Nobiletin attenuates doxorubicin-induced cardiotoxicity by promoting pyruvate kinase M2 tetramerization

BACKGROUND Doxorubicin (DOX) is an effective chemotherapeutic agent whose clinical use is limited by dose-dependent cardiotoxicity. Although nobiletin (NOB) exhibits cardioprotective effects in cardiovascular diseases, its role and underlying mechanisms in doxorubicin-induced cardiotoxicity (DIC) remain unclear. METHODS DIC models were established in mice and AC16 cardiomyocytes. Cardiac and mitochondrial function were assessed by echocardiography, Masson's trichrome staining, transmission electron microscopy, and mitochondrial functional assays. Potential targets of NOB were predicted by PharmMapper and validated by molecular docking and molecular dynamics simulations. RESULTS NOB attenuated DOX-induced cardiac dysfunction, myocardial fibrosis, cardiomyocyte apoptosis, mitochondrial dysfunction, and oxidative stress. Mechanistically, NOB promoted pyruvate kinase M2 (PKM2) tetramerization, preserving cardiac function and reducing cardiomyocyte atrophy and fibrosis, with effects comparable to the PKM2 tetramer stabilizer TEPP-46. PKM2 knockdown abolished the protective effects of NOB on mitochondrial function and mitochondrial fission. Moreover, re-expression of wild-type PKM2, but not a tetramerization-deficient mutant, restored the impaired oxygen consumption rate and extracellular acidification rate in NOB-treated cardiomyocytes. CONCLUSIONS NOB protects against DOX-induced cardiotoxicity by promoting PKM2 tetramerization, thereby preserving mitochondrial function, restoring cellular energy metabolism, and reducing oxidative stress and cardiomyocyte apoptosis. These findings identify PKM2 tetramerization as a potential therapeutic target for DIC.