■ Nitrogen monoxide and oxidative stress: composition and intensity of cellular oxidative bursts cocktail. A study through artificial electrochemical synapses on single human fibroblasts

Positioning an ultramicroelectrode at micrometric distances from an isolated living cell ensures tgha any electroactive material released by the cell is collected and analyzed by the electrode surface. The film of extracellular fluid comprised between the cell and the electrode surfaces defines an artificial synaptic cleft of a few hundred femtoliters volume, in which the release of minute molecular amounts of chemicals produces a sudden and important concentration rise. This guarantees the detection of the released species with an extremely high signal-to-noise ratio, as well as a determination of its instant released flux since the collection efficiency is quantitative. In other words, the assembly cell/liquid cleft/ultramicroelectrode behaves as an artificial neuronal synapse. In this review we wish to elaborate on how this artificial synaptic arrangement may be used to monitor an oxidative stress response stimulated in a human fibroblast, and demonstrate that such long-time conjectured oxidative cellular bursts involve a subtle cocktail of femtomoles of hydrogen peroxide, nitrogen monoxide, peroxynitrite and nitrite ions. The analysis performed establishes that this delicate cocktail results from the ultimate combinations of equimolar primary productions of superoxide ion and nitrogen monoxide by two distinct enzymatic systems which are presumably operating in distinct compartments of the cell: NADPH-oxidase type enzymes for the generation of superoxide, and NO-synthases for that of nitrogen monoxide.