title: S-nitrosation of mitochondrial connexin 43 regulates mitochondrial function.
abstract: S-nitrosation (SNO) of connexin 43 (Cx43)-formed channels modifies dye uptake in astrocytes and gap junctional communication in endothelial cells. Apart from forming channels at the plasma membrane of several cell types, Cx43 is also located at the inner membrane of myocardial subsarcolemmal mitochondria (SSM), but not in interfibrillar mitochondria (IFM). The absence or pharmacological blockade of mitochondrial Cx43 (mtCx43) reduces dye and potassium uptake. Lack of mtCx43 is associated with loss of endogenous cardioprotection by ischemic preconditioning (IPC), which is mediated by formation of reactive oxygen species (ROS). Whether or not mitochondrial Lucifer Yellow (LY), ion uptake, or ROS generation are affected by SNO of mtCx43 and whether or not cardioprotective interventions affect SNO of mtCx43 remains unknown. In SSM from rat hearts, application of NO donors (48 nmol to 1 mmol) increased LY uptake (0.5 mmol SNAP 38.4 ± 7.1 %, p < 0.05; 1 mmol GSNO 28.1 ± 7.4 %, p < 0.05) and the refilling rate of potassium (SNAP 227.9 ± 30.1 %, p < 0.05; GSNO 122.6 ± 28.1 %, p < 0.05). These effects were absent following blockade of Cx43 hemichannels by carbenoxolone as well as in IFM lacking Cx43. Unlike potassium, the sodium permeability was not affected by application of NO. Furthermore, mitochondrial ROS formation was increased following NO application compared to control SSM (0.5 mmol SNAP 22.9 ± 1.8 %, p < 0.05; 1 mmol GSNO 40.6 ± 7.1 %, p < 0.05), but decreased in NO treated IFM compared to control (0.5 mmol SNAP 14.4 ± 4 %, p < 0.05; 1 mmol GSNO 13.8 ± 4 %, p < 0.05). NO donor administration to isolated SSM increased SNO of mtCx43 by 109.2 ± 15.8 %. Nitrite application (48 nmol) to mice was also associated with elevated SNO of mtCx43 by 59.3 ± 18.2 % (p < 0.05). IPC by four cycles of 5 min of ischemia and 5 min of reperfusion increased SNO of mtCx43 by 41.6 ± 1.7 % (p < 0.05) when compared to control perfused rat hearts. These data suggest that SNO of mtCx43 increases mitochondrial permeability, especially for potassium and leads to increased ROS formation. The increased amount of SNO mtCx43 by IPC or nitrite administration may link NO and Cx43 in the signal transduction cascade of cardioprotective interventions.
authors.affiliation: Systems Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Soetkamp
authors.forename: Tiffany T
authors.initials: TT
authors.lastname: Nguyen
authors.forename: Sara
authors.initials: S
authors.lastname: Menazza
authors.forename: Christine
authors.initials: C
authors.lastname: Hirschhäuser
authors.forename: Ulrike B
authors.initials: UB
authors.lastname: Hendgen-Cotta
authors.forename: Tienush
authors.initials: T
authors.lastname: Rassaf
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Schlüter
authors.forename: Kerstin
authors.initials: K
authors.lastname: Boengler
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Murphy
authors.forename: Rainer
authors.initials: R
authors.lastname: Schulz
mesh_terms: D000818:Animals; D015153:Blotting, Western; D018031:Connexin 43 / Q000378:metabolism*; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008929:Mitochondria, Heart / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D015538:Nitrosation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D017382:Reactive Oxygen Species
chemical_list: D018031:Connexin 43; D017382:Reactive Oxygen Species