Characterization of the electrochemical oxidation of peroxynitrite: relevance to oxidative stress bursts measured at the single cell level.

The electrochemical signature of peroxynitrite oxidation is reported for the first time, and its mechanism discussed in the light of data obtained by steady-state and transient voltammetry at microelectrodes. Peroxynitrite is an important biological species generated by aerobic cells presumably via the near diffusion-limited coupling of nitric oxide and superoxide ion. Its production by living cells has been previously suspected during cellular oxidative bursts as well as in several human pathologies (arthritis, inflammation, apoptosis, ageing, carcinogenesis, Alzheimer disease, AIDS, etc.). However, this could only be inferred on the basis of characteristic patient metabolites or through indirect detection, or by observation of follow-up species resulting supposedly from its chemical reactions in vivo. In this work, thanks to the independent knowledge of the electrochemical characteristics of ONO2- oxidation, the kinetics and intensity of this species released by single human fibroblasts could be established directly and quantitatively based on the application of the artificial synapse method. It was then observed and established that fibroblasts submitted to mechanical stresses produce oxidative bursts, which involve the release within less than a tenth of a second of a complex cocktail composed of several femtomoles of peroxynitrite, hydrogen peroxide, nitric oxide, and nitrite ions.