Journal
CARDIOVASCULAR RESEARCH
Volume 77, Issue 2, Pages 432-441Publisher
ELSEVIER SCIENCE BV
DOI: 10.1093/cvr/cvm047
Keywords
reactive oxygen species (ROS); Ca2+ sparks; oxidative stress; cardiac myocytes; mitochondria
Categories
Ask authors/readers for more resources
Aims The cardiac ryanodine receptor (RyR) Ca2+ release channel homotetramer harbours similar to 21 potentially redox-sensitive cysteine residues on each subunit and may act as a sensor for reactive oxygen species (ROS), linking ROS homeostasis to the regulation of Ca2+ signalling. In cardiac myocytes, arrayed RyRs or Ca2+ release units are packed in the close proximity of mitochondria, the primary source of intracellular ROS production. The present study investigated whether and how mitochondria-derived ROS regulate Ca2+ spark activity in intact cardiac myocytes. Methods and results Bidirectional manipulation of mitochondrial ROS production in intact rat cardiac myocytes was achieved by photostimulation and pharmacological means. Simultaneous measurement of intracellular ROS and Ca2+ signals was performed using confocal microscopy in conjunction with the indicators 5-(-6)-chtoromethyl-2',7'-dichlorodihydrofluorescein diacetate (for ROS) and rhod-2 (for Ca2+). Photoactivated or antimycin A (AA, 5 mu g/mL)-induced mitochondrial ROS production elicited a transient increase in Ca2+ spark activity, followed by gradual spark suppression. Intriguingly, photo-activated mitochondrial ROS oscillations subsequent to the initial peaks mirrored phasic depressions of the spark activity, suggesting a switch of ROS modulation from spark-activating to spark-suppressing. Partial deletion of Ca2+ stores in the sarcoplasmic reticulum contributed in part to the gradual, but not the phasic, spark depression. H2O2 at 200 mu M elicited a bidirectional effect on sparks and produced sustained spark activation at 50 mu M. Lowering basal mitochondrial ROS production, scavenging baseline ROS, and applying the sulphydryl-reducing agent dithiothreitol diminished the incidence of spontaneous Ca2+ sparks and abolished the Ca2+ spark responses to mitochondrial ROS. Conclusion Mitochondrial ROS exert bidirectional regulation of Ca2+ sparks in a dose- and time (history)dependent manner, and basal ROS constitute a hitherto unappreciated determinant for the production of spontaneous Ca2+ sparks. As such, ROS signalling may play an important rote in Ca2+ homeostasis as well as Ca2+ dysregulation in oxidative stress-related diseases.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available