Snir Jonatan A, Suchy Mojmir, Lawrence Keith St, Hudson Robert H E, Pasternak Stephen H, Bartha Robert
Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada.
Centre for Functional and Metabolic Mapping, Robarts Research Institute, University of Western Ontario, London, Ontario, Canada.
J Alzheimers Dis. 2015;48(1):73-87. doi: 10.3233/JAD-150123.
Cathepsin D (CatD) is a lysosomal protease that is elevated early in Alzheimer's disease (AD). We have previously developed a Targeted contrast agent (CA) to detect CatD activity in vivo, consisting of a magnetic resonance imaging/fluorescent moiety linked to a cell penetrating peptide (CPP) by means of a CatD cleavage site and have demonstrated its uptake in the brain of an AD mouse model.
The purpose of this study was to characterize the in vivo retention of a near infra-red fluorescent dye labeled version of this CA.
Six adult C57Bl/6 wild-type mice and six adult 5XFAD transgenic AD mice were studied using a small animal imaging system at five and twelve months of age using our novel Targeted CA, or two different control CAs; a Non-Targeted (lacking the CatD cleavage site) and a Non-Penetrating (lacking the CPP). Following intravenous CA administration, the optical signal was recorded within the brain and uptake and washout curves were measured and fitted to a one-phase exponential decay curve.
In all wild-type and 5XFAD mice, the washout of the Targeted CA that included a CPP domain was significantly slower than the washout of the Non-Penetrating and Non-Targeted CA. Furthermore, the washout of the CatD Targeted CA was significantly slower in the 5XFAD mice compared to the age matched wild-type controls (p < 0.05) at 5 and 12 months of age. Control CAs showed no differences in washout.
The prolonged retention of the CatD targeted CA in 5XFAD mice suggests this agent may be useful for AD detection.
组织蛋白酶D（CatD）是一种溶酶体蛋白酶，在阿尔茨海默病（AD）早期水平升高。我们之前开发了一种靶向造影剂（CA），用于在体内检测CatD活性，它由通过CatD切割位点与细胞穿透肽（CPP）连接的磁共振成像/荧光部分组成，并已证明其在AD小鼠模型脑中的摄取。
本研究的目的是表征这种CA的近红外荧光染料标记版本在体内的滞留情况。
使用我们新型的靶向CA或两种不同的对照CA（一种非靶向CA（缺乏CatD切割位点）和一种非穿透性CA（缺乏CPP）），在6只成年C57Bl/6野生型小鼠和6只成年5XFAD转基因AD小鼠5个月和12个月大时，使用小动物成像系统进行研究。静脉注射CA后，记录脑内的光信号，并测量摄取和洗脱曲线，并拟合为单相指数衰减曲线。
在所有野生型和5XFAD小鼠中，包含CPP结构域的靶向CA的洗脱明显慢于非穿透性和非靶向CA的洗脱。此外，在5个月和12个月大时，与年龄匹配的野生型对照相比，5XFAD小鼠中CatD靶向CA的洗脱明显更慢（p<0.05）。对照CA在洗脱方面没有差异。
CatD靶向CA在5XFAD小鼠中的长时间滞留表明该试剂可能对AD检测有用。
