The angiotensin AT 2 -receptor agonist compound 21 is an antagonist for the thromboxane TP-receptor - Implications for preclinical studies and future clinical use

• Published in: Peptides (New York, N.Y. : 1980) N.Y. : 1980), 2023-06, Vol.164, p.170990
• Main Authors: Fredgart, Maise H, Leurgans, Thomas M, Stenelo, Martin, Nybo, Mads, Bloksgaard, Maria, Lindblad, Lena, De Mey, Jo G R, Steckelings, U Muscha
• Format: Article
• Language: English
• Subjects: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid - pharmacology; Angiotensins; Animals; Humans; Mice; Mice, Inbred C57BL; Phenylephrine - pharmacology; Receptors, Thromboxane; Thromboxane A2 - pharmacology; Thromboxanes
• ISSN: 1873-5169
• DOI: 10.1016/j.peptides.2023.170990

Since the AT -receptor (AT R) agonist C21 has structural similarity to the AT -receptor antagonists Irbesartan and Losartan, which are antagonists not only at the AT R, but also at thromboxane TP-receptors, we tested the hypothesis that C21 has TP-receptor antagonistic properties as well. Isolated mouse mesenteric arteries from C57BL/6 J and AT R-knockout mice (AT R ) were mounted in wire myographs, contracted with either phenylephrine or the thromboxane A (TXA ) analogue U46619, and the relaxing effect of C21 (0.1 nM - 10 µM) was investigated. The effect of C21 on U46619-induced platelet aggregation was measured by an impedance aggregometer. Direct interaction of C21 with TP-receptors was determined by an β-arrestin biosensor assay. C21 caused significant, concentration-dependent relaxations in phenylephrine- and U46619-contracted mesenteric arteries from C57BL/6 J mice. The relaxing effect of C21 was absent in phenylephrine-contracted arteries from AT R mice, whereas it was unchanged in U46619-contracted arteries from AT R mice. C21 inhibited U46619-stimulated aggregation of human platelets, which was not inhibited by the AT R-antagonist PD123319. C21 reduced U46619-induced recruitment of β-arrestin to human thromboxane TP-receptors with a calculated K of 3.74 µM. We conclude that in addition to AT R-agonistic properties, C21 also acts as low-affinity TP-receptor antagonist, and that - depending on the constrictor - both mechanisms can be responsible for C21-induced vasorelaxation. Furthermore, by acting as a TP-receptor antagonist, C21 inhibits platelet aggregation. These findings are important for understanding potential off-target effects of C21 in the preclinical and clinical context and for the interpretation of C21-related myography data in assays with TXA -analogues as constrictor.