Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Mol Pharm. 2011 Oct 3;8(5):1962-9. doi: 10.1021/mp200087v. Epub 2011 Aug 15.
The present study was designed to clarify the possibility for application of nitroxide derivatives in magnetic resonance imaging (MRI) of hypercholesterolemia-mediated renal dysfunction in mice, as well as to assess the effectiveness of antilipidemic drugs (cholestyramine and ezetimibe). The mice were separated in four groups: (i) on a normal diet (ND) without medication (control); (ii) on a high cholesterol diet (CD) without medication; (iii) CD mice receiving cholestyramine; and (iv) CD mice receiving ezetimibe. In CD mice without medication, a hypercholesterolemia was developed, detected by the increasing of total plasma cholesterol and non-HDL cholesterol, and decreasing of HDL cholesterol. The hypercholesterolemia compromised renal function: blood urea nitrogen, creatine and uric acid increased significantly, accompanied with development of glomerulosclerosis, enhancement of the amount of neutrophils and overexpression of metalloproteinase-9. The mice were subjected to anesthesia and MR imaging was performed on 7 T magnet (T1-weighted incoherent gradient-echo sequence; fast low-angle shot). The region-of-interest was selected within the kidney. The images were obtained before and after injection of contrast probe [carbamoyl-PROXYL (CMP) or Gd-DTPA]. In the kidney of ND mice, the MRI signal intensity increased after injection of CMP, reached a maximum (very well-defined renal filtration peak) and decreased to the baseline level within 14 min. In kidney of CD mice, the CMP-mediated enhancement of MRI signal was not detected. Antilipidemic drugs patially abolished the effect of hypercholesterolemia on CMP-enhanced MRI in the kidney. The kinetic curves of Gd-enhanced MRI signal had also different profiles in the kidney of ND and CD mice. They were similar to the profiles of the kinetic curves, obtained from MR urography of healthy human and human with renal pathology, respectively. The present study suggests that CMP is a suitable MRI contrast probe for visualization of hypercholesterolemia-induced renal dysfunction in intact animals and the assessment of the efficacy of antilipidemic drugs. The probe was applied at a concentration that was 3 times lower than the LD50 for intravenous administration in mice. Since the probe is excreted by the kidney, it could be considered harmless for mammalians in the selected dose and appropriate candidate for translational research.
本研究旨在阐明氮氧自由基衍生物在磁共振成像（MRI）检测小鼠高脂血症介导的肾功能障碍中的应用可能性，并评估降脂药物（考来烯胺和依折麦布）的疗效。将小鼠分为四组：（i）正常饮食（ND）无药物组（对照组）；（ii）高胆固醇饮食（CD）无药物组；（iii）CD 给予考来烯胺组；（iv）CD 给予依折麦布组。CD 未用药组出现高胆固醇血症，表现为总血浆胆固醇和非高密度脂蛋白胆固醇升高，高密度脂蛋白胆固醇降低。高胆固醇血症导致肾功能受损：血尿素氮、肌酐和尿酸显著升高，同时伴有肾小球硬化、中性粒细胞数量增加和基质金属蛋白酶-9过度表达。对小鼠进行麻醉，在 7T 磁体上进行 MRI 检查（T1 加权非相干梯度回波序列；快速小角度激发）。在肾脏内选择感兴趣区。在注射对比探针[氨甲酰基-PROXYL（CMP）或 Gd-DTPA]前后获得图像。在 ND 小鼠的肾脏中，注射 CMP 后 MRI 信号强度增加，达到最大值（非常清晰的肾滤过峰），并在 14 分钟内降至基线水平。在 CD 小鼠的肾脏中，未检测到 CMP 介导的 MRI 信号增强。降脂药物部分消除了高胆固醇血症对肾脏 CMP 增强 MRI 的影响。Gd 增强 MRI 信号的动力学曲线在 ND 和 CD 小鼠的肾脏中也具有不同的形态。它们分别与健康人及肾病理患者的磁共振尿路造影获得的动力学曲线形态相似。本研究表明，CMP 是一种适用于可视化完整动物高胆固醇血症诱导的肾功能障碍和评估降脂药物疗效的 MRI 对比探针。该探针的浓度比在小鼠中静脉注射的 LD50 低 3 倍。由于探针通过肾脏排泄，因此在所选剂量下对哺乳动物无害，是转化研究的合适候选者。
