Abstract 13050: S-Nitrosylation of Mitochondrial Connexin 43: A possible Mechanism Mediating Ischemic Preconditioning in Rat Hearts
Background: S-nitrosylation (SNO), which is transiently increased following ischemic preconditioning (IPC), modifies the function of connexin 43 (Cx43)-formed channels at the sarcolemma of cardiomyocytes. Apart from forming hemichannels and gap junctions at the sarcolemma of cardiomyocytes, Cx43 is located also at the inner membrane of subsarcolemmal mitochondria (SSM), and lack of mitochondrial Cx43 (mtCx43) is associated with loss of cardioprotection by IPC. Furthermore, the absence of mtCx43 or pharmacological blockade of Cx43 hemichannels reduces mitochondrial dye (Lucifer yellow) and potassium uptake. Whether or not mitochondrial Lucifer Yellow or ion uptake is affected by SNO and whether or not IPC affects SNO of mtCx43 remains unknown.
Methods and Results: In SSM from rat hearts, application of NO-donors (SNAP 0.5 mM, GSNO 0.5 mM) increased mitochondrial LY uptake (SNAP: n = 6, 33,6 ± 14.1%, p≤0.01; GSNO: n = 6, 21.8 ± 9.4%, p≤0.05) and the refilling rate of potassium (SNAP: n = 9, 300.7 ± 116,8% ,p≤0.001; GSNO: n = 5, 112.4 ± 42.3%, p≤0.05) following mitochondrial matrix potassium depletion, but not in interfibrillar mitochondria (IFM). These effects were completely blocked by the Cx43 hemichannel blocker, carbenoxolone. Unlike potassium the sodium permeability was not affected by application of NO. SNAP administration increased SNO of mtCx43 by 71.3 ± 38% (n = 6, p≤0.05; analyzed using a modified biotin switch method and Western blot). Similarly, in isolated rat hearts preconditioned by 4 cycles of ischemia/reperfusion, SNO of mtCx43 was increased by 22.4 ± 9.4% (n = 14, p≤0.05) when compared to rat hearts undergoing control perfusion.
Conclusion: The data suggest that SNO of mtCx43 increases mitochondrial permeability, especially for potassium. The increased amount of SNO mtCx43 by IPC may link NO and Cx43 in the signal transduction cascade of cardioprotection.
- © 2013 by American Heart Association, Inc.