The long noncoding RNA NKILA protects against myocardial ischaemic injury by enhancing myocardin expression via suppressing the NF-κB signalling pathway

Background: The lncRNA NKILA has been reported to interact with NF-kappa B and has an important role in various human diseases. However, the role of NKILA in myocardial ischaemic injury is still unknown. Methods: We established cell and animal models of myocardial ischaemic injury. We confirmed our findings by overexpressing NKILA, silencing myocardin and using an NE-kappa B pathway inhibitor in a hypoxia/reoxygenation (H/R) model of H9c2 cells. An animal model of ischaemia-reperfusion (I/R) injury was established by LAD ligation. Overexpression of NKILA was achieved by adeno-associated virus (AAV) injection through the tail vein. Annexin-V/PI staining and flow cytometric analysis were performed to test cell apoptosis. ELISAs were used to determine the secretion of inflammatory factors. TIC, HE and TUNEL staining were performed to study myocardial pathological injury. qRT-PCR or Western blotting were used to test the expression levels of NKILA, myocardin, the NF-kappa B pathway and apoptosis-related proteins. Results: H/R and I/R treatment significantly suppressed the expression of NKILA and activated the NF-kappa B pathway, resulting in the loss of myocardin. Overexpressing NKILA led to the suppression of the NF-kappa B pathway and successfully prevented the cell apoptosis and inflammatory responses caused by H/R stimulation in H9c2 cells. Silencing myocardin reversed the protective effect of NKILA and led to severe injury in the H9c2 cells that underwent H/R. Furthermore, the NF-kappa B pathway inhibitor BAY11-7028 reduced the H/R injury in H9c2 cells with little effect on NKILA expression. Similar results were confirmed in an animal model of myocardial I/R injury and showed that overexpression of NKILA inhibited I/R-triggered myocardial injury in vivo. Conclusion: NKILA enhanced the expression of myocardin via inhibiting the NF-kappa B signalling pathway and preventing cell apoptosis and the inflammatory response of cardiomyocytes, thus ameliorating myocardial I/R injury.