Cardioprotection by Ischemic Postconditioning Is Lost in Aged and STAT3-Deficient Mice

The cardioprotection by ischemic preconditioning is lost in aged wild-type and in STAT3 (signal transducer and activator of transcription 3)-deficient mice. The aim of the present study was to analyze whether or not ischemic postconditioning (iPoco) was effective in aged mice hearts and whether iPoco was dependent on STAT3. Young (3 months) and aged (>13 months) C57Bl6/J mice underwent 30 minutes of ischemia and 2 hours of reperfusion without or with iPoco (3 cycles of 10 seconds of ischemia/10 seconds of reperfusion [3×10] or 5 cycles of 5 seconds of ischemia/5 seconds of reperfusion [5×5] at the beginning of reperfusion). In young mice, both iPoco3×10 and iPoco5×5 reduced infarct size (IS), whereas in aged mice, only iPoco5×5 was effective in reducing IS. In young mice, iPoco3×10 increased the phosphorylated over total STAT3 (phosphorylated STAT3/STAT3) ratio at 10 minutes of reperfusion in the postconditioned anterior wall compared with the control posterior wall. In aged mice hearts, total STAT3 and p...