脊髓背角环磷酸腺苷直接激活的交换蛋白在大鼠炎性痛中的作用

Effect of exchange protein directly activated by cyclic adenosine monophosphate in the dorsal horn of the spinal cord on regulation of rat inflammatory pain

目的探讨大鼠脊髓背角环磷酸腺苷直接激活的交换蛋白(Epac)在炎性痛调节过程中的作用。方法清洁级健康成年雄性SD大鼠84只,3月龄,采用双侧后爪趾底皮下注射弗氏完全佐剂(CFA)100μL建立炎性痛模型。采用Western blot法于建模前及建模后1、3、6、9、14 d大鼠脊髓腰膨大检测Epacl、Epac2蛋白相对含量;采用免疫荧光法检测脊髓背角Epacl阳性细胞数。按随机数字表法分为三组:对照组(C组)、生理盐水组(NS组)和Epac激动剂8p-CPT-2′-O-Me-cAMP(8p-CPT)组,C组不做任何处理,NS组和8p-CPT组分别于建模后6 d,鞘内给予NS、8p-CPT 10μL。于建模前1 h、给药前1 h及给药后30 min、1 h、2 h和3 h测定热刺激缩足潜伏期(TWL),观察大鼠痛行为学变化;于给药后1 h采用免疫荧光法检测三组大鼠脊髓背角基因蛋白c-Fos阳性细胞数。结果建模后3、6 d腰膨大脊髓Epacl蛋白相对含量明显低于建模前和建模后1 d[(0.74±0.09)、(0.77±0.08)比(1.00±0.00)、(0.99±0.07),P<0.05],Epac2蛋白相对含量各时间点差异均无统计学意义(P>0.05)。建模后3、6、9、14 d脊髓背角Epac1阳性细胞数明显低于建模前[(34.25±4.99)个、(24.00±8.04)个、(31.50±3.51)个、(43.00±8.98)个比(61.75±4.99)个,P均<0.05],建模后3、6、9 d脊髓背角Epac1阳性细胞数明显低于建模后1 d[(34.25±4.99)个、(24.00±8.04)个、(31.50±3.51)个比(58.00±5.35)个,P均<0.05]。给药前1 h及给药后30 min、1 h、2 h和3 h NS组和8p-CPT组TWL均明显低于C组[(6.8±1.0)s、(7.1±0.8)s比(13.3±1.6)s,(7.3±0.9)s、(9.2±1.0)s比(13.2±1.5)s,(6.9±1.2)s、(9.9±1.3)s比(13.9±1.8)s,(7.0±0.7)s、(8.7±1.2)s比(13.2±1.2)s,(7.0±0.9)s、(7.1±0.9)s比(13.2±1.4)s,P均<0.05],给药后30 min、1 h和2 h 8p-CPT组TWL均明显高于NS组(P均<0.05)。给药后1 h NS组和8p-CPT组脊髓背角c-Fos阳性细胞数明显高于C组[(75.25±8.42)个、(40.50±6.81)个比(25.25±5.25)个,P均<0.05],8p-CPT组脊髓背角c-Fos阳性细胞数明显低于NS组(P<0.05)。结论CFA诱导的慢性炎性痛可以降低脊髓背角Epac1蛋白含量,引起局部神经元异常激活,增强外周伤害性刺激应激反应。

Objective To assess the effect of exchange protein directly activated by cyclic adenosine monophosphate(Epac)in the dorsal horn of the spinal cord on regulation of rat inflammatory pain.Methods A total of 84 clean grade healthy adult male Sprague-Dawley rats of three months of age were injected with 100μL of the Freund's complete adjuvant(CFA)into the double hind claws to establish the animal model of inflammatory pain.Western blot was performed to assay level of Epac1 and Epac2 protein in spinal intumescentia lumbalis in the rats.After that,rats were randomized into control(C),normal saline(NS)and Epac agonist 8p-CPT-2'-O-Me-cAMP(8p-CPT)groups.Rats in C group did not receive any treatments,whereas rats in the NS and 8p-CPT groups were treated with 10μL of 8p-CPT and Epac agonist,respectively,on Day 6 after model establishment.Thermal withdrawal latency(TWL)was measured 1 h before mode establishment,1 h before reagent administration,30 min,1 h,2 h,and 3 h after reagent administration to observe changes in rat pain behavior.Immunofluorescence was performed to detect number of c-Fos-positive cells in the spinal dorsal horn 1 h after reagent administration.Results Epac1 expression was significantly reduced on Day 3 and 6 after model establishment in the spinal intumescentia lumbalis compared to that of the control and Day 1 after model establishment(0.74±0.09 and 0.77±0.08 vs.1.00±0.00 and 0.99±0.07;P<0.05),whereas Epac2 expression showed no significant changes(P>0.05).However,number of Epac1-positive cells in the spinal dorsal horn was significantly decreased on Day 3,6,9,and 14 after model establishment compared to that of control rats(34.25±4.99,24.00±8.04,31.50±3.51,and 43.00±8.98 vs.61.75±4.99;P<0.05).Level of Epac1-positive cells in the spinal dorsal horn was also significantly decreased on Day 3,6,and 9 days after model establishment compared that of Day 1 day after model establishment(34.25±4.99,24.00±8.04,and 31.50±3.51 vs.58.00±5.35;P<0.05).TWL levels on NS and 8p-CPT groups were significantly lower than that of C group at 1 h before reagent administration and 30 min,1 h,2 h,and 3 h after reagent administration(6.8±1.0 and 7.1±0.8 vs.13.3±1.6,7.3±0.9,and 9.2±1.0 vs.13.2±1.5,6.9±1.2,and 9.9±1.3 vs.13.9±1.8,7.0±0.7,and 8.7±1.2 vs.13.2±1.2,7.0±0.9,and 7.1±0.9 vs.13.2±1.4 s;All P<0.05).TWL level of the 8p-CPT group of rats was significantly higher than that of NS group at 30 min,1 h,and 2 h after reagent administration(P<0.05).Furthermore,compared with the C group,number of c-Fos-positive cells in the spinal dorsal horn of the NS and 8p-CPT groups was significantly increased 1 h after reagent administration(75.25±8.42 and 40.50±6.81 vs.25.25±5.25;P<0.05).Compared with the NS group,number of c-Fos-positive cells in the spinal dorsal horn of the 8p-CPT group was significantly decreased 1 h after reagent administration(P<0.05).Conclusion Chronic inflammation-induced pain using CFA suppressed expression of Epac1 protein in the spinal dorsal horn,caused abnormal activation of local neurons and enhanced the peripheral nociceptive stimulus stress response.