Toxicity is not only a function of damage mechanisms, but is also determined by cellular resilience factors. Glutathione has been reported as essential element to counteract negative influences.... Show moreToxicity is not only a function of damage mechanisms, but is also determined by cellular resilience factors. Glutathione has been reported as essential element to counteract negative influences. The present work hence pursued the question how intracellular glutathione can be elevated transiently to render cells more resistant toward harmful conditions. The antibiotic nitrofurantoin (NFT) was identified to stimulate de novo synthesis of glutathione in the human hepatoma cell line, HepG2, and in primary human hepatocytes. In intact cells, activation of NFT yielded a radical anion, which subsequently initiated nuclear-factor-erythroid 2-related-factor-2 (Nrf2)-dependent induction of glutamate cysteine ligase (GCL). Application of siRNA-based intervention approaches confirmed the involvement of the Nrf2-GCL axis in the observed elevation of intracellular glutathione levels. Quantitative activation of Nrf2 by NFT, and the subsequent rise in glutathione, were similar as observed with the potent experimental Nrf2 activator diethyl maleate. The elevation of glutathione levels, observed even 48 h after withdrawal of NFT, rendered cells resistant to different stressors such as the mitochondrial inhibitor rotenone, the redox cycler paraquat, the proteasome inhibitors MG-132 or bortezomib, or high concentrations of NFT. Repurpose of the antibiotic NFT as activator of Nrf2 could thus be a promising strategy for a transient and targeted activation of the endogenous antioxidant machinery. Graphical abstract. Show less
The aim of the research described in this thesis entitled ‘The use of transcriptomics data in detecting non-genotoxic carcinogens’ was to develop in vitro tests to improve testing strategies for... Show moreThe aim of the research described in this thesis entitled ‘The use of transcriptomics data in detecting non-genotoxic carcinogens’ was to develop in vitro tests to improve testing strategies for cancer hazard assessment of chemicals, to reduce the use of in vivo experiments. The scope of this thesis was twofold. First, an improved in vitro approach to assess genotoxicity was developed, with the intention to reduce the number of misleading positive test results. The emphasis was on characterization of the cell system, primary hepatocytes derived from transgenic mice. Results showed that this cell system will be of added value in genotoxicity testing. In the second part of this thesis, the focus was on the development of a ‘trancriptomics’-based approach to detect modes of action of non-genotoxic carcinogens. It has been demonstrated that the described comparison approach is promising in recognizing gene expression patterns, which can be related to modes of action. In addition, the approach is also suitable to detect toxicity of chemicals in general. In conclusion, through the development of in vitro approaches, as described within this thesis, an important contribution in the improvement of testing strategies for cancer hazard assessment of chemicals has been delivered. Show less
Stephenne, X.; Foretz, M.; Taleux, N.; Zon, G.C. van der; Sokal, E.; Hue, L.; ... ; Guigas, B. 2011
