Fisetin orchestrates neuroinflammation resolution and facilitates spinal cord injury recovery through enhanced autophagy in pro-inflammatory glial cells

Abstract

Background: Neuroinflammation, a critical component of the secondary injury cascade post-spinal cord injury, involves the activation of pro-inflammatory cells and release of inflammatory mediators. Resolution of neuroinflammation is closely linked to cellular autophagy. This study investigates the potential of Fisetin, a natural anti-inflammatory compound, to ameliorate neuroinflammation and confer spinal cord injury protection through the regulation of autophagy in pro-inflammatory cells.

Methods: Utilizing a rat T10 spinal cord injury model with distinct treatment groups (Sham, Fisetin-treated, and Fisetin combined with autophagy inhibitor), alongside in vitro models involving lipopolysaccharide (LPS)-stimulated microglial cell activation and co-culture with neurons, we employed techniques such as transcriptomic sequencing, histological assessments (immunofluorescence staining, etc.), molecular analyses (PCR, WB, ELISA, etc.), and behavioral evaluations to discern differences in neuroinflammation, autophagy, neuronal apoptosis, and neurological function recovery.

Results: Fisetin significantly augmented autophagic activity in injured spinal cord tissue, crucially contributing to neurological function recovery in spinal cord-injured rats. Fisetin's autophagy-dependent effects were associated with a reduction in neuronal apoptosis at the injury site. The treatment reduced the population of CD68+ and iNOS+ cells, coupled with decreased pro-inflammatory cytokines IL-6 and TNF-α levels, through autophagy-dependent pathways. Fisetin pre-treatment attenuated LPS-induced pro-inflammatory polarization of microglial cells, with this protective effect partially blocked by autophagy inhibition. Fisetin-induced autophagy in the injured spinal cord and pro-inflammatory microglial cells was associated with significant activation of AMPK and inhibition of mTOR.

Conclusion: Fisetin orchestrates enhanced autophagy in pro-inflammatory microglial cells through the AMPK-mTOR signaling pathway, thereby mitigating neuroinflammation and reducing the apoptotic effects of neuroinflammation on neurons. This mechanistic insight significantly contributes to the protection and recovery of neurological function following spinal cord injury, underscoring the vital nature of Fisetin as a potential therapeutic agent.

Keywords: AMPK; Apoptosis; Autophagy; Fisetin; Microglia; Spinal cord injury.