脊髓caspase-1在大鼠切口痛中的作用

Role of caspase-1 in spinal cord in a rat model of incisional pain

目的评价脊髓caspase-1在大鼠切口痛中的作用。方法取鞘内置管成功的成年雄性SD大鼠18只，体重250～280 g，采用随机数字表法分为3组（n＝6）：切口痛组（I组）、切口痛＋二甲基亚砜组（ID组）和切口痛＋caspase-1抑制剂Ac-YVAD-CMK组（IA组）。于切口痛模型制备前10 min，I组鞘内注射0.9%生理盐水20 μl；ID组鞘内注射二甲基亚砜20 μl，然后用0.9%生理盐水10 μl冲洗导管；IA组鞘内注射Ac-YVAD-CMK 1 nmol/μl（溶于20 μl二甲基亚砜中），然后用0.9%生理盐水10 μl冲洗导管。分别于鞘内置管前2 h（T0）、鞘内置管后3 d（T1）、模型制备后2、6、24和48 h（T2-5）时测定术侧足机械缩足反应阈。于T5时痛阈测定结束后，处死大鼠，取脊髓腰膨大，采用Western blot法检测caspase-1（p20）表达，采用ELISA法检测IL-1β含量。结果与T0比较，I组和ID组T2-5机械缩足反应阈降低（P〈0.05），IA组T1-5机械缩足反应阈差异无统计学意义（P〉0.05）；与I组和ID组比较，IA组T2-5机械缩足反应阈升高，脊髓caspase-1（p20）表达水平和IL-1β含量降低（P〈0.05）；I组和ID组各时点机械缩足反应阈、脊髓caspase-1（p20）表达和IL-1β含量比较差异无统计学意义（P〉0.05）。结论脊髓caspase-1的活化可促进IL-1β的释放，从而参与大鼠切口痛的病理生理过程。

Objective To evaluate the role of caspase-1 in the spinal cord in a rat model of incisional pain.Methods Eighteen adult male Sprague-Dawley rats, weighing 250-280 g, in which intrathecal catheters were successfully implanted, were divided into 3 groups（n=6 each）using a random number table： incision pain group（group I）, incision pain plus dimethyl sulfoxide group（group ID）and incision pain plus caspase-1 inhibitor（Ac-YVAD-CMK）group（group IA）. At 10 min before establishment of the model, 0.9% normal saline 20 μl was intrathecally injected in group I, dimethyl sulfoxide 20 μl was intrathecally injected and then the catheter was washed with 0.9% normal saline 10 μl in group ID, and Ac-YVAD-CMK 1 nmol/μl（dissolved in 20 μl dimethyl sulfoxide）and then the catheter was washed with 0.9% normal saline 10 μl in group IA.The mechanical paw withdrawal threshold（MWT）of the ipsilateral hind paw was measured at 2 h before intrathecal catheterization（T0）, 3 days after intrathecal catheterization（T1）and 2, 6, 24 and 48 h after establishment of model（T2-5）. The rats were sacrificed after the last measurement of pain threshold at T5, and lumbar enlargement segments of the spinal cord were removed for detection of caspase-1（p20）expression and interleukin-1beta（IL-1β）content by Western blot and enzyme-linked immunosorbent assay, respectively.Results Compared with the baseline at T0, the MWT was significantly decreased at T2-5 in I and ID groups（P〈0.05）, and no significant change was found in MWT at T1-5 in group IA（P〉0.05）. Compared with I and ID groups, the MWT at T2-5 was significantly increased at T2-5, and the caspase-1（p20）protein expression and IL-1β content were decreased in group IA（P〈0.05）. There was no significant difference in MWT, expression of caspase-1（p20）protein or IL-1β content between group I and group ID（P〉0.05）.Conclusion The activation of caspase-1 in the spinal cord can promote the release of IL-1β and thus is involved in the incision pain in rats.