Atrial fibrillation (AF) is the most common sustained arrhythmia and a major clinical challenge, yet the mechanisms sustaining AF remain incompletely understood. We investigated the contribution of the circulating proteome to AF using serum from 23 patients with persistent AF and preserved left ventricular ejection fraction before and after electrical cardioversion before invasive PVI. Patients underwent comprehensive phenotyping, including invasive left atrial pressure measurements, 3D electroanatomic mapping, left atrial strain analysis, and left atrial volume assessment. Proteomic profiling identified 504 proteins that met filtering criteria (>80% valid values), revealing differential expression of YWHAZ/YWHAE (14-3-3 proteins), MMP9, and Cathepsin G, implicating pathways involved in intracellular signaling and structural remodeling.
Functional studies using patient-derived serum in ex vivo mouse heart preparations demonstrated that AF serum increased arrhythmogenicity compared with sinus rhythm (SR) serum. Patch-clamp recordings in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) showed that AF serum markedly altered sodium channel function, reducing peak INa amplitude, current density, and exhibited a tendency toward action potential shortening. Furthermore, line-scan confocal imaging in human iPSC-derived atrial cardiomyocytes demonstrated that AF serum induced marked calcium handling abnormalities, including increased calcium spark frequency and altered calcium transient kinetics (F/F0, time to peak, decay constant, and TF50). Importantly, pharmacological inhibition of YWHAE/14-3-3 signaling significantly altered these calcium abnormalities, indicating a conserved electrophysiological response across experimental models.
Collectively, these findings demonstrate that the AF-associated circulating secretome directly modulates atrial electrophysiology by modulating sodium channel function and intracellular calcium handling, with 14-3-3 signaling emerging as a potential therapeutic target. Ongoing studies are examining whether these alterations are linked to changes in atrial conduction velocity and effective refractory period, whether 14-3-3 signaling influences Nav1.5 localization, and whether chronic serum exposure induces substantial changes in calcium handling properties.
Keywords: Atrial fibrillation, proteomics, secretome, 14-3-3, MMP9, atrial cardiomyopathy
