Specific MicroRNAs comparisons in hypoxia and morphine preconditioning against hypoxia-reoxgenation injury with and without heart failure.

Aims: Ischemia reperfusion (I/R) injury is an inevitable event arising during the cardiovascular diseases development and the process of potent surgical treatments. microRNAs (miRNAs) are critical regulators of multiple cell processes including I/R injury. The present study aims to quantify miRNA alterations and regulated genes upon hypoxia-reoxygenation (H/R) injury in a rat heart failure model comparing with normal cardiomyocytes.

Main Methods: Chronic heart failure was established by injecting doxorubicin (2mg/kg/week) for 6weeks, then H/R was performed on primary cultured cardiomyocytes isolated from normal and failed heart. Cellular injury was evaluated by detecting LDH release levels, cell variability and apoptotic rate. Dysregulated miRNAs in control, hypoxia preconditioning (HPC) and morphine preconditioning (MPC) groups under two conditions were quantified by microarray analysis. Fas protein expression was analyzed using Western Blotting analysis.

Key Findings: Chronic heart failure was confirmed with lower ejection fraction (EF), and significant cellular injury. HPC could reverse the injury induced by H/R in normal heart rather than failed heart, otherwise, MPC significantly attenuated cellular injury dose dependently in both conditions. There was 12 miRNAs significantly altered after doxorubicin injection, 7 downregulated and 5 upregulated. miR-133b-5p, miR-6216, miR-664-1-5p and let7e-5p were differentially expressed after HPC and MPC treatments. The direct interaction between miR-133b-5p and target gene Fas were established. The Fas protein expression was manipulated by MPC not HPC affording protective effect against H/R injury.

Significance: We investigated that miR-133b-5p might play a particularly important role in the cardioprotective effect of MPC by regulating the target gene Fas.