The protective effects of retinoic acid-induced protein 14 on ischemia/reperfusion-induced myocardial apoptosis involves over-autophagy repression.

Uncontrolled activation of autophagy following ischemia/reperfusion (I/R) injury leads to cell death. The superfamily of ankyrin repeat proteins (N-Ank protein) was reported to be involved in autophagy regulation and cardiac protection. Bioinformatics analysis was performed (GSE61592 and GSE160516) and ten N-Ank proteins were differentially expressed in I/R models. Retinoic acid-induced protein 14 (RAI14), a member of N-Ank protein family, was upregulated in I/R-injured cardiac tissue and was first selected for research. A mouse I/R model was established by ligating the left anterior descending coronary artery to induce 90 min of ischemia, followed by 72 h of reperfusion. RAI14 was found upregulated in ischemic penumbra. RAI14 overexpression in cardiac tissue by injecting adeno-associated virus-9-RAI14 plasmid system via tail vein improved cardiac function and reduced infarct and apoptosis. Furthermore, the activated autophagy in ischemic penumbra of I/R mice was reversed by RAI14 overexpression along with decreased microtubule-associated protein 1 light chain 3 beta (LC3) II and increased autophagy receptor p62 expressions. RAI14 silence showed an opposite effect. A cell model was established by using mouse cardiomyocytes HL-1 underwent hypoxia/reoxygenation (H/R) treatment. Similarly, H/R also enhanced RAI14 expression and RAI14 overexpression inhibited H/R-induced apoptosis and autophagy in HL-1 cells. Mechanistically, autophagy inhibitor, the AKT/mTOR pathway, was found to be suppressed in mouse and cell models whereas RAI14 overexpression activated this pathway. Collectively, we demonstrated that compensatory increase of RAI14 inhibited I/R-induced myocardial injury by preventing excessive autophagy through activating the AKT/mTOR pathway, which providing an idea to explore strategies for preventing I/R injury.