Abstract 10488: Overexpression of MFN2 Alleviates Sorafenib-Induced Cardiomyocyte Necroptosis via the MAM-CaMKIIδ Pathway in vitro and in vivo

Background: The continued success of oncological therapeutics is dependent on the mitigation of treatment-related adverse events, particularly cardiovascular toxicities. As such, there is an important need to understand the basic mechanisms of drug toxicities and to explore the differences in the fundamental signaling pathways between cancer cells and non-cancer cells for the maintenance of function and survival of these cells. Our aim in this study was to elucidate the underlying mechanisms of sorafenib (Sor)-induced cardiomyocyte damage. Methods: Primary mouse cardiomyocytes were prepared and treated with Sor and various other treatments. Cardiomyocyte necroptosis was detected by flow cytometry, western blotting, and CCK8 assays. Mitochondrial Ca 2+ uptake was detected by Rhod-2 probes using confocal imaging. Morphological changes in mitochondria and mitochondria-associated endoplasmic reticulum (ER) membranes (MAM) were imaged using transmission electron microscopy (TEM) and confocal microscopy. Results: We reported that RIP3/MLKL cascade activation, mitochondrial Ca 2+ overload, and the subsequent increase in calmodulin-dependent protein kinase II delta (CaMKIIδ) contributed to Sor-induced cardiac necroptosis. Excess MAM formation and close ER-mitochondria contact were key in the pathogenesis of Sor-induced Ca 2+ overload. Furthermore, we found that reduced mitofusin-2 (MFN2) levels corresponded to repressed MAM biogenesis and increased mitochondria-MAM tethering in cardiomyocytes. Sor-induced Mammalian Target of Rapamycin (mTOR) inactivation, followed by the activation and nuclear translocation of Transcription Factor EB (TFEB), contributed to mitophagy and MFN2 degradation. In an in vivo model, we reported that an increase in MFN2 expression specifically improved Sor-induced cardiomyocyte necroptosis by repressing the MAM-CaMKIIδ-MCU pathway. Conclusions: Sorafenib mediated cardiomyocyte necroptosis through the mTOR-MFN2-MAM-Ca 2+ -RIP3-CaMKIIδ pathway in vitro and in vivo . The overexpression of MFN2 could rescue Sor-induced cardiomyocyte necroptosis without disturbing the anti-tumor effects.