The characterization of potent novel warfarin analogs

Racemic sodium warfarin, Coumadin, is widely used in the prevention of thromboembolic disease. The present study was undertaken to characterize three novel classes of warfarin analogs, and to compare them with the warfarin enantiomers. All three classes of compounds inhibit vitamin K epoxide reductase, the enzyme inhibited by racemic warfarin. The alcohol and the ester analogs have reduced protein binding compared with R-(+)-warfarin. The ester and the fluoro-derivatives have similar in vivo anticoagulant activity in the rat to that of S-(-)-warfarin. Thus, it is possible to synthesize novel warfarin analogs that differ from racemic warfarin or its enantiomers in certain selected properties.

Design, synthesis and structure-activity relationship studies of novel 4,4-bis(trifluoromethyl)imidazolines as acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors and antihypercholesterolemic agents

Novel 4,4-bis(trifluoromethyl)imidazolines have been found to be the potent acyl-CoA cholesterol acyltransferase (ACAT) inhibitors. ACAT is responsible for cholesterol esterification in the intestine, liver, and the arterial wall. These novel imidazolines also inhibit cholesterol ester formation in the macrophage. Several compounds have shown potent serum cholesterol-lowering activity in several animal models. Para-substitution of the 2-phenyl is critical for in vitro and in vivo activity. The 4,4-bis(trifluoromethyl)imidazolines with a para-cyano group on 2-phenyl and a 4-alkylcyclohexyl amide as the side-chain at the 5-position possess the most potent inhibitory activity in this series. Based on biochemical studies, this series acts as a competitive inhibitor with respect to cholesterol binding at the enzyme, which distinguishes it from most of the ACAT inhibitors discovered to date. Preliminary biological studies supported by X-ray crystal structures, molecular modeling, and structure-activity relationship (SAR) studies suggest that this series may be a cholesterol mimic.

EDU pretreatment decreases polymorphonuclear leukocyte migration into rat lung airways

Pretreatment with the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has previously been shown to reduce polymorphonuclear leukocyte (PMN) infiltration into the airways of ozone-exposed rats. The present study further examined the effects of 1 and 2 days EDU pretreatment on rat lung inflammatory responses by determining PMN infiltration in response to intratracheal instillation with the chemoattractant formyl-norleucine-leucine-phenylalanine (fNLP). Maximal recovery of PMNs by bronchoalveolar lavage was observed 4 hr after fNLP instillation with no alteration in the numbers of recoverable macrophages and lymphocytes. Although 1-day pretreatment with EDU did not affect PMN recovery from fNLP-instilled rat lungs, 2 days of EDU pretreatment prevented PMN infiltration as indicated by PMN recoveries that were similar to those obtained from saline-instilled lungs. Measurements of lung-marginated and interstitial pools of inflammatory cells using collagenase tissue digestion demonstrated no effect of 2 days EDU pretreatment. Although 2 days EDU pretreatment alone did not alter blood PMN content, lung permeability, and the lavage recoveries of inflammatory cells, blood PMN responses to chemotactic stimuli in vitro were impaired. In addition, EDU was shown to directly inhibit PMN chemotaxis and superoxide anion generation in vitro. These data demonstrated that EDU acts by interfering with PMN activation and migration rather than by decreasing PMN availability. EDU, by modulating the inflammatory response, represents a useful compound for preventing PMN-associated amplification of acute lung injuries.

EDU decreases polymorphonuclear leukocyte production of reactive oxygen intermediates

The ability of the heterocyclic compound EDU (N-[2-(2-oxo-1-imidazolindinyl)-ethyl]-N'-phenylurea) to affect polymorphonuclear leukocyte (PMNL) activation was examined by measuring superoxide anion, hydrogen peroxide and hydroxyl radical release from human PMNLs stimulated by phorbol ester. Results demonstrated that EDU effectively interferes with PMNLs reactive oxygen intermediate production, making it a potentially useful compound to be used to modulate PMNL-associated oxidant damage of inflamed tissues.

Persistent cardioprotection by azapropazone in a canine model of coronary artery thrombosis and thrombolysis

Activated neutrophils and possibly xanthine oxidase-derived free radicals are believed to be mediators of ischemia and reperfusion-induced myocardial damage. We studied the cardioprotective effect of the neutrophil stabilizer and xanthine oxidase inhibitor azapropazone in dogs subjected to thrombotic occlusion of the left anterior descending coronary artery (LAD), induced by intracoronary introduction of a copper coil, followed 60 min later by thrombolytic treatment with intracoronary streptokinase and 4-day reperfusion; we then determined infarct size by triphenyltetrazolium stain. Azapropazone [100 mg/kg intravenously (i.v.) followed by a 24-h i.v. infusion of 10 mg/kg/h, n = 8] or vehicle (n = 10) treatments were started immediately before the streptokinase infusion. Steady-state plasma levels of azapropazone ranged from 97 to 163 micrograms/ml during the infusion. Myocardial blood flow and underperfused area at risk were determined using radiolabeled microspheres. Results were as follows (mean +/- SEM): area at risk (percentage of left ventricle) azapropazone 22.7 +/- 3.16 and vehicle 21.8 +/- 4.13; infarct size (percentage of area at risk), azapropazone 45.1 +/- 11.8 and vehicle 75.7 +/- 10.6, p less than 0.03; collateral blood flow (ml/min/g), azapropazone 0.27 +/- 0.02 and vehicle 0.23 +/- 0.02; total ischemic period (min), azapropazone 106 +/- 5.9 and vehicle 91.5 +/- 4.9. Azapropazone had no effects on heart rate (HR), blood pressure (BP), or rate/pressure product (RPP). These dta show that azapropazone limits infarct size in a canine model of coronary thrombosis and long-term reperfusion and that this cardioprotection is independent of cardiovascular parameters.

Pretreatment with EDU decreases rat lung cellular responses to ozone

The phenylurea compound EDU (N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N'-phenylurea) has been shown to protect plants from the damaging effects of ozone exposure. Models of rat lung injury, based on acute exposure to 2 ppm ozone for 3 hr and on exposure to 0.85 ppm ozone for 2 days, were used to determine whether EDU pretreatment of rats protected lungs from oxidant injury. Rats were pretreated with 100 mg/kg body wt EDU by ip administration for 2 days prior to and on the days of ozone exposure. No adverse toxicological effects of EDU pretreatment were observed. Lung superoxide dismutase (SOD) and catalase (CAT) activities were significantly enhanced from 636 to 882 U/lung and from 599 to 856 U/lung, respectively. One day following acute exposure (2 ppm for 3 hr), an ozone-induced increase of polymorphonuclear leukocytes (PMNs) from 0.01 to 1.18 million cells/lung was decreased to 0.68 million by EDU pretreatment. No alteration occurred in the degree of lung permeability indicated by increased lavage fluid albumin. EDU pretreatment also significantly decreased ozone-induced increases in PMN recovery after 2 days exposure to 0.85 ppm ozone from 5.54 to 2.12 million cells/lung. However, in this second case, EDU pretreatment reduced the observed ozone damage, indicated by a decrease in lavage fluid albumin and by a decrease in the macrophage and lymphocyte infiltration associated with this length of ozone exposure. The observation that EDU-treated cultured pulmonary arterial endothelial cells increased SOD and CAT activities identified a potential lung site of EDU interaction. These data demonstrated that although EDU pretreatment appears not to prevent initial ozone damage, it does reduce the infiltration of PMNs and might therefore prevent amplification of the injury associated with this cell type.

Induction of antioxidant enzyme activities by a phenylurea derivative, EDU

Oxygen free radicals have the potential to mediate cell injury. Defenses against such radicals include the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX). The purposes of this study were (1) to develop an in vitro model using human cells in which to investigate a potential pharmacologic agent as an inducer of these antioxidant enzymes; (2) to investigate the phenylurea derivative N-[2-(2-oxo-1-imidazolindinyl)ethyl]-N-phenylurea (EDU) in this model with paraquat (PQ) serving as the positive control; and (3) to determine if induction of the antioxidant enzymes by EDU occurs in vivo. Human gingival fibroblasts (Gin-1) were used as the target cell in vitro; PQ and EDU, an inducer of SOD and CAT activities in plants, were evaluated as antioxidant enzyme inducers. Total SOD activity in Gin-1 cells increased 2-fold (p less than 0.05) in the presence of 1.0 mM PQ for 18-48 hr compared with untreated controls. Gin-1 cells incubated with 0.25-2.0 mM PQ for 24 hr had significantly increased total SOD (1.5 to 2.0-fold; p less than 0.05). CAT activity increased with 1.0 and 2.0 mM PQ (p less than 0.05). In the presence of PQ, GSH-PX activity decreased (p less than 0.05) in a concentration-dependent manner, indicating inactivation of this enzyme. No toxicity, indicated by lactate dehydrogenase released into the incubation medium, was noted at PQ concentrations below 5.0 mM. In the presence of 0.125-2.0 mM EDU, total SOD activity in Gin-1 cells significantly increased (1.5 to 2.0-fold; p less than 0.05). CAT activity significantly increased in a dose-dependent manner (p less than 0.05), while GSH-PX activity remained constant following exposure to 0.125-2.0 mM EDU. Intraperitoneal administration of EDU to rats twice a day for 2 days at 100 mg/kg induced SOD activity in heart, liver, and lung compared to controls (p less than 0.05). CAT activity increased in the liver 56% and in the lung 36% (p less than 0.05). GSH-PX activity remained constant. Our findings indicate that Gin-1 cells are a useful model in which to study inducers of antioxidant enzymes in vitro and that the phenylurea compound EDU induces SOD and CAT activities both in vitro and in vivo.