p38MAPK信号通路在右美托咪定抗布比卡因神经毒性损伤中的作用

Role of p38MAPK signal transduction pathway in dexmedetomidine against neurotoxicity induced by bupivacaine

目的评价p38MAPK信号通路在右美托咪定抗布比卡因神经毒性损伤中的作用。方法取鞘内置管成功的SD大鼠72只,采用随机数字表法将其分为六组,每组12只:二甲基亚砜对照组(C组)、p38MAPK抑制剂组(SB组)、右美托咪定组(D组)、布比卡因组(B组)、右美托咪定+布比卡因组(DB组)及p38MAPK抑制剂+布比卡因组(SBB组)。C组鞘内注射二甲基亚砜20μl,SB组和B组分别鞘内注射p38MAPK抑制剂30μg和5%布比卡因20μl,DB组和SBB组在鞘内注射5%布比卡因20min前分别腹腔注射右美托咪定75μg/kg和鞘内注射p38MAPK抑制剂30μg;D组腹腔注射右美托咪定75μg/kg。于鞘内置管前(T_0)、鞘内给药前(T_1)、鞘内给药后4、8、12h和1、2、3、4、5、6d(T_2~T_(10))时测定大鼠后肢机械缩足阈值(MWT)和热缩足反射潜伏期(TWL);于给药24h后每组随机取6只大鼠,取L4~5脊髓组织,TUNEL法检测凋亡细胞;Western blot法检测pp38MAPK蛋白表达水平。结果与T_0时比较,T_2~T_9时B组、T_2~T_7时DB组和T_2~T_5时SBB组MWT明显升高,T_2~T_9时B组、T_2~T_6时DB组和T2~T5时SBB组TWL明显延长(P<0.05);与C组比较,T_2~T_9时B组MWT明显升高、TWL明显延长,B组细胞凋亡指数及pp38MAPK蛋白表达明显升高(P<0.05);与B组比较,T_2~T_9时DB、SBB组MWT明显下降,TWL明显缩短,B组细胞凋亡指数及p-p38MAPK蛋白表达明显下降(P<0.05)。结论右美托咪定可通过抑制神经细胞凋亡来减轻布比卡因诱发的大鼠脊髓神经毒性,其机制与抑制p38MAPK信号通路活化有关。

Objective To evaluate the role of p38 MAPK signal transduction pathway in dexmedetomidine against neurotoxicity induced by bupivacaine.Methods Seventy-two adult male SD rats,successfully implanted with intrathecal catheter without complications,were randomly divided into 6groups：control group（group C）;p38MAPK inhibitor group（group SB）;dexmedetomidine group（group D）;bupivacaine group（group B）;dexmedetomidine and bupivacaine group（group DB）;p38MAPK inhibitor and bupivacaine group（group SBB）.DMSO 20μl were injected intrathecally in group C;p38MAPK inhibitor 30μg and 5% bupivacaine were respectively injected intrathecally in group SB and B;group DB and SBB were respectivel pretreated with dexmedetomidine 75μg/kg intraperitoneally and p38 MAPK inhibitor 30μg intrathecal injection 20 min before intrathecally injected5% bupivacaine.Dexmedetomidine 75μg/kg was injected intraperitoneally in group D.Mechanical withdrawal threshold（MWT）and thermal withdrawal latency（TWL）were measured before intrathecal catheter was implanted（T0）,before intrathecal administration（T1）and at 4,8 and 12 hand on1,2,3,4,5and 6days after intrathecal administration（T2-T（10））.At 24 hafter intrathecal administration,6rats were randomly chosen from each group and sacrificed.The lumbar segment（L4-5）of the spinal cord was removed for detecting neuronal apoptosis（by TUNEL）and phosporylated p38MAPK（p-p38MAPK）expression（by Western blot）.Results Compared with T0,MWT was significantly increased and TWL was prolonged at T2-T9 in group B,MWT at T2-T7 was significantly increased and TWL at T2-T6 was prolonged in group DB,MWT was significantly increased and TWL was prolonged at T2-T5 in group SBB（P〈0.05）.Compared with group C,no significant difference was found in MWT,TWL,the apoptotic index and expression of p-p38 MAPK in groups D and SB.MWT was significantly increased and TWL was prolonged at T2-T9 in group B,the apoptotic index and expression of p-p38 MAPK were significantly increased in group B（P 0.05）.Compared with group B,MWT and TWL at T2-T9,the apoptotic index and expression of p-p38 MAPK were significantly decreased in groups DB and SBB（P〈0.05）.Conclusion Dexmedetomidine can inhibit spinal neurotoxicity induced by bupivacaine in rats via inhibiting apoptosis in spinal cord,and inhibition of p38 MAPK signal transduction pathway may be involved in the underlying mechanism.