Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Cell Mol Life Sci. 2022 Apr 7;79(5):224. doi: 10.1007/s00018-022-04212-6.
Hematoma leads to progressive neurological deficits and poor outcomes after intracerebral hemorrhage (ICH). Early clearance of hematoma is widely recognized as an essential treatment to limit the damage and improve the clinical prognosis. CD163, alias hemoglobin (Hb) scavenger receptor on microglia, plays a pivotal role in hematoma absorption, but CD163 on neurons permits Hb uptake and results in neurotoxicity. In this study, we focus on how to specially promote microglial but not neuronal CD163 mediated-Hb uptake and hematoma absorption.
RNA sequencing was used to explore the potential molecules involved in ICH progression, and hematoma was detected by magnetic resonance imaging (MRI). Western blot and immunofluorescence were used to evaluate the expression and location of fractalkine (FKN) after ICH. Erythrophagocytosis assay was performed to study the specific mechanism of action of FKN in hematoma clearance. Small interfering RNA (siRNA) transfection was used to explore the effect of peroxisome proliferator-activated receptor-γ (PPAR-γ) on hematoma absorption. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum FKN concentration in ICH patients.
FKN was found to be significantly increased around the hematoma in a mouse model after ICH. With its unique receptor CX3CR1 in microglia, FKN significantly decreased the hematoma size and Hb content, and improved neurological deficits in vivo. Further, FKN could enhance erythrophagocytosis of microglia in vitro via the CD163/ hemeoxygenase-1 (HO-1) axis, while AZD8797 (a specific CX3CR1 inhibitor) reversed this effect. Moreover, PPAR-γ was found to mediate the increase in the CD163/HO-1 axis expression and erythrophagocytosis induced by FKN in microglia. Of note, a higher serum FKN level was found to be associated with better hematoma resolution in ICH patients.
We systematically identified that FKN may be a potential therapeutic target to improve hematoma absorption and we shed light on ICH treatment.
血肿导致脑出血（ICH）后进行性神经功能缺损和不良预后。广泛认为早期清除血肿对于限制损伤和改善临床预后至关重要。CD163，又名小胶质细胞上的血红蛋白（Hb）清道夫受体，在血肿吸收中起关键作用，但神经元上的 CD163 允许 Hb 摄取并导致神经毒性。在这项研究中，我们专注于如何专门促进小胶质细胞而不是神经元 CD163 介导的 Hb 摄取和血肿吸收。
使用 RNA 测序探索参与 ICH 进展的潜在分子，并用磁共振成像（MRI）检测血肿。Western blot 和免疫荧光用于评估 ICH 后 fractalkine（FKN）的表达和定位。红细胞吞噬作用测定用于研究 FKN 在血肿清除中的具体作用机制。使用小干扰 RNA（siRNA）转染探索过氧化物酶体增殖物激活受体-γ（PPAR-γ）对血肿吸收的影响。酶联免疫吸附试验（ELISA）用于测定 ICH 患者血清中 FKN 浓度。
在 ICH 后小鼠模型中，发现 FKN 在血肿周围明显增加。FKN 及其在小胶质细胞上的独特受体 CX3CR1，可显著减小血肿体积和 Hb 含量，并改善体内神经功能缺损。此外，FKN 可以通过 CD163/血红素加氧酶-1（HO-1）轴增强小胶质细胞的红细胞吞噬作用，而 AZD8797（一种特异性 CX3CR1 抑制剂）则逆转了这种作用。此外，发现 PPAR-γ介导 FKN 诱导的小胶质细胞中 CD163/HO-1 轴表达和红细胞吞噬作用的增加。值得注意的是，ICH 患者血清中较高的 FKN 水平与血肿溶解较好相关。
我们系统地鉴定出 FKN 可能是改善血肿吸收的潜在治疗靶点，并为 ICH 治疗提供了启示。
