LAUSR

AIMS Genetic and pharmacological inhibition of mitochondrial fission induced by acute myocardial ischaemia/reperfusion injury has been shown to reduce myocardial infarct size. The clinically used anti-hypertensive and heart failure medication, hydralazine, is known to have anti-oxidant and anti-apoptotic effects. Here, we investigated whether hydralazine confers acute cardioprotection by inhibiting Drp1-mediated mitochondrial fission. METHODS AND RESULTS Pre-treatment with hydralazine was shown to inhibit both mitochondrial fission and mitochondrial membrane depolarisation induced by oxidative stress in HeLa cells. In mouse embryonic fibroblasts (MEFs), pre-treatment with hydralazine attenuated mitochondrial fission and cell death induced by oxidative stress, but this effect was absent in MEFs deficient in the mitochondrial fission protein, Drp1. Molecular docking and surface plasmon resonance studies demonstrated binding of hydralazine to the GTPase domain of the mitochondrial fission protein, Drp1 (KD 8.6 ± 1.0 µM), and inhibition of Drp1 GTPase activity in a dose-dependent manner. In isolated adult murine cardiomyocytes subjected to simulated ischaemia/reperfusion injury (IRI), hydralazine inhibited mitochondrial fission, preserved mitochondrial fusion events, and reduced cardiomyocyte death (hydralazine 24.7 ± 2.5% vs control 34.1 ± 1.5%, P = 0.0012). In ex vivo perfused murine hearts subjected to acute IRI, pre-treatment with hydralazine reduced myocardial infarct size (as % left ventricle: hydralazine 29.6 ± 6.5% vs vehicle control 54.1 ± 4.9%, P = 0.0083), and in the murine heart subjected to in vivo IRI, the administration of hydralazine at reperfusion, decreased myocardial infarct size (as % area-at-risk: hydralazine 28.9 ± 3.0% vs vehicle control 58.2 ± 3.8%, P < 0.001). CONCLUSION We show that, in addition to its anti-oxidant and anti-apoptotic effects, hydralazine, confers acute cardioprotection by inhibiting IRI-induced mitochondrial fission, raising the possibility of repurposing hydralazine as a novel cardioprotective therapy for improving post-infarction outcomes. TRANSLATIONAL PERSPECTIVE Hydralazine is used clinically as a treatment for patients with hypertension and chronic heart failure, and experimental studies have known it to have anti-oxidant and anti-apoptotic effects. In our study, we show that administration of hydralazine immediately prior to reperfusion inhibited ischaemia/reperfusion injury-induced mitochondrial fission, and reduced myocardial infarct size. These findings raise the possibility of repurposing hydralazine as a novel potential cardioprotective therapy, which can be administered to acute myocardial infarction patients immediately prior to reperfusion by primary percutaneous coronary intervention, to reduce myocardial infarct size and prevent heart failure.