Ferritinophagy activation and sideroflexin1-dependent mitochondria iron overload is involved in apelin-13-induced cardiomyocytes hypertrophy

Excess iron accumulation and cardiac oxidative stress have been shown as important mediators of cardiac hypertrophy, whereas it remains largely elusive about the occurrence of mitochondrial iron overload and its significance during cardiac hypertrophy. In the present study, we aim to investigate the role of NCOA4-mediated ferritinophagy and SFXN1-dependent mitochondria iron overload in apelin-13-induced cardiomyocytes hypertrophy. Apelin-13 significantly promotes ferric citrate (FAC)-induced total cellular and mitochondria ion production, as well as mitochondria ROS contents. Mechanistically, apelin-13 effectively induces the expression of SFXN1, a mitochondria iron transporting protein and NCOA4, a cargo receptor of ferritinophagy in dose and time-dependent manner. Conversely, blockade of APJ by F13A abolishes these stimulatory effects. In addition, apelin-13-triggered mitochondria iron overload is reversed by the genetic inhibition of SFXN1 and NCOA4. NCOA4 deficiency via its silencing also interferes with the enhanced expression of SFXN1 evoked by apelin-13. In apelin-13-treated H9c2 cells, the promotion in cell diameter, volume as well as protein contents are obviously suppressed by the knockdown of NCOA4 and SFXN1 with their corresponding siRNAs. Remarkably, the human and murine hypertrophic hearts models, as well as apelin-13-injected mice models, present evident cardiac mitochondrial iron deposition and raised expressions of NCOA4 and SFXN1. Taken together, these results provide experimental evidences that NCOA4-mediated ferritinophagy might be defined as an essential mechanism leading to apelin-13-cardiomyocytes hypertrophy in SFXN1-dependent mitochondria iron overload manners.