title: Nitroxyl triggers Ca2+ release from skeletal and cardiac sarcoplasmic reticulum by oxidizing ryanodine receptors.
abstract: The biological activity of nitric oxide (NO) and NO-donors has been extensively investigated yet few studies have examined those of nitroxyl (HNO) species even though both exist in chemical equilibrium but oxidize thiols by different reaction mechanisms: S-nitrosation versus disulfide bond formation. Here, sodium trioxodinitrate (Na2N2O3; Angeli's salt; ANGS) was used as an HNO donor to investigate its effects on skeletal (RyR1) and cardiac (RyR2) ryanodine receptors. At steady-state concentrations of nanomoles/L, HNO induced a rapid Ca2+ release from sarcoplasmic reticulum (SR) vesicles then the reducing agent dithiothreitol (DTT) reversed the oxidation by HNO resulting in Ca2+ re-uptake by SR vesicles. With RyR1 channel proteins reconstituted in planar bilayers, HNO added to the cis-side increased the open probability (Po) from 0.056+/-0.026 to 0.270+/-0.102 (P<0.005, n=4) then DTT (3 mM) reduced Po to 0.096+/-0.040 (P<0.01, n=4). In parallel experiments, the time course of HNO production from ANGS was monitored by EPR and UV spectroscopy and compared with the rate of SR Ca2+ release indicating that picomolar concentrations of HNO triggered SR Ca2+ release. Controls showed that the hydroxyl radical scavenger, phenol did not alter ANGS-induced SR Ca2+ release, indicating that hydroxyl radical production from ANGS did not account for Ca2+ release from the SR. The findings indicate that HNO is a more potent activator of RyR1 than NO and that HNO activation of RyRs may contribute to NO's activation of RyRs and to the therapeutic effects of HNO-releasing prodrugs in heart failure.
authors.affiliation: Department of Cell Biology and Physiology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15213, USA.
authors.forename: Eunji
authors.initials: E
authors.lastname: Cheong
authors.forename: Vassil
authors.initials: V
authors.lastname: Tumbev
authors.forename: Jon
authors.initials: J
authors.lastname: Abramson
authors.forename: Guy
authors.initials: G
authors.lastname: Salama
authors.forename: Detcho A
authors.initials: DA
authors.lastname: Stoyanovsky
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D004229:Dithiothreitol / Q000494:pharmacology; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D017665:Hydroxyl Radical / Q000737:chemistry / Q000378:metabolism; D066298:In Vitro Techniques; D018482:Muscle, Skeletal / Q000737:chemistry*; D009206:Myocardium / Q000737:chemistry*; D009573:Nitrites / Q000494:pharmacology; D009589:Nitrogen Oxides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D011817:Rabbits; D019163:Reducing Agents / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013347:Subcellular Fractions / Q000737:chemistry; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism
chemical_list: D009573:Nitrites; D009589:Nitrogen Oxides; D019163:Reducing Agents; D019837:Ryanodine Receptor Calcium Release Channel; C021229:oxyhyponitrite; D017665:Hydroxyl Radical; C039900:nitroxyl; D004229:Dithiothreitol