Pharmacological evaluation of both enantiomers of (R,S)-BM-591 as thromboxane A2 receptor antagonists and thromboxane synthase inhibitors.
The aim of this work is to evaluate the anti-thromboxane activity of two pure enantiomers of (R,S)-BM-591, a nitrobenzene sulfonylurea chemically related to torasemide, a loop diuretic. The drug affinity for thromboxane A2 receptor (TP) of human washed platelets has been determined. In these experiments, (R)-BM-591 (IC50 = 2.4+/-0.1 nM) exhibited a significant higher affinity than (S)-BM-591 (IC50 = 4.2+/-0.15 nM) for human washed platelets TP receptors. Both enantiomers were stronger ligands than SQ-29548 (IC50 = 21.0+/-1.0 nM) and sulotroban (IC50 = 930+/-42 nM), two reference TXA2 receptor antagonists. Pharmacological characterisations of (S)-BM-591 and (R)-BM-591 were compared in several models. Thus, (R)-BM-591 strongly prevented platelet aggregation induced by arachidonic acid (AA) (600 microM) and U-46619 (1 microM) while (S)-BM-591 showed a lower activity. On isolated tissues pre-contracted by U-46619, a stable TXA2 agonist, (S)-BM-591 was more potent in relaxing guinea-pig trachea (EC50 = 0.272+/-0.054 microM) and rat aorta (EC50 = 0.190+/-0.002 microM) than (R)-BM-591 (EC50 of 9.60+/-0.63 microM and 0.390+/-0.052 microM, respectively). Moreover, at 1 microM, (R)-BM-591 totally inhibited TXA2 synthase activity, expressed as TXB2 production from human platelets, while at the same concentration, (S)-BM-591 poorly reduced the TXB2 synthesis (22%). Finally, in rats, both enantiomers lost the diuretic activity of torasemide. In conclusion, (R)-BM-591 exhibits a higher affinity and antagonism on human platelet TP receptors than (S)-BM-591 as well as a better thromboxane synthase inhibitory potency. In contrast, (S)-BM-591 is more active than the (R)-enantiomer in relaxing smooth muscle contraction of rat aorta and trachea guinea pig. Consequently, (R)-BM-591 represents the best candidate for further development in the field of thrombosis disorders.
Rolin
S
S
Department of Pharmacy, University of Namur, Rue de Bruxelles 61, B-5000 Namur, Belgium.
Dogne
J M
JM
Vastersaegher
C
C
Hanson
J
J
Masereel
B
B
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000502:physiology; D004231:Diuresis / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D009126:Muscle Relaxation; D009574:Nitro Compounds / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000037:antagonists & inhibitors*; D013237:Stereoisomerism; D013449:Sulfonamides / Q000494:pharmacology*; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors*
C500044:BM-591; D004791:Enzyme Inhibitors; D009574:Nitro Compounds; D010975:Platelet Aggregation Inhibitors; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D013449:Sulfonamides; D013930:Thromboxane-A Synthase