Atrial fibrillation (AF) is a common arrhythmia and clinical challenge, yet the molecular mechanisms underlying atrial cardiomyopathy remain poorly defined. We investigated the role of the circulating proteome in AF pathogenesis using serum from 23 patients with persistent AF and preserved left ventricular ejection fraction. Patients underwent detailed phenotyping, including invasive left atrial pressure measurement, atrial strain analysis, and left atrial volume assessment. Proteomic analysis identified 504 proteins meeting the threshold of over 80% valid data entries post-filtering, with differential expression of YWHAZ/YWHAE (14-3-3 proteins), MMP9, and Cathepsin G, suggesting alterations in intracellular signaling and structural remodeling pathways associated with AF. Functional assays using patient-derived serum in ex vivo mouse heart preparations demonstrated that AF serum promoted arrhythmogenesis compared to sinus rhythm (SR) serum, as evidenced by an increased number and duration of atrial arrhythmia. Similarly, line-scan confocal imaging of human iPSC-derived atrial cardiomyocytes and isolated adult mouse cardiomyocytes revealed AF serum-induced calcium handling abnormalities, including elevated calcium spark frequency and altered kinetics (F/F₀, time to peak, decay constant, and TF₅₀). Pharmacological inhibition of YWHAE significantly reversed these calcium dysregulations, supporting a conserved electrophysiological response across models. These findings point to a critical role of the AF-associated secretome in modulating atrial electrophysiology, with 14-3-3 signaling emerging as a potential therapeutic target. By integrating patient-specific molecular signatures with functional validation in relevant cardiac models, this study advances our understanding of AF pathogenesis and opens new avenues for mechanistically guided therapy in atrial cardiomyopathy.
Keywords: Atrial fibrillation, proteomics, secretome, 14-3-3, MMP9, atrial cardiomyopathy
