Atrial Samples Research Articles

Overexpression of the PTEN Gene in Myocardial Tissues of Coronary Bypass Surgery Patients.

Coronary artery disease is a complex disorder that causes death worldwide. One of the genes involved in developing this disease may be PTEN. This study aimed to investigate the PTEN gene and protein expression in tissue and blood samples taken from coronary bypass surgery patients. Molecular studies were performed at Erciyes University Genome and Stem Cell Center (GENKOK). Right atrial appendage and blood samples were taken from the central vein of 22 coronary bypass surgery patients before starting and ending cardiopulmonary bypass. PTEN expression was determined using quantitative real-time PCR and western blot analysis. The significance level was accepted as p<0.05. There was no significant difference in the PTEN gene expression in blood samples taken before and after cardiopulmonary bypass. However, a substantial increase in both protein and gene expression levels of P-PTEN and PTEN was observed in the tissue samples. Myocardial expression of the PTEN gene was significantly increased at the end of the cardiopulmonary bypass. PTEN gene expression in the post-cardiopulmonary bypass period was increased when compared to the pre-bypass period, but it was insignificant when compared to healthy controls. This study first revealed the role of the PTEN gene by analyzing both mRNA and protein expression in coronary bypass patients, appearing in both myocardial tissue and blood samples. Increased levels of PTEN may be a marker in myocardial tissue for patients with coronary artery disease.

Expression and Impact of Adenosine A3 Receptors on Calcium Homeostasis in Human Right Atrium.

Increased adenosine A2A receptor (A2AR) expression and activation underlies a higher incidence of spontaneous calcium release in atrial fibrillation (AF). Adenosine A3 receptors (A3R) could counteract excessive A2AR activation, but their functional role in the atrium remains elusive, and we therefore aimed to address the impact of A3Rs on intracellular calcium homeostasis. For this purpose, we analyzed right atrial samples or myocytes from 53 patients without AF, using quantitative PCR, patch-clamp technique, immunofluorescent labeling or confocal calcium imaging. A3R mRNA accounted for 9% and A2AR mRNA for 32%. At baseline, A3R inhibition increased the transient inward current (ITI) frequency from 0.28 to 0.81 events/min (p < 0.05). Simultaneous stimulation of A2ARs and A3Rs increased the calcium spark frequency seven-fold (p < 0.001) and the ITI frequency from 0.14 to 0.64 events/min (p < 0.05). Subsequent A3R inhibition caused a strong additional increase in the ITI frequency (to 2.04 events/min; p < 0.01) and increased phosphorylation at s2808 1.7-fold (p < 0.001). These pharmacological treatments had no significant effects on L-type calcium current density or sarcoplasmic reticulum calcium load. In conclusion, A3Rs are expressed and blunt spontaneous calcium release at baseline and upon A2AR-stimulation in human atrial myocytes, pointing to A3R activation as a means to attenuate physiological and pathological elevations of spontaneous calcium release events.

Role of epicardial adipose tissue in human atrial fibrillation.

A recent meta-analysis among which four reports were conducted in Japan demonstrated that epicardial adipose tissue (EAT) is closely associated with an increased risk of atrial fibrillation (AF) recurrence after catheter ablation. We previously investigated the role of EAT in AF in humans. Left atrial (LA) appendage samples were obtained from AF patients during cardiovascular surgery. Histologically, the severity of fibrotic EAT remodeling was associated with LA myocardial fibrosis. Total collagen in the LA myocardium (i.e., LA myocardial fibrosis) was positively correlated with proinflammatory and profibrotic cytokines/chemokines, including interleukin-6, monocyte chemoattractant protein-1, and tumor necrosis factor-α, in EAT. Human peri-LA EAT and abdominal subcutaneous adipose tissue (SAT) were obtained by autopsy. EAT- or SAT-derived conditioned medium was applied to the rat LA epicardial surface using an organo-culture system. EAT-conditioned medium induced atrial fibrosis in organo-cultured rat atrium. The profibrotic effect of EAT was greater than that of SAT. The fibrotic area of the organo-cultured rat atrium treated with EAT from patients with AF was greater than in patients without AF. Treatment with human recombinant angiopoietin-like protein 2 (Angptl2) induced fibrosis in organo-cultured rat atrium, which was suppressed by concomitant treatment with anti-Angptl2 antibody. Finally, we attempted to detect fibrotic EAT remodeling on computed tomography (CT) images, which demonstrated that the percent change in EAT fat attenuation was positively correlated with EAT fibrosis. Based on these findings, we conclude that the percent change in EAT fat attenuation determined using CT non-invasively detects EAT remodeling.

Circulating MicroRNAs as Specific Biomarkers in Atrial Fibrillation: A Meta-Analysis.

Atrial fibrillation (AF) is the most frequently occurring supraventricular arrhythmia. Although microRNAs (miRNAs) have been associated with AF pathogenesis, standard protocols for quantifying and selecting specific miRNAs for clinical use as biomarkers should be optimized. In this study, we evaluated the clinical application of miRNAs as biomarkers for the prognosis and diagnosis of AF. Literature searches were conducted on PubMed, Cochrane Library, and EMBASE. We included prospective or retrospective observational studies that had been published as of 14 February 2022; our main objective was to analyze the relationship between circulating miRNAs and AF. The data were extracted using the descriptors "Atrial fibrillation AND miRNA", "Atrial fibrillation AND diagnostic AND miRNA", and "Atrial fibrillation AND prognosis AND miRNA". No filters were applied for period delimitation, type of publication, or language. Studies using samples isolated from blood plasma and TaqMan and RT-qPCR for detecting and quantifying miRNAs were selected, and those that used atrial tissue samples were excluded. We identified 272 articles and excluded 102 duplicated articles. Two authors independently read the titles and abstracts of 170 out of 272 articles and selected 56 potential articles, 6 of which were selected for final review. Our analysis revealed a significant association between AF and miR-4798 [OR = 1.90 (95% CI 1.45-2.47)], AF and miRNA-133a [2.77 (2.73-2.82)], AF and miRNA-150 [3.77 (1.50-9.46); I2 = 70%], AF and miRNA-21 [2.23 (1.20-4.17); I2 = 99%], AF and hsa-miRNA4443 [2.32 (2.20-2.44)], and AF and miR-20a-5p [3.67 (1.42-9.49)]. The association between miRNAs and AF showed an OR of 2.51 [95% CI 1.99-3.16; I2 = 99%]. Our meta-analysis demonstrated that circulating miRNAs are potential biomarkers of AF, as they exhibit stable expression post-sample collection. In addition to regulating cellular processes, such as proliferation, differentiation, development, and cell death, miRNAs were found to be linked to arrhythmia development.

Impaired calcium handling mechanisms in atrial trabeculae of diabetic patients.

The aim of this study was to investigate cardiomyocyte Ca2+ handling and contractile function in freshly excised human atrial tissue from diabetic and non-diabetic patients undergoing routine surgery. Multicellular trabeculae (283 ± 20 μm in diameter) were dissected from the endocardial surface of freshly obtained right atrial appendage samples from consenting surgical patients. Trabeculae were mounted in a force transducer at optimal length, electrically stimulated to contract, and loaded with fura-2/AM for intracellular Ca2+ measurements. The response to stimulation frequencies encompassing the physiological range was recorded at 37°C. Myofilament Ca2+ sensitivity was assessed from phase plots and high potassium contractures of force against [Ca2+ ]i . Trabeculae from diabetic patients (n=12) had increased diastolic (resting) [Ca2+ ]i (p=0.03) and reduced Ca2+ transient amplitude (p=0.04) when compared to non-diabetic patients (n=11), with no difference in the Ca2+ transient time course. Diastolic stress was increased (p=0.008) in trabeculae from diabetic patients, and peak developed stress decreased (p ≤ 0.001), which were not accounted for by reduction in the cardiomyocyte, or contractile protein, content of trabeculae. Trabeculae from diabetic patients also displayed diminished myofilament Ca2+ sensitivity (p=0.018) compared to non-diabetic patients. Our data provides evidence of impaired calcium handling during excitation-contraction coupling with resulting contractile dysfunction in atrial tissue from patients with type 2 diabetes in comparison to the non-diabetic. This highlights the importance of targeting cardiomyocyte Ca2+ homeostasis in developing more effective treatment options for diabetic heart disease in the future.

Integrated whole transcriptome analysis for the crucial regulators and functional pathways related to cardiac fibrosis in rats.

Cardiac fibrosis has gradually gained significance in the field of cardiovascular disease; however, its specific pathogenesis remains unclear. This study aims to establish the regulatory networks based on whole-transcriptome RNA sequencing analyses and reveal the underlying mechanisms of cardiac fibrosis. An experimental model of myocardial fibrosis was induced using the chronic intermittent hypoxia (CIH) method. Expression profiles of long non-coding RNA (lncRNA), microRNA (miRNA), and messenger RNA (mRNA) were acquired from right atrial tissue samples of rats. Differentially expressed RNAs (DERs) were identified, and functional enrichment analysis was performed. Moreover, a protein-protein interaction (PPI) network and competitive endogenous RNA (ceRNA) regulatory network that are related to cardiac fibrosis were constructed, and the relevant regulatory factors and functional pathways were identified. Finally, the crucial regulators were validated using qRT-PCR. DERs, including 268 lncRNAs, 20 miRNAs, and 436 mRNAs, were screened. Further, 18 relevant biological processes, such as "chromosome segregation, " and 6 KEGG signaling pathways, such as "cell cycle, " were significantly enriched. The regulatory relationship of miRNA-mRNA-KEGG pathways showed eight overlapping disease pathways, including "pathways in cancer." In addition, crucial regulatory factors, such as Arnt2, WNT2B, GNG7, LOC100909750, Cyp1a1, E2F1, BIRC5, and LPAR4, were identified and verified to be closely related to cardiac fibrosis. This study identified the crucial regulators and related functional pathways in cardiac fibrosis by integrating the whole transcriptome analysis in rats, which might provide novel insights into the pathogenesis of cardiac fibrosis.

Metformin Acutely Mitigates Oxidative Stress in Human Atrial Tissue: A Pilot Study in Overweight Non-Diabetic Cardiac Patients.

Metformin, the first-line drug in type 2 diabetes mellitus, elicits cardiovascular protection also in obese patients via pleiotropic effects, among which the anti-oxidant is one of the most investigated. The aim of the present study was to assess whether metformin can acutely mitigate oxidative stress in atrial tissue harvested from overweight non-diabetic patients. Right atrial appendage samples were harvested during open-heart surgery and used for the evaluation of reactive oxygen species (ROS) production by means of confocal microscopy (superoxide anion) and spectrophotometry (hydrogen peroxide). Experiments were performed after acute incubation with metformin (10 µM) in the presence vs. absence of angiotensin II (AII, 100 nM), lipopolysaccharide (LPS, 1 μg/mL), and high glucose (Gluc, 400 mg/dL). Stimulation with AII, LPS, and high Gluc increased ROS production. The magnitude of oxidative stress correlated with several echocardiographic parameters. Metformin applied in the lowest therapeutic concentration (10 µM) was able to decrease ROS generation in stimulated but also non-stimulated atrial samples. In conclusion, in a pilot group of overweight non-diabetic cardiac patients, acute incubation with metformin at a clinically relevant dose alleviated oxidative stress both in basal conditions and conditions that mimicked the activation of the renin-angiotensin-aldosterone system, acute inflammation, and uncontrolled hyperglycemia.

Identification of the Potential Molecular Mechanism of TGFBI Gene in Persistent Atrial Fibrillation.

Transforming growth factor beta-induced protein (TGFBI, encoded by TGFBI gene), is an extracellular matrix protein, widely expressed in variety of tissues. It binds to collagens type I, II, and IV and plays important roles in the interactions of cell with cell, collagen, and matrix. It has been reported to be associated with myocardial fibrosis, and the latter is an important pathophysiologyical basis of atrial fibrillation (AF). However, the mechanism of TGFBI in AF remains unclear. We aimed to detect the potential mechanism of TGFBI in AF via bioinformatics analysis. The microarray dataset of GSE115574 was examined to detect the genes coexpressed with TGFBI from 14 left atrial tissue samples of AF patients. TGFBI coexpression genes were then screened using the R package. Using online analytical tools, we determined the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, Gene Ontology (GO) annotation, and protein-protein interaction (PPI) network of TGFBI and its coexpression genes. The modules and hub genes of the PPI-network were then identified. Another dataset, GSE79768 was examined to verify the hub genes. DrugBank was used to detect the potential target drugs. In GSE115574 dataset, a total of 1818 coexpression genes (769 positive and 1049 negative) were identified, enriched in 120 biological processes (BP), 38 cellular components (CC), 36 molecular functions (MF), and 39 KEGG pathways. A PPI-network with average 12.2-degree nodes was constructed. The genes clustered in the top module constructed from this network mainly play a role in PI3K-Akt signaling pathway, viral myocarditis, inflammatory bowel disease, and platelet activation. CXCL12, C3, FN1, COL1A2, ACTB, VCAM1, and MMP2 were identified and finally verified as the hub genes, mainly enriched in pathways like leukocyte transendothelial migration, PI3K-Akt signaling pathway, viral myocarditis, rheumatoid arthritis, and platelet activation. Pegcetacoplan, ocriplasmin, and carvedilol were the potential target drugs. We used microdataset to identify the potential functions and mechanisms of the TGFBI and its coexpression genes in AF patients. Our findings suggest that CXCL12, C3, FN1, COL1A2, ACTB, VCAM1, and MMP2 may be the hub genes.

The rs13376333 risk allele mimics the effect of atrial fibrillation on SK-current density and afterdepolarizations in human atrial myocytes

Abstract Background Various genome wide association studies have associated the single nucleotide polymorphism (SNP) rs13376333 with increased risk of atrial fibrillation. This SNP is intronic to the KCNN3 gene that codes for the small conductance calcium-activated potassium channel type 3 (SK3), but functional electrophysiological effects of the risk variant are not known. Purpose This study aimed to study the effects of atrial fibrillation and the rs13376333 risk SNP on the apamine sensitive SK-current and on afterdepolarizations in human atrial myocytes. Methods Myocytes were isolated from human right atrial samples, and subjected to perforated patch-clamp technique to measure the apamine (100 nM) sensitive SK-current elicited by a voltage-ramp protocol, spontaneous transient inward Na-Ca exchange currents (ITI) or afterdepolarizations at rest. To assess the impact of the rs13376333 risk variant, patients without atrial fibrillation were genotyped and divided into risk and control groups according to the genotype at rs13376333. Results At membrane potentials above −40 mV, the SK-current density increased with increasing membrane potentials. At +20mV the density was significantly smaller (0.18±0.04 pA/pF) in 5 patients with atrial fibrillation than in 24 patients without this arrhythmia (0.65±0.12 pA/pF, p&amp;lt;0.01). On the other hand, the ITI density was larger in 10 patients with than 23 without atrial fibrillation (0.71±0.16 vs. 0.30±0.03 pA/pF, p&amp;lt;0.01), supporting the notion that a smaller SK-current in myocytes from patients with atrial fibrillation cannot counter-balance the calcium-release induced ITI, resulting in a larger net ITI density and a higher incidence of detectable afterdepolarizations in these patients. In line with this notion, inhibition of the SK-current with 100 nM apamine increased the frequency of afterdepolarization between −85 and −75 mV from 1.2±0.3 to 2.5±0.5 events/min (p=0.03) in patients without atrial fibrillation. Analysis of the current-voltage relationship for the SK-current in atrial myocytes from patients with the rs13376333 risk variant showed that these patients presented a significantly smaller apamine-sensitive SK current (p&amp;lt;0.001, n=15). At +20 mV the SK-density was 60% smaller in patients carrying a rs13376333 risk allele (0.43±0.18 vs. 1.08±0.27 pA/pF) mimicking the depression of the SK-current observed in the patients with atrial fibrillation. Conclusion Both the rs13376333 risk allele and atrial fibrillation is associated with a reduced SK-current in human atrial myocytes, which may contribute to the higher incidence of afterdepolarizations in these conditions. Thus, restoration of SK-channel function in patients with a rs1337633 risk SNP or with atrial fibrillation may help reduce the incidence of afterdepolarizations in these patients. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Spanish Ministry of Science and Innovation

The ideal environment for the development of postcardiac surgery atrial fibrillation: evidence for endothelial activation and poor cell-cell interaction

Abstract Introduction The development of post-operative atrial fibrillation (POAF) after cardiac surgeryis associated with pre-existing endothelial activation and systemic inflammation due to adhesion and transmigration of leukocytes into the interstitium. The electrical remodelling associated with AF causes changes in connexins, resulting in ineffective electrical coupling between cells and thus ineffective cell-cell communication.There is also an association between the inflammatory state, and the presence of cardiac fibrosis, oxidative stress and myocyte apoptosis. Purpose Our aim was to investigate the pathophysiologicaland regulatory mechanisms of AF through endothelial activation and inflammatory status, as well as cell-cell interactions (connexins) in relation to POAF amongst a cohort of patients undergoing cardiac surgery. Methods We studied prospective patients who underwent CABG (52.9%) or cardiac valve (47.1%) surgery without previous documented AF. Patients with permanent AF who underwent CABG or cardiac valve surgery were also included as positive controls. Plasma samples were collected at baseline and 24 hours after surgery, to assess the impact of surgery. To detect endothelial activation, vascular cell adhesion protein-1 (VCAM-1 (CD106)) was evaluated by ELISA assay in plasma samples. Expression of connexin 40 and 43 were measured by inmunohistochemistry in atrial tissue samples. Results We included 117 patients (75.2% males, median age 67 [IQR 59.5–73.0] years), of whom17 (14.5%) patients had permanent AF; 27 (23.1%) developed POAF and 73 (62.4%) had no AF detected. We found higher baseline VCAM-1 levels versus 24-hour samples overall (p=0.001). When comparing groups, baseline VCAM-1 levels were higher in patients with permanent AF compared to non-AF (p=0.035); and in permanent AF compared to POAF (p=0.049). VCAM-1 levels at 24h followed the same trends between permanent AF and non-AF (p=0.001), and permanent AF versus POAF (p=0.013) (Table 1). VCAM-1 levels over the third tertile (i.e.&amp;gt;49.77 ng/ml) increased the risk of AF almost 3-fold (OR 2.85, 95% CI 1.06–7.70; p=0.039). There was a significant decrease in the expression of connexion 40 in patients with AF (ie. patients with permanent AF or POAF) compared to non-AF patients (1.00 [0.50–2.31] vs. 2.48 [1.94–3.00], p=0.044), while connexin 43 was non-significantly different (1.07 [0.41–1.75] vs. 2.00 [0.63–2.25], p=0.289) (Table 2). Conclusions VCAM-1 levels were upregulated in patients with permanent AF and POAF compared to patients without AF, and remained higher even after surgery, thus demonstrating a relevantendothelial activation. The pro-inflammatory state presented in these patients with AF, along with decreased connexin 40 expression impacting cell-to-cell conduction, suggests a potential combination for atrial remodelling and incident AF. Funding Acknowledgement Type of funding sources: None.

Mining of Potential Biomarkers and Pathway in Valvular Atrial Fibrillation (VAF) via Systematic Screening of Gene Coexpression Network.

Purpose We apply the bioinformatics method to excavate the potential genes and therapeutic targets associated with valvular atrial fibrillation (VAF). Methods The downloaded gene expression files from the gene expression omnibus (GEO) included patients with primary severe mitral regurgitation complicated with sinus or atrial fibrillation rhythm. Subsequently, the differential gene expression in left and right atrium was analyzed by R software. Additionally, weighted correlation network analysis (WGCNA), principal component analysis (PCA), and linear model for microarray data (LIMMA) algorithm were used to determine hub genes. Then, Metascape database, DAVID database, and STRING database were used to annotate and visualize the gene ontology (GO) analysis, KEGG pathway enrichment analysis, and PPI network analysis of differentially expressed genes (DEGs). Finally, the TFs and miRNAs were predicted by using online tools, such as PASTAA and miRDB. Results 20,484 differentially expressed genes related to atrial fibrillation were obtained through the analysis of left and right atrial tissue samples of GSE115574 gene chip, and 1,009 were with statistical significance, including 45 upregulated genes and 964 downregulated genes. And the hub genes implicated in AF of NPC2, ODC1, SNAP29, LAPTM5, ST8SIA5, and FCGR3B were screened. Finally, the main regulators of targeted candidate biomarkers and microRNAs, EIF5A2, HIF1A, ZIC2, ELF1, and STAT2, were found in this study. Conclusion These hub genes, NPC2, ODC1, SNAP29, LAPTM5, ST8SIA5, and FCGR3B, are important for the development of VAF, and their enrichment pathways and TFs elucidate the involved molecular mechanisms and assist in the validation of drug targets.

Baseline profile and results of atrial fibrillation ablation in patients with arrhythmia-induced cardiomyopathy

Abstract Background Atrial fibrillation (AF) is known to trigger a reversible dilated cardiomyopathy referred as arrhythmia-induced CM (AiCM). However, it remains unclear why some patients are more prone to develop AiCM than others and there is scarce information about their clinical outcomes after AF ablation. Purpose We ought to find clinical and analytical predictors for the development of AiCM and recovery of LVEF in patients referred for AF ablation. Methods A prospective multicenter study of consecutive patients undergoing point-by-point radiofrequency (RF) catheter ablation between September 2016 and November 2021 was conducted. The low voltage areas and left atrial (LA) volume were analyzed offline on high density electroanatomical maps collected prior to RF ablation. Peripheral blood sample for biomarker analysis (Gal-3, FABP4 and sRAGE) were obtained at the time of the procedure. Results 803 consecutive patients were included, median age was 61 and 240 (30,81%) were women. AF pattern was paroxysmal in 254 (32,60%) and persistent in 534 (68,55%; of whom, long-standing persistent in 113 (14,51%) patients). The median follow-up period was 23.83 months [IQR 9 to 36]. The multivariate analysis revealed LA area, width of QRS segment, persistent AF and chronic kidney disease (CKD) as independent predictors for AiCM. Recurrence-free survival was not different amog both cohorts (Figure 1). The median increase in LVEF from baseline to the 6-month follow-up visit in patients with AiCM was 16% (CI 14.31–18.47) without changes in the non-AiCM group. The median LVEF previously to CA from patients in the AiCM group was 38% (IQR 30–45%) and after the procedure 57% (IQR 50–60%) [see figure 2]. Conclusions AiCM is characterized to have a particularly complex pathophysiology not fully understood thus far. Pulmonary vein isolation in patients is safe and suitable for patients that suffered from tachycardiomyopathy. We found that persistent AF and chronic kidney disease play a key role in its development. Neither peripheral blood biomarkers nor left atrial samples showed relevant association with its occurrence. Funding Acknowledgement Type of funding sources: None.

Predictive value of HMGB1 for atrial fibrillation recurrence after cryoballoon ablation in paroxysmal atrial fibrillation patients.

Cryoballoon ablation (CBA) is recommended for patients with symptomatic drug refractory paroxysmal atrial fibrillation (pAF). However, substantial atrial fibrillation (AF) recurrence is common during follow-up. Searching for a potential biomarker representing both myocardial injury and inflammation to identify patients at high risk of AF recurrence after CBA is very meaningful for postoperative management of AF patients. To evaluate the clinical efficacy of high-mobility group box 1 (HMGB1) protein released from the left atrium to predict AF recurrence in pAF patients after CBA at 1-year follow-up. We included 72 pAF patients who underwent CBA. To determine the expression levels of HMGB1, left atrial blood samples were collected from the patients before CBA and after the procedure through the transseptal sheath. Patients were followed up for AF recurrence for 1 year. A total of 19 patients of the 72 experienced AF recurrence. The level of postoperative HMGB1 (HMGB1post) was higher in the AF recurrence group than in the AF non recurrence group (p = .03). However, no differences were noted in the levels of other biomarkers such as preoperative high-sensitivity C-reactive protein (hs-CRP), postoperativehs-CRP, and preoperative HMGB1 between the two groups. Multiple logistic regression analysis revealed that a higher level of serum HMGB1post was associated with AF recurrence (odds ratio: 5.29 [1.17-23.92], p = .04). Receiver operating characteristic analysis revealed that HMGB1post had a moderate predictive power for AF recurrence (area under the curve: 0.68; sensitivity: 72%; and specificity: 68%). The 1-year AF-free survival was significantly lower in patients with a high HMGB1post level than in those with a low HMGB1post level (hazard ratio: 3.81 [1.49-9.75], p = .005). In pAF patients who under went CBA, the level of HMGB1 after CBA was associated with AF recurrence and demonstrated a moderate predictive power. Thus, we offer a potential biomarker to identify pAF patients at high risk of AF recurrence.

Effects and pharmacological mechanism of Zhigancao Decoction on electrical and structural remodeling of the atrium of rabbits induced by rapid atrial pacing.

Zhigancao decoction (ZD) has a long history in China as a traditional Chinese medicine compound for the treatment of tachyarrhythmias. This study mainly explored the pharmacological mechanism of Zhigancao Decoction in preventing atrial fibrillation by altering the electrical and structural remodeling of the atrial in rabbits. In total, 30 male New Zealand white rabbits were randomly divided into 3 groups (ten rabbits for each). The first group was sham-operated (control group). The second group was intervened by the rapid right atrium pacing (RAP) to induce atrial fibrillation (AF group), while the third group was given ZD gavage and RAP (AF + ZD group). All rabbits were anesthetized before two monophasic action potential (MAP) catheters were sequentially inserted into the right atrium. After 8h of rapid right atrial pacing, the electrophysiological indexes and the induction rate of atrial fibrillation were observed in the three groups of rabbits, and the left atrial myocardium samples were taken to observe the ultrastructure. Single atrial myocytes were separated by enzymolysis, and the L-type calcium current (ICa-L) of atrial myocytes in different experimental groups was observed by whole-cell patch clamp technique. The fluorescence intensity of Ca2+ in atrial myocytes was observed after Fluo-3/AM fluorescent staining. The main components of ZD were identified by liquid chromatography-mass spectrometry-mass spectrometry (LC-MS/MS) method. Compared with the AF group, the maximum ascent rate (Max dV/dt) and plateau potential were significantly reduced in the ZD group, the action potential duration at 10% and 20% (APD10, APD20) were significantly shortened (P < 0.01), action potential duration at 50%, 70%, and 90% (APD50, APD70, APD90) were significantly prolonged, and atrial effective refractory period (AERP) was significantly prolonged (P < 0.01) in the ZD group. In the ZD group, the ICa-L amplitudes of rabbit atrial myocytes under each clamping voltage were significantly smaller than those in the AF group (P < 0.01) and the control group (P < 0.05). The Ca2+ fluorescence intensity in the rabbit atrial myocytes in the ZD group was significantly weaker than that in the AF group (P < 0.01) and the control group (P < 0.05). Electron microscopy displayed that the control group had neatly arranged atrial tissue myofilaments and intact mitochondria. However, the ultrastructural damage of the AF group was severe compared with that of the ZD group. LC-MS/MS analysis confirmed that ZD contained several antiarrhythmic compounds including ginsenoside, isoliensinine, catalpol, glycyrrhizinate and hesperetin. Rapid atrial pacing (RAP) could cause the electrical and structural remodeling of rabbit atrial myocytes. ZD might reverse the atrial electrical remodeling but could have little effect on structural remodeling, which might be the mechanism of ZD treatment on atrial fibrillation.

Integrated Analysis of the microRNA-mRNA Network Predicts Potential Regulators of Atrial Fibrillation in Humans.

Atrial fibrillation (AF) is a form of sustained cardiac arrhythmia and microRNAs (miRs) play crucial roles in the pathophysiology of AF. To identify novel miR–mRNA pairs, we performed RNA-seq from atrial biopsies of persistent AF patients and non-AF patients with normal sinus rhythm (SR). Differentially expressed miRs (11 down and 9 up) and mRNAs (95 up and 82 down) were identified and hierarchically clustered in a heat map. Subsequently, GO, KEGG, and GSEA analyses were run to identify deregulated pathways. Then, miR targets were predicted in the miRDB database, and a regulatory network of negatively correlated miR–mRNA pairs was constructed using Cytoscape. To select potential candidate genes from GSEA analysis, the top-50 enriched genes in GSEA were overlaid with predicted targets of differentially deregulated miRs. Further, the protein–protein interaction (PPI) network of enriched genes in GSEA was constructed, and subsequently, GO and canonical pathway analyses were run for genes in the PPI network. Our analyses showed that TNF-α, p53, EMT, and SYDECAN1 signaling were among the highly affected pathways in AF samples. SDC-1 (SYNDECAN-1) was the top-enriched gene in p53, EMT, and SYDECAN1 signaling. Consistently, SDC-1 mRNA and protein levels were significantly higher in atrial samples of AF patients. Among negatively correlated miRs, miR-302b-3p was experimentally validated to suppress SDC-1 transcript levels. Overall, our results suggested that the miR-302b-3p/SDC-1 axis may be involved in the pathogenesis of AF.

Atrial fibrillation in the presence and absence of heart failure enhances expression of genes involved in cardiomyocyte structure, conduction properties, fibrosis, inflammation, and endothelial dysfunction

Little is known about genome-wide changes in the atrial transcriptome as a cause or consequence of atrial fibrillation (AF), and the effect of its common and clinically relevant comorbidity-heart failure (HF). The purpose of this study was to explore candidate disease processes for AF by investigating gene expression changes in atrial tissue samples from patients with and without AF, stratified by HF. RNA sequencing was performed in right and left atrial appendage tissue in 195 patients undergoing open heart surgery from centers participating in the CATCH-ME consortium (no history of AF, n = 91; paroxysmal AF, n = 53; persistent/permanent AF, n = 51). Analyses were stratified into patients with/without HF (n = 75/120) and adjusted for age, sex, atrial side, and a combination of clinical characteristics. We identified 35 genes associated with persistent AF compared to patients without a history of AF, both in the presence or absence of HF (false discovery rate <0.05). These were mostly novel associations, including 13 long noncoding RNAs. Genes were involved in regulation of cardiomyocyte structure, conduction properties, fibrosis, inflammation, and endothelial dysfunction. Gene set enrichment analysis identified mainly inflammatory gene sets to be enriched in AF patients without HF, and gene sets involved in cellular respiration in AF patients with HF. Analysis of atrial gene expression profiles identified numerous novel genes associated with persistent AF, in the presence or absence of HF. Interestingly, no consistent transcriptional changes were associated with paroxysmal AF, suggesting that AF-induced changes in gene expression predominate other changes.

Abstract P2087: ERBB4-Selective And Sustained Activation By NRG1 Attenuates Atrial Fibrosis And Fibrillation

Introduction: Atrial fibrillation (AF) results from electrical and structural remodeling of the atria, in which inflammation and fibrosis play an important role. Current therapy is limited to antiarrhythmic drugs and ablations, but does not target the structural problem. Recent studies showed that neuregulin-1 (NRG1), an epidermal growth factor family member, has anti-fibrotic and anti-inflammatory effects in the myocardium. Purpose: To test the effects of JK07, a NRG1 antibody fusion comprising an ERBB3 antagonistic antibody which selectively signals through ERBB4 preferentially over ERBB3, on atrial fibrosis and AF inducibility. Methods: Atrial samples were harvested from male rats (Wistar Han, 10 weeks old), cut into small pieces (1-2mm 2 ) and kept in low serum medium in the presence or absence of JK07 (5nM). Col1a1 and Col3a1 mRNA was quantified after 24-72 hours. AF inducibility was tested in a first AF model in which male mice (C57BL/6N, 12-15 weeks old) were treated with angiotensin-II (Ang-II, 4 weeks, osmotic mini-pumps, 3000 ng/kg/min), and in a second AF model in which mice were fed with a high fat diet (HFD, 8 weeks, 60% Kcal fat) inducing severe weight gain (56±3% increase compared to 23±4% with regular chow). In both models, AF inducibility was tested by 5 runs of programmed electrical stimulation (PES) with a trans-jugular octapolar catheter. AF inducibility (% mice inducible by ≥3 PES-runs) and duration of PES-induced AF (AF duration) were recorded. Mice were randomized for treatment with vehicle or JK07 (2x/week, 1mg/kg, IV, n=5-7/group). Results: In cultured atrial samples, Col1a1 and Col3a1 mRNA expression gradually increased up to 2-3 fold over 3 days. JK07 robustly attenuated this effect by 59±17% (p&lt;0.05). In mice, both Ang-II and HFD significantly increased AF inducibility and AF duration. In Ang-II mice, JK07 attenuated AF inducibility (from 57% to 20%) and AF duration (from 33.3 ± 15.1 to 1.5 ± 1s). In HFD mice, JK07 significantly attenuated AF inducibility (from 57% to 0%) and AF duration (from 10.9±3.2s to 0.76±0.5s, p&lt;0.05). Conclusions: These results show anti-fibrotic effects by selective ERBB4 stimulation with JK07 in atrial tissue in vitro, together with AF-preventive effects in two unrelated mouse models.

Unsupervised machine learning reveals epicardial adipose tissue subtypes with distinct atrial fibrosis profiles in patients with persistent atrial fibrillation: A prospective 2-center cohort study

Epicardial adipose tissue (EAT) accumulation is associated with the progression of atrial fibrillation. However, the histological features of EATs are poorly defined and their correlation with atrial fibrosis is unclear. The purpose of this study was to identify and characterize EAT subgroups in the persistent atrial fibrillation (PeAF) cohorts. EATs and the corresponding left atrial appendage samples were obtained from patients with PeAF via surgical intervention. Adipocyte markers, that is, Uncoupling Protein 1, Transcription Factor 21, and CD137, were examined. On the basis of expression of adipocyte markers, patients with PeAF were categorized into subgroups by using unsupervised clustering analysis. Clinical characteristics, histological analyses, and outcomes were subsequently compared across the clusters. External validation was performed in a validation cohort. The ranking of feature importance revealed that the 3 adipocyte markers were the most relevant factors for atrial fibrosis compared with other clinical indicators. On the k-medoids analysis, patients with PeAF could be categorized into 3 clusters in the discovery cohort. The histological studies revealed that patients in cluster 1 exhibited statistically larger size of adipocytes in EATs and severe atrial fibrosis in left atrial appendages. Findings were replicated in the validation cohort, where severe atrial fibrosis was noted in cluster 1. Moreover, in the validation cohort, there was a high degree of overlap between the supervised classification results and the unsupervised cluster results from the k-medoids method. Machine learning-based cluster analysis could identify subtypes of patients with PeAF having distinct atrial fibrosis profiles. Additionally, EAT whitening (increased proportion of white adipocytes) may be involved in the process of atrial fibrosis.

Abstract GS106: Asporin, An Extracellular Matrix Protein, Is A Beneficial Regulator Of Cardiac Remodeling

Heart failure is accompanied by adverse cardiac remodeling involving extracellular matrix (ECM). Cardiac ECM acts as a major reservoir for many proteins including growth factors, cytokines, collagens, and proteoglycans. Activated fibroblasts during cardiac injury can alter the composition and activity of these ECM proteins. Through unbiased analysis of a microarray dataset of human heart tissue comparing normal hearts (n=135) to hearts with ischemic cardiomyopathy (n=94), we identified Asporin (ASPN) as the top differentially regulated gene (DEG) in ischemic cardiomyopathy; its gene-ontology terms relate closely to fibrosis and cell death. ASPN is a Class I small leucine repeat protein member implicated in cancer, osteoarthritis, and periodontal ligament mineralization. However, its role in cardiac remodeling is still unknown. Here, we initially confirmed our big dataset analysis through cells, mice, and clinical atrial biopsy samples to demonstrate increased ASPN expression after pressure overload or cardiac ischemia/reperfusion injury. We tested the hypothesis that ASPN, being a TGFβ1 inhibitor, can attenuate fibrosis in mouse models of cardiac injury. We found that ASPN is released by cardiac fibroblasts and attenuates TGFβ signaling. Moreover, ASPN -/- mice displayed increased fibrosis and decreased cardiac function after pressure overload by transverse aortic constriction (TAC) in mice. In addition, ASPN protected cardiomyocytes from hypoxia/reoxygenation-induced cell death and regulated autophagy and mitochondrial bioenergetics in cardiomyocytes. Increased infarct size after ischemia/reperfusion injury in ASPN -/- mice confirmed ASPN’s contribution to cardiomyocyte viability. Echocardiography revealed a greater reduction in left ventricular systolic function post-I/R in the ASPN -/- animals compared to wild type. Furthermore, we developed an ASPN-mimic peptide using molecular modeling and docking which when administered to mice prevented TAC-induced fibrosis and preserved heart function. The peptide also reduced infarct size after I/R in mice, demonstrating the translational potential of ASPN-based therapy. Thus, we establish the role of ASPN as a critical ECM molecule that regulates cardiac remodeling to preserve heart function.

Poorly controlled hypertension is associated with increased coronary myogenic tone in patients undergoing cardiac surgery with cardiopulmonary bypass

ObjectiveCardioplegia and cardiopulmonary bypass dysregulate coronary vasomotor tone, which can be further affected by common comorbidities in patients undergoing cardiac surgery. This study investigates differences in coronary myogenic tone and vasomotor responses to phenylephrine before and after cardioplegia and cardiopulmonary bypass based on hypertension history. MethodsCoronary arterioles before and after cardioplegia and cardiopulmonary bypass were dissected from atrial tissue samples in patients with no hypertension, well-controlled hypertension, or uncontrolled hypertension, as determined by documented history of hypertension, antihypertensive agent use, and clinical blood pressure measurements averaged over 1 year. Myogenic tone in response to stepwise increases in intraluminal pressure was studied between pressure steps. Microvascular reactivity in response to phenylephrine was assessed via vessel myography. Protein expression was measured with immunoblotting. ResultsCoronary myogenic tone was significantly increased in the uncontrolled hypertension group compared with the no hypertension and well-controlled hypertension groups before cardioplegia and cardiopulmonary bypass at higher intraluminal pressures, and after cardioplegia and cardiopulmonary bypass across all intraluminal pressures (P < .05). Contractile responses to phenylephrine were significantly enhanced in patients in the uncontrolled hypertension group compared with the well-controlled hypertension group before cardioplegia and cardiopulmonary bypass, and in the uncontrolled hypertension group compared with the no hypertension and well-controlled hyertension groups after cardioplegia and cardiopulmonary bypass (P < .05). There were no differences in myogenic tone or phenylephrine-induced reactivity between the no hypertension and well-controlled hypertension groups (P > .05). There was increased expression of phosphorylated protein kinase C alpha in the uncontrolled hypertension group after cardiopulmonary bypass compared with before cardiopulmonary bypass and increased phosphorylated extracellular signal-regulated kinase 1/2 in the uncontrolled hypertension compared with the no hypertension group after cardiopulmonary bypass (P < .05). ConclusionsUncontrolled hypertension is associated with increased coronary myogenic tone and vasoconstrictive response to phenylephrine that persists after cardioplegia and cardiopulmonary bypass.