P2563Effects of rivaroxaban on cardiac remodeling after experimental myocardial infarction in mice

Background

Rivaroxaban, a direct activated factor X (FXa) inhibitor, has been established for prevention and treatment of arterial and venous thrombosis. Although FXa plays an important role in thrombosis, FXa also involves in inflammation via the protease-activated receptor (PAR)-1 and PAR-2 pathway. We assessed the hypothesis that rivaroxaban might protect cardiac remodeling after myocardial infarction (MI) in mice.

Methods

MI was induced in wild-type mice by permanent ligation of the left anterior descending coronary artery. At 1 day after MI, mice were randomly assigned to the rivaroxaban and vehicle groups. In the rivaroxaban group, the mice were provided with regular chow diet including rivaroxaban (2400ppm) after the randomization. We evaluated the cardiac function by echocardiography, expression of mRNA and protein in the infarcted and non-infarcted area 7 days after MI. Furthermore, we measured infarct size, infiltration of inflammatory cells by pathological analysis 7 days after MI.

Results

The fractional shortening (%FS) and Interventricular Septal thickness in diastole (IVSTd) was significantly improved 7 days after MI in the rivaroxaban group compared with the vehicle group (%FS, p=0.01; IVSTd, p=0.013). As for pathological analysis, rivaroxaban decreased infarct size (p=0.026) and the number of infiltrated macrophages in the non-infarcted area (p=0.011) compared with vehicle. The mRNA expression in tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β in the infarcted area and atrial natriuretic peptide (ANP) in the non-infarcted area was significantly lower in the rivaroxaban group compared with the vehicle (TNF-α, p=0.015; TGF-β, p=0.019; ANP, p=0.012). PAR-1 and PAR-2 mRNA expression in the infarcted area significantly decreased 7 days after MI in the rivaroxaban group compared with the vehicle (PAR-1, p=0.005; PAR-2, p=0.037). Furthermore, western blot analysis demonstrated that the phosphorylation of Extracellular Signal-regulated Kinase (ERK) and c-Jun N-terminal Kinase (JNK) in the non-infarcted area significantly decreased 7 days after MI in the rivaroxaban group compared with the vehicle (ERK, p=0.015; JNK, p=0.002).

Conclusions

The present study showed that rivaroxaban protected against cardiac dysfunction, probably due to the suppression of PAR-mediated increase of pro-inflammatory cytokines post-MI. Rivaroxaban might be potentially effective for improving the cardiac remodeling after MI.

Acknowledgement/Funding

This study was supported in part by trust-research grant from Bayer Yakuhin, Ltd.

Assessment of platelet-derived thrombogenicity with the total thrombus-formation analysis system in coronary artery disease patients receiving antiplatelet therapy

BACKGROUND

Accurate evaluation of thrombogenicity helps to prevent thrombosis and excessive bleeding. The total thrombus-formation analysis system (T-TAS) was developed for quantitative analysis of platelet thrombus formation by the use of microchips with thrombogenic surfaces (collagen, platelet chip [PL-chip]; collagen plus tissue factor, atherome chip [AR-chip]). We examined the utility of the T-TAS in the assessment of the efficacy of antiplatelet therapy in patients with coronary artery disease (CAD).

METHODS AND RESULTS

In this cross-sectional study, 372 consecutive patients admitted to the cardiovascular department were divided into three groups: patients not receiving any antiplatelet therapy (control, n = 56), patients receiving aspirin only (n = 69), and patients receiving aspirin and clopidogrel (n = 149). Blood samples were used for the T-TAS to measure the platelet thrombus-formation area under the curve (AUC) at various shear rates (1500 s(-1) [PL18 -AUC10 ] and 2000 s(-1) [PL24 -AUC10 ] for the PL-chip; 300 s(-1) [AR10 -AUC30 ] for the AR-chip). The on-clopidogrel platelet aggregation was measured by the use of P2Y12 reaction units (PRUs) with the VerifyNow system. The mean PL24 -AUC10 levels were 358 ± 111 (± standard deviation) (95% confidence interval [CI] 328.9-387.1) in the control group, 256 ± 108 (95% CI 230.5-281.5) in the aspirin group, and 113 ± 91 (95% CI 98.4-127.6) in the aspirin/clopidogrel group. In the aspirin/clopidogrel group, the PL24 -AUC10 was higher in poor metabolizers (PMs) with cytochrome P450 2C19(CYP2C19) polymorphisms (152 ± 112, 95% CI 103.4-200.6) than in the non-PM group (87 ± 74, 95% CI 73.8-100.2).

CONCLUSIONS

Our findings suggest that the PL24 -AUC10 level measured by the T-TAS is a potentially suitable index for the assessment of antiplatelet therapy in CAD patients.