Yin Jian, Li Ran, Liu Wenchao, Chen Yunchang, Zhang Xin, Li Xifeng, He Xuying, Duan Chuanzhi
The National Key Clinic Specialty, The Neurosurgery Institute of Guangdong Province, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Neurosurgery, Zhujiang Hospital, Southern Medical University, Guangzhou, China.
Departments of Neurosurgery, Hanghzou Red Cross Hospital, Hangzhou, China.
Front Neurosci. 2018 Feb 27;12:96. doi: 10.3389/fnins.2018.00096. eCollection 2018.
Early brain injury (EBI) following subarachnoid hemorrhage (SAH) can lead to inflammation and neuronal dysfunction. There is a need for effective strategies to mitigate these effects and improve the outcome of patients who experience SAH. The mRNA-destabilizing protein tristetraprolin (TTP) is an anti-inflammatory factor that induces the decay of cytokine transcripts and has been implicated in diseases such as glioma. However, the mechanism of action of TTP in EBI after SAH is unclear. The present study investigated the effects of TTP regulation via phosphorylation in a rat model of SAH by protein phosphatase (PP)2A, which is a pleiotropic enzyme complex with multiple substrate phospho-proteins. We hypothesized that inhibitory phosphorylation of TTP by PP2A would reduce neuroinflammation and apoptosis. To evaluate the function of each factor, the PP2A agonist FTY720, short interfering (si)RNAs targeting TTP and PP2A were administered to rats by intracerebroventricular injection 24 h before SAH. Rats were evaluated with SAH grade, neurological score, brain water content and by western blotting, and terminal deoxynucleotidyltransferase dUTP nick-end labeling. We found that endogenous PP2A and TTP levels were increased after SAH. FTY720 induced PP2A activation would lead to dephosphorylation and activation of TTP and decreased production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-8. SiRNA-mediated TTP knockdown abolished anti-inflammatory effects of FTY720 treatment, indicating that PP2A was associated with TTP activation . Decreased TNF-α, IL-6, and IL-8 levels were associated with improvement of neurological function, reduction of brain edema, suppression of caspase-3, and up-regulation of B cell lymphoma-2. These results demonstrated that PP2A activation could enhance the anti-inflammatory and anti-apoptotic effects of TTP, by which it might shed light on the development of an effective therapeutic strategy against EBI following SAH.
蛛网膜下腔出血（SAH）后的早期脑损伤（EBI）可导致炎症和神经元功能障碍。需要有效的策略来减轻这些影响并改善SAH患者的预后。mRNA去稳定蛋白锌指蛋白36（TTP）是一种抗炎因子，可诱导细胞因子转录本的降解，并与胶质瘤等疾病有关。然而，TTP在SAH后EBI中的作用机制尚不清楚。本研究通过蛋白磷酸酶（PP）2A在SAH大鼠模型中研究了TTP磷酸化调控的作用，PP2A是一种具有多种底物磷酸化蛋白的多效性酶复合物。我们假设PP2A对TTP的抑制性磷酸化会减少神经炎症和细胞凋亡。为了评估每个因素的功能，在SAH前24小时通过脑室内注射将PP2A激动剂FTY720、靶向TTP和PP2A的短发夹RNA（shRNA）给予大鼠。通过SAH分级、神经功能评分、脑含水量以及蛋白质印迹和末端脱氧核苷酸转移酶dUTP缺口末端标记对大鼠进行评估。我们发现SAH后内源性PP2A和TTP水平升高。FTY720诱导的PP2A激活会导致TTP的去磷酸化和激活，并降低肿瘤坏死因子（TNF）-α、白细胞介素（IL）-6和IL-8的产生。SiRNA介导的TTP敲低消除了FTY720治疗的抗炎作用，表明PP2A与TTP激活有关。TNF-α、IL-6和IL-8水平的降低与神经功能的改善、脑水肿的减轻、半胱天冬酶-3的抑制以及B细胞淋巴瘤-2的上调有关。这些结果表明，PP2A激活可以增强TTP的抗炎和抗凋亡作用，这可能为开发针对SAH后EBI的有效治疗策略提供线索。
