Hematoma is a crucial factor leading to poor prognosis after intracerebral hemorrhage (ICH). Promoting microglial phagocytosis to enhance hematoma resolution may be an important therapeutic target for recovery after ICH. C-C chemokine receptor 4 (CCR4) is important for regulating immune balance in the central nervous system. However, whether CCR4 activation can attenuate hematoma after ICH remains unknown. We aimed to evaluate whether CCL17 (a specific ligand of CCR4) treatment can promote hematoma resolution through CCR4/ERK/Nrf2/CD163 pathway after ICH. A total of 261 adult male CD1 mice were used. Mice were subjected to intrastriatal injection of autologous blood to induce ICH and randomly assigned to receive recombinant CCL17 (rCCL17) or vehicle which was administered intranasally at 1 h after ICH. To elucidate the underlying mechanism, C021, a selective inhibitor of CCR4 and ML385 and a selective inhibitor of Nrf2 were administered 1 h prior to ICH induction. Clustered regularly interspaced short palindromic repeats (CRISPR) knockout for CD163 was administered by intracerebroventricular injection at 48 h before ICH. Brain edema, short- and long-term neurobehavior evaluation, hematoma volume, hemoglobin content, western blot, and immunofluorescence staining were performed. Endogenous CCL17, CCR4, and CD163 expression increased and peaked at 72 h after ICH. CCR4 was expressed by microglia. CCR4 activation with rCCL17 significantly improved neurobehavioral scores and reduced hematoma volume and brain edema compared with vehicle. Moreover, rCCL17 treatment significantly promoted phosphorylation of ERK1/2, increased the expression Nrf2, and upregulated CD163 expression after ICH. The protective effects of rCCL17 were abolished by administration of C021, ML385, and CD163 CRISPR knockout. This study demonstrated that CCR4 activation with rCCL17 promoted hematoma resolution by increasing CD163 expression and CCR4/ERK/Nrf2 pathway activation after ICH, thereby reducing brain edema and improving neurological function. Overall, our study suggests that CCR4 activation may be a potential therapeutic strategy to attenuate hematoma in early brain injury after ICH.

血肿是导致脑出血（ICH）后预后不良的关键因素。促进小胶质细胞吞噬作用以增强血肿消退可能是 ICH 后恢复的重要治疗靶点。CC 趋化因子受体 4 (CCR4) 对调节中枢神经系统的免疫平衡很重要。然而，CCR4 激活是否可以减轻 ICH 后的血肿仍然未知。我们旨在评估 CCL17（CCR4 的特定配体）治疗是否可以通过 ICH 后的 CCR4/ERK/Nrf2/CD163 途径促进血肿消退。总共使用了 261 只成年雄性 CD1 小鼠。小鼠接受自体血纹状体内注射以诱导 ICH 并随机分配接受重组 CCL17 (rCCL17) 或在 ICH 后 1 小时鼻内给药的载体。为了阐明潜在的机制，C021，在 ICH 诱导前 1 小时给予 CCR4 和 ML385 的选择性抑制剂以及 Nrf2 的选择性抑制剂。在 ICH 前 48 小时通过脑室内注射施用 CD163 的成簇规则间隔短回文重复序列 (CRISPR) 敲除。进行脑水肿、短期和长期神经行为评估、血肿体积、血红蛋白含量、蛋白质印迹和免疫荧光染色。内源性 CCL17、CCR4 和 CD163 表达增加并在 ICH 后 72 小时达到峰值。CCR4 由小胶质细胞表达。与载体相比，用 rCCL17 激活 CCR4 可显着改善神经行为评分并减少血肿体积和脑水肿。此外，rCCL17 处理显着促进了 ERK1/2 的磷酸化，增加了 Nrf2 的表达，并在 ICH 后上调了 CD163 的表达。rCCL17 的保护作用被 C021、ML385 和 CD163 CRISPR 敲除后消除。本研究表明，用 rCCL17 激活 CCR4 通过增加 ICH 后 CD163 表达和 CCR4/ERK/Nrf2 通路激活促进血肿消退，从而减少脑水肿并改善神经功能。总体而言，我们的研究表明，CCR4 激活可能是减轻 ICH 后早期脑损伤血肿的潜在治疗策略。