title: Evaluation of the effects of anti-thromboxane agents in platelet-vessel wall interaction.
abstract: We evaluated the capacity of anti-aggregating agents to influence thromboxane A(2) and prostacyclin formation, arachidonic acid-endoperoxide redirection, platelet aggregation and vessel tone, in isolated rabbit aorta incubated with homologous platelets. Picotamide (N,N'bis(3-pyridinylmethyl)-4-methoxy-isophthalamide), the only dual thromboxane A(2)-synthase inhibitor/receptor antagonist in clinical use, inhibited arachidonic acid-induced platelet aggregation with low potency, increased 180-fold by aorta presence. It inhibited thromboxane A(2) formation in platelets and, in aorta presence, increased prostacyclin formation. Ozagrel (OKY-046, (E)-3-(4-(1-imidazolylmethyl)phenyl)-2-propenoic acid), a pure thromboxane A(2)-synthase inhibitor, behaved similarly to picotamide, although the aorta caused a higher (600-fold) shift. The potency of the antagonist SQ 29,548 (1S-(1 alpha,2 beta(5Z),3 beta,4 alpha))-7-(3((2-((phenylamino)carbonyl)hydrazino)methyl)-7-oxabicyclo(2.2.1)hept-2-yl)-5-heptenoic acid) was unaffected by aorta. In coincubation experiments, arachidonic acid-challenge increased thromboxane A(2)-dependent vessel tone; picotamide increased prostacyclin and reduced thromboxane A(2) formation and vasoconstriction. Ozagrel mimicked picotamide; aspirin (acetylsalicylic acid) reduced aorta contractility, thromboxane A(2) and prostacyclin formation. SQ 29,548 reduced vasoconstriction without affecting eicosanoids. We demonstrate the importance of redirection of eicosanoids in the mechanism of action of thromboxane A(2) inhibitors/antagonists within platelet-vascular wall interactions. These findings bear relevance in the development of novel anti-thrombotic drugs.
authors.affiliation: Department of Pharmacological Sciences, University of Milan, via Balzaretti 9, 20133, Milan, Italy.
authors.forename: Carola
authors.initials: C
authors.lastname: Buccellati
authors.forename: Paola
authors.initials: P
authors.lastname: Ciceri
authors.forename: Rossana
authors.initials: R
authors.lastname: Ballerio
authors.forename: Cesare
authors.initials: C
authors.lastname: Casagrande
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Folco
authors.forename: Simonetta
authors.initials: S
authors.lastname: Nicosia
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D016718:Arachidonic Acid / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002450:Cell Communication / Q000187:drug effects; D015237:Dinoprost / Q000096:biosynthesis; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008689:Methacrylates / Q000494:pharmacology; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D010795:Phthalic Acids / Q000494:pharmacology; D015539:Platelet Activation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011817:Rabbits; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors*; D013928:Thromboxane A2 / Q000096:biosynthesis; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors*
chemical_list: C078129:6-keto-prostaglandin F2alpha; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D008689:Methacrylates; D010795:Phthalic Acids; D010975:Platelet Aggregation Inhibitors; D017482:Receptors, Thromboxane; D016718:Arachidonic Acid; D013928:Thromboxane A2; C011581:picotamide; C045749:SQ 29548; D015237:Dinoprost; D013930:Thromboxane-A Synthase; C034364:ozagrel; D001241:Aspirin