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

 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25 μg·kg-1 Dex；Con组和Iso组则在相同的时点注射150 μL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p-JNK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。

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

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.