Umeda Kousuke, Tanaka Sachi, Ihara Fumiaki, Yamagishi Junya, Suzuki Yutaka, Nishikawa Yoshifumi
National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan.
Division of Animal Science, Department of Agricultural and Life Sciences, Faculty of Agriculture, Shinshu University, Minamiminowa, Nagano, Japan.
PLoS One. 2017 Nov 14;12(11):e0187703. doi: 10.1371/journal.pone.0187703. eCollection 2017.
Toxoplasma gondii is capable of persisting in the brain, although it is efficiently eliminated by cellular immune responses in most other sites. While Toll-like receptor 2 (TLR2) reportedly plays important roles in protective immunity against the parasite, the relationship between neurological disorders induced by T. gondii infection and TLR2 function in the brain remains controversial with many unknowns. In this study, primary cultured astrocytes, microglia, neurons, and peritoneal macrophages obtained from wild-type and TLR2-deficient mice were exposed to T. gondii tachyzoites. To characterize TLR2-dependent functional pathways activated in response to T. gondii infection, gene expression of different cell types was profiled by RNA sequencing.
During T. gondii infection, a total of 611, 777, 385, and 1105 genes were upregulated in astrocytes, microglia, neurons, and macrophages, respectively, while 163, 1207, 158, and 1274 genes were downregulated, respectively, in a TLR2-dependent manner. Overrepresented Gene Ontology (GO) terms for TLR2-dependently upregulated genes were associated with immune and stress responses in astrocytes, immune responses and developmental processes in microglia, metabolic processes and immune responses in neurons, and metabolic processes and gene expression in macrophages. Overrepresented GO terms for downregulated genes included ion transport and behavior in astrocytes, cell cycle and cell division in microglia, metabolic processes in neurons, and response to stimulus, signaling and cell motility in macrophages.
To our knowledge, this is the first transcriptomic study of TLR2 function across different cell types during T. gondii infection. Results of RNA-sequencing demonstrated roles for TLR2 varied by cell type during T. gondii infection. Our findings facilitate understanding of the detailed relationship between TLR2 and T. gondii infection, and elucidate mechanisms underlying neurological changes during infection.
尽管弓形虫在大多数其他部位能被细胞免疫反应有效清除，但它能够在大脑中持续存在。虽然据报道Toll样受体2（TLR2）在针对该寄生虫的保护性免疫中发挥重要作用，但弓形虫感染诱发的神经紊乱与大脑中TLR2功能之间的关系仍存在争议，有许多未知因素。在本研究中，将从野生型和TLR2缺陷型小鼠获得的原代培养星形胶质细胞、小胶质细胞、神经元和腹腔巨噬细胞暴露于弓形虫速殖子。为了表征响应弓形虫感染而激活的TLR2依赖性功能途径，通过RNA测序对不同细胞类型的基因表达进行了分析。
在弓形虫感染期间，星形胶质细胞、小胶质细胞、神经元和巨噬细胞中分别有611、777、385和1105个基因上调，而分别有163、1207、158和1274个基因以TLR2依赖性方式下调。TLR2依赖性上调基因的过度富集基因本体（GO）术语与星形胶质细胞中的免疫和应激反应、小胶质细胞中的免疫反应和发育过程、神经元中的代谢过程和免疫反应以及巨噬细胞中的代谢过程和基因表达相关。下调基因的过度富集GO术语包括星形胶质细胞中的离子转运和行为、小胶质细胞中的细胞周期和细胞分裂、神经元中的代谢过程以及巨噬细胞中的刺激反应、信号传导和细胞运动。
据我们所知，这是首次在弓形虫感染期间对不同细胞类型的TLR2功能进行转录组学研究。RNA测序结果表明，在弓形虫感染期间，TLR2的作用因细胞类型而异。我们的研究结果有助于理解TLR2与弓形虫感染之间的详细关系，并阐明感染期间神经变化的潜在机制。
