Erschienen in:
01.11.2008 | ORIGINAL CONTRIBUTION
Ischemia-reperfusion injury and cardioprotection: investigating PTEN, the phosphatase that negatively regulates PI3K, using a congenital model of PTEN haploinsufficiency
verfasst von:
Hilary K. Siddall, Clare E. Warrell, Prof. Derek M. Yellon, Mihaela M. Mocanu
Erschienen in:
Basic Research in Cardiology
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Ausgabe 6/2008
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Abstract
Activation of the PI3K/Akt pathway protects the heart from ischemia-reperfusion injury (IRI). The phosphatase PTEN is the main negative regulator of this pathway. We hypothesized that reduced PTEN levels could protect against IRI. Isolated perfused mouse hearts from PTEN+/− and their littermates PTEN+/+ (WT), were subjected to 35 min global ischemia and 30 min reperfusion, with and without 2, 4 or 6 cycles ischemic preconditioning (IPC). The end point was infarct size, expressed as a percentage of the myocardium at risk (I/R%). PTEN and Akt levels were determined using Western blot analysis. Unexpectedly, there were no significant differences in infarction between PTEN+/− and WT (42.1 ± 5.0% Vs. 45.6 ± 3.3%). However, the preconditioning threshold was significantly reduced in the PTEN+/− Vs. WT, with 4 cycles of IPC being sufficient to reduce I/R%, compared to 6 cycles in the WT (4 cycles IPC: 29.8. ± 3.69% in PTEN+/− Vs. 45.5. ± 5.08% in WT, P < 0.01). In addition, the ratio between the phospho/total Akt (Ser473 and Thr308) was slightly but significantly increased in the PTEN+/− indicating an upregulation of PI3K/Akt pathway. Interestingly, the levels of the other phosphatases that may negatively regulate the PI3K/Akt pathway (PP2A, SHIP2 and PHLPP) were not significantly different between littermates and PTEN+/−. In conclusion, PTEN haploinsufficiency alone does not induce cardioprotection in this model; however, it reduces the threshold of protection induced by IPC.