The MAPK pathway is involved in the regulation of rapid pacing-induced ionic channel remodeling in rat atrial myocytes

The potential role of miRNAs in the pathogenesis of cardiovascular diseases - A focus on signaling pathways interplay

For the past two decades since their discovery, scientists have linked microRNAs (miRNAs) to posttranscriptional regulation of gene expression in critical cardiac physiological and pathological processes. Multiple non-coding RNA species regulate cardiac muscle phenotypes to stabilize cardiac homeostasis. Different cardiac pathological conditions, including arrhythmia, myocardial infarction, and hypertrophy, are modulated by non-coding RNAs in response to stress or other pathological conditions. Besides, miRNAs are implicated in several modulatory signaling pathways of cardiovascular disorders including mitogen-activated protein kinase, nuclear factor kappa beta, protein kinase B (AKT), NOD-like receptor family pyrin domain-containing 3 (NLRP3), Jun N-terminal kinases (JNKs), Toll-like receptors (TLRs) and apoptotic protease-activating factor 1 (Apaf-1)/caspases. This review highlights the potential role of miRNAs as therapeutic targets and updates our understanding of their roles in the processes underlying pathogenic phenotypes of cardiac muscle.

MicroRNA Let-7a, -7e and -133a Attenuate Hypoxia-Induced Atrial Fibrosis via Targeting Collagen Expression and the JNK Pathway in HL1 Cardiomyocytes

Fibrosis is a hallmark of atrial structural remodeling. The main aim of this study was to investigate the role of micro-ribonucleic acids (miRNAs) in the modulation of fibrotic molecular mechanisms in response to hypoxic conditions, which may mediate atrial fibrosis. Under a condition of hypoxia induced by a hypoxia chamber, miRNA arrays were used to identify the specific miRNAs associated with the modulation of fibrotic genes. Luciferase assay, real-time polymerase chain reaction, immunofluorescence and Western blotting were used to investigate the effects of miRNAs on the expressions of the fibrotic markers collagen I and III (COL1A, COL3A) and phosphorylation levels of the stress kinase c-Jun N-terminal kinase (JNK) pathway in a cultured HL-1 atrial cardiomyocytes cell line. COL1A and COL3A were found to be the direct regulatory targets of miR-let-7a, miR-let-7e and miR-133a in hypoxic atrial cardiac cells in vitro. The expressions of COL1A and COL3A were influenced by treatment with miRNA mimic and antagomir while hypoxia-induced collagen expression was inhibited by the delivery of miR-133a, miR-let-7a or miR-let-7e. The JNK pathway was critical in the pathogenesis of atrial fibrosis. The JNK inhibitor SP600125 increased miRNA expressions and repressed the fibrotic markers COL1A and COL3A. In conclusion, MiRNA let-7a, miR-let-7e and miR-133a play important roles in hypoxia-related atrial fibrosis by inhibiting collagen expression and post-transcriptional repression by the JNK pathway. These novel findings may lead to the development of new therapeutic strategies.

Identification of circRNA-miRNA-mRNA Regulatory Network and Autophagy Interaction Network in Atrial Fibrillation Based on Bioinformatics Analysis

Background

Circular RNA (circRNA) has been receiving increased attention in the research of atrial fibrillation (AF). Our study aims to find potential circRNAs and identify the circRNA-miRNA-mRNA regulatory network in AF based on bioinformatics analysis.

Methods

GSE129409 was retrieved from the Gene Expression Omnibus (GEO) database, and we used R software to analyze the differentially expressed circRNAs (DECs). Subsequently, we used several bioinformatics methods to obtain the target miRNAs and the target genes. Next, we performed Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the target genes. Then, we used Cytoscape 3.8.2 software to visualize and construct the circRNA-miRNA-mRNA regulatory network, the protein–protein interaction (PPI) network, and the autophagy-related genes network.

Results

We identified a total of 21 DECs, including 6 upregulated DECs and 15 downregulated DECs. After further analysis, we obtained a circRNA-miRNA-mRNA regulatory network consisting of 11 DECs, 9 target miRNAs and 410 target genes, and a PPI network. Finally, the potential novel genes of autophagy in AF were revealed by bioinformatics analysis.

Conclusion

This study could explore the potential role of circRNA, autophagy-related genes and construct the circRNA-miRNA-mRNA regulation network in AF.

Integrative transcriptomic, proteomic, and machine learning approach to identifying feature genes of atrial fibrillation using atrial samples from patients with valvular heart disease

Background

Atrial fibrillation (AF) is the most common arrhythmia with poorly understood mechanisms. We aimed to investigate the biological mechanism of AF and to discover feature genes by analyzing multi-omics data and by applying a machine learning approach.

Methods

At the transcriptomic level, four microarray datasets (GSE41177, GSE79768, GSE115574, GSE14975) were downloaded from the Gene Expression Omnibus database, which included 130 available atrial samples from AF and sinus rhythm (SR) patients with valvular heart disease. Microarray meta-analysis was adopted to identified differentially expressed genes (DEGs). At the proteomic level, a qualitative and quantitative analysis of proteomics in the left atrial appendage of 18 patients (9 with AF and 9 with SR) who underwent cardiac valvular surgery was conducted. The machine learning correlation-based feature selection (CFS) method was introduced to selected feature genes of AF using the training set of 130 samples involved in the microarray meta-analysis. The Naive Bayes (NB) based classifier constructed using training set was evaluated on an independent validation test set GSE2240.

Results

863 DEGs with FDR < 0.05 and 482 differentially expressed proteins (DEPs) with FDR < 0.1 and fold change > 1.2 were obtained from the transcriptomic and proteomic study, respectively. The DEGs and DEPs were then analyzed together which identified 30 biomarkers with consistent trends. Further, 10 features, including 8 upregulated genes (CD44, CHGB, FHL2, GGT5, IGFBP2, NRAP, SEPTIN6, YWHAQ) and 2 downregulated genes (TNNI1, TRDN) were selected from the 30 biomarkers through machine learning CFS method using training set. The NB based classifier constructed using the training set accurately and reliably classify AF from SR samples in the validation test set with a precision of 87.5% and AUC of 0.995.

Conclusion

Taken together, our present work might provide novel insights into the molecular mechanism and provide some promising diagnostic and therapeutic targets of AF.

p38 MAPK Pathway in the Heart: New Insights in Health and Disease

The p38 mitogen-activated kinase (MAPK) family controls cell adaptation to stress stimuli. p38 function has been studied in depth in relation to cardiac development and function. The first isoform demonstrated to play an important role in cardiac development was p38α; however, all p38 family members are now known to collaborate in different aspects of cardiomyocyte differentiation and growth. p38 family members have been proposed to have protective and deleterious actions in the stressed myocardium, with the outcome of their action in part dependent on the model system under study and the identity of the activated p38 family member. Most studies to date have been performed with inhibitors that are not isoform-specific, and, consequently, knowledge remains very limited about how the different p38s control cardiac physiology and respond to cardiac stress. In this review, we summarize the current understanding of the role of the p38 pathway in cardiac physiology and discuss recent advances in the field.

The role of stretch, tachycardia and sodium-calcium exchanger in induction of early cardiac remodelling

Stretch and tachycardia are common triggers for cardiac remodelling in various conditions, but a comparative characterization of their role in the excitation‐transcription coupling (ETC) and early regulation of gene expression and structural changes is lacking. Here, we show that stretch and tachycardia directly induced hypertrophy of neonatal rat cardiac myocytes and also of non‐myocytes. Both triggers induced similar patterns of hypertrophy but had largely distinct gene expression profiles. ACTA1 served as good hypertrophy marker upon stretch, while RCAN1 was found increased in response to tachycardia in a rate‐dependent fashion. Mechanistically, several calcium‐handling proteins, including the sodium‐calcium exchanger (NCX), contributed to ETC. Phosphorylation of the calcium/calmodulin‐dependent protein kinase II (CaMKII) was elevated and occurred downstream of NCX activation upon tachycardia, but not stretch. Microarray profiling revealed that stretch and tachycardia regulated around 33% and 20% genes in a NCX‐dependent manner, respectively. In conclusion, our data show that hypertrophy induction by stretch and tachycardia is associated with different gene expression profiles with a significant contribution of the NCX.

AKT and ERK1/2 activation via remote ischemic preconditioning prevents Kcne2-dependent sudden cardiac death

Sudden cardiac death (SCD) is the leading global cause of mortality. SCD often arises from cardiac ischemia reperfusion (IR) injury, pathologic sequence variants within ion channel genes, or a combination of the two. Alternative approaches are needed to prevent or ameliorate ventricular arrhythmias linked to SCD. Here, we investigated the efficacy of remote ischemic preconditioning (RIPC) of the limb versus the liver in reducing ventricular arrhythmias in a mouse model of SCD. Mice lacking the Kcne2 gene, which encodes a potassium channel β subunit associated with acquired Long QT syndrome were exposed to IR injury via coronary ligation. This resulted in ventricular arrhythmias in all mice (15/15) and SCD in 5/15 mice during reperfusion. Strikingly, prior RIPC (limb or liver) greatly reduced the incidence and severity of all ventricular arrhythmias and completely prevented SCD. Biochemical and pharmacological analysis demonstrated that RIPC cardioprotection required ERK1/2 and/or AKT phosphorylation. A lack of alteration in GSK‐3β phosphorylation suggested against conventional reperfusion injury salvage kinase (RISK) signaling pathway protection. If replicated in human studies, limb RIPC could represent a noninvasive, nonpharmacological approach to limit dangerous ventricular arrhythmias associated with ischemia and/or channelopathy‐linked SCD.

Identification of Long Non-Coding RNA and Circular RNA Expression Profiles in Atrial Fibrillation

BACKGROUND

Long non-coding RNA (lncRNA) and circular RNA (circRNA) have both been found to play important roles in cardiovascular diseases, including myocardial infarction, heart failure, and atherosclerosis. However, the role of lncRNA and circRNA in atrial fibrillation (AF) has rarely been investigated. This study aimed to identify lncRNA and circRNA expression profiles in AF patients.

METHODS

Atrial tissues from seven patients with AF and seven matched controls were collected. The lncRNA and circRNA expression profiles of atrial tissues were identified using Hiseq/Proton RNA sequencing. Validation was performed by reverse transcription quantitative real-time PCR (qRT-PCR) on 35 pairs of AF patients and controls. Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed. A competing endogenous RNA (ceRNA) network was constructed.

RESULTS

A total of 557 lncRNAs and 280 circRNAs were significantly differentially expressed with fold change >1.5 (p<0.05). An lncRNA Voltage Dependent Anion Channel 2 Pseudogene 2 (VDAC2P2) and two circRNAs chr13_41887361_41865736_-21625 and chr13_100368574_100301460_-67114 were validated, using qRT-PCR, to have significantly different expression levels. GO and KEGG pathway analysis showed that some pathways such as ribosome and chromatin modification, Rap1 signalling and cardiac muscle contraction were involved in the pathogenesis of AF. Competing endogenous RNAs were predicted based on constructional network analysis. The LncRNA-miRNA-mRNA and circRNA-miRNA-mRNA networks were constructed by co-expressing lncRNA/circRNA and mRNAs, which were competitively combined with miRNAs.

CONCLUSION

This study characterised lncRNA and circRNA expression and their interaction with mRNA and miRNA in AF.

Evidence for Arrhythmogenic Effects of A2A-Adenosine Receptors

Adenosine can be released from the heart and may stimulate four different cardiac adenosine receptors. A receptor subtype that couples to the generation of cyclic adenosine monophosphate (cAMP) is the A_2A-adenosine receptor (A_2A-AR). To better understand its role in cardiac function, we studied mechanical and electrophysiological effects in transgenic mice that overexpress the human A_2A-AR in cardiomyocytes (A_2A-TG). We used isolated preparations from the left atrium, the right atrium, isolated perfused hearts with surface electrocardiogram (ECG) recording, and surface body ECG recordings of living mice. The hypothesized arrhythmogenic effects of transgenicity per se and A_2A-AR stimulation were studied. We noted an increase in the incidence of supraventricular and ventricular arrhythmias under these conditions in A_2A-TG. Moreover, we noted that the A_2A-AR agonist CGS 21680 exerted positive inotropic effect in isolated human electrically driven (1 Hz) right atrial trabeculae carneae. We conclude that A_2A-ARs are functional not only in A_2A-TG but also in isolated human atrial preparations. A_2A-ARs in A_2A-TG per se and their stimulation can lead to cardiac arrhythmias not only in isolated cardiac preparations from A_2A-TG but also in living A_2A-TG.

Metformin Regulates the Expression of SK2 and SK3 in the Atria of Rats With Type 2 Diabetes Mellitus Through the NOX4/p38MAPK Signaling Pathway

We previously found that metformin regulates the ion current conducted by the small conductance calcium-activated potassium channels (SK channels) in the atria of rats with type 2 diabetes mellitus (T2DM) as well as the mRNA and protein expression of the SK2 and SK3 subtypes of SK channels. In this study, we hypothesized that the nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4)/p38 mitogen-activated protein kinase (p38MAPK) signaling pathway was involved in the metformin-mediated regulation of SK2 and SK3 expression in the atria of rats with T2DM. We randomly divided Wistar rats into the control group, the untreated T2DM group, the metformin-treated group, the group receiving subcutaneous injections of the nicotinamide adenine dinucleotide phosphate oxidase (NOX) inhibitor diphenyleneiodonium (DPI), and the group receiving tail vein injections of the p38MAPK agonist anisomycin. Real-time polymerase chain reaction, Western blot, and immunohistochemistry were applied to examine the expression levels of SK2, SK3, NOX4, and phospho-p38MAPK (p-p38MAPK) mRNAs and proteins in the atrial tissue of relevant groups. We observed that the expression levels of NOX4 mRNA and protein and p-p38MAPK protein were significantly elevated in the atria of rats with T2DM compared with the control group. In addition, SK2 protein expression was reduced, whereas SK3 protein expression was increased. The 8-week treatment with metformin markedly reduced the expression levels of NOX4 mRNA and protein and p-p38MAPK protein, upregulated the SK2 expression, and downregulated the SK3 expression. Tail vein injection with anisomycin significantly increased the p-p38MAPK expression while further inhibiting the expression of SK2 and enhancing the expression of SK3. Subcutaneous injection with DPI considerably inhibited the expression of NOX4, further enhanced the expression of SK2 and suppressed the expression of SK3. In addition, subcutaneous injection with DPI significantly suppressed the phosphorylation of p38MAPK. In conclusion, the NOX4/p38MAPK signaling pathway mediates the downregulation of SK2 and the upregulation of SK3 in the atria of rats with T2DM. Long-term metformin treatment upregulates SK2 protein expression and downregulates SK3 protein expression by inhibiting the NOX4/p38MAPK signaling pathway.

Treatment with verapamil for restoration of sinus rhythm in atrial fibrillation with rapid ventricular response: A case report

RATIONALE

Atrial fibrillation (AF) is a common arrhythmia disease that can cause thromboembolic disease and/or heart failure, resulting in increased mortality. Propafenone, amiodarone, and flecainide are recommended for converting AF to sinus rhythm. Beta blockers, verapamil, diltiazem, and digoxin are recommended for controlling AF with fast ventricular rate (VR). In this case report, we found that verapamil successfully converted AF into sinus rhythm.

PATIENT CONCERNS

A 92-year-old woman presented with fast VR AF with a history of coronary heart disease, hypertension, and diabetes.

DIAGNOSES

Verapamil can successfully convert AF into sinus rhythm.

INTERVENTIONS AND OUTCOMES

The patient was treated with amiodarone or propafenone, yet still had AF. After stopping amiodarone and propafenone, the patient was given verapamil to control the VR, and following 9 days of treatment the patient switched to sinus rhythm. When verapamil treatment was stopped, the patient experienced AF recurrence. Upon receiving verapamil again, the AF again converted into sinus rhythm.

LESSONS

For the treatment of AF, nondihydropyridine calcium antagonists can be tried in the absence of antiarrhythmic drugs.