Rivaroxaban treatment prevents atrial myocyte hypertrophy in goats with persistent atrial fibrillation by inhibition of protease activated receptor 1

Abstract Background Atrial fibrillation (AF) is associated with increased risk of stroke and hypercoagulability. Coagulation factors mediate remodelling processes via activation of protease-activated receptors (PARs) in various organs. Purpose We investigated whether Factor Xa (FXa) inhibition via rivaroxaban protects against atrial structural remodelling in goats with persistent AF and characterised the effect of FXa and thrombin on pro-hypertrophic and pro-inflammatory changes in human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM). Methods Three groups of goats were tested: CTRL AF (control AF, n=10), RIVA AF (rivaroxaban treatment during AF, n=11), and SHAM (no AF, n=10). AF was maintained by burst pacing for 16 weeks. AF stability was assessed via flecainide cardioversion attempts. During the final experiment, hemodynamics, atrial electrophysiological properties and AF complexity were measured. Tissue samples were collected for histological and gene expression analyses. Human iPSC-CM were stimulated with PAR-1 agonist, FXa or thrombin with and without their inhibitors. Expression of pro-hypertrophic and pro-inflammatory genes was assessed by qRT-PCR after 24 hours of incubation. Results Rivaroxaban treatment inhibited thrombin generation in RIVA AF goats (baseline: 249 ± 42nM vs. final: 69 ± 33nM). 16 weeks of AF induced atrial myocyte hypertrophy in CTRL AF (13.5 µm [95%CI: 12.9, 14.0] vs. SHAM: 12.5 µm [95%CI: 12.0, 13.0]), which was fully prevented by rivaroxaban (12.2 µm [95%CI: 11.7, 12.7]). Hemodynamics and AF stability were not altered by rivaroxaban treatment. PAR1 agonist triggered overexpression of the pro-hypertrophic genes NPPA (±2-fold) and NPPB (±4-fold) and significantly upregulated the pro-inflammatory gene CCL2 (±3-fold) in iPSC-CM. Similarly, thrombin, the most potent PAR1 activator, led to a significant overexpression of NPPA (±2-fold), NPPB (±10-fold) and CCL2 (±5-fold) mRNA, which was prevented by its direct inhibitor dabigatran. The pro-hypertrophic effect of FXa on iPSC-CM was found to be mediated by thrombin contamination in the FXa preparation. Conclusion Prolonged rivaroxaban treatment reduces systemic thrombin generation and prevents AF-induced atrial myocyte hypertrophy through inhibition of PAR1 activation.