title: Mitochondrial production of reactive oxygen species contributes to the β-adrenergic stimulation of mouse cardiomycytes.
abstract: The sympathetic adrenergic system plays a central role in stress signalling and stress is often associated with increased production of reactive oxygen species (ROS). Furthermore, the sympathetic adrenergic system is intimately involved in the regulation of cardiomyocyte Ca2+ handling and contractility. In this study we hypothesize that endogenously produced ROS contribute to the inotropic mechanism of β-adrenergic stimulation in mouse cardiomyocytes. Cytoplasmic Ca2+ transients, cell shortening and ROS production were measured in freshly isolated cardiomyocytes using confocal microscopy and fluorescent indicators. As a marker of oxidative stress, malondialdehyde (MDA) modification of proteins was detected with Western blotting. Isoproterenol (ISO), a β-adrenergic agonist, increased mitochondrial ROS production in cardiomyocytes in a concentration- and cAMP–protein kinase A-dependent but Ca2+-independent manner. Hearts perfused with ISO showed a twofold increase in MDA protein adducts relative to control. ISO increased Ca2+ transient amplitude, contraction and L-type Ca2+ current densities (measured with whole-cell patch-clamp) in cardiomyocytes and these increases were diminished by application of the general antioxidant N-acetylcysteine (NAC) or the mitochondria-targeted antioxidant SS31. In conclusion, increased mitochondrial ROS production plays an integral role in the acute inotropic response of cardiomyocytes to β-adrenergic stimulation. On the other hand, chronically sustained adrenergic stress is associated with the development of heart failure and cardiac arrhythmias and prolonged increases in ROS may contribute to these defects.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, 171 77 Stockholm, Sweden.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Andersson
authors.forename: Jérémy
authors.initials: J
authors.lastname: Fauconnier
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamada
authors.forename: Alain
authors.initials: A
authors.lastname: Lacampagne
authors.forename: Shi-Jin
authors.initials: SJ
authors.lastname: Zhang
authors.forename: Abram
authors.initials: A
authors.lastname: Katz
authors.forename: Håkan
authors.initials: H
authors.lastname: Westerblad
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008810:Mice, Inbred C57BL; D008929:Mitochondria, Heart / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques; D017382:Reactive Oxygen Species / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
chemical_list: D000318:Adrenergic beta-Agonists; D000975:Antioxidants; D017382:Reactive Oxygen Species; D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol; D000111:Acetylcysteine