Naringenin alleviates spinal cord injury by ameliorating macrophage/microglia autophagy via progranulin stabilisation.

BACKGROUND

Autophagy plays a crucial role in the recovery of neural function after spinal cord injury (SCI) by modulating the inflammatory microenvironment. Naringenin (NGN) is a flavanone with anti-inflammatory activity; however, the effects and specific mechanisms of NGN on autophagy in SCI remain unclear.

PURPOSE: To elucidate the therapeutic effect of NGN on SCI and its role in modulating macrophage/microglia autophagy by stabilising progranulin (PGRN).

METHODS

A traumatic SCI mouse model was established via spinal cord clamping. Motor function was assessed by the Basso Mouse Scale, inclined grid test, and footprint analysis. Tissue inflammation, apoptosis, and autophagy were evaluated via enzyme linked immunosorbent assay, western blotting, and immunofluorescence analysis. The LC3-GFP-mCherry system and transmission electron microscopy were used to assess autophagic flux in vitro, and the neuroprotective effects of NGN were evaluated using a cell co-culture system. Interactions between NGN and PGRN were analysed by molecular docking, thermal shift, and protein degradation assays. The PGRN-dependent therapeutic potential of NGN was validated using Grn-/- mice.

RESULTS

Administration of NGN orally ameliorated the recovery of locomotor function in SCI mice; attenuated the inflammatory response and improved autophagic flux in injured spinal cord tissue. In vitro, NGN enhanced cell proliferation, improved autophagic flux, and suppressed the inflammatory response in BV2 cells. Chloroquine pretreatment abolished NGN's anti-inflammation and neuroprotective effects, highlighting the involvement of autophagy. Mechanistically, we identified PGRN as a novel binding protein with NGN. NGN upregulated PGRN at the post-translational level in BV2. Furthermore, PGRN deficiency blocked the therapeutic effects of NGN in SCI mice.

CONCLUSION

These findings highlight a novel mechanism by which NGN critically regulates autophagy-related inflammation in macrophage/microglia through interaction with PGRN. Overall, NGN shows promising potential as a therapeutic SCI drug.