Exogenous zinc protects cardiac cells from reperfusion injury by targeting mitochondrial permeability transition pore through inactivation of glycogen synthase kinase-3β

Abstract

The purpose of this study was to determine whether exogenous zinc prevents cardiac reperfusion injury by targeting the mitochondrial permeability transition pore (mPTP) via glycogen synthase kinase-3beta (GSK-3beta). The treatment of cardiac H9c2 cells with ZnCl2 (10 microM) in the presence of zinc ionophore pyrithione for 20 min significantly enhanced GSK-3beta phosphorylation at Ser9, indicating that exogenous zinc can inactivate GSK-3beta in H9c2 cells. The effect of zinc on GSK-3beta activity was blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY-294002 but not by the mammalian target of rapamycin (mTOR) inhibitor rapamycin or the PKC inhibitor chelerythrine, implying that PI3K but not mTOR or PKC accounts for the action of zinc. In support of this interpretation, zinc induced a significant increase in Akt but not mTOR phosphorylation. Further experiments found that zinc also increased mitochondrial GSK-3beta phosphorylation. This may indicate an involvement of the mitochondria in the action of zinc. The effect of zinc on mitochondrial GSK-3beta phosphorylation was not altered by the mitochondrial ATP-sensitive K+ channel blocker 5-hydroxydecanoic acid. Zinc applied at reperfusion reduced cell death in cells subjected to simulated ischemia/reperfusion, indicating that zinc can prevent reperfusion injury. However, zinc was not able to exert protection in cells transfected with the constitutively active GSK-3beta (GSK-3beta-S9A-HA) mutant, suggesting that zinc prevents reperfusion injury by inactivating GSK-3beta. Cells transfected with the catalytically inactive GSK-3beta (GSK-3beta-KM-HA) also revealed a significant decrease in cell death, strongly supporting the essential role of GSK-3beta inactivation in cardioprotection. Moreover, zinc prevented oxidant-induced mPTP opening through the inhibition of GSK-3beta. Taken together, these data suggest that zinc prevents reperfusion injury by modulating the mPTP opening through the inactivation of GSK-3beta. The PI3K/Akt signaling pathway is responsible for the inactivation of GSK-3beta by zinc.

Effect of zinc supplements in the attenuated cardioprotective effect of ischemic preconditioning in hyperlipidemic rat heart

“…It has been reported that the level of zinc decreased during reperfusion by excessive zinc loss in ischemic/reperfusion injury (Chanoit et al 2008;Xu et al 2014). Besides this finding, the lipid activates the PKC which triggers the zinc release, so, we envisage the hyperlipidemia model for study.…”

Morphine prevents the mitochondrial permeability transition pore opening through NO/cGMP/PKG/Zn2+/GSK-3β signal pathway in cardiomyocytes

“…Therefore, it is reasonable to conclude that morphine modulates the mPTP opening by inactivating GSK-3␤ through Zn 2ϩ . As to the mechanism by which mobilized Zn 2ϩ inactivates GSK-3␤, we assume that Zn 2ϩ may inhibit GSK-3␤ through the Akt/ phosphatidylinositol 3-kinase signaling pathway, as we documented previously (4).…”

“…First, exogenous NO (11) mobilizes intracellular Zn 2ϩ through the cGMP/PKG pathway and morphine can produce NO in cardiomyocytes (20). Second, Zn 2ϩ inhibits the mPTP opening by inactivating GSK-3␤ in cardiac cells (4).…”

“…Recently, it has been reported that the treatment of isolated rat hearts at reperfusion with Zn 2ϩ ionophore pyrithione induces cardioprotection against ischemiareperfusion injury (23). Recent studies from our laboratory have shown that Zn 2ϩ modulates oxidant-induced mPTP opening in isolated rat cardiomyocytes (20) and prevents reperfusion injury by targeting mPTP in cardiac H9c2 cells (4). In this study, the inhibitory effect of morphine on the mPTP was partially but significantly blocked by both the PKG inhibitor KT5823 and the Zn 2ϩ chelator TPEN, suggesting that morphine protects mitochondria by mobilizing Zn 2ϩ via the cGMP/PKG pathway.…”

Zn2+ Activates Large Conductance Ca2+-activated K+ Channel via an Intracellular Domain

“…Moreover, [Zn 2ϩ ] i may increase concomitantly with [Ca 2ϩ ] i under pathological conditions such as ischemia/hypoxia (5,6,10,11), in which intracellular Ca 2ϩ overload is suspected to contribute to cell death in these conditions (12). However, whether such increases in [Zn 2ϩ ] i contribute to the deleterious effect or play a compensatory cell-protective effect is not clear (5,11,(13)(14)(15)(16).…”