Activation of Autophagic Flux Blunts Cardiac Ischemia/Reperfusion Injury.

Academic Article

Abstract

  • Rationale: Reperfusion injury accounts for up to half of myocardial infarct size, and meaningful clinical therapies targeting it do not exist. We have reported previously that autophagy is reduced during reperfusion and that HDAC inhibition enhances cardiomyocyte autophagy and blunts ischemia/reperfusion (I/R) injury when administered at the time of reperfusion. However, whether inducing autophagy per se, as opposed to other effects triggered by HDAC inhibition, is sufficent to protect against reperfusion injury is not clear. Objective: We set out to test whether augmentation of autophagy using a specific autophagy-inducing peptide, Tat-Beclin, protects the myocardium through reduction of reactive oxygen species (ROS) during reperfusion injury. Methods and Results: Eight to twelve-week-old, wild-type, C57BL6 mice and drug-inducible cardiomyocyte-specific ATG7 knockout mice (to test the dependency on autophagy) were randomized into two groups: exposed to a control Tat-Scrambled (TS) peptide or a Tat-Beclin (TB) peptide. Each group was subjected to I/R surgery (45min coronary ligation, 24h reperfusion). Infarct size, systolic function, autophagic flux, and ROS were assayed. Cultured neonatal rat ventricular myocytes (NRVMs) were exposed to TB during simulated ischemia/reperfusion injury. ATG7 knockdown by siRNA in NRVMs was used to evaluate the role of autophagy. TB treatment at reperfusion reduced infarct size by 20% (absolute reduction; 50% relative reduction) and improved contractile function. Improvement correlated with increased autophagic flux in the border zone with less oxidative stress. ATG7 KO mice did not manifest TB-promoted cardioprotection during I/R. In NRVMs subjected to I/R, TB reduced cell death by 41% and reduced I/R-induced ROS generation. Conversely, ATG7 knockdown in NRVMs abolished these beneficial effects of TB on cell death and ROS reduction. Conclusions: Induction of autophagy at the time of reperfusion is sufficient to mitigate myocardial reperfusion injury by reducing ROS and cell death. Maintenance of appropriate autophagic flux may emerge as a viable clinical therapy to reduce reperfusion injury in acute myocardial infarction.
  • Authors

    Published In

    Keywords

  • Beclin, cardiomyopathy, histone deacetylase, ischemia/reperfusion
  • Digital Object Identifier (doi)

    Pubmed Id

  • 3393493
  • Author List

  • Xie M; Cho GW; Kong Y; Li DL; Altamirano F; Luo X; Morales CR; Jiang N; Schiattarella GG; May HI