Zhang Yuhao, Laumet Geoffroy, Chen Shao-Rui, Hittelman Walter N, Pan Hui-Lin
From the Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine and.
Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.
J Biol Chem. 2015 Jun 5;290(23):14647-55. doi: 10.1074/jbc.M115.650218. Epub 2015 Apr 29.
Pannexin-1 (Panx1) is a large-pore membrane channel involved in the release of ATP and other signaling mediators. Little is known about the expression and functional role of Panx1 in the dorsal root ganglion (DRG) in the development of chronic neuropathic pain. In this study, we determined the epigenetic mechanism involved in increased Panx1 expression in the DRG after nerve injury. Spinal nerve ligation in rats significantly increased the mRNA and protein levels of Panx1 in the DRG but not in the spinal cord. Immunocytochemical labeling showed that Panx1 was primarily expressed in a subset of medium and large DRG neurons in control rats and that nerve injury markedly increased the number of Panx1-immunoreactive DRG neurons. Nerve injury significantly increased the enrichment of two activating histone marks (H3K4me2 and H3K9ac) and decreased the occupancy of two repressive histone marks (H3K9me2 and H3K27me3) around the promoter region of Panx1 in the DRG. However, nerve injury had no effect on the DNA methylation level around the Panx1 promoter in the DRG. Furthermore, intrathecal injection of the Panx1 blockers or Panx1-specific siRNA significantly reduced pain hypersensitivity induced by nerve injury. In addition, siRNA knockdown of Panx1 expression in a DRG cell line significantly reduced caspase-1 release induced by neuronal depolarization. Our findings suggest that nerve injury increases Panx1 expression levels in the DRG through altered histone modifications. Panx1 up-regulation contributes to the development of neuropathic pain and stimulation of inflammasome signaling.
泛素连接蛋白-1（Panx1）是一种大孔膜通道，参与三磷酸腺苷（ATP）和其他信号介质的释放。关于Panx1在慢性神经性疼痛发展过程中在背根神经节（DRG）中的表达及功能作用，人们了解甚少。在本研究中，我们确定了神经损伤后DRG中Panx1表达增加所涉及的表观遗传机制。大鼠脊神经结扎显著增加了DRG中Panx1的mRNA和蛋白水平，但脊髓中未增加。免疫细胞化学标记显示，在对照大鼠中，Panx1主要表达于中大型DRG神经元亚群，神经损伤显著增加了Panx1免疫反应性DRG神经元的数量。神经损伤显著增加了DRG中Panx1启动子区域周围两种激活组蛋白标记（H3K4me2和H3K9ac）的富集，并降低了两种抑制组蛋白标记（H3K9me2和H3K27me3）的占有率。然而，神经损伤对DRG中Panx1启动子周围的DNA甲基化水平没有影响。此外，鞘内注射Panx1阻滞剂或Panx1特异性小干扰RNA（siRNA）可显著降低神经损伤诱导的疼痛超敏反应。此外，在DRG细胞系中通过siRNA敲低Panx1表达可显著降低神经元去极化诱导的半胱天冬酶-1释放。我们的研究结果表明，神经损伤通过改变组蛋白修饰增加了DRG中Panx1的表达水平。Panx1上调有助于神经性疼痛的发展和炎性小体信号的激活。
