Abstract：
Ocular complications of diabetes mellitus (DM) are the leading cause of vision loss. Ocular inflammation often occurs in the early stage of DM; however, there are no proven quantitative methods to evaluate the inflammatory status of eyes in DM. The 18 kDa translocator protein (TSPO) is an evolutionarily conserved cholesterol binding protein localized in the outer mitochondrial membrane. It is a biomarker of activated microglia/macrophages; however, its role in ocular inflammation is unclear. In this study, fluorine-18-DPA-714 ([18F]-DPA-714) was evaluated as a specific TSPO probe by cell uptake, cell binding assays and micro positron emission tomography (microPET) imaging in both in vitro and in vivo models. Primary microglia/macrophages (PMs) extracted from the cornea, retina, choroid or sclera of neonatal rats with or without high glucose (50 mM) treatment were used as the in vitro model. Sprague-Dawley (SD) rats that received an intraperitoneal administration of streptozotocin (STZ, 60 mg/kg once) were used as the in vivo model. Increased cell uptake and high binding affinity of [18F]-DPA-714 were observed in primary PMs under hyperglycemic stress. These findings were consistent with cellular morphological changes, cell activation, and TSPO up-regulation. [18F]-DPA-714 PET imaging and biodistribution in the eyes of DM rats revealed that inflammation initiates in microglia/macrophages in the early stages (3 weeks and 6 weeks), corresponding with up-regulated TSPO levels. Thus, [18F]-DPA-714 microPET imaging may be an effective approach for the early evaluation of ocular inflammation in DM.
摘要：
糖尿病（DM）的眼部并发症是导致视力丧失的主要原因。眼部炎症常发生在DM的早期;然而,目前尚无经证实的定量方法来评估DM患者眼部的炎症状态.18kDa转运蛋白(TSPO)是位于线粒体外膜中的进化上保守的胆固醇结合蛋白。它是活化的小胶质细胞/巨噬细胞的生物标志物；然而，其在眼部炎症中的作用尚不清楚。在这项研究中,氟-18-DPA-714（[18F]-DPA-714）通过细胞摄取作为特异性TSPO探针进行评估，体外和体内模型中的细胞结合测定和微正电子发射断层扫描（microPET）成像。从角膜提取的初级小胶质细胞/巨噬细胞（PM），视网膜,使用或不使用高糖（50mM）处理的新生大鼠的脉络膜或巩膜作为体外模型。接受腹膜内链脲佐菌素（STZ，60mg/kg一次)作为体内模型。在高血糖应激下的原代PM中观察到细胞摄取增加和[18F]-DPA-714的高结合亲和力。这些发现与细胞形态变化一致，细胞激活,和TSPO上调。[18F]-DPA-714PET成像和DM大鼠眼睛中的生物分布显示，炎症在早期阶段（3周和6周）在小胶质细胞/巨噬细胞中开始，与上调的TSPO水平相对应。因此，[18F]-DPA-714microPET成像可能是早期评估DM眼部炎症的有效方法。
