CD22 exacerbates brain injury in subarachnoid hemorrhage by inhibiting microglial phagocytic function.

Abstract

Introduction: Subarachnoid hemorrhage (SAH) is a neurological emergency with a high mortality rate. The phagocytic and homeostatic functions of microglial cells play a crucial role after SAH. This study aims to investigate the mechanism of CD22-mediated abnormal microglial phagocytosis in brain injury caused by SAH.

Materials and methods: BV2 microglial cells were exposed to 10 µM oxyhemoglobin for 24 hours to establish an in vitro SAH model. After CD22 knockdown, cell viability was assessed using the cell counting kit-8. The microglial phagocytic function was evaluated using pHrodo Red E.coli BioParticles and fluorescence microscopy. The expression levels of Kruppel-like factor 4 (KLF4), miR-150-3p, and CD22 were analyzed by real-time quantitative reverse transcription polymerase chain reaction and Western blot analysis. The binding relationship of KLF4 to the miR-150-3p promoter and the binding relationship of miR-150-3p to the CD22 3'UTR sequence were analyzed. Overexpression of KLF4 and inhibition of miR-150-3p in SAH cells were conducted to validate the mechanism.

Results: SAH inhibited the microglial phagocytic function. CD22 was overexpressed in the SAH cell model. CD22 inhibition increased the microglial phagocytic function. miR-150-3p targeted and inhibited CD22 expression. Overexpression of miR-150-3p resulted in downregulation of CD22 and increased phagocytic function in microglial cells. KLF4 bound to the miR-150-3p promoter and promoted miR-150-3p expression. Overexpression of KLF4 reversed the inhibitory effect of miR-150-3p inhibition on phagocytic function in SAH cell model.

Conclusion: KLF4 enhances the microglial phagocytic function in SAH by promoting miR-150-3p and inhibiting CD22.