MicroRNA-6954-3p down-regulation contributes to orofacial neuropathic pain in mice via targeting voltage-gated sodium channel β2 subunit protein

The voltage-gated sodium channel β2 subunit protein (SCN2B) plays a crucial role in neuropathic pain. However, the role and mechanisms of SCN2B in orofacial neuropathic pain are still unclear. This study aimed to investigate the upstream regulatory mechanisms of SCN2B in the trigeminal ganglion (TG) underlying orofacial neuropathic pain. Chronic constriction injury of the infraorbital nerve (CCI-ION) of mice was performed to establish the model of orofacial neuropathic pain. Von-Frey filament test was performed to detect the head withdrawal threshold (HWT) of mice. RT-qPCR, WB, FISH, and IF were used to detect the expression and distribution of SCN2B and miR-6954-3p in the TG of mice. A luciferase activity assay was carried out to prove the binding between SCN2B mRNA and miR-6954-3p. After the CCI-ION surgery, the levels of Scn2b mRNA and protein significantly increased and miR-6954-3p decreased in the TG of mice with decreasing HWT. IF staining revealed that SCN2B was expressed specifically in the TG neurons. Silencing SCN2B in the TG of CCI-ION mice significantly increased the HWT. Importantly, the 3' untranslated region (UTR) of Scn2b mRNA was proved to bind with miR-6954-3p. FISH and IF staining demonstrated that miR-6954-3p was expressed in TG neurons and co-expressed with SCN2B. Furthermore, intra-ganglionic injection of miR-6954-3p agomir into the TG of CCI-ION mice resulted in the down-regulation of SCN2B and increased the HWT. These findings suggest that the down-regulation of miR-6954-3p in the TG promotes orofacial neuropathic pain by promoting SCN2B expression following trigeminal nerve injury. Perspective This study points to the important role of SCN2B in orofacial neuropathic pain. Furthermore, miR-6954-3p is proven to regulate the expression of SCN2B by binding to the 3' UTR of Scn2b mRNA. These findings indicate that SCN2B and miR-6954-3p are potential therapeutic targets for the treatment of orofacial neuropathic pain.