Aberrant S-nitrosylation mediates calcium-triggered ventricular arrhythmia in the intact heart.
Nitric oxide (NO) derived from the activity of neuronal nitric oxide synthase (NOS1) is involved in S-nitrosylation of key sarcoplasmic reticulum (SR) Ca(2+) handling proteins. Deficient S-nitrosylation of the cardiac ryanodine receptor (RyR2) has a variable effect on SR Ca(2+) leak/sparks in isolated myocytes, likely dependent on the underlying physiological state. It remains unknown, however, whether such molecular aberrancies are causally related to arrhythmogenesis in the intact heart. Here we show in the intact heart, reduced NOS1 activity increased Ca(2+)-mediated ventricular arrhythmias only in the setting of elevated myocardial [Ca(2+)](i). These arrhythmias arose from increased spontaneous SR Ca(2+) release, resulting from a combination of decreased RyR2 S-nitrosylation (RyR2-SNO) and increased RyR2 oxidation (RyR-SOx) (i.e., increased reactive oxygen species (ROS) from xanthine oxidoreductase activity) and could be suppressed with xanthine oxidoreductase (XOR) inhibition (i.e., allopurinol) or nitric oxide donors (i.e., S-nitrosoglutathione, GSNO). Surprisingly, we found evidence of NOS1 down-regulation of RyR2 phosphorylation at the Ca(2+)/calmodulin-dependent protein kinase (CaMKII) site (S2814), suggesting molecular cross-talk between nitrosylation and phosphorylation of RyR2. Finally, we show that nitroso-redox imbalance due to decreased NOS1 activity sensitizes RyR2 to a severe arrhythmic phenotype by oxidative stress. Our findings suggest that nitroso-redox imbalance is an important mechanism of ventricular arrhythmias in the intact heart under disease conditions (i.e., elevated [Ca(2+)](i) and oxidative stress), and that therapies restoring nitroso-redox balance in the heart could prevent sudden arrhythmic death.
Heart and Vascular Research Center, MetroHealth Campus of Case Western Reserve University, Cleveland, OH 44109, USA.
Michael J
MJ
Cutler
Bradley N
BN
Plummer
Xiaoping
X
Wan
Qi-An
QA
Sun
Douglas
D
Hess
Haiyan
H
Liu
Isabelle
I
Deschenes
David S
DS
Rosenbaum
Jonathan S
JS
Stamler
Kenneth R
KR
Laurita
D000818:Animals; D001145:Arrhythmias, Cardiac / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D006168:Guinea Pigs; D009206:Myocardium / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors; D009603:Nitroso Compounds / Q000378:metabolism*; D018384:Oxidative Stress; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism
D009603:Nitroso Compounds; D019837:Ryanodine Receptor Calcium Release Channel; D052248:Nitric Oxide Synthase Type I; D002118:Calcium