Altered ROS production, NF-κB activation and interleukin-6 gene expression induced by electrical stimulation in dystrophic mdx skeletal muscle cells

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningfagfællebedømt

Duchenne muscular dystrophy is a fatal X-linked genetic disease, caused by mutations in the dystrophin gene, which cause functional loss of this protein. This pathology is associated with an increased production of reactive oxygen (ROS) and nitrogen species. The aim of this work was to study the alterations in NF-κB activation and interleukin-6 (IL-6) expression induced by membrane depolarization in dystrophic mdx myotubes. Membrane depolarization elicited by electrical stimulation increased p65 phosphorylation, NF-κB transcriptional activity and NF-κB-dependent IL-6 expression in wt myotubes, whereas in mdx myotubes it had the opposite effect. We have previously shown that depolarization-induced intracellular Ca2+ increases and ROS production are necessary for NF-κB activation and stimulation of gene expression in wt myotubes. Dystrophic myotubes showed a reduced amplitude and area under the curve of the Ca2+ transient elicited by electrical stimulation. On the other hand, electrical stimuli induced higher ROS production in mdx than wt myotubes, which were blocked by NOX2 inhibitors. Moreover, mRNA expression and protein levels of the NADPH oxidase subunits: p47phox and gp91phox were increased in mdx myotubes. Looking at ROS-dependence of NF-κB activation we found that in wt myotubes external administration of 50μM H2O2 increased NF-κB activity; after administration of 100 and 200μM H2O2 there was no effect. In mdx myotubes there was a dose-dependent reduction in NF-κB activity in response to external administration of H2O2, with a significant effect of 100μM and 200μM, suggesting that ROS levels are critical for NF-κB activity. Prior blockage with NOX2 inhibitors blunted the effects of electrical stimuli in both NF-κB activation and IL-6 expression. Finally, to ascertain whether stimulation of NF-κB and IL-6 gene expression by the inflammatory pathway is also impaired in mdx myotubes, we studied the effect of lipopolysaccharide on both NF-κB activation and IL-6 expression. Exposure to lipopolysaccharide induced a dramatic increase in both NF-κB activation and IL-6 expression in both wt and mdx myotubes, suggesting that the altered IL-6 gene expression after electrical stimulation in mdx muscle cells is due to dysregulation of Ca2+ release and ROS production, both of which impinge on NF-κB signaling. IL-6 is a key metabolic modulator that is released by the skeletal muscle to coordinate a multi-systemic response (liver, muscle, and adipocytes) during physical exercise; the alteration of this response in dystrophic muscles may contribute to an abnormal response to contraction and exercise.

OriginalsprogEngelsk
TidsskriftBiochimica et Biophysica Acta - Molecular Basis of Disease
Vol/bind1852
Udgave nummer7
Sider (fra-til)1410-1419
Antal sider10
ISSN0925-4439
DOI
StatusUdgivet - 2015
Eksternt udgivetJa

Bibliografisk note

(Ekstern)
Funding Information:
This work was supported by FONDECYT 1110467 (EJ) and ACT1111 (EJ) and FONDECYT 3140491 (DV). Research reported in this publication was supported in part by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Number AR43140 and AR052534 (JRL and PDA). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

Publisher Copyright:
© 2015 .

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