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Front. Physiol. | doi: 10.3389/fphys.2018.00126

Localization and Expression of Nuclear Factor of Activated T-cells 5 in Myoblasts Exposed to Pro-inflammatory Cytokines or Hyperosmolar Stress and in Biopsies from Myositis Patients

 Sandrine Herbelet1*,  Elly De Vlieghere1, Amanda Gonçalves2,  Boel De Paepe1, Karsten Schmidt3, Eline Nys1, Laurens Weynants1,  Joachim Weis4, Gert Van Peer1,  Jo Vandesompele1,  Jens Schmidt3,  Olivier De Wever1 and  Jan L. De Bleecker1
  • 1Ghent University, Belgium
  • 2Flanders Institute for Biotechnology, Belgium
  • 3Universitätsmedizin Göttingen, Germany
  • 4Uniklinik RWTH Aachen, Germany

Aims: Regeneration in skeletal muscle relies on regulated myoblast migration and differentiation, in which the transcription factor nuclear factor of activated T-cells 5 (NFAT5) participates. Impaired muscle regeneration and chronic inflammation are prevalent in myositis. Little is known about the impact of inflammation on NFAT5 localization and expression in this group of diseases. The goal of this study was to investigate NFAT5 physiology in unaffected myoblasts exposed to cytokine or hyperosmolar stress and in myositis. Methods: NFAT5 intracellular localization and expression were studied in vitro using a cell culture model of myositis. Myoblasts were exposed to DMEM solutions enriched with pro-inflammatory cytokines IFN-γ with IL-1β or hyperosmolar DMEM obtained by NaCl supplementation. NFAT5 localization was visualized using immunohistochemistry (IHC) and Western blotting (WB) in fractionated cell lysates. NFAT5 expression was assessed by WB and RT-qPCR. In vivo localization and expression of NFAT5 were studied in muscle biopsies of patients diagnosed with polymyositis (n=6), dermatomyositis (n=10), inclusion body myositis (n=11) and were compared to NFAT5 localization and expression in non-myopathic controls (n=13). Muscle biopsies were studied by means of quantitative IHC and WB of total protein extracts. Results: In unaffected myoblasts, hyperosmolar stress ensues in NFAT5 nuclear translocation and increased NFAT5 mRNA and protein expression. In contrast, pro-inflammatory cytokines did not lead to NFAT5 nuclear translocation nor increased expression. Cytokines IL-1β with IFN-γ induced colocalization of NFAT5 with histone deacetylase 6 (HDAC6), involved in cell motility. In muscle biopsies from dermatomyositis and polymyositis patients, NFAT5 colocalized with HDAC6, while in IBM, this was often absent. Conclusions: Our data suggest impaired NFAT5 localization and expression in unaffected myoblasts in response to inflammation. This disturbed myogenic NFAT5 physiology could possibly explain deleterious effects on muscle regeneration in myositis.

Keywords: NFAT5, Myoblasts, Pro-inflammatory cytokines, hyperosmolar stress, Myositis

Received: 12 Oct 2017; Accepted: 07 Feb 2018.

Edited by:

Dario Coletti, Sapienza Università di Roma, Italy

Reviewed by:

Kunihiro Sakuma, Tokyo Institute of Technology, Japan
Nissrine Daou, Université Pierre et Marie Curie, France  

Copyright: © 2018 Herbelet, De Vlieghere, Gonçalves, De Paepe, Schmidt, Nys, Weynants, Weis, Van Peer, Vandesompele, Schmidt, De Wever and De Bleecker. 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) and the copyright owner 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: DVM. Sandrine Herbelet, HERBELET., Ghent University, De Pintelaan 185, Ghent, 9000, Please Select, Belgium, Sandrine.Herbelet@UGent.be