神经病理性痛大鼠脊髓背角血管内皮生长因子与ERK信号通路的关系

Relationship between VEGF and ERK signaling pathway in spinal dorsal horns of rats with neuropathic pain

目的 评价神经病理性痛大鼠脊髓背角血管内皮生长因子（VEGF）与胞外信号调节激酶（ERK）信号通路的关系.方法 雄性SD大鼠20只,2月龄,体重160 ～ 320 g,采用随机数字表法,将其分为4组（n=5）：假手术组（S组）、神经病理性痛组（CCI组）、生理盐水组（NS组）和VEGF抗体组.S组仅暴露左侧坐骨神经但不进行结扎,其余各组采用坐骨神经慢性压迫性损伤（CCI）法制备神经病理性痛模型.VEGF抗体组于CCI术后2h开始鞘内注射VEGF抗体0.3 μg/15 μl,每2d注射1次,共4次;NS组给予等容量生理盐水.于CCI术前1d（T1）、CCI术后1、3、5、7 d（T2-5）时测定机械痛阈（PWMT）和热痛阈（PWTL）.痛阈测定后处死大鼠,取L4-6脊髓组织,分别采用免疫组化法和Westernblot法测定磷酸化ERK（p-ERK）表达.结果 与S组比较,CCI组和VEGF抗体组T2-5时PWMT和PWTL降低,脊髓背角p-ERK表达上调（P＜0.05）;与CCI组比较,VEGF抗体组T3-5时PWMT和PWTL升高,脊髓背角p-ERK表达下调（P＜0.05）.结论 脊髓背角VEGF通过激活ERK信号通路参与大鼠神经病理性痛的形成和维持.

Objective To evaluate the relationship between vascular endothelial growth factor （VEGF） and extracellular signal-regulated kinase （ERK） signaling pathway in spinal dorsal horns of rats with neuropathic pain.Methods Twenty male Sprague-Dawley rats,aged 2 months,weighing 160-320 g,were randomly divided into 4 groups （n =5 each）：sham operation group （group S）; chronic constrictive injury （CCI） group; normal saline group （NS group）; VEGF antibody group.Neuropathic pain was induced by CCI.The animals were anesthetized with intraperitoneal 10% chloral hydrate 350 mg/kg.The left sciatic nerve was exposed and 4 ligatures were placed on the sciatic nerve at 1 mm intervals.In group S,the left sciatic nerve was only exposed but not ligated.In VEGF antibody group,VEGF antibody 0.3μg/15 μl was injected intrathecally every 2 days for 4 times starting from 2 h after CCI,while the equal volume of normal saline was injected in NS group.Paw withdrawal threshold to von Frey filament stimulation （PWMT） and paw withdrawal latency to nociceptive thermal stimulation （PWTL） were measured at 1 day before CCI （T1）,and 1,3,5 and 7 days after CCI （T2-5）.The rats were sacrificed after PWMT and PWTL were measured and the L4-6 segments of the spinal cord were removed for determination of phosphorylated ERK （p-ERK） expression in spinal dorsal horns by immunohistochemistry and Western blot.Results Compared with group S,PWMT and PWTL were significantly decreased at T2-5,and the p-ERK expression in spinal dorsal horns was up-regulated in CCI and VEGF antibody groups （P 〈 0.05）.Compared with CCI group,PWMT and PWTL were significantly increased at T3-5,and the p-ERK expression in spinal dorsal horns was down-regualted in VEGF antibody group （P 〈 0.05）.Conclusion VEGF in the spinal dorsal horn is involved in the development and maintenance of neuropathic pain in rats through activating ERK signaling pathway.