Abstract
Cardiac diseases persistently increase the contractility demands of cardiac myocytes, which require activation of the sympathetic nervous system and subsequent increases in myocyte Ca(2+) transients. Persistent exposure to sympathetic and/or Ca(2+) stress is associated with myocyte death. This study examined the respective roles of persistent beta-adrenergic receptor (beta-AR) agonist exposure and high Ca(2+) concentration in myocyte death. Ventricular myocytes (VMs) were isolated from transgenic (TG) mice with cardiac-specific and inducible expression of the beta(2a)-subunit of the L-type Ca(2+) channel (LTCC). VMs were cultured, and the rate of myocyte death was measured in the presence of isoproterenol (ISO), other modulators of Ca(2+) handling and the beta-adrenergic system, and inhibitors of caspases and reactive oxygen species generation. The rate of myocyte death was greater in TG vs. wild-type myocytes and accelerated by ISO in both groups, although ISO did not increase LTCC current (I(Ca-L)) in TG-VMs. Nifedipine, an LTCC antagonist, only partially prevented myocyte death. These results suggest both LTCC-dependent and -independent mechanisms in ISO induced myocyte death. ISO increased the contractility of wild type and TG-VMs by enhancing sarcoplasmic reticulum function and inhibiting sarco(endo)plasmic reticulum Ca(2+)-ATPase, Na(+)/Ca(2+) exchanger, and CaMKII partially protected myocyte from death induced by both Ca(2+) and ISO. Caspase and reactive oxygen species inhibitors did not, but beta(2)-AR activation did, reduce myocyte death induced by enhanced I(Ca-L) and ISO stimulation. Our results suggest that catecholamines induce myocyte necrosis primarily through beta(1)-AR-mediated increases in I(Ca-L), but other mechanisms are also involved in rodents.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Adrenergic beta-1 Receptor Agonists*
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Adrenergic beta-2 Receptor Agonists
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Adrenergic beta-Agonists / pharmacology*
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Animals
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Antioxidants / pharmacology
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Calcium Channel Blockers / pharmacology
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Calcium Channels, L-Type / drug effects*
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Calcium Channels, L-Type / genetics
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Calcium Channels, L-Type / metabolism
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Calcium Signaling / drug effects*
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / antagonists & inhibitors
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Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
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Caspase Inhibitors
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Caspases / metabolism
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Cell Survival / drug effects
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Cells, Cultured
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Cysteine Proteinase Inhibitors / pharmacology
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Isoproterenol / pharmacology*
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Membrane Potentials
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Mice
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Mice, Transgenic
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Myocardial Contraction / drug effects*
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Myocytes, Cardiac / drug effects*
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Myocytes, Cardiac / metabolism
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Myocytes, Cardiac / pathology
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Necrosis
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Protein Subunits
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Reactive Oxygen Species / metabolism
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Receptors, Adrenergic, beta-1 / metabolism
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Receptors, Adrenergic, beta-2 / metabolism
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Sarcoplasmic Reticulum / drug effects
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Sarcoplasmic Reticulum / metabolism
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Sarcoplasmic Reticulum Calcium-Transporting ATPases / antagonists & inhibitors
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Sarcoplasmic Reticulum Calcium-Transporting ATPases / metabolism
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Sodium-Calcium Exchanger / antagonists & inhibitors*
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Sodium-Calcium Exchanger / metabolism
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Time Factors
Substances
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Adrb1 protein, mouse
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Adrenergic beta-1 Receptor Agonists
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Adrenergic beta-2 Receptor Agonists
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Adrenergic beta-Agonists
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Antioxidants
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Calcium Channel Blockers
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Calcium Channels, L-Type
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors
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Protein Subunits
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Reactive Oxygen Species
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Receptors, Adrenergic, beta-1
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Receptors, Adrenergic, beta-2
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Sodium-Calcium Exchanger
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Calcium-Calmodulin-Dependent Protein Kinase Type 2
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Caspases
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Sarcoplasmic Reticulum Calcium-Transporting ATPases
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Isoproterenol