, 4-[[3-[(1-methyl-2-benzimidazolyl)methoxy]phenyl]-amino] -4-oxobutanoic acid methyl ester 4, inhibited both LTD4- and OA-induced bronchospasm by 83% and 60%, respectively, at 50 mg/kg intraduodenally. Compound 4 was studied in the Ames assay employing five strains of bacteria (TA1535, TA1537, TA1538, TA98, and TA100) with and without S-9 rat liver enzyme metabolic activation, and there was no significant number of reversions noted.

Inhibition of leukotriene-induced contraction of guinea pig trachea by 5-lipoxygenase inhibitors.

The effects of the 5-lipoxygenase inhibitors nordihydroguiaretic acid (NDGA), 5, 8, 11, 14-eicosatetraynoic acid (ETYA), 1-phenyl-3-pyrazolidone (phenidone) and BW-755c, on the contractile response to LTC4 or LTD4 were examined on the isolated guinea pig trachea. Responses to either LTC4 or LTD4 were obtained on indomethacin treated tissues, in the presence of either L-serine-borate complex or L-cysteine, respectively, to inhibit metabolic conversion of the leukotrienes. NDGA (30 microM) and ETYA (100 microM) produced a selective competitive antagonism of LTD4-induced contractions, while phenidone antagonized both LTC4- and LTD4-induced responses in a non-competitive manner. In contrast, BW-755c (30 microM) did not significantly antagonize LTC4 or LTD4 concentration-response curves. The results suggest that leukotriene antagonism may be produced by large concentrations of some 5-lipoxygenase inhibitors.

Novel 1,3-bis(aryloxy)propanes as leukotriene D4 antagonists.

The synthesis and structure-activity relationships of a number of 1,3-bis(aryloxy)propanes, which are in vivo antagonists of LTD4 in the guinea pig, are described. One of these compounds, 4 (Wy-44,329), was not only approximately equipotent with the standard 1 (FPL 55712) in the LTC4 (ID50 = 0.17 and 0.23 mg/kg iv, respectively) and LTD4 (ID50 = 0.11 and 0.15 mg/kg iv, respectively) challenge models but also possessed greater potency in the ovalbumin challenge model (ID50 = 0.47 mg/kg and 4.1 mg/kg iv, respectively) and a longer duration of action. This compound was a competitive LTD4 antagonist on guinea pig ileum (pA2 = 9.4) and possessed mediator release (rat PCA, ID50 = 0.26 mg/kg iv) and 5-lipoxygenase (IC50 = 32 microM vs. 5-HETE) inhibitory activities.