ROS and NO trigger early preconditioning: relationship to mitochondrial K_ATP channel

Abstract

NO trigger early preconditioning: relationship to mitochondrial K ATP channel. Am J Physiol Heart Circ Physiol 284: H299-H308, 2003. First published September 26, 2002 10.1152/ajpheart.00706.2002Reactive oxygen species (ROS) and nitric oxide (NO) are implicated in induction of ischemic preconditioning. However, the relationship between these oxidant signals and opening of the mitochondrial ATP-dependent potassium (K ATP) channel during early preconditioning is not fully understood. We observed preconditioning protection by hypoxia, exogenous H 2O2, or PKC activator PMA in cardiomyocytes subjected to 1-h ischemia and 3-h reperfusion. Protection was abolished by K ATP channel blocker 5-hydroxydecanoate (5-HD) in each case, indicating that these triggers must act upstream from the K ATP channel. Inhibitors of NO synthase abolished protection in preconditioned cells, suggesting that NO is also required for protection. DAF-2 fluorescence (NO sensitive) increased during hypoxic triggering. This was amplified by pinacidil and inhibited by 5-HD, indicating that NO is generated subsequent to K ATP channel activation. Exogenous NO during the triggering phase conferred protection blocked by 5-HD. Exogenous NO also restored protection abolished by 5-HD or N -nitro-L-arginine methyl ester in preconditioned cells. Antioxidants given during pinacidil or NO triggering abolished protection, confirming that ROS are generated by K ATP channel activation. Coadministration of H 2O2 and NO restored PMA-induced protection in 5-HD-treated cells, indicating that ROS and NO are required downstream from the K ATP channel. We conclude that ROS can trigger preconditioning by causing activation of the K ATP channel, which then induces generation of ROS and NO that are both required for preconditioning protection. hydrogen peroxide; nitric oxide; ischemia; cardiomyocytes PRECONDITIONING CONFERS PROTECTION against ischemiareperfusion injury in the heart. After a brief triggering stimulus is applied, the "early window" of protection begins within minutes and lasts for several hours. The persistence of protection after removal of the trigger indicates that a signal transduction pathway has been activated. Numerous triggers of preconditioning have been identified, including brief hypoxia/ischemia, opioids, ACh, bradykinin, activators of PKC, and pharmacological agents that activate the mitochondrial ATPdependent potassium (mitoK ATP ) channel (10,13,15,16,26,39,50). However, the signal transduction sequence activated by these triggers is not fully understood.Reactive oxygen species (ROS) have been implicated as participants in the signaling pathway involved in preconditioning triggering (1,2,4,23,41). We previously reported (42, 50) that exogenous H 2 O 2 induces preconditioning in cardiomyocytes and that mitochondrial ROS are involved in the triggering by hypoxia or by ACh administration. However, an interesting controversy has developed regarding the relationship between the mitoK ATP channel activation and the ROS signal during triggering. On...

Cardioprotection and mitochondrial S-nitrosation: Effects of S-nitroso-2-mercaptopropionyl glycine (SNO-MPG) in cardiac ischemia–reperfusion injury

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Reversible redox-dependent modulation of mitochondrial aconitase and proteolytic activity during in vivo cardiac ischemia/reperfusion

“…Preconditioning, a series of brief periods of ischemia and reperfusion, protects the myocardium from deleterious events associated with extended durations of ischemia and reperfusion (7)(8)(9). Cardioprotection afforded by preconditioning appears mediated, in part, by the production of oxygen radicals (35)(36)(37)(38)(39)(40) and is associated with reductions in Ca 2ϩ overload (7,(41)(42)(43) and free radical production (44) during extended periods of ischemia͞ reperfusion.…”

Performance of diamino fluorophores for the localization of sources and targets of nitric oxide

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