Camera-based Measurements of Intracellular [Na+] in Murine Atrial Myocytes

Garber, Libet; Joca, Humberto C.; Coleman, Andrew; Boyman, Liron; Lederer, W. Jonathan; Greiser, Maura

doi:10.3791/59600

Cited by 3 publications

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“…Previous work by Despa & Bers, our group and others has shown that [Na + ]i in quiescent ventricular myocytes from rodents ranges from 10 to 14 mM 8,9,25,[46][47][48] . Despite its importance for cardiac myocyte function and its emerging role in atrial disease (e.g.…”

Section: In Addition [Na + ]I and [Ca 2+ ]I In Cardiac Myocytesmentioning

confidence: 83%

“…Intracellular [Na + ]i and [Ca 2+ ]i were measured in atrial and ventricular myocytes. [Na + ]i was measured in intact myocytes using the Na + -sensitive, ratiometric indicator SBFI as described previously 25,26 . Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Despite its importance for cardiac myocyte function and its emerging role in atrial disease (e.g. atrial fibrillation 12,26 ) data on atrial Na + homeostasis are sparse 25 . The present study provides the first comprehensive quantitative assessment of atrial [Na + ]i and its physiological regulation.…”

Section: In Addition [Na + ]I and [Ca 2+ ]I In Cardiac Myocytesmentioning

confidence: 99%

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Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes

Karbowski,

Boyman,

Garber

et al. 2023

Preprint

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BackgroundThe intracellular Na+concentration ([Na+]i) is a crucial but understudied regulator of cardiac myocyte function. The Na+/K+ATPase (NKA) controls the steady-state [Na+]iand thereby determines the set-point for intracellular Ca2+. Here, we investigate the nanoscopic organization and local adrenergic regulation of the NKA macromolecular complex and how it differentially regulates the intracellular Na+and Ca2+homeostases in atrial and ventricular myocytes.MethodsMulticolor STORM super-resolution microscopy, Western Blot analyses, and in vivo examination of adrenergic regulation are employed to examine the organization and function of Na+nanodomains in cardiac myocytes. Quantitative fluorescence microscopy at high spatiotemporal resolution is used in conjunction with cellular electrophysiology to investigate intracellular Na+homeostasis in atrial and ventricular myocytes.ResultsThe NKAα1 (NKAα1) and the L-type Ca2+-channel (Cav1.2) form a nanodomain with a center-to center distance of ∼65 nm in both ventricular and atrial myocytes. NKAα1 protein expression levels are ∼3 fold higher in atria compared to ventricle. 100% higher atrial INKA, produced by large NKA “superclusters”, underlies the substantially lower Na+concentration in atrial myocytes compared to the benchmark values set in ventricular myocytes. The NKA’s regulatory protein phospholemman (PLM) has similar expression levels across atria and ventricle resulting in a much lower PLM/NKAα1 ratio for atrial compared to ventricular tissue. In addition, a huge PLM phosphorylation reserve in atrial tissue produces a high ß-adrenergic sensitivity of INKAin atrial myocytes. ß-adrenergic regulation of INKAis locally mediated in the NKAα1-Cav1.2 nanodomain via A-kinase anchoring proteins.ConclusionsNKAα1, Cav1.2 and their accessory proteins form a structural and regulatory nanodomain at the cardiac dyad. The tissue-specific composition and local adrenergic regulation of this “signaling cloud” is a main regulator of the distinct global intracellular Na+and Ca2+concentrations in atrial and ventricular myocytes.

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Section: In Addition [Na + ]I and [Ca 2+ ]I In Cardiac Myocytesmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: In Addition [Na + ]I and [Ca 2+ ]I In Cardiac Myocytesmentioning

confidence: 99%

See 1 more Smart Citation

Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes

Karbowski,

Boyman,

Garber

et al. 2023

Preprint

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“…One of the proposed mechanisms is increased late Na + current (late I Na ), which was detected in the atrial myocytes of patients with SDB (Lebek et al, 2020b;Lebek et al, 2022). However, data regarding Na + in the mouse atrial myocytes is scarce as the biomaterial is limited by the small murine atrium and methodological challenges (Garber et al, 2022). Garber et al (2017Garber et al ( , 2022 recommend calibrating each myocyte individually, which we did not perform for every cell in this study with the aim of increasing the yield.…”

Section: Disturbance Of Atrial Na + Homeostasis As a Novel Pathologic...mentioning

confidence: 99%

“…However, data regarding Na + in the mouse atrial myocytes is scarce as the biomaterial is limited by the small murine atrium and methodological challenges (Garber et al, 2022). Garber et al (2017Garber et al ( , 2022 recommend calibrating each myocyte individually, which we did not perform for every cell in this study with the aim of increasing the yield. Consequently, the converted Na + concentrations may be more general estimates.…”

Section: Disturbance Of Atrial Na + Homeostasis As a Novel Pathologic...mentioning

confidence: 99%

CaMKIIδ-dependent dysregulation of atrial Na+ homeostasis promotes pro-arrhythmic activity in an obstructive sleep apnea mouse model

Hegner,

Ofner,

Schaner

et al. 2024

Front. Pharmacol.

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BackgroundObstructive sleep apnea (OSA) has been linked to various pathologies, including arrhythmias such as atrial fibrillation. Specific treatment options for OSA are mainly limited to symptomatic approaches. We previously showed that increased production of reactive oxygen species (ROS) stimulates late sodium current through the voltage-dependent Na+ channels via Ca2+/calmodulin-dependent protein kinase IIδ (CaMKIIδ), thereby increasing the propensity for arrhythmias. However, the impact on atrial intracellular Na+ homeostasis has never been demonstrated. Moreover, the patients often exhibit a broad range of comorbidities, making it difficult to ascertain the effects of OSA alone.ObjectiveWe analyzed the effects of OSA on ROS production, cytosolic Na+ level, and rate of spontaneous arrhythmia in atrial cardiomyocytes isolated from an OSA mouse model free from comorbidities.MethodsOSA was induced in C57BL/6 wild-type and CaMKIIδ-knockout mice by polytetrafluorethylene (PTFE) injection into the tongue. After 8 weeks, their atrial cardiomyocytes were analyzed for cytosolic and mitochondrial ROS production via laser-scanning confocal microscopy. Quantifications of the cytosolic Na+ concentration and arrhythmia were performed by epifluorescence microscopy.ResultsPTFE treatment resulted in increased cytosolic and mitochondrial ROS production. Importantly, the cytosolic Na+ concentration was dramatically increased at various stimulation frequencies in the PTFE-treated mice, while the CaMKIIδ-knockout mice were protected. Accordingly, the rate of spontaneous Ca2+ release events increased in the wild-type PTFE mice while being impeded in the CaMKIIδ-knockout mice.ConclusionAtrial Na+ concentration and propensity for spontaneous Ca2+ release events were higher in an OSA mouse model in a CaMKIIδ-dependent manner, which could have therapeutic implications.

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Calcium Signaling Silencing in Atrial Fibrillation: Implications for Atrial Sodium Homeostasis

Kaplan

Joca

Boyman

et al. 2021

IJMS

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Atrial fibrillation (AF) is the most common type of cardiac arrhythmia, affecting more than 33 million people worldwide. Despite important advances in therapy, AF’s incidence remains high, and treatment often results in recurrence of the arrhythmia. A better understanding of the cellular and molecular changes that (1) trigger AF and (2) occur after the onset of AF will help to identify novel therapeutic targets. Over the past 20 years, a large body of research has shown that intracellular Ca2+ handling is dramatically altered in AF. While some of these changes are arrhythmogenic, other changes counteract cellular arrhythmogenic mechanisms (Calcium Signaling Silencing). The intracellular Na+ concentration ([Na+])i is a key regulator of intracellular Ca2+ handling in cardiac myocytes. Despite its importance in the regulation of intracellular Ca2+ handling, little is known about [Na+]i, its regulation, and how it might be changed in AF. Previous work suggests that there might be increases in the late component of the atrial Na+ current (INa,L) in AF, suggesting that [Na+]i levels might be high in AF. Indeed, a pharmacological blockade of INa,L has been suggested as a treatment for AF. Here, we review calcium signaling silencing and changes in intracellular Na+ homeostasis during AF. We summarize the proposed arrhythmogenic mechanisms associated with increases in INa,L during AF and discuss the evidence from clinical trials that have tested the pharmacological INa,L blocker ranolazine in the treatment of AF.

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Camera-based Measurements of Intracellular [Na+] in Murine Atrial Myocytes

Cited by 3 publications

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Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes

Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes

CaMKIIδ-dependent dysregulation of atrial Na+ homeostasis promotes pro-arrhythmic activity in an obstructive sleep apnea mouse model

Calcium Signaling Silencing in Atrial Fibrillation: Implications for Atrial Sodium Homeostasis

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Camera-based Measurements of Intracellular [Na+] in Murine Atrial Myocytes

Cited by 3 publications

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Na+/K+ATPase-Cav1.2 nanodomain differentially regulates intracellular [Na+], [Ca2+] and local adrenergic signaling in cardiac myocytes

Na+/K+ATPase-Cav1.2 nanodomain differentially regulates intracellular [Na+], [Ca2+] and local adrenergic signaling in cardiac myocytes

CaMKIIδ-dependent dysregulation of atrial Na+ homeostasis promotes pro-arrhythmic activity in an obstructive sleep apnea mouse model

Calcium Signaling Silencing in Atrial Fibrillation: Implications for Atrial Sodium Homeostasis

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Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes

Na⁺/K⁺ATPase-Ca_v1.2 nanodomain differentially regulates intracellular [Na⁺], [Ca²⁺] and local adrenergic signaling in cardiac myocytes