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ORIGINAL RESEARCH article

Front. Physiol.
Sec. Striated Muscle Physiology
Volume 15 - 2024 | doi: 10.3389/fphys.2024.1489439
This article is part of the Research Topic Physiology of Human Myopathies View all 4 articles

Nutraceuticals Silybin B, resveratrol, and epigallocatechin-3 gallate (EGCG) bind to cardiac muscle troponin to restore the loss of lusitropy caused by cardiomyopathy mutations in vitro, in vivo, and in silico

Provisionally accepted
Zeyu Yang Zeyu Yang 1Alice Sheehan Alice Sheehan 1Andrew E. Messer Andrew E. Messer 1Sharmane Tsui Sharmane Tsui 1Alexander Sparrow Alexander Sparrow 2Charles Redwood Charles Redwood 2Vladimir Kren Vladimir Kren 3Ian R. Gould Ian R. Gould 1Steven B. Marston Steven B. Marston 1*
  • 1 Imperial College London, London, United Kingdom
  • 2 University of Oxford, Oxford, England, United Kingdom
  • 3 Academy of Sciences of the Czech Republic (ASCR), Prague, Prague, Czechia

The final, formatted version of the article will be published soon.

    Cardiac muscle possesses a unique modulatory mechanism that allows the heart to meet increased oxygen demand during exercise. Adrenergic activation of protein kinase A (PKA) targets the sarcolemma, sarcoplasmic reticulum, and contractile apparatus to increase contractile force and heart rate. In the thin filaments of the contractile apparatus, cardiac troponin I (cTnI) Ser22 and Ser23 in the cardiacspecific N-terminal peptide (NcTnI: residues 1 to 32) are the targets for PKA phosphorylation. The effect of phosphorylation is a 2-3 fold decrease of affinity of cTn for Ca 2+ due to altered cTnC-cTnI interactions, associated with a higher rate of Ca 2+ dissociation from cTnC leading to a faster relaxation rate of the cardiac muscle (lusitropy).Cardiomyopathy-linked mutations primarily affect Ca 2+ regulation or the PKAdependent modulatory system, such that Ca 2+ -sensitivity becomes independent of phosphorylation level (uncoupling) and this could be sufficient to induce cardiomyopathy.A drug that could restore the phosphorylation-dependent modulation of Ca 2+sensitivity could have potential for treatment of these pathologies. We have found that a number of small molecules, including silybin B, resveratrol and EGCG, can restore coupling in single filament assays.We did molecular dynamics simulations of the unphosphorylated and phosphorylated cardiac troponin core with the G159D DCM mutation. We found that silybin B, EGCG and resveratrol restored the phosphorylation-induced change in most metrics to wildtype values, whilst silybin A, an inactive isomer of silybin B, did not. We analysed the atomic-level changes induced by ligand binding to explain recoupling.In parallel, we have extended our in vitro and in silico studies to intact cardiomyocytes. Mutations that uncouple in vitro blunt the increased relaxation speed response to β1 adrenergic stimulation and we found that resveratrol, EGCG and silybin B could restore the β1 adrenergic response, whereas silybin A does not.The changes induced by small molecules are all consistent between various measurement techniques from the atomic to the cellular level.

    Keywords: cardiomyopathy, Lusitropy, PKA phosphorylation, troponin (cTnI), Myocyte contraction, molecular dynamics simulation, EGCG, silybin

    Received: 01 Sep 2024; Accepted: 06 Nov 2024.

    Copyright: © 2024 Yang, Sheehan, Messer, Tsui, Sparrow, Redwood, Kren, Gould and Marston. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Steven B. Marston, Imperial College London, London, United Kingdom

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