Activated factor X (FXa) is an important player in the coagulation cascade responsible for
thrombin generation, which is activated during
atrial fibrillation. Increasing evidence suggests that FXa influences cell signalling in various cell types by activating
protease-activated receptors (PARs). It is so far not known if molecular effects of FXa affect atrial signal transduction. To study the effects of FXa, human atrial tissue slices were cultivated with FXa up to 24h. Additionally, rapid pacing was applied at 4Hz to resemble
atrial fibrillation. The inhibitory impact of FXa antagonist (
Rivaroxaban),
protease-activated receptor 1 antagonist (
SCH79797), and
protease-activated receptor 2 antagonist (GB83) were analysed under experimental conditions. The exposure of atrial tissue to FXa resulted in the 1.7 fold upregulation of PAR2-mRNA, activation of MAP
kinases (ERK1/2) and NF-κB signalling. Furthermore FXa increased the expression of adhesion molecule
ICAM-1 (1.82 ± 0.20),
chemokine IL-8 (1.94 ± 0.20), as well as prothrombotic molecule
PAI-1 (1.52 ± 0.17). The combination of rapid pacing and FXa caused significant upregulation of PAR1 (2.82 ± 0.22), PAR2 (2.66 ± 0.40),
ICAM-1 (2.13 ± 0.25),
IL-8 (2.22 ± 0.24), LOX-1 (2.59 ± 0.35), and
PAI-1 (2.65 ± 0.52) at the
mRNA level.
Rivaroxaban and GB83 prevented upregulation of PARs,
ICAM-1, LOX-1,
IL-8, and activation of MAP
kinases. The elevation in the expression of
PAI-1 was hindered in the presence of
SCH79797, or
Rivaroxaban. The present study indicates that FXa mediates inflammatory signalling in atrial tissue. Importantly, FXa and
tachyarrhythmia act synergistically to increase expression of
protease-activated receptors and inflammatory mediators.
Rivaroxaban prevented effectively FXa-induced molecular effects in human atrial tissue particularly during rapid pacing.