Pfister Sandra L
Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI 53226, USA.
Hypertension. 2004 Feb;43(2):428-33. doi: 10.1161/01.HYP.0000110906.77479.91. Epub 2004 Jan 12.
This study examined the role of platelet microparticles in thromboxane A2 (TXA2) production. Incubation of microparticles with [14C]arachidonic acid and A23187 produced 14C-labeled TXB2, the stable metabolite of TXA2. To investigate the possibility that endothelial cells (ECs) transfer arachidonic acid to platelet microparticles and promote TXB2 synthesis, ECs with their cellular lipids prelabeled with tritiated arachidonic acid were incubated with microparticles. In the absence of microparticles, there was no production of tritiated TXB2 by the ECs. However, when microparticles were coincubated with prelabeled ECs, tritiated arachidonic acid was metabolized to tritiated TXB2. Aspirin was then used to inhibit cyclooxygenase. ECs coincubated with aspirin-treated platelet microparticles did not produce TXB2, as measured by radioimmunoassay. In contrast, aspirin-treated ECs coincubated with microparticles produced TXB2, and its production was enhanced by methacholine (10(-4) mol/L), indicating that endothelially derived arachidonic acid, and not endothelially derived prostaglandin endoperoxide, was transferred to the microparticle and further metabolized to TXA2. Additional studies with rabbit aorta and pulmonary artery investigated whether microparticles contributed to vascular contractions. Preincubation with microparticles enhanced arachidonic acid-induced contractions in the aorta and methacholine-induced contractions in the pulmonary artery. The thromboxane receptor antagonist SQ29548 and the thromboxane synthase inhibitor dazoxiben blocked these effects. Because TXA2 is an important mediator in various pathophysiologic states, including hypertension, the ability of platelet microparticles to act as a cellular source of TXA2 might provide new insight into the role of platelets and platelet microparticles in the control of vascular tone.
本研究检测了血小板微粒在血栓素A2（TXA2）生成中的作用。将微粒与[14C]花生四烯酸和A23187一起孵育，产生了14C标记的TXB2，即TXA2的稳定代谢产物。为了研究内皮细胞（ECs）将花生四烯酸转移至血小板微粒并促进TXB2合成的可能性，将预先用氚标记的花生四烯酸标记细胞脂质的ECs与微粒一起孵育。在没有微粒的情况下，ECs不会产生氚标记的TXB2。然而，当微粒与预先标记的ECs共同孵育时，氚标记的花生四烯酸被代谢为氚标记的TXB2。然后使用阿司匹林抑制环氧化酶。通过放射免疫测定法检测，与经阿司匹林处理的血小板微粒共同孵育的ECs未产生TXB2。相比之下，经阿司匹林处理的ECs与微粒共同孵育产生了TXB2，并且其生成可被乙酰甲胆碱（10(-4) mol/L）增强，这表明内皮来源的花生四烯酸而非内皮来源的前列腺素内过氧化物被转移至微粒并进一步代谢为TXA2。对兔主动脉和肺动脉进行的其他研究调查了微粒是否会导致血管收缩。预先与微粒孵育可增强花生四烯酸诱导的主动脉收缩以及乙酰甲胆碱诱导的肺动脉收缩。血栓素受体拮抗剂SQ29548和血栓素合酶抑制剂达唑氧苯可阻断这些作用。由于TXA2是包括高血压在内的各种病理生理状态中的重要介质，血小板微粒作为TXA2细胞来源的能力可能为血小板和血小板微粒在血管张力控制中的作用提供新的见解。
