Nitric Oxide Modulates Ca2+ Leak and Arrhythmias via S-Nitrosylation of CaMKII

BACKGROUND: Nitric oxide (NO) has been identified as a signaling molecule generated during beta-adrenergic receptor stimulation in the heart. Furthermore, a role for NO in triggering spontaneous Ca2+ release via S-nitrosylation of CaMKII delta (Ca2+/calmodulin kinase II delta) is emerging. NO donors are routinely used clinically for their cardioprotective effects on the heart, but it is unknown how NO donors modulate the proarrhythmic CaMKII to alter cardiac arrhythmia incidence. We test the role of S-nitrosylation of CaMKII delta at the Cysteine-273 inhibitory site and cysteine-290 activating site in cardiac Ca2+ handling and arrhythmogenesis before and during beta-adrenergic receptor stimulation. METHODS: We measured Ca2+-handling in isolated cardiomyocytes from C57BL/6J wild-type (WT) mice and mice lacking CaMKII delta expression (CaMKII delta-KO) or with deletion of the S-nitrosylation site on CaMKII delta at cysteine-273 or cysteine-290 (CaMKII delta-C273S and -C290A knock-in mice). Cardiomyocytes were exposed to NO donors, S-nitrosoglutathione (GSNO; 150 mu M), sodium nitroprusside (200 mu M), and beta-adrenergic agonist isoproterenol (100 nmol/L). RESULTS: Both WT and CaMKII delta-KO cardiomyocytes responded to isoproterenol with a full inotropic and lusitropic Ca2+ transient response as well as increased Ca2+ spark frequency. However, the increase in Ca2+ spark frequency was significantly attenuated in CaMKII delta-KO cardiomyocytes. The protection from isoproterenol-induced Ca2+ sparks and waves was mimicked by GSNO pretreatment in WT cardiomyocytes but lost in CaMKII delta-C273S cardiomyocytes. When GSNO was applied after isoproterenol, this protection was not observed in WT or CaMKII delta-C273S but was apparent in CaMKII delta-C290A. In Langendorff-perfused isolated hearts, GSNO pretreatment limited isoproterenol-induced arrhythmias in WT but not CaMKII delta-C273S hearts, while GSNO exposure after isoproterenol sustained or exacerbated arrhythmic events. CONCLUSIONS: We conclude that prior S-nitrosylation of CaMKII delta at cysteine-273 can limit subsequent beta-adrenergic receptor-induced arrhythmias, but that S-nitrosylation at cysteine-290 might worsen or sustain beta-adrenergic receptor-induced arrhythmias. This has important implications for the administration of NO donors in the clinical setting.