Cadmium nanoparticles citrullinate cytokeratins within lung epithelial cells: cadmium as a potential cause of citrullination in chronic obstructive pulmonary disease
Received 19 September 2017
Accepted for publication 11 December 2017
Published 31 January 2018 Volume 2018:13 Pages 441—449
Checked for plagiarism Yes
Review by Single-blind
Peer reviewers approved by Dr Charles Downs
Peer reviewer comments 3
Editor who approved publication: Dr Richard Russell
David Hutchinson,1,2 Judith Müller,3 Joseph E McCarthy,4 Yurii K Gun’ko,4,5 Navin Kumar Verma,6 Xuezhi Bi,7 Luisana Di Cristo,8 Laura Kickham,8 Dania Movia,8 Adriele Prina-Mello,5,8 Yuri Volkov5,8,9
1Royal Cornwall Hospital NHS Trust, Treliske, 2University of Exeter Medical School Cornwall, UK; 3University of Basel, Basel, Switzerland; 4School of Chemistry, 5Advanced Materials for BioEngineering Research Centre (AMBER), Trinity College Dublin, Dublin, Ireland; 6Lee Kong Chian School of Medicine, Nanyang Technological University, 7Bioprocessing Technology Institute, A*STAR Graduate Academy, Singapore; 8Department of Clinical Medicine, School of Medicine, Trinity College Dublin, Dublin, Ireland; 9International Laboratory of Magnetically Controlled Nanosystems for Theranostics of Oncological and Cardiovascular Diseases, ITMO University, St. Petersburg, Russia
Objective: The objective of the study was to determine whether the cadmium-derived materials induce intracellular protein citrullination.
Methods: Human A549 lung epithelial cells were exposed to cadmium in soluble and nanoparticulate forms represented by cadmium chloride (CdCl2) and cadmium oxide (CdO), respectively, and their combinations with ultrafine carbon black (ufCB) produced by high temperature combustion, imitating cigarette burning. Protein citrullination in cell lysates was analyzed by Western immunoblotting and verified by immunofluorescent confocal microscopy. Target citrullinated proteins were identified by proteomic analysis.
Results: CdO, ufCB and its combination with CdCl2 and CdO after high temperature combustion induced protein citrullination in cultured human lung epithelial cells, as detected by immunoblotting with anti-citrullinated protein antibody. Cytokeratins of type II (1, 2, 5, 6A, 6B and 77) and type I (9, 10) were identified as major intracellular citrullination targets. Immunofluorescent staining confirmed the localization of citrullinated proteins both in the cytoplasm and cell nuclei.
Conclusion: Cadmium oxide nanoparticle exposure facilitated post-translational citrullination of proteins.
Keywords: cadmium, COPD, nanoparticles, cytokeratins, citrullination, autoimmunity, proteomics
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