Atrial arrhythmogenesis in a rabbit model of chronic obstructive pulmonary disease

Ziprasidone triggers inflammasome signaling via PI3K-Akt-mTOR pathway to promote atrial fibrillation

BACKGROUND

Second-generation antipsychotics increase the risk of atrial fibrillation. This study explores whether the atypical antipsychotic ziprasidone triggers inflammasome signaling, leading to atrial arrhythmia.

METHODS

Electromechanical and pharmacological assessments were conducted on the rabbit left atria (LA). The patch-clamp technique was used to measure ionic channel currents in single cardiomyocytes. Detection of cytosolic reactive oxygen species production was performed in atrial cardiomyocytes.

RESULTS

The duration of action potentials at 50 % and 90 % repolarization was dose-dependently shortened in ziprasidone-treated LA. Diastolic tension in LA increased after ziprasidone treatment. Ziprasidone-treated LA showed rapid atrial pacing (RAP) triggered activity. PI3K inhibitor, Akt inhibitor and mTOR inhibitor abolished the triggered activity elicited by ziprasidone in LA. The NLRP3 inhibitor MCC950 suppressed the ziprasidone-induced post-RAP-triggered activity. MCC950 treatment reduced the reverse-mode Na+/Ca2+ exchanger current in ziprasidone-treated myocytes. Cytosolic reactive oxygen species production decreased in ziprasidone-treated atrial myocytes after MCC950 treatment. Protein levels of inflammasomes and proinflammatory cytokines, including NLRP3, caspase-1, IL-1β, IL-18, and IL-6 were observed to be upregulated in myocytes treated with ziprasidone.

CONCLUSIONS

Our findings suggest ziprasidone induces atrial arrhythmia, potentially through upregulation of the NLRP3 inflammasome and enhancement of reactive oxygen species production via the PI3K/Akt/mTOR pathway.

Piscidin-1 regulates lipopolysaccharide-induced intracellular calcium, sodium dysregulation, and oxidative stress in atrial cardiomyocytes

Lipopolysaccharide (LPS) triggers an inflammatory response, causing impairment of cardiomyocyte Ca2+ and Na+ regulation. This study aimed to determine whether piscidin-1 (PCD-1), an antimicrobial peptide, improves intracellular Ca2+ and Na+ regulation in LPS-challenged atrial cardiomyocytes. Rabbit atrial cardiomyocytes were enzymatically isolated from the left atria. Patch-clamp ionic current recording, intracellular Ca2+ monitoring using Fluo-3, and detection of cytosolic reactive oxygen species production were conducted in control, LPS-challenged, and LPS+PCD-1-treated atrial cardiomyocytes. LPS-challenged cardiomyocytes showed shortened durations of action potential at their 50% and 90% repolarizations, which was reversed by PCD-1 treatment. LPS-challenged cardiomyocytes showed decreased L-type Ca2+ channel currents and larger Na+/Ca2+ exchange currents compared to controls. While LPS did not affect the sodium current, an enhanced late sodium current with increased cytosolic Na+ levels was observed in LPS-challenged cardiomyocytes. These LPS-induced alterations in the ionic current were ameliorated by PCD-1 treatment. LPS-challenged cardiomyocytes displayed lowered Ca2+ transient amplitudes and decreased Ca2+ stores and greater Ca2+ leakage in the sarcoplasmic reticulum compared to the control. Exposure to PCD-1 attenuated LPS-induced alterations in Ca2+ regulation. The elevated reactive oxygen species levels observed in LPS-challenged myocytes were suppressed after PCD-1 treatment. The protein levels of NF-κB and IL-6 increased following LPS treatment. Decreased sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a protein levels were observed in LPS-challenged cardiomyocytes. PCD-1 modulates LPS-induced alterations in inflammatory and Ca2+ regulatory protein levels. Our results suggest that PCD-1 modulates LPS-induced alterations in intracellular Ca2+ and Na+ homeostasis, reactive oxygen species production, and the NF-κB inflammatory pathway in atrial cardiomyocytes.

Incident atrial fibrillation in relation to ventilatory parameters: a prospective cohort study

BACKGROUND

There is a paucity of data on the association between respiratory function and atrial fibrillation (AF). This study aimed to assess the relationship between forced expiratory volume (FEV1), forced vital capacity (FVC), and FEV1/FVC and incident AF.

METHODS

We performed an analysis of prospectively collected data from the UK Biobank. We included all participants with available spirometry and excluded those with a prior AF. Incident AF was ascertained through hospitalization and death records, and dose-response associations were assessed using multivariable Cox regression analysis with adjustment for known AF risk factors.

RESULTS

We studied 348,219 white individuals (54.1% female) with a median age of 58.1 (IQR 50.8-63.5) years. Over a median follow-up time of 11.5 years (IQR: 11.0-12.6 years), a total of 18,188 incident AF events occurred. After standardization to sex, age, and height, the risk of AF consistently increased with decreasing FEV1 percentage predicted, FEV1 z-score, and FVC z-score. The risk of AF linearly increased with decreasing FEV1/FVC ratio, and those that had airway obstruction as defined by an FEV1/FVC ratio < 0.70 had a 23% greater risk of incident AF (aHR 1.23, 95% CI 1.19-1.28) compared to those without airway obstruction. Patients with known chronic obstructive pulmonary disease and asthma were at 40% (aHR 1.40, 95% CI 1.29-1.51) and 17% (aHR 1.17, 95% CI 1.12-1.22) increased risk of incident AF.

CONCLUSION

These findings indicate that reduced ventilatory function is associated with increased risk of AF independently of age, sex, smoking, and other known AF risk factors.

Inhibition of Voltage-Gated Na+ Currents Exerted by KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea), an Inhibitor of Na+-Ca2+ Exchanging Process

KB-R7943, an isothiourea derivative, has been recognized as an inhibitor in the reverse mode of the Na⁺-Ca²⁺ exchanging process. This compound was demonstrated to prevent intracellular Na⁺-dependent Ca²⁺ uptake in intact cells; however, it is much less effective at preventing extracellular Na⁺-dependent Ca²⁺ efflux. Therefore, whether or how this compound may produce any perturbations on other types of ionic currents, particularly on voltage-gated Na⁺ current (I_Na), needs to be further studied. In this study, the whole-cell current recordings demonstrated that upon abrupt depolarization in pituitary GH₃ cells, the exposure to KB-R7943 concentration-dependently depressed the transient (I_Na(T)) or late component (I_Na(L)) of I_Na with an IC₅₀ value of 11 or 0.9 μM, respectively. Likewise, the dissociation constant for the KB-R7943-mediated block of I_Na on the basis of a minimum reaction scheme was estimated to be 0.97 μM. The presence of benzamil or amiloride could suppress the I_Na(L) magnitude. The instantaneous window Na⁺ current (I_Na(W)) activated by abrupt ascending ramp voltage (V_ramp) was suppressed by adding KB-R7943; however, subsequent addition of deltamethrin or tefluthrin (Tef) effectively reversed KB-R7943-inhibted I_Na(W). With prolonged duration of depolarizing pulses, the I_Na(L) amplitude became exponentially decreased; moreover, KB-R7943 diminished I_Na(L) magnitude. The resurgent Na⁺ current (I_Na(R)) evoked by a repolarizing V_ramp was also suppressed by adding this compound; moreover, subsequent addition of ranolazine or Tef further diminished or reversed, respectively, its reduction in I_Na(R) magnitude. The persistent Na⁺ current (I_Na(P)) activated by sinusoidal voltage waveform became enhanced by Tef; however, subsequent application of KB-R7943 counteracted Tef-stimulated I_Na(P). The docking prediction reflected that there seem to be molecular interactions of this molecule with the hNa_V1.2 or hNa_V1.7 channels. Collectively, this study highlights evidence showing that KB-R7943 has the propensity to perturb the magnitude and gating kinetics of I_Na (e.g., I_Na(T), I_Na(L), I_Na(W), I_Na(R), and I_Na(P)) and that the Na_V channels appear to be important targets for the in vivo actions of KB-R7943 or other relevant compounds.

Ziprasidone Induces Rabbit Atrium Arrhythmogenesis via Modification of Oxidative Stress and Sodium/Calcium Homeostasis

Background: Atypical antipsychotics increase the risk of atrial arrhythmias and sudden cardiac death. This study investigated whether ziprasidone, a second-generation antipsychotic, affected intracellular Ca²⁺ and Na⁺ regulation and oxidative stress, providing proarrhythmogenic substrates in atriums. Methods: Electromechanical analyses of rabbit atrial tissues were conducted. Intracellular Ca²⁺ monitoring using Fluo-3, the patch-clamp method for ionic current recordings, and a fluorescence study for the detection of reactive oxygen species and intracellular Na⁺ levels were conducted in enzymatically dissociated atrial myocytes. Results: Ziprasidone-treated atriums showed sustained triggered activities after rapid pacing, which were inhibited by KN-93 and ranolazine. A reduced peak L-type Ca²⁺ channel current and enhanced late Na⁺ current were observed in ziprasidone-treated atrial myocytes, together with an increased cytosolic Na⁺ level. KN-93 suppressed the enhanced late Na⁺ current in ziprasidone-treated atrial myocytes. Atrial myocytes treated with ziprasidone showed reduced Ca²⁺ transient amplitudes and sarcoplasmic reticulum (SR) Ca²⁺ stores, and increased SR Ca²⁺ leakage. Cytosolic and mitochondrial reactive oxygen species production was increased in atrial myocytes treated with ziprasidone. TNF-α and NLRP3 were upregulated in ziprasidone-treated myocytes, and the level of phosphorylated calcium/calmodulin-dependent protein kinase II protein was increased. Conclusions: Our results suggest that ziprasidone increases the occurrence of atrial triggered activity and causes intracellular Ca²⁺ and Na⁺ dysregulation, which may result from enhanced oxidative stress and activation of the TNF-α/NLRP3 inflammasome pathway in ziprasidone-treated myocytes.

Chronic obstructive pulmonary disease and atrial fibrillation: an interdisciplinary perspective

Chronic obstructive pulmonary disease (COPD) is highly prevalent among patients with atrial fibrillation (AF), shares common risk factors, and adds to the overall morbidity and mortality in this population. Additionally, it may promote AF and impair treatment efficacy. The prevalence of COPD in AF patients is high and is estimated to be ∼25%. Diagnosis and treatment of COPD in AF patients requires a close interdisciplinary collaboration between the electrophysiologist/cardiologist and pulmonologist. Differential diagnosis may be challenging, especially in elderly and smoking patients complaining of unspecific symptoms such as dyspnoea and fatigue. Routine evaluation of lung function and determination of natriuretic peptides and echocardiography may be reasonable to detect COPD and heart failure as contributing causes of dyspnoea. Acute exacerbation of COPD transiently increases AF risk due to hypoxia-mediated mechanisms, inflammation, increased use of beta-2 agonists, and autonomic changes. Observational data suggest that COPD promotes AF progression, increases AF recurrence after cardioversion, and reduces the efficacy of catheter-based antiarrhythmic therapy. However, it remains unclear whether treatment of COPD improves AF outcomes and which metric should be used to determine COPD severity and guide treatment in AF patients. Data from non-randomized studies suggest that COPD is associated with increased AF recurrence after electrical cardioversion and catheter ablation. Future prospective cohort studies in AF patients are needed to confirm the relationship between COPD and AF, the benefits of treatment of either COPD or AF in this population, and to clarify the need and cost-effectiveness of routine COPD screening.

Peak atrial longitudinal strain is predictive of atrial fibrillation in patients with chronic obstructive pulmonary disease and coronary artery disease

Background

The peak atrial longitudinal strain (PALS) has been validated in the prediction of atrial fibrillation (AF) in the general population. If this finding can be applied to patients with chronic obstructive pulmonary disease (COPD) and concomitant coronary artery disease (CAD) is unknown.

Methods and results

We analyzed two different study populations of patients with COPD and acute CAD in SCAP trial (Clinical trial.org identifier NCT02324660) and COPD and stable CAD in the NATHAN‐NEVER trial (clinical trial.org identifier NCT02519608). All patients enrolled underwent spirometry and clinical specialistic evaluation to test COPD diagnosis. During the index evaluation, all patients underwent echocardiography. The primary endpoint of the study was the occurrence of AF. Overall, 175 patients have been enrolled. PALS was significantly lower in patients with COPD compared to patients without COPD (26% ± 8% vs. 30% ± 8% for PALS4CV, P = .003). After a mean follow‐up of 49 ± 15 months, 26 patients experienced at least one episode of AF. At multivariable analysis, only PALS (HR: 0.92, 95% CI: 0.86‐0.98, P = .014) resulted as an independent predictor of AF in COPD patients with CAD, with the best cutoff value of 25.5% (sensitivity 87% and specificity 70%).

Conclusion

The present study confirmed a high incidence of AF events in COPD patients and that PALS is altered and able to independently predict AF in a specific cohort of patients with CAD and COPD. This study points out the need to integrate PALS measurement in the echocardiographic workup of all COPD patients, to early identify those at high risk of AF development.

Pulmonary Disease, Pulmonary Hypertension and Atrial Fibrillation

Atrial fibrillation is associated with aging, obesity, heart disease, diabetes, and/or hypertension. Recent evidence suggests that parenchymal and vascular lung diseases increase atrial fibrillation risk. We review the epidemiology, clinical features, pathophysiologic mechanisms, and treatment implications of atrial fibrillation associated with diseases of the lungs and their vasculature, especially pulmonary hypertension. We also consider other features of pulmonary disease-associated atrial fibrillation. A key mediator of these conditions is right heart disease and right atrial remodeling. We pay particular attention to the pathophysiology and treatment challenges in atrial fibrillation associated with right heart disease induced by pulmonary diseases, including pulmonary hypertension.