Intracellular zinc release-activated ERK-dependent GSK-3Β-p53 and Noxa-Mcl-1 signaling are both involved in cardiac ischemic-reperfusion injury

Abstract

Oxidative stress and nitrosative stress are both suggested to be involved in cardiac ischemia-reperfusion (I/R) injury. Using time-lapse confocal microscopy of cardiomyocytes and high-affinity O 2 and Zn 2 probes, this study is the first to show that I/R, reactive oxygen species (ROS), and reactive nitrogen species (RNS) all cause a marked increase in the O 2 i, resulting in cytosolic and mitochondrial Zn 2 release. Exposure to a cell-penetrating, high-affinity Zn 2 i chelator, TPEN, largely abolished the Zn 2 i release and markedly protected myocytes from I/R-, ROS-, RNS-, or Zn 2/K (Zn 2 i supplementation)-induced myocyte apoptosis for at least 24 h after TPEN removal. Flavonoids and U0126 (a MEK1/2 inhibitor) largely inhibited the myocyte apoptosis and the TPEN-sensitive I/R-or Zn 2 i supplement-induced persistent extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, dephosphorylation of p-Ser9 on glycogen synthase kinase 3Β (GSK-3Β), and the translocation into and accumulation of p-Tyr216 GSK-3Β and p53 in, the nucleus. Silencing of GSK-3Β or p53 expression was cardioprotective, indicating that activation of the ERK-GSK-3Β-p53 signaling pathway is involved in Zn 2-sensitive myocyte death. Moreover, the ERK-dependent Noxa-myeloid cell leukemia-1 (Mcl-1) pathway is also involved, as silencing of Noxa expression was cardioprotective and U0126 abolished both the increase in Noxa expression and in Mcl-1 degradation. Thus, acute upstream Zn 2 i chelation at the start of reperfusion and the use of natural products, that is, flavonoids, may be beneficial in the treatment of cardiac I/R injury. © 2011 Macmillan Publishers Limited All rights reserved.