Department of Veterinary Physiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Neuroscience. 2013 Feb 12;231:49-60. doi: 10.1016/j.neuroscience.2012.11.032. Epub 2012 Nov 29.
Progranulin (PGRN), a multifunctional growth factor, appears to play a role in neurodegenerative diseases accompanied by neuroinflammation. In this study, we investigated the role of PGRN in neuroinflammation, especially in the activation of microglia, by means of experimental traumatic brain injury (TBI) in the cerebral cortex of mice. The expression of GRN mRNA was increased in association with neuroinflammation after TBI. Double-immunohistochemical study showed that PGRN-immunoreactive (-IR) cells were mainly overlapped with CD68-IR cells, suggesting that the main source of PGRN was CD68-positive activated microglia. To investigate the role of PGRN in inflammatory responses related to activated microglia, we compared the immunoreactivity and expression of ionized calcium-binding adaptor molecule 1 (Iba1), CD68, and CD11b as markers for activated microglia between wild-type (WT) and GRN-deficient (KO) mice. The number of Iba1- and CD11b-IR cells and gene expression of Iba1 and CD11b were not significantly different between WT and KO mice, while the number of CD68-IR cells and CD68 expression in KO mice were significantly greater than those in WT mice. Double-immunohistochemical study showed that CD68-IR microglia were also IR for TGFβ1, and TGFβ1 expression and Smad3 phosphorylation in KO mice were elevated compared to WT mice. Moreover, double-immunostaining between phospho-Smad3 and glial fibrillary acidic protein suggested increased TGFβ1-Smad3 signal mainly by astrocytes. The levels of protein carbonyl groups, which reflect protein oxidation, and laminin immunoreactivity, which is associated with angiogenesis, were also significantly increased in KO mice compared to WT mice. These results suggest that PGRN is produced in CD68-positive microglia and suppresses excessive inflammatory responses related to activated microglia after TBI in mice.
颗粒体蛋白聚糖 (PGRN) 是一种多功能生长因子，似乎在伴有神经炎症的神经退行性疾病中发挥作用。在这项研究中，我们通过对小鼠大脑皮质的实验性创伤性脑损伤 (TBI) 研究了 PGRN 在神经炎症中的作用，特别是在小胶质细胞的激活中的作用。TBI 后，GRN mRNA 的表达与神经炎症相关增加。双免疫组织化学研究表明，PGRN-免疫反应性 (IR) 细胞主要与 CD68-IR 细胞重叠，表明 PGRN 的主要来源是 CD68 阳性激活的小胶质细胞。为了研究 PGRN 在与激活的小胶质细胞相关的炎症反应中的作用，我们比较了野生型 (WT) 和 GRN 缺陷型 (KO) 小鼠中作为激活的小胶质细胞标志物的离子钙结合衔接分子 1 (Iba1)、CD68 和 CD11b 的免疫反应性和表达。WT 和 KO 小鼠之间 Iba1 和 CD11b-IR 细胞的数量以及 Iba1 和 CD11b 的基因表达没有显着差异，而 KO 小鼠中 CD68-IR 细胞的数量和 CD68 的表达明显高于 WT 小鼠。双免疫组织化学研究表明，CD68-IR 小胶质细胞也对 TGFβ1 呈免疫反应，并且 KO 小鼠中的 TGFβ1 表达和 Smad3 磷酸化水平高于 WT 小鼠。此外，磷酸化 Smad3 和神经胶质纤维酸性蛋白之间的双重免疫染色表明 TGFβ1-Smad3 信号主要通过星形胶质细胞增加。与蛋白氧化相关的蛋白羰基水平和与血管生成相关的层粘连蛋白免疫反应性也明显高于 WT 小鼠。这些结果表明，PGRN 是由 CD68 阳性小胶质细胞产生的，并在 TBI 后抑制小鼠中与激活的小胶质细胞相关的过度炎症反应。
