Dataset Information

Fast skeletal muscle troponin activator CK-2066260 mitigates skeletal muscle weakness independently of the underlying cause.

ABSTRACT:

Background

Muscle weakness is a common symptom in numerous diseases and a regularly occurring problem associated with ageing. Prolonged low-frequency force depression (PLFFD) is a form of exercise-induced skeletal muscle weakness observed after exercise. Three different intramuscular mechanisms underlying PLFFD have been identified: decreased sarcoplasmic reticulum Ca²⁺ release, decreased myofibrillar Ca²⁺ sensitivity, and myofibrillar dysfunction. We here used these three forms of PLFFD as models to study the effectiveness of a fast skeletal muscle troponin activator, CK-2066260, to mitigate muscle weakness.

Methods

Experiments were performed on intact single muscle fibres or fibre bundles from mouse flexor digitorum brevis, which were stimulated with electrical current pulses, while force and the free cytosolic [Ca²⁺ ] ([Ca²⁺ ]_i ) were measured. PLFFD was induced by three different stimulation protocols: (i) repeated isometric contractions at low intensity (350 ms tetani given every 5 s for 100 contractions); (ii) repeated isometric contractions at high intensity (250 ms tetani given every 0.5 s for 300 contractions); and (iii) repeated eccentric contractions (350 ms tetani with 20% length increase given every 20 s for 10 contractions). The extent and cause of PLFFD were assessed by comparing the force-[Ca²⁺ ]_i relationship at low (30 Hz) and high (120 Hz) stimulation frequencies before (control) and 30 min after induction of PLFFD, and after an additional 5 min of rest in the presence of CK-2066260 (10 ?M).

Results

Prolonged low-frequency force depression following low-intensity and high-intensity fatiguing contractions was predominantly due to decreased sarcoplasmic reticulum Ca²⁺ release and decreased myofibrillar Ca²⁺ sensitivity, respectively. CK-2066260 exposure resulted in marked increases in 30 Hz force from 52 ± 16% to 151 ± 13% and from 6 ± 4% to 98 ± 40% of controls with low-intensity and high-intensity contractions, respectively. Following repeated eccentric contractions, PLFFD was mainly due to myofibrillar dysfunction, and it was not fully reversed by CK-2066260 with 30 Hz force increasing from 48 ± 8% to 76 ± 6% of the control.

Conclusions

The fast skeletal muscle troponin activator CK-2066260 effectively mitigates muscle weakness, especially when it is caused by impaired activation of the myofibrillar contractile machinery due to either decreased sarcoplasmic reticulum Ca²⁺ release or reduced myofibrillar Ca²⁺ sensitivity.

SUBMITTER: Cheng AJ

PROVIDER: S-EPMC7749611 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Publications

Fast skeletal muscle troponin activator CK-2066260 mitigates skeletal muscle weakness independently of the underlying cause.

Cheng Arthur J AJ Ström Jennifer J Hwee Darren T DT Malik Fady I FI Westerblad Håkan H

Journal of cachexia, sarcopenia and muscle 20200921 6

<h4>Background</h4>Muscle weakness is a common symptom in numerous diseases and a regularly occurring problem associated with ageing. Prolonged low-frequency force depression (PLFFD) is a form of exercise-induced skeletal muscle weakness observed after exercise. Three different intramuscular mechanisms underlying PLFFD have been identified: decreased sarcoplasmic reticulum Ca<sup>2+</sup> release, decreased myofibrillar Ca<sup>2+</sup> sensitivity, and myofibrillar dysfunction. We here used thes ...[more]

PMID: 32954682

Similar Datasets

Project description:BackgroundAgeing skeletal muscle undergoes chronic denervation, and the neuromuscular junction (NMJ), the key structure that connects motor neuron nerves with muscle cells, shows increased defects with ageing. Previous studies in various species have shown that with ageing, type II fast-twitch skeletal muscle fibres show more atrophy and NMJ deterioration than type I slow-twitch fibres. However, how this process is regulated is largely unknown. A better understanding of the mechanisms regulating skeletal muscle fibre-type specific denervation at the NMJ could be critical to identifying novel treatments for sarcopenia. Cardiac troponin T (cTnT), the heart muscle-specific isoform of TnT, is a key component of the mechanisms of muscle contraction. It is expressed in skeletal muscle during early development, after acute sciatic nerve denervation, in various neuromuscular diseases and possibly in ageing muscle. Yet the subcellular localization and function of cTnT in skeletal muscle is largely unknown.MethodsStudies were carried out on isolated skeletal muscles from mice, vervet monkeys, and humans. Immunoblotting, immunoprecipitation, and mass spectrometry were used to analyse protein expression, real-time reverse transcription polymerase chain reaction was used to measure gene expression, immunofluorescence staining was performed for subcellular distribution assay of proteins, and electromyographic recording was used to analyse neurotransmission at the NMJ.ResultsLevels of cTnT expression in skeletal muscle increased with ageing in mice. In addition, cTnT was highly enriched at the NMJ region-but mainly in the fast-twitch, not the slow-twitch, muscle of old mice. We further found that the protein kinase A (PKA) RIα subunit was largely removed from, while PKA RIIα and RIIβ are enriched at, the NMJ-again, preferentially in fast-twitch but not slow-twitch muscle in old mice. Knocking down cTnT in fast skeletal muscle of old mice: (i) increased PKA RIα and reduced PKA RIIα at the NMJ; (ii) decreased the levels of gene expression of muscle denervation markers; and (iii) enhanced neurotransmission efficiency at NMJ.ConclusionsCardiac troponin T at the NMJ region contributes to NMJ functional decline with ageing mainly in the fast-twitch skeletal muscle through interfering with PKA signalling. This knowledge could inform useful targets for prevention and therapy of age-related decline in muscle function.

Dataset Information

Fast skeletal muscle troponin activator CK-2066260 mitigates skeletal muscle weakness independently of the underlying cause.

Background

Methods

Results

Conclusions

Publications

Fast skeletal muscle troponin activator CK-2066260 mitigates skeletal muscle weakness independently of the underlying cause.

Similar Datasets

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