Ong Sang-Bing, Hall Andrew R, Dongworth Rachel K, Kalkhoran Siavash, Pyakurel Aswin, Scorrano Luca, Hausenloy Derek J
Dr. Derek J. Hausenloy, The Hatter Cardiovascular Institute, University College London Hospital, 67 Chenies Mews, London, WC1E 6HX, UK, Tel.: +44 203 447 9894, Fax: +44 203 447 9505, E-mail:
Thromb Haemost. 2015 Mar;113(3):513-21. doi: 10.1160/TH14-07-0592. Epub 2014 Sep 25.
The mechanism through which the protein kinase Akt (also called PKB), protects the heart against acute ischaemia-reperfusion injury (IRI) is not clear. Here, we investigate whether Akt mediates its cardioprotective effect by modulating mitochondrial morphology. Transfection of HL-1 cardiac cells with constitutively active Akt (caAkt) changed mitochondrial morphology as evidenced by an increase in the proportion of cells displaying predominantly elongated mitochondria (73 ± 5.0 % caAkt vs 49 ± 5.8 % control: N=80 cells/group; p< 0.05). This effect was associated with delayed time taken to induce mitochondrial permeability transition pore (MPTP) opening (by 2.4 ± 0.5 fold; N=80 cells/group: p< 0.05); and reduced cell death following simulated IRI (32.8 ± 1.2 % caAkt vs 63.8 ± 5.6 % control: N=320 cells/group: p< 0.05). Similar effects on mitochondrial morphology, MPTP opening, and cell survival post-IRI, were demonstrated with pharmacological activation of Akt using the known cardioprotective cytokine, erythropoietin (EPO). The effect of Akt on inducing mitochondrial elongation was found to be dependent on the mitochondrial fusion protein, Mitofusin-1 (Mfn1), as ablation of Mfn1 in mouse embryonic fibroblasts (MEFs) abrogated Akt-mediated mitochondrial elongation. Finally, in vivo pre-treatment with EPO reduced myocardial infarct size (as a % of the area at risk) in adult mice subjected to IRI (26.2 ± 2.6 % with EPO vs 46.1 ± 6.5 % in control; N=7/group: p< 0.05), and reduced the proportion of cells displaying myofibrillar disarray and mitochondrial fragmentation observed by electron microscopy in adult murine hearts subjected to ischaemia from 5.8 ± 1.0 % to 2.2 ± 1.0 % (N=5 hearts/group; p< 0.05). In conclusion, we found that either genetic or pharmacological activation of Akt protected the heart against acute ischaemia-reperfusion injury by modulating mitochondrial morphology.
蛋白激酶Akt（也称为PKB）保护心脏免受急性缺血再灌注损伤（IRI）的机制尚不清楚。在此，我们研究Akt是否通过调节线粒体形态来介导其心脏保护作用。用组成型活性Akt（caAkt）转染HL-1心肌细胞改变了线粒体形态，表现为主要呈现伸长线粒体的细胞比例增加（caAkt组为73±5.0%，对照组为49±5.8%：每组80个细胞；p<0.05）。这种效应与诱导线粒体通透性转换孔（MPTP）开放所需时间延迟有关（延长2.4±0.5倍；每组80个细胞：p<0.05）；并且在模拟IRI后细胞死亡减少（caAkt组为32.8±1.2%，对照组为63.8±5.6%：每组320个细胞：p<0.05）。使用已知的心脏保护细胞因子促红细胞生成素（EPO）对Akt进行药理学激活，对线粒体形态、MPTP开放和IRI后细胞存活也有类似影响。发现Akt诱导线粒体伸长的作用依赖于线粒体融合蛋白Mitofusin-1（Mfn1），因为在小鼠胚胎成纤维细胞（MEF）中敲除Mfn1可消除Akt介导的线粒体伸长。最后，在成年小鼠IRI模型中，EPO的体内预处理减少了心肌梗死面积（占危险区域面积的百分比）（EPO组为26.2±2.6%，对照组为46.1±6.5%；每组7只：p<0.05），并且在成年小鼠缺血心脏中，通过电子显微镜观察到的显示肌原纤维紊乱和线粒体碎片化的细胞比例从5.8±1.0%降至2.2±1.0%（每组5个心脏；p<0.05）。总之，我们发现Akt的基因激活或药理学激活均可通过调节线粒体形态保护心脏免受急性缺血再灌注损伤。
