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Keywords:

  • amperometry;
  • electrochemistry;
  • electrodes;
  • lapachones;
  • macrophages;
  • oxidative stress

Abstract

Thumbnail image of graphical abstract

Artificial synapses for femtomolar detection: Amperometry at platinized carbon fibre electrodes has been used to unravel the complexity of β-lapachone's effects on cellular oxidative stress. α-Lapachone, the pharmacologically inactive para-quinone isomer, did not display such characteristics, but over longer incubation periods both quinones induced apoptosis. The observed effects were interpreted in terms of two mechanisms involving opposite reactivities of quinones in living cells.

β-Lapachone (1) has been widely used for its pharmacological activity, particularly against cancer. However, its mechanism of action at the cellular level remains unclear, although a common major hypothesis involves its prooxidant properties. Electrochemical measurements with microelectrodes were taken in order to quantitatively investigate the activity of 1 at different concentrations and several incubation times, on the oxidative bursts released by single macrophages. The exact natures of the electroactive reactive oxygen species (ROS) and reactive nitrogen species (RNS) released by macrophages under the effect of 1 were characterized, and their fluxes were measured quantitatively. This allowed the reconstruction of the primary O2.− and NO production by the cells. In the first hour, at 10 μM, the decrease in the oxidative burst involved mainly RNS, while the amount of H2O2 was found to be higher than in controls. After a longer incubation time—that is, 4 h—at 1 μM, the total amount of ROS and RNS had increased, with significant enhancements of H2O2 and NO. In contrast, α-lapachone, the pharmacologically inactive para-quinone isomer, was unable to increase the production of RONS by macrophages significantly. Over much longer incubation periods (about one day), however, each quinone induced cell death by apoptosis. All these effects were interpreted by consideration of two different mechanisms involving opposite reactivities of quinones in living cells.