Selective blocking of CXCR2 prevents and reverses atrial fibrillation in spontaneously hypertensive rats

Protective effect of esculentoside A against myocardial infarction via targeting C-X-C motif chemokine receptor 2

Myocardial infarction (MI) is the primary cause of cardiac mortality. Esculentoside A (EsA), a triterpenoid saponin, has anti-inflammatory and antioxidant activities. However, its effect on MI remains unknown. In this study, the protective effect and mechanisms of EsA against MI were investigated. EsA significantly alleviated hypoxia-induced HL-1 cell injury, including increasing cell viability, inhibiting reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) and lactate dehydrogenase (LDH) leakage. In mouse MI model by left coronary artery (LAD) ligating, EsA obviously restored serum levels of creatine kinase isoenzymes (CK-MB), cardiac troponin I (cTnI), superoxide dismutase (SOD) and malondialdehyde (MDA). In addition, the cardioprotective effect of EsA was further confirmed by infarct size, electrocardiogram and echocardiography. Mechanistically, the targeted binding relationship between EsA and C-X-C motif chemokine receptor 2 (CXCR2) was predicted by molecular docking and dynamics, and validated by small molecule pull-down and surface plasmon resonance tests. EsA inhibited CXCR2 level both in vitro and in vivo, correspondingly alleviated oxidative stress by suppressing NOX1 and NOX2 and relieved inflammation through inhibiting p65 and p-p65. It demonstrated that EsA could play a cardioprotective role by targeting CXCR2. However, the effect of EsA against MI was abolished in combination with CXCR2 overexpression both in vitro and in vivo. This study revealed that EsA showed excellent cardioprotective activities by targeting CXCR2 to alleviate oxidative stress and inflammation in MI. EsA may function as a novel CXCR2 inhibitor and a potent candidate for the prevention and intervention of MI in the future.

ACE2 activation alleviates sepsis-induced cardiomyopathy by promoting MasR-Sirt1-mediated mitochondrial biogenesis

Sepsis-induced cardiomyopathy (SIC), caused by a dysregulated host response to infection, is a major contributor to high mortality. Angiotensin-converting enzyme 2 (ACE2), a crucial component of the renin-angiotensin system (RAS), has protective effects against several cardiovascular diseases, such as myocardial infarction and heart failure. However, the role of ACE2 in the pathogenesis of SIC and underlying mechanisms remain unknown. The present study was designed to examine the effects of ACE2 activation or inhibition on SIC in C57BL/6 mice. The ACE2 activator diminazene aceturate (DIZE) and ACE2 inhibitor MLN-4760 were applied for treatment. Myocardial function, inflammatory response, oxidative stress, apoptosis and mitochondrial biogenesis were investigated. Major assays were echocardiography, H&E staining, immunofluorescence staining, DHE staining, TUNEL staining, Western blot, qPCR analysis, ELISA and corresponding kits. We confirmed that ACE2 was markedly downregulated in septic heart tissues. Pharmacological activation of ACE2 by DIZE ameliorated cecal ligation puncture (CLP)-induced mortality, cardiac dysfunction, inflammatory response, oxidative stress and the cardiomyocyte apoptosis by promoting MasR-Sirt1-mediated mitochondrial biogenesis. In contrast, SIC was aggravated via inhibiting MasR-Sirt1-mediated mitochondrial biogenesis by the use of ACE2 inhibitor MLN-4760. Consequently, activation of ACE2 may protect against SIC by promoting MasR-Sirt1-mediated mitochondrial biogenesis.

NADPH Oxidases and Oxidative Stress in the Pathogenesis of Atrial Fibrillation

Atrial fibrillation (AF) is the most common type of cardiac arrhythmia and its prevalence increases with age. The irregular and rapid contraction of the atria can lead to ineffective blood pumping, local blood stasis, blood clots, ischemic stroke, and heart failure. NADPH oxidases (NOX) and mitochondria are the main sources of reactive oxygen species in the heart, and dysregulated activation of NOX and mitochondrial dysfunction are associated with AF pathogenesis. NOX- and mitochondria-derived oxidative stress contribute to the onset of paroxysmal AF by inducing electrophysiological changes in atrial myocytes and structural remodeling in the atria. Because high atrial activity causes cardiac myocytes to expend extremely high energy to maintain excitation-contraction coupling during persistent AF, mitochondria, the primary energy source, undergo metabolic stress, affecting their morphology, Ca2+ handling, and ATP generation. In this review, we discuss the role of oxidative stress in activating AF-triggered activities, regulating intracellular Ca2+ handling, and functional and anatomical reentry mechanisms, all of which are associated with AF initiation, perpetuation, and progression. Changes in the extracellular matrix, inflammation, ion channel expression and function, myofibril structure, and mitochondrial function occur during the early transitional stages of AF, opening a window of opportunity to target NOX and mitochondria-derived oxidative stress using isoform-specific NOX inhibitors and mitochondrial ROS scavengers, as well as drugs that improve mitochondrial dynamics and metabolism to treat persistent AF and its transition to permanent AF.

Bioinformatics and Next-Generation Data Analysis for Identification of Genes and Molecular Pathways Involved in Subjects with Diabetes and Obesity

Background and Objectives: A subject with diabetes and obesity is a class of the metabolic disorder. The current investigation aimed to elucidate the potential biomarker and prognostic targets in subjects with diabetes and obesity. Materials and Methods: The next-generation sequencing (NGS) data of GSE132831 was downloaded from Gene Expression Omnibus (GEO) database. Functional enrichment analysis of DEGs was conducted with ToppGene. The protein-protein interactions network, module analysis, target gene-miRNA regulatory network and target gene-TF regulatory network were constructed and analyzed. Furthermore, hub genes were validated by receiver operating characteristic (ROC) analysis. A total of 872 DEGs, including 439 up-regulated genes and 433 down-regulated genes were observed. Results: Second, functional enrichment analysis showed that these DEGs are mainly involved in the axon guidance, neutrophil degranulation, plasma membrane bounded cell projection organization and cell activation. The top ten hub genes (MYH9, FLNA, DCTN1, CLTC, ERBB2, TCF4, VIM, LRRK2, IFI16 and CAV1) could be utilized as potential diagnostic indicators for subjects with diabetes and obesity. The hub genes were validated in subjects with diabetes and obesity. Conclusion: This investigation found effective and reliable molecular biomarkers for diagnosis and prognosis by integrated bioinformatics analysis, suggesting new and key therapeutic targets for subjects with diabetes and obesity.

The Potential Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Cardiovascular System, Respiratory System and Skin

In this paper, we present a literature review of the role of CXC motif chemokine ligand 1 (CXCL1) in physiology, and in selected major non-cancer diseases of the cardiovascular system, respiratory system and skin. CXCL1, a cytokine belonging to the CXC sub-family of chemokines with CXC motif chemokine receptor 2 (CXCR2) as its main receptor, causes the migration and infiltration of neutrophils to the sites of high expression. This implicates CXCL1 in many adverse conditions associated with inflammation and the accumulation of neutrophils. The aim of this study was to describe the significance of CXCL1 in selected diseases of the cardiovascular system (atherosclerosis, atrial fibrillation, chronic ischemic heart disease, hypertension, sepsis including sepsis-associated encephalopathy and sepsis-associated acute kidney injury), the respiratory system (asthma, chronic obstructive pulmonary disease (COPD), chronic rhinosinusitis, coronavirus disease 2019 (COVID-19), influenza, lung transplantation and ischemic-reperfusion injury and tuberculosis) and the skin (wound healing, psoriasis, sunburn and xeroderma pigmentosum). Additionally, the significance of CXCL1 is described in vascular physiology, such as the effects of CXCL1 on angiogenesis and arteriogenesis.

Associations of urinary polycyclic aromatic hydrocarbon metabolites and blood pressure with the mediating role of cytokines: A panel study among children

Little was known regarding the relations of polycyclic aromatic hydrocarbon (PAH) mixture with children's blood pressure (BP) and its potential mechanism. We conducted a panel study with up to 3 visits across 3 seasons in 2017-2018 among 103 children aged 4-13 years. Urinary PAH metabolites (OH-PAHs) were measured by gas chromatograph-tandem triple quadrupole mass spectrometer, and serum cytokines were detected by Bio-Rad 48-Plex Screening Panel. We employed linear mixed-effects models to assess the relations of each urinary OH-PAH with BP, least absolute shrinkage and selection operator (LASSO), and weighted quantile sum (WQS) regression to evaluate associations of OH-PAHs mixture with BP, and mediation analyses for the role of serum cytokines. We found the consistently positive associations of 1-hydroxynaphthalene and 9-hydroxyphenanthrene (9-OHPh) with systolic BP (SBP), 4-OHPh, and 9-OHPh with diastolic BP (DBP) and mean arterial pressure (MAP) in a dose-responsive manner. For instance, each 1-fold increment of 9-OHPh was related with increase of 0.92% (95% confidence interval (CI): 0.25%, 1.60%) in SBP, 1.32% (95%CI: 0.25%, 2.39%) in DBP, and 1.15% (95%CI: 0.40%, 1.88%) in MAP. Meanwhile, based on LASSO and WQS regression, OH-PAHs mixture was linked with increased DBP and MAP, to which 9-OHPh and 4-OHPh were the major contributors. Such relationships were modified by passive smoking status and 3-4 times stronger in passive smokers than non-passive smokers. A 1-fold increase in 9-OHPh was associated with an elevation of 3.51% in SBP among passive smokers while that of 0.55% in SBP among non-passive smokers. Furthermore, 4-OHPh and 9-OHPh were related to multiple cytokines elevation, of which platelet-derived growth factor (PDGF) mediated 9.99% and 12.57% in 4-OHPh-related DBP and MAP elevation, respectively. Accordingly, urinary OH-PAHs dominated by 9-OHPh and 4-OHPh were dose-responsively associated with elevated BP whereby a mechanism partly involving PDGF among children.

Association between serum albumin levels and paroxysmal atrial fibrillation by gender in a Chinese population: a case–control study

Background

Hypoalbuminemia is linked to the emergence of cardiovascular events. However, there is an unclear association between serum albumin (ALB) and gender in paroxysmal AF patients. This retrospective study aimed to explore the association between ALB levels and paroxysmal AF by gender in a Chinese population.

Methods

This study included patients with paroxysmal AF who were hospitalized consecutively in China from January 2019 to September 2021. Controls with sinus rhythm and without paroxysmal AF were matched (2:1) to cases by gender and age. Pearson correlation analysis was used to study the correlation between ALB and blood lipid profiles, multivariate regression models were performed to investigate the association between ALB and paroxysmal AF.

Results

There were 305 patients with paroxysmal AF and 610 patients with controls included in this study. Low ALB in male with AF patients were significantly associated with paroxysmal AF (OR = 0.889, 95% CI 0.832–0.950). ALB was positively correlated with triglyceride (TG) (r = 0.212, p < 0.001), total cholesterol (TC) (r = 0.381, p = 0.002), low-density lipoprotein cholesterol (LDL-C) (r = 0.263, p < 0.001), and high-density lipoprotein cholesterol (HDL-C) (r = 0.329, p < 0.001).

Conclusion

Low ALB in male patients is significantly associated with paroxysmal AF in a Chinese population. Monitoring for hypoalbuminemia in men might help reduce the incidence of paroxysmal AF.

Bioinformatics analysis of the circRNA-miRNA-mRNA network for atrial fibrillation

Atrial fibrillation (AF) is a chronic and progressive disease, with advancing age, the morbidity of which will increase exponentially. Circular ribonucleic acids (RNAs; circRNAs) have gained a growing attention in the development of AF in recent years. The purpose of this study is to explore the mechanism of circRNA regulation in AF, in particular, the intricate interactions among circRNA, microRNA (miRNA), and messenger RNA (mRNA). Three datasets (GSE129409, GSE68475, and GSE79768) were obtained from the Gene Expression Omnibus database to screen differentially expressed (DE) circRNAs, DE miRNAs, and DE mRNAs in AF, respectively. Based on circRNA-miRNA pairs and miRNA-mRNA pairs, a competing endogenous RNAs (ceRNAs) network was built. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis of DE mRNAs in the network were performed and protein-protein interaction (PPI) networks were established to identify hub genes. Finally, a circRNA-miRNA-hub gene subnetwork was constructed. A total of 103 DE circRNAs, 16 DE miRNAs, and 110 DE mRNAs were screened in AF. Next, ceRNAs network in AF was constructed with 3 upregulated circRNAs, 2 downregulated circRNAs, 2 upregulated miRNAs, 2 downregulated miRNAs, 17 upregulated mRNAs, and 24 downregulated mRNAs. Thirty GO terms and 6 KEGG pathways were obtained. Besides, 6 hub genes (C-X-C chemokine receptor type 4 [CXCR4], C-X-C chemokine receptor type 2 [CXCR2], C-X-C motif chemokine 11 [CXCL11], neuromedin-U, B1 bradykinin receptor, and complement C3) were screened from constructing a PPI network. Finally, a circRNA-miRNA-hub gene subnetwork with 10 regulatory axes was constructed to describe the interactions among the differential circRNAs, miRNA, and hub genes. We speculated that hsa_circRNA_0056281/hsa_circRNA_0006665 -hsa-miR-613-CXCR4/CXCR2/CXCL11 regulatory axes and hsa_circRNA_0003638-hsa-miR-1207-3p-CXCR4 regulatory axis may be associated with the pathogenesis of AF.

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.

Identification of genes and key pathways underlying the pathophysiological association between nonalcoholic fatty liver disease and atrial fibrillation

Background

Atrial fibrillation (AF) is one of the most prevalent sustained cardiac arrhythmias. The latest studies have revealed a tight correlation between nonalcoholic fatty liver disease (NAFLD) and AF. However, the exact molecular mechanisms underlying the association between NAFLD and AF remain unclear. The current research aimed to expound the genes and signaling pathways that are related to the mechanisms underlying the association between these two diseases.

Materials and methods

NAFLD- and AF- related differentially expressed genes (DEGs) were identified via bioinformatic analysis of the Gene Expression Omnibus (GEO) datasets GSE63067 and GSE79768, respectively. Further enrichment analysis of Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG), the construction of a protein–protein interaction (PPI) network, the identification of significant hub genes, and receiver operator characteristic curve analysis were conducted. The gene-disease interactions were analyzed using the Comparative Toxicogenomics Database. In addition, the hub genes were validated by quantitative Real-Time PCR (qRT-PCR) in NAFLD cell model.

Results

A total of 45 co-expressed differentially expressed genes (co-DEGs) were identified between the NAFLD/AF and healthy control individuals. GO and KEGG pathway analyses revealed that the co-DEGs were mostly enriched in neutrophil activation involved in the immune response and cytokine-cytokine receptor interactions. Moreover, eight hub genes were selected owing to their high degree of connectivity and upregulation in both the NAFLD and AF datasets. These genes included CCR2, PTPRC, CXCR2, MNDA, S100A9, NCF2, S100A12, and S100A8.

Conclusions

In summary, we conducted the gene differential expression analysis, functional enrichment analysis, and PPI analysis of DEGs in AF and NAFLD, which provides novel insights into the identification of potential biomarkers and valuable therapeutic leads for AF and NAFLD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01300-1.

Cardiac Macrophages and Their Effects on Arrhythmogenesis

Cardiac electrophysiology is a complex system established by a plethora of inward and outward ion currents in cardiomyocytes generating and conducting electrical signals in the heart. However, not only cardiomyocytes but also other cell types can modulate the heart rhythm. Recently, cardiac macrophages were demonstrated as important players in both electrophysiology and arrhythmogenesis. Cardiac macrophages are a heterogeneous group of immune cells including resident macrophages derived from embryonic and fetal precursors and recruited macrophages derived from circulating monocytes from the bone marrow. Recent studies suggest antiarrhythmic as well as proarrhythmic effects of cardiac macrophages. The proposed mechanisms of how cardiac macrophages affect electrophysiology vary and include both direct and indirect interactions with other cardiac cells. In this review, we provide an overview of the different subsets of macrophages in the heart and their possible interactions with cardiomyocytes under both physiologic conditions and heart disease. Furthermore, we elucidate similarities and differences between human, murine and porcine cardiac macrophages, thus providing detailed information for researchers investigating cardiac macrophages in important animal species for electrophysiologic research. Finally, we discuss the pros and cons of mice and pigs to investigate the role of cardiac macrophages in arrhythmogenesis from a translational perspective.

The Role of CXC Chemokines in Cardiovascular Diseases

Cardiovascular disease (CVD) is a class of diseases with high disability and mortality rates. In the elderly population, the incidence of cardiovascular disease is increasing annually. Between 1990 and 2016, the age-standardised prevalence of CVD in China significantly increased by 14.7%, and the number of cardiovascular disease deaths increased from 2.51 million to 3.97 million. Much research has indicated that cardiovascular disease is closely related to inflammation, immunity, injury and repair. Chemokines, which induce directed chemotaxis of reactive cells, are divided into four subfamilies: CXC, CC, CX3C, and XC. As cytokines, CXC chemokines are similarly involved in inflammation, immunity, injury, and repair and play a role in many cardiovascular diseases, such as atherosclerosis, myocardial infarction, cardiac ischaemia-reperfusion injury, hypertension, aortic aneurysm, cardiac fibrosis, postcardiac rejection, and atrial fibrillation. Here, we explored the relationship between the chemokine CXC subset and cardiovascular disease and its mechanism of action with the goal of further understanding the onset of cardiovascular disease.

Time series proteome profile analysis reveals a protective role of citrate synthase in angiotensin II-induced atrial fibrillation

BACKGROUND

Angiotensin (Ang) II and elevated blood pressure are considered to be the main risk factors for atrial fibrillation. However, the proteome profiles and key mediators/signaling pathways involved in the development of Ang II-induced atrial fibrillation remain unclear.

METHODS

Male wild-type C57BL/6 mice (10-week old) were infused with Ang II (2000 ng/kg per min) for 1, 2, or 3 weeks, respectively. Time series proteome profiling of atrial tissues was performed using isobaric tags for relative and absolute quantitation and liquid chromatography coupled with tandem mass spectrometry.

RESULTS

We identified a total of 1566 differentially expressed proteins (DEPs) in the atrial tissues at weeks 1, 2, and 3 after Ang II infusion. These DEPs were predominantly involved in mitochondrial oxidation-reduction and tricarboxylic acid cycle in Ang II-infused atria. Moreover, coexpression network analysis revealed that citrate synthase, a rate-limiting enzyme in the tricarboxylic acid cycle, was localized at the center of the mitochondrial oxidation-reduction process, and its expression was significantly downreguated in Ang II-infused atria at different time points. Cardiomyocyte-specific overexpresion of citrate synthase markedly reduced atrial fibrillation susceptibility and atrial remodeling in mice. These beneficial effects were associated with increased ATP production and mitochondrial oxidative phosphorylation system complexes I-V expression and inhibition of oxidative stress.

CONCLUSION

The current study defines the dynamic changes of the DEPs involved in Ang II-induced atrial fibrillation, and identifies that citrate synthase plays a protective role in regulating atrial fibrillation development, and increased citrate synthase expression may represent a potential therapeutic option for atrial fibrillation treatment.

CXCL12/CXCR4 axis as a key mediator in atrial fibrillation via bioinformatics analysis and functional identification

Atrial fibrillation (AF) is an increasingly prevalent arrhythmia with significant health and socioeconomic impact. The underlying mechanism of AF is still not well understood. In this study, we sought to identify hub genes involved in AF, and explored their functions and underlying mechanisms based on bioinformatics analysis. Five microarray datasets in GEO were used to identify the differentially expressed genes (DEGs) by Robust Rank Aggregation (RRA), and hub genes were screened out using protein-protein interaction (PPI) network. AF model was established using a mixture of acetylcholine and calcium chloride (Ach-CaCl2) by tail vein injection. We totally got 35 robust DEGs that mainly involve in extracellular matrix formation, leukocyte transendothelial migration, and chemokine signaling pathway. Among these DEGs, we identified three hub genes involved in AF, of which CXCL12/CXCR4 axis significantly upregulated in AF patients stands out as one of the most potent targets for AF prevention, and its effect on AF pathogenesis and underlying mechanisms were investigated in vivo subsequently with the specific CXCR4 antagonist AMD3100 (6 mg/kg). Our results demonstrated an elevated transcription and translation of CXCL12/CXCR4 axis in AF patients and mice, accompanied with the anabatic atrial inflammation and fibrosis, thereby providing the substrate for AF maintenance. Blocking its signaling via AMD3100 administration in AF model mice reduced AF inducibility and duration, partly ascribed to decreased atrial inflammation and structural remodeling. Mechanistically, these effects were achieved by reducing the recruitment of CD3+ T lymphocytes and F4/80+ macrophages, and suppressing the hyperactivation of ERK1/2 and AKT/mTOR signaling in atria of AF model mice. In conclusion, this study provides new evidence that antagonizing CXCR4 prevents the development of AF, and suggests that CXCL12/CXCR4 axis may be a potential therapeutic target for AF.

Uncovering potential novel biomarkers and immune infiltration characteristics in persistent atrial fibrillation using integrated bioinformatics analysis

Atrial fibrillation (AF) is the most common cardiac arrhythmia. This study aimed to identify potential novel biomarkers for persistent AF (pAF) using integrated analyses and explore the immune cell infiltration in this pathological process. Three pAF datasets (GSE31821, GSE41177, and GSE79768) from the Gene Expression Omnibus (GEO) database were integrated with the elimination of batch effects. 264 differentially expressed genes (DEGs) were identified using Linear models for microarray data (LIMMA), 12 modules were screened out by weighted gene co-expression network analysis (WGCNA) in pAF compared with normal controls. Subsequently, common genes (CGs) were identified as the intersection of DEGs and genes in the most significant module. Functional enrichment analysis showed that CGs were mainly enriched in the "Calcineurin-NFAT (nuclear factor of activated T-cells)" signaling pathway, particularly regulator of calcineurin 1 (RCAN1), and protein phosphatase 3 regulatory subunit B, alpha (PPP3R1). Ulteriorly, the microRNA-transcription factor-mRNA network revealed that microRNA-34a-5p could target both RCAN1 and PPP3R1 in the pAF pathogenesis. Finally, immune infiltration analysis by CIBERSORT, a versatile computational method, displayed a higher level of monocytes, dendritic cells and neutrophils, as well as a lower level of CD8+ T cells and T cells regulatory (Tregs) in pAF compared with the control group. In conclusion, our present study revealed several novel pAF-associated genes, miRNAs, and pathways, including microRNA-34a-5p, which might target RCAN1 and PPP3R1 to regulate pAF through the calcineurin-NFAT signaling pathway. In addition, there was a difference in immune infiltration between patients with pAF and normal groups and immune cells might interact with specific genes in pAF.

Identification of key immune-related genes and immune infiltration in atrial fibrillation with valvular heart disease based on bioinformatics analysis

Background

Atrial fibrillation (AF) is the most common persistent arrhythmia. Valvular heart disease (VHD) and AF frequently coexist. In our study, from performing bioinformatics analysis, we sought to identify immune-related genes (IRGs) and explore the role of immune cell infiltration in AF-VHD in depth, aiming at investigating the potential molecular mechanism and developing new therapeutic targets for AF, including AF-VHD.

Methods

The gene expression of the GSE41177 and GSE79768 datasets were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were analyzed via the limma package in Bioconductor with R software. Differentially expressed immune-related genes (DEIRGs) were selected via combination ImmPort database with DEGs, and the enrichment function and pathway analysis were explored. A protein-protein interaction (PPI) network was built with a Search Tool for the Retrieval of Interacting Genes/Proteins plugin in Cytoscape. The CIBERSORT algorithm was used to evaluate immune infiltration in the left atrial (LA) tissues between AF-VHD and sinus rhythm (SR) patients. Finally, a correlation analysis between key DEIRGs and infiltrating immune cells was performed.

Results

A total of 130 DEIRGs were detected. Enrichment function of DEIRGs demonstrated that they are significant in immune and inflammatory responses. The key DEIRGs assessed by the PPI network and involved in both the immune and inflammatory responses were the C-X-C motif chemokine ligand (CXCL) 1, pro-platelet basic protein (PPBP), CXCL12, and C-C motif chemokine ligand 4 (CCL4). The immune infiltration findings indicated that, compared with the LA tissues from SR patients, the tissues from AF-VHD patients contained a higher proportion of gamma delta T cells, but a lower proportion of CD8 and regulatory T cells. The results of correlation analysis demonstrated that CXCL1 was positively correlated with activated mast cells and significantly negatively correlated with resting mast cells. PPBP, CXCL12, and CCL4 were positively correlated with the infiltration of various immune cells, such as neutrophils, plasma cells, and resting dendritic cells.

Conclusions

The key immune-related genes and the differences in immune infiltration in LA tissues play an essential role in the occurrence and progression of AF-VHD.

Selective blocking of CXCR2 prevents and reverses atrial fibrillation in spontaneously hypertensive rats

Atrial fibrillation (AF) is associated with inflammation and oxidative stress. Recently, we demonstrated that the chemokine‐receptor CXCR2 plays a critical role in the recruitment of monocytes/macrophages and the development of hypertension and cardiac remodelling. However, the role of CXCR2 in the pathogenesis of hypertensive AF remains unclear. AF was induced in Wistar‐Kyoto rats (WKYs) and spontaneously hypertensive rats (SHRs) administered with the CXCR2 inhibitor SB225002. Atrial remodelling, pathological changes and electrophysiology were examined. Our results showed that the chemokine CXCL1 and its receptor CXCR2 were markedly increased in atrial tissue of SHRs compared with WKYs. The administration of SB225002 to SHRs significantly reduced the elevation of blood pressure, AF inducibility and duration, atrial remodelling, recruitment of macrophages, superoxide production and conduction abnormalities compared with vehicle treatment. The administration of SB225002 to SHRs also reversed pre‐existing AF development, atrial remodelling, inflammation and oxidative stress. These effects were associated with the inhibition of multiple signalling pathways, including TGF‐β1/Smad2/3, NF‐κB‐P65, NOX1, NOX2, Kir2.1, Kv1.5 and Cx43. In conclusion, this study provides new evidence that blocking CXCR2 prevents and reverses the development of AF in SHRs, and suggests that CXCR2 may be a potential therapeutic target for hypertensive AF.