Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 2 de 2
Filter
Add more filters










Database
Language
Publication year range
1.
Circulation ; 142(2): 161-174, 2020 07 14.
Article in English | MEDLINE | ID: mdl-32264695

ABSTRACT

BACKGROUND: The cyclic AMP (adenosine monophosphate; cAMP)-hydrolyzing protein PDE4B (phosphodiesterase 4B) is a key negative regulator of cardiac ß-adrenergic receptor stimulation. PDE4B deficiency leads to abnormal Ca2+ handling and PDE4B is decreased in pressure overload hypertrophy, suggesting that increasing PDE4B in the heart is beneficial in heart failure. METHODS: We measured PDE4B expression in human cardiac tissues and developed 2 transgenic mouse lines with cardiomyocyte-specific overexpression of PDE4B and an adeno-associated virus serotype 9 encoding PDE4B. Myocardial structure and function were evaluated by echocardiography, ECG, and in Langendorff-perfused hearts. Also, cAMP and PKA (cAMP dependent protein kinase) activity were monitored by Förster resonance energy transfer, L-type Ca2+ current by whole-cell patch-clamp, and cardiomyocyte shortening and Ca2+ transients with an Ionoptix system. Heart failure was induced by 2 weeks infusion of isoproterenol or transverse aortic constriction. Cardiac remodeling was evaluated by serial echocardiography, morphometric analysis, and histology. RESULTS: PDE4B protein was decreased in human failing hearts. The first PDE4B-transgenic mouse line (TG15) had a ≈15-fold increase in cardiac cAMP-PDE activity and a ≈30% decrease in cAMP content and fractional shortening associated with a mild cardiac hypertrophy that resorbed with age. Basal ex vivo myocardial function was unchanged, but ß-adrenergic receptor stimulation of cardiac inotropy, cAMP, PKA, L-type Ca2+ current, Ca2+ transients, and cell contraction were blunted. Endurance capacity and life expectancy were normal. Moreover, these mice were protected from systolic dysfunction, hypertrophy, lung congestion, and fibrosis induced by chronic isoproterenol treatment. In the second PDE4B-transgenic mouse line (TG50), markedly higher PDE4B overexpression, resulting in a ≈50-fold increase in cardiac cAMP-PDE activity caused a ≈50% decrease in fractional shortening, hypertrophy, dilatation, and premature death. In contrast, mice injected with adeno-associated virus serotype 9 encoding PDE4B (1012 viral particles/mouse) had a ≈50% increase in cardiac cAMP-PDE activity, which did not modify basal cardiac function but efficiently prevented systolic dysfunction, apoptosis, and fibrosis, while attenuating hypertrophy induced by chronic isoproterenol infusion. Similarly, adeno-associated virus serotype 9 encoding PDE4B slowed contractile deterioration, attenuated hypertrophy and lung congestion, and prevented apoptosis and fibrotic remodeling in transverse aortic constriction. CONCLUSIONS: Our results indicate that a moderate increase in PDE4B is cardioprotective and suggest that cardiac gene therapy with PDE4B might constitute a new promising approach to treat heart failure.


Subject(s)
Cyclic Nucleotide Phosphodiesterases, Type 4/genetics , Gene Expression , Heart Failure/etiology , Myocardium/metabolism , Ventricular Remodeling/genetics , Adrenergic beta-Agonists/pharmacology , Animals , Cyclic AMP/metabolism , Cyclic Nucleotide Phosphodiesterases, Type 4/metabolism , Disease Models, Animal , Disease Susceptibility , Genetic Therapy , Genetic Vectors/genetics , Heart Failure/diagnosis , Heart Failure/drug therapy , Heart Failure/metabolism , Heart Function Tests , Humans , Isoproterenol/pharmacology , Mice , Mice, Transgenic , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/metabolism , Phenotype , Receptors, Adrenergic, beta/metabolism , Transduction, Genetic , Ventricular Remodeling/drug effects
2.
Exp Physiol ; 104(8): 1237-1249, 2019 08.
Article in English | MEDLINE | ID: mdl-31116459

ABSTRACT

NEW FINDINGS: What 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)P2 ) 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)P2 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)P2 ) 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 ICa,L amplitude by ∼72%. These parameters were not affected in atrial cells, excluding direct side effects of imipramine. ß-Adrenergic receptor (ß-AR) stimulation of the remaining ICa,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 Ca2+ 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 Ca2+ homeostasis perturbations. Real-time cAMP variations induced by Iso using a Förster resonance energy transfer biosensor revealed ∼27% decreased cAMP elevation upon ß-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 ß-AR stimulation. Besides, we provide new insights on how an imipramine overdose may affect cardiac function and suggest that PI(4,5)P2 is crucial for maintaining T-tubule structure.


Subject(s)
Formamides/pharmacology , Heart Ventricles/drug effects , Imipramine/pharmacology , Myocytes, Cardiac/drug effects , Action Potentials/drug effects , Animals , Antidepressive Agents/pharmacology , Calcium/metabolism , Calcium Channels, L-Type/metabolism , Cell Membrane/drug effects , Cell Membrane/metabolism , Excitation Contraction Coupling/drug effects , Heart Atria/drug effects , Heart Atria/metabolism , Heart Ventricles/metabolism , Isoproterenol/pharmacology , Male , Myocardial Contraction/drug effects , Myocytes, Cardiac/metabolism , Rats , Rats, Wistar , Sarcomeres/drug effects , Sarcomeres/metabolism
SELECTION OF CITATIONS
SEARCH DETAIL
...