The discovery of novel, potent and highly selective inhibitors of inducible nitric oxide synthase (iNOS).

By careful analysis of experimental X-ray ligand crystallographic protein data across several inhibitor series we have discovered a novel, potent and selective series of iNOS inhibitors exemplified by compound 8.

Inhibitors of nitric oxide synthase in inflammatory arthritis.

There is considerable evidence that excessive nitric oxide (NO) synthesized from L-arginine by inducible nitric oxide synthase (iNOS) plays an important pathological role in inflammatory arthritis. Since NO synthesized by constitutive isoforms of NOS has a physiological role, a great deal of activity has been directed at identifying inhibitors of NOS that are selective for the induced isoform. The major chemical areas that have been described so far in the search for such selective iNOS inhibitors and the activity of some of these compounds in animal models of arthritis are reviewed.

1,2-Dihydro-4-quinazolinamines: potent, highly selective inhibitors of inducible nitric oxide synthase which show antiinflammatory activity in vivo.

The discovery of a novel class of nitric oxide synthase (NOS) inhibitors, 2-substituted 1,2-dihydro-4-quinazolinamines, and the related 4'-aminospiro[piperidine-4,2'(1'H)-quinazolin]-4'-amines is described. Members of both series exhibit nanomolar potency and high selectivity for the inducible isoform of the enzyme (i-NOS) relative to the constitutive isoforms in vitro. Efficacy in acute and chronic animal models of inflammatory disease following oral administration has also been demonstrated using these compounds.

Thienopyridines: nitric oxide synthase inhibitors with potent in vivo activity.

5-Substituted 7-amino-4,5-tetrahydrothieno[2,3-c]pyridines and 6-substituted 4-amino-6,7-dihydrothieno[3,2-c]pyridines were shown to be exceptionally potent inhibitors of inducible and neuronal nitric oxide synthase. Selectivity and potency could be modulated by variation of the 5- or 6-substituent. Compound 3e showed potent in vivo inhibition of iNOS.

An anti-platelet-endothelial cell adhesion molecule-1 antibody inhibits leukocyte extravasation from mesenteric microvessels in vivo by blocking the passage through the basement membrane.

Platelet-endothelial cell adhesion molecule-1 (PECAM-1, CD31) plays an active role in the process of leukocyte migration through cultured endothelial cells in vitro and anti-PECAM-1 antibodies (Abs) inhibit accumulation of leukocytes into sites of inflammation in vivo. Despite the latter, it is still not clear at which stage of leukocyte emigration in vivo PECAM-1 is involved. To address this point directly, we studied the effect of an anti-PECAM-1 Ab, recognizing rat PECAM-1, on leukocyte responses within rat mesenteric microvessels using intravital microscopy.

The induction of nitric oxide synthase and intestinal vascular permeability by endotoxin in the rat.

1. The effect of endotoxin (E. coli lipopolysaccharide) on the induction of nitric oxide synthase (NOS) and the changes in vascular permeability in the colon and jejunum over a 5 h period have been investigated in the rat.

Role of oxygen radicals and arachidonic acid metabolites in the reverse passive Arthus reaction and carrageenin paw oedema in the rat.

1. The role of arachidonic acid metabolites and oxygen radicals in carrageenin-induced rat paw oedema and dermal reverse passive Arthus reaction (RPA) have been investigated. 2.

Nitric oxide synthase activity in ulcerative colitis and Crohn's disease.

Excessive nitric oxide (NO) production by an isoform of NO synthase that can be induced by inflammatory stimuli leads to changes in vascular permeability and to tissue injury. We measured NO synthase activities in mucosa and muscle from the colons of control patients (n = 11) and patients with ulcerative colitis (6) or Crohn's disease (4). NO synthase activity in colonic mucosa of ulcerative colitis patients was 0.

Induction of nitric oxide synthase in rat intestine and its association with tissue injury.

Induction of a calcium-independent nitric oxide synthase (NOS) has been detected in the rat small intestine and colon, 3-5 h following endotoxin (3 mg kg-1 i.v.).

Colorectal leukotriene B4 synthesis in vitro in inflammatory bowel disease: inhibition by the selective 5-lipoxygenase inhibitor BWA4C.

The in vitro synthesis of leukotriene B4 (LTB4) was evaluated in colorectal biopsy specimens and resection tissue from patients with inflammatory bowel disease. The in vitro formation of LTB4 from biopsy tissues stimulated with calcium ionophore A23187 correlated with the degree of mucosal inflammation assessed at sigmoidoscopy, and with neutrophil infiltration measured as myeloperoxidase activity. Biopsy specimens from patients taking prednisolone formed less LTB4 than those from patients not on prednisolone, with comparable levels of inflammation seen at sigmoidoscopy.

Actions of nitric oxide on the acute gastrointestinal damage induced by PAF in the rat.

The actions of nitric oxide (NO) on the acute gastrointestinal damage induced by platelet-activating factor (PAF) have been investigated in the rat. S-nitroso-N-acetyl penicillamine, which spontaneously generates NO, dose-dependently inhibited PAF-induced gastrointestinal plasma leakage, a measure of the initiation of vascular damage. The inhibitor of NO synthase, NG-monomethyl-L-arginine substantially potentiated gastrointestinal damage and plasma leakage induced by E.

Protective effect of S-nitroso-N-acetyl-penicillamine in endotoxin-induced acute intestinal damage in the rat.

Macroscopic jejunal damage and plasma leakage induced within 15 min by E. coli lipopolysaccharide (LPS 50 mg kg-1 i.v.

Role of nitric oxide in maintaining vascular integrity in endotoxin-induced acute intestinal damage in the rat.

1. The role of endogenous nitric oxide (NO) in maintaining intestinal vascular integrity following acute endotoxin (E. coli.

Relationship between PAF-acether and thromboxane A2 biosynthesis in endotoxin-induced intestinal damage in the rat.

PAF-receptor antagonists are known to inhibit gastrointestinal damage induced by endotoxin. In the present study, the interaction between the biosynthesis of PAF and thromboxane (TX) A2, as putative mediators of the acute intestinal damage induced by endotoxin, has been investigated in the anaesthetised rat. Bolus intravenous administration of lipopolysaccharide from E.

Synthesis of nitric oxide from L-arginine by neutrophils. Release and interaction with superoxide anion.

Stimulated rat peritoneal neutrophils release a platelet inhibitory factor with the pharmacological properties of NO. This release is inhibited by NG-monomethyl-L-arginine and L-canavanine, indicating that it occurs through a mechanism similar to that in vascular endothelial cells and macrophages. As the degree of stimulation increases, the factor released is progressively inactivated by concomitant release of superoxide anions.

Involvement of leukotrienes in acute gastric damage.

The leukotrienes have potent inflammatory actions which could be of importance in gastric mucosal integrity. In animals, LTC4 produces vasoconstriction in the gastric mucosa. Furthermore, acute gastric damage produced by ethanol is accompanied by marked increases in the mucosal formation of LTC4 and LTB4.

Failure of the inhibition of rat gastric mucosal 5-lipoxygenase by novel acetohydroxamic acids to prevent ethanol-induced damage.

1. The role of leukotriene B4 (LTB4) and LTC4 as mediators of gastric mucosal damage following ethanol challenge in vivo has been investigated using two selective 5-lipoxygenase inhibitors, BW A4C and BW A137C. 2.

Relationship between arachidonic acid metabolism, myeloperoxidase activity and leukocyte infiltration in a rat model of inflammatory bowel disease.

The relationship between 14C-arachidonic acid (14C-AA) metabolism, myeloperoxidase activity (MPO) and leukocyte infiltration was studied in a chronic model of inflammatory bowel disease, induced by a single intrarectal application of the hapten, trinitrobenzene sulphonic acid (TNB). The colonic damage produced by TNB was accompanied, after 12-36 hours, by a marked increase in MPO, which was directly correlated to leukocyte infiltration, assessed histologically. There was also a marked increase in the metabolism of 14C-AA, by homogenates of inflamed colon, to 12-, 15-HETE and 6-keto-PGF1 alpha as indices of lipoxygenase and cyclo-oxygenase metabolism respectively.

Inhibition by 16,16-dimethyl PGE2 of ethanol-induced gastric mucosal damage and leukotriene B4 and C4 formation.

The effects of PGE2 and its stable analogue, 16,16 dimethyl PGE2 (dmPGE2) were investigated on ethanol-induced gastric mucosal haemorrhagic lesions and leukotriene formation in the rat. Exposure of the rat gastric mucosa to ethanol in-vivo, produced a concentration-related increase in the mucosal formation of leukotriene B4 (LTB4) which was correlated with macroscopically-apparent haemorrhagic damage to the mucosa. Challenge with absolute ethanol likewise enhanced the mucosal formation of LTC4 whereas the mucosal formation of 6-keto-PGF1 alpha was unaffected.

The effect of anti-inflammatory drugs on eicosanoid formation in a chronic model of inflammatory bowel disease in the rat.

1. The effects of anti-inflammatory drugs on eicosanoid formation and colonic damage in a chronic model of inflammatory bowel disease (IBD) in the rat were investigated. 2.