Institute of Neuroscience, Laboratory for Translational Pain Medicine, Department of Neurobiology, Soochow University, Suzhou, Peoples Republic of China.
Am J Physiol Gastrointest Liver Physiol. 2013 May 1;304(9):G763-72. doi: 10.1152/ajpgi.00466.2012. Epub 2013 Feb 28.
The pathogenesis of pain in irritable bowel syndrome (IBS) is poorly understood, and treatment remains difficult. We have previously reported that colon-specific dorsal root ganglion (DRG) neurons were hyperactive in a rat model of IBS induced by neonatal colonic inflammation (NCI). This study was designed to examine plasticity of voltage-gated Na(+) channel activities and roles for the endogenous hydrogen sulfide-producing enzyme cystathionine β-synthetase (CBS) in chronic visceral hyperalgesia. Abdominal withdrawal reflex (AWR) scores were recorded in response to graded colorectal distention in adult male rats as a measure of visceral hypersensitivity. Colon-specific DRG neurons were labeled with 1,1'-dioleyl-3,3,3',3-tetramethylindocarbocyanine methanesulfonate and acutely dissociated for measuring Na(+) channel currents. Western blot analysis was employed to detect changes in expressions of voltage-gated Na(+) (Na(V)) channel subtype 1.7, Na(V)1.8, and CBS. NCI significantly increased AWR scores when compared with age-matched controls. NCI also led to an ~2.5-fold increase in Na(+) current density in colon-specific DRG neurons. Furthermore, NCI dramatically enhanced expression of Na(V)1.7, Na(V)1.8, and CBS in colon-related DRGs. CBS was colocalized with Na(V)1.7 or -1.8 in colon-specific DRG neurons. Administration of O-(carboxymethyl)hydroxylamine hemihydrochloride (AOAA), an inhibitor for CBS, remarkably suppressed Na(+) current density and reduced expression of Na(V)1.7 and Na(V)1.8. More importantly, intraperitoneal or intrathecal application of AOAA attenuated AWR scores in NCI rats in a dose-dependent manner. These data suggest that NCI enhances Na(+) channel activity of colon DRG neurons, which is most likely mediated by upregulation of CBS expression, thus identifying a potential target for treatment for chronic visceral pain in patients with IBS.
肠易激综合征（IBS）疼痛的发病机制尚不清楚，治疗仍然困难。我们之前报道过，在由新生结肠炎症（NCI）诱导的 IBS 大鼠模型中，结肠特异性背根神经节（DRG）神经元过度活跃。本研究旨在研究电压门控 Na(+)通道活性的可塑性以及内源性产生硫化氢的酶胱硫醚β-合酶（CBS）在慢性内脏痛觉过敏中的作用。通过记录成年雄性大鼠对分级结直肠扩张的腹部退缩反射（AWR）评分来作为内脏敏感性的指标。使用 1,1'-二油酰基-3,3,3',3-四甲基吲哚碳氰化物甲磺酸酯对结肠特异性 DRG 神经元进行标记，并进行急性分离以测量 Na(+)通道电流。采用 Western blot 分析检测电压门控 Na(+)（Na(V))通道亚型 1.7、Na(V)1.8 和 CBS 的表达变化。NCI 与年龄匹配的对照组相比，AWR 评分显著增加。NCI 还导致结肠特异性 DRG 神经元中 Na(+)电流密度增加约 2.5 倍。此外，NCI 还显著增强了与结肠相关的 DRG 中 Na(V)1.7、Na(V)1.8 和 CBS 的表达。CBS 与结肠特异性 DRG 神经元中的 Na(V)1.7 或 Na(V)1.8 共定位。CBS 的抑制剂 O-（羧甲基）羟胺半盐酸盐（AOAA）的给药显著抑制了 Na(+)电流密度，并降低了 Na(V)1.7 和 Na(V)1.8 的表达。更重要的是，腹腔内或鞘内给予 AOAA 以剂量依赖性方式减弱了 NCI 大鼠的 AWR 评分。这些数据表明，NCI 增强了结肠 DRG 神经元的 Na(+)通道活性，这很可能是通过上调 CBS 表达介导的，从而为 IBS 患者的慢性内脏疼痛治疗确定了一个潜在的靶点。
