右美托咪啶通过抑制p38和JNK活化减少异氟醚诱导的新生大鼠海马神经元凋亡

Dexmedetomidine reduced isoflurane-induced neuroapoptosis by inhibiting activation of p38 and JNK proteins in hippocampus of neonatal rats

目的:探讨右美托咪啶(dexmedetomidine,Dex)对异氟醚(isoflurane,Iso)诱导的新生大鼠海马神经元凋亡的影响及其与p38丝裂原活化蛋白激酶(p38 mitogen-activated protein kinase,p38)和c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)蛋白活化的关系。方法:48只出生后7 d的SD大鼠随机分为对照组(Con组)、Dex组、Iso组和Iso+Dex组。前2组吸入空气,后2组吸入0.75%Iso 6 h。Dex组和Iso+Dex组在麻醉前20 min和麻醉开始后2 h、4 h经腹腔注射25μg·kg-1Dex;Con组和Iso组则在相同的时点注射150μL生理盐水。麻醉结束后使用TUNEL法检测海马神经元凋亡;Western blotting检测海马组织激活型caspase-3、p38、磷酸化p38(p-p38)、JNK和磷酸化JNK(p-JNK)蛋白表达的变化。结果:(1)Iso组海马CA1区TUNEL阳性细胞数较Con组增加447.57%(P<0.01),Dex抑制Iso诱导的TUNEL阳性细胞增加达75.18%(P<0.01)。(2)Iso组海马组织激活型caspase-3的表达比Con组增加126.29%(P<0.01);Dex显著抑制了Iso诱导的caspase-3活化(P<0.01)。(3)Iso组海马p-p38/p38和p-JNK/JNK比值均较Con组明显增加(P<0.01);Dex显著抑制了Iso诱导的p-p38和pJNK表达增加(P<0.01)。结论:Dex能通过减少海马神经元凋亡来减轻Iso对新生大鼠的脑毒性。抑制p38和JNK的磷酸化可能是Dex发挥保护作用的机制之一。

AIM：To investigate the effect of dexmedetomidine （Dex） on neuronal apoptosis induced by isoflurane （Iso） and its relationship with the expression of p38 mitogen-activated protein kinase （p38） and c-Jun N-terminal kinase （JNK） proteins in the hippocampus of neonatal rats. METHODS：Forty-eight neonatal SD rats at postnatal day 7 were randomly divided into control group （Con）, Dex group, Iso group and Iso combined with Dex （Iso＋Dex） group. Rats in Iso and Iso＋Dex groups were exposed to 0.75% Iso for 6 h, while rats in Con and Dex groups were exposed to air for 6 h. Rats were intraperitoneally injected with 25 μg·kg-1 Dex （Dex and Iso＋Dex groups） or 150 μL saline （Con and Iso groups） 20 min before exposure and 2 and 4 h after exposure. After the termination of anesthesia, the neuronal apoptosis in hippocampal CA1 region was detected by TUNEL staining, and the protein expression of cleaved caspase-3, phospho-p38 （p-p38）, p38, phospho-JNK （p-JNK） and JNK in hippocampal tissues was detected by Western blotting. RESULTS：The number of TUNEL positive cells in hippocampal CA1 region of the rats in Iso group was increased by 447.57% （P〈0.01） compared with Con group, while Dex significantly inhibited the increased TUNEL positive cells in Iso group by 75.18% （P〈0.01）. The expression of cleaved caspase-3 protein in Iso group was increased by 126.29% （P〈0.01） compared with Con group, while Dex reversed the increased cleaved caspase-3 protein expression （P〈0.01）. Iso significantly increased the phosphorylation of p38 and JNK proteins （P〈0.01）, while Dex reversed the increased p-p38 and p-JNK proteins （P〈0.01）. CONCLUSION：Dex attenuates Iso-induced neuroapoptosis in the hippocampus of neonatal rats through inhibiting the phosphorylation of p38 and JNK proteins.