Morusin Alleviates Spinal Cord Injury in Rats by Regulating Macrophage Reprogramming Through Targeting <scp>RELA</scp> and <scp>NRF2</scp>

Inflammatory responses and subsequent microglial polarization play a critical role in the secondary damage that follows spinal cord injury (SCI). Morusin, a natural flavonoid with anti-inflammatory properties, has therapeutic potential in SCI; however, its molecular mechanisms and direct targets remain unclear. This study aimed to elucidate both the neuroprotective effects of Morusin against SCI and the underlying mechanisms, with a particular focus on its role in modulating microglial/macrophage polarization. The therapeutic efficacy of Morusin was evaluated in a rat model of SCI using behavioral, histological, and immunofluorescence analyses. In vitro, its anti-inflammatory and polarization-modulating effects were examined in lipopolysaccharide (LPS)-stimulated BV2 microglia. Neuroprotection was assessed in a cellular co-culture system. To identify the direct target of Morusin, we integrated drug affinity responsive target stability with mass spectrometry and validated the findings using cellular thermal shift assay and siRNA knockdown. Administration of Morusin significantly improved functional recovery, attenuated neuroinflammation, and reduced tissue damage in SCI rats. In cellular assays, Morusin potently suppressed LPS-induced M1 polarization and enhanced IL-4-induced M2 polarization. Mechanistically, Morusin directly bound to RELA, inhibiting the NF-κB pathway, while concurrently activating the NRF2/HO-1 signaling axis. This study demonstrated that Morusin alleviates SCI by directly targeting RELA (p65) to inhibit NF-κB-driven M1 polarization, while simultaneously promoting NRF2/HO-1-mediated M2 polarization. These findings not only revealed a novel dual mechanism of action for Morusin but also underscored its potential as a lead compound for the targeted therapies against SCI.