The PRMT2/FOXA2/miR-323-3p/Kv2.1 signaling axis in sensory neurons controls neuropathic pain

Although miRNA-mediated epigenetic regulation has been investigated as a potential therapeutic strategy for diseases, its exact functional regulatory contributions to neuropathic pain have not yet been fully elucidated. Herein, we revealed miR-323-3p as a key functional noncoding RNA in modulating trigeminal neuropathic pain. Through combined high-throughput sequencing and qPCR analysis, we revealed that miR-323-3p was most significantly upregulated in the injured trigeminal ganglion (TG). The administration of a miR-323-3p antagomir via intra-TG injection or blockade of miR-323-3p through lentiviral delivery specifically targeting neurons in injured TGs suppressed established trigeminal neuropathic pain. While miR-323-3p inhibition had no effect on inflammatory pain, local induction of miR-323-3p in naive TGs directly elicited pain hypersensitivity. Mechanistically, nerve injury caused upregulated protein expression of arginine methyltransferase 2 (PRMT2), which promotes asymmetric demethylation of H3R8 (H3R8me2a), thereby facilitating the binding of the forkhead box A2 (FOXA2) transcription factor to the miR-323-3p promoter and resulting in the upregulation of miR-323-3p expression. Furthermore, the increase in miR-323-3p expression induced significant reductions in Kv2.1 protein expression and channel currents, resulting in TG neuronal hyperexcitability. Conversely, downregulation of miR-323-3p in the injured TG reversed the decrease in Kv2.1 expression and attenuated nerve injury-induced mechanical allodynia. Thus, miR-323-3p upregulation is causally involved in the development of trigeminal neuropathic pain through the regulation of Kv2.1 channels in the TG. The mechanistic understanding of the PRMT2/FOXA2/miR-323-3p/Kv2.1 signaling axis in sensory neurons may enable the discovery of new therapeutic targets for neuropathic pain management.尽管微RNA（miRNA）介导的表观遗传调控已被研究作为疾病的潜在治疗策略，但其对神经病理性疼痛的确切功能性调控作用尚未完全阐明。在此，我们揭示miR-323-3p是调控三叉神经病理性疼痛的关键功能性非编码RNA。通过联合高通量测序与实时定量聚合酶链反应（qPCR）分析，我们发现miR-323-3p在损伤的三叉神经节（TG）中表达上调最为显著。通过三叉神经节内注射miR-323-3p拮抗剂（antagomir），或通过靶向损伤三叉神经节神经元的慢病毒递送阻断miR-323-3p，均可抑制已建立的三叉神经病理性疼痛。尽管抑制miR-323-3p对炎性疼痛无影响，但在未受损伤的三叉神经节中局部诱导miR-323-3p表达，可直接引发痛觉超敏。机制研究表明，神经损伤可导致精氨酸甲基转移酶2（PRMT2）的蛋白表达上调，其可促进组蛋白H3精氨酸8位不对称二甲基化（H3R8me2a），进而促进叉头框蛋白A2（FOXA2）转录因子与miR-323-3p启动子结合，最终导致miR-323-3p表达上调。此外，miR-323-3p表达升高可显著降低钾离子通道2.1（Kv2.1）的蛋白表达与通道电流，进而引发三叉神经节神经元过度兴奋。反之，在损伤的三叉神经节中下调miR-323-3p表达，可逆转钾离子通道2.1（Kv2.1）表达的降低，并减轻神经损伤诱导的机械性痛觉超敏。综上，miR-323-3p表达上调通过调控三叉神经节内的钾离子通道2.1（Kv2.1）通道，因果性地参与了三叉神经病理性疼痛的发生发展。阐明感觉神经元中PRMT2/FOXA2/miR-323-3p/Kv2.1信号轴的调控机制，可为神经病理性疼痛的治疗发掘新的靶点。