PI3K-Akt通路对老年心肌缺血预适应模型大鼠线粒体通透性转换孔开放程度的影响

目的：探讨PI3K-Akt通路对老年心肌缺血预适应（IPC）模型大鼠线粒体通透性转换孔（mPTP）开放程度的影响，阐明其可能机制。方法：21~23月龄Wistar大鼠35只随机分为缺血再灌注（I/R）组、I/R+PI3K抑制剂Wortmannin（Wort）组、IPC组、IPC+Wort组和假手术组，每组7只。分别建立I/R、IPC模型，Wort组大鼠再灌注前尾静脉注射Wort 0.6 mg·kg^-1。120 min再灌注结束后，提取心肌组织蛋白，Western blotting法检测大鼠心肌组织中Akt及p-Akt蛋白相对表达水平。差速离心法分离大鼠心肌线粒体，酶标仪检测线粒体内超氧化物水平、超氧化物歧化酶（SOD）活性及心肌mPTP开放程度。结果：与I/R组 （0.288±0.071）比较，IPC组大鼠心肌组织p-Akt蛋白相对表达水平（0.346±0.051）明显升高（P < 0.05），I/R+Wort组大鼠心肌组织中p-Akt蛋白相对表达水平（0.044±0.010）明显降低（P < 0.01）。与I/R组（0.216±0.024）比较，IPC组大鼠粒线粒体超氧化物水平（0.187±0.022）明显降低（P < 0.05），I/R+Wort组大鼠粒线粒体超氧化物水平（0.218±0.029）无明显变化（P > 0.05）。与I/R组（1.15±0.15）比较，IPC组大鼠线粒体SOD活性（1.39±0.14）明显升高（P < 0.05），I/R+Wort组大鼠线粒体SOD活性（1.17±0.21）无明显变化（P > 0.05）。在6~20min时，与I/R组比较，IPC组大鼠心肌mPTP开放程度明显降低（P < 0.05），I/R+Wort组大鼠心肌mPTP开放程度无明显变化（P > 0.05）；与IPC组比较，IPC+Wort组大鼠心肌mPTP开放程度明显增加（P < 0.05）。结论：老年大鼠IPC可通过激活PI3K-Akt通路抑制心肌mPTP的开放。

Effect of PI3K-Akt signaling pathway on openness degree of mitochondrial permeability transition pore in aged model rats of myocardial ischemic preconditioning

Objective: To study the effect of PI3K-Akt signaling pathway on the openness degree of mitochondrial permeability transition pore (mPTP)in the aged model rats of myocardial ischemic preconditioning (IPC),and to clarify its possible mechanism.Methods:Thirty-five Wistar Wistar rats (aged 21-23 months)were randomly divided into ischemia reperfusion (I/R)group,I/R+Wort (Wortmannin,inhibitor of PI3K)group,IPC group and IPC+ Wort group (n=7).The models of I/R and IPC were established and 0.6 mg·kg-1 Wort were injected to the caudal veins of the rats in Wort group before reperfusion. After 120 min reperfusion, the myocardium tissue protein was extracted, and the Akt and p-Akt protein expression levels were detected by Western blotting method.The myocardial mitochondrial of rats was separated through differential centrifugation, and the superoxide level, SOD level and openness degrees of mPTP were determined by microplate reader. Results:Compared with I/R group (0.288±0.071),the expression level of p-Akt protein in myocardium tissue of the rats in IPC group (0.346±0.051)was increased (P <0.05),and the expression level of p-Akt im myocardium tissue of the rats in I/R+ Wort group (0.044 ± 0.010)was decreased (P < 0.01).Compared with I/R group (0.216± 0.024),the superoxide level in mitochondrial of the rats in IPC group (0.187 ± 0.022)was decreased (P <0.05),and the superoxide level in mitochondrial in I/R + Wort group (0.218 ± 0.029)had no significant change (P >0.05).Compared with I/R group (1.15±0.15),the SOD activity in mitochondrial of the rats in IPC group (1.39±0.14)was increased (P <0.05),and the SOD activity in mitochondrial of the rats in I/R+ Wort group (1.17±0.21)had no significant change (P >0.05).Compared with I/R group,the mPTP openness degree in IPC group was decreased (P <0.05)during 6 to 2 min,however the openness degree in I/R+Wort group had no significant change (P > 0.05).Compared with IPC group,the mPTP openness degree in IPC+ Wort group was increased (P < 0.05).Conclusion:The IPC of aged rats can inhibit the openness of mitochondrial permeability transition pore through activating the PI3K-Akt signaling pathway.