Christophe Thurieau

Agonistic and antagonistic properties of the bradykinin B2 receptor antagonist, Hoe 140, in isolated blood vessels from different species

1 Hoe 140, a recently described bradykinin B2 antagonist, and NPC 567 from an earlier generation of bradykinin B2 antagonists, were tested in rabbit and sheep isolated blood vessels. 2 In rabbit jugular vein, a bradykinin B2 preparation, NPC 567 was an antagonist (apparent pA2: 8.67 ± 0.16) with marked residual agonistic activity (log[EC50]: −7.29 ± 0.13). Hoe 140 was a potent non‐competitive antagonist devoid of agonistic properties (slope of the Schild plot: 2.02; estimated pA2: 9.04). 3 In rabbit aorta, a bradykinin B1 preparation, NPC 567 was a competitive antagonist (pA2: 6.32 ± 0.13) but Hoe 140 was ineffective. The two antagonists did not show any agonistic properties in this tissue. 4 In sheep femoral artery without endothelium, bradykinin and Hoe 140 induced contractions with identical efficacy and similar potency (log[EC50]: −8.05 ± 0.12, −7.73 ± 0.10; maximal contraction in % of KCl [60 mm]: 59.5 ± 15.1, 62.0 ± 13.1; for bradykinin and Hoe 140, respectively). In contrast NPC 567 was an extremely weak agonist. The contractile responses to bradykinin and Hoe 140 were inhibited by NPC 567 (apparent pKB: 6.89 ± 0.22 and 6.58 ± 0.08 versus bradykinin and Hoe 140, respectively) but not by a B1 bradykinin antagonist, suggesting that the receptor involved was a bradykinin B2 receptor. 5 In sheep femoral artery with endothelium, bradykinin induced a biphasic response: an endothelium‐dependent relaxation and a contraction which were both inhibited by NPC 567 (apparent pKB: 7.10 ± 0.15) and Hoe 140 (pA2: 8.38 ± 0.12). As bradykinin B2 receptor antagonists, Hoe 140 and NPC 567 were less potent in the sheep femoral artery than in the rabbit jugular vein. Neither Hoe 140 nor NPC 567 were agonists for the endothelial receptor. 6 This study demonstrates that Hoe 140, a new bradykinin B2 receptor antagonist, is more selective and more potent than NPC 567; however, it may possess, depending on the tissue studied, marked residual agonistic properties. Furthermore, bradykinin B2 receptors are subject to important species specificity. Finally, two different bradykinin B2 receptor subtypes may coexist in the sheep femoral artery with endothelium.

Venous and arterial endothelial cells respond differently to thrombin and its endogenous receptor agonist

The effects of thrombin and a peptide mimicking the amino terminus of its receptor, Res (42-55), on vascular reactivity were compared in isolated canine blood vessels. In saphenous veins contracted with endothelin-1, both thrombin and Res (42-55) caused relaxation in rings with endothelium and contraction in rings without endothelium. In coronary arteries, thrombin caused similar responses while Res (42-55) only caused contraction. These data suggest that different thrombin receptors are present on venous and arterial endothelial cells.

In vitro effects of HOE 140 in human bronchial and vascular tissue

Bradykinin is a potent inflammatory mediator which may be involved in various airway diseases. A selective and potent antagonist of the bradykinin B2 receptor has recently been discovered (HOE 140: D-Arg-[Hyp3,Thi5,D-Tic7,Oic8]bradykinin). The purpose of this study was to evaluate the potency of this compound in isolated human tissue (bronchus, pulmonary artery endothelium, umbilical artery and vein smooth muscle). Bradykinin induced contractions of the isolated human bronchus and umbilical artery and vein (the umbilical vessels were pretreated with indomethacin and L-nitro-arginine to inhibit prostaglandin and nitric oxide synthesis). It provoked an endothelium-dependent relaxation in the human pulmonary artery. HOE 140 was a non-competitive antagonist in human bronchial tissue (pKB: 8.19 +/- 0.30) and a competitive one in vascular tissue (pA2: 7.97 +/- 0.12, 8.16 +/- 0.16 and 8.00 +/- 0.11 in human pulmonary artery, umbilical artery and vein respectively). The effect of HOE 140 was selective as it did not influence the umbilical vein contractile response to serotonin and histamine. HOE 140 up to 3 x 10(-6) M was devoid of residual agonistic activity in the various human preparations studied. Furthermore, although the effects of HOE 140 were fully reversible, in isolated bronchial airways and umbilical veins, HOE 140 (10(-6) M) still possessed activity 1 h after being washed out in both tissues. Our results indicate that HOE 140 is a potent and potentially long-acting antagonist of the human bradykinin B2 receptor.

Bradykinin B2 Receptor Involvement in Rabbit and Murine Models of Septic Shock

The purpose of our work was to evaluate the role of bradykinin B2 receptors in the early phase (first 3 h) of bacterial lipopolysaccharide (LPS)-induced shock in anesthetized and mechanically ventilated rabbits and to determine if HOE 140, a specific, potent, and long-acting bradykinin B2-receptor antagonist, could improve survival in two murine models of septic shock. In rabbits, LPS injection induced rapid hypotension associated with metabolic acidosis. Three hours after the injection of LPS, we observed leukopenia, thrombocytopenia, and a moderate increase in arterial blood cyclic GMP. The injection-of HOE 140 [1.7-mumol/kg bolus intravenously (i.v.) 20 min before LPS] inhibited the decrease in blood pressure, but did not influence any of the other parameters studied. Mice were subjected to intraperitoneal (i.p.) injection of LPS, which induced almost 100% mortality in the 4 days after the injection. Pretreatment with HOE 140 (1 mg/kg i.p.) 30 min before the LPS injection and 4, 8, and 24 h afterward the injection did not improve survival at any given time during the 4 days of the study. Cecal ligation and puncture in mice induced a mortality rate > 90% in < or = 10 days. HOE 140 (1 mg/kg i.v.) given 30 min before cecal ligation did not significantly improve the survival rate. In contrast with previous reports, in the present study in a rabbit model of endotoxic shock (early phase) and in two murine models of septic shock, the involvement of bradykinin B2 receptors appeared to be minimal.

p-Guanidinobenzoyl-[Hyp3, Thi5, D-Tic7, Oic8]bradykinin is almost completely devoid of the agonist effect of HOE140 on the endothelium-free femoral artery of sheep.

Abstract Substitution of the N-terminal arginine of [D-Arg 0 , Hyp 3 , Thi 5 , D-Tic 7 , Oic 8 ]bradykinin (HOE140) by 4-guanidinobenzoic acid results in an analogue with at least the same antagonistic potency on rabbit smooth muscle preparations but with considerable reduction of its agonistic properties on the endothelium-free femoral artery of sheep.

Solution conformation by NMR and molecular modeling of three sulfide-free somatostatin octapeptide analogs compared to angiopeptin

SummaryThe conformation in dimethylsulfoxide of the somatostatin derivative angiopeptin and of three disulfide-free analogs was estimated by two-dimensional nuclear magnetic resonance spectroscopy at room temperature. The resulting 3D molecular graphics were compared and shown to reflect the observed differences in the inhibition of restenosis after rat aorta balloon injury by these octapeptide inhibitors. Angiopeptin and its active analog 2 displayed a relatively rigid conformation of the cyclic hexapeptide backbone due to the presence of two well-defined hydrogen bonds, further stabilized by a third hydrogen bond outside the ring. No such constraints were detected for the two biologically inactive analogs, which, compared to 2, had a two-atom longer or shorter hexapeptide ring. The well-defined structure of compound 2 may serve as an improved pharmacophore for this new class of drugs.