Abstract: BACKGROUND: Previous animal studies have shown that riluzole can inhibit neuroinflammatory response after spinal cord injury and promote functional recovery in injured rats, but the study on whether it can regulate the expression of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in the acute stage is lacking. 
OBJECTIVE: To observe whether riluzole can reduce microglial pyroptosis and promote functional recovery after spinal cord injury by modulating NLRP3 inflammasome through animal experiments, histological experiments and molecular biology experiments.
METHODS: Female SD rats were divided into sham operation, model and riluzole groups, with 12 rats in each group. In addition to the sham operation group, T10 spinal cord injury was conducted in rats. The model group was treated with intraperitoneal administration of riluzole with solvent cyclodextrin. The riluzole group was treated with a 4 mg/kg dose of riluzole injection. The effect of riluzole on motor function recovery was assessed using the BBB score and inclined plane test. The recovery of sensory-evoked potential and motor-evoked potential was measured by electrophysiology. Hematoxylin-eosin staining was used to evaluate spinal cord tissue repair. The regulatory effects of riluzole on NLRP3, Caspase-1 and gasdermin D protein expression in spinal cord tissues were detected by western blot assay. ELISA was utilized to detect the expression levels of inflammatory factors interleukin-1β and interleukin-18. The effects of riluzole on the expression of NLRP3, Caspase-1, gasdermin D and interleukin-1β in microglial cells of the injured spinal cord were determined by immunofluorescence staining. 
RESULTS AND CONCLUSION: (1) At 35 days after spinal cord injury, BBB score and inclined plane test score in the riluzole group were higher than those in the model group (P < 0.05). (2) At 3 days after spinal cord injury, the protein expressions of NLRP3, cleaved Caspase-1, gasdermin D-N (N-terminal domain), interleukin-1β, and interleukin-18 in the spinal cord homogenate of the riluzole group were significantly lower than those of the model group (P < 0.05). (3) At 3 days after spinal cord injury, the fluorescence intensity of NLRP3, Caspase-1, gasdermin D and interleukin-1β in the riluzole group was significantly lower than that in the model group (P < 0.05). (4) At day 35 after spinal cord injury, hematoxylin-eosin staining showed that the area of spinal cord injury in the riluzole group was smaller than that in the model group. Electrophysiological tests showed that the latency periods of sensory-evoked potential and motor-evoked potential in the riluzole group were shorter than those in the model group, and the latency period of wave amplitude in the riluzole group was higher than that in the model group. (5) These results suggest that riluzole can promote the repair of injured spinal cord tissue, promote the repair of nerve conduction function, and further promote the recovery of motor function in rats with spinal cord injury, which may be achieved through the regulation of NLRP3 inflammasome and the reduction of microglial pyroptosis. 

Key words: riluzole, spinal cord injury, NLRP3, microglia, pyroptosis