Department of Neurology, Xinqiao Hospital & The Second Affiliated Hospital, The Army (Third Military) Medical University, Chongqing, China.
Graduate School, The Army (Third Military) Medical University, Chongqing, China.
Brain Behav. 2020 Jun;10(6):e01618. doi: 10.1002/brb3.1618. Epub 2020 Apr 13.
Excessive neuroinflammation aggravates the brain injury caused by intracerebral hemorrhage (ICH), while the upstream mechanisms that initiate neuroinflammation remain unclear. Toll-like receptor 4 (TLR4) signaling is important to trigger inflammatory responses in ICH, and cold-inducible RNA-binding protein (CIRP) has been shown as a novel ligand of TLR4 by recent studies. However, whether the CIRP could trigger the neuroinflammation via activating TLR4 signaling in ICH still needs to be investigated.
Human serum CIRP levels were measured using the ELISA kits. Western blot, FJB staining, brain water content, and neurological deficit scores were used to investigate the roles of CIRP in brain injury caused by ICH.
First, we found increased CIRP levels in the blood of patients with ICH when compared to the control individuals, and the ICH patients with mRS > 2 have higher serum CIRP levels in contrast to those with mRS ≤ 2. In the ICH mice, we also found that brain CIRP protein and mRNA levels were also increased after ICH. Furthermore, using the CIRP mice, we found that CIRP mice had less brain damages showing in less FJB cells, reduced brain water content (BWC) and lower neurological deficit scores (NDS) compared to that in WT mice after ICH. Cytokines including IL-6, TNF-α, and IL-1β from CIRP mice were attenuated after ICH. CIRP mice also exhibited reduced TLR4 expression which was accompanied by the decreased activity of NF-κB. This suggests that TLR4 signaling might be involved in CIRP-mediated inflammatory injury possibly via NF-κB activation after ICH.
Our findings suggest that CIRP may activate TLR4 signaling, and further inducing NF-κB activation to increase the expression levels of cytokines and aggravate inflammatory injury in ICH. Targeting CIRP may be a promising strategy for ICH treatment.
过度的神经炎症会加重脑出血（ICH）引起的脑损伤，而引发神经炎症的上游机制尚不清楚。Toll 样受体 4（TLR4）信号对于触发 ICH 中的炎症反应很重要，最近的研究表明冷诱导 RNA 结合蛋白（CIRP）是 TLR4 的一种新型配体。然而，CIRP 是否可以通过激活 TLR4 信号在 ICH 中引发神经炎症仍需进一步研究。
采用 ELISA 试剂盒检测人血清 CIRP 水平。采用 Western blot、FJB 染色、脑水含量和神经功能缺损评分检测 CIRP 在 ICH 引起的脑损伤中的作用。
首先，与对照组相比，我们发现 ICH 患者的血液中 CIRP 水平升高，且 mRS>2 的 ICH 患者的血清 CIRP 水平高于 mRS≤2 的患者。在 ICH 小鼠中，我们还发现 ICH 后大脑 CIRP 蛋白和 mRNA 水平也增加。此外，使用 CIRP 小鼠，我们发现与 WT 小鼠相比，CIRP 小鼠在 ICH 后大脑损伤较小，FJB 细胞减少，脑水含量（BWC）降低，神经功能缺损评分（NDS）降低。CIRP 小鼠的细胞因子（包括 IL-6、TNF-α 和 IL-1β）在 ICH 后减少。CIRP 小鼠还表现出 TLR4 表达减少，这伴随着 NF-κB 活性降低。这表明 TLR4 信号可能参与 CIRP 介导的炎症损伤，可能通过 NF-κB 激活。
我们的研究结果表明，CIRP 可能通过激活 TLR4 信号，进一步诱导 NF-κB 激活，增加细胞因子的表达水平，加重 ICH 中的炎症损伤。靶向 CIRP 可能是治疗 ICH 的一种有前途的策略。
