Myeloperoxidase acts as a profibrotic mediator of atrial fibrillation

The role of NETosis in heart failure

The hallmark of heart failure (HF) is structural myocardial remodeling including cardiomyocyte hypertrophy, fibrosis, cardiomyocyte cell death, and a low-grade aseptic inflammation. The initiation and maintenance of persistent chronic low-grade inflammation in HF are not fully understood. Oxidative stress-mediated neutrophil extracellular traps (NETs) are the main immune defense mechanism against external bacterial infections. Furthermore, NETs play important roles in noninfectious diseases. In the settings of myocardial infarction, myocarditis, or cardiomyopathies, neutrophils infiltrate the cardiac tissue and undergo NETosis that further aggravate the inflammation. A number of stimuli may cause NETosis that is a form of programmed cell death of neutrophils that is different from apoptosis of these cells. Whether NETosis is directly involved in the pathogenesis and development of HF is still unclear. In this review, we analyzed the mechanisms and markers of NETosis, especially placing the accent on the activation of the neutrophil-specific myeloperoxidase (MPO), elastase (NE), and peptidylarginine deiminase 4 (PAD4). These conclusions are supported by the recent genetic and pharmacological studies which demonstrated that MPO, NE, and PAD4 inhibitors are effective at least in the settings of post-myocardial infarction adverse remodeling, cardiac valve diseases, cardiomyopathies, and decompensated left ventricular hypertrophy whose deterioration can lead to HF. This is essential for understanding NETosis as a contributor to pathophysiology of HF and developments of new therapies of HF.

The pivotal role of neutrophil extracellular traps in cardiovascular diseases: Mechanisms and therapeutic implications

Cardiovascular diseases (CVDs) continue to pose a significant burden on global health, prominently contributing to morbidity and mortality rates worldwide. Recent years have witnessed an increasing recognition of the intricate involvement of neutrophil extracellular traps (NETs) in the pathology of diverse cardiovascular conditions. This review provides a comprehensive analysis of the multifaceted functions of NETs in cardiovascular diseases, shedding light on the impact on atherosclerosis, myocardial infarction, heart failure, myocarditis, atrial fibrillation, aortic stenosis, and the potential therapeutic avenues targeting NETs.

Comprehensive mendelian randomization reveals atrial fibrillation-breast cancer relationship and explores common druggable targets

Background

Atrial fibrillation (AF) and breast cancer pose significant risks to human health. The reasons behind the concurrent occurrence of AF and breast cancer remain unclear, leading to complex treatment approaches. Mendelian Randomization (MR) analyses aim to offer genetic evidence supporting the causation of AF and breast cancer and to investigate common druggable genes associated with both conditions.

Methods

We used two-samples of MR to sequentially explore the causal relationship between atrial fibrillation and breast cancer, and between atrial fibrillation and breast cancer therapeutic drugs, and verified the stability of the results through colocalization analysis. We utilized the Connectivity map database to infer the direction of drug effects on disease. Finally, we explored druggable genes that play a role in AF and breast cancer and performed a Phenome-wide MR analysis to analyze the potential side effects of drug targets.

Results

We found 15 breast cancer therapeutic drugs that significantly support a causal association between AF and breast cancer through expression in blood and/or atrial appendage tissue. Among these, activation of ANXA5 by Docetaxel, inhibition of EIF5A by Fulvestrant, and inhibition of GNA12 by Tamoxifen increased the risk of AF, while inhibition of ANXA5 by Gemcitabine and Vinorebine and inhibition of PCGF6 by Paclitaxel reduced the risk of AF. Inhibition of MSH6 and SF3B1 by Cyclophosphamide, as well as inhibition of SMAD4 and PSMD2 and activation of ASAH1 and MLST8 by Doxorubicin can have bidirectional effects on AF occurrence. XBP1 can be used as a common druggable gene for AF and breast cancer, and there are no potential side effects of treatment against this target.

Conclusion

This study did not find a direct disease causality between AF and breast cancer but identified 40 target genes for 15 breast cancer therapeutic drugs associated with AF, clarified the direction of action of 8 breast cancer therapeutic drugs on AF, and finally identified one common druggable target for AF and breast cancer.

Elevated circulating levels of neutrophil extracellular traps after cardiopulmonary bypass surgery as risk factors of postoperative atrial fibrillation and mortality

Background

Cardiopulmonary bypass (CPB) can trigger a systemic inflammatory response during the perioperative period, which may lead to the consumption of the contact system and the production of neutrophil extracellular traps (NETs). This study attempted to determine whether the formation of NETs and contact activation are a vivid occurrence during CPB and whether they are related to post-operative atrial fibrillation (AF) and survival.

Methods

A prospective observational study was conducted in 97 patients who underwent aortic valve and/or aorta replacement surgery with CPB. Circulating markers of NETs [histone-DNA complex, cell-free double stranded DNA (dsDNA), neutrophil elastase] and the contact system [prekallikrein, high molecular weight kininogen (HMWK), activated factor XII (FXIIa)] were measured at four-time points: before surgery (T0), immediately after surgery (T1), 1 day after surgery (T2), and 3 days after surgery (T3).

Results

Elevated levels of circulating NETs markers were observed across post-CPB time. Significantly elevated levels of histone-DNA complex and cell-free dsDNA measured T3 were detected in patients with post-operative AF compared to those without. In logistic regression analysis, levels of histone-DNA complex and cell-free dsDNA measured at T3 were significant markers of risk for occurrence of AF. The levels of cell-free dsDNA measured T2 were significantly higher in non-survivors than in survivors. The level of cell-free dsDNA showed significant prognostic value.

Conclusions

NETs markers may be useful for the assessment of risk for post-operative AF and mortality. Conduct of additional research regarding the role of NETs as clinical markers and as a therapeutic target in CPB is anticipated.

Myeloperoxidase and its derivative hypochlorous acid combined clinical indicators predict new-onset atrial fibrillation in sepsis: a case-control study

BACKGROUD

New-onset atrial fibrillation (NOAF) is a common complication of sepsis and linked to higher death rates in affected patients. The lack of effective predictive tools hampers early risk assessment for the development of NOAF. This study aims to develop practical and effective predictive tools for identifying the risk of NOAF.

METHODS

This case-control study retrospectively analyzed patients with sepsis admitted to the emergency department of Xinhua Hospital, Shanghai Jiao Tong University School of Medicine from September 2017 to January 2023. Based on electrocardiographic reports and electrocardiogram monitoring records, patients were categorized into NOAF and non-NOAF groups. Laboratory tests, including myeloperoxidase (MPO) and hypochlorous acid (HOCl), were collected, along with demographic data and comorbidities. Least absolute shrinkage and selection operator regression and multivariate logistic regression analyses were employed to identify predictors. The area under the curve (AUC) was used to evaluate the predictive model's performance in identifying NOAF.

RESULTS

A total of 389 patients with sepsis were included in the study, of which 63 developed NOAF. MPO and HOCl levels were significantly higher in the NOAF group compared to the non-NOAF group. Multivariate logistic regression analysis identified MPO, HOCl, tumor necrosis factor-α (TNF-α), white blood cells (WBC), and the Acute Physiology and Chronic Health Evaluation II (APACHE II) score as independent risk factors for NOAF in sepsis. Additionally, a nomogram model developed using these independent risk factors achieved an AUC of 0.897.

CONCLUSION

The combination of MPO and its derivative HOCl with clinical indicators improves the prediction of NOAF in sepsis. The nomogram model can serve as a practical predictive tool for the early identification of NOAF in patients with sepsis.

Comprehensive Analysis of Immune Cell Infiltration and M2-Like Macrophage Biomarker Expression Patterns in Atrial Fibrillation

Background

Macrophages play a crucial role in the progression of AF, closely linked to atrial inflammation and myocardial fibrosis. However, the functions and molecular mechanisms of different phenotypic macrophages in AF are not well understood. This study aims to analyze the infiltration characteristics of atrial immune cells in AF patients and further explore the role and molecular expression patterns of M2 macrophage-related genes in AF.

Methods

This study integrates single-cell and large-scale sequencing data to analyze immune cell infiltration and molecular characterization of the LAA in patients with AF, using SR as a control group. CIBERSORT assesses immune cell types in LAA tissues; WGCNA identifies signature genes; cell clustering analyzes cell types and subpopulations; cell communication explores macrophage interactions; hdWGCNA identifies M2 macrophage gene modules in AF. AF biomarkers are identified using LASSO and Random Forest, validated with ROC curves and RT-qPCR. Potential molecular mechanisms are inferred through TF-miRNA-mRNA networks and single-gene enrichment analyses.

Results

Myeloid cell subsets varied considerably between the AF and SR groups, with a significant increase in M2 macrophages in the AF group. Signals of inflammation and matrix remodeling were observed in AF. M2 macrophage-related genes IGF1, PDK4, RAB13, and TMEM176B were identified as AF biomarkers, with RAB13 and TMEM176B being novel markers. A TF-miRNA-mRNA network was constructed using target genes, which are enriched in the PPAR signaling pathway and fatty acid metabolism.

Conclusion

Over infiltration of M2 macrophages may be an important factor in the progression of AF. The M2 macrophage-related genes IGF1, RAB13, TMEM176B and PDK4 may regulate the progression of AF through the PPAR signaling pathway and fatty acid metabolism.

Effects of Heart Failure Therapies on Atrial Fibrillation: Biological and Clinical Perspectives

Heart failure (HF) and atrial fibrillation (AF) are prevalent cardiovascular diseases that contribute significantly to morbidity, mortality, hospitalisation, and healthcare costs. It is not uncommon for these conditions to coexist and have mutually reinforcing effects. A critical factor in the aetiology of these conditions is oxidative stress, driven by reactive oxygen species (ROS), which contributes to atrial remodelling and fibrosis. The recent introduction of new drugs for the treatment of heart failure has also had an impact on the management of atrial fibrillation due to their influence on oxidative stress. The objective of this review is to analyse the effects of these therapies, including their role in mitigating ROS, on the prevention and treatment of AF in HF patients.

Myeloperoxidase as a Promising Therapeutic Target after Myocardial Infarction

Coronary artery disease (CAD) and myocardial infarction (MI) remain leading causes of death and disability worldwide. CAD begins with the formation of atherosclerotic plaques within the intimal layer of the coronary arteries, a process driven by persistent arterial inflammation and oxidation. Myeloperoxidase (MPO), a mammalian haem peroxidase enzyme primarily expressed within neutrophils and monocytes, has been increasingly recognised as a key pro-inflammatory and oxidative enzyme promoting the development of vulnerable coronary atherosclerotic plaques that are prone to rupture, and can precipitate a MI. Mounting evidence also implicates a pathogenic role for MPO in the inflammatory process that follows a MI, which is characterised by the rapid infiltration of activated neutrophils into the damaged myocardium and the release of MPO. Excessive and persistent cardiac inflammation impairs normal cardiac healing post-MI, resulting in adverse cardiac outcomes and poorer long-term cardiac function, and eventually heart failure. This review summarises the evidence for MPO as a significant oxidative enzyme contributing to the inappropriate inflammatory responses driving the progression of CAD and poor cardiac healing after a MI. It also details the proposed mechanisms underlying MPO's pathogenic actions and explores MPO as a novel therapeutic target for the treatment of unstable CAD and cardiac damage post-MI.

Association between psoriasis and atrial fibrillation: A Systematic review and meta-analysis

INTRODUCTION

Psoriasis is a prevalent inflammatory skin condition characterized by erythematous plaques with scaling. Recent research has demonstrated an increased risk of cardiovascular diseases in patients with psoriasis; however, current evidence on atrial fibrillation (AF) risk in psoriasis is limited.

MATERIALS AND METHODS

A systematic literature search was performed on major bibliographic databases to retrieve studies that evaluated AF risk in patients with psoriasis. The DerSimonian and Laird random effects model was used to pool the hazard ratios (HR) with 95 % confidence intervals (CI). Subgroup analysis was conducted by dividing the patients into mild and severe psoriasis groups. Publication bias was assessed by visual inspection and Egger's regression test. Statistical significance was set at p < 0.05.

RESULTS

Seven studies were included, with 10,974,668 participants (1,94,230 in the psoriasis group and 10,780,439 in the control group). Patients with psoriasis had a significantly higher risk of AF [Pooled HR: 1.28; 95 % CI: 1.20, 1.36; p < 0.00001]. In subgroup analysis, patients with severe psoriasis [HR: 1.32; 95 % CI: 1.23, 1.42; p < 0.00001] demonstrated a slightly higher risk of AF, although statistically insignificant (p = 0.17), than the mild psoriasis group [HR: 1.21; 95 % CI: 1.10, 1.33; p < 0.0001]. Egger's regression test showed no statistically significant publication bias (p = 0.24).

CONCLUSION

Our analysis demonstrated that patients with psoriasis are at a significantly higher risk of AF and hence should be closely monitored for AF. Further large-scale and multicenter randomized trials are warranted to validate the robustness of our findings.

Astragaloside IV inhibits angiotensin II-induced atrial fibrosis and atrial fibrillation by SIRT1/PGC-1α/FNDC5 pathway

Aims and objectives

Astragaloside IV (AS-IV) has been found to possess anti-oxidative, anti-inflammatory, and anti-apoptotic properties, but its effect on atrial fibrosis is yet to be determined. This research investigates the protective role of AS-IV in angiotensin II (Ang II)-induced atrial fibrosis and atrial fibrillation (AF).

Methods

C57BL/6 male mice aged 8-10 weeks (n = 40) were subcutaneously administered Ang II (2.0 mg/kg/day) or saline, with AS-IV (80 mg/kg) intraperitoneally administered 2 h before Ang II infusion for 4 weeks. Biochemical, histological, and morphological analyses were carried out. Using transesophageal burst pacing, AF was generated in vivo.

Results

Here, we report that AS-IV treatment inhibited Ang II-induced AF development in mice (58 ± 5.86 vs 15.13 ± 2.16 %, p < 0.001). Ang II + AS-IV therapy was effective in reducing the atrial fibrotic area and decreasing the increase in smooth muscle alpha-actin (α-SMA)-positive myofibroblasts brought on by Ang II treatment (fibrotic area: 26.25 ± 3.81 vs 8.62 ± 1.83 %, p < 0.001 and α-SMA: 65.62 ± 10.63 vs 17.25 ± 1.78 %, p < 0.001). The reactive oxygen species (ROS) production was reduced by pretreatment with Ang II + AS-IV (9.20 ± 0.92 vs 2.63 ± 0.22 %/sec, p < 0.001). In addition, Ang II + AS-IV treatment suppressed oxidative stress in Ang II-induced atrial fibrosis (malondialdehyde: 701.78 ± 85.01 vs 504.07 ± 25.62 pmol/mg protein, p < 0.001; superoxide dismutase: 13.82 ± 1.25 vs 29.54 ± 2.45 U/mg protein, p < 0.001 and catalase: 11.43 ± 1.19 vs 20.83 ± 3.29 U/mg protein, p < 0.001, respectively). Moreover, Ang II + AS-IV decreased the expression of α-SMA, collagen III and collagen I (3.32 ± 0.53 vs 1.41 ± 0.20 fold, p < 0.001; 3.41 ± 0.55 vs 1.48 ± 0.18 fold, p < 0.001; 2.34 ± 0.55 vs 0.99 ± 0.17 fold, p < 0.001, respectively) while increasing the protein expression of sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), and fibronectin type III domain-containing protein 5 (FNDC5) in Ang II-treated mice (0.22 ± 0.02 vs 0.57 ± 0.08 fold, p < 0.001; 0.28 ± 0.04 vs 0.72 ± 0.05 fold, p < 0.001; 0.38 ± 0.03 vs 0.68 ± 0.06 fold, p < 0.001, respectively).

Conclusion

Our data led us to speculate that AS-IV may protect against Ang II-induced atrial fibrosis and AF via upregulation of the SIRT1/PGC-1α/FNDC5 pathway.

Oxidized high-density lipoprotein associates with atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is the most common heart arrhythmia and considered to be a progressive chronic disease associated with increased morbidity and mortality. Recent data suggest a link between inflammation, oxidative stress, and AF, although the underlying mechanisms are not fully understood. Because oxidized lipoproteins cause structural damage and electrophysiologic changes in cardiomyocytes, it is feasible that the transformation of atheroprotective high-density lipoprotein (HDL) into dysfunctional HDL contributes to the development of AF.

OBJECTIVE

The purpose of this study was to determine whether a reduced antioxidant function of HDL is associated with the presence of AF.

METHODS

In this multicenter cross-sectional cohort study, we assessed HDL function in sera of 1206 participants. Patients were divided into groups according to the presence of AF (n = 233) or no AF (n = 973). A validated cell-free biochemical assay was used to determine reduced HDL antioxidant function as assessed by increased normalized HDL lipid peroxide content (nHDLox).

RESULTS

Participants with AF had a 9% higher mean relative nHDLox compared to persons without AF (P = .025). nHDLox was strongly associated with AF in all models of logistic regression, including the analysis adjusted for age, sex, and risk factors for AF (all P ≤.01).

CONCLUSION

Reduced antioxidant HDL function is associated with the presence of AF, which supports growing evidence that impaired lipoprotein function is linked to electrophysiological changes in cardiomyocytes. nHDLox is one of several contributors to the initiation and perpetuation of AF.

Exercise-Dependent Modulation of Immunological Response Pathways in Endurance Athletes With and Without Atrial Fibrillation

BACKGROUND

Atrial fibrillation (AF) is a common arrhythmia characterized by uncoordinated atrial electrical activity. Lone AF occurs in the absence of traditional risk factors and is frequently observed in male endurance athletes, who face a 2- to 5-fold higher risk of AF compared with healthy, moderately active males. Our understanding of how endurance exercise contributes to the pathophysiology of lone AF remains limited. This study aimed to characterize the circulating protein fluctuations during high-intensity exercise as well as explore potential biomarkers of exercise-associated AF.

METHODS AND RESULTS

A prospective cohort of 12 male endurance cyclists between the ages of 40 and 65 years, 6 of whom had a history of exercise-associated AF, were recruited to participate using a convenience sampling method. The circulating proteome was subsequently analyzed using multiplex immunoassays and aptamer-based proteomics before, during, and after an acute high-intensity endurance exercise bout to assess temporality and identify potential markers of AF. The endurance exercise bout resulted in significant alterations to proteins involved in immune modulation (eg, growth/differentiation factor 15), skeletal muscle metabolism (eg, α-actinin-2), cell death (eg, histones), and inflammation (eg, interleukin-6). Subjects with AF differed from those without, displaying modulation of proteins previously known to have associations with incident AF (eg, C-reactive protein, insulin-like growth factor-1, and angiopoietin-2), and also with proteins having no previous association (eg, tapasin-related protein and α2-Heremans-Schmid glycoprotein).

CONCLUSIONS

These findings provide insights into the proteomic response to acute intense exercise, provide mechanistic insights into the pathophysiology behind AF in athletes, and identify targets for future study and validation.

Isopropyl 3-(3,4-dihydroxyphenyl) 2-hydroxypropanoate protects septic myocardial injury via regulating GAS6/Axl-AMPK signaling pathway

In a previous study, we used metabolomic techniques to identify a new metabolite of Danshen Dripping Pills called isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate (IDHP), which has potential as a drug candidate for cardiovascular diseases. This study aimed to explore the protective effects of IDHP against septic myocardial injury, as well as its molecular mechanism. Wild type or GAS6 knockout mice injured by cecal ligation and puncture (CLP) were used to observe the effect of IDHP. Here, we found that a specific concentration of IDHP (60 mg/kg) significantly increased the survival rate of septic mice to about 75 % at 72 h post CLP, and showed improvements in sepsis score, blood biochemistry parameters, cardiac function, and myocardial tissue damage. Furthermore, IDHP inhibited myocardial oxidative stress, inflammatory response, apoptosis, and mitochondrial dysfunction. Molecularly, we discovered that IDHP treatment reversed the CLP-induced downregulation of GAS6, Axl, and p-AMPK/AMPK expression. In addition, GAS6 knockout reversed the positive effect of IDHP in septic mice, indicated by more severe myocardial tissue damage, oxidative stress, inflammatory response, and mitochondrial dysfunction. GAS6 knockout also resulted in decreased levels of GAS6, Axl, and p-AMPK/AMPK. Taken together, our study provides evidence that IDHP has significant cardioprotective effects against sepsis by regulating the GAS6/Axl-AMPK signaling pathway. This finding has important therapeutic potential for treating sepsis.

Implications for neutrophils in cardiac arrhythmias

Cardiac arrhythmias commonly occur as a result of aberrant electrical impulse formation or conduction in the myocardium. Frequently discussed triggers include underlying heart diseases such as myocardial ischemia, electrolyte imbalances, or genetic anomalies of ion channels involved in the tightly regulated cardiac action potential. Recently, the role of innate immune cells in the onset of arrhythmic events has been highlighted in numerous studies, correlating leukocyte expansion in the myocardium to increased arrhythmic burden. Here, we aim to call attention to the role of neutrophils in the pathogenesis of cardiac arrhythmias and their expansion during myocardial ischemia and infectious disease manifestation. In addition, we will elucidate molecular mechanisms associated with neutrophil activation and discuss their involvement as direct mediators of arrhythmogenicity.

Connecting atrial fibrillation to digestive neoplasms: exploring mediation via ischemic stroke and heart failure in Mendelian randomization studies

Background

Notwithstanding the acknowledged interplay between atrial fibrillation (AF) and the emergence of digestive system neoplasms, the intricacies of this relationship remain ambiguous. By capitalizing univariable Mendelian Randomization (MR) complemented by a mediated MR tactic, our pursuit was to elucidate the causative roles of AF in precipitating digestive system malignancies and potential intermediary pathways.

Method

This research endeavor seeks to scrutinize the causal clinical implications of whether genetic predispositions to AF correlate with an increased risk of digestive system malignancies, employing MR analytical techniques. Utilizing a dataset amalgamated from six studies related to AF, encompassing over 1,000,000 subjects, we performed univariable MR assessments, employing the random-effects inverse-variance weighted (IVW) methodology as our principal analytical paradigm. Subsequently, a mediated MR framework was employed to probe the potential mediating influence of AF on the nexus between hypertension (HT), heart failure (HF), ischemic stroke (IS), coronary artery disease (CAD), and digestive system neoplasms.

Result

The univariable MR evaluation unveiled a notable causal nexus between the genetic inclination toward AF and the genetic susceptibility to colon, esophageal, and small intestine malignancies. The mediated MR scrutiny ascertained that the genetic inclination for AF amplifies the risk profile for colon cancer via IS pathways and partially explains the susceptibility to esophageal and small intestine tumors through the HF pathway.

Conclusion

Our investigative endeavor has highlighted a definitive causative association between genetic inclination to AF and specific digestive system neoplasms, spotlighting IS and HF as instrumental mediators. Such revelations furnish pivotal perspectives on the complex genetic interconnections between cardiovascular anomalies and certain digestive tract tumors, emphasizing prospective therapeutic and diagnostic worthy of pursuit.

The Role of Immune Cells Driving Electropathology and Atrial Fibrillation

Atrial fibrillation (AF) is the most common progressive cardiac arrhythmia worldwide and entails serious complications including stroke and heart failure. Despite decades of clinical research, the current treatment of AF is suboptimal. This is due to a lack of knowledge on the mechanistic root causes of AF. Prevailing theories indicate a key role for molecular and structural changes in driving electrical conduction abnormalities in the atria and as such triggering AF. Emerging evidence indicates the role of the altered atrial and systemic immune landscape in driving this so-called electropathology. Immune cells and immune markers play a central role in immune remodeling by exhibiting dual facets. While the activation and recruitment of immune cells contribute to maintaining atrial stability, the excessive activation and pronounced expression of immune markers can foster AF. This review delineates shifts in cardiac composition and the distribution of immune cells in the context of cardiac health and disease, especially AF. A comprehensive exploration of the functions of diverse immune cell types in AF and other cardiac diseases is essential to unravel the intricacies of immune remodeling. Usltimately, we delve into clinical evidence showcasing immune modifications in both the atrial and systemic domains among AF patients, aiming to elucidate immune markers for therapy and diagnostics.

Soluble PILRα: A novel plasma biomarker for atrial fibrillation progression and recurrence after catheter ablation

BACKGROUND

We aimed to identify plasma biomarkers of atrial fibrillation (AF) progression and recurrence after catheter ablation.

METHODS

Using AF gene profiling data from GEO database, a weighted gene co-expression network analysis (WGCNA) was conducted to determine the most significant module and hub genes associated with AF. Subsequently, 318 consecutively admitted patients who had undergone radiofrequency catheter ablation were enrolled in this study.

RESULTS

WGCNA results revealed that paired immunoglobulin-like type 2 receptor alpha (PILRA) was the only black module gene highly correlated with clinical traits. Plasma soluble PILRα (sPILRα) levels were elevated in patients with AF and significantly elevated in patients with persistent versus paroxysmal AF (4.64 ± 2.74 vs. 3.04 ± 1.56 ng/mL, p < 0.001). Elevated sPILRα level was an independent risk factor for AF progression even after adjusting for traditional factors (adjusted odds ratio: 3.06, 95 % confidence interval [CI]: 1.88-5.27, p < 0.001) and AF recurrence after catheter ablation in patients with persistent AF (adjusted hazards ratio: 4.41, 95 % CI: 1.22-15.92, p = 0.023).

CONCLUSIONS

WGCNA screening of GEO microarray gene profiling data showed PILRA expression levels to be correlated with AF progression and recurrence after catheter ablation in patients with persistent AF.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Patients With Atrial Fibrillation" provides recommendations to guide clinicians in the treatment of patients with atrial fibrillation.

METHODS

A comprehensive literature search was conducted from May 12, 2022, to November 3, 2022, encompassing studies, reviews, and other evidence conducted on human subjects that were published in English from PubMed, EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline. Additional relevant studies, published through November 2022, during the guideline writing process, were also considered by the writing committee and added to the evidence tables, where appropriate.

STRUCTURE

Atrial fibrillation is the most sustained common arrhythmia, and its incidence and prevalence are increasing in the United States and globally. Recommendations from the "2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" and the "2019 AHA/ACC/HRS Focused Update of the 2014 AHA/ACC/HRS Guideline for the Management of Patients With Atrial Fibrillation" have been updated with new evidence to guide clinicians. In addition, new recommendations addressing atrial fibrillation and thromboembolic risk assessment, anticoagulation, left atrial appendage occlusion, atrial fibrillation catheter or surgical ablation, and risk factor modification and atrial fibrillation prevention have been developed.

Free Radical Lipid Peroxidation Induced by Reactive Halogen Species

The review is devoted to the mechanisms of free radical lipid peroxidation (LPO) initiated by reactive halogen species (RHS) produced in mammals, including humans, by heme peroxidase enzymes, primarily myeloperoxidase (MPO). It has been shown that RHS can participate in LPO both in the initiation and branching steps of the LPO chain reactions. The initiation step of RHS-induced LPO mainly involves formation of free radicals in the reactions of RHS with nitrite and/or with amino groups of phosphatidylethanolamine or Lys. The branching step of the oxidative chain is the reaction of RHS with lipid hydroperoxides, in which peroxyl and alkoxyl radicals are formed. The role of RHS-induced LPO in the development of human inflammatory diseases (cardiovascular and neurodegenerative diseases, cancer, diabetes, rheumatoid arthritis) is discussed in detail.

Detection and modification of biomarkers of inflammation determining successful rhythm control in patients with atrial fibrillation

INTRODUCTION

Multiple pathophysiological mechanisms are involved in the pathogenesis of atrial fibrillation (AF). Growing evidence suggests that both local and systemic inflammation plays a key role even in early stages and its progression towards persisting and permanent AF. Rhythm control therapy via pulmonary vein isolation or cardioversion is the cornerstone of AF therapy for most symptomatic patients, yet arrhythmia recurrence after treatment is still common, especially in patients with persistent AF.

MATERIAL AND METHODS

In this review, we summarize the current state of knowledge of biomarkers of inflammation with prognostic value in patients with atrial fibrillation as well as anti-inflammatory medication with potential benefits after rhythm control therapy.

RESULTS AND DISCUSSION

Both onset of AF, progression and arrhythmia recurrence after rhythm control therapy can be caused by local and systemic inflammation. Various inflammatory biomarkers have been established to predict treatment success. Furthermore, additional anti-inflammatory therapy may significantly improve success rates.

Sleeve Gastrectomy Provides Cardioprotection from Oxidative Stress In Vitro Due to Reduction of Circulating Myeloperoxidase

Bariatric surgery, including sleeve gastrectomy (SG), improves systolic and diastolic function, which is independent of weight loss in rodent models. The cause of weight loss-independent improvements in cardiac function are unknown but may originate from the gastrointestinal tract. In this study, we investigated whether a circulating blood factor is a mechanism for acute cardioprotection after SG by testing the utility of rodent SG plasma to reduce metabolic stress in vitro. For the initial experiment, obese male Zucker rats underwent SG, ad lib sham, or pair-fed sham surgeries (n = six SG, n = eight SH, n = eight PF). For all other studies, a second group of Zucker rats underwent SG or ad lib sham surgeries (n = eight SH, n = six SG). Six weeks following surgery, plasma was collected from each group, both in the fasting and post-prandial (pp) state. This plasma was then pooled per surgical group and nutrient state and tested in multiple in vitro cell culture and extra-cellular assays to determine the effect of SG on myotubular metabolic stress compared to the sham surgeries. Post-prandial SG plasma (ppSG), but not fasting SG, pp, or fasting sham plasma, reduced the metabolic stress of the H9c2 cells as measured by lactate dehydrogenase (LDH) release (p < 0.01). Unlike SG, weight reduction through pair-feeding did not prevent H9c2 metabolic stress. The PpSG plasma had the slowest rate of extracellular hydrogen peroxide consumption and peroxidatic activity compared to the pp sham, fasting SG, and fasting sham groups. Redox testing of plasma with aminiobenzoic acid hydrazide and edaravone suggested a pattern supporting myeloperoxidase (MPO), or other peroxidases, as the primary component responsible for reduced metabolic stress with ppSG plasma. The PpSG plasma contained 35% less circulating MPO protein as compared to the pp sham and fasting SG plasma. The plasma from an MPO global knockout rat also prevented metabolic stress of the H9c2 cells, compared to the significant increase in LDH release from the plasma of the WT controls (p < 0.01). The MPO global knockout plasma also had a rate of extracellular hydrogen peroxide consumption and peroxidatic activity comparable to the ppSG plasma. These studies suggest that one of the weight loss-independent mechanisms by which SG improves myocellular function could be a reduced pro-oxidative environment due to lower circulating levels of MPO. It appears that the gastrointestinal tract is of critical importance to these findings, as the MPO levels were only lowered after enteral, nutrient stimulation in the SG rats. If this surgical effect is confirmed in humans, SG may be a unique surgical treatment for multiple diseases with a pathogenesis of inflammation and oxidative damage, including obesity-associated heart failure with preserved ejection fraction.

Current Data and Future Perspectives on Patients with Atrial Fibrillation and Cancer

Atrial fibrillation (AF) is an increasingly recognized comorbidity in patients with cancer. Indeed, cancer patients have a significantly higher incidence of AF than that observed in the general population. A reciprocal relationship between these two diseases has been observed, as much as some assume AF to be a marker for occult cancer screening, especially in older adults. The pathophysiological mechanisms are many and varied, including the underlying pro-inflammatory state, specific treatments (chemo- and radiotherapy), and surgery. The therapeutic management of patients with cancer and AF involves the same rhythm and frequency control strategies as the general population; however, the numerous interactions with chemotherapeutics, which lead to a significant increase in side effects, as well as the extreme fragility of the patient, should be considered. Anticoagulant therapy is also a complex challenge to address, as bleeding and stroke risk scores have not been fully assessed in this subpopulation. Furthermore, in large studies establishing the efficacy of direct oral anticoagulants (DOACs), cancer patients have been underrepresented. In this review, we elaborate on the mechanisms linking AF to cancer patients with a particular focus on the therapeutic challenges in this population.

Integrative bioinformatics analysis reveals STAT2 as a novel biomarker of inflammation-related cardiac dysfunction in atrial fibrillation

Atrial fibrillation (AF) is a common critical cause of stroke and cardiac dysfunction worldwide with lifetime risks. Viral infection and inflammatory response with myocardial involvement may lead to an increase in AF-related mortality. To dissect the potential sequelae of viral infection in AF patients, especially the coronavirus disease 2019 (COVID-19), based on AF and COVID-19 databases from Gene Expression Omnibus, weighted gene co-expression network analysis was used to identify key genes in heart tissues and peripheral blood mononuclear cells. Here, HSCT, PSMB9, STAT2, and TNFSF13B were identified as common risk genes of AF and COVID-19 patients. Correlation analysis of these genes with AF and COVID-19 showed a positive disease relevance. silencing of STAT2 by small interfering RNA significantly rescued SARS-CoV-2 XBB1.5 pseudovirus-induced cardiac cell contraction dysfunction in vitro. In conclusion, we identified STAT2 may be a novel biomarker of inflammation-related cardiac dysfunction in AF.

Evaluation of Nitrosative/Oxidative Stress and Inflammation in Heart Failure with Preserved and Reduced Ejection Fraction

Heart failure (HF) is a complex syndrome characterized by impaired cardiac function. Two common subtypes of HF include heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). In this study, we aimed to evaluate and compare the plasma levels of 3-nitrotyrosine (3-NT)-as a marker of nitrosative/oxidative stress and myeloperoxidase (MPO)-as an indicator of inflammation between HFpEF and HFrEF. Twenty-seven patients diagnosed with HFpEF and twenty-two with HFrEF were enrolled in this study. Additionally, forty-one patients were recruited for the control group. An echocardiographic assessment was conducted, followed by the collection of blood samples from all participants. Subsequently, the levels of 3-NT and MPO were quantified using the ELISA method. Comprehensive clinical characteristics and medical histories were obtained. Circulating levels of 3-NT were significantly higher in the HFpEF patients than in the control and the HFrEF groups. Nitrosative/oxidative stress is significantly intensified in HFpEF but not in HFrEF.

The neutrophil-to-lymphocyte ratio is a potential biomarker for the occurrence of atrial fibrillation in patients with obstructive sleep apnea: A BIOMARKER OF AF IN OSA PATIENTS

BACKGROUND

Obstructive sleep apnea (OSA) affects the occurrence of atrial fibrillation (AF) and usually coexists with AF. Chronic inflammation has been identified as an important factor in the development of AF, and the neutrophil-to-lymphocyte ratio (NLR) has been identified as a biomarker that positively correlates with the degree of inflammation. However, little information regarding how NLR correlates with AF in OSA patients.

METHODS

Our study enrolled 368 patients with OSA between September 2018 and April 2023. All data were collected after admission. Independently associated factors were assessed by multivariate logistic regression and then constructed a nomogram to predict AF risk. Nomogram's calculation model was evaluated using receiver operating characteristic (ROC) curves, calibration curves, and decision curve analysis (DCA). The correlation between CHA2DS2-VASc scores and NLR was assessed using Spearman correlation.

RESULTS

Multivariate logistic regression showed that high level log-transformed NLR (OR, 1.664; 95% CI, 1.026-2.699; P = 0.039) was independently associated with the presence of AF in patients with OSA. The concordance index (0.817, 95% CI, 0.770-0.864), ROC curve, calibration curve, and DCA of the nomogram indicated this model had well clinical utility. Also, the nomogram's calculation model could identify patients who are at a higher risk of developing AF, and the CHA2DS2-VASc score was positively correlated with NLR in patients with AF (P < 0.05).

CONCLUSION

The elevated NLR may serve as a promising biomarker for assessing the risk of AF in individuals with OSA. The nomogram's calculation model may be utilized as a tool to estimate the probability of AF occurrence in OSA patients.

Heart Failure With Preserved Ejection Fraction: An Evolving Understanding

Heart failure (HF) with preserved ejection fraction (HFpEF) is a clinical syndrome in which patients have signs and symptoms of HF due to high left ventricular (LV) filling pressure despite normal or near normal LV ejection fraction. It is more common than HF with reduced ejection fraction (HFrEF), and its diagnosis and treatment are more challenging than HFrEF. Although hypertension is the primary risk factor, coronary artery disease and other comorbidities, such as atrial fibrillation (AF), diabetes, chronic kidney disease (CKD), and obesity, also play an essential role in its formation. This review summarizes current knowledge about HFpEF, its pathophysiology, clinical presentation, diagnostic challenges, current treatments, and promising novel treatments. It is essential to continue to be updated on the latest treatments for HFpEF so that patients always receive the most therapeutic treatments. The use of GnRH agonists in the management of HFpEF, infusion of Apo a-I nanoparticle, low-level transcutaneous vagal stimulation (LLTS), and estrogen only in post-menopausal women are promising strategies to prevent diastolic dysfunction and HFpEF; however, there is still no proven curative treatment for HFpEF yet.

Plasma myeloperoxidase: association with atrial fibrillation progression and recurrence after catheter ablation

Background

Myeloperoxidase (MPO), released by activated neutrophils, is significantly increased in atrial fibrillation (AF). MPO may play a role in the progression of atrial fibrillation and further involved in AF recurrence after catheter ablation. We compared plasma MPO levels in paroxysmal and persistent AF and explored their role in AF recurrence after catheter ablation.

Methods

Plasma MPO levels were measured in consecutive patients with paroxysmal AF (n = 225) and persistent AF (n = 106). Samples of patients were collected from the femoral vein during catheter ablation and all patients included were followed up after catheter ablation.

Results

Plasma MPO levels increased from paroxysmal AF to persistent AF patients (56.31 [40.33-73.51] vs. 64.11 [48.65-81.11] ng/ml, p < 0.001). MPO significantly correlated with left atrium volume (LAV) and there existed a significant interaction between the two in relation to AF recurrence (p for interaction <0.05). During a median follow-up of 14 months, 28 patients with paroxysmal AF (12.44%) and 27 patients with persistent AF (25.47%) presented with recurrence after catheter ablation. The percentage of recurrence increased stepwise with increasing tertiles of MPO levels in both paroxysmal AF and persistent AF. MPO levels remained independently associated with AF recurrence after adjusting for potential confounding variables.

Conclusion

MPO levels were higher in persistent AF than in paroxysmal AF and MPO was positively correlated with LAV in AF. Elevated MPO levels may predispose a switch in AF phenotype and AF recurrence after catheter ablation.

A Systematic Review and Meta-Analysis on Effectiveness of Mineralocorticoid Receptor Antagonists in Reducing the Risk of Atrial Fibrillation

Mineralocorticoid receptor antagonists (MRAs) are known to improve clinical outcomes in heart failure, particularly heart failure with reduced ejection fraction. However, the effect of MRAs on the incidence of and recurrence of atrial fibrillation (AF) is not well established. Therefore, databases, such as PubMed, EMBASE, and Cochrane Central, were searched from inception to September 2021 for randomized controlled trials of MRAs with AF as an outcome. Risk ratios (RRs) with 95% confidence interval (CIs) were combined using the random-effects model. A total of 10 randomized controlled trials (n = 11,356) were included. Our pooled analysis demonstrates that MRAs reduce the risk of AF occurrence by 23% compared with the control therapy (RR 0.77, 95% CI 0.65 to 0.91, p = 0.003, I2 = 40%). Subgroup analysis demonstrated that MRAs reduced the risk of both new-onset AF (RR 0.84, 95% CI 0.61 to 1.16, p = 0.28, I2 = 43%) and recurrent AF (RR 0.73, 95% CI 0.59 to 0.90, p = 0.004, I2 = 26%) similarly; p interaction = 0.48. Our meta-analysis concludes that MRAs reduce the risk of development of AF overall, with consistent effects in new-onset and recurrent AF.

Recruited macrophages elicit atrial fibrillation

Atrial fibrillation disrupts contraction of the atria, leading to stroke and heart failure. We deciphered how immune and stromal cells contribute to atrial fibrillation. Single-cell transcriptomes from human atria documented inflammatory monocyte and SPP1+ macrophage expansion in atrial fibrillation. Combining hypertension, obesity, and mitral valve regurgitation (HOMER) in mice elicited enlarged, fibrosed, and fibrillation-prone atria. Single-cell transcriptomes from HOMER mouse atria recapitulated cell composition and transcriptome changes observed in patients. Inhibiting monocyte migration reduced arrhythmia in Ccr2-∕- HOMER mice. Cell-cell interaction analysis identified SPP1 as a pleiotropic signal that promotes atrial fibrillation through cross-talk with local immune and stromal cells. Deleting Spp1 reduced atrial fibrillation in HOMER mice. These results identify SPP1+ macrophages as targets for immunotherapy in atrial fibrillation.

The effect of icosapent ethyl on left atrial and left ventricular morphology

Atrial fibrillation (AF) is a common arrhythmia associated with poor outcomes. N-3 fatty acids have been shown to provide significant cardiovascular risk reduction, but they may exacerbate the risk of AF. The pathway by which N-3 fatty acids may be arrhythmogenic is unknown. One possible mechanism involves cardiac chamber morphology alteration. The purpose of this study was to investigate the effect of icosapent ethyl (IPE) on left atrial (LA) size and left ventricular (LV) mass. This study used coronary computed tomographic angiography images gathered from the Effect of Icosapent Ethyl on Progression of Coronary Atherosclerosis (EVAPORATE) trial. EVAPORATE was a randomised, double-blind, placebo-controlled study finding a significant reduction in coronary atherosclerosis progression in patients with residually elevated triglycerides despite statin therapy on 4 g IPE daily versus 4 g placebo daily. Computed tomography images were used to measure LA size and LV mass at 0 and 18 months. Of 80 enrolled patients, 68 were included in the final analysis. Baseline demographics and risk factors were similar between IPE and placebo cohorts. LA anterior- posterior diameter measured on axial (p=0.51) and sagittal (p=0.52) orientations were not different over time. Also, there was no difference between groups in the change in LA volume (p=0.84). Change in LV mass was similar between groups (p=0.13). In conclusion, this study did not detect differences in LA size or LV mass over 18 months between patients on 4 g daily IPE versus placebo.

Novel Biomarkers and the Multiple-Marker Approach in Early Detection, Prognosis, and Risk Stratification of Cardiac Diseases: A Narrative Review

Cardiac diseases are a primary cause of mortality worldwide, underscoring the importance of early identification and risk stratification to enhance patient outcomes. Biomarkers have become important tools for the risk assessment of cardiovascular disease and monitoring disease progression. This narrative review focuses on the multiple-marker approach, which involves simultaneously evaluating several biomarkers for the early detection and risk stratification of heart diseases. The review covers the clinical applications of novel biomarkers, such as high-sensitivity troponin, galectin-3, source of tumorigenicity 2, B-type natriuretic peptide and N-terminal pro-B-type natriuretic peptide, growth differentiation factor 15, myeloperoxidase, fatty acid-binding protein, C-reactive protein, lipoprotein-associated phospholipase A2, microRNAs, circulating endothelial cells, and ischemia-modified albumin. These biomarkers have demonstrated potential in identifying people who are at high risk for developing heart disease and in providing prognostic data. Given the complexity of cardiac illnesses, the multiple-marker approach to risk assessment is extremely beneficial. Implementing the multiple-marker strategy can improve risk stratification, diagnostic accuracy, and patient care in heart disease patients.

The Possible Influence of Vitamin D Levels on the Development of Atrial Fibrillation-An Update

Atrial fibrillation (AF) is a severe and most common supraventricular arrhythmia in humans, which, if left untreated or treated ineffectively, can lead to ischemic stroke or heart failure. It has been suggested that serum vitamin D (VitD) deficiency may be one of the critical factors influencing the onset of AF, especially in the period after cardiac surgery, such as coronary artery bypass grafting. Several papers have indicated that VitD supplementation reduces the risk of AF, significantly reducing the proportion of patients between the control and study groups in both the pre- and postoperative periods. Factors that increase the risk of AF from VitD deficiency are also further indicated, and these are age, gender, weight, season or comorbidities. In addition, the cardiodepressive mechanism of VitD is not fully understood; however, it is suggested that it acts through at least two pathways. The first indicates a direct effect of VitD on atrial muscle degradation, while the second is related to the modulation of cardiovascular depression factors. Despite many reports showing correlations between no VitD concentrations on the development of AF, this topic is still widely debated and the results from these papers are still subject to doubt. Therefore, this review aims at describing in detail the problem of correlation between VitD deficiency and the development of AF associated mainly with the postoperative period, i.e., after cardiac surgery, especially pathogenesis, and results of this correlation, taking into account recent studies, limitations and future perspectives. Due to the fact that this is still a topical problem, we believe that the collection of the latest reports and a detailed description of the problem is most appropriate in this case.

Atrial epicardial adipose tissue abundantly secretes myeloperoxidase and activates atrial fibroblasts in patients with atrial fibrillation

BACKGROUND

Epicardial adipose tissue (EAT) secretome induces fibrosis. Fibrosis, primarily extracellular matrix (ECM) produced by fibroblasts, creates a substrate for atrial fibrillation (AF). Whether the EAT secretome from patients with AF activates human atrial fibroblasts and through which components, remains unexplored.

RESEARCH AIMS

(a) To investigate if the EAT secretome from patients with versus without AF increases ECM production in atrial fibroblasts. (b) To identify profibrotic proteins and processes in the EAT secretome and EAT from patients with, who will develop (future onset), and without AF.

METHODS

Atrial EAT was obtainded during thoracoscopic ablation (AF, n = 20), or open-heart surgery (future onset and non-AF, n = 35). ECM gene expression of human atrial fibroblasts exposed to the EAT secretome and the proteomes of EAT secretome and EAT were assessed in patients with and without AF. Myeloperoxidase and neutrophil extracellular traps (NETs) were assessed immunohistochemically in patients with paroxysmal, persistent, future onset, and those who remain free of AF (non-AF).

RESULTS

The expression of COL1A1 and FN1 in fibroblasts exposed to secretome from patients with AF was 3.7 and 4.7 times higher than in patients without AF (p < 0.05). Myeloperoxidase was the most increased protein in the EAT secretome and EAT from patients with versus without AF (FC 18.07 and 21.57, p < 0.005), as was the gene-set neutrophil degranulation. Immunohistochemically, myeloperoxidase was highest in persistent (FC 13.3, p < 0.0001) and increased in future onset AF (FC 2.4, p = 0.02) versus non-AF. Myeloperoxidase aggregated subepicardially and around fibrofatty infiltrates. NETs were increased in patients with persistent versus non-AF (p = 0.03).

CONCLUSION

In AF, the EAT secretome induces ECM gene expression in atrial fibroblasts and contains abundant myeloperoxidase. EAT myeloperoxidase was increased prior to AF onset, and both myeloperoxidase and NETs were highest in persistent AF, highlighting the role of EAT neutrophils in the pathophysiology of AF.

Association between circulating leukocytes and arrhythmias: Mendelian randomization analysis in immuno-cardiac electrophysiology

Background

Cardiac arrhythmia is a common disease associated with high mortality and morbidity. Circulating leukocyte counts, which serve as a biomarker for assessing systemic immune status, have been linked to arrhythmias in observational studies. However, observational studies are plagued by confounding factors and reverse causality, whether alterations in circulating leukocyte components are causally associated with arrhythmias remains uncertain. The present study explored this question based on genetic evidence.

Methods and findings

We performed Mendelian randomization (MR) analysis to evaluate whether alterations in leukocyte counts affect aggregated risk of all types of arrhythmia or risk of five specific types of arrhythmia. Single-nucleotide polymorphisms serving as proxies for leukocyte differential counts were retrieved from the Blood Cell Consortium, and statistical data on arrhythmias were obtained from the UK Biobank), FinnGenand a meta-analysis of genome-wide association studies for atrial fibrillation. We applied inverse variance-weighted method as the primary analysis, complemented by a series of sensitivity analyses. Bidirectional analyses were conducted to assess reverse causality. Finally, multivariable MR was performed to study the joint effects of multiple risk factors. We found that genetically predicted differential leukocyte counts were not significantly associated with aggregated occurrence of all types of arrhythmia. In contrast, each 1-standard deviation increase in lymphocyte count was associated with 46% higher risk of atrioventricular block (OR 1.46, 95% CI 1.11–1.93, p=0.0065). A similar effect size was observed across all MR sensitivity analyses, with no evidence of horizontal pleiotropy. Reverse MR analysis suggested that atrioventricular block was unlikely to cause changes in lymphocyte count. Primary MR analysis based on the inverse-variance weighted method suggested that changes in neutrophil count alter risk of right bundle branch block, and changes in basophil count alter risk of atrial fibrillation. However, these causal relationships were not robust in sensitivity analyses. We found no compelling evidence that neutrophil or lymphocyte counts cause atrial fibrillation.

Conclusion

Our data support higher lymphocyte count as a causal risk factor for atrioventricular block. These results highlight the importance of immune cells in the pathogenesis of specific cardiac conduction disorders.

microRNAs as Biomarkers of Endothelial Dysfunction and Therapeutic Target in the Pathogenesis of Atrial Fibrillation

The pathophysiology of atrial fibrillation (AF) may involve atrial fibrosis/remodeling and dysfunctional endothelial activities. Despite the currently available treatment approaches, the progression of AF, its recurrence rate, and the high mortality risk of related complications underlay the need for more advanced prognostic and therapeutic strategies. There is increasing attention on the molecular mechanisms controlling AF onset and progression points to the complex cell to cell interplay that triggers fibroblasts, immune cells and myofibroblasts, enhancing atrial fibrosis. In this scenario, endothelial cell dysfunction (ED) might play an unexpected but significant role. microRNAs (miRNAs) regulate gene expression at the post-transcriptional level. In the cardiovascular compartment, both free circulating and exosomal miRNAs entail the control of plaque formation, lipid metabolism, inflammation and angiogenesis, cardiomyocyte growth and contractility, and even the maintenance of cardiac rhythm. Abnormal miRNAs levels may indicate the activation state of circulating cells, and thus represent a specific read-out of cardiac tissue changes. Although several unresolved questions still limit their clinical use, the ease of accessibility in biofluids and their prognostic and diagnostic properties make them novel and attractive biomarker candidates in AF. This article summarizes the most recent features of AF associated with miRNAs and relates them to potentially underlying mechanisms.

Myeloperoxidase in the pericardial fluid improves the performance of prediction rules for postoperative atrial fibrillation

OBJECTIVES

After surgery, inflammation is a prominent factor influencing postoperative atrial fibrillation. Myeloperoxidase is a major contributor to inflammatory responses after surgical tissue damage. We evaluated whether myeloperoxidase is associated with postoperative atrial fibrillation clinically and in an animal model.

METHODS

This prospective cohort study included patients undergoing isolated coronary artery bypass grafting. Myeloperoxidase concentrations in blood and pericardial fluid were determined at baseline and 6, 12, and 18 hours after coronary artery bypass grafting. Myeloperoxidase activity in blood, pericardial fluid, and atrium were also evaluated in a canine coronary artery bypass grafting model. Electrophysiologic, histologic, and immunohistochemistry analyses were performed to explore underlying mechanisms.

RESULTS

Postoperative atrial fibrillation occurred in 45 of 137 patients (32.8%). Patients with postoperative atrial fibrillation had significantly higher serum and pericardial myeloperoxidase levels. Individual clinical and surgical factors had moderate predictive value (area under the curve, 0.760) for postoperative atrial fibrillation. Discrimination improved remarkably when myeloperoxidase was combined with other parameters (area under the curve, 0.901). Pericardial myeloperoxidase at 6 hours postoperatively was the strongest independent predictor of postoperative atrial fibrillation (odds ratio, 19.215). The rate of postoperative atrial fibrillation increased exponentially across pericardial myeloperoxidase grades. Compared with controls, coronary artery bypass grafting-treated dogs showed higher atrial fibrillation vulnerability and maintenance, shorter atrial effective refractory period, attenuated connexin 43 expression, and increased myocardial and pericardial myeloperoxidase activity. Connexin 43 expression and atrial effective refractory period were strongly negatively correlated with myocardial and pericardial myeloperoxidase activity.

CONCLUSIONS

Myeloperoxidase is linked to postoperative atrial fibrillation, and the ability to predict postoperative atrial fibrillation was remarkably improved by adding pericardial myeloperoxidase. Myeloperoxidase-related atrial structural and electrical remodeling is a physiologic substrate for this arrhythmia.

Characterization of Myeloperoxidase in the Healthy Equine Endometrium

Myeloperoxidase (MPO), as a marker of neutrophil activation, has been associated with equine endometritis. However, in absence of inflammation, MPO is constantly detected in the uterine lumen of estrous mares. The aim of this study was to characterize MPO in the uterus of mares under physiological conditions as a first step to better understand the role of this enzyme in equine reproduction. Total and active MPO concentrations were determined, by ELISA and SIEFED assay, respectively, in low-volume lavages from mares in estrus (n = 26), diestrus (n = 18) and anestrus (n = 8) in absence of endometritis. Immunohistochemical analysis was performed on 21 endometrial biopsies randomly selected: estrus (n = 11), diestrus (n = 6) and anestrus (n = 4). MPO, although mostly enzymatically inactive, was present in highly variable concentrations in uterine lavages in all studied phases, with elevated concentrations in estrus and anestrus, while in diestrus, concentrations were much lower. Intracytoplasmic immunoexpression of MPO was detected in the endometrial epithelial cells, neutrophils and glandular secretions. Maximal expression was observed during estrus in mid and basal glands with a predominant intracytoplasmic apical reinforcement. In diestrus, immunopositive glands were sporadic. In anestrus, only the luminal epithelium showed residual MPO immunostaining. These results confirm a constant presence of MPO in the uterine lumen of mares in absence of inflammation, probably as part of the uterine mucosal immune system, and suggest that endometrial cells are a source of uterine MPO under physiological cyclic conditions.

Characteristics of immune clusters and cell abundance in patients with different subtypes of nonparoxysmal atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice. Inflammation plays an important role in the initiation and perpetuation of AF. The present study was conducted to characterize immune clusters in nonparoxysmal AF and to distinguish immune subtypes of nonparoxysmal AF. Immune-related algorithms (CIBERSORT, ESTIMATE, and ssGSEA) were used to evaluate the immune cluster characterization and cell abundance, and multivariable logistics analysis was performed to determine the most relevant immune cells. We identified differentially expressed genes (DEGs) and used consensus clustering analysis to identify nonparoxysmal AF subtypes. Weighted gene coexpression network analysis (WGCNA) was used for finding highly correlated gene sets and attach to external sample traits. And it was conducted twice to identify the immune- and subtype- related modules. Finally, Metascape was used to compare the biological functions of the two nonparoxysmal AF subtypes we obtained. CytoHubba was used to identify the hub genes of these two subtypes. Based on the results of bioinformatics analysis, regulatory T cells, resting NK cells, active mast cells and neutrophils were considered to be closely related to nonparoxysmal AF. The brown module was identified as the most relevant module to the above immune cells by WGCNA. We identified two major nonparoxysmal AF subtypes by consensus clustering analysis and their enriched biological functions by Metascape. The hub genes are TYROBP, PTPRC, ITGB2, SPI1, PLEK, and CSF1R in permanent AF and JAM3, S100P, ARPC5, TRIM34, and GREB1L in persistent AF. This study revealed two major nonparoxysmal AF subtypes and eleven hub genes, which provide potential therapeutic targets for anti-inflammatory treatments of nonparoxysmal AF.

Immune infiltration and immunophenotyping in atrial fibrillation

Atrial fibrillation (AF) is a relatively common arrhythmia in clinical practice. Although significant progress has been achieved in the treatment of AF and its associated complications, research on AF prevention lags behind, mainly due to the lack of a deep understanding of AF pathogenesis. In recent years, as our knowledge has grown, the role of the inflammatory/immune response in the occurrence and progression of AF has gradually gained attention. In this paper, based on existing gene expression data in the Gene Expression Omnibus database, a detailed description of immune infiltration status in AF is presented using a series of analytical methods, including differential analysis, Gene Ontology categorization, Kyoto Encyclopedia of Genes and Genomes enrichment analysis, and weighted gene coexpression network analysis, and analysis tools such as CIBERSORTx and Cytoscape. Several new AF/immune infiltrations-related signature genes were identified, and the AF/immune infiltration pathology was classified based on these immune signature genes, thus providing novel insights into the pathogenesis of AF based on the inflammatory response.

microRNAs as biomarkers of risk of major adverse cardiovascular events in atrial fibrillation

Atrial fibrillation is a complex and multifactorial disease. Although prophylactic anticoagulation has great benefits in avoiding comorbidities, adverse cardiovascular events still occur and thus in recent decades, many resources have been invested in the identification of useful markers in the prevention of the risk of MACE in these patients. As such, microRNAs, that are small non-coding RNAs whose function is to regulate gene expression post-transcriptionally, have a relevant role in the development of MACE. miRNAs, have been investigated for many years as potential non-invasive biomarkers of several diseases. Different studies have shown their utility in the diagnosis and prognosis of cardiovascular diseases. In particular, some studies have associated the presence of certain miRNAs in plasma with the development of MACE in AF. Despite these results, there are still many efforts to be done to allow the clinical use of miRNAs. The lack of standardization concerning the methodology in purifying and detecting miRNAs, still provides contradictory results. miRNAs also have a functional impact in MACE in AF through the dysregulation of immunothrombosis. Indeed, miRNAs may be a link between MACE and inflammation, through the regulation of neutrophil extracellular traps that are a key element in the establishment and evolution of thrombotic events. The use of miRNAs as therapy against thromboinflammatory processes should also be a future approach to avoid the occurrence of MACE in atrial fibrillation.

Protective Effects of Therapeutic Neutrophil Depletion and Myeloperoxidase Inhibition on Left Ventricular Function and Remodeling in Myocardial Infarction

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide. Improved survival has led to an increasing incidence of ischemic cardiomyopathy, making it a major reason for hospitalization in the western world. The inflammatory response in the ischemic myocardium determines the extent of structural remodeling and functional deterioration, with neutrophils (PMN) being a key modulator of the propagation and resolution of inflammation. The heme enzyme myeloperoxidase (MPO) is abundantly expressed in PMN and is an important mediator of their inflammatory capacities. Here, we examine the effects of PMN reduction, MPO deficiency and MPO inhibition in two murine models of MI. Reduction in PMN count resulted in less scar formation and improved cardiac function. Similar results were obtained in genetically MPO deficient mice, suggesting that MPO is a critical factor in PMN-mediated cardiac remodeling. To test our findings in a therapeutic approach, we orally administered the MPO inhibitor AZM198 in the context of MI and could demonstrate improved cardiac function and reduced structural remodeling. Therefore, MPO appears to be a favorable pharmacological target for the prevention of long-term morbidity after MI.

The Role of Major Inflammatory Biomarkers in the Pathogenesis of Atrial Fibrillation

Many studies have reported a relationship between inflammation and atrial fibrillation (AF). According to the literature, inflammation is the key component in pathophysiological processes during the development of AF; the amplification of inflammatory pathways triggers AF, and, at the same time, AF increases the inflammatory state. The plasma levels of several inflammatory biomarkers are elevated in patients with AF; therefore, inflammation might contribute to both the maintenance and occurrence of AF and its thromboembolic complications. Numerous inflammatory markers have been linked to AF, including CD40 ligand, fibrinogen, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein-1, myeloperoxidase, plasminogen activator inhibitor-1, and serum amyloid A. There are many pathophysiological aspects of AF that are linked to these inflammatory biomarkers, including atrial structural remodeling and atrial dilatation, increased atrial myocyte expression, fluctuations in calcium cycling, cardiac remodeling promotion, increased cardiac myocyte proliferation and terminal differentiation, production of several MMPs, the pathogenesis of atherosclerosis and cardiomyocyte apoptosis, an increased degree of fibrosis in atrial myocardium, and the progression and development of atherogenesis and atherothrombosis. The present review article aims to provide an updated overview and focus on the basic role of different biomarkers of inflammation in the pathophysiological aspects of the pathogenesis of AF.

Screening of atrial fibrillation diagnostic markers based on a GEO database chip and bioinformatics analysis

Background

Study have shown that atrial fibrillation (AF) is a disease with genetic risk, and its pathogenesis is still unclear. This study sought to screen the gene microarray data of AF patients and to perform a bioinformatics analysis to identify AF signature diagnostic genes.

Methods

The AF gene sets from the Gene Expression Omnibus (GEO) database were screened, and the differentially expressed genes (DEGs) were identified after the normalization of the data set by R software. We conducted a gene set enrichment analysis, a protein-protein interaction (PPI) network analysis, a gene-gene interaction (GGI) network analysis, and an immuno-infiltration analysis. The core genes were identified from the DEGs, and base on receiver operating characteristic, the top 5 core genes in the 2 data sets were selected as diagnostic factors and a nomogram was constructed. The miRNA of the core genes were predicted and an immune cell correlation analysis was performed.

Results

A total of 20 DEGs were identified. The functions of these DEGs were mainly related to muscle contraction, autophagosome, and bone morphogenetic protein (BMP) binding, and focused on the calcium signaling pathway, ferroptosis, the extracellular matrix-receptor interaction, and other pathways. A total of 5 core genes [i.e., GPR22 (G protein-coupled receptor 22), COG5 (component of oligomeric golgi complex 5), GALNT16 (polypeptide N-acetylgalactosaminyltransferase 16), OTOGL (otogelin-like), and MCOLN3 (mucolipin 3)] were identified, and a linear model for risk prediction was constructed, which has good prediction ability. Plasma cells and Macrophages M2 were significantly increased in AF, while T cells follicular helper and Dendritic cells activated were significantly decreased.

Conclusions

In our study, we identified 5 potential diagnostic key genes (i.e., GPR22, COG5, GALNT16, OTOGL, and MCOLN3). Our findings may provide a theoretical basis for susceptibility analyses and target drug development in AF.

Myeloperoxidase Levels in Pericardial Fluid Is Independently Associated with Postoperative Atrial Fibrillation after Isolated Coronary Artery Bypass Surgery

BACKGROUND

Postoperative atrial fibrillation (POAF) is the most common complication after surgery for atherosclerotic cardiovascular disease (ASCVD) and leads to extended hospital stays and increased mortality. Myeloperoxidase (MPO) in postoperative pericardial drainage fluid is associated with an increased risk of POAF; however, the correlations between MPO in intraoperative pericardial fluid and POAF remain largely unknown. The aim of the study was to evaluate whether MPO is associated with POAF.

METHODS

A total of 97 patients with no history of atrial arrhythmia who had undergone coronary artery bypass surgery (CABG) were identified. We prospectively measured the levels of MPO in intraoperative pericardial fluid and blood using the human magnetic Luminex assay. Then, the occurrence of atrial fibrillation was continuously observed by postoperative ECG and telemetry strips until discharge.

RESULTS

Our data showed that POAF occurred in 24 of 97 patients (24.74%). MPO levels in blood were higher in the POAF group than the SR group (p = 0.064). Patients with POAF had significantly higher intraoperative pericardial fluid MPO levels than patients who remained in SR (p = 0.021). There was no significant correlation between pericardial fluid MPO levels and blood MPO levels (r = -0.47, p = 0.770). In a multivariable logistic regression model, pericardial fluid MPO levels were significantly associated with a higher risk of POAF (odds ratio = 1.016, 95% confidence interval, 1.001-1.031; p = 0.031).

CONCLUSIONS

Higher intraoperative pericardial fluid MPO levels are linked with POAF in patients undergoing CABG. This finding provides insight into a possible mechanism of MPO in pericardial fluid increase susceptibility to developing POAF in patients undergoing CABG.

Spiropyran-Merocyanine Based Photochromic Fluorescent Probes: Design, Synthesis, and Applications

Due to ever-increasing insights into their fundamental properties and photochromic behaviors, spiropyran derivatives are still a target of interest for researchers. The interswitching ability of this photochrome between the spiropyran (SP) and merocyanine (MC) isoforms under external stimuli (light, cations, anions, pH etc.) with different spectral properties as well as the protonation-deprotonation of its MC form allows researchers to use it suitably in sensing purposes by developing different colorimetric and fluorometric probes. Selective and sensitive recognition can be achieved by little modification of its SP moiety and functional groups. In this review, we emphasize the recent advancements (from 2019 to 2022) of spiropyran-merocyanine based fluorogenic and chromogenic probes for selective detection of various metal ions, anions, neutral analytes, and pH. We precisely explain their design strategies, sensing mechanisms, and biological and environmental applications. This review may accelerate the improvements in designing more advanced probes with innovative applications in the near future.

Hypochlorous Acid Chemistry in Mammalian Cells—Influence on Infection and Role in Various Pathologies

This review discusses the formation of hypochlorous acid HOCl and the role of reactive chlorinated species (RCS), which are catalysed by the enzyme myeloperoxidase MPO, mainly located in leukocytes and which in turn contribute to cellular oxidative stress. The reactions of RCS with various organic molecules such as amines, amino acids, proteins, lipids, carbohydrates, nucleic acids, and DNA are described, and an attempt is made to explain the chemical mechanisms of the formation of the various chlorinated derivatives and the data available so far on the effects of MPO, RCS and halogenative stress. Their presence in numerous pathologies such as atherosclerosis, arthritis, neurological and renal diseases, diabetes, and obesity is reviewed and were found to be a feature of debilitating diseases.

Discovery of AZD4831, a Mechanism-Based Irreversible Inhibitor of Myeloperoxidase, As a Potential Treatment for Heart Failure with Preserved Ejection Fraction

Myeloperoxidase is a promising therapeutic target for treatment of patients suffering from heart failure with preserved ejection fraction (HFpEF). We aimed to discover a covalent myeloperoxidase inhibitor with high selectivity for myeloperoxidase over thyroid peroxidase, limited penetration of the blood-brain barrier, and pharmacokinetics suitable for once-daily oral administration at low dose. Structure-activity relationship, biophysical, and structural studies led to prioritization of four compounds for in-depth safety and pharmacokinetic studies in animal models. One compound (AZD4831) progressed to clinical studies on grounds of high potency (IC₅₀, 1.5 nM in vitro) and selectivity (>450-fold vs thyroid peroxidase in vitro), the mechanism of irreversible inhibition, and the safety profile. Following phase 1 studies in healthy volunteers and a phase 2a study in patients with HFpEF, a phase 2b/3 efficacy study of AZD4831 in patients with HFpEF started in 2021.

Immune remodeling and atrial fibrillation

Atrial fibrillation (AF) is a highly prevalent arrhythmia that causes high morbidity and mortality. However, the underlying mechanism of AF has not been fully elucidated. Recent research has suggested that, during AF, the immune system changes considerably and interacts with the environment and cells involved in the initiation and maintenance of AF. This may provide a new direction for research and therapeutic strategies for AF. In this review, we elaborate the concept of immune remodeling based on available data in AF. Then, we highlight the complex relationships between immune remodeling and atrial electrical, structural and neural remodeling while also pointing out some research gaps in these field. Finally, we discuss several potential immunomodulatory treatments for AF. Although the heterogeneity of existing evidence makes it ambiguous to extrapolate immunomodulatory treatments for AF into the clinical practice, immune remodeling is still an evolving concept in AF pathophysiology and further studies within this field are likely to provide effective therapies for AF.

Epicardial Adipose Tissue and Cardiac Arrhythmias: Focus on Atrial Fibrillation

Atrial Fibrillation (AF) is the most frequent cardiac arrhythmia and its prevalence increases with age. AF is strongly associated with an increased risk of stroke, heart failure and cardiovascular mortality. Among the risk factors associated with AF onset and severity, obesity and inflammation play a prominent role. Numerous recent evidence suggested a role of epicardial adipose tissue (EAT), the visceral fat depot of the heart, in the development of AF. Several potential arrhythmogenic mechanisms have been attributed to EAT, including myocardial inflammation, fibrosis, oxidative stress, and fat infiltration. EAT is a local source of inflammatory mediators which potentially contribute to atrial collagen deposition and fibrosis, the anatomical substrate for AF. Moreover, the close proximity between EAT and myocardium allows the EAT to penetrate and generate atrial myocardium fat infiltrates that can alter atrial electrophysiological properties. These observations support the hypothesis of a strong implication of EAT in structural and electrical atrial remodeling, which underlies AF onset and burden. The measure of EAT, through different imaging methods, such as echocardiography, computed tomography and cardiac magnetic resonance, has been proposed as a useful prognostic tool to predict the presence, severity and recurrence of AF. Furthermore, EAT is increasingly emerging as a promising potential therapeutic target. This review aims to summarize the recent evidence exploring the potential role of EAT in the pathogenesis of AF, the main mechanisms by which EAT can promote structural and electrical atrial remodeling and the potential therapeutic strategies targeting the cardiac visceral fat.