Background and purpose: Tiotropium bromide (TB) is a long acting muscarinic receptor antagonist used to manage chronic obstructive pulmonary disease (COPD). Recent meta-analyses suggest an increased risk of cardiovascular events with TB. Ca2+/calmodulin dependent kinase II (CaMKII) and L-type Ca2+ channels regulate Ca2+ concentrations allowing management of Ca2+ across membranes. Pathological increases in Ca2+ are initially slow and progressive, however once the cytosolic concentration rises >1–3 μM from ~100 nM, calcium overload occurs and can lead to cell death. Ipratropium bromide, a short acting muscarinic receptor antagonist has previously been found to induce Ca2+ mediated eryptosis. The aim of this study was to investigate the role of Ca2+ in Tiotropium bromide mediated cardiotoxicity. Experimental approach: Isolated Sprague-Dawley rat hearts were perfused with TB (10–0.1 nM) ± KN-93 (400 nM) or nifedipine (1 nM). Hearts were stained to determine infarct size (%) using triphenyltetrazolium chloride (TTC), or snap frozen to determine p-CaMKII (Thr286) expression. Cardiomyocytes were isolated using a modified Langendorff perfusion and enzymatic dissociation before preparation for Fluo 3-AM staining and flow cytometric analysis. Key results: TB increased infarct size compared to controls by 6.91–8.41%, with no effect on haemodynamic function. KN-93/nifedipine with TB showed a 5.90/7.38% decrease in infarct size compared to TB alone, the combined use of KN-93 with TB also showed a significant increase in left ventricular developed pressure whilst nifedipine with TB showed a significant decrease in coronary flow. TB showed a 42.73% increase in p-CaMKII (Thr286) versus control, and increased Ca2+ fluorescence by 30.63% in cardiomyocytes. Conclusions and implications: To our knowledge, this is the first pre-clinical study to show that Tiotropium bromide induces Ca2+ signalling via CaMKII and L-type Ca2+ channels to result in cell damage. This has significant clinical impact due to long term use of TB in COPD patients, and warrants assessment of cardiac drug safety.
Bibliographical noteNOTICE: this is the author’s version of a work that was accepted for publication in Toxicology and Applied Pharmacology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Toxicology and Applied Pharmacology, 384, (2019)DOI: 10.1016/j.taap.2019.114778
© 2019, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/10.1016/j.taap.2019.114778
- Long acting muscarinic receptor antagonist
- Tiotropium bromide
- Ca2+/Calmodulin Kinase II (CaMKII)
ASJC Scopus subject areas