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  • Title: Inhibition of apoptotic responses after ischemic stress in isolated hearts and cardiomyocytes.
    Author: Hofstaetter B, Taimor G, Inserte J, Garcia-Dorado D, Piper HM.
    Journal: Basic Res Cardiol; 2002 Nov; 97(6):479-88. PubMed ID: 12395210.
    Abstract:
    Recent findings on the induction of anti-apoptotic gene expression in ischemic/reperfused hearts encouraged us to investigate whether ischemic/reperfused hearts may be protected against apoptosis induction. To analyze this hypothesis we performed studies on isolated perfused hearts of rat. For apoptosis induction, hearts were perfused with the NO donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP, 10 microM) for 30 minutes. Four hours thereafter apoptosis was detected by DNA laddering and TUNEL assay. Under normoperfusion SNAP induced 5.5 +/- 1.4 TUNEL-positive myocytes per tissue section (vs. 1.8 +/- 0.5 in controls). But when hearts were subjected to 20 minutes of no flow ischemia, which was sufficient for energy depletion of the hearts without inducing severe necrotic or apoptotic cell death, reperfusion in the presence of SNAP did not induce apoptosis. To analyze if this mode of protection is a property of the cardiomyocytes, we performed corresponding experiments on ventricular cardiomyocytes of rat. Again, under normoxic conditions SNAP (100 (microM) increased the number of TUNEL-positive cells to 12.6 +/- 4.9 % (vs. 5.4 +/- 0.7 % in controls). But when SNAP was added after 3 h of simulated ischemia, which was sufficient for energy depletion of the cells without inducing apoptotic cell death, the number of apoptotic cells did not increase. The ischemia-induced protection of hearts and cardiomyocytes goes along with an increased expression of several anti-apoptotic genes, mainly of the bcl-2 family. This indicates that ischemic conditions induce an anti-apoptotic gene program in cardiomyocytes, which may also be responsible for the observed anti-apoptotic actions in the intact ischemic/reperfused myocardium.
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