Reactive oxygen species contribute to the development of arrhythmogenic Ca2 waves during -adrenergic receptor stimulation in rabbit cardiomyocytes. Journal Article

Authors: Bovo, E; Lipsius, S. L.; Zima, A. V.
Article Title: Reactive oxygen species contribute to the development of arrhythmogenic Ca2 waves during -adrenergic receptor stimulation in rabbit cardiomyocytes.
Abstract: While -adrenergic receptor (-AR) stimulation leads to positive inotropic effects, it can also induce arrhythmogenic Ca2+ waves. -AR stimulation increases mitochondrial oxygen consumption and, thereby, the production of reactive oxygen species (ROS). We therefore investigated the role of ROS in the generation of Ca2+ waves during -AR stimulation in rabbit ventricular myocytes. Isoproterenol (ISO) increased Ca2+ transient amplitude during systole, sarcoplasmic reticulum (SR) Ca2+ load and the occurrence of Ca2+ waves during diastole. These effects, however, developed at different time points during ISO application.While SR Ca2+ release and load reached a maximum level after 3 min, Ca2+ waves occurred at the highest frequency only after 6 min of ISO application.Measurement of intra-SR-free Ca2+ concentration ([Ca2+]SR) showed an initial increase of SR Ca2+ load followed by a gradual decline over time during ISO application. This decline of [Ca2+]SR was not due to decreased SR Ca2+ uptake, but instead was the result of increased SRCa2+ leak mainly in the form of Ca2+ waves. ISO application led to significant RyR phosphorylation at the protein kinase A (PKA)-specific site, which remained relatively stable throughout -AR activation.Moreover, -AR stimulation significantly increased ROS production after 4-6 min of ISO application. The ROS scavenger Tiron and the superoxide dismutase mimetic MnTBPA abolished the ISO-mediated ROS production. The mitochondria-specific antioxidant Mito-Tempo and an inhibitor of the electron transport chain, rotenone, also effectively prevented the ISO-mediated ROS production. Scavenging ROS during ISO application decreased the occurrence of Ca2+ waves and partially prevented augmentation of SRCa2+ leak, but did not affect the increase of Ca2+ transient amplitude. Treatment of myocytes with ISO for 15 min significantly reduced the free thiol content in RyRs. These data suggest that increased mitochondrial ROS production during -AR stimulation causes RyR oxidation. Together with RyR phosphorylation, oxidation of RyRs increases diastolic SR Ca2+ leak to a critical level leading to the generation of arrhythmogenic Ca2+ waves.
Journal Title: Journal of Physiology
Volume: 590
Issue: Pt 14
ISSN: 0022-3751
Publisher: Unknown  
Journal Place: England
Date Published: 2012
Start Page: 3291
End Page: 3304
Language: English
Notes: ID: 12621; Status: MEDLINE; Publishing Model: Journal available in: Print-Electronic Citation processed from: Internet; NLM Journal Code: jqv, 0266262; Other ID: Source: NLM. PMC3459043