Luo L, Tong J, Li L, Jin M
Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China.
Nan Fang Yi Ke Da Xue Xue Bao. 2022 Aug 20;42(8):1256-1262. doi: 10.12122/j.issn.1673-4254.2022.08.20.
The purpose of this study was to determine whether xenon post-conditioning affects mTOR signaling as well as endoplasmic reticulum stress (ERS)-apoptosis pathway in rats with spinal cord ischemia/reperfusion injury.
Fifty male rats were randomized equally into sham-operated group (Sham group), I/R model group (I/R group), I/R model+ xenon post-conditioning group (Xe group), I/R model+rapamycin (a mTOR signaling pathway inhibitor) treatment group (I/R+ Rapa group), and I/R model + xenon post- conditioning with rapamycin treatment group (Xe + Rapa group).. In the latter 4 groups, SCIRI was induced by clamping the abdominal aorta for 85 min followed by reperfusion for 4 h. Rapamycin (or vehicle) was administered by daily intraperitoneal injection (4 mg/kg) for 3 days before SCIRI, and xenon post-conditioning by inhalation of 1∶1 mixture of xenon and oxygen for 1 h at 1 h after initiation of reperfusion; the rats without xenon post-conditioning were given inhalation of nitrogen and oxygen (1∶ 1). After the reperfusion, motor function and histopathologic changes in the rats were examined. Western blotting and real-time PCR were used to detect the protein and mRNA expressions of GRP78, ATF6, IRE1α, PERK, mTOR, p-mTOR, Bax, Bcl-2 and caspase-3 in the spinal cord.
The rats showed significantly lowered hind limb motor function following SCIRI ( < 0.01) with a decreased count of normal neurons, increased mRNA and protein expressions of GRP78, ATF6, IRE1α, PERK, and caspase-3, and elevated p-mTOR/mTOR ratio and Bax/Bcl-2 ratio ( < 0.01). Xenon post-conditioning significantly decreased the mRNA and protein levels of GRP78, ATF6, IRE1α, PERK and caspase-3 ( < 0.05 or 0.01) and reduced p-mTOR/mTOR and Bax/Bcl-2 ratios ( < 0.01) in rats with SCIRI; the mRNA contents and protein levels of GRP78 and ATF6 were significantly decreased in I/R+Rapa group ( < 0.01). Compared with those in Xe group, the rats in I/R+Rapa group and Xe+Rapa had significantly lowered BBB and Tarlov scores of the hind legs ( < 0.01), and caspase-3 protein level and Bax/Bcl-2 ratio were significantly lowered in Xe+Rapa group ( < 0.05 or 0.01).
By inhibiting ERS and neuronal apoptosis, xenon post- conditioning may have protective effects against SCIRI in rats. The mTOR signaling pathway is partially involved in this process.
本研究旨在确定氙气后处理是否会影响脊髓缺血/再灌注损伤大鼠的mTOR信号通路以及内质网应激（ERS）-凋亡途径。
将50只雄性大鼠随机均分为假手术组（假手术组）、缺血/再灌注模型组（缺血/再灌注组）、缺血/再灌注模型+氙气后处理组（氙气组）、缺血/再灌注模型+雷帕霉素（一种mTOR信号通路抑制剂）治疗组（缺血/再灌注+雷帕霉素组）和缺血/再灌注模型+氙气后处理联合雷帕霉素治疗组（氙气+雷帕霉素组）。在后面4组中，通过夹闭腹主动脉85分钟然后再灌注4小时诱导脊髓缺血/再灌注损伤。在脊髓缺血/再灌注损伤前3天，每天腹腔注射雷帕霉素（或溶剂）（4mg/kg），再灌注开始1小时后，通过吸入氙气和氧气的1∶1混合气体1小时进行氙气后处理；未进行氙气后处理的大鼠吸入氮气和氧气（1∶1）。再灌注后，检查大鼠的运动功能和组织病理学变化。采用蛋白质印迹法和实时聚合酶链反应检测脊髓中GRP78、ATF6、IRE1α、PERK、mTOR、磷酸化mTOR（p-mTOR）、Bax、Bcl-2和caspase-3的蛋白质和信使核糖核酸（mRNA）表达。
脊髓缺血/再灌注损伤后大鼠后肢运动功能显著降低（P<0.01），正常神经元数量减少，GRP78、ATF6、IRE1α、PERK和caspase-3的mRNA和蛋白质表达增加，p-mTOR/mTOR比值和Bax/Bcl-2比值升高（P<0.01）。氙气后处理显著降低脊髓缺血/再灌注损伤大鼠GRP78、ATF6、IRE1α、PERK和caspase-3的mRNA和蛋白质水平（P<0.05或0.01），降低p-mTOR/mTOR和Bax/Bcl-2比值（P<0.01）；缺血/再灌注+雷帕霉素组GRP78和ATF6的mRNA含量和蛋白质水平显著降低（P<0.01）。与氙气组相比，缺血/再灌注+雷帕霉素组和氙气+雷帕霉素组大鼠后腿的BBB和Tarlov评分显著降低（P<0.01），氙气+雷帕霉素组caspase-3蛋白水平和Bax/Bcl-2比值显著降低（P<0.05或0.01）。
通过抑制内质网应激和神经元凋亡，氙气后处理可能对大鼠脊髓缺血/再灌注损伤具有保护作用。mTOR信号通路部分参与了这一过程。
