Abstract: BACKGROUND: MiR-204-5p is a potential biomarker of neuropathic pain, but its role and mechanism in neuropathic pain have not been clarified.
OBJECTIVE: To investigate the effect and molecular mechanism of miR-204-5p on neuropathic pain caused by chronic constriction injury in rats. 
METHODS: (1) A total of 90 male Sprague-Dawley rats were randomized into sham group, model group, empty vector group, miR-204-5p overexpression group, scramble group, and aurora kinase B (AURKB) interference group, with 15 rats in each group. The rat neuropathic pain model was established based on chronic constriction injury of the sciatic nerve. After modeling, rats in each group were injected with the following recombinant lentiviruses (empty vector, miR-204-5p 
overexpression vector, scrambled shRNA, AURKB shRNA), and the injection volume was 1 μg. The expression levels of miR-204-5p and AURKB mRNAs in the dorsal root ganglia of rats were measured by RT-qPCR before surgery and on the 7th and 14th days after surgery. Mechanical allodynia and thermal hyperalgesia were assessed by paw withdrawal threshold and paw withdrawal latency before surgery and on the 3rd, 7th, 14th, and 21st days after surgery. The levels of inflammatory cytokines in dorsal root ganglion tissues of rats were determined by ELISA on the 7th day after surgery. (2) 100 nmol/L lipopolysaccharide was used to induce inflammation in rat microglia cell line (HAPI). The cells were divided into control group, lipopolysaccharide group, lipopolysaccharide+NC mimic group, lipopolysaccharide+miR-204-5p mimic group, lipopolysaccharide+miR-204-5p mimic+empty vector group, lipopolysaccharide+miR-204-5p mimic+AURKB overexpression group. The levels of inflammatory cytokines in HAPI cells were detected using enzyme-linked immunosorbent assay. The expression levels of AURKB and Wnt/β-catenin pathway proteins in HAPI cells were detected by western blot assay. The targeting relationship between miR-204-5p and AURKB was verified by dual luciferase reporter gene assay. 
RESULTS AND CONCLUSION: Compared with the sham operation group, the expression of miR-204-5p in the dorsal root ganglion of rats with chronic constriction injury was significantly reduced. Compared with the model group, overexpression of miR-204-5p significantly increased the paw withdrawal threshold value and paw withdrawal latency. In rats with chronic constriction injury of the sciatic nerve and HAPI cells activated by lipopolysaccharide, overexpression of miR-204-5p could inhibit the secretion of inflammatory cytokines. The dual luciferase reporter gene confirmed AURKB as the downstream target gene of miR-204-5p. The expression level of AURKB mRNA was significantly increased in the dorsal root ganglion of rats with chronic constriction injury. Whereas silencing of AURKB could inhibit neuropathic pain and neuroinflammation. In lipopolysaccharide-induced HAPI cells, the overexpression of miR-204-5p reduced the expression of Wnt/β-catenin signaling pathway proteins by inhibiting the expression of AURKB, thereby reducing neuroinflammation. All the findings indicate that miR-204-5p relieves neuropathic pain in rats with chronic constriction injury of the sciatic nerve through the AURKB/Wnt/β-catenin pathway.

Key words: miR-204-5p, neuropathic pain, AURKB, chronic constriction injury, rat, Wnt pathway