Spinal Sirtuin 3 Contributes to Electroacupuncture Analgesia in Mice with Chronic Constriction Injury-Induced Neuropathic Pain

Background: Electroacupuncture (EA) is a traditional Chinese therapeutic technique that has a beneficial effect on neuropathic pain; however, the specific mechanism remains unclear. In this study, we investigated whether EA inhibits spinal CA/calmodulin-dependent protein kinase II (CaMKIIα) phosphorylation through Sirtuin 3 (SIRT3) protein, thus relieving neuropathic pain.

Materials and methods: We used wild-type and SIRT3 knockout (SIRT3^-/-) mice and used chronic constriction injury (CCI) as a pain model. We performed Western blotting, immunostaining, von Frey, and Hargreaves tests to gather biochemical and behavioral data. Downregulation and overexpression and spinal SIRT3 protein were achieved by intraspinal injection of SIRT3 small interfering RNA and intraspinal injection of lentivirus-SIRT3. To test the hypothesis that CaMKIIα signaling was involved in the analgesic effects of EA, we expressed CaMKIIα-specific designer receptors exclusively activated by designer drugs (DREADDs) in the spinal dorsal horn (SDH) of mice.

Results: These results showed that the mechanical and thermal hyperalgesia induced by CCI was related to the decreased spinal SIRT3 expression in the SDH of mice. A significant reduction of mechanical and thermal thresholds was found in the SIRT3^-/- mice. SIRT3 overexpression or EA treatment alleviated CCI-induced neuropathic pain and prevented the spinal CaMKIIα phosphorylation. Most importantly, EA increased the expression of spinal SIRT3 protein in the SDH. Downregulation of spinal SIRT3 or CaMKIIα Gq-DREADD activation inhibited the regulatory effect of EA on neuropathic pain.

Conclusion: Our results showed that CaMKIIα phosphorylation was inhibited by spinal SIRT3 in neuropathic pain and that EA attenuated CCI-induced neuropathic pain mainly by upregulating spinal SIRT3 expression in the SDH of mice.