Abstract 105: The nitroso-redox-induced SR Ca2+ leak is temperature-sensitive: Role of Nitric Oxide Synthase 1
Sarcomeric reticulum (SR) Ca2+ leak contributes to an impaired Ca2+ cycling and contractile dysfunction of the heart. Leak is thought to be regulated by post-translational modifications of RyR2 associated with nitroso-redox (NO/redox) imbalance. Ca2+ cycling is affected by both NO signaling and temperature.
We hypothesized that NO/redox balance modulates SR Ca2+ leak in a temperature–dependent manner.
We used tetracaine to investigate SR Ca2+ leak in cardiomyocytes (CMs) using a model of NO/redox imbalance (NOS1−/− mice) or WT mice. Reactive oxygen species (ROS) were measured by H2DCF. The expression of NOS isoforms was assessed by real time PCR. Experiments were carried out at 23°C - 37°C.
The SR Ca2+ leak increased as the temperature decreased from 34°C to 23°C in WT CMs whereas, in NOS1−/− CMs, the leak suddenly increased when the temperature surpassed 30°C (Fig. A). SR Ca2+ content in NOS1−/− CMs was reduced at 37°C compared to 23°C (42.7 mol/L vs. 115.6 mol/L, respectively; p=0.001), whereas it was unaffected in WT CMs. Differences in Ca2+ leak between WT and NOS1−/− were magnified according the SR Ca2+ load increased. Contrarily to WT, there was a trend to rise in ROS production at temperatures over 30°C in NOS1−/− CMs (Fig. B). There was a linear association between ROS and leak in both strains. The NOS isoforms were unaffected by temperature in WT.
Our observations show that Ca2+ leak increases when the temperature drops below 34°C; however, in the absence of NOS1 activity, the leak rises at temperatures greater than 30°C, and is associated with more ROS production. These results suggest that Ca2+ leak from the SR is regulated by a temperature-dependent balance between NO and ROS.
- © 2013 by American Heart Association, Inc.