NO mobilizes intracellular Zn²⁺ via cGMP/PKG signaling pathway and prevents mitochondrial oxidant damage in cardiomyocytes

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• 作者：Youngho Jang ; Huihua Wang ; Jinkun Xi ; Robert A. Mueller ; Edward A. Norfleet ; Zhelong Xu
• 关键词：Nitric oxide ; Mitochondria ; Protein kinase G
• 刊名：Cardiovascular Research
• 出版年：2007
• 出版时间：15 July 2007
• 年：2007
• 卷：75
• 期：2
• 页码：426-433
• 全文大小：654 K

文摘

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 (ΔΨ_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 K_ATP channel opening may account for this effect. Since chelation of Zn²⁺ blocked the preventive effect of SNAP on H₂O₂-induced loss of ΔΨ_m and exogenous zinc (1 μM ZnCl₂) prevented dissipation of ΔΨ_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 ΔΨ_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 K_ATP 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.