Atrial endothelial cells senescence promotes thrombogenicity, inflammation and extracellular matrix remodeling: Role of the local Ang II/AT1 receptor pathway

Introduction Ageing promotes atrial remodeling that paves way to atrial fibrillation and thrombogenicity. Preclinical studies on endothelial atrial cells are lacking. Objective This study aims to characterize phenotypical changes associated with atrial endothelial cells senescence and to decipher the link between ageing and thrombogenicity. Methods Atrial endothelial cells (AEC) were obtained from freshly harvested porcine left atria. Endothelial senescence was assessed by senescence-associated beta-galactosidase activity (SA-β-gal), using flow cytometry, protein expression by Western blot analysis and platelet aggregation using an aggregometer. Replicative senescence was induced by passaging AEC from passage P1 to P4, and premature endothelial cell senescence by exposing AEC to L-NAME, an endothelial NO synthase (eNOS) inhibitor or H2O2. Results AEC senescence was characterized by an increase in SA-β-gal activity and an up-regulation of p53, a key regulator of cellular senescence, and of p21 and p16, key cyclin-dependent kinase inhibitors. Senescent AEC phenotype was characterized by: – cell thrombogenicity through an up-regulation of tissue factor expression, shedding of procoagulant microparticles, eNOS down-regulation and reduced NO-mediated inhibition of platelet aggregation; – cell adhesion through up-regulation of ICAM-1; – proteolysis and fibrosis remodeling through MMP-2, 9 and TGF-β1 expression; – up-regulation of the local Ang II system through enhanced AT1 receptors (AT1R) and angiotensin-converting enzyme (ACE) expression. Losartan, an AT1 receptor antagonist, and Perindoprilat, an ACE inhibitor, prevented atrial endothelial cell senescence. Conclusions Thus atrial endothelial senescence promotes thrombogenicity, inflammation, matrix remodeling and the up-regulation of the local Ang II system. They further suggest that targeting the Ang II/AT1R pathway may be a promising therapeutic strategy to delay atrial endothelial ageing.