Ji-Tian Xu

Neuropathic pain is frequently comorbidity with cognitive deficits. Neuralized1 (Neurl1)-mediated ubiquitination of CPEB3 in the hippocampus is critical in learning and memory. However, the role of Neurl1 in the cognitive impairment in neuropathic pain remains elusive. Herein, we found that lumbar 5 spinal nerve ligation (SNL) in male rat-induced neuropathic pain was followed by learning and memory deficits and LTP impairment in the hippocampus. The Neurl1 expression in the hippocampal CA1 was decreased after SNL. And this decrease paralleled the reduction of ubiquitinated-CPEB3 level and reduced production of GluA1 and GluA2. Overexpression of Neurl1 in the CA1 rescued cognitive deficits and LTP impairment, and reversed the reduction of ubiquitinated-CPEB3 level and the decrease of GluA1 and GluA2 production following SNL. Specific knockdown of Neurl1 or CPEB3 in bilateral hippocampal CA1 in naïve rats resulted in cognitive deficits and impairment of synaptic plasticity. The rescued cognitive function and synaptic plasticity by the treatment of overexpression of Neurl1 before SNL were counteracted by the knockdown of CPEB3 in the CA1. Collectively, the above results suggest that the downregulation of Neurl1 through reducing CPEB3 ubiquitination and, in turn, repressing GluA1 and GluA2 production and mediating synaptic plasticity impairment in hippocampal CA1 leads to the genesis of cognitive deficits in neuropathic pain.

Compelling evidence has shown that Neuralized1 (Neurl1) facilitates hippocampal-dependent memory storage by modulating cytoplasmic polyadenylation element-binding protein 3 (CPEB3)-dependent protein synthesis. In the current study, we investigated the role of Neurl1 in the pathogenesis of neuropathic pain and the underlying mechanisms. The neuropathic pain was evaluated by lumbar 5 spinal nerve ligation (SNL) in rats. Immunofluorescence staining, Western blotting, qRT-PCR, and coimmunoprecipitation (Co-IP) were performed to investigate the underlying mechanisms. Our results showed that SNL led to an increase of Neurl1 in the spinal dorsal horn. Spinal microinjection of AAV-EGFP-Neurl1 shRNA alleviated mechanical allodynia; decreased the level of CPEB3 ubiquitination; inhibited the production of GluA1, GluA2, and PSD95; and reduced GluA1-containing AMPA receptors in the membrane of the dorsal horn following SNL. Knockdown of spinal CPEB3 decreased the production of GluA1, GluA2, and PSD95 in the dorsal horn and attenuated abnormal pain after SNL. Overexpression of Neurl1 in the dorsal horn resulted in pain-related hypersensitivity in naïve rats; raised the level of CPEB3 ubiquitination; increased the production of GluA1, GluA2, and PSD95; and augmented GluA1-containing AMPA receptors in the membrane in the dorsal horn. Moreover, spinal Neurl1 overexpression-induced mechanical allodynia in naïve rats was partially reversed by repeated intrathecal injections of CPEB3 siRNA. Collectively, our results suggest that SNL-induced upregulation of Neurl1 through CPEB3 ubiquitination-dependent production of GluA1, GluA2, and PSD95 in the dorsal horn contributes to the pathogenesis of neuropathic pain in rats. Targeting spinal Neurl1 might be a promising therapeutic strategy for the treatment of neuropathic pain.

Aims: Lysine‐specific demethylase 6B (KDM6B) serves as a key mediator of gene transcription. It regulates expression of proinflammatory cytokines and chemokines in variety of diseases. Herein, the role and the underlying mechanisms of KDM6B in inflammatory pain were studied.Methods: The inflammatory pain was conducted by intraplantar injection of complete Freund's adjuvant (CFA) in rats. Immunofluorescence, Western blotting, qRT‐PCR, and chromatin immunoprecipitation (ChIP)‐PCR were performed to investigate the underlying mechanisms.Results: CFA injection led to upregulation of KDM6B and decrease in the level of H3K27me3 in the dorsal root ganglia (DRG) and spinal dorsal horn. The mechanical allodynia and thermal hyperalgesia following CFA were alleviated by the treatment of intrathecal injection of GSK‐J4, and by microinjection of AAV‐EGFP‐KDM6B shRNA in the sciatic nerve or in lumbar 5 dorsal horn. The increased production of tumor necrosis factor‐α (TNF‐α) following CFA in the DRGs and dorsal horn was inhibited by these treatments. ChIP‐PCR showed that CFA‐induced increased binding of nuclear factor κB with TNF‐α promoter was repressed by the treatment of microinjection of AAV‐EGFP‐KDM6B shRNA.Conclusions: These results suggest that upregulated KDM6B via facilitating TNF‐α expression in the DRG and spinal dorsal horn aggravates inflammatory pain.

Aims: Gastric hypersensitivity (GHS) is a characteristic pathogenesis of functional dyspepsia (FD). DNA methyltransferase 1 (DNMT1) and acid‐sensing ion channel 1 (ASIC1) are associated with GHS induced by prenatal maternal stress (PMS). The aim of this study was to investigate the mechanism of DNMT1 mediating the analgesic effect of folic acid (FA) on PMS‐induced GHS.Methods: GHS was quantified by electromyogram recordings. The expression of DNMT1, DNMT3a, DNMT3b, and ASIC1 were detected by western blot, RT‐PCR, and double‐immunofluorescence. Neuronal excitability and proton‐elicited currents of dorsal root ganglion (DRG) neurons were determined by whole‐cell patch clamp recordings.Results: The expression of DNMT1, but not DNMT3a or DNMT3b, was decreased in DRGs of PMS rats. FA alleviated PMS‐induced GHS and hyperexcitability of DRG neurons. FA also increased DNMT1 and decreased ASIC1 expression and sensitivity. Intrathecal injection of DNMT1 inhibitor DC‐517 attenuated the effect of FA on GHS alleviation and ASIC1 downregulation. Overexpression of DNMT1 with lentivirus not only rescued ASIC1 upregulation and hypersensitivity, but also alleviated GHS and hyperexcitability of DRG neurons induced by PMS.Conclusions: These results indicate that increased DNMT1 contributes to the analgesic effect of FA on PMS‐induced GHS by reducing ASIC1 expression and sensitivity.