Interaction Between Neuronal NOS Signaling and Temperature Influences SR Ca2+ Leak: Role of Nitroso-Redox Balance
Rationale: While nitric oxide (NO) signaling modulates cardiac function and excitation-contraction coupling, opposing results due to inconsistent experimental conditions, particularly with respect to temperature, confound the ability to elucidate NO signaling pathways. Here we show that temperature significantly modulates NO effects.
Objective: Test the hypothesis that temperature profoundly impacts nitroso-redox equilibrium, thereby affecting sarcomeric reticulum (SR) Ca2+ leak.
Methods and Results: We measured SR Ca2+ leak in cardiomyocytes from wild-type (WT), NO/redox imbalance (NOS1−⁄−), and hyper S-nitrosylation (GSNOR−⁄−) mice. In WT cardiomyocytes, SR Ca2+ leak increased as temperature decreased from 37°C to 23°C, whereas, in NOS1‒/‒ cells, the leak suddenly increased when the temperature surpassed 30ºC. GSNOR‒/‒ cardiomyocytes exhibited low leak throughout the temperature range. Exogenously added NO had a biphasic effect on NOS1‒/‒ cardiomyocytes; reducing leak at 37ºC but increasing it at sub-physiologic temperatures. Oxypurinol and Tempol diminished the leak in NOS1−⁄− cardiomyocytes. Cooling from 37° to 23°C increased ROS generation in WT but decreased it in NOS1−⁄− cardiomyocytes. Oxypurinol further reduced ROS generation. At 23°C in WT cells, leak was decreased by tetrahydrobiopterin, an essential NOS cofactor. Cooling significantly increased SR Ca2+ content in NOS1−⁄− cells but had no effect in WT or GSNOR−⁄−.
Conclusions: Ca2+ leak and temperature are normally inversely proportional, whereas NOS1 deficiency reverses this effect, increasing leak and elevating ROS production as temperature increases. Reduced denitrosylation (GSNOR deficiency) eliminates the temperature dependence of leak. Thus, temperature regulates the balance between NO and ROS which in turn has a major impact on SR Ca2+.
- Therapeutic Hypothermia
- Nitroso-Redox imbalance
- Calcium Handling
- calcium signaling
- nitric oxide
- nitric oxide synthase
- reactive oxygen species
- Received September 8, 2014.
- Revision received October 14, 2014.
- Accepted October 16, 2014.