Luo Dan, Chen Lei, Yu Baoping
Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, China; Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China.
Department of Gastroenterology, Renmin Hospital of Wuhan University, Wuhan, China; Key Laboratory of Hubei Province for Digestive System Diseases, Wuhan, China.
Biochem Biophys Res Commun. 2017 Jun 17;488(1):204-210. doi: 10.1016/j.bbrc.2017.05.036. Epub 2017 May 5.
The mechanisms underlying chronic and persistent pain associated with chronic pancreatitis (CP) are not completely understood. The cholinergic system is one of the major neural pathways of the pancreas. Meanwhile, this system plays an important role in chronic pain. We hypothesized that the high affinity choline transporter CHT1, which is a main determinant of cholinergic signaling capacity, is involved in regulating pain associated with CP.
CP was induced by intraductal injection of 2% trinitrobenzene sulfonic acid (TNBS) in Sprague-Dawley rats. Pathological examination was used to evaluate the inflammation of pancreas and hyperalgesia was assessed by measuring the number of withdrawal events evoked by application of the von Frey filaments. CHT1 expression in pancreas-specific dorsal root ganglia (DRGs) was assessed through immunohistochemistry and western blotting. We also intraperitoneally injected the rats with hemicholinium-3 (HC-3, a specific inhibitor of CHT1). Then we observed its effects on the visceral hyperalgesia induced by CP, and on the acetylcholine (ACh) levels in the DRGs through using an acetylcholine/acetylcholinesterase assay kit.
Signs of CP were observed 21 days after TNBS injection. Rats subjected to TNBS infusions had increased sensitivity to mechanical stimulation of the abdomen. CHT1-immunoreactive cells were increased in the DRGs from rats with CP compared to naive or sham rats. Western blots indicated that CHT1 expression was significantly up-regulated in TNBS-treated rats when compared to naive or sham-operated rats at all time points following surgery. In the TNBS group, CHT1 expression was higher on day 28 than on day 7 or day 14, but there was no statistical difference in CHT1 expression on day 28 vs. day 21. Treatment with HC-3 (60 μg/kg, 80 μg/kg, or 100 μg/kg) markedly enhanced the mechanical hyperalgesia and reduced ACh levels in a dose-dependent manner in rats with CP.
We report for the first time that CHT1 may be involved in pain modulation in CP, as it plays an important role in pain inhibition. Increased CHT1 activity or the up-regulation of its expression may be used to treat pain in patients with CP.
与慢性胰腺炎（CP）相关的慢性持续性疼痛的潜在机制尚未完全明确。胆碱能系统是胰腺的主要神经通路之一。同时，该系统在慢性疼痛中起重要作用。我们推测，作为胆碱能信号传导能力的主要决定因素，高亲和力胆碱转运体CHT1参与调节与CP相关的疼痛。
通过向Sprague-Dawley大鼠胰管内注射2%三硝基苯磺酸（TNBS）诱导CP。采用病理检查评估胰腺炎症，通过测量应用von Frey细丝诱发的缩足反应次数评估痛觉过敏。通过免疫组织化学和蛋白质印迹法评估胰腺特异性背根神经节（DRG）中CHT1的表达。我们还向大鼠腹腔注射半胱氨酸-3（HC-3，CHT1的特异性抑制剂）。然后观察其对CP诱导的内脏痛觉过敏的影响，以及通过使用乙酰胆碱/乙酰胆碱酯酶检测试剂盒对DRG中乙酰胆碱（ACh）水平的影响。
TNBS注射21天后观察到CP的体征。接受TNBS输注的大鼠对腹部机械刺激的敏感性增加。与未处理或假手术大鼠相比，CP大鼠DRG中CHT1免疫反应性细胞增加。蛋白质印迹表明，与未处理或假手术大鼠相比，TNBS处理的大鼠在手术后所有时间点CHT1表达均显著上调。在TNBS组中，第28天CHT1表达高于第7天或第14天，但第28天与第21天CHT1表达无统计学差异。用HC-3（60μg/kg、80μg/kg或100μg/kg）处理以剂量依赖方式显著增强CP大鼠的机械性痛觉过敏并降低ACh水平。
我们首次报道CHT1可能参与CP的疼痛调节，因为它在疼痛抑制中起重要作用。CHT1活性增加或其表达上调可用于治疗CP患者的疼痛。
