Circulating Nitrite Contributes to Cardioprotection by Remote Ischemic Preconditioning
Rationale: Remote ischemic preconditioning (rIPC) with short episodes of ischemia and reperfusion (I/R) of an organ remote from the heart is a powerful approach to protect against myocardial I/R injury. The signal transduction pathways for the crosstalk between the remote site and the heart remain unclear in detail.
Objective: To elucidate the role of circulating nitrite in cardioprotection by rIPC.
Methods and Results: Mice were subjected to 4 cycles of no-flow ischemia with subsequent reactive hyperemia within the femoral region and underwent in vivo myocardial I/R (30 min/5 min or 24 h). The mouse experiments were conducted using genetic and pharmacological approaches. Shear stress dependent stimulation of endothelial nitric oxide synthase (eNOS) within the femoral artery during reactive hyperemia yielded substantial release of nitric oxide (NO•), subsequently oxidized to nitrite and transferred humorally to the myocardium. Within the heart, reduction of nitrite to NO• by cardiac myoglobin (Mb) and subsequent S-nitrosation of mitochondrial membrane proteins reduced mitochondrial respiration, reactive oxygen species (ROS) formation and myocardial infarct size. Pharmacological and genetic inhibition of NO•/nitrite generation by eNOS at the remote site or nitrite bioactivation by Mb within the target organ abrogated the cardioprotection by rIPC. Transfer experiments of plasma from healthy volunteers subjected to rIPC of the arm identified plasma nitrite as a cardioprotective agent in isolated Langendorff mouse heart preparations exposed to I/R.
Conclusions: Circulating nitrite derived from shear stress dependent stimulation of eNOS at the remote site of rIPC contributes to cardioprotection during I/R.
- Received February 25, 2014.
- Revision received March 16, 2014.
- Accepted March 18, 2014.