Imaging of translocator protein upregulation is selective for pro-inflammatory polarized astrocytes and microglia
Imaging of translocator protein upregulation is selective for pro-inflammatory polarized astrocytes and microglia
复制标题
DOI：
10.1002/glia.23716
复制
发表时间：
2019-09-03
期刊：
影响因子：
6.2
通讯作者：
Sibson, Nicola R.
中科院分区：
文献类型：
--
作者：
Pannell, Maria;Economopoulos, Vasiliki;Sibson, Nicola R.
转运蛋白（TSPO）的表达在活化的胶质细胞中增加，并已被用作PET成像中神经炎症的标志物。然而，TSPO上调反映促炎或抗炎表型的程度仍不清楚。我们的目的是确定星形胶质细胞和小胶质细胞/巨噬细胞中的TSPO上调是否限于特定的炎症表型。通过流式细胞术在用脂多糖（LPS）、肿瘤坏死因子（TNF）或白细胞介素-4（IL-4）刺激的培养的星形胶质细胞、小胶质细胞和巨噬细胞中评估TSPO上调。随后，向小鼠脑内注射TNF诱导腺病毒（AdTNF）或IL-4。通过免疫组织化学/荧光和流式细胞术评估TSPO和促/抗炎标志物的胶质细胞表达。最后，注射AdTNF或IL-4的小鼠通过注射TSPO放射性配体F-18-DPA-713进行PET成像，然后进行离体放射自显影。在体外和体内注射AdTNF后，促炎性小胶质细胞/巨噬细胞和星形胶质细胞中的TSPO表达显著增加（p < .001，相对于对照半球），这是通过组织学和FACS确定的。PET成像和放射自显影均显示AdTNF注射小鼠同侧半球中F-18-DPA-713结合显著增加（p <0.001）。相比之下，在IL-4注射后没有观察到组织学上和通过FACS评估的TSPO表达或通过PET/放射自显影术评估的配体结合的增加。综上所述，这些结果表明，TSPO成像特异性地揭示了大脑中活化的神经胶质细胞的促炎群体响应于炎症刺激。由于神经胶质细胞的炎症表型对它们在神经系统疾病中的作用至关重要，这些发现可能会增强TSPO成像的实用性和应用。
Translocator protein (TSPO) expression is increased in activated glia, and has been used as a marker of neuroinflammation in PET imaging. However, the extent to which TSPO upregulation reflects a pro- or anti-inflammatory phenotype remains unclear. Our aim was to determine whether TSPO upregulation in astrocytes and microglia/macrophages is limited to a specific inflammatory phenotype. TSPO upregulation was assessed by flow cytometry in cultured astrocytes, microglia, and macrophages stimulated with lipopolysaccharide (LPS), tumor necrosis factor (TNF), or interleukin-4 (Il-4). Subsequently, mice were injected intracerebrally with either a TNF-inducing adenovirus (AdTNF) or IL-4. Glial expression of TSPO and pro-/anti-inflammatory markers was assessed by immunohistochemistry/fluorescence and flow cytometry. Finally, AdTNF or IL-4 injected mice underwent PET imaging with injection of the TSPO radioligand F-18-DPA-713, followed by ex vivo autoradiography. TSPO expression was significantly increased in pro-inflammatory microglia/macrophages and astrocytes both in vitro, and in vivo after AdTNF injection (p < .001 vs. control hemisphere), determined both histologically and by FACS. Both PET imaging and autoradiography revealed a significant (p < .001) increase in F-18-DPA-713 binding in the ipsilateral hemisphere of AdTNF-injected mice. In contrast, no increase in either TSPO expression assessed histologically and by FACS, or ligand binding by PET/autoradiography was observed after IL-4 injection. Taken together, these results suggest that TSPO imaging specifically reveals the pro-inflammatory population of activated glial cells in the brain in response to inflammatory stimuli. Since the inflammatory phenotype of glial cells is critical to their role in neurological disease, these findings may enhance the utility and application of TSPO imaging.