Farrerol confers neuroprotection in spinal cord injury by regulating macrophages/microglia polarization through the JAK2/STAT3 pathway

BACKGROUND AND AIMS: Spinal cord injury (SCI) causes secondary damage characterized by neuroinflammation and imbalanced macrophages/microglia polarization, worsening neuronal loss and functional decline. Farrerol (FAR), a natural flavonoid with anti-inflammatory properties, has not been studied for SCI treatment. This work assesses FAR's neuroprotection through macrophages/microglia polarization regulation and explores its mechanisms. METHODS: C57BL/6 mice with spinal cord injury were randomly assigned to three groups: Sham, SCI, and SCI + FAR. Motor function was evaluated using locomotor scoring, while lesion size, myelin integrity, and neuronal apoptosis were assessed via histology, immunofluorescence, and Western blot. Spinal inflammatory cytokine, macrophages/microglia activation, and polarization were analyzed by qRT-PCR, ELISA, immunofluorescence, and flow cytometry. LPS-stimulated BV2 microglia and BV2-HT22 co-cultures evaluated FAR's effects on cytokine secretion, macrophages/microglia phenotypes, and neuronal survival. Signaling mechanisms were further examined via Western blot and immunofluorescence. RESULTS: FAR treatment significantly enhanced motor recovery in SCI mice, evidenced by elevated Basso Mouse Scale (BMS) scores, increased inclined plane angles, improved swimming performance, and refined gait patterns. It reduced lesion area, preserved myelin integrity, and attenuated neuronal apoptosis. FAR downregulated pro-inflammatory cytokines (TNF-α, IL-1β, IL-6), suppressed macrophages/microglia hyperactivation while upregulating IL-10, and shifted M1/M2 polarization toward neuroprotective M2 phenotypes. In LPS-stimulated BV2 microglia, FAR attenuated inflammatory responses, inhibited M1 markers, enhanced M2 markers, and rescued HT22 neuronal apoptosis in co-cultures. These therapeutic effects may be mediated through suppression of JAK2/STAT3 phosphorylation. CONCLUSIONS: FAR promotes functional recovery after spinal cord injury by modulating macrophages/microglia M1/M2 polarization through JAK2/STAT3 pathway inhibition, thereby attenuating neuroinflammation and neuronal death. These findings provide novel evidence supporting targeted immunomodulation for SCI treatment.