Enhanced atrial internal-external neural remodeling facilitates atrial fibrillation in the chronic obstructive sleep apnea model

Huangqi Guizhi Wuwu Decoction alleviates diabetic cardiovascular autonomic neuropathy via AMPK/TrkA/TRPM7 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic cardiac autonomic neuropathy (DCAN) is one of the serious complications of diabetes and greatly increased the risk of cardiovascular disease mortality. Huangqi Guizhi Wuwu Decoction (HGWD) has been proven effective for DCAN, while the underlying mechanism remains unclarified.

AIM OF THE STUDY

To observe the clinical efficacy of HGWD on DCAN and elucidate its potential mechanisms with the animal model.

MATERIALS AND METHODS

In this study, a total of 202 patients who met the inclusion criteria were recruited for the clinical trial and were randomly divided into two groups. Betaloc® Zok was used as the positive drug. The effect of HGWD on heart rate variability in DCAN patients was observed. To further clarify its underlying mechanism, the contents of the 7 major components of HGWD were determined by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). The potential mechanism of HGWD in treating DCAN was predicted using network pharmacology combined with molecular docking and protein-protein docking. The diabetic rat model was induced using the high-fat diet (HFD) and streptozotocin (STZ) injection. After successful modeling, rats were pretreated with adeno-associated viral vectors containing transient receptor potential melastatin type 7 (TRPM7) recombinant plasmids (pAAV-TRPM7) for 4 weeks.

RESULTS

Clinical research showed that HGWD could reduce the number of ventricular premature beats, improve heart rate variability, and correct the imbalance of cardiac autonomic nerves in DCAN patients. In vivo experiments demonstrated that HGWD reduced susceptibility to arrhythmia, ameliorated diabetes-induced myocardial fibrosis, inhibited cardiac autonomic remodeling, and promoted repair of cardiac sympathetic nerves in diabetic rats. Mechanistically, HGWD had an ameliorative effect on DCAN by up-regulating the AMPK/TrkA (adenosine 5'-monophosphate-activated protein kinase/tyrosine kinase receptor A) pathway, thereby inhibiting the TRPM7 channel.

CONCLUSIONS

HGWD inhibited cardiac autonomic nervous system remodeling, reduced susceptibility to ventricular arrhythmias, and improved DCAN through the regulation of the AMPK/TrkA/TRPM7 pathway, which provided the strong support for its clinical application.

Quantitative histologic assessment of atrial fibrillation-associated fibrosis in animal models: A systematic review

Atrial fibrillation (AF) is the most common sustained arrhythmia, and cardiac fibrosis is a major component in driving its progressive nature. Quantitative histologic assessment of fibrosis in animal models is crucial for understanding AF, but current published studies present various methodologies that limit comparison. This systematic review examines 195 AF studies across multiple animal models (mice, rats, goats, dogs, pigs, and horses) to summarize (1) quantified fibrosis results and (2) methodologies for histologic fibrosis assessment; and (3) evaluate antifibrotic therapies used in these studies. The fibrosis quantified across the studies ranged from 0.34%-60.2% depending on the animal, intervention model, and quantification method. The findings underscore the need for a standardized fibrosis quantification protocol in AF research, enabling comparison across studies and offering greater insight into potential pharmacologic interventions.

The effect of continuous positive airway pressure therapy on atrial fibrillation in patients with obstructive sleep apnea

Obstructive sleep apnea (OSA) stands as an autonomous risk factor for a broad spectrum of cardiovascular diseases, particularly atrial fibrillation (AF), which is closely associated with heightened morbidity and mortality rates. The intricate pathophysiological pathways linking OSA to AF encompass chronic intermittent hypoxia, disruptions in the autonomic nervous system, inflammatory responses, and alterations in ion channel function. Continuous positive airway pressure (CPAP) therapy emerges as the frontline treatment for moderate to severe OSA, effectively alleviating symptomatic manifestations and potentially mitigating cardiovascular risks. However, the influence of CPAP on AF among OSA patients remains a subject of debate. Some investigations underscore its beneficial effects, including the reversal of atrial remodeling, enhanced atrial conduction, decreased AF incidence, and improved outcomes post-AF ablation in CPAP-treated individuals. Conversely, other studies reveal neutral or insignificant impacts. This review delves into the repercussions of CPAP therapy on AF in OSA patients, exploring potential explanations for the discrepancies observed across existing research endeavors. By consolidating current evidence and pinpointing areas ripe for further inquiry, this review aspires to inform clinical decision-making regarding the management of OSA-related AF.

The Autonomic Coumel Triangle: A New Way to Define the Fascinating Relationship between Atrial Fibrillation and the Autonomic Nervous System

Arrhythmogenic substrate, modulating factors, and triggering factors (the so-called Coumel's triangle concept) play a primary role in atrial fibrillation (AF) pathophysiology. Several years have elapsed since Coumel and co-workers advanced the concept of the relevance of autonomic nervous system (ANS) influences on atrial cells' electrophysiological characteristics. The ANS is not only associated with cardiac rhythm regulation but also exerts an important role in the triggering and maintenance of atrial fibrillation. This review aims to describe in detail the autonomic mechanisms involved in the pathophysiology of atrial fibrillation (AF), starting from the hypothesis of an "Autonomic Coumel Triangle" that stems from the condition of the fundamental role played by the ANS in all phases of the pathophysiology of AF. In this article, we provide updated information on the biomolecular mechanisms of the ANS role in Coumel's triangle, with the molecular pathways of cardiac autonomic neurotransmission, both adrenergic and cholinergic, and the interplay between the ANS and cardiomyocytes' action potential. The heterogeneity of the clinical spectrum of the ANS and AF, with the ANS playing a relevant role in situations that may promote the initiation and maintenance of AF, is highlighted. We also report on drug, biological, and gene therapy as well as interventional therapy. On the basis of the evidence reviewed, we propose that one should speak of an "Autonomic Coumel's Triangle" instead of simply "Coumel's Triangle".

Advances in animal models of obstructive sleep apnea

Animal experiments play an important role in the study of the pathogenesis of human diseases and new methods of diagnosis and treatment. Due to the great differences in the anatomical structure and physiology of the upper airway between animals and humans, there is currently no animal model that can fully simulate the pathological anatomy and pathophysiological characteristics of human obstructive sleep apnea (OSA) patients. Herein, we summarizes the construction methods of several OSA animal models that have been widely used in the studies published in the last 5 years, the advantages and limitations of each model as well as related evaluation techniques are described. This information has potential to provide further guide for the development of OSA related animal experiments.

Increased β1-adrenergic receptor antibody confers a vulnerable substrate for atrial fibrillation via mediating Ca2+ mishandling and atrial fibrosis in active immunization rabbit models

BACKGROUND

Autoimmune disorder is the emerging mechanism of atrial fibrillation (AF). The β1-adrenergic receptor antibody (β1-AAb) is associated with AF progress. Our study aims to investigate whether β1-AAbs involves in atrial vulnerable substrate by mediating Ca2+ mishandling and atrial fibrosis in autoimmune associated AF.

METHODS

Active immunization models were established via subcutaneous injection of the second extracellular loop (ECL2) peptide for β1 adrenergic receptor (β1AR). Invasive electrophysiologic study and ex vivo optical mapping were used to evaluate the changed electrophysiology parameters and calcium handling properties. Phospho-proteomics combined with molecular biology assay were performed to identify the potential mechanisms of remodeled atrial substrate elicited by β1-AAbs. Exogenous β1-AAbs were used to induce the cellular phenotypes of HL-1 cells and atrial fibroblasts to AF propensity.

RESULTS

β1-AAbs aggravated the atrial electrical instability and atrial fibrosis. Bisoprolol alleviated the alterations of action potential duration (APD), Ca2+ transient duration (CaD), and conduction heterogeneity challenged by β1-AAbs. β1-AAbs prolonged calcium transient refractoriness and promoted arrhythmogenic atrial alternans and spatially discordant alternans, which were partly counteracted through blocking β1AR. Its underlying mechanisms are related to β1AR-drived CaMKII/RyR2 activation of atrial cardiomyocytes and the myofibroblasts phenotype formation of fibroblasts.

CONCLUSION

Suppressing β1-AAbs effectively protects the atrial vulnerable substrate by ameliorating intracellular Ca2+ mishandling and atrial fibrosis, preventing the process of the autoimmune associated AF.

Neurotrophins in the Neuropathophysiology, Course, and Complications of Obstructive Sleep Apnea-A Narrative Review

Obstructive sleep apnea (OSA) is a disorder characterized by chronic intermittent hypoxia and sleep fragmentation due to recurring airway collapse during sleep. It is highly prevalent in modern societies, and due to its pleiotropic influence on the organism and numerous sequelae, it burdens patients and physicians. Neurotrophins (NTs), proteins that modulate the functioning and development of the central nervous system, such as brain-derived neurotrophic factor (BDNF), have been associated with OSA, primarily due to their probable involvement in offsetting the decline in cognitive functions which accompanies OSA. However, NTs influence multiple aspects of biological functioning, such as immunity. Thus, extensive evaluation of their role in OSA might enlighten the mechanism behind some of its elusive features, such as the increased risk of developing an immune-mediated disease or the association of OSA with cardiovascular diseases. In this review, we examine the interactions between NTs and OSA and discuss their contribution to OSA pathophysiology, complications, as well as comorbidities.

Vagal milieu or electrophysiologic substrate? The link between atrial fibrillation and obstructive sleep apnea

Atrial fibrillation is the most common cardiac arrhythmia with its prevalence expected to increase to 12.1 million people in the United States by 2030. Chronic underlying conditions that affect the heart and lungs predispose patients to develop atrial fibrillation. Obstructive sleep apnea is strongly associated with atrial fibrillation. Several pathophysiological mechanisms have been proposed to elucidate this relationship which includes electrophysiological substrate modification and the contribution of the autonomic nervous system. In this comprehensive review, we highlight important relationships and plausible causality between obstructive sleep apnea and atrial fibrillation which will improve our understanding in the evaluation, management, and prevention of atrial fibrillation. This is the most updated comprehensive review of the relationship between obstructive sleep apnea and atrial fibrillation.

Muscarinic receptor regulation of chronic pain-induced atrial fibrillation

Atrial fibrillation (AF), one of the most common arrhythmias, is associated with chronic emotional disorder. Chronic pain represents a psychological instability condition related to cardiovascular diseases, but the mechanistic linkage connecting chronic pain to AF occurrence remains unknown. Wild-type C57BL/6J male mice were randomly divided into sham and chronic pain groups. Autonomic nerve remodeling was reflected by the increased atrial parasympathetic tension and muscarinic acetylcholine receptor M2 expression. AF susceptibility was assessed through transesophageal burst stimulation in combination with electrocardiogram recording and investigating AERP in Langendorff perfused hearts. Our results demonstrated the elevated protein expression of muscarinic acetylcholine receptor M2 in the atria of mice subjected to chronic pain stress. Moreover, chronic pain induced the increase of atrial PR interval, and atrial effective refractory periods as compared to the sham group, underlying the enhanced susceptibility of AF. Thus, autonomic cholinergic nerve may mediate mice AF in the setting of chronic pain.

Continuous Positive Airway Pressure Treatment Decreases the Risk of Atrial Fibrillation Recurrence in Patients with Obstructive Sleep Apnea after Radiofrequency Ablation

This study aimed to determine the effect of continuous positive airway pressure (CPAP) therapy on patients with atrial fibrillation (AF) and obstructive sleep apnea (OSA) after radiofrequency ablation (RFCA).OSA predicts recurrence of AF in patients with AF and OSA after RFCA. However, the effect of CPAP therapy on recurrence of AF in these patients after RFCA is poorly known.All 122 patients who underwent RFCA from 2017 to 2020 were diagnosed OSA by polysomnography. A total of 62 patients were treated by CPAP, while the remaining 60 were not treated by CPAP. The recurrence of atrial tachyarrhythmia and use of antiarrhythmic drugs were compared between the two groups during a follow-up of 12 months. The outcome of these patients with OSA was compared to a group of 60 AF patients undergoing RFCA without OSA.Patients undergoing CPAP therapy had a higher AF-free survival rate compared to non-CPAP-treated patients (70.3% versus 31.5%; P = 0.02). LAD was associated with the risk of AF recurrence in patients with OSA (HR per mm increase: 1.0; 95% CI: 1.06-1.21; P = 0.01). The CPAP nonusers had more than two-fold increased risk of AF recurrence following pulmonary vein isolation (HR: 2.37; 95% CI: 1.21-4.96; P = 0.02).CPAP treatment highly increased arrhythmia-free survival in AF patients accompanied by OSA after RFCA and reduced recurrence of AF in these patients.

Sleep apnea and atrial fibrillation: challenges in clinical and translational research

INTRODUCTION

Sleep-disordered breathing (SDB) is present in 21-74% of all patients with atrial fibrillation (AF). Treatment of SDB by positive airway pressure may help to prevent recurrence of AF after electrical cardioversion and help to improve AF ablation success rates in non-randomized studies.

AREAS COVERED

In this review, the current understanding of the atrial arrhythmogenic pathophysiology of SDB is summarized, and diagnostic and therapeutic challenges in AF patients are discussed. Current international recommendations are presented, and a comprehensive literature search is undertaken.

EXPERT OPINION

AF patients with SDB rarely report SDB-related symptoms such as daytime sleepiness. Therefore, systematic home sleep testing evaluation should be considered for all patients eligible for rhythm control strategy. A close interdisciplinary collaboration between the electrophysiologist/cardiologist, nurses and sleep-specialists are required for the management of SDB in AF patients. An arrhythmia-orientated assessment of SDB may better quantify SDB-related AF risk in an individual patient and may help to better guide targeted and personalized SDB treatment in AF patients as a component of rhythm and symptom control strategies. Finally, randomized controlled trials are needed to confirm the relationship between SDB and AF, and the benefits of routine testing and treatment of SDB in AF patients.