Nitroxides Increase the Detectable Amount of Nitric Oxide Released from Endothelial Cells

Stefan Zöllner, Reiner F. Haseloff, Igor A. Kirilyuk, Ingolf E. Blasig, Gabor M. Rubanyi
1997 Journal of Biological Chemistry  
Nitroxides are known to exert superoxide dismutasemimetic properties and to decrease O 2 . -and H 2 O 2 -mediated cytotoxicity. However, the effect of nitroxides on ⅐ NO homeostasis has not been studied yet. The present study investigates the effect of nitroxides on the detectable amount of ⅐ NO released by 3-morpholinosydnonimine (SIN-1) and cultured endothelial cells. Cultured bovine aortic and atrial endothelial cells stimulated with 10 M A23187 released a stable flux of ⅐ NO, as detected by
more » ... ⅐ NO chemiluminescence. Addition of 100 units/ml SOD or 10 M of the nitroxides 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL), 3-carboxy-proxyl, and 3-ethoxycarbonyl-proxyl, increased the chemiluminescence signal. The effect of these nitroxides on the amount of ⅐ NO released from cell monolayers was dose-dependent, with the highest efficacy between 30 and 100 M. EPR spin trapping in SIN-1 solutions revealed the formation of ⅐ OH adducts from spontaneous dismutation of O 2 . and concomitant reaction with H 2 O 2 . Both SOD and TEMPOL increased the signal intensity of the ⅐ OH adduct by accelerating the dismutation of O 2 . . The results of this study demonstrate that the SOD-mimetic activity of nitroxides increases the amount of bioavailable ⅐ NO in vitro.
doi:10.1074/jbc.272.37.23076 pmid:9287307 fatcat:524wopc3kbd7jgcdjvspx53hmu