Evaluation of a 125I-labelled benzazepinone derived voltage-gated sodium channel blocker for imaging with SPECT
作者:Carlos Pérez-Medina、Niral Patel、Mathew Robson、Adam Badar、Mark F. Lythgoe、Erik Årstad
DOI:10.1039/c2ob26695d
日期:——
Voltage-gated sodium channels (VGSCs) are a family of transmembrane proteins that mediate fast neurotransmission, and are integral to sustain physiological conditions and higher cognitive functions. Imaging of VGSCs in vivo holds promise as a tool to elucidate operational functions in the brain and to aid the treatment of a wide range of neurological diseases. To assess the suitability of 1-benzazepin-2-one derived VGSC blockers for imaging, we have prepared a 125I-labelled analogue of BNZA and evaluated the tracer in vivo. In an automated patch-clamp assay, a diastereomeric mixture of the non-radioactive compound blocked the Nav1.2 and Nav1.7 VGSC isoforms with IC50 values of 4.1 ± 1.5 μM and 0.25 ± 0.07 μM, respectively. [3H]BTX displacement studies revealed a three-fold difference in affinity between the two diastereomers. Iodo-destannylation of a tin precursor with iodine-125 afforded the two diastereomerically pure tracers, which were used to assess binding to VGSCs in vivo by comparing their tissue distributions in mice. Whilst the results point to a lack of VGSC binding in vivo, SPECT imaging revealed highly localized uptake in the interscapular region, an area typically associated with brown adipose tissue, which in addition to high metabolic stability of the iodinated tracer, demonstrate the potential of 1-benzazepin-2-ones for in vivo imaging.
电压门控钠通道(VGSCs)是一类跨膜蛋白,介导快速神经传递,对维持生理条件和更高认知功能至关重要。在活体内成像VGSCs有望作为一种工具,阐明大脑的功能,并有助于治疗多种神经疾病。为了评估衍生自1-苯并氮杂氢化噻吩-2-酮的VGSC封闭剂在成像中的适用性,我们制备了一个标记有125I的BNZA类似物,并在体内评估了该示踪剂。在自动化贴片钳实验中,非放射性化合物的一个消旋体混合物以4.1 ± 1.5 μM和0.25 ± 0.07 μM的IC50值分别阻断Nav1.2和Nav1.7 VGSC亚型。[3H]BTX替代研究显示这两种消旋体之间的亲和力存在三倍差异。使用碘-125对锡前体进行碘脱锡反应得到两种消旋体纯的示踪剂,这两者被用来通过比较它们在小鼠中的组织分布来评估在体内对VGSC的结合。虽然结果显示在体内缺乏VGSC的结合,SPECT成像显示在肩胛间区域的高度局部化摄取,该区域通常与棕色脂肪组织相关,这不仅表明碘化示踪剂具有很高的代谢稳定性,还展示了1-苯并氮杂氢化噻吩-2-酮在活体成像中的潜力。