Abstract
BACKGROUND: Contractile dysfunction, hypertrophy, and cell death during heart failure are linked to altered Ca(2+) handling and elevated levels of the hormone AngII (angiotensin II), which signals through G(q)-coupled AT(1)Rs (AngII type 1 receptors), initiating hydrolysis of phosphatidylinositol (4,5)-bisphosphate. Chronic elevation of AngII contributes to cardiac pathology, but the mechanisms linking sustained AngII signaling to heart dysfunction remain incompletely understood. Here, we demonstrate that chronic AngII exposure profoundly disrupts cardiac phosphoinositide (PI) homeostasis, triggering a cascade of cellular adaptations that ultimately impair cardiac function. METHODS: Mice received 1-week infusions of AngII, bisperoxovanadium 1,10 phenanthroline, both, or saline via osmotic minipumps. We used mass spectrometry, super-resolution microscopy, electrophysiology, confocal imaging, immunoblot, echocardiography, and histology to assess PI levels, Ca(V)1.2 localization, Ca(2+) handling, protein phosphorylation, cardiac function, and fibrosis. RESULTS: Chronic AngII infusion caused widespread PI imbalance, reducing PI, phosphatidylinositol (4,5)-bisphosphate, and phosphatidylinositol (3,4,5)-trisphosphate levels. Ca(V)1.2 channels are redistributed from t-tubules to endosomal compartments. Despite reduced sarcolemmal channel expression, Ca(2+) currents and transients were maintained through enhanced PKA (protein kinase A)-mediated and CaMKII (Ca(2+)/calmodulin-dependent protein kinase II)-mediated phosphorylation of Ca(2)(+)-handling proteins. However, this compensation proved insufficient as cardiac function progressively declined, marked by pathological hypertrophy, t-tubule disruption, and diastolic dysfunction. PTEN (phosphatase and tensin homolog) inhibition preserved Akt signaling and protected against cardiac dysfunction and fibrosis without preventing cellular remodeling or altered calcium handling. CONCLUSIONS: These findings reveal a complex interplay between PI signaling, ion channel trafficking, and compensatory phospho-regulation in AngII-induced cardiac pathology. We establish phosphatidylinositol (3,4,5)-trisphosphate depletion as a critical link between chronic AngII signaling and cardiac dysfunction. The dissociation between persistent cellular remodeling and preserved organ function with PTEN inhibition reveals that cardioprotection occurs primarily through reduced fibrosis. PTEN inhibition, thus, emerges as a promising therapeutic strategy for heart failure associated with pathological renin-angiotensin system activation, with potential to complement existing therapies by targeting antifibrotic responses.