Department of Anesthesiology, Jinling Hospital, Medical School of Nanjing University, Nanjing, China.
Department of Medical Imaging, Jinling Hospital, Medical School of Nanjing University, Nanjing, China.
Brain Behav Immun. 2020 Oct;89:300-313. doi: 10.1016/j.bbi.2020.07.009. Epub 2020 Jul 17.
Activation of astrocytes and abnormal synaptic glutamate metabolism are closely associated with the induction and maintenance of neuropathic pain (NP), but the exact mechanism underlying this association remains unclear. N-myc downstream-regulated gene 2 (NDRG2), a novel tumor-suppressor protein and stress-response gene, is involved in the pathogenesis of several neurodegenerative diseases. However, its role in nociceptive transduction has rarely been investigated. Here, we found that NDRG2, which was mainly expressed in the astrocytes in the central nervous system (CNS), was increased in the spinal cord of a spinal nerve ligation (SNL) rat model for NP. Suppression of NDRG2 by intrathecal injection of an NDRG2-RNAi-adenovirus significantly alleviated SNL-induced mechanical and thermal hypersensitivity, as well as elevated astrocytic glutamate transporter 1 (GLT-1) expression and downregulated pro-inflammatory cytokine levels, in the spinal dorsal horn of rats on Day 10 after SNL. Furthermore, in lipopolysaccharide (LPS)-stimulated primary astrocytic cultures derived from neonatal rats, inhibition of NDRG2 significantly reversed both the LPS-induced activation of astrocytes and decreased expression of GLT-1. By contrast, overexpression of NDRG2 by an adenoviral vector carrying NDRG2 resulted in astrocytic activation, aberrant glutamatergic neurotransmission, and spontaneous nociceptive responses in rats. Intrathecal injection of AG490, which is an inhibitor of the Janus tyrosine kinase and signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway, significantly attenuated both mechanical and thermal hyperalgesia, as well as inhibited reactive astrocytes and restored normal expression levels of astrocytic GLT-1, in the spinal dorsal horn of NDRG2-overexpression rats. In conclusion, spinal astrocytic NDRG2 is critical in the maintenance of NP. Moreover, NDRG2 modulates astrocytic activation and inflammatory responses via regulating GLT-1 expression through the JAK/STAT3 signaling pathway. Our findings suggested that NDRG2 could be a novel therapeutic target for the treatment of NP.
星形胶质细胞的激活和异常的突触谷氨酸代谢与神经性疼痛(NP)的诱导和维持密切相关,但这种关联的确切机制尚不清楚。N- MYC 下游调节基因 2(NDRG2)是一种新型的肿瘤抑制蛋白和应激反应基因,参与了几种神经退行性疾病的发病机制。然而,其在伤害性感受转导中的作用很少被研究。在这里,我们发现 NDRG2 主要在中枢神经系统(CNS)的星形胶质细胞中表达,在 NP 的脊神经根结扎(SNL)大鼠模型的脊髓中增加。鞘内注射 NDRG2-RNAi-腺病毒抑制 NDRG2,可显著缓解 SNL 诱导的机械和热敏感性,以及升高的星形胶质细胞谷氨酸转运体 1(GLT-1)表达和下调促炎细胞因子水平,在 SNL 后第 10 天的大鼠脊髓背角。此外,在由新生大鼠原代星形胶质细胞培养物中,抑制 NDRG2 可显著逆转 LPS 诱导的星形胶质细胞激活和 GLT-1 表达下调。相反,通过携带 NDRG2 的腺病毒载体过表达 NDRG2 可导致大鼠星形胶质细胞激活、异常的谷氨酸能神经传递和自发性痛觉反应。鞘内注射 Janus 酪氨酸激酶和信号转导子和转录激活子 3(JAK/STAT3)信号通路的抑制剂 AG490,可显著减轻机械性和热痛觉过敏,并抑制反应性星形胶质细胞,恢复 NDRG2 过表达大鼠脊髓背角星形胶质细胞 GLT-1 的正常表达水平。总之,脊髓星形胶质细胞 NDRG2 在 NP 的维持中至关重要。此外,NDRG2 通过调节 GLT-1 表达来调节星形胶质细胞的激活和炎症反应,通过 JAK/STAT3 信号通路。我们的研究结果表明,NDRG2 可能是治疗 NP 的一种新的治疗靶点。