I4, a new synthetic sulfonylurea compound, inhibits the action of TXA2 in vivo and in vitro on platelets and aorta vascular smooth muscle

Introduction: 1-[4-[2-(4-Bromobenzene-sulfonamino)ethyl] phenylsulfonyl]-3-(trans-4-methylcy-clohexyl) urea(I-4, CAS865483-06-3); a totally synthetic new sulfonylurea compound, combining the hypoglycemic active structure of Glimepiride (CAS 93479-97-1) and anti-TXA(2) receptor (TP) active structure of BM-531(CAS 284464-46-6), was designed and synthesized. Its effects on TXA(2) synthesis and TP have not been reported yet. Aim: To study the inhibitory effects of I-4 and its mechanisms of action on TXA(2) and TP. Methods: Platelet aggregation studies were performed on human platelet, rat whole blood platelet and rabbit platelet, platelets aggregation was induced by TP agonist U-46619(stable analog of TXA(2), CAS 56985-40-1). Plasma TXB2 and 6-keto-prostaglandin F-1 alpha (6-keto-PGF(1 alpha)) were used as markers to determine the effect of I-4 on thromboxane synthesis. Fluo-3-AM was used to measure the cytosolic Ca2+ concentrations ([Ca2+](i)) in rabbit platelet. Aorta rings with and without endothelium were prepared and aorta endothelium were induced by U-46619. A model of type 2 diabetes mellitus was established by intraperitoneal injection of low dose of streptozocin to rats fed a high-calorie diet. Both normal rats and type 2 diabetic rats were used to assay the inhibitory effect of I-4 on platelet aggregation induced by U-46619. Results: I-4 exhibited a higher inhibitory potency than Glimepiride on U-46619 induced platelet aggregation in vitro and in vivo. I-4 increased the ratio of plasma PGI(2)/TXA(2) and decreased [Ca2+](i) release from platelet internal stores. In addition, I-4 presented a vasorelaxant activity on isolated rat aorta contraction induced by U-46619. Oral administration of I-4 (1 similar to 10 mg/kg) markedly and dose-dependently inhibited platelet aggregation in both normal rats and type 2 diabetic rats. Conclusion: I-4 significantly inhibited platelet aggregation induced by U-46619 in vitro and in vivo, and rat aorta contraction. It probably acts by partly blocking TXA(2) action, decreasing the platelet intracellular Ca2+, and increasing the PGI(2)/TXA(2) ratio. (C) 2012 Elsevier Ltd. All rights reserved.