Biology subjects

Herring, N.

Publications and source records attributed to Herring, N..

5 recordsLinked to original sources

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↗

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↗

bioRxiv2020

Mechanistic insights into ventricular arrhythmogenesis of hydroxychloroquine and azithromycin for the treatment of COVID-19

Background: Recent reports on the use of hydroxychloroquine (HCQ) alone, or combined with azithromycin (AZM) in the management of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have raised cardiac safety concerns. Currently, there is limited mechanistic data evaluating cardiac safety with HCQ and AZM therapy. Methods: Using comprehensive In Vitro ProArrhythmia Assay (CiPA) Schema IC50 paradigms, we examined the cardiac electrophysiological effects of HCQ and HCQ/AZM. Molecular modelling explored HCQ and AZM binding properties to hERG. Langendorff-perfused guinea-pig hearts were electrically and optically mapped by multi-electrode array and voltage (RH237) and Ca2+ (Rhod-2 AM) dyes. Human action potential and ion current reconstructions were performed in silico. Results: HCQ blocked IKr and IK1 with IC50 concentrations (10+-0.6 and 34+-5.0 microM) within the therapeutic range observed clinically. HCQ also blocked INa and ICaL but at higher IC50, whilst Ito and IKs were unaffected. Contrastingly, AZM produced minor inhibition of INa, ICaL, IKs, and IKr,, with no effect on IK1 and Ito. HCQ + AZM combined inhibited IKr and IK1 with IC50s of 7.7 +- 0.8 microM and 30.4 +- 3.0 microM, but spared INa, ICaL and Ito,. Molecular modelling confirmed potential HCQ binding to hERG. Cardiac mapping and ECG studies in isolated hearts demonstrated that HCQ slowed heart rate and ventricular conduction with associated prolongation of PR, QRS and QT intervals. Optical mapping demonstrated, and prolonged, more heterogeneous, action potential durations and intracellular Ca2+ transients. These effects were accentuated with combined HCQ+AZM treatment, which elicited electrical alternans, re-entrant circuits and wave breaks. Reconstruction in a human in-silico model demonstrated that this is attributable to the integrated action of HCQ and AZM reducing IKr, IKs and IK1. Conclusions: These data provide an electrophysiological basis for recent FDA guidelines cautioning against combined HCQ/AZM administration for the treatment of Covid-19 on the grounds of potential cardiac safety. We would strongly recommend monitoring of electrocardiographic QT interval with the use of this combination of medications.Competing Interest StatementThe authors have declared no competing interest.

pharmacology and toxicology↗

bioRxiv2019

M-current downregulation leads to stellate ganglia sympathetic hyperactivity associated with hypertension

The activity of cardiac sympathetic nerves from the stellate ganglia is increased in many cardiovascular diseases contributing to the pathophysiology, however the mechanisms underlying this are unknown. Moreover, clinical studies show their surgical removal is an effective treatment, despite the biophysical properties of these neurons being largely unstudied. Here we demonstrate that stellate ganglia neurons from prehypertensive spontaneously hypertensive rats are hyperactive and describe in detail their electrophysiological phenotype guided by single cell RNA-sequencing, molecular biology and perforated patch-clamp to uncover the underlying mechanism. The expression of key transcripts was confirmed in human stellate ganglia. We further demonstrate the contribution of a plethora of ion channels to stellate ganglia neuronal firing, and show that hyperexcitability was curbed by M-current activators, non-selective sodium current blockers or inhibition of Nav1.1-1.3, Nav1.6 or INaP. These findings have implications for target discovery to reduce cardiac sympathetic activity without resorting to surgery.

neuroscience↗

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↗