超声造影剂对犬缺血再灌注心肌的靶向显像及其机制研究

The mechanism of contrast echocardiography for myocardial ischemia-reperfusion assessments using leukocyte-targeted contrast agent

目的用自制的靶向超声造影剂实现无创性地评价犬心肌缺血再灌注,同时研究其靶向性作用机制。方法将自行研制的表面活性剂超声造影剂“表活显”(surfactantfluorocarbon-filledmicrobubbles,SFCMB)与磷脂酰丝氨酸(phosphatidylserine,PS)结合,制备成靶向超声造影剂(SFCMB-PS),在实时心肌超声造影(MCE)条件下,用SFCMB-PS对犬心肌缺血再灌注模型进行延迟心肌显像。流式细胞术测定白细胞激活前和激活后与SFCMB-PS的结合情况以及在补体和β2整合素中的Mac-1缺乏时激活的白细胞与SFCMB-PS的结合情况。结果延迟心肌显像表明缺血再灌注区的造影剂回声较正常区的回声明显增强。流式细胞术证明了PS结合在造影剂微泡的表面,未激活的白细胞与微泡的结合率为(5.27±0.75)%,激活的白细胞与微泡的结合率为(39.67±6.83)%,结合率明显提高(P<0.01);补体和β2整合素中的Mac-1缺乏时,两者的结合明显受到抑制,结合率降到(12.27±1.66)%(P<0.01)和(10.90±2.40)%(P<0.01)。结论SFCMB-PS可以无创性地评价缺血再灌注损伤心肌的部位及其严重程度。SFCMB-PS是通过β2整合素中的Mac-1和补体介导途径与激活的白细胞结合并进入细胞内的。

Objective To noninvasively assess myocardlum ischemia-reperfusion （I-R） injury using targeted ultrasound contrast agent and study the possible mechanism. Methods Nine open-chest dog myocardium I-R models were established, followed by injecting targeted ultrasound contrast agent （SFCMB-PS） in which phosphatidylserine （PS） was incorporated into the shell of the self-made surfactant fluorocarbon-filled contrast agent. Delayed real-time myocardial contrast echocardlography （MCE） imaging was employed to evaluate the myocardial I-R in the dogs. Flow cytometry detected the attachment of SFCMB-PS targeted to inactivated or activated leukocytes and leukocytes to serous incubated into β2-integrin Mac-1 or complement-deficit. Results Compared to normal imaging, the acoustic densities of I-R myocardlum regions were significantly increased on MCE images. Flow cytometry results revealed that the conjugation rates of SFCMB-PS to inactivated and activated leukocytes were （5.27 ±0.75） % and （39.67 ±6.83） % respectively（ P 〈0.01） ; the conjugation rates of serous complement and β2-integrin Mac-1 deficit were obviously inhibated and decreased to （12.27 ± 1.66） % and （10.90 ± 2.40） % ,respectively [All P 〈0.01 vs （39.67 ± 6.83） %]. Conclusions The region and severity of myocardial I-R injury can be noninvasively assessed with SFCMB-PS. The possible mechanism of SFCMB-PS targeted to activated leukocytes is due to β2-integrin Mac-1 and complement inducement.