Mitochondrial Dysfunction in Atrial Fibrillation-Mechanisms and Pharmacological Interventions.
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ABSTRACT:
SUBMITTER: Muszynski P
PROVIDER: S-EPMC8199309 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The molecular mechanisms underlying atrial fibrillation (AF), the most common form of arrhythmia, are poorly understood and therefore target-specific treatment options remain an unmet clinical need. Excitation-contraction coupling in cardiac myocytes requires high amounts of adenosine triphosphate (ATP), which is replenished by oxidative phosphorylation in mitochondria. Calcium (Ca2+) is a key regulator of mitochondrial function by stimulating the Krebs cycle, which produces nicotinamide adenine dinucleotide for ATP production at the electron transport chain and nicotinamide adenine dinucleotide phosphate for the elimination of reactive oxygen species (ROS). While it is now well established that mitochondrial dysfunction plays an important role in the pathophysiology of heart failure, this has been less investigated in atrial myocytes in AF. Considering the high prevalence of AF, investigating the role of mitochondria in this disease may guide the path towards new therapeutic targets. In this review, we discuss the importance of mitochondrial Ca2+ handling in regulating ATP production and mitochondrial ROS emission and how alterations, particularly in these aspects of mitochondrial activity, may play a role in AF. In addition to describing research advances, we highlight areas in which further studies are required to elucidate the role of mitochondria in AF.
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Project description:Atrial fibrillation (AF), the most common progressive tachyarrhythmia, results in structural remodeling which impairs electrical activation of the atria, rendering them increasingly permissive to the arrhythmia. Previously, we reported on endoplasmic reticulum stress and NAD+ depletion in AF, suggesting a role for mitochondrial dysfunction in AF progression. Here, we examined mitochondrial function in experimental model systems for AF (tachypaced HL-1 atrial cardiomyocytes and Drosophila melanogaster) and validated findings in clinical AF. Tachypacing of HL-1 cardiomyocytes progressively induces mitochondrial dysfunction, evidenced by impairment of mitochondrial Ca2+-handling, upregulation of mitochondrial stress chaperones and a decrease in the mitochondrial membrane potential, respiration and ATP production. Atrial biopsies from AF patients display mitochondrial dysfunction, evidenced by aberrant ATP levels, upregulation of a mitochondrial stress chaperone and fragmentation of the mitochondrial network. The pathophysiological role of mitochondrial dysfunction is substantiated by the attenuation of AF remodeling by preventing an increased mitochondrial Ca2+-influx through partial blocking or downregulation of the mitochondrial calcium uniporter, and by SS31, a compound that improves bioenergetics in mitochondria. Together, these results show that conservation of the mitochondrial function protects against tachypacing-induced cardiomyocyte remodeling and identify this organelle as a potential novel therapeutic target.
| S-EPMC6829298 | biostudies-literature
Project description:Atrial fibrillation (AF) complicating cardiac surgery continues to be a major problem that increases the postoperative risk of stroke, myocardial infarction, heart failure and costs and can affect long-term survival. The incidence of AF after surgery has not significantly changed over the last two decades, despite improvement in medical and surgical techniques. The mechanism and pathophysiology underlying postoperative AF (PoAF) is incompletely understood and results from a combination of acute and chronic factors, superimposed on an underlying abnormal atrial substrate with increased interstitial fibrosis. Several anti-arrhythmic and non-anti-arrhythmic medications have been used for the prevention of PoAF, but the effectiveness of these strategies has been limited due to a poor understanding of the basis for the increased susceptibility of the atria to AF in the postoperative setting. In this review, we summarize the pathophysiology underlying the development of PoAF and evidence behind pharmacological approaches used for its prevention in the postoperative setting.
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Project description:Atrial fibrillation (AF) is the most common arrhythmia worldwide. It is associated with increased mortality and morbidity, especially due to the increased risk of ischemic stroke and systemic embolism in these patients. For this reason, thromboembolism prevention is the cornerstone of managing AF, and oral anticoagulation is nowadays the first-line treatment. However, since most thrombi form in the left atrial appendage and anticoagulant therapy may have side effects and be contraindicated in some patients, surgical and percutaneous left atrial appendage occlusion (LAAO) have emerged as a non-pharmacological alternative. This review summarizes all existing evidence on surgical and percutaneous LAAO.
| S-EPMC10488500 | biostudies-literature
Project description:BackgroundThe mechanism of sinoatrial node (SAN) dysfunction in atrial fibrillation (AF) is unclear.ObjectiveThe purpose of this study was to test the hypothesis that defective spontaneous sarcoplasmic reticulum (SR) Ca(2+) release (Ca(2+) clock) is in part responsible for SAN dysfunction in AF.MethodsArrhythmic events and SAN function were evaluated in pacing-induced AF dogs (n = 7) and in normal dogs (n = 19) with simultaneous intracellular calcium (Ca(i)) and membrane potential recording.ResultsAF dogs had frequent sinus pauses during Holter monitoring. Isolated right atrium (RA) from AF dogs showed slower heart rate (P = .001), longer SAN recovery time (P = .001), and longer sinoatrial conduction time (P = .003) than normal. In normal RAs, isoproterenol 0.3 and 1 mumol/L increased heart rate by 96% and 105%, respectively. In contrast, in RAs from AF dogs, isoproterenol increased heart rate by only 60% and 72%, respectively. Isoproterenol induced late diastolic Ca(i) elevation (LDCAE) at superior SAN in all 19 normal RAs but in only 3 of 7 AF RAs (P = .002). In AF RAs without LDCAE (n = 4), heart rate increased by the acceleration of ectopic foci. Caffeine (20 mmol/L) injection increased heart rate with LDCAE in all 6 normal RAs but did not result in LDCAE in any of the 5 AF RAs (P = .002). Type 2 ryanodine receptor (RyR2) in the superior SAN of AF dogs was decreased to 33% of normal (P = .02).ConclusionSAN dysfunction in AF is associated with Ca(2+) clock malfunction, characterized by unresponsiveness to isoproterenol and caffeine and down-regulation of RyR2 in SAN.
| S-EPMC2925681 | biostudies-literature
Project description:Background: Non-alcoholic fatty liver disease (NAFLD) and atrial fibrillation (AF) are major health burdens, with emerging evidence suggesting NAFLD as a significant risk factor for AF, but the mechanism is remain unclear. Methods: In this study, we analyzed gene expression data from NAFLD (GSE89632) and AF (GSE75092) datasets from the Gene Expression Omnibus. We identified co-upregulated and co-downregulated genes between NAFLD and AF, assessed diagnostic potential of specific genes, conducted immune infiltration analysis, and performed molecular docking studies with sodium glucose co-transporter 2 inhibitors (SGLT2i). Results: We identified eight co-upregulated and 31 co-downregulated genes between NAFLD and AF. Genes such as AMOT, PDE11A, TYMS, TMEM98, and PTGS2 demonstrated substantial diagnostic potential for identifying NAFLD patients at risk of AF. Immune infiltration analysis discovered an elevated presence of CD8 T cells, γδ T cells, and M2 macrophages in NAFLD livers, linking systemic inflammation to NAFLD and AF. Additionally, studies have shown that a connection between mitochondrial dysfunction and several hub genes like DGAT1, TYMS, and PTGS2, suggesting that mitochondrial disturbances may underpin the systemic inflammation in NAFLD, which possibly exacerbating AF. Molecular docking studies indicated that empagliflozin's binding affinity with key genes such as DGAT1, TYMS, and PTGS2 presents a novel therapeutic avenue for NAFLD-associated AF. Conclusion: Our study firstly discovered that AMOT, PDE11A, TYMS, TMEM98, and PTGS2 are associated with NAFLD-related AF and hold strong diagnostic values. Our study also indicates that mitochondrial dysfunction and systemic inflammation may be potential mechanisms bridging NAFLD and AF. Additionally, we identified empagliflozin as a potentially effective therapeutic agent for NAFLD-related AF at the molecular structure level. These novel insights contribute to the further understanding, diagnosis, and intervention of NAFLD-related AF.
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Project description:INTRODUCTION:Postoperative atrial fibrillation (POAF) is the most common complication following cardiac surgery, and randomised clinical trials (RCTs) and systematic reviews have been conducted to compare and evaluate different pharmacological interventions for preventing POAF. This study aimed to explore the effect of different pharmacological interventions for prophylaxis against POAF after cardiac surgery using network meta-analysis (NMA). METHODS AND ANALYSIS:A systematic search will be performed in PubMed, EMBASE and the Cochrane Library to identify RCTs, systematic reviews, meta-analyses or NMA of different pharmacological interventions for POAF. We will evaluate the risk of bias of the included RCTs according to the Cochrane Handbook V.5.1.0, and use GRADE to assess the quality of evidence. Standard pairwise meta-analysis, trial sequential analysis and Bayesian network meta-analysis will be used to compare the efficacy of different pharmacological interventions. ETHICS AND DISSEMINATION:Ethics approval and patient consent are not required as this study is a meta-analysis based on published studies. The results of this NMA and trial sequential analysis will be submitted to a peer-reviewed journal for publication. PROTOCOL REGISTRATION NUMBER:CRD42017067492.
| S-EPMC5778318 | biostudies-literature
Project description:Oxidative stress has been suggested to play a role in the pathogenesis of atrial fibrillation (AF). Indeed, the prevalence of AF increases with age as does oxidative stress. However, the mechanisms linking redox state to AF are not well understood. In this study we identify a link between oxidative stress and aberrant intracellular Ca(2+) release via the type 2 ryanodine receptor (RyR2) that promotes AF. We show that RyR2 are oxidized in the atria of patients with chronic AF compared with individuals in sinus rhythm. To dissect the molecular mechanism linking RyR2 oxidation to AF we used two murine models harboring RyR2 mutations that cause intracellular Ca(2+) leak. Mice with intracellular Ca(2+) leak exhibited increased atrial RyR2 oxidation, mitochondrial dysfunction, reactive oxygen species (ROS) production and AF susceptibility. Both genetic inhibition of mitochondrial ROS production and pharmacological treatment of RyR2 leakage prevented AF. Collectively, our results indicate that alterations of RyR2 and mitochondrial ROS generation form a vicious cycle in the development of AF. Targeting this previously unrecognized mechanism could be useful in developing effective interventions to prevent and treat AF.
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Project description:Atrial fibrillation (AF) is the most common supraventricular arrhythmia affecting up to 1% of the general population. Its prevalence dramatically increases with age and could reach up to ∼10% in the elderly. The management of AF is a complex issue that is object of extensive ongoing basic and clinical research, it depends on its genetic and epigenetic causes, and it varies considerably geographically and also according to the ethnicity. Mechanistically, over the last decade, Genome Wide Association Studies have uncovered over 100 genetic loci associated with AF, and have shown that European ancestry is associated with elevated risk of AF. These AF-associated loci revolve around different types of disturbances, including inflammation, electrical abnormalities, and structural remodeling. Moreover, the discovery of epigenetic regulatory mechanisms, involving non-coding RNAs, DNA methylation and histone modification, has allowed unravelling what modifications reshape the processes leading to arrhythmias. Our review provides a current state of the field regarding the identification and functional characterization of AF-related genetic and epigenetic regulatory networks, including ethnic differences. We discuss clear and emerging connections between genetic regulation and pathophysiological mechanisms of AF.
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Project description:Postoperative atrial fibrillation (POAF) is the most common type of secondary atrial fibrillation (AF) and despite progress in prevention and treatment, remains an important clinical problem for patients undergoing a variety of surgical procedures, and in particular cardiac surgery. POAF significantly increases the duration of postoperative hospital stay, hospital costs, and the risk of recurrent AF in the years after surgery; moreover, POAF has been associated with a variety of adverse cardiovascular events (including stroke, heart failure, and mortality), although it is still unclear if this is due to causal relation or simple association. New data have recently emerged on the pathophysiology of POAF, and new preventive and therapeutic strategies have been proposed and tested in randomized trials. This review summarizes the current evidence on the pathogenesis, incidence, prevention, and treatment of POAF and highlights future directions for clinical research.
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