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. Overall design: mRNA profiles in rat TG tissue on day 14 after CCI-ION operation (n=3) or sham operation (n=3)