Voltage-gated calcium channel blockers deregulate macroautophagy in cardiomyocytes

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• 作者：Charumathi Pushparaj ; Arindam Das ; Rosa Purroy ; Mireia Nà ; ger ; Judit Herreros ; Reinald Pamplona ; Carles Cantí ; ; ^{c.canti@mex.udl.cat" class="auth_mail" title="E-mail the corresponding author}
• 关键词：ER ; endoplasmic reticulum ; SERCA ; sarco/endoplasmic reticulum Ca2+-ATPase ; E&ndash ; C ; excitation&ndash ; contraction ; VGCCs ; voltage-gated calcium channels ; CMs ; cardiac myocytes ; UPR ; unfolded protein response ; MDC ; monodansylcadaverine ; LR ; lysotracker red ; GADD153/CHOP ; CEBP-homologous protein ; GRP78/BIP ; 78 kDa glucose-regulated protein ; XBP-1 ; XhoI site&ndash ; binding protein 1 ; Atg ; autophagy related gene ; LC3 ; microtubule-associated protein1 light chain 3 ; p62 ; polyubiquitin-binding protein
• 刊名：International Journal of Biochemistry and Cell Biology
• 出版年：2015
• 出版时间：November 2015
• 年：2015
• 卷：68
• 期：Complete
• 页码：166-175
• 全文大小：1662 K

文摘

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 Ca²⁺ 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 Ca²⁺ 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.