Inorganic nitrite modulates miRNA signatures in acute myocardial in vivo ischemia/reperfusion.

Acute myocardial infarction is the leading cause of mortality in the industrialized world. While it is essential to attempt an early reperfusion of ischemic myocardial territories, reperfusion itself adds damage to the heart, the ischemia-reperfusion (I/R) injury. Particularly the injury resulting from the very first minutes of reperfusion remains incompletely understood. MicroRNAs (miRNAs) are dynamic regulators in I/R injury. Nitric oxide (•NO) signaling, in turn, interacts with miRNA signaling. Our previous investigations showed that •NO signaling in I/R could be modulated by nitrite. We therefore sought to investigate the role of miRNAs in nitrite cardioprotection with focus on the first few minutes of reperfusion. The study was conducted in mice in vivo with 30 min of ischemia and 5 min of reperfusion. Mice received a single-dose of nitrite or saline intracardially 5 min prior to reperfusion. We identified nine miRNAs to be up-regulated after 5 min of reperfusion. The up-regulation of almost half of those miRNAs (miR-125a-5p, miR-146b, miR-339-3p, miR-433) was inhibited by nitrite treatment, perpetuating baseline values. In silico analysis revealed the Irak-M gene to be a target of miR-146b and miR-339-3p. Correspondingly, a rise in Irak-M transcript and protein levels occurred by nitrite treatment within the early phase of reperfusion. The results demonstrate that already a very short phase of reperfusion is sufficient for significant dysregulation in cardiac miRNAs expression and that nitrite preserves baseline values of miRNAs in the scale of only a few minutes. These findings hint at a potential novel cardioprotective mechanism of nitrite signaling.