Synthesis of imidazopyridines and purines as potent inhibitors of leukotriene A4 hydrolase.

The synthesis and biological evaluation of a series of heterocyclic analogues of the previously reported LTA(4) hydrolase inhibitor 1b are described. Imidazopyridine and purine analogues are specifically highlighted with several demonstrating excellent potency in our in vitro assays, as well as good oral activity in a mouse ex vivo assay.

Pyrrolidine and piperidine analogues of SC-57461A as potent, orally active inhibitors of leukotriene A(4) hydrolase.

The synthesis and biological evaluation of a series of functionalized pyrrolidine- and piperidine-containing analogues of our lead LTA(4) hydrolase inhibitor, SC-57461A, is described. A number of compounds showed excellent potency in our in vitro screens and several demonstrated good oral activity in a mouse ex vivo assay. These efforts led to the identification of SC-56938 (14) as a potent, orally active inhibitor of LTA(4) hydrolase.

Synthesis of potent leukotriene A(4) hydrolase inhibitors. Identification of 3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid.

Leukotriene B(4) (LTB(4)) is a potent, proinflammatory mediator involved in the pathogenesis of a number of diseases including inflammatory bowel disease, psoriasis, rheumatoid arthritis, and asthma. The enzyme LTA(4) hydrolase represents an attractive target for pharmacological intervention in these disease states, since the action of this enzyme is the rate-limiting step in the production of LTB(4). Our previous efforts focused on the exploration of a series of analogues related to screening hit SC-22716 (1, 1-[2-(4-phenylphenoxy)ethyl]pyrrolidine) and resulted in the identification of potent, orally active inhibitors such as 2.

Pharmacological characterization of SC-57461A (3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid HCl), a potent and selective inhibitor of leukotriene A(4) hydrolase II: in vivo studies.

Leukotriene (LT) A(4) hydrolase is a dual function enzyme that is essential for the conversion of LTA(4) to LTB(4) and also possesses an aminopeptidase activity. SC-57461A (3-[methyl[3-[4-phenylmethyl)phenoxy]propyl]amino]propanoic acid HCl) is a potent inhibitor of human recombinant LTA(4) hydrolase (epoxide hydrolase and aminopeptidase activities, K(i) values = 23 and 27 nM, respectively) as well as calcium ionophore-induced LTB(4) production in human whole blood (IC(50) = 49 nM). In the present study, we investigated its action in several animal models.

Pharmacological characterization of SC-57461A (3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid HCl), a potent and selective inhibitor of leukotriene A(4) hydrolase I: in vitro studies.

Leukotriene (LT) B(4) is an inflammatory mediator that has been implicated in the pathogenesis of various diseases, including inflammatory bowel disease and psoriasis. As the rate-limiting step for LTB(4) production, LTA(4) hydrolase represents an attractive target for therapeutic agents that interfere with LTB(4) production. In the present study we evaluated a chemically novel compound designated SC-57461A (3-[methyl[3-[4-(phenylmethyl)phenoxy]propyl]amino]propanoic acid HCl) as an inhibitor of LTA(4) hydrolase.

Structure-activity relationship studies on 1-[2-(4-Phenylphenoxy)ethyl]pyrrolidine (SC-22716), a potent inhibitor of leukotriene A(4) (LTA(4)) hydrolase.

Leukotriene B(4) (LTB(4)) is a pro-inflammatory mediator that has been implicated in the pathogenesis of a number of diseases including inflammatory bowel disease (IBD) and psoriasis. Since the action of LTA(4) hydrolase is the rate-limiting step for LTB(4) production, this enzyme represents an attractive pharmacological target for the suppression of LTB(4) production. From an in-house screening program, SC-22716 (1, 1-[2-(4-phenylphenoxy)ethyl]pyrrolidine) was identified as a potent inhibitor of LTA(4) hydrolase.

Eicosanoids and histamine mediate C5a-induced electrolyte secretion in guinea pig ileal mucosa.

C5a is a biologically active polypeptide formed during the course of complement activation and is known to possess histamine-releasing and neutrophil chemotactic properties. In the present study, we have demonstrated that C5a can regulate electrolyte transport across guinea pig ileum, and we have investigated its mechanism of action. Segments of ileum stripped of longitudinal muscle were mounted in Ussing chambers (Krebs' buffer, 37 degrees C, 95% O2/5% CO2) for monitoring short-circuit current (Isc).

Colitis reduces short-circuit current response to inflammatory mediators in rat colonic mucosa.

Inflammatory mediators may contribute to the diarrhea associated with colitis. Although the secretory action of such mediators is reported in normal tissue, there is little information regarding their effects on inflamed tissue. We examined the short-circuit current response (Isc) to these mediators, in mitomycin-C (MC)-induced colitis, a model with histological similarities to colitis in man.

Second-generation leukotriene B4 receptor antagonists related to SC-41930: heterocyclic replacement of the methyl ketone pharmacophore.

Our previous reports have highlighted the first-generation leukotriene B4 (LTB4) receptor antagonist SC-41930 (7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]3,4- dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid) which has potent oral, topical, and intracolonic activity in various animal models of inflammation. Extensive structure-activity relationship studies, in which a series of heterocyclic replacements for the methyl ketone functional group of SC-41930 was explored, identified SC-50605 (7-[3-[2-(cyclopropylmethyl)-3-methoxy-4- (4-thiazolyl)phenoxy]propoxy]-3,4-dihydro-8-propyl-2H-1-benzopyran-2- carboxylic acid) as an optimized analog within a series of thiazoles. SC-50605 was found to be significantly more potent than SC-41930 in LTB4 receptor binding, chemotaxis, and degranulation assays.

The in vitro pharmacology of SC-51146: a potent antagonist of leukotriene B4 receptors.

Previously, we reported that SC-41930 is a potent leukotriene B4 (LTB4) receptor antagonist. An analog of SC-41930, SC-51146, was evaluated as an antagonist of LTB4 receptors. SC-51146 was shown to bind to LTB4 high affinity binding sites on human neutrophils (PMN) with a dissociation constant (KD) value of 1.

Characterization of human uroguanylin: a member of the guanylin peptide family.

Guanylin, a peptide homologue of the bacterial heat-stable enterotoxins (ST), is an endogenous activator of guanylate cyclase C (GC-C). We have initiated a search for other members of the guanylin peptide family and in the current study describe a "guanylin-like peptide" from human urine. Bioactivity was monitored by determining the effect of urine extracts on T84 cell guanosine 3',5'-cyclic monophosphate (cGMP) levels.

Stereospecific actions of misoprostol on rat colonic electrolyte transport.

Misoprostol (Miso) produces a mild, transient diarrhea in some patients, which is believed to be partly due to intraluminal fluid accumulation. To better understand this diarrheagenic action, we compared the effects of Miso, its 4 stereoisomers (11R16R, 11R16S, 11S16S, 11S16R), misoprostol free acid (Miso-FA), and 16,16-dimethyl PGE2 (dmPGE2) on rat colonic electrolyte transport in vitro. Increases in short-circuit current (Isc) were measured (after serosal addition) in segments of mucosa stripped of muscularis and mounted in Ussing chambers.

Effect of the thiol-oxidizing agent diamide on NH2Cl-induced rat colonic electrolyte secretion.

The granulocyte-derived oxidant, monochloramine (NH2Cl), is known to stimulate chloride ion secretion in rat distal colonic mucosa mounted in Ussing chambers, through mechanisms that are sensitive and insensitive to tetrodotoxin (TTX). The possible role of intracellular thiols, in the mechanism of action of NH2Cl as a secretagogue, was evaluated with the thiol-oxidizing agent diamide and by measuring tissue sulfhydryl levels in response to NH2Cl. Serosal exposure to the antioxidant glutathione (0.

An in vitro system to screen for diarrheagenic chemicals.

We examined an in vitro system to screen for diarrheagenic chemicals using an established intestinal cell line (T84 human colonic carcinoma). The cells were grown on Millicell-PCF (polycarbonate membrane) wells. The cells were seeded at approximately 5 x 10(6) cells/30mm well and incubated for 9-11 days in a 5% CO2 incubator saturated with water at 37 degrees C.

The design and synthesis of second generation leukotriene B4 (LTB4) receptor antagonists related to SC-41930.

SC-41930, 7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4- dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid, is a selective, orally active, LTB4 receptor antagonist currently in clinical trials for psoriasis and ulcerative colitis. Exhaustive SAR studies found a potential backup compound, SC-50605, which was 7-16 times more potent than SC-41930 in LTB4 receptor binding, chemotaxis and degranulation assays. SC-50605 also inhibited LTB4-induced intradermal chemotaxis in cavine skin at an oral dose of 0.

Human guanylin: cDNA isolation, structure, and activity.

Guanylin is a mammalian peptide homologue of heat-stable enterotoxins that acts on intestinal guanylate cyclase to elicit an increase in cyclic GMP. We have isolated a cDNA encoding an apparent precursor of guanylin from a human intestinal cDNA library. The mRNA is expressed at high levels in human ileum and colon.

Endothelin-1 stimulates contraction and ion transport in the rat colon: different mechanisms of action.

Endothelin-like immunoreactivity has been detected in all regions of the rat gastrointestinal tract. In the present study, we studied the effect of endothelin-1 (ET-1) on muscle contraction and ion transport in the rat colon. Isometric tension was recorded in colonic muscle strips oriented along their longitudinal axis.

Ca-mediated stimulation of Cl secretion by reactive oxygen metabolites in human colonic T84 cells.

Monochloramine (NH2Cl), a granulocyte-derived reactive oxygen metabolite (ROM), increases short-circuit current (Isc) in cultured T84 monolayers in a concentration-dependent manner up to nonlethal concentrations of 75 microM. Isc increases slowly after NH2Cl, reaching a peak value of 18 +/- 2 microA/cm2 20 min after addition. The Isc changes are persistent (lasting over 20-30 min), depend on medium Cl, and are inhibitable with bumetanide.

Multiple actions of the leukotriene B4 receptor antagonist SC-41930.

7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)-propoxy]-3,4-dihydro-8- propyl-2H-1-benzopyran-2-carboxylic acid (SC-41930), a leukotriene B4 (LTB4) receptor antagonist with anti-inflammatory activity in animal models of colitis, was evaluated for effects on superoxide, LTB4 and prostaglandin E2 production. SC-41930 inhibited human neutrophil (PMN) superoxide generation maximally stimulated by f-Met-Leu-Phe (IC50 4 microM) and C5a (IC50 approximately 12 microM). Moreover, postreceptor stimulation of superoxide production by NaF (a G protein activator), but not by phorbol myristate acetate, was significantly inhibited by SC-41930, indicating that SC-41930 may act via attenuation of a G protein-mediated signal transduction.

Cholecystokinin-mediated ileal electrolyte transport in the guinea pig. Characterization of receptor subtype.

Cholecystokinin (CCK) receptors are currently divided into at least two subtypes: a CCK-A subtype, responsive to the sulfated form of cholecystokinin octapeptide (CCK-8) and selectively antagonized by L-364,718, and a CCK-B subtype, which shares equal affinities for gastrin and CCK-8. In the present study the receptor subtype that mediates guinea pig ileal secretion by evaluating the potencies of CCK- and gastrin-related peptides to evoke increases in transmucosal short-circuit current was characterized. The antagonist potencies of L-365,260 (CCK-B selective) and L-364,718 (CCK-A selective) against CCK-8 were also determined.

Neurokinin A increases short-circuit current across rat colonic mucosa: a role for vasoactive intestinal polypeptide.

1. Neurokinin A (NKA) is a mammalian tachykinin distributed principally in the nervous system, including the myenteric innervation of the gut. 2.

Aminoalkynyldithianes. A new class of calcium channel blockers.

Several dithiane derivatives, prepared as intermediates for compounds structurally related to the therapeutically useful antimuscarinic agent oxybutynin, were effective inhibitors of calcium ion induced contraction of guinea pig ileal strips and of KCl-induced calcium entry into neuronal cells. Although the first member of this series, 2-[5-(diethylamino)-3-pentynyl]-1,3-dithiane (2a), was only marginally effective, its condensation product with diphenyl ketone, i.e.

Monochloramine, a neutrophil-derived oxidant, stimulates rat colonic secretion.

Neutrophil-derived oxidants may be involved in inflammatory bowel disease. Stable oxidants formed by halogenation of primary amines (e.g.

Scavenging effect of 5-aminosalicylic acid on neutrophil-derived oxidants. Possible contribution to the mechanism of action in inflammatory bowel disease.

Inflammatory phagocytic leukocytes produce superoxide and hydrogen peroxide and secrete myeloperoxidase (MPO) into the extracellular medium. MPO catalyzes the oxidation of Cl- by H2O2 to yield chlorinated oxidants (e.g.