Jorge Casals-Stenzel

Protective effect of WEB 2086, a novel antagonist of platelet activating factor, in endotoxin shock

WEB 2086, a novel specific platelet activating factor (PAF) antagonist derived from triazolodiazepines, inhibited in a dose-related manner the hypotensive and lethal effect of PAF as well as of E. coli endotoxin in the rat. The hypotension induced by endotoxin (15 mg/kg i.v.) or PAF (30 ng/(kg X min) i.v.) in anaesthetized rats was prevented by oral (1-10 mg/kg) and inhibited or reversed by i.v. (0.1-5.0 mg/kg or 0.1-1.0 mg/kg) doses of WEB 2086. Similar oral and i.v. doses of WEB 2086 protected conscious rats from PAF (15 micrograms/kg i.v.)- and endotoxin (7.5 mg/kg i.v.)-induced death. The results obtained with WEB 2086 confirm that PAF has an important role in the pathophysiology of endotoxin shock. This compound may have a therapeutic effect in human septic shock.

Effects of WEB 2086, a novel antagonist of platelet activating factor, in active and passive anaphylaxis

WEB 2086, a novel specific platelet activating factor (PAF) antagonist derived from triazolodiazepines, inhibited in a dose-related manner the PAF-dependent component of anaphylaxis as well as PAF-induced effects in mice and guinea pigs. In mice a lethal anaphylactic shock and a PAF-induced (100 micrograms/kg i.v.) death was inhibited by i.v. WEB 2086. The ED50 values were 13.6 and 0.37 mg/kg i.v., respectively. In actively sensitized guinea pigs, the anaphylactic lung reaction (bronchoconstriction), but not the corresponding hypotension, was prevented by oral (0.05-0.5 mg/kg) doses of WEB 2086. In contrast, in passively sensitized animals a dose-dependent inhibition of the pulmonary (bronchoconstriction) and blood pressure (hypotension) reaction due to anaphylaxis was achieved by i.v. WEB 2086. Similarly, oral (0.05-0.5 mg/kg) and i.v. (0.005-0.05 mg/kg) WEB 2086 inhibited PAF-induced reduction in respiratory flow (bronchoconstriction) and hypotension in guinea pigs. The ED50 values were 0.070 and 0.066 mg/kg p.o., and 0.017 and 0.015 mg/kg i.v., respectively. In conclusion, PAF seems to play a more major role in passive than in active anaphylaxis in guinea pigs. These results provide further evidence for an important role of PAF in anaphylaxis and support the hypothesis that PAF is involved in asthma and other allergic diseases.

Triazolodiazepines: dissociation of their Paf (platelet activating factor) antagonistic and CNS activity

1 The relationship between the activity of thieno‐ or benzo‐triazolodiazepines on platelet‐activating factor (Paf)‐induced effects and on the CNS (central nervous system) was studied in vitro and in vivo. 2 Brotizolam and triazolam inhibited Paf‐induced human platelet aggregation. The IC50 ‐ values were 0.54 and 7.6 μm, respectively. This inhibitory effect was not blocked by the specific central‐type benzodiazepine (BDZ) antagonist, Ro 15–1788, or the specific peripheral‐type BDZ ligand, Ro 5–4846. These BDZ ligands also showed an inhibitory effect on Paf‐induced platelet aggregation (IC50 = 200 and 560 μm, respectively). Ro 15–1788 or Ro 5–4846 in combination with brotizolam or triazolam enhanced the Paf inhibitory effect of these triazolodiazepines. 3 In guinea‐pigs, Ro 15–1788, 100 mg kg‐1p.o. and 10 mg kg‐1 i.v. completely inhibited the hypnogenic effect of 10 mg kg−1 p.o. and 1 mg kg−1 i.v. of brotizolam, respectively. Similar results were obtained with triazolam but at higher doses. 4 In anaesthetized guinea‐pigs, a dose of 100 mg kg‐1 p.o. of Ro 15–1788 did not inhibit bronchoconstriction and hypotension caused by Paf (30 ngkg−1 min−1 i.v.). The combination of brotizolam (10 mg kg−1 p.o.) or triazolam (200 mg kg−1 p.o.) with this BDZ antagonist (100 and 400 mg kg‐1 p.o., respectively) did not affect the Paf inhibitory activity of these triazolodiazepines. 5 These results show that the Paf antagonistic properties of the triazolodiazepines can be dissociated from their CNS activity. It is conceivable that compounds of this structural type could be the forerunners of a novel series of potent Paf antagonists.

Thieno-triazolo-1,4-diazepines as antagonists of platelet-activating factor: Present status

The platelet-activating factor, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, (PAF) antagonistic activity of thienotriazolodiazepines has recently been described. The lead compound in this series was brotizolam, which also exhibits sedative and hypnotic effects. By combination of brotizolam with the benzodiazepine receptor antagonist RO 15-1788, PAF antagonistic and central nervous system (CNS) activities could be segregated. Systematic structure variation has led to potent and selective PAF antagonists without CNS effects. WEB 2086 and its analogues WEB 2170 and STY 2108 are representative examples of this structural type and have shown a high potency and selectivity in PAF-induced and PAF-dependentin vitro tests and in experimental models. Studies in healthy volunteers have demonstrated potent pharmacological activity and good safety and tolerance of oral, intravenous or inhaled WEB 2086 in man. These agents should therefore prove useful for the further elucidation of the pathophysiological role of PAF and provide an opportunity for therapeutic applications in diseases in which the involvement of PAF has been implicated.

Use of WEB 2086 and WEB 2170 as platelet-activating factor antagonists.

Publisher Summary The chapter presents a study on the utilization of WEB 2086 and WEB 2170 as platelet-activating factor (PAF) antagonists. The chapter presents the physicochemical properties and the pharmacological use of these new PAF antagonists. Since the discovery of the platelet-activating factor (PAF, 1- O -aikyl-2- acetyl- sn -glycerophosphorylcholine) in 1972, the interest in studying its physiological and pharmacological responses as well as its pathophysiological role has created a demand for specific and potent PAF antagonists. The search for these antagonists yielded several types of compounds differing in origin and structure .Among these, two synthetic compounds derived from the thienotriazolodiazepine brotizolam, a hypnotic, have recently been described under the code number WEB 2086 and WEB 2170. These compounds are specific and very potent PAF antagonists, free from hypnotic and sedative activity. They are expected to facilitate research in this area and to be therapeutically useful. WEB 2086 and WEB 2170 belong to the group of thienotriazolo-l,4-diazepines (hetrazepines). WEB 2086 and WEB 2170 are potent and selective antagonists of PAF in vitro and, more importantly , in vivo with a long duration of action. For oral use in rats, WEB 2170 may be preferred to WEB 2086 because of the higher potency and long duration of action. Both compounds are suitable tools for investigating the significance of PAF in the pathophysiology of different diseases.

Bronchial and vascular effects of Paf in the rat isolated lung are completely blocked by WEB 2086, a novel specific Paf antagonist.

1 The effect of the platelet‐activating factor (Paf) antagonist, WEB 2086, on Paf‐induced increase of pulmonary artery perfusion pressure (Pp), bronchial inflation pressure (Pi) and wet‐to‐dry lung weight ratios (W/D) was investigated in the rat isolated lung. 2 Lungs were perfused with Krebs‐Ringer solution (KRS) as controls or with KRS containing WEB 2086 (0.1, 1.0, 10.0 or 100 μgml−1) and then injected with a bolus of 20 μg Paf. 3 A dose‐related inhibition of the Paf‐induced increase of Pp, Pi and W/D was observed, being almost maximal for the 10.0 μg ml−1 and complete for the 100 μg ml−1 doses of WEB 2086 when compared to controls. 4 It is concluded that WEB 2086 is a highly effective and specific Paf antagonist in the pulmonary vasculature and bronchial tract.

Detection and comparative evaluation of aldosterone antagonists in glucocorticoid-treated, adrenalectomized rats.

An improved method for the evaluation of aldosterone antagonists in adrenalectomized, glucocorticoid-treated rats is described. The method involved assessing the pharmacological effects of spironolactone and potassium canrenoate and comparing them with the action of prorenone and potassium prorenoate, respectively. Adrenalectomized rats were pretreated with fluocortolone caproate (10 mg/kg s.c.), a long-acting glucocorticoid, immediately after surgery. Fluocortolone (1.25 mg/kg s.c.), a short acting preparation, was administered 4 days after this treatment. On the 5th day after adrenalectomy, the actual diuresis experiment was performed. The rats received a continuous i.v. infusion of aldosterone [1 microgram/(kg x h)] for 10, 15 or 20 h. Spirnolactone or prorenone (6.7, 13.4 or 26.8 mg/kg of each steroid) were administered in single oral doses 1 h before or 4 h after the start of the i.v. infusion. Potassium canrenoate and potassium prorenoate (1.9, 3.8, or 6.7 mg/(kg x h) of each compound) were infused intravenously over 10 or 15 h. Urine was collected in 1 h fractions and the anti-aldosterone activity was assessed by the ability of the compounds to reverse the aldosterone effect on the Na/K ratio. The anti-aldosterone activity of the steroids studies was clearly detectable with the method described. Prorenone was as potent as spironolactone and potassium prorenoate was on the average 3.9 times as potent as potassium canrenoate. The method appears suitable for the characterization of the time course and duration of anti-aldosterone activity and for the calculation of relative potencies in comparison to standard compounds.