Renalase is a novel target gene of hypoxia-inducible factor-1 in protection against cardiac ischaemia-reperfusion injury

Aims Renalase, an enzyme that can metabolize catecholamine, was recently reported to attenuate the ischaemia/reperfusion (I/R)-induced cardiac injury. This work was undertaken to investigate the functions and regulation mechanisms of renalase in protection against cardiac I/R injury. Methods and results An elevated level of renalase was found in C57BL/6 mice challenged with I/R injury. Then, we generated a mouse model with cardiac administration of cholesterol-conjugated renalase siRNA followed by I/R operation. The mice treated with renalase siRNA exhibited increased infarction size and decreased cardiac function compared with the scramble siRNA group. Subsequently, we identified four potential hypoxia-inducible factor-1 alpha (HIF-1α)-binding motifs in the promoter of renalase through bioinformatics approaches. Dual-luciferase reporter assay, electrophoretic mobility shift assay, chromatin immunoprecipitation assay, and western blot were conducted and demonstrated that renalase was a novel target gene of HIF-1α. Furthermore, administration of renalase reduced the infarct area and rescued the deterioration of cardiac function in myocardial HIF-1α knockdown mice subjected to I/R injury. In addition, the levels of norepinephrine in serum as well as nicotinamide adenine dinucleotide (NAD⁺) and ATP in myocardium were determined, which implied that cardiac protection of renalase against I/R may be related, at least in part, to its metabolism of catecholamine and regulation of energy. Conclusion These findings have revealed renalase as a novel target gene of HIF-1α in protection against myocardial I/R injury, which provided a basis for therapeutic strategies for enhancing cardiomyocyte survival in patients associated with ischaemic heart diseases.