Lysine-specific demethylase 1 in primary sensory neurons participates in chronic compression of dorsal root ganglion–induced neuropathic pain

Low back and radicular pain syndromes, usually caused by local inflammation and irritation to the nerve root and dorsal root ganglion (DRG), are common throughout medical practice, but sufficient pain relief is scarce. In this study, we employed a chronic compression of DRG (CCD)–induced radicular pain model in rats to explore whether lysine-specific demethylase 1 (LSD1), a histone demethylase and transcriptional co-repressor, is involved in the pathological process of radicular pain. We found that LSD1 was expressed in various-sized DRG neurons by immunohistochemistry. CCD induced the upregulation of LSD1 in compressed L₄–L₅ DRGs. Moreover, either LSD1 small interfering RNAs or LSD1 inhibitor attenuated CCD–induced pain hypersensitivities. LSD1 was also upregulated in the injured lumbar 4 (L₄) DRG in a spinal nerve ligation (SNL)–induced neuropathic pain mouse model. Nevertheless, LSD1 was not altered in L₃–L₅ DRGs in complete Freund's adjuvant–induced inflammatory pain mouse model, paclitaxel– or streptozotocin–induced neuropathic pain models. Furthermore, knockdown of LSD1 in the injured L₄ DRG reversed SNL–induced pain hypersensitivities in mice. Therefore, we speculate that nerve injury induced the upregulation of LSD1 in the injured DRGs, which contributes to neuropathic pain hypersensitivities; thus, LSD1 may serve as a potential target for the treatment of radicular pain and neuropathic pain.