Remarkable increases of α1-antichymotrypsin in brain tissues of rodents during prion infection

α1-Antichymotrypsin (α1-ACT) belongs to a kind of acute-phase inflammatory protein. Recently, such protein has been proved exist in the amyloid deposits which is the hallmark of Alzheimer's disease, but limitedly reported in prion disease. To estimate the change of α1-ACT during prion infection, the levels of α1-ACT in the brain tissues of scrapie agents 263K-, 139A- and ME7-infected rodents were analyzed, respectively. Results shown that α1-ACT levels were significantly increased in the brain tissues of the three kinds of scrapie-infected rodents, displaying a time-dependent manner during prion infection. Immunohistochemistry assays revealed the increased α1-ACT mainly accumulated in some cerebral regions of rodents infected with prion, such as cortex, thalamus and cerebellum. Immunofluorescent assays illustrated ubiquitously localization of α1-ACT with GFAP positive astrocytes, Iba1-positive microglia and NeuN-positive neurons. Moreover, double-stained immunofluorescent assays and immunohistochemistry assays using series of brain slices demonstrated close morphological colocalization of α1-ACT signals with that of PrP and PrP^Sc in the brain slices of 263K-infected hamster. However, co-immunoprecipitation does not identify any detectable molecular interaction between the endogenous α1-ACT and PrP either in the brain homogenates of 263K-infected hamsters or in the lysates of prion-infected cultured cells. Our data here imply that brain α1-ACT is increased abnormally in various scrapie-infected rodent models. Direct molecular interaction between α1-ACT and PrP seems not to be essential for the morphological colocalization of those two proteins in the brain tissues of prion infection.

α1-抗胰凝乳蛋白酶（α1-Antichymotrypsin, α1-ACT）属于一类急性期炎症蛋白。近期研究证实，该蛋白可存在于阿尔茨海默病的标志性病理特征——淀粉样蛋白沉积中，但目前针对其在朊病毒病中的报道较为有限。为探究α1-ACT在朊病毒感染过程中的表达变化，本研究分别检测了感染瘙痒病病原体263K、139A及ME7的啮齿动物脑组织中α1-ACT的水平。结果显示，三种瘙痒病病原体感染的啮齿动物脑组织内α1-ACT水平均显著升高，且在朊病毒感染进程中呈现时间依赖性变化。免疫组织化学实验表明，上调的α1-ACT主要聚集于朊病毒感染啮齿动物的特定脑区，包括大脑皮层、丘脑与小脑。免疫荧光实验显示，α1-ACT广泛定位于胶质纤维酸性蛋白（Glial Fibrillary Acidic Protein, GFAP）阳性星形胶质细胞、Iba1阳性小胶质细胞以及NeuN阳性神经元中。此外，通过对系列脑切片开展双重免疫荧光染色及免疫组织化学实验，证实263K感染仓鼠的脑切片中，α1-ACT信号与朊蛋白（Prion Protein, PrP）及瘙痒病相关朊蛋白（PrP^Sc）的信号存在紧密的形态学共定位。然而，无论是在263K感染仓鼠的脑匀浆中，还是在朊病毒感染的培养细胞裂解液中，免疫共沉淀实验均未检测到内源性α1-ACT与PrP之间存在可检测的分子相互作用。本研究数据提示，多种瘙痒病感染啮齿动物模型的脑组织中α1-ACT存在异常升高；α1-ACT与PrP之间的直接分子相互作用，似乎并非二者在朊病毒感染脑组织中实现形态学共定位的必要条件。