JNK信号通路在右美托咪定减轻利多卡因致大鼠脊髓神经毒性中的作用

Role of JNK signaling pathway in dexmedetomidine-induced reduction of spinal neurotoxicity induced by lidocaine in rats

目的 评价c-Jun氨基末端激酶（JNK）信号通路在右美托咪定减轻利多卡因致大鼠脊髓神经毒性中的作用.方法 取鞘内置管成功的成年雄性SD大鼠72只,体重280～ 320 g,采用随机数字表法分为6组（n=12）：对照组（C组）、JNK信号通路阻断剂组（SP组）、右美托咪定组（D组）、利多卡因组（L组）、右美托咪定＋利多卡因组（DL组）和JNK信号通路阻断剂＋利多卡因组（SPL组）.C组鞘内注射二甲基亚砜20μl,SP组和L组分别鞘内注射JNK信号通路阻断剂SP600125 30μg和10％利多卡因20μl,DL组和SPL组鞘内注射10％利多卡因前20 min时分别腹腔注射右美托咪定75 μg/kg和鞘内注射JNK信号通路阻断剂SP600125 30 μg;D组腹腔注射右美托咪定75 μg/kg.于鞘内置管前（T0）、鞘内给药前（T1）、鞘内给药后4、8、12 h、1、2、3、4、5和6d（T2-10）时测定大鼠后肢机械缩足反应阈（MWT）和热缩足潜伏期（TWL）;于给药24 h后每组随机取6只大鼠,取L4.5脊髓组织,采用TUNEL法检测凋亡细胞并计算细胞凋亡指数;采用Western blot法检测磷酸化JNK （p-JNK）表达.结果 与C组比较,SP组和D组MWT、TWL、细胞凋亡指数及p-JNK表达差异无统计学意义（P＞0.05）,L组T2.8时、DL组T2.6时及SPL组T2-5时MWT升高,L组T2-8时、DL组T2-5时及SPL组T2-4时TWL延长,DL组、SPL组及L组细胞凋亡指数及p-JNK表达水平升高（P＜0.05）;与L组比较,DL组和SPL组T2-8时MWT下降、TWL缩短,细胞凋亡指数及p-JNK表达水平下降（P＜0.05）.结论 右美托咪定减轻利多卡因致大鼠脊髓神经毒性的机制可能与抑制JNK信号通路活化有关.

Objective To evaluate the role of C-Jun N-Terminal kinase （JNK） signaling pathway in dexmedetomidine-induced reduction of spinal neurotoxicity induced by lidocaine in rats.Methods Seventy-two adult male Sprague-Dawley rats, weighing 280-320 g, in which intrathecal catheters were successfully implanted without complications, were randomly divided into 6 groups （n =12 each） using a random number table： control group （group C）;SP600125 （JNK signaling pathway blocker） group （group SP）;dexmedetomidine group （group D）;lidocaine group （group L）;dexmedetomidine ＋ lidocaine group （group DL）;SP600125＋lidocaine group （group SPL）.Dimethyl sulfoxide （DMSO） 20 μl was injected intrathecally in group C.SP600125 30 μg and 10% lidocaine 20 μl were injected intrathecally in SP and L groups, respectively.At 20 min after intrathecal injection of 10% lidocaine, dexmedetomidine 75 μg/kg was injected intraperitoneally in group DL, and SP600125 30 μg was injected intrathecally in group SPL.Dexmedetomidine 75 μg/kg was injected intraperitoneally in group D.The mechanical paw withdrawal threshold （MWT） and thermal paw withdrawal latency （TWL） were measured before intrathecal catheters were implanted （T0）, before intrathecal administration （T1）, and at 4, 8 and 12 h and 1, 2, 3, 4, 5 and 6 days after intrathecal administration （T2-10）.At 24 h after intrathecal administration, 6 rats randomly selected from each group were sacrificed.The lumbar segment （L4-5） of the spinal cord was removed for detection of cell apoptosis （by TUNEL） and phosphorylated JNK （p-JNK） expression （by Western blot）.The apoptotic index was calculated.Results Compared with group C, no significant change was found in the MWT, TWL, apoptotic index and expression of p-JNK in SP and D groups （P〉0.05）, the MWT at T2-8 in group L, at T2-6 in group DL and at T2-5 in group SPL were significantly increased, the TWL at T2-8 in group L, at T2-5 in group DL and at T2-4 in group SPL were prolonged, and the apoptotic index and expression of p-JNK were increased in DL, SPL and L groups （P〈0.05）.Compared with group L, the MWT was significantly decreased, and the TWL was shortened at T2-8, and the apoptotic index and expression of p-JNK were decreased in DL and SPL groups （P〈0.05）.Conclusion The mechanism by which dexmedetomidine mitigates spinal neurotoxicity induced by lidocaine is related to inhibited activation of JNK signaling pathway in rats.