title: Voltage-gated calcium channel blockers deregulate macroautophagy in cardiomyocytes.
abstract: Voltage-gated calcium channel blockers are widely used for the management of cardiovascular diseases, however little is known about their effects on cardiac cells in vitro. We challenged neonatal ventricular cardiomyocytes (CMs) with therapeutic L-type and T-type Ca(2+) channel blockers (nifedipine and mibefradil, respectively), and measured their effects on cell stress and survival, using fluorescent microscopy, Q-PCR and Western blot. Both nifedipine and mibefradil induced a low-level and partially transient up-regulation of three key mediators of the Unfolded Protein Response (UPR), indicative of endoplasmic (ER) reticulum stress. Furthermore, nifedipine triggered the activation of macroautophagy, as evidenced by increased lipidation of microtubule-associated protein 1 light chain 3 (LC3), decreased levels of polyubiquitin-binding protein p62/SQSTM1 and ubiquitinated protein aggregates, that was followed by cell death. In contrast, mibefradil inhibited CMs constitutive macroautophagy and did not promote cell death. The siRNA-mediated gene silencing approach confirmed the pharmacological findings for T-type channels. We conclude that L-type and T-type Ca(2+) channel blockers induce ER stress, which is divergently transduced into macroautophagy induction and inhibition, respectively, with relevance for cell viability. Our work identifies VGCCs as novel regulators of autophagy in the heart muscle and provides new insights into the effects of VGCC blockers on CMs homeostasis, that may underlie both noxious and cardioprotective effects.
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Charumathi
authors.initials: C
authors.lastname: Pushparaj
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Arindam
authors.initials: A
authors.lastname: Das
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Purroy
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: Nàger
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Judit
authors.initials: J
authors.lastname: Herreros
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain.
authors.forename: Reinald
authors.initials: R
authors.lastname: Pamplona
authors.affiliation: Universitat de Lleida, Institut de Recerca Biomèdica de Lleida (IRBLleida), Spain. Electronic address: c.canti@mex.udl.cat.
authors.forename: Carles
authors.initials: C
authors.lastname: Cantí
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001343:Autophagy / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D005786:Gene Expression Regulation; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D020748:Mibefradil / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D000071456:Sequestosome-1 Protein; D015398:Signal Transduction; D019284:Thapsigargin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D020747:Calcium Channels, T-Type; D006360:Heat-Shock Proteins; D018942:Macrolides; D020748:Mibefradil; D008869:Microtubule-Associated Proteins; D009543:Nifedipine; D000071456:Sequestosome-1 Protein; D019284:Thapsigargin; C500994:Cacna1g protein, rat; C509958:Cacna1h protein, rat; C419385:L-type calcium channel alpha(1C); C526109:Anxa3 protein, rat; C491079:Sqstm1 protein, rat; C093712:Cacna1d protein, rat; C040929:bafilomycin A1
keywords: Autophagy; Calcium channel blockers; Cardiomyocytes; Pharmacology; Unfolded protein response