Protective role of intracellular zinc in myocardial ischemia/reperfusion is associated with preservation of protein kinase C isoforms

The recent discovery of zinc signals and their essential role in the redox signaling network implies that zinc homeostasis and the function of zinc- containing proteins are probably altered as a result of oxidative stress, suggesting new targets for pharmacological intervention. We hypothesized that the level of intracellular labile zinc is changed in hearts subjected to ischemia/ reperfusion (I/R) and investigated whether the maintenance of myocardial zinc status protected heart functions. Using fluorescent imaging, we demonstrated decreased levels of labile zinc in the I/R hearts. Phorbol 12- myristate 13- acetate, a known trigger of zinc release, liberated zinc ions in control hearts but failed to produce any increase in zinc levels in the I/R rat hearts. Adding the zinc ionophore pyrithione at reperfusion improved myocardial recovery up to 100% and reduced the incidence of arrhythmias more than 2-fold. This effect was dose-dependent, and high concentrations of zinc were toxic. Adding membrane- impermeable zinc chloride was ineffective. Hearts from rats receiving zinc pyrithione supplements in their diet fully recovered from I/R. The recovery was associated with the prevention of degradation of the two protein kinase C isoforms, delta and epsilon, during I/R. In conclusion, our results suggest a protective role of intracellular zinc in myocardial recovery from oxidative stress imposed by I/R. The data support the potential clinical use of zinc ionophores in the settings of acute redox stress in the heart.