Biology subjects

Burton, R. A. B.

Publications and source records attributed to Burton, R. A. B..

11 recordsLinked to original sources

bioRxiv2026

BeatRatePy - Automated Hight-Throughput Python-Based Beat Rate Quantification and Generation of Speed and Contraction Traces

Analysing cardiac motion from label free imaging can be difficult, especially when recordings vary in quality or show complex movement. We developed a Python-based pipeline that automatically measures beat rate, contraction, speed from transmitted light timelapse data. The workflow runs in a Jupyter notebook and uses straightforward steps that can be followed easily, making the analysis accessible including to users with limited coding experience. Using human iPSC-derived cardiomyocytes imaged on a Zeiss Cell Discoverer 7, the pipeline produced beat rates, contraction and contraction speed measurements that matched expected behaviour. To test wider use, we applied the same workflow to killifish larvae heart recordings and public datasets, changing only basic input parameters. The pipeline performed consistently across these different systems and did not require changes to the underlying code. By supporting clear parameter control and use across laboratories, microscopy platforms and repositories, this approach strengthens reproducible analysis of cardiac motion from label free imaging.

cell biology↗

bioRxiv2026

Integrated Transcriptomic Profiling Reveals MAPK14-Related Inflammatory Signalling Associated with Postoperative Atrial Fibrillation

Postoperative atrial fibrillation (POAF) affects up to half of patients after cardiac surgery and raises long-term risk of stroke and death. Why only some patients develop it, despite similar surgical exposure, remains poorly understood. We studied a pilot cohort of 20 patients undergoing cardiac surgery in Northwest England, comparing those who developed POAF within four days (n=10) with those who did not (n=10). Circulating plasma RNA was profiled using the NanoString nCounter Cardiovascular Disease panel, and differentially expressed genes were mapped onto protein-protein interaction networks using STRING and Cytoscape. Candidate genes were then validated by RT-qPCR in the same cohort, alongside serial ELISA measurement of plasma MAPK14 protein. Peripheral blood monocyte, neutrophil and total white blood cell counts were also compared between the two groups on postoperative Days 1, 2 and 4. Screening identified MAPK14, COX6C and COX7B as elevated in POAF, with PTPN12 reduced. These genes clustered within a connected inflammatory and stress-response network, and pathway enrichment pointed to immune activation. RT-qPCR confirmed higher MAPK14, COX6C and COX7B expression in POAF patients. Plasma MAPK14 rose after surgery in both groups, with the largest increase in POAF patients on day two, though this did not reach significance. Peripheral blood monocyte counts were significantly higher in POAF patients than in those without POAF at all three postoperative timepoints, whereas neutrophil and total white blood cell counts did not differ significantly between groups. These early findings identify a circulating plasma RNA signature linked to MAPK14-related inflammatory signalling as a candidate marker of POAF susceptibility, warranting confirmation in a larger, adequately powered cohort.

physiology↗

bioRxiv2026

Molecular and Structural Basis of Cardiac Remodelling in Niemann-Pick Type C

Key Point SummaryNiemann-Pick disease type C (NPC) patients showed a high prevalence of ECG abnormalities, with additional echocardiographic evidence of altered left-ventricular structure and function. Npc1-/- mouse hearts exhibited age-associated glycosphingolipid accumulation accompanied by marked myocardial fibrosis and increased collagen deposition. Ex vivo electrophysiology revealed QT prolongation and atrioventricular conduction defects in Npc1-/- hearts, particularly under {beta}-adrenergic stress. Transcriptomic profiling identified inflammatory and fibrotic pathway activation consistent with the structural and electrophysiological abnormalities observed. Together, these findings demonstrate previously unrecognised cardiac involvement in NPC and support routine cardiac screening to improve clinical management. Niemann-Pick disease type C (NPC) is a rare autosomal recessive neurodegenerative lysosomal storage disease caused by pathogenic variants in NPC1 or NPC2. Sudden death can occur due to seizures, but cardiac involvement has not been well defined. We performed 12-lead electrocardiograms (ECG) in 14 adult NPC patients (8 male, 6 female). Cardiac structure and function were examined in Npc1-/- adult mouse hearts, alongside wild-type controls. Glycosphingolipid accumulation was quantified by high-performance liquid chromatography, fibrosis and collagen deposition were quantified using Massons Trichrome (M&T) and Picrosirius Red (PR) staining. Whole-heart morphology, including chamber size and wall thickness, was assessed. Ex vivo ECG recordings assessed conduction abnormalities and arrhythmias. RNA-seq transcriptomics characterised molecular pathways altered in Npc1-/- hearts. 8/14 patients showed ECG abnormalities including abnormal QRS transitions (N=8), increased QRS amplitude (N=4), fascicular block (N=2), and abnormal T wave inversion (N=1). 13 patients also had transthoracic echocardiograms identifying mildly impaired LV systolic function (N=2) and increased wall thickness/LV mass (N=4). In Npc1-/- mice, age-related glycosphingolipid accumulation was associated with pronounced ventricular fibrotic remodelling. There was a significant increase in stained connective tissue area and connective tissue to cardiac tissue ratio in both M&T and PR staining. ECG from Langendorff-perfused Npc1-/- hearts showed QT prolongation and atrioventricular conduction abnormalities under isoprenaline stress. Transcriptomics revealed major changes in Npc1-/- hearts, consistent with histological fibrosis and linking NPC to inflammation-driven remodelling and arrhythmogenesis. These findings support routine cardiac screening in NPC patients and highlight the need for further studies to improve management and treatment.

physiology↗

bioRxiv2026

Lysosomal abundance in young and aged mouse hearts assessed by In Vivo Imaging Systems (IVIS) Lysotracker imaging and autophagy-related gene expression

Lysosomal function is essential for cardiac proteostasis and cellular health, yet its regulation during ageing remains poorly defined. We hypothesised that ageing alters both the abundance of acidic organelles and the machinery supporting their acidification. Using fluorescence-based In Vivo Imaging Systems (IVIS) with Lysotracker Red in young (2-4 months) and aged (18 months) mouse hearts, we quantified whole-heart acidic-vesicle signals and assessed expression of lysosomal and autophagy-related genes (Lamp2, Atp6v1a, Sqstm1, Cd63, Atg12, Nfe2l2, M6pr) by RT-qPCR. Whole-heart labelled Lysotracker fluorescence did not differ significantly between age groups, indicating preservation of the total acidic-vesicle pool. No changes in Atp6v1a and Lamp2 expression suggest acidification capacity and structural stability are maintained, whereas the minor, upregulation of Sqstm1 might indicate increased autophagic demand and altered vesicle trafficking, which warrants further investigation. No statistical significant changes in M6pr, Atg12, or Nfe2l2 were detected, suggesting transcriptional stability in enzyme trafficking, core autophagy, and oxidative stress pathways. Regionally, atria showed higher Lysotracker signal than ventricles, consistent with known enrichment of acidic vesicular stores in atrial physiology. These findings highlight the utility of IVIS imaging of Lysotracker-labelled hearts, providing rapid whole-organ assessment of acidic vesicle distribution, albeit with limited depth resolution. Complementary techniques such as RT-qPCR analysis is essential to interpret IVIS findings, enabling insight into underlying molecular changes in lysosomal and autophagy pathways during cardiac ageing.

physiology↗

bioRxiv2024

Lysosomal calcium signalling contributes to the acute α-adrenergic response via calcium-stimulated adenylyl cyclase 1 and 8

Inositol trisphosphate (IP3), a calcium (Ca2+)-mobilizing second messenger, releases Ca2+ from the sarcoplasmic reticulum (SR) via IP3 receptors and modulates adenylyl cyclase (AC) activity in atrial myocytes. Lysosomes participate in Ca2+ homeostasis by mobilising Ca2+ in response to Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP). We postulate that both downstream activation of Ca2+ sensitive AC (AC1 and AC8) and lysosomal Ca2+ signalling in response to IP3R activation contribute to atrial myocyte function and pacemaking. Ectopic application of phenylephrine (PE) increased chronotropy and inotropy and this response was reduced in the presence of NAADP pathway inhibitors (BZ-194 and SAN4825) and Bafilomycin A1. PE increased cyclic adenosine 3-5 monophosphate (cAMP) activity in neonatal rat atrial myocytes (NRAMs) and this was inhibited by NAADP pathway inhibitors. This inhibition was not observed in neonatal rat ventricular myocytes (NRVMs), revealing specificity of this response to NRAMs. We investigated expression of AC1 and AC8 as a possible explanation to these observations. Genetic perturbation of AC1 and AC8 by double-knockout of Adcy1 and Adcy8 in a mouse model showed a decrease in positive chronotropic and inotropic response upon cumulative dose of PE in atrial tissue, reduced PE stimulated amplitude of Ca2+ transient in isolated atrial myocytes and presented decreased cytosolic cAMP levels in response to PE in neonatal atrial myocytes that was not inhibited by NAADP pathway inhibitors. Our data identifies a link between NAADP and -adrenergic signalling pathways in atrial myocytes, highlighting that lysosomal Ca2+ is an important component of -adrenergic stimulation in the cardiac atria and warrants further investigation.

physiology↗

bioRxiv2024

Atrial Granules in Atrial Cardiomyocytes as Acidic Calcium Stores

Acidic calcium stores significantly influence basal calcium transient amplitude and {beta}-adrenergic responses in cardiomyocytes. Atrial myocytes express a small acidic organelle called atrial granules (AG), which store and excrete atrial natriuretic peptide and are not expressed by healthy ventricular myocytes. AG are known to be acidic with a high calcium content. The number and position of these calcium-rich organelles relative to other signaling sites has not been investigated. Staining of acidic organelles in adult guinea pig cardiomyocytes showed the presence of fluorescent acidic puncta throughout the cytosol. Atrial myocytes exhibited an increased concentration of acidic organelles at the nuclear poles. Live cell fluorescent studies using PBA to inhibit peptidylglycine -amidating monooxygenase, a crucial component of AG membranes, effectively eliminated staining at the nuclear poles and most acidic puncta in atrial cells. The application of PBA to ventricular myocytes did not affect LysoTracker staining. Electron microscopy studies on goat atrial fibrillation (AF) and sham control tissue, allowed visualization of AGs. Quantitative analysis revealed AGs to be in close apposition to the sarcoplasmic reticulum and mitochondria. AGs were significantly increased in AF goat samples when compared to sinus rhythm from 3D electron tomography images. Our imaging studies suggest that AGs make up a large percentage of atrial acidic stores, with AG associated with the sarcoplasmic reticulum and their number increasing during AF. We raise the question whether the positioning of AGs are strategic to communicate with other calcium organelles. Further studies to investigate whether AGs contribute to physiological calcium signalling are required.

physiology↗

bioRxiv2024

Lysosomal signalling pathways influence heart rhythm, and regulate atrial function

In the heart, endogenous nicotinic acid adenine dinucleotide phosphate (NAADP) triggers lysosomal calcium (Ca2+) release to augment sarcoplasmic reticulum (SR) Ca2+ sequestration, producing larger Ca2+ transients. However, the role of lysosomal Ca2+ signals in pacemaker activity, a distinct Ca2+-operated function of the sinoatrial node (SAN), or in the atrial myocardium has not been investigated. Pharmacological or genetic ablation of the NAADP pathway inhibits the spontaneous beating rate response to beta-adrenergic stimulation in intact SAN. We found intracellular signaling microdomains between lysosomes and neighboring SR or mitochondria in mouse, and goat tissue. The spatial relationship between lysosomes and other Ca2+-handling organelles are altered in goat atrial fibrillation. Furthermore, we demonstrate atrial myocytes produce cAMP in response to lysosomal signaling, adding a novel trigger for cyclic nucleotide signaling. Our findings support the hypothesis that lysosomal Ca2+ signaling contributes to regulation of cardiomyocyte cAMP levels and pacemaker activity.

physiology↗

bioRxiv2023

Compartmentalisation proteomics revealed endolysosomal protein network changes in a goat model of atrial fibrillation

Endolysosomes (EL) are known for their role in regulating both intracellular trafficking and proteostasis. EL help facilitate elimination of damaged membrane and cytosolic proteins, protein aggregates, membranous organelles and also play an important role in calcium signalling. Despite the importance of EL, their specific role in cardiovascular disease is not well understood. In particular, its unclear how EL contribute to atrial pathology over longer time frames. To shed light on this question, we conducted a comprehensive analysis that involved proteomics, transcriptomics, integrated analysis, electron tomography, western blotting, and enzyme assays. To identify the role of EL in atrial fibrillation (AF), we applied a recently published organelle protein isolation method. We used this method to study biopsies from AF goat model and analyse the EL-specific proteins and pathways involved in this condition. Our results revealed the upregulation of the AMPK pathway and the expression of EL-specific proteins that were not found in whole tissue lysates (TL), including GAA, DYNLRB1, CLTB, SIRT3, CCT2, and muscle-specific HSPB2. We also observed structural anomalies, such as autophago-vacuole formation, irregularly shaped mitochondria, and glycogen deposition, which provide insights into the ELs contribution to AF and related pathways and molecular mechanisms. Overall, our findings suggest that EL play an important role in the development of AF over longer time frames, and provide a more detailed understanding of the underlying molecular processes involved.

molecular biology↗

bioRxiv2022

Cross-talk between cAMP and Ca2+ signalling in cardiac pacemaker cells involves IP3-evoked Ca2+ release and stimulation of adenylyl cyclase 1

Atrial arrhythmias, such as atrial fibrillation (AF), are a major mortality risk and a leading cause of stroke. The IP3 signalling pathway has been proposed as an atrial specific target for AF therapy, and atrial IP3 signalling has been linked to the activation of calcium sensitive adenylyl cyclases AC1 and AC8. Here we investigated the involvement of AC1 in the response of intact mouse atrial tissue and isolated guinea pig atrial and sinoatrial node (SAN) cells to the -adrenoceptor agonist phenylephrine (PE) using the selective AC1 inhibitor ST034307. The maximum rate change of spontaneously beating mouse right atrial tissue exposed to PE was reduced from 14.46 % to 8.17% (P = 0.005) in the presence of 1 M ST034307, whereas the increase in tension generated in paced left atrial tissue in the presence of PE was not inhibited by ST034307 (Control = 14.20 %, ST034307 = 16.32 %; P > 0.05). Experiments were performed using isolated guinea pig atrial and SAN cells loaded with Fluo-5F-AM to record changes in calcium transient amplitude (CaT) generated by 10M PE in the presence and absence of 1M ST034307. ST034307 significantly reduced the beating rate of SAN cells (0.34-fold decrease; P = 0.004), but did not result in an inhibition of CaT amplitude increase in response to PE in atrial cells. The results presented here demonstrate the involvement of AC1 in the downstream response of atrial pacemaker activity to -adrenoreceptor stimulation and IP3R calcium release.

pharmacology and toxicology↗

bioRxiv2021

Cardiac Atrial Compartmentalisation Proteomics: A Modified Density Gradient Method to Analyse Endo-lysosomal Proteins

The importance of lysosomes in cardiac physiology and pathology are well established, and evidence for roles in calcium signalling are emerging. We describe a label-free proteomics method suitable for small cardiac tissue biopsies based on density-separated fractionation, which allows study of endo-lysosomal (EL) proteins. Density gradient fractions corresponding to tissue lysate; sarcoplasmic reticulum (SR), mitochondria (Mito) (1.3 g/ml); and EL with negligible contamination from SR or Mito (1.04 g/ml), were analysed using Western Blot, enzyme activity assay and LC-MS/MS analysis (adapted discontinuous Percoll, and sucrose differential density gradient). Kyoto Encyclopedia of Genes and Genomes, Reactome, Panther and Gene Ontology pathway analysis showed good coverage of RAB proteins and lysosomal cathepsins (including cardiac-specific cathepsin D) in the purified EL fraction. Significant EL proteins recovered included catalytic activity proteins. We thus present a comprehensive protocol and dataset of guinea-pig atrial EL organelle proteomics using techniques also applicable for non-cardiac tissue.

molecular biology↗

bioRxiv2019

Optical interrogation of sympathetic neuronal effects on macroscopic cardiac monolayer dynamics

Alterations in autonomic function are known to occur in cardiac conditions including sudden cardiac death. Cardiac stimulation via sympathetic neurons can potentially trigger arrhythmias. Dissecting direct neural-cardiac interactions at the cellular level is technically challenging and understudied due to the lack of experimental model systems and methodologies. Here we demonstrate the utility of optical interrogation of sympathetic neurons and their effects on macroscopic cardiac monolayer dynamics to address research targets such as the effects of adrenergic stimulation via the release of neurotransmitters, the effect of neuronal numbers on cardiac wave behaviour and the applicability of optogenetics in mechanistic in vitro studies. We combine photo-uncaging or optogenetic neural stimulation with imaging of cardiac monolayers to measure electrical activity in an automated fashion, illustrating the power and high throughput capability of such interrogations. The methods described highlight the challenges and benefits of co-cultures as experimental model systems.

biophysics↗