IP3R drives cardiomyocyte injury by enhancing MAM-mediated Ca2+ transfer and mitochondrial dysfunction

IP3R expression is markedly upregulated in angiotensin II-induced cardiomyocyte injury. • IP3R knockdown attenuates MAM-mediated mitochondrial Ca 2+ overload and dysfunction. • IP3R drives ER-mitochondria Ca 2+ transfer by enhancing MAM formation. • Targeting IP3R may represent a novel therapeutic strategy for heart failure. Background Heart failure (HF) is the terminal stage of various cardiovascular diseases. Mitochondrial Ca 2+ overload and dysfunction mediated by mitochondria-associated ER membranes (MAMs) are recognized contributors to HF pathogenesis; however, the underlying molecular mechanisms remain incompletely understood. Methods An in vitro model of cardiomyocyte injury was established using angiotensin II (Ang II)-stimulated H9c2 cells. IP3R was knocked down using specific siRNA. Cell viability (CCK-8), apoptosis (Annexin V/TUNEL), and hypertrophy (phalloidin staining) were assessed. IP3R expression and mitochondrial complex subunits were analyzed by western blotting. MAM formation was examined by transmission electron microscopy and immunofluorescence co-localization. Mitochondrial function was evaluated by measuring ATP levels, ROS (MitoSOX), mitochondrial membrane potential (TMRM), and Ca 2+ uptake (Rhod-2). Results Ang II stimulation reduced cell viability, induced hypertrophy and apoptosis, and promoted MAM formation. Mechanistically, Ang II upregulated IP3R expression and enhanced MAM-mediated mitochondrial Ca 2+ overload, leading to decreased mitochondrial membrane potential, elevated ROS, and reduced ATP production. Notably, genetic knockdown of IP3R attenuated these pathological changes, reducing MAM formation and mitochondrial Ca 2+ overload while restoring mitochondrial function and cell viability. Conclusion Our findings suggest that IP3R may exacerbate cardiomyocyte injury by facilitating MAM-mediated Ca 2+ transfer and mitochondrial dysfunction, indicating that targeting IP3R could represent a potential therapeutic strategy for HF. However, the upstream mechanisms of IP3R upregulation and the causal role of mitochondrial Ca 2+ uptake require further investigation.