Fuglesteg B N, Tiron C, Jonassen A K, Mjøs O D, Ytrehus K
Department of Medical Physiology, Faculty of Medicine, University of Tromsø, Tromsø, Norway.
Acta Physiol (Oxf). 2009 Feb;195(2):273-82. doi: 10.1111/j.1748-1716.2008.01901.x.
To compare the possible role of Akt and mammalian target of rapamycin (mTOR) in mediating cardioprotection against ischaemia under three different conditions: (1) During ischaemic preconditioning (IPC), (2) when insulin was given as a pretreatment agent (InsPC) and (3) when insulin was given as a reperfusion cell survival agent (Ins(R)).
Isolated perfused rat hearts were subjected to IPC (3 x 5 min) or InsPC (50 mU mL(-1); 3 x 5 min), before 30 min of regional ischaemia followed by 120 min of reperfusion +/- 1L-6-hydroxymethyl-chiro-inositol-2-[(R)-2-O-methyl-3-O-octadecylcarbonate] (HIMO) (20 microm; Akt inhibitor) or rapamycin (1 nm; mTOR inhibitor). In addition, insulin (3 mU mL(-1)) was given at the onset of reperfusion, +/- HIMO or rapamycin. Risk zone (R) and infarct size (I) were determined with Evans blue and tetrazolium staining respectively. Western blot analysis was performed on tissue from Langendorff-perfused rat hearts and cell lysates from cultured HL1 cells.
IPC, InsPC and InsR treatment resulted in a significant reduction in infarct size compared to controls (all P < 0.05). This protective effect of IPC and insulin was abolished by the inhibitors. However, the putative Akt inhibitor, although capable of abolishing cardioprotection induced by insulin, was not able to inhibit insulin-induced phosphorylation of Akt in Langendorff-perfused rat hearts and cultured HL1 cells. The target for this compound therefore remains to be determined.
IPC and insulin (either as InsPC or Ins(R)) appear to activate mTOR, and this kinase seems to play an essential role in cardioprotection against ischaemia and reperfusion injury as rapamycin blocked the protection.
比较Akt和雷帕霉素哺乳动物靶点（mTOR）在三种不同条件下介导心肌缺血保护作用中的可能作用：（1）缺血预处理（IPC）期间；（2）胰岛素作为预处理剂给药时（InsPC）；（3）胰岛素作为再灌注细胞存活剂给药时（Ins(R)）。
分离的灌注大鼠心脏先进行IPC（3×5分钟）或InsPC（50 mU mL(-1)；3×5分钟）处理，然后进行30分钟的局部缺血，接着进行120分钟的再灌注，同时给予或不给予1L-6-羟甲基-手性-肌醇-2-[(R)-2-O-甲基-3-O-十八烷基碳酸酯]（HIMO）（20 microm；Akt抑制剂）或雷帕霉素（1 nm；mTOR抑制剂）。此外，在再灌注开始时给予胰岛素（3 mU mL(-1)），同时给予或不给予HIMO或雷帕霉素。分别用伊文思蓝和四氮唑染色法测定危险区（R）和梗死面积（I）。对Langendorff灌注大鼠心脏组织和培养的HL1细胞裂解物进行蛋白质印迹分析。
与对照组相比，IPC、InsPC和InsR处理均导致梗死面积显著减小（所有P<0.05）。抑制剂消除了IPC和胰岛素的这种保护作用。然而，推测的Akt抑制剂虽然能够消除胰岛素诱导的心脏保护作用，但在Langendorff灌注大鼠心脏和培养的HL1细胞中却不能抑制胰岛素诱导的Akt磷酸化。因此，该化合物的作用靶点仍有待确定。
IPC和胰岛素（无论是作为InsPC还是Ins(R)）似乎都能激活mTOR，并且该激酶似乎在心肌缺血再灌注损伤的保护作用中起重要作用，因为雷帕霉素阻断了这种保护作用。
