Recombinant Artemin-Fc Fusion Protein Attenuates TLR4/NF-κB-Associated Neuroinflammation and Modulates Inhibitory/Excitatory Synaptic Marker Expression After Spinal Cord Injury.

AIMS: Spinal cord injury (SCI) can cause severe neurological dysfunction and the occurrence of chronic neuropathic pain, which can manifest as the occurrence of abnormal pain and hyperalgesia. Artemin (ARTN) is a member of the glial cell-derived neurotrophic factor (GDNF) family ligand and can improve neural injury and regulate the occurrence of neuropathic pain. However, the process by which ARTN regulates inflammation and the sensitization of the dorsal horn of the spinal cord related to pain after SCI is still unclear.

METHODS

ARTN-Fc fusion protein was constructed and administered intrathecally to mice after SCI. Motor recovery and pain-related behaviors were evaluated using behavioral, gait, electrophysiological, paw withdrawal latency, and formalin-induced Fos assays. Molecular changes were assessed by Western blotting, immunofluorescence, and immunohistochemistry. In vitro, a BV2-PC12 Transwell co-culture system was used to examine the effect of ARTN-Fc on activated microglia-mediated neuronal injury.

RESULTS

ARTN-Fc treatment significantly improved motor recovery and reduced thermal hyperalgesia after SCI. Mechanistically, ARTN-Fc promoted microglial M2 polarization, inhibited TLR4/NF-κB activation, suppressed pro-inflammatory cytokine expression, and attenuated NLRP3 inflammasome/pyroptosis-related signaling. In the spinal dorsal horn, ARTN-Fc increased inhibitory GABAergic markers, including vGAT and GAD1, while reducing the excitatory marker vGluT2, suggesting altered inhibitory/excitatory synaptic marker expression. In vitro, ARTN-Fc reduced neuronal apoptosis mediated by activated microglia.

CONCLUSION

Taken together, the results suggest that ARTN-Fc is a potential therapeutic agent for SCI repair and neuropathic pain treatment by inhibiting the TLR4/NF-κB pathway to suppress neuroinflammation and modulating inhibitory/excitatory synaptic marker expression in the spinal dorsal horn.