scholarly journals Piezo1 and BKCa channels in human atrial fibroblasts: interplay and remodelling in atrial fibrillation

2021 ◽  
Author(s):  
Dorothee Jakob ◽  
Alexander Klesen ◽  
Benoit Allegrini ◽  
Elisa Darkow ◽  
Diana Aria ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Ion Channels ◽  
Sinus Rhythm ◽  
Calcium Influx ◽  
Primary Cultures ◽  
Developed Countries ◽  
Bkca Channels ◽  
Calcium Dependent ◽  
Selective Channel ◽  
In Cells

AbstractAimsAtrial Fibrillation (AF) is an arrhythmia of increasing prevalence in the aging population of developed countries. One of the important indicators of AF is sustained atrial dilatation, highlighting the importance of mechanical overload in the pathophysiology of AF. The mechanisms by which atrial cells, including fibroblasts, sense and react to changing mechanical forces, are not fully elucidated. Here, we characterise stretch-activated ion channels (SAC) in human atrial fibroblasts and changes in SAC-presence and -activity associated with AF.Methods and ResultsUsing primary cultures of human atrial fibroblasts, isolated from patients in sinus rhythm or sustained AF, we combine electrophysiological, molecular and pharmacological tools to identify SAC. Two electrophysiological SAC-signatures were detected, indicative of cation-nonselective and potassium-selective channels. Using siRNA-mediated knockdown, we identified the nonselective SAC as Piezo1. Biophysical properties of the potassium-selective channel, its sensitivity to calcium, paxilline and iberiotoxin (blockers), and NS11021 (activator), indicated presence of calcium-dependent ‘big potassium channels’, BKCa. In cells from AF patients, Piezo1 activity and mRNA expression levels were higher than in cells from sinus rhythm patients, while BKCa activity (but not expression) was downregulated. Both Piezo1-knockdown and removal of extracellular calcium from the patch pipette resulted in a significant reduction of BKCa current during stretch. No co-immunoprecipitation of Piezo1 and BKCa was detected.ConclusionsHuman atrial fibroblasts contain at least two types of ion channels that are activated during stretch: Piezo1 and BKCa. While Piezo1 is directly stretch-activated, the increase in BKCa activity during mechanical stimulation appears to be mainly secondary to calcium influx via SAC such as Piezo1. During sustained AF, Piezo1 is increased, while BKCa activity is reduced, highlighting differential regulation of both channels. Our data support the presence and interplay of Piezo1 and BKCa in human atrial fibroblasts in the absence of physical interactions between the two channel proteins.

scholarly journals Piezo1 and BKCa channels in human atrial fibroblasts: interplay and remodelling in atrial fibrillation

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
D Jakob ◽  
A Klesen ◽  
B Allegrini ◽  
E Darkow ◽  
D Aria ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Calcium Influx ◽  
Primary Cultures ◽  
Science Research ◽  
Bkca Channels ◽  
National Budget ◽  
Funding Sources ◽  
Public Grant ◽  
In Cells

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministry of Science, Research and Arts Baden-Württemberg (MWK-BW Sonderlinie Medizin) Atrial Fibrillation (AF) is an arrhythmia of increasing prevalence. One of the important indicators for AF is sustained atrial dilatation, highlighting the importance of mechanical overload in the pathophysiology of AF. The mechanisms by which atrial cells, including fibroblasts, sense and react to such changing mechanical forces, are not fully elucidated. Here, we characterise stretch-activated ion channels (SAC) in human atrial fibroblasts and changes in their expression and activity associated with AF. Using primary cultures of human atrial fibroblasts, isolated from patients in sinus rhythm or with sustained AF, we combine electrophysiological, molecular and pharmacological tools to identify SAC. Two electrophysiological SAC-signatures were detected, indicative of cation-nonselective and potassium-selective channels. Using siRNA-mediated knockdown, we identified the nonselective SAC as Piezo1. Biophysical properties of the potassium-selective channel and its pharmacology indicated presence of ‘big potassium channels’, BKCa. In cells from AF patients, Piezo1 activity and mRNA expression levels were higher than in cells from sinus rhythm patients, while BKCa activity (but not expression) was downregulated. Both Piezo1-knockdown and removal of extracellular calcium from the patch pipette resulted in a significant reduction of stretch-induced BKCa current. No co-immunoprecipitation of Piezo1 and BKCa was detected. Human atrial fibroblasts express functional Piezo1 and BKCa channels. While Piezo1 is directly stretch-activated, the increase in BKCa activity during mechanical stimulation appears to be mainly secondary to calcium influx via SAC such as Piezo1. During sustained AF, Piezo1 is increased, while BKCa activity is reduced, highlighting differential regulation of both channels. Our data show the presence and activity of Piezo1 and BKCa in human atrial fibroblasts and suggest an interplay between the two in the absence of direct physical interactions.

scholarly journals Role of domain calcium in purinergic P2X2 receptor channel desensitization

2015 ◽  
Vol 308 (9) ◽  
pp. C729-C736 ◽  
Author(s):  
Claudio Coddou ◽  
Zonghe Yan ◽  
Stanko S. Stojilkovic
Keyword(s):  
Calcium Influx ◽  
Receptor Desensitization ◽  
P2x2 Receptor ◽  
Calcium Dependent ◽  
Independent Process ◽  
Rapid Current ◽  
Intracellular Domains ◽  
Whole Cell Recordings ◽  
In Cells

Activation of P2X2 receptor channels (P2X2Rs) is characterized by a rapid current growth accompanied by a decay of current during sustained ATP application, a phenomenon known as receptor desensitization. Using rat, mouse, and human receptors, we show here that two processes contribute to receptor desensitization: bath calcium-independent desensitization and calcium-dependent desensitization. Calcium-independent desensitization is minor and comparable during repetitive agonist application in cells expressing the full size of the receptor but is pronounced in cells expressing shorter versions of receptors, indicating a role of the COOH terminus in control of receptor desensitization. Calcium-dependent desensitization is substantial during initial agonist application and progressively increases during repetitive agonist application in bath ATP and calcium concentration-dependent manners. Experiments with substitution of bath Na+ with N-methyl-d-glucamine (NMDG+), a large organic cation, indicate that receptor pore dilation is a calcium-independent process in contrast to receptor desensitization. A decrease in the driving force for calcium by changing the holding potential from −60 to +120 mV further indicates that calcium influx through the channel pores at least partially accounts for receptor desensitization. Experiments with various receptor chimeras also indicate that the transmembrane and/or intracellular domains of P2X2R are required for development of calcium-dependent desensitization and that a decrease in the amplitude of current slows receptor desensitization. Simultaneous calcium and current recording shows development of calcium-dependent desensitization without an increase in global intracellular calcium concentrations. Combined with experiments with clamping intrapipette concentrations of calcium at various levels, these experiments indicate that domain calcium is sufficient to establish calcium-dependent receptor desensitization in experiments with whole-cell recordings.

scholarly journals Ion channels in a context of the development of new molecular targets for regulation of uterine contractions

2020 ◽  
Vol 83 (4) ◽  
pp. 24-28
Author(s):  
V. Tatarina ◽  
I. Sukha ◽  
R. Lavryk ◽  
O. Artemenko ◽  
O. Moroz
Keyword(s):  
Ion Channels ◽  
Liposomal Form ◽  
Bkca Channels ◽  
Pregnant Rats ◽  
Calcium Dependent ◽  
Uterine Contractions ◽  
Regulatory Cascades ◽  
Insufficient Response ◽  
End Stage ◽  
Smooth Muscle Contractions

Many women now have complications in childbirth due to poor labor, which often threatens both mother and fetus. Also,the problem of prevention and treatment of premature uterine contractions is unresolved. Therefore, in this work we investigated the influence of ion channels as the end stage effectors of the regulatory cascades in the contractility of myometrium. To better understand the participation of TRPC4, TRPV4 and BKCa ion channels in myometrial contractility, we conducted experiments, keeping in mind the fact that changes in ionic conductivity of the plasma membrane regulate spontaneous and agonist-induced contractions. On the myometrial preparations of pregnant rats usingisolated tissue tensiometry, the amplitude of contractile force was recorded under the activation of these ion channels by their selective agonists. Obtained results allow us to consider (-) – englerin A as a way to stimulate uterine contractions in case of insufficient response to oxytocin, because at a concentration of 1 nM a significant increase in contraction force was developed and did not differ statistically from the response to oxytocin or carbacholin. The use of an agonist at concentrations of 30-100 nM causes some suppression of contractility. Based on the results describing the role of TRPV4 channels, namely the reduction of uterine smooth muscle contractions in response to their selective agonist GSK1016790A administration, we suggest that the main effect of activation of these channels depends on the expression and activity of adjacent calcium-dependent potassium channels. Our experiments found that the use of the liposomal form of quercetin to activate BKCa channels inhibits the excitability of myometrial cells more effectively than that dissolved in DMSO, which is promising for the correction of premature or excessive uterine activity.

Body Mass Index can influence Connexin 43 distribution in patients with atrial fibrillation or sinus rhythm

2014 ◽  
Vol 62 (S 01) ◽  
Author(s):  
S. Dhein ◽  
S. Rothe ◽  
A. Busch ◽  
H. Bittner ◽  
M. Kostelka ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Body Mass Index ◽  
Sinus Rhythm ◽  
Body Mass ◽  
Connexin 43

New Drugs for Thromboembolic Prevention in Atrial Fibrillation

2010 ◽  
Vol 6 (4) ◽  
pp. 64
Author(s):  
Jose L Merino ◽  
Jose López-Sendón ◽  
◽  
Keyword(s):  
Atrial Fibrillation ◽  
Vitamin K ◽  
Negative Impact ◽  
Vitamin K Antagonists ◽  
Coagulation Factor ◽  
Developed Countries ◽  
New Drugs ◽  
Risk Scores ◽  
Bleeding Events ◽  
Risk Patients

Atrial fibrillation (AF) is the most frequent sustained arrhythmia and its prevalence is increasing in developed countries. This progressive increase and the negative impact of this arrhythmia on the patient’s prognosis make AF one of the main healthcare problems faced today. This has led to intense research into the main aspects of AF, one of them being thromboembolism prevention. AF patients have a four to five times higher risk of stroke than the general population. Several factors increase thromboembolic risk in patients with AF and the use of risk scores, such as the Congestive Heart Failure, Hypertension, Age Greater than 75, Diabetes, and Prior Stroke or Transient Ischemic Attack (CHADS2), have been used to identify the best candidates for anticoagulation. Antithrombotic drugs are the mainstay of therapy for embolic prevention. The clinical use of these drugs is based on the risk–benefit ratio, where benefit is the reduction of stroke and systemic embolic events and risk is mostly driven by the increase in bleeding events. Generally, antiplatelets are indicated for low-risk patients in light of the fact anticoagulants are the drug of choice for moderate- or high-risk patients. Vitamin K antagonists have been the only option for oral anticoagulation for the last 50 years. However, these drugs have many pharmacodynamic and pharmacokinetic problems. The problems of anticoagulation with vitamin K antagonists have led to the investigation of new drugs that can be administered orally and have a better dose–response relationship, a shorter half-life and, in particular, higher efficacy and safety without the need for frequent anticoagulation controls. The drugs that have been studied most thoroughly in patients with AF are inhibitors of the activated coagulation factor X and inhibitors of coagulation factor II (thrombin), including ximelagatran and dabigatran. In addition, non-pharmacological therapies have been developed to prevent recurrent embolism in certain patient populations.

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