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N4‐Acetylcytidine (ac4C), a highly conserved post‐transcriptional machinery with extensive existence for RNA modification, plays versatile roles in various cellular processes and functions. However, the molecular mechanism by which ac4C modification mediates neuropathic pain remains elusive. Here, it is found that the enhanced ac4C modification promotes the recruitment of polysome in Vegfa mRNA and strengthens the translation efficiency following SNI. Nerve injury increases the expression of NAT10 and the interaction between NAT10 and Vegfa mRNA in the dorsal horn neurons, and the gain and loss of NAT10 function further confirm that NAT10 is involved in the ac4C modification in Vegfa mRNA and pain behavior. Moreover, the ac4C‐mediated VEGFA upregulation contributes to the central sensitivity and neuropathic pain induced by SNI or AAV‐hSyn‐NAT10. Finally, SNI promotes the binding of HNRNPK in Vegfa mRNA and subsequently recruits the NAT10. The enhanced interaction between HNRNPK and NAT10 contributes to the ac4C modification of Vegfa mRNA and neuropathic pain. These findings suggest that the enhanced interaction between HNRNPK and Vegfa mRNA upregulates the ac4C level by recruiting NAT10 and contributes to the central sensitivity and neuropathic pain following SNI. Blocking this cascade may be a novel therapeutic approach in patients with neuropathic pain. [ABSTRACT FROM AUTHOR]

Effective treatments for neuropathic pain are lacking due to our limited understanding of the mechanisms. The circRNAs are mainly enriched in the central nervous system. However, their function in various physiological and pathological conditions have yet to be determined. Here, we identified circFhit, an exon-intron circRNA expressed in GABAergic neurons, which reduced the inhibitory synaptic transmission in the spinal dorsal horn to mediate spared nerve injury-induced neuropathic pain. Moreover, we found that circFhit decreased the expression of GAD65 and induced hyperexcitation in NK1R+ neurons by promoting the expression of its parental gene Fhit in cis. Mechanistically, circFhit was directly bound to the intronic region of Fhit, and formed a circFhit/HNRNPK complex to promote Pol II phosphorylation and H2B monoubiquitination by recruiting CDK9 and RNF40 to the Fhit intron. In summary, we revealed that the exon-intron circFhit contributes to GABAergic neuron-mediated NK1R+ neuronal hyperexcitation and neuropathic pain via regulating Fhit in cis. [ABSTRACT FROM AUTHOR]

Background Although the action mechanism of antineoplastic agents is different, oxaliplatin, paclitaxel, or bortezomib as first-line antineoplastic drugs can induce painful neuropathy. In rodents, mechanical allodynia is a common phenotype of painful neuropathy for 3 chemotherapeutics. However, whether there is a common molecular involved in the different chemotherapeutics-induced painful peripheral neuropathy remains unclear. Methods Mechanical allodynia was tested by von Frey hairs following i.p. injection of vehicle, oxaliplatin, paclitaxel, or bortezomib in Sprague-Dawley rats. Reduced representation bisulfite sequencing and methylated DNA immunoprecipitation were used to detect the change of DNA methylation. Western blot, quantitative polymerase chain reaction, chromatin immunoprecipitation, and immunohistochemistry were employed to explore the molecular mechanisms. Results In 3 chemotherapeutic models, oxaliplatin, paclitaxel, or bortezomib accordantly upregulated the expression of transient receptor potential cation channel, subfamily C6 (TRPC6) mRNA and protein without affecting the DNA methylation level of TRPC6 gene in DRG. Inhibition of TRPC6 by using TRPC6 siRNA (i.t., 10 consecutive days) relieved mechanical allodynia significantly following application of chemotherapeutics. Furthermore, the downregulated recruitment of DNA methyltransferase 3 beta (DNMT3b) at paired box protein 6 (PAX6) gene led to the hypomethylation of PAX6 gene and increased PAX6 expression. Finally, the increased PAX6 via binding to the TPRC6 promoter contributes to the TRPC6 increase and mechanical allodynia following chemotherapeutics treatment. Conclusions The TRPC6 upregulation through DNMT3b-mediated PAX6 gene hypomethylation participated in mechanical allodynia following application of different chemotherapeutic drugs. [ABSTRACT FROM AUTHOR]

Palmitoylation of δ-catenin is critical to synapse plasticity and memory formation. We found that δ-catenin palmitoylation is also instrumental in the development of neuropathic pain. The abundances of palmitoylated δ-catenin and the palmitoyl acyltransferase DHHC3 were increased in dorsal root ganglion (DRG) sensory neurons in rat models of neuropathic pain. Inhibiting palmitoyl acyltransferases or decreasing δ-catenin abundance in the DRG by intrathecal injection of 2-bromopalmitate or shRNA, respectively, alleviated oxaliplatin or nerve injury-induced neuropathic pain in the rats. The palmitoylation of δ-catenin, which was induced by the inflammatory cytokine TNF-α, facilitated its interaction with the voltage-gated sodium channel Nav1.6 and the kinesin motor protein KIF3A, which promoted the trafficking of Nav1.6 to the plasma membrane in DRG neurons and contributed to mechanical hypersensitivity and allodynia in rats. These findings suggest that a palmitoylation-mediated KIF3A/δ-catenin/Nav1.6 complex enhances the transmission of mechanical and nociceptive signals; thus, blocking this mechanism may be therapeutic in patients with neuropathic pain. [ABSTRACT FROM AUTHOR]

Purpose: Bortezomib (BTZ), a widely used chemotherapeutic drug, is closely associated with the development of painful peripheral neuropathy, but the mechanism underlying the induction of this disorder by BTZ remains largely unclear. To examine this association, we have evaluated the activation of mitogen-activated protein kinase (MAPK) family members in the spinal dorsal horn and the role of tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) in BTZ-induced allodynia in rats. Methods: Male Sprague-Dawley rats were used as the model animals. The paw withdrawal test, in which mechanical stimuli (von Frey hairs) is applied to the plantar surface of the hindpaw, was used to determine any changes in the paw withdrawal threshold of the treated rats. A PE-10 catheter was placed intrathecally to deliver TNF-α neutralizing antibody, IL-1 receptor antagonist (IL-1ra) or the c-Jun N-terminal kinase (JNK) inhibitor SP600125. The mRNA levels of various cytokines were measured by real-time quantitative PCR. The expression of TNF-α, IL-1β and mitogen-activated protein kinase (MAPK) family members in the spinal dorsal horn was measured by western blot analysis and immunohistochemistry. All data were expressed as the mean ± standard error of the mean and analyzed using the SPSS version 13.0 software program. Results: The BTZ treatment induced an upsurge in the mRNA and protein levels of TNF-α in the neurons and IL-1β in the astrocytes in the spinal dorsal horn. It also significantly upregulated the phosphorylation of JNK but not of extracellular signal-regulated kinases (ERK) and p38-MAPK in astrocytes of the spinal dorsal horn. Inhibition of TNF-α or IL-1β ameliorated JNK activation and mechanical allodynia induced by BTZ. Co-administration of thalidomide (TNF-α synthesis inhibitor) and IL-1ra prevented BTZ-induced mechanical allodynia. Conclusion: Our results suggest that the TNF-α or IL-1β/JNK pathway in the spinal dorsal horn may play a critical role in the development of painful peripheral neuropathy induced by BTZ. [ABSTRACT FROM AUTHOR]

Background: The major dose-limiting toxicity of paclitaxel, one of the most commonly used drugs to treat solid tumor, is painful neuropathy. However, the molecular mechanisms underlying paclitaxel-induced painful neuropathy are largely unclarified.Methods: Paw withdrawal threshold was measured in the rats following intraperitoneal injection of paclitaxel. The qPCR, western blotting, protein or chromatin immunoprecipitation, ChIP-seq identification of NFATc2 binding sites, and microarray analysis were performed to explore the molecular mechanism.Results: We found that paclitaxel treatment increased the nuclear expression of NFATc2 in the spinal dorsal horn, and knockdown of NFATc2 with NFATc2 siRNA significantly attenuated the mechanical allodynia induced by paclitaxel. Further binding site analysis utilizing ChIP-seq assay combining with gene expression profile revealed a shift of NFATc2 binding site closer to TTS of target genes in dorsal horn after paclitaxel treatment. We further found that NFATc2 occupancy may directly upregulate the chemokine CXCL14 expression in dorsal horn, which was mediated by enhanced interaction between NFATc2 and p300 and consequently increased acetylation of histone H4 in CXCL14 promoter region. Also, knockdown of CXCL14 in dorsal horn significantly attenuated mechanical allodynia induced by paclitaxel.Conclusion: These results suggested that enhanced interaction between p300 and NFATc2 mediated the epigenetic upregulation of CXCL14 in the spinal dorsal horn, which contributed to the chemotherapeutic paclitaxel-induced chronic pain. [ABSTRACT FROM AUTHOR]

Circular RNAs are non-coding RNAs, and are enriched in the CNS. Dorsal horn neurons of the spinal cord contribute to pain-like hypersensitivity after nerve injury in rodents. Here we show that spinal nerve ligation is associated with an increase in expression of circAnks1a in dorsal horn neurons, in both the cytoplasm and the nucleus. Downregulation of circAnks1a by siRNA attenuates pain-like behaviour induced by nerve injury. In the cytoplasm, we show that circAnks1a promotes the interaction between transcription factor YBX1 and transportin-1, thus facilitating the nucleus translocation of YBX1. In the nucleus, circAnks1a binds directly to the Vegfb promoter, increases YBX1 recruitment to the Vegfb promoter, thereby facilitating transcription. Furthermore, cytoplasmic circAnks1a acts as a miRNA sponge in miR-324-3p-mediated posttranscriptional regulation of VEGFB expression. The upregulation of VEGFB contributes to increased excitability of dorsal horn neurons and pain behaviour induced by nerve injury. We propose that circAnks1a and VEGFB are regulators of neuropathic pain. Circular RNAs are non-coding RNAs that are enriched in the CNS, but their role in chronic pain is not known. Here the authors show that CircAnks1a in dorsal horn neurons contributes to pain-like hypersensitivity in a rodent model of neuropathic pain, via a VEGF mechanism. [ABSTRACT FROM AUTHOR]

Background: Studies showed that upregulation of Nav1.6 increased the neuronal excitability and participated in neuropathic pain in the dorsal root ganglion (DRG). However, the molecular mechanisms underlying Nav1.6 upregulation were not reported yet.Methods: The paw withdrawal threshold was measured in the rodents following lumbar 5 ventral root transection (L5-VRT). Then qPCR, western blotting, immunoprecipitation, immunohistochemistry, and chromatin immunoprecipitation assays were performed to explore the molecular mechanisms in vivo and in vitro.Results: We found that the levels of Nav1.6 and phosphorylated STAT3 were significantly increased in DRG neurons following L5-VRT, and TNF-α incubation also upregulated the Nav1.6 expression in cultured DRG neurons. Furthermore, immunoprecipitation and chromatin immunoprecipitation assays demonstrated that L5-VRT increased the binding of STAT3 to the Scn8a (encoding Nav1.6) promoter and the interaction between STAT3 and p300, which contributed to the enhanced transcription of Scn8a by increasing histone H4 acetylation in Scn8a promoter in DRG. Importantly, intraperitoneal injection of the TNF-α inhibitor thalidomide reduced the phosphorylation of STAT3 and decreased the recruitment of STAT3 and histone H4 hyperacetylation in the Scn8a promoter, thus subsequently attenuating Nav1.6 upregulation in DRG neurons and mechanical allodynia induced by L5-VRT.Conclusion: These results suggested a new mechanism for Nav1.6 upregulation involving TNF-α/STAT3 pathway activation and subsequent STAT3-mediated histone H4 hyperacetylation in the Scn8a promoter region in DRG, which contributed to L5-VRT-induced neuropathic pain. [ABSTRACT FROM AUTHOR]