Management of atrial fibrillation

Pan-Cancer Analysis of Atrial-Fibrillation-Related Innate Immunity Gene ANXA4

Background: Atrial fibrillation (AF) is the most common tachyarrhythmia around the world. Cancer is one of the main causes of death worldwide. A recent study demonstrated that cancer was associated with an increased incidence of AF. In the present study, we aimed to explore possible mechanisms and potential common therapeutic targets between AF and cancer.

Methods: Differentially expressed proteins between AF and sinus rhythm were identified utilizing proteomics analysis. Weighted gene correlation network analysis was applied to cluster proteins into different modules and investigate associations between modules and AF. Hub immune-related genes were selected via InnateDB database and verified using qRT-PCR. RNA sequencing and clinical data of 33 different cancer types were achieved from The Cancer Genome Atlas (TCGA). The correlations between ANXA4 expression and the prognosis were calculated utilizing Cox regression analysis and Kaplan-Meier survival analysis. Spearman's rank correlation test was used to assess associations between ANXA4 and immune infiltration and DNA methylation. Enrichment analysis was performed through gene ontology and gene set enrichment analysis (GSEA).

Results:ANXA4 was identified as hub immune-related gene between AF and sinus rhythm. Expression levels of ANXA4 increased in diverse cancer types. Survival analysis suggested prognostic significance of ANXA4 expression levels in various cancer types. Immune correlation analysis indicated that ANXA4 expression levels were associated with tumor immune infiltration in most cancer types. ANXA4 might influence the efficacy of immunotherapy via tumor burden and microsatellite instability. GSEA results indicated that high ANXA4 expression groups were mainly enriched in peroxisome, bile acid biosynthesis, and p53 pathway.

Conclusion:ANXA4 was identified as a hub immune-related gene in AF, which has never been reported. Pan-cancer analysis indicated its potential as a novel clinical prognostic marker and therapeutic target in diverse cancer types. ANXA4 might play crucial roles in AF and cancer, and targeted therapy for ANXA4 might reduce the incidence of AF in cancer patients.

Proteomic Analysis of Atrial Appendages Revealed the Pathophysiological Changes of Atrial Fibrillation

Atrial fibrillation (AF), known as the most common arrhythmia in the developed world, affects 1.5–2.0% of the population. Numerous basic studies have been carried out to identify the roles of electric and structural remodeling in the pathophysiological changes of AF, but more explorations are required to further understand the mechanisms of AF development. Proteomics enables researchers to identify protein alterations responsible for the pathological developing progresses of diseases. Compared to the genome, the proteome is closely related to the disease phenotype and can better manifest the progression of diseases. In this study, AF patients proteomically analyzed to identify possible mechanisms. Totally 20 patients undergoing cardiac surgery (10 with paroxysmal AF and 10 with persistent AF) and 10 healthy subjects were recruited. The differentially expressed proteins identified here included AKR1A1, LYZ, H2AFY, DDAH1, FGA, FGB, LAMB1, LAMC1, MYL2, MYBPC3, MYL5, MYH10, HNRNPU, DKK3, COPS7A, YWHAQ, and PAICS. These proteins were mainly involved in the development of structural remodeling. The differently expressed proteins may provide a new perspective for the pathological process of AF, and may enable useful targets for drug interference. Nevertheless, more research in terms of multi-omics is required to investigate possible implicated molecular pathways of AF development.

Cyclin Dependent Kinase 1 (CDK1) Activates Cardiac Fibroblasts via Directly Phosphorylating Paxillin at Ser244

Atrial fibrillation has caused severe burden for people worldwide. Differentiation of fibroblasts into myofibroblasts, and consequent progress in atrial structural remodeling have been considered the basis for persistent atrial fibrillation, yet little is known about the molecular mechanisms underlying the process. Here, we show that cyclin-dependent kinase 1 (CDK1) is activated in atrial fibroblasts from patients with atrial fibrillation (AFPAF) and in platelet derived growth factor BB (PDGF-BB)-treated atrial fibroblasts from patients with sinus rhythm (AFPSR). We also demonstrate that inhibition of CDK1 suppresses fibroblast differentiation and focal adhesion (FA) complex formation. The FA protein paxillin is phosphorylated directly at Ser244 by CDK1. Importantly, transfection of a paxillin construct harboring a Ser to Ala mutation causes FA complex disassembly and greatly inhibits fibroblast activation. AFPSRs applied with a lentiviral vector carrying the shRNA sequence of paxillin dramatically prevents PDGF-BB induced functional activation. Taken together, all these results suggest that phosphorylation of paxillin at Ser244 by CDK1 is a key mechanism in fibroblast differentiation and could eventually assist atrial fibrosis.

Atrial remodeling, fibrosis, and atrial fibrillation

The fundamental mechanisms governing the perpetuation of atrial fibrillation (AF), the most common arrhythmia seen in clinical practice, are poorly understood, which explains in part why AF prevention and treatment remain suboptimal. Although some clinical parameters have been identified as predicting a transition from paroxysmal to persistent AF in some patients, the molecular, electrophysiological, and inflammation changes leading to such a progression have not been described in detail. Oxidative stress, atrial dilatation, calcium overload, inflammation, microRNAs, and myofibroblast activation are all thought to be involved in AF-induced atrial remodeling. However, it is unknown to what extent and at which time points such alterations influence the remodeling process that perpetuates AF. Here we postulate a working model that might open new pathways for future investigation into mechanisms of AF perpetuation. We start from the premise that the progression to AF perpetuation is the result of interplay among manifold signaling pathways with differing kinetics. Some such pathways have relatively fast kinetics (e.g., oxidative stress-mediated shortening of refractory period); others likely depend on molecular processes with slower kinetics (e.g., transcriptional changes in myocyte ion channel protein expression mediated through inflammation and fibroblast activation). We stress the need to fully understand the relationships among such pathways should one hope to identify novel, truly effective targets for AF therapy and prevention.