Direct Thrombin Inhibitors Prevent Left Atrial Remodeling Associated With Heart Failure in Rats

Characterization of Biomarkers of Thrombo-Inflammation in Patients with First-Diagnosed Atrial Fibrillation

Patients with first-diagnosed atrial fibrillation (FDAF) exhibit major adverse cardiovascular events (MACEs) during follow-up. Preclinical models have demonstrated that thrombo-inflammation mediates adverse cardiac remodeling and atherothrombotic events. We have hypothesized that thrombin activity (FIIa) links coagulation with inflammation and cardiac fibrosis/dysfunction. Surrogate markers of the thrombo-inflammatory response in plasma have not been characterized in FDAF. In this prospective longitudinal study, patients presenting with FDAF (n = 80), and 20 matched controls, were included. FIIa generation and activity in plasma were increased in the patients with early AF compared to the patients with chronic cardiovascular disease without AF (controls; p < 0.0001). This increase was accompanied by elevated biomarkers (ELISA) of platelet and endothelial activation in plasma. Pro-inflammatory peripheral immune cells (TNF-α+ or IL-6+) that expressed FIIa-activated protease-activated receptor 1 (PAR1) (flow cytometry) circulated more frequently in patients with FDAF compared to the controls (p < 0.0001). FIIa activity correlated with cardiac fibrosis (collagen turnover) and cardiac dysfunction (NT-pro ANP/NT-pro BNP) surrogate markers. FIIa activity in plasma was higher in patients with FDAF who experienced MACE. Signaling via FIIa might be a presumed link between the coagulation system (tissue factor-FXa/FIIa-PAR1 axis), inflammation, and pro-fibrotic pathways (thrombo-inflammation) in FDAF.

Clinical outcomes and anticoagulation therapy in elderly non-valvular atrial fibrillation and heart failure patients

AIMS

Atrial fibrillation (AF) and heart failure (HF) often coexist. Older age is strongly associated with stroke, HF, and mortality. The association between coexistence of HF and a risk of clinical outcomes and the effectiveness of anticoagulation therapy including direct oral anticoagulants (DOACs) in elderly patients with AF and HF have not been investigated. We aimed to evaluate 2 years of outcomes and to elucidate the efficacy of DOACs or warfarin in elderly AF patients in the All Nippon AF In the Elderly (ANAFIE) Registry with and without a history of HF.

METHODS AND RESULTS

The ANAFIE Registry is a multicentre, prospective observational study following elderly non-valvular AF patients aged ≥75 years for 2 years. Hazard ratios (HRs) were calculated based on the presence or absence of an HF diagnosis and DOAC or warfarin use at enrolment. Among 32 275 eligible patients, 12 116 (37.5%) had been diagnosed with HF. Patients with HF had significantly higher rates of HF hospitalization or cardiovascular death (HR 1.94, P < 0.001), cardiovascular events (HR 1.59, P < 0.001), cardiovascular death (HR 1.49, P < 0.001), all-cause death (HR 1.32, P < 0.001), and net clinical outcome including stroke/systemic embolism, major bleeding, and all-cause death (HR 1.23, P < 0.001), compared with those without HF; however, HRs for stroke/systemic embolism (HR 0.96, P = 0.56) and major bleeding (HR 1.14, P = 0.13) were similar. DOAC use was associated with a low risk of stroke/systemic embolism (HR 0.86, P = 0.19 in HF; HR 0.79, P = 0.016 in non-HF; P for interaction = 0.56), major bleeding (HR 0.71, P = 0.008 in HF; HR 0.75, P = 0.016 in non-HF; P for interaction = 0.74), HF hospitalization or cardiovascular death (HR 0.81, P < 0.001 in HF; HR 0.78, P < 0.001 in non-HF; P for interaction = 0.26), cardiovascular events (HR 0.83, P < 0.001 in HF; HR 0.82, P = 0.001 in non-HF; P for interaction = 0.65), cardiovascular death (HR 0.84, P = 0.12 in HF; HR 0.75, P = 0.035 in non-HF; P for interaction = 0.18), all-cause death (HR 0.89, P = 0.082 in HF; HR 0.80, P = 0.001 in non-HF; P for interaction = 0.091), and net clinical outcome (HR 0.88, P = 0.019 in HF; HR 0.81, P < 0.001 in non-HF; P for interaction = 0.21) compared with warfarin, irrespective of the presence or absence of HF. Analysis using the propensity score matching method showed similar associations.

CONCLUSIONS

Non-valvular AF patients aged ≥75 years with a history of HF had higher risks of cardiovascular events and mortality. DOACs were favourable to warfarin regardless of the coexistence of HF. These results might encourage the use of DOACs in elderly patients with non-valvular AF with or without HF.

Future Perspectives to Improve CHA2DS2VASc Score: The Role of Left Atrium Remodelling, Inflammation and Genetics in Anticoagulation of Atrial Fibrillation

In 10% of ischemic strokes, non-valvular atrial fibrillation (NVAF) is detected retroactively. Milder, or even asymptomatic forms of NVAF have shown high mortality, thrombotic risk, and deterioration of cognitive function. The current guidelines for the diagnosis and treatment of AF contain "grey areas", such as the one related to anticoagulant treatment in men with CHA2DS2-VASc score 1 and women with score 2. Moreover, parameters such as renal function, patient weight or left atrium remodelling are missing from the recommended guidelines scores. Vulnerable categories of patients including the elderly population, high hemorrhagic risk patients or patients with newly diagnosed paroxysmal episodes of atrial high rate at device interrogation are at risk of underestimation of the thrombotic risk. This review presents a systematic exposure of the most important gaps in evaluation of thrombotic and hemorrhagic risk in patients with NVAF. The authors propose new algorithms and risk factors that should be taken into consideration for an accurate thrombotic and hemorrhagic risk estimation, especially in vulnerable categories of patients.

Prophylactic rivaroxaban in the early post-discharge period reduces the rates of hospitalization for atrial fibrillation and incidence of sudden cardiac death during long-term follow-up in hospitalized COVID-19 survivors

Introduction: While acute Coronavirus disease 2019 (COVID-19) affects the cardiovascular (CV) system according to recent data, an increased CV risk has been reported also during long-term follow-up (FU). In addition to other CV pathologies in COVID-19 survivors, an enhanced risk for arrhythmic events and sudden cardiac death (SCD) has been observed. While recommendations on post-discharge thromboprophylaxis are conflicting in this population, prophylactic short-term rivaroxaban therapy after hospital discharge showed promising results. However, the impact of this regimen on the incidence of cardiac arrhythmias has not been evaluated to date. Methods: To investigate the efficacy of this therapy, we conducted a single center, retrospective analysis of 1804 consecutive, hospitalized COVID-19 survivors between April and December 2020. Patients received either a 30-day post-discharge thromboprophylaxis treatment regimen using rivaroxaban 10 mg every day (QD) (Rivaroxaban group (Riva); n = 996) or no thromboprophylaxis (Control group (Ctrl); n = 808). Hospitalization for new atrial fibrillation (AF), new higher-degree Atrioventricular-block (AVB) as well as incidence of SCD were investigated in 12-month FU [FU: 347 (310/449) days]. Results: No differences in baseline characteristics (Ctrl vs Riva: age: 59.0 (48.9/66.8) vs 57 (46.5/64.9) years, p = n.s.; male: 41.5% vs 43.7%, p = n.s.) and in the history of relevant CV-disease were observed between the two groups. While hospitalizations for AVB were not reported in either group, relevant rates of hospitalizations for new AF (0.99%, n = 8/808) as well as a high rate of SCD events (2.35%, n = 19/808) were seen in the Ctrl. These cardiac events were attenuated by early post-discharge prophylactic rivaroxaban therapy (AF: n = 2/996, 0.20%, p = 0.026 and SCD: n = 3/996, 0.30%, p < 0.001) which was also observed after applying a logistic regression model for propensity score matching (AF: χ ²-statistics = 6.45, p = 0.013 and SCD: χ ²-statistics = 9.33, p = 0.002). Of note, no major bleeding complications were observed in either group. Conclusion: Atrial arrhythmic and SCD events are present during the first 12 months after hospitalization for COVID-19. Extended prophylactic Rivaroxaban therapy after hospital discharge could reduce new onset of AF and SCD in hospitalized COVID-19 survivors.

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.

Enhanced Thrombin Generation Is Associated with Worse Left Ventricular Scarring after ST-Segment Elevation Myocardial Infarction: A Cohort Study

Acute myocardial infarction (AMI) is associated with heightened thrombin generation. There are limited data relating to thrombin generation and left ventricular (LV) scarring and LV dilatation in post-MI LV remodeling. We studied 113 patients with ST-segment elevation myocardial infarction (STEMI) who had undergone primary percutaneous coronary intervention (PPCI) (n = 76) or pharmaco-invasive management (thrombolysis followed by early PCI, n = 37). Endogenous thrombin potential (ETP) was measured at baseline, 1 month and 6 months. Cardiovascular magnetic resonance imaging was performed at baseline and 6 months post-MI. Outcomes studied were an increase in scar change, which was defined as an increase in left ventricular infarct size of any magnitude detected by late gadolinium enhancement, adverse LV remodeling, defined as dilatation (increase) of left ventricular end-diastolic volume (LVEDV) by more than 20% and an increase in left ventricular ejection fraction (LVEF). The mean age was 55.19 ± 8.25 years and 91.2% were men. The baseline ETP was similar in the PPCI and pharmaco-invasive groups (1400.3 nM.min vs. 1334.1 nM.min, p = 0.473). Each 10-unit increase in baseline ETP was associated with a larger scar size (adjusted OR 1.020, 95% CI 1.002–1.037, p = 0.027). Baseline ETP was not associated with adverse LV remodeling or an increase in LVEF. There was no difference in scar size or adverse LV remodeling among patients undergoing PPCI vs. pharmaco-invasive management or patients receiving ticagrelor vs. clopidogrel. Enhanced thrombin generation after STEMI is associated with a subsequent increase in myocardial scarring but not LV dilatation or an increase in LVEF at 6 months post-MI.

Pirfenidone attenuates cardiac hypertrophy against isoproterenol by inhibiting activation of the janus tyrosine kinase-2/signal transducer and activator of transcription 3 (JAK-2/STAT3) signaling pathway

Cardiovascular risk factors have attracted increasing attention in recent years with the acceleration of population aging, amongst which cardiac hypertrophy is the initiating link to heart failure. Pirfenidone is a promising agent for the treatment of idiopathic pulmonary fibrosis and has recently proven to exert inhibitory effects on the inflammatory response. This study proposes to explore the potential pharmacological action of pirfenidone in treating cardiac hypertrophy in a rodent model. Four groups of mice were used in the present study: the control, ISO (5 mg/kg/day) for 7 days, pirfenidone (200 mg/kg/day) for 14 days, and spironolactone (SPI) (200 mg/kg/day) for 14 days groups. Increased heart weight index, left ventricle (LV) weight index, LV wall thickness, declined LV volume, and elevated serum levels of CK-MB, AST, and LDH were observed in ISO-challenged mice, all of which were dramatically reversed by the administration of pirfenidone or SPI. Furthermore, an elevated cross-sectional area of cardiomyocytes in the wheat germ agglutinin (WGA) staining of heart cross-sections, upregulated atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), β-Myosin Heavy Chain (β-MHC), and excessively released tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6) in cardiac tissues were observed in the ISO group but greatly alleviated by pirfenidone or SPI. Lastly, the promoted expression levels of p-JAK-2/JAK-2 and p-STAT3/STAT-3 in the cardiac tissues of ISO-challenged mice were significantly repressed by pirfenidone or SPI. Collectively, our data reveals a therapeutic property of pirfenidone on ISO-induced cardiac hypertrophy in mice.  

The role of senescence in the pathogenesis of atrial fibrillation: A target process for health improvement and drug development

Cellular senescence is a state of growth arrest that occurs after cells encounter various stresses. Senescence contributes to tumour suppression, embryonic development, and wound healing. It impacts on the pathology of various diseases by secreting inflammatory chemokines, immune modulators and other bioactive factors. These secretory biosignatures ultimately cause inflammation, tissue fibrosis, immunosenescence and many ageing-related diseases such as atrial fibrillation (AF). Because the molecular mechanisms underpinning AF development remain unclear, current treatments are suboptimal and have serious side effects. In this review, we summarize recent results describing the role of senescence in AF. We propose that senescence factors induce AF and have a causative role. Hence, targeting senescence and its secretory phenotype may attenuate AF.

Many Good Reasons to Switch from Vitamin K Antagonists to Non-Vitamin K Antagonists in Patients with Non-Valvular Atrial Fibrillation

Non-vitamin K oral anticoagulants (NOACs) are the first choice for prophylaxis of cardioembolism in patients with non-valvular atrial fibrillation (AF) who are anticoagulant-naïve, as well as the preferable anticoagulation strategy in those who are on vitamin K antagonists (VKAs), but with a low time in therapeutic range (TTR). Nonetheless, there are many good reasons to consider switching from VKAs to NOACs also when TTR is >70%. From the pharmacological standpoint, anticoagulation with VKAs may remain erratic even in those patients who have high TTR values, owing to the mode of action of this drug class. Furthermore, experimental data suggest that, unlike VKAs, NOACs favorably modulate the effects of factor Xa and thrombin in the cardiovascular system through the protease-activated receptor family. Clinically, the most striking advantage provided by NOACs over VKAs, irrespective of the TTR, is the substantially lower risk of intracranial hemorrhage. NOACs have also been associated with less deterioration of renal function as compared with VKAs and may confer protection against cardiovascular events not strictly related to AF, especially the acute complications of peripheral artery disease. In this narrative review, we discuss the evidence according to which it is warranted to systematically substitute NOACs for VKAs for the prevention of AF-related stroke and systemic embolism.

A Thrombin-Responsive Nanoprobe for In Vivo Visualization of Thrombus Formation through Three-Dimensional Optical/Computed Tomography Hybrid Imaging

Early spontaneous detection of thrombin activation benefits precise theranostics for thrombotic vascular disease. Herein, a thrombin-responsive nanoprobe conjugated by a FITC dye, PEGylated Fe₃O₄ nanoparticles, and a thrombin-sensitive peptide (LASG) was constructed to visualize thrombin activation and subsequent thrombosis in vivo. The FITC dye was linked to the LASG coated on the Fe₃O₄ nanoparticles for sensing the thrombin activity via the Förster resonance energy transfer effect. In vitro fluorescence imaging showed that the fluorescence signal intensity increased significantly after incubation with thrombin in contrast to that of the control group (p < 0.05), and the signal intensity was enhanced with the increase in thrombin concentration. Further in vivo fluorescence imaging also revealed that the signal elevated markedly in the left common carotid artery (LCCA) lesion of the mice thrombosis model after nanoprobe injection, in contrast to that of the control + nanoprobe group (p < 0.05). Moreover, the thrombin inhibitor bivalirudin could decrease the filling defect of the LCCA. Three-dimensional fusion images of micro-CT and fluorescence confirmed that filling defects in the LCCA were nicely colocalized with fluorescence signal caused by nanoprobes. The nanoplatform based on a thrombin-activatable visualization system could provide smart responsive and dynamic imaging of thrombosis in vivo.

Cardiac Dysfunction in a Mouse Vascular Dementia Model of Bilateral Common Carotid Artery Stenosis

Background: Cardiac function is associated with cognitive function. Previously, we found that stroke and traumatic brain injury evoke cardiac dysfunction in mice. In this study, we investigate whether bilateral common carotid artery stenosis (BCAS), a model that induces vascular dementia (VaD) in mice, induces cardiac dysfunction. Methods: Late-adult (6-8 months) C57BL/6J mice were subjected to sham surgery (n = 6) or BCAS (n = 8). BCAS was performed by applying microcoils (0.16 mm internal diameter) around both common carotid arteries. Cerebral blood flow and cognitive function tests were performed 21-28 days post-BCAS. Echocardiography was conducted in conscious mice 29 days after BCAS. Mice were sacrificed 30 days after BCAS. Heart tissues were isolated for immunohistochemical evaluation and real-time PCR assay. Results: Compared to sham mice, BCAS in mice significantly induced cerebral hypoperfusion and cognitive dysfunction, increased cardiac hypertrophy, as indicated by the increased heart weight and the ratio of heart weight/body weight, and induced cardiac dysfunction and left ventricular (LV) enlargement, indicated by a decreased LV ejection fraction (LVEF) and LV fractional shortening (LVFS), increased LV dimension (LVD), and increased LV mass. Cognitive deficits significantly correlated with cardiac deficits. BCAS mice also exhibited significantly increased cardiac fibrosis, increased oxidative stress, as indicated by 4-hydroxynonenal and NADPH oxidase-2, increased leukocyte and macrophage infiltration into the heart, and increased cardiac interleukin-6 and thrombin gene expression. Conclusions: BCAS in mice without primary cardiac disease provokes cardiac dysfunction, which, in part, may be mediated by increased inflammation and oxidative stress.

Arrhythmia Recurrence After Atrial Fibrillation Ablation: Impact of Warfarin vs. Non-Vitamin K Antagonist Oral Anticoagulants

PURPOSE

Both warfarin and non-vitamin K antagonist oral anticoagulants (NOACs) have pleiotropic effects including anti-inflammatory and anti-fibrotic properties. This study aims to explore whether arrhythmia recurrence after AF ablation is influenced by the choice of oral anticoagulant.

METHODS

We retrospectively studied all patients who underwent primary AF ablation between 2011 and 2017 and divided them into two groups according to the anticoagulant used: Warfarin vs. NOACs. The primary endpoint was atrial tachyarrhythmia recurrence after ablation.

RESULTS

Of the 1106 patients who underwent AF ablation in the study period (median age 62.5 years; 71.5% males, 48.2% persistent AF), 697 (63%) received warfarin and 409 (37%) received NOACs. After a median of 26.4 months follow-up, arrhythmia recurrence was noted in 368 patients in warfarin group and 173 patients in NOACs group, with a 1-year recurrence probability of 35% vs. 36% (log rank P = 0.81) and 5-year recurrence probability of 62% vs. 63% (Log rank P = 0.32). However, NOACs use was associated with a higher probability of recurrence (46% for 1 year, 68% for 5 years) in patients with persistent AF compared with those taking warfarin (34% for 1 year, 63% for 5 years; log rank P = 0.01 and P = 0.02 respectively). Multivariate analysis indicated that in patients with persistent AF, use of NOACs was an independent risk factor of atrial tachyarrhythmia recurrence after ablation (HR 1.39, 95% CI 1.07-1.81, P = 0.013).

CONCLUSION

In this large contemporary cohort, overall AF recurrence after ablation was similar with NOACs or warfarin use. However, in patients with persistent AF, NOACs use was associated with a higher probability of arrhythmia recurrence and was an independent risk factor of recurrence at long-term follow-up.

Chinese Herbs and Repurposing Old Drugs as Therapeutic Agents in the Regulation of Oxidative Stress and Inflammation in Pulmonary Diseases

Several pro-inflammatory factors and proteins have been characterized that are involved in the pathogenesis of inflammatory diseases, including acute respiratory distress syndrome, chronic obstructive pulmonary disease, and asthma, induced by oxidative stress, cytokines, bacterial toxins, and viruses. Reactive oxygen species (ROS) act as secondary messengers and are products of normal cellular metabolism. Under physiological conditions, ROS protect cells against oxidative stress through the maintenance of cellular redox homeostasis, which is important for proliferation, viability, cell activation, and organ function. However, overproduction of ROS is most frequently due to excessive stimulation of either the mitochondrial electron transport chain and xanthine oxidase or reduced nicotinamide adenine dinucleotide phosphate (NADPH) by pro-inflammatory cytokines, such as interleukin-1β and tumor necrosis factor α. NADPH oxidase activation and ROS overproduction could further induce numerous inflammatory target proteins that are potentially mediated via Nox/ROS-related transcription factors triggered by various intracellular signaling pathways. Thus, oxidative stress is considered important in pulmonary inflammatory processes. Previous studies have demonstrated that redox signals can induce pulmonary inflammatory diseases. Thus, therapeutic strategies directly targeting oxidative stress may be effective for pulmonary inflammatory diseases. Therefore, drugs with anti-inflammatory and anti-oxidative properties may be beneficial to these diseases. Recent studies have suggested that traditional Chinese medicines, statins, and peroxisome proliferation-activated receptor agonists could modulate inflammation-related signaling processes and may be beneficial for pulmonary inflammatory diseases. In particular, several herbal medicines have attracted attention for the management of pulmonary inflammatory diseases. Therefore, we reviewed the pharmacological effects of these drugs to dissect how they induce host defense mechanisms against oxidative injury to combat pulmonary inflammation. Moreover, the cytotoxicity of oxidative stress and apoptotic cell death can be protected via the induction of HO-1 by these drugs. The main objective of this review is to focus on Chinese herbs and old drugs to develop anti-inflammatory drugs able to induce HO-1 expression for the management of pulmonary inflammatory diseases.

Blockade of PAR-1 Signaling Attenuates Cardiac Hypertrophy and Fibrosis in Renin-Overexpressing Hypertensive Mice

Background

Although PAR‐1 (protease‐activated receptor‐1) exerts important functions in the pathophysiology of the cardiovascular system, the role of PAR‐1 signaling in heart failure development remains largely unknown. We tested the hypothesis that PAR‐1 signaling inhibition has protective effects on the progression of cardiac remodeling induced by chronic renin–angiotensin system activation using renin‐overexpressing hypertensive (Ren‐Tg) mice.

Methods and Results

We treated 12‐ to 16‐week‐old male wild‐type (WT) mice and Ren‐Tg mice with continuous subcutaneous infusion of the PAR‐1 antagonist SCH79797 or vehicle for 4 weeks. The thicknesses of interventricular septum and the left ventricular posterior wall were greater in Ren‐Tg mice than in WT mice, and SCH79797 treatment significantly decreased these thicknesses in Ren‐Tg mice. The cardiac fibrosis area and monocyte/macrophage deposition were greater in Ren‐Tg mice than in WT mice, and both conditions were attenuated by SCH79797 treatment. Cardiac mRNA expression levels of PAR‐1, TNF‐α (tumor necrosis factor‐α), TGF‐β1 (transforming growth factor‐β1), and COL3A1 (collagen type 3 α1 chain) and the ratio of β‐myosin heavy chain (β‐MHC) to α‐MHC were all greater in Ren‐Tg mice than in WT mice; SCH79797 treatment attenuated these increases in Ren‐Tg mice. Prothrombin fragment 1+2 concentration and factor Xa in plasma were greater in Ren‐Tg mice than in WT mice, and both conditions were unaffected by SCH79797 treatment. In isolated cardiac fibroblasts, both thrombin and factor Xa enhanced ERK1/2 (extracellular signal‐regulated kinase 1/2) phosphorylation, and SCH79797 pretreatment abolished this enhancement. Furthermore, gene expression of PAR‐1, TGF‐β1, and COL3A1 were enhanced by factor Xa, and all were inhibited by SCH79797.

Conclusions

The results indicate that PAR‐1 signaling is involved in cardiac remodeling induced by renin–angiotensin system activation, which may provide a novel therapeutic target for heart failure.

Pharmacological Inhibition of Serine Proteases to Reduce Cardiac Inflammation and Fibrosis in Atrial Fibrillation

Systemic inflammation correlates with an increased risk of atrial fibrillation (AF) and thrombogenesis. Systemic inflammation alters vessel permeability, allowing inflammatory and immune cell migration toward target organs, including the heart. Among inflammatory cells infiltrating the atria, macrophages and mast cell have recently attracted the interest of basic researchers due to the pathogenic mechanisms triggered by their activation. This chemotactic invasion is likely implicated in short- and long-term changes in cardiac cell-to-cell communication and in triggering fibrous tissue accumulation in the atrial myocardium and electrophysiological re-arrangements of atrial cardiomyocytes, thus favoring the onset and progression of AF. Serine proteases are a large and heterogeneous class of proteases involved in several processes that are important for cardiac function and are involved in cardiac diseases, such as (i) coagulation, (ii) fibrinolysis, (iii) extracellular matrix degradation, (iv) activation of receptors (i.e., protease-activated receptors [PPARs]), and (v) modulation of the activity of endogenous signals. The recognition of serine proteases substrates and their involvement in inflammatory/profibrotic mechanisms allowed the identification of novel cardio-protective mechanisms for commonly used drugs that inhibit serine proteases. The aim of this review is to summarize knowledge on the role of inflammation and fibrosis as determinants of AF. Moreover, we will recapitulate current findings on the role of serine proteases in the pathogenesis of AF and the possible beneficial effects of drugs inhibiting serine proteases in reducing the risk of AF through decrease of cardiac inflammation and fibrosis. These drugs include thrombin and factor Xa inhibitors (used as oral anticoagulants), dipeptidyl-peptidase 4 (DPP4) inhibitors, used for type-2 diabetes, as well as novel experimental inhibitors of mast cell chymases.

Thrombin Induces Angiotensin II-Mediated Senescence in Atrial Endothelial Cells: Impact on Pro-Remodeling Patterns

BACKGROUND

Besides its well-known functions in hemostasis, thrombin plays a role in various non-hemostatic biological and pathophysiologic processes. We examined the potential of thrombin to promote premature atrial endothelial cells (ECs) senescence.

METHODS AND RESULTS

Primary ECs were isolated from porcine atrial tissue. Endothelial senescence was assessed by measuring beta-galactosidase (SA-β-gal) activity using flow cytometry, oxidative stress using the redox-sensitive probe dihydroethidium, protein level by Western blot, and matrix metalloproteinases (MMPs) activity using zymography. Atrial endothelial senescence was induced by thrombin at clinically relevant concentrations. Thrombin induced the up-regulation of p53, a key regulator in cellular senescence and of p21 and p16, two cyclin-dependent kinase inhibitors. Nicotinamide adenine dinucleotide phosphate NADPH oxidase, cyclooxygenases and the mitochondrial respiration complex contributed to oxidative stress and senescence. Enhanced expression levels of vascular cell adhesion molecule (VCAM)-1, tissue factor, transforming growth factor (TGF)-β and MMP-2 and 9 characterized the senescence-associated secretory phenotype of atrial ECs. In addition, the pro-senescence endothelial response to thrombin was associated with an overexpression of both angiotensin converting enzyme and AT1 receptors and was inhibited by perindoprilat and losartan.

CONCLUSIONS

Thrombin promotes premature ageing and senescence of atrial ECs and may pave the way to deleterious remodeling of atrial tissue by a local up-regulation of the angiotensin system and by promoting pro-inflammatory, pro-thrombotic, pro-fibrotic and pro-remodeling responses. Hence, targeting thrombin and/or angiotensin systems may efficiently prevent atrial endothelial senescence.

Cathepsin A Mediates Ventricular Remote Remodeling and Atrial Cardiomyopathy in Rats With Ventricular Ischemia/Reperfusion

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The role of the protease cathepsin A for the progression of left ventricular remote remodeling and atrial cardiomyopathy in ischemic cardiomyopathy is unknown.

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In rats with ventricular ischemia and reperfusion, cathepsin A is up-regulated in the left ventricular and atrial tissue remote from the infarcted area.

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Pharmacological inhibition of cathepsin A protease activity by SAR significantly reduces remote ventricular remodeling and atrial extracellular matrix remodeling, represented by fibrosis formation and connexin 43 lateralization.

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Prevention of ventricular remote remodeling and atrial cardiomyopathy by SAR increased ventricular viable myocardium and atrial emptying function reducing susceptibility to atrial fibrillation.

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Remote ventricular and atrial extracellular matrix remodeling may represent a promising target for pharmacological atrial fibrillation upstream therapy following myocardial infarction.

After myocardial infarction, remote ventricular remodeling and atrial cardiomyopathy progress despite successful revascularization. In a rat model of ventricular ischemia/reperfusion, pharmacological inhibition of the protease activity of cathepsin A initiated at the time point of reperfusion prevented extracellular matrix remodeling in the atrium and the ventricle remote from the infarcted area. This scenario was associated with preservation of more viable ventricular myocardium and the prevention of an arrhythmogenic and functional substrate for atrial fibrillation. Remote ventricular extracellular matrix remodeling and atrial cardiomyopathy may represent a promising target for pharmacological atrial fibrillation upstream therapy following myocardial infarction.

Straight to the heart: Pleiotropic antiarrhythmic actions of oral anticoagulants

Mechanistic understanding of atrial fibrillation (AF) pathophysiology and the complex bidirectional relationship with thromboembolic risk remains limited. Oral anticoagulation is a mainstay of AF management. An emerging concept is that anticoagulants may themselves have potential pleiotropic disease-modifying effects. We here review the available evidence for hemostasis-independent actions of the oral anticoagulants on electrical and structural remodeling, and the inflammatory component of the vulnerable substrate.

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.

NEW-ONSET ATRIAL FIBRILLATION IN SETTINGS OF ACUTE CORONARY SYNDROME. CURRENT ISSUES

The present review is focuses on new onset atrial fibrillation (AF) in conditions of acute coronary syndrome (ACS). Literature sources from PubMed and Scopus was used. AF is common in the general population and in the ACS population, at that new onset AF, and AF, which was by the time of ACS development are determined. Appearance of AF is more likely amongst the elderly patients with congestive heart failure, with signs of the hemodynamic instability and with the left atrium dilatation. It is well-known about the predictors of adverse outcome in ACS. According to some literature data new onset AF leads to worsening of prognosis, and in line with other sources a reason of its association with high level of mortality is due to the severity of ACS and appearance of AF is not independent predictor of death. The absence of subjective symptoms at the time of paroxysm of new onset AF does not allow estimating its duration and distinguishing between the new onset AF, persistent and constant AF. It is possible to trace the relationship between the myocardial ischemia and AF appearance. Inefficient reperfusion during percutaneous coronary intervention or thrombolytic therapy is accompanied by the onset of AF, on the contrary, when effective patency of coronary artery is achieved, AF appears significantly less often. New onset AF in ACS, in particular, accompanied by cardiogenic shock, requires emergency pharmacological or electrical cardioversion. In some cases, active cardioversion is not necessary, because of spontaneous cardiac rhythm conversion. In conclusions, it is necessary to point out, that ambiguity and multifactority of this problem demands investigation of arrhythmogenesis mechanisms and development of special risk stratification instruments for the new onset AF in ACS.

Attenuation of type-1 diabetes-induced cardiovascular dysfunctions by direct thrombin inhibitor in rats: a mechanistic study

Chronic diabetes is associated with ventricular dysfunctions in the absence of hypertension and coronary artery diseases. This condition is termed as diabetic cardiomyopathy (DCM). There is no favourable treatment available for the management of diabetic cardiomyopathy. Recent studies have reported increase in circulating thrombin level among diabetic patients which is responsible for hypercoagulability of blood. Thrombin induces inflammation and fibrosis, and enhances cardiac cell growth and contractility in vitro. In this study, we have investigated the effects of argatroban; a direct thrombin inhibitor against DCM in streptozotocin-induced type-1 diabetes. Diabetes was induced by single dose of streptozotocin (STZ; 50 mg/kg, i.p.) in male Sprague-Dawley rats. After 4 weeks of diabetes induction, the animals were treated with argatroban (0.3 and 1 mg/kg, i.p. daily) for the next 4 weeks. The effect of argatroban was evaluated against diabetes-associated cardiac dysfunction, structural alteration and protein expression. STZ-induced diabetic rats exhibited significant decline in left ventricular functions. Four weeks of treatments with argatroban significantly improved ventricular functions without affecting heart rate. Further, it also protected heart against structural changes induced by diabetes as shown by reduction in fibrosis, hypertrophy and apoptosis. The improvement in cardiac functions and structural changes was associated with significant reduction in left ventricular expression of thrombin receptor also termed as protease-activated receptor-1 or PAR1, p-AKT (ser-473), p-50 NFκB and caspase-3 proteins. This study demonstrates beneficial effects of argatroban via improvement in cardiac functions and structural changes in STZ-induced DCM. These effects may be attributed through reduction in cardiac inflammation, fibrosis and apoptosis.

Thrombin induces protease-activated receptor 1 signaling and activation of human atrial fibroblasts and dabigatran prevents these effects

BACKGROUND

Data with animal cells and models suggest that thrombin activates cardiac fibroblasts (Fib) to myofibroblasts (myoFib) via protease-activated receptor 1 (PAR1) cleavage, and in this way promotes adverse atrial remodeling and, thereby, atrial fibrillation (AF).

OBJECTIVE

Here, we explored the effects of thrombin on human atrial Fib and whether they are antagonized by the clinically available direct thrombin inhibitor, dabigatran.

METHODS

Fib isolated from atrial appendages of patients without AF undergoing elective cardiac surgery were evaluated for PAR expression and treated with thrombin with or without dabigatran. PAR1 cleavage, downstream signaling and myoFib markers were investigated by immunofluorescence and Western blot. Collagen synthesis, activity of matrix metalloprotease (MMP)-2 and proliferation were assessed by Picro-Sirius red staining, gelatinolytic zymography and BrdU incorporation, respectively. Fib function was studied as capability to contract a collagen gel and stimulate the chemotaxis of peripheral blood monocytes from healthy volunteers.

RESULTS

Primary human atrial Fib expressed PAR1, while levels of the other PARs were very low. Thrombin triggered PAR1 cleavage and phosphorylation of ERK1/2, p38 and Akt, elicited a switch to myoFib enriched for αSMA, fibronectin and type I collagen, and induced paracrine/autocrine transforming growth factor beta-1, cyclooxygenase-2, endothelin-1 and chemokine (C-C motif) ligand 2 (CCL2); conversely, MMP-2 activity decreased. Thrombin-primed cells displayed enhanced proliferation, formed discrete collagen-containing cellular nodules, and stimulated the contraction of a collagen gel. Furthermore, their conditioned medium caused monocytes to migrate. All these effects were prevented by dabigatran.

CONCLUSION

These results with human cells complete the knowledge about thrombin actions on cardiac Fib and strengthen the translational potential of the emerging paradigm that pharmacological blockade of thrombin may counteract molecular and cellular events underlying AF.