Transcription factor ETS proto-oncogene 1 contributes to neuropathic pain by regulating histone deacetylase 1 in primary afferent neurons

Involvement of HDAC2-mediated kcnq2/kcnq3 genes transcription repression activated by EREG/EGFR-ERK-Runx1 signaling in bone cancer pain

Bone cancer pain (BCP) represents a prevalent symptom among cancer patients with bone metastases, yet its underlying mechanisms remain elusive. This study investigated the transcriptional regulation mechanism of Kv7(KCNQ)/M potassium channels in DRG neurons and its involvement in the development of BCP in rats. We show that HDAC2-mediated transcriptional repression of kcnq2/kcnq3 genes, which encode Kv7(KCNQ)/M potassium channels in dorsal root ganglion (DRG), contributes to the sensitization of DRG neurons and the pathogenesis of BCP in rats. Also, HDAC2 requires the formation of a corepressor complex with MeCP2 and Sin3A to execute transcriptional regulation of kcnq2/kcnq3 genes. Moreover, EREG is identified as an upstream signal molecule for HDAC2-mediated kcnq2/kcnq3 genes transcription repression. Activation of EREG/EGFR-ERK-Runx1 signaling, followed by the induction of HDAC2-mediated transcriptional repression of kcnq2/kcnq3 genes in DRG neurons, leads to neuronal hyperexcitability and pain hypersensitivity in tumor-bearing rats. Consequently, the activation of EREG/EGFR-ERK-Runx1 signaling, along with the subsequent transcriptional repression of kcnq2/kcnq3 genes by HDAC2 in DRG neurons, underlies the sensitization of DRG neurons and the pathogenesis of BCP in rats. These findings uncover a potentially targetable mechanism contributing to bone metastasis-associated pain in cancer patients.

Spinal-Specific Super Enhancer in Neuropathic Pain

Dysfunctional gene expression in nociceptive pathways plays a critical role in the development and maintenance of neuropathic pain. Super enhancers (SEs), composed of a large cluster of transcriptional enhancers, are emerging as new players in the regulation of gene expression. However, whether SEs participate in nociceptive responses remains unknown. Here, we report a spinal-specific SE (SS-SE) that regulates chronic constriction injury (CCI)-induced neuropathic pain by driving Ntmt1 and Prrx2 transcription in dorsal horn neurons. Peripheral nerve injury significantly enhanced the activity of SS-SE and increased the expression of NTMT1 and PRRX2 in the dorsal horn of male mice in a bromodomain-containing protein 4 (BRD4)-dependent manner. Both intrathecal administration of a pharmacological BRD4 inhibitor JQ1 and CRISPR-Cas9-mediated SE deletion abolished the increased NTMT1 and PRRX2 in CCI mice and attenuated their nociceptive hypersensitivities. Furthermore, knocking down Ntmt1 or Prrx2 with siRNA suppressed the injury-induced elevation of phosphorylated extracellular-signal-regulated kinase (p-ERK) and glial fibrillary acidic protein (GFAP) expression in the dorsal horn and alleviated neuropathic pain behaviors. Mimicking the increase in spinal Ntmt1 or Prrx2 in naive mice increased p-ERK and GFAP expression and led to the genesis of neuropathic pain-like behavior. These results redefine our understanding of the regulation of pain-related genes and demonstrate that BRD4-driven increases in SS-SE activity is responsible for the genesis of neuropathic pain through the governance of NTMT1 and PRRX2 expression in dorsal horn neurons. Our findings highlight the therapeutic potential of BRD4 inhibitors for the treatment of neuropathic pain.SIGNIFICANCE STATEMENT SEs drive gene expression by recruiting master transcription factors, cofactors, and RNA polymerase, but their role in the development of neuropathic pain remains unknown. Here, we report that the activity of an SS-SE, located upstream of the genes Ntmt1 and Prrx2, was elevated in the dorsal horn of mice with neuropathic pain. SS-SE contributes to the genesis of neuropathic pain by driving expression of Ntmt1 and Prrx2 Both inhibition of SS-SE with a pharmacological BRD4 inhibitor and genetic deletion of SS-SE attenuated pain hypersensitivities. This study suggests an effective and novel therapeutic strategy for neuropathic pain.

The Epigenetics of Neuropathic Pain: A Systematic Update

Epigenetics deals with alterations to the gene expression that occur without change in the nucleotide sequence in the DNA. Various covalent modifications of the DNA and/or the surrounding histone proteins have been revealed, including DNA methylation, histone acetylation, and methylation, which can either stimulate or inhibit protein expression at the transcriptional level. In the past decade, an exponentially increasing amount of data has been published on the association between epigenetic changes and the pathomechanism of pain, including its most challenging form, neuropathic pain. Epigenetic regulation of the chromatin by writer, reader, and eraser proteins has been revealed for diverse protein targets involved in the pathomechanism of neuropathic pain. They include receptors, ion channels, transporters, enzymes, cytokines, chemokines, growth factors, inflammasome proteins, etc. Most work has been invested in clarifying the epigenetic downregulation of mu opioid receptors and various K+ channels, two types of structures mediating neuronal inhibition. Conversely, epigenetic upregulation has been revealed for glutamate receptors, growth factors, and lymphokines involved in neuronal excitation. All these data cannot only help better understand the development of neuropathic pain but outline epigenetic writers, readers, and erasers whose pharmacological inhibition may represent a novel option in the treatment of pain.

Circ_0059662 exerts a positive role in oxygen-glucose deprivation/reoxygenation-induced SK-N-SH cell injury

Circular RNA (circRNA) is identified as a potential regulator of ischemic stroke (IS) progression. Through GEO database screening, it was found that circ_0059662 was highly expressed in acute IS patients. However, whether circ_0059662 participated in the IS process has not been studied. Oxygen-glucose deprivation/reoxygenation (OGD/R)-induced SK-N-SH cells were established to mimic IS cell models. The expression of circ_0059662, miR-579-3p, and ETS proto-oncogene 1 (ETS1) was measured via quantitative real-time PCR. Cell counting kit 8 assay, EdU assay and flow cytometry were utilized to detect cell proliferation and apoptosis. Western blot was employed to measure protein expression. ELISA was used to detect the levels of inflammation factors, and oxidative stress was determined by assessing SOD activity and MDA level. The relationship between miR-579-3p and circ_0059662 or ETS1 was examined via dual-luciferase reporter assay, RNA pull-down assay and RIP assay. Circ_0059662 was a circular RNA with highly expression in OGD/R-induced SK-N-SH cells. In OGD/R-induced cell injury, circ_0059662 knockdown promoted cell proliferation, and inhibited cell apoptosis, inflammation and oxidative stress. Circ_0059662 served as miR-579-3p sponge to positively regulate ETS1 expression. MiR-579-3p inhibitor and ETS1 overexpression could reverse the inhibition effect of circ_0059662 knockdown on OGD/R-induced cell injury. Besides, MiR-579-3p also could relieve OGD/R-induced SK-N-SH cell apoptosis, inflammation and oxidative stress by targeting ETS1. Our findings indicated that circ_0059662 knockdown alleviated OGD/R-induced SK-N-SH cell injury by sponging miR-579-3p to regulate ETS1 expression.