Biology subjects

Roderick, L.

Publications and source records attributed to Roderick, L..

5 recordsLinked to original sources

bioRxiv2025

Loss of MGST1 during fibroblast differentiation enhances vulnerability to oxidative stress in human heart failure

BackgroundOxidative stress (OS) resulting from an imbalance between reactive oxygen species (ROS) production and antioxidant defences is a major mechanism exacerbating HF, involving activation of cardiac fibroblasts (FB) and fibrosis. In addition to reducing ROS production and/or scavenging, boosting cellular anti-oxidant capacity is a potential strategy, with FB an interesting target. MethodsWe interrogated single-nucleus RNA sequencing (snRNA-seq) data from human failing and non-failing hearts to identify OS modulating genes. Differential gene expression analysis in FB and comparison with other cell types was used for identification of candidate genes. The functional role of the identified candidate was studied in primary isolated human FB in culture, using knock-down strategies and phenotype manipulation using TGF-{beta}1. ResultsAcross the different cardiac cell types, FB showed the greatest enrichment for OS-modulating genes downregulated in HF. Of these genes, the microsomal glutathione S-transferase 1 (MGST1), was exclusively expressed and downregulated in FB, inversely correlating with elevated ROS levels in HF tissue. TGF-{beta}1 treatment of non-HF FB reduced MGST1 expression. MGST1 knockdown in non-HF FB raised expression of periostin, but not of collagen. ROS production and susceptibility to oxidative damage and lipid peroxidation were also increased. Downregulation of ferroptosis-suppressing and iron-handling genes inversely correlated with MGST1 expression. ConclusionLoss of MGST1 in HF is unique to FB, linked to FB activation. It impairs FB antioxidant capacity, exacerbating oxidative stress, and reduces resistance to ferroptosis. Through these mechanisms, loss of FB MGST1 induces a deleterious positive feedback on cardiac remodelling in human HF.

cell biology↗

bioRxiv2025

Early onset of Ca2+ waves and synchronization in multicellular clusters facilitate focal arrhythmogenesis in human heart failure

BackgroundSpontaneous Ca2+ release events and waves are frequent in isolated ventricular cardiomyocytes from failing hearts (HF) and are proposed to initiate arrhythmias in the intact heart. However, evidence supporting whether single-cell Ca2+ waves trigger tissue-wide depolarization in the intact heart is scarce, particularly in human HF. We characterized Ca2+ waves at single-cell resolution within the multicellular network of the intact heart and identified propagating dynamics and mechanisms facilitating arrhythmogenesis at tissue level. MethodsLiving myocardial slices (LMS) from HF and non-HF human hearts were prepared from left ventricular tissue and paced at 2 Hz under adrenergic stimulation. Ca2+ transients and waves were recorded by wide-field imaging of Fluo-8. Ca2+ waves in relation to single-cell structures within each LMS were identified using custom algorithms. Computational modelling assessed whether experimentally observed HF Ca2+ waves dynamics can lead to focal excitation in tissue models. ResultsFollowing pacing, early onset Ca2+ waves, initiating within the first 2 seconds, were more frequent in HF compared to non-HF, and HF cardiomyocytes had more foci, where Ca2+ waves originate, than non-HF. Spatial mapping showed that early onset waves in HF occurred frequently in clusters of neighboring cells. Although early onset Ca2+ waves propagated similar distances in HF and non-HF cardiomyocytes, they more frequently crossed cell boundaries in HF. Particularly, HF LMS exhibited more side-to-side Ca2+ propagation, correlating with increased connexin 43 distribution to lateral membranes. Furthermore, HF LMS exhibited more local and global triggered Ca2+ activities compared to non-HF LMS, correlating with local tissue depolarization. Simulations of HF Ca2+ wave dynamics in remodeled tissue demonstrated a greater capacity to elicit focal excitation. ConclusionsIn human HF, a higher incidence of early onset Ca2+ waves combines with altered intercellular connectivity to create synchrony in clusters of nearby cells that can overcome the current sink, thereby increasing arrhythmia susceptibility. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/651991v1_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@12582forg.highwire.dtl.DTLVardef@5b9893org.highwire.dtl.DTLVardef@17de348org.highwire.dtl.DTLVardef@1d4c420_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2023

Precision sampling of discrete sites identified during in-vivo functional testing in the mammalian heart

Ventricular arrhythmias after myocardial infarction (MI) originate from discrete areas within the MI border zone (BZ), identified during functional electrophysiology tests. Accurate sampling of arrhythmogenic sites for ex vivo study remains challenging, yet is critical to identify their tissue, cellular and molecular signature. In this study, we developed, validated, and applied a targeted sampling methodology based on individualized 3D prints of the human-sized pig heart. To this end, 3D anatomical models of the left ventricle were created from magnetic resonance imaging and fused with biplane fluoroscopy. Regions of interest for sampling were annotated on the anatomical models, from which we created a unique 3D printed cast with custom slits identifying the annotated regions for sampling. The methodology was validated by retrieving ablation lesions created at predefined locations on the anatomical model. We applied the methodology to sample arrhythmia-vulnerable regions after MI during adrenergic stimulation. A novel pipeline of imaging was developed to create a 3D high-resolution map of each sample, highlighting the complex interplay of cellular organization, and altered innervation in the BZ.

bioengineering↗

bioRxiv2022

Intracellular calcium elevations drive the nucleation of FIP200- and ATG13-containing pre-autophagosomal structures that become omegasomes

Ca2+ modulates autophagy at multiple steps including the induction and maturation of autophagosomes, but the magnitude and spatiotemporal properties of this calcium signal and its ultimate effect on the autophagic machinery are unclear. Focusing on the induction step leading to omegasome formation, we report that low but sustained elevations in cytosolic calcium levels induce omegasome formation but treatments that only transiently elevate calcium do not. The calcium-induced structures are early intermediates that mature into omegasomes but do not constitute full autophagosomes because they are partially devoid of late autophagy proteins ATG16 and LC3. In addition to omegasomes, all four components of the ULK complex (ULK1, FIP200, ATG13, ATG101) respond to calcium modulation: they translocate to early autophagy puncta in complete medium upon calcium elevation, and are inhibited from translocation during starvation by calcium chelation with BAPTA-2 AM. The principal early step affected by calcium lies downstream of mTORC1 inactivation and upstream of VPS34 activation, coinciding biochemically with phosphorylation of ATG13 at serine 318, which is known to require ULK1 activity. However, although the calcium-mediated step requires ATG9, FIP200 and ATG13, it does not require ULK1/2, suggesting that calcium does not directly regulate ULK1 activity but rather it regulates the mechanism by which the ULK complex components ATG13 and FIP200, together with ATG9, nucleate pre-autophagosomal precursors. This calcium-induced nucleation is sufficient to drive autophagy induction up to the omegasome step, but not beyond it.

cell biology↗

bioRxiv2020

Genes Encoding ACE2, TMPRSS2 and Related Proteins Mediating SARS-CoV-2 Viral Entry are Upregulated with Age in Human Cardiomyocytes

Age is an independent risk factor for adverse outcome in patients following COVID-19 infection. We hypothesised that differential expression of genes encoding proteins proposed to be required for entry of SARS-Cov-2 in aged compared to younger cardiomyocytes might contribute to the susceptibility of older individuals to COVID-19-associated cardiovascular complications.We generated strand-specific RNA-sequencing libraries from RNA isolated from flow-sorted cardiomyocyte nuclei from left ventricular tissue. RNASeq data were compared between five young (19-25yr) and five older (63-78yr) Caucasian males who had not been on medication or exhibited evidence of cardiovascular disease post-mortem.Expression of relevant genes encoding ACE2, TMPRSS2, TMPRS11D, TMPRS11E, FURIN, CTSL, CTSB and B0AT1/SLC6A19 were upregulated in aged cardiomyocytes and the combined relative cardiomyocyte expression of these genes correlated positively with age. Genes encoding proteins in the RAAS and interferon/interleukin pathways were also upregulated such as ACE, AGTR1, MAS1 and IL6R.Our results highlight SARS-CoV-2 related genes that have higher expression in aged compared with young adult cardiomyocytes. These data may inform studies using selective enzyme inhibitors/antagonists, available as experimental compounds or clinically approved drugs e.g. remdesivir that has recently been rapidly accepted for compassionate use, to further understand the contribution of these pathways in human cardiomyocytes to disease outcome in COVID-19 patients.Competing Interest StatementThe authors have declared no competing interest.View Full Text

cell biology↗