Chen John W, Querol Sans Manel, Bogdanov Alexei, Weissleder Ralph
Center for Molecular Imaging Research, Massachusetts General Hospital, Harvard Medical School, 5404 Building 149, 13th St, Charlestown, MA 02129, USA.
Radiology. 2006 Aug;240(2):473-81. doi: 10.1148/radiol.2402050994.
To evaluate whether contrast agents for molecular magnetic resonance (MR) imaging can demonstrate the in vivo activity of myeloperoxidase, an enzyme that is secreted by stimulated polymorphonuclear leukocytes, monocytes, and macrophages during inflammation.
Animal experiments were approved by the animal care committee. Protocols for the procurement and use of human blood were approved by the institutional review board. Informed consent was obtained from each donor, and HIPAA guidelines were followed for humans. Two paramagnetic myeloperoxidase substrates--that is, gadolinium-5-hydroxytryptamide-tetraazacyclododecane tetraacetic acid (Gd-5-HT-DOTA) and Gd-bis-5-HT-diethylenetriaminepentaacetic acid (Gd-bis-5-HT-DTPA)--were synthesized. Indium 111-labeled bis-5-HT-DTPA was used to determine biodistribution and target localization. A total of 22 mice were used in three models. In the first model, human myeloperoxidase was embedded in a basement membrane matrix gel and was injected intramuscularly. In the second model, lipopolysaccharide (LPS) from Escherichia coli was embedded in a basement membrane matrix gel and was injected intramuscularly to induce endogenous myeloperoxidase secretion. In the third model, LPS was injected intramuscularly to induce myositis. Statistical significance was calculated for contrast-to-noise ratio (CNR) curves by using the Kolmogorov-Smirnov test.
After the administration of Gd-bis-5-HT-DTPA, strong MR signal enhancement (up to 2.5-fold increase in CNR, P < .001) was observed in vivo for implants that contained human myeloperoxidase. In the LPS-induced myositis model, a smaller visible difference was seen (1.3-fold increase in CNR, P < .001), which was consistent with the fact that endogenous mouse myeloperoxidase is only about 10%-20% as active as human myeloperoxidase. Prolonged contrast material enhancement was observed in the myeloperoxidase-containing areas that were injected with Gd-5-HT-DOTA or Gd-bis-5-HT-DTPA but was not observed in areas that were injected with Gd-DTPA or Gd-dopamine-DOTA (P < .05). Single photon emission computed tomography combined with computed tomography was used to confirm the increased retention of contrast agents at sites that contained human myeloperoxidase, and the results of biodistribution studies demonstrated a more than fourfold increase radiotracer accumulation at these sites.
Human and mouse myeloperoxidase activity in myeloperoxidase implants and inflamed tissues can be visualized and reported in vivo by using myeloperoxidase-sensitive "smart" molecular imaging probes.
评估用于分子磁共振（MR）成像的造影剂能否显示髓过氧化物酶的体内活性，髓过氧化物酶是一种在炎症期间由受刺激的多形核白细胞、单核细胞和巨噬细胞分泌的酶。
动物实验经动物护理委员会批准。人类血液的采集和使用方案经机构审查委员会批准。获得每位捐赠者的知情同意，并遵循了关于人类的健康保险流通与责任法案（HIPAA）指南。合成了两种顺磁性髓过氧化物酶底物，即钆 - 5 - 羟色胺 - 四氮杂环十二烷四乙酸（Gd - 5 - HT - DOTA）和钆 - 双 - 5 - HT - 二乙烯三胺五乙酸（Gd - bis - 5 - HT - DTPA）。铟111标记的双 - 5 - HT - DTPA用于确定生物分布和靶定位。在三个模型中共使用了22只小鼠。在第一个模型中，将人髓过氧化物酶包埋在基底膜基质凝胶中并肌肉注射。在第二个模型中，将来自大肠杆菌的脂多糖（LPS）包埋在基底膜基质凝胶中并肌肉注射以诱导内源性髓过氧化物酶分泌。在第三个模型中，肌肉注射LPS以诱导肌炎。使用柯尔莫哥洛夫 - 斯米尔诺夫检验计算对比噪声比（CNR）曲线的统计学显著性。
给予Gd - bis - 5 - HT - DTPA后，在体内观察到含有人类髓过氧化物酶的植入物有强烈的MR信号增强（CNR增加高达2.5倍，P <.001）。在LPS诱导的肌炎模型中，可见差异较小（CNR增加1.3倍，P <.001），这与内源性小鼠髓过氧化物酶的活性仅为人髓过氧化物酶活性的约10% - 20%这一事实一致。在注射Gd - 5 - HT - DOTA或Gd - bis - 5 - HT - DTPA的含髓过氧化物酶区域观察到造影剂增强持续存在，但在注射Gd - DTPA或Gd - 多巴胺 - DOTA的区域未观察到（P <.05）。单光子发射计算机断层扫描结合计算机断层扫描用于确认造影剂在含有人类髓过氧化物酶的部位的滞留增加，生物分布研究结果表明这些部位的放射性示踪剂积累增加了四倍以上。
通过使用对髓过氧化物酶敏感的“智能”分子成像探针，可以在体内可视化并报告髓过氧化物酶植入物和炎症组织中的人类和小鼠髓过氧化物酶活性。
