Induction of oxidative stress and SOS response in Escherichia coli by vegetable extracts: the role of hydroperoxides and the synergistic effect of simultaneous treatment with cisplatinum

Plasmids containing a transcription fusion of Escherichia coli PatG, SoxS and recA promoters to the Photorhabdus luminescens lux operon ( lux CDABE) were constructed. The bioluminescence method of assessing oxidative stress and SOS response in E. coli cells was applied to test the genotoxicity of cisplatinum and vegetable extracts. Strains MG1655 (pKatG-lux) and MG1655 (pSoxS-lux) were used in the oxidative stress procedure. Strain MG1655(pRecA-lux) was used to test the genotoxicity of the chemicals. All vegetable extracts induced oxidative stress and SOS response. A marked synergistic response was observed when MG1655 (pRecA-lux) cells were exposed to both cisplatinum and vegetable extracts; the level of luminescence measured in the presence of both inducers was much higher than the sum of the levels of luminescence observed with vegetable extracts or cisplatinum alone. The hydroperoxide content in vegetable extracts and in X63-Ag8.6.5.3 myeloma cells was determined. Vegetable extracts were shown to inhibit the HeLa cell growth.