Direct, real-time sensing of free radical production by activated human glioblastoma cells.

Primary brain injury initiates a cascade of events which result in secondary brain damage. Although, at present, the biochemical and molecular mechanisms of nerve cell death are not well understood, sufficient evidence now exists to implicate free radicals in this brain injury response. In the light of the current understanding on the role of free radicals in cell mortality, we report on the use of two specific sensors, which we use to measure the direct, simultaneous and real time electrochemical detection of both superoxide (O2.-) and nitric oxide (NO), produced by activated glioblastoma cells. The development and application of these novel methods has enabled us to show that both the cytokine-mediated induction of the enzymes responsible for the generation of these radical species, and the metabolic requirements of the cell can modulate cell messenger release. Importantly, the data collected provides dynamic information on the time course of free radical production, as well as their interactions and their involvement in the process of cell death. In particular, one of the major advances afforded by this technology is the demonstration that suppression of one of either of the two cellular generated radical species (NO and O2.-) leads directly to a corresponding increase in the species that was not being deliberately inhibited or scavenged. This finding may indicate a mechanism involving inter-enzyme regulation of free radical production in glial cells (a phenomenon which may, in future, also be shown to operate in other relevant cell models).