Inhibition of coagulation factor Xa improves myocardial function during CVB3-induced myocarditis

Cytotoxic CD8+ T Cells Are Involved in the Thrombo-Inflammatory Response during First-Diagnosed Atrial Fibrillation

BACKGROUND

Atrial myopathy and atrial fibrillation (AF) accompany thrombo-inflammation. This facilitates disease progression and promotes major adverse cardiovascular events (MACEs). Thrombin receptor (protease-activated receptor 1, PAR1) signalling is central in mediating thrombo-inflammation. We hypothesised that PAR1 signalling links coagulation and inflammation through cytotoxic CD8⁺ T lymphocytes in patients presenting with first-diagnosed AF (FDAF).

METHODS

A total of 210 patients were studied. We included data and blood samples from patients presenting with FDAF (n = 160), cardiac tissue from patients with paroxysmal AF (n = 32) and 20 controls.

RESULTS

During early AF, a pro-inflammatory and cytotoxic subset of T lymphocytes (CD8⁺) circulated more frequently when compared to patients with chronic cardiovascular disease but without AF, accompanied by elevated plasma levels of CD8⁺ effector molecules, which corresponded to biomarkers of adverse cardiac remodelling and atrial dysfunction. Activation of tissue factor (TF) and PAR1 was associated with pro-inflammatory and cytotoxic effector functions. PAR1-related CD8⁺ cell activation was more frequent in FDAF patients that experienced a MACE.

CONCLUSIONS

In patients with FDAF, the TF-factor Xa-factor IIa-axis contributes to thrombo-inflammation via PAR1 in CD8⁺ T cells. Intervening in this cascade might be a promising synergistic approach to reducing disease progression and the vascular complications of AF.

Potential Therapeutic Roles for Direct Factor Xa Inhibitors in Coronavirus Infections

Human factor Xa (FXa) is a serine protease of the common coagulation pathway. FXa is known to activate prothrombin to thrombin, which eventually leads to the formation of cross-linked blood clots. While this process is important in maintaining hemostasis, excessive thrombin generation results in a host of thrombotic conditions. FXa has also been linked to inflammation via protease-activated receptors. Together, coagulopathy and inflammation have been implicated in the pathogenesis of viral infections, including the current coronavirus pandemic. Direct FXa inhibitors have been shown to possess anti-inflammatory and antiviral effects, in addition to their established anticoagulant activity. This review summarizes the pharmacological activities of direct FXa inhibitors, their pharmacokinetics, potential drug–drug interactions and adverse effects, and the details of clinical trials involving direct FXa inhibitors in coronavirus disease 2019 (COVID-19) patients.

Direct oral anticoagulants and vitamin K antagonists are linked to differential profiles of cardiac function and lipid metabolism

BACKGROUND

Experimental data indicate that direct acting oral anticoagulants (DOAC) and vitamin K antagonists (VKA) may exert differential effects on cardiovascular disease.

METHODS

Data from the prospective, observational, single-center MyoVasc Study were used to examine associations of DOAC as compared to VKA with subclinical markers of cardiovascular disease, cardiac function, and humoral biomarkers in heart failure (HF).

RESULTS

Multivariable analysis adjusted for age, sex, traditional cardiovascular risk factors, comorbidities, and medications with correction for multiple testing demonstrated that DOAC therapy was among all investigated parameters an independent significant predictor of better diastolic function (E/E': β - 0.24 [- 0.36/- 0.12]; P < 0.0001) and higher levels of ApoA1 (β + 0.11 g/L [0.036/0.18]; P = 0.0038) compared to VKA therapy. In propensity score-weighted analyses, the most pronounced differences between DOAC and VKA-based therapy were also observed for E/E' (∆ - 2.36) and ApoA1 (∆ + 0.06 g/L). Sensitivity analyses in more homogeneous subsamples of (i) individuals with AF and (ii) individuals with asymptomatic HF confirmed the consistency and robustness of these findings. In the comparison of factor IIa and Xa-directed oral anticoagulation, no differences were observed regarding cardiac function (E/E' ratio: β_{IIa inhibitor} - 0.22 [- 0.36/- 0.08] vs. β_{Xa inhibitor} - 0.24 [- 0.37/- 0.11]) and lipid metabolism (ApoA1: β_{IIa inhibitor} 0.10 [0.01/0.18] vs. β_{Xa inhibitor} 0.12 [0.04/0.20]) compared to VKA therapy.

CONCLUSION

This study provides the first evidence for differential, non-conventional associations of oral anticoagulants on cardiac function and lipid metabolism in humans. The potentially beneficial effect of DOACs in the highly vulnerable population of HF individuals needs to be further elucidated and may have implications for individually tailored anticoagulation therapy.

The coagulation system in host defense

The blood coagulation system and immune system of higher organisms are thought to have a common ancestral origin. During infections, the blood coagulation system is activated and components of the hemostatic system are directly involved in the immune response and immune system modulations. The current view is that the activation of coagulation is beneficial for infections with bacteria and viruses. It limits pathogen dissemination and supports pathogen killing and tissue repair. On the other hand, over-activation can lead to thrombosis with subsequent depletion of hemostatic factors and secondary bleeding. This review will summarize the current knowledge on blood coagulation and pathogen infection with focus on most recent studies of the role of the different parts of the blood coagulation system in selected bacterial and viral infections.

Effects of the factor Xa inhibitor, fondaparinux, on the stability of atherosclerotic lesions in apolipoprotein E-deficient mice

BACKGROUND

Atherosclerosis is a progressive inflammatory disease that can lead to sudden cardiac events by plaque rupture and subsequent thrombosis. Factor Xa (FXa) not only occupies a crucial position in the coagulation cascade responsible for thrombin generation, but also has pro-inflammatory effects. The hypothesis that Fondaparinux, the selective FXa inhibitor, attenuates plaque progression and promotes stability of atherosclerotic lesions was assessed.

METHODS AND RESULTS

Fondaparinux (5 mg/kg body weight/day) or 0.9% saline was intraperitoneally administered for 4 weeks to apolipoprotein E-deficient mice (n=12 per group) with established atherosclerotic lesions in the innominate arteries. Fondaparinux did not remarkably decrease the progression of atherosclerosis development in apolipoprotein E-deficient mice, but increased the thickness of fibrous cap (P=0.049) and decreased the ratio of necrotic core (P=0.001) significantly. Moreover, Fondaparinux reduced the staining against Mac-2 (P=0.017), α-SMA (P=0.002), protease-activated receptor (PAR)-1 (P=0.001), PAR-2 (P=0.003), CD-31 (P=0.024), MMP-9 (P=0.000), MMP-13(P=0.011), VCAM-1 (P=0.041) and the mRNA expression of inflammatory mediators (P<0.05) significantly, such as interleukin (IL)-6, MCP-1, IFN-γ, TNF-α, IL-10 and Egr-1.

CONCLUSIONS

Fondaparinux, the selective FXa inhibitor, can promote the stability of atherosclerotic lesions in apolipoprotein E-deficient mice, possibly through inhibiting expression of the inflammatory mediators in plaque and reduced synthesis of MMP-9 and MMP-13.

Premature rupture of the fetal membrane combined with subclinical chorioamnionitis negatively affects pregnancy outcomes by a mechanism associated with reduced levels of matrix metalloproteinase-2

The present study aimed to investigate whether premature rupture of the fetal membrane, combined with subclinical chorioamnionitis, affects pregnancy outcomes. In addition, the association between premature rupture of the fetal membrane (PROM) and the levels of matrix metalloproteinase-2 (MMP-2), an inactive proenzyme that can be activated by other factors or signals in humans, was examined. In total, 80 pregnant patients with PROM were classified into the experimental and control groups, according to their final placental pathological diagnosis results. The 40 patients in the experimental group suffered from subclinical chorioamnionitis, while the 40 patients in the control group exhibited no lesions of the placenta or fetal membrane. Tissue samples were collected and the total protein and mRNA were extracted for western blot and quantitative polymerase chain reaction analyses. ELISA was performed in order to detect the levels of MMP-2 in the serum of the two groups of patients. The rates of cesarean section, puerperal infection, postpartum hemorrhage, preterm incidence, placenta accreta, residual placental blood and stillbirth were all significantly higher in the experimental group compared with the control group. In addition, the mRNA and protein expression levels of MMP-2 were reduced in the experimental group compared with the control group. ELISA results indicated that the serum MMP-2 concentrations were also reduced in the patients with PROM. Therefore, the present study demonstrated that the PROM, combined with subclinical chorioamnionitis, significantly affected pregnancy outcomes and was associated with reduced levels of MMP-2.

Role of protease-activated receptors for the innate immune response of the heart

Protease-activated receptors (PARs) are a family of G-protein-coupled receptors with a unique activation mechanism via cleavage by the serine proteases of the coagulation cascade, immune cell-released proteases, and proteases from pathogens. Pathogens, such as viruses and bacteria, cause myocarditis and heart failure and PAR1 was shown to positively regulate the anti-viral innate immune response via interferon β during virus-induced myocarditis. In contrast, PAR2 negatively regulated the innate immune response and inhibited the interferon β expression. Thus, PARs play a central role for the innate immune response in the heart.

Multiple roles of the coagulation protease cascade during virus infection

The coagulation cascade is activated during viral infections. This response may be part of the host defense system to limit spread of the pathogen. However, excessive activation of the coagulation cascade can be deleterious. In fact, inhibition of the tissue factor/factor VIIa complex reduced mortality in a monkey model of Ebola hemorrhagic fever. Other studies showed that incorporation of tissue factor into the envelope of herpes simplex virus increases infection of endothelial cells and mice. Furthermore, binding of factor X to adenovirus serotype 5 enhances infection of hepatocytes but also increases the activation of the innate immune response to the virus. Coagulation proteases activate protease-activated receptors (PARs). Interestingly, we and others found that PAR1 and PAR2 modulate the immune response to viral infection. For instance, PAR1 positively regulates TLR3-dependent expression of the antiviral protein interferon β, whereas PAR2 negatively regulates expression during coxsackievirus group B infection. These studies indicate that the coagulation cascade plays multiple roles during viral infections.