Synergistic lethal effect between hydrogen peroxide and neocuproine (2,9-dimethyl 1,10-phenanthroline) in Escherichia coli

Despite 2,9-dimethyl I,10-phenanthroline (NC) has been extensively used as a potential inhibitor of damage due to oxidative stress in biological syste ms, the incubation of E. coli cultures with the copper ion chelator NC prio r to the challenge with hydrogen peroxide caused a lethal synergistic effec t. The SOS response seems to be involved in the repair of the synergistic l esions through the recombination pathway. Furthermore, there is evidence fo r the UvrABC excinuclease participation in the repair of the synergistic le sions, and the base excision repair may also be required for bacterial surv ival to the synergistic effect mainly at high concentrations of H2O2, being the action of Fpg protein an important event, Incubation of lexA (Ind(-)) cultures with iron (LI) ion chelator 2,2'-dipyridyl simultaneously with NC prevented the lethal synergistic effect. This result suggests an important role of the Fenton reaction on the phenomenon. NC treatment was able to inc rease the number of DNA strand breaks (DNAsb) induced by 10 mM of H2O2 in l exA (Ind-) strain and the simultaneous treatment with 2,2'-dipyridyl was ab le to block this effect. (C) 1999 Elsevier Science B.V. All rights reserved .