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Imipramine as an alternative to formamide to detubulate rat ventricular cardiomyocytes
Author(s) -
Bourcier Aurelia,
Barthe Marion,
Bedioune Ibrahim,
Lechêne Patrick,
Miled Hela Ben,
Vandecasteele Grégoire,
Fischmeister Rodolphe,
Leroy Jérôme
Publication year - 2019
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep087760
Subject(s) - imipramine , chemistry , pharmacology , myocyte , biophysics , medicine , biology , alternative medicine , pathology
New FindingsWhat is the central question of this study? Can imipramine, an antidepressant agent that is a cationic amphiphilic drug that interferes with the phosphatidylinositol 4,5‐bisphosphate (PI(4,5)P 2 ) interactions with proteins maintaining the tubular system, be validated as a new detubulating tool?What is the main finding and its importance? Imipramine was validated as a more efficient and less toxic detubulating agent of cardiomyocytes than formamide. New insights are provided on how PI(4,5)P 2 is crucial to maintaining T‐tubule attachment to the cell surface and on the cardiotoxic effects of imipramine overdoses.Abstract Cardiac T‐tubules are membrane invaginations essential for excitation–contraction coupling (ECC). Imipramine, like other cationic amphiphilic drugs, interferes with phosphatidylinositol 4,5‐bisphosphate (PI(4,5)P 2 ) interactions with proteins maintaining the tubular system connected to the cell surface. Our main purpose was to validate imipramine as a new detubulating agent in cardiomyocytes. Staining adult rat ventricular myocytes (ARVMs) with di‐4‐ANEPPS, we showed that unlike formamide, imipramine induces a complete detubulation with no impact on cell viability. Using the patch‐clamp technique, we observed a ∼40% decrease in cell capacitance after imipramine pretreatment and a reduction of I Ca,L amplitude by ∼72%. These parameters were not affected in atrial cells, excluding direct side effects of imipramine. β‐Adrenergic receptor (β‐AR) stimulation of the remaining I Ca,L with isoproterenol (Iso) was still effective. ECC was investigated in ARVMs loaded with Fura‐2 and paced at 1 Hz, allowing simultaneous measurement of the Ca 2+ transient (CaT) and sarcomere shortening (SS). Amplitude of both CaT and SS was decreased by imipramine and partially restored by Iso. Furthermore, detubulated cells exhibited Ca 2+ homeostasis perturbations. Real‐time cAMP variations induced by Iso using a Förster resonance energy transfer biosensor revealed ∼27% decreased cAMP elevation upon β‐AR stimulation. To conclude, we validated a new cardiomyocyte detubulation method using imipramine, which is more efficient and less toxic than formamide. This antidepressant agent induces the hallmark effects of detubulation on ECC and its β‐AR stimulation. Besides, we provide new insights on how an imipramine overdose may affect cardiac function and suggest that PI(4,5)P 2 is crucial for maintaining T‐tubule structure.