Mitochondria as a target for the cardioprotective effects of nitric oxide in ischemia-reperfusion injury

During cardiac ischemia-reperfusion ( IR) injury, excessive generation of reactive oxygen species ( ROS) and overload of Ca2+ at the mitochondrial level both lead to opening of the mitochondrial permeability transition ( PT) pore on reperfusion. This can result in the depletion of ATP, irreversible oxidation of proteins, lipids, and DNA within the cardiomyocyte, and can trigger cell-death pathways. In contrast, mitochondria are also implicated in the cardioprotective signaling processes of ischemic preconditioning ( IPC), to prevent IR-related pathology. Nitric oxide (NO center dot) has emerged as a potent effector molecule for a variety of cardioprotective strategies, including IPC. Whereas NO center dot is most noted for its activation of the "classic" soluble guanylate cyclase ( sGC) signaling pathway, emerging evidence indicates that NO center dot can directly act on mitochondria, independent of the sGC pathway, affording acute cardioprotection against IR injury. These direct effects of NO center dot on mitochondria are the focus of this review.