ORCID Profile
0000-0002-7122-4656
Current Organisations
University of Queensland
,
Queensland University of Technology
,
University of Melbourne
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Publisher: Wiley
Date: 07-07-2017
DOI: 10.1111/BPH.13897
Publisher: Elsevier BV
Date: 11-2021
DOI: 10.1016/J.PBIOMOLBIO.2021.04.008
Abstract: The sinus node (SN) is the heart's primary pacemaker. Key ion channels (mainly the funny channel, HCN4) and Ca 68 and 60 TFs significantly more or less expressed in the SN vs. RA respectively. Among those more expressed were ISL1 and TBX3 (involved in embryonic development of the SN) and 'novel' RUNX1-2, CEBPA, GLI1-2 and SOX2. These TFs were predicted to regulate HCN4 expression in the SN. Markers for different cells: fibroblasts (COL1A1), fat (FABP4), macrophages (CSF1R and CD209), natural killer (GZMA) and mast (TPSAB1) were significantly more expressed in the SN vs. RA. Interestingly, RUNX1-3, CEBPA and GLI1 also regulate expression of these cells. MiR-486-3p inhibits HCN4 and markers involved in immune response. In conclusion, RUNX1-2, CSF1R, TPSAB1, COL1A1 and HCN4 are highly expressed in the SN but not miR-486-3p. Their complex interactions can be used to treat SN dysfunction such as bradycardia. Interestingly, another research group recently reported miR-486-3p is upregulated in blood s les from severe COVID-19 patients who suffer from bradycardia.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2021
DOI: 10.1161/CIRCGEN.120.003144
Abstract: KCNMA1 encodes the α-subunit of the large-conductance Ca 2+ -activated K + channel, K Ca 1.1, and lies within a linkage interval for atrial fibrillation (AF). Insights into the cardiac functions of K Ca 1.1 are limited, and KCNMA1 has not been investigated as an AF candidate gene. The KCNMA1 gene was sequenced in 118 patients with familial AF. The role of K Ca 1.1 in normal cardiac structure and function was evaluated in humans, mice, zebrafish, and fly. A novel KCNMA1 variant was functionally characterized. A complex KCNMA1 variant was identified in 1 kindred with AF. To evaluate potential disease mechanisms, we first evaluated the distribution of K Ca 1.1 in normal hearts using immunostaining and immunogold electron microscopy. K Ca 1.1 was seen throughout the atria and ventricles in humans and mice, with strong expression in the sinus node. In an ex vivo murine sinoatrial node preparation, addition of the K Ca 1.1 antagonist, paxilline, blunted the increase in beating rate induced by adrenergic receptor stimulation. Knockdown of the K Ca 1.1 ortholog, kcnma1b , in zebrafish embryos resulted in sinus bradycardia with dilatation and reduced contraction of the atrium and ventricle. Genetic inactivation of the Drosophila K Ca 1.1 ortholog, slo , systemically or in adult stages, also slowed the heartbeat and produced fibrillatory cardiac contractions. Electrophysiological characterization of slo -deficient flies revealed bursts of action potentials, reflecting increased events of fibrillatory arrhythmias. Flies with cardiac-specific overexpression of the human KCNMA1 mutant also showed increased heart period and bursts of action potentials, similar to the K Ca 1.1 loss-of-function models. Our data point to a highly conserved role of K Ca 1.1 in sinus node function in humans, mice, zebrafish, and fly and suggest that K Ca 1.1 loss of function may predispose to AF.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 20-10-2020
Abstract: The sinus node (SN) is the primary pacemaker of the heart. SN myocytes possess distinctive action potential morphology with spontaneous diastolic depolarization because of a unique expression of ion channels and Ca 2+ ‐handling proteins. MicroRNAs (miRs) inhibit gene expression. The role of miRs in controlling the expression of genes responsible for human SN pacemaking and conduction has not been explored. The aim of this study was to determine miR expression profile of the human SN as compared with that of non‐pacemaker atrial muscle. SN and atrial muscle biopsies were obtained from donor or post‐mortem hearts (n=10), histology/immunolabeling were used to characterize the tissues, TaqMan Human MicroRNA Arrays were used to measure 754 miRs, Ingenuity Pathway Analysis was used to identify miRs controlling SN pacemaker gene expression. Eighteen miRs were significantly more and 48 significantly less abundant in the SN than atrial muscle. The most interesting miR was miR‐486‐3p predicted to inhibit expression of pacemaking channels: HCN1 (hyperpolarization‐activated cyclic nucleotide‐gated 1), HCN4, voltage‐gated calcium channel (Ca v )1.3, and Ca v 3.1. A luciferase reporter gene assay confirmed that miR‐486‐3p can control HCN4 expression via its 3′ untranslated region. In ex vivo SN preparations, transfection with miR‐486‐3p reduced the beating rate by ≈35±5% ( P .05) and HCN4 expression ( P .05). The human SN possesses a unique pattern of expression of miRs predicted to target functionally important genes. miR‐486‐3p has an important role in SN pacemaker activity by targeting HCN4, making it a potential target for therapeutic treatment of SN disease such as sinus tachycardia.
Publisher: American Chemical Society (ACS)
Date: 19-10-2020
Publisher: Wiley
Date: 30-04-2021
DOI: 10.1002/PRP2.760
Abstract: Omecamtiv mecarbil (OM) is a novel medicine for systolic heart failure, targeting myosin to enhance cardiomyocyte performance. To assist translation to clinical practice we investigated OMs effect on explanted human failing hearts, specifically contractile dynamics, interaction with the β 1 –adrenoceptor (AR) agonist (−)‐noradrenaline and spontaneous contractions. Left and right ventricular trabeculae from 13 explanted failing hearts, and trabeculae from 58 right atrial appendages of non‐failing hearts, were incubated with or without a single concentration of OM for 120 min. Time to peak force (TPF) and 50% relaxation ( t 50% ) were recorded. In other experiments, trabeculae were observed for spontaneous contractions and cumulative concentration‐effect curves were established to (−)‐noradrenaline at β 1 ‐ARs in the absence or presence of OM. OM prolonged TPF and t 50% in ventricular trabeculae (600 nM, 2 µM, p .001). OM had no significant inotropic effect but reduced time dependent deterioration in contractile strength compared to control ( p .001). OM did not affect the generation of spontaneous contractions. The potency of (−)‐noradrenaline (pEC 50 6.05 ± 0.10), for inotropic effect, was unchanged in the presence of OM 600 nM or 2 µM. Co‐incubation with (−)‐noradrenaline reduced TPF and t 50% , reversing the negative diastolic effects of OM. OM, at both 600 nM and 2 µM, preserved contractile force in left ventricular trabeculae, but imparted negative diastolic effects in trabeculae from human failing heart. (−)‐Noradrenaline reversed the negative diastolic effects, co‐administration may limit the titration of inotropes by reducing the threshold for ischemic side effects.
No related grants have been discovered for Peter Molenaar.