Selvaraj Uma Maheswari, Ujas Thomas A, Kong Xiangmei, Kumar Ashwani, Plautz Erik J, Zhang Shanrong, Xing Chao, Sudduth Tiffany L, Wilcock Donna M, Turchan-Cholewo Jadwiga, Goldberg Mark P, Stowe Ann M
Department of Neurology & Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX, United States.
Department of Neurology, Center for Advanced Translational Stroke Science, University of Kentucky, Lexington, KY, United States.
Brain Behav Immun. 2021 Jul;95:502-513. doi: 10.1016/j.bbi.2021.05.001. Epub 2021 May 5.
Stroke is a debilitating disorder with significant annual mortality and morbidity rates worldwide. Immune cells are recruited to the injured brain within hours after stroke onset and can exhibit either protective or detrimental effects on recovery. However, immune cells, including CD8 T cells, persist in the injured brain for weeks, suggesting a longer-term role for the adaptive immune system during functional recovery. The aim of this study was to determine if the delayed secondary diapedesis of CD8 T cells into the ischemic brain negatively impacts functional recovery after transient ischemic stroke in male mice.
Mice exhibited an increased number of leukocytes in the ipsilesional hemispheres at 14 days (3-fold; p < 0.001) and 30 days (2.2-fold; p = 0.02) after transient middle cerebral artery occlusion (tMCAo) compared to 8 days post-tMCAo, at which time acute neuroinflammation predominantly resolves. Moreover, mice with higher ipsilesional CD8 T cells at 30 days (R = 0.52, p < 0.01) exhibited worse functional recovery. To confirm a detrimental role of chronic CD8 T cell diapedesis on recovery, peripheral CD8 T cells were depleted beginning 10 days post-tMCAo. Delayed CD8 T cell depletion improved motor recovery on the rotarod (F = 4.264; p = 0.048) compared to isotype control-treated mice. CD8 T cell-depleted mice also exhibited 2-fold (p < 0.001) reduced leukocyte infiltration at 30 days post-tMCAo. Specifically, macrophage, neutrophil, and CD4 T cell numbers were reduced in the ipsilesional hemisphere of the CD8 T cell-depleted mice independent of inflammatory status of the post-stroke CNS (e.g. microglial phenotype and cytokine production). RNAseq identified a unique profile for brain infiltrating CD8 T cells at 30 days post-tMCAo, with 46 genes differentially expressed relative to CD8 T cells at 3 days post-tMCAo.
Our data reveal a role for CD8 T cells in the chronic phase post-stroke that can be therapeutically targeted. We demonstrate long-term CD8 T cell recruitment into the ipsilesional hemisphere that affects both immune cell numbers present in the injured brain and functional recovery through one month after stroke onset.
中风是一种使人衰弱的疾病，在全球范围内每年都有很高的死亡率和发病率。中风发作后数小时内，免疫细胞就会被募集到受损的大脑中，它们对恢复可能产生保护作用或有害作用。然而，包括CD8 T细胞在内的免疫细胞会在受损大脑中持续存在数周，这表明适应性免疫系统在功能恢复过程中具有长期作用。本研究的目的是确定CD8 T细胞延迟二次渗出到缺血性脑内是否会对雄性小鼠短暂性脑缺血发作后的功能恢复产生负面影响。
与短暂性大脑中动脉闭塞（tMCAo）后8天相比，tMCAo后14天（3倍；p < 0.001）和30天（2.2倍；p = 0.02）时，小鼠患侧半球的白细胞数量增加，此时急性神经炎症主要消退。此外，在30天时患侧CD8 T细胞数量较高的小鼠（R = 0.52，p < 0.01）功能恢复较差。为了证实慢性CD8 T细胞渗出对恢复的有害作用，从tMCAo后10天开始清除外周CD8 T细胞。与同型对照处理的小鼠相比，延迟清除CD8 T细胞改善了转棒试验中的运动恢复（F = 4.264；p = 0.048）。在tMCAo后30天，清除CD8 T细胞的小鼠白细胞浸润也减少了2倍（p < 0.001）。具体而言，在清除CD8 T细胞的小鼠患侧半球中，巨噬细胞、中性粒细胞和CD4 T细胞数量减少，与中风后中枢神经系统的炎症状态无关（例如小胶质细胞表型和细胞因子产生）。RNA测序确定了tMCAo后30天时脑内浸润CD8 T细胞的独特特征，与tMCAo后3天时的CD8 T细胞相比，有46个基因差异表达。
我们的数据揭示了CD8 T细胞在中风后慢性期的作用，这一作用可作为治疗靶点。我们证明了CD8 T细胞长期募集到患侧半球，这会影响中风发作后一个月内受损大脑中存在的免疫细胞数量和功能恢复。
