Biology subjects

Peyronnet, R.

Publications and source records attributed to Peyronnet, R..

7 recordsLinked to original sources

bioRxiv2024

Disturbed repolarisation-relaxation coupling during acute ischaemia permits systolic mechano-arrhythmogenesis.

BackgroundThe hearts mechanical state feeds back to its electrical activity, potentially contributing to arrhythmias. Mechano-arrhythmogenesis has been mechanistically explained during electrical diastole, when cardiomyocytes are at their resting membrane potential. During electrical systole, cardiomyocytes are refractory right from the onset of depolarisation, while during repolarisation they appear to be protected from mechano-arrhythmogenesis by near-simultaneous restoration of resting membrane potential and cytosolic calcium concentration ([Ca2+]i): repolarisation-relaxation coupling (RRC). Yet, systolic mechano-arrhythmogenesis has been reported in ischaemic myocardium, with unclear underlying mechanisms. We hypothesise that ischaemia-induced alteration of RRC gives rise to a vulnerable period for mechano-arrhythmogenesis. MethodsAcute left-ventricular (LV) regional ischaemia was induced by coronary artery ligation in Langendorff-perfused rabbit hearts, with mechanical load controlled by an intraventricular balloon. Mechanical activity was assessed by echocardiography and arrhythmia incidence by electrocardiogram. Single LV cardiomyocytes were exposed to simulated ischaemia or pinacidil (ATP-sensitive potassium channel opener). Stretch was applied in diastole or late systole using carbon fibres. Stretch characteristics and arrhythmia incidence were assessed by sarcomere length measurement. In both models, RRC was assessed by simultaneous voltage-[Ca2+]i fluorescence imaging and mechano-arrhythmogenesis mechanisms were pharmacologically tested. ResultsIn whole heart, acute regional ischaemia leads to systolic stretch and disturbed RRC at the ischaemic border. These electro-mechanical changes were associated with waves of arrhythmias, which were reduced by mechanical unloading, electro-mechanical uncoupling, or buffering of [Ca2+]i. In LV cardiomyocytes, physiological RRC is associated with a low incidence of systolic mechano-arrhythmogenesis, while a vulnerable period emerged by prolonged RRC during ischaemia. The increase in systolic mechano-arrhythmogenesis was reduced by restoring RRC, chelating [Ca2+]i, blocking mechano-sensitive transient receptor potential kinase ankyrin 1 channels (TRPA1), or buffering reactive oxygen species (ROS) levels. ConclusionProlonged RRC allows for systolic mechano-arrhythmogenesis in acute ischaemia, involving contributions of elevated [Ca2+]i, TRPA1 activity, and ROS, which represent potential anti-arrhythmic targets. GRAPHICAL ABSTRACT LEGENDRole of disturbed repolarisation-relaxation coupling (RRC), transient receptor potential kinase ankyrin 1 (TRPA1) channels, cytosolic calcium concentration ([Ca2+]i), and reactive oxygen species (ROS) in ventricular systolic mechano-arrhythmogenesis. Schematic of the proposed mechanisms underlying the TRPA1- and Ca2+-mediated increase in systolic mechano-arrhythmogenesis with disturbed RRC. AITC, Allyl isothiocyanate (TRPA1 channel activator); AP, action potential; BAPTA ([Ca2+]i buffer); CaT, Ca2+ transient; DNT, dantrolene (ryanodine receptor stabiliser); DPI, diphenyleneiodonium (ROS production blocker); GLIB, glibenclamide (KATP channel blocker); HC-300031 (TRPA1 channel blocker); KATP, ATP-sensitive potassium channel; NAC, N-acetyl-L-cysteine (ROS chelator); NCX, sodium-Ca2+ exchanger; PIN, pinacidil (KATP channel activator); ROS, reactive oxygen species; SI, simulated ischaemia; STP, streptomycin (non-specific mechano-sensitive ion channel blocker).

physiology↗

bioRxiv2024

Repolarisation-relaxation dyscoupling and TRPA1 activation permit systolic mechano-arrhythmogenesis

BackgroundThe hearts mechanical state feeds back to its electrical activity, potentially contributing to arrhythmias (mechano-arrhythmogenesis, MAR). MAR has been mechanistically explained during electrical diastole, when cardiomyocytes are at their resting membrane potential. Conversely, during electrical systole, cardiomyocytes appear to be protected from MAR, even as membrane potential and cytosolic calcium concentration ([Ca2+]i) are simultaneously restored to resting levels during repolarisation (repolarisation-relaxation coupling, RRC). Yet, systolic MAR has been reported in ischaemic myocardium, with unclear underlying mechanisms. MethodsRabbit left ventricular cardiomyocytes were electrically paced and exposed to a simulated ischaemia solution (including hyperkalaemia, acidosis, and block of oxidative phosphorylation) or pinacidil (to simulate ischaemia-induced opening of ATP-sensitive potassium [KATP] channels), with or without glibenclamide (to block KATP channels). RRC was assessed by simultaneous measurement of membrane voltage and [Ca2+]i dynamics with fluorescence imaging. Acute stretch at increasing magnitudes was applied using carbon fibres, with stretch timed to diastole or late systole. Stretch mechanics and the incidence of MAR was assessed by video-based measurement of sarcomere length. Mechanisms contributing to MAR were assessed by buffering [Ca2+]i (BAPTA-AM), stabilising ryanodine receptors (dantrolene), non-specifically blocking mechano-sensitive channels (streptomycin), activating (AITC) or blocking (HC-030031) transient receptor potential kinase ankyrin 1 channels (TRPA1), or chelating (NAC) or blocking production of (DPI) reactive oxygen species (ROS). ResultsIt was reconfirmed that MAR during physiological RRC is rare, while ischaemia- or pharmacologically-induced RRC dyscoupling generates a vulnerable period for systolic MAR. This systolic MAR depends on TRPA1, [Ca2+]i, and ROS, which contribute to stretch-induced excitation and arrhythmia sustenance. An increase in systolic MAR can be prevented by mitigating RRC dyscoupling with KATP channel block, or by blocking TRPA1, buffering [Ca2+]i, or reducing ROS. ConclusionRRC dyscoupling may be arrhythmogenic in ischaemia and other pathologies associated with systolic MAR, and TRPA1 may be a novel anti-arrhythmic target.

physiology↗

bioRxiv2023

Structure and dynamics of human cardiac fibroblast nanotubes

Efficient and dynamic interactions between cardiac fibroblasts and their environment are essential for the maintenance of tissue homeostasis in healthy hearts and play an important role during pathological remodelling. Here, we investigate a relatively obscure mechanism through which human atrial fibroblasts communicate with each other, with other cells, and with the extracellular matrix (ECM) - nanotubes (NT). We investigated NT structure and dynamics in primary right atrial fibroblasts isolated from patients in sinus rhythm (SR) and atrial fibrillation (AF), in an immortalised human atrial fibroblasts cell line, and in intact human tissue, using a wide range of imaging approaches (including confocal microscopy, label-free reflection microscopy, rotating coherent scattering microscopy, and cryo-electron tomography). We show that fibroblasts maintain continuous NT activity in vitro, with numerous protrusions constantly probing the surrounding environment. NT structure and activity change during AF and following pharmacological (transforming growth factor-{beta}, latrunculin B) and environmental (hypoxia) interventions. We also show that cardiac fibroblast NT mediate intercellular organelle exchange and dynamically interact with ECM. Finally, we present evidence for the presence of fibroblast-borne NT in human atrial tissue. Our results advance our understanding of how cardiac fibroblasts interact with their environment. NT are versatile structures capable of both sensory and actuating functions, and offer a dynamic and rapid communication conduit that facilitates cell-cell and cell-extracellular matrix interactions.

cell biology↗

bioRxiv2023

Piezo1 stretch-activated channel activity differs between bone marrow-derived and cardiac tissue-resident macrophages

Macrophages (M{Phi}) play pivotal roles in tissue homeostasis and repair. Their mechanical environment recently emerged as a key modulator of various cell functions, and M{Phi} mechanosensitivity is likely to be critical for cellular activity in particular in a rhythmically contracting organ such as the heart. M{Phi}, in-vitro-differentiated from bone marrow (M{Phi}BM), form a popular cell model for research. This study explores the activity of stretch-activated ion channels (SAC) in murine M{Phi}BM and compares it to SAC activity in cardiac tissue-resident M{Phi} (M{Phi}TR). Our main findings are: i) M{Phi}BM and M{Phi}TR have stretch-induced currents, indicating expression of functional SAC at their plasma membrane; ii) the current profiles in M{Phi}BM and in M{Phi}TR show characteristics of cation non-selective SAC; iii) unlike in M{Phi}BM, Piezo1 ion channel activity at the plasma membrane of M{Phi}TR is not detectable, neither by assessing electrophysiological activity using the patch clamp technique, nor by measuring cytosolic calcium concentration upon perfusion with Yoda1, a Piezo1 channel agonist. In mature scars after ventricular cryoablation, stretch-induced current characteristics of M{Phi}TR are not significantly different compared to non-injured control tissue, even though scars are expected to contain a mix of pre-existing and circulation-recruited M{Phi}. This suggests that M{Phi} invading injured cardiac tissue either phenoconvert their mechanosensitivity from M{Phi}BM to M{Phi}TR, or that the in vitro differentiation protocols used to obtain M{Phi}BM generate cells that differ from M{Phi} recruited from the circulation during tissue repair in vivo. Further investigations will explore SAC identity in lineage-traced M{Phi} in scar tissue, and compare mechanosensitivity of circulating monocytes with that of M{Phi}BM. Key pointsO_LIM{Phi}BM and M{Phi}TR have stretch-induced currents, indicating expression of functional SAC at their plasma membrane; C_LIO_LIThe current profiles in M{Phi}BM and in M{Phi}TR show characteristics of cation non-selective SAC; C_LIO_LIUnlike in M{Phi}BM, Piezo1 ion channel activity at the plasma membrane of M{Phi}TR is not detectable C_LI

biophysics↗

bioRxiv2023

Non-preferential, but detrimental accumulation of macrophages with clonal hematopoiesis-driver mutations in cardiovascular tissues

Clonal hematopoiesis of indeterminate potential (CHIP) is an acquired genetic risk factor for cardiovascular (CV) disease, supposedly mediated by pro-inflammatory recruited monocytes1-15. However, how these cells and their progeny behave in the CV tissue remains unclear. Here, we studied human carotid artery plaque and heart tissue samples from DNMT3A or TET2 mutation carriers to quantify the relative accumulation of mutated macrophages and to characterize tissue macrophages from carriers compared to non-carriers. Using droplet digital polymerase chain reaction (ddPCR), we detected similar sizes of CHIP clones in circulating monocytes and macrophages from atheromas and heart tissues, even among CCR2+ (infiltrative), and CCR2- (resident) cardiac macrophages. Using bulk RNA-sequencing (RNA-seq), we revealed a pro-inflammatory gene profile of myeloid cells from CHIP carriers compared to non-carriers. In summary, quantitatively, CHIP mutated myeloid cells did not preferentially accumulate in CV tissues, but qualitatively, they expressed a more disease-prone phenotype.

immunology↗

bioRxiv2022

TREK-1 knock-down in human atrial fibroblasts leads to a myofibroblastic phenotype: a role in phenoconversion and overview of mechano-sensitive channel mRNA expression in cardiac diseases.

Cardiac cell mechanical environment changes on a beat-by-beat basis and also in the course of various cardiac diseases. Cells sense and adapt to such mechanical cues via specialized mechano-sensors mediating adaptive signaling cascades. Here, we report TREK-1 mRNA expression and activity in human atrial fibroblasts and reveal a cross talk between TREK-1 and fibroblast phenoconversion. With the aim to reveal additional candidates underlying mechano-transduction relevant to cardiac diseases, we investigated mechano-sensitive ion channels (MSC) mRNA expression in diseased and non-diseased human hearts. Our results showed higher TREK-1 expression and activity in fibroblasts compared to myofibroblasts and we found that TREK-1 down-regulation leads a more myofibroblastic phenotype suggesting a role for this mechano-sensor in phenoconversion. In addition, TREK-1 is preferentially expressed in the left atrium compared to the right one and its expression is not significantly changed when fibroblasts from patients in sinus rhythm vs. sustained atrial fibrillation are compared. At the whole-heart level, numerous MSC were differentially expressed between atrial and ventricular or between non-diseased and diseased tissue samples. Thus, we identify atrial fibroblast-specific TREK-1 expression and activity and reveal a role of TREK-1 in atrial fibroblast pheno-conversion. We also provide a comprehensive overview of cardiac MSC mRNA expression in atrial and ventricular tissue from diseased and non-diseased patients, identifying potential novel candidates underlying mechanotransduction in cardiac diseases.

cell biology↗

bioRxiv2021

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

AimsAtrial 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.

molecular biology↗