Copyright © 2007, European Society of Cardiology
NO mobilizes intracellular Zn2+ via cGMP/PKG signaling pathway and prevents mitochondrial oxidant damage in cardiomyocytes
Department of Anesthesiology, CB#7010 University of North Carolina at Chapel Hill Chapel Hill, NC 27599-7010, United States
* Corresponding author. Tel.: +1 919 843 4174; fax: +1 919 843 3805. zxu{at}aims.unc.edu
Objective Our aim was to determine if NO prevents mitochondrial oxidant damage by mobilizing intracellular free zinc (Zn2+).
Methods Zn2+ levels were determined by imaging enzymatically isolated adult rat cardiomyocytes loaded with Newport Green DCF. Mitochondrial membrane potential (
m) was assessed by imaging cardiomyocytes loaded with tetramethylrhodamine ethyl ester (TMRE).
Results S-nitroso-N-acetylpenicillamine (SNAP) dramatically increased Zn2+, which was blocked by both ODQ and NS2028, two specific inhibitors of guanylyl cyclase. The protein kinase G (PKG) inhibitor KT5823 blocked the effect of SNAP while the PKG activator 8-Br-cGMP mimicked the action of SNAP, indicating that the cGMP/PKG pathway is responsible for the effect of SNAP. The increased Zn2+ was prevented by 5-hydroxydecanoate (5HD) but was mimicked by diazoxide, implying that mitochondrial KATP channel opening may account for this effect. Since chelation of Zn2+ blocked the preventive effect of SNAP on H2O2-induced loss of m and exogenous zinc (1 µM ZnCl2) prevented dissipation of m, Zn2+ may play a critical role in the protective effect of NO. The MEK (mitogen-activated protein kinase or extracellular signal-regulated kinase) inhibitor PD98059 blocked the preventive effects of SNAP and zinc on m, indicating that extracellular signal-regulated kinase (ERK) mediates the protective effect of both these compounds on mitochondrial oxidant damage. A Western blot analysis further showed that ZnCl2 significantly enhances phosphorylation of ERK, confirming the involvement of ERK in the action of Zn2+.
Conclusions In isolated cardiomyocytes, NO mobilizes endogenous zinc by opening mitochondrial KATP channels through the cGMP/PKG pathway. In these cells, Zn2+ may be an important mediator of the action of NO on the mitochondrial death pathway.
KEYWORDS Nitric oxide; Mitochondria; Protein kinase G
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